US2631687A - Rotary plate electrical precipitator - Google Patents

Description

March 17, 1953 J, DOHRER 2,631,687

ROTARY PLATE ELECTRICAL PRECIPITATOR Filed April 21, 1951 4 Sheets-Sheet 1 //\/A/E NTU FRANCIS J. DOHIZEIZ v MMJ/M March 17, 1953 DOHRER 2,631,687

ROTARY PLATE ELECTRICAL PRECIPITATOR Filed April 21, 1951 4 Sheets-Sheet 2 2 z 4. Z25 Z6 25 25 5 Z2 '4 23 F [I ";|l:.-

' w 'rgmgr m 30 .30 76 //\//E/\/ TU FRANCIS J. DOHRER @M/M Q March 17, 1953 J, DOHRER 2,631,687

ROTARY PLATE ELECTRICAL PRECIPITATOR Filed April 21, 1951 4 Sheets-Sheet 3 [46 {70 g I I //\/A/E/\ TUE FRANCE J. DOHRER.

A TTUFQA/gWE 4 Sheets-Sheet 4 M G/V7271? mamas J. DOHRE-R F- J. DOHRER ROTARY PLATE ELECTRICAL PRECIPITATOR March 17, 1953 Filed April 21, 1951' Patented Mar. 17, 1953 ROTARY PLATE ELECTRICAL PRECIPITATOR Francis J. Dohrer, Seattle, Wash.

Application April 21, 1951, Serial No. 222,209

14 Claims. 1

This invention relates to improvements in the removal of dust and other suspended particles from an air or gas stream by electrical precipitation, and is a continuation-in-part of my prior 1 application Ser. No. 787,843, filed November 24,

1'94? (now abandoned).

Many forms of electrical precipitators have heretofore been devised for removing foreign materials carried in suspension in a flowing gaseous stream. The process as generally practiced involves directing the dust laden gas stream through an ionizing zone to electrically charge any particles of matter in the stream. The gas stream carrying such charged particles is then channelled immediately through a precipitating zone having conducting surfaces which are charged with a unidirectional electrical polarity opposite in sign to that of the charged particles. The charged particles in the gas stream are thereby subjected to the attractive influence of the opposite polarity on the conducting surfaces, with the result that the particles are deflected toward such surfaces by a gravitational movement which tends to separate the particles from the air stream. The electrical phase of the separating action is completed when the particles reach the conducting surfaces and attach themselves thereto while the gaseous stream proceeds, relieved of much of its burden of suspended matter.

In precipitators heretofore known and used, the electrical phases of the separating action, comprising the charging of the dust particles and the precipitating of the charged particles on conducting plates, have been quite efficiently accomplished, under favorable conditions, so that a gaseous stream containing very fine particles, even as fine as smoke particles, can be very effectively cleaned. Prior devices, however, are inadequate to handle large concentrations of dust, and they offer no satisfactory solution to the ultimate problem of removing the adhering particles from the collecting surfaces after they have been captured and accumulated by electrical precipitation. Expedients such as vibrating the dust covered surfaces to shake the particles loose, or washing the surfaces with water or oil, have been commonly resorted to, but such expedients usually require that the precipitating machine, or at least a part of it, be shut down from time to time to clean out the dust. Intermittent washing or cleaning of the collecting surfaces is inherently unsatisfactory because the dust accumulation tends to insulate the surfaces so that the machine can operate at its highest efiiciency only immediately after cleaning. Moreover, there is a time element involved in that the dust after a time may leave the collecting surfaces and re-enter the gas stream if the surfaces arenot oiled to hold the dust. Such equipment, therefore, becomes cumbersome and complicated and unsuitable for continuous automatic operation. Arrangements have also been proposed for cleaning out the dust while the machine is in operation, but known machines of this type leave the dust in a fluid medium requiring further treatment for ultimate disposal of the dust.

Conventional electrical precipitating machines are limited in use to gas streams carryingfrelatively small concentrations of dust particles; otherwise they would accumulate dust so quickly that the charged plates would lose their power of attraction and require cleaning so often as to render them impractical for use where the gas stream carried large concentrations of dust, as in industrial plants.

The general objects of the present invention are, therefore, to provide an improved apparatus for accomplishing the electrical precipitation of dust and the like from an air or gaseous stream in a continuous operation in compact and inexpensive automatic equipment not requiring frequent attention. Other objects are to provide an apparatus for the purpose described which will operate substantially indefinitely, without attention or interruption to service, which may be employed to separate different kinds and sizes of dust particles, and which involves a relatively small unit of equipment wherein all parts of the equipment are allowed to function at all times without any part being taken out of service periodically for cleaning. Another object is to provide apparatus for separating dust from an air stream and delivering it to a point of disposal in a substantially solid and quiescent state and not entrained in a gas or liquid requiring still further separation. Another object is to provide apparatus for keeping the precipitating plates clean to operate at their highest efficiency at all times. Another object is to provide apparatus for handling gas streams carrying a relatively large concentration of dust, such as is found in industrial plants, wherein the accumulated dust is removed quickly and continuously from the charged plates so that clean surfaces are presented continuously on which to precipitate the dust particles.

