| 摘要 |
PROBLEM TO BE SOLVED: To improve a joining quality by stably, surely and tightly attaching a third (intermediate) electrode for generating the heat at the initial stage of electric conduction and melting and removing the insulating film on a work to a first (normally, upper part) electrode. SOLUTION: A pressure adjusting screw 64 receiving one end of a compression coil spring 70 is fixed to a fixed position on a bolt 62 unless this screw is turned with the external force and further, fixed to a fixed position to an upper arm 24 through the bolt 62. On the other hand, a spring receiving member 68 for receiving the other end of the compression coil spring 70 and further, an intermediate arm 28 are supported so as to be rotation-displaceable to the upper arm 24 through a shaft 48 at the upper end part of this arm. Then the tip part of the intermediate electrode 34 fitted to the lower end part (electrode holder part) of the intermediate arm 28 is abutted on the one side surface at the tip part of the upper electrode 30 fitted to the lower end part (electrode holder part) of the upper arm 24. In this way, the pressure caused by the compressive deformation of the compression coil spring 70, presses the intermediate electrode 34 to the upper electrode 30 and acts as a pressurized force which stably holds the tight-attaching force between both electrodes 30 and 34.
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