POWDER SPRAY SYSTEM

• US 3,746,254 A
• Filed: 11/02/1971
• Issued: 07/17/1973
• Est. Priority Date: 11/02/1971
• Status: Expired due to Term

• Current Assignee: Charles H. Riedy, Lane S. Duncan, Simon Z. Tamny
• Original Assignee: Charles H. Riedy, Lane S. Duncan, Simon Z. Tamny
• Inventors: Duncan, Lane S., Tamny, Simon Z., Riedy, Charles H.
• Primary Examiner(s): Wood, Jr., M. Henson
• Assistant Examiner(s): Mar, Michael
• Application Number:
  US05/194,830
• Time in Patent Office: 623 Days
• Field of Search: 239/15,85,142,143,144,600 302/52 317/3,262
• US Class Current: 239/697
• CPC Class Codes: B05B 5/032 for spraying particulate materials
• CPC Class Codes: B05B 5/1683 specially adapted for particulate materials
• CPC Class Codes: B05B 7/1445 involving vibrations B05B7/145 takes precedence
• CPC Class Codes: B05B 7/1477 means for supplying to several spray apparatus

Abstract

An electrostatic spray system for applying a solid particulate powder material to the surface of an article or substrate. The system includes a pneumatic conveyer line including a vacuum region for withdrawing powder from a hopper and entraining it in an air stream, after which it is propelled to an electrostatic spray gun while entrained in the air stream. To facilitate quick color or powder changes, the system includes an improved hopper having a check valve in the bottom which automatically closes when the hopper is removed from a supporting base and which is automatically opened when the hopper is placed upon the base. The system also includes a quick change hose connection at the handle of the gun for clamping and unclamping new hoses which extend between the hopper support and the electrostatic gun. To meter and control the rate of flow of powder from the hopper, the system includes a pneumatic metering control in the form of a variable air curtain injected into a powder flow passage located between the bottom of the hopper and the pneumatic conveyer line. As the pressure in this curtain is increased the flow in the system is reduced. The system also includes a pneumatic vibrator which is connected to a source of air pressure through a regulator common with the pneumatic conveyer so that the rate of vibration is always directly proportional to air flow in the pneumatic conveyer and to the vacuum in the conveyer which controls powder flow from the hopper. The electrostatic gun of this system has an adjustment for varying the shape of the spray pattern emerging from the gun while separating the flow of powder from the flow of entrainment air. The adjustment is so constructed that the size and dimensions of the discharge orifice of the gun are maintained fixed throughout the range of adjustment.

Claims

1. An electrostatic spraying system for spraying solid particulate powder material comprising a hopper having a bottom discharge opening through which powder material may flow outwardly from said hopper, a pneumatic conveyer line, a flow passage extending between and interconnecting said pneumatic conveyer line and said hopper discharge opening, said pneumatic conveyer line including means for creating a region of substantial vacuum in the area of intersection of said pneumatic conveyer line with said flow passage whereby powder material may be drawn through said metering passage into said pneumatic conveyer by the vacuum created in said region, electrostatic spray means in fluid communication with said pneumatic conveyer line, means for supplying gas at a pressure above that of the atmosphere to said pneumatic conveyer line, and the improvement which comprises metering means for controlling the rate of flow of solid particulate material from said hopper into said flow passage, said metering means comprising means located remote from the area of intersection of said pneumatic conveyer line and said flow passage for directing a curtain of gas at a pressure above that of the atmosphere radially into said passage in a direction generally normal to the direction of flow of solid particulate flow through said passage.

2. The electrostatic spray system of claim 1 in which said metering means includes an annular chamber opening into said flow passage and means for supplying gas at a pressure above that of the atmosphere to said chamber.

3. An electrostatic spraying system for spraying solid particulate powder material comprising a hopper having a bottom discharge opening through which powder material may flow outwardly from said hopper, a pneumatic conveyer line, a flow passage extending between and interconnecting said pneumatic conveyer line and said hopper discharge opening, said pneumatic conveyer line including means for creating a region of substantial vacuum in the area of intersection of said pneumatic conveyer line with said flow passage whereby powder material may be drawn through said metering passage into said pneumatic conveyer by the vacuum created in said region, electrostatic spray means in fluid communication with said pneumatic conveyer line, means for supplying gas at a pressure above that of the atmosphere to said pneumatic conveyer line, and metering means for controlling the rate of flow of solid particulate material from said hopper into said flow passage, said metering means comprising an annular channel surrounding and opening into said flow passage adjacent said hopper discharge opening and means for supplying gas at a pressure above that of the atmosphere into said channel, said annular channel being located remote from said area of intersection of said pneumatic conveyer line with said passage.

