CA1108068A - Air purification filter and method - Google Patents
Air purification filter and methodInfo
- Publication number
- CA1108068A CA1108068A CA302,962A CA302962A CA1108068A CA 1108068 A CA1108068 A CA 1108068A CA 302962 A CA302962 A CA 302962A CA 1108068 A CA1108068 A CA 1108068A
- Authority
- CA
- Canada
- Prior art keywords
- air
- filter medium
- filter
- air purification
- housing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000004887 air purification Methods 0.000 title claims abstract description 48
- 238000000034 method Methods 0.000 title claims abstract description 15
- 239000002245 particle Substances 0.000 claims abstract description 38
- 238000011144 upstream manufacturing Methods 0.000 claims abstract description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 56
- 239000000126 substance Substances 0.000 claims description 31
- 230000003472 neutralizing effect Effects 0.000 claims description 26
- 230000005686 electrostatic field Effects 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 8
- 239000000919 ceramic Substances 0.000 claims description 3
- 239000013618 particulate matter Substances 0.000 claims description 3
- 239000002984 plastic foam Substances 0.000 claims description 3
- 239000002609 medium Substances 0.000 description 88
- 239000007789 gas Substances 0.000 description 40
- 235000019645 odor Nutrition 0.000 description 28
- 230000000694 effects Effects 0.000 description 10
- 239000003610 charcoal Substances 0.000 description 9
- 229940106265 charcoal Drugs 0.000 description 9
- 150000002500 ions Chemical class 0.000 description 8
- 238000000746 purification Methods 0.000 description 8
- 239000000779 smoke Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 241000208125 Nicotiana Species 0.000 description 3
- 235000002637 Nicotiana tabacum Nutrition 0.000 description 3
- 244000052616 bacterial pathogen Species 0.000 description 3
- 238000005520 cutting process Methods 0.000 description 3
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- 239000000499 gel Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 230000004323 axial length Effects 0.000 description 2
- 235000019504 cigarettes Nutrition 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
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- 238000010438 heat treatment Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 230000004224 protection Effects 0.000 description 2
- 239000000341 volatile oil Substances 0.000 description 2
- 102100027522 Baculoviral IAP repeat-containing protein 7 Human genes 0.000 description 1
- 101710177963 Baculoviral IAP repeat-containing protein 7 Proteins 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 235000005979 Citrus limon Nutrition 0.000 description 1
- 244000131522 Citrus pyriformis Species 0.000 description 1
- 241000581835 Monodora junodii Species 0.000 description 1
- 241000220317 Rosa Species 0.000 description 1
- 229920002125 Sokalan® Polymers 0.000 description 1
- 239000006096 absorbing agent Substances 0.000 description 1
- 230000002730 additional effect Effects 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
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- 229920002678 cellulose Polymers 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000000332 continued effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 235000013305 food Nutrition 0.000 description 1
- 239000003205 fragrance Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000012432 intermediate storage Methods 0.000 description 1
- STEPQTYSZVCJPV-UHFFFAOYSA-N metazachlor Chemical compound CC1=CC=CC(C)=C1N(C(=O)CCl)CN1N=CC=C1 STEPQTYSZVCJPV-UHFFFAOYSA-N 0.000 description 1
- 230000001473 noxious effect Effects 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 238000011045 prefiltration Methods 0.000 description 1
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- 230000000391 smoking effect Effects 0.000 description 1
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- 239000002562 thickening agent Substances 0.000 description 1
- 239000003440 toxic substance Substances 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
- B03C3/02—Plant or installations having external electricity supply
- B03C3/04—Plant or installations having external electricity supply dry type
- B03C3/14—Plant or installations having external electricity supply dry type characterised by the additional use of mechanical effects, e.g. gravity
- B03C3/155—Filtration
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
- F24C15/00—Details
- F24C15/20—Removing cooking fumes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S55/00—Gas separation
- Y10S55/36—Kitchen hoods
Abstract
AIR PURIFICATION FILTER AND METHOD
ABSTRACT OF THE DISCLOSURE
The invention provides an air purification filter for use in kitchens, restaurants, living areas and the like. The filter is provided in a housing having an inlet and an outlet for the air, the air preferably being driven through the interior of the housing by a fan. A
microporous filter is provided in the housing, through which the air is constrained to pass. The microporous filter is directly electrically charged to one polarity and particles in the air are charged to the opposite polarity upstream of the filter so that they carry a charge when entering the microporous filter. The particles are thus attracted to, and deposited on, the interior surfaces of the microporous filter as the air passes therethrough. Hence, the filter traps even the minute particles that would normally pass through it.
ABSTRACT OF THE DISCLOSURE
The invention provides an air purification filter for use in kitchens, restaurants, living areas and the like. The filter is provided in a housing having an inlet and an outlet for the air, the air preferably being driven through the interior of the housing by a fan. A
microporous filter is provided in the housing, through which the air is constrained to pass. The microporous filter is directly electrically charged to one polarity and particles in the air are charged to the opposite polarity upstream of the filter so that they carry a charge when entering the microporous filter. The particles are thus attracted to, and deposited on, the interior surfaces of the microporous filter as the air passes therethrough. Hence, the filter traps even the minute particles that would normally pass through it.
Description
:``
SUMMARY OF THE INVENTION
The present invention relates to a method and apparatus for the purification of gases, finding particular applicability in the removal of smoke and kitchen odors in closed systems, such as restaurants, kitchens and the living areas o residences and offi~es.
As opposed to traditional electrostatic plate or grid filters requiring frequent exchange of filter media and problems in reducing odors particularly aEter prolonged use, the present invention provides an improved method and apparatus, as follows.
According to one aspect of the invention, there is provided an air purification filter comprising: a housing; an inlet in the housing for air to be purified a microporous filter medium in the housing so that the air to be purified passes therethrough; an outlet in the housing for the purified air; means for directly electrica~ly charging said microporous filter medium to one polarity; and means for electrically charging particles in the air to be purified to an opposite polar-ity upstream of th~e filter medium so that they carry that charge when entering the filter medium, whereby when said charged particles enter the filter medium they are attracted to the oppositely charged filter medium and held thereby and separated from the air.
According to another aspect of the invention there is provided a method of removing particulate matter from the air which comprises passing particulate-laden air charged to one polarity through a microporous filter medium which has been charged to the opposite polarity in a manner such that the charge is distributed throughout said microporous filter medium.
, ~,, 1 Thus when the charged particles enter the filter medium they are attracted to the oppositely charged filter medium and held thereby and separated from the air.
The microporous filter medium should have the ability to be charged, and in a preferred embodiment is activated charcoal. It will be appreciated that ceramic and plastic foam materials also have such attributes. ~or example, a metallized plastic foam may be used. The means for directly electrically charging the microporous filter medium provide an electric field in the microporous medium itself, with which to attract the oppositely charged particles. Thus, the microporous filter medium is an electrostatic filter. This is distinguished from the prior art downstream use of .
- la -::, ":
activated charcoal as a supplement to an electrostatic plate or grid filter, where the primary electrostatic filtering takes place through the electrostatic grid. Additionally, the charge is ~ placed directly on the microporous filter medium, as opposed to ¦ being transferred from the housing of the microporous filter med-ium. The charge is advantageously placed on the downstream side of the microporous filter medium, to provide -the optimal distribu-tion of the eharge throughout the microporous filter medium.
The means or electrically charging the particles pre-ferably is an electrode having sharp or pointed edges which facili-tates the ionlzation o~ the air. A piurality OL needles arranged in a plane perpendicular to the air flow is one embodiment of this invention. A wire may also be stretched in the direction of the air flow, or the edge of a blade may be used. In a further embodi-ment of the invention an odor neutralizing substance, which may be¦a scentstone ~Duflstein), a gel or a liquid, may be placed upstreaml from the microporous filter medium and carry the opposite charge of the microporous filter medium. Such odor neutralizing sub-stanee may be selec-ted dependent upon the type of air which is ~0 being purified. For example, where the air includes a particular noxious chemical substance which in the past has been known to be attracted to a particular type of odor neutralizing substance,such substanee may be incorporated as the odor neutralizing substance of this aspect of the invention. With the enhanced effect of the charged odor neutralizing substance, it will be seen that the in-~corporation of the odor neutralizing substance may be used to effectively combat particularly troublesome odors included in the air stream.
In a preferred form o~ the present invention, an independent electrostatic filter plate having a charge opposite to that of the microporous filter medium may be placed in the air stream. This also serves to facilitate ionization of the gas.
The amount of current which is used should be suffi-cient to provide adequate charging of the air and the filter medium to cause an attraction between the oppo-sitely charged particles and filter. A direct current of preferably from about 6 to about 15 kV and at least l watt, and preferably 2 to 50 watts, is used. The gas flow proceeds at a speed of from about 0.05 to about 0.5 meters per second, and preferably from about 0.1 to about 0.25 meters per second.
It will be appreciated that a fan included in the system to more rapidly force the air through the system may be of particular advantage.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated by the drawings wherein:
Fig. 1 illustrates an experimental model which has been used to test the efficiency of the system;
Fig. 2a shows an overall view of an air purification system;
~:.
: ' . . . .
F.ig. 2b is a cross-s~ction of Fig. 2a;
Fig. 3 shows an air filter including a low capacity heater which generates the air flow through the filter;
Fig. 4 illustrates a higher capacity air puri:Eication filter;
Fi~. 5 illustrates an air pu`rification filter utilizing a cylindrical microporous medium;
Fig. 6 illustrates a wall mounted air purification filter;
~'lg. / illustrates a kitcnen air purification filt~r;
Fig. 8 illustrates a cylindrical activated charcoal filter.
