US2215298A - Electrical precipitator device - Google Patents

Description

Sept. 17, 1940. PEGG 2,215,298

ELECTRICAL PREGIPITATOR DEVICE Filed July 26, 1939 a smu-snm 1 WITNESSES: l8 6 INVENTOR Edward HRPegy.

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WITNESSES: INVENTOR I Edward h. E. Peggy.

a 7M M4 B ATTORNEY Patented Sept. 17, 1940 UNITED [STATES PATENT OFFICE ELECTRICAL PRECIPITATOR DEVICE Edward H. R. Pegs, Lakewood, Ohio, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 26, 1939, sci-m No. 286,577

'22 Claims.

My invention relates to a construction adapted for a precipitator employed to electrically precipitate from air, or other gaseous mediums, any contained or suspended dust particles, or fogs, or other particulate matter, which for brevity, is hereinafter collectively referred to as dust.

More particularly, my invention relates to a gas-purifying devicein which the gas is first blown through an ionizing zone wherein the dust is given an electric charge, and then blown through a separate precipitating zone wherein the charged dust is electrically collected or precipitated. A preferred form of such unit comprises an ionizing chamber having electrodes for establishing an ionized field about one of the electrodes usually in the form of awire and thereby charging the dust; while the precipitating zone usually comprises a plurality of spaced alternately insulated and uninsulated plates, between the spaces of which the charged dust passes. By applying a potential to these alternate plates, the charged dust is made to migrate toward one of them and precipitate thereon.

In accordance with my invention, I provide a cell unit or device which contains both the ionizing chamber and the precipitating or dust collecting chamber, it being a primary object of my invention'to provide a simplified construction of the cell unit which is economical to manufacture, and capable of easy manipulation for inspection, repair, or cleaning.

It is an object of my invention to construct such a cell unit as a whole with an outer casing formed especially to contain the ionizing and collecting chambers, and forming part of each, and in addition, having a side or sides so formed that they may act eiilciently as one of the electrodes in the ionizing chamber, and as two of the plates of the collecting chamber.

It is a further object of my invention to provide, for the ionizing chamber, a structure embodying as a unit or item one of the electrodes and one or a pair of ionizing wires; the unit or item as a whole being capable of ready and easy insertion into or removal from the cell unit. Such a construction enables me to assemble the major part of the ionizing chamber outside the cell unit, and moreover enables me to minimize the number of difierent standard items required for the construction of cell units of difierent widths. The items are so designed that by merely juxtaposing two, or at the most, three, different types of standard items, I can accommodate any width of cell unit.

It is an ancillary object of my invention to provide a construction for a cell unit from which the part containing or supporting the fine ionizing wires can easily be removed so that the wires may be replaced or cleaned, and which can thereafter be easily replaced in the cell unit.

The many features of my invention enable me to obtain a cell unit of minimum size which is complete in itself, having therein an ionizingchamber and collecting chamber, and which may be employed side by side with other cell units to accommodate a large range of different sizes of air cleaning systems.

Other and more particular objects of my invention will be apparent from the following description thereof taken in conjunction with the accompanying drawings, in which:

Figure 1 is a longitudinal cross-sectional view through a cell unit built in accordance with my invention, with the arrows indicating the direction of gas flow Fig. 2 is a top view of the cell unit with certain parts omitted for the sake of clarity;

Fig. 3 is a cross-sectional view taken along the line IIIIlI of Fig. 1;

Fig. 4 is a front view of a removable item for the ionizing chamber;

Fig. 5 is an enlarged sectional view taken on the line VV of Fig. 4;

Fig. 6 is a top view of a ground electrode for the item of Fig. 4;

Figs. 7 and 8 are, respectively, views from opposite ends of the electrode of Fig. 6;

Figs. ,9 and 10 are, respectively, enlarged, front and side views of a hook member for securing one end of the removable item of Fig. 4, to the casing of the cell unit;

Fig. 11 is an enlarged side view of an end bracket for supporting an end of an ionizing wire comprising part of the removable item of Fig. 4;

Figs. 12, 13 and 14 are, respectively, front, side and top views of one of two similar members comprising the outer casing for the cell unit of my invention;

Figs. 15, 16 and 1'7 are enlarged, partial side views of an outer casing side showing modified forms of obtaining a united ground electrode for the ionizing chamber; and

Fig. 18 is a view corresponding to that of Fig. 5, but showing a modified form of a removable item for an ionizing chamber, any number of which may be employed with the removable item of Fig. 4 for cell units of any desired width.

