Plasma torch

Details Plasma torch Plasma torch

1997-08-04

1999-10-12

Paschall, Mark

Electric heating

Metal heating

By arc

21912149, 21912148, 219 75, B23K 1000

Patent

active

059650397

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a plasma torch in which its good accessibility to a working zone is required as in a welding or cutting operation.


BACKGROUND ART

In a plasma cutting or welding process, especially where a workpiece or a pair of workpieces having a configuration in which the accessibility of a plasma torch thereto is poor, it has been necessary to employ a plasma torch having an elongated forward end.
If, however, such a plasma torch having an elongated forward end is employed, a problem has been encountered a large welding or cutting current a torch nozzle tends to be melted and damaged due to an insufficient cooling thereof. The required cooling effect does then become insufficient since it is unable to ensure a sufficient water coolant passage up to a point of the arc restraining region or the forward end of the said torch nozzle that tends to be elevated in temperature by an arc heat as well as by a radiation heat from the work due to the dimensional limitation of the said plasma torch.
In an attempt to meet with this problem, there has hitherto been proposed a modified plasma torch, as disclosed in Japanese Examined Patent Publication No. Sho 62-47630 or Japanese Examined Patent Publication No. Sho 63-39347, that is designed to make its forward end flat, thereby enhancing its accessibility to a workpiece in two side directions, and at the same time to provide a cooling water passage around a torch nozzle, thereby enhancing the ability to cool the torch nozzle.
Such a plasma torch in the prior art has its forward end flat in horizontal cross sectional, approximately rectangular, configuration and its torch nozzle whose axis is located as coincident with a center line of its torch body. And, the said plasma torch has a cooling water feed passage and a cooling water return passage distributed at both sides of the said torch nozzle, the two passages being configured to communicate with each other at the forward end of the said torch nozzle so that said both sides and said forward end of the torch nozzle may be cooled.
There has also been proposed in the prior art a plasma torch of another configuration, as disclosed in Japanese Unexamined Utility Model Publication No. Hei 1-60783, in which an electrode thereof is fitted and supported in an electrically conducting section of its torch body and a torch nozzle is disposed outside of this electrode via a spacer (constituted of a guide cylinder) of an insulating material. And, in it, the shortest gap section between the electrode and the torch nozzle is provided in the vicinity of an electrode forward end so that a dielectric breakdown due to a high frequency voltage which develops when a pilot arc is ignited may occur in the said shortest gap section (in the vicinity of the electrode forward end) while preventing an abnormal discharge which might otherwise be produced in any area other than the electrode forward end within the torch body.
Also, there has been a plasma torch of still another design in the prior art, as disclosed in Japanese Unexamined Patent Publication No. Hei 5-379, Japanese Examined Patent Publication No. Sho 56-4351, which is provided with a cap that is attached to an electrical insulator mounted to surround the forward end of its torch body whereby a welding or a cutting operation is carried out while maintaining a standoff constant by holding the said cap in contact with a workpiece.
It may be noted that a conventional plasma torch of "flat" type as mentioned above has the advantage that the closeness of the outer surfaces of both sides in two directions of the thinner portion of its horizontal cross sectional configuration from the axis of the torch nozzle leads to a good accessibility to a workpiece at these both sides, which in turn leads to the ability to weld while displacing towards the thicker portion of the said cross sectional configuration. The plasma torch can even be inserted even into a groove section if the root faces of a groove edge butt section of thick plates are to be welded together

REFERENCES:
patent: 4087670 (1978-05-01), Miller
patent: 4423304 (1983-12-01), Bass et al.
patent: 4792657 (1988-12-01), Conley
patent: 4924060 (1990-05-01), Delzenne
patent: 5220150 (1993-06-01), Pfender et al.
patent: 5328516 (1994-07-01), Dietiker
patent: 5412173 (1995-05-01), Muehlberger
patent: 5519183 (1996-05-01), Mueller

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