US3424129A - Spray booth - Google Patents

Description

Jan. 28, 1969- D. J. PEEPS ET AL 3,424;129

SPRAY BOOTH Filed April 20, 1967 Sheet of 4 INVENTORS. pal/4w J @595 a? Lav/5 M Un [A/ BY 8 pm V, AIME/V6745.

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SPRAY BOOTH Filed April 20,. 1967 Sheet 4 of 4 L i a 1 4' AZ "4' 51 1? Z United States Patent 3,424,129 SPRAY BOOTH Donald J. Peeps, Rossford, and Lewis M. Owen, Toledo,

Ohio, assignors to The DeVilbiss Company, Toledo Ohio, a corporation of Ohio Filed Apr. 20, 1967, Ser. No. 632,297

US. Cl. 118-314 14 Claims Int. Cl. B05c 11/16, 5/00 ABSTRACT OF THE DISCLOSURE A spray booth is provided in which air is directed into the booth primarily around the spray heads and is exhausted from the booth at a remote location. "Flow of air is thus established toward the article being coated with little turbulence and air is supplied where it is needed the most, thereby minimizing air requirements for the spray booth. The equipment, including spray heads, reciprocators, and controls are not located directly in the coating chamber and are not subject to spray backlash, thereby reducing cleaning and increasing operating time. The oporator is similarly situated, eliminating the requirement for using a respirator and reducing possible hazard to him. 'IIhe spray heads are sometimes moved toward and away from the coating chamber in order to accommodate articles of different sizes. In such an instance, the spray booth also has means to maintain the position of entry of the air constant relative to the spray heads.

This invention relates to spray apparatus for coating articles and specifically to a spray booth using much less air than is commonly required and in which air is directed with little turbulence around the spray heads and toward the articles.

In a spray booth, the principal reason for moving air therethromgh and exhausting air therefrom is to maintain sprayed coating material particles in the air below an explosive concentration; the air requirements for this purpose are relatively small. However, much higher air volume has been needed in spray booths to protect the operator therein. Consequently, the air volume requirements in a spray booth could be reduced substantially if the operator were situated in a separate area or chamber substantially free of sprayed particles. Similarly, spray booths require relatively high volume to carry away overspray and prevent spray backlash onto the coating material equipment, which causes frequent shutdowns and cleaning. The high aid volume again could be substantially reduced if such equipment were positioned similarly to the operator.

In accordance with the invention, it has been found that a spray booth can be divided into two chambers with a wall therebetween located near the spray heads and having an inlet opening around the spray heads for directing air past the spray heads and toward the article being coated. The air can then be exhausted from the spray booth at a location remote from the spray heads and the inlet opening in order to direct the air where it is needed the most and to minimize turbulence in the air flow. The operator as well as the spray head reciprocators, controls, and related components are then located in the spray booth on the side of the wall opposite the article being coated. The air entering the opening around the spray heads can move at relatively high velocity, even though of relatively low volume, because of the restricted size of the opening. This velocity virtually eliminates any possibility of overspray coming back through the opening and into contact with the operator or the spray applicator components. Hence, with the use of relatively low volume air, the operator and the components are protected from "ice overspray. After the air passes through the restricted opening into the coating chamber, it can disperse so that its velocity drops substantially. In this manner, the spray particles are not carried at relatively high velocity to the article being coated, in which case a substantial part of the particles is carried past the article as overspray.

The substantial reduction of air requirements enables a substantial reduction in the size of blowers and ducts employed, which reduces their initial as well as operating costs. Further, the air supply to spray booths is heated, particularly for operator comfort, and the cost of heating is often a substantial cost in the overall operation of spray booths. By substantially reducing the air requirements to the spray booth, heating cost of the air is also substantially reduced.

In some applications, the spray heads are moved toward and away from the center of the booth as the size of the articles being coated varies in thickness. Thus, the spray heads are moved back from the booth center for thicker articles and forwardly into the booth for thinner articles. In such an instance, the relationship of the spray heads to the inlet opening through which air is supplied into the chamber will vary and change the air flow characteristics around the spray heads. To maintain the air flow characteristics constant and uniform with respect to the spray heads, the present invention provides walls or shrouds forming a relatively narrow air inlet around the spray heads and arranged to move with the spray heads as they are moved into and out of the chamber. A wall defining part of the coating chamber is provided with a passage which cooperates with the shroud so that substantially no air can pass between the passage walls and the shroud. In this manner, all of the air flowing into the chamber passes around the spray heads in a constant pattern, regardless of the position of the spray heads relative to the article being coated, to maintain constant air flow characteristics relative to the spray heads.

