US2650672A - Electrostatic precipitator - Google Patents

Description

ELECTROSTATIC PRECIPITATOR Filed April 6, 1948 4 Sheets-Sheet 1 FIG.

INVENTORSl l Rober'f L. Buff BY Elmer G. HHs

Sept. 1, 1953 R. L. BARR ET AL ELECTROSTATIC PRECIPITATOR 4 Sheets-Sheet 2 Filed April 6, 1948 301g 29% f2s FIG. 3

FIG. 4

JNVENTORS 'Rober' L. Burr BY Elmer G. Hills ma?? www AtivA Sept. l, 1953 R. L. BARR ETAL 2,550,672

ELECTROSTAT IC PREC IP ITATR Filed April 6, 1948 4 Sheets-Sheet .'5

INVENTORS Robert L. Burr 45W Eimer G. Hills Sept l, 1953 R. L.. BARR ETAL 2,650,672

ELECTROSTATIC PRECIPITATOR Filed April 6, 1948 4 Sheets-Sheet 4 INVENTORS Rober 1 Burr By E\mer G. Hills AH v.

Sept. 1, 1953 ELECTROSTATIC PRECIPITATOR Robert L. Barn Glenview, and Elmer G. Hills, Chicago, Ill., assignors, by mesne assignments, to `Vl7est,ingl1ouse Electric "Corporation," East Pittsburgh, Pa., a corporation of Pennsylvania Application April 6, 1948, Serial No. 19,377

(Cl. 18S- 7) 5 Claims.

This invention relates to apparatus for removing particles of foreign matter from gases by means of electrostatic precipitation and more particularly to an improved vprecipitator `unit which is suitable for use in homes, oiiices and the like for cleaning the air that is to be breathed.

It has been found `that the operation of `such precpitator units has .been improved by the use of high frequency .energy for ionization. However, a precipitator utilizing a high frequency power supply presents problems `in interconnecting the various units because .of power loss in corona on interconnecting cables and the detuning effect of lead capacities on the high frequency generator. The high voltages .required in precipitator units are a further hazard to persons who may come in contact with the precipitator lunit as contact with any portion of the high voltage power supply might result in 'shock or serious personal injury. The fan for causing circulation of air throughthe precipitator is another source of danger as accidental contact therewith, especially by children, might cause serious injury. The positioning of the fan in the unit can be arranged to eliminate such danger, but the positioning must be such thata smooth .now of the yair to be cleaned over the ionizer and dust collector is providedin order that highly effective precipitation is obtained.

In present precipitator structures, the ionizer and dust collectorare relatively complicated with the result that precipitators have been yrelatively expensive. Such collectors used at present are very difficult to clean, which cleaning is necessary at frequent intervals to provide satisfactory installations, hot Water pipes are permanently connected to the precipitator and an arrangement is provided whereby the collector may be hushed with hot water when `the precipitator is dirty. This results in anexpensive and compli- .cated installation, and has not been entirely satis- 35 operation of the precipitator unit. In some home A further object of this invention is to pro- 2 provide an improved `ionizing structure which is of simple construction.

A feature of this invention is the provision of an electrostatic precipitator in which the high voltage power supply, the ionizer structure and the collector plates are so positioned that connecting leads are short and a relatively few insulators for the high voltage leads are required.

A further fea-ture of this invention is the provision of a precipitator structure in which the components are so arranged that air may be circulated therethrough in a smooth even flow.

A still further feature of this invention is the provision of a collector Astructure which may be made of cardboard or similar inexpensive nsulation material with conducting areas thereon.

