CA1172443A

CA1172443A - Spray booth apparatus

Info

Publication number: CA1172443A
Application number: CA000389280A
Authority: CA
Inventors: Erhard Kock; Leo J. Zielinski
Original assignee: Individual
Current assignee: ABB Flexible Automation Inc
Priority date: 1980-12-11
Filing date: 1981-11-03
Publication date: 1984-08-14
Also published as: BE891292A; GB2089233A; FR2495963B1; DE3149253A1; JPS57117368A; MX153786A; SE8107414L; JPS6130631B2; IT1140099B; DE3149253C2; NL8105488A; BR8107864A; FR2495963A1; SE447067B; AU546396B2; CH655860A5; GB2089233B; IT8125509A0; AU7785081A

Abstract

ABSTRACT OF THE DISCLOSURE An improved water-wash spray booth of the type in which exhaust air lifts liquid from a reservoir to a trough and such lifted liquid flows from the trough over a floodsheet back to the reservoir. An open top chamber is positioned immediately below the liquid surface within the reservoir and is connect-ed at its bottom to a conduit which discharges into the re-servoir at a location spaced from the chamber. A flow of liquid from the trough above the floodsheet induces a turbulent flow of liquid from the surface of the reservoir downwardly through the chamber and out the conduit for breaking up paint particles into smaller particles. -16-

Description

z~43 BACKGROUND OF THE I NVENTI ON

1 The present invention relates to the separation of

2 li~uid and solid particles from a ~as and more particularly to an improved spray booth for removing paint overspray from 4 air.
Water-wash spray booths ar~ wcll known in the art and ~ generally comprise a water curtain flowing over a so-called 7 floodsheet against which overspray from one or more sp~ay guns 8 is directed. The overspray mingles with the water flowing 9 over the floodsheet ànd is collected in a reservoir. Many spray booths rely on a pump for the supply of water to the 11 water curtain, although recently many "pumpless" booths have 12 become known in the art. These booths rely on a very high 13 velocity exhaust air stream to pick up water from the reser-14 voir and to mingle it with the overspray. The entrained water 15 i5 separated from ~he exhaust air prior to discharge of the 1~ cleansed air by the exhaust fan. The separated water is used 17 to maintain the floodsheet. Early booths of this type require 18 considerable maintenance since thc paint laden water is con-19 tinuously recirculated through the system and also because there i5 a tendency for the paint to float as a foam on the 21 surface in the reservoir.
22 In an improved water-wash spray booth, as described in 23 Kearney United States patent 4,096,066, water flows from the ~4 floodsheet into a main reservoir or holding tank. An opened 26 top cone or chamber, sometimes rcferred to as a Dehon cone, 2~ i5 positioned immediately below the surface level within the 27 reservoir. A pump continuously draws liquid from the reser-;11 7~443 1 voir and causes a high velocity stream of such liquid to flow 2 through a venturi and back into the reservoir. Through this 5 arrangement, both foamed paint particles floating on the sur-4 face of the reservoir and paint particles suspended within the liquid are drawn into the chamber and forced through the ~ venturi back into the reservoir. This device breaks up the 7 paint particles into very small particles which more easily 8 separate solvent from paint solids so that the solids can 9 eventually settle as a dense mat on the bottom of the reser-voir. This system has greatly reduced the volume of paint 11 waste disposal ~rom the spray ~ooth and also has reduced 12- maintenance on the spray booth. However, periodic maintenance still is re~uired on the pump which circulates liquid from 14 the reservoir through the Dehon cone or chamber and through 1~ the venturi back to ~he reservoir.

