Thermal junction for a cryogenic vessel

Claim 1

In a cryogenic vessel having a plurality of containers supported one within another in spaced apart relation, one of said containers being an inner cryogenic fluid-storage container adapted to store helium therein, another being an outer jacket enclosing all of said containers, and still another being an intermediate heat shield enclosing the inner container and having a coolant conduit disposed in heat exchange relation therewith and adapted to receive nitrogen coolant to serve as a cooling medium for said intermediate heat shield, a flow conduit connected in flow communication with said inner container and extending through both said intermediate heqt shield and outer jacket and defining a flow path for such cryogenic fluid whereby a significant temperature gradient is defined at certain times between said flow conduit and intermediate heat shield, and thermal junction mechanism mechanically interconnecting said intermediate heat shield and flow conduit to support one with respect to the other and establish a thermal resistance therebetween, said mechanism comprising: a support plate of relatively good thermal conductivity having an opening passing said flow conduit therethrough and being mechanically connected therewith to interrelate the plate and flow conduit structurally and define a relatively good thermal flow path therebetween; said intermediate heat shield having an opening therein of substantially greater cross section than that of said flow conduit and freely passing the same therethrough in spaced relation with the edges thereof; said support plate and intermediate heat shield being provided with a plurality of aligned pairs of aperture adapted to pass fasteners therethrough; and a plurality of fasteners respectively extending through said paired apertures and mechanically securing said support plate snugly to said intermediate heat shield in direct contiguous relation therewith to establish a thermal flow path therebetween; said thermal junction mechanism providing optimum thermal conductivity between said flow conduit and intermediate heat shield at both a no-flow condition through said flow conduit at which maximum thermal conductivity is desired to limit inward migration of heat to said inner container and a fluid flow condition at which minimum thermal conductivity is desired to limit over cooling of said intermediate heat shield and the coolant in heat exchange relation therewith.