A double extractor and an electrode supply station are provided for automatically replacing electrodes in opposing jaws of a resistance welding machine. With coated sheet steels now used for car body structures, it is found that electrodes must be replaced more often. The automatic replacement system is programmed to replace electrodes when the welding machine is idle such as between the movement of car bodies or other structures moving on a conveyor. A double extractor has a first position for extracting top electrodes and a second position for extracting bottom electrodes. Both positions have a plurality of gripping fingers operated by a cam, which simultaneously twist and pull-off the electrodes from the jaw. After the jaw has been removed, the gripping fingers release the old electrode.

Apparatus for automatically replacing welding electrodes

An apparatus for removing an electrode chip of a resistance welding machine from a shank holding the electrode chip thereon comprising a shank holder to hold the shank, an electrode chip holder having a pair of holder halves to hold the electrode chip on the shank therebetween and means to move the electrode chip holder in a direction which is parallel to an axis of the shank so that the electrode chip holder move far away from the shank.

Apparatus for removing an electrode chip from a shank of a resistance welding machine

This welding electrode is one wherein the welding cap 3 of the electrode body 1 carries a contact tip 4 which is securely fastened to it by brazing. Thus, the replacement of this contact tip can be carried out very easily by stopping the circulation of the cooling water in the electrodes, by applying them to a resistive metal sheet and by passing through them a current of sufficient intensity to cause the brazing ring 5 which securely fastens the contact tip 4 to the welding cap 3 to melt. The removal of a worn tip 4 and the replacement of a new tip 4 are carried out in the same manner. The welding electrode also has a contact tip 4 provided with a brazing ring 5, as well as to an automatically operating machine for replacing the tips 4 away from the line for welding the metal sheets T.

Spot resistance-welding electrode; contact tip for such an electrode; machine for exchanging these tips

An electrode cap removing station (32) includes a linearly reciprocal drive member (42). Two electrode cap engaging members (66, 68), each having opposed facing knife edges (110, 118), are pivotally connected at one end to a body (48) surrounding the linear drive member (42). Cam follower members (100) mounted on the linear drive member (42) engage cams (90) during reciprocal movement of the drive member (42) to pivot the electrode cap engaging members (66, 68) from an open, spaced apart position to closed position in which the opposed knife edges (110, 118) engage the joint between an electrode cap (16) and a welding electrode (12, 14) to forcibly separate the electrode cap (16) from the welding electrode (12, 14). In an electrode cap mounting station (34), a similar linear drive member (140) pivots first and second electrode cap mounting members (166, 168).

Automatic welding electrode cap changer

The opening degree of the two arms of a welding gun movable by a robot to a plurality of welding spots, each of the arms being equipped with an electrode tip, is detected when the arms are closed with no work clamped between them and compared with a lower-limit opening degree value. The lower-limit opening degree value is previously set to be equal to the opening degree experienced when the electrode tips are reduced to their lower usability limit. The comparison determines if the tips need to be replaced. After replacement, the opening degree observed with the gun closed with no work clamped between the tips is compared to an upper-limit opening degree value, previously set, to operate an alarm if a defective tip or an incorrectly mounted tip is present.

Method of controlling electrode tip of welding gun in automatic welding machine

An apparatus for exchanging electrode chips used for resistance welding. The apparatus includes a base to which a shaft is rotatably mounted. A power source is connected to one end of the shaft to rotate the shaft. An electrode chip-withdrawing knife tool is made of a board connected to the other end of the shaft. The knife tool is provided with recesses which are radially directed about the axis of the shaft. The recesses have their respective knife edge portions each of which is fitted into an annular groove formed between the step portion at the front end of the shank of each arm of a welding gun and the electrode chip fitted over the shank. An electrode chip supply holder in which new polished electrode chips are received is held by a guide member.

Masashi Kitadate

Papers

Apparatus and method for exchanging electrode chips used for resistance welding