US3727380A - Electrostatic precipitator - Google Patents

Abstract

An electrostatic precipitator is disclosed in which identical printed-circuit boards are used at either end of a plurality of collector plates both to provide electrical connections and to space the plates. The plates each have at either end a support tab and a contact tab, both of which register in slots in the respective printed circuit board. The boards have printed bus bars connecting the contact tabs of the plates with the same potential, and these bus bars are coated first with a conductive resilient coating and then with a resilient non-conductive coating.

Description

[451 Apr. 17, 1973 United States Patent [191 Remick ELECTROSTATIC PRECIPITATOR [75] Inventor:

3,242,649 3/1966 Rivers....................................55/l32 Cassius D. Remick, Waterloo, Ontario, Canada [73] Assignee: Electrohome Limited Primary Examiner-Dennis E. Talbert, Jr. Attorney-Peter W. McBurney et al.

[ ABSTRACT An electrostatic precipitator is disclosed in which Kitchener,

Ontario, Canada identical printed-circuit boards are used at either end of a plurality of collector plates both to provide electrical connections and to space the plates. The plates each have at either end a support tab and a contact both of which register in slots in the respective printed circuit board. The boards have printed bus bars connecting the contact tabs of the plates with the same potential, and these bus bars are coated first with a conductive resilient coating and then with a resilient non conductive coating.

.0 m 47 4 3 05 4UM34U 1 311 6 ,..I, h a -l 95B va- 49 N 7 5 4% 1 10" fl B 7 5 3 1 ,5 w 7 n 9 N 1 W43 a u mk W1 1 9w m2 msf m m "4" 1 "l l I l. 0 "fim B N L h..../ '05 n. m p s n F A U h F .l] l 1] 2 l 2 8 2 2 5 55 [all References Cited UNITED STATES PATENTS 7 Claims, 3 Drawing Figures 4/1962 Mueller(I.........."1.1.10.3 5726ix PATENTED APR 1 7 5 sum 1 BF 2 m 4 8 M L ENTOR CASSIUS E MKLK ELECTROSTATIC PRECIPITATOR This invention relates generally to electrostatic precipitators, of the kind adapted to remove particles such asdust, smoke and pollen from the air or other gas being passed through the precipitator. More specifically, this invention relates to that portion of an electrostatic precipitator construction which involves the mounting of the collector plates and their electrical connections.

The general theory behind the construction of electrostatic precipitators is well known. Essentially, the air, and its load of particles such as dust, pollen, etc., is caused to pass through two zones, the ionizing zone and the collection zone. Ordinarily, the ionizing zone is characterized by a plurality of positively charged parallel wires, while the collection zone contains a series of alternately arranged positive and negative plates between which the air must pass. Normally, particles that have become positively charged in the ionizing zone are collected on the negative plates in the collection zone. However, some of the positively charged particlesmay pick up more electrons than they require to become neutral, in which case they become negatively charged and go to the positive plates.

One of the disadvantages of conventional construe tions of electrostatic precipitators relates to the fact that the design of the collector plates and the means by which they are supported and charged is such as to require expensive equipment to hold the collector plates in the desired spaced relationships during assembly.

In view of the foregoing disadvantage of conven tional electrostatic precipitators, it is an object of this crimped over, a printed bus bar on said board joining all said contact slots, a resilient, adhesive, conductive coating masking the bus bar and the crimped contact tabs, and a resilient, adhesive, non-conductive coating covering the conductive coating.

One embodiment of this invention is shown in the accompanying drawings, in which like numerals denote like parts throughout the several views, and in which:

FIG. 1 is a partly broken-away, partly exploded, perspective view of an electrostatic precipitator construction embodying this invention;

FIG. 2 is a partial elevation view taken at the line 2- 2 in FIG. 1; and

FIG. 3 is a sectional view taken at the line 3-3 in FIG. 2.

