WO1996003219A1

WO1996003219A1 - System for cleaning accumulation on powder spray gun

Info

Publication number: WO1996003219A1
Application number: PCT/US1995/008465
Authority: WO
Inventors: Thomas E. Hollstein; Jonathan C. Tosh
Original assignee: Nordson Corporation
Priority date: 1994-07-25
Filing date: 1995-07-06
Publication date: 1996-02-08
Also published as: AU3093595A

Abstract

A system and method for blowing-off accumulated powder coating particles from the nozzle and deflector (114) of an electrostatic powder spray coating gun with a stream of pressurized air directed through a flexible tube (74) which flexes when the pressurized air is pulsed therethrough. In another embodiment, an air ring (90) mounted on the gun directs pressurized air against the nozzle. In another embodiment, pressurized air is deflected from a deflector cap (116) back onto the front face of the deflector and onto the nozzle to blow-off accumulated powder therefrom.

Description

SYSTEMFORCLEANINGACCUMULAΗONONPOWDERSPR_{AY GUN}

FIELD OF THE INVENTION

This invention relates to the field of powder guns for electrostatic application of powder coating materials. More particularly, the invention relates to a system for blowing-off accumulated powder from the nozzle and deflector of a powder gun.

BACKGROUND OF THE INVENTION

In the application of solid particulate material, such as powdered paints in industrial finishing applications, the powder material is commonly conveyed to a spray gun under pressure and then dispensed from a spray nozzle attached to the gun as a powder entrained, air stream towards an object or target substrate to be coated or painted. The particles of powder being dispensed from the spray gun are imparted with an electrical charge to electrostatically attract them towards the target substrate which is held at electrical ground potential. The material being dispensed from the spray gun is in particulate form and it is necessary to direct the material in a broadened spray pattern to obtain uniform, smooth and wide coverage of the surface of the substrate being coated. After coating, the target substrate is usually conveyed into an oven for heating and melting the powder coating material onto the surface of the substrate.

The powder spray gun used to spray the powder entrained, air stream is generally constructed with a gun barrel having a powder flow passage therethrough and a spray nozzle mounted at the forward end thereof. The spray nozzle can be formed with a generally circular- shaped discharge opening, as disclosed in U.S. Patent Nos. 4,380,320, 4,811,898 and 5,056,720, assigned to Nordson Corp., the assignee of the present invention, which patents are incorporated in their entirety herein, through which powder coating particles are emitted to form a generally conical shaped spray pattern upon the target substrate to be coated.

In order to maximize coverage of the target substrate with coating particles, a strong electrostatic field is created between an electrode and the target substrate so the coating particles are adequately charged and then strongly attracted to the target substrate. Typically, an electrode is mounted at the forward end of the spray gun, in the vicinity of the discharge opening of the spray nozzle, to impart the electrostatic charge to the powder coating particles emitted from the spray nozzle.

In known electrostatic powder spray guns, a mechanical deflector is mounted at the nozzle end of the gun. The deflector extends into the flow of powder being emitted from the gun and deflects the powder into a conical spray pattern. That is, the deflector is impacted by the powder coating material being emitted from the gun and directs the powder radially outwardly to form a conical spray pattern. As stated above, however, the powder is in particulate form and is carried by air under pressure, and as a result, forms a cloud which tends to cause the powder impinging on the deflector to build up on both the surface of the deflector as well as on the external surface of the nozzle. After a given amount of buildup, a clump of the accumulated coating material can drop off and hit the target substrate thereby marring the finish. This is particularly true when the gun is mounted overhead of the substrate.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and system for cleaning the nozzle and deflector of an electrostatic powder spray coating gun from accumulated powder coating particles which obviate the problems and limitations of the prior art systems.

It is a further object of the present invention to provide an improved method and system for blowing-off accumulated powder coating particles from the nozzle and deflector of an electrostatic powder spray coating gun.

