Patent ID: 7017882

Claim:
An assembly for use in controlling a flow of fluid through a conduit, said assembly comprising a valve movable between a closed condition at least partially blocking fluid flow through the conduit and an open condition in which said valve is ineffective to block fluid flow through the conduit, a housing, a valve stem connected with said valve and at least partially enclosed by said housing, a drive member disposed in engagement with said valve stem, a gear assembly at least partially disposed in said housing and connected with said drive member, a clutch assembly at least partially disposed in said housing and operable between an engaged condition and a disengaged condition, an electric motor at least partially disposed in said housing and operable to move said drive member relative to said valve stem under the influence force transmitted from said electric motor through said gear assembly and through said clutch assembly to said drive member when said clutch assembly is in the engaged condition, a spring connected with said housing and said drive member, said spring being stressed to store energy upon movement of said drive member relative to said valve stem, said spring being effective to move said drive member relative to said valve stem to move said valve from the open condition to the closed condition, first and second pressure chambers disposed in said housing, said first pressure chamber having a side surface connected with said valve stem, said second pressure chamber having a side surface connected with said valve stem, a first conduit extending through said valve and through a portion of said valve stem to conduct fluid pressure from a first side of said valve to said first pressure chamber, and a second conduit to conduct fluid pressure from a second side of said valve to said second pressure chamber.