Attention is now directed to FIG. 1, in which an electrostatic precipitator 10 is seen to include anextemal rectangular frame 12, a plurality of collector plates 14, an ionizing wire 15, and two protective screens 16 and 17. Two printed circuit boards 19 and 20 are also provided, one at either end of the collector plates 14, and both arranged perpendicularly thereto.

As can be seen, the rectangular frame 12 is U-shaped in cross-section having a main wall 22 and two perpendicular flanges 24. In the embodiment shown, the frame 12 is in two L-shaped parts manufactured of sheet metal, the flanges 24 being appropriately notched at locations corresponding to the corners of the electrostatic precipitator. Metal screws 26 or other suitable attachment means are employed to secure the loose ends of the frame 12 together at the comers 28 and 29, as shown.

All of the collector plates 14 have the same length (the dimension perpendicular to the plane of the printed circuit boards 19 and 20), but they are not all of the same width. The plates 14 are preferably of aluminum or aluminum alloy. The plates 14 should have substantially smooth and non-porous (i.e. relatively closed) surfaces so that collected dirt will be washed out easily and will not have a tendency to adhere to the surface.

As seen in FIG. 2, the collector plates are arranged in repeating sets of four. The uppermost set of four collector plates includes a negative plate 30 of a width corresponding to the width of the printed circuit board 19. Immediately beneath the negative plate 30, and spaced in parallel relation therefrom, is a positive plate 32, whose width is just over half that of the negative plate 30. The positive plate 32 is set slightly inwardly from the left-hand edge of the negative plate 30 and the printed circuit board 19. Next beneath the positive plate 32, and spaced in parallel relation thereto, is a negative plate 34, the left-hand edge of which is aligned with that of the first negative plate 30. The right-hand edge of the negative plate 34 is positioned leftwardly of the right-hand edge of the positive plate 32. In fact, the plates 32 and 34 are identical, but are reversed end-toend. Thus they are both of the same width. Next beneath the negative plate 34 is another positive plate 36 identical to the first positive plate 32 and aligned therewith. Thus, the right-hand edges of the plates 32 and 36 are aligned, while the left-hand edges of the plates 30 and 34 are aligned.

, shown in the drawings, each plate has an integral contact tab and an integral support tab at either end. Specifically, the upper negative plate 30 has a contact tab 38 and a support tab 40, while positive plate 32 has a contact tab' 42 and a support tab 44. Negative plate 34, has a contact tab 45 and a support tab 46, while positive plate 36 has a contact tab 48 and a supporttab 50. The repeating sets of these four plates have identical tabs to those described immediately above. For every plate, the contact tabs are longer than the support tabs.

As seen in FIGS. 1 and 2, the printed circuit board 19 has a plurality of spaced slots 52 along its left-hand edge for receiving the contact tabs 38 and 40 of the negative plates 30 and 34, and has a plurality of spaced slots 53 along its right-hand edge for receiving the support tabs 40 of the wide negative plates 30. The support tabs 46 of the narrow negative plates 34 are received in a series of slots 55 as shown in FIG. 1. A further series of slots 57 are adapted to receive the contact tabs 42 and 48 of the positive plates 32 and 36, while a series of slots 58 are adapted to receive the support tabs 44 and 50 of the positive plates 32 and 36. Preferably, the printed circuit board 19 is symmetrical about a transverse mid-line, so that the boards 19 and 20 can be identical, but reversed end-to-end so that the bus bars to be described below always are located on the outer face.

Each plate has an integral, arcuate, raised rib 60 aligned with pairs of tabs on its ends. Both ends of each plate are identical, which means that the same tabs occur in the same positions at either end, and thus each raised rib 60 has a tab at either end. Because the tab is, in effect, an extension of the raised rib, the tab is also arcuate in cross-section. The arcuate nature of the tabs is clearly seen in FIGS. 1 and 2. The purpose of the raised ribs 60 is to add strength and rigidity to the collector plates.

