Prepackaged guard device sub-assembly for pressure responsive instruments

Claim 1

A subcombination flange type guard apparatus for a pressure sensitive instrument comprising in combination: a. a housing defining a central passage extending between an inlet for receiving a pressure change communicated from a connected fluid source and outlet for communicating with a pressure sensitive instrument; b. a diaphragm supported contiguously subtending said housing adapted to be exposed at its underside to a connected fluid source for transmitting pressure changes of the fluid source through said housing passage; c. a passage defining annular sleeve of non-metallic composition positioned with one end contiguous to said diaphragm oppositely of said housing, said sleeve defining a gasket sealing surface at its free end surrounding its passage and a radially extending annular shoulder at an intermediate location peripherally between its ends; d. securement means securing said housing, diaphragm unit and sleeve as a prepackaged sub-assembly in their operative relation to each other, said securement means including an annular mounting flange encircling said housing and L-shaped threaded fasteners mounted angularly displaced in said flange and each having a foot by which to grip the underside of said shoulder in securing said diaphragm in sandwiched relation between said sleeve and said housing; e. installation means provided for enabling said sub-assembly to be installed into sealed relation with a pressure source while maintaining the operative relation effected by said securement means, said installation means comprising a plurality of bolt apertures defined in said mounting flange displaced from said fasteners for receiving bolts capable of securing the sealing face of said sleeve into sealing relation with a received gasket and matchup sleeve at the pressure source; and f. a metallic liner positioned intervening between the foot of said fasteners and the underside of said sleeve shoulder.