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.

Description

THE FIELD OF THE INVENTION

This invention relates to a passive thermal switch apparatus and associated methods of use, and more particularly, a compact thermal switch to produce alteration between high and low thermal conductance above and below a selected set-point. This switching between high and low thermal conductance enables amelioration of component and system temperatures due to changes of external conditions. The switch actuates passively, meaning the switch will respond to the change in environment or applied heat without interaction, or control of a motor, sensor, signal, etc.

BACKGROUND OF THE INVENTION

Generally, a thermal switch may be described as a device that can open and close depending on the temperature to alter the thermal conductance. This opening and closing of the thermal switch alters the heat flow between components within a system to maintain temperature around a selected set point. They may also be used as thermostats and overheat protection in certain heating and cooling systems.

Thermal switches may also be used in systems designed for use in space where there are significant changes in both heat dissipation and environmental conditions. A thermal switch may be used for thermal management in satellites. It would be an advance in the art to provide a compact thermal switch that allows alteration of thermal conductance. A thermal switch may come in at least two sized conductance values. For example, a thermal switch may be provided in a 10W conductance value and in a 25W conductance value.

SUMMARY OF THE INVENTION

A passive thermal switch may be described as being comprised of three separate subsystems: a support structure, or simply a structure for housing the components and providing the interface to external devices; a thermal conduction path; and an actuation device. The thermal switch may actuate passively, meaning the thermal switch will respond to the environment of the satellite without control of a motor, sensor, signal, etc.

The structural subsystem may be described as functioning to secure the inner thermal flow and actuation mechanisms. The structure may be designed to provide the necessary mechanical shock and structural load properties for the thermal switch. The structure may function to provide the ability for the thermal switch to withstand the necessary shock and load.

In one embodiment, the structure may also function to provide or contribute to the closed thermal resistance. In this way, the structure may be considered part of the thermal flow subsystem acting as the heat path for closed resistance.

The structure subsystem has no connection to the actuation subsystem. The thermal flow subsystem functions as the heat path up through the bottom plate and into the actuation subsystem. The thermal flow and actuation subsystems are connected with the bellows, which is filled with a phase-change material (PCM) that causes it to actuate when heat is passed into it. This acts as the heat path for the closed thermal resistance.

In one embodiment, a passive thermal switch may be comprised of a housing, wherein the housing may contain at least a bellows assembly and a tension pin, and the bellows assembly may contain a phase-change material. A cap may be positioned above the housing, wherein the cap may be connected to at least two thermal straps and the thermal straps may be connected to a support structure and the cap may also be 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 may be sized and shaped to fit over the cap and the housing and also be connected to the housing, or to a rim along the bottom of the housing. A thermal path may have a closed position and an open position, where the closed position may be described as when the cap is in contact with the housing and the open position may be described as when the cap is not in contact with the housing.

The thermal straps of the passive thermal switch may be any suitable number and may be inter-connectable. The thermal path may include a spherical contact interface between the cap and the housing that may enable superior contact area and reduce any risks of misalignment between the cap and housing. The spherical contact interface may include a coating, such as a coating of gold on a curvature of the cap. The phase-change material may be n-tetradecane, n-tridecane, or the like. The thermal path may be described as enabling the transfer of heat through the housing and through the cap and through the support structure. The passive thermal switch may also comprise a spring or bias member between the tension pin and the housing, and may also comprise another spring or bias member between the tension pin and the bellows assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects and features of the present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings in which:

FIG. 1 is a perspective view of a passive thermal switch;

FIG. 2A is a side-view perspective of a passive thermal switch;

FIG. 2B is a cut-away side-view perspective of a passive thermal switch;

FIG. 3 is an exploded view of a passive thermal switch;

FIG. 4 is a partial-exploded view of a passive thermal switch;

FIG. 5 is a partial exploded view of a passive thermal switch;

FIG. 6 is a cut-away perspective view of a passive thermal switch;

FIG. 7 is a schematic diagram of a cut-away view of a passive thermal switch;

FIG. 8 is a schematic diagram of a cut-away view of a passive thermal switch in a closed position;

FIG. 9 is a schematic diagram of a cut-away view of a passive thermal switch in an open position;

