Electrostatic-fluidized bed coating of wire

• US 4,188,413 A
• Filed: 01/20/1978
• Issued: 02/12/1980
• Est. Priority Date: 10/18/1976
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Lupinski, John H., Gorowitz, Bernard
• Primary Examiner(s): Kaplan, Morris
• Application Number:
  US05/871,153
• Time in Patent Office: 753 Days
• Field of Search: 427/21, 427/27, 427/32, 427/28, 427/29, 427/30, 427/33, 118/DIG. 5, 118/DIG. 19, 118/DIG. 22, 118/627, 118/629, 118/630, 118/654
• US Class Current: 427/459
• CPC Class Codes: B05C 19/025 Combined with electrostatic means
• CPC Class Codes: H01B 13/0033 by electrostatic coating

Abstract

An elongate electrical conductor is continuously coated with electrostatically charged powder by passing the conductor upwardly through a tube into the upper portion of a container having a charged fluidized bed of the powder in a lower portion thereof. The tube extends upwardly through the bed and the tube height is adjusted relative to the upper surface of the bed to control the thickness of the powder coating. An array of electrodes having associated switches permits application of uniform coatings to conductors having a variety of shapes. Two or more conductors may be uniformly coated from the same fluidized bed in a container having a baffle which divides the upper portion into two or more compartments and spaced apart tubes extend upwardly into the different compartments.

Claims

1. A process for continuously applying a controlled thickness coating on an elongate electrical conductor, comprising the steps of

(a) providing an upwardly extending hollow member having an upwardly facing port,

(b) providing a bed of powder about said hollow member,

(c) fluidizing said bed to an extent such that the upper surface of the bed is below the port,

(d) electrically charging the fluidized bed with an electrical potential different from the electrical potential of the conductor by electrically charging electrode means disposed within said bed,

(e) said conductor being a rectangular wire having an elongate cross-sectional shape including opposite narrow ends interconnected by a pair of elongate opposite sides,

(f) disposing said electrode means in a angularly spaced apart, generally horizontal array with at least one charged electrode porjecting radially inwardly toward each elongate cross-section side of the rectangular wire and no electrode projecting inwardly toward either of said cross-sectional narrow sides,

(g) advancing the conductor along a path through said hollow member and upwardly out of said port to effect coating of the powder onto the conductor,

(h) adjusting the height of the port above the upper surface of the bed to control the thickness of the powder coating.

2. The process of claim 1, wherein the fluidizing step includes passing a gaseous medium upwardly through the bed at a sufficiently low rate to substantially avoid entrainment of powder by the gaseous medium in a zone above the bed.

3. The process of claim 2, further including the step of vibrating said bed while the steps of fluidizing and electrically charging and conductor advancing are being carried out.

4. The process of claim 1, wherein the powder is fusible and further including fusing the powder coating to form a film.

5. The process of claim 1, wherein the hollow member is a tube.

6. The process of claim 1, wherein the upper surface of the bed is at least 0.2 inch above said electrode means.

7. The process of claim 1, wherein said charging step is additionally carried out by electrically charging a gaseous medium exteriorly of the bed and said fluidizing step is carried out by passing the charged gaseous medium upwardly through the bed.

8. The process of claim 2, wherein said rate corresponds to a superficial velocity of said gaseous medium from about 0.01 to about 0.10 feet per second, the average diameter of the particles of said powder being from about 3 to about 200 microns.

9. The process of claim 8, wherein said superficial velocity is from about 0.01 to about 0.03 feet per second.

10. The process of claim 9, wherein said average diameter is from about 3 to about 74 microns.

11. The process of claim 1, wherein said plurality of charged electrodes is constituted by four charged electrodes so arranged that first and second pairs of adjacent inner ends thereof are at first and second pairs of adjacent apexes of a regular hexagon, each of the remaining two apexes separating said first and second apex pairs and being aligned with said opposite narrow ends of said rectangular wire.

12. The process of claim 1, wherein the ratio of cross-sectional length to cross-sectional width of said rectangular wire is 2:

1 or more.

13. The process of claim 14, wherein the ratio of cross-sectional length to cross-sectional width of said rectangular wire is 2:

1 or more.

