US2385077A

US2385077A - Spray booth

Info

Publication number: US2385077A
Application number: US486814A
Authority: US
Inventors: George A Harker; Gustafsson Eric; Allen George; Nelson Roy
Original assignee: Binks Sames Corp
Current assignee: Binks Sames Corp
Priority date: 1940-03-06
Filing date: 1943-05-13
Publication date: 1945-09-18
Anticipated expiration: 1962-09-18

Description

Sept. 18, 1945. e. A. HARKER ET AL SPRAY BOOTH Filed May 13, 1945 5 Sheets-Sheet l Z w w win w 25 15%! N {we W m P7 pt 18,194s. G. A. HARKER Em 2,385 77 SPRAY BOOTH Filed May 13, 1943 5 Sheets-Sheet 2 p 8,1945. G. A. HARKER Em 2,385,071

SPRAY BOOTH Filed May 15, 1943 3 Sheets-Sheet 3 jfforvzey Patented Sept." 18, 1945 SPRAY BOOTH George A. Barker and Eric Gustalsson, Chicago, s

George Allen, North Lake V illage. and Roy Nelson, Chicago, Ill., assignorl to Blnks Manufactoring Company, of Delaware Chicago, 11]., a corporation Application May 13, 1943, Serial No. 486,814

7 Claims. (Cl. 261-ll .8)

The present invention relates to spray booths and particularly to the wash type of spray booth.

In spray booths of this type the spray laden air usually flows from the work locus downwardly and rearwardly in the work chamber and over a water receptacle at the rear lower portion of the booth and beneath the lower end of the water curtain apron where a water curtain flows downwardly in a sheet to wash out suspended particles from the air as it flows rearwardly over the water receptacle and through the water curtain flowing down from the lower end of the apron into the receptacle. The air then usually flows through a washing chamber at the rear of the apron for further washing out of suspended material. Examples of such structures are disclosed in the Gustafsson Patent No. 2,180,586, granted November 21, 1939, the Roche, Jr., et al. Patent No. 2,227,465, granted January "I, 1941, and the Roche, Jr., et al. Patent No. 2,266,335, granted December 16, 1941.

Among the objects of the invention is to provide a novel means for causing an upward flow ing a downwardly flowing sheet or curtain of water over an apron extending down into and below the normal level of the water in the receptacle in the lower rear portion of the booth whereby the washed out material is caused to be deposited onto or into the water in the forward portion of the receptacle and in front of the apron. By reason of the apron extending down into the water in the water receptacle, passage of air to the rear of the apron is prevented at the lower end of this apron. Any sprayed particles hurled or projected toward the apron will be carried down by the sheet or curtain of water flowing down over the face of the apron and into the forward portion of the receptacle.

The invention also comprehends the further upward flow of the air through a secondmore or less horizontally projected sheet of water for further washing of the air, this second sheet being so projected against a forward part oi the booth, as a rearwardiy extending wall forwardly spaced from the upper portion of the apron, as to distribute the water on said wall and form the above first mentioned more or less horizontally projected sheet of water for first washin the upward flowing air, and to form a water curtain or sheet on the face of the apron.

Further, the invention also provides for a further sheet of water, which may be in one form of device a third sheet, which is projected more or less horizontally and toward a second apron located spacedly rearwardly of the previously mentioned apron to form a sheet or curtain flowing downwardly over the forward face of the second-apron and to pour from the lower end of the second apron down into the receptacle. The lower end of the second apron is spacedly above the water in the receptacle to provide a passage for the air to a washing chamber at the rear of the second apron. The air passes downwardly through said further sheet of water into the chamber provided between the first and second aprons thus receiving its further washing in said further sheet. Then the air passes through a still further sheet of water, which may be in one form of device, a fourth sheet or curtain of water flowing downwardly from thelower end of the second apron in the passage beneath said lower end of'the second apron, thus receiving its further, such as a fourth, washing. Then the air flows upwardly in a wash chamber between said second apron and the rear wall of the device where the air receives the flnal, such as a flith, washin as it passes through more or less horizontally projected sheets of water in said washing chamberr The invention may also comprehend means for increasing the number of washings of the traveling stream of air to more efliciently remove the residual particles or the like of suspended material, depending upon the kind of material being suspended, some being more diiflcult of removal than others. As for instance, as the air stream passes upwardly from in front of the first apron and then reversely to and into the space rearwardly of the first apron and between said first apron and the second apron, the means for projecting the washing liquid, such as water, may cast or project a plurality of sheets of water transversely of said stream of air, such as forwardly, upwardly and rearwardly.