It is, therefore, a principal object of the invention to provide a spray booth which requires a substantially lower volume of air than heretofore, resulting in a substantially lower operating cost.

Another object of the invention is to provide a spray booth having means for directing air entering a coating material chamber thereof past the spray heads and toward the workpiece in a non-turbulent manner.

A further object of the invention is to provide a spray booth having a coating material chamber and an air supply chamber for an operator and spray components with a restricted opening between the chambers through which air and coating material particles are supplied to the coating material chamber, thereby reducing contamination of the coating material components by overspray.

Yet another object of the invention is to provide a spray booth having spray heads movable toward and away from a coating material chamber, and having means for directing substantially constant flow of air past the spray heads toward the article, regardless of the position of the spray heads relative to the article.

Other objects and advantages of the invention will be apparent from the following detailed description of preferred embodiments thereof, reference being made to the accompanying drawings, in which:

FIG. 1 is a perspective view, wth parts broken away, of a spray booth embodying the invention;

FIG. 2 is a view in vertical, transverse cross section of the spray booth of FIG. 1;

FIG. .3 is a view in horizontal cross section of the spray booth of FIGS. 1 and 2;

FIG. 4 is a slightly enlarged, detailed view of part of the spray apparatus of FIG. 3;

FIG. 5 is a fragmentary view in horizontal cross section of a modified spray booth; and

FIG. 6 is a view on horizontal cross section of modified spray apparatus and air inlet openings.

A spray booth according to the invention is indicated at 10 and includes a central coating material chamber 12, preferably somewhat wider than the widest article expected to be coated therein. The spray booth can be used with an overhead conveyor 14- to provide a semicontinuous operation, the conveyor extending centrally longitudinally through the chamber 12. While the conveyor 14 is shown as being overhead, a floor conveyor may be used. In either case, the article is preferably grounded electrically through its support when electrostatic coating is employed. The length of the chamber 12 depends in part on the coating operations. For example, for an automobile body, a first part of the length of the chamber can be used to coat the sides of the body, a second part can be used to coat the top, hood, and trunk lid, and a third part employed for touch-up work.

The principles of the invention also apply to any conventional spray booth in which articles are moved into the chamber through a side opening, coated, and removed through the same opening. However, the use of the invention in connection with a continuous type booth in which openings are provided at both ends for the ingress and egress of articles is particularly advantageous. With air applied directly at the location where it is neeeded, around the spray heads, and directed toward the articles being coated, air that enters through the end wall article openings does not seriously interfere with the coating process.

A relatively high velocity is only needed at the restricted opening around the spray heads rather than across the entire spray booth as has heretofore been necessary. The air can disperse after entering the coating material chamber through the restricted opening and thereby slow down substantially. Consequently, there is no high velocity air carrying the coating material particles to and past the article being coated which tends to increase overspray. The high velocity air only at the spray head opening is sufficient to prevent backlash of coating materialparticles to the spray heads and into the air supply chamber where they could contaminate the coating material apparatus and be a hazard to the operator. Since a substantially lower volume of air is required for spray booth, only a sufiicient amount to provide the necessary velocity through the opening, the ductwork and fans or blowers employed can be substantially reduced in size. This results in both a lower initial cost and lower operating cost. Further, the cost of heating the air, which is a substantial factor, especially in colder climates, is also correspondingly reduced.

