Two step pressure intensifier system

A two-step fluid pressure intensifier system comprising first, second and third operative piston and cylinder units arranged in coaxial alignment, the pistons of the first and second units being rigidly fixed to a common piston rod, the first piston having a greater effective working area than the second and the second piston having a greater effective working area than the third piston, a working fluid chamber located between the cylinders of the first and second units, through which the piston rod passes, the cylinder of the second unit being provided with a fluidic connection between it and the fluid chamber, the fluid chamber and the cylinder of the second unit containing a common working fluid, the piston rod being provided with a reduced cross-section portion between the pistons of the third and second units, the reduced cross-section portion residing within the fluidic connection when the piston rod is at the unactuated position of a working cycle, in order that there be fluidic communication between the chamber and the cylinder of the second unit, the third piston and cylinder unit being constituted by the unreduced cross-section portion of the piston rod and the fluidic connection, the third piston and cylinder unit only becoming operative as such at a predetermined position of the piston rod as it moves in the working stroke direction from the unactuated position, the second piston and cylinder arrangement being provided with limited working fluid flow-by during a working stroke to allow continued movement of the piston rod, in the working stroke direction, under impetus from a fluid pressure supplied to the first piston and cylinder unit to produce a working stroke cycle, and wherein a first increase in pressure of the working fluid in the cylinder of the second unit is produced by the initial movement of the piston of that unit and after movement of the piston rod a greater distance, in the working stroke direction, than said predetermined position, the pressure of the working fluid in the cylinder of the second unit is further increased and is primarily solely determined by the third piston and cylinder unit, means being provided to utilize the pressurized working fluid in the second unit.