Method and device for cleaning a spray gun assembly
BACKGROUND OF THE INVENTION 
     1. Field of the Invention--This invention relates to a novel method and device for cleaning a spray gun assembly that is contaminated with liquid spray material of any type. The novel cleaning method and cleaning device is especially useful for removing residual rapidly-curing spray paint from all of the inside and outside surfaces of a spray gun assembly. 
     2. Description of the Prior Art--A spray gun assembly includes a spray gun, a gun cup having an open end for storing liquid spray material, such as spray paint, while the gun is being used and means for operatively connecting the gun cup to the gun. The gun assembly may be of the siphon-feed type, the gravity-feed type, or the forced-feed type. 
     With any of these types, it is absolutely necessary to thoroughly clean all parts of the assembly of spray material promptly after every use. In an automobile body repair shop, it is common practice to use a spray gun assembly several times in a single day with different paints. Cleaning the spray gun assembly after each use is ordinarily a time consuming and labor intensive task. With the increasing use of catalyzed spray paints, the cleaning problem is aggravated because residual paint in the spray gun assembly cures in a much shorter time than do uncatalyzed paints. Spray paints and spray-painting equipment are described in Automotive Collision Work by Edward D. Spicer, American Technical Society, Chicago, 1972 and Paint &amp; Body Handbook by Don Taylor and Larry Hofer, HP Books, Tucson, Arizona, 1984. 
     Several devices for cleaning or washing contaminated tools are described in prior patents, for example, U.S. Pat. Nos. 3,416,544 issued to J. Paiva; 4,101,340 issued to B. Rand; 4,108,379 issued to H. J. Talley; 4,443,269 issued to J. A. Capella et al.; 4,561,903 issued to R. L. Blaul; 4,612,025 issued to R. W. Sampey; and 4,630,625 issued to J. A. Capella et al. 
     Each of these prior devices is relatively bulky and requires considerable hand manipulation of the tools by the operator for carrying out the cleaning. Because of the size of these prior devices, noise generated therein is not well contained. Some of the prior devices include blowers for circulating vapor-laden air in the devices and/or pumps for circulating liquid solvents in the system. The use of such blowers and/or pumps on combustible liquids and vapors is hazardous and requires substantial safety precautions to be taken. In general, these prior devices are not particulary adapted for cleaning spray-gun assemblies, and are especially not adapted for use in automobile body repair shops. 
     OBJECTS OF THE INVENTION 
     An object of this invention is to provide a novel method and a novel device for cleaning a spray gun assembly. 
     A further object is to provide a device of this type which is relatively compact, relatively light in weight and relatively low in cost. 
     Another object is to provide a device of this type which requires a minimum of labor and time to thoroughly clean a spray gun assembly. 
     A still further object is to provide a device of this type that is powered entirely by compressed air, does not employ electricity or blowers or pumps and is provided with a means for protecting personnel from noxious fumes and from excessive noise. 
     Another object is to provide a novel method and a novel device that is particularly adapted for rapidly cleaning residual catalyzed spray paint from spray-gun assemblies in automobile body repair shops. 
     SUMMARY OF THE INVENTION 
     The foregoing objects may be realized with the novel method and novel device for cleaning a spray gun assembly which includes a spray gun, a gun cup, and a means for operatively connecting the cup to the gun. The method includes: 
     (a) positioning the spray gun, with the cup-connecting means attached thereto, on a stationary support in a closed chamber, 
     (b) positioning the gun cup in a rotatable cup holder in the closed chamber, 
     (c) passing compressed air and cleaning liquid through the interior of the gun and the cup-connecting means, and 
     (d) simultaneously with step (c), rotating the cup holder, spraying the exterior surfaces of the gun, the cup-connecting means, and the rotating cup with cleaning liquid, and spraying the interior surfaces of the rotating cup with cleaning liquid. 
     In a preferred embodiment, the spray produced by cleaning the interior surfaces of the gun is used to rotate the cup holder and the cup contained therein. The method includes supplying compressed air from outside the chamber and exhausting air from the chamber. The method preferably includes the steps of filtering the cleaning liquid and absorbing fumes in the air exhausting from the chamber. 