4. The electrostatic spraying system of claim 3 which further includes a pneumatic vibrator means and a single regulating means for simultaneously varying the air pressure to said pneumatic conveyer line and to said vibrator means.

5. The electrostatic spraying system of claim 3 in which said electrostatic spray means includes an electrostatic spray Gun having a pneumatic-powder transfer conduit in fluid communication with said pneumatic conveyer line, said conduit terminating in a discharge nozzle, electrostatic charging means for applying electrostatic charge to powder as it is ejected from said nozzle, a source of electrical potential, an electrical circuit including an electric switch interconnecting said source of potential to said electrostatic charging means, a normally open first pneumatic flow control valve in said gun, a manually operated trigger for closing said first valve when said trigger is actuated to initiate powder flow from said gun, and a pneumatic circuit for connecting a source of air pressure to said first pneumatic valve, said pneumatic circuit including a second pneumatic flow control valve, said second pneumatic flow control valve being operable to effect closing of said electrical switch and charging of said electrostatic charging means upon closing of said first pneumatic valve.

6. The electrostatic spraying system of claim 5 in which said electrical circuit further includes a solenoid of a solenoid-operated valve, said solenoid-operated valve being operable to open the flow of gas to said pneumatic conveyer line upon closing of said electrical switch.

7. The electrostatic spraying system of claim 3 which further comprises quick-change means for facilitating replacement of one hopper having one particulate powder material therein with a second hopper having a second particulate powder material therein, said quick-change means comprising a valve in the bottom of said hopper, and means for opening said valve in response to location of said hopper on said support block.

8. The electrostatic spraying system of claim 7 in which said valve comprises a ball check located in the bottom of said hopper operable to close said hopper discharge opening upon removal of said hopper from said support block.

9. The electrostatic spraying system of claim 8 in which said valve opening means comprises a fixed rigid element extending upwardly from said hopper support block.

10. The electrostatic spraying system of claim 3 which further includes a hose connecting said electrostatic spray means to said pneumatic conveyer line and quick change clamping means on said electrostatic spray means for clamping said hose to said electrostatic spray means.

11. The electrostatic system of claim 3 in which said electrostatic spray means comprises an electrostatic spray gun having an electrically nonconductive barrel, a recess in one end of said barrel, said recess being surrounded by an axially extending flange of said barrel, a slide movably mounted within said recess internally of said flange, a continuous material passage extending axially through said barrel and said adjustable slide and terminating in an outlet orifice in said slide, a spray-shaping horn fixedly secured to said slide and located in said passage adjacent said orifice, means for applying an electrical charge to powder material as it is ejected from said orifice, and means for adjusting said slide relative to said barrel flange to vary the spray pattern emerging from said material passage without changing the dimensions of said material passage at said outlet orifice.

12. An electrostatic spraying system for spraying solid particulate powder material comprising a hopper having a bottom discharge opening through which powder material may flow outwardly from said hopper, a pneumatic conveyer line, a flow passage extending between and interconnecting said pneumatic conveyer line and said hopper discharge opening, said pneumatic conveyer line including means for creating a region of substantial vacuum in the area of intersection of said pneumatic conveyer line with said flow passage whereby powder material may be drawn through said metering passage into said pneumatic conveyer by the vacuum created in said region, electrostatic spray means in fluid communication with said pneumatic conveyer line, pneumatic metering means for controlling the rate of flow of solid particulate material from said hopper, pneumatic vibrator means for vibrating said hopper to maintain a flow of powder from said bottom discharge opening, a source of air pressure, an air line connecting said source of air pressure to both said metering means and said pneumatic conveyer line, and a single regulator means in said air line for simultaneously varying the air pressure in said pneumatic conveyer line and in said pneumatic vibrator means.

13. An electrostatic spraying system for spraying solid particulate powder material comprising a hopper having a bottom discharge opening through which powder material may flow outwardly from said hopper, a pneumatic conveyer line, a flow passage extending between and interconnecting said pneumatic conveyer line and said hopper discharge opening, means for supplying gas at a pressure above that of the atmosphere to said pneumatic conveyer line, an electrostatic spray gun including a pneumatic-powder transfer conduit in fluid communication with said pneumatic conveyer line, said conduit terminating in a discharge nozzle, electrostatic charging means for applying an electrostatic charge to powder as it is ejected from said nozzle, a source of electrical potential, an electrical circuit including an electrical switch interconnecting said source of potential to said electrostatic charging means, a normally open first pneumatic flow control valve in said gun, a manually operated trigger for closing said first valve when said trigger is actuated to initiate powder flow from said gun, a pneumatic circuit for connecting a source of air pressure to said first pneumatic valve, said pneumatic circuit including a second pneumatic flow control valve, said second pneumatic flow control valve being operable to effect closing of said electrical switch and charging of said electrostatic charging means upon closing of said first pneumatic valve.

