THERMAL ACTUATOR

Disclosed is a thermal actuator that utilizes the dimensional change of a phase change media hermetically sealed within a shell. This thermal actuator may be utilized in a variety of environments where electric thermostatic actuators are impossible or impractical.

BACKGROUND OF THE INVENTION

In numerous applications control devices are required to switch between various states at given temperatures, or temperature ranges. These devices may be active or passive. An example of a passive low temperature device is an automotive thermostat, which typically operates below 130° C. These thermostats may utilize wax pellets whose composition is chosen for the temperature range to be served. Other passive devices may include bimetallic strips, whose temperature-affected shape change is utilized to facilitate a physical actuation.

These designs are typically only viable at low temperature, and currently, there are no passive thermostats capable of applying large mechanical forces with reliable operation at higher temperatures. Bimetallic thermostats are most often used with active electronic control where the bimetallic elements close contacts for an electric circuit. There is a need for a self-contained, mechanical thermostatic control device that is operable at higher temperatures and is capable of providing sufficient actuation force.

One embodiment that has been contemplated is disclosed in U.S. Nonprovisional patent application Ser. No. 13/801,734, entitled “High-Temperature Thermal Actuator Utilizing Phase Change Material” by Michael B. Riley et al., filed Mar. 13, 2013, the entire content of which is hereby specifically incorporated herein by reference for all it discloses and teaches.

SUMMARY OF THE INVENTION

An embodiment of the present invention may therefore comprise: a sealed volumetric confine comprising: an upper endplate orthogonal to an axial orientation; a lower endplate orthogonal to an axial orientation, approximately parallel to, and offset by, a distance from the upper endplate; at least one flexible support wall that is disposed in a circumferential orientation to engage the upper endplate and the lower endplate, thereby forming the sealed confine; and, a phase change media disposed within the confine, the phase change media that responds to a temperature change to exert dimensional force in the axial orientation upon a change of state, thereby changing the distance between the upper endplate and the lower endplate.

An embodiment of the present invention may also comprise: a method of affecting mechanical displacement with a thermal actuator comprising: providing a sealed volumetric confine comprising: an upper endplate orthogonal to an axial orientation; a lower endplate orthogonal to an axial orientation, approximately parallel to, and offset by, a distance from the upper endplate; at least one flexible support wall that is disposed in a circumferential orientation to engage the upper endplate and the lower endplate, thereby forming the sealed confine; providing a phase change media within the volume of the confine; heating or cooling the phase change media beyond a phase transition point thereby affecting a change in state of the phase change media by changing the temperature of the phase change media disposed within the confine thereby affecting a change in volume of the confine; and, creating a change in displacement between the upper endplate the lower endplate with the force exerted by the phase change media upon the change of state.

DETAILED DESCRIPTION OF THE INVENTION

While this invention is susceptible to embodiment in many different forms, it is shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not to be limited to the specific embodiments described.

FIG. 1is an embodiment of a simple cylindrical container assembly100for a high temperature thermal actuator of the type that was described in U.S. application number Ser. No. 13/801,734, entitled “High-Temperature Thermal Actuator Utilizing Phase Change Material”, filed Mar. 13, 2013, the entire disclosure of which is hereby specifically incorporated by reference for all that it discloses and teaches. The exemplary embodiment of container100depicted inFIG. 1provides an enclosure that deforms along axis of deformation108in response to the dimensional change of a phase change media (not shown), hermetically sealed within a cylindrical support wall106encased with disks (upper endplate102and lower endplate104) in this embodiment. The upper endplates102and104may be welded, brazed, glued, press fit, or any other manner of joining that may facilitate a hermetic seal.

The functional temperature range for the embodied design may be within 200° C. to 1000° C. range, with volume and displacement change and be tunable to allow accurate temperature actuation by an appropriate selection of phase change medium. The system, as disclosed, is capable of providing large actuation forces with a long life cycle at relatively low cost.

Specific usage constraints are easily addressed with the aforementioned system. In various applications, such as hot or cold climates/environments, the activation (phase change) temperatures may be shifted to an optimal point by varying the formulation, concentration and geometry of the phase change media. This provides a great advantage over conventional low-temperature thermostatic valves that are driven by bimetallic elements, low temperature paraffin filled pistons or thermocouples.