These and other objects and advantages will become apparent as the description proceeds with reference to the accompanying drawings illustrating two embodiments of the invention. It is to be understood, however, that the drawings are for the purpose of illustrating the invention, and not for the purpose of limitation. Various changes in th construction and arrangement of the apparatus will occur to persons skilled in the art, and all such modifications within the scope of the appended claims are included in the invention.

In practicing the present'invention, thega's to be cleaned is first directed through an ionizing zone having ionizing electrodes to produce electrical charges of a given polarity on particles passing through the zone. A precipitatin'gizone follows the ionizing zone and comprises-spaced, moving precipitating surfaces on charged oncular plates or discs which revolve in the gas stream. The movement :of the precipitating plates is arranged to carry the precipitated dust, which has accumulated thereon, out'of the flow -of .gas and into a quiescent electrode cleaning "chamber. in the-electrode cleaning chamber the dust is'wiped off the precipitating plates by "wipers which are also rotatably mounted and dejposited inthe bottom of the chamber on an endfless "belt conveyor which carries the dust in a "substantially solid and quiescent state to a suitable storage bin or other point of disposal entirely removed from "the original gas stream. "Suitable seals andwipe'rs are provided to pre- Vent "dust in the electrode "cleaning chamber from re-entering the gas stream in the precipitating "chamber. The process is continuous and can run indefinitely, makingit especiallys'uitable for "ventilating and. air conditioning systems han- "dlin'g air for breathinglpurposes, "for'c'leaning air and gases discharged from manufacturing processes, and for the recovery of valuable dust therefrom. The movable parts of the apparatus "may be operated at different speeds to vary the capacity of a particular apparatus without changing its size, or affecting its efficiency, so that .by conventionalstandards a relatively small apparatus can' remove an unusually large amount of dust in a given'time.

In the drawings:

Figure 1 is a longitudinal'se'ctional view, taken on the line ll of Figure 2, showing an apparatus embodying the principles of the invention;

Figure 2 is a cross sectional view taken on the .line 2-2 of Figure 1;

Figure 3 is afragmentary sectional view taken .on the .line 3-3 ofFigure'I;

.Figure 4 is a fragmentary Jsectionaliview' taken on theline 4- 4 .of Figure 1,;

.Figure 5 is a sectional view "in side elevation illustratinga second andpreferred embodiment of the invention;

Figure Sis a .top'plan view of the apparatus shown in Figure 5, with the top of the casing removed and certain parts broken away;

Figure 7 is an enlarged sectional view taken on the line 'l----'! of Figure 5;

Figure 8 is a sectional view taken on the line 8-8 of Figure 7 Figure 9 is a perspective view of one of the seal supports shown in Figure 5; and

Figure 10 is a fragmentary perspective view .of an oil pipe for the felt wipers.

The present treatment is intended to operate upon the dust and other particulate matter in a stream of movinggas, and so the apparatus for carrying out the method of the inventioncomprisesa casing 9 having a passage for directing such a moving stream of gas therethrough. Gas to be cleaned is directed into an intake passage in containing the necessary elements of an ionizing zone for producing electrical charges on the particles carried in suspension in the gas stream. The ionizing zone consists of a plurality of rod-like negative electrodes =II grounded to the outer casing 9 and a .series of positive wires-I12 disposed between the negative electrodesand insulated from the casing, as shown in Figure 3. One end of each wire i2 is anchored in a stationary fitting l3 insu latedly mounted in one wall of the passage l0 and "the other end of the wire is attached to a -suitable tensioning device in an opposite wall of .the passage. The tensioning device in the present instance comprises a shank l4 having an eye ou oneienduforattachment to the electrode wire [2 and threads on the other end to receive a tensioning nut i5 bearing against the outer end of a tubular fitting ieiinsulated'ly mounted in the casing. Theelectrodes 1 .andiz are renergized to a suitablepotential bya conventional source of unidirectional voltage so that when'a stream of gas carrying dust'particles is directed through the ionizing zone in the passage Hi, the dust particles receive positive charges from the ionizing 'wires !2 in 'a manner well understood in the art. Thus the wire l'l-from the casing 9 is connected with the "negative side of the voltage source and the wire I efrom all the electrodes 12 is connected with the positive 'side of the voltage source.