FIG. 10A is a perspective view of a structure or frame for a passive thermal switch;

FIG. 10B is an exploded perspective view of a structure or frame for a passive thermal switch;

FIG. 11 is a perspective view of a structure fixture assembly for a passive thermal switch;

FIG. 12A is a perspective view of a cap for a passive thermal switch;

FIG. 12B is a cut-away side view of a cap for a passive thermal switch;

FIG. 13A is a perspective view of a housing for a passive thermal switch;

FIG. 13B is a cut-away side view of a housing for a passive thermal switch;

FIG. 14A is a perspective view a bellows assembly for a passive thermal switch;

FIG. 14B is a cut-away side view of a bellows assembly for a passive thermal switch;

FIG. 15 is a perspective view of a thermal strap for a passive thermal switch;

FIG. 16 is a perspective view of a tension pin for a passive thermal switch;

FIG. 17 is a perspective view of a tension pin for a passive thermal switch; and

FIG. 18 is a cut-away perspective view of a passive thermal switch.

DETAILED DESCRIPTION OF THE INVENTION

It will be readily understood that the components of the present invention, as generally described herein, could be arranged and designed in a wide variety of different configurations or embodiments. Thus, the following more detailed description of the embodiments of the system, product and method of the present invention, is not intended to limit the scope of the invention, as claimed, but is merely representative of various embodiments of the invention.

Referring more particularly to FIG. 1, and generally to FIGS. 1-9, a passive thermal switch 10, or apparatus 10, may be comprised of multiple subsystems, with each subsystem having multiple components. A passive thermal switch 10 may be comprised a structure 20, a housing 30, a cap 40, a bellows assembly 60, and at least one thermal strap 50. Various structural connectors may be used to secure individual components, subsystems, or both. For example, a socket head screw 80 may be used to connect a thermal switch 10 to a separate device utilizing the thermal switch, i.e., a satellite or other device.

A structure 20, or frame 20, may be comprised of a structure top plate 22, a structure bottom ring 24, and structure tubes 26 connecting the structure top plate 22 to the structure bottom ring 24. The structure 20 may sit on top of and be connected to the housing rim 32. A socket head screw 80 may be used to connect the structure bottom ring 24 to the housing rim 32. The structure 20 may enclose or protect the cap 40 and the housing 30. A cap 40 may be positioned above the housing 30. One or more thermal straps 50 may be positioned above the cap 40 and below the structure top plate 22.

Referring more particularly to FIGS. 2A and 2B, and generally to FIGS. 1-9, a passive thermal switch 10 may be comprised of multiple components. A structure 20 may have a structure top plate 22, a structure bottom ring 24, and structure tubes 26 connecting the structure top plate 22 and the structure bottom ring 24. A housing 30 may have a housing wall 34 and a housing rim 32. A cap 40 may be positioned above the housing 30. At least one thermal strap 50 may be positioned above the cap 40.

A housing 30 may be configured like a bowl, or cylindrical enclosure with a rounded top, or container. The housing 30 may contain a tension pin 74, wherein the tension pin 74 has a circular base 73 and a post 75. The circular base 73 may be positioned at the bottom of the housing 30 and the post 75 of the tension pin 74 may pass through and be positioned in the middle or center of the housing 30. A bellows assembly 60 with bellows 66 may be contained within the housing 30. The bellows screw plate 62 may be secured within the housing by button head screws 86 and by the tension pin shaft 75 passing through the center of the bellows assembly 60.

Referring more particularly to FIG. 3, and generally to FIGS. 1-9, one embodiment of a passive thermal switch 10 may be comprised of multiple components arranged as illustrated. A variety of connectors may be used to connect and secure components depending on the individual need and situation between components. Generally, the arrangement of the thermal switch may be described starting from the bottom and moving toward the top of FIG. 3.