In this embodiment, for a particular diameter, the height of the cylindrical wall206defines the enclosed volume of phase change material. Different applications with different thermal requirements, and therefore, different volume expansions lead to customization of the tube height. This customization affects the dimension of only one part for each diameter, thus providing a simple manner in which to execute variations in expansion characteristics.

FIG. 3is another exemplary embodiment of a cylindrical container300for a high-temperature thermal actuator.FIG. 3exemplifies a container300that can be filled with a phase change media (not shown), disposed within the sealed confines, and acting to exert dimensional force in at least one direction in response to a temperature change that causes the media to undergo a change in phase. This change in phase may be solid-to-liquid, liquid-to-solid, liquid-to-gas, solid-to-gas or a change in the crystalline arrangement within the material that causes a volumetric or dimensional change in the material in response to a change in temperature that is beyond thermal expansion. The module300in this example consists of one or more essentially corrugated endplates (metal disks)302and304and a cylindrical support wall306. The corrugated metal disks are opposing sides of an envelope, the volume of which is defined by the radius of the disk and the spacing, which is determined in this example by the cylindrical support wall306. This may be welded, brazed, glued, press fit, or any other manner of joining that may facilitate a hermetic seal of the phase change media chamber300. The corrugations enable distribution of stresses across multiple bends, increasing overall displacement of the opposing centers of the endplates302and304, while remaining at stress levels below the point of permanent deformation.

FIG. 4is a lateral cross-section of a container such as that which was disclosed as container300inFIG. 3for a thermal expansion module for a high-temperature thermal actuator. The corrugated upper endplate402has concentric corrugations that are mirrored on the corrugated lower endplate404. The volume of phase change media50may be varied to achieve the desired displacement of the centers of plates402and404towards or away from each other primarily via the height of cylindrical support wall406. Translation of this particular displacement would be acting along the axis of deformation408.

FIG. 5illustrates yet another embodiment of a container such as that which was disclosed as container300inFIG. 3. In this case, the concentric corrugations of upper endplate502and lower endplate504are offset to “nest” into one another. This geometry allows for a smaller contained volume if desired. In addition, there is now a smaller distance from the surface of container500to any location within the phase change media50, as compared to the geometry of corrugated endplates402and404inFIG. 4for the same separation of the flat surfaces along the axes of deformation408and508. This tighter spacing would facilitate heat transfer into and out of the phase change media50.

Inorganic salt combinations, as well as additional mentioned phase change material (PCM) examples, may provide PCM's that exhibit the property that their volume increases with the transition from solid to liquid phase. Unary (single component) PCM's make the volume change at a fixed temperature, but PCM mixtures and alloys may change volume over a broader temperature range. The volume change realized upon melting provides application as a thermostatic actuator at temperatures and/or forces that are impossible for wax pellet and passive bimetallic element thermostats. Specifically tailored PCM mixtures make it possible to design a range of thermostats that will open progressively over temperature ranges that may be tailored within certain constraints. Specific materials and mixtures may be used to achieve desired application-specific temperature activation ranges, these may include but are not limited to: inorganic salts; metals; non-metals; mixtures of metals and non-metals; or any combination thereof.

Total deflection experienced by the actuator is constrained by the need to keep stresses within acceptable limits, and compatibility between the PCM and the enclosure material is a consideration due to corrosion issues. In addition to a tailored temperature range, melting PCM's may exert enormous pressures due to the incompressibility of liquid, thereby mitigating issues regarding the actuation force required to displace an actuator.

If a PCM solidifies with voids when pressure inside the container is lower than the external pressure, a spring-loaded mechanism may be applied to avoid the formation of vacuum voids. Thus, the phase change media chamber is consistently constrained to a minimum volume.

The advantages of PCM's, and in particular inorganic salts, metals and nonmetals for use in the embodiments of the disclosed thermostatic actuator include; the ability to tailor the temperature range over which the thermostat opens/closes; negligible thermal growth from room temperature to actuation temperature relative to actuation displacement; displacement can be tailored by the combination of the fractional volume change of the PCM and the enclosed volume of PCM; forces generated during the phase change process are more than sufficient to move most spring return valves; the system operates in very diverse space requirements, temperature ranges and actuator displacements; and, mechanical amplification may be employed to achieve a broad range of actuation displacements.