The cell unit of my invention can be used in, industrial electrical dust precipitator systems, or for systems in which dust is removed from air to be breathed or on any other suitable system in which it is desired to remove the dust from gases. adaptable to a precipitator such as shown and described in Patent No. 2,129,783, granted to G. W. Penney on September 13, 1938, and assigned to the Westinghouse Electric 8: Manufactoring Company. A significant feature of the precipitator described in the patent, and therefore also of my cell unit, is that the ionizing wire or wires are oi? such small diameter that utilizable ionization of the dust in the gas may be obtained at a wire charging voltage yielding negligible ozone generation and requiring low power input when the precipitator is used commercially in air cleaning systems. An ionizing wire of less than 32 mils thickness may be utilized, but in ordinary practice, the wire is much finer than this upper limit and is frequently a tungsten wire 5 mils or thereabouts in diameter.

Cooperating with one or more of such ionizing wires to establish an electrostatic field is one or more tubular ground electrodes of relatively large diameter compared to the tungsten wires and may be, for example, at least 1%" for a unit built in accordance with my invention.

The diameter of the ionizing wire is comparatively relatively small or fine compared to the diameter of the tubular, ground electrode; and conversely, the electrode is relatively large compared to the ionizing wire, and, in general, it is preferred that the ground electrode be larger than the ionizing wire. A direct current high potential is applied across the electrodes and the ionizing wire for creating the electrostatic field necessary for ionization, and in practice it is preferred that one side of this potential be grounded, preferably the side connected to the larger electrodes. These electrodes may, therefore, be designated as ground electrodes for the purposes of identification.

Referring more particularly to the drawings, the call unit comprises an outer casing 2, having an ionizing zone -4, and a precipitator or collecting zone B.

The casing itself is rectangular in cross section, as more particularly indicated in Figs. 2 and 3, and has open ends. The ionizing zone includes the ionizing chamber at the gas inlet side of the casing and adjacent to the ionizing chamber is the precipitating chamber which occupies the major part of the space within the casing. In such a unit gas enters the ionizing chamber where the dust in the gas is suitably ionized and continues to fiow through the casing where the collecting chamber will precipitate the ionized dust.

The particular casing of my cell unit is formed from two properly fabricated sheets of metal, each of which ultimately assumes a form such as shown in Figs. 12-14. As may be observed from these figures, in final form each of these members of the casing is L-shaped when viewed from the top, one arm of the L comprising one side U of the casing and the other arm comprising a side lfl perpendicular to the side 8. The free end of the side It is bent over to provide a perpendicular flange I2 which may be suitably drilled or otherwise formed with holes l4 which cooperate with similarly placed holes in the free end of a side 8' of the second member so that the two members may be suitably secured together to form the. casing 2.. the second member hav- However, my cell unit is especiallying a similar flange cooperating with the side l of the first member.

In the embodiment shown in Fig. 13 the side 8 has a portion extending above the end of the side II and this portion is turned back upon itself to provide a fiat part i6 abutting the inside surface of the side 8, and a curved portion l8 extending from the fiat part IS, this curved portion I8 serving as a ground electrode in the ionizing chamber. The length of the extending portion of the side 8 forming the bent-over elements l6 and i8 is suitably determined so that the bend 2! at the top of the side 8 is approximately fiush with the contiguous edge of the side I0, and the curved portion II, which serves as a ground electrode and will be so designated, is properly spaced with respect to the ionizing wires later assembled in the casing.

When two members, such as shown in Figs. 12, 13 and 14, are assembled to form the rectangular outer casing of the cell unit, the two ground electrodes II will be substantially parallel, and transverse of the sides 8. These electrodes form part of the ionizing chamber, and in accordance with my invention the rest of the ionizing chamber is formed primarily by an item of construction indicated in its entirety by the reference character 22 (Figs. 4 and 5). This item is built about a ground electrode 24 which is a hollow metallic tube of a length slightly less than the distance between the inside surfaces of the casing sides ll and II.

The electrode 24 acts as a support for two insulators 2i and 28' intermediate its ends and to serve this purpose, the electrode is drilled to provide two parallel holes 28 and 28'. Bolts II and fl'pass through the holes 22 and 2!, respectively, to secure one end of the insulators 26 and 2|, respectively, to the electrode 24, in an obvious manner, for supporting and securing the insulators to the electrode 24 intermediate its ends. The size of the insulators and the position of the holes in it are chosen so that the peripheries oi the insulators are well spaced from the ends of the tube 24. This permits any apparatus supported by the other ends of the insulators to be properly insulated from the sides II and ID of the casing.

