Arc thermal spray gun and gas cap therefor

• US 5,964,405 A
• Filed: 02/20/1998
• Issued: 10/12/1999
• Est. Priority Date: 02/20/1998
• Status: Expired due to Term

• Current Assignee: Sulzer Metco Incorporated (Sulzer AG)
• Original Assignee: Sulzer Metco Incorporated (Sulzer AG)
• Inventors: Dirmeier, Ludwig, Bohm, Reinhard, Benary, Raphael
• Primary Examiner(s): Kashnikow, Andres
• Assistant Examiner(s): Ganey, Steven J.
• Application Number:
  US09/027,123
• Time in Patent Office: 599 Days
• Field of Search: 239/79, 239/81, 239/83, 239/84, 239/290, 239/296, 239/418, 239/419, 239/422, 219/76.14, 219/76.16, 219/121.47, 219/121.51
• US Class Current: 239/84
• CPC Class Codes: B05B 7/224 the material having originally the shape of a wire, rod or the like

Abstract

An arc spray gun has a pair of tubular wire guides that guide two metal wires to a point of contact at the wire tips where an arc current through the wires effect an arc, thereby melting the tips. Primary gas channeling on a central axis issues a primary gas flow that atomizes the molten metal and effects a spray stream thereof. A gas cap has at least four orifices arcuately spaced equally about the central axis. The orifices direct secondary gas jets inwardly with a forward directional component toward a point of intersection of the orifice axes on the central axis. The point of intersection is located proximate the point of contact and spaced downstream therefrom sufficiently for the jets not to interfere substantially with the atomization. The spray stream thereby is constricted and accelerated by the secondary gas jets.

Claims

1. An arc spray apparatus comprising a spray gun body, a pair of tubular wire guides held convergingly by the gun body so as to guide two metal wires to a point of contact at spraying tips of the wires, a wire feeding mechanism operatively connected to feed the wires respectively through the wire guides, primary gas channeling in the gun body on a central axis located centrally with respect to the wire guides, and a gas cap attached to the gun body coaxially with the central axis, the wires being receptive of an arc current to effect an arc and thereby molten metal at the spraying tips, the primary gas channeling being receptive of a primary source of compressed gas to issue a primary gas flow for atomization of the molten metal and production of a spray stream thereof, the gas cap having a plurality of at least four orifices arcuately spaced equally about the central axis, the orifices being simultaneously receptive of a secondary source of compressed gas and having orifice axes oriented at an angle with the central axis such that the orifices direct secondary gas jets inwardly with a forward directional component toward a point of intersection of the orifice axes on the central axis, the point of intersection being located proximate the point of contact and spaced downstream therefrom sufficiently for the jets not to interfere substantially with the arc and the atomization, and the orifices being of circular cross section with substantially equal dimensions and having an aspect ratio of length to diameter, with the aspect ratio being sufficiently high and the angle being selected so that, with sufficient secondary gas pressure, the spray stream is constricted with substantially circular cross section and accelerated by the secondary gas jets.

2. The arc spray apparatus of claim 1 wherein the plurality of orifices comprises an even number of orifices in pairs of diametrically opposite orifices.

3. The arc spray apparatus of claim 1 wherein the point of intersection is located between about 0.5 and 1 cm from the point of contact.

4. The arc spray apparatus of claim 1 wherein the plurality is between 10 and 20 inclusively.

5. The arc spray apparatus of claim 1 wherein the orifices converge toward the point of intersection on the central axis at an angle with the axis between about 30°

and about 40°

.

6. The arc spray apparatus of claim 1 wherein the orifices have an aspect ratio of length to diameter of at least 4:

1.

7. The arc spray apparatus of claim 1 wherein the gas cap has a forwardly expanding inner surface surrounding the point of contact, with the orifices exiting from the expanding inner surface.

8. The arc spray apparatus of claim 7 wherein the gas cap further has a forwardly tapering inner surface located rearwardly of the expanding inner surface, so as to constrict the primary gas flow to a primary jet to effect the atomization.