Fur-therobjectseatures and advantages of the invention will be `apparent from a consideration of the following description taken in connection with the accompanying drawings in which:

Fig. 1 is a perspective view of a precipitator unit in accordance with the invention with parts brokenaway to show the construction;

Fig. 2 is a perspective vieW of the ionizer structure of Fig. l;

Fig. 3 illustrates a modied ionizer structure;

Fig. 4 is `a cross-sectional view of one of the insulating rods of the Aionizing structure of Fig. 2 showing the clip for supporting the ionizing conductor; d

Fig. 5 is a perspective view of the collector structure of Fig. v1

Figa-6 and? illustrate another embodiment of the collector structure;

Figs. 8 to 11, inclusive, show details of the structure of Figs. 6 and 7 Fig. 12 illustrates anarrangement for supporting the collector structure of Figs. 6 to ll in a preciptator unit;

Fig. 13 is aperspective v'iewof still another embodiment of the collectorstructure.; and

Fig. 14 is a diagramma-tic view showing the electrical .circuits of the cleaner of Fig. l.

In practicing the A*invention there is provided an electrostatic `precipitator .unit including a cabinet which is intheiform of `an end table or the like. The cabinet in'cludesan ionizing stru"- ture, collector structure, a power supply for the ionizer and collector, and a fan for circulating air to be cleaned through the precipitator unit. The power supply. is positioned above and adjaent -to the ionizer and collector so that short leads can be .providedsimplifying the insulation of the leads and .preventing vobjectionable capac- 3 ity loads on the power supply circuit. The position of the ionizing structure and the collector structure in the cabinet is such that a steady flow of air can be provided thereto and also so that the collector structure can be easily reinoved without moving other components of the precipitator unit." 'I'he collector structure may be made of cardboard so constructed that the structure can be folded and shipped or stored in a very small space. Certain portions of the cardboard structure are renderedA conducting so that the collector can be energized as will be described hereinafter.

In the drawings, in Fig. 1 there is illustrated the cabinet or case I in which the components of the electrostatic precipitator or gas cleaner are housed. The fan I4 draws air successively through the intake openings I5 in the sides and bottom of the cabinet, the ionizing structure l2, and the collector structure and then forces the cleaned air out through exhaust opening i6. The power supply 22 furnishes high voltage unidirectional current for exciting the collector structure and high frequency high voltage superimposed upon the direct current voltage existing across the electrodes of collector Il for exciting the electrodes of the ionizer structure I2. Baiile prevents the ow of air above the ionizer structure so that lall air being drawn through the apparatus must pass through the ionizing structure where it is ionized thus causing any particles of dust, pollen or other foreign matter to become electrically charged. Collector fits tightly against ionizer I2 such that all the air being drawn into the ionizer must go through the collector where any charged foreign particles are caused to move perpendicularly to the iiow of air under the forces of the electrostatic iields existing in the collector until said particles strike and adhere to the plates of the collector. The cabinet |0 is provided with a removable end wall 23 which allows the collector I I to be removed for cleaning or replacement by being drawn under fan |4 through the end of the case.

For making electrical contact to the collector and permitting easy removal thereof, spring conducting means I9 is provided which presses against the top of collector forming an electrical contact to said top, which is one of the terminals of the collector. A second spring conducting means |8 presses against collector terminal 24 in the same manner as the contact I9 so that contact is broken and made successively as the collector is removed from and replaced in the case. The fan I4 is mounted directly in front of exhaust opening I6 where it effectively prevents the projection of any conducting object through the opening to make contact with the electrodes of collector |I thereby causing electrical shock to the holder of said conducting object. As the fan rotates in a direction to exhaust the air it will tend to push any object out of the cabinet rather than draw it in. A suitable grille may be provided over the exhaust opening to further prevent entry of foreign material. By being mounted above the collector II, lthe fan need not be moved upon withdrawal of the collector.

The power supply 22 may be mounted on the top wall of the cabinet immediately above the ionizing structure I2 and the collector so that connections can be made thereto by relatively short leads. This reduces undesired couplings through the leads and also reduces the number 4 of high voltage insulators required for support-'- ing the leads. The oscillator tube 2| of the power supply and the low voltage rectifying tube 20 used in the production of direct current for the oscillator plate supply from an alternating current power line are located such that they can be replaced without opening the power supply box. The operation of the power supply 22 will be described more in detail hereinafter.

