Integral internal pressure relief valve

In a hermetic reciprocating piston compressor including, in assembled order, a cylinder head, a cylinder head gasket, a valve plate, a valve plate gasket, and a crankcase, the cylinder head having a discharge pressure chamber communicating with the bottom surface of the cylinder head through a discharge aperture, a pressure relief valve, comprising:

• a valve body defined by a bore in the cylinder head, the valve body including an inlet aperture communicating with the bottom surface of the cylinder head and an outlet aperture communicating with a source of compressor suction pressure;
• a pressure valve mechanism located within the valve body providing pressure relief valving between the inlet aperture and outlet aperture said pressure valve mechanism including an apertured piston, a ball and a spring;
• means for retaining said valve mechanism in said valve body including a deformable disk-shaped valve seat member having a through aperture therein, said valve seat member contacting said cylinder head gasket and secured in said valve body by an annular undercut in said valve body, said spring contracting said apertured piston to bias said ball against said valve seat member;
• and
• duct means external to the cylinder head for providing sealed communication between the discharge aperture and the inlet aperture, whereby excessive pressure in the discharge chamber is vented successively through the discharge aperture, the duct means, the inlet aperture, the valve mechanism, and the outlet aperture into the source of compressor suction pressure.