Conductive Thermal Actuator Switch Based on Phase Change Material (PCM)

Abstract

The device includes a plurality of thermal actuator switches (100, 500, 700, 902-904, 1002-1004) configured to control the transfer of thermal energy. The thermal actuator switches are arranged in a stacked configuration. Each switch includes first and second plates (102-104, 502-504, 702-704) and a piston (108-110, 508-510, 708-710) movable between the plates. Each switch also includes a phase change material (112, 512, 712) configured to (i) expand to cause a surface of the piston to move to a first position, and (ii) contract to cause a surface of the piston to move to a second position. The surface of the piston is in thermal contact with the first plate and increases the transfer of thermal energy between the plates when in one of the first and second positions. The surface of the piston is spaced from the first plate and decreases the transfer of thermal energy between the plates when in the other of the first and second positions. Different ones of the switches contain different phase change materials that expand or contract at different temperatures.

Description

Technical Field

[0001] The present disclosure generally relates to thermal systems. More specifically, the present disclosure relates to conductive thermal actuator switches based on phase change materials (PCMs).

Background Art

[0002] Thermal management is generally required or desired for various electronic devices, power systems, and other devices or systems where thermal energy (heating) can negatively impact or damage the performance of a device or system component. For example, batteries are often heated during use, and thermal management is generally required or desired to maintain the battery within a specified temperature range. These temperature ranges can be defined to maintain the operating efficiency of the battery, ensure the long-term use of the battery, or avoid damage to the battery.

Summary of the Invention

[0003] The present disclosure relates to conductive thermal actuator switches based on phase change materials (PCMs).

[0004] In the first embodiment, the apparatus includes a plurality of thermal actuator switches configured to control the transfer of thermal energy through the apparatus, and the thermal actuator switches are arranged in a stacked configuration. Each thermal actuator switch includes a first plate and a second plate, and a piston movable between the first plate and the second plate. Each thermal actuator switch also includes a phase change material configured to (i) expand and move the surface of the piston to a first position and (ii) contract and move the surface of the piston to a second position. The surface of the piston is in thermal contact with the first plate and, when in one of the first position and the second position, increases the transfer of thermal energy between the first plate and the second plate. The surface of the piston is spaced from the first plate and, when in the other of the first position and the second position, decreases the transfer of thermal energy between the first plate and the second plate. Different thermal actuator switches include different phase change materials that expand or contract at different temperatures.

[0005] In the second embodiment, the system includes at least one heat source and at least one heat sink. The system also includes a plurality of thermal actuator switches configured to control the transfer of thermal energy between at least one heat source and at least one heat sink, and the thermal actuator switches are arranged in a stacked configuration. Each thermal actuator switch includes a first plate and a second plate, and a piston movable between the first plate and the second plate. Each thermal actuator switch also includes a phase change material configured to (i) expand and move the surface of the piston to a first position and (ii) contract and move the surface of the piston to a second position. The surface of the piston is in thermal contact with the first plate and, when in one of the first position and the second position, increases the transfer of thermal energy between the first plate and the second plate. The surface of the piston is spaced from the first plate and, when in the other of the first position and the second position, decreases the transfer of thermal energy between the first plate and the second plate. Different thermal actuator switches include different phase change materials that expand or contract at different temperatures.

[0006] In a third aspect, the method includes receiving thermal energy from at least one heat source with a plurality of thermal actuator switches, the thermal actuator switches being arranged in a stacked configuration. The method also includes using the thermal actuator switches to control the transfer of thermal energy between at least one heat source and at least one heat sink. Each thermal actuator switch includes a first plate and a second plate, and a piston movable between the first plate and the second plate. Each thermal actuator switch also includes a phase change material configured to (i) expand to move the surface of the piston to a first position and (ii) contract to move the surface of the piston to a second position. The surface of the piston is in thermal contact with the first plate and, when in one of the first position and the second position, increases the transfer of thermal energy between the first plate and the second plate. The surface of the piston is spaced from the first plate and, when in the other of the first position and the second position, decreases the transfer of thermal energy between the first plate and the second plate. Different thermal actuator switches include different phase change materials that expand or contract at different temperatures.

[0007] Other technical features will be readily apparent to those skilled in the art from the following drawings, description, and claims.

[0008] To understand the present disclosure more fully, reference is now made to the following description in connection with the accompanying drawings.

Brief Description of the Drawings

[0009]

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DETAILED DESCRIPTION

[0010] The figures 1 through 11 described below, and the various embodiments used to explain the principles of the present disclosure, are merely exemplary and should in no way be construed as limiting the scope of the present disclosure. Those skilled in the art will understand that the principles of the present disclosure can be implemented in any type of device or system that is appropriately arranged.

[0011] As described above, thermal management is generally required or desired for various electronic devices, power systems, and other devices or systems where thermal energy (heating) can negatively impact or damage the performance of the device or system components. For example, batteries are often heated during use, and thermal management is generally required or desired to maintain the battery within a predetermined temperature range. These temperature ranges can be defined to maintain the operating efficiency of the battery, ensure the long-term use of the battery, or avoid damage to the battery.

[0012] The present disclosure provides various thermal actuator switches that can be used for thermal management or other purposes. Each of the thermal actuator switches includes a piston that can be used to form and break thermal connections, or otherwise facilitate or impede the transfer of thermal energy between at least one heat source (such as a power dissipation or heating device) and at least one heat sink (such as a cold plate). At least one phase change material (PCM) within each thermal actuator switch can change phase, expand / contract based on local heating / cooling within the thermal actuator switch, and move the piston within the thermal actuator switch. In some cases, when the phase change material within the thermal actuator switch is heated, the phase change material expands and moves the piston within the thermal actuator switch to form (or improve) a thermal connection between the heat source(s) and the heat sink(s). When the phase change material within the thermal actuator switch is cooled, the phase change material can contract and use a spring loading mechanism, magnet, or other return mechanism to push or pull the piston and break (or reduce) the thermal connection between the heat source(s) and the heat sink(s). Other arrangements can have a phase change material that expands when cooled and contracts when heated, which can again move the piston to form (or improve) and break (or reduce) the thermal connection.