In one embodiment, a housing cover 39 may be described as providing a base or support for a housing 30 of a thermal switch 10. The housing cover 39 may fit into the bottom opening of the housing 30 in a manner that enables the enclosure of a stroke spring 70, a tension pin 74, a compression pin 76, a flanged sleeve bearing 78, a pressure spring 72, and a bellows assembly 60 within the housing 30. The housing cover 39 may be secured to the housing rim 32 by use of one or more flat head screws 84, or the like. Any suitable securement mechanism may be used. When the housing cover 39 is secured in place, the stroke spring 70, the tension pin 74, the compression pin 76, the flanged sleeve bearing 78, the pressure spring 72, and the bellows assembly 60 are contained within the housing 30.

However, the top of the tension pin 74 may protrude through the housing aperture 37 and through the cap aperture 44. The top of the tension pin 74 may then be secured in place by use of a pin disc 56 and a dowel pin 54. The pin disc 56 may have a vertical hole and a horizontal hole. The vertical hole may be configured to accept the top of the tension pin 74 and the horizontal hole may be configured to accept the dowel pin 54. The dowel pin 54 is positioned through the aligning holes in the pin disc 56 and in the top of the tension pin 74, thus securing the tension pin 74 relative to the housing 30 and the cap 40 in a manner that maintains the position of the bellows assembly 60 within the housing 30. In one embodiment, the top of the tension pin 74 may be secured in place by use of a pin nut 58.

A cap 40 may be positioned above the housing top 36. One or more thermal straps 50 may be positioned above the cap 40. The thermal straps 50 may be secured to the cap top 42 by use of one or more flat head screws 84, or the like. Any suitable securement mechanism may be used. The thermal straps 50 may also be secured to the structure top plate 22 by use of one or more flat head screws 84, or the like. Any suitable securement mechanism may be used. Thus, the thermal straps 50 establish a connection between the structure top plate 22 and the cap 40.

The structure bottom ring 24 may be secured to the housing rim 32 by use of one or more socket head screws 80, where a washer 82 may be used between the head of the socket head screw 80 and the surface to which it is being secured. Any suitable securement mechanism may be used. Thus, the structure 20 may enclose the thermal straps 50, the cap 40, and the housing 30 with its housing wall 34 and housing top 36.

Referring more particularly to FIG. 4, and generally to FIGS. 1-9, one embodiment of a passive thermal switch 10 may be comprised of multiple components arranged as illustrated. Generally, the arrangement of the thermal switch may be described starting from the bottom and moving toward the top of FIG. 4.

A housing cover 39 may be described as a base or support for the contents of the housing 30. A pressure spring 72 may be positioned between the housing cover 39 and the base of a tension pin 73. The shaft of the tension pin 75 may be enclosed by a compression pin 76. Another pressure spring 72 may be positioned to encircle the tension pin shaft 75 and be placed between the base of the tension pin 73 and the bellows assembly 60, or more particularly, between the base of the tension pin 73 and the bellows bottom plate 64 of the bellows assembly 60.

The housing cover 39 may be secured to the housing rim 32 by use of one or more flat head screws 84, or the like. Any suitable securement mechanism may be used. When the housing cover 39 is secured to the housing rim 32, the housing 30 may contain the stroke spring 70, the tension pin base 73 and tension pin shaft 75, the compression pin 76, the pressure spring 72, and the bellows assembly 60.

The top of the tension pin 74 may protrude through the housing aperture 37 and through the cap aperture 44, such that the top of the tension pin 74 protrudes above the cap top 42. The top of the tension pin 74 may then be secured in place by use of a pin disc 56 and a dowel pin 54. The pin disc 56 may have a vertical hole and a horizontal hole. The vertical hole may be configured to accept the top of the tension pin 74 and the horizontal hole may be configured to accept the dowel pin 54. The dowel pin 54 is positioned through the aligning holes in the pin disc 56 and in the top of the tension pin 74, thus securing the tension pin 74 relative to the housing 30 and the cap 40 in a manner that maintains the position of the bellows assembly 60 within the housing 30. In one embodiment, the top of the tension pin 74 may then be secured in place by use of a pin nut 58.

The two wave disc springs 72 provide a force or bias member that urges components in opposite directions. For example, a stroke spring 70 may urge the base of the tension pin 73 away from the housing cover 39. A pressure spring 72 may urge the bellows assembly 60 away from the base of the tension spring 73. Thus, the springs 70 and 72 may prevent the bellows assembly 60 from becoming stuck or lodged in one position. Any suitable spring may be used to urge the tension pin base 73 in an appropriate direction. Also, any suitable configuration of springs may be utilized, including one or more springs on either side of the tension pin base 73.