18 According to the present invention, an improved water-19 wash spray booth is provided for collecting paint overspray and for separating such overspray from exhaust air drawn 21 through the spray booth. Paint overspray is directed towards 2~ a floodsheet over which a curtain of water flows. The water 23 curtain and paint collected in the water fall into a reservoir.
24 ~n exhaust fan draws air around the floodsheet and into an 26 upwardly directed entrainment duct. Along with such air, 2~ liquid particles are drawn from the surface of the reservoir 21 upwaxdly through the duct. The air and entrained liquid are 1 dra~n through a liquid separator which separates the liquid ~ including any entrained paint particles from the air and allows the dry air to be exhausted. The separated liquid 4 flows to a trough and thence overflows an edge of the trough ~ and 10ws downwardly over the floodsheet to form the water 8 curtain. ~he reservoir which receives the paint laden water 7 from the floodsheet is divided into at least two regions.
8 The paint laden water from the floodsheet is collected in 9 the first and second regions. The liquid in the first region flows to the second region and finally is drawn up through 11 the entrainment ducts and xecirculated through the spray booth.
12 An upwardly opening chamber or Dehon cone is positioned 13 within the second reservoir region and has a bottom opening 14 which is connected to a conduit which discharges into the first reservoir region below the liquid surface. In addition 1~ to forming a water curtain over the floodsheet, water supplied 17 to th2 trough above the floodsheet flows down a pipe to a 18 downwardly directed nozzle positioned above surface level 19 within the reservoir. The nozzle is positioned above and directs a water jet towards the bottom outlet of the chamber 21 or Dehon c~ne to induce a flow of liquid from the surface of 22 the second reservoir region downwardly through the chamber 23 or cone, through the conduit and into the first reservoir 24 region. The flow of liquid from the surface of the second re-servoir region downwardly throucJh the chamber or cone and 2a through the conduit back to the first region is turbulent 27 and breaks up the paint particles within the reservoir to ~8 allow the solids in such paint particles to settle to the 29 bottom of thP reservoir, forming a dense blanket. If desired, a modification may be made by incorporating a venturi within 1 the conduit connecting the chamber or Dehon cone with the 2 first reservoir region. By using a downwardly directed flow

3 of water from the trough to induce a flow of liquid from the

4 surface of the reservoir downwardly through the chamber or 6 cone, the need for a pump for producing such a li~uid flow ~ is eliminated. Consequently, maintenance required on the 7 spray booth is greatly reduced over that required in prior 8 art spray booths having liquid pumps since the only moving 9 element within the spray booth is the exhaust fan which con-tacts the exhaust air from which moisture and paint have been 11 removed.
12 Accordingly, it is an object of the invention to pro-vide an improved water-wash spray hooth.
14 Another object of the invention is to provide an improved water-wash spray booth which requires no liquid pump for 1~ operation.
17 Other objects and advantages of the invention will be-18 come apparent from the following detailed description, with 19 reference being made to the accompanying drawings.

22 Fig. 1 is a fragmentary perspective view of a paint 23 spray booth constructed in accordance with the present inven-24 tion;
2~ Fig. 2 is a cross-sectional clevational view taken through 2~ the spray booth of Fig. 1;
27 Fig. 3 is a cross-sectional view taken along lines 3-3 28 of Fig. l;

-~72~43 1 Fig. 4 is a fragmentary cross-sectional elevational 2 view showing a modified nozzle and chamber f~r inducing a S li~uid flow to break up paint particles within the reservoir 4 of the spray booth of the present invention; and Fig. 5 is a fragmentary cross-sectional elevational ~ view showing a further modified chamber and nozzle for induc-7 ing a liquid flow to break up paint particles within the re-8 servoir of the spray booth of the present invention.

DESCRIPTION OF THE PREFE~RED EMBODIMENT
11 Turning now to the drawings and particularly to Figs.
12 1-3, a fragmentary portion of a water-wash spray booth 10 1~ constructed in accordance with the present invention is illu-14 strated. The spray booth 10 includes a body or housing 11 defining a side opening 12. A workpiece 13 to be sprayed with 18 paint from a spray gun 14 is positioned in front of the side 17 opening 12 so that overspray is directed at a floodsheet 15.
18 The floodsheet 15 is positioned below an upper edge 16 on a 19 trough 17. The edge 16 is horizontally disposed so that a ~ continuous flow of water supplied to the trough 17 uniformally 21 flows over the edge 16 and cascades as a water curtain down 22 the surface of the floodsheet 15. Water flowing from the 23 floodsheet 15 falls into a first region 18 and a second re-24 gion 22 of a reservoir 19 defined by the lower part of the 26 housing 11. From the first reservoir region 18, the collect-2~ ed paint and water flow around a partition 20 and over one or 27 more submexged baffles 21 to thc second reservoir region 22.