     The novel device includes a closed chamber which has therein: (a) a rotatable cup holder for holding the gun cup with its open end downward, (b) a means for spraying the inside of the gun cup when it is held in the cup holder, (c) a stationary gun support for holding the spray gun, (d) a means for producing an air jet (which may be sprayed from the gun) which interacts to rotate the cup holder, (e) means for supplying compressed air to the gun support, to the air jet-producing means and to the cup-spraying means, and (f) means for supplying cleaning liquid to the gun support and the cup-spraying means. 
     In one form of use, the novel device, the spray gun and the cup-connecting means are installed on the gun support, and the gun cup is installed, open end downward, in the cup holder. Compressed air from outside the chamber is passed into a manifold inside the chamber and then distributed to the gun support and the cup-spraying means. Simultaneously, cleaning liquid from a pool of liquid is drawn into the gun and sprayed out, thereby cleaning the inside surfaces of the gun. The spray from the gun is directed to cause the cup holder to rotate and to clean the outside surfaces of the cup. Also, spray from the cup-spraying means sprays the lip and insides of the rotating gun cup, cleaning the inside surfaces of the cup. 
     In the preferred embodiments, at least two (2) auxiliary spray nozzles, similarly connected to the manifold and the liquid in the pool, spray cleaning liquid against and thereby cleaning the outer surfaces of the spray gun and the attached gun-cup connecting means. The preferred embodiments of the novel device also includes a filter inside the chamber for fitering cleaning liquid drawn from the liquid pool, and a relief vent in a wall of the chamber covered with fume-absorbent material. In one arrangement, the relief vent has attached thereto a cartridge providing an upwardly-directed path, first through a porous medium and then through a mass of activated charcoal. A return means including a return trap is provided in the cartridge for liquids captured in the path which are draining back through the vent. 
     In all of the embodiments, the novel device is powered entirely by compressed air. The novel device does not employ electricity, blowers or pumps. All of the active parts are entirely enclosed in the chamber thereby protecting personnel from noxious fumes and from excessive noise, particularly the noise generated by compressed air escaping through he various nozzles in the device. 
     The novel device is relatively compact, relatively light in weight, and relatively low in cost. Nevertheless, a minimum of labor and time is required to install, thoroughly clean, and remove a spray gun assembly from the novel device. The entire cycle is easily completed in a few minutes, making the novel method and novel device ideal for use in job shops. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially broken-away elevational view of a preferred embodiment of the novel device with a spray gun assembly mounted therein and the cover in place. 
     FIG. 2 is a plan view of the embodiment shown in FIG. 1 with the cover removed. 
     FIG. 3 is a fragmentary sectional view of the fume-absorption means mounted in the cover of the embodiment shown in FIG. 1. 
     FIG. 4 is a fragmentary, partially broken-away elevational view of the liquid filter in the bottom of the chamber shown in FIGS. 1 and 2. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION INCLUDING THE PREFERRED EMBODIMENTS 
     The following description of some of the preferred embodiments of the concepts of this invention is made in reference to the accompanying figures. Where an individual structural element is depicted in more than one figure, it is assigned a common reference numeral for simplification of identification and understanding. 
     The preferred embodiment of the novel device shown in FIGS. 1 and 2 comprises a closed generally rectangular chamber (21) comprising a bottom wall (23), main side walls (25) integral with the bottom wall (23) and a removable cover (27). The cover (27) includes a top wall (29), auxiliary side walls (31) that are integral with the top wall (29) and fit closely inside the main sidewalls (25), and a liquid-resistant seal (33) that rests on the top edges of the main sidewalls (25). The seal (33) is a downward-opening groove around the auxiliary sidewalls (31) formed by attaching an angle-piece to the outside surfaces of the auxiliary sidewalls (31). 
     All of the parts of the chamber (21) are preferably fabricated from metal stock, preferably one-quarter inch (1/4 in.) aluminum-alloy sheet and one-half inch by one-half inch (1/2 in.×1/2 in.) aluminum angle. The overall dimensions of the covered chamber (21) is about twenty inches (20 in.) wide, about twenty inches (20 in.) high and about fifteen inches (15 in.) deep. The auxiliary sidewalls (31) are about seven inches (7 in.) high and overlap the main sidewalls (25) by about three inches (3 in.). The seal (33) includes a gasket (35) that rests between the upper edge of the main side walls (25) and the attached angle piece. There is a drain hole in about the center of the bottom wall (23) for draining liquid from the inside of the chamber (21) through a drain valve (36). 