14. The electrostatic spraying system of claim 13 in which said electrical circuit further includes a solenoid of a solenoid-operated valve, said solenoid-operated valve being operable to open the flow of gas to said pneumatic conveyer line upon closing of said electrical switch.

15. The electrostatic spray system of claim 13 in which said second pneumatic flow control valve comprises a cylinder including a magnet movable within the cylinder in response to air flow therethrough, said switch being a magnetic reed switch located in proximity to said magnet such that movement of said magnet in said cylinder effects closing of said switch.

16. An electrostatic spraying system for spraying solid particulate powder material comprising a hopper having a bottom discharge opening through which powder material may flow outwardly from said hopper, a pneumatic conveyer line, a hopper support block, a flow passage extending through said block between said pneumatic conveyer line and said hopper discharge opening, electrostatic spray means in fluid communication with said pneumatic conveyer line, means for supplying gas at a pressure above that of the atmosphere to said pneumatic conveyer line, and the improvement which comprises quick-change means for facilitating replacement of one hopper having one solid particulate powder material therein with a second hopper having a second particulate powder material therein, said quick-change means comprising a valve in the bottom of said hopper, and means for opening said valve in response to location of said hopper on said support block.

17. The electrostatic spray system of claim 16 in which said valve comprises a ball check located in the bottom of said hopper operable to close said hopper discharge opening upon removal of said hopper from said support block.

18. The electrostatic spray system of claim 17 in whicH said valve opening means comprises a fixed rigid element extending upwardly from said hopper support block.

19. The electrostatic spray system of claim 16 which further includes pneumatic metering means for controlling the rate of flow of solid particulate material from said hopper, said metering means comprising means for directing a flow of gas radially into said flow passage.

20. The electrostatic spray system of claim 19 which further includes a pneumatic vibrator means and single regulating means for simultaneously varying the air pressure to said pneumatic conveyer line and to said vibrator means.

21. The electrostatic spray system of claim 16 in which said electrostatic spray means includes an electrostatic spray gun having a pneumatic-powder transfer conduit in fluid communication with said pneumatic conveyer line, said conduit terminating in a discharge nozzle, electrostatic charging means for applying electrostatic charge to powder as it is ejected from said nozzle, a source of electrical potential, an electrical circuit including an electric switch interconnecting said source of potential to said electrostatic charging means, a normally open first pneumatic flow control valve in said gun, a manually operated trigger for closing said first valve when said trigger is actuated to initiate powder flow from said gun, and a pneumatic circuit for connecting a source of air pressure to said first pneumatic valve, said pneumatic circuit including a second pneumatic flow control valve, said second pneumatic flow control valve being operable to effect closing of said electrical switch and charging of said electrostatic charging means upon closing of said first pneumatic valve.

22. The electrostatic spray system of claim 21 in which said electrical circuit further includes a solenoid of a solenoid-operated valve, said solenoid-operated valve being operable to open the flow of gas to said pneumatic conveyer line upon closing of said electrical switch.

23. The electrostatic spray system of claim 16 which further includes a hose connecting said electrostatic spray means to said pneumatic conveyer line and quick-change clamping means on said electrostatic spray means for clamping said hose to said electrostatic spray means, said quick-change means including a pivoted clamp and means for locking said clamp in a closed position.

24. The electrostatic spray system of claim 16 in which said electrostatic spray means comprises an electrostatic spray gun having an electrically nonconductive barrel, a recess in one end of said barrel, said recess being surrounded by an axially extending flange of said barrel, a slide movably mounted within said recess internally of said flange, a continuous material passage extending axially through said barrel and said adjustable slide and terminating in an outlet orifice in said slide, a spray-shaping horn fixedly secured to said slide and located in said passage adjacent said orifice, means for applying an electrical charge to powder material as it is ejected from said orifice, and means for adjusting said slide relative to said barrel flange to vary the spray pattern emerging from said material passage without changing the dimensions of said material passage at said outlet orifice.