[0013] In this way, the phase change material within each thermal actuator switch can be used to passively switch the thermal actuator switch. Also, by using the operation of each thermal actuator switch to control the contact surface area between the piston and another component of the thermal actuator switch, it becomes possible to easily control heat energy transfer using the surface area. In some embodiments, the operation of each thermal actuator switch is linear based on the movement of the piston. Further, by using a return mechanism, each thermal actuator switch can be used to repeatedly form or interrupt (or increase or decrease) the thermal connection between the heat source(s) and the heat sink(s).

[0014] In addition, a plurality of thermal actuator switches may be used in any suitable series and / or parallel arrangement(s) to provide a desired thermal energy transfer path between at least one heat source and at least one heat sink. For example, a parallel array of thermal actuator switches may be positioned across at least one battery or other heat source(s) and may be used to transfer thermal energy away from the heat source(s). This can be useful, for example, in reducing or avoiding the generation of a temperature gradient across the surface(s) of the heat source(s). As another example, a plurality of thermal actuator switches may be stacked in series, with different thermal actuator switches having phase change materials that expand / contract at different temperature thresholds. This may, for example, enable the overall thermal transfer behavior of the thermal actuator switches to be adjusted to suit a particular application. As a specific example, this may enable the stacked thermal actuator switches to form / interrupt (or facilitate / suppress) one or more thermal connections between the heat source(s) and the heat sink(s) at different temperatures. As a result, for example, one of a plurality of stacked thermal actuator switches may form or improve a thermal connection between the heat source(s) and the heat sink(s) at a lower temperature to enable a first thermal energy transfer rate, or another one of the stacked thermal actuator switches may form or improve the same or a different thermal connection between the heat source(s) and the heat sink(s) at a higher temperature to enable a second (higher) thermal energy transfer rate. Combinations of these approaches may also be used, such as when multiple sets of serially-connected (stacked) thermal actuator switches are arranged in a parallel array.

[0015] Figures 1 through 4 show an exemplary PCM-based conductive thermal actuator switch 100 according to the present disclosure. In particular, FIGS. 1 and 3 show perspective views of the thermal actuator switch 100 in different operating configurations, and FIGS. 2 and 4 show cross-sectional views of the thermal actuator switch 100 in different operating configurations. Note that certain components of the thermal actuator switch 100 in FIGS. 1 and 3 are shown in a transparent schematic form for ease of illustration and explanation.

[0016] As shown in FIGS. 1 and 2, the thermal actuator switch 100 may include a housing, such as one formed using an upper plate 102 and a lower plate 104, or may be associated with a housing. Each plate 102 and 104 represents a structure that can be thermally coupled to at least one heat source or at least one heat sink. For example, the upper plate 102 may be thermally coupled to at least one heat sink, and the lower plate 104 may be thermally coupled to at least one heat source (or vice versa). Each plate 102 and 104 may be formed using any suitable material(s), such as one or more metals or other materials (s) having a high thermal conductivity. Also, each plate 102 and 104 may be formed in any suitable manner. Additionally, each plate 102 and 104 may have any suitable size, shape, and dimensions.

[0017] In some cases, plates 102 and 104 may optionally be separated by a thermal insulation material 106, which is only shown in FIGS. 2 and 4 for ease of illustration. The thermal insulation material 106 can serve to reduce or minimize the thermal conductivity between plates 102 - 104 and, except when necessary or desirable, can serve to reduce or minimize the transfer of thermal energy between plates 102 - 104 themselves. The thermal insulation material 106 may be formed from any suitable material(s), such as a thermally insulating epoxy or other material(s), and this material can be used to attach plates 102 - 104 or glass fiber washers or other structure(s) positioned between plates 102 - 104. Also, the thermal insulation material 106 may be formed in any suitable manner. Additionally, the thermal insulation material 106 can have any suitable size, shape, and dimensions.

[0018] A piston formed by piston base 108 and piston plate 110 is positioned between plates 102 and 104 and is movable. For example, the upper plate 102 may include a recess formed between the side wall portions of the plate 102, and at least a part of the piston plate 110 is positioned within this recess and can be movable up and down. Similarly, the lower plate 104 may include a recess formed between the side wall portions of the plate 104, and at least a part of the piston base 108 is positioned within that recess and can be movable up and down. The piston formed by piston base 108 and piston plate 110 can be formed using any suitable material(s), such as one or more metals or other material(s) with high thermal conductivity. Also, the piston may be formed in any suitable manner. Additionally, the piston can have any suitable size, shape, and dimensions.

[0019] As shown in this example, the piston base 108 may take the form of an annular cylinder or other structure having an internal cavity, and the phase change material 112 is positioned within the internal cavity of the piston base 108. In this particular example, the phase change material 112 is positioned between the piston plate 110 and a portion of the lower plate 104 that protrudes into the piston base 108. Thereby, the phase change material 112 can contact a portion of the lower plate 104, and the lower plate 104 can prevent the downward movement of the phase change material 112. The phase change material 112 represents at least one material that can expand and contract in an appropriate amount based on temperature.

[0020] When the phase change material 112 is used in the thermal actuator switch 100 to move the piston plate 110 between different positions, the heat energy transfer between the plates 102 and 104 is promoted or suppressed. For example, in FIGS. 1 and 2, the phase change material 112 is in a contracted state, which may occur in some cases when the phase change material 112 is at a lower temperature. In this state, the piston plate 110 is separated from the upper plate 102, at least along the main upper surface of the piston plate 110. Here, the side surface of the piston plate 110 may or may not contact the upper plate 102. In this operating arrangement, the heat energy transfer between the plates 102 - 104 can be reduced or minimized. As a result, there may be little heat energy transfer between the heat source(s) and the heat sink(s) that are thermally coupled to the plates 102 - 104. In some embodiments, the piston plate 110 may be completely separated from the plate 102 or may not contact the plate at all in this operating arrangement.

[0021] In FIGS. 3 and 4, the phase change material 112 is in an expanded state, which may occur when the phase change material 112 is at a higher temperature in some cases. In this state, the piston plate 110 contacts the upper plate 102 at least along the main upper surface of the piston plate 110. Here too, the side surface of the piston plate 110 may or may not contact the upper plate 102. In this operating arrangement, when both the piston base 108 and the piston plate 110 contact both plates 102 - 104 simultaneously, a path for heat energy to flow between the plates 102 - 104 through the higher conductivity piston is provided, so that the heat energy transfer between the plates 102 - 104 can be increased or maximized. As a result, the heat energy transfer between the heat source(s) and the heat sink(s) thermally coupled to the plates 102 - 104 can be much higher. Here, it should be noted that the thermal insulation material 106 can serve to thermally insulate the plates 102 - 104 from each other, such as when the thermal insulation material 106 has a thickness sufficient to produce a high thermal resistance. Thereby, heat energy flows directly between the plates 102 - 104 themselves and does not inadvertently short-circuit (either completely or to some extent) the intended function of the actuator with heat, but mainly travels between the plates 102 - 104 through the piston.

