Swirl gun for powder particles

• US 20040061007A1
• Filed: 09/27/2002
• Published: 04/01/2004
• Est. Priority Date: 09/27/2002
• Status: Active Grant

• Current Assignee: ABB Incorporated (ABB Limited)
• Original Assignee: ABB Incorporated (ABB Limited)
• Inventors: Milojevic, Dragoslav K., Koster, Melissa L., Rennie, Christopher M., Borner, Gunter, Ciarelli, Gary J.
• Granted Patent: US 6,874,712 B2
• Time in Patent Office: Days
• US Class Current: 239/690
• CPC Class Codes: B05B 5/032 for spraying particulate materials
• CPC Class Codes: B05B 5/0533 Electrodes specially adapted therefor; Arrangements of electrodes

Abstract

A powder spraying gun generates a desired pattern of electrostatically charged particles for coating a workpiece without rotating parts or particle deflectors. The powder pattern is generated with a funnel-shaped output in conjunction with air introduced into a powder charging chamber of the gun in a tangential swirling motion. The swirling air is additionally used to purge agglomerated powder particles from the charging electrodes in the charging chamber. The charging chamber surface is fashioned from material exhibiting low friction or high resistance to powder impact fusion.

Claims

1. A powder spraying gun for electrostatic powder coating application comprising:

a gun body having an interior powder charging chamber defining a surface extending along an axis of the gun body and fashioned from a material exhibiting resistance to powder impact fusion;

a powder supply input in fluid communication with the powder charging chamber at a first end thereof and extending at an angle to the axis different from 90°

;

an output chamber having a funnel-shaped output in fluid communication with the powder charging chamber at a second end thereof;

a ground electrode extending into the first end of the powder charging chamber; and

a plurality of interior charging electrodes radially extending into the powder charging chamber.

2. The powder spraying gun of claim 1 further comprising:

a compressed air inlet adapted for coupling to a source of compressed air; and

a plurality of air conduits each tangentially opening at the surface of the powder charging chamber between pairs of the plurality of interior charging electrodes and in fluid communication with the compressed air inlet for introducing air in a swirling pattern into the charging chamber for imparting a swirling motion to powder particles and for purging powder particles adhering to exposed surfaces of the interior charging electrodes.

3. The powder spraying gun of claim 1 further comprising a plurality of exterior charging electrodes extending through the funnel-shaped output and positioned so as to be capable of creating an external electrostatic field between the gun output and a workpiece to be coated.

4. The powder spraying gun of claim 2 further comprising a plurality of exterior charging electrodes extending through the funnel-shaped output and positioned so as to be capable of creating an external electrostatic field between the gun output and a workpiece to be coated.

5. The powder spraying gun of claim 1 wherein the funnel-shaped output has a funnel wall forming an angle between about 120°

and about 180°

.

6. The powder spraying gun of claim 1 wherein the surface of the powder charging chamber is comprised of a removable insert of the material exhibiting resistance to powder impact fusion.

7. The powder spraying gun of claim 1 wherein the material exhibiting resistance to powder impact fusion comprises plastic.

8. The powder spraying gun of claim 6 wherein the material exhibiting resistance to powder impact fusion comprises plastic.

9. The powder spraying gun of claim 1 wherein the funnel-shaped output has an external diameter of about 25 mm. to about 70 mm.

10. The powder spraying gun of claim 1 wherein the powder charging chamber has a diameter of about 13 mm. to about 20 mm.

11. The powder spraying gun of claim 1 wherein the powder charging chamber has a diameter of about 15 mm. to about 17 mm.

23. The powder spraying gun of claim 1 further comprising a plurality of interior charging electrodes radially extending through the powder charging chamber and positioned between pairs of the plurality of air conduits.

12. A powder spraying gun for electrostatic powder coating application comprising:

a gun body having an interior powder charging chamber defining a surface extending along an axis of the gun body;

a powder supply input in fluid communication with the powder charging chamber at a first end thereof and extending at an angle to the axis different from 90°

;

an output chamber having a funnel-shaped output in fluid communication with the powder charging chamber at a second end thereof;

a ground electrode extending into the first end of the powder charging chamber;

a plurality of interior charging electrodes radially extending into the powder charging chamber;

a compressed air inlet adapted for coupling to a source of compressed air; and

a plurality of air conduits each tangentially opening at the surface of the powder charging chamber between pairs of the plurality of interior charging electrodes and in fluid communication with the compressed air inlet for introducing air in a swirling pattern into the charging chamber for imparting a swirling motion to powder particles and for purging powder particles adhering to exposed surfaces of the interior charging electrodes.

