Patent Publication Number: US-10766048-B2

Title: Apparatus for cleaning spray guns and bells

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a National Stage Entry into the United States Patent and Trademark Office from International PCT Patent Application No. PCT/CA2016/051365, having an international filing date of Nov. 22, 2016, the contents of which is incorporated herein by reference in its entirety. 
     FIELD OF INVENTION 
     This invention relates to a method and apparatus used in conjunction with robotic paint atomizers, including single gun, double gun and bell atomizers. In particular, the invention relates to an apparatus for cleaning paint spray guns and bells. 
     BACKGROUND OF THE INVENTION 
     Paint spray guns and bells are used in a variety of industries to project paint onto an object. The words “spray gun” and “bell” may be used interchangeably in the present patent specification and claims. In the automobile industry, a particular paint spray gun/bell may be used to spray a number of paint coats of different colours onto parts for automobiles. The paint spray gun/bell must be regularly cleaned to remove curing and dry paint on the atomizer end of the spray gun/bell, and prior to the use of paint of a new colour to remove remnants of the first paint. Paint spray guns/bells are cleaned by projecting solvents at high velocity at them while contained within a chamber apparatus. The high velocities are required to remove dried paint from the atomizer end of the gun/bell. The cleaning is effected in a separate vessel to prevent leakage of spent solvent. 
     Canadian Patent No. 2,238,019 teaches a method and apparatus for cleaning spray guns. The apparatus for cleaning spray guns has a closed vessel having an inlet, a drain and a port for receiving an atomizer of a spray gun. A spray impeller is rotatable mounted within the vessel and in fluid communication with the inlet. The spray impeller has offset cleaning nozzles for projecting a cleaning spray towards the spray gun and a rotational nozzle for projecting a rotational spray to effect rotation of the spray impeller. The port has a seal for sealing while receiving the spray gun and positioning the atomizer of the spray gun in the cleaning spray. 
     Although the patented apparatus is effective for cleaning spray gun atomizers, it has been noted that a significant amount of spent cleaning solvent remains on the atomizer after it has been cleaned and removed from the closed vessel. The remaining solvent can represent a source of contamination in the paint booth. It would be desirable to have a cleaning apparatus that removes residual cleaning solvent from the atomizer before it is released from the closed vessel of the cleaning apparatus. 
     In an assembly line situation paint is applied in a cyclical process as many vehicles or components pass down the assembly line. So too, the apparatus for cleaning spray gun atomizers functions in a cyclical process: receiving an atomizer, effecting the cleaning, releasing the atomizer, and recovery and preparing to receive the next atomizer. It would be desirable for the cleaning apparatus to more efficiently capture and drain spent cleaning solvent from the closed vessel so that the duration of the recovery and preparation step could be reduced. 
     Paint residues which have been cleaned from paint guns can become deposited on the walls of the closed vessel. Over time a build up of paint can form, which if left could hamper the operation of the cleaning apparatus. Periodically the apparatus for cleaning spray guns must, itself, be taken off-line and cleaned. Down time for cleaning the apparatus for cleaning spray guns can disrupt the production cycle of the paint booth and potentially an entire assembly line. It would be advantageous for the apparatus for cleaning spray guns to have a mechanism for preventing retention of residual paint on the walls of the closed vessel. 
     While the apparatus described in Canadian Patent No. 2,238,019 does clean most surfaces of a spray gun atomizer, it can fail to clean the centre atomizer alley of the atomizer. It would be advantageous to provide an improved apparatus for cleaning spray guns which is capable of cleaning the centre atomizer alley in addition to cleaning other surfaces of the spray gun/bell. A further advantage could be realized if the means for cleaning the centre atomizer alley could function independently of the other cleaning nozzles, to permit the selective targeting of particular surfaces to customize the cleaning to match the particular type and model of spray gun being used on a given assembly line. 
