By-pass valve with pressure relief feature

Claim 1

An air by-pass and pressure relief valve having a valve body, an inlet port, an outlet port and a by-pass port in said valve body, a wall dividing said valve body, said wall having an opening therethrough to define a main valve seat, a diaphragm housing secured to a first end of said valve body, a diaphragm secured to said valve body by said diaphragm housing, said diaphragm defining a vacuum chamber and a second chamber, a vacuum inlet fitting into said vacuum chamber, a valve stem secured to said diaphragm by a pair of backing plates, one on each side of said diaphragm, a biasing spring abutting one of said backing plates to bias said diaphragm in a first direction opposing the bias of vacuum applied to said vacuum inlet fitting, biasing spring confining means constituting a vacuum chamber closure, said air by-pass and pressure relief valve further comprising A. an outlet valve head slideably mounted on said valve stem and positioned by a first shoulder on said stem, said outlet valve head operable to open and close said main valve seat, B. a by-pass valve head slideably mounted on said valve stem and positioned by a second shoulder on said stem, said by-pass valve head operable to open and close a by-pass valve seat port defined by a by-pass valve seat in a partition separating said valve body from at least one by-pass discharge opening, and C. a by-pass valve biasing spring abutting said by-pass valve head to bias said by-pass valve head toward the said by-pass valve seat during normal operation but moveable away from said by-pass valve seat on over pressure conditions, said by-pass valve biasing spring also abutting a spring retaining member fastened to an end of said stem opposite said diaphragm.