Patent ID: 8286543

Claim:
A valve assembly for controlling the supply of pressurized fluid to a piston slidably disposed within an actuating cylinder for movement along a longitudinal axis thereof between a rest position where the piston is adjacent a first end of the cylinder and an extended position where the piston is adjacent a second end of the cylinder, the valve assembly comprising: a first passage provided at the first end for enabling a flow of the fluid within the cylinder during operation, a pressure of the fluid applying to alternative driving sides of the piston for alternatively moving the piston between the rest position and the extended position; a first valve piston mounted at the first end adjacent said first passage for movement along a direction substantially parallel to the axis, said first valve piston comprising a first surface and a projecting member extending away from said first surface towards the second end along said direction; a second valve piston mounted adjacent said first valve piston for movement along said direction and comprising a second surface adapted to cooperate with said first surface; and a sealing member positioned adjacent said first passage and operatively connected to said first valve piston for movement therewith along said direction; wherein upon reaching the rest position the piston contacts said projecting member for propelling said first valve piston along said direction towards said second valve piston and abutting said second surface against said first surface, thereby moving said sealing member in alignment with said first passage for providing a seal at an interface between an outer surface of said sealing member and an inner surface of said first passage and stopping said fluid flow; and further wherein when the piston is moved from the rest position to the extended position, the fluid drives said abutting first and second valve pistons along said direction towards the second end and brings said second surface out of abutment with said first surface, thereby moving said sealing member out of alignment with said first passage and releasing said seal for enabling said fluid flow.