[0022] In this way, the thermal actuator switch 100 uses the phase change material 112 to passively control the heat transfer between the heat source(s) and the heat sink(s) that are thermally coupled to the plates 102 - 104. That is, the thermal actuator switch 100 can operate the piston plate 110 between two positions by using the volume expansion and volume contraction characteristics of the phase change material 112, thereby increasing and decreasing the surface contact area between the upper plate 102 and the piston plate 110 based on temperature. In some cases, the movement of the piston plate 110 may be performed in a completely passive manner, meaning that it is moved by the expansion and contraction of the phase change material 112 based on the heat energy received from the heat source(s) and not received by the heat sink(s). In some cases, no additional heater or cooler may be required to cause the expansion or contraction of the phase change material 112 (although this may not be the case in other embodiments).

[0023] Furthermore, here, the thermal actuator switch 100 may enable rigid contact between the heat source(s) and the heat sink(s). In some cases, the thermal actuator switch 100 enables rigid contact over the entire volume between the heat source(s) and the heat sink(s). This is because the plates 102 - 104 can be fixedly coupled to each other, and in some cases (such as for mechanical coupling), a stable surface can be increased along the upper surface of the upper plate 102 and along the bottom surface of the lower plate 104. Additionally, depending on the design of the thermal actuator switch 100, the thermal actuator switch 100 can provide thermally adjustable separation in the "through" direction (the vertical direction in FIGS. 1 - 4) and thermally adjustable separation in the "in-plane" direction (the horizontal direction in FIGS. 1 - 4).

[0024] Note that the heat source(s) and heat sink(s) used with the thermal actuator switch 100 may represent any suitable source(s) and destination(s) of thermal energy. For example, in a "low temperature environment" scenario, at least one heater may be used to heat one or more devices. In this scenario, the one or more devices being heated can represent the heat source, and at least one cold plate can be provided to represent the heat sink. Here, when excess thermal energy is imparted to one or more devices by the heater, one or more thermal actuator switches 100 can be used to remove the excess thermal energy from the one or more devices to the cold plate(s). In this example, the limited heater power may be conserved while increasing or maximizing the structural support for one or more devices (since the thermal actuator switches 100 can remain mainly in the open position shown in FIGS. 1 and 2). Here, the one or more devices may represent any suitable device(s) suitable for being heated, such as one or more batteries, processors, or other devices used in a low temperature environment (e.g., space applications). In some cases, one or more thermal actuator switches 100 can be opened and closed to help keep one or more devices between the upper and lower limits of the target operating temperature or within the target operating temperature range.

[0025] In the "high temperature environment" scenario, one or more devices may generate heat, and at least one cold plate can be used to receive thermal energy from one or more devices and cool one or more devices. In this scenario, one or more devices can represent heat sources, and at least one cold plate can represent a heat sink. Here, one or more thermal actuator switches 100 can be used to facilitate the transfer of thermal energy between one or more devices and the cold plate(s). In this example, maximum dissipation of thermal energy to the heat sink can be achieved, such as when the thermal actuator switches 100 mainly remain in the closed position shown in FIGS. 3 and 4. Here, one or more devices may represent any device(s) suitable for being cooled, such as one or more batteries, processors, or other devices. Again, in some cases, one or more thermal actuator switches 100 can be opened and closed to maintain one or more devices between the upper and lower limits of the target operating temperature or within the target operating temperature range.

[0026] Here, when the phase change material 112 contracts, the piston may require external assistance to separate the piston plate 110 from the upper plate 102. Here, any return mechanism suitable for providing the force required to separate the piston plate 110 from the upper plate 102 can be used. In some embodiments, for example, one or more springs 114 can be positioned between the piston plate 110 and the upper plate 102. In this example, the upper plate 102 includes a recess 116, although the recess may also be included in or alternatively included in the piston plate 110. As shown in FIGS. 1 and 2, when the phase change material 112 contracts, the spring 114 can help push the piston plate 110 away from the upper plate 102. As shown in FIGS. 3 and 4, when the phase change material 112 expands, it can overcome the spring force of the spring 114 and compress the spring 114, thereby enabling the piston plate 110 to contact the upper plate 102.

[0027] Note that the use of one or more springs 114 represents an example of a return mechanism for moving the piston plate 110 away from the upper plate 102. However, other return mechanisms are possible. For example, at least one magnet 118 may be positioned within or on the piston plate 110, and the at least one magnet 118 may be attracted to one or more magnets 120 within or on the lower plate 104 and / or repelled by one or more magnets 122 within or on the upper plate 102. In these embodiments, any suitable number of magnets may be used at any suitable location within the piston plate 110 and one or more of the plates 102-104. The use of magnetism may present some reliability improvements over the use of springs 114 (e.g., potential hysteresis associated with mechanical springs), although the actual reliability of springs and magnets can vary depending on the implementation.

[0028] One or more examples of the thermal actuator switch 100 may be found in a number of applications. For example, the thermal actuator switch 100 may be used in a number of devices where a battery, processor, or other component needs to be maintained at a predetermined temperature or within a predetermined temperature range. As a specific example, the thermal actuator switch 100 may be used in satellites, drones, and other systems where it is necessary or desirable to limit power consumption and a passive design can improve long-term reliability. As another specific example, the thermal actuator switch 100 may be used in a manufacturing system or manufacturing messaging system, such as an additive manufacturing system. Generally, the present disclosure is not limited to any particular use of the thermal actuator switch 100, and the present disclosure is not limited to any particular type of heat source(s) and heat sink(s) used with the thermal actuator switch 100. manufacturing: additive manufacturing: laminated manufacturing) system. Generally, the present disclosure is not limited to any particular use of the thermal actuator switch 100, and the present disclosure is not limited to any particular type of heat source(s) and heat sink(s) used with the thermal actuator switch 100.

