Patent ID: 8294463

Claim:
A valve for controlling cryogen egress from a cryogen vessel, comprising: a valve housing having a low pressure side and a high pressure side with a fluid path between said low pressure side and said high pressure side; a valve element located in said fluid path in said housing between said low pressure side and said high pressure side; a mechanism in said housing that holds said valve element against a valve seat in said fluid path to close said fluid path, and that causes displacement of said valve element from said valve seat to open said fluid path in response to a differential pressure between said high pressure side and said low pressure side that exceeds a predetermined threshold; said mechanism also comprising a cam shaft that is rotatable to displace said valve element from said valve seat to open said fluid path independently of said differential pressure; and a first cam carried by and co-rotatable with said cam shaft that engages said valve element dependent on rotation of said cam shaft to move said valve element relative to said valve seat, and a second cam carried by and co-rotatable with said cam shaft, and a cam follower, said second cam being rotated by said cam shaft into contact with said cam follower and said second cam and said cam follower, in combination, defining an angular range of rotation of said cam shaft.