Electrostatic Precipitator For High Temperature Operation

Abstract

The precipitator has a series of flat vertical plates which are elongated in a horizontal direction. To prevent buckling of the plates from horizontal expansion when heated, the plates are fixedly mounted in their central portions and allowed to float on end supports so that the ends of the plates may expand freely in opposite directions away from their centers. The end supports comprise rods equipped with necked spacers which maintain uniform spacing of the plates while permitting horizontal movements on the rods during heating and cooling.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is directed to one of the components of the system in my co-pending application Ser. No. 168,019, filed Aug. 2, 1971, on POLLUTION-FREE KITCHEN VENTILATOR.

BACKGROUND OF THE INVENTION

This invention relates to improvements in an electrostatic precipitator for high temperature operation.

The kitchen ventilator disclosed in my above-mentioned application Ser. No. 168,019 includes an electrostatic precipitator, following a grease extractor, for removing smoke and other airborne contaminants in an airstream from a cooking area. The ventilator may extend for a considerable distance horizontally above a series of various types of cooking equipment units which produce grease fumes, smoke, steam and the like that must be removed from the kitchen. In order to treat all the air flowing through a wide ventilating duct, elongated electric precipitating plates are disposed across the whole cross sectional area of the duct, these plates being mounted in cells which are arranged side by side for convenient installation and servicing. The cells are self-draining for hot detergent water washing from time to time within the ventilating duct.

Thus, in normal usage the precipitator plates are exposed to elevated temperatures from the hot air, smoke, fumes and steam rising from the cooking equipment. Flames from a cooking surface may enter the duct from time to time. Also, grease in lower portions of the duct may ignite, exposing the precipitator plates to flame temperatures briefly until the fire extinguishing system comes into operation.

Elevated temperatures from such sources are destructive of conventional precipitators, causing the plates to warp and buckle making the precipitators inoperable. For effective operation the precipitator plates must remain flat and uniformly spaced apart from each other in order to maintain an effective electrostatic field between each pair of plates. The greater the length of the plates the more susceptible they are to damage from thermal expansion and contraction.

Objects of the invention are, therefore, to provide an improved electrostatic precipitator for high temperature operation, to provide an improved precipitator for a kitchen ventilator, to provide a precipitator which is not damaged by brief exposure to flame temperature, and to provide an improved mounting arrangement for the precipitator plates which allows them to expand and contract freely on heating and cooling without warping or buckling.

SUMMARY OF THE INVENTION

In the present construction, the precipitator plates are kept narrow in a vertical direction so that vertical expansion and contraction is not destructive. The plates are elongated in a horizontal direction and provision is made for expansion and contraction in this direction without restraint so that the plates may elongate and contract without distortion.

This is accomplished by providing fixed mountings for the plates at their centers and providing supports which allow free movements of the outer ends away from and toward the centers. The outer ends of the plates have horizontally elongated openings receiving spacers which allow expansion and contraction in a horizontal direction while maintaining uniform spacing between the plates. With this improved type of mounting, the plates are not damaged even by fire in the duct whereby the precipitator is capable of withstanding the extreme conditions encountered in kitchen ventilators.

The invention will be better understood and the foregoing and other objects and advantages will become apparent from the following description of the preferred embodiment illustrated on the accompanying drawing. Various changes may be made, however, in the details of construction and arrangement of parts and certain features may be used without others. All such modifications within the scope of the appended claims are included in the invention.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an isometric view of an electric precipitator cell embodying the ivention;

FIG. 2 is a view on the line 2--2 in FIG. 1;

FIG. 3 is a view on the line 3--3 in FIG. 1;

FIG. 4 is a view on the line 4--4 in FIG. 3; and

FIG. 5 is an isometric view of necked spacer.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In a kitchen ventilator a plurality of precipitator cells C are mounted side by side across the width of a vertical duct so that all of the air moving upward through the duct must pass between vertical metal plates A and B. The plates A and B are relatively narrow in a vertical direction whereby the amount of vertical expansion and contraction on heating and cooling is insignificant and requires no special provision to prevent warping and buckling.

The plates A and B, however, are sufficiently long in a horizontal direction as to cause such expansion and contraction movements to become destructive. If the plates are fixedly mounted at all points of support according to conventional practice, the expansion and contraction distortions are of sufficient magnitude to warp and buckle the plates, rendering the precipitator inoperable.

This difficulty is overcome by fixedly mounting the plates only at their centers and allowing the ends to expand and contract away from and toward the centers. This allows each cell to have a relatively large horizontal width dimension so that an excessive number of cells will not be required to span the width of a wide ventilating duct.

The plates A are fixedy mounted at their centers on two metal rods 10 and the plates B are fixedly mounted at their centers on a metal rod 11. Rods 10 have heads on their right ends engaging a back metal wall 12 of the cell frame. The left ends of rods 10 and 11 project through a front metal wall 15 of the cell and are equipped with nuts 13 and 14. The lower rod 10 also supports one end of a handle 16 for removing the cell from the ventilating duct.

The plates A have holes 20 which fit the rods 10, these plates being separated by plain, cylindrical, metal spacers 21 on the bolts. As shown in FIG. 2, the nut 13 on each rod 10 clamps the plates A tightly between spacers 21 making electrical connection therewith and grounding the plates A to the end walls 12 and 15. One of the rods 10 is utilized for an external ground connection. Plates B have large circular openings 22 surrounding spacers 21 at a distance to avoid making electrical contact with the spacers.