Along its right-hand edge, the collector plate 19 has a plurality of cut-away indentations 62, one between each adjacent pair of support tabs 40 of the wide negative plates 30. The indentations 62 are all substantially rectangular. Secured to the printed circuit board 19 along the inner extremities of the cut-away indentations 62 is a bronze bar 64 which has a plurality of resilient, wire-supporting fingers 66 which extend alternately up and down so that each finger has its end generally situated mid-way of one of the cut-away indentations 62. The end of each finger, whether an upwardly extending or downwardly extending finger, has a V-notch which is adapted to receive the wire 15. Each finger is arcuately curved away from the plates, so that when the wire is tightly wound, it is maintained under tension by the resilience of the fingers 66. The bronze bar 64 is soldered or otherwise firmly adhered against a printed copper bus bar 660 on the board 19.

The printed circuit board 19 has applied thereto a printed negative bus bar 67 and a printed positive bus bar 69. As can be seen, the printed positive bus bar 69 is arranged vertically and joins all of the vertically aligned slots 57, which are adapted to receive the contact tabs 42 and 48 of the positive collector plates 32 and 36. The bus bar 69 has a soldering extension 69a at the top for soldering purposes. The printed negative bus bar 67 extends down the left-hand edge of the board 19, and links all of the spaced slots 52 which are adapted to receive the contact tabs 38 and 45 of the negative collector plates 30 and 34. The printed negative bus bar 67 also extends across the upper extremity of the board 19.

As seen in FIGS. 1 and 2, the board 19 also has a number of spaced circular apertures 70, in which spacing members 72 are adapted to be received. Each spacing member 72 has a conically flared portion 73 and a reduced stem 74 adapted to be received snugly in a circular aperture 70. The purpose of the spacing members 72 is to maintain a desired spacing between the frame 12 and the printed circuit board 19, and also as support in case the unit is dropped on' its side. The printed circuit board 19 has, at either end, two extensions 76 which are adapted to be received in slots 78 provided therefor in the frame 12. The registry of the extensions 76 in the slots 78 accurately locates the boards 19 and all of the collector plates with respect to the frame 12.

All of the tabs, whether contact tabs or support tabs, have a small adjacent shoulder 80, the purpose of which is to space the main body of the plate from the printed circuit board 19.

The assembly of the electrostatic precipitator of this invention will now be described.

Firstly, the different collector plates and two printed circuit boards are assembled so that the different tabs register with the appropriate slots, as shown in the Figures. The two printed circuit boards would be identical, but reversed. That is, the far printed circuit board 20 in FIG. 1 would have the indentations 62 at its right-hand edge as seen in FIG. 1, but would have the bronze bar 64, with its arcuate resilient fingers 66, located on the far side as viewed in FIG. 1. The bronze bar 64 and the fingers 66 would also be reversed, in the sense that the fingers 66 would be arcuately curved away from the collector plates on the far side of the electrostatic precipitator as viewed in FIG. 1. It is not necessary that both printed circuit boards 19 and 20 have applied thereto the printed positive and negative bus bars 69 and 67 as shown in FIGS. 1 and 2, although this is desirable because of the resulting advantage of uniformity, since the boards 19 and 20 would then be identical.

It will be appreciated from what follows that it would be possible also to have one of the printed bus bars located on one of the printed circuit boards, and the other located on the other printed circuit board. For example, the printed negative bus bar 67 could be located on the near printed circuit board 19 in FIG. 1, while the positive bus bar 69 could be located on the far printed circuit board 20 in FIG. I. In the embodiment shown, however, it will be assumed that the printed bus bars 67 and 69 are located on both printed circuit boards 19 and 20.

When the collector plates and the printed circuit boards have been assembled in the required arrangement, the contact tabs 38, 42, 45 and 48 of all of the collector plates are crimped over as seen in FIGS. 1 and 2. This crimping can be done manually or by machine. The support tabs 40, 44, 46 and 50, are left uncrimped.