The substantial reduction in air volume achieveable with the use of the invention is illustrated by an example of a conventional spray booth. In the spray booth, which measures 12 feet by 12 feet, an air volume of 14,400 c.f.m. was required to attain an air velocity of 100 f.p.m. in the booth. While a much lower velocity could have been employed to maintain the concentration of volatile coating material particles below an explosive level, the higher velocity was necessary to carry off the overspray and prevent excessive contamination of the coating equipment and undue hazard to the operator. A wall was then installed dividing the spray booth into a coating material chamber in which the articles were coated and an air supply chamber containing the coating material components and the operator, and an opening measuring 2 feet 6 inches wide by 12 feet high was made in the wall around the spray heads. With this opening, an air volume of only 3300 c.f.m. was required to achieve an air velocity of 110 f.p.m. through the opening. This velocity was sufiicient to prevent coating material particles entering the opening into the air supply chamber and yet the air dispersed after passing through the restricted opening so as not to carry the coating material particles at an excessive speed toward and past the articles being coated.

By way of another example, in one 40 foot long continuous booth, 90,000 c.f.m. of air was previously required to assure an adequate flow. This continuous booth was used to coat automobile bodies and a 10 foot section at the exit end was employed to touch-up the bodies. When the system according to the invention was employed in this booth, the air requirement was reduced to only 36,000 c.f.m. and could have been lower except for the fact that the conventional air exhaust system was still employed in the touch-up area, constituting about onefourth of the boothlength.

An article designated A can be carried through the chamber 12 on hangers 16 suspended from the conveyor 14 with the articles moving into the chamber through an opening 18 (FIG. 3) and out of the chamber through an opening 20, each of which openings can be adjustable with sliding doors to maintain the openings as small as possible for the width of the particular article being coated.

Both sides of the article can be coated by spray units 22 which include coating or spray heads 24 mounted on a suitable supporting post or stem 26, with the spray heads supplied with coating material from a container which can be located away from the spray area. The stem 26 is preferably reciprocated to assure uniform coating of a large article from the plurality of spray heads. A suitable reciprocator may be disposed in a housing 28. The entire unit including the spray heads, supporting frame, and the reciprocator housing can be mounted on a carriage 30 having wheels 32 movable on tracks 34. This enables the spray heads to be moved in and out with respect to the chamber 12 to maintain a given distance between the spray heads and the adjacent surfaces of the articles being coated. The spray heads may also be moved in and out for each article being coated, if the width thereof varies from one end to the other. A remote power supply (not shown) is provided to establish an electrostatic field adjacent the spray heads, in a known manner.

The spray units 22, each comprising a bank of spray guns and their operating mechanism, are located in virtually separate outer, air supply chambers 36 on each side of the coating chamber 12 and separated therefrom by sidewalls or partitions 38. Air for the coating chamber 12 is supplied through the chambers 36, in this instance, from outside the building in which the spray booth is located. For this purpose, a main supply duct 40 is connected to two branch ducts 42, which communicate with the supply chambers 36, with the main duct 40 having an inlet outside the building. A heater 44 and a suitable supply blower 46 are located in the main duct 42 for supplying and-Warming the outside air.

The air from the supply chamber 36 passes into the coating material chamber 12 through restricted openings designated 48 formed in the partition or wall 38, with side edges of the openings 48 being defined by side plates 50. The volume of air need be only enough to establish a velocity through the openings 48 sufiicient to prevent deposit of coating material particles onto the spray heads 24 or the related components in the supply chamber 36. The necessary air flow in the coating material chamber for preventing coating apparatus contamination and hazard to the operator will then be much closer to that required to maintain the concentration below the minimum explosion level.

In order to maintain the air flow characteristics constant around the spray heads 24, regardless of their position, a shroud or inlet 52 formed by inwardly directed plates or walls 54 is mounted on each of the carriages 30 and movable therewith. As shown particularly in FIG. 4, outer peripheral edge portions 56 of the plates 54 extend close to the side plates 50 so that substantially no air will pass therebetween. Inner edges 58 of the shroud plates 54 form an opening of constant area around the spray heads 24 so that the area of this opening and the relationship of the opening to the spray heads remains constant regardless of the position of the spray heads.