25. An electrostatic spray system for spraying solid particulate powder material comprising a hopper having a bottom discharge opening through which powder material may flow outwardly from said hopper, a pneumatic conveyer line, a flow passage extending between and interconnecting said pneumatic conveyer line and said hopper discharge opening, an electrostatic spray gun, a hose connecting said spray gun to said pneumatic conveyer line, said spray gun having an electrically nonconductive barrel, a handle secured to said barrel, a material passage in said barrel terminating in an outlet orifice, means for applying an electrical chaRge to material as it is ejected from said orifice, an electrical resistor, first electrically conductive connector means connecting one end of said resistor to said electrical charge applying means, a high voltage power supply, second electrically conductive connector means connecting said resistor to said high voltage power supply, the improvement which comprises quick change clamping means in the handle of said gun for clamping said hose in said gun in a position in which it is in fluid communication with said material passage of said gun barrel, said quick change means including a pivoted clamp and means for locking said clamp in a closed position.

26. A nozzle for use with a spray gun for the application of powder coating material by electrostatic means in which the powder is entrained in an air stream and carried to the nozzle through a passageway, said nozzle including an orifice in which the flows of air and powder are treated as two substantially independent flow regimes, said orifice comprising pneumatic flow path means for controlling the direction of the air flow therein in accordance with the hydraulic flow and boundary layer characteristics of the orifice, and powder flow path means for controlling the direction of the powder flow in accordance with the impact reflection of the powder particles from the surfaces in the orifice, whereby the flow paths of the air and powder are made separately controllable.

27. The nozzle of claim 26 in which said pneumatic flow path means includes means for controlling the air flow in a substantially radially outward direction upon exit from the orifice and the powder flow path means includes means for simultaneously controlling the powder flow in a substantially forward direction upon exit from the orifice.

28. An electrostatic spray system for spraying solid particulate powder material comprising a hopper having a bottom discharge opening through which powder material may flow outwardly from said hopper, a pneumatic conveyer line, a flow passage extending between and interconnecting said pneumatic conveyer line and said hopper discharge opening, means for supplying gas at a pressure above that of the atmosphere to said pneumatic conveyer line, an electrostatic spray gun, a hose connecting said spray gun to said pneumatic conveyer line, said spray gun having an electrically nonconductive barrel, a recess in the one end of said barrel, said recess being surrounded by a flange of said barrel, a slide movably mounted within said recess internally of said flange, a continuous material passage in said barrel and said adjustable slide terminating in an outlet orifice in said slide, a spray shaping horn fixedly secured to said slide and located in said passage adjacent said orifice, means for applying an electrical charge to material as it is ejected from said orifice, an electrical resistor, first electrically conductive connector means connecting one end of said resistor to said electrical charge applying means, a high voltage power supply, second electrically conductive connector means connecting said resistor to said high voltage power supply, and means for adjusting said slide relative to said barrel flange to vary the spray pattern emerging from said material passage without changing the dimensions of said material passage at said outlet orifice.

29. An electrostatic spray gun for use in a powder spray system of the type having a hopper and a hopper discharge passage through which particulate powder material may flow into a pneumatic conveyer line, which electrostatic spray gun comprises an electrically nonconductive barrel, a recess in the one end of said barrel, said recess being surrounded by an axially extending flange of said barrel, a slide movably mounted within said recess internally of said flange, a continuous material passage extending axially in said barrel and said adjustable slide terminating in an outlet orifice in said slide, a spray shaping horn fixedly secured to said slide and located in said passage adjacent said orifice, means for applying an electrical charge to material as it is ejected from said orifice, a high voltage power supply, electrically conductive connector means connecting said electrical charge applying means to said high voltage power supply, and means for adjusting said slide relative to said barrel flange to vary the spray pattern emerging from said material passage without changing the dimensions of said material passage at said outlet orifice.

30. The electrostatic spray gun of claim 29 which further includes a hose for connecting said electrostatic spray gun to said pneumatic conveyer line and quick change clamping means on said electrostatic spray gun for releasably clamping said hose to said electrostatic spray gun.

31. An electrostatic spray gun for use in a powder spray system of the type having a hopper and a hopper discharge passage through which particulate powder material may flow into a pneumatic conveyer line, which electrostatic spray gun comprises an electrically nonconductive barrel, a recess in one end of said barrel, said recess being surrounded by an axially extending flange of said barrel, a slide movably mounted within said recess internally of said flange, a continuous material passage extending axially in said barrel and said adjustable slide terminating in an outlet orifice in said slide, a spray shaping horn fixedly secured to said slide and located in said passage adjacent said orifice, means for applying an electrical charge to powder material as it is ejected from said orifice, and means for adjusting said slide relative to said barrel flange to vary the spray pattern emerging from said material passage without changing the dimensions of said material passage at said outlet orifice.