Yet another object is to provide a method and system for blowing-off accumulated powder coating particles from the nozzle and deflector of an electrostatic powder spray coating gun with a stream of pressurized air directed against the external surface of the nozzle and onto the front surface of the deflector.

Still another object of the present invention to provide an improved method and system for blowing-off accumulated powder coating particles from the nozzle and deflector of an electrostatic powder spray gun by directing pressurized air through a flexible tube against the external surface of the nozzle and onto the front surface of the deflector.

Yet another object of the present invention to provide an improved method and system for blowing-off accumulated powder coating particles from the nozzle and deflector of an electrostatic powder spray gun by directing pulses of pressurized air through a flexible tube so that the tube flexes and changes the striking point of the air against the external surface of the nozzle.

According to the invention, a system for cleaning the nozzle and deflector of an electrostatic powder spray coating gun from accumulated powder coating particles includes the gun barrel of the powder spray gun having a powder flow passageway therethrough with an open forward end from which particulate powder coating material is emitted. A nozzle having a discharge opening for emitting the particulate powder coating material is mounted within the powder flow passageway at the forward end of the gun barrel. A deflector having a concave or convex shaped front surface is mounted in and projects outward from the forward end of the nozzle in the path of the particulate powder coating material emitted from the discharge opening of the nozzle to deflect the powder into a conical spray pattern. A flexible tube can be mounted to the spray gun for directing a flow of pressurized air onto the external surface of the nozzle and onto the front face of the deflector to blow-off any accumulated powder therefrom. The flexibility of the tube enables the flow of pressurized air to flex the tube and change the striking point of the air against the external surface of the nozzle to more thoroughly clean the nozzle during blow-off.

According to an alternative embodiment of the invention, an air ring having an inlet opening connected to a source of pressurized air and a plurality of outlet openings is mounted onto the external surface of the powder gun barrel for directing jets of pressurized air through the plurality of outlet openings across the external surface of the nozzle to blow-off any accumulated powder therefrom.

Also according to the invention, a method of cleaning the nozzle and deflector of an electrostatic powder spray coating gun comprises the following steps. The spray gun is provided with a barrel having a powder flow passageway therethrough, a nozzle having a discharge opening mounted at the forward end thereof, and a deflector mounted in and projecting outward from the discharge opening of the nozzle. A particulate powder coating material from the powder gun is sprayed between the discharge opening of the nozzle and the deflector. A flow of pressurized air is directed through a flexible tube onto the external surface of the nozzle and onto the front face of the deflector to blow-off any accumulated powder therefrom. The flow of pressurized air through the flexible tube is pulsed on and off causing the tube to flex so that the striking point of the air against the external surface of the nozzle changes to more thoroughly clean the nozzle during blow-off. The flow of pressurized air through the tube only is turned on when the emission of particulate powder coating material from the discharge opening of the nozzle is turned off.

According to another embodiment of the invention, an electrostatic powder spray coating gun comprises a gun barrel with a powder flow passageway therethrough. A nozzle, mounted at the forward end of the gun barrel, has a discharge opening for emitting the particulate powder coating material from the powder flow passageway. A gas passageway through the wall of the gun barrel is connected to a source of pressurized gas to emit an annular stream of pressurized gas from the forward end of the gun barrel. A support tube is mounted generally axially within both the gun barrel and the nozzle and has a forward end extending out of the discharge opening of the nozzle. A sleeve, terminating in an open end at. the forward end of the gun barrel, surrounds the support tube and defines a generally central, annular gas flow passageway which communicates with the gas passageway through the wall of the gun barrel. A deflector having a central bore therethrough is mounted on the forward end of the support tube in abutting relation with the sleeve to define a generally central annular gas flow passageway through which the gas flow from the gas passageway between the support tube and the sleeve issues out of the front facing surface of the deflector. A gas deflector cap, mounted on the forward end of the support tube, has a planar deflecting surface spaced from the open end of the deflector for deflecting the pressurized gas issuing from the open end of the deflector back onto the front face of the deflector and onto the external surface of the nozzle to blow-off any accumulated powder therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure, operation, and advantages of the presently preferred embodiment of the invention will become further apparent upon consideration of the following description taken in conjunction with the accompanying drawings, wherein: Fig. 1 is a side elevational view of a system for cleaning the nozzle and deflector of an electrostatic powder spray coating gun from accumulated powder coating particles, in accordance with the invention;