¦ DETAILED DESCRIPTION OF THE INVENTION
It will be appreciated that through the present inven-tion a relatively small filter system may be used which, due tothe incorporation of a microporous fil.ter medium such as activated charcoal, has a superior effect to filter systems having many times the volume of the filter of the present invention. Thus, by using activated charcoal as a material in place of a grid o-f metal plates, for example, it may be seen that with the vast sur-face area of a microporous filter medium, it is possible to ~ar more efficiently remove a high percenta~e of particles from an air stream than with the traditional electrostatic grid filter.
¦It is important for the efficient operation of the filter of the 25 1¦ present invention that the microporous filter material itsel~ be directly charged, as opposed to merely placing the microporous filter medium in-to a charged housing. The charge is pre~erahly ~placed on the microporous filter medium itsel~ on the downstream , ll ¦side of the microporous filter medium so that it is away from the ¦direction of the approaching gas current having the opposite ¦potential, thereby insuring that all internal surface areas of the activated charcoal participate as an elec-trostatic filter, as ¦ opposed to merely a mechanical filter.
The means for electrically charging the particles in the air to be purified in its generic aspect may include such conven-tional charging means as a wire. It has been discovered, however, l that it is preferable to have one or more sharp needl~s or a sharp¦
¦ cutting edge placed in the path of the gas stream. In tests with I
the air purification filter of the present invention it has been ! ;
found that the effectiveness of removing polluted gases such as room air having cigarette smoke is improved greatly through the `
¦use of the present invention as opposea to a conventional electro-Istatic filter having the traditional plates. This improvement results from the combination of the microporous filter medium with th~ extremely large surface area taken together with the electro-static filtering based upon what is traditionally a mechanical filter, i.e., the microporous filter medium of activated charcoal.
~0 One of the advantages of a microporous filter medium is that various types of microporous filter media have specific effects on specific types of gases. For example, ac-tivated char-coal absorbs carbon monoxide while having little eEfect on o-ther ¦toxic substances such as found in cigaret~e and tobacco smoke or food odors in restaurants. According to a preferred embodiment of the present invention, activated charcoal is used as the filter medium, together with an odor neutralizing substance placed up-_5_ 11/313~G8 ~¦stream of the activated charcoal which is selected based upon the¦¦type of impurity in the air which is better attaehed by such a ¦¦odor neutralizing substance as opposed to activated eharcoal.
For example, a scentstone (Dufts~ein) attrac-ts certain types of odors, such as etheric oils that may be found in kitehen odors.
The scentstone is placed upstream of the filter medium, but in the area where the air has been eharged to a potential opposite to that of the filter medium. The seentstone is advantageously ll~harc~d ~ h a like p~tèntial t~ that of the filter medium. Seent ¦!stones are in porous form and are obtainable as well as high density solids. The sentstone used in the invention is an anti-odorous substance known per se, and may be a combination consistinc lof an aromatic principle or fragrance or a composition made from ¦Isuch odoriferous substances and a carrier substance known per se, l~hich may be fugitive, such as a liquid, or solid hydrocarbon or ¦an a~ueous meaium thickened with an organic or inorganie thickener~
¦such as a colloidal carboxy vinyl polymer. Preferably the perEume composition provides a fresh smelling odor, such as o~ an apple, orange, lemon or rose. This gives the treated air a fresh odor ~0 IAnd binds and absorbs the bad smell of the air to be purified.
For several tes-ts, a scentstone was used according to the ¦apparatus of Fig. 6, the scentstone being of the type L.V. 2037 ¦¦"green apple" was used on a high capillary cellulose carrier ¦¦supplied by Globus Werke, Fritz Schulz, D-8858 Neuburg/Donau, ¦IGermany and having the dimensions 11 x 5.5 x 0.4 cm. A simllar ¦type of anti-odorous substance i~ offered by Waldwick Plastic, Ine. , 21-23 Industrial Park, Waldwick, New ~ersey 06701l U.S.A.
Experimental tests further showed in a restaurant ~ambiency that even with use of the scentstone for six weeks in an electrostatic field, no appreciable decrease of the odor-binding ability o~ the scentstone in combination with the filter was observed.
The external shape of a scenstone may be adapted to the dimensions of the filter in order to assure the optimum contact ~
of as many gas particles as possible with the scentstone. ~ .
porous scentstone may advantageously be used and adaptèd to the cross-sectional dimension of the gas path so that ~ery large in-ternal surface of the scentstone come into contact with the gas.
~The scentstone having the opposite potential to that of the filter `~-:
medium, it acts to ionize the yas passing through or along it.
¦The charge is advantageously applied to the odor neutralizing substance such as the scentstone downstream from the gas flow so that the scentstone acts as a pole with a relatively large surface.
It may also be advantageous to impale the scentstone : :
onto a thorn passing slightly through it, or a sharp edge which ~:
simultaneously serves to hold the scentstone. In this case 20 ionizati~ of the passing gas occur9 mainly at the protruding `
" . ...
19~ 68 edge or point; the scentstone is now only a secondary point of origin for the lines of the field and will be used xapidly which may be advantageous if continuous purification with strongly smelling etheric oils in the air is not a necessary or desirable feature.
The odor neutralizing substance may also be in a liquid or gel form. When in a liquid form, there is advantageously pro-vided a passage through which the gas mus-t pass through the liquid t and with the liquid being given a charge opposite to that of the 10 ¦filter meclium.
¦ Experiments with odor neutralizing substances in their ¦solid form have been conducted to test the purification of office ¦rooms that are filled with tobacco smoke. Using a scentstone, la ~ood iltration action has been observed after relatively long ¦use concerning numerous pollutants, although a relatively shorter duration is noted for kitchen exhaust systems for normal kitchen odors. Through the aspect of the invention providing both the use of a microporous filter andan odor neutralizing substance wi~h the opposite potential of the filter mediu~nexcellent re-sults have been obtained. It will be observed that a particularadvanta~e of the present invention is -that with the combination of the odor neutralizing substance and the microporous filter medium that after a considerably long period of opera-tion the system works well, as opposed to systems of the priGr art where relatively good results may be obtained initially but aftex con-tinued operatior1 o the system results fall off markedly 8'~
The degree of efficiency of the air purification filter of the invention may vary somewhat depending upon such factors as the cross-sectional area of the filter, the speed of -the gas current, the particle size of the impurities,,and their weight, and the composition of the microporous filter material. The degree o ionization of the gas prior to entry into the microporous fil-t~r medium is considered to be of major importance. Tests have shown that the distance between the electrodes, that is the dis-tance between the microporous filter medium and the means for electrlcally charging the ~articles in the air has only a rela-tively minor effect on the e-Eficiency of the filt~r. Rather, raising the applied tension to raise the degree of ionization leads to an improved effeciiveness of the filter. Improvement is also achieved when a plurality of poles are used as the means for : :
electrically charging particles. It is also important that the electrode which forms the means for electrically charging par-ticles has the highest possible ioniæation e:Efect which is achieved by field concentration, therefore concentration is given .
in the irst instance to razor blade-like cutting edge electrodes or needle or brush electrodesO
In some European countries it is believed that through ionization of the air (such as-the.liberation of positive ions from ¦television sets) that it may be beneficial to reduce such a posi-~tive ion concentration. It is also believed in some European Icountries that an excess of positive ions also may lead to an increase in dust development in the rooms. The air purification filter of the present invention may, therefore, be used to co~
Ij ~
incidentall~ counteract such a build-up of positive ions liberated ~rom television sets by attaching the ~ree sharp edge or pointed pole forming the means for electrically charging particles o~ the air purification filter to the negative clamp o-E the high tension generator while the positive terminal is connected -to the surface of the microporous filter medium. If the scentstone is usedl it should be connected on the side opposite to the direction of the gas current to the negative terminal oE the high tension genera-tor. If the scentstone, however, is equipped on one side with d nee~l~ sllape or sharp eciged I.letallic ~oIliza~o,l el~rn~r.~r it Inay be advantageous to attach the opposite pole to the scen-tstone on a side opposite to the microporous filter medium so that the ¦scentstone again can act as a large surface source pole. The air ¦purification filter of the present invention thereby has a ne~
¦effect of liberating negative ions. From the standpoint of re-¦moving particulate matter from the air, it is not critical ¦whether the microporous ~ilter medium is positive or negative ¦tprovided the particles are oppositely charged) r with the above ¦choice of polarities being given only Erom -the standpoint of the ~preE~rence noted in certain European countries for decreasiny -the number o~ positive ions in the air. Where this is not a fac-tor, it will be appreciated that either positive or negative polarity may be given to the microporous filter medium.
The theory of positive ions in the air is explained in ¦ German Patent 1,261~295 at page 22. In addition, to demonstrate the lack of criticality in the polarity of -the microporous Eilter ¦medium charge and also to make it possible to adjust the deyree ..
- ~.0-~ f~6 of ionization of the room air, the air purification filter may be provided witn means to make it possible to switch the polarity~
ThUS, a reVersing switch may be provided which can be equipped with a time device so that the fiela may be reversed from time to time. If it is desired to minimize ionization of the air from the air purification :Eilter, it is possible to insert an ion absorber, such as a metal grid, into the housing downstream oE the microporous filter medium. Although activated charcoal is pre-dominately mentioned as an example of the microporous filter med-1~ ium, i_ shoul~ ~e reco~nized that o~her mi~_o~orou~ ~;;ter m~diamay also be used. Such other microporous filter media may be used provided that they contain a layer on the microporous interna surface which is at least electrically semi-conductive so that the electrostatic field is fully effective. Ceramic filters, microporous resin filters, silica gels, and other materials which have been made conductive to at least a certain extent may be used in place of the activated charcoal. It will also be appreciated that the air purification filter may be used in conj~mction with other devices, such as the inclusion of an ultraviolet radiation ~0 device to help kill germs in the air. It should also be recognize~
that while primary emphasis has been given in this specification to the cleaning o~ room air with smoking odors or kitchen odors, ~he type of air which may be purified is not so limited.
