Patent ID: 8100046

Claim:
A piston-cylinder unit (working cylinder), primarily for use in the manufacture of motor vehicle bodywork, with at least one piston which is longitudinally and sealingly displaceable in a cylinder by fluid pressure and which is on one side assigned a piston rod which is made to project from the cylinder and which powers device parts for tensioning and/or joining and/or stamping and/or embossing and/or punching and/or welding, if necessary, under interposition of gear parts, where during the idle stroke (setting stroke) of the piston the fluid feed is controlled in such a way that only the inertia and/or gravitational forces and/or frictional forces of moveable parts are overcome and the piston is not loaded with pressure from the fluid until the power stroke, characterized in that a transverse duct is connected to the working cylinder chamber, which transverse duct is connected at one end to a fluid source or is to be evacuated of air and can be connected to the cylinder return chamber via a longitudinal duct disposed in a wall of the cylinder and via a branch duct via a longitudinal duct into a piston valve, where the longitudinal duct can be connected via a branch duct alternately to the longitudinal duct or a duct which can be connected either to the fluid source or is to be evacuated of air via the cylinder return chamber.