Fig. 2 is a partial side cross sectional view of Fig. 1 showing the electrostatic spray gun;

Fig. 3 is a view taken along line 3-3 of Fig. 1 illustrating the air flow around the nozzle and across the front surface of the deflector;

Fig. 4 is a side elevational view of the electrostatic spray gun of this invention incorporating an alternative deflector with a convex shaped, outwardly facing surface;

Fig. 5 is a side elevational view of an alternative embodiment of the electrostatic spray gun, in accordance with the invention, with a cylindrically shaped air manifold having a plurality of openings about its forward end surface to direct an air flow around the nozzle and across the front surface of the deflector;

Fig. 6 is an enlarged side elevational view of an alternative embodiment of the electrostatic spray gun, in accordance with the invention, showing the flow paths of the pressurized air and fluidized powder spray coating material in and out of the nozzle; and

Fig. 7 is a view taken along line 7-7 of Fig. 6 showing longitudual grooves around the diameter of a support tube which form a gas passageway.

DETAILED DESCRIPTION OF THE INVENTION

Referring to Figs, l, 2, and 3, a system 8 is shown for cleaning the nozzle and deflector of an electrostatic powder spray coating gun 10 from which a stream of fluidized powder coating particles issues in a desired conical spray pattern. System 8 is especially suited to cleaning the nozzle and deflector of spray coating gun 10 from accumulated powder coating particles. The spray gun 10, such as a VERSA-SPRAY IPS-100 gun manufactured by Nordson Corporation of Amherst, Ohio, the assignee of the present invention, has a body assembly 12, an electrically non-conductive barrel assembly 14, and an electrically non-conductive nozzle assembly 16 secured to the forward end of barrel assembly 14. Powder coating material, fluidized by a pressurized gas such as air, is supplied to gun 10 under pressure through a hose 18, such as by a pump from an external hopper or tank (not shown) . Hose 18 is connected to a fitting 20 mounted in an opening 22 through the wall of barrel assembly 14.

A high voltage source of electrical energy is supplied to body assembly 12 of spray gun 10 by a cable 24 from an external electrical power source 25. The high voltage cable 24 extends through body assembly 12 and terminates in barrel 14. Cable 24 is in electrical contact with a compressed electrical conductive spring 26 that, provides an electrical connection between the end of the cable 24 and a resistor 28. An electrode assembly 30 is attached at one end to the resistor 28 and has an other opposite end that extends out of the nozzle assembly 16. Electrode assembly 30, which is connected through the resistor 28 and spring 26 to the high voltage source of electrical energy, charges the powder spray coating material being emitted from nozzle assembly 16 of gun 10. Alternatively, the voltage multiple could be housed in the spray gun with only a low voltage line connected to the gun.

Referring to Fig. 2, nozzle assembly 16 is mounted in the forward open end of the barrel assembly 14 and includes a central throughbore 48 which defines an annular passageway through which the fluidized powder coating material entering gun 10 through the opening in the wall of barrel assembly 14 is emitted.

A funnel-shaped deflector 56, having a central bore 57 therethrough, is frictionally mounted on the forward end of electrode assembly 30 so that the tip end of electrode assembly 30 extends slightly beyond the large, forward end of funnel-shaped deflector 56. The forward end of funnel-shaped deflector 56, as shown in FIGs. 1-3, is constructed with a concave surface 58.