[0029] Figures 5 and 6 show another exemplary PCM-based conductive thermal actuator switch 500 according to the present disclosure. Thermal actuator switch 500 has many of the same design characteristics (as well as the same advantages, benefits, and uses) as the thermal actuator switch 100 described above. For the sake of brevity, only some of these design characteristics will be described below, but the various design characteristics, advantages, benefits, and uses of the thermal actuator switch 100 described above are equally applicable to the thermal actuator switch 500.

[0030] As shown in FIGS. 5 and 6, thermal actuator switch 500 includes an upper plate 502 and a lower plate 504, which may optionally be separated by a thermal insulation material 506. A piston formed by a piston base 508 and a piston plate 510 is positioned between plates 502 and 504 and is movable. For example, upper plate 502 may include a recess formed between the side wall portions of plate 502, and at least a portion of piston base 508 is positioned within this recess and can be movable up and down. Similarly, lower plate 504 may include a recess formed between the side wall portions of plate 504, and at least a portion of piston plate 510 is positioned within that recess and can be movable up and down. In some cases, piston base 508 may take the form of an annular cylinder or other structure having an internal cavity. In this example, upper plate 502 itself defines an internal cavity, within which a phase change material 512 is positioned, and the internal cavity of upper plate 502 may or may not be present within the internal cavity of upper plate 502 (depending on the design of the piston). In this particular example, phase change material 512 is positioned between piston base 508 and a portion of upper plate 502. Thereby, phase change material 512 can contact a portion of upper plate 502, and upper plate 502 can prevent the upward movement of phase change material 512. Phase change material 512 represents at least one material that can expand and contract in an appropriate amount based on temperature.

[0031] In this example, a piston can be used to selectively form (or improve) and block (or reduce) the thermal connection between plates 502 and 504. More specifically, when the phase change material 512 is in the expanded state as shown in FIG. 5, the piston plate 510 is released from one or more flanges or other protrusions 524 of the lower plate 504, helping to reduce or decrease the thermal connection. When the phase change material 512 is in the contracted state as shown in FIG. 6, the piston plate 510 is pushed into one or more flanges or other protrusions 524 of the lower plate 504, helping to form or improve the thermal connection. However, it should be noted that the positions of the piston plate 510 and the flange(s) or other protrusion(s) 524 of the lower plate 504 can be reversed, such as when the piston plate 510 is positioned on top of the flange(s) or other protrusion(s) 524 of the lower plate 504. In that case, the expansion of the phase change material 512 can form / improve the thermal connection by pushing the piston plate 510 into the flange(s) or other protrusion(s) 524, and the contraction of the phase change material 512 can block / reduce the thermal connection by allowing the piston plate 510 to move away from the flange(s) or other protrusion(s) 524.

[0032] One or more springs 514 are used as a return mechanism to provide the force required to push the piston plate 510 into the flange or other protrusion 524 of the lower plate 504 (in the arrangement shown here), or to release the piston plate 510 from the flange or other protrusion 524 of the lower plate 504 (in an alternative arrangement where the piston plate 510 is above the flange or other protrusion 524). However, it should be noted that other return mechanisms, such as at least a portion of the magnets 118 - 122 described above, may be used for the thermal actuator switch 500. Although not shown here, recesses may be formed in the lower plate 504 for each spring 514 in a manner similar to the recess 116 described above.

[0033] One or more thermal straps 526 may optionally be positioned within the phase change material 512 and may extend from the upper plate 502 to the piston base 508. By using the thermal strap(s) 526 to assist in heating the phase change material 512 more rapidly in response to a temperature increase or cooling the phase change material 512 more rapidly in response to a temperature decrease, the phase change material 512 can be assisted in undergoing a phase change more rapidly. The thermal strap(s) 526 may allow for a small amount of heat energy transfer between the upper plate 502 and the piston base 508, although there may be little to no heat energy transfer between the plates 502 and 504 while the piston plate 510 is spaced from the flange or protrusion 524. Each thermal strap 526 may be formed from any suitable material(s), such as one or more metals, a pyrolytic graphite sheet, or other material(s) having a high thermal conductivity. Also, each thermal strap 526 may be formed in any suitable manner and may have any suitable size, shape, and dimensions. Additionally, any suitable number of thermal straps 526, including a single strap, may be used herein.

[0034] Figures 7 and 8 show yet another exemplary PCM-based conductive thermal actuator switch 700 according to the present disclosure. The thermal actuator switch 700 has many of the same design characteristics (as well as the same advantages, benefits, and uses) as the thermal actuator switches 100 and 500 described above. For the sake of brevity, only some of these design characteristics are described below, but the various design characteristics, advantages, benefits, and uses of the thermal actuator switches 100 and 500 described above are equally applicable to the thermal actuator switch 700.

[0035] As shown in FIGS. 7 and 8, the thermal actuator switch 700 includes an upper plate 702 and a lower plate 704, which may optionally be separated by a thermal insulation material 706. A piston formed by a piston base 708 and a piston plate 710 is positioned between the plates 702 and 704 and is movable. For example, the upper plate 702 may include a recess formed between the side wall portions of the plate 702, and at least a part of the piston base 708 is positioned within this recess and can be movable up and down. Similarly, the lower plate 704 may include a recess formed between the side wall portions of the plate 704, and at least a part of the piston plate 710 is positioned within that recess and can be movable up and down. In some cases, the piston base 708 may take the form of an annular cylinder or other structure having an internal cavity. In this example, the upper plate 702 itself defines an internal cavity within which a phase change material 712 is positioned, and the internal cavity of the upper plate 702 may or may not be present within the internal cavity of the upper plate 702 (depending on the piston design). In this particular example, the phase change material 712 is positioned between the piston base 708 and a part of the upper plate 702. Thereby, the phase change material 712 can contact a part of the upper plate 702, and the upper plate 702 can prevent the upward movement of the phase change material 712. The phase change material 712 represents at least one material that can expand and contract in an appropriate amount based on temperature.