A bar 32 extends'parallel to the electrode 24 and is secured to the other ends of the insu lators by any suitable means such as bolts and nuts 34 and 34', respectively. The bar 42 is of shorter length than the electrode 24 and is symmetrically placed with respect thereto. This bar serves to support a plurality of end brackets 38 and I8, and as many intermediate brackets II as the length of the particular cell unit requires, it being understood, of course, that the dimensions of the cell unit may be varied.

The brackets are generally U-shaped, as more particularly shown in Figs. 2 and 5, and are preferably welded to the bar 32 although any other .provided with notches 4' and 48', respectively and the ionizing wires BI and 42 are stretched between the end brackets and secured thereto, a turn or two being wound around the arms of the brackets at the notches 48 and 48' so that'the wires may be suitably maintained in tension.

The intermediate brackets, such as 38, are employed to insure against breakage of the ionizing wires, and to facilitate hanging of the wires, since it has been found that if the wires are long, it is preferable to confine them at frequent intervals, say about every eight inches, to protect them against vibration, or breakage, or in remote cases against excessive sagging- The intermediate brackets 38 are also U-shaped and generally lie in a plane with the cross arm transverse to the bar 32 and the electrode 28, and have depending arms provided with extremities which have apertures located so that the ionizing wire may be passed therethrough or hooked therein. A form of intermediate bracket is disclosed and claimed in patent application filed July 26, 1939, Serial No. 286,589 of R. A. Nielsen, filed concurrently herewith and assigned to the Westinghouse Electric 8: Manufacturing Company. For the present description of this intermediate bracket, it sufllces to state that its arms are approximately perpendicular to the central portion, while needles form the extremities of the arms, with the eyes of the needle substantially in line with the ionizing wires.

From the preceding description of the structure oi. the item of Fig. 4, it is quite apparent that the electrode 28, the insulators, the bar 81, the ionizing wire supporting brackets, and the ionizing wires form a complete unit or item by themselves. To enable this unit or item to be properly placed and secured in the casing, one

end of the electrode 28 has a metallic pin 88 passing therethrough with protruding ends, and welded or otherwise secured to the electrode, while the other end is plugged by a metallic insert 58 which has a central, threaded aperture 60.

A hook member 82 adapted to latch the ends of the pin 56 is suitably fastened in proper position to one side ll of the cell unit casing, while the opposite side ll of the casing is provided with an aperture'through which a bolt or screw 84 may be inserted for en aging the threaded aperture 80 at the other end of the electrode 24. It is quite obvious that by tightening the bolt 64, the pin 56 is securely seated in the hooks 68 of the hook member 82 and that the entire unit 22 will be suitably and rigidly secured in the cell unit.

In accordance with my invention, the parts of the item 22 are so proportioned that the ionizing wires 58 and 52, the ground electrodes l8, and the ground electrode 24 are all aligned, with an ionizing wire intermediate a pair of the ground electrodes, and preferably centrally. positioned between them in the plane of their axes. It may be observed that the end brackets 86 and I6 terminate somewhat short of the sides ill and I8 so that the metallic ionizing parts which include the bar 82, the ionizing wires and the wiresupporting brackets for the wires are suitably insulated from the metallic casing. In the preferred form of connecting electrical potential to the ionizing chamber, the casing is grounded as indicated schematically at 88, and is negative with respect to the potential of the ionizing parts, before mentioned, to which the positive terminal of the direct current source of energy may be connected as schematically indicated by the uppermost plus sign in Fig. 1.

Immediately below the ionizing chamber, an

X-shaped.cross-brace II is welded between two opposed sides of the casing and helps to maintain the cell unit rigid. Below this brace is the precipitating chamber 8.

The precipitating chamber includes a plurality of slotted bars 12 welded or otherwise secured to I the sides 8 and 8 of the casing, and between which the grounded plates I8 are secured.

Intermediate the cross-brace I8 and the upper grounded bar I! are additional cross-pieces 18 extending between two sides 8 and 8 of the casing, and to which are secured insulators 18 which insulatedly support through the medium of suitable brackets "88, additional slotted bars 82. A somewhat similar construction is provided at the other end of the collecting zone to provide additional slotted supporting bars 84. Insulated plates 88 are secured in the slots of the bars 82 and 8|. It may be observed that the farthermost ones of the plates 88 are spaced from the sides I! and I0 so'that, in effect, the last two sides form part of the collecting chamber.

