Relief valve core

Claim 1

A pressure vessel having a tubular valve housing mounted in an opening therein, the housing having an interiorly threaded upper portion and an upwardly-facing valve seat therebelow; and a relief valve core in the housing comprising; a. an exteriorly threaded cylindrical body engaging the interior threads of the housing, the body having an axial recess extending up from the lower end thereof and a bridge extending transversely across the upper end thereof, the bridge having a bore on the axis of the body with a bevelled lead-in from the underside of the bore; b. a downwardly-facing plunger cup disposed at the lower end of the core and having a radial wall and a connected downward sidewall; c. a sealing washer disposed in the cup and adapted to seat on the upwardly-facing valve seat to close the valve; d. a stub shaft having a short section above the cup and extending axially through the center of the radial wall of the cup and being snugly embraced by the sealing washer; e. pin means extending freely upward through the bore in the bridge and having an outwardly sloping shoulder and an enlarged head below the bridge, the shoulder engaging the bevelled leadin of the bridge; and f. a spiral compression spring secured to the head at its upper end and wrapped around the short section of the shaft at its lower end; whereby when the body is screwed into the housing, the body may be rotated without rotation of the sealing washer.