[0036] In this example, a piston can be used to selectively form (or improve) and block (or reduce) the thermal connection between plates 702 and 704. More specifically, when the phase change material 712 is in an expanded state as shown in FIG. 7, the piston plate 710 is released from one or more flanges or other protrusions 724 of the lower plate 704, helping to reduce or decrease the thermal connection. When the phase change material 712 is in a contracted state as shown in FIG. 8, the piston plate 710 is pushed into one or more flanges or other protrusions 724 of the lower plate 704, helping to form or improve the thermal connection. However, it should be noted that the positions of the piston plate 710 and the flange(s) or other protrusion(s) 724 of the lower plate 704 can be reversed, such as when the piston plate 710 is positioned above the flange(s) or other protrusion(s) 724 of the lower plate 704. In that case, the expansion of the phase change material 712 can form / improve the thermal connection by pushing the piston plate 710 into the flange(s) or other protrusion(s) 724, and the contraction of the phase change material 712 can block / reduce the thermal connection by allowing the piston plate 710 to move away from the flange(s) or other protrusion(s) 724.

[0037] One or more springs 714 can be used as a return mechanism to provide the force necessary to push the piston plate 710 into the flange or other protrusion 724 of the lower plate 704 (in the arrangement shown here), or to release the piston plate 710 from the flange or other protrusion 724 of the lower plate 704 (in an alternative arrangement where the piston plate 710 is above the flange or other protrusion 724). However, it should be noted that other return mechanisms, such as at least a portion of the magnets 118-122 described above, can also be used for the thermal actuator switch 700. Although not shown here, recesses can be formed in the lower plate 704 for each spring 714 in a manner similar to the recess 116 described above.

[0038] One or more protrusions 726 of the upper plate 702 can extend into the internal cavity in which the phase change material 712 is positioned. Additionally or alternatively, one or more protrusions 728 of the piston base 708 can extend into the internal cavity in which the phase change material 712 is positioned. In some cases, both the protrusion 726 and the protrusion 728 can be used and arranged alternately in different lateral positions or used in other ways. Either or both of the protrusions 726 and 728 can be used to provide a larger surface area through which thermal energy can flow into and out of the phase change material 712, the upper plate 702, or the piston base 708. As a result, either or both of the protrusions 726 and 728 can be used to assist in heating the phase change material 712 more rapidly in response to a temperature increase or cooling the phase change material 712 more rapidly in response to a temperature decrease, thereby assisting the phase change material 712 to undergo a phase change more rapidly. Each of the protrusions 726 and 728 can be formed in any suitable manner and can have any suitable size, shape, and dimensions. Also here, any suitable number of protrusions 726 (including those without protrusions) and / or any suitable number of protrusions 728 (including those without protrusions) can be used.

[0039] Depending on the implementation, various types of phase change materials 112, 512, 712 can be used in thermal actuator switches 100, 500, 700. Examples of phase change materials that can be used include water, paraffin wax, hydrate salts, solder, or indium alloys. In some embodiments, the phase change material is selected such that the phase change material contracts at a lower temperature and expands at a higher temperature. Various forms of paraffin wax, hydrate salts, solder, and indium alloys are examples of phase change materials that behave in this manner. In other embodiments, the phase change material is selected such that the phase change material expands at a lower temperature and contracts at a higher temperature. Water is an example of a phase change material that behaves in this manner. Thus, the selection of the phase change material used can (at least partially) depend on (i) whether or not the thermal connection between the upper plate and the lower plate is formed or improved in response to the expansion or contraction of the phase change material, and (ii) whether or not the thermal connection between the upper plate and the lower plate is interrupted or reduced in response to the expansion or contraction of the phase change material.

[0040] Figures 1 to 8 show examples of the conductive thermal actuator switches 100, 500, 700 based on PCM, but various modifications may be made to Figures 1 to 8. For example, the sizes, shapes, and dimensions of each thermal actuator switch 100, 500, 700 and its components may vary as necessary or as desired. For example, the shape or aspect ratio of each piston may be optimized to achieve a desired balance between the amount of movement and the force. In some cases, the piston plates 110, 510, 710 may be kept as thin as possible so that the sides of the piston plates 110, 510, 710 do not contact the housing (mainly the upper or lower plate) of the thermal actuator switches 100, 500, 700. Also, a low thermal conductivity material may be positioned on or along the interface between the piston plates 110, 510, 710 and the upper or lower plate, which can increase the thermal resistance at those positions and reduce friction. Furthermore, various additional features may be used with the thermal actuator switches 100, 500, 700. As a specific example, one or more thermal interface materials may be used at the contact interfaces between the piston plates 110, 510, 710 and the upper and lower plates 102 - 104, 502 - 504, 702 - 704 to limit the thermal resistance. As another specific example, one or more thermal interface materials may be used at the contact interfaces between the thermal actuator switches 100, 500, 700 and the heat source(s) / heat sink(s) to limit the thermal resistance. As yet another specific example, thermal insulation may be used to help ensure that heat energy transfer occurs substantially through the pistons of the thermal actuator switches 100, 500, 700. In addition, multiple phase change materials 112, 512, 712 may be used in the thermal actuator switches 100, 500, 700, such as when the housing of the thermal actuator switches 100, 500, 700 can handle an appropriate stress near the transition temperature of the phase change materials 112, 512, 712.

[0041] The terms "upper" and "lower" are used to describe the plates 102-104, 502-504, 702-704 of thermal actuator switches 100, 500, 700, but it should be noted that this does not impose any structural or usage limitations on the thermal actuator switches 100, 500, 700. The terms "upper" and "lower" are used merely for convenience to refer to the position of the plates as specifically shown in the figures. Each of the thermal actuator switches 100, 500, 700 can be implemented or used in the reverse manner, horizontally, or in any other suitable orientation or arrangement, as required or desired.

[0042] Also note that any combination of the features shown in FIGS. 1-8 can be used in a single thermal actuator switch, regardless of whether that specific combination of features is shown in the figures or described above. Thus, for example, thermal actuator switch 100 may include a plate 102 or 104 having one or more flanges or other protrusions 524 or 724. Also, thermal actuator switches 100 and 700 may include a thermal strap 526, or thermal actuator switches 100 and 500 may include one or both of protrusions 726 and 728. Additionally, each thermal actuator switch can include any suitable number of each component shown in the figure(s).

[0043] FIG. 9 shows an exemplary first stacked arrangement 900 of a PCM-based conductive thermal actuator switch according to the present disclosure. As shown in FIG. 9, the stacked arrangement 900 includes a plurality of thermal actuator switches 902-904 thermally (and optionally mechanically) coupled in series. Each of the thermal actuator switches 902-904 can represent a distinct example of the thermal actuator switches 100, 500, or 700 described above, but each of the thermal actuator switches 902-904 can have any other suitable design in which a piston moves based on the expansion / contraction of a phase change material.

