| 摘要 |
PROBLEM TO BE SOLVED: To secure safety in the operation of an electric servo-spot welding machine. SOLUTION: In a spot welding machine where an electric tip is driven by a servomotor, whether pressurization is normal or abnormal is detected by the change of a torque limit value which appears when the electrode tip is moved at a constant motor speed. When the pressurization is abnormal, an external signal is output so that the electrode tip in a movable side is released toward a return side. Thus, an accident where a hand or a finger is pressed and injured by a strong pressurizing force can be prevented from occurring.
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