The air purification of the present invention may be used in of-~5 fices, residences, laboratories, conference rooms and also inhospitals. For example, in hospitalsr the ac-tivated charcoal fil-~ter medium may be used eithex alone as a part of the presen-t air purification filter, or together with the treatmen-t of the same 8'~iB
air with ultraviolet light to aid in the killing of germs. In restaurants and homes it is important to purify kitchen exhaust vapors, with it having been found that an odor neutralizing sub-stance may advantageously be used as a part of -the air purifica-tion filter. Automotive systems also may be considered, both interms of purification oE the air in the interior of the car Which is recirculated, and also in areas of heavy city traf~ic where it may be desirable to purify the "fresh" air which includes the city odors -- smoke stacks, exhausts from other automobiles, etc. Larger units may be used for air purification in traffic intensive areas where there is limited air circulation, particu-larly crowded intersections in downtown centers and tunnels.
Factory workshops are another area where the air purification fil-ter of the present invention may be used, such as electric welding areas. The efficacy of the air purification filter is demonstratec using thQ experimental arrangement of F-g. 1. Into a plastic tube 1 with an internal diameter of about 10 cm there was introduced an activated charcoal filter 2 to block the current of gas which flowc upward in the tube 1. Filter 2 was attached to the posi-tive pole 20 o~ a high tension generator 3 which has a power of less than 10 watts and yields a direct current tension of 5-15 kV. In prin-cipal, any method could be used which is suitable for the genera-tion of high tension direct current of a relatively low power swch ~as a high tension transformer of line voltage with subsequent ¦¦ratification, voltage double cascade switching wi-.h diode ¦elements and intermediate storage and condensers. The negative ¦~pole of the high tension current and generator 3 ¦~was attached ~y way of conduit 4 in cylinder 1 to needle electrode -ll .
~ 1~8q~'6~3 '~5 and the point oE which is placed about into the middle of the ¦lac~ivated charcoal tablet which is used as the filter medium 2 ¦¦The position of the point relative to the cross-section of the ~ filter is of relatively minor importance, it being more important that the charge is placed on the downstream side of the filter medium 2. The axial distance between the filter 2 and the elec-trode S is also of relatively minor importance~ It is, rather, important that the point of the electrode 5 is the point closest t~ t~e filt~x medil~ 2 for t~e electrostatic field developed be-tween electrode 5 and filter 2.
The purification effect r~as de-termined primarily by use of air strongly laden with cigarette tobacco smoke. In an em-bodiment not shown in Fig. 1, a second activated charcoal filter tablet was placed in the cylinder 1, while maintaining constant voltageand the number of electrodes 5. However, the utilization f the current caused by ionization yielded a filter efiect with a single charcoal table that was effective in removing over 90%
of the particles, so that it was found unnecessary as a practical ~atter to have more than the one activated charcoal tablet.
~0 An improvement of the filter effect was achieved by ubstituting for the needle electrode 5 a sharp edged blade, in the test a razor blade being used as the sharp edged hlade. As in the case of a needle electrode, the results with-a blade electrode ¦provide a high concentration of the electric field at the poin-t or ¦Ithe edge with a strong ionization effect. A further improvement i achieved by raising the degree of ionization through raising the field intensity of the electrostatic field by raising the potential different between the electrode 5 and the filter 2. This also .~. . . .
,: , .
1 ~L'1;1~1~6~3 applies with raising the number of electrodes 5 with constant voltage.
Changing the polarization at the high tension gene~a-l tors so that electrode 5 is positive and filter medium 2 is nega-¦ tive yielded no noticeable change in results, demonstrating thatthe selection of polarity is unimportant, provided that the filter medium 2 and the electrode 5 are oppositely charged.
Fig.2a shows an air purification filter for room air l purification. A housing lO having a closed backside contains an ¦ exchangeable microporous filter medium ll, which prefera~ly is activated charcoal in the form of a cylinder which is charged with la positive or negative potential using a high tension generator ¦which is contained in the device. In the front of the housing lO
la fan 12 is arranged which, where needed, forces air through the l~ ¦filter housing. Between the fan l~ and the microporous filter ¦medium ll there is found a structure 13 which ionizes the gas ¦passing through the housing. This construction is shown in more ¦detail in Fig. 2b which shows an isolated ring 14 to which there ¦iS attached a multiplicity of needle electrodes pointing inwardly ¦and Which may suitably be bent in the direction of the current.
¦These electrodes are connected to the alternate pole of the high ¦tension generator. As the gas moved by fan 12 ~lows along the ¦electrode 15 the gas is ionized and then passes into -the electro-¦statically active microporous filter medium, here made of ac-tivate ¦charcoal, ll. Tne arrangement of the ionization electrode 15 can, of course, be structurally different. Thus, al-though a ring with needle-like projections is illustrated, one may provide a star-shaped arrangement of blades which are attached to a coarial cente~
' li .
. ", . - .
ù6B
instead of the internal chamber of the filter cylinder in which arrangement an equal dlstance to the internal surfa~e of the filte~
is pre~erably maintained on all sides. It is also possible to use l wires although the ionization effect of wires is not as good as that achieved with sharped edged blades or needle electrodes, The device according to Fig . 3 corresponds to the struc-ture of Fig. 2a with the distinction that the fan 12 is exchanged for a heating device 16. The heat drives the air upwardly through the housing 10, the thus heated air being passed through the electrode3 15 and ~hus belng lonized. '~he air :LS drawn into the system through the air admission slits 17, and after having been heated by the heating device 16 and ionized by the electrodes 15 it then passes through the filter medium 11 housed in the upper part of the housing lQ.
15Fig. 4 is a higher capacity device in which polluted ¦air is sucked into housing 10 by use of blowers 12/1 and 12/2 ar-ranged at opposite sidewalls of the housing. The air then flows along an arrangement of ionization electrodes 15/1, 15/2, and the thus ionized particles then pass through the microporous filter ~0 medium 11, preferably of activated charcoal. It is recognized that there may be situations where air is particularly dirty and many of the particles would be screened through more traditional air filtration systems. For exa~ple, many of the particles in ~.^
particularly dirty air could be pre-screened through a mechanical filter 17 and/or an ultraviolet light :~ilter 18 may be placed up-stream of the air particularly for killing germs. It will be appreciated that the filter of Fig. 4 may be used without the \ mechanice pre-filter 17 or the U7 li~ht filter 18, or togetber 8~6~
with either one or both of these. The combination of these addi-tional elements may be particularly use~ul in industrial air cleaning and in laboratories. In the case of the arrangement of Fig. 4 for industrial scale operations, an- even higher degree of purification is achieved if the needle ring electrodes are re-placed by ~lade or comb electrodes arranged in star form inside cylindrical filter element 11. Optimal air passage and current value of about 0.25 meters per second with profusion from all sides may be used for hospital operating rooms. This also may lC be used '~r residentia a~eas, such a, livin~ ~coms. Tlle ~e ired air passage and current value of 0.25 meters per second may be achieved through exit of the purified air over a large area ~rom microporoous filter medium 11 as illustrated in Figs. 2-4.
In Fig. 5 an air purification filter in accordance with the present invention is shown with a hollow cylinder of activated charcoal used as the filter medium 11 and equipped with electrode 20 ~hich is formed on the inside as a cutting blade elec-trode running in axial direction with four blades 21 arranged in star-shape. The sharp free edges of blade 21 all have the same radial distance from the internal surface of microporous filter medium 11 along the axial length of the ~ilter. The gas supply, for ex-ample, results by means of a fan (not shown) and runs in the direc tion of the arrows shown in Fig. 5. Along the sharp edges of blades 21 the gas is ionized and then runs through filter medium 11 which has a high counter potential to the potential of elec-itrode 20.
It will be recognized that if a higher ca~city is de-¦sired the activated air purification filter may comprise a '6 8 plu~ality of microporous filter elements 11, such as the utili~a-tion of two or more activated charcoal cylindxical filters.
Ionization can also be improved by increasing the number of blades from four to eight to the star-shaped electrodes 21. Instead Of blades 21 there may also be used comb-like elements. Microporous filter medium 11 is preferably closed at the end by a lid (not shown) in order to cause optimal radial distribution of the gas ~in a low e~it rate from the filter With a high gas through-put~
~ Fi~. 6 is a schematic diagram for an air purification lG device whic~l nas been ~es~ed -or office rocms aIld restdurants~ It contains essentially a rectangular or oval filter housing 10 with an opening for admission of air 41 and an exit 42 which are equipped with protective gratings 57 and 58, respectively.
Ventilator 12 is driven by an electric motor which pulls the air in direction A over the entrance opening 41 and causes the puri-fied air which is passed through microporous filter medium 11 through the exit 42 in direction B. The path of the current oE
air in housing 10 is directed by walls 22, 23 as well as conduct-ing sheet 8, the function of which is described in more detail ~0 hereinafter. In the path oE the stream through the filter housing .
the air to ~e purified first meets scentstone 7 ~hich is affixed to plate 24, which plate is isolated ~rom housing 10 and equipped with a central thorn 54. Thorn 54 can s-tick out to a minor ex-tent above the scentstone into the surface of the passing air. On the side 26 opposite the plane along which the air passes, the isolated plate 24 can show a break 59 at which scentstone 7 has immediate electric contact at 25 and is connected with a negative pole (not shown) high tension direct current source in the above mentioned manner which may for example be housed in filter housing 10. ~he scentstone 7 suitably in conjunction with a thorn 54 and beyond it, acts as a source pole of an electrostatic field the counter pole o~ which ends in microporous filter medium 11 in a manner described in more detail below. At passing air along scentstone 7 the latter is partially ionized already, and the results are an enhanced elimination of polluted air particles by means of the scentstone.
In the further path of the stream the air then meets at first the so-called external ionization 9 which consists of one or more wires or of a brush form metal electrode or, for example, a sharp edged metal piece in the form of a star. Important for the external ionization 9 are sharp or pointed edges at which there occurs high field concentration and corresondingly there results a good ionization of the gas stream thereby. Of course, it ~ .
i~ to be recognized that the external ionization suggested in outline form in Fig. 10 is maintained isolated in filter housing 10 and also connected with a negative pole of the high tension source in the equipment.