The ionizing structure I2 is shown in greater detail in Fig. 2. End plates 33 and 34 are held in position by top and bottom members 3| and '32 respectively. A plurality of separating plates 24 are held substantially parallel to plates 33 and 34 by being spot welded or otherwise fastened to the members 3| and 32. Insulating rods 25 and 26 are held by spring clips 35 which are supported on the end plates 33 and 34. The rods 25 and 26 are mounted so that they pass through recesses in the separating plates 24 and are held substantially parallel to top and bottom plates 3| and 32. A plurality of clips 3B support the thin conductor 21 on the rods 25 and 26 so that `the conductor 21 is suspended between and substantially parallel to the conducting plates 24. The detailed structure of the clips 36 is shown in Fig. 4. The clips include loops 89 through which the conductor 21 can be hooked. Conductor 29 held in place by electrically insulating bushing 28 extends through top plate 3| to make contact electrically to conductor 21 and forms one terminal of the ionizing structure. Conductor 30 electrically connected to the top plate 3| forms the second terminal of the ionizing structure. One long edge 32a of the bottom plate 32 may be bent upward such that it extends as high as the top of rod 25 and one long edge of top plate 3| may be bent downward such that it extends down as low as the bottom edge of rod 26. The two bent portions of the plates 3| and 32 form baffles which prevent air from being drawn through the ionizing structure through paths other than between conductors 21 and nlates 24 where the ionization is the most intense.

In Fig. 3 there is shown a second form that the ionizing structure l2 may take in which relatively large conductive electrodes 24 are held in position by members 40 and 4| to which they are spot welded or otherwise fastened. Members 40 and 4| have long edges bent respectively down and up which may be fastened to the baffling edges of plates 3| and 32 respectively, The edge of member 4I is indicated by 4| a and is secured to the barile edge 32a by screws 42. The edges o1' member 40 and plate 3| do not show in the drawing. Dielectric rods 38 extend through openings in the plates 40 and 4| such that they bear against plates 3| and 32 which latter plates prevent their slipping out of the openings in plates 40 and 4|. A plurality of conductive means 31 are held near the dielectric rods 38 by clip means 36 as used in the structure of Fig. 2 and illustrated in Fig. 4. Conductor means 39 connects all conductors 31 together and to the ionizer terminal 29. The dielectric rods 38 increase the electrical stress concentration along portions of conductors 31 when a high frequency component of voltage is applied between terminals 29 and 30 of the ionizing structure thus increasing the amount of ionization produced. This is disclosed and claimed in the copending application of Elmer G. Hills, Serial No. 731,734, led March 1,9 El294'7, now Patent 2,585,777 dated February 12.

The collector structure of Fig. 1 is shown in more detail in'Fig. 5. Collector plates 41 and 48 are supported on top and bottom plates 44 and 44a which are fastened to side plates 45 and 45a. The collector plates 48 are insulated from the supporting structure by insulator bushing 46. The top and bottom edges of plates 45 and 45a are formed or bent such that they are substantially parallel to plates 44 and 44a and these edges are spot welded or otherwise fastened to the top and bottom plates. Similarly collector plates 41 have their top and bottom edges bent and fastened to plates 44. Interleaved between plates 41 and insulated therefrom are plates 48 which are maintained in position by being spot welded or otherwise fastened to strips 49 by triangular shaped corners which are bent substantially at right angles to the strips 49 such that they are substantially parallel to the plates 48. Strips 4Q are maintained in position by the insulating bushings 46 which hold the strips substantially parallel to plates 44 and 44a. Collector plates 423 are not as high as plates 41 and are spaced therefrom by a distance greater than the spacing between plates 4B and 41. This is necessary as high stress concentrations would exist along the relatively sharp edges of plates 48 which would cause electrical arcs to plates 44 and 44a although the voltage existing between plates 4l and 48 would be less than the arc over voltage for the spacings of the plates. An electrical conductor 24 extends through a hole in plate fifi and through one of the bushings 46 to make contact with one of the conducting strips 4S thus forming one terminal of the collector structure. The other terminal is formed by the supporting structure. The connection of the collector in the precepitator unit is illustrated in Fig. l.