The portion of FIG. 4 that is circled and labeled “FIG. 5” is shown in more detail in FIG. 5. Referring more particularly to FIG. 5, and generally to FIGS. 1-9, one embodiment of a passive thermal switch 10 may be comprised of multiple components arranged as illustrated. Generally, the arrangement of the thermal switch components may be described starting from the bottom and moving toward the top of FIG. 5.

One or more thermal straps 50 may be positioned above the cap 40. The thermal straps 50 may be configured to interlock in a square-like pattern. One or more flat head screws 84 may be used to secure the thermal straps 50 to each other. The thermal straps may then be positioned and secured between the cap top 42 and the structure top plate 22 when the structure 20 is placed over the thermal straps 50, the cap 40, and the housing 30.

One or more socket head screws 80 may be used to secure various structures together. For example, socket head screws 80 may be used to secure the structure bottom ring 24 to the housing rim 32. Socket head screws 80 may be used to secure the thermal switch 10, the structure 20, or structure top plate 22, to other devices. Washers 82 may be used in conjunction with socket head screws 80 when securing components of the thermal switch, when securing the thermal switch in place within a larger device, or both.

Referring more particularly to FIG. 6, and generally to FIGS. 1-9, one embodiment of a passive thermal switch 10 may be comprised of multiple components arranged as illustrated. A thermal switch may comprise a bellows assembly 60, which bellows assembly 60 (in conjunction with the tension pin 74) may function to actuate the thermal switch between the open and closed positions. Generally, a bellows assembly 60 may be contained within a housing 30, or within the housing walls 34.

A bellows assembly 60 may be comprised of a bellows screw plate 62, a bellows bottom plate 64, and bellows 66 positioned between the bellows screw plate 62 and the bellows bottom plate 64. The bellows 66 may be configured to have inside bellows and outside bellows, where the inside bellows and outside bellows define a bellows cavity 68. The bellows 66 may be comprised of any suitable material, for example and not by way of limitation, stainless steel, metal, aluminum, or the like. In operation, the bellows do not expand radially.

The bellows cavity 68 may contain a phase-change material (PCM) that melts when the thermal switch needs to close and freezes when the thermal switch needs to open. Any suitable material may be used as the PCM inside the bellows cavity 68, for example and not by way of limitation, n-dodecane, n-tridecane, n-tetradecane, n-hexadecane, or the like. The PCM may be selected based on its melting point and how that melting point can bring about the desired results for a thermal switch containing that PCM. For example, and not by way of limitation, n-dodecane has a melting point of −12° C., n-tridecane has a melting point of −6° C., n-tetradecane has a melting point of 5° C., and n-hexadecane has a melting point of 18° C. Thus, the PCM may be selected based on the desired temperature that will actuate the thermal switch.

In one embodiment, a thermal switch may be described as having a thermal path subsystem. For example, the thermal path subsystem for a thermal switch in the closed position and utilized in a satellite may be described as proceeding from a satellite electrical box to the housing 30 to the cap 40 to the thermal straps 50 to the structure top plate 22 and finally to a satellite radiator. In one embodiment, a thermal path may be represented by arrows that indicate a possible thermal path from the housing 30, or through the housing wall 34, and through the housing top 36 and/or the bellows screw plate 62, and through the tension pin 74, and through the cap 40, and into the structure top plate 22. A thermal path may be described as proceeding through the thermal switch by various paths, for example and not by way of limitation, from the housing 30 through the cap 40, the thermal straps 50, and through the structure top plate 22. Any suitable thermal path may be utilized. In one embodiment, the thermal path may be configured so the thermal straps 50 make the connection between the satellite radiator and the cap 40. The thermal resistance should be as low as possible. Also, the structure tubes 26 may be as thermally resistive as possible with respect to open thermal resistance. Also, the thermal switch can provide a suitable thermal path between any two desired devices, components, or both.