Further downstream the air meets conducting plate 8, which can, for example r be glued to an isolated base 53 in housing 10. The conducting plate 8 is also connected with a negative pole of the high tension source; on one hand it serves for uniform distribution oE the gas stream over the area of microporous filter medium 11 and on the other hand it acts as an additional ionization and also furnishes additional ionization of the gas stream.
Filter medium 11 which can be exGhanged through an opening (not shown) in the housing between conducking , - 18 ~
separating walls 22 and 23 is in the example here illu5-trated made of activated charcoal. ~ circumferential ]ayer 6 is provided which iS impenetrable for gas and which also serves to insulate the filter from the ilousing lO. The active charcoal tablet forming the microporous filter medium ll is connected at least at point 55 directly with positive pole (+) with the high tension source (not illustrated) at the side turned away from conducting sheet 8 in the direction of the path of the gas.
The high tension source furnishes a potential of, for example, lO kV with a power of about 5 to about lO wat~s by attachinq the high tension potential to the downstream surface of the microporous filter medium which achieves the result that essentially the entire large inner surface of the activated charcoal tablet acts as a positive pole of the electrostatic field.
The entire apparatus can be constructed on a relatively small scale. In order to obtain a sufficient separation of the air coming in an unpurified form in the direction A
from the purified air flowing away in the direction B one can place a separating sheet approximately in the middle of the housing. It is also possible to turn the air admission opening 4~1 by about 90 aqainst the exit opening 42, thus, for example placing it into the side surface of housing lO. Microporous filter medium ll can be easily exchanqed as can the scentstone 7. However, even with continuous use, as for example in the case of a restaurant, this exchange does not need to occur for some time, several months at least being possible for operation of the system without the necessity of changing either the filter medium ll or the scentstone.
-- 19 ~
?.
B
In accordance with Fig . 7, ~he filter housing 10 has the shape of a cylinder and at 27 shows a sub-division so that the microporous filter medium 11 is readily exchan~ed.
~ere, the microporous filter medium 11 is an activated charcoal tablet. The positive flow o~ the high tension source (not shown) is again attached at 55 to the micro-porous filter medium at the gas exist face opposite the plane of the gaseous stream. The external border 6 of the microporous filter medium 11 again prevents an exit of the gas in the original direction and serves simultaneously for high tension insulation of the microporous filter medium 11 against housing 10 as well as against ring 28 by which microporous filter medium 11 is secured in housing 10 against axial displacement.
In the course of the gas stream from A to B prior to passage through the microporous filter medium 11 the gas passes scentstone 7 which is mounted e~changeably in mount 29, This scentstone 7 shows a multiplicity of channels 44 for air passage running in an axial direction, while on the side opposite to the direction of the gas current A there protrudes small metallic points or edges 56. In this case, scentstone 7 is attached electrically to the negative pole of the high tension source at the side of the gas stream at 30. The additional e~ternal ionization 9 is placed between the scentstone 7 and the microporous filter medium 11; in this case it is a ring 60 isolated from housing 10 and equipped with a multiplicity of needle points 61 protruding into the stream. Equally effect~
ively one may use a sharp edge or jagged tooth formation , 30 of elements by which effective ionization of the gas in the path between scentstone 7 and microporous filter i I !
¦me~ium 11 is assured. The external ionization 9 is again con-nected to the negative pole of the high tension source by a rin~
60.
The fllter arrangement according to Fig. 7 is especially suitable for puriiication of kitchen exhaust gases because the air to be purified is exposed shortly a-Eter admission into en-trance openin~ 41 to very intensive contact with scentstone 7 whic has a negative high tension potential. Ventilator 12 again serves as a vacuum ventilator, equally well, one could use a pres~ure 10 Ifan on th~ side of the admission of the air.
In the case of the filter device according to the inven-tion as illustrated in Fig. 8, one uses as the exchangeable microporous filter medium 11 a cylinder of activated charcoal.
¦AS the filter housing 10 is in a cylindrical form but shows in ;
15 the area of microporous filter medium 11 a multiplicity of air openings 62 and can thus consist of a shaped materlal 64. For r protection against, for example, children reaching into the apparatus a grating may be provided as grate protec-tion 57, pro-vided at the side of the entrance of the air. As microporous 20 ~ilter medium 11 activated charcoal is used which is filled into the space between the two sheet metal cases 31 and 32 arranged coaxial towards one another. The fron-t end of the cylindrically formed microporous filter medium 11 is again covered with a gas impenetrable layer 6. On the area opposite to the gas current A
25 ¦ the cylindrically formed microporous filtcr medium 11 is closed llby lid 33.
¦ The air is sucked in the direction ~ by ventila-tor 1 ~land pressed in axial direction into internal space 7 of the cylindrically formed microporous filter medium 11; thus it passes ionization device 34, which is in the form oE a metallic wire round brush and is ionized at the numerous wire points stickin~ out in all radial directions. The round brush-type ionization device shows a length which, for example, corresponds to the axial length of the micro-porous filter medium 11 and is connected to the negative pole of a high tension source (not shown) which is main-tained isolated on the inside of the cylindrically formed microporous filter medium co-axially on this same axis.
By the change of direction in the inside of the cylindrically formed microporous filter medium 11 there results at the numerous points of the brush-like edges 34 a high degree of ionization. The air thus ionized enters through numerous openings into the inner cage of the filter and into charcoal and thus comes into intimate contact with the large surface of the counter pole of the activated charcoal. The positive potential charging the active charcoal derived from the high tension source is again applied immediately by way of an isolated lead 35 at 55 at a place away from the air current.
In order to be able to exchange the microporous filter medium 11 readily and to provide resistance against the high tension that serves within filter housing 10 a can-like cage 36 with numerous perforations made of a resinous material may be used which permits good gas passage in radial direction. It is important that the application of the positive potential to the microporous filter medium 11 does not occur through the outer perforated cage 32 but rather immediately to the activated charcoal material because otherwise the field linçs between the negatively - 22 ~
charged ionization device 34 and the positive counter pole do not end in the charcoal material but mainly in the metallic cage.
It will be understood that the above-described embodiment may also be combined with an odor neutralizing substance, preferably subjected to a negative potential in accordance with the manner previously discussed.
The capacity of the high tension source is suitably related to the capacity and the place of use of the filter. With smaller to medium size devices one uses direct high voltage of about 6 to about 20 kilovolts, prefer~bly up to 15 kiolvolts, with power of about 2 to about 50 watts preferably up to 30 watts. With high capacity devices such as for the exhaust of large com-mercial kitchens such as in restaurants, there may be suitable for filter media with large diameters potential differentia~ls of up to 30 kV with ionization power of up to several hundred watts.
The foregoing description serves to illustrate the invention, the metes and bounds of the invention being defined by the appended claims.
. .
SUMMARY OF THE INVENTION
The present invention relates to a method and apparatus for the purification of gases, finding particular applicability in the removal of smoke and kitchen odors in closed systems, such as restaurants, kitchens and the living areas o residences and offi~es.
As opposed to traditional electrostatic plate or grid filters requiring frequent exchange of filter media and problems in reducing odors particularly aEter prolonged use, the present invention provides an improved method and apparatus, as follows.
According to one aspect of the invention, there is provided an air purification filter comprising: a housing; an inlet in the housing for air to be purified a microporous filter medium in the housing so that the air to be purified passes therethrough; an outlet in the housing for the purified air; means for directly electrica~ly charging said microporous filter medium to one polarity; and means for electrically charging particles in the air to be purified to an opposite polar-ity upstream of th~e filter medium so that they carry that charge when entering the filter medium, whereby when said charged particles enter the filter medium they are attracted to the oppositely charged filter medium and held thereby and separated from the air.
According to another aspect of the invention there is provided a method of removing particulate matter from the air which comprises passing particulate-laden air charged to one polarity through a microporous filter medium which has been charged to the opposite polarity in a manner such that the charge is distributed throughout said microporous filter medium.
, ~,, 1 Thus when the charged particles enter the filter medium they are attracted to the oppositely charged filter medium and held thereby and separated from the air.
The microporous filter medium should have the ability to be charged, and in a preferred embodiment is activated charcoal. It will be appreciated that ceramic and plastic foam materials also have such attributes. ~or example, a metallized plastic foam may be used. The means for directly electrically charging the microporous filter medium provide an electric field in the microporous medium itself, with which to attract the oppositely charged particles. Thus, the microporous filter medium is an electrostatic filter. This is distinguished from the prior art downstream use of .
- la -::, ":
activated charcoal as a supplement to an electrostatic plate or grid filter, where the primary electrostatic filtering takes place through the electrostatic grid. Additionally, the charge is ~ placed directly on the microporous filter medium, as opposed to ¦ being transferred from the housing of the microporous filter med-ium. The charge is advantageously placed on the downstream side of the microporous filter medium, to provide -the optimal distribu-tion of the eharge throughout the microporous filter medium.
The means or electrically charging the particles pre-ferably is an electrode having sharp or pointed edges which facili-tates the ionlzation o~ the air. A piurality OL needles arranged in a plane perpendicular to the air flow is one embodiment of this invention. A wire may also be stretched in the direction of the air flow, or the edge of a blade may be used. In a further embodi-ment of the invention an odor neutralizing substance, which may be¦a scentstone ~Duflstein), a gel or a liquid, may be placed upstreaml from the microporous filter medium and carry the opposite charge of the microporous filter medium. Such odor neutralizing sub-stanee may be selec-ted dependent upon the type of air which is ~0 being purified. For example, where the air includes a particular noxious chemical substance which in the past has been known to be attracted to a particular type of odor neutralizing substance,such substanee may be incorporated as the odor neutralizing substance of this aspect of the invention. With the enhanced effect of the charged odor neutralizing substance, it will be seen that the in-~corporation of the odor neutralizing substance may be used to effectively combat particularly troublesome odors included in the air stream.
