Drive Arrangement For Rotary Valve In A Cryogenic Refrigerator

Abstract

A cryogenic refrigerator comprising a rotary valve which controls the flow of high pressure gas into the refrigerator and the return of the gas from the refrigerator, the cryogenic refrigerator further comprising rotary fluid motor arranged to drive the rotary valve.

1 . A cryogenic refrigerator comprising a rotary valve which controls the flow of high pressure gas into the refrigerator and the return of the gas from the refrigerator, the cryogenic refrigerator further comprising a rotary fluid motor arranged to drive the rotary valve, wherein the rotary fluid motor is constructed of non-magnetic material for use in a high-strength, or sensitive, magnetic field. 
     
     
         2 . A cryogenic refrigerator according to  claim 1  wherein the rotary fluid motor is a multi-vane type rotary fluid motor. 
     
     
         3 . A cryogenic refrigerator according to  claim 1 , wherein the rotary fluid motor is arranged to drive the rotary valve via a gearing unit. 
     
     
         4 . A cryogenic refrigerator according to  claim 1 , in association with a pump situated remotely from the rotary fluid motor, said pump being arranged to circulate fluid to the rotary fluid motor. 
     
     
         5 . A cryogenic refrigerator according to  claim 1 , wherein the rotary fluid motor is propelled by a flow of gas derived from a compressed gas supply being switched in the rotary valve. 
     
     
         6 . A cryogenic refrigerator according to  claim 1 , in association with a cryostat used to house magnet coils of a nuclear magnetic resonance (NMR) or magnetic resonance imaging (MRI) system. 
     
     
         7 . (canceled)