In order to maintain a smooth flow of air and reduce turbulence to a minimum, the air is exhausted from the chamber 12 at a location remote from the inlet openings 48. In the form of the booth shown, exhaust openings for the air from the booth are provided in the floor of the coating chamber 12 by grating 60. The exhaust openings can be located across the entire floor or only a portion thereof on the side of the chamber spaced from the spray heads. The air exhausted through the grating can be pulled through lower exhaust chambers or water tanks 62 and upwardly through vertical exhaust ducts 64 having headers 66 by exhaust fans 68. Water is sprayed from the headers 66 over bafiles 67 to clean the air as it flows through the exhaust ducts 64. As shown, the exhaust ducts are located in the supply chambers 36, at spaced portions thereof. The chambers 36 also have access doors 70 for an operator who can work in the chambers 36 without hazard from the coating material particles which are kept entirely out of the chambers.

In one form, the capacity of the exhaust fans 68 is slightly less than the capacity of the supply fans or blowers 46 so that a slight positive pressure will be maintained in the chamber 12, thereby preventing the flow of air-borne particles, such as dust, into the chamber 12 through the end openings 18 and 20.

While the exhaust openings in the form shown are located in the floor of the chamber 12, the exhaust openings can also be located in the sidewall directly opposite the spray heads so that the flow of air in such an instance is across the booth and around the articles. In either case, the exhaust openings are remote from the inlets to provide a smooth flow of air and maintain minimum turbulence in the chamber. When the spray heads and air inlets are located overhead, as adjacent a topcoating device, the exhaust openings again can be in the floor, as shown, or in lower portions of the sidewalls of the coating chamber. Further, while the spray heads are shown as being mechanically manipulated, they can also be manually manipulated by an operator in the supply chamber 36.

A slightly modified spray booth 72 is partly shown in FIG. 5. This booth again is of the continuous type with a suitable conveyor for carrying articles A therethrough. In this instance, the articles A, to be coated on both sides again, do not vary more than a few inches in thickness. Consequently, spray heads 74 are supported on stationary control housings 76. The spray heads can reciprocate but need not move in and out with respect to the workpiece.

In this instance, the spray booth apparatus is located in an existing enclosed area or room designated 78 which can be provided with a forced supply of air by fans 80 if desired, although this is not essential if the room is of sufficient size and has sufficient openings. As with the booth 10, walls or bafiles 82 divide the spray booth into coating material chambers 84 and air supply chambers 86. All of the air for the coating material chambers is thereby supplied through inlet openings indicated at 88 having side plates 89 directing the air inwardly. As with the previous spray booth, the air in this instance flows at relatively high velocity through the openings 88 so that a relatively small volume of air will provides sufiicient velocity to prevent coating material backlash. The control housings 76 and similar components will remain uncontamina-ted and an operator can be in or adjacent the supply chambers 86 without hazard.

The air is exhausted from locations spaced from the inlet openings 88, with the air flowing from the inlets to the exhaust outlets past the articles A. In this instance, the outlets are provided by a plurality of bafiies 90 through which the air travels by a circuitous route to exhaust ducts 91 which are equipped with the usual exhaust blowers (not shown).

Frequently, the flow of air in a spray booth will change over a period of time as conditions change, e.g. the filters becoming partially clogged, etc. In such an instance, the pressure differential between the air supply and coating material chambers may vary and change the flow pattern. To minimize this variation and also to supply some additional air between the articles A, louvers 92 can be employed in the sidewalls 82, located adjacent the inlet opening 88 in this instance. The air through the louvers 92 helps balance pressure differential between the chambers by increasing air flow into the coating chamber as the pressure differential increases, and vice versa. The louvers also reduce any tendency for the overspray to be deposited on articles adjacent the one being coated.

It will be seen that the spray booth 72 of FIG. 5 differs from the previous one in several respects. The spray heads 74 are stationary in this instance. The air supply chambers 86 do not have a direct supply of air. The air is exhausted from the opposite sidewall of the spray booth. Finally, the control louvers are employed to balance and influence air flow.

Referring to FIG. 6, a slightly modified spray device is shown. In this instance, spray heads 94 are mounted in two banks on posts or stems 96 which are connected by a cross bar 98 to structural members 100 and a housing 102. The housing 102 in this instance is mounted by means of a carriage 104 on tracks 106 for movement toward and away from the workpiece. Where the banks of spray heads 94 are spaced apart more than about four feet, an inlet opening generally designated 108 is equipped with a central bafile or wall 110 blocking space in the opening 108 between the banks of the spray heads 94. The bafiie 110 can be mounted on a shroud 112 encompassing both banks of spray heads and having side plates 114 cooperating with side plates 116 adjacent the edges of the opening 108. The spray heads and shroud can be partially suspended by an overhead trolley, in this instance, and move in and out with the carriage 104. Particularly if the control housing 102 and the spray heads 94 are stationary, the shroud 112 and the baffle 110 can be stationary with respect to the opening 108.

