Powder spray gun

• US 6,478,242 B1
• Filed: 01/31/2000
• Issued: 11/12/2002
• Est. Priority Date: 09/16/1999
• Status: Expired due to Term

• Current Assignee: Nordson Corporation
• Original Assignee: Nordson Corporation
• Inventors: Knobbe, Alan J., Meyers, Paul F., Peddie, Andrew M., Bowman, Bryan J., Thompson, Daniel J., Traylor, John C. A., Wolanin, John B.
• Primary Examiner(s): Doerrler, William C.
• Assistant Examiner(s): Nguyen, Dinh Q.
• Application Number:
  US09/490,099
• Time in Patent Office: 1,016 Days
• Field of Search: 239/690-708, 239/600, 239/590, 427/458, 451/102
• US Class Current: 239/690
• CPC Class Codes: B05B 1/04 in flat form, e.g. fan-like, sheet-like
• CPC Class Codes: B05B 15/62 Arrangements for supporting spraying apparatus, e.g. suction cups
• CPC Class Codes: B05B 5/032 for spraying particulate materials

Abstract

An electrostatic spray gun apparatus includes a spray gun housing and a nozzle attached to a spray end of the housing, and a powder path that extends in a substantially straight line along an axis of the housing from the powder inlet to the powder outlet. The powder path is in the form of an enclosed smooth powder passage that is substantially continuous and uninterrupted from the powder inlet to the powder outlet to eliminate substantially all recesses or gaps that could capture or trap powder. The powder passage is formed by a plurality of tubular segments that are aligned along the housing axis and abut end to end. that when assembled in the housing axially compress the segments together to substantially eliminate dead spots or recesses to form the continuous smooth powder path. A gun purge function is provided that allows a purge line to be installed on the gun assembly. A cartridge valve and conductor assembly is provided between the gun electrode in the nozzle and the output of the voltage multiplier. The cartridge includes a conductive path to provide electrical continuity from the multiplier to the gun electrode, and also includes valve, preferably in the form of a stem check valve, that closes when the gun electrode is removed or at least unseated from the nozzle. The gun also includes a tube mount arrangement wherein the tube mount is rigidly held together with the gun housing in axial compression by a tie bar.

Claims

1. An electrostatic powder spray gun comprising:

a gun housing having a nozzle end and an inlet end;

said inlet end having a powder inlet connectable to a supply of powder to be sprayed and said nozzle having an electrode and a powder outlet through which powder is sprayed toward a surface; and

a powder path that extends through said housing from said powder inlet to said powder outlet in a straight line along a single axis of said housing;

said powder path being defined by a plurality of linear tubular segments held together in axial compression by a threaded connection which is threaded along said axis.

2. The apparatus of claim 1 wherein said powder path comprises an uninterrupted smooth powder passage along which powder is conveyed from said inlet to said outlet, there being substantially no gaps and voids in said passage to collect powder.

3. The apparatus of claim 1 wherein said powder path comprises a substantially continuous and smooth powder passage through which powder is conveyed from said inlet to said outlet;

said passage being free of gaps that could trap powder.

4. The apparatus of claim 3 wherein said powder path comprises a plurality of linear tubular segments aligned along said axis and abutting each other end to end.

5. The apparatus of claim 4 comprising axially threaded connectors that securely compress said segments together with substantially no gaps therebetween.

6. The apparatus of claim 4 wherein said tubular segments are defined by a powder hose inlet coupling, a powder feed tube and a nozzle powder passage.

7. The apparatus of claim 6 wherein said tubular segments when joined define an annular passageway from said powder inlet to said powder outlet.

8. The apparatus of claim 1 comprising a power supply disposed in said housing off axis relative to said powder path;

said electrode being electrically connected to said power supply by an electrical conductor that extends along a path that is non-parallel to said axis.

9. A powder spray apparatus comprising:

first and second housing sections aligned end to end with respect to each other along an axis;

a nozzle assembly mounted on one end of said second housing section and a powder inlet disposed at one end of said first housing section;

a powder path that extends through said housing from said powder inlet to said powder outlet in a straight line along a single axis of said housing; and

means for holding said housing sections together in axial compression;

said means comprising a threaded connection which is threaded along said axis.

10. Powder spray gun comprising:

a spray gun housing;

a nozzle attached to said housing;

an electrode disposed in said nozzle;

a power supply disposed within said spray gun housing;

a cartridge housing that retains an electrical contact at respective ends thereof with a conductor therethrough; and

a valve disposed in said cartridge housing;

said conductor providing electrical continuity through said valve;

said valve being open when said conductor makes electrical contact with the spray gun electrode and said valve being closed when said conductor is not in electrical contact with the gun electrode;

said valve when closed preventing powder from passing from said nozzle to said housing interior and said power supply.

11. The apparatus of claim 10 wherein said contacts are spring biased apart from each other, said spring biasing one of said contacts to a position to close said valve when said electrode is removed from said nozzle.

12. The apparatus of claim 11 comprising an air passage through said cartridge to air wash said electrode when said electrode is electrically connected to said conductor.