14. The process of claim 1, further comprising the steps of

(G) providing a second upwardly extending hollow member having a second upwardly facing port,

(H) providing a second bed of powder about said second hollow member,

(I) fluidizing said second bed to an extent such that the upper surface thereof is below said second port,

(J) electrically charging the fluidized second bed with an electrical potential different from the electrical potential of a second elongate electrical conductor,

(K) advancing said second conductor along a path through said second hollow member and upwardly out of said second port to effect coating of powder from said second bed onto said second conductor,

(L) adjusting the height of said second port above the upper surface of said second fluidized bed to control the thickness of the powder coating on said second conductor,

(M) containing said fluidized beds in a lower portion of a container having an upper portion where the coating of both conductors is effected, and

(N) providing barrier means dividing said upper portion of the container into two separate regions such that each region is disposed above only one of said hollow member ports, said barrier means having a lower end spaced above a container member supporting the bed thereabove, said lower end of said barrier means being disposed lower than each of said ports,

and wherein the fluidized first-mentioned bed and the fluidized second bed constitute adjoining portions of a common fluidized bed, whereby charged particles are transfered from said common fluidized bed to each conductor in the region of the upper portion of the container adjacently above the port of the hollow member through which such conductor is advanced.

15. A process for continuously coating an elongate electrical conductor, comprising the steps of

(a) providing an upwardly extending hollow member having an upwardly facing port,

(b) providing a plurality of horizontally spaced apart electrodes about said hollow member and near said port,

(c) providing a bed of powder about said hollow member

(d) fluidizing said bed to an extent such that the upper surface of the bed is intermediate the port and said electrodes,

(e) electrically charging the electrodes with an electrical potential different from the electrical potential of the conductor,

(f) advancing the conductor along a path through said hollow member and upwardly out of said port to effect coating of the powder onto the conductor,

(g) providing a second upwardly extending hollow member having a second upwardly facing port,

(h) providing a second plurality of horizontally spaced apart electrodes about said second hollow member and near said second port,

(i) providing a second bed of powder about said second hollow member,

(j) fluidizing said second bed to an extent such that the upper surface thereof is intermediate said second port and said electrodes of said second plurality,

(k) electrically charging said plurality of electrodes with an electrical potential different from the electrical potential of a second elongate electrical conductor,

(l) advancing said second conductor along a path through said second hollow member and upwardly out of said second port to effect coating of powder from said second bed onto said second conductor,

(m) containing said fluidized bed in a lower portion of a container having an upper portion where the coating of both conductors is effected,

(n) providing barrier means dividing said upper portion of the container into two separate regions such that each region is disposed above only one of said hollow member portions, said barrier means having a lower end spaced above a lower member of the container, said member supporting the beds thereabove, said lower end of said barrier means being disposed lower than each of said ports,

and wherein the fluidized first-mention bed and the fluidized second bed constitute adjoining portions of a common fluidized bed, whereby charged particles are transferred from said common fluidized bed to each conductor in the region of the upper portion of the container adjacently above the port of the hollow member through which such conductor is advanced.

16. The process of claim 15, wherein each conductor is wire having circular cross-section, each electrode means includes a generally horizontal array of a plurality of angularly spaced apart electrically charged electrodes, each hollow member is a substantially vertical tube extending upwardly through a different one of the arrays, each electrode of each array projecting inwardly toward one of said tubes, the angular spacing between each pair of adjacent electrodes in each array is uniform, the radial distance from each tube to the inner end of each electrode in the array through which such tube extends is the same, and the inner ends of the electrodes of each array are at apexes of a regular polygon, the advance of each wire being through the center of the tube through which such wire is advanced.

17. The process of claim 16, wherein each array comprises six charged electrodes, and the inner ends of said six electrodes are at the apexes of a regular hexagon.

18. The process of claim 15, wherein each conductor is rectangular wire having an elongate cross-sectional shape including opposite narrow ends interconnected by a pair of elongate opposite sides, each electrode means includes a generally horizontal array of angularly spaced apart electrically charged electrodes, each hollow member is a substantially vertical tube extending upwardly through a different one of the arrays, at least one charged electrode of each array projecting radially inwardly toward each elongate cross-section side of the rectangular wire being advanced through the tube extending through such array with no charged electrode projecting inwardly toward either of the narrow ends of such rectangular wire.

19. The process of claim 18, wherein each array of charged electrodes is constituted by four charged electrodes so arranged that first and second pairs of adjacent inner ends thereof are at first and second pairs of adjacent apexes of regular hexagon, each of the remaining two apexes separating said first and second apex pairs and being aligned with the opposite narrow ends of the rectangular wire being advanced through the tube extending through such array.

20. The process of claim 18, wherein the ratio of cross-sectional length to cross-sectional width of each rectangular wire is 2:

1 or more.

21. The process of claim 19, wherein the ratio of cross-sectional length to cross-sectional width of each rectangular wire is 2:

1 or more.

22. The process of claim 15, further including adjusting the height of each port above the upper surface of the common fluidized bed to control the thickness of the powder coating on the conductor advanced out of such port.

23. The process of claim 15, wherein each hollow member is substantially vertical.

24. The process of claim 23, further including adjusting the height of each port above the upper surface of the common fluidized bed to control the thickness of the powder coating on the conductor advanced out of such port.