System 8 includes a control system 32. Control system 32 can turn the electrical power to gun 10 on and off through signal line 34 to power source 25. The air supply to a powder pump (not shown) for fluidizing the powder in a powder hopper (not shown) and conveying it to gun 10 through hose 18 can be turned on and off through signal line 36. In addition, the pressurized air conveyed to tube 40 from a source of pressurized air (not shown) , can be pulsed on and off by a control valve 41 which is activated in response to a signal from control 32 through a signal line 42, as discussed in more detail below. The terms "air" and "gas" are used interchangeably throughout the specification.

A principal feature of this invention is the provision of a hollow tube 40 mounted to the gun barrel 14 for directing a flow of pressurized or compressed air onto the external surface 43 of nozzle assembly 16 and onto the front face 58 of deflector 56 to blow-off any accumulated powder therefrom. Tube 40 is constructed of a flexible material, such as plastic or plexiglass, and is adjustably secured in a tube holder 60. Tube holder

60 is preferably secured to body assembly 12 and includes a pair of spaced, clamping sections 62 and 64 which have central openings that encircle a first section 69 of tube 40 and are tightened with conventional means, such as screws 66 and 68, respectively, to secure tube 40 in a desired position. One end 70 of first section 69 of tube 40 is connected to a source of pressurized gas or air (not shown) . A second section 74 of tube 40 is integrally adjoined to first section 69 and is shaped to initially project in a direction away from the external surface of gun barrel 14 and then back in an inclined direction towards the external surface 43 of nozzle section 16. The second section 74 can include a first portion 78 which adjoins first section 69 and extends at an inclined angle in a direction away from the external surface of gun barrel 14. A second portion 80 of section 74 adjoins first portion 78 and extends substantially parallel to the external surface of gun barrel 14. A third portion 82 of section 74 is adjoined to second portion 80 and extends at an inclined angle in the direction towards the surface 43 of nozzle section 16. The outlet opening 76 of tube 40 is preferably spaced from the external surface 43 of nozzle assembly 16 a distance of between about .01 to about .50 inches and preferably about .06 inches. The outlet opening 76 is disposed near outlet end of nozzle assembly 16. Preferably, a center line 84 through the third portion 82 of tube 40 forms an angle "a" of between about 20 degrees and 60 degrees with respect to the longitudinal center line 86 through gun 10. More preferably, the angle "a" is about thirty five to about forty five degrees with respect to the longitudinal center line 86 so that the stream of compressed air exiting tube 40 is directed against external surface 43 of nozzle assembly 16. The stream of compressed air tends to follow the contour of nozzle assembly 16 and then swirl around the front end of nozzle assembly 16 to blow-off any accumulated powder thereon as well as on the front face 58 of deflector 56. By adjusting the angle "a" and the spacing of outlet opening 76 with respect to the external surface 43 of nozzle section 16, the most efficient blow-off of accumulated powder on the external surface 43 of nozzle section as well as the front surface 58 of deflector 56 can be achieved.

While tube 40 is described with a specific construction, it is also within the terms of the invention, to provide any construction which enables the outlet end 76 of the tube to direct pressurized air against the external surface 43 of nozzle assembly 16 and onto the deflector 56. Moreover, while tube 40 is illustrated as being attached directly to gun 10, it can be secured to some other component of system 8 to achieve the desired results.

Another factor in increasing the effectiveness with which accumulated powder is blown-off from the nozzle and the deflector is the construction of tube 40 of a flexible material, such as plastic or plexiglass. By pulsing the pressurized air delivered through tube 40, the tube tends to flex and pivot about the intersection of the first and second sections 69 and 74, respectively, so that the flow of compressed air through outlet end 76 of tube 40 changes its point of contact on external surface 43 of nozzle section 16 and cleans off a larger area than if the tube 40 were rigid. Preferably, the internal diameter of tube 40 is between about .06 and about .25 inches. If the internal diameter were too small, such as less than about .06 inches, the diameter of the air flow would be too small to effectively wrap around and blow-off the accumulated powder from the entire external surface 43 of nozzle assembly 16. Conversely, if the internal diameter were too large, such as greater than about .25 inches, the velocity of the air would not be high enough to properly blow-off r.he accumulated powder from external surface 43.

