Power transmission

A hydraulic pressure relief valve comprising:

• a. a body;
• b. a system pressure passage and a tank return passage formed in said body in spaced relationship;
• c. a main bore formed in said body extending between said pressure passage and said tank return passage;
• d. a main valve mounted for movement in said main bore yieldingly urged to shut off fluid flow between said system pressure and said tank return passages;
• e. a pilot bore formed in said body spaced from said main bore and having first and second ends, said first end in communication with both said system pressure passage and said main bore;
• f. a bleed flow passage formed in said body extending from said main bore to said pilot bore;
• g. a drain passage formed in said body extending from said pilot bore to said tank return passage;
• h. a pilot valve mounted for movement in said pilot bore yieldingly urged to shut off fluid flow between said bleed flow and said drain passages;
• i. a bleed flow orifice positioned in said body to restrict fluid flow from said system pressure passage to said bleed flow passage;
• j. a metering slot formed in said pilot valve adapted upon movement of said pilot valve to meter fluid flow from said bleed flow passage to said drain passage;
• k. a contained volume adapted for containing compressed fluid formed in said body spaced from said pilot bore and in communication with both said system pressure passage and said second end of the pilot bore;
• and
• 1. a damping orifice formed in said body in communication with and between said system pressure passage and both said contained volume and said second end of the pilot bore;
• said damping orifice restricting fluid flow from said system pressure passage to both said second end of the pilot bore and said contained volume.

A rate limiting pilot valve for a hydraulic pressure circuit, said pilot valve comprising:

• a. a body;
• b. a bore formed in said body having a pressure end and a spring end spaced from said pressure end, said pressure end adapted for connection to a source of system pressure;
• c. a bleed flow chamber formed in said bore and adapted for connection to a source of fluid bleed flow from a main valve in the circuit;
• d. a drain chamber formed in said bore and adapted for connection to a tank return;
• e. an accumulator chamber adapted for containing a volume of compressed fluid in open communication with said spring end;
• f. a damping orifice in communication with said spring end of the bore and said accumulator chamber and adapted for connection between said source of system pressure and both said spring end and said accumulator chamber for restricting fluid flow from said source of system pressure to both said spring end and said accumulator chamber;
• g. a differential area piston mounted for movement in said bore;
• and
• h. a metering slot formed in said piston between said bleed flow chamber and said drain chamber and adapted upon movement of said piston to meter fluid flow from said bleed flow chamber to said drain chamber.