Electric heating – Metal heating – By arc
Patent
1997-07-09
1999-02-23
Paschall, Mark H.
Electric heating
Metal heating
By arc
219 75, 21912136, 21912151, 439 10, B23K 1000
Patent
active
058747079
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a processing torch, such as a plasma torch, in which a torch body can be assembled separably into a torch base and a torch head.
BACKGROUND ART
A first conventional fixing means (1) for a connecting portion between the torch base and the torch head is a cap nut type threading structure as disclosed in the Japanese Examined Patent Publication No. Heisei 3-27309 and Japanese Examined Patent Publication No. Heisei 5-5589.
A second conventional fixing means (2) is the combination of a claw shaped projecting portion which is provided on one of the torch head and the torch base and inclined projection which is provided on the other of the torch head and the torch base so as to establish thread-type engagement between the torch head and the torch body by relative rotation, as disclosed in Japanese Examined Patent Publication No. Showa 63-13793 and Japanese Unexamined Utility Model Publication No. Heisei 3-14076.
A third conventional fixing means (3) is a quick joint system, in which a steel ball is engaged with a recessed portion, as disclosed in Japanese Examined Utility Model Publication No. Showa 5-19186 and Japanese Unexamined Patent Publication No. Heisei 6-198450.
In the processing torch, expendables, such as an electrode, a nozzle and so forth, are included. For reducing the burden of exchanging, and for shortening of exchanging time, a separable assembling type processing torch has been considered, whereby when the torch head is released from the torch base, a water passage is separated at the connecting portion to cause leakage of the water to make the connecting surface wet.
Upon separation of the torch head and the torch base, a water pump is stopped. The water may not flow in the connecting portion. Therefore, it is considered that leakage of water may not be caused. However, water remains in the path from the pump and the torch, and this remaining water may flow out from the connecting portion upon separation, to cause water leakage. Then, upon arc firing, electric leakage or insulation failure can be caused.
Therefore, in order to prevent the water leakage, it becomes necessary to have a water stop mechanism upon separation of the torch. The one disclosed in Japanese Unexamined Patent Publication No. Heisei 6-198450 and Japanese Unexamined Patent Publication No. Showa 62-275580, while a difference of water passage and gas passage is present, closes the passage upon separation, and upon assembling, the passage is opened by the projection.
The above prior art (1) is reliable as a secure fixing means, but the cap nut has to be rotated for several turns upon connection and separation, resulting in a long period for connection and separation. Certain measure may be taken by making the thread pitch of the cap nut greater to reduce rotation angle for threading. However, when the pitch is made greater, greater rotation torque becomes necessary to exert the same threading force. Therefore, it is not expedient to provide the greater pitch for significant load upon exchanging of the torch head. On the other hand, in case of the cap nut, it is easy to cause crushing of the thread. Thus, in consideration of automatic exchange by a machine, special measure has to be taken so as not to crush the thread.
In the above-mentioned prior art (2), the claw shaped projection is hooked to the projection with an inclination to generate an axial force by the inclination without using threading. In this system, sufficient tightening which can not be established or engagement which can be easily loosened results when an error occurs in the relative position of the projections in the axial direction. Therefore, in order to be certainly fixed, adjustment of both projections becomes necessary. Also, since a plurality of torch heads are connected as exchanged to one torch base, adjustment of the relative position of the projections becomes necessary for every torch head, resulting in a long period for performing an exchanging operation.
Furthermore, another problem of the forego
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patent: 5328516 (1994-07-01), Dietiker
Iida Noboru
Sato Hitoshi
Yamashita Toshio
Yoshimitsu Toshio
Komatsu Industries Corporation
Komatsu Ltd.
Paschall Mark H.
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