Apparatus for producing an instantaneous pressure on a workpiece

Apparatus for producing an instantaneous pressure on a workpiece, comprising a main cylinder having a pair of opposite ends;

• a working piston axially movable in said main cylinder between a working stroke and a return stroke and dividing the main cylinder into two compartments;
• a piston rod projecting through one of the compartments and one of the ends of the main cylinder to the outside of the latter and engaging with the free end thereof a workpiece;
• a gas under pressure in the other compartment and acting on one side of the working piston tending thereby to move said working piston along its working stroke;
• means including a control valve for feeding a pressure fluid into said one compartment to act on the other side of said working piston;
• means forming an enclosed space communicating with said one compartment so as to be filled with said pressure fluid;
• a control piston movable from a first position extending into said space to a second position withdrawn out of said space, one end face of the control piston being, in said first position, free of pressure, and pressure means acting on the other face of the control piston for biasing the same to said first position, said control piston having a volume to produce during its movement to said second position an instantaneous relief of the pressure of the pressure fluid acting on the other side of said working piston so that the gas pressure acting on the one side of the working piston will produce a corresponding instantaneous pressure by the piston rod on the workpiece;
• and means for moving said control piston from said first to said second position thereof.