Patent ID: 6957660

Claim:
A pressure relief valve comprising: a body having a bore with an inlet and an outlet; a sensing piston movably received within the bore and defining a sensing chamber in the bore, the sensing piston having a surface exposed to pressure in the sensing chamber; a valve piston moveable within the bore along an axis and abutting the sensing piston, wherein the valve piston has a first position which opens a path between the inlet and the outlet and has a second position in which the path is closed, wherein when the path is closed pressure at the inlet only acts on the valve piston transverse to the axis; a damping orifice through which fluid flows bidirectionally between the inlet and the sensing chamber to thereby limit a rate at which the sensing piston responds to pressure changes at the inlet; and a spring biasing the valve piston into the second position and wherein pressure within the sensing chamber that is greater than a threshold level causes the valve piston to move to the first position.