Referring more particularly to FIG. 7, and generally to FIGS. 1-9, one embodiment of a passive thermal switch 10 may be comprised of multiple components arranged as illustrated. A thermal switch may comprise a bellows assembly 60 that further comprises springs for dampening vibrations that may be experienced by the thermal switch. Generally, a bellows assembly 60 may be contained within a housing 30, or within the housing walls 34. A system of springs may also be found within the housing 30. Any suitable springs may be used.

A stroke spring 70 may be positioned between the housing cover 39 and the base 73 of the tension pin 74. A pressure spring 72 may be positioned between the base 73 of the tension pin 74 and the bellows bottom plate 64. This configuration may be used to function so that the cap 40 and tension pin 74 do not see resonance.

For example, if a thermal switch is used in a satellite, the satellite will have to be launched. During a launch sequence, the thermal switch may be in a closed position, meaning that the cap 40 will be in contact with the housing top 36. The spring system described herein may be designed and used to prevent resonance in the cap 40 and tension pin 74 during a launch sequence.

Referring more particularly to FIG. 8, and generally to FIGS. 1-9, one embodiment of a passive thermal switch 10 may be comprised of multiple components arranged as illustrated. A thermal switch may have a configuration that can be described as a closed configuration, or closed position. In a closed position, the cap 40 will be in contact with the housing top 36. In a closed position, the thermal switch 10 may have a thermal resistance of from approximately 0.80 K/W to approximately 1.20 K/W, with an average thermal resistance of approximately 0.964 K/W.

Referring more particularly to FIG. 9, and generally to FIGS. 1-9, one embodiment of a passive thermal switch 10 may be comprised of multiple components arranged as illustrated. A thermal switch may have a configuration that can be described as an open configuration, or open position. In an open position, the cap 40 will not be in contact with the housing top 36. In an open position, the thermal switch 10 may have a thermal resistance of from approximately 3200 K/W to approximately 3600 K/W, with an average thermal resistance of approximately 3400 K/W.

As the phase-change material in the bellows cavity 68 freezes and contracts, the height of the bellows assembly 60 will decrease. If the bellows are fully contracted, the height of the bellows assembly 60 may be approximately 1.0 inch (2.54 cm).

As the phase-change material in the bellows cavity 68 melts, or liquefies, and expands, the height of the bellows assembly 60 will increase. If the bellows are fully expanded, the height of the bellows assembly 60 may be from approximately 1.0525 inches to approximately 1.070 inches (2.67 cm to 2.72 cm).

As the bellows assembly 60 expands and increases in height, the bellows bottom plate 64 exerts pressure on the base 73 of the tension pin 74, and the cap 40 is pulled toward the housing top 36 as the tension pin 74 is pressed downward. As the cap 40 is pulled toward the housing top 36, the thermal straps 50 may “lengthen” or stretch a small amount and maintain their connection between the cap 40 and the structure top plate 22. As the cap 40, or cap curvature 46, moves toward the housing top 36, the thermal resistance decreases and allows for more thermal conductance. Thus, heat travels easier along the thermal path of the thermal switch when the thermal switch is in the closed position.

As the bellows assembly 60 decreases in height, the bellows bottom plate 64 relieves pressure on the base 73 of the tension pin 74, and the cap 40 is pushed away from the housing top 36 as the tension pin 74 is pressed upwards by the pressure spring 72 and stroke spring 70. As the cap 40 is pressed upwards and away from the housing top 36, the thermal straps 50 may maintain their connection between the cap 40 and the structure top plate 22. As the cap 40, or curvature 46, moves away from the housing top 36, the thermal resistance increases and allows for less thermal conductance.

Referring to FIGS. 10A and 10B, the structure 20 and its component pieces may be comprised of any suitable material, including without limitation, aluminum, stainless steel, G10 or garolite, or the like. A suitable material may be described as non-reactive with oxygen and strong enough to withstand the anticipated stresses. The structure top plate 22 and structure bottom ring 24 may be of solid, monolithic construction. The structure tubes 26 may be of solid or hollow construction.

One purpose of the structure 20 is to provide the thermal switch with the capability of bolting electrical components to the radiator of a satellite. The structure 20 should be designed to withstand bending and twisting. Composite structure tubes 26 may be used to connect the structure top plate 22 and the structure bottom ring 24. The structure tubes 26 may be strong and non-conductive. The structure top plate 22 and the structure bottom ring 24 may be composed of aluminum to allow for a high thermal resistance and to help ensure the thermal switch in the open position has the desired thermal resistance. The structure tubes 26 may be epoxied into the connection holes in the structure top plate 22 and the structure bottom ring 24 to provide a strong, resilient bond. In another embodiment, the structure tubes 26 may be epoxied into connection holes in the housing rim 32 (see, e.g., FIG. 9).

Referring to FIG. 11, in one embodiment, a structure fixture assembly may be comprised of a fixture top 29, a structure top plate 22, a structure bottom ring 24, a fixture base 27, and a fixture column 28 arranged as shown in FIG. 11. For example, a fixture base 27 may be connected to a structure bottom ring 24. The base of a fixture column 28 may be connected to the fixture base 27 and the top of the fixture column 28 may be connected to a fixture top 29, with the fixture top 29 connected to a structure top plate 22. The components of a structure fixture assembly may be comprised of any suitable material, including without limitation, aluminum, stainless steel, G10 or garolite, or the like. A suitable material may be described as non-reactive with oxygen and strong enough to withstand the anticipated stresses.

Referring to FIGS. 12A and 12B, a cap 40 may comprised of any suitable material, including without limitation, aluminum, stainless steel, G10 or garolite, or the like. A suitable material may be described as non-reactive with oxygen and strong enough to withstand the anticipated stresses. A cap 40 may be configured to have a cap top 42, a cap aperture 44, and a cap curvature 46. The cap curvature 46 may be configured to fit with the housing top 36 so as to provide the maximum surface contact between the cap curvature 46 and the housing top 36 and to prevent misalignment between the cap 40 and the housing 30. In one embodiment, a cap curvature 46 may be coated with a substance to increase heat conductance, such as gold, or the like. In one embodiment, a housing top 36 may be coated with a substance to increase heat conductance, such as gold, or the like.

Referring to FIGS. 13A and 13B, a housing 30, including a housing rim 32, a housing wall 34, and a housing top 36 may be comprised of any suitable material, including without limitation, aluminum, stainless steel, G10 or garolite, or the like. A suitable material may be described as non-reactive with oxygen and strong enough to withstand the anticipated stresses. The housing wall 34 and housing top 36 may define a housing cavity 38. As shown previously, the housing cavity 38 may be sized and configured to contain a bellows assembly 60.

Referring to FIGS. 14A and 14B, a bellows assembly may be comprised of a bellows screw plate 62, a bellows bottom plate 64, and bellows 66. The bellows 66 may include an inside bellows and an outside bellows. The bellows 66 are connected to the bellows screw plate 62 at one end and the bellows bottom plate 64 at the other end. The bellows screw plate 62, bellows bottom plate 64, and bellows 66 define a bellows cavity 68. The bellows cavity 68 may contain a phase-change material that changes in volume based on temperature, thus enabling the bellows assembly 60 to actuate the thermal switch based on temperature conditions.

The bellows screw plate 62 and the bellows bottom plate 64 may be comprised of any suitable material, including without limitation, aluminum, stainless steel, G10 or garolite, or the like. A suitable material may be described as non-reactive with oxygen and strong enough to withstand the anticipated stresses. The bellows 66 may be comprised of any suitable material, including without limitation, metal, aluminum, stainless steel, G10, or the like. A suitable material may be described as non-reactive with oxygen and malleable or flexible enough to withstand the accordion-style motion of the bellows.

Referring to FIG. 15, a thermal strap 50 may be configured to allow for interlocking contact with other thermal straps and provide a connection between a cap 40 and a structure top plate 22. A thermal strap 50 may be comprised of any suitable material, including without limitation, metal, aluminum, stainless steel, copper, or the like. A suitable material may be described as non-reactive with oxygen and flexible enough to withstand the anticipated expansion and contraction, or slight movement, of the cap 40 relative to the structure top plate 22.