Various modifications of the above described embodiments of the invention will be apparent to those skilled in the art, and it is to be understood that such modifications can be made without departing from the scope of the invention, if they are within the spirit and the tenor of the accompanying claims.

We claim:

1. Apparatus for aiding in coating articles comprising means forming a coating chamber, a support in said chamber for an article to be coated, means forming an air supply chamber, a wall common to the coating chamber and said air supply chamber having an air inlet opening therein between said air supply chamber and said coating chamber to direct air from said air supply chamber to said coating chamber, a spray head adjacent said inlet opening for directing coating material particles toward the article, a shroud having an opening therein positioned around said spray head and mounted in said inlet opening in a predetermined position relative to said spray head for directing air from said air supply chamber through said shroud past said spray head, and means for exhausting air from said coating chamber at a location remote from said inlet opening so that the coating material particles and the air travel in the same general direction across said coating chamber to minimize turbulence as the air flows through said coating chamber from said inlet opening around said spray head and to the exhaust.

2. Apparatus according to claim 1 wherein said exhaust means is located in the floor of the coating chamber.

3. Apparatus according to claim 1 wherein said article supporting means supports said article at least partly in the path of the air flowing from said air inlet opening to said exhaust means.

4. Apparatus according to claim 1 characterized further by said air supply chamber being enclosed on all sides and having access means by which an operator can enter said air supply chamber.

5. Apparatus according to claim 1 characterized further by said shroud having an additional opening therein between the coating chamber and the air supply chamber, and an additional spray head in said additional opening.

6. Apparatus according to claim 1 characterized further by air supply means communicating between said air supply chamber and ambient, outside air for supplying outside air directly to said air supply chamber.

7. Apparatus for aiding in coating articles, said apparatus comprising means forming a coating chamber, a support in said chamber for supporting an article to be coated, a spray head, a carriage supporting said spray head for movement toward and away from the article, a wall common to said coating chamber and an air supply chamber, said wall having an opening between said chambers, means associated with said opening and forming a passage in the direction of the path of movement of said carriage, and means on said carriage and movable therewith in said passage forming an air inlet around said spray head.

8. Apparatus according to claim 7 characterized by said air inlet forming means extending close to said passage means so that air flow between said supply chamber and said coating chamber is substantially restricted to the air inlet around said spray head for any operating position of said carriage relative to the article.

9. Apparatus according to claim 8 wherein said passage means has a length at least equal to the length of the path of said carriage.

10. Apparatus according to claim 8 wherein said air inlet means on said carriage comprises slanted wall means, the outer edges of which extend closely to said passage means and the inner edges of which form the inlet opening to direct the air inwardly toward the path of particles issuing from the spray heads.

11. Apparatus according to claim 8 wherein said passage is formed by parallel plates affixed to said wall and said air inlet forming means comprises ashroud formed partially around said spray head and being of truncated conical shape in horizontal cross section with the outer edges of the shroud disposed closely adjacent said plates for all positions of said spray head.

12. Apparatus according to claim 7 characterized further by means forming an air exhaust opening spaced remotely from said air inlet.

13. Apparatus according to claim 7 characterized further by said inlet forming means having an additional inlet opening between said coating chamber and said air supply chamber, an additional spray head in said additional inlet opening.

14. Apparatus according to claim 7 characterized further by said air supply chamber being enclosed on all sides and having access means by which an operator can enter said air supply chamber.

References Cited UNITED STATES PATENTS 2,230,646 2/41 Klausmeyer.

2,445,074 7/48 McCue.

3,170,384 2/65 Krantz et al. 98l15 X 3,270,711 9/66 Leach 118326 X 3,279,421 10/66 Tilney et al. 118-323 X WALTER A. SCHEEL, Primary Examiner.

J. P. MCINTOSH, Assistant Examiner.

U.S. Cl. X.R.

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