Abstract:
A paint gun cleaning apparatus is provided that prevents the collection of overspray on the discharge end of the paint gun. The cleaning apparatus includes a drum that defines an aperture for insertion of at least the discharge end of a paint gun. The apparatus also includes a fin assembly inside of the drum for directing paint and solvent discharged from the paint gun away from the paint gun. A splash cone also helps direct discharge away from the center of the drum, laterally toward the fin assembly. The apparatus also includes a source of suction for drawing material discharged from the paint gun away from the discharge end of the paint gun. By preventing the collection of overspray it is not necessary for an operator to wipe the gun clean.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an apparatus used in conjunction with a paint gun having a bell atomizer, and specifically a cleaning apparatus used during paint color change operations. 
   2. Description of Related Art 
   Paint guns with bell atomizers are often a part of paint machines used extensively within industry for high volume painting operations such as the painting of motor vehicles. Often, the paint machine is robotically controlled. A paint and solvent mixture is forced through the paint machine until the mixture reaches the paint gun. A discharge end of the paint gun includes a rotating bell shaped member that aids in atomizing the paint and solvent mixture, thus, allowing superior application of the mixture. 
   Periodically the color of paint within the paint machine is changed. Prior to introducing a new color mixture into the machine, a strictly solvent blend is circulated through the machine to clean out traces of the previous color mixture. Then, the new color mixture is added to the machine and sprayed through the paint gun for a predetermined period of time before the mixture is applied to products. During changeover, collection of any overspray consisting of the solvent or new color mixture on the paint gun, including the bell, is to be avoided. 
   Current practice during changeover involves spraying the solvent into a funnel. This practice has inherent drawbacks. Although the funnel collects the overspray, it does not prevent overspray from accumulating on the discharge end of the paint gun (i.e. the nozzle and rotating bell). It is necessary for an operator to physically wipe the overspray off of the paint gun with a rag. This is a time consuming process and a safety hazard. The bell of the paint gun rotates at 35,000 rpm during operation and although the means of driving the bell is disconnected during changeover, the operator has to wait for the bell to stop rotating to wipe it or contact the moving bell with the rag. 
   What is desired is an improved method and/or apparatus that can reduce changeover time by preventing the collection of overspray on the paint gun and also increase operator safety. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention overcomes these and other disadvantages in the prior art. The paint gun cleaning apparatus prevents the collection of overspray on the discharge end of the paint gun. Thus, it is not necessary for an operator to wipe the gun clean. 
   In accordance with the present invention, the cleaning apparatus includes a drum that defines an aperture for insertion of at least the discharge end of a paint gun. The apparatus also includes a fin assembly inside of the drum for directing paint and solvent discharged from the paint gun away from the paint gun. A splash cone helps direct discharge away from the center of the drum, laterally toward the fin assembly. The apparatus also includes a source of suction for drawing material discharged from the paint gun away from the discharge end of the paint gun. 
   These and other aspects of the invention are herein described in particularized detail with reference to the accompanying figures. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  is a vertical cross-sectional view of a paint gun cleaning apparatus of the present invention; 
       FIG. 2  is a horizontal cross sectional view of the paint gun cleaning apparatus; 
       FIG. 3  is a perspective view of the inner structure of the paint gun cleaning apparatus; 
       FIG. 4  is a vertical cross sectional view of a second embodiment of the paint gun cleaning apparatus; 
       FIG. 5  is a front elevational view of the paint gun cleaning apparatus; 
       FIG. 6  is a perspective view of the second embodiment of the fin assembly of the paint gun cleaning apparatus; and 
       FIG. 7  is a side elevational view of the second embodiment of the fin assembly of the paint gun cleaning apparatus. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings, specifically  FIGS. 1 and 3 , a preferred paint gun cleaning apparatus  10  according to the present invention is illustrated. The gun cleaning apparatus  10  includes a drum  12  having an outer skin  14  and inner structure  16 , a fin assembly  18  housed within the inner structure  16 , and multiple sources of suction  20 ,  22 . 
   Referring to  FIG. 1 , the drum outer skin  14  includes a base section  24 , mid-section  26  and a lid section  28 . The outer skin  14  is supported at a desirable height by four legs  30  (not all shown). The mid-section  26  has a generally circular cross section and extends between the base section  24  and the lid section  28 , the mid section  26  overlapping some or all of the base section  24 . The base section  24  has a generally conical shape that tapers downwardly from a junction with the mid-section  26  to a first circular flange  32 . One end of a threaded nipple  34  is attached to the first flange  32  and a first source of suction  20  is attached to the opposite end of the threaded nipple  34 . A second flange  38  is placed on a portion of the conical base section  24  around an aperture extending therethrough. A second source of suction  22  is attached to the second flange  38 . 