At this point it may be noted that the easing sides are usually provided with additional apertures or means for securing the different elements such as the supporting bar I8, the ground plate supporting bars I2, and that furthermore, suillciently large apertures are provided in the sides to convey a high potential to the insulated plates of the precipitating chamber, and, if desired, to the ionizing elements of the ionizing chamber. The manner in which the source of power can be connected to my cell is obvious to one skilled in the art, and may take the form shown in the aforesaid Penney patent.

From the construction of my invention as described, it is apparent that a cell unit has been provided in which there is very little, if any, space wasted. Since it has been designed with an outer rectangular casing, it is apparent that a plurality of such units may be assembled side by side to accommodate as large a volume of gas as a particular installation demands.

In Figs. 15, 16 and 17, I show modified forms of ground electrodes united with sides of the casing. In Fig. 15 an elongated sheet of proper size may first be formed with two flat end portions 90 extending from the edges of a semior particylindrical central portion 92. The ends 98 can be welded or otherwise secured to the side 8" of the casing, which corresponds to the sides 8 and 8', so that the curve portion 92 serves as one of the ground electrodes for the ionizing chamber. In Fig. 16, the ground electrode 94 is formed very similar to the manner in which the ground electrode l8 of the first embodiment is formed, that is, an end portion of the side of the casing is turned back upon itself. The distinction between the ground electrode of Fig. 16 and that of Fig. 13 lies in the fact that the edge of the ground electrode 94 terminates close to the side 8" of the casing, whereas that of the electrode I8 .is spaced somewhat from the side 8 of the casing. In Fig. 1'7 the casing side has been bent or pressed to provide the ground electrode.

The shape that the ground electrodes may take or the manner in which it is united with a side of the casing is subject to obvious modifications. However, as fully described in the aforemen tioned Penney patent I prefer to have a curved surface for cooperating with the ionizing wire, and to have the length of the ground electrode at least as large, and preferably slightly larger, than the length of the ionizing wire.

can be used, per se, with a casing with sides as shown in Figs. 12 through 14. A cell unit thus constructed would comprise three ground electrodes with two intermediate ionizing wires. In the event that a wider cell unit is desired, the removable item 22 may still be employed in cooperation with a second standard removable item indicated in its entirety by the reference numeral 86, and shown in Fig. 18. This item 96 is similar in all respects to the item 22 except that it employs L-shaped brackets rather than U-shaped brackets.

As may be observed in Fig. 18', the removable item 96 includes the ground electrode 24", insulators 26", a bar 32", and brackets indicated at 98 which differ only from the brackets of item 22 in having one arm rather than two.

In forming a wider cell unit, the item 96 may be secured in the casing in the same way that the item 22 is, with the electrode 24" in line with, and to the side of, one of the ionizing wires 50 or 52. This will place an ionizing wire I between one of the electrodes I8 and the electrode 24" and will produce a unit including four ground electrodes and three ionizing wires. Accordingly it is manifest that by juxtapositicning a single item 22 with one or more items 96 I can attain as wide a cell unit as may be desired.

However, I can obtain a wider cell unit in another manner by employing only items such as the item 22, together with items consisting of a lone ground electrode similar to the electrode 24 As an example for the alternative construction of an ionizing chamber which comprises five ground electrodes and four intermediate ionizing wires, two items 22 may be properly. positioned in an appropriate casing with a tubular electrode between the centrally disposed ionizing wires, this lone electrode being obviously tubular with fastening means at each end whereby it may be fastened to the casing in parallel relation to, and between the two removable items .22. F

While I have described my invention in preferred forms thereof, I desire it to be distinctly understood that I am not altogether limited to these forms which in and of themselves suggest other forms and embodiments.

I claim as my invention:

1. In a device of the class described generally having an ionizing zone and a precipitating zone successively in the path of a gas-flow; an outer casing having therein an ionizer chamber, said casing including opposed sides; said ionizer chamber including as a united unit: a relatively large, curved electrode, at least one relatively fine wire, and means to support said wire insulated from said electrode and said'casing; and fastening means on opposed sides of said casing, and cooperating with .said electrode detachably to secure said unit to said casing.

2. In a device of the class described generally having an ionizing zone and a precipitating zone successively in the path of a gas-flow; an outer metallic casing having therein an ionizer chamber, said casing including opposed sides; said ionizer chamber including as a united unit: grounding means comprising a relatively large, curved electrode, at least one relatively fine ionizing wire, and means to support said wire insulated from said grounding means and said casing; fastening means on opposed sides of said casing, and cooperating with said grounding means to detachably secure said unit to said casing with said large electrode in intimate con ducting contact to said casing.