FIG. 6Ais an exemplary embodiment of an exploded view of a bellows assembly600utilizing a combination of bellows and a cylindrical container for a high-temperature thermal actuator. The bellows upper endplate632is attached to bellows support wall636, making bellows upper portion620. The bellows lower support wall646is attached to flange648in the lower portion and is capped with lower endplate642at the upper end, giving a geometry that looks like a formal top hat, comprising the bellows lower portion622. The bellows upper and lower portions620and622are hermetically sealed with phase change material (not shown) filling the enclosed cavity between them. The diameter of lower support wall646will be sized to ensure appropriate guidance of bellows of the bellows support wall636as it lengthens and shortens, preventing undesirable buckling of the bellows.

FIG. 6Bis a cross sectional, side-view of an embodiment of a thermal expansion module650for the high-temperature thermal actuator of bellows assembly600shown inFIG. 6A. As detailed inFIG. 6B, a phase change media50is disposed within the sealed confines of a thermal expansion module650and acts to exert dimensional force in at least one direction along axis of deformation608in response to a temperature change that causes the media to undergo dimensional change due to a change in phase. The shape and height of lower support wall646relative to bellows support wall636is designed to accommodate the required volume change of phase change media50with the desired displacement of upper endplate632and the upper surface of the lower endplate642, thereby ensuring that stresses in the corrugations of bellows support wall636are within acceptable limits. The diameter of lower support wall646is sized to ensure appropriate guidance of bellows support wall636as it lengthens and shortens, preventing undesirable buckling of the bellows.

Upper endplate632and lower endplate642at the top of lower support wall608are the surfaces that will transfer longitudinal displacement of bellows assembly650to an external mechanism benefitting from the displacement within the sealed confine which is in the shape of a capped hollow cylinder.

Volume change of the phase change material50will result in a change in the height of upper endplate632, and a change in the distance between the surfaces of the lower endplate642and upper endplate632. The volume of phase change material between the surfaces of the lower endplate642and upper endplate632facilitates that the height change of the bellows support wall636will be less than the fraction volume change of phase change material50when changing state from solid to liquid or vice versa as phase change media may move from the annular cavity between walls636and646into the diskshaped cavity between endplates632and642or vice versa.

FIG. 7Ais another exemplary embodiment of an exploded view of a bellows assembly700utilizing a combination of internal bellows and an external cylindrical container for a high-temperature thermal actuator. The lower bellows support wall746is attached to flange748and an upper endplate732(obscured and shown in phantom lines) and these fit within upper cylindrical support wall736. The upper cylindrical support wall736and lower bellows support wall746are hermetically sealed with the flange748and filled with phase change material (not shown) filling the enclosed cavity. The diameter of the upper cylindrical support wall736will be sized to ensure appropriate guidance of the lower bellows support wall746as it lengthens and shortens, preventing undesirable buckling of the bellows.

FIG. 7Bis a cross sectional side-view of an embodiment of the thermal expansion module for a high-temperature thermal actuator bellows assembly750that was shown inFIG. 7A. As detailed inFIG. 7B, a phase change media50is disposed within the sealed confines of a thermal expansion module and acts to exert dimensional force in at least one direction along axis of deformation708in response to a temperature change that causes the media to undergo dimensional change due to a change in phase. The shape and height of upper cylindrical support wall736relative to lower bellows support wall746is designed to accommodate the required volume change of phase change media50with the desired displacement of upper endplate732and the lower endplate742capping lower bellows support wall746, thereby ensuring that stresses in the corrugations of lower bellows support wall746are within acceptable limits. The diameter of the upper cylindrical support wall736is sized to ensure appropriate guidance of lower bellows support wall746as it lengthens and shortens, preventing undesirable buckling of bellows.

Volume change of the phase change material50within the sealed confine, which is in the shape of a capped hollow cylinder, will result in a change in the height of lower bellows support wall746, and a change in the distance between the surfaces of the upper endplate732and the lower endplate742. The volume of phase change material between the surfaces of the upper endplate732and the lower endplate742at the upper cylindrical support wall736facilitates that the height change of the upper cylindrical support wall736will be less than fraction volume change of phase change material50when changing state from solid to liquid or vice versa, as phase change media may move from the annular cavity between walls736and746into the disk-shaped cavity between endplates732and742or vice versa.