13. The powder spraying gun of claim 12 further comprising a plurality of exterior charging electrodes extending through the funnel-shaped output and positioned so as to be capable of creating an external electrostatic field between the gun output and a workpiece to be coated.

14. The powder spraying gun of claim 12 wherein the funnel-shaped output has a funnel wall forming an angle between about 120°

and about 180°

.

15. The powder spraying gun of claim 12 wherein the surface of the powder charging chamber is comprised of material exhibiting resistance to powder impact fusion.

16. The powder spraying gun of claim 15 wherein the material exhibiting resistance to powder impact fusion comprises plastic.

17. The powder spraying gun of claim 15 wherein the surface of the powder charging chamber is defined by a removable insert of the material exhibiting resistance to powder impact fusion.

18. The powder spraying gun of claim 17 wherein the material exhibiting resistance to powder impact fusion comprises plastic.

19. The powder spraying gun of claim 12 wherein the funnel-shaped output has an external diameter of about 25 mm. to about 70 mm.

20. The powder spraying gun of claim 12 wherein the powder charging chamber has a diameter of about 13 mm. to about 20 mm.

21. The powder spraying gun of claim 12 wherein the powder charging chamber has a diameter of about 15 mm. to about 17 mm.

22. A powder spraying gun for electrostatic powder coating application comprising:

a gun body having an interior powder charging chamber defining a surface extending along an axis of the gun body and fashioned from a material exhibiting resistance to powder impact fusion;

a powder supply input in fluid communication with the powder charging chamber at a first end thereof and extending at an angle to the axis different from 90°

;

an output chamber having a funnel-shaped output in fluid communication with the powder charging chamber at a second end thereof;

a ground electrode extending into the first end of the powder charging chamber;

a plurality of exterior charging electrodes extending through the funnel-shaped output;

a compressed air inlet adapted for coupling to a source of compressed air; and

a plurality of air conduits each tangentially opening at the surface of the powder charging chamber and in fluid communication with the compressed air inlet for introducing air in a swirling pattern into the charging chamber for imparting a swirling motion to powder particles.

24. The powder spraying gun of claim 22 wherein the funnel-shaped output has a funnel wall forming an angle between about 120°

and about 180°

.

25. The powder spraying gun of claim 22 wherein the surface of the powder charging chamber is defined by a removable insert of the material exhibiting resistance to powder impact fusion.

26. The powder spraying gun of claim 22 wherein the material exhibiting resistance to powder impact fusion comprises plastic.

27. The powder spraying gun of claim 25 wherein the material exhibiting resistance to powder impact fusion comprises plastic.

28. The powder spraying gun of claim 22 wherein the funnel-shaped output has an external diameter of about 25 mm. to about 70 mm.

29. The powder spraying gun of claim 22 wherein the powder charging chamber has a diameter of about 13 mm. to about 20 mm.

30. The powder spraying gun of claim 22 wherein the powder charging chamber has a diameter of about 15 mm. to about 17 mm.

31. A powder spraying gun for electrostatic powder coating application comprising:

a gun body extending along a longitudinal axis thereof from a first end to a second end;

a substantially cylindrical powder charging chamber in the gun body having a removable insert defining a chamber surface, the insert fashioned from a material resistant to powder impact fusion, the chamber extending along the longitudinal axis toward the second end from a chamber input intermediate the first and second ends;

a powder supply input in fluid communication with the chamber input and extending at an angle to the longitudinal axis different from 90°

;

a swirl bell cup having a funnel-shaped output in fluid communication with the powder charging chamber and coupled to the second end of the gun body;

a hollow tubular ground electrode having at least one orifice therein and extending from the first end of the gun body to an electrode head at the chamber input;

a ground electrode cleaning air input adapted for coupling a source of compressed air to the hollow tubular ground electrode and out of the at least one orifice so as to purge particles adhering to the electrode head;

a plurality of interior charging electrodes radially extending into the powder charging chamber via a first conductive plastic ring mounted around the insert downstream of the powder supply input;

a plurality of air conduits each tangentially opening at the surface of the insert between pairs of the plurality of interior charging electrodes;

a swirl air input at the first end of the gun body in fluid communication with the plurality of air conduits and adapted for coupling to a source of compressed air for imparting a swirling motion to powder particles in the vicinity of the tangential openings and for simultaneously purging powder particles adhering to the plurality of interior charging electrodes; and

a plurality of exterior charging electrodes mounted to a second conductive plastic ring mounted to the insert adjacent the first conductive plastic ring and extending through the swirl bell cup and positioned so as to be capable of creating an external electrostatic field between the gun output and a workpiece to be coated.