     The cover (27) includes a handle (37) of three-eighths inch (3/8 in.) diameter aluminum-alloy rod that is bent and attached at its ends to the outside surface of the top wall (29). The cover (27) includes also a means (39), shown in greater detail in FIG. 3, for absorbing fumes in the air escaping from inside the chamber (21) when the device is in operation. As shown in FIG. 3, the fume-absorption means (39) includes a cylindrical cannister (41) having a threaded cannister nipple (43) screwed into a two-inch diameter vent aperture in the top wall (29). The cannister (41) has solid sides and contains an annular first region (45) from the cannister nipple (43), a annular second region of open space (47) permitting the filtered air to flow downward inside the first annular region (45), a central cylindrical third region (49) of activated charcoal particles for absorbing fumes from filtered air passing upwardly through the charcoal, and a top closure (51) having an open screen (53) permitting filtered and fume-reduced air to escape from the cannister (41). There is a liquid &#34;J-shaped&#34; trap (55) between the first and second regions permitting the back flow of liquid and blocking the back flow of filtered air. 
     As shown in FIGS. 1 and 2, a tubular compressed air manifold (57) extends along the lower inside corners of the chamber (21). A first supply segment (59) of the manifold extends upward along the inside surface of one sidewall (61) and connects to a tubular supply nipple (63) which extends through the one sidewall (61) and terminates in a chamber compressed-air connection means (65) for a source of compressed air. A second tubular segment (67) extends along the bottom inside of the chamber (21) and then upward at an angle terminating in a gun fitting (69) for receiving the compressed-air connection means (78) on a spray gun (71) and for supporting the spray gun (71) in a position to direct a spray whose axis is about horizontal as shown in FIG. 1. The cup-connecting means (72) including the cover (74) for the cup (85) is attached to the gun (71). 
     The manifold has a third tubular segment (75) which extends along the bottom inside of the chamber (21) terminating in a first venturi connection (77). A first nozzle (79) extends upwardly from the discharge side of the first venturi (77). A freely movable circular spacer (81) and then a rotatable cup holder (83) rests on the first venturi connection (77) around the first nozzle (79). The cup holder (83) can hold the spray cup (85) with its open end downward. The cup holder (83) has vanes (87) to catch the spray from the gun (71) whereby to rotate the cup holder (83). The cup holder (83) also has vertical rows of open slots (89) to allow spray from the gun (71) to impinge on the outside of the cup (85) and to allow the liquid to drain away from the cup holder (83). The cup holder (83) also has stabilizing blades (91) inside the cup (85) to reduce rocking by the cup (85) as it rotates in the cup holder. 
     The manifold (57) also has a third tubular segment (93) and a fourth tubular segment (95) which extend inwardly along the bottom of the chamber (21) and then upwardly, each segment terminating in a second and a third venturi connection (97 and 99, respectively). A second and a third nozzle (101 and 103) extend from the discharge sides of the second and third venturi connections (97 and 99, respectively) in a generally horizontal direction directed at each side of the spray gun (71). The second and third venturi connections (97 and 99) and nozzles (101 and 103) are shown in FIG. 2, but not in FIG. 1 in order to simply the drawing. 
     A pool of cleaning liquid (105) is in the bottom of the chamber (21) to a depth of about three to four inches (3 to 4 in.). A filter (107) for the liquid is positioned on the bottom of the chamber (21) in the pool (105) to be under the spray gun (71) when it is mounted on the gun fitting (69). The gun siphon tube (109) of the gun (71) extends into the center of the filter (107). Also, first, second and third siphon tubes (111, 113 and 115) extend from the suction ports of the first, second and third venturi connections (77, 97 and 99, respectively) into the filter (107) around the gun siphon tube (109). 
     The filter (107) for the cleaning liquid is shown in more detail in FIG. 4. The filter (107) comprises an annular porous filter element (117) clamped between a circular bottom plate (119) and a circular metal top plate (121) by clamps (123) which are attached to bottom wall (23) of the chamber (21). The cleaning liquid (105) of the pool completely fills the filter (107) with the surface (127) of the pool at about the level of the top plate (121). The top plate (121) has a plurality of holes through which the siphon tubes (109, 111, 113 and 115) pass. 