A modied collector structure is illustrated in Figs. 6 to l2 which is of inexpensive construction so that it can be disposed of after use. Disposable collector structures are disclosed and claimed in the copending application of Robert L. Barr, Serial No. 719,893, filed January 2, 1947. The structure of Figs. 6` to l2 is a simplified structure which includes a top plate 14, two sets of collector plates le and 1l, end plates 19 and a bottom plate 86. The top plate or supporting member 14 is held by staples, glue, or other means to one of the edges 15 of each of the plates l5 which edge is folded at substantially right angles to the main portion of the plate 16 when the collector is in opened condition. In a similar manner the top plate 14 is held to one of the edges 1S of each of two end plates 19, and is held to the folded edge Se of each of the plates 11 which plates are interleaved between the plates 'it of the nrst set. In a similar manner a bottom plate S6 is fastened to the, other folded edge of each of the plates 1S, 11 and 19.

The top plate 14 is rendered conducting over a large portion 82 thereof `and includes a narrow conducting strip 3'! which is insulated from the conducting portion 82 (Fig. 8). The end plates 'i9 are rendered conducting over a portion substantially ccextensive with the portion 82 of the top plate as shown in Fig. l0. The plates 16 of the llrst set may be identical with thel end plates 19 or may be of the construction shown in Fig. 9 in which the plates l are shorter than the other plates being substantially coextensive with the conducting portion 82 of the top plate. In this case the plates are rendered conducting over their entire area. The plates11of the second set are rendered electrically conductive throughout a substantial portion of their areas, as shown by 8| in Fig. l1, buit are left Vnon-conducting throughout the non-shaded areas 80, 8'3 and 84. Plates l'i are so oriented in the structure that-the conducting' portion 85 at the top of each plate contacts the strip 31 of the top plate which is rendered conducting. The strip t1 forms one terminal of the collector structure. Insulated portions 83 and S4 along the edges of plates 11 insulate the conducting portions 8i from the conducting portion 32 of the top plate 'i4 and, therefore, from plates 'le and 19. The plates 19 (Fig. 10) have insulated portions 9@ such that the folded portions 85 of the outer two plates 11 will not provide short circuits to the end plates 18 through which an electrical discharge might take place.

.fl-.ll the plates of the entire collector structure can be made of cardboard, or some similar ma-` terial sufficiently stiil to support its own weight,

which has been rendered electrically conductiveV as by a printing process, by having metallic foil fastened to at least one side, by a chemical process, or by any other means. The insulating material may preferably be rendered nreproof and non-hydroscopic so that the insulating properties thereof are improved. The lines along which the edges of plates 15, 11 and 19 are folded may be flexible enough to allow the entire structure to collapse as indicated in Fig. 'l in which the structure is in a partialv state of collapse. Such a collapsible collector struc ture could be held in an open condition by the t shape of the precipitator case and by runners S3 as illustrated in Fig. 1. To prevent bending of the collector plates when they are made oi light. inexpensive material to form a disposable structure, supporting end structures el?, as illustrated in Fig. l2, which are made of insulating material can be used. The structures invclude a plurality of stamped sheets 9i secured together by spacers '$32. The sheets have toothed edges including grooves 93 which support ther edges of the collector plates and points 94 for ease in positioning the end structures relative. to the plates. By providing openings 95 in the sheets, the paths along the sheets for leakage currents between the plates are increased. lThe end structures do not materially offset the free new of air through the collector structure. In. Fig. l2 there is shown spring clips 9E which may be provided for holding the collector structure in position in the case of the precipitator unit. The clips are positioned in recesses Q1 in the side walls of the case and the ends thereof may engage the sheets 9i of the end structure atl. By pressing the ends of the clips into recesses E31 the clips may be releasedfto permit removal of the collector structure for cleaning or re placing.

rlhe manner of making electrical connection to the disposable collector structures is also shown in Fig. l2. In this ligure the spring conductor means I e is shown hinged so that the end thereof contacts the conducting'strip 31 of the top plate 'E4 of the collector structure. Any suitable means can be provided for alternatively securing the hinged portion of the conductor in the positions shown in Figs. 1 and l2.