32. The electrostatic spray gun of claim 31 which further includes a hose for connecting said electrostatic spray gun to said pneumatic conveyer line and quick change clamping means on said electrostatic spray gun for clamping said hose to said electrostatic spray gun, said quick change means including a means for receiving and locking said hose to the spray gun.

33. An electrostatic spray gun for use in a powder spray system of the type having a hopper and a hopper discharge passage through which particulate powder material may flow into a pneumatic conveyor line, which pneumatic conveyer line terminates at said electrostatic spray gun, which electrostatic spray gun comprises an electrically nonconductive barrel, a continuous material passage extending axially in said barrel and terminating in an outlet orifice, a spray shaping horn located in said passage adjacent said orifice, means for applying an electrical charge to powder material as it is ejected from said orifice, and means for adjusting the pattern of powder material ejected from said orifice without changing the dimensions of said material passage at said outlet orifice.

34. An electrostatic spray gun for use in a powder spray system of the type having a hopper and a hopper discharge passage through which particulate powder material may flow into a pneumatic conveyor line, which pneumatic conveyer line terminates at said electrostatic spray gun, which electrostatic spray gun comprises an electrically nonconductive barrel, an annular member located adjacent the discharge end of said barrel, a pattern adjusting member located internally of said annular member, a continuous material passage extending axially through said barrel and terminating in an outlet orifice, a spray shaping horn mounted upon said pattern adjusting member, means for applying an electrical charge to powder material as it is ejected from said orifice, and means for adjusting one of said members relative to the other to vary The spray pattern emerging from said orifice without changing the dimensions of said material passage at said outlet orifice.

35. An electrostatic spray gun for use in a powder spray system of the type having a hopper and a hopper discharge passage through which particulate powder material may flow into a pneumatic conveyor line, which pneumatic conveyor line terminates at said electrostatic spray gun, which electrostatic spray gun comprises an electrically nonconductive barrel, a continuous material passage extending axially in said barrel and terminating in an outlet orifice, a spray shaping horn located in said passage adjacent said orifice, means for applying an electrical charge to powder material as it is ejected from said orifice, and means for separating air entrained powder material from the entrainment air stream as said powder is ejected from said orifice.

36. The electrostatic spray gun of claim 35 in which said separating means includes means for focusing said powder toward the axis of said passage while simultaneously directing said air stream radially away from axis.

37. An electrostatic spray gun for use in a powder spray system of the type having a hopper and a hopper discharge passage through which particulate powder material may flow into a pneumatic conveyor line, which pneumatic conveyor line terminates at said electrostatic spray gun, which electrostatic spray gun comprises an electrically nonconductive barrel, an annular member located adjacent the discharge end of said barrel, a pattern adjusting member located internally of said annular member, a continuous material passage extending axially through said barrel and terminating in an outlet orifice, a spray shaping horn mounted upon said pattern adjusting member, means for applying an electrical charge to powder material as it is ejected from said orifice, and separating means including means for adjusting one of said members relative to the other to control and vary the degree of separation of air entrained powder from the entrainment air stream as said powder emerges from said orifice.

38. The electrostatic spray gun of claim 37 in which said separating means includes means for focusing said powder toward the axis of said passage while simultaneously directing said air stream radially away from said axis.

39. The electrostatic spray gun of claim 38 in which said focusing means includes a curved outer end surface on said annular member.

40. The electrostatic spray gun of claim 39 in which said curved outer surface is convex.

41. An electrostatic spray gun for use in a powder spray system of the type having a hopper and a hopper discharge passage through which particulate powder material may flow into a pneumatic conveyor line, which pneumatic conveyor line includes a hose for connecting said pneumatic conveyor line to the electrostatic spray gun, which electrostatic spray gun comprises an electrically nonconductive barrel, a material passage in said barrel terminating in an outlet orifice, means for applying an electrical charge to said material as it is ejected from said orifice, an electrical resistor, first electrically conductive connector means connecting one end of said resistor to said electrical charge applying means, a high voltage power supply, second electrically conductive connector means connecting said resistor to said high voltage power supply, and a quick change clamping means in said gun for clamping said hose in said gun in a position in which it is in fluid communication with said material passage of said gun barrel, said quick change means including a pivoted clamp and means for locking said clamp in a closed position, said electrostatic spray gun barrel having a recess in one end, said recess being surrounded by an axially extending flange of said barrel, a slide movably mounted within said recess internally of said flange, a materiAl passage extending axially through said adjustable slide and terminating at an outlet orifice in said slide, a spray shaping horn fixedly secured to said slide and located in said slide passage adjacent said orifice, and means for adjusting said slide relative to said barrel flange to vary the spray pattern emerging from said material passage without changing the dimensions of said material passage at said outlet orifice.