In a preferred form o~ the present invention, an independent electrostatic filter plate having a charge opposite to that of the microporous filter medium may be placed in the air stream. This also serves to facilitate ionization of the gas.
The amount of current which is used should be suffi-cient to provide adequate charging of the air and the filter medium to cause an attraction between the oppo-sitely charged particles and filter. A direct current of preferably from about 6 to about 15 kV and at least l watt, and preferably 2 to 50 watts, is used. The gas flow proceeds at a speed of from about 0.05 to about 0.5 meters per second, and preferably from about 0.1 to about 0.25 meters per second.
It will be appreciated that a fan included in the system to more rapidly force the air through the system may be of particular advantage.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated by the drawings wherein:
Fig. 1 illustrates an experimental model which has been used to test the efficiency of the system;
Fig. 2a shows an overall view of an air purification system;
~:.
: ' . . . .
F.ig. 2b is a cross-s~ction of Fig. 2a;
Fig. 3 shows an air filter including a low capacity heater which generates the air flow through the filter;
Fig. 4 illustrates a higher capacity air puri:Eication filter;
Fi~. 5 illustrates an air pu`rification filter utilizing a cylindrical microporous medium;
Fig. 6 illustrates a wall mounted air purification filter;
~'lg. / illustrates a kitcnen air purification filt~r;
Fig. 8 illustrates a cylindrical activated charcoal filter.
¦ DETAILED DESCRIPTION OF THE INVENTION
It will be appreciated that through the present inven-tion a relatively small filter system may be used which, due tothe incorporation of a microporous fil.ter medium such as activated charcoal, has a superior effect to filter systems having many times the volume of the filter of the present invention. Thus, by using activated charcoal as a material in place of a grid o-f metal plates, for example, it may be seen that with the vast sur-face area of a microporous filter medium, it is possible to ~ar more efficiently remove a high percenta~e of particles from an air stream than with the traditional electrostatic grid filter.
¦It is important for the efficient operation of the filter of the 25 1¦ present invention that the microporous filter material itsel~ be directly charged, as opposed to merely placing the microporous filter medium in-to a charged housing. The charge is pre~erahly ~placed on the microporous filter medium itsel~ on the downstream , ll ¦side of the microporous filter medium so that it is away from the ¦direction of the approaching gas current having the opposite ¦potential, thereby insuring that all internal surface areas of the activated charcoal participate as an elec-trostatic filter, as ¦ opposed to merely a mechanical filter.
The means for electrically charging the particles in the air to be purified in its generic aspect may include such conven-tional charging means as a wire. It has been discovered, however, l that it is preferable to have one or more sharp needl~s or a sharp¦
¦ cutting edge placed in the path of the gas stream. In tests with I
the air purification filter of the present invention it has been ! ;
found that the effectiveness of removing polluted gases such as room air having cigarette smoke is improved greatly through the `
¦use of the present invention as opposea to a conventional electro-Istatic filter having the traditional plates. This improvement results from the combination of the microporous filter medium with th~ extremely large surface area taken together with the electro-static filtering based upon what is traditionally a mechanical filter, i.e., the microporous filter medium of activated charcoal.
~0 One of the advantages of a microporous filter medium is that various types of microporous filter media have specific effects on specific types of gases. For example, ac-tivated char-coal absorbs carbon monoxide while having little eEfect on o-ther ¦toxic substances such as found in cigaret~e and tobacco smoke or food odors in restaurants. According to a preferred embodiment of the present invention, activated charcoal is used as the filter medium, together with an odor neutralizing substance placed up-_5_ 11/313~G8 ~¦stream of the activated charcoal which is selected based upon the¦¦type of impurity in the air which is better attaehed by such a ¦¦odor neutralizing substance as opposed to activated eharcoal.
For example, a scentstone (Dufts~ein) attrac-ts certain types of odors, such as etheric oils that may be found in kitehen odors.
The scentstone is placed upstream of the filter medium, but in the area where the air has been eharged to a potential opposite to that of the filter medium. The seentstone is advantageously ll~harc~d ~ h a like p~tèntial t~ that of the filter medium. Seent ¦!stones are in porous form and are obtainable as well as high density solids. The sentstone used in the invention is an anti-odorous substance known per se, and may be a combination consistinc lof an aromatic principle or fragrance or a composition made from ¦Isuch odoriferous substances and a carrier substance known per se, l~hich may be fugitive, such as a liquid, or solid hydrocarbon or ¦an a~ueous meaium thickened with an organic or inorganie thickener~
¦such as a colloidal carboxy vinyl polymer. Preferably the perEume composition provides a fresh smelling odor, such as o~ an apple, orange, lemon or rose. This gives the treated air a fresh odor ~0 IAnd binds and absorbs the bad smell of the air to be purified.
For several tes-ts, a scentstone was used according to the ¦apparatus of Fig. 6, the scentstone being of the type L.V. 2037 ¦¦"green apple" was used on a high capillary cellulose carrier ¦¦supplied by Globus Werke, Fritz Schulz, D-8858 Neuburg/Donau, ¦IGermany and having the dimensions 11 x 5.5 x 0.4 cm. A simllar ¦type of anti-odorous substance i~ offered by Waldwick Plastic, Ine. , 21-23 Industrial Park, Waldwick, New ~ersey 06701l U.S.A.
Experimental tests further showed in a restaurant ~ambiency that even with use of the scentstone for six weeks in an electrostatic field, no appreciable decrease of the odor-binding ability o~ the scentstone in combination with the filter was observed.
The external shape of a scenstone may be adapted to the dimensions of the filter in order to assure the optimum contact ~
of as many gas particles as possible with the scentstone. ~ .
porous scentstone may advantageously be used and adaptèd to the cross-sectional dimension of the gas path so that ~ery large in-ternal surface of the scentstone come into contact with the gas.
~The scentstone having the opposite potential to that of the filter `~-:
medium, it acts to ionize the yas passing through or along it.
¦The charge is advantageously applied to the odor neutralizing substance such as the scentstone downstream from the gas flow so that the scentstone acts as a pole with a relatively large surface.
It may also be advantageous to impale the scentstone : :
onto a thorn passing slightly through it, or a sharp edge which ~:
simultaneously serves to hold the scentstone. In this case 20 ionizati~ of the passing gas occur9 mainly at the protruding `
" . ...
19~ 68 edge or point; the scentstone is now only a secondary point of origin for the lines of the field and will be used xapidly which may be advantageous if continuous purification with strongly smelling etheric oils in the air is not a necessary or desirable feature.
The odor neutralizing substance may also be in a liquid or gel form. When in a liquid form, there is advantageously pro-vided a passage through which the gas mus-t pass through the liquid t and with the liquid being given a charge opposite to that of the 10 ¦filter meclium.
¦ Experiments with odor neutralizing substances in their ¦solid form have been conducted to test the purification of office ¦rooms that are filled with tobacco smoke. Using a scentstone, la ~ood iltration action has been observed after relatively long ¦use concerning numerous pollutants, although a relatively shorter duration is noted for kitchen exhaust systems for normal kitchen odors. Through the aspect of the invention providing both the use of a microporous filter andan odor neutralizing substance wi~h the opposite potential of the filter mediu~nexcellent re-sults have been obtained. It will be observed that a particularadvanta~e of the present invention is -that with the combination of the odor neutralizing substance and the microporous filter medium that after a considerably long period of opera-tion the system works well, as opposed to systems of the priGr art where relatively good results may be obtained initially but aftex con-tinued operatior1 o the system results fall off markedly 8'~
The degree of efficiency of the air purification filter of the invention may vary somewhat depending upon such factors as the cross-sectional area of the filter, the speed of -the gas current, the particle size of the impurities,,and their weight, and the composition of the microporous filter material. The degree o ionization of the gas prior to entry into the microporous fil-t~r medium is considered to be of major importance. Tests have shown that the distance between the electrodes, that is the dis-tance between the microporous filter medium and the means for electrlcally charging the ~articles in the air has only a rela-tively minor effect on the e-Eficiency of the filt~r. Rather, raising the applied tension to raise the degree of ionization leads to an improved effeciiveness of the filter. Improvement is also achieved when a plurality of poles are used as the means for : :
electrically charging particles. It is also important that the electrode which forms the means for electrically charging par-ticles has the highest possible ioniæation e:Efect which is achieved by field concentration, therefore concentration is given .
in the irst instance to razor blade-like cutting edge electrodes or needle or brush electrodesO
In some European countries it is believed that through ionization of the air (such as-the.liberation of positive ions from ¦television sets) that it may be beneficial to reduce such a posi-~tive ion concentration. It is also believed in some European Icountries that an excess of positive ions also may lead to an increase in dust development in the rooms. The air purification filter of the present invention may, therefore, be used to co~
Ij ~
incidentall~ counteract such a build-up of positive ions liberated ~rom television sets by attaching the ~ree sharp edge or pointed pole forming the means for electrically charging particles o~ the air purification filter to the negative clamp o-E the high tension generator while the positive terminal is connected -to the surface of the microporous filter medium. If the scentstone is usedl it should be connected on the side opposite to the direction of the gas current to the negative terminal oE the high tension genera-tor. If the scentstone, however, is equipped on one side with d nee~l~ sllape or sharp eciged I.letallic ~oIliza~o,l el~rn~r.~r it Inay be advantageous to attach the opposite pole to the scen-tstone on a side opposite to the microporous filter medium so that the ¦scentstone again can act as a large surface source pole. The air ¦purification filter of the present invention thereby has a ne~
¦effect of liberating negative ions. From the standpoint of re-¦moving particulate matter from the air, it is not critical ¦whether the microporous ~ilter medium is positive or negative ¦tprovided the particles are oppositely charged) r with the above ¦choice of polarities being given only Erom -the standpoint of the ~preE~rence noted in certain European countries for decreasiny -the number o~ positive ions in the air. Where this is not a fac-tor, it will be appreciated that either positive or negative polarity may be given to the microporous filter medium.