In similar arrangement, the plates B have small circular openings 25 to fit the rod 11 and plates A have large circular openings 26 which surround spacers 21 on rod 11 at a distance. Nut 14 clamps plates B between spacers 21 whereby the plates B are electrically connected to rod 11 which serves as an electrical terminal connection for the insulated plates B. Nut 14 is tightened on an insulating block 27 having a shoulder 28 which centers the insulating block in a hole 29 in front plate 15. Insulating block 27 has a projection 30 to clamp the front plate B against the first spacer 21 on rod 11. A head on the opposite end of rod 11 engages a similar insulating block 27 in back wall 12. When the nuts 13 are tightened on the two rods 10 and the nut 14 is tightened on rod 11, the centers of all the plates A AND B are fixedly mounted in the frame of cell C.

As seen in FIG. 3, the ends of plates A are slidably supported on rods 35 and the ends of plates B are slidably supported on rods 36. The right end of rod 35 has a head engaging the outside of back end wall 12 and the left ends of both rods are threaded to receive nuts 37 and 38. These rods support the plates by means of necked metal spacers 40. Each spacer 40 has a neck 41 on one end of a length slightly exceeding the thickness of plates A and B. Thus, when the nut 37 is tightened against front wall 15 and the nut 38 is tightened against insulating block 27, the spacers 40 are clamped tightly against each other without clamping the plates A and B. A head on the opposite end of rod 36 engages a similar insulating block 27 in back wall 12.

Each plate A and B has a horizontally elongated opening 45 receiving the neck 41 on a spacer 40. The vertical dimension of opening 45 slightly exceeds the diameter of neck 41 to allow relative vertical movement between the plate and the spacer but the vertical dimension of opening 45 is insufficient to permit the main body of the spacer to pass through the opening. At each opening 45 a plate is confined between a shoulder 42 on one spacer and the end of the adjacent spacer. The horizontal dimension of opening 45 is sufficient to provide for the horizontal expansion and contraction of the plates.

Plates A have large openings 47 surrounding the spacers 40 on rod 36 and plates 8 have large openings 47 surrounding the spacers 40 on rod 35.

As seen in FIG. 1, a rod 35 secures the left end of handle 16 and additional rods 35 loosely support upper portions of the outer ends of the plates A. Additional rods 36 loosely support plates B in other locations as shown.

The frame of cell C further includes a bottom plate 55 having vertical air guide vanes 56 struck out from the plate, leaving an open bottom at 57. Horizontal ionizing wires extend between vanes 56, these wires (not shown) being supported at their ends on a pair of bars 60 at opposite ends of the cell. The ends of bars 60 are supported in insulating blocks 61, each bar having a terminal 62 for convenient external circuit connection to one or the other.

In operation in a ventilating duct, the airstream flows in an upward direction between vanes 56 and precipitating plates A and B. The ionizing wires between vanes 56 impart strong electrical charges on particles of smoke and other airborne contaminants and the electrical field existing between plates A and B effects precipitation of the charged particles on the plates. Hot detergent water sprays in the duct wash the accumulation of particles off the plates from time to time, this water draining through the open bottom of the cell between vanes 56.

A high temperature condition in the duct does not warp the precipitating plates because the outer ends of all the precipitating plates have freedom of movement on supporting rods 35 and 36 during expansion and contraction. The uniform spacing of the plates is thereby maintained and the precipitator is not damaged by high temperature conditions.

Claims

Having now described my invention and in what manner the same may be used, what I claim as new and desire to protect by letters Patent is:

1. An electrostatic precipitator comprising a group of metal plates, means fixedly mounting central portions of said plates in spaced parallel relation, and means supporting marginal portions of the plates for expansion and contraction movements away from and toward said central portions.

2. A precipitator as defined in claim 1, said plates being of elongated rectangular shape and said marginal supporting means being disposed at opposite ends of the plates.

3. A precipitator as defined in claim 1, said central mounting means comprising a rod extending through said plates, spacers on said rod between said plates, and means on said rod clamping said plates and spacers together; said marginal supporting means comprising rods extending through said plates, spacers on said rods between said plates, necks on said spacers of slightly greater length than the thickness of the plates, said necks extending through openings in said plates and bearing against adjacent spacers on said rods, said openings being larger than said necks, and means on said rods clamping said necked spacers together end to end while permitting freedom of movement of said plates on said neck portions of said spacers.

4. A precipitator as defined in claim 3, all of said spacers being metal.

5. A precipitator as defined in claim 3, said plates comprising a first set of plates for energization at one potential, a second set of plates for energization at a different potential, the plates of said two sets being alternately disposed, said spacers on said central mounting rod clamping said first set of plates and extending through large openings in said second set of plates, and said necked spacers on said marginal supporting rods extending through large openings in said second set of plates; a second central mounting rod having spacers clamping said second set of plates and extending through large openings in said first set of plates; and additional marginal supporting rods having necked spacers supporting said second set of plates and extending through large openings in said first set of plates, whereby said two sets of plates are insulated from each other.

6. A precipitator as defined in claim 1, said plates being disposed in vertical positions, and a series of vertical guide vanes under the lower edges of said plates for directing an upward current of air between said plates.

7. A precipitator as defined in claim 6 including a pair of ionizing wire supports extending along opposite ends of said guide vanes.