9. The arc spray apparatus of claim 7 wherein the expanding inner surface diverges from the central axis at an angle between about 30°

and about 50°

with the axis, and the orifice axes converge toward the point of intersection on the central axis at an angle with the central axis between about 30° and

about 40°

with the axis.

10. An arc spray apparatus comprising a spray gun body, a pair of tubular wire guides held convergingly by the gun body so as to guide two metal wires to a point of contact at spraying tips of the wires, a wire feeding mechanism operatively connected to feed the wires respectively through the wire guides, primary gas channeling in the gun body on a central axis located centrally with respect to the wire guides, and a gas cap attached to the gun body coaxially with the central axis, the wires being receptive of an arc current to effect an arc and thereby molten metal at the spraying tips, the primary gas channeling being receptive of a primary source of compressed gas to issue a primary gas flow for atomization of the molten metal and production of a spray stream thereof;

wherein;

the gas cap has a plurality of at least four orifices arcuately spaced equally about the central axis, the orifices having orifice axes and being receptive of a secondary source of compressed gas and being oriented to direct secondary gas lets inwardly with a forward directional component toward a point of intersection of the orifice axes on the central axis, the point of intersection being located proximate the point of contact and spaced downstream therefrom sufficiently for the lets not to interfere substantially with the arc and the atomization;

the gas cap further has a forwardly expanding inner surface surrounding the point of contact, with the orifices exiting from the expanding inner surface;

the expanding inner surface diverges from the central axis at an angle between about 30° and

about 50°

with the axis, and the orifice axes converge toward the point of intersection on the central axis at an angle with the central axis between about 30° and

about 40°

with the axis; and

the plurality of orifices comprises an even number of orifices in pairs of diametrically opposite orifices, the point of intersection is located between about 0.5 cm and 1 cm from the point of contact, and the plurality is between 10 and 20 inclusively, whereby the spray stream is constricted and accelerated by the secondary gas jets.

11. The arc spray apparatus of claim 10 wherein the gas cap further has a forwardly tapering inner surface located rearwardly of the expanding inner surface, so as to constrict the primary gas flow to a primary jet to effect the atomization.

12. A gas cap for an arc spray apparatus, the apparatus including a spray gun body, a pair of tubular wire guides held convergingly by the gun body so as to guide two metal wires to a point of contact at spraying tips of the wires, a wire feeding mechanism operatively connected to feed the wires respectively through the wire guides, and primary gas channeling in the gun body on a central axis located centrally with respect to the wire guides, the wires being receptive of an arc current to effect an arc and resulting molten metal at the spraying tips, and the primary gas channeling being receptive of a primary source of compressed gas to issue a primary gas flow for atomization of the molten metal and production of a spray stream thereof;

wherein;

the gas cap comprises a cap structure adapted to fit the gas cap to the gun body coaxially with the central axis, the gas cap having a plurality of at least four orifices arcuately spaced equally about the central axis, such that, with the gas cap fitted to the gun body, the orifices are simultaneously receptive of a secondary source of compressed gas, the orifices having orifice axes oriented at an angle with the central axis such that the orifices direct secondary gas jets inwardly with a forward directional component toward a point of intersection of the orifice axes on the central axis, the point of intersection being located proximate the point of contact and spaced downstream therefrom sufficiently for the jets not to interfere substantially with the arc and the atomization, and the orifices being of circular cross section with substantially equal dimensions and having an aspect ratio of length to diameter, with the aspect ratio being sufficiently high and the angle being selected so that, with sufficient secondary gas pressure, the spray stream is constricted with substantially circular cross section and accelerated by the secondary gas jets.

13. The gas cap of claim 12 wherein the plurality of orifices comprises an even number of orifices in pairs of diametrically opposite orifices.

14. The gas cap of claim 12 wherein the point of intersection is located between about 0.5 and 1 cm from the point of contact.

15. The gas cap of claim 12 wherein the plurality is between 10 and 20 inclusively.

16. The gas cap of claim 12 wherein the orifices converge toward the point of intersection on the central axis at an angle with the axis between about 30°

and about 40°

.

17. The arc spray apparatus of claim 12 wherein the orifices have an aspect ratio of length to diameter of at least 4:

1.

