Method and apparatus for demounting a spot welded metal plate

摘要

A method and apparatus for demounting a metal plate spot welded to a metal member. In accordance with the method, a hollow electrode rod is placed in opposition to the periphery of a spot weld between the metal plate and the metal member, an electric arc is formed between the electrode rod and the metal plate, the periphery of the spot weld is melted with arc heat, and the resultant molten metal is drawn up through the hollow portion of the electrode rod. The method may be performed with an apparatus having a hollow internal rod which includes an electrode rod retaining portion at a forward tip end thereof. A rod retaining mechanism retains the internal rod for free longitudinal movement in opposite forward and rearward directions, elastically urged in the forward direction. A sliding block is movable in the forward and rearward directions, urged forward by an elastic member. Structure is provided to prevent movement of the sliding block forward of a predetermined forward position. A device is provided for engaging the sliding block with the internal rod and moving the sliding block and internal rod in a rearward direction to a predetermined rearward position. Also provided is a device for releasing engagement between the sliding block and the internal rod, a guide piece mounted on the retaining mechanism for establishing a reference position from which the free end of the electrode rod is movable a predetermined distance rearward of a metal member to be treated, and structure for drawing melted metal rearward through the hollow electrode rod and internal rod.