~0 1 As will be described hereinafter, the solids from a majority 2 of the paint accumulated in the reservoir 19 settle within the first region 18.
4 The reservoir 19 includes a third region 23 separated ~ from the first and second regions 18 and 22 by a baffle 24.
8 A submerged opening 25 in the baffle 24 connects the second 7 re~ervoir region 22 with the third reservoir region 23, The 8 ~bmerged opening 25 allows water to flow from the second 9 region 22 to the third region 23 while the baffle 24 confines ~loating paint to the first and second regions 18 and 22.
11 Room air along with any paint overspray which does not læ strike the workpiece 13 or the floodsheet 15 is drawn around 13 the periphery of the floodsheet 15 into a back portion o~
14 the housing 11. From here, the air an~ entrained paint are drawn vertically upwardly through an entrainment duct 26.
1~ The entrainment duct has a lower opening 27 spaced just 17 above the liquid surface in the third reservoir region 23.
18 The velocity of the air drawn into the duct 26 through the 19 opening 27 is sufficiently high so as to entrain a great ~olume of liquid from the reservoir surface and mingle such 21 entrained li~uid with the uprushing air stream. Preferably, 22 several of the entrainment ducts 26 are spaced across the 23 back of the spray booth housing 11. ~t the top of each en-24 trainment duct 26, the liquid laden air is diverted laterally 2~ by a splitter assembly 55 and then proceeds through a series 2~ of baffles 28. The air is forced to rapidly change direction 27 and decrease in velocity at these points so that a significant ~8 2~