Referring to FIG. 16, a tension pin 74 may be configured to support and maintain the vertical positioning of a bellows assembly 60. The tension pin 74 may be described as having a base, or circular base 73. The tension pin 74 may be described as having a shaft 75 and top, where the top includes a hole for receiving a pin, such as a dowel pin 54. The tension pin 74 may be comprised of any suitable material, including without limitation, aluminum, stainless steel, titanium, G10 or garolite, or the like. A suitable material may be described as non-reactive with oxygen and strong enough to support the component structures contained within the housing 30. The tension pin 74 may be described as a thermally isolating lifting rod that can create separation in the open position with a very low thermal conductance while staying out of the high force load path of the closed position.

A compression pin 76 may be configured as a cylinder sized and shaped to fit over the shaft of a tension pin 74. The compression pin 76 may be comprised of any suitable material, including without limitation, aluminum, stainless steel, G10 or garolite, or the like. A suitable material may be described as non-reactive with oxygen and similar in strength to the tension pin 74. A flanged sleeve bearing 78 may be sized and shaped to fit over the shaft of a tension pin 74 and enable rotation of the bellows assembly 60 around the tension pin 74. The stroke spring 70 and the pressure spring 72 may be comprised of any suitable material. A suitable material may be described as resilient enough to provide the necessary spring force.

Referring to FIG. 17, a tension pin 74 may be configured to support and maintain the vertical positioning of a bellows assembly 60. The tension pin 74 may be described as having a base, or circular tension pin base 73. The tension pin 74 may be described as having a shaft 75 and a top, where the top includes threads 57 for securing the tension pin 74 with a pin nut 58. The tension pin 74 may be comprised of any suitable material, including without limitation, aluminum, stainless steel, titanium, G10 or garolite, or the like. A suitable material may be described as non-reactive with oxygen and strong enough to support the component structures contained within the housing 30. The tension pin 74 may be described as a thermally isolating lifting rod that can create separation in the open position with a very low thermal conductance while staying out of the high force load path of the closed position. In one embodiment, a tension pin 74 may be configured to be used without a compression 76 or a flanged sleeve bearing 78.

Referring to FIG. 18, and generally to FIGS. 1-18, one embodiment of a passive thermal switch 10 may be comprised of multiple components arranged as illustrated. A housing 30 may contain a bellows assembly 60, a pressure spring 72 and a tension pin 74. The housing may be comprised of a housing wall 34, a housing top 36, and a housing cover 39. The bellows assembly 60 may be comprised of a bellows screw plate 62, a bellows bottom plate 64, and bellows 66. The pressure spring 72 may be positioned between the base 73 of the tension pin 74 and the bellows bottom plate 64. Thus, the pressure spring 72 is urging the tension pin 74 upwards and away from the housing cover 39. A cap 40 is positioned above the housing 30. The shaft 75 of the tension pin 74 protrudes above the cap top 42 such that the tension pin threads 57 may be engaged with a pin nut 58, thus securing the tension pin 74 in place in a manner that allows relative motion between the cap 40 and the housing 30. One or more thermal straps 50 may be connected to the cap 40 and to the structure top plate 22.

In one embodiment, the structure 20 may be comprised of a structure top plate 22, a structure bottom ring 24 and a structure shield 25. The structure shield 25 may be configured as a cylinder, where that cylinder may have one or more apertures to allow for structural connections, thermal accommodations, or other reasons. The structure shield 25 may provide thermal isolation for the thermal switch. The structure shield 25 may be comprised of any suitable material, including without limitation, aluminum, stainless steel, titanium, G10 or garolite, composites, or the like. A suitable material may be described as non-reactive with oxygen and strong enough to provide the desired support and thermal isolation. The structure shield 25 may be positioned and connected between the structure top plate 22 and the structure bottom ring 24 in any suitable manner, including without limitation by the use of an epoxy. Any suitable connection means may be used.

The subject invention may be more easily comprehended by reference to the specific embodiments recited herein, which are representative of the invention. However, it must be understood that the specific embodiments are provided only for the purpose of illustration, and that the invention may be practiced in a manner separate from what is specifically illustrated without departing from its scope and spirit.

Claims

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; anda 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; anda 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; anda 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.