The theory of positive ions in the air is explained in ¦ German Patent 1,261~295 at page 22. In addition, to demonstrate the lack of criticality in the polarity of -the microporous Eilter ¦medium charge and also to make it possible to adjust the deyree ..
- ~.0-~ f~6 of ionization of the room air, the air purification filter may be provided witn means to make it possible to switch the polarity~
ThUS, a reVersing switch may be provided which can be equipped with a time device so that the fiela may be reversed from time to time. If it is desired to minimize ionization of the air from the air purification :Eilter, it is possible to insert an ion absorber, such as a metal grid, into the housing downstream oE the microporous filter medium. Although activated charcoal is pre-dominately mentioned as an example of the microporous filter med-1~ ium, i_ shoul~ ~e reco~nized that o~her mi~_o~orou~ ~;;ter m~diamay also be used. Such other microporous filter media may be used provided that they contain a layer on the microporous interna surface which is at least electrically semi-conductive so that the electrostatic field is fully effective. Ceramic filters, microporous resin filters, silica gels, and other materials which have been made conductive to at least a certain extent may be used in place of the activated charcoal. It will also be appreciated that the air purification filter may be used in conj~mction with other devices, such as the inclusion of an ultraviolet radiation ~0 device to help kill germs in the air. It should also be recognize~
that while primary emphasis has been given in this specification to the cleaning o~ room air with smoking odors or kitchen odors, ~he type of air which may be purified is not so limited.
The air purification of the present invention may be used in of-~5 fices, residences, laboratories, conference rooms and also inhospitals. For example, in hospitalsr the ac-tivated charcoal fil-~ter medium may be used eithex alone as a part of the presen-t air purification filter, or together with the treatmen-t of the same 8'~iB
air with ultraviolet light to aid in the killing of germs. In restaurants and homes it is important to purify kitchen exhaust vapors, with it having been found that an odor neutralizing sub-stance may advantageously be used as a part of -the air purifica-tion filter. Automotive systems also may be considered, both interms of purification oE the air in the interior of the car Which is recirculated, and also in areas of heavy city traf~ic where it may be desirable to purify the "fresh" air which includes the city odors -- smoke stacks, exhausts from other automobiles, etc. Larger units may be used for air purification in traffic intensive areas where there is limited air circulation, particu-larly crowded intersections in downtown centers and tunnels.
Factory workshops are another area where the air purification fil-ter of the present invention may be used, such as electric welding areas. The efficacy of the air purification filter is demonstratec using thQ experimental arrangement of F-g. 1. Into a plastic tube 1 with an internal diameter of about 10 cm there was introduced an activated charcoal filter 2 to block the current of gas which flowc upward in the tube 1. Filter 2 was attached to the posi-tive pole 20 o~ a high tension generator 3 which has a power of less than 10 watts and yields a direct current tension of 5-15 kV. In prin-cipal, any method could be used which is suitable for the genera-tion of high tension direct current of a relatively low power swch ~as a high tension transformer of line voltage with subsequent ¦¦ratification, voltage double cascade switching wi-.h diode ¦elements and intermediate storage and condensers. The negative ¦~pole of the high tension current and generator 3 ¦~was attached ~y way of conduit 4 in cylinder 1 to needle electrode -ll .
~ 1~8q~'6~3 '~5 and the point oE which is placed about into the middle of the ¦lac~ivated charcoal tablet which is used as the filter medium 2 ¦¦The position of the point relative to the cross-section of the ~ filter is of relatively minor importance, it being more important that the charge is placed on the downstream side of the filter medium 2. The axial distance between the filter 2 and the elec-trode S is also of relatively minor importance~ It is, rather, important that the point of the electrode 5 is the point closest t~ t~e filt~x medil~ 2 for t~e electrostatic field developed be-tween electrode 5 and filter 2.
The purification effect r~as de-termined primarily by use of air strongly laden with cigarette tobacco smoke. In an em-bodiment not shown in Fig. 1, a second activated charcoal filter tablet was placed in the cylinder 1, while maintaining constant voltageand the number of electrodes 5. However, the utilization f the current caused by ionization yielded a filter efiect with a single charcoal table that was effective in removing over 90%
of the particles, so that it was found unnecessary as a practical ~atter to have more than the one activated charcoal tablet.
~0 An improvement of the filter effect was achieved by ubstituting for the needle electrode 5 a sharp edged blade, in the test a razor blade being used as the sharp edged hlade. As in the case of a needle electrode, the results with-a blade electrode ¦provide a high concentration of the electric field at the poin-t or ¦Ithe edge with a strong ionization effect. A further improvement i achieved by raising the degree of ionization through raising the field intensity of the electrostatic field by raising the potential different between the electrode 5 and the filter 2. This also .~. . . .
,: , .
1 ~L'1;1~1~6~3 applies with raising the number of electrodes 5 with constant voltage.
Changing the polarization at the high tension gene~a-l tors so that electrode 5 is positive and filter medium 2 is nega-¦ tive yielded no noticeable change in results, demonstrating thatthe selection of polarity is unimportant, provided that the filter medium 2 and the electrode 5 are oppositely charged.
Fig.2a shows an air purification filter for room air l purification. A housing lO having a closed backside contains an ¦ exchangeable microporous filter medium ll, which prefera~ly is activated charcoal in the form of a cylinder which is charged with la positive or negative potential using a high tension generator ¦which is contained in the device. In the front of the housing lO
la fan 12 is arranged which, where needed, forces air through the l~ ¦filter housing. Between the fan l~ and the microporous filter ¦medium ll there is found a structure 13 which ionizes the gas ¦passing through the housing. This construction is shown in more ¦detail in Fig. 2b which shows an isolated ring 14 to which there ¦iS attached a multiplicity of needle electrodes pointing inwardly ¦and Which may suitably be bent in the direction of the current.
¦These electrodes are connected to the alternate pole of the high ¦tension generator. As the gas moved by fan 12 ~lows along the ¦electrode 15 the gas is ionized and then passes into -the electro-¦statically active microporous filter medium, here made of ac-tivate ¦charcoal, ll. Tne arrangement of the ionization electrode 15 can, of course, be structurally different. Thus, al-though a ring with needle-like projections is illustrated, one may provide a star-shaped arrangement of blades which are attached to a coarial cente~
' li .
. ", . - .
ù6B
instead of the internal chamber of the filter cylinder in which arrangement an equal dlstance to the internal surfa~e of the filte~
is pre~erably maintained on all sides. It is also possible to use l wires although the ionization effect of wires is not as good as that achieved with sharped edged blades or needle electrodes, The device according to Fig . 3 corresponds to the struc-ture of Fig. 2a with the distinction that the fan 12 is exchanged for a heating device 16. The heat drives the air upwardly through the housing 10, the thus heated air being passed through the electrode3 15 and ~hus belng lonized. '~he air :LS drawn into the system through the air admission slits 17, and after having been heated by the heating device 16 and ionized by the electrodes 15 it then passes through the filter medium 11 housed in the upper part of the housing lQ.
15Fig. 4 is a higher capacity device in which polluted ¦air is sucked into housing 10 by use of blowers 12/1 and 12/2 ar-ranged at opposite sidewalls of the housing. The air then flows along an arrangement of ionization electrodes 15/1, 15/2, and the thus ionized particles then pass through the microporous filter ~0 medium 11, preferably of activated charcoal. It is recognized that there may be situations where air is particularly dirty and many of the particles would be screened through more traditional air filtration systems. For exa~ple, many of the particles in ~.^
particularly dirty air could be pre-screened through a mechanical filter 17 and/or an ultraviolet light :~ilter 18 may be placed up-stream of the air particularly for killing germs. It will be appreciated that the filter of Fig. 4 may be used without the \ mechanice pre-filter 17 or the U7 li~ht filter 18, or togetber 8~6~
with either one or both of these. The combination of these addi-tional elements may be particularly use~ul in industrial air cleaning and in laboratories. In the case of the arrangement of Fig. 4 for industrial scale operations, an- even higher degree of purification is achieved if the needle ring electrodes are re-placed by ~lade or comb electrodes arranged in star form inside cylindrical filter element 11. Optimal air passage and current value of about 0.25 meters per second with profusion from all sides may be used for hospital operating rooms. This also may lC be used '~r residentia a~eas, such a, livin~ ~coms. Tlle ~e ired air passage and current value of 0.25 meters per second may be achieved through exit of the purified air over a large area ~rom microporoous filter medium 11 as illustrated in Figs. 2-4.
In Fig. 5 an air purification filter in accordance with the present invention is shown with a hollow cylinder of activated charcoal used as the filter medium 11 and equipped with electrode 20 ~hich is formed on the inside as a cutting blade elec-trode running in axial direction with four blades 21 arranged in star-shape. The sharp free edges of blade 21 all have the same radial distance from the internal surface of microporous filter medium 11 along the axial length of the ~ilter. The gas supply, for ex-ample, results by means of a fan (not shown) and runs in the direc tion of the arrows shown in Fig. 5. Along the sharp edges of blades 21 the gas is ionized and then runs through filter medium 11 which has a high counter potential to the potential of elec-itrode 20.
It will be recognized that if a higher ca~city is de-¦sired the activated air purification filter may comprise a '6 8 plu~ality of microporous filter elements 11, such as the utili~a-tion of two or more activated charcoal cylindxical filters.
