US2505907A - Discharge electrode - Google Patents

Description

y 1950 A. F. MEsToN DISCHARGE ELECTRODE 2 Sheets-Sheet 1 Filed Octl 51, 1946 IN V EN TOR. Arch/bald F. Me .slon

y 1950 A. F. MESTON 2,505,907

DISCHARGE ELECTRODE Filed 001',- 51, 1946 v 2 Sheets-Sheet 2 INVEN TOR.

Archzlba/d F. Median JMY W W fiatented May 2, 1950 UNITED STATES PATENT OFFICE DISCHARGE ELECTRODE Archibald Meston, Bound: Brook, N. J assignoz" to Research Corporation, New York, N.. Y., a corporationof New York Application October 31, 1946, Serial No.*-707,=006

11- Claims.

2.The present invention'relates. to a discharge electrode for apparatus .usefulin electrically removing suspendedparticles from'gases and to a process and apparatus for. making such electrodes. It is especiallytadapted tow providing electrical .precipitators twith pronged stifi electrodes .which may be supported atone end only. Electrical Lprecipitators or". the type; commonly called Cottrell rprecipitators comprise at least two complementary electrodes one of which isan extended surface electrode upon which the precipitated particles are collected and another. is a socalled discharge.electrode with points, prongs,

-or. sharp edges from which non-disruptive dis- :chargesemanate when a strong electric field ter- .minates uponthem. It is advantageous under some conditions to make the discharge electrode stiff so that it .remainsinalignment adjacent to .the collecting electrode while being supported at one end only. Such electrodes are of course, of i more substantial construction. than the flexible wires, small rods,.or strips :that are in common use as discharge electrodes. .Many of the stiff electrodes in use at the present time are obtained only at considerable cost due to the multiplicity of parts andthe careful workmanshiprequired in their manufacture.

It is a principal object of the invention to provide a stiff electrode of the type identified above made of materials and parts which can be readily .obtained and easily fabricated at low cost.

object of the invention is to provide a discharge electrode having electric discharge elements integral therewith.

Another object of the invention is to provide a discharge electrode comprising a stiit supporting member and an extendedrelatively flexible ..,member. havingelectric discharge elementsxintegral therewith, the electrode being character- .ized by novel fastening means for Joining thetwo members thus permitting ready joining or separation of the members.

i Itis an object of the invention to provide a stiff discharge electrode for electricalprecipitators which has but few parts and which can through simple changes in the fabrication and/or 1 manipulationof the parts be altered in its electrical discharge characteristics. mentioned can be made throughout the length of the electrode or. can-be made locally so as to l provide different electrical characteristics atdif- .ferent locations along the length of the eleca trode.

The changes A further objectis to provide a dlscharge:electrodelhaving a. plurality of portions similarly 1 made andof the same general construction'but and which can-:be readilynmanipulatedto provide changes .inuthe dimensions and size of'the electrode" whereby the..discharge characteristics of the electrode are. altered.

It is also an objectii'ofithe invention to provide improved apparatus for making the electrodes of "the invention.

The manner. in which the above objects and other advantages of the 'inventionmay be realized is set forth in the following detailed description illustrated by the'appended drawingsin which:

Fig. 1-. is-a: sectional view ofa complementary electrode structure including a discharge. electrode embodying theprinciples' of'the invention;

Fig.2 is a'fragmentary view of a metalstrip incorporatedinthe discharge electrode ofFig. 1;

Fig. 3 is an cnlalrged detall 'view of a portion of the discharge electrode;

Fig. 4 is a sectionaliview taken along the line L4 of'Fig'. 3;

Fig. 5 is an elevational viewbf an alternative form of 1 precipitating electr'ode including discharge and nondischargeportions and embodying i theprinciples oftheinvention;

Figs; 6 and 7 are fragmentary elevation and sectional views respectively of a modified form 01 metal strip employed in making discharge electrodes Figs. 8 and: 9 are fragmentary elevation and sectional views respectively of another-modified form of metal strip;

Fig. 10 is a plan view ofiapparatusfor winding the discharge electrodes;

ll, 12-and :13 are tenlare'ed detail views in side elevation of partsof theapparatus shown inFig. l0; and

Fig. 14 is a further enlarged detail perspective semidiagrammatic view of. a portion of the apparatus of Fig. 10 illustrating themanner in which the discharge prongs of the felectrodecare raised duringwinding.

