ELECTROSTATIC POWDER COATING APPARATUS

• US 3,667,675 A
• Filed: 02/16/1971
• Issued: 06/06/1972
• Est. Priority Date: 02/16/1971
• Status: Expired due to Term

• Current Assignee: Richard M. Sherman, Robert M. Webb
• Original Assignee: Richard M. Sherman, Robert M. Webb
• Inventors: Sherman, Richard M., Webb, Robert M.
• Primary Examiner(s): Wood, Jr., M. Henson
• Assistant Examiner(s): Culp, Jr., Thomas C.
• Application Number:
  US05/115,685
• Time in Patent Office: 476 Days
• Field of Search: 239/15,3 317/3
• US Class Current: 239/698
• CPC Class Codes: B05B 5/032 for spraying particulate materials

Abstract

An electrostatic powder coating apparatus for coating the surfaces of articles with pulverulent materials having an ionization member which serves as both an improved charging means and a pattern forming deflecting means including a probe portion positioned immediately to the rear of a deflecting member and a probe portion extending past a forward-most surface of the deflecting member, with said portions of the probe being maintained at an electrical potential substantially different than that of the article to be coated.

Claims

1. An electrostatic powder coating apparatus for electrostatically coating the surfaces of articles with pulverulent materials comprising:

a gun body having a longitudinal passage therethrough, said longitudinal passage having an inlet for receiving pulverulent materials and a discharge for discharging said pulverulent materials from the gun body toward an article to be coated;

an elongated ionization member having a first end disposed within said longitudinal passage and a second end spaced forward from the discharge of said gun, said ionization member further including a probe extending from said first end to said second end of said ionization member, said probe being constructed of an electrically conductive material, a body member constructed of an electrically non-conductive material surrounding said probe and extending from said first end to a point along said probe such that substantially all of said probe disposed within said passage is surrounded by said body member, a deflecting member for deflecting pulverulent materials being discharged from said discharge, said deflecting member being constructed of an electrically non-conductive material and disposed near said second end such that said deflecting member is spaced from said body member so that a portion of the probe immediately to the rear of said deflecting member is exposed to pulverulent materials passing through said passage and such that a portion of said probe passes through said deflecting member and extends past an exterior surface of said deflecting member; and

means for connecting a high voltage energy source with said probe so as to maintain a high voltage difference between said probe and the article to be coated.

2. The electrostatic powder coating apparatus of claim 1 having a sleeve member construCted of electrically non-conductive material which is slidably mounted to said gun body adjacent to the discharge of said longitudinal passage for axial movement therealong, said sleeve member being movable from a retracted position to a plurality of extended positions in which the front end of said sleeve member is forwardly spaced from the discharge of said passage.

3. The electrostatic powder coating apparatus of claim 2 having means for axially moving said sleeve member and means for retaining said sleeve member in any desired axial position and limiting the axial movement of said sleeve member.

4. The electrostatic powder coating apparatus of claim 3 wherein said means for retaining said sleeve member in a desired axial position includes a threaded member extending through a portion of said sleeve member and engaging a longitudinal channel on the surface of said gun body.

5. The electrostatic powder coating apparatus of claim 1 having a contact member constructed of an electrically conductive material, said contact member being secured to said body member and electrically connected to said probe.

6. The electrostatic powder coating apparatus of claim 5 wherein said means for connecting a high voltage energy source with said probe includes an electrically conducting member projecting into said passage and engaging said contact member for electrically connecting the high voltage source with said contact member and for limiting the movement of said ionization member into said passage.

7. The electrostatic powder coating apparatus of claim 1 having a plurality of fins integrally formed with said body member, said fins being circumferentially spaced about the periphery of said body member and extending radially outwardly therefrom for retaining said ionization member within said passage.

8. The electrostatic powder coating apparatus of claim 7 having a contact member constructed of an electrically conductive material, said contact member being mounted to a portion of said fins and electrically connected to said probe, such that a portion of said contact member is radially spaced from said body member.

9. The electrostatic powder coating apparatus of claim 8 wherein there are four fins constructed of a relatively flexible material for resiliently retaining said ionization member within said passage and wherein said means for connecting a high voltage energy source with said probe includes an electrically conducting member projecting into said passage between an adjacent pair of said fins and engaging said contact member for electrically connecting the high voltage source with said contact member and for limiting the movement of said ionization member into said passage.