   The lid section  28  is detachably fit over an open top end  42  of the mid-section  26 . The lid section  28  has a dome shape that is truncated to provide a planer top center portion  44 . An aperture  46  is defined in the center portion  44  through which a paint gun discharge end  48  (nozzle and bell) extends during changeover events. The aperture  46  is surrounded by a beveled flange  50  that extends inwardly. The shape of the beveled flange  50  matches the shape of an associated portion of the paint gun discharge end  48  and as a result a rough seal is formed when the paint gun  48  is inserted into the aperture  46  and against the beveled flange  50 . Preferably a gap of 1.25 centimeters (0.5 inches) is maintained between the paint gun  48  and the beveled flange  50 . A rubber seal  52  is attached to the beveled flange  50  to protect the paint gun discharge end  48  from rebounding paint and/or solvent. 
   Referring to  FIG. 5 , the lid section  28  is removable, and can be locked in place, preferably using pins  54 . Two or more ears  56  are attached to the bottom outer edge of the lid section  28  and project toward the mid-section  26 . Each ear  56  defines an aperture. An identical number of similarly shaped ears  58  are attached to the upper outer edge of the mid-section  26  and project toward the lid section  28 . When the lid section  28  is in place, apertures within corresponding ears  56 ,  58  on the lid section  28  and mid-section  26  are aligned and a pin  54  placed therethrough to lock the lid section  28  in place. 
   Referring to  FIG. 1 , the inner structure  16  is positioned between the outer skin  14  and the fin assembly  18 . The inner structure  16  has a shape similar to that of the outer skin  14  and includes a dome-shaped top section  60 , cylindrical middle section  62 , and conical bottom section  64 . The dome-shaped top section  60  defines a central aperture  66  that is aligned with the aperture  46  in the outer skin lid section  28  and provides access to the inside of the inner structure  16 . The central aperture  66  has a diameter sufficient to provide passage for the beveled flange  50  of the outer skin  14 . The conical bottom section  64  of the inner structure  16  defines an outlet  68  at its bottom for the passage of collected paint and solvent. The outlet  68  is aligned with the first circular flange  32  in the outer skin  14 . 
   Referring to  FIG. 3 , the dome-shaped top section  60  includes a lip  70  of a slightly reduced diameter at its base that fits into the cylindrical middle section  62 . The cylindrical middle section  62  defines three slots  72  equally spaced around the top diameter of the middle section  62  that are used to support the fin assembly  18 . A group of spacers  74  are attached to the outer surface of the inner structure middle section  62  to space the inner structure  16  from the outer skin  14 . The spacers  74  are also attached to the outer skin  14  by welding or screws, thus, the spacers  74  support the inner structure  16 . Four upper spacers  74  are placed at equal intervals around the perimeter of the top of the cylindrical middle section  62 . Four lower spacers  74  are placed at equal intervals around the perimeter of the bottom of the cylindrical middle section. Naturally, more or less than eight spacers may be used. 
   Referring to  FIGS. 2 ,  6  and  7 , the fin assembly  18  includes a series of fins  76 , a central collar  78 , and a splash cone  80 . The central collar  78  and splash cone  80  are coaxial and aligned with the beveled flange  50  and the first circular flange  32  in the outer skin  14  and define an inner mount to which each of the fins  76  attach. Each fin  76  extends in a spokelike manner from the round central collar  78  toward the middle section  62  of the inner structure  16 . Each fin  76  is a generally rectangular member that is oriented generally vertical lengthwise. Each fin may be vertical as represented in  FIG. 2  or slightly angled (up to 15 degrees from vertical) as represented in an alternate embodiment of the invention shown in  FIGS. 6 and 7 . Each fin  76  is bent along a vertical axis giving the fin two separate planer sections  82 ,  84 , although any fin shape may be used (e.g. curved fin). The first planar section  82  of the fin  76  is affixed to the central collar  78  and projects radially outward therefrom. The second planar section  84  is between the first fin section  82  and middle section  62  of the inner structure  16  and is bent clockwise in relation to the first section  82  when viewed from the top of the inner structure  16  (See  FIG. 2 ). Preferably, eight fins  76  protrude from the central collar  78  (See  FIG. 2 ) at equally spaced intervals, although any number of fins  76  may be used (See  FIG. 6 ). The fins  76  block any rotational movement of paint and/or solvent particles discharged from the paint gun  48 . The angle of the fins  76  helps to prevent undue turbulence within the drum. The central collar  78  is affixed to the fins  76  at a position approximately one third of the fin length down from the top end of each fin  76 . 
   A splash cone  80  is also attached to the inner edge of each fin  76 , the splash cone  80 , like the central collar  78 , being situated in the center of the inner structure  16 . The splash cone  80  is oriented pointing upward and prevents collected paint and solvent from splashing back upward toward the paint gun  48 . The splash cone  80  is positioned approximately two thirds of the way down the length of the fins  76 . 