It will be appreciated that it is hightly desirable to have the two vertical rows of crimped contact tabs separated from each other by the greatest possible distance, for two reasons. The first reason is of course to reduce the risk of electric arc-over between the bus bars, these being adapted to carry a very high voltage. The second reason is that the spread-apart crimping locations hold the two printed circuit boards 19 and 20 tightly against the plates while the subsequent operations, now to be described, are performed. If both lines of crimped contact tabs were close together along one edge of the printed circuit boards 19 and 20, it would be possible to pull the free" edge of each board away from the collector plates, which is very undesirable. To achieve separation of the two rows of crimped contact tabs, the support tabs for the negative plates are all to the right of the negative contact tabs, while the support tabs for the positive plates are all to the left of the positive contact tabs.

After the two rows of positive and negative contact tabs have been crimped over as shown in FIG. 2, both the tabs and the associated bus bars are masked by the application of a coating 82 of conductive, resilient cement. This coating prevents arcs between the crimped contact tabs and the bus bars to which these tabs are intended to be connected, and therefore eliminates radio interference arising from arcing. Because of its resilient nature, the coating 82 also prevents rattles. Preferably, the cement is a carbon-filled silicon rubber which is resistant and will withstand the vibration of the plates caused by air flow for an extended period of time. One material which has been found satisfactory as the coating 82 in the electrostatic precipitator according to this invention is known as Dow-Coming Silastic 735 RTV. The contact tabs are crimped not only to securely hold the printed circuit boards 19 and 20, but also to reduce the necessary amount of the coating 82, which is costly at the present time. There is no need to crimp the support tabs because they are shorter than the contact tabs.

Following'the application of the conductive resilient coating 82, a further coating 84 of non-conductive (insulative) resilient material is applied over the entire board except for the bronze bar 64 to which the ionizing wire support fingers 66 are attached. This coating 84 entirely covers the projecting support tabs of the collector plates, as well as the earlier coating of conductive resilient material. It also covers the spacing members 72 and anchors them in place. The non-conductive resilient coating 84 prevents arc-overs across the surface of the board, and prevents rattling at the support tabs. One material which has been found satisfactory for the coating 84 is Dow-Coming 145 protective coating. This material does not dry rigid and therefore can withstand vibrations. FIG. 2 shows only the conductive coating 82. The non-conductive coating is seen in section in FIGS. 1 and 3.

After the plates and printed circuit boards have been assembled as above described, the ionizing wire can be wrapped sinusoidally about the fingers 66. The wrapping of the ionizing wire can take place prior to the application of the two coatings, if desired.

In the appended claims, the expression "printed circuit boar is intended to cover any plate-like element of stiff, non-conductive or insulative material which is capable of receiving a printed circuit or bus bar on onesurface. Board is here used in its broadest sense, and is not limited to wood, wood products or cellulosic materials.

What I claim as my invention is: I

1. In an electrostatic precipitator construction which includes a plurality of parallel, aligned and alternately arranged positive and negative plates, the combination of:

a non-conductive printed circuit board disposed adjacent the ends of the plates and perpendicular thereto, 4

anv integral contact tab on each positive plate r'egistering in a positive contact slot in said board and crimped over,

a printed positive bus bar on said board joining all said positive contact slots,

an integral contact tab on each negative plate registering in a negative contact slot in said board and crimped over, a printed negative bus bar on said board said negative contact slots,

each plate having at least one integral support tab spaced from its contact tab and registering in a support slot in said board,

a resilient, adhesive, conductive coating masking each bus bar and its crimped contact tabs, and

a resilient, adhesive, non-conductive coating covering the conductive coating.