From the ionizing zone :the dust laden gas is directed througha precipitating zone in an arouate passage "or chamber defined inpart by an outer casing wall 26 whichforms a'continuation of the entrance passage [0 and is maintained at the negative potential of the electrodes H. The dust is .removed from thegas in the precipitating .zoneand the gas is discharged in a clean condition through an outlet T2! which is adapted to be connected with the duct system .receiving the flow of gas. The inside walls of the casing in the precipitatingzone are covered with insulating material 22 to prevent contact of the gas stream with these negative surfaces. Mounted within the casing 26 and insulated therefrom by the insulation 22 are a plurality of parallel, positive plates .23 of generally arcuate shape extending through the length of the precipitatingzonein .the gas passage. The gas stream .first encounters these plates at their :upper .ends .24 just behind theelectrodes H and i2 and .leaves the plates at itheirlower ends 25 :at .the entrance .to Ithe outlet passage 21. The plates 123 .are clamped between a series .of 'arcuate :insulatingspacers L26 oy aplurality of bolts 27. The bolts 27, orat least one of them, may be .in electrical contact with the plates 23 but insulated from the casing '9, andsuch bolt may be brought out through an insulating bushing in the'casing for connection with a positive wire 28 to establish a positive electrical connection with the plates 23.

Interposed between the stationary positive plates 23 are a series of circular negative plates 36 carried by a shaft 31 which is mounted for rotation in bearings 32. The plates 30 are held in fixed positions on the shaft by a long key 33 and a series of insulating spacing collars 34. The plates 30 through their attachment to the shaft 3i are grounded to the negative potential of the casing 53 and form the precipitating, or dust collecting, electrodes in the precipitating zone. The peripheries of the :plates 30 revolve the precipitating zone.

.in grooves 316 in the insulating strips 28. Around the spacing collars 3-4 the stationary plates 23 are notched at 31 to provide a small clearance V for the rotating parts. Thus it will be seen that the gases to be cleaned are caused to travel between the quite closely spaced plates 23 and 30 for a considerable distance in the precipitating zone. Dust particles in the gases carrying positive charges received in the ionizing zone are thereby caused to travel between the plates 23 and 30 subject to the repelling effect of the positive charge on plates 23 and the these plates being the only negative surfaces in The negative plates 36, however, are in constant rotation in the direction of the arrow4G by operation of a drive pulley 4! on the shaft 3| so that the dust adhering to these plates is being constantly removed from the precipitating chamber and introduced into an electrode cleaning chamber 42 on the opposite side of the shaft 3|. The pulley 4| is preferably driven by an adjustable speed motor or variable ratio drive to control the shaft speed.

In the cleaning chamber 42, the precipitator plates 3!! rotate between spaced insulating wiper arms 45 which rotate in the direction of the arrow 46 to wipethe dust off the plates and drop it in the bottom of the chamber. The arms 45 are mounted on hubs 41 keyed to a shaft 48 which is mounted in bearings in a manner similar to the shaft 4|. The shaft 48 is driven from the shaft 3| which serves as a drive shaft for the machine, by a belt 50 running on pulleys and 52 on the two shafts. The hubs 41 are designed to position a set of wiper arms 45 between each pair of revolving plates 30 and also between the end plates 30 and. end walls 53 in the chamber 42, which end walls may be a part of the casing 9 and at the same electrical potential. The chamber 42 has an upper wall 54 curved concentric with the shaft 48 to lie closely adjacent the outer ends of the rotating arms 45 and terminating at its upper end close to the revolving plates 3!). Wedge-shaped projections 55 are formed on the ends of the arms to lead them between the spaced plates 30, and the main body of each arm is made concave on its leading side to provide wiping and scraping edges 5l' to clean the plates 39.

A dust wiper and air seal comprising strips of I felt orother resilient insulating material 68 is arranged beneath the shaft 3| to close the space through the plates 30 between the electrode cleaning chamber 42 and the gas passage through the precipitating zone. The strips 60 are secured to opposite sides of the fixed plates 23 by rivets 6| having recessed heads as shown in Figure 4, so that these strips press and wipe against both sides of the revolving plates 30 to wipe these plates clean of dust as they return to the gas stream. In this manner, a clean plate section is exposed to the dust particles in the gas stream, and the dust which has been wiped ofi is prevented from passing out of the chamber 42 to reenter the gas stream. The strips 60 extend along the arcuate inner edges of the plates 23 from a wall 62 up to and beyond the edges of the slots 31 and into wiping engagement with the insulating spacers 34 to form a seal at this point. On one side the edges of the strips 60 have a small clearance from the ends of the wiper arms 45. A sufficient number of wiper arms 45 are provided substantially to close the open space between strips 60 and the wall 54' to prevent any appreciable air movement in the chamber 42. Any gas borne dust entering the chamber 42 through this open space is captured by the plates 30 and immediately wiped off by the wipers 45.