Ionization can also be improved by increasing the number of blades from four to eight to the star-shaped electrodes 21. Instead Of blades 21 there may also be used comb-like elements. Microporous filter medium 11 is preferably closed at the end by a lid (not shown) in order to cause optimal radial distribution of the gas ~in a low e~it rate from the filter With a high gas through-put~
~ Fi~. 6 is a schematic diagram for an air purification lG device whic~l nas been ~es~ed -or office rocms aIld restdurants~ It contains essentially a rectangular or oval filter housing 10 with an opening for admission of air 41 and an exit 42 which are equipped with protective gratings 57 and 58, respectively.
Ventilator 12 is driven by an electric motor which pulls the air in direction A over the entrance opening 41 and causes the puri-fied air which is passed through microporous filter medium 11 through the exit 42 in direction B. The path of the current oE
air in housing 10 is directed by walls 22, 23 as well as conduct-ing sheet 8, the function of which is described in more detail ~0 hereinafter. In the path oE the stream through the filter housing .
the air to ~e purified first meets scentstone 7 ~hich is affixed to plate 24, which plate is isolated ~rom housing 10 and equipped with a central thorn 54. Thorn 54 can s-tick out to a minor ex-tent above the scentstone into the surface of the passing air. On the side 26 opposite the plane along which the air passes, the isolated plate 24 can show a break 59 at which scentstone 7 has immediate electric contact at 25 and is connected with a negative pole (not shown) high tension direct current source in the above mentioned manner which may for example be housed in filter housing 10. ~he scentstone 7 suitably in conjunction with a thorn 54 and beyond it, acts as a source pole of an electrostatic field the counter pole o~ which ends in microporous filter medium 11 in a manner described in more detail below. At passing air along scentstone 7 the latter is partially ionized already, and the results are an enhanced elimination of polluted air particles by means of the scentstone.
In the further path of the stream the air then meets at first the so-called external ionization 9 which consists of one or more wires or of a brush form metal electrode or, for example, a sharp edged metal piece in the form of a star. Important for the external ionization 9 are sharp or pointed edges at which there occurs high field concentration and corresondingly there results a good ionization of the gas stream thereby. Of course, it ~ .
i~ to be recognized that the external ionization suggested in outline form in Fig. 10 is maintained isolated in filter housing 10 and also connected with a negative pole of the high tension source in the equipment.
Further downstream the air meets conducting plate 8, which can, for example r be glued to an isolated base 53 in housing 10. The conducting plate 8 is also connected with a negative pole of the high tension source; on one hand it serves for uniform distribution oE the gas stream over the area of microporous filter medium 11 and on the other hand it acts as an additional ionization and also furnishes additional ionization of the gas stream.
Filter medium 11 which can be exGhanged through an opening (not shown) in the housing between conducking , - 18 ~
separating walls 22 and 23 is in the example here illu5-trated made of activated charcoal. ~ circumferential ]ayer 6 is provided which iS impenetrable for gas and which also serves to insulate the filter from the ilousing lO. The active charcoal tablet forming the microporous filter medium ll is connected at least at point 55 directly with positive pole (+) with the high tension source (not illustrated) at the side turned away from conducting sheet 8 in the direction of the path of the gas.
The high tension source furnishes a potential of, for example, lO kV with a power of about 5 to about lO wat~s by attachinq the high tension potential to the downstream surface of the microporous filter medium which achieves the result that essentially the entire large inner surface of the activated charcoal tablet acts as a positive pole of the electrostatic field.
The entire apparatus can be constructed on a relatively small scale. In order to obtain a sufficient separation of the air coming in an unpurified form in the direction A
from the purified air flowing away in the direction B one can place a separating sheet approximately in the middle of the housing. It is also possible to turn the air admission opening 4~1 by about 90 aqainst the exit opening 42, thus, for example placing it into the side surface of housing lO. Microporous filter medium ll can be easily exchanqed as can the scentstone 7. However, even with continuous use, as for example in the case of a restaurant, this exchange does not need to occur for some time, several months at least being possible for operation of the system without the necessity of changing either the filter medium ll or the scentstone.
-- 19 ~
?.
B
In accordance with Fig . 7, ~he filter housing 10 has the shape of a cylinder and at 27 shows a sub-division so that the microporous filter medium 11 is readily exchan~ed.
~ere, the microporous filter medium 11 is an activated charcoal tablet. The positive flow o~ the high tension source (not shown) is again attached at 55 to the micro-porous filter medium at the gas exist face opposite the plane of the gaseous stream. The external border 6 of the microporous filter medium 11 again prevents an exit of the gas in the original direction and serves simultaneously for high tension insulation of the microporous filter medium 11 against housing 10 as well as against ring 28 by which microporous filter medium 11 is secured in housing 10 against axial displacement.
In the course of the gas stream from A to B prior to passage through the microporous filter medium 11 the gas passes scentstone 7 which is mounted e~changeably in mount 29, This scentstone 7 shows a multiplicity of channels 44 for air passage running in an axial direction, while on the side opposite to the direction of the gas current A there protrudes small metallic points or edges 56. In this case, scentstone 7 is attached electrically to the negative pole of the high tension source at the side of the gas stream at 30. The additional e~ternal ionization 9 is placed between the scentstone 7 and the microporous filter medium 11; in this case it is a ring 60 isolated from housing 10 and equipped with a multiplicity of needle points 61 protruding into the stream. Equally effect~
ively one may use a sharp edge or jagged tooth formation , 30 of elements by which effective ionization of the gas in the path between scentstone 7 and microporous filter i I !
¦me~ium 11 is assured. The external ionization 9 is again con-nected to the negative pole of the high tension source by a rin~
60.
The fllter arrangement according to Fig. 7 is especially suitable for puriiication of kitchen exhaust gases because the air to be purified is exposed shortly a-Eter admission into en-trance openin~ 41 to very intensive contact with scentstone 7 whic has a negative high tension potential. Ventilator 12 again serves as a vacuum ventilator, equally well, one could use a pres~ure 10 Ifan on th~ side of the admission of the air.
In the case of the filter device according to the inven-tion as illustrated in Fig. 8, one uses as the exchangeable microporous filter medium 11 a cylinder of activated charcoal.
¦AS the filter housing 10 is in a cylindrical form but shows in ;
15 the area of microporous filter medium 11 a multiplicity of air openings 62 and can thus consist of a shaped materlal 64. For r protection against, for example, children reaching into the apparatus a grating may be provided as grate protec-tion 57, pro-vided at the side of the entrance of the air. As microporous 20 ~ilter medium 11 activated charcoal is used which is filled into the space between the two sheet metal cases 31 and 32 arranged coaxial towards one another. The fron-t end of the cylindrically formed microporous filter medium 11 is again covered with a gas impenetrable layer 6. On the area opposite to the gas current A
25 ¦ the cylindrically formed microporous filtcr medium 11 is closed llby lid 33.
¦ The air is sucked in the direction ~ by ventila-tor 1 ~land pressed in axial direction into internal space 7 of the cylindrically formed microporous filter medium 11; thus it passes ionization device 34, which is in the form oE a metallic wire round brush and is ionized at the numerous wire points stickin~ out in all radial directions. The round brush-type ionization device shows a length which, for example, corresponds to the axial length of the micro-porous filter medium 11 and is connected to the negative pole of a high tension source (not shown) which is main-tained isolated on the inside of the cylindrically formed microporous filter medium co-axially on this same axis.
By the change of direction in the inside of the cylindrically formed microporous filter medium 11 there results at the numerous points of the brush-like edges 34 a high degree of ionization. The air thus ionized enters through numerous openings into the inner cage of the filter and into charcoal and thus comes into intimate contact with the large surface of the counter pole of the activated charcoal. The positive potential charging the active charcoal derived from the high tension source is again applied immediately by way of an isolated lead 35 at 55 at a place away from the air current.
In order to be able to exchange the microporous filter medium 11 readily and to provide resistance against the high tension that serves within filter housing 10 a can-like cage 36 with numerous perforations made of a resinous material may be used which permits good gas passage in radial direction. It is important that the application of the positive potential to the microporous filter medium 11 does not occur through the outer perforated cage 32 but rather immediately to the activated charcoal material because otherwise the field linçs between the negatively - 22 ~
charged ionization device 34 and the positive counter pole do not end in the charcoal material but mainly in the metallic cage.
It will be understood that the above-described embodiment may also be combined with an odor neutralizing substance, preferably subjected to a negative potential in accordance with the manner previously discussed.
The capacity of the high tension source is suitably related to the capacity and the place of use of the filter. With smaller to medium size devices one uses direct high voltage of about 6 to about 20 kilovolts, prefer~bly up to 15 kiolvolts, with power of about 2 to about 50 watts preferably up to 30 watts. With high capacity devices such as for the exhaust of large com-mercial kitchens such as in restaurants, there may be suitable for filter media with large diameters potential differentia~ls of up to 30 kV with ionization power of up to several hundred watts.
The foregoing description serves to illustrate the invention, the metes and bounds of the invention being defined by the appended claims.
. .
Claims (33)
1. An air purification filter comprising:
a housing;
an inlet in the housing for air to be purified;
a microporous filter medium in the housing so that the air to be purified passes therethrough;
an outlet in the housing for the purified air;
means for directly electrically charging said microporous filter medium to one polarity; and means for electrically charging particles in the air to be purified to an opposite polarity upstream of the filter medium so that they carry that charge when entering the filter medium, whereby when said charged particles enter the filter medium they are attracted to the oppositely charged filter medium and held thereby and separated from the air.
a housing;
an inlet in the housing for air to be purified;
a microporous filter medium in the housing so that the air to be purified passes therethrough;
an outlet in the housing for the purified air;
means for directly electrically charging said microporous filter medium to one polarity; and means for electrically charging particles in the air to be purified to an opposite polarity upstream of the filter medium so that they carry that charge when entering the filter medium, whereby when said charged particles enter the filter medium they are attracted to the oppositely charged filter medium and held thereby and separated from the air.
2. An air purification filter of claim 1, wherein said microporous filter medium is at least semi-conductive, whereby essentially all of said filter medium is charged.
