Passive thermal switch apparatus and methods of use

Abstract

A passive thermal switch apparatus to produce an alteration between high and low thermal conductance above and below a selected set-point. The changing of thermal conductance enables amelioration of component and system temperatures and protection of components from extreme change of external or directly imposed heat load conditions. The switch actuates passively, meaning the switch will respond to the change in environment or applied heat without external interaction of control of a motor, sensor, signal, etc.

What is claimed and desired to be secured by United States Letters Patent is: 
     
         1 . A passive thermal switch, comprising:
 a housing, wherein the housing contains at least a bellows assembly and a tension pin, and the bellows assembly contains a phase-change material;   a cap positioned above the housing, wherein the cap is connected to a support structure and to the tension pin in a manner that enables the tension pin to move the cap in relation to the housing and in response to changes in the volume of the phase-change material;   the support structure is sized and shaped to fit over the cap and the housing and be connected to the housing; and   a thermal path, wherein the thermal path has a closed position, when the cap is in contact with the housing, and an open position, when the cap is not in contact with the housing.   
     
     
         2 . The passive thermal switch of  claim 1 , further comprising one or more thermal straps connected between the support structure and the cap. 
     
     
         3 . The passive thermal switch of  claim 2 , wherein the thermal path comprises a spherical contact interface between the cap and the housing that reduces risk of misalignment. 
     
     
         4 . The passive thermal switch of  claim 3 , wherein the spherical contact interface includes a coating. 
     
     
         5 . The passive thermal switch of  claim 2 , wherein the phase-change material is selected from the group consisting of: n-dodecane, n-tridecane, n-tetradecane, and n-hexadecane. 
     
     
         6 . The passive thermal switch of  claim 5 , wherein the thermal path is capable of transferring heat through the housing and through the cap and through the thermal straps and through the support structure. 
     
     
         7 . The passive thermal switch of  claim 5 , wherein the housing further contains at least one spring between the bellows assembly and the tension pin. 
     
     
         8 . The passive thermal switch of  claim 7 , wherein the housing further contains at least one spring between the tension pin and the housing. 
     
     
         9 . The passive thermal switch of  claim 8 , wherein the thermal resistance in the closed position is approximately 1.0 K/W. 
     
     
         10 . A passive thermal switch, comprising:
 a housing, wherein the housing contains at least a bellows assembly, a tension pin, a first spring positioned between the housing and the tension pin and a second spring positioned between the tension pin and the bellows assembly, and the bellows assembly contains a phase-change material;   a cap positioned above the housing, wherein the cap is connected to at least two thermal straps and the thermal straps are connected to a support structure, and the cap is also connected to the tension pin in a manner that enables the tension pin to move the cap in relation to the housing and in response to changes in the volume of the phase-change material;   the support structure is sized and shaped to fit over the cap and the housing and be connected to the housing; and   a thermal path, wherein the thermal path has a closed position, when the cap is in contact with the housing, and an open position, when the cap is not in contact with the housing.   
     
     
         11 . The passive thermal switch of  claim 10 , wherein the phase-change material is selected from the group consisting of: n-dodecane, n-tridecane, n-tetradecane, and n-hexadecane. 
     
     
         12 . The passive thermal switch of  claim 11 , wherein the cap further comprises a coated curvature. 
     
     
         13 . The passive thermal switch of  claim 12 , wherein the first spring is a back pressure spring and the second spring is a wave disc spring. 
     
     
         14 . The passive thermal switch of  claim 12 , wherein the support structure is comprised of a structure top plate, a structure bottom ring, and a structure shield. 
     
     
         15 . The passive thermal switch of  claim 14 , wherein the thermal resistance in the closed position is approximately 1.0 K/W. 
     
     
         16 . The passive thermal switch of  claim 14 , wherein the support structure is connected to a radiator of a satellite. 
     
     
         17 . A passive thermal switch, comprising:
 a housing, wherein the housing contains at least a bellows assembly, a tension pin, a first spring positioned between the housing and the tension pin and a second spring positioned between the tension pin and the bellows assembly, and the bellows assembly contains a phase-change material selected from the group consisting of: n-dodecane, n-tridecane, n-tetradecane, and n-hexadecane;   a cap positioned above the housing, wherein the cap is connected to four inter-connected thermal straps and the thermal straps are connected to a support structure, and the cap is also connected to the tension pin in a manner that enables the tension pin to move the cap in relation to the housing and in response to changes in the volume of the phase-change material;   the support structure is sized and shaped to fit over the cap and the housing and be connected to the housing, wherein the support structure is comprised of a structure top plate, a structure bottom ring, and a structure shield; and   a thermal path, wherein the thermal path has a closed position, when the cap is in contact with the housing, and an open position, when the cap is not in contact with the housing.   
     
     
         18 . The passive thermal switch of  claim 17 , wherein the thermal path, when in the closed position, proceeds through the housing and through the cap and through the thermal straps and through the support structure. 
     
     
         19 . The passive thermal switch of  claim 17 , wherein the support structure is connected to a satellite. 
     
     
         20 . The passive thermal switch of  claim 17 , wherein the tension pin is a thermally isolating lifting rod to create separation in the open position with very low thermal conductance while staying out of the high force load path of the closed position.