Dust wiped from the plates 36 is dropped by gravity from the wiper arms 45 and directed by deflector plates 64 onto a belt conveyor 65 which carries it out to an airtight storage bin 68. This bin is sealed from the chamber 42 by flexible flights 61 on the conveyor which wipe against the top and bottom wall surface surfaces 68 and 69. The belt 65 runs on an idler roll H3 and a driving roll H which is rotated by the drive shaft 3|.

' Connected with the shaft 12 for the driving roll is a gear box 13 having an outside pulley 14 driven by a belt l5 from a pulley 16 on the shaft 31. While the machine is in operation the belt 85 thereby operates continuously to remove dust from the bottom of chamber 42 and deposit it in a quiescent state in the storage bin 66. A pair of guide plates 1! sup-port the conveyor belt between the end rollers and hold the flexible flights 61 in contact with the walls 58 and 59 to maintain a substantially airtight seal on the top and bottom sides of the conveyor flights. A cleanout opening '18 having a cover plate i9 is provided in the sides of the casing for cleaning out dust from time to time which may leak into the space between the upper and lower flights of the conveyor.

Thus, it will be observed that the steps of the method carried out by the present apparatus comprise, specifically, the charging of the dust particles in a stream of gas with an electrical charge of predetermined polarity, the precipitation of the charged particles of dust on precipitating plates carrying a. charge of opposite polarity, the movement of the dust on the precipitating plates out of the moving gas stream and into a quiescent chamber, the wiping of the dust from the precipitating plates in the quiescent chamber, the removal of the dust from this chamber in a substantially solid and quiescent state and the deposition of the dust in such state into a sealed storage bin. Inherent advantages in this method of treatment are, as stated in the objects of the invention, continuous operation and the accumulation of the dust in a condition which requires no further treatment prior to its ultimate disposal. If the dust is of no value, it may easily be disposed of and, if it is of value, as is aften the case with dust recovered from a gas stream in industrial operations, it is in a convenient form for any treatment which may be necessary to recover its valuable constituents.

Another advantage of the present method and apparatus resides in the fact that the wiping and cleaning action on the precipitating plates takes place in a chamber-removed from the positive plates so that, even with the power connected, electrical leakage and flashovers are not caused by the disturbance or accumulation of material on the wiping means which might otherwise, in conventional arrangements, cause such material to bridge the gap between plates of opposite polarity. In handling dust of a metallic nature, or other electrically conductive dust, in a conventional stationary plate precipitator, it is quite possible to accumulate a depth of precipitated dust to reduce the gap between plates of opposite polarity so there is possibility of a short circuit.

If the-presencepf material: on the ,wiperiarmssdi shouldestablish conducting paths across the faces of these; arms, such conducting paths merely bridgeythedistance,between adjacent plates of the same polarity and cannot establish a short circuit between. plates of opposite polarity. By

suitably-controlling the speed of the drive shaft IN the precipitating plates 39 may be rotatedfast enough to prevent any bridging'accumulation of the-material in the precipitating zone to produce leakage pathsbetween the rotary. and stationary plates of opposite polarity.

The rotating precipitating plates, 30 are sub- .iected to a firstwiping and cleaning action by the: wiper-- arms 45,, andthen before the surfaces are. re-introducedinto the precipitating zonein theggas streamthey areagain wiped cIean'bythe stationary wiper strips'fifl. The dust on the precipitating plates is not disturbed while it is exposed to the gas stream, but only after it has been rotated out of the gas stream and into the quiescent chamber 42. By rotating the precipitatingplates at a speed sufiicient to maintainthem in. a: fairly clean condition in the precipitating zone, the machine may be operated at all times at a; high efficiency since the dust will be prevented from forming an insulating coating thereon. The relatively small plate area in the present machine is thereby equivalent, in dust removal capacity, toa very much greater plate area in conventional precipitators.

The present machine operates continuously at a high efiiciency because the incoming dustladen gas first contacts the precipitating surfaces on which dust has already been precipitated. Then, as the gas stream continues through the precipitating zone, it progressively encounters areas of the plates on which less and less dust has precipitated. In other words, the farther the. dust particles travel through the precipitating zone, the stronger is the attraction of the plates to accomplish the final cleaning, owing to less concentration of dust in the gas and cleaner plate surfaces.

The precipitating plates 30 may be oiled from time to time if desired, either by direct application of oilto the plates or by application of oil to thewiper arms 45 or wiper strips 60. However, there is less necessity for oiling the precipitating plates in the present machine than in conventional machines because the dust is not required to cling to the platesfor a long time. The necessary clinging interval may bemade as. short as desired by selecting an. appropriate rotational speed.