Also, for the purpose of preventing the adhering of residual and suspended particles of material carried by the air stream, as it change its course from in front of the front apron to in front of the rear apron, to the wall over or about said stream, means may also be provided for projecting, as from the already mentioned water sheet projecting means or from additional sheet projecting means, sheets of water over and along.

the surface of such wall, the water of such latter water sheets resultantly uniting with the water sheets flowing down over the surfaces of the aprons; both the forward and rear aprons.

As a further feature which the novel device may comprehend is the provision of means in the washing chamber at the rear of the second or rear apron for eifecting a multiple washing of the risin stream of air; such means comprehending the projecting or casting, more or less horizontally, of a plurality of vertically spaced sheets of water.

Other objects, advantages, capabilities, features, process steps and the like are comprehended by the invention as will later appear and as are inherently possessed by the invention.

Referring to the drawings:

Fig. 1 is a vertical transverse sectional view of a spray booth constructed in accordance with the invention;

Fig. 2 is a transverse sectional view on an enlarged scale of the water sheet forming means;

Fig. 3 is a fragmentary perspective view of the water sheet forming means;

Figs. 4, 5, 6 and 7 are fragmentary sectional views of different or alternative forms of water projecting, washing, and curtain forming means; and,

Fig. 8 is a fragmentary sectional view of an alternative form of washing. means for multiple washing.

Referring more in detail to the drawings, the embodiment selected to illustrate the invention is shown with the booth having a rear Wall E, a top 2, end or side walls 3, a front wall i, and a water receptacle located at the rear lower portion of the booth and extending between the end Walls 3. On the top 2 is an exhaust chamber G on which is mounted a motor I operatively connected by a belt 8 to a fan 9, the belt 8 passing through a belt casing Ill. The exhausted air passes out up through an outlet I I.

Intermediately of the rear wall 8 and the forward wall 4 is provided an upright and preferably inclined wall or apron I2 having its lower end I3 spaced above the water H in the receptacle 5 to provide a passage I 5 below the 1 lower end I 3 of said apron I2 and above the water I4. The upper end of the apron l2 has an extension it which curve upwardly and forwardly to join the front wall 6. The apron I2 and its extension I6 extend to the end walls 3.

Between the rear wall I and the apron I2 is provided a washing chamber i! in the upper portion of which is located a suitable water eliminator I3, and above the eliminator I8 and between the rear wall I and the extension I6 is provided a discharge chamber I9 having a discharge port 20 opposite the fan 9. This chamber is of larger cross sectional area at the top then the chamber I"! to afford the use of a large capacity fan and to lower the velocity of fiow of air prior to its engagement by the fan blades.

Spaced forwardly of the apron I2 is provided another wall or apron 2| extending between the walls 3 and preferably held in inclined position as shown .by any suitable means such as bars (not shown) connected to the walls 3 and the apron 2i. The apron 2i is composed, of segments 22, 23 and 2d removably connected together by suitable joint means 25 and 250.. Each joint comprises an upper flange 26' of a lower segment slidably fitting into a channel 21 at the lower end of an upper segment, as shown in Fig. 1. When it is desired to remove or replace a segmentit is only necessary to' move the seg-- ment whereby the flange 23 slides out of or into the channel 21. The upper segment 24 is fastened to the lower side of a water distributing duct 28 in any suitable manner.

The front wall 4 has a depending rearwardly inclined wall portion or apron 28 extending between the walls 3 and having its lower edge 53% spaced forwardly of the upper portion of the apron 2i to provide an elongated opening or port 3i between said lower edge 33 and said upper portion of the apron 2|, through which opening 3i the air passes upwardly into the chamber 82 provided within the walls 4 and I 3 (see Fig. l) and across which opening a sheet of water is projected to the upper end portion of the apron 2i to wash said air and to separate out particles of materialcarried by the air.

Between the apron 2i and I2 is provided a chamber 33 which is wider at its base than at its upper end, that is, where it joins the chamber '32.

A distributing duct 28a is also provided in the chamber I! and both ducts 28 and 28a extend through the side or end walls 3 and are connected in a circulating system having a suitable pump (not shown), the pump having its intake (not shown) connecting at a low point with the rear portion of the receptacle 5.

