Abstract: A power piston apparatus, comprising two or more double acting hydraulic piston drive means in which the cross-sectional areas of the pistons are identical and the cylinder spaces or chambers of which are hydraulically interconnected in crossed fashion above and below the pistons in the case of two cylinders, while being connected in series in the case of more than two cylinders having separately closed oil spaces of identical volumes, with each such oil space being connected to a positive-pressure oil supply through check valves for replenishing the leakage oil, and wherein said piston drive means have associated therewith metering cylinders with a coaxial and/or parallel direction of stroke, i.e. with mechanical connections between the ends of the piston rods.

Abstract: An impact shaping apparatus is provided having a hydraulic actuator associated to the shaping tool. A gas spring of adjustable spring constant is in permanent fluid connection with the hydraulic actuator so as to allow for adjustment of the impact characteristics in accordance with the cold-working characteristics of the material to be shaped. The gas spring is formed by a cylinder and a floating piston arranged therein and defining a first working space communicating with the hydraulic actuator and a second working space containing a mass of gas.