Itis, of course, appreciated that the electrical polarity maybe reversed, if desired, merely by interchanging the leads from the-source of supply to make, the electrodes I2 and stationary plates 2.3,negative. and the, electrodes II, casing 9 and rotating plates 30 positive. This could be readily accomplished by making the wires I8 and 28 negative connections and the wire I! a positive connection.

Figures. to 10. illustrate a preferred embodiment having both positive and negative rotating plates in the gas passage. Eachof these sets of plates rotates out of the gas passage and into a quiescentwiping chamber, where they are cleaned by rotating wiper arms, there being a first wiping chamber on one side of the gas passage for the negative plates and asecond wiping chamber on the opposite side of the gas passage for the positive plates- The gasfiow is directed in a straight linethrough narrow. spaces. betweenzthe. two;sets

' of; rotating-plates; and all, the metallicsurfaces subjecttothe collectionof dustare .wiped clean by the; continuous motion of. the. precipitating plates and wiping arms, sothat the. machine may bekept. inncontinuousoperation. and never need beshut; down for cleaning purposes.

The. gas'to be cleaned is ,ledinto the machine through an inletconduit... I00, equipped with a screen, indicated by the conventional symbol'at IOI. in Figurefi, but which, preferably, comprises a light steel plate punched ,withone-quarter inch holes to equalize the distribution of. air flow over the cross sectional. area of. the. gas passage. The lower end of. this conduit contains. a. plurality of transverse, parallel, metal, negative electrode rods. I02 which: may begrounded. tothe metal conduit section. Between. and .shghtly below, the negative rods. I02. are a series of positively charged ionizingwires. I03. insulatedly mounted in the manner illustrated in Figure 3.. The rods I02 and wires. I03. comprise theionizing zone of the precipitator just ahead of the precipitating zone. The gases, pass straight downwardly through the machine in .streamlinedfiow without turbulence and exit through a discharge conduit I04.

The-precipitating elements comprise. a first set of circular metallic. plates I05 mounted in spaced relation on a splinedshaft I06, and a second set of plates I01 similarly mounted on a parallel shaft I08, with the two setsofplates parallel and spaced equidistantly as shownin Figure 6. One set of plates is connected to the positive potential side of the source of precipitating voltage, and the shaft for these plates is mounted in suitable insulating bearings to insulate the plates and shaft from the casing. and. other metallic parts of the machine. The shaft for the other ,set of plates is connected. to the. negative side of the source of precipitating voltage, and may also be mounted in insulating bearings if it is desired to maintain a different potential on the negative plates than is applied to the negative ionizing rods I02. Shafts I06 and .I08 are rotated in opposite directions by a. common drive shaft 0 to turn both sets of plates. counter to the, direction of gas flow. A doublebevel gear drive is illustrated in Figure 6, using gears molded from a suitable insulating composition. Pulleys III are belted to a source of power providing a relatively slow rotational speed. Only sufiicient poweris required to overcome the. friction. of the, wipers which. clean. the plates.

Shafts I06. and I08'are. spacedapart a distance slightly greaterthanthe widthof the'inl'et and discharge. conduits asviewedlinFigure 5;,and the platesal 05 and, I0! have sufficient radius to extend across. the space. between the two shafts. Thus, the plates I05. and I0! overlap across the width ofthe. gas. passage to define a precipitating zone IIZ which. subjects the entire gas stream and all the. particles carried thereby to the electrostatic precipitating actionof' both sets of plates. Above the shafts I06 and I 08'the gas passage is not definednby lateral walls,, but below these shafts a plurality of felt wipers. I I 5.flll' and seal the spaces betweenthe rotating platesand define lateral walls on opposite. sides ofthe lower part of the precipitating zone. Wipers H5 have upper arcuate portions IIB. to. clear the plates on the opposite shaftand funnel the gas into the discharge conduit I04 instreamlinedflow. without turbulence.

A series of wiper arms: l20-mounted on a shaft I2I rotatebetweeuthe. plates. I05 .in...wiping engagement therewith to, remove the precipitated dust, and a similar set of wiper arms I22 are mounted on a second shaft I23 on the opposite side of the machine to wipe the plates I01. Both sets of wiper arms are preferably made of a suitable plastic or other insulating material, and have the same form of construction described in reference to the wiper arms 45 in Figure 1. As illustrated in Figure 8, each wiper arm has a forwardly projecting tip end I24 with inclined lateral edges I25 to enter easily between the precipitating plates. The active sides of the arms are concave in cross section to present scraping edges I26 against the plates. Wiper arm shafts I2I and I23 are driven by pulleys I2! and belts I28 from the shafts I06 and I08. Shaft I2I rotates in the same direction as shaft I06, and shaft I23 rotates in the same direction as shaft I08, so that the wiper arms will move counter to the direction of the plate surfaces engaged thereby. Sinceno one wiper arm engages plates at different potential, accumulations of dust on the wiper arms, even if conductive, cannot cause flashovers between the plates. The continuous cleaning of the plates prevents accumulations from building up between plates at different potential.

