Vuilleumier refrigerator with separate pneumatically operated cold displacer

Claim 1

A cryogenic refrigerator comprising; a cold cylinder having a cold end and having a cold cylinder area, a displacer reciprocably mounted within said cold cylinder and separating said cold cylinder into a cold volume at the cold end of said cold cylinder and a warm volume at the other end thereof, said displacer having a smaller area at said warm volume than said cold volume, a regenerator connected between said warm volume and said cold volume and a pneumatic spring, for urging said cold displacer toward both the cold and the warm ends of said cold cylinder, said displacer being freely reciprocable in said cold cylinder except for said pneumatic spring and pressure in said cold and warm volumes acting on the differential area of said displacer facing said cold volume and said warm volume, the improvement comprising: a thermal pulse generator connected to said warm volume of said cold cylinder for providing pressure pulses for causing reciprocation of said cold displacer in said cold cylinder, said thermal pulse generator comprising: a hot cylinder having a hot end and a warm end, a displacer reciprocably mounted in said hot cylinder for separating said hot cylinder into a hot volume and a warm volume, said warm volume of said thermal pulse generator being connected to said warm volume of said cold cylinder, a regenerator connected between said hot volume and said warm volume and means for heating the hot end of said hot cylinder, refrigerant gas in said volumes, said refrigerant gas increasing in pressure in all of said volumes as said hot displacer displaces refrigerant gas into said hot volume and decreasing in pressure as said hot displacer displaces gas out of said hot volume into said warm volume.