In operation of system 8, as illustrated in Figs. 1- 3, the control device 32 turns on both the electrical power to gun 10 through signal line 34 and the air supply to the powder pump through signal line 36. The powder in a powder hopper is fluidized and conveyed by the pump to gun 10 through hose 18. The powder conveyed to gun 10 is sprayed as a cloud from nozzle 16 onto a workpiece (not shown), typically located below gun 10. The powder accumulates on the external surface 43 of nozzle section 16 and on the outer face 58 of deflector 56. When the spraying of the workpiece is completed, control device 32 turns off the air supply to the powder pump and the powder flow to gun 10 is stopped. Once the powder flow is turned off, control device 32 activates control 41 and pulses air through tube 40. As discussed before, tube 40 is flexible and the pulses of air flex tube 40 and cause the stream of pressurized air emitted from end 76 of tube 40 to follow the contour of the external surface 43 of nozzle assembly 16 and then swirl around across the front- face 58 of deflector 56 to blow-off any powder accumulated either on external surface 43 or on front face 58. The gun is now ready to powder coat the next workpiece without the risk of depositing onto the workpiece, excess powder which has collected on the nozzle or the deflector. This system is especially advantageously used on overhead guns coating automobiles. When used with such guns, the nozzle and deflector can be cleaned off between cars so that powder is not allowed to collect on the nozzles and deflectors and fall onto the automobile body during the coating operation.

While the Figs. 1 through 3 illustrate a single tube 40 mounted on gun 12, it is also within the terms of the present invention to dispose two or more tubes, substantially identical to tube 40, about gun 10 so that their outlet ends are disposed at an equal radial distance from centerline 86 and at a substantially equal angle to each other.

While a deflector 56 with a concave front surface 58, as shown in Figs. 1 and 3, can be adequately cleaned of any accumulated powder using the tube 40 as described above, it is also within the terms of the invention to provide a deflector 87, as shown in Fig. 4, with a front face 88 shaped with a convex outer surface to reduce the tendency of the coating powder from accumulating thereon. The convex shape also enhances the ease with which the pressurized air flow from tube 40 can blow-off any accumulation of powder thereon.

In further embodiment, as shown in Fig. 5, an air ring 90 is mounted onto the barrel 14. Air ring 90 has an inlet opening 92 connected by a hose 94 to a source of pressurized air (not shown) and a plurality of outlet openings 96. Air ring 90 is positioned so that jets of pressurized air, exhausting through the plurality of outlet openings 96, flow across the external surface 43 of nozzle assembly 16 to blow-off any accumulated powder therefrom. As discussed before, the air has a tendency to travel around and stay attached to external surface 43 of nozzle assembly 16 and then wrap around and past the front face 58 of deflector 56 to blow-off any accumulations of powder thereon.

Referring to Figs. 6 and 7, there is shown an alternative embodiment of a powder gun 100 wherein a gun barrel 102, similar to gun barrel 14 of the embodiment shown in Figs. 1 and 3, has an additional gas passageway 104 through the wall 105 of gun barrel 102 which is adapted to be connected to a source of pressurized gas (not shown) . The gas flow through passageway 104 provides a central stream of pressurized gas which is emitted from the forward end of gun barrel 102. A nozzle 16' is mounted within the powder flow passageway at the forward end of gun barrel 102. Throughout the specification primed numbers represent structure elements which are substantially identical to structure elements represented by the same unprimed number. A support tube 106 is mounted within both gun barrel 102 and nozzle section 16' and includes a forward end section 108 which extends out of the discharge opening of nozzle section 16'' and a rearward end section 109 which encircles resistor 28'. The forward end section 108 includes a rod 111 which is preferably threadedly secured at one end to rearward end section 109 and includes a central through bore 113 through which the tip end of electrode assembly 30' extends. A plurality of longitudinally extending grooves 115 are equally spaced about the diameter of support tube 106 and are in communication with the gas passageway 104 through the wall of gun barrel 102. While four semicircular-shaped grooves 115 are illustrated, it is within the terms of the invention to use any desired number of grooves and with each having any desired shape.