Another embodiment of the collector structure is shown in Fig. 13 in which two conductive sheets iii and t2 may be rendered conductive. The sheets may be made of paper,. plastic, screen wire `or other material which can 'be 'rendered electrically conducting. insulating member 53,

which may be corrugated paper,'plastic or other insulating material, maintains a substantially constant separation between sheets and 52 throughout the areas of said sheets while allowing air passages between said sheets. The edges of sheets 5| and 52 are brought out and connected to terminals 54 which are the terminals of the collector structure. The structure lends itself to economy of manufacture by its ability to be rolled into a shape as shown in Fig. 13 out of a sheet constructed somewhat like a sandwich. The air channels existing between sheets 5| and 52 and portions of insulating material 53 are substantially parallel to the axis of the structure into which the collector is rolled.

In the electrical circuit of Fig. 14 standard alternating current power is provided for the precipitator unit from the local power line by plug 55. The power is brought in through interlock switch 56 by means of conductors 59 to low voltage power supply means 51 as well as to electric fan means |4. The interlock switch may be arranged to de-energize the unit when the end 23 of the case Il) is removed. The power supply 5l provides heater and plate power for electron discharge valve 2| and may be of standard construction. A tank circuit composed of inductor 6| and capacitor 62 is connected in the plate circuit of valve 2|. Magnetically coupled to inductor 5| is the high voltage secondary coil 66. Electrostatically coupled to the high voltage coil 6E is conductor 65 which provides a feedback path from the plate to the grid circuit of valve 2| so that an electrical oscillator circuit is provided. Grid leak resistor 64 provides a direct current path to the cathode from the grid of the oscillator to prevent blocking of the grid. Because the conductor 55, the coil 66 and the insulation between them form an electrical condenser through which the feedback energy for exciting the grid of the oscillator passes, a phase shift occurs which decreases the amplitude of oscillation. Condenser B3 connected between the grid and cathode of oscillator 2| corrects for this phase shift. Although the valve 2| is illustrated as a tetrode having a screen grid to which potential is applied through resistor 6|), it is obvious that other types of valves can be used.

The high voltage appearing across the terminals of coil 6&5 due to the coupling of the coil to the tank coil 6| of the oscillator is applied between the cathode of rectifier 68 and one electrode of the collector structure. The anode of rectier 68 is connected (through ground) to the other terminal of the collector structure such that the rectier recties the output of coil 66 thus applying a unidirectional, pulsating electrical current to the collector structure. Inductor 61 is magnetically coupled to coil 66 such that the proper high frequency voltage is induced in it to heat the cathode of rectier 68. Because of the electrical capacitance of the collector and the high frequency of the output voltage of coil 5t the voltage appearing between the electrodes of the collector is substantially unidirectional and of constant amplitude. The use of the collector as the lter condenser of the power supply is disclosed and claimed in the copending application of Elmer G. Hills, Serial No. 642,473, i'lled January 21, 1946. One terminal ID of the ionizing structure is connected by means of a. ground path to the grounded side of the collector structure. The other terminal 13 of the ionizer is connected by means of short, direct conductor B9 to the cathode of the rectier 68. Because of this connection the voltage applied to the terminals of the ionizing structure is the sum of the substantially direct current voltage existing across the collector and the alternating current voltage of high frequency existing across coil Increased ionization due to the combination of direct current and high frequency alternating current voltages being applied to the ionizing structure is thus realized. At the same time, high intensity constant electrostatic fields are caused to exist between the plates of the collector structure.

It is seen from the above that we have provided an improved precipitator unit which is of small and compact construction suitable for use in a home. The specific arrangement of the components results in a very efcient unit. The use of the collector as the power supply filter results in decrease in the cost of the unit. The improved collector structures simplify the maintenance of the precipitator unit, the disposable collectors eliminating the difficult cleaning of the collectors which was formerly required. The structure of the disposable collectors is such that they can be inexpensively constructed and folded for storage and shipment in a relatively small space.