The dust removed from the precipitating plates by the wiper arms I20 and I22 is deposited on a pair of conveyors I30 and I3I similar to the conveyor 65 in Figures 1 and 2. The conveyor units may take other forms, but they should be of a type which can remove accumulated dirt while the machine is operating and still maintain an air seal at the point or points where the dirt leaves the casing of the machine. Oonveyor pulley I32 in Figure 6 may be belted to the source of power for pulleys I I I.

Arcuate insulating plates I35 conform to the contours of the two sets of precipitating plates to close the top of the machine above these plates. 1

Other casing sections I36 and I3! of metal are concentric with the wiper arm shafts to enclose the rotating wiper arms and form a pair of quiescent chambers I40 and MI above the conveyors I30 and I3I. Flat vertical walls I38 lined with insulating material I39 form front and back sides on the housing as shown in Figure 6.

Figure 9 is a perspective view of a seal support, designated generally by the numeral I45. These supports are preferably molded from a plastic or other suitable insulating material to support a series of felt sealing wipers forming slotted walls between the quiescent chambers I40 and MI and the opposite sides of thegas passage. Each supporting member comprises a web I46 having spaced shoulders I41 for mounting the previously mentioned felt wipers I I and- I I6 and providing a vertical oil groove I48 behind these wipers. On the other side of the support member is an arcuate shoulder I49 for mounting wipers I50 substantially engaging the ends of the rotating wiper arms I20 and I22. By reason of the close spacing between the ends of the wiper arms and wipers I50, and the close spacing between the ends of the wiper arms and walls I36, the wiper arms form a rotating closure substantially sealing off the quiescent chambers I40 and I 4| from the gas passage and effectively preventing any dust introduced into the quiescent chambers from returning to the gas passage.

Bosses I5I on the upper ends of the supporting members I45 are equipped with openings I52 to receive the shafts I06 and I08, these bosses serving as spacers for the plates I05 and I01. These plates have freelongitudinal movement on their enter the precipitating zone.

respective splined shafts for positioning the plates between the bosses. The lower end of each groove I48 terminates in a horizontal channel section I54 adapted to receive the oil supply pipe I55 shown in Figure 10. Pipe I55 is equipped with an opening I56 to register with the groove I48 in each of the wiper supports I45, as shown in Figure 7, when the parts are assembled. One end of each pipe I55 is capped at I57 and clamped against the outer casing of the machine by nut I58, and the other end is connected to a vertical supply oil pipe I60 leading to an oil tank I6I. Thus the oil fills the grooves I48 whereby the precipitating plates are oiled by wipers II5 as they Nuts I58 provide means for clamping an entire assemblage of supports I tightly together, and the abutting surfaces may be gasketed around pipe I55 to prevent leakage of oil from channel sections I54. Collars I59 on the other ends of the pipes provide 'fixed abutments for the clamping action.

Cleanout doors H0 in Figure 5 provide access for removing dirt from floor III that may find 'its Way into the spaces between Wipers I and H5. figs floor is spaced below the lower edges of webs 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 1s: 1. An electrical precipitator for removing dust particles and the like from a stream of gas, comprising a housing with walls defining a stream-- lined, non-turbulent gas passage having an inlet and outlet in a common plane, ionizing electrodes defining an ionizing zone adjacent said inlet, a quiescent chamber having walls defining an opening into one side of said passage in said common plane, a plurality of precipitating plates extending into said passage and chamber and mounted for rotation through said opening in planes parallel with said common plane, and moving wipers between said plates in said quiescent chamber closing said opening, said Wipers extending to the walls of said chamber and substantially sealing said chamber from said pas sage.

2. An electrical precipitator for removing dust particles and the like from a stream of gas, comprising a plurality of circular parallel rotating precipitating plates, a gas passage enclosing a sector of said plates, all parts of said passage extending parallel with said plates for streamlined, non-turbulent flow, ionizing electrodes defining an ionizing zone in said passage ahead of said plates, a quiescent chamber enclosing the remaining sector of said plates, moving wipers in said quiescent chamber substantially sealing the spaces between portions of said plates entering said quiescent chamber, and aditional wipers sealing the spaces between portions of said plates leaving said quiescent chamber.