3. An air purification filter of claim 2, wherein said means for directly electrically charging said microporous filter medium includes an electrode which is adjacent to a surface of said filter medium located on the downstream extremity thereof.
4. An air purification filter of claim 1, wherein said means for electrically charging particles has a sharp or pointed edge to facilitate optimum charging of said particles.
5. An air purification filter of claim 4, wherein said sharp or pointed edge is shaped as a needle.
6. An air purification filter of claim 4 comprising a plurality of needles arranged in a plane perpendicular to the air flow, said needles being approximately equi-distant from each other to optimize the charging of all particles in the air flow.
7. An air purification filter of claim 4, wherein said means for electrically charging particles includes at least one wire stretched in the direction of the air flow.
8. An air purification filter of claim 4, wherein said sharp or pointed edge is the edge of a blade.
9. An air purification filter comprising:
a housing;
an inlet in the housing for air to be purified;
an activated charcoal filter medium in the housing so that the air to be purified passes therethrough;
an outlet in the housing for the purified air;
means for directly electrically charging said activated charcoal filter medium to one polarity; and means for electrically charging particles in the air to be purified to an opposite polarity upstream of the filter medium so that they carry that charge when entering the filter medium, whereby when said charged particles enter the filter medium they are attracted to the oppositely charged filter medium and held thereby and separated from the air.
a housing;
an inlet in the housing for air to be purified;
an activated charcoal filter medium in the housing so that the air to be purified passes therethrough;
an outlet in the housing for the purified air;
means for directly electrically charging said activated charcoal filter medium to one polarity; and means for electrically charging particles in the air to be purified to an opposite polarity upstream of the filter medium so that they carry that charge when entering the filter medium, whereby when said charged particles enter the filter medium they are attracted to the oppositely charged filter medium and held thereby and separated from the air.
10. An air purification filter of claim 9, wherein said means for directly electrically charging said micro-porous filter medium includes an electrode which is adjacent to a surface of said filter medium located on the downstream extremity thereof.
11. An air purification filter of claim 9, wherein said means for electrically charging particles has a sharp or pointed edge to facilitate optimum charging of said particles.
12. An air purification filter of claim 11, wherein said sharp or pointed edge is shaped as a needle.
13. An air purification filter of claim 11, comprising a plurality of needles arranged in a plane perpendicular to the air flow, said needles being approximately equi-distant from each other to optimize the charging of all particles in the air flow.
14. An air purification filter of claim 11, wherein said means for electrically charging particles includes at least one wire stretched in the direction of the air flow.
15. An air purification filter of claim 11, wherein said sharp or pointed edge is the edge of a blade.
16. An air purification filter of claim 2, wherein said microporous filter medium is a ceramic or plastic foam material.
17. An air purification filter comprising:
a housing;
an inlet in the housing for air to be purified;
an odor neutralizing substance in the housing;
a microporous filter medium through which the air to be purified passes which is downstream from said odor neutralizing substance;
an outlet in the housing for the thus purified air;
means for directly electrically charging said microporous filter medium;
means for electrically charging said odor neutrali-zing substance to the opposite polarity; and means for electrically charging particles in the air to be purified to said opposite polarity up-stream of said microporous filter medium so that they carry that charge when passing and entering the filter medium, whereby odor-raising particles are attracted to said odor nertralizing substance and when said charged particles enter the filter medium they are attracted to the oppositely charged filter medium and held thereby and separated from the air.
a housing;
an inlet in the housing for air to be purified;
an odor neutralizing substance in the housing;
a microporous filter medium through which the air to be purified passes which is downstream from said odor neutralizing substance;
an outlet in the housing for the thus purified air;
means for directly electrically charging said microporous filter medium;
means for electrically charging said odor neutrali-zing substance to the opposite polarity; and means for electrically charging particles in the air to be purified to said opposite polarity up-stream of said microporous filter medium so that they carry that charge when passing and entering the filter medium, whereby odor-raising particles are attracted to said odor nertralizing substance and when said charged particles enter the filter medium they are attracted to the oppositely charged filter medium and held thereby and separated from the air.
18. An air purification filter of claim 17, wherein said odor neutralizing substance is a gel.
19. An air purification filter of claim 17, wherein said odor neutralizing substance is a liquid.
20. An air purification filter of claim 17, wherein said odor neutralizing substance is a scentstone.
21. An air purification filter of claim 20, wherein said scentstone contains a plurality of perforations through which said air may flow.
22. An air purification filter of claim 17 including upstream of said odor neutralizing substance an electro-static filter plate having said opposite polarity.
23. An air purification filter of claim 4, wherein said microporous filter medium is a cylinder and said means for electrically charging particles is within said cylinder.
24. An air purification filter of claim 1, wherein a fan is included in said housing so that the air is forced through said filter medium at an increased rate.
25. A method of removing particulate matter from the air which comprises passing particulate-laden air charged to one polarity through a microporous filter medium which has been charged to the opposite polarity in a manner such that the charge is distributed throughout said microporous filter medium.
26. A method of claim 25, wherein said microporous filter medium is activated charcoal.
27. A method of claim 26, wherein the differences of polarity are produced by an electrostatic field having at least one watt power.
28. A method of claim 27, wherein an electrostatic field having a direct current of 6 to 15 kV and 2 to 50 watt is used.
29. A method of claim 25, wherein the velocity of the gas flow is from about 0.05 to 0.5 meter per second.
30. A method of claim 29, wherein said velocity is from 28.
0,1 to 0.25 meter per second.
0,1 to 0.25 meter per second.
31. A method of claim 25, wherein an odor neutralizing substance is placed in the path of the air to be purified upstream of said microporous filter medium, said odor neutralizing substance carrying a like charge as said particulate-laden air.
32. A method of claim 31, wherein said odor neutralizing substance is a scentstone.
33. A method of claim 25, wherein said odor neutralizing substance is a gel or liquid.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2721528.7 | 1977-05-12 | ||
| DE19772721528 DE2721528C2 (en) | 1977-05-12 | 1977-05-12 | Electrostatic filter device for cleaning gases |
| DEP2802965.4 | 1978-01-24 | ||
| DE19782802965 DE2802965C2 (en) | 1978-01-24 | 1978-01-24 | Filter device for cleaning gases |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1108068A true CA1108068A (en) | 1981-09-01 |
Family
ID=25772019
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA302,962A Expired CA1108068A (en) | 1977-05-12 | 1978-05-09 | Air purification filter and method |
Country Status (14)
| Country | Link |
|---|---|
| US (1) | US4244710A (en) |
| JP (1) | JPS549069A (en) |
| AT (1) | AT372300B (en) |
| CA (1) | CA1108068A (en) |
| CH (1) | CH629684A5 (en) |
| DK (1) | DK157736B (en) |
| FI (1) | FI68367C (en) |
| FR (1) | FR2390209A1 (en) |
| GB (1) | GB1604670A (en) |
| IE (1) | IE46781B1 (en) |
| IT (1) | IT1094668B (en) |
| LU (1) | LU79573A1 (en) |
| NL (1) | NL7805070A (en) |
| SE (1) | SE444892B (en) |
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| US636304A (en) * | 1898-03-30 | 1899-11-07 | Alexander Vosmaer | Apparatus for effecting silent electrical discharges. |
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| FR1029116A (en) * | 1950-12-05 | 1953-05-29 | Electrostatic filter | |
| US2974747A (en) * | 1956-03-20 | 1961-03-14 | Borg Warner | Electric precipitators |
| DE2000768A1 (en) * | 1970-01-09 | 1971-07-22 | Simon Fa Karl | Method and device for separating kitchen fumes from air |
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-
1978
- 1978-04-17 CH CH408478A patent/CH629684A5/en not_active IP Right Cessation
- 1978-04-24 FI FI781268A patent/FI68367C/en not_active IP Right Cessation
- 1978-05-02 LU LU79573A patent/LU79573A1/en unknown
- 1978-05-09 CA CA302,962A patent/CA1108068A/en not_active Expired
- 1978-05-09 IE IE945/78A patent/IE46781B1/en not_active IP Right Cessation
- 1978-05-09 US US05/904,305 patent/US4244710A/en not_active Expired - Lifetime
- 1978-05-10 DK DK204678A patent/DK157736B/en not_active Application Discontinuation
- 1978-05-10 FR FR7813820A patent/FR2390209A1/en active Granted
- 1978-05-10 GB GB18670/78A patent/GB1604670A/en not_active Expired
- 1978-05-10 AT AT0339378A patent/AT372300B/en not_active IP Right Cessation
- 1978-05-10 SE SE7805356A patent/SE444892B/en not_active IP Right Cessation
- 1978-05-11 NL NL7805070A patent/NL7805070A/en active Search and Examination
- 1978-05-11 JP JP5644178A patent/JPS549069A/en active Pending
- 1978-05-12 IT IT23345/78A patent/IT1094668B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| IE780945L (en) | 1978-11-12 |
| IE46781B1 (en) | 1983-09-21 |
| NL7805070A (en) | 1978-11-14 |
| SE7805356L (en) | 1978-11-13 |
| FR2390209A1 (en) | 1978-12-08 |
| DK157736B (en) | 1990-02-12 |
| CH629684A5 (en) | 1982-05-14 |
| LU79573A1 (en) | 1978-11-03 |
| AT372300B (en) | 1983-09-26 |
| JPS549069A (en) | 1979-01-23 |
| IT7823345A0 (en) | 1978-05-12 |
| ATA339378A (en) | 1983-02-15 |
| FI68367B (en) | 1985-05-31 |
| FI781268A (en) | 1978-11-13 |
| GB1604670A (en) | 1981-12-16 |
| US4244710A (en) | 1981-01-13 |
| FR2390209B1 (en) | 1985-03-22 |
| IT1094668B (en) | 1985-08-02 |
| FI68367C (en) | 1985-09-10 |
| SE444892B (en) | 1986-05-20 |
| DK204678A (en) | 1978-11-13 |
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