An elongated sleeve 110 is secured at one end by O- rings 113 in gun barrel 102 and surrounds support tube 106 to define a central gas flow passageway 112 on the rearward end section 109 between the inner surface of sleeve 110 and grooves 115. Sleeve 110 terminates witn a funnel-shaped deflector 114 having a central bore 119 which surrounds rod 111. The gas flow passageway 112 also includes an annular passageway 117 between rod 111 and sleeve 100. While deflector 114 is illustrated as being integrally formed with sleeve 110, it is also within the terms of the invention to provide a two piece construction including a sleeve and a deflector when they are threaded together, for example. A deflector cap 116 is mounted on the forward end of rod 111 and has a planer deflecting rearward facing surface 118 spaced from the open end of deflector 114 for deflecting the pressurized gas issuing from the open end of deflector 114 back onto the front face 120 of deflector 114 and then blowing acculated powder off of the external surface 43' of nozzle 16'. If necessary, the ring shown in Fig. 5 or the tube of Fig. 1 could be added to better clean the external surface of the nozzle and the deflector.

It is apparent that there has been provided in accordance with this invention a system and method for cleaning the nozzle and deflector of an electrostatic powder spray coating gun from accumulated powder coating particles which obviate the problems and limitations of the prior art systems. According to the invention, an improved system and method for blowing-off accumulated powder coating particles from the nozzle and deflector of an electrostatic powder spray coating gun is accomplished by directing a stream of pressurized air through a flexible tube against the external surface of the nozzle and onto the front surface of the deflector. Also according to the invention, the pressurized air may be pulsed through the flexible tube so that the tube flexes and changes the striking point of the air against the external surface of the nozzle. Also, according to the invention, an air ring mounted in the gun directs a plurality of air jets against the nozzle to blow off accumulated powder. In another embodiment, pressurized air issues out of the front facing surface of the deflector against a deflector cap spaced from the open end of the deflector and deflects back onto the front face of the deflector and onto the external surface of the nozzle to blow-off accumulated powder therefrom.

While the invention has been described in combination with embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing teachings. Accordingly, the invention is intended to embrace all such alternatives, modifications and variations as fall within the spirit and scope of the appended claims.

Claims

We claim:

1. A system for cleaning the nozzle and deflector of an electrostatic powder spray coating gun, comprising: a gun barrel of said powder gun having a powder flow passageway therethrough with an open forward end from which particulate powder coating material is emitted; a nozzle mounted within said powder flow passageway at said forward end of said gun barrel, said nozzle having a discharge opening for emitting said particulate powder coating material; a deflector mounted in said forward end of said nozzle in the path of said particulate powder coating material emitted from said discharge opening of said nozzle; and a tube for directing a flow of pressurized air onto at least one of the external surface of said nozzle and the front face of said deflector to blow-off accumulated powder therefrom.

2. The system of claim 1 wherein said tube directs said flow of pressurized air onto both said external surface of said nozzle and onto said front face of said deflector.

3. The system of claim 1 wherein said tube is mounted to said powder gun.

4. The system of claim 1 wherein said tube is constructed of a flexible material so that said flow of pressurized air causes said tube to flex and move its position relative to said external surface of said nozzle to more thoroughly clean said nozzle during blow-off.

5. The system of claim 4 wherein said tube is adjustably secured by a tube holder to said gun barrel whereby the direction of said flow of pressurized air towards said nozzle can be changed.

6. The system of claim 4 wherein said tube is constructed of plastic.

7. The system of claim 5 wherein said tube has a first section which is secured to said powder gun by said tube holder and a second section with a first portion that extends at an inclined direction away from said external surface of said gun barrel and a second portion that extends at an inclined direction towards said external surface of said gun barrel whereby the outlet opening of said tube directs said flow of pressurized air against said external surface of said nozzle and onto the front face of said deflector.

8. The system of claim 1 wherein said front face of said deflector has a concave shaped surface.

9. The system of claim 1 wherein said front face of said deflector has a convex shaped surface.

10. The system of claim 1 further including a controller to pulse on and off said flow of pressurized air from said tube.

11. The system of claim 10 wherein said controller stops said flow of said particulate powder coating material from said discharge opening of said nozzle before pulsing said stream of pressurized air on and off.

12. The method of cleaning the nozzle and deflector of an electrostatic powder spray coating gun, comprising the steps of: providing a gun barrel of said powder gun having a powder flow passageway therethrough with a nozzle having a discharge opening mounted at said forward end of said gun barrel and a deflector mounted in said discharge opening of said nozzle; spraying particulate powder coating material from said powder gun between said discharge opening of said nozzle and said deflector; and directing a flow of compressed air onto at least one of the external surface of said nozzle and the front face of said deflector to blow-off accumulated powder therefrom.

13. The method of claim 12 including the step of directing said flow of pressurized air through a flexible tube so that said flow of pressurized air causes said tube to flex and change the striking point of said air against said external surface of said nozzle to more thoroughly clean said nozzle during blow-off.

14. The method of claim 13 further including the step of pulsing said flow of pressurized air on and off.

15. The method of claim 14 further including the step stopping the spray of said particulate powder coating material from said discharge opening of said nozzle prior to pulsing said flow of pressurized air on and off.

16. The method of claim 12 wherein said flow of pressurized air is directed onto both said external surface of said nozzle and onto said front face of said deflector.

17. A system for cleaning the nozzle and deflector of an electrostatic powder spray coating gun, comprising: a gun barrel of said powder gun having a powder flow passageway therethrough with an open forward end from which particulate powder coating material is emitted; a nozzle mounted within said powder flow passageway at said forward end of said gun barrel, said nozzle having a discharge opening for emitting said particulate powder coating material; a deflector mounted in said forward end of said nozzle in the path of said particulate powder coating material emitted from said discharge opening of said nozzle; and an air ring having an inlet opening connected to a source of pressurized air and a plurality of outlet openings, said air ring mounted onto said powder gun for directing jets of pressurized air through said plurality of outlet openings and across said external surface of said nozzle to blow-off accumulated powder therefrom.

18. The system of claim 17 wherein said air ring directs jets of pressurized air across both said external surface of said nozzle and said front face of said deflector.

19. A system for cleaning the nozzle and deflector of an electrostatic powder spray coating gun, comprising: a gun barrel of said powder gun having a powder flow passageway therethrough with an open forward end from which particulate powder coating material is emitted; a gas inlet passageway adapted to be connected to a source of pressurized gas to provide a central stream of pressurized gas emitted from said forward end of said gun barrel; a nozzle mounted within said powder flow passageway at said forward end of said gun barrel, said nozzle having a discharge opening for emitting said particulate powder coating material; a support tube mounted generally axially within said gun barrel having a forward end; a sleeve surrounding at least a part of said support tube and defining a gas flow passageway therebetween, said flow passageway communicating with said gas inlet passageway, said sleeve terminating in an open end at said forward end of said gun barrel; a deflector having a central bore therethrough mounted to said forward end of said sleeve to define a section of said gas flow passageway through which said gas flow is directed so as to issue out of the front facing surface of said deflector; and a gas deflector cap mounted adjacent said deflector for deflecting said flow of pressurized gas issuing from said section of said gas flow passageway back onto said front facing surface of said deflector to blow-off accumulated powder therefrom.

20. The system of claim 19 wherein said flow of issuing gas deflects onto both said external surface of said nozzle and said front face of said deflector.

21. The system of claim 19 wherein said deflector is mounted to said sleeve by being integrally connected thereto.