1 quantity of the entrained liquid falls from the air stream 2 into a ~ump 29. A second series of baffles 30 cause a further 3 rapid change in the direction of air flow as the air is drawn 4 into plenum chamber 31. The baffles 28 and 30 which cause rapid changes in the air flow directlon function as a liquid ~ aliminator for removing the entrained liquid from the exhaust 7 aix. Prom the plenum chamber 31, the dry air is drawn over 8 a perforated ~affle plate 3~ and is drawn upwardly through a 9 exhaust 33 by a suitable fan 35 or blower located within the exhaust 33.
11 As the liquid laden air is drawn through the baffles 28 12 and 30 for extracting water and paint particles from such 13 air, the liquid settles into the sump 2'~. From the sump 29, 14 the liquid passes downwardly through drain pipes 34 which lead to the trough 17. A sufficient water flow passes through lB the drain pipes 34 to the trough 17 so as to maintain the water 17 curtain over the floodsheet 15~ The drain pipes 34 extend 18 below the lip or edge 16 of the trough 17 so that the bottom 19 36 of the drain pipes are always bclow the surface level of liquid in the trough 17. This prevents the fan 25 from 21 drawing air upwardly through the drain pipes 33.
22 In accordance with the present invention, a chamber 38 23 is located within the second reservoir region 22. The chamber 24 38 preferably i9 in the shape of an inverted cone and has 2~ an upper opening 39 located just bclow the liquid surface 2B level within the reservoir 19. ~ conduit 40 connects to the 27 bottom of the chamber 38 and leads throu~h the partition 20 ~7~
1 into the first reservoir reqion 18 at a point spaced below 2 the liquid surface. The chamber 38 functions in a manner S similar to that described in the above mentioned Kearney 4 United States patent 4,096,066. Reservoir liquid and paint floating on the surface of liquid in the reservoir 19 are ~ drawn into the upper end of the chamber 38 and turbulently 7 caused to flow downwardly and through the conduit 40. The 8 turbulent flow breaks up the paint paxticles into smaller 9 particles and disperses such particles into the first reser-voir region 18. As the paint particles break up into smaller 11 particles, solvent separates from the paint solids and the 12 paint solids settle to the bottom of the reservoir 19 and 13 form a dense mat 41. By removing the floating paint particles 14 from the surface of the liquid in the reservoir 19 and caus-ing such particles along with larger paint particles dispersed 1~ in the reservoir liquids to settle as a dense mat on the 17 bottom of the reservoir 19, maintenance of the spray booth 18 10 is greatly reduced.
19 In accordance with the present invention, the flow of liquid including floating paint particles and larger dispersed 21 paint particles within the reservoir 19 is induced downwardly 22 through the chamber 38 by means of a liquid jet. The liquid 23 jet is produced from liquid flowing from the trough 17 through 24 a standpipe 37 and a down pipe 42. The standpipe 37 extends 26 above the level of the bottoms 36 o the drain pipes 34 and 2~ below the lip ox edge 16 of the trough 17 so that liquid 27 will flow from the trough 17 into the standpipes 37. However, -~7~3 1 the standpipe 37 will not lower the liquid level in the trough 2 17 below the bottoms 36 of the dr~in pipes 34 so air cannot 3 be drawn into the drain pipes 34. The down pipe 42 connects 4 from the standpipe 37 in the trou~h 17 to a downwardly directed nozzle 43. The nozzle 43 is located above the cham-~ ber 38 and is positioned to direct a high veloci y stream 7 of liquid through the upper chamber opening 39 towards the 8 inlet to the conduit 40. The downward flow of liquid into the ~ chamber 38 induces a flow of liquid from the liquid surface within the reservoir region 22 downwardly through the chamber 11 38 and the conduit 40 and into the reservoir region 18.
12 The li~uid jet also induces a hi~h turbulence in the liquid 13 flow throuqh the conduit 40 to E~cilitate brcaking up the 14 paint particles dxawn downwardly from the reservoir surface through the chamber 38 and the conduit 40 and ejected into 1~ the reservoir region 18. As the paint particles are broken 17 up into smaller particles, the solvent in the paint is more 18 readily stripped from the solids, thereby allowing the heavier 19 solids to settle out in the first reservoir region 18 to form the mat 41. Consequently, very few suspended solids remain 21 in the liquid flowing into the third reservoir region 23 22 which is drawn upwardly through the entrainment ducts 26 and 23 supplied to -the trough 17. Since the liquid is circulated 24 through the spray booth 10 without the use of a liquid pump 26 and also since a liquid pump is not required for causing a 2~ flow of surface liquid in the rescrvoir 19 through the chamber 27 38, maintenance on the spray booth lO is qreatly reduced over -- -- ;

~ ~L7~3 1 prior art spray booths which require the use of a pump for 2 circulating liquids through a chamber such as the chamber 3 38. Turnin~ now to Fig. 4, a modified device using a Dehon 4 cone 44 is illustrated for use in the spray booth 10. The

5 Dehon cone 44 has an upper opening 45 which is positioned ~ immediately ~elow the liquid surface level within the spray 7 booth reservoir. The Dehon cone 44 also has a lower outlet g 46 connected to a conduit 47 for discharging fluicl into a 9 lower region of the reservoir. The nozzle 43 is positioned immediately above the liquid surface level within the reser-11 voir for directing a liquid jet from the trough (trough 17 12 in Figs. 1 and 2) into the cone 44 for inducing a flow of 13 surface liquid from the reservoir through the conduit 47~
14 A venturi 49 is located within the conduit 47. The venturi 16 49 increases the flow velocity and may help establish tur~
1~ bulence within the conduit 47. In a further modification, }7 the nozzle 43 may be replaced by or supp~emented with a nozzle 18 50 conn~cted to a down pipe 42' (shown in dashed 1ines~ for 19 extending into the conduit 47 and directing a liquid jet towards a conduit outlet ~not shown) for inducing a flow of 21 liquid from the reservoir surfacc downwardly through the 2~ cone 49 and through the conduit 47. Again, the liquid jet 23 emanating from the nozzle 50 is formed from liqu d flowing 24 from the trough 17 (Figs. 1 and 2) and through the down pipe 42' without the use of a separate pump for causing a liquid 2~ flow through the cone 44.

