Abstract: An automatic welding apparatus comprises a welding torch including an electrode and a fixture for fixing a workpiece, and a relative positional relation of the welding torch and the workpiece fixture is controlled such that the electrode of the welding torch is moved to trace the welding line of the workpiece, whereby automatic welding is achieved. The automatic welding apparatus further comprises a switch for selectively connecting the electrode of the welding torch to a welding power supply or a detecting power supply, and a sensor for sensing a current or a voltage between the electrode and the workpiece when the electrode is switched to the detecting power supply, whereby the relative positional relation between the welding torch and the workpiece is detected in response to the output of the sensor, and thus a welding point or a welding line is sensed.

Abstract: A clutch mechanism for winch comprising first and second planetary gear sets mounted on an input shaft so as to selectively connect an output shaft with said input shaft in the same or opposite direction of rotation. The clutch mechanism also includes a brake mounted on said output shaft, said brake normally acting on said output shaft so that the output shaft cannot be rotated.