Referring to the drawings, particularly to Fig. 1 thereof, the discharge electrode with which the invention is concerned is designated as a unitary structure by numeral 20? It has a base member 21 which may be a tube, or a rod; a strip 22, including integrally rooted prong or pointed elements 23, which is wound helically around member 21 and fastened, as by tack welding, to member 2! at the ends 24, 24 of the strip and elsewhere along its length as may be desired; and means 25, usually at one end of the electrode only, for fastening the electrode to a suitable support. Such means may include a collar 28 fastened to base 2| about five inches from the upper end of the base and a threaded end with nut 2! at the extreme upper end of the base. The discharge electrode can be fastened to such electrically insulated structures as are at present used in electrical precipitators, but a deeper support such as the one formed by angles 28, 28 separated by a sleeve 29 surrounding base member 2|, has been found desirable, especially where the discharge electrode is supported at one end only, yet must be held in a rigidly fixed position, or in the center of tubular collecting electrode 38, for instance. When the complementary electrodes are arranged as shown, electrode 20 is electrically connected to any conventional source of high voltage current, such as that indicated diagrammatically at 3|, and collecting electrode 38 is commonly connected to ground, as indicated at 32.

The constructionof electrode 20 is shown in greater detail in Figs. 2, 3 and 4. The base member 2| is shown as a metal tube of such diameter and wall thickness as may be necessary to provide the rigidit required. Tubes with diameters ranging from inch to 1. inch are generally satisfactory, a tube inch outside diameter and having a wall thickness of about inch being typical for electrodes from 3 to 7 feet long. Round bars or bars of other cross section may be used but tubes are preferred for several reasons, one being the facility a rather thin against thin strips. The strip shown in Fig. 2 may be made of band iron, such as that used to reinforce shipping containers, or may be made of strips sheared from sheets and welded end to end where strips of considerable length are needed.

The strip is slit or lanced at intervals along one side, as shown, the slits 33 being at an acute angle with the edge of the strip and extending from the edge to about the center of the strip. When such a strip is wound around a base member, themain body of the strip conforms to the surface of the base member but the discharge portions 23 do not bend; instead they stand out tangentially to the surface of base member 2| as indicated at 23' in Fig. 4.

It is one object of the present invention to bend I these portions-they commonly are bent along walled tube provides for tack welding are met within gaseous suspensions are not electrically charged equally ,well under the same conditions and it has been proposed to progressively alter the corona discharge and field strength characteristics of the treating path through which the gases, from which suspended particles are to be removed, flow. The electrode illustrated in Fig. 5 provides such variable conditions. It is made up of two discharge sections 35 and 36, a nondischarge sections 31, and a supporting member 30. Sections 35 and 36 are both made in accordance with the teachings of the invention but section 35 is made to provide a stronger discharge and a weaker average electric field than section 36. These results are accomplished by making prongs 4| longer and base tube 40 smaller in diameter in section 35 than the corresponding parts 42 and 43 respectively, in section 36. Prongs 4| can be altered in length by altering the length of cuts 33, Fig. 2, and their number can be varied by changing thespacing between cuts. The farther a discharge point is positioned away from the base member and from other points the more intense the discharge at constant voltage and spacing between complementary electrodes. Section 31 is shown in the form of a smooth collar. It may be formed from a short tube by turning in the ends and it may be of larger diameter than the base members 49 and 43 because a shorter electrode-to-electrode spacing can be had without spark-over where the surfaces of the complementary electrodes are free from prongs or other surface portions of small radius. No corona discharge is expected from member 31 but because of its large diameter and resulting proximity to a complementary electrode, as would be the case if it were positioned axially in the tubular electrode 30, Fig. 1, an electric field of very high average intensity will terminate on its surface. This latter feature is advantageous to provide a final cleaning of the gas in some types of electrical precipitators.

The composite electrode illustrated in Fig. 5 is made by first joining the base members 40 and 43 together, as by telescoping one into the other, and thereafter wrapping them with appropriate metal strips. Or, the base members can be wrapped first and assembled afterwards, which is to be preferred when a considerable number of electrodes are to be made.

Alternative forms of wrapping strips having integrally rooted discharge elements are shown in Figs. 6 and 7 and Figs. 8 and 9. In Figs. 6 and 7, the strip 45 instead of having discharge points formed by making a single cut in the edge of the strip has discharge points 46 defined by a V-shaped cut made near the center of the strip. The discharge points 48, in the modification shown in Figs. 8 and 9, are formed by perforating or puncturing the strip 41 at spaced intervals with an instrument which leaves the turned edges of the holes in a jagged condition.