Both distributing means shown in Fig. 1 are alike and are shown more in detail in Figs. 2 and 3. Each distributing means comprises a duct 28 or 28a having spaced above the duct an elongated distributing plate 34 extending between the walls 3 and being arc shaped or curved in cross section with the concave side opposite the top portion of the duct. The top portion of the duct has a series of discharge orifices 35 through which the water is projected upwardly against the concave or lower side of the plate 36. By so curving the plate 343 the water is componently forced to move more or less longitudinally of the plate, and at various angles, and also transversely so that a continuous and substantially uniform sheet of water will be projected from each

edge

36 and 31 of the plate 34 and for the whole length of the plate.

Hence, in chamber 32 is projected a forwardly directed sheet 38 of water to impinge on the wall 29, and a rearwardly directed sheet 39 of water to impinge on the apron I2, and in the chamber If is projected a forwardly directed sheet 40 of water to impinge on the rear face of the apron I2, and a rearwardly directed sheet of water 5| to impinge on-the forward face of the rear wall I.

The sheet 38 of water impinging on the wall 29 is distributed on said wall 29 to form a sheet of of water which is projected across the opening 3! to impinge on the apron 2I and thence to flow down as a curtain or sheet 43 of water on the forward face of the apron 2| and thence into the forward portion 44 of the receptacle 5 where the washed down material floats on or remains in the water in the forward portion 44 of the receptacle 5 The sheet 39 of water impinging the upper portion of the apron I2 flows down as a curtain or sheet 35 over the forward face of the apron l2 and falls down as a curtain or sheet from the lower end of the apron I 2 through the opening iii and into the rear portion of the receptacle 5. At the same time due to the turbulence created by the flow of air and the projection of the water sheets water also moves in a sheet or curtain down along the rear face of the apron 2i to maintain it constantly wet and to carry down any particles of material that might have moved in that direction. Likewise the sheet d8 of water from the distributor 2311 impinging on the rear face of the wall or apron II forms a sheet or curtain 41 which i'iows down to the end I! and through the opening ll, uniting with the curtain flowinB down from the front of the apron II as described above. Also the sheet ll impinges the rear wall I and flows down as a curtain or sheet 48 over the face of the rear wall! as shown in Fig. 1.

By having the. apron 2| extend below the water level in the receptacle I the air is prevented from passing through the lower part of the water curtain flowing down the apron 2| and is wholly forced upwardly through the opening 8| between the wall portion or apron II and the upper portion -of the apron 2i and through the sheet 42. Also by having the apron inclined as shown a greater area of space is provided between the lower end portions of the aprons 2| and if so that there is a slowing down of the air movement before it makes its turn to pass beneath the lower end of the apron i2 and into the washing chamber II. The air passage from the work locus which is forward of the apron ii to the wash chamber H, as shown in Fig. 1 includes the opening or port ll, the chamber 32, the chamber II, and the passage it.

Whatever part of the spray, from the spray gun used in the work locus forwardly of the apron 2 l that may strike the water curtain flowing down over the forward face of the apron 2|, which spray usually comprises heavy particles of pigments or the like, will be carried down by the water curtain into the receptacle at the front side of the apron 2i, and such heavy pigments or the like do not come into contact with any of the sheets of water projected across the passage of the air stream at any locus in the device. Thus such pgments remain at the front side of the apron ii. To prevent the pigments or like particles reachin the rear portion of the receptacle or tank 8, where it is usual to connect the intake to the water circulating pump for the distributing ducts 28 and 28s, it is preferable to provide a barrier or wall i8 extending between the side or end walls 3 and having its upper edge 88 below the normal level W of the water M in the tank 5, such edge is also being at a higher level than the lower edge 5! of the apron ti or of its lower segment 22, and spaced rearwsrdly from the apron segment 22 so as to afford a free passage of the clear liquid or water over the edge it of the barrier it in maintainin the water level so in the tank 5. By such means the pigments or similar material particles are hel in the forward end of the water tanki.

From tests we have made we have found that the greater portion of the volume of material, from at least75%, to 99%, depending on the kind of spray material used, in the material laden air stream, is carried to and down the front of the apron 2i and in the forward portion oi the receptacle 5. Only the finer or residual particles are carried up and over the apron 2i to be washed out by the successive water sheets projected across the path of the air stream.

Thus, in the device as shown in Fig. 1, the air receives multiple washings or cleanings by passing through at'least five sheets of washing liquid, that is, successively through

sheets

62, 38, 3!, ii, and 4t and ti. The wet air then passes through the eliminator where the moisture is extracted from the air so that the air passing through the fan 9 is substantially dry.

Referring to Figs. 4 and 5, the distributing duct 28 is shown as located above the distributor plates a and "b with the convex side of the plate "a opposed to the duct 28 and the concave side of the plate Nb opposed'to the duct II, so as to prolect forward sheets I! and II of water toward and to the inclined wall portion 20' toward producing the sheet II and the curtain ll on the apron 2i, and rearward sheets I4 and It of water toward and to the upper portion of the rear apron l2 toward producing the downward flowing sheet or curtain Al on the apron if. The upper part of the duct 20 is provided with a series of openings or slots for the upward projection of water I! into sheet form toward and against the upper portion of the wall II to impinge thereagainst with sufficient force to spread out into water sheets 61 and I! which run along the surfaces of the wall portion It and 4 and to resultantly unite with the water sheets or curtains II and II flowing down over the aprons II and II. In this way the adhering of the particles to the wall portion I3 is prevented, and the wall portion II is maintained clean.

The same effect may be produced by the provision, as shown in Figs. 6 and 7, of auxiliary ducts ll! provided with series of openings or slots for the projection of water sheets Ill and BI along the surfaces of the wall portions it and 4 to resultantly unite with the water forming the water curtains 4! and II over the aprons II and II. In Fig. 7 are shown distributor plates 34c and lid above and below the distributor duct 2| with the convex sides of the plates lie and d op td to the duct 20, and the duct 28 having upper and lower openings for. the projection against and distribution along and over the surfaces of the plates Me and d of water sheets '2 and N projected forwardly to and against the-wall-l and water sheets 04 and 65 projected rearwardly to and against the rear portion of the wall II and the upper portion of the apron l2, providing for the resultant formation of the water curtains l! and 48. Because of the divergent projection of the water sheets 82 and 88 against the wall 4 it is preferable to provide the latter with an extension to whereby the wall part 28 may be lower and a yet afford ample width for the opening 3i between the lower edge of the wall part 29 and the upper portion of the front apron 2i.

Fig. 8 shows the duct 28a in the washing cham-- ber l1 and having in addition a distributor plate beneath the duct 28a and openings in its lower wall for projecting water against the plate It which distributes it into water sheets 81 and ll respectively projected forwardly and rearwardly against the walls 82 and i to resultantly blend with the

water sheets

41 and 46. This means provides for sheets of water 87 and GI spacedly relative to the sheets of water 40 and ii for increasing the washing eifect.

Thus, when regarding Figs. 4 to 8 inclusive, it will be apparent that the passing of the air stream from the space forwardly of the apron 2 l to the eliminator it will cause the air to receive from six to eight washings from the several water sheets through which the air stream passes. At the same time all surfaces which might otherwise receive particles of suspended matter will be con stantly washed and maintained clean.

While we have herein described and upon the drawings shown an illustrative embodiment ofthe invention, it is to be understood that the invention is not limited thereto but comprehends other constructions, details, arrangement of parts, features, process steps and the like without departing, from the spirit oi the invention.

Having thus disclosed the invention, we claim: 1. In a spray booth type of gas cleaner having is work locus, is wash chamber, en sir possess extending from said locus to acid chamber, end a liquid receptacle in the lower part of sold locus; ssid passage comprising en opron located in on upright position and rearwerdly or sold locus, s frontal well provided specedly forwardly oi the upper portion oi sold apron and having e depending liquid sheet iorming epron inclined rearwerdly end downwardly toward said upright apron with its lower edge spaced forwardly of said upright spron to provide on opening for the upward flow of air through said opening forwardly of said upper portion of said upright apron, and means at the upper end oi ssid upright apron for projecting a sheet of liquid to said inclined portion for forming on the latter another sheet of water to flow over ssid inclined portion and demos said opening to said upright spron, a second upright apron located spacedly reerwsrdly of said first mentioned apron and having its lower end specedly shove said receptacle to provide on opening for passage of air therethroush, sold liquid sheet rojecting means having menus for projecting a sheet or liquid resrwardly to the upper portion of said second apron to form it ourtain of liquid flowing down over the front isce of said second apron and to form a curtein flowing down from the lower end of sold second epron into said receptacle. I

2. In a sprsy booth type of gas clesner having a worls locus, a. wash chamber, on air passage extending from said locus to said chamber, and a liquid receptacle in the lower pert of said locus; said psssege comprising an spron located in an upright position and rearwordly of said locus, a frontal well provided spscedly forwardly of the upper portion of sold apron and having a. de-

pending liquid sheet forming apron inclined reorwardly and downwardly toward said upright apron with its lower edge spaced forwardly of said upright spron to provide an opening for the upward flow of air through said opening forwordly of said upper portion or sold upright having means for projecting o sheet of liquid rearwardly to the upper portion of said second apron to form n curtain of liquid flowing down over the front face of said second apron and to form a curtain flowing down from the lower end of said second apron into said receptacle, the up-- per portion of said second apron having an extension extending upwardly and forwardly to said frontal wall to form an upper chamber for reverse flow of the air therethrough whereby the air flows downwardly between the upper portions of said first and second aprons.

3. In a spray booth type of gas cleaner having a work locus, a wash chamber, an air passage extending from said locus to said chamber, and a. liquid receptacle in the lower part of said locus; said passage comprising an apron located in an upright position and rearwarclly of said locus, a frontal wall provided spacedly forwardly of the upper portion of said apron and having a depending liquid sheet forming apron inclined rearwardly sud downwardly toward cold upright apron with its lower edge spaced forwardly of said up-= right epron to provide an opening for the upward flow oi air through said opening forwardly of said upper portion oi said upright apron, and means st the upper end of said upright apron for pro= lecting e sheet of liquid to sold inclined portion for forming on the latter another sheet oi water to flow over said inclined portion and across sold opening to said upright apron, a. second upright apron located spscedly reerwsrdly of said first mentioned apron and having its lower end spacedly shove said receptacle to provide an opening for passage of air therethroush, said liquid sheet projecting means having means for proiectlng s. sheet of liquid resrwardly to the upper portion oi said second apron to form a curtain of liquid flowing down over the trout face of sold second apron and to form e. curtain flowing down from the lower end of said second apron into said receptacle, a wash chamber located at the rear oi said second chamber and communicat ng with the space forwardly of said second apron by way of the opening beneath the lower end oi said second apron, and means in said wash chem'cer for projecting a, sheet of liquid transversely thereof to wash the sir flowing upwardly through said chamber.

In a spray booth type of gas cleaner having s. work locus, a, wash chamber, on air passage extending from said locus to said chamber, and u liquid receptsnle in the lower part of said locus; said passage comprising an apron located in an upright position and reorwerdly of said locus, s frontal wall provided spacedly forwardly of the upper portion oi said apron and having at depending liquid sheet forming apron inclined rearwerdly end downwardly toward said upright apron with its lower edge spaced forwardly of said upright apron to provide an opening for the up ward flow of sir through said opening iorwerdly of said upper portion of said upright apron, and means at the upper end of said upright apron for projecting a sheet of liquid to said inclined portion for forming on the latter smother sheet of water to flow over said inclined portion and across said opening to said upright apron, a second upright apron located spmedly rearwardly of said first mentioned apron and having its lower end spacedly above said receptacle to provide an opening for passage of air therethrough, said liquid sheet projecting means having means for projecting a sheet of liquid rearwardly to the upper portion oi said second apron to form a curtain of liquid flowing down over the front face of said second apron and to form a curtain flowing down from the lower end of said second apron into said receptacle, a. wash chamber located at the rear of said second chamber and communicating with the space forwardly of said second apron by way of the opening beneath the lower end of saldsec- 0nd apron, and means in said wash chamber for projecting a, sheet of liquid transversely thereof to wash the air flowing upwardly through said chamber, each of said liquid sheet projecting means comprising a duct having a. series of apertures in the upper portion thereof for projecting liquid streams upwardly therethrough, and a deflector member spacedly located above said apertures to deflect said liquid streams into sheet form- 5. In a spray booth type of gas cleaner having a work locus, a. wash chamber, an air passage extending from said locus to said chamber, and a. liquid receptacle in the lower part or said locus;

said passage comprising an apron located in an upright position and rearwardly of said locus, a frontal wall provided'spacedly forwardly of the upper portion of said apron and having a depending liquid sheet forming apron inclined rear-' wardly and downwardly toward said upright apron with its lower edge spaced forwardly, of said upright apron to provide an opening for the upward flow of air through said opening forwardly of said upper portion of said upright apron, and means at the upper end of said upright apron for projecting a sheet of liquid to said inclined portion for forming on the latter another sheet of water to flow over said inclined portion and across said opening to said upright apron, a second upright apronlocated spacedly rearwardly of said first mentioned apron and having its lower end spacedly above said receptacle to provide an opening for passage of air therethrough, said iquid sheet projecting means having means for projecting a sheet of liquid rearwardly to the upper portion of said second apron to form a curtain of liquid flowing down over the front face of said second apron and to form a curtain flowing down from the lower end of said second apron into said receptacle, a wash chamber located at the rear of said second chamber and communicating with the space forwardly of said second apron by way of the opening beneath the lower end of said second apron, and means in said wash chamber for projectinga sheet of liquid transversely thereof to wash the air flowing upwardly through said chamber, each of said liquid sheet projecting means comprising a duct having a series of apertures in the upper Portion thereof for projecting liquid streams upwardly therethrough, and a deflector member spacedly located above said apertures to deflect said liquid streams into sheet form, said deflector being curved in cross section with the concaved side thereof opposite said apertures.

6. In a spray booth type of gas cleaner having a work locus, a wash chamber, an air passage, extending from said locus to said chamber, and a liquid receptacle in the lower part of said locus; said passage comprising an apron located in an upright position and rearwardly of said locus, a frontal wall provided spacedly forwardly of the upper portion of said apron and having a depending liquid sheet forming apron inclined rearwardly and downwardly toward saidupright apron with its lower edge spaced forwardly of said upright apron to provide an opening for the upward flow of air through said opening forwardly of said upper portion of said upright apron, and means at the upper end of 'said upright apron for projecting a sheet of liquid to said inclined portion for forming on the latter another sheet of water to flow over said inclined portionand across said opening-to said upright apron, a second upright apron located spacedly rearwardly of said first mentioned apron and having its lower end spacedly above said receptacle to provide an opening for passage of air therethrough, said liquid sheet projecting means having means for projecting a sheet of liquid rearwardly to the upper portion of said second apron to form a curtain of liquid flowing down over the front face of said second apron and to form a curtain flowing down from the lower end of said second apron into said receptacle, the upper portion of said second apron having an extension extending upwardly and forwardly to said frontal wall to form an upper chamber for reverse flow of the air therethrough whereby the air flows downwardly between the upper portions of said first and second aprons, and means in said upper chamber for projecting a sheet of liquid against said extension for distributing the liquid in a sheet over the surface of said upper chamber to maintain said surface clean.

7. In a spray booth type of gas cleaner having a work locus, a wash chamber, an air passage extending from said locus to said chamber, and a liquid receptacle in the lower part of said locus;

said passage comprisin an apron located in an upright position and rearwardly of said locus, a frontal wall provided spacedly forwardly of the upper portion of said apron and having a depending liquid sheet forming apron inclined rearwardly and downwardly toward said upright apron with its lower edge spaced forwardly of said upright apron to provide an opening for the upward flow of air through said opening forwardly of said upper portion of said upright apron, and means at the upper end of said upright apron for projecting a sheet of liquid to said inclined portion for forming on the latter another sheet of water to flow over said inclined portion and across said opening to said upright apron, a second upright apron located spacedly rearwardly of said first mentioned apron and having its lower end spacedly above said receptacle to provide an opening for passage of air therethrough, said liquid sheet projecting means having means forv projecting a sheet of liquid rearwardly to the upper portion of said second apron to form a curtain of liquid flowing down over the front face of said second apron and to form a curtain flowing down from the lower end of said second apron into said receptacle, the upper portion of said second apron having an extension extending upwardly and forwardly to said frontal wall to form an upper chamber for reverse flow of the air therethrough whereby the air flows downwardly between the upper portions of said first and second aprons, said sheet projecting means at the upper end of said upright apron being provided,

with means for projecting a sheet of liquid against said extension for distributing the liquid in a sheet over the surface of said upper chamber to maintain said surface clean.

GEORGE A. HARKER. ERIC GUSTAFSSON. GEORGE ALLEN. ROY NEISON.