[0044] In some embodiments, the thermal actuator switches 902-904 include different phase change materials 112, 512, 712. For example, the thermal actuator switch 902 may have one or more phase change materials 112, 512, 712 with a low transition temperature, and the thermal actuator switch 904 may have one or more phase change materials 112, 512, 712 with a high transition temperature (or vice versa). In some cases, the lower transition temperature may be about 5°C or within a range including 5°C, and the higher transition temperature may be about 25°C or within a range including 25°C. Thus, this stacked arrangement 900 allows one of the thermal actuator switches 902-904 to close at a lower temperature (e.g., by expanding or contracting its phase change materials 112, 512, 712), and both of the thermal actuator switches 902-904 to close at a higher temperature. As a result, this helps to provide thermally adjustable thermal isolation in the "through" direction.

[0045] Similar to the thermal actuator switches 100, 500, or 700 described above, the stacked arrangement 900 enables passive control of heat energy transfer between at least one heat source 906 and at least one heat sink 908. The at least one heat source 906 represents any suitable heat energy source, and the at least one heat sink 908 represents any suitable destination for heat energy. Note that the at least one heat source 906 may optionally include or be associated with one or more heaters 910 in a low temperature environment where one or more heaters 910 may be required to heat one or more devices.

[0046] FIG. 10 shows an exemplary second stacked arrangement 1000 of a PCM-based conductive thermal actuator switch according to the present disclosure. The stacked arrangement 1000 here is similar to the stacked arrangement 900. As shown in FIG. 10, the stacked arrangement 1000 includes a plurality of thermal actuator switches 1002-1004 thermally coupled in series. Each of the thermal actuator switches 1002-1004 may represent a distinct example of the thermal actuator switches 100, 500, or 700 described above, but each of the thermal actuator switches 1002-1004 may have any other suitable design in which a piston moves based on the expansion / contraction of a phase change material.

[0047] In some embodiments, the thermal actuator switches 1002-1004 include different phase change materials 112, 512, 712. For example, the thermal actuator switch 1002 may have one or more phase change materials 112, 512, 712 with a low transition temperature, and the thermal actuator switch 1004 may have one or more phase change materials 112, 512, 712 with a high transition temperature (or vice versa). In some cases, the lower transition temperature may be about 5° C. or within a range including 5° C., and the higher transition temperature may be about 25° C. or within a range including 25° C. Thus, this stacked arrangement 1000 allows one of the thermal actuator switches 1002-1004 to close at a lower temperature (e.g., by expanding or contracting its phase change material 112, 512, 712) and both of the thermal actuator switches 1002-1004 to close at a higher temperature. As a result, this helps to provide thermally adjustable thermal isolation in the "through" direction.

[0048] In this configuration, the stacked arrangement 1000 is not physically positioned between at least one heat source 1006 and at least one heat sink 1008. Instead, the stacked arrangement 1000 is positioned elsewhere and uses heat conductors 1010 and 1012 to thermally couple the thermal actuator switches 1002 and 1004 to the heat source(s) 1006 and the heat sink(s) 1008. Each of the heat conductors 1010 and 1012 represents any suitable structure configured to transfer thermal energy between the thermal actuator switch. Substantially here, the heat conductors 1010 and 1012 function as heat straps for supplying thermal energy between the stacked arrangement 1000. Each of the heat conductors 1010 and 1012 may be formed using any suitable material(s), such as one or more metals, pyrolytic graphite sheets, or other material(s) having a high thermal conductivity. Each of the heat conductors 1010 and 1012 may be formed in any suitable manner. Additionally, each of the heat conductors 1010 and 1012 may have any suitable size, shape, and dimensions.

[0049] The thermal insulation material 1014 may optionally be positioned between the heat conductors 1010 and 1012 or a part of the heat conductors 1010 and 1012. The thermal insulation material 1014 can serve to reduce the heat conduction between the heat conductors 1010 and 1012 in order to suppress direct heat energy transfer between the heat conductors 1010 and 1012. The thermal insulation material 1014 may be formed from any suitable material(s), such as a thermally insulating epoxy or other material(s) used to hold the heat conductors 1010 and 1012, or a glass fiber sheet or other structure(s) positioned between the heat conductors 1010 and 1012. Also, the thermal insulation material 1014 may be formed by any suitable method. Additionally, the thermal insulation material 1014 can have any suitable size, shape, and dimensions. Note that if the heat conductors 1010 and 1012 extend beyond the thermal insulation material 1014 (as shown in the embodiment of FIG. 10), it should be noted that the heat conductors 1010 and 1012 may be strengthened as necessary or desired. For example, at least a portion of the heat conductors 1010 and 1012 that extend beyond the thermal insulation material 1014 may be formed using a pyrolytic graphite sheet or other material(s) and may be strengthened using Kapton® or other strengthening material(s).

[0050] In some embodiments, each of the stacked arrangements 900, 1000 of the PCM-based conductive thermal actuator switches may be implemented as follows. The thermal actuator switch can be placed closer to the heat sink, and when it operates (closes), heat energy transport by the switch becomes possible at a higher temperature. The thermal actuator switch can be placed closer to the heat source, and when it operates (closes), heat energy transport by the switch becomes possible at a lower temperature. This may be done to help prevent a thermal actuator switch with a higher operating temperature from "clamping" to a high ambient temperature at some point beyond the control of the overall system (since there may be no active cooling within the loop). Instead, a thermal actuator switch with a higher operating temperature can be clamped to a lower temperature that can be controlled (e.g., via a heater). In some cases, the way the two stacked switches open and close can be opposite to each other, such as when one switch has a phase change material that expands at a higher temperature and the other switch has a phase change material that contracts at a higher temperature. In certain embodiments, water can be used for one of the stacked switches because it tends to behave in a way opposite to many other phase change materials. However, note that the placement of the switches can be adjusted as needed or desired so that the desired operation of the switches is achieved.