Apparatus especially adapted for making the electrodes herein disclosed can be variously constructed as to details and can be operated in connection with other mechanisms, either mechanically or manually operated, of various types.

Conveniently, an ordinary machinists lathe may be provided with novel attachments to adapt the same to the purposes of thepresent invention. In Fig. 10 there is shown, in plan view, a fragment of a machinists lathe including the bed runners 49 and 50, the usual carriage 5| that is translatable along the bed runners. the usual cross slide 52 and compound rest 53. These parts usual hand wheels and operating handles (not shown). As is also conventional, the carriage may be automatically driven by a lead screw at a preselectable rate proportional to the speed of rotation of the spindle that turns the work.

The attachments which are added to the lathe are (A) means for holding the lanced strip and feeding it, preferably under slight tension, at the proper angle upon the turning base member, here shown as a tube, (B) a follower rest for providing local support to the tube just in front of the strip as it is placed on the tube, and (C) means for contacting the points which project outwardly at a slight angle from the strip after winding and urging them to an upright, radial, position. Means C is not always used. All three of these attachments are mounted on the cross slide of the carriage of the lathe and travel with it at the rate the winding strip progresses along the tube. The strip holder A is placed on the front or near end of the slide, being mounted on the compound tool rest 53 so that it can be turned at different angles. The follower rest B and the point lifter C are mounted on the far end of the slide and can be adjusted as to transverse position by turning the cross feed hand wheel (not shown).

Strip holder A is shown in side elevation in Fig. 11, a portion of the side plate being broken away to show interior construction. It has a base 54 attached for instance by welds 55, to a body member 56. The base 54 has open slots 51 for the entry of bolts by which it may be fastened to compound rest 53. The body 56 is fiat on all sides except the top which has a trough-like depression 58 that extends from one side of the body to the other, the width of the body being somewhat greater than the width of the strip to be wound. A complementary member 59 provides a top for the body 56. It is flat on all sides except the bottom which is cut out with a trough-like depression El] and this depression forms with depression 58, a small chamber, open at both sides, to be occupied by rolls GI and 62. A small slot 63 is cut in each end of top member 59 for the entrance and egress of the strips to be guided by fixture A. The slots are positioned to guide the strips under rolls 6| and over roll 62, the relative position of the rolls causing the strip to bend slightly in passing through the fixture thus setting up a tension in the strips. Flat side members 64 are fastened with bolts 65 to the sides of members and 59 thereby holding them together and closing the sides of chamber 5B, 66. Also, holes in side members [it provide bearings for the trunnions 66 on the ends of rolls 6|, 62.

Follower rest B, shown in side elevation in Fig. 12, is made up of a base 57 with holes 68 for fastening means, and an upright member 69, rigidly attached to base 61, and in which a bearing 70 had been formed for supporting base tubes 2| of electrodes during manufacture.

Fixture C, a right side view of which having parts broken away is illustrated in Fig. 13, has a base H on which an upright member 72 is rotatably mounted with a threaded fastening, to be looked in the position and elevation desired by set screw it; an elbow shaped member 14 rigidly fastened to upright member 12 and which in turn supports with a threaded fastening another e'bow shaped member 15, a set screw 16 being provided to lock elbow member 15 in any desired position in elbow member 14; a sleeve prongs 23.

member H, that is screwed intoelbow "I5and locked in desiredrotative position by set screw 13, having a cylindrical cavity 19 adapted to retain bearing means, for example, two needle bearings 88 separated by a tubular spacer 8| and a thrust bearing comprising a single ball 82 in the bottom of the cavity; a rotatable shaft83 one end of which is positioned in cavity"|9 supported therein in bearings and against ball 82 and the other end being fastened at right angles to a bar 84, and having a pin 85 projecting from the side thereof intermediate the ends and adapted for contact, against an abutment 86 on the end of member l1; and spring means 81 held in tension between an extension 88 on set screw 78 and a fastening 89 on the far side of shaft 33, on the rear end of bar 84, for instance.

Fig. 14 shows how the parts of fixture C are arranged to provide proper contact with prongs 23 to raise them during the winding operation. Telescoped members ll and 83 are inclined upwardly towards the junction of members 83 and 84 at an angle of about 8 to 12 degrees with the horizontal, and member 84 is inclined downwardly from the junction at about the same angle with the horizontal. These angles are determined after suitable trials and are then held by tightening set screws 76 and 18, respectively. Simultaneously, the height of bar member 8 4 and the angle with the axis of base member 2| at which it is most advantageously held (about 12-15 degrees has been found satisfactory) is determined. This is done by raising and rotating member 72. The importance of the angle with the hor;zontal at which member 33 is held, or otherwise stated, the angle which the axis of rotation of yieldable shaft member 83 makes with the plane of strip 22 as it approaches base 2|, is seen when it is recognized that the closer the angle is to 90 degrees the sooner bar member. 84 will slip off a discharge point 23 during erection of the latter, causing rotation of shaft B3 in sleeve Tl as it does so. This relationship provides close control over the final position of When a prong 23 first strikes lifting bar 84, upon rotation of base 2|, it tends to push the bar down and pin 85 is pushedagainst abutment 86. As prong member 23 is lifted towards radial position, as shown in dotted lines in Fig. 14, the force on bar 84 changes in direction until, when the surface of prong 23 is at an angle some.- what less than 90 degrees with the axis of rotation of shaft 83 it has an upward component which lifts the end of bar 8 1 and lets it slip over the end of the prong. Spring 8"! immediately pulls the end of the bar down again, making it ready to lift the next prong.

The apparatus is operated as follows: A strip of the width and thickness desiredis run through shears, not shown, which partially slit or lance the strip to make, for instance, the cuts 33, Fig. 2. The lanced strip is then rolled on bobbins, or the like, of relatively large diameter. The end of the strip is put through fixture A and. attached under a jaw of the lathe chuck when the chuck is tightened to grasp an end of a base member 2|. A few turns of the strip are wound, the lathe turning clockwise (when facing the chuck). If it is desired that the edges of the strip touch as shown in Fig. 3, and they need not for the purposes of the invention, compound tool rest 53 is turned to and locked at the angle at which this result is realized. The cross slide 52 is set with the follower rest B in contact with base member 2|, and the position of fixture C is checkedin lathe chuck (not shown).

:the tube.

' accordance withthe relationships previously emphasized. The proper gears to match the travel of the carriage with the speed of the spindle taking into account the width of the strip being wound have, of course, been determined and made available on the lathe. Winding can now proceed until the base member is completely covered with the pronged strip or to the extent best suited to the purposes in mind. The strips having discharge points or prongs 1* can be attached to the supporting rods or tubes in various ways. The preferred way is by spot .welding. In attaching the end of a strip to a tube which has been fastened in the winding machine the end of the strip is passed through the guide mechanism A, which is to maintain the strip at the proper angle during winding, and made to contact the surface of the tube near the The electrode holding arm of an electric spot welder (such apparatus is well-known to the art and is not shown) which is ordinarily back out of the way is pulled down upon the end of the strip and a small but secure weld is made attaching. the end of the strip to the far end of the strip and at intermediate points therealong.

It is not necessary, however, to use the welding machine during the winding period. The starting end of the strip can be caught in the chuck with the tube and in addition a simple retaining ringit may be a short piece of wire 9!} (Fig. 10). twisted tight with hand pliers-man be used to fasten the strip to the tube, as a temporary fastening at least; a similar fastening can be applied at the other end of the strip after the Winding operation has been completed. Wound tubes with such fastenings can be placed in a rack as made and taken in lots to a welding machine which is advantageously used in conjunction with a specially designed holding frame which combination produces rapid, uniform, and permanent welding of the strips to the tubes. Any temporary holding means, such as clasps or wire ties,

be a permanent part of the electrode assembly.

The wound strip after being suitably fastened along its contiguous edges, as by welding, may be withdrawn from the base member which has served as a mandrel in the winding operation, and when fitted with a suitable supporting attachment at one end thereof, may be used as a discharge electrode. lhis is particularly feasible for electrodes of relatively short length, but by selection of metal strip stock of proper thickness and strength relatively long electrodes of adequate stiffness may be provided without the necessity for a coextensive base member.

It will be apparent that, particularly when a permanent base member is part of the electrode construction the edges of the successive turns of the strip do not need to be in contact.

From the foregoing description it will be seen that the present invention provides an improved discharge electrode and process and apparatus for making the same, the electrode being characterized by discharg points integrally rooted with a When the strip is wound on the tube to the extent desired, other welds are made at hellcallywound conductive strip,- the strip preferably being wound upon a base member. It will also be appreciated that the process and apparatus of the invention are extremely simple and provide desirable adjuncts to the manufacture of the electrode.

I claim:

l. A discharge electrode comprising an elongated base member, a metal strip wound about said base member in a helix, and a plurality of discharge elements comprising projecting portions of said strip integrally rooted with the helical portion thereof and formed by slitting the strip angularly inwardly from one edge thereof and bending outwardly the prong included between the slit and the edge of said strip.