FIG. 8Ais an exemplary embodiment of an exploded view of a multiple bellows assembly800utilizing a combination of internal and external concentric bellows for a high-temperature thermal actuator. In this embodiment, inner bellows support wall846and outer bellows support wall836are sealed on one end with an upper bellows sealing flange838and with a lower bellows sealing flange848on the opposing end. Displacement from the upper flange838and lower flange848is transferred via upper endplate832and lower endplate852or flange858. Upper endplate832and the flange858must be in contact with upper bellows sealing flange838and lower bellows sealing flange848respectively such that a change of volume within the flanged space exerts a longitudinal force on the sealing flanges838and848. The diameter of the cylindrical portion of the lower support wall856is sized to fit closely inside the inner bellows support wall846to provide appropriate guidance of the bellows assembly as it lengthens and shortens, preventing undesirable buckling of the multiple bellows assembly800.

FIG. 8Bis a cross sectional side-view of the embodiment of the multiple bellows assembly850shown inFIG. 8A. In this embodiment, a phase change media50is disposed within the sealed confines of a thermal expansion module and acts to exert dimensional force in at least one direction along axis of deformation808in response to a temperature change that causes the media to undergo dimensional change due to a change in phase. The volume of phase change media50contained between outer bellows support wall836and inner bellows support wall846, and between the upper bellows sealing flange838and the lower bellows sealing flange848is designed to deliver the desired height change of the bellows assembly850, ensuring that stresses in the corrugations of outer bellows support wall836and inner bellows support wall846are within acceptable limits. The diameter of lower support wall856is sized to ensure appropriate guidance of inner bellows support wall846(and by extension outer bellows support wall836) as it lengthens and shortens, thereby preventing undesirable buckling of these bellows836and846. The separation between the top of lower endplate852and upper endplate832may be varied continuously from almost touching to any distance desired. Such separation choice allows for a wide range of packaging options for a thermostatic actuator.

The change in volume fraction of the phase change material50, which is in the shape of a hollow cylinder, will result in the same fraction change in the length of the walls of outer bellows support wall836and the inner bellows support wall846, and by extension, the same change in the distance between the surfaces of the upper endplate832and the lower endplate852or the flange858.

In the case of the bellows configuration, it is also contemplated that the “top hat” geometry be designed to reduce displacement upon volume increase of the phase change material, as demonstrated inFIG. 9A. This geometry is similar to the embodiment ofFIG. 6A, with the exception that the lower flange948is wider than the flange648, and it mates to an external support wall966. The upper flange968is also connected to the external support wall966. The combination of the upper support wall966and the upper flange968look like an open cylinder with an annular cap on top.

FIG. 9Bis a cross-sectional, side view of the geometry shown inFIG. 9A, with the components in their assembled positions. A lower flange948joins a lower support wall946, a bellows support wall936and an external support wall966. Upon increase in volume of phase change media50, the distance between the lower flange948(and lower endplate942) and the upper endplate932will increase, but at the same time the distance between the upper endplate932and the upper flange968will decrease. A return spring970(not shown inFIG. 9A) may be used to ensure that the distance between the upper endplate932and the upper flange968will decrease as phase change media50reduces its volume.

An increase in distance between the upper endplate932and the lower endplate942(or lower flange948) will allow an actuation motion that pushes on the actuator. An increase in distance between the upper endplate932and the upper flange968will allow an actuation motion that pulls on the actuator.

FIG. 10is a cross-sectional, side view similar to the geometry shown inFIG. 9B, but with the external support wall1066attached to an upper endplate1032and to the lower flange1068. In this case, the lower flange1068will move towards both the lower endplate1042and the upper flange1048upon an increase in volume of phase change media50. This configuration allows the bellows assembly1050to be packaged in such a way that the connections points to an actuator (not shown), may fit within the envelope defined by a lower endplate1042, a lower support wall1046, a return spring1070and a lower flange1068.

Because of the aforementioned advantages, the disclosed embodiments lend to a wide variety of applications. For example, the volume of the phase change media can be tailored to produce a range of deflections (within the stress constraints) with the same outer shell, and the temperature range can be tailored by the selection of the phase change media. In this manner, bellows-style actuators for different temperatures and displacements can be made from relatively common components. Thus, