Method and apparatus for minimizing motional heat leak in cryogenic apparatus

Claim 2

In a thermodynamic expansion apparatus wherein a piston reciprocates between two different temperature levels to define at least one chamber of variable volume within an integral housing serving as the sole means for enclosing said chamber and wherein heat exchange means are located internal of said piston and are used to isolate at least two temperature levels, the improvement comprising a sleeve liner of a low thermal conductivity, low heat capacity material affixed to and forming a part of the internal wall of said housing and extending between said temperature levels.

Claim 3

In a thermodynamic expansion apparatus wherein a piston reciprocates between two different temperature levels to define at least one chamber of variable volume within an integral housing serving as the sole means for enclosing said chamber and wherein heat exchange means are located internal of said piston and are used to isolate at least two temperature levels, the improvement comprising a sleeve liner of a low thermal conductivity, low heat capacity material affixed to and forming a part of the internal wall of said housing and extending between said temperature levels.

Claim 4

In a thermodynamic expansion apparatus wherein a piston reciprocates between two different temperature levels to define at least one chamber of variable volume within an integral housing serving as the sole means for enclosing said chamber and wherein heat exchange means are located internal of said piston and are used to isolate at least two temperature levels, the improvement comprising a sleeve liner of a low thermal conductivity, low heat capacity material affixed to and forming a part of the internal wall of said housing and extending between said temperature levels.

Claim 5

An apparatus in accordance with claim 1 wherein said sleeve liner is formed of a nonmetallic material.

Claim 6

An apparatus in accordance with claim 1 characterized as being an expansion engine.

Claim 7

An apparatus in accordance with claim 1 characterized as being a thermal compressor.

Claim 8

An apparatus in accordance with claim 1 characterized as being a cryogenic refrigerator or liquefier.

Claim 9

In cryogenic apparatus wherein a piston reciprocates between two different temperature levels to define at least one refrigeration chamber of variable volume within an integral housing serving as the sole means for enclosing said chamber and into which high-pressure initially cooled fluid is delivered by way of a heat exchanger, located internal of said piston, for expansion and final cooling, the improvement comprising a sleeve liner of a low thermal conductivity, low heat capacity material affixed to and forming a part of the internal wall of said housing.

Claim 10

In cryogenic apparatus wherein a piston reciprocates between two different temperature levels to define at least one refrigeration chamber of variable volume within an integral housing serving as the sole means for enclosing said chamber and into which high-pressure initially cooled fluid is delivered by way of a heat exchanger, located internal of said piston, for expansion and final cooling, the improvement comprising a sleeve liner of a low thermal conductivity, low heat capacity material affixed to and forming a part of the internal wall of said housing.

Claim 11

An apparatus in accordance with claim 6 wherein said sleeve liner extends within said housing over a length no greater than that which is substantially equivalent to the length of said piston plus the length of the stroke of said piston but is discontinuous throughout those sections of said housing corresponding to the position of any heat stations associated therewith.

Claim 12

An apparatus in accordance with claim 6 wherein said sleeve liner ranges from about 0.002 to 0.100 inch in thickness.

Claim 13

An apparatus in accordance with claim 6 wherein said low thermal conductivity, low heat capacity material is a non-metallic material.

Claim 14

An apparatus in accordance with claim 9 wherein said nonmetallic material comprises polytetrafluoroethylene.

Claim 15

An apparatus in accordance with claim 9 wherein said nonmetallic material is Micarta.

Claim 16

An apparatus in accordance with claim 9 wherein said nonmetallic material is a ceramic or refractory.

Claim 17

A cryogenic apparatus, comprising in combination a. an integral fluid-tight housing serving as the sole means for defining an enclosure therein; b. piston means movable between two different temperature levels within said enclosure defined by said housing to define at least one refrigeration chamber of variable volume; c. a fluid flow path including heat exchange means located internally of said piston means adapted to deliver initially cooled high-pressure fluid into said refrigeration chamber; d. heat station means external of said housing adapted to effect indirect heat exchange between the fluid in said refrigeration chamber and a load; and e. a sleeve liner of a low thermal conductivity, low heat capacity material affixed to the internal wall of said housing and defining therewith a continuously smooth surface, said sleeve liner extending within said housing over a length no greater than that which is substantially equivalent to the length of said piston plus the length of the stroke of said piston but being discontinuous through those sections of said housing corresponding to the position of said heat station means.

Claim 18

A cryogenic apparatus, comprising in combination a. an integral fluid-tight housing serving as the sole means for defining an enclosure therein; b. piston means movable between two different temperature levels within said enclosure defined by said housing to define at least one refrigeration chamber of variable volume; c. a fluid flow path including heat exchange means located internally of said piston means adapted to deliver initially cooled high-pressure fluid into said refrigeration chamber; d. heat station means external of said housing adapted to effect indirect heat exchange between the fluid in said refrigeration chamber and a load; and e. a sleeve liner of a low thermal conductivity, low heat capacity material affixed to the internal wall of said housing and defining therewith a continuously smooth surface, said sleeve liner extending within said housing over a length no greater than that which is substantially equivalent to the length of said piston plus the length of the stroke of said piston but being discontinuous through those sections of said housing corresponding to the position of said heat station means.

Claim 19

A cryogenic apparatus in accordance with claim 13 wherein said piston also defines a warm chamber of variable volume and said fluid flow path provides fluid communication between said refrigeration chamber and said warm chamber.

Claim 20

A cryogenic apparatus in accordance with claim 13 wherein said piston means comprises multiple sections each of which is movable between two different temperature levels thereby defining multiple refrigeration chambers.

Claim 21

A cryogenic apparatus in accordance with claim 13 including external high-pressure fluid supply means and external low-pressure fluid reservoir means in fluid communication with said fluid flow path.

Claim 22

A cryogenic apparatus in accordance with claim 13 including additional piston means independently movable within said housing to define a compressor chamber of variable volume.

Claim 23

A cryogenic apparatus in accordance with claim 17 including an additional sleeve liner of a low thermal conductivity low heat capacity material affixed to the internal wall of said housing extending within said housing over a length no greater than that which is substantially equivalent to the length of said additional piston means plus the length of the stroke of said additional piston means but being discontinuous through those sections of said housing corresponding to the position of said heat station means.

Claim 24

A cryogenic apparatus in accordance with claim 13 including additional piston means independently movable within said housing to define a compressor chamber of variable volume and with said piston means which defines said refrigeration chamber to define a chamber of variable volume maintained at a temperature intermediate between said compressor chamber and said refrigeration chamber, and wherein heat station means are associated with each of said chambers.