In the following claims the word collector shall mean any structure into which the gas containing electrically charged particles of foreign matter is drawn and upon the electrodes of which these particles are deposited; the word ionizer shall mean any device which causes the gas being drawn through it to become ionized such that particles of foreign mattei' passing through it will become charged; the word fan shall be understood to designate any means for causing a gas ilow through the precipitator unit; the word case shall be understood to mean any suitable covering or cabinet for housing the gas cleaning apparatus including the various brackets or other means for maintaining the relative positions of the components of the apparatus; the words power supply shall be understood to mean the equipment for generating the exciting voltages for the ionizer and collector which itself may receive energy from a source external to the gas cleaning apparatus.

While certain embodiments of our invention have been described for the purpose of illustration, it should be understood that the invention is not limited to the exact circuits and arrangements of apparatus herein described, as modifications thereof may be suggested by those skilled in the art without departure from the essence of the invention as defined in the appended claims.

We claim:

1. An electrostatic gas cleaning apparatus comprising a case, an ionizer, a collector, a fan, and a power supply. said case having top, bottom, end, and side walls, one of said end walls being removable and having an exhaust opening in the upper portion thereof, intake openings said case adjacent the end opposite said one end, said ionizer and said collector being supported in said case on said bottom wall intermediate the ends thereof with said ionizer adjacent said intake openings and said collector adjacent said exhaust opening, said fan being supported from said top wall of said case in front of said exhaust opening and arranged to draw gas through said intake openings of the case, and through said ionizer and said collector and exhaust said gas through said exhaust opening, said power supply being supported by said top wall of said case above said ionizer and said collector and including conductor means projecting therefrom, said collector being removable from said case when said one end wall is removed and having terminals thereon adapted to engage said conductor means so that connections to said collector are automatically made and broken when said collector is placed in said case and removed therefrom.

2. Apparatus in accordance with claim 1 in which said collector is disposable and includes a plurality of plates made of material which is sufciently stiff to support the weight thereof, means for securing said plates together to form a boxlike structure including a plurality of plates which are substantially evenly spaced, said securing rneans being suciently flexible to allow said collector to collapse so that said collector forms a ilat structure.

3. Apparatus in accordance with claim 1 in which said collector includes a plurality of plates made of insulating material which is sufficiently stiff to support the weight thereof, said plates including a supporting plate and rst and second sets of plates supported therefrom and extending at right angles thereto, plates of said rst set being interleaved between said plates of said second set with said plates of both sets being substantially evenly spaced, said plates of said first set being rendered conducting throughout a portion of their areas, said plates of said second set being rendered conducting throughout a portion of their areas, said supporting plate being rendered conducting on two portions thereof with one conducting portion contacting said conducting portions of said first set of plates and the other conducting portion contacting said conl0 ducting portions of said second set of plates, said conducting portions of said supporting plate forming said terminals of said collector.

4. Apparatus in accordance with claim l in which said collector includes a plurality of plates made of relatively thin material, said plates being substantially evenly spaced, and including end structures including a plurality of spaced insulating sheets extending at right angles to said. plates and having toothed edges with alternate points and grooves spaced to correspond to the spacing of said plates, said end structures engaging said collector with said grooves determining the position of said plates.

5. Apparatus in accordance with claim 1 in which said collector is disposable and includes a plurality of plates made of insulating material which has been rendered reproof and non-liy droscopic with said plates being rendered conducting over certain portions thereof.

ROBERT L. BARR.

ELMER G. HILLS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 670,169 Allen Mar. 19, 1901 1,992,974 Thomson Mar. 5, 1935 2,233,639 Pegg Mar. 4, 1941 2,449,681 Wilson Sept. 21, 1948 2,486,520 Dahlman Nov. 1 1949 2,528,842 Penney Nov. 7, 1950 FOREIGN PATENTS Number Country Date 360,119 Germany Sept. 29, 1922

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