Reset relief valve

A reset relief valve comprising:

• a body having an inlet port, an outlet port, and an interior wall partially defining an enclosed chamber;
• a piston disposed in said body and moveable between a first position at which said piston is disposed in fluid flow-blocking relationship between said inlet port and said outlet port of the body and a second position at which said piston is removed from said fluid flow-blocking position;
• said piston having a head which partially defines a first chamber and at least one flow passageway extending between said chamber in said body and a second chamber having a lower surface defined in part by a disc disposed in a cavity in said piston head;
• a bonnet attached to said body;
• a stem bushing disposed in said bonnet in spaced relationship with the head of said piston, said stem bushing having a surface defining another portion of said first chamber and an internal bore in which said stem is slidably supported;
• at least one spring and at least two pivotally interconnected link members operatively disposed between said spring and said stem;
• and
• crank assembly for selectively engaging said pivotally interconnected link members for urging said piston into said first position.