Claims
- 1. A plasma-MIG welding torch, which comprises a cylindrical housing; a single nozzle non-consumable electrode positioned adjacent one end of said cylindrical housing, said single nozzle having a central orifice, an annular opening surrounding said central orifice, and a plurality of ribs extending radially from said central orifice to said cylindrical housing and providing electrical connection therebetween; means for flowing a thermally ionizable gas stream from a common gas source through said single nozzle non-consumable electrode toward a workpiece to thereby split said gas stream into a central gas column surrounded by a parallelly flowing annular gas sheath both having the same composition as they flow past the single nozzle outlet; means for feeding a consumable electrode through said central gas column toward the workpiece; a first circuit means consisting basically of said consumable electrode, a first power supply, and said workpiece for establishing a MIG-arc between the consumable electrode and the workpiece; a second circuit means consisting basically of a second power supply, said single nozzle non-consumable electrode, and said workpiece for establishing a plasma arc between the single nozzle non-consumable electrode and the workpiece to ionize said central gas column and sustain a plasma flow enveloping said MIG-arc without ionizing the surrounding annular gas sheath, said annular gas sheath remaining relatively colder than the resulting central plasma gas column; and a cylindrical gas conductor surrounding said single nozzle non-consumable electrode and forming an extension of said cylindrical housing, said cylindrical gas conductor being electrically insulated from said cylindrical housing and terminating in an outlet aperture downstream of said single nozzle non-consumable electrode, the cross-sectional area of the gas conductor outlet aperture being smaller than the combined cross-sectional areas of the single nozzle central orifice and the surrounding single nozzle annular opening, whereby the relatively colder gas sheath is constricted by said gas conductor outlet aperture and is driven into the central plasma gas column and expanded by the latter by heating to thereby also constrict the central plasma gas column and increase its flow rate.
- 2. A plasma-MIG welding torch according to claim 1, in which the ratio of the cross-sectional area of the gas conductor outlet aperture to the combined cross-sectional areas of the single nozzle central orifice and the surrounding single nozzle annular opening is smaller than 1:1.3 and larger than 1:4.
- 3. A plasma-MIG welding torch according to claim 1, in which the cross-sectional area of the gas conductor outlet aperture is equal to or smaller than the cross-sectional area of the single nozzle central orifice.
- 4. A plasma-MIG welding torch according to claim 1, in which the single nozzle central orifice and the gas conductor outlet aperture each has a circular cross section, and the single nozzle central orifice and the gas conductor outlet aperture each has a diameter of at least 6 mm and at the most 12 mm.
Priority Claims (1)
Number |
Date |
Country |
Kind |
7704527 |
Apr 1977 |
NLX |
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Parent Case Info
This is a division of application Ser. No. 896,235, filed Apr. 13, 1978, now U.S. Pat. No. 4,234,778 issued Nov. 18, 1980.
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3242305 |
Kane et al. |
Mar 1966 |
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3366772 |
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Jan 1968 |
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3969603 |
Boughton et al. |
Jul 1976 |
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4016397 |
Essers et al. |
Apr 1977 |
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4101751 |
Urbanic et al. |
Jul 1978 |
|
4234778 |
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Nov 1980 |
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Foreign Referenced Citations (2)
Number |
Date |
Country |
2449795 |
May 1975 |
DEX |
1444880 |
Aug 1976 |
GBX |
Divisions (1)
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Number |
Date |
Country |
Parent |
896235 |
Apr 1978 |
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