13. A powder spray apparatus comprising:

first and second housing sections aligned end to end with respect to each other along an axis;

a nozzle assembly at one end of said second housing section and a powder inlet disposed at one end of said first housing section;

a powder path that extends through said housing from said powder inlet to said powder outlet in a straight line along a single axis of said housing; and

an axially extending member that holds said housing sections together in axial compression by a threaded connection which is threaded along said axis.

14. The apparatus of claim 13 wherein said member comprises a rigid tube that closely surrounds a powder feed tube that extends axially through said housing sections.

15. The apparatus of claim 13 wherein said member comprises a powder feed tube.

16. The apparatus of claim 13 wherein said second housing comprises a powder spray gun.

17. The apparatus of claim 16 wherein said first housing is a tubular support for said spray gun.

18. The apparatus of claim 16 comprising a powder feed tube extending through said first and second housings.

19. An electrostatic powder spray gun comprising:

a gun housing having a nozzle end and an inlet end;

said inlet end having a powder inlet connectable to a supply of powder to be sprayed and said nozzle having an electrode and a powder outlet through which powder is sprayed toward a surface; and

a powder path that extends through said housing from said powder inlet to said powder outlet in a straight line along a single axis of said housing, wherein said nozzle comprises an electrode holder disposed in said powder path;

said electrode being connected to a power supply through a valve that blocks powder flow to said power supply when said electrode holder is unseated in said nozzle.

20. The apparatus of claim 19 wherein said valve comprises a check valve having a valve stem that is displaced by said electrode holder to open said valve when said electrode holder is seated in said nozzle.

21. The apparatus of claim 20 wherein said valve is disposed in a replaceable cartridge within said housing.

22. The apparatus of claim 21 wherein said housing comprises a housing insert that is snap-fit inserted into and retained in said housing without threaded connection;

said housing insert being removable for access to said cartridge valve;

said cartridge being disposed in said housing insert.

23. The apparatus of claim 21 wherein said cartridge comprises an electrical conductor that makes electrical contact with said power supply at one end of the cartridge when the power supply is installed in said housing, and that makes electrical contact with said electrode when said electrode holder is installed in said nozzle.

24. An electrostatic powder spray gun comprising:

a gun housing having a nozzle end and an inlet end;

said inlet end having a powder inlet connectable to a supply of powder to be sprayed and said nozzle having an electrode and a powder outlet through which powder is sprayed toward a surface; and

a powder path that extends through said housing from said powder inlet to said powder outlet in a straight line along a single axis of said housing, wherein said housing comprises first and second housing sections joined end to end;

said housing sections enclosing a powder feed tube, an air line and an electrical cable from said inlet to said outlet;

said housing sections being held together in axial compression by a tie bar that extends from said powder inlet.

25. The apparatus of claim 24 wherein said tie bar extends from said powder inlet at one end of said first housing section to a terminus within said second housing section;

said second housing section having a first end abutting a second end of said first housing, said second housing section having a second end;

said nozzle being mounted on and removable from said second housing section second end.

26. The apparatus of claim 25 wherein said second housing section comprises a removable housing insert that snap fits into said second housing;

said insert comprising a threaded bore;

said tie bar having a first threaded end that is threadably seated in said threaded bore.

27. The apparatus of claim 26 wherein said tie bar comprises a second threaded end;

the apparatus further comprising a nut that when threaded onto said tie bar second threaded end draws together said housing sections in compression.

28. A powder spray apparatus comprising:

first and second housing sections aligned end to end with respect to each other along an axis;

a nozzle assembly mounted on one end of said second housing section and a powder inlet disposed at one end of said first housing section; and

means for holding said housing sections together in axial compression;

said means for holding comprises a tie-bar attached at a first end to the second housing;

said tie-bar at a second end being adapted to receive a member that forces said housings together in compression when installed on the tie-bar.

29. The apparatus of claim 28 wherein said member comprises a nut that is threaded onto said tie-bar second end and axially forces said first housing toward said second housing.

30. The apparatus of claim 29 comprising a powder feed tube that extends through said housings to said nozzle, said powder feed tube being concentrically inserted into said tie-bar and extending therethrough.

31. A powder spray apparatus comprising:

first and second housing sections aligned end to end with respect to each other along an axis;

a nozzle assembly at one end of said second housing section and a powder inlet disposed at one end of said first housing section; and

an axially extending member that holds said housing sections together in axial compression, wherein said member comprises a rigid bar attached at first and second ends respectively to said first and second housing sections.

32. A powder spray apparatus comprising:

first and second housing sections aligned end to end with respect to each other along an axis;

a nozzle assembly at one end of said second housing section and a powder inlet disposed at one end of said first housing section; and

an axially extending member that holds said housing sections together in axial compression, wherein said member comprises a tie-bar.

33. A powder spray apparatus comprising:

first and second housing sections aligned end to end with respect to each other along an axis;

a nozzle assembly at one end of said second housing section and a powder inlet disposed at one end of said first housing section; and

an axially extending member that holds said housing sections together in axial compression, wherein said member comprises a flexible cable.