7 3. An electrical precipitator for removing dust particles and the like from a stream of gas, comprising a plurality of circular parallel rotating precipitating plates, a gas passage enclosing a sector of said plates, all parts of said passage extending parallel with said plates for streamlined non-turbulent flow, ionizing electrodes defining an ionizing zone in said passage ahead of said plates, a quiescent chamber enclosing the remaining sector of said plates and having an open-.- ing into said passage, rotary wipers in said quiescent chamber substantially sealing the spaces between portions of said plates entering said an ina? quiescent chamber, anclarcuate stationary wipers closely adjacent the ends of said rotary wipers at one side of said opening sealing the spaces between portions of said plates leaving said quiescent chamber, said chamber having arcuate wall portions closely adjacent the ends of said rotary wipers at the opposite side of said opening.

4. An electrical precipitator for removing dust particles and the like from a stream of gas, comprising a plurality of circular parallel rotating precipitating plates, a gas passage enclosing a sector of said plates, additional plates in said passage between and insulated from said rotating plates, all parts of said passage extending parallel with said plates for streamlined, nonturbulent flow, ionizing electrodes defining an ionizing zone in said passage ahead of said plates, a quiescent chamber enclosing the remaining sector of said rotating plates and having an opening into said passage, moving wipers in said quiescent chamber closing a portion of said openingand substantially sealing the spaces between portions of said rotating plates entering said quiescent chamber, and additional wipers closing the remainder of said opening and sealing the spaces between portions of said rotating plates leaving said quiescent chamber.

5. An electrical precipitator for removing dust particles and the like from a stream of gas, comprising a housing with walls defining a streamlined gas passage having an inlet and outlet in the same plane, ionizing electrodes defining an ionizing zone adjacent said inlet, a plurality of precipitating plates mounted on a shaft for rotation in said passage in planes parallel With the gas stream, a quiescent chamber on one side of said gas passage enclosing areas of said precipitating plates, an opening between said gas passage and quiescent chamber for the rotation of said plates to carry precipitated material from said gas passage into said quiescent chamber, movable wipers engaging portions of said plates entering said chamber and arranged to substantially seal a part of said opening, and stationary wipers engaging portions of said plates leaving said quiescent chamber to seal the remainder of said opening.

6. Anelectrical precipitator for removing dust particles and the like from a stream of gas, comprising a housing defining a streamlined gas passage having an inlet and outlet, ionizing electrodes defining an ionizing zone adjacent said inlet, a plurality of precipitating plates mounted on a shaft for rotation in said passage in planes parallel with the gas stream, walls extending up to the periphery of said precipitating plates at two spaced points to define a quiescent chamber at one side of'said gas passage enclosing areas'of said precipitating plates, stationary wipers extending between said plates from one of said Walls to said shaft to seal the spaces between portions of'the plates leaving said quiescent chamber, and a plurality of rotary radial wiper arms sweeping between said plates from said shaft to said other'wall to substantially seal the spaces between portions of said plates entering said quiescent chamber.

7. In an electrical precipitator for removing dust particles and the like from a stream ofgas, a housing having walls defining a streamlined, non-turbulent gas passage with an inlet and outlet, ionizing electrodes defining an ionizing zone in said inlet, a quiescent chamber at one side of said passage having an opening into said passage, a shaft mounted in said opening between said passage and chamber and having a plurality of 1'2 precipitating plates extending into said passage on oneside of said shaft and extending into said chamber on the opposite side of said shaft, said plates being rotatable in planes parallel with the gas stream in said passage, a shaft in said quiescent chamber having a plurality of rotary :wiper arms sweeping between said plates in said chamber, a slotted Wall extending along one side 'of said quiescent chamber to said first Shaft to separate said chamber from said passageand having stationary Wipers'to seal'the spaces between portions of said plates leaving said quiescent chamber and entering said passage, and a wall on the opposite side of said quiescent chamber, said two walls being arcuate in shape and spaced closely adjacent the tips of said wiper arms and said wiper arms forming a revolving closure between portions of said plates entering said chamher.

8. An electrical precipitator for removing dust particles and the like from a stream of gas-comprising a housing with walls defininga streamlined .gas passage having an inlet and outlet, ionizing :electrodesdefining anionizin zone adjacent said inlet, walls defining aquiescentchamher at one side of said gas passagecommunicating with said gas passage, a series .of precipitating plates having portions insaid gas passage and portions in said quiescentchamber andmounted for rotation in planes parallel with the ,gas stream in said passage, a series of moving wipers arranged to seal the spaces between .portionso'f said plates entering said chamber, stationary wipers arranged to seal thespaces-betweenportions of said plates leaving saidrchamber, adust collecting conveyor of sufiicientlengthandwidth to extend under substantially all parts of said moving wipers for removing dust from'said chamher, and sealing means between said conveyor. and chamber walls.