2. A discharge electrode comprising an elongated base member, a metal strip wound about said base member in a helix, and plurality of discharge elements comprising projecting portions of said strip integrally rooted with the helical portion thereof and formed by making a V-shaped slit through said strip and bending outwardly the prong included between the edges of said slit.

3. A discharge electrode comprising an elongated cylindrical base member, a metallic sleeve positioned around the central portion of said base member, a nondischarging collar positioned around said base lnember near one end thereof and adjacent to said sleeve, a. metal strip wound about said base member in a helix extending from near the other end of said base member to said sleeve, another metal strip wound about said sleeve in a substantially contiguous helix and extending substantially from end to end of said sleeve, and a plurality of discharge elements comprising pointed projecting portions of said strips integrally rooted with the helical portions thereof.

4. Method of making a discharge electrode which comprises slitting a metal strip angularly inwardly from an edge thereof at spaced intervals, winding said strip upon an elongated base member in a helix, and bending outwardly the prongs included between said slits and the adjacent edge portions of said strip.

5. Method of making a discharge electrode which comprises slitting a meta1 strip angularly inwardly from an edge thereof at spaced intervals, winding said strip upon an elongated base member in a helix, bending outwardl the prongs included between said slits and the adjacent edge portions of said strip, and welding said strip to said base member.

6. Method of making a discharge electrode which comprises slitting a metal strip angularly inwardly from an edge thereof at spaced intervals, winding said strip upon an elongated cylindrical base member in a helix, and bending outwardly the prongs included between said slits and the adjacent edge portions of said strip.

7. Method of making a discharge electrode which comprises slitting a metal strip angularly inwardly from an edge thereof at spaced intervals, winding said strip upon an elongated cylindrical base member in a helix, bending outwardly the prongs included between said slits and the adjacent edge portions of said strip, and welding said strip to said base member. i

8. Apparatus for making a discharge electrode including a metal strip wound in a helix to form an elongated cylindrical member which comprises means for mounting a cylindrical base element for rotation about its longitudinal axis, means for rotating said base element, carriage means mounted for translation parallel to the axis of said base element, means for translating said car=- riage at a rate proportional to the speed of rotation of said base element, means mounted on said carriage for guiding a strip of metal having spaced slits defining integrally rooted discharge prongs lying in the plane of the strip in Winding relation to said base element and for tensioning said metal strip as it is found upon said base element, and additional means mounted upon said carriage means adjacent to the surface of the base element for engaging the discharge prongs as the strip is wound upon the base element and raising the prongs to substantially radial position.

9. Apparatus for making a discharge electrode including a metal strip wound in a helix to form an elongated cylindrical member which comprises means for mounting a cylindrical base element for rotation about its longitudinal axis, means for rotating said base element, carriage means mounted for translation parallel to the axis of said base element, means for translating said oarriage at a rate proportional to the speed of rotation of said base element, means mounted on said carriage for guiding a strip of metal having spaced slits defining integrally rooted discharge prongs lying in the plane of the strip in winding relation to said base element and for tensioning said metal strip as it is wound upon said base element, and additional means mounted upon said carriage means adjacent to the surface of the base element for engaging the discharge prongs as the strip is wound upon the base element and raising the prongs to substantially radial position, said additional means comprising a bar yieldingly biased to rest position at an angle to the axis of rotation of the base element and urged by said prongs out of the path thereof when the latter have been raised to radial position.

10. A discharge electrode comprising an elongated base member, a conductive strip wound about said base member in a helix, and a plurality of discharge elements each comprising a projecting portion of said strip formed by slitting the strip to define a prong extending longitudinally of the strip, said prong being integrally rooted to the strip at the base of the prong, and bending the prong outwardly from the strip.

11. Method of making a discharge electrode which comprises slitting a metal strip at spaced points therealong to form prongs extending longitudinally of the strip, said prongs being integrally rooted to the strip at their bases, and winding said strip upon an elongated base member in a helix having said prongs projecting therefrom.

ARCI HBALD F. MESTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 777,817 Stolp Dec. 20, 1904 1,067,974 Cottrell July 22, 1913 1,357,201 Nesbit Oct. 26, 1920 2,061,516 Frese Nov. 17, 1936 2,195,431 Shively et a1 Apr. 2, 1940 2,231,330 Gove Feb. 11, 1941 2,352,651 Meston July 4, 1944 FOREIGN PATENTS Number Country Date 299,476 Germany July 1.7, 1917 344,705 Germany Nov. 28, 1921

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