Device for the positioning of an operating member, and a welding apparatus using the same

A positioning device in which an operating member is solid with a mechanical touching member and is displaced together with it by computer controlled displacement devices; both the operating and the touching members are mounted on a common supporting member, thus forming a touching and operating unit on which act the computer controlled displacement devices. The computer is programmed in order to determine by means of the touching member, and to memorize, the positions of a plurality of points on which the operating member should perform its operation, then determining by interpolation the entire work trajectory of the operating member, which may particularly be a welding head; in this case, several touching and operating units form part of a welding apparatus, and particularly of a so-called coupler, intended to automatically perform the inner weldings between the sections of a piping, such as an oil pipeline or the like.