Cryogenic cooling apparatus

Abstract

Cryogenic cooling apparatus comprising an inlet path through which refrigerant gas is caused to flow, a Joule-Thomson expansion nozzle which communicates with the inlet path and in which, in use, a proportion of the refrigerant gas is caused to liquefy and an outlet path communicating with the outlet of the expansion nozzle, the inlet path being in heat exchange relationship with the outlet path. An elongate valve needle cooperates with the outlet side of the expansion nozzle and together with the latter constitutes a valve. A sensor is disposed in the space on the outlet side of the expansion nozzle and is arranged progressively to close the valve as the amount of liquid refrigerant in contact with it increases. The valve needle defines a bypass passage which extends along its entire length and remains open at all times. The apparatus is accommodated within a container, to the outer surface of a portion of the wall of which a thermal load is connected. The outlet end of the bypass passage is directed towards the portion of the container wall carrying the thermal load and thus ensures that the refrigerant in the vicinity of the said portion is maintained in a state of agitation at all times.

What is claimed as new and desired to be secured by letters patent of the United States is: 
     
       1. Cryogenic cooling apparatus, said apparatus being accommodated within a container which has a wall, a thermal load being connected to the outer surface of a portion of said wall, said apparatus comprising an inlet path through which, in use, refrigerant gas is caused to flow, a Joule-Thomson expansion nozzle which has an outlet and communicates with said inlet path and in which, in use, a proportion of said refrigerant gas is caused to liquefy, an outlet path communicating with said outlet of said expansion nozzle, said inlet path being arranged in heat exchange relationship with said outlet path, an elongate valve needle cooperating with the outlet side of said expansion nozzle and together with the latter constituting a valve, a sensor disposed in a space on the outlet side of said expansion nozzle and arranged progressively to close said valve as the amount of liquid refrigerant in contact with it increases, said valve needle affording a bypass passage which extends over its entire length and remains open at all times, said bypass passage having an outlet end which is directed towards said portion of said wall. 
     
     
       2. Apparatus as claimed in claim 1 which includes a holder and wherein said expansion nozzle is fixed and said valve needle is carried by said holder which is arranged to be moved as the amount of liquid refrigerant contacting said sensor varies. 
     
     
       3. Apparatus as claimed in claim 2 which includes a bellows and a gas space and said sensor defines a sensing space, said holder being connected to said bellows, said bellows being received within said gas space and said gas space communicating with said sensing space, whereby as the amount of liquid refrigerant in contact with said sensor increases the pressure within the said gas and sensing spaces decreases and said bellows expands to move said valve needle towards said expansion nozzle.