Oil pressure switch having improved diaphragm seal

Claim 1

An oil pressure switch comprising a housing having an inlet end connectable to an oil pressure line to admit oil from said line within said housing, a flexible membrane secured in said housing and having opposed surfaces, one of said surfaces being in contact with oil admitted to said housing, the other of said surfaces being in engagement with a displaceable member supporting a spring biased electrical contact, said spring biased contact being in abutting engagement with a stationary electrical contact, external connection means for said stationary electrical contact, said membrane being displaced by oil pressure in an oil pressure line connected to said inlet end whereby said spring biased contact is caused to be displaced against its spring biased direction to cause disengagement with said stationary electrical contact, said flexible membrane being a flat member of flexible impervious material having a peripheral ridge of larger thickness than the major portion of said flat member, said ridge being clamped in a continuous cavity which is of larger cross-sectional area than the cross-section of said ridge, said ridge being oval in cross-section with the long central axis of said oval extending transversely of the planar axis of said flat member, said continuous cavity being defined between opposed surfaces of two displaceable wall sections of said housing, said cavity having a substantially circular cross-section clamping portion with a narrow throat opening on an inner side thereof, said narrow throat opening being of smaller width than the thickness of said major portion of said flat member whereby said flat member adjacent said ridge will be maintained in compression along said narrow throat opening, said oval ridge being compressed in said continuous cavity from opposed sides in the direction of said long central axis, said housing being constituted by a base section and a cap section, said inlet end being provided in said base section, said continuous cavity being defined between opposed surfaces of said base and cap sections, said continuous cavity being located in an area of said housing about said inlet end to seal said inlet end from the inner area of said cap section which constitutes a switching chamber, both said electrical contacts being located at least partly in said chamber, a contact support block of non-conductive material being in engagement with said other of said surfaces of said membrane, said support block having an outer stop face, said stationary contact having a flanged end with a flat contact surface spaced from said outer stop face, said spring biased electrical contact being urged in guided engagement with said support block and having a flange wall in abutting engagement with said flanged end to limit said displacement of said spring biased electrical contact, said displacement of said membrane being limited by abutment of said outer stop face with said flat contact surface.