     SUMMARY OF THE INVENTION 
     A cleaner for spray guns comprises a vessel having an inlet, a drain and a port for receiving an atomizer of a spray gun. An impeller is rotatably mounted within said the vessel in fluid communication with the inlet. The impeller has an offset cleaning nozzle for projecting a cleaning spray towards said port, a rotational nozzle for projecting a rotational spray to effect rotation of the impeller and an air wipe down for removing excess solvent from the atomizer of the spray gun as it leaves the cleaner following a wash cycle. 
     The air wipe down comprises a cap attached to the vessel. The cap has a neck extending upwardly therefrom. The neck of the cap and a sleeve which is coaxial with the neck of the cap together define a channel for fluid communication with an air source. The sleeve defining a plurality of air holes therethrough in fluid communication with the channel to direct a flow of air toward the atomizer of the spray gun. The air holes are machined at a downward angle. 
     The cleaner further comprising a helical flushing means. The helical flushing means comprises a plurality of flushing holes machined through the neck of the cap at an angled offset to direct a lateral flow of air toward the inner wall of the vessel when in fluid connection with an air source. 
     The cleaner comprises a solvent purge assembly to wash the inner walls of the vessel. The solvent purge assembly comprises an outer ring attached to the inner wall of the vessel and an inner ring mounted within the outer ring and forming a solvent channel therebetween. The outer ring defines a plurality of solvent holes therethrough in fluid connection with the solvent channel. When the solvent purge assembly is in fluid communication with a solvent source, the solvent holes direct the solvent down the inner walls of the vessel. 
     The cleaner further comprises an air and solvent separation fitting for improved solvent drainage efficiency. The air and solvent separation fitting comprises an outer pipe fitted at the top thereof for sealing fluid connection to the drain of the vessel. The outer pipe defines a plurality of perforations open to the environment positioned adjacent it stop. A tapered inner pipe is mounted coaxially within the outer pipe to extend below the perforations in the outer pipe forming a venting gap between the outer pipe and the inner pipe. 
     The impeller of the cleaner comprises a domed housing having a first channeled arm and a second channeled arm threaded and welded at opposite ends of the domed housing. Each of the first channeled arm and the second channeled arm define a rotational nozzle. Each of the first channeled arm and the second channeled arm has a cleaning nozzle threadably engaged thereto. A central nozzle is threadably engaged to the top of the domed housing. A fluid conduit is provided for fluid communication between the inlet and the first and second channeled arms. 
     A hollow stem is independently in fluid communication bewteen the central cleaning nozzle the inlet. The fluid conduit defines an annular fluid path surrounding the hollow stem. The central nozzle is attached to a hollow stem that is attached to a separate fluid path and is independently operated depending upon the need. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a an exploded front elevational view of a first embodiment of a spray gun cleaning apparatus of the present invention; 
         FIG. 2  is a non-exploded partial sectional side view of the cleaning vessel side of  FIG. 1 ; 
         FIG. 3  is an enlarged sectional view of the seal for receiving a spray gun of  FIG. 1 ; 
         FIG. 4  is an enlarged sectional side view of purge adapter assembly of  FIG. 1 ; 
         FIG. 5A  is a perspective view of the air and solvent separation system of  FIG. 1 ; 
         FIG. 5B  is a sectional view of the air and solvent separation system. 
         FIG. 6  is a cross sectional view of the duel port impeller of  FIG. 1   
         FIG. 7  is a schematic representation of the spray paths of the cleaning nozzles in the vessel of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 and 2 , a cleaner for cleaning paint from spray guns/bells is illustrated and identified by general reference numeral  10 . 
     The cleaner  10  generally comprises a base  12 , a closed vessel  14  having a base  12 . At the top of the vessel  14  is a spray gun mount  16  for receiving a spray gun/bell  18 . The vessel  14  is a generally hollow vessel having a drain  22  at the bottom thereof, an inlet  24  and a top annular plate having an opening therein. The opening is closed by a cover assembly  28 . The cover assembly  28  defines a port identified in  FIG. 1  by reference arrow  29  which receives the atomizer  30  of spray gun/bell  18  in a sealing engagement. 
     The cover assembly  28  comprises a cap  31  which is affixed to the vessel  14 . The cap  31  is substantially annular and comprises a base ring  33 , from which depends skirt  27  overlapping a portion of the vessel  14 . A neck  35  extends upwardly from the base ring  33  of cap  31 . The outer diameter of the neck  35  is smaller than the outer diameter of the base ring  33 . The inner surface of the neck  35  of cap  31  is identified by reference  37 . The neck  35  tapers inwardly near its top end to form the port  29 , which receives the atomizer  30 . The neck  35  is notched adjacent the port  29  to form a ledge to sealingly receive an O-ring  80 . 
     As shown in  FIGS. 2 and 3  a substantially cylindrical sleeve  39  rests on the base ring of the cap  31  and is substantially coaxial with the neck  35  of cap  31 . The sleeve  39  has, an outer wall  41 , a contoured inner wall  43 , a top  45  and a bottom  47 . A portion of the contoured inner wall  43  is threaded to engage a threaded portion of the base ring  33  of the cap  31 . The remainder of the inner wall  43  does not contact the cap  31 . Instead, a channel  53  is formed between the neck  35  of cap  31  and the upper portion of the inner wall  43  of the sleeve  39  for fluid communication through air inlet  49  in the sleeve  39  with an air source (not shown). Air inlet  49  permits fluid communication between the channel  53  and an air source. 
     AIR WIPE DOWN—The cleaner  10  comprises an air wipe down, shown generally by arrow  25  in  FIG. 3 , for removing excess solvent from the atomizer  30  of the spray gun  18  as it leaves the cleaner following a wash cycle. The sleeve  39  defines an air supply opening  49  for fluid connection between an air source (not shown) and the channel  53 . The top  45  of the sleeve  39  is substantially flat adjacent its outer wall  41 ; but tapers to form an annular overhang  51  over the inner wall  43 . The overhang  51  of sleeve  39  defines a plurality of air holes  55  therethrough. The air holes  55  are in fluid communication with the channel  53 . As can be seen in  FIG. 3 , it is preferred for the air holes  55  to be machined at a downward angle in the dihedral plane. When air pressure is activated, air is forced from the channel  53  along the downward path through the air holes  55  in the annular overhang  51  of the sleeve  39 . The air exits the air holes  55  in a plurality of air streams directed downwardly and inwardly (as shown by the arrows labelled “A” in  FIG. 3 ) toward the centre of the port  29  to create a tornado type of airflow and provide an air wipe down of the atomizer of the spray gun  18  as it exits the cleaner  10 . Residual solvent is blown back into the vessel  14 , reducing the amount of solvent which is lost to the environment. 
     A seal is formed around the spray gun when the atomizer is inserted into through the port  29  for cleaning. An O-ring  80  is seated on the annular overhang  51  to sealingly receive the spray gun. To assemble, the sleeve  39  is press fit into the cap  31 , with the O-ring inserted between to prevent leakage of air and solvent. 
     HELICAL FLUSHING MEANS—The cleaner  10  is further provided with a helical flushing means to cause solvent within the vessel  14  to be pushed downward in a swirling pattern along the walls of the vessel  14 . The helical flushing means is identified generally by reference arrow  23  in  FIG. 3  This swirling action of the helical flushing means  23  helps to remove paint residue from the walls of the vessel  14  and to push the solvent and paint residue down the drain opening in the bottom of the vessel  14 . The helical flushing is accomplished means of an angularly directed flow of air (represented by the arrows labelled “B” in  FIG. 3 ) introduced in to the vessel  14 . The flushing means  23  comprises a plurality of flushing holes  57  machined through the neck  35 . It is preferred, though not necessary, to use the same air supply as the one used for the air wipe down  25 . As illustrated in  FIG. 3 , the plurality of flushing holes are in fluid connection with the channel  53  which is itself in fluid communication with an air supply (not shown). It is preferred for the flushing holes  57  to be oval in cross section. Moreover, the flushing holes  57  are machined at an angled offset so that as the air emerges from the flushing holes  57  the flow is directed in a lateral direction. As the air flow contacts the inner surface  37  of the neck  35  and then the inner walls of the vessel  14  a helical flow pattern is formed causing the solvent to be pushed in a swirling manner down toward the drain  22  opening in a manner analogous to the flushing action in a toilet bowl. 
     The cover assembly  28  is preferably constructed from an engineered thermoplastic having characteristics of high stiffness, low friction and excellent dimensional stability. By way of example, the assembly may be constructed from polyoxymethylene which is available under the trademark DELRIN®. 
     SOLVENT PURGE ASSEMBLY—The cleaner  10  is further equipped with a solvent purge assembly  59  to wash the inner walls of the vessel. As shown in  FIGS. 2 and 4 , the purge assembly  59  is mounted within the vessel  14 . The purge assembly  59  is constructed in two parts: an inner ring  61  and an outer ring  63 . The outer ring  63  is the same size as the vessel  14  causing the outer ring  63  to sit on top of the vessel with the inner ring  61  going into the vessel and bolted to the lip of the vessel. The outer ring  63  defines a plurality of solvent holes  65  therethrough. The inner ring  61  fits with the outer ring  63  and is held in place with a flush fit leaving a solvent channel  67  therebetween. The solvent channel  67  is in fluid connection with a solvent source (not shown). When the solvent source is activated solvent is forced through the solvent channel  67  and then flows through the solvent holes  65 , which are in fluid communication with the solvent channel  67 .  FIG. 4  shows a portion of the outer ring  63  cut away and one solvent hole in cross section (identified by reference numeral  65 A) to illustrate the fluid communication between the solvent channel  67  and the solvent holes  65 . The solvent holes  65  are directed downward and at an angle to the plane, and the solvent holes  65  open into the interior of the vessel  14 . The solvent is forced out of the solvent holes  65  at high velocity, whereupon the solvent hits the sides of the interior of the vessel in a swirl like fashion to purge any paint residue stuck to the inner walls of the vessel  14  down into the drain. The base of the vessel is bevelled  69  in order to move solvent and paint residue down to the drain  22 . 
     AIR SOLVENT SEPARATION FITTING—As illustrated in  FIGS. 1, 5A and 5B , the cleaner  10  further comprises an air and solvent separation fitting  71  for improved solvent drainage efficiency. The air and solvent separation fitting  71  comprises an outer pipe  73  fitted at the top  75  thereof for sealing fluid connection with the drain  22  of the vessel  14  and fitted at the bottom  77  thereof for sealing fluid communication to a drainage system (not shown). The outer pipe  73  defines a plurality of perforations  79  positioned adjacent the top  75  of the outer pipe  73 . A tapered inner pipe  81  is mounted coaxially within the outer pipe  73  and extends below the perforations  79  in the outer pipe  73 . The tapered contour  83  of the inner pipe  81  directs the flow of solvent and air toward the bottom of the outer pipe  73 . The positioning of the tapered contour  83  of the inner pipe  81  relative to the outer pipe  73  creates a venting gap  85 . As mixed air and solvent flow through the fitting, air can dissipate into the venting gap  85 . The air can then escape through the perforations  79 , and the solvent and paint residue drop to the bottom of the outer pipe and into the drainage system. Removing the air reduces turbulence in the fluid flow of the solvent and paint and speeds the drainage process. The escape of air through the perforations  79  also helps to prevent a pressure build up within the vessel  14  which might otherwise be caused by the influx of air through the air wipe down and the helical flushing mechanism. 
     DUEL IMPELLER—Prior art versions of the cleaner employed a single port impeller inside the vessel of the cleaner to direct streams of solvent toward the atomizer of a spray gun. As shown in  FIGS. 2 and 6 , the cleaner  10  according to the present invention comprises a duel port impeller  36  which adds a centre cleaning nozzle  91  that can independently direct a spray of solvent to clean the centre galley in the atomizer  30  of a spray gun  18 . An inlet fitting  24  is provided to the wall of the vessel  14 . The inlet fitting  24  is connected to a pipe or tube  32 , which connects to an elbow fitting  34 . The elbow fitting  34  has a vertical axis substantially collinear with a central vertical axis of vessel  14 . Extending upwardly from the elbow fitting and in fluid communication with the inlet fitting  24  is duel impeller  36 . Inlet fitting  24 , pipe  32  and elbow fitting  34  all have sufficient structural integrity to firmly support duel impeller  36 . Channeled arms  38  and  40  are threadingly engaged to the housing  50  and extend diagonally outwardly from impeller  36  preferably at an angle of 45° towards its axis of rotation. Offset cleaning nozzles  42  are threadingly engaged to each of the arms  38  and  40 . The offset cleaning nozzles  42  can be mounted at variable angles to direct solvent streams toward hard to reach places on the atomizer  30  of the spray gun  18  hence customizing our design according to the needs of the buyer. In  FIG. 6 , one of the nozzles  42  on each arm is directed inwardly toward the centre of the vessel  14  and the other is directed upwardly. The arms  38  and  40  each define rotational nozzles  44  positioned at their distal ends. The rotational nozzles  44  are horizontally directed. When fluid is expelled from the rotational nozzles  44  in horizontal streams projecting tangentially and hitting the inner wall of the vessel to create a centrifugal force which causes the impellers to spin 
     Referring now to  FIG. 6 , the dual impeller  36  is illustrated in greater detail. Pipe  32  defines a first fluid channel  46  and a second fluid channel  48 . The fluid channel  46  connects to a first flow control valve  52  positioned just above the elbow fitting  34 . The second fluid channel  48  connects to a second fluid control valve  54 . A base fitting  60  has a central aperture having an internal thread therein. Bolt  64  has a central capillary opening  66  through the stem of bolt  64 . Bolt  64  is threaded for engaging the threaded aperture of base fitting  60 . The capillary opening  66  is connected in fluid communication with the second fluid control valve  54  to the second fluid channel  48 . When the bolt  64  is tightened until bushings are compressed fluid communication is allowed between the second fluid channel  48  and a fluid conduit  56  through the impeller. The fluid conduit  56  is branched to provide fluid communication through both of the channeled the arms  38  and  40  to feed the cleaning nozzles  42  and rotational nozzles  44  on each of the arms  38  and  40 . The fluid conduit  56  defines an annular fluid path surrounding a central void. Once the cleaning apparatus  10  is assembled and sealed, fluid is able to communicate within the fluid inlet system from the inlet fitting  24 , through the second fluid channel  48  in the pipe  32 , through second control valve  54 , through capillary opening  66  and into fluid conduit  56  and, outwardly in opposite directions through arms  38  and  40 , to the rotational nozzles  44  finally upwardly at a  45 ° angle through cleaning nozzles  42 . 
     A central cleaning nozzle  91  extends distally from the domed housing  50  at the centre point of the dome. The central cleaning nozzle  91  is also in fluid communication with the fluid inlet  24 , but it has entirely independent flow path. The first channel  46  in pipe  32  is connected to first fluid control valve  52 , which is connected in fluid communication to a hollow stem  58  which passes through coaxially through the capillary opening  66  in the bolt  64 . There is no fluid communication between the hollow stem  58  and the capillary opening  66 . The stem  58  passes into the impeller and upwardly coaxially through the central void in the conduit  56  and connects in fluid communication to the central cleaning nozzle  91 . The operation of the central cleaning nozzle  91  can be controlled completely independently of the cleaning nozzles  42  on the arms  38 ,  40 . The central cleaning nozzle  91  located on top of the domed impeller housing  50  is directed to clean the center galley of the atomizer when needed. Not all atomizers require this feature. This center individually operated nozzle  91  becomes a fluid saving device as, the need for the center galley clean is most often required independent of the total atomizer cleaning function. The central cleaning nozzle  91  being independent of the full cleaning cycle also has the advantage that it can be disabled during the cycle again proving fluid savings. 
     In order to clean the spray guns and the nozzles thereof, the cleaning fluid or solvent must be complimentary to the paint being used. Solvents such as acetone, methyl ethyl ketone, alcohol and other solvents known in the trade may be used. Since toxic or corrosive solvents are being used, the components of the cleaning apparatus  10  are preferably made of stainless steel and Teflon coated to minimize the residue sticking on the walls of the vessel. 
     In use, the atomizer  30  of spray gun  18  is presented to port  29 . The tapered contour of the annular overhang  51  assists in aligning the atomizer  30  of the spray gun  18  through the port  29  to extend inside the vessel  14 . The spray gun  18  is pressed firmly against the O-ring  80  to prevent solvents from escaping therebetween. 
     Solvent in fluid form and under air pressure is injected into the vessel  14  through inlet  24 . Fluid will travel through pipe  32  independently through fluid first and second fluid channels  46  and  48 . The fluid travelling through first fluid channel  46  flows under control by valve  52  into stem  58  to feed central cleaning nozzle  91 . The fluid travelling through the second fluid channel  48  flows under control by valve  54  and into the capillary opening  66  in bolt  64 , and then up into impeller  36 , passing up through fluid conduit  56 , and outwardly through arms  38  and  40 . The fluid will escape through rotational nozzles  44 , which will cause a tangential spray in opposite directions, urging the impeller  36  to rotate about its axis of rotation. The spray from rotational nozzles  44  will also project cleaning fluid onto the inside walls of vessel  14 . The fluid will also travel up to cleaning nozzles  42  to project a cleaning spray of fluid at atomizer  30  of spray gun  18 . As is apparent, since impeller  36  is rotating and the cleaning nozzles  42  are offset from the axis of rotation of the impeller, the cleaning spray from cleaning nozzles  42  will also rotate and will apply fluid circumferentially about the atomizer  30  at different angles to target various hard to reach areas of the atomiser.  FIG. 7  schematically shows in dashed lines the expected tangential spray paths from one of the cleaning nozzles  42  on arm  40  and both cleaning nozzles  42  on arm  38 . The spray path from central nozzle  91  is also shown as a dashed line and travels as a stream from the central nozzle  91  directly upward to the centre galley of the atomizer  30  of the spray gun  18 . 
     The interior of the vessel  14  and all parts of the cleaner  10  that are exposed to and may come in direct contact with any purged paint, any contamination or any outside paint booth materials may be coated in a polytetrafluoroethylene based material, such as the coating marketed under the trademark TEFLON™. The use of a non-stick coating on the all of the exposed components will provide smoother, slippery surfaces over which solvent and paint residues may travel more quickly down the walls of the vessel toward the drain. Paint residues carried along more quickly have less time to dry in place or build up on the inner walls of the vessel  14 , the arms and cleaning nozzles of the impeller etc., making the overall cleaning process more efficient. 
     The cleaner  10  can be custom configured to provide variable cleaning actions including custom configurations for the vessel cleaning through the purge ring when necessary. Each project requires different solutions and the cleaner is capable of providing custom solutions. The duel impeller system can be custom configured to attack all and any areas of the contaminated atomizer either in one complete operation or in separate and individual programmed sequences that allows for time and fluid savings. The positioning of the cleaning nozzles and the length and angle of the impeller arms can all be custom configured to the exact requirements for cleaning any particular one of the atomizers and guns that are available. The impellers are custom configured for each atomizer. If a user changes the atomizer on its paint line in future, a new impeller having the desired specifications can be retrofit into the cleaner  10 . 
     The Impeller of claim is propelled by air which is fed through the outside mounted check valve assembly channelled to the base of the impeller via a solid bar with dual feeding galleys. The impeller body is domed and twin arms which also are channeled direct the atomized mixture from the base to the nozzles on each arm. The nozzles can be custom directed at the exact areas on the atomizer where the contamination is present. These can be angled through 45 degrees. The nozzles can also be adjusted through 180 degrees to vary the amount of time that the spray is directed vertical and/or horizontal. The variable adjustments that are custom configured for each independent model of atomizer insure maximum effect and minimum fluid usage.