Bonding method of binding strap end portions by spot-welding

摘要

A method for bonding overlapped end portions of a binding strap encircled about articles to be bound and tightened to a tensioned state by means of a gripper disposed at a gripping station for gripping a leading end portion of the binding strap, and drive rollers driven in their reverse mode so as to retract a trailing end portion of the binding strap, comprises the steps of interposing a plate electrode between the article being bound and the overlapped portions of the binding strap, lowering a single electrode tip, disposed above the overlapped portions of the binding strap, into contact with the overlapped portions of the binding strap such that the latter is compressed between the electrode tip and the plate electrode, and energizing the electrodes so as to perform a spot-welding operation at a first location, upon said overlapped portions of the binding strap, which is remote from the gripping station. The electrode tip is then raised and moved to a second location closer to the gripping station at which the electrode tip is again lowered into contact with the overlapped portions of the binding strap such that the latter is against compressed between the two electrodes. Upon energization of the electrodes, a second spot-welding operation is performed. A cutter disposed at the gripping station is actuated, so as to sever the trailing end portion of the binding strap from the residual supply portion of the binding strap, either before or after performance of the second spot-welding operation. In either case, the second spot-welding operation is performed under essentially no-load or no-tension conditions.