Pressure valve

A pressure valve actuated by pressurized fluid supplied from a pressurized fluid source, comprising:

• a housing having a high-pressure space and a low-pressure space separated by a partition in said housing;
• openings in said housing for supplying said pressurized fluid into said spaces from said fluid source;
• an axial bore in said partition;
• and a cylindrical valve member reciprocatingly supported in said axial bore;
• axial passages in the body of said valve member for alternatingly establishing communication between said spaces upon displacement of said valve member;
• a pressure-relief piston accommodated in said low-pressure space and biased away from said partition, said pressure-relief piston being movable in said low-pressure space under the action of said pressurized fluid supplied to initiate the pressure-relieving of said high-pressure space and acting upon the end face of said pressure-relief piston, remote from said valve member;
• an axial bore in said pressure-relief piston;
• an auxiliary piston accommodated in said axial bore of said pressure-relief piston and cooperating with said valve member for transmitting thereto the displacement of said pressure-relief piston under the action of the fluid pressure supplied to effect the pressure-relieving of said high-pressure space;
• throttling passages in the body of said valve member adjacent to said low-pressure space and communicating with said axial passages of said valve member, said throttling passages of said valve member offering a flow passage area which is substantially smaller than that offered by said axial passages, said throttling passages being arranged to provide a first stage during the operation of pressure-relieving of said high-pressure space, said high-pressure space and said low-pressure space communicating via said throttling passages of said valve member until said pressure-relief piston abuts said partition and said pressurized fluid drives said auxiliary piston during a second stage to communicate said low pressure space with said high pressure space via said axial passages and wherein the dimensions of said low-pressure space, of said pressure-relief and auxiliary pistons and of said valve member are so selected that with said pressure-relief piston in its extreme position of abutting against said partition under the action thereupon of the fluid pressure supplied to initiate the pressure-relieving of said high-pressure space, said high-pressure space and said low-pressure space communicating with each other via said throttling passages of said valve member, thereby providing for a smooth reduction of the pressure in said high-pressure space.