Ball check valve

A ball check valve assembly for use in a valve body comprising a base and a housing securable together by mating screw threads, said assembly comprising

• a rigid spherical valve closure element, and
• a subassembly comprising
• an elastomeric O ring, an elastomeric retainer, and an insert element relatively rigid with respect to said O ring and retainer,
• said insert element providing
• a first surface,
• an assembly fluid conduit terminating at said first surface in a port of circular cross section for communication with a base fluid conduit in the base,
• within said assembly fluid conduit, an O ring seat surface aligned with said port, and
• a spacer portion radially outward of said seat and extending generally away from said first surface, having a dimension adjacent said seat greater than the cross sectional diameter of said O ring when unstressed,
• said retainer providing
• a bearing surface spaced from said port and disposed for sealing contact with the valve body housing,
• O ring capture means adjacent said bearing surface for limiting travel of said O ring away from said port, providing a central aperture,
• a generally cylindrical sealing wall adjacent said bearing surface and aligned with said retainer,
• said insert element being retained within said retainer, and said O ring being retained by said seat surface, said spacer, and said capture means,
• said capture means aperture diameter being great enough to admit said closure element into sealing position with respect to said port, said O ring having an ID less than the diameter of said closure element and an OD greater than that of said capture means aperture, and said seat surface having an OD at least about 1/2% greater than the OD of said O ring,
• whereby in use said O ring moves transverse to the direction of travel of said closure element responsive to such travel, for closure element impact on said O ring distributed relatively equally over the contacted O ring surface for a range of closure element travel paths, said bearing surface and said sealing wall being effective to seal against leakage of fluid outwardly of said valve body.