18. The gas cap of claim 12 wherein the gas cap has a forwardly expanding inner surface surrounding the point of contact, with the orifices exiting from the expanding inner surface.

19. The gas cap of claim 18 wherein the gas cap further has a forwardly tapering inner surface located rearwardly of the expanding inner surface, so as to constrict the primary gas flow to a primary jet to effect the atomization.

20. The gas cap of claim 18 wherein the inner surface diverges from the central axis at an angle between about 30°

and about 50°

with the axis, and the orifices converge toward the point of intersection on the central axis at an angle with the axis between about 30° and

about 40°

with the axis.

21. A gas cap for an arc spray apparatus, the apparatus including a spray gun body, a pair of tubular wire guides held convergingly by the gun body so as to guide two metal wires to a point of contact at spraying tips of the wires, a wire feeding mechanism operatively connected to feed the wires respectively through the wire guides, and primary gas channeling in the gun body on a central axis located centrally with respect to the wire guides, the wires being receptive of an arc current to effect an arc and resulting molten metal at the spraying tips, and the primary gas channeling being receptive of a primary source of compressed gas to issue a primary gas flow for atomization of the molten metal and production of a spray stream thereof;

wherein;

the gas cap comprises a cap structure adapted to fit the gas cap to the gun body coaxially with the central axis, the gas cap having a plurality of at least four orifices arcuately spaced equally about the central axis, the orifices having orifice axes and being receptive of a secondary source of compressed gas and being oriented to direct secondary gas lets inwardly with a forward directional component toward a point of intersection of the orifice axes on the central axis, the point of intersection being located proximate the point of contact and spaced downstream therefrom sufficiently for the lets not to interfere substantially with the arc and the atomization;

the gas cap further has a forwardly expanding inner surface surrounding the point of contact, with the orifices exiting from the expanding inner surface;

the inner surface diverges from the central axis at an angle between about 30° and

about 50°

with the axis, and the orifices converge toward the point of intersection on the central axis at an angle with the axis between about 30° and

about 40°

with the axis; and

the plurality of orifices comprises an even number of orifices in pairs of diametrically opposite orifices, the point of intersection is located between about 0.5 cm and 1 cm from the point of contact, and the plurality is between 10 and 20 inclusively, whereby the spray stream is constricted and accelerated by the secondary gas jets.

22. The gas cap of claim 21 wherein the gas cap further has a forwardly tapering inner surface located rearwardly of the expanding inner surface, so as to constrict the primary gas flow to a primary jet to effect the atomization.

23. A gas cap for an arc spray gun, comprising a cap structure adapted to fit the gas cap to a gun body of a two-wire arc spray gun coaxially with a central axis, the gas cap having a plurality of at least four orifices arcuately spaced equally about the central axis, such that, with the gas cap fitted to the gun body, the orifices are simultaneously receptive of a secondary source of compressed gas, the orifices being of substantially equal dimensions and having orifice axes converging toward a point of intersection on the central axis at an angle with the central axis between about 30°

and about 40°

, and the orifices having an aspect ratio of length to diameter of at least 4;

1.

24. The gas cap of claim 23 wherein the plurality of orifices comprises an even number of orifices in pairs of diametrically opposite orifices, and the plurality is between 10 and 20 inclusively.

25. The gas cap of claim 23 wherein the gas cap has a forwardly expanding inner surface surrounding the point of contact, with the orifices exiting from the expanding inner surface.

26. The gas cap of claim 24 wherein the gas cap further has a forwardly tapering inner surface located rearwardly of the expanding inner surface.

27. The gas cap of claim 25 wherein the inner surface diverges from the central axis at an angle between about 30°

and about 50°

with the axis.

28. The gas cap of claim 27 wherein the plurality of orifices comprises an even number of orifices in pairs of diametrically opposite orifices, the point of intersection is located between about 0.5 cm and 1 cm from the point of contact, and the plurality is between 10 and 20 inclusively.

29. The gas cap of claim 28 wherein the gas cap further has a forwardly tapering inner surface located rearwardly of the expanding inner surface, so as to constrict the primary gas flow to a primary jet to effect the atomization.