     To practice the novel method and to use the preferred embodiment shown in FIGS. 1 and 2, a spray gun (71) with the cup connection means (72) attached is mounted on the gun positioning means by pressing the gun compressed-air connection means (73) of the spray gun (71) into the gun fitting (69), and with the siphon tube (109) in the filter (107). With this mounting, the gun (71) can be positioned any where along an arc which points the spray axis of the gun along a line across the cup holder (83). A gun position is chosen which will impinge the spray from the gun (71) on the vanes (87) so as to rotate the cup holder (83). The gun cup (85) is placed open end down in the cup holder (83). Cleaning liquid (105) is in pool at the bottom of the chamber (21). The cover (27) is placed in position as shown in FIG. 1. Then, a source of compressed air of about 120 psi is connected to the chamber compressed air connection means (65). 
     Compressed air flows into the chamber (21) through the nipple (63) and into the header (57), where it is distributed to the gun (71), and the first, second and third venturi connections (77, 97 and 99, respectively). Compressed air flowing through the gun (71) and the venturi connections (77, 97 and 99) draws cleaning fluid from the filter (107) through the respective siphon tubes (109, 111, 113 and 115) and sprays it out through the gun nozzle (125) and first, second and third nozzles (79, 101 and 103). The spray from gun nozzle (125) rotates the cup holder (83) and cleans the outside of the cup (85). The spray from the first nozzle (79) cleans the inside of the cup (85). The spray from the second and third nozzles (101 and 103) cleans the cleans the outside surfaces of the gun (71). The air and cleaning liquid passing through the inside surfaces of the gun (71) cleans the insides of the gun. 
     The cleaning effect can be made more or less vigorous by increasing or decreasing, respectively, the air pressure introduced at the nipple (63). All of the sprayed liquid drains back into the pool of liquid (105), so that the surface level of the pool remains substantially constant. However, since the cleaning liquid (105) is drawn from the center of the filter (107), the draining liquid must pass through the porous filter element (117) to be recycled in the chamber (21). The compressed air introduced into the chamber (21) pushes air in the chamber (21) out through the cannister nipple (43) and the fume-absorption means (39) so that air pressure does not build up in the chamber (21). The cleaned gun assembly can be removed from the chamber (21) by turning off the air pressure, removing the cover (27) and taking out the cup (85) and the gun (71). 
     The cleaning step can be completed in time periods as short as thirty (30) seconds. The entire cycle of loading cleaning and unloading can be completed in periods as short as 120 seconds. Thus, in an ordinary job-type paint shop, a succession of many different paint jobs can be conducted with the same equipment without fear of contamination of the paints from one job into another. The amount of equipment required is greatly reduced and the amount of labor and time spent in cleaning the equipment is materially reduced. Equally important is that catalyzed paints, which set up in periods of time as short as thirty (30) minutes, can be used, and the residual paint in the spray gun assembly can be removed within minutes after the painting is completed thereby protecting the equipment from loss. 
     A feature of the novel method and device is that it is powered entirely with compressed air and that there is no buildup of pressure within the device. Thus, there is no danger of fire or combustion of the fumes from the paint or the cleaning fluid within the device. Any of various cleaning fluids can be used, and used should be governed by mandatory or recommended safety practice. A preferred cleaning fluid is a good grade of paint thinner. Methyl ethyl ketone can also be used although it is not preferred. 
     Another feature of the novel method and device is the low level of noise imposed on the environment. Although a large amount of compressed air passing out of the various nozzles of the novel device does generate substantial noise, the noise is contained in the chamber, which is closed. Also, since the cleaning cycle is very short, the duration of the generated noise is quite short. 
     There are many variations in both the method and the device. For example, the rotatable cup holder can be rotated with other compressed-air means such as a supplementary jet for that purpose. Also, the chamber can be designed to load two or more spray gun assemblies at one time. Also, one or more windows can be built into the walls of the chamber, and there can be other sealing arrangements between the main portion and the cover of the chamber. 
     The foregoing figures and descriptions thereof are provided as illustrative of some of the preferred embodiments of the concepts of this invention. While these embodiments represent what is regarded as the best modes for practicing this invention, they are not intended as delineating the scope of the invention which is set forth in the following claims.