Electric heating – Metal heating – By arc
Patent
1990-02-22
1992-03-31
Paschall, M. H.
Electric heating
Metal heating
By arc
21912152, 21912151, 2191215, 219 75, B23K 900
Patent
active
051010887
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a torch for plasma cutting and welding, comprising a tubular casing of which one end is provided with a nozzle having an orifice, a nonmelting electrode which is centered such in the casing that its one end is located directly opposite the orifice, a gas duct extending from a gas inlet connectable to a gas source, past the electrode and to the orifice, and an electrode terminal connectable to a power source.
BACKGROUND ART
For some twenty years, the extremely high heat energy of an ionized gas flow has been used for cutting and welding metals, spraying powder compositions etc. When this technique is used for cutting (plasma cutting), the cutting speed can be increased and the range of cutting applications can be extended, compared to conventional gas cutting. In welding, highly reliable joints are obtained, since the method is far less susceptible to variations during welding (varying distances to the workpiece) than other welding methods. In plasma welding, the heating zone in the workpiece is reduced, and the method is also electricity-saving. Since the method came into industrial use, the torches have not changed to any appreciable extent. Thus, the nonmelting electrode connected to the negative pole of a current source and centered in a casing is passed by a gas which then escapes through an orifice at the electrode tip in which it is ionized by the arc generated between the electrode and the workpiece connected to the positive pole of the power source. Through the years, the material of the electrode has however developed according to the character of the plasma generating gas (oxidizing, inert or reducing), and now the electrode frequently consists of a copper holder having an insert of an active material in the arc generation area. Different ways of fixing and centering the electrode as well as different cooling methods, have been used.
DISCLOSURE OF THE INVENTION
The object of the present invention is, while maintaining the original concept, to improve the design of the electrode and its fixation in the casing and, in this context, to reduce the risk of accidents and to provide an improved gas conduit in the casing. This object is achieved by means of the structure which is defined in detail in the characterizing clauses of the appended claims.
A plasma cutting torch will now be described, since this embodiment is the easiest application of the invention, but it will be appreciated that the inventive concept is applicable also to plasma welding units and spraying units.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in detail with reference to the accompanying drawings in which a preferred embodiment of the invention is shown schematically. FIG. 1 is an axial section of a torch adapted for liquid cooling, and FIG. 2 is an identical view of the torch, but modified for air cooling. FIG. 3 illustrates an intermediate insulator for the torch shown in FIG. 2.
BEST MODE FOR CARRYING OUT THE INVENTION
The drawing illustrates a torch connected to a power unit and a gas source which are not shown since they can be of conventional design. A handle 30 is integrated with the torch and passes into a hose which holds all the conduits which are necessary for the torch. The torch comprises a casing having a front body 10, a rear body 11 and an intermediate insulator 12 disposed therebetween. The insulator 12 accurately fits into the bodies 10, 11 disposed on both sides thereof, and all parts are held together by an outer plastic cover 29 which will be described in detail below. As will appear from the drawing, the front body 10 is tubular, and its one end is provided with an internal thread 13. In its opposite end, the body 10 is formed with a groove for receiving one end of the intermediate insulator 12. The rear body 11 is formed with a matching groove for receiving the intermediate insulator in its end facing the front body. In its opposite end, the rear body 11 has an internal thread 14. A nozzle 15 of conventional design is s
REFERENCES:
patent: 3294953 (1966-12-01), Spies
patent: 3562486 (1971-02-01), Hatch
patent: 3794806 (1974-02-01), Klasson
patent: 3813510 (1974-05-01), Hatch
patent: 4517437 (1985-05-01), Yerushalmy et al.
patent: 4581516 (1986-04-01), Hatch
patent: 4769524 (1988-09-01), Hardwick
patent: 4877937 (1989-10-01), Muller
Andersson Jan-Eric
Shojai Hamid
Paschall M. H.
S P T Plasmateknik Aktiebolag
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