~ ~7Z~3 1 Still a further modified structure is shown in Fig. 5 ~ in which two nozzles 51 and 5~ are positioned above the upper 3 opening 53 of a Dehon cone 54 for directing fluid ~ets down 4 wardly through the cone 54 towards a conduit 55. The no~zles

6 51 and 52 may be connected to separate down pipes from the ~ liquid trou~h located above a floodsheet in a spray booth.

7 It will be appreciated that various modifications and

8 change~ may be made in the above described spray booth~

9 In accordance with the present invention, a pumpless water-wash spray booth of known design is provided with a chamber 11 located within and immediately below the surface of a li~uid 12 reservoir. A flow of liquid induces a downward Elow of liquid 13 from the reservoir surface throu~h the chamber for breaking 14 up paint particles within the reservoir so that they may settle to the bottom of the reservoir. The flow of water is lff achieved without the use of a mechanical pump.

~4

Claims

WHAT WE CLAIM IS:

1. A paint spray booth comprising a wall, a -trough positioned above said wall, means for supplying a continuous flow of liquid to said trough, such liquid flowing from said trough as a curtain over said wall for entraining paint over-spray, reservoir means having first and second regions with said first region located below said wall for receiving such liquid curtain, such received liquid flowing from said first reservoir region to said second reservoir region, a chamber having an upper opening disposed immediately below the liquid surface in said second reservoir region and having a bottom, conduit means connecting said chamber bottom with said first reservoir region, and down pipe means connected to carry a flow of liquid from said trough to said reservoir for inducing a turbulent flow of liquid from the surface of said second reservoir region downwardly through said chamber and through said conduit to said first reservoir region.

2. A paint spray booth, as set forth in claim 1, where-in said chamber has the shape of an inverted cone.

3. A paint spray booth, as set forth in claim 2, wherein said down pipe means includes a nozzle spaced above the reservoir liquid surface above said cone shaped chamber, said nozzle directing a flow of liquid from said trough down-wardly at the interior of said cone shaped chamber towards said conduit means whereby liquid discharged from said nozzle causes a turbulent flow of liquid from the reservoir surface downwardly through said cone shaped chamber into said conduit means.

4. A paint spray booth, as set forth in claim 1, and further including means for exhausting air from said spray booth, and wherein said means for supplying a continu-ous flow of liquid to said trough includes means for entraining reservoir liquid in such exhaust air, said exhausting means drawing such exhaust air and entrained liquid above said trough, means for separating such entrained liquid from such exhaust air, and gravity operated means for supplying such separated liquid to said trough.

5. A paint spray booth, as set forth in cliam 4, wherein said gravity operated means comprises at least one drain pipe carrying such separated liquid from said separat-ing means to a predetermined location in said trough below the liquid surface level in said trough, and wherein said down pipe means includes stand pipe means for supplying a flow of liquid from said trough to said down pipe means from above such predetermined location.

6. In a paint spray booth in which exhaust air supplies a flow of liquid from a reservoir to a trough, the improve-ment comprising a chamber having a upper opening disposed immediately below the liquid surface in said reservoir, said chamber having a bottom, conduit means connecting said cham-ber bottom with a location in said reservoir spaced from said chamber, and down pipe means connected to carry a stream of liquid from said trough to said reservoir for inducing a turbulent flow of liquid from the liquid surface in said reservoir downwardly through said chamber and through said conduit means.

7. An improved paint spray booth, as set forth in claim 6, wherein said chamber has the shape of an inverted cone, and wherein said down pipe means includes a nozzle spaced above the reservoir liquid surface above said cone shaped chamber, said nozzle directing a flow of liquid from said trough downwardly at the interior of said cone shaped chamber towards said conduit means whereby liquid discharge from said nozzle causes a turbulent flow of liquid from the reservoir surface downwardly through said cone shaped chamber into said conduit means.

8. An improved paint spray booth, as set forth in claim 6, wherein said down pipe means includes a nozzle having an opening located to discharge a flow of liquid from said trough directly into said conduit means for inducing a tur-bulent flow of liquid from the reservoir surface downwardly through said chamber and into said conduit means.