[0051] Figures 9 and 10 show examples of the stacked arrangements 900, 1000 of the PCM-based conductive thermal actuator switches, but various changes can be made to Figures 9 and 10. For example, the stacked arrangement of the PCM-based conductive thermal actuator switches can be used in any suitable way. Also, the stacked arrangement of the PCM-based conductive thermal actuator switches may include more than two thermal actuator switches, and the thermal actuator switches may or may not include more than two phase change materials that expand / contract at different temperatures.

[0052] FIG. 11 shows an exemplary array 1100 of conductive thermal actuator switches based on PCM according to the present disclosure. As shown in FIG. 11, the array 1100 includes array elements, and each array element includes a thermal actuator switch 1102. As can be seen here, the thermal actuator switches 1102 are arranged in parallel, which means that the thermal actuator switches 1102 can be used independently to transfer thermal energy between at least one heat source and at least one heat sink. Each thermal actuator switch 1102 may represent a distinct example of the thermal actuator switches 100, 500, or 700 described above, but each thermal actuator switch 1102 may have any other suitable design in which the piston moves based on the expansion / contraction of the phase change material. In some embodiments, each array element of the array 1100 shown in FIG. 11 may include a stacked arrangement of multiple thermal actuator switches 1102, such as the arrangement shown in FIG. 9.

[0053] The use of the parallel arrangement of the thermal actuator switches 1102 can be useful for controlling the temperature of one or more devices and controlling the temperature gradient across one or more devices. For example, one or more devices can be maintained within a desired temperature range and have a desired temperature gradient (or a temperature gradient within a desired temperature gradient range) across one or more surfaces of the device(s). In this example, the thermal actuator switches 1102 are generally placed in the solder, and these solders are arranged in a staggered pattern with respect to each other (meaning that each thermal actuator switch 1102 is not aligned with the thermal actuator switches 1102 in adjacent solders). This type of arrangement may be useful in assisting in reducing or minimizing lateral heat transfer between the thermal actuator switches 1102. However, aligned thermal actuator switches 1102 may also be used.

[0054] Note that the size of the thermal actuator switch 1102 shown here can vary, as can the spacing between the thermal actuator switches 1102 of each row and the spacing between the thermal actuator switches 1102 of different rows. In some cases, the spacing between the thermal actuator switches 1102 can be at least partially filled by one or more thermal insulation materials, etc., and these one or more thermal insulation materials assist in substantially restricting heat conduction at the location where the thermal actuator switches 1102 are positioned.

[0055] FIG. 11 shows an example of an array 1100 of conductive thermal actuator switches based on PCM, but various modifications can be made to FIG. 11. For example, the parallel arrangement of the conductive thermal actuator switches based on PCM can be used in any suitable manner. Also, the array 1100 of conductive thermal actuator switches based on PCM may include any suitable number of thermal actuator switches 1102 in any suitable layout.

[0056] The following describes exemplary embodiments of the present disclosure for implementing or related to conductive thermal actuator switches based on PCM. However, other embodiments can be used in accordance with the teachings of the present disclosure.

[0057] In the first embodiment, the device includes a plurality of thermal actuator switches configured to control the transfer of thermal energy through the device, and the thermal actuator switches are arranged in a stacked configuration. Each thermal actuator switch includes a first plate, a second plate, and a piston movable between the first plate and the second plate. Each thermal actuator switch also includes a phase change material configured to (i) expand and move the surface of the piston to a first position and (ii) contract and move the surface of the piston to a second position. The surface of the piston is in thermal contact with the first plate and, when in one of the first position and the second position, increases the transfer of thermal energy between the first plate and the second plate. The surface of the piston is spaced from the first plate and, when in the other of the first position and the second position, decreases the transfer of thermal energy between the first plate and the second plate. Different thermal actuator switches include different phase change materials that expand or contract at different temperatures.

[0058] In the second embodiment, the system includes at least one heat source and at least one heat sink. The system also includes a plurality of thermal actuator switches configured to control the transfer of thermal energy between the at least one heat source and the at least one heat sink, and the thermal actuator switches are arranged in a stacked configuration. Each thermal actuator switch includes a first plate and a second plate, and a piston movable between the first plate and the second plate. Each thermal actuator switch also includes a phase change material configured to (i) expand and move the surface of the piston to a first position and (ii) contract and move the surface of the piston to a second position. The surface of the piston is in thermal contact with the first plate and, when in one of the first position and the second position, increases the transfer of thermal energy between the first plate and the second plate. The surface of the piston is spaced from the first plate and, when in the other of the first position and the second position, decreases the transfer of thermal energy between the first plate and the second plate. Different thermal actuator switches include different phase change materials that expand or contract at different temperatures.

[0059] In a third aspect, the method includes receiving thermal energy from at least one heat source with a plurality of thermal actuator switches, the thermal actuator switches being arranged in a stacked configuration. The method also includes using the thermal actuator switches to control the transfer of thermal energy between at least one heat source and at least one heat sink. Each thermal actuator switch includes a first plate, a second plate, and a piston movable between the first plate and the second plate. Each thermal actuator switch also includes a phase change material configured to (i) expand to move the surface of the piston to a first position and (ii) contract to move the surface of the piston to a second position. The surface of the piston is in thermal contact with the first plate and, when in one of the first position and the second position, increases the transfer of thermal energy between the first plate and the second plate. The surface of the piston is spaced from the first plate and, when in the other of the first position and the second position, decreases the transfer of thermal energy between the first plate and the second plate. Different thermal actuator switches include different phase change materials that expand or contract at different temperatures.

[0060] Any single one or any suitable combination of the following features may be used with the first, second, or third embodiment. Each thermal actuator switch may include a return portion configured to move the piston when the phase change material contracts. The return portion of each thermal actuator switch may include one or more springs or magnets. The thermal actuator switch may include first and second thermal actuator switches, the first and second thermal actuator switches may each include first and second phase change materials, respectively, and the first phase change material may expand or contract at a different temperature than the second phase change material. The array may include a plurality of array elements, and each array element may include two or more thermal actuator switches in a stacked configuration. A plurality of heat straps may transport thermal energy between the thermal actuator switches.

[0061] It may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The terms "include" and "comprise," and derivatives thereof, mean including without limitation. The term "or" is inclusive and means and / or. The phrase "associated with," and derivatives thereof, may mean including, included within, interconnected with, containing, contained within, connected to or with, coupled to or with, capable of communicating with, cooperating with, interleaved with, juxtaposed with, nearest to, bound to or with, having, having the properties of, related to or with, etc. The phrase "at least one of" when used with a list of items means that different combinations of one or more of the listed items may be used and only one item in the list may be required. For example, "at least one of A, B, and C" includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C.