9. An electrical dust precipitator comprising an arcuate streamlined gas passage havingan inlet and outlet, ionizing electrodes defining an ionizingzone adjacent said inlet, a quiescent chamber disposed at the center of curvatureof said arcuate passageand having an opening into said passage, a series of precipitating plates extending into said passage and chamber and mounted for rotation intosaid chamber through said opening in planes parallel with the gas stream in said passage, rotary wiper arms extending betweenportions of said plates entering said chamber to'close :said opening and substantially sealsaid chamber from said passage in the region of said entering portions, and stationary wipers sealing the spaces lgetween portions of said plates leaving said cham- 10. An electrical precipitator for removing dust particles and the like from a stream of gas, comprising a housing With-Walls defining a streamlined, non-turbulent gas flow passage having an inlet and outlet, ionizing electrodes defining an ionizing zone adjacent said inlet, a set of precipitating plates mounted for rotation-in said passage in planes parallel with the gas stream, a second set of parallel plates in said passage between and insulated from said first set, a quiescent chamber at one side of saidgasipassage enclosing portions ofsaid first'set of plates-and having an opening into saidcpassage, and stationary and moving wipers between the plates ofsaid first set cooperating with said housing to-close said opening and substantially seal said quiescent chamber irom said-gas passage.

11. An electrical precipitator'for removing dust particles and the like from a stream of gas, comprising a gas passage, a quiescent chamber at one side of said passage, a plurality of precipitating plates mounted on a shaft between said passage and chamber for rotation of the plates in planes parallel with the direction of gas flow through said passage, portions of said plates on one side of said shaft extending into said gas passage and portions of said plates on the other side of said shaft extending into said quiescent chamber, stationary wipers extending between portions of said plates leaving said chamber and entering said passage, means for oiling said wipers, and rotary radial wiper arms mounted on a shaft in said chamber to sweep between said portions of said plates in said chamber.

12. An electrical precipitator for removing dust particles and the like from a stream of gas, comprising a gas passage having an inlet, ionizing zone, precipitating zone and outlet disposed in a straight line, quiescent chambers on two opposite lateral sides of said passage, a set of positive precipitating plates mounted for rotation in planes parallel with the direction of the gas flow and having portions disposed in said passage and other portions disposed outside of said passage in one of said quiescent chambers, a set of negative precipitating plates mounted for rotation in planes parallel with the direction of the gas flow, said negative plates having portions disposed in said passage between and parallel with said positive plates and other portions disposed outside of said passage in said other quiescent chamber, and rotary wipers outside of said passage in said quiescent chambers to clean the surfaces of said plates.

13. An electrical precipitator for removing dust particles and the like from a stream of gas, comprising a gas passage extending in a straight line, quiescent chambers on two opposite sides of said passage, a set of negative precipitating plates mounted on a shaft at one side of said passage for rotation in planes parallel to the direction of gas flow in said passage, said plates extending into said gas passage on one side of said shaft and into one of said quiescent chambers on the other side of said shaft, a set of positive plates mounted on a shaft on the opposite side of said gas passage for rotation in parallel interjacent relation with said first set of plates, portions of said positive plates on one side of said shaft extending into said gas passage between said negative plates and portions of said positive plates on the other side of said second shaft extending into said second quiescent chamber, stationary wipers extending between said negative plates on one side of said passage and stationary wipers extend.- ing between said positive plates on the opposite side of said passage, and rotary radial wiper arms sweeping between said plates in each of said chambers.

14. An electrical precipitator for removing dust particles and the like from a stream of gas, comprising a straight vertical gas passage, quiescent chambers on two opposite sides of said passage, a set of negative precipitating plates mounted on a shaft at one side of said passage between said passage and one of said quiescent chambers for rotation of the plates in planes parallel to the direction of gas flow in said passage, portions of said plates extending into said passage and portions of said plates extending into said one chamber, a set of positive precipitating plates mounted on a shaft at the opposite side of said passage between said passage and the other quiescent chamber for rotation in planes parallel with said negative plates, said positive plates having portions extending into said gas passage between said negative plates and other portions extending into said other quiescent chamber, stationary wipers extending between said plates to each of said shafts to seal the spaces between portions of said plates leavin said chambers and entering said passage, rotary wiper arms sweeping between said portions of said plates in said chambers, the tips of said arms moving closely adjacent said stationary wipers, and a wall portion in each of said chambers disposed closely adjacent the tips of said wiper arms, said wiper arms forming a revolving closure in each chamber between said wall portions and said stationary wipers to substantially seal the spaces between portions of said plates entering said chambers from said passage.

FRANCIS J. DOHRER.

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

UNITED STATES PATENTS Number Name Date 2,333,431 Lincoln Nov. 2, 1943 FOREIGN PATENTS Number Country Date 617,411 France Nov. 20, 1926 750,383 France May 22, 1933

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