2. In an electrostatic precipitator construction which includes a plurality of parallel, aligned and spacedapart collector plates, the combination of:

a non-conductive printed circuit board disposed adjacent the ends of the plates and perpendicular thereto,

some at least of the plates each having an integral contact tab registering in a contact slot in said board and crimped over,

a printed bus bar on said board joining all said contact slots,

a resilient, adhesive, conductive coating masking the bus bar and the crimped contact tabs, and

joining all a resilient, adhesive, non-conductive coating covering the conductive coating.

3. The invention claimed in claim 1, in which said positive contact slots and said negative contact slots are arranged in two parallel, spaced-apart lines.

'4. The invention claimed in claim I, in which the support tabs are uncrimped, and in which said non-com ductive coating extends to mask and cover all said support tabs.

5. The invention claimed in claim 1, in which a bronze bar is affixed to said printed circuit board and has a plurality of pairs of oppositely extending fingers aligned with the bronze bar, each finger being V- notched at its end and being adapted to resiliently sup- 'port one reach of an ionization wire.

6. The invention claimed in claim 1, in which two' nonconductive printed circuit boards are provided, one adjacent either end of the plates, each board having affixed thereto remote from the plates a bronze bar, each bronze bar having a plurality of pairs of oppositely extending fingers aligned with the bronze bar, each finger being V-notched at its end, and in which there is further provided an ionization wire resiliently supported in sinusoidal configuration between said fingers of said bronze bars.

7. The invention claimed in claim 3, in which the support tabs for the negative plates and the positive contact tabs lie to the same side of the line of negative contact tabs, and in which the support tabs for the positive plates and the negative contact tabs lie to the same side of the line of positive contact tabs.

Claims (7)

1. In an electrostatic precipitator construction which includes a plurality of parallel, aligned and alternately arranged positive and negative plates, the combination of: a non-conductive printed circuit board disposed adjacent the ends of the plates and perpendicular thereto, an integral contact tab on each positive plate registering in a positive contact slot in said board and crimped over, a printed positive bus bar on said board joining all said positive contact slots, an integral contact tab on each negative plate registering in a negative contact slot in said board and crimped over, a printed negative bus bar on said board joining all said negative contact slots, each plate having at least one integral support tab spaced from its contact tab and registering in a support slot in said board, a resilient, adhesive, conductive coating masking each bus bar and its crimped contact tabs, and a resilient, adhesive, non-conductive coating covering the conductive coating.

2. In an electrostatic precipitator construction which includes a plurality of parallel, aligned and spaced-apart collector plates, the combination of: a non-conductive printed circuit board disposed adjacent the ends of the plates and perpendicular thereto, some at least of the plates each having an integral contact tab registering in a contact slot in said board and crimped over, a printed bus bar on said board joining all said contact slots, a resilient, adhesive, conductive coating masking the bus bar and the crimped contact tabs, and a resilient, adhesive, non-conductive coating covering the conductive coating.

3. The invention claimed in claim 1, in which said positive contact slots and said negative contact slots are arranged in two parallel, spaced-apart lines.

4. The invention claimed in claim 1, in which the support tabs are uncrimped, and in which said non-conductive coating extends to mask and cover all said support tabs.

5. The invention claimed in claim 1, in which a bronze bar is affixed to said printed circuit board and has a plurality of pairs of oppositely extending fingers aligned with the bronze bar, each finger being V-notched at its end and being adapted to resiliently support one reach of an ionization wire.

6. The invention claimed in claim 1, in which two nonconductive printed circuit boards are provided, one adjacent either end of the plates, each board having affixed thereto remote from the plates a bronze bar, each bronze bar having a plurality of pairs of oppositely extending fingers aligned with the bronze bar, each finger being V-notched at its end, and in which there is further provided an ionization wiRe resiliently supported in sinusoidal configuration between said fingers of said bronze bars.

7. The invention claimed in claim 3, in which the support tabs for the negative plates and the positive contact tabs lie to the same side of the line of negative contact tabs, and in which the support tabs for the positive plates and the negative contact tabs lie to the same side of the line of positive contact tabs.

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