[0062] The description in this disclosure should not be read as implicitly suggesting that any particular element, step, or function is an essential or critical element that must be included within the scope of the claims. The scope of the patent subject matter is defined only by the allowed claims. Further, no claim invokes 35 U.S.C. § 112(f) with respect to either the appended claims or elements of the claims, unless the exact phrase "means for" or "step for" is expressly used in a particular claim and is followed by a participle phrase that recites a function. The use of terms such as "mechanism," "module," "device," "unit," "component," "element," "member," "apparatus," "machine," "system," "processor," or "controller" in a claim is understood (but not limited to) to refer to structures known to those of ordinary skill in the art that are further modified or enhanced by the characteristics of the claim itself and is intended to refer to those and not to invoke 35 U.S.C. § 112(f).

[0063] Although the present disclosure has described specific embodiments and generally related methods, alternative and substitute forms of these embodiments and methods will be apparent to those of ordinary skill in the art. Accordingly, the foregoing description of the exemplary embodiments does not define or constrain the present disclosure. Other changes, substitutions, and alternatives are possible without departing from the spirit and scope of the present disclosure as defined by the following claims.

Claims

1. An apparatus comprising a plurality of thermal actuator switches, wherein the thermal actuator switches are configured to control the transfer of thermal energy through the apparatus, are arranged in a stacked configuration, each thermal actuator switch comprising a first plate and a second plate, a piston movable between the first plate and the second plate, and a phase change material configured to (i) expand to move the surface of the piston to a first position and (ii) contract to move the surface of the piston to a second position, the surface of the piston being thermally in contact with the first plate and configured to increase the transfer of thermal energy between the first plate and the second plate, and the surface of the piston also being spaced from the first plate and configured to decrease the transfer of thermal energy between the first plate and the second plate, the phase change material, wherein different ones of the thermal actuator switches include different phase change materials that expand or contract at different temperatures, apparatus.

2. The apparatus of claim 1, wherein each thermal actuator switch further comprises a return portion configured to move the piston when the phase change material contracts.

3. The apparatus of claim 2, wherein the return portion of each thermal actuator switch includes one or more springs.

4. The apparatus of claim 2, wherein the return portion of each thermal actuator switch includes a plurality of magnets.

5. The apparatus of claim 1, wherein the thermal actuator switches include a first thermal actuator switch and a second thermal actuator switch, the first thermal actuator switch and the second thermal actuator switch each including a first phase change material and a second phase change material, respectively, the first phase change material being configured to expand or contract at a different temperature than the second phase change material.

6. An array comprising a plurality of array elements, each array element including two or more of the thermal actuator switches within the stacked configuration, the apparatus of claim 1.

7. The apparatus of claim 1, further comprising a plurality of heat straps configured to transport thermal energy between the thermal actuator switches.

8. At least one heat source, ​ At least one heat sink, and a plurality of thermal actuator switches configured to control the transfer of thermal energy between the at least one heat source and the at least one heat sink, a system comprising: the thermal actuator switches are arranged in a stacked configuration, each thermal actuator switch includes a first plate and a second plate, a piston movable between the first plate and the second plate, and a phase change material configured to (i) expand to move the surface of the piston to a first position and (ii) contract to move the surface of the piston to a second position, the surface of the piston being thermally in contact with the first plate and configured to increase the transfer of thermal energy between the first plate and the second plate, the surface of the piston also being spaced from the first plate and configured to decrease the transfer of thermal energy between the first plate and the second plate, the phase change material, wherein the different thermal actuator switches include different phase change materials that expand or contract at different temperatures, a system.

9. Each thermal actuator switch further includes a return portion configured to move the piston when the phase change material contracts, according to the system of claim 8.

10. The return portion of each thermal actuator switch includes one or more springs, according to the system of claim 9.

11. The return portion of each thermal actuator switch includes a plurality of magnets, according to the system of claim 9.

12. The thermal actuator switches include a first thermal actuator switch and a second thermal actuator switch, the first thermal actuator switch and the second thermal actuator switch each include a first phase change material and a second phase change material, respectively, the first phase change material is configured to expand or contract at a different temperature than the second phase change material, according to the system of claim 8.

13. The array includes a plurality of array elements, each array element includes two or more of the thermal actuator switches within the stacked configuration, according to the system of claim 8.

14. ​ The system according to claim 8, further comprising a plurality of heat straps configured to transport thermal energy between (i) the at least one heat source and the at least one heat sink and (ii) the thermal actuator switch.

15. Receiving thermal energy from at least one heat source by a plurality of thermal actuator switches, wherein the thermal actuator switches are arranged in a stacked configuration, Using the thermal actuator switch to control the transfer of the thermal energy between the at least one heat source and the at least one heat sink, A method comprising: Each thermal actuator switch comprises A first plate and a second plate, A piston movable between the first plate and the second plate, and A phase change material configured to (i) expand and move the surface of the piston to a first position and (ii) contract and move the surface of the piston to a second position, wherein the surface of the piston is in thermal contact with the first plate and configured to increase the thermal energy transfer between the first plate and the second plate, and the surface of the piston is spaced from the first plate and configured to decrease the thermal energy transfer between the first plate and the second plate, the phase change material, Including The different thermal actuator switches include different phase change materials that expand or contract at different temperatures.

16. The method according to claim 15, further comprising, in each thermal actuator switch, using a return portion to move the piston when the phase change material contracts.

17. The return portion of each thermal actuator switch includes one or more springs or magnets. The method according to claim 16.

18. The thermal actuator switch includes a first thermal actuator switch and a second thermal actuator switch, The first thermal actuator switch and the second thermal actuator switch each include a first phase change material and a second phase change material, The first phase change material is configured to expand or contract at a different temperature than the second phase change material. The method according to claim 15.

19. The array includes a plurality of array elements, The method according to claim 15, wherein each array element includes two or more of the thermal actuator switches within the stacked configuration.

20. The method according to claim 15, further comprising transporting thermal energy between (i) the at least one heat source and the at least one heat sink and (ii) the thermal actuator switch using a plurality of heat straps.

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