Electrical resistance welding guns having workpiece clamping and

Abstract

An electrical resistance welding gun includes a hydraulically or pneumatically actuated clamping device for forcing workpieces into contact with one another, and a device for preloading and maintaining loaded contact between welding electrodes located on opposite sides of the workpieces. The electrodes are preloaded by a compression spring whose force is entirely independent of the action of the hydraulically-catuated clamping device. The electrode is supplied with electrical welding power and is cooled by circulating coolant through the electrode. A piezo-electric sensor provides an indication of the electrode biasing force and of changes in this force during welding. The force signal from the sensor may be used for feedback control of weld current and length of the period during which weld current is applied. The initial electrode force is easily adjustable by changing the effective length of the spring.