10. The electrostatic powder coating apparatus of claim 9 wherein said contact member is a relatively circular ring having an external diameter conforming substantially to the internal diameter of said passage and having an internal diameter substantially greater than the external diameter of said body member such that pulverulent material passage through said passage must pass between said body member and said ring.

11. The electrostatic powder coating apparatus of claim 1 wherein said deflecting member includes a concave surface which is perpendicular to the longitudinal axis of said probe and which is the surface of said deflecting member past which a portion of said probe extends.

12. The electrostatic powder coating apparatus of claim 11 wherein said concave surface joins with a second surface of said deflecting member to form an edge such that all portions of said edge are spaced forwardly from the discharge of said passage at least as far as the portion of said probe extending past said concave surface.

13. The electrostatic powder coating apparatus of claim 2 having a contact member constructed of an electrically conductive material, said contact member being connected with said body member and electrically connected to said probe.

14. The electrostatic powder coating apparaTus of claim 2 having a plurality of fins integrally formed with said body member, said fins being circumferentially spaced about the periphery of said body member and extending radially outwardly therefrom for retaining said ionization member within said longitudinal passage.

15. The electrostatic powder coating apparatus of claim 2 wherein said deflecting member includes a concave surface which is perpendicular to the longitudinal axis of said probe and which is the surface of said deflecting member past which a portion of said probe extends.

16. The electrostatic powder coating apparatus of claim 13 having a plurality of fins integrally formed with said body member, said fins being circumferentially spaced about the periphery of said body member and extending radially outwardly therefrom for retaining said ionization member within said longitudinal passage.

17. The electrostatic powder coating apparatus of claim 13 wherein said deflecting member includes a concave surface which is perpendicular to the longitudinal axis of said probe and which is the surface of said deflecting member past which a portion of said probe extends.

18. The electrostatic powder coating apparatus of claim 16 wherein said deflecting member includes a concave surface which is perpendicular to the longitudinal axis of said probe and which is the surface of said deflecting member past which a portion of said probe extends.

19. The electrostatic powder coating apparatus of claim 18 wherein said contact member is mounted to a portion of said fins and is adapted for engaging a conducting member projecting into said passage for electrically connecting the high voltage source with said probe and for limiting the movement of said ionization member into said passage, and wherein said concave surface joins with a second surface of said deflecting member to form an edge such that all portions of said edge are spaced forwardly from the discharge of said passage at least as far as the portion of said probe extending past said concave surface.

20. A charging and deflecting unit for use in an electrostatic powder coating apparatus for electrostatically coating the surfaces of articles with pulverulent materials, said apparatus having a passage through which dispersed pulverulent materials are conveyed and a discharge end of said passage through which said pulverulent materials are discharged, said charging and deflecting unit comprising:

an electrically non-conductive deflecting member around which pulverulent material must be deflected upon leaving the discharge end of said gun, said deflecting member being spaced forwardly from the discharge end of said passage and oriented centrally along the extended longitudinal axis of said passage;

a central charging electrode portion positioned immediately to the rear of said deflecting member and exposed to the pulverulent materials being discharged from said passage;

a forward charging electrode portion positioned immediately forward of said deflecting member;

means connecting said charging electrode portion and said forward charging electrode portion with a high voltage power source for maintaining both of said electrode portions at an electrical potential substantially different from that of said article to be coated; and

a sleeve member constructed of electrically non-conductive material which is slidably mounted to said gun body adjacent to the discharge end of said passage for axial movement therealong, said sleeve member being movable from a retracted position to a plurality of extended positions in which the front end of said member is forwardly spaced from the discharge end of said passage for thereby varying the pattern of said pulverulent materials being discharged from said passage.

21. The charging and deflecting unit of claim 20 wherein said central charging electrode portion is spaced forward of the discharge end of said passage.

22. The charging and deflecting unit of claim 20 wherein said deflecting member includes a concave surface substantially perpendicular to the extended longitudinal axis of said passage and wherein said concave surface joins with a second surface of said deflecting member to form an edge such that all portions of said edge are spaced forwardly from the discharge end of said passage at least as far as said forward charging electrode portion.

23. The charging and deflecting unit of claim 20 having a body member rigidly connected with said central charging electrode portion and said deflecting member, said body member extending into said passage and being resiliently retained therein for supporting said deflecting member.

24. The charging and deflecting unit of claim 23 wherein a portion of said central charging electrode portion extends through said body member.