   A hoop  86  made of small diameter rod extends around the outside of the fin assembly  18  at a position near the top of the fin assembly  18 . Three small sections of angle stock  88  are welded to the hoop  86  at equally spaced intervals. The angle stock  88  allows the fin assembly  18  to be secured to the inner structure  16 . Specifically, the sections of angle stock  88  fit within the slots  72  formed in the inner structure middle section  62  described hereinbefore and allow the fin assembly  18  to be dropped in or pulled out from the top of the drum  12 . 
   Referring to  FIG. 1 , a source of suction  20  is attached to the nipple  34  attached to the circular flange  32 . The source of suction  20  preferably is a Threaded Line Vac manufactured by Exair corporation of Cincinnati, Ohio. A second nipple  35  is affixed to the source of suction  20  opposite the nipple  34 . A conical trap  90  is located on a discharge side of the source of suction  20  to remove collected paint and solvent. Collected paint and solvent is continuously or periodically removed from the trap  90  in a manner well known in the art. A second source of suction  22  is attached to the second flange  38  and on request provides additional suction into the drum  12 . The second source of suction preferably is a Super Air Amplifier manufactured by Exair corporation of Cincinnati Ohio and described in U.S. Pat. No. 5,402,938 to Sweeney, the entirety of which is incorporated by reference herein. Both the Threaded Line Vac and Super Air Amplifier utilize high pressure compressed air to create a high fluid flow rate from the inside to the outside of the drum. 
   Referring to  FIGS. 1 and 3 , the paint gun cleaning apparatus  10  functions to draw paint, solvent, and mixtures thereof away from the discharge end of the paint gun  48  during color changeovers. When a changeover event is initiated, the paint gun  48  is moved robotically to the cleaning apparatus  10 . The discharge end of the paint gun  48  is placed within the aperture defined by the outer skin lid section  28 . The beveled surface on the paint gun fits against the beveled flange  50  and the seal  52  on the outer skin  14 , although a gap is maintained therebetween to avoid over pressurizing the drum. One or both sources of suction  20 ,  22  are activated to provide a pressure gradient within the drum  12  that draws paint and solvent from the paint gun  48  to the bottom of the drum  12 . The suction source(s)  20 ,  22  are operating as the paint gun  48  enters the aperture. 
   Once the paint gun  48  is in place, a jet of increased pressure air is blown through the paint gun  48  to help clear the gun of paint of the color being changed. A solvent stream is then forced through the paint gun and into the cleaning apparatus  10 . The air jet and solvent steps are each repeated two more times. Then, a stream of paint of a new color is added to the paint gun. 
   Paint and solvent expelled from the paint gun  48 , especially particles moving in a rotational manner, contact the surface of the fins  76  and collect thereon. The angle of the fins helps minimize the amount of paint and solvent that rebounds off the fins and back toward the paint gun  48 . Preferably, the fins  76  are angled with the bottom of the fin advanced clockwise with relation to the top of the fin. This orientation helps collect paint and solvent being discharged from the paint gun in a clockwise direction. The paint and solvent then flow downwardly due to suction and gravity. Paint and solvent drips from the bottom of the fins  76  to the conical bottom section  64  of the inner structure  16  and proceeds to the outlet  68  at the lowest point of the bottom section  64 . The collected paint and solvent drops from the bottom section  64  of the inner structure  16  to the base  24  of the outer skin  14 , then through the first source of suction  20  and into the trap  90 . The location of the second vacuum flange  38  on the conical base section  24  of the outer skin  14  prevents migration of the paint and solvent up the slope and into the second flange  38 . Thus, no trap is required in conjunction with the second source of suction  22 . Preferably the second source of suction provides a high fluid flow rate from the inside to the outside of the drum. The first source of suction provides a lower fluid flow rate as compared to the first source of suction, with the lower flow rate being sufficient to prevent migration of paint and solvent into the second source of suction. 
   The spray cone  80  prevents any paint or solvent below the spray cone  80  from rebounding upward to the paint gun  48 . The spray cone  80  also deflects paint and solvent coming from the discharge end of the paint gun  48  laterally to the fin assembly  18 . 
   The paint gun cleaning apparatus  10  of the present invention provides significant advantages over current devices and practices. Because overspray is drawn away from the discharge end of the paint gun  48  (nozzle and rotating bell), the discharge end stays clean and does not need to be later wiped off by an operator. Safety is improved because an operator does not have to contact the rotating bell or, alternatively, wait for the bell to stop rotating. 
   In an alternative embodiment of the invention, illustrated in  FIG. 4 , the generally conical base section  24  includes a horizontal portion  92 . The second flange  38  is affixed to the base section at the horizontal portion  92 . Also alternatively, know vacuum pumps or blowers may be used in place of the suction sources described above. 
   Although the invention has been shown and described with reference to certain preferred and alternate embodiments, the invention is not limited to these specific embodiments. Minor variations and insubstantial differences in the various combinations of materials and methods of application may occur to those of ordinary skill in the art while remaining within the scope of the invention as claimed and equivalents.