Valved coupling for ultra high purity gas distribution systems

A valved coupler for ultra high purity gas distribution, comprising

• a valve housing having an external surface, an internal surface defining a gas-carrying chamber, and first and second aperture-defining surfaces extending from said internal surface to said external surface and defining first and second apertures permitting gas flow between said gas-carrying chamber and an external environment to which the external surface of the housing is exposed,
• a valve stem having proximal and distal ends slidably mounted within said housing for linear movement between a first position and a second position, along an axis extending through said first aperture, said valve stem having a sealing surface at said distal end,
• a substantially planar flexible diaphragm having an outer periphery and an inner periphery, said inner periphery sealingly engaged to said valve stem, said outer periphery sealingly engaged to said internal surface of said housing, dividing said internal surface of said housing into two sections, said aperture-defining surfaces extending between said external surface and a common section of said internal surface of said housing,
• wherein at said first position, said sealing surface of said valve stem engages said first aperture-defining surface of said housing, and said distal end of said valve stem is substantially coplanar with said external surface of said housing in a region bordering said first aperture-defining surface, whereby when said first aperture is sealed by said valve stem only said first aperture-defining surface of said housing and said distal end of said valve stem are exposed to the external environment.