3. In a device of the class described generally having an ionizing zone and a precipitating zone successively in the path 01' a gas-flow; an outer metallic casing having therein an ionizer chamber, said casing including pairs of opposed parallel sides; said ionizer chamber including as a united unit: grounding means comprising a relatively large, tubular electrode, ionizer means comprising at least one relatively fine wire, and means to support said wire insulated from said grounding means and said casing; means to secure said unit to said casing with said electrode substantially parallel to a pair of said opposed sides, the last said means including devices on another pair of said opposed side cooperating with expedients on each end of said grounding means to detachably secure the said unit to said casing.

4. In a device of theclass described generally having an ionizing zone and a precipitating zone successively in the path of a gas-flow; a metallic outer casing having therein an ionizer chamber, said casing being substantially rectangular in cross-section, relatively large electrodes extending from opposite sides of said casing andcomprising part of said ionizer chamber, said electrodes being united with said casing and in the nature of parti-cylinders with their curved portions toward the inside of said casing; said ionizer chamber further comprising a relatively large electrode between and substantially parallel to the first said electrodes, a plurality of ionizing wires, and means to support said wires intermediate said electrodes, and insulated from said electrodes and said casing.

5. In a device of the class described generally having an ionizing zone and a precipitating zone successively in the path of a gas-flow; a metallic outer casing having therein an ionizer chamber and a precipitator chamber, said casing being substantially rectangular in cross-section with the ionizer chamber near one end thereof and the precipitator chamber adjacent to said ionizer chamber; relatively large electrodes extending from opposite sides of said casing and comprising part of said ionizer chamber, said electrodes being united with said casing and in the nature of parti-cylinders with their curved portions toward the inside of said casing; said ionizer chamber further comprising as a united unit; a relatively large electrode substantially parallel to the first said electrodes, a plurality of ionizing wires, and means to support said wires intermediate said electrodes, and insulated from said electrodes and said casing; and fastening means cooperating with the sides of the casing other than the first said sides, and with said unit to detachably secure said unit in said casing.

'6. In a device of the class described generally having an ionizing zone and a precipitating zone successively in the path of a gas-flow; a metallic outer casing having therein an ionizer chamber and an adjacent precipitator chamber, said casing being substantially rectangular in cross section with pairs of opposed parallel sides; said precipitator chamber comprising a plurality of alternately insulated and uninsulated, substantially uniformly spaced, precipitator electrodes.

parallel to a pair of said opposed sides which, in effect, form uninsulated electrodes; said ionizer chamber comprising a plurality of uninsulated, relatively large, curved electrodes substantially parallel to a second pair of said opposed sides, the last said sides each being united with one of having an ionizing zone and a precipitating zone successively in the path of a gas-flow; a metallic outer casing having therein an ionizer chamber and an adjacent precipitator chamber, said casing being substantially rectangular in cross section with a pair of opposed parallel sides; said precipitator chamber comprising a plurality of alternately insulated and uninsulated substantially uniformly spaced, precipitator electrodes parallel to a pair of said opposed sides which, in eflect, form uninsulated electrodes; a cross brace between said chambers secured-to sides of said casing to reenforce it; a pair of spaced insulators mounted between said chambers; supporting and spacing means for said insulated plates, the last said means being secured to said insulators, said insulators being for the most part below said brace and insulatedly spaced therefrom; said ionizer chamber comprising a plurality uninsulated, relatively large, curved electrodes transverse to said plates, ionizing wires, and means including insulators supporting said ionizing wires intermediate said curved electrodes, said means spaced from said brace, the last said insulators being on the side of said ionizer chamher away from said brace.

8. In a device of the class described generally having an ionizer chamber and a precipitator chamber in the path of a gas-flow; an outer metallic casing for said ionizer and precipitator chambers, said casing being substantially rectangular in cross section and open at both ends, said casing including a substantially L-shaped member forming two sides of said casing, one of said sides having a curved electrode united therewith, of parti-cylindrical form and extending transverse to the free edge of said side.

9. In a device of the class described generally having an ionizer chamber and a precipitator chamber in the path of a gas-flow; an outer metallic casing for said ionizer and precipitator chambers, said casing being substantially rectangular in cross section .and including a substantially flat side parallel to the direction of air flow, and comprising part of saidionizer chamber, said side including a turned-over edge having a curved surface protruding toward the inside of said casing.

10. In an electrical precipitator for removing dust from gases, comprising an ionizer chamber through which a gas flows so that the dust therein may be ionized by passing through an electrostatic field, an electrode involved in establishing said field, said chamber including an extended substantially flat, metallic side, said electrode havinga parti-cylindrical curved portion extending transverse to the gas-flow and united to a portion of said side with the curved surface away from said side.

11. The structure of claim 10 in which said electrode has flat portions in the same plane as said side and extending laterally from edges of said curved portion, and said flat portions are secured to said side.

12. The structure of claim 10 in which said electrode is part of said side and is formed by other, and an extremity forming said particylindrical portion having an extreme edge in proximity to the plane of said side.

14. An item for an electrical precipitator which removes dust from gases by providing an ionizing zone through which the gas flows so that the dust therein may be ionized, comprising an elongated relatively large, tubular electrode, having means at each end by which said electrode may be supported in said precipitator, a relatively fine ionizing wire substantially parallel to said electrode, and means to support said ionizing wire on said electrode, the last said means comprising a plurality of spaced insulators insulating said wire from said electrode.

15. The structure of claim 14 in which said electrode is hollow and the first said means comprises a pin secured to and across one end of said electrode, and a plug secured to the other end of said electrode, said plug having bolt accommodations.

16. An item for an electrical precipitator which removes dust from gases by providing an ionizing zone through which the gas flows so that the dust therein may be ionized comprising an elongated, relatively large, electrode, a plurality of insulators, means to secure one end of said insulators and said electrode together with the insulators spaced along said electrode, armed brackets supported by the other end of said insulators, a relatively fine ionizing wire, the arms of said brackets forming supports for supporting said wire in spaced and insulated relation to said electrode.

17. An item for an electrical precipitator which removes dust from gases by providing an ionizing zone through which the gas flows so that the dust therein may be ionized, comprising, an elongated, sustantially-straight, tubular electrode, a plurality of insulators, means to secure one end of said insulators to said electrode intermediate the ends thereof, U-shaped brackets, means to secure said brackets to the other end of said insulators with the arms of the U straddling said electrode in spaced relation thereto, and ionizing wires secured to said arms that are on the same side of said electrode.

18. The structure of claim 17 in which said brackets are similar and said arms are at an angle to said electrode, extending toward, but not as far as, the ends of said electrode.

19. An electrical precipitator having as a part thereof; a metallic casing having sides; and as an additional part: a substantially straight tubular electrode, a plurality of insulators, means to support an end of each of said insulators on said electrode intermediate the ends thereof, a plurality of armed brackets, means to secure said brackets to the other end of said insulators with their arms in spaced relation to said electrode, ionizer means including an ionizing wire secured to certain of said arms in spaced relation to said electrode, and paralleling said electrode; and means to secure said additional part in said casing whereby said brackets and ionizing wire are in spaced relation to said casing sides.

20. An item for an electrical precipitator which removes dust from gases by providing an ionizing zone through which the gas flows so that the dust therein may be charged, comprising an elongated relatively large, tubular electrode, having means by which said electrode may be supported in said precipitator, a relatively fine ionizing wire substantially parallel to said electrode, and means for supporting said ionizing wire, the last said means being supported-by said electrode intermediate the ends of said electrode, the last said means comprising insulator means insulating said wire from said electrode.

21. An electrical precipltator having as a part thereof; a metallic casing having a side providing an electrode; andas an additional part a relatively large ground electrode, one or more ionizing wires, means for supporting said wire or wires in spaced and insulated relation to the last said electrode, the last said means being supported by the last said electrode; and means for securing said additional part in said casing with one of said ionizing wires in spaced and insulated relation to said casing side whereby an ionized field can be established between said casing side, said electrode and said one, ionizing wire.

22. In an electrical gas-purifying Drecipitator for removing dust-particles from a flowing gas by first charging the dust-particles in an ionized electrostatic field and then acting on the charged dustvparticles in a non-ionized electrostatic field, said fields being arranged successively in the direction of gas-flow, electrode means involved in establishing said fields, comprising a substantially integral electrode extending in both said fields, said electrode having a substantially flat plate portion for said non-ionized electrostatic field, said plate portion substantially paralleling the direction of gas-flow, said electrode also having a curved portion for said ionized electrostatic field, said curved portion being substantially transverse to the direction of gas-flow.

' EDWARD H. R. PEGG.

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