Electric heating – Metal heating – By arc
Patent
1995-10-31
1998-03-17
Paschall, Mark H.
Electric heating
Metal heating
By arc
21912145, 2191241, 21912157, B23K 1000
Patent
active
057289913
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a plasma are welding apparatus for welding together a plurality of plate materials laid one over another and also to a welding method in which such an apparatus is used.
BACKGROUND ART
As a welding apparatus for spot welding together a pair of plate materials laid one over the other by using an are, there has hitherto been known an are spot welding apparatus as disclosed in Japanese Unexamined Patent Publication No. Sho 58-116981.
Such an arc spot welding apparatus as in the prior art has been configured as shown in FIG. 1 attached hereto. Thus, the apparatus includes: an arc spot welding machine a of which a base is mounted on an arm of a welding robot (not shown) and of which an end portion is provided with a welding torch d; and an air cylinder c which is coupled to the welding machine a via an arm b to move integrally with the welding machine a and which has a pressing member f coupled to a frontal end thereof. And, after the torch d is set in position to oppose to a front side plate material e at a predetermined distance therefrom (viz. a parameter that is called "standoff"), the air cylinder unit c is actuated to cause its thrust member f to be pressed against the front side plate material e, thus expelling any gap between the latter and a rear side plate material g then to weld the two plate materials e and g together by means of the welding torch d. In the Figure, symbol h designates a table for supporting the rear side plate material g.
In the above mentioned conventional technique, it has thus been a practice that the welding torch d is set at a predetermined position before the air cylinder unit c is operated to move the front side plate member e under the pressing member f by the distance corresponding to the gap between the two plate materials. It has then be unavoidable that a deviation results from an originally set value in the spacing (i.e. "standoff") between the end portion of the welding torch d and the front side plate material e, to be welded to the rear side material.
This has led to a requirement that when the welding torch d is preset in position, a dimension corresponding to the gap between the two plate materials e and g needs then to be taken into account, making the associated positioning control complicated. Also, if the front side plate material e may not deform as desired, there arises a problem that an arc spot welding may not proceed as at a desirable spacing, hence disabling a predetermined strength of welding to be attained.
While the above mentioned prior art problems discussed are in regard to those in the arc spot welding technique, similar problems arise in a plasma arc welding apparatus.
Also, there has hitherto been known in the prior art a plasma arc welding apparatus with a plasma torch that can manually be handled by an operator. A plasma torch of this kind as used in the prior art is configured as shown in FIG. 2 attached hereto. It is seen that a handle k is securely fixed on a side surface of a torch body j that has a plasma nozzle i at its frontal end. In the so configured prior art plasma torch, the plasma nozzle i is formed integrally with the torch body j, and this requires, in adjusting and maintaining a distance (i.e. "standoff") from the frontal end of the nozzle i to a workpiece, that only the operator's reliance on a eye measurement be adopted. Thus, the adjustment and maintenance of the standoff, which is one of the most important factors in plasma arc welding and should, in its optimum values, vary depending upon particular materials and thicknesses of various weld workpieces, have significantly been accomplished manually. Hence, with a plasma torch of the construction mentioned above, it has been customary that only an operator of considerable skill would be capable of achieving a stabilized welding operation.
Accordingly, with the above mentioned points taken into account, it is an important object of the present invention to provide a plasma arc welding apparatus as well as a welding method us
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patent: 5147997 (1992-09-01), Haberman
patent: 5550344 (1996-08-01), Winterfelt
Horiai Kunio
Kitahashi Masamitsu
Kurokawa Iwao
Minonishi Mikio
Takada Hiroshi
Kabushiki Kaisha Komatsu Seisakusho
Kananen Ronald P.
Paschall Mark H.
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