Patent ID: 7520250

Claim:
A breather assembly for ventilation and pressure control within a crankcase of a positive displacement motor or pump, the breather assembly comprising: an intake/exhaust port through said crankcase with a valve seat for said port on an exterior surface of said crankcase; a flexible valve membrane positioned over said port on said valve seat on the exterior of said crankcase for flexing outwardly to exhaust air under positive pressure from said crankcase to atmosphere and to close said port when the crankcase pressure is neutral or negative; an irregular surface on a face of said valve membrane facing to and engaging said valve seat, said irregular surface having a texture which permits air to flow over said seat and into said port in a controlled quantity when a negative air pressure condition is attained in said crankcase whereby a predetermined vacuum level is maintained in said crankcase; and a filter positioned over said membrane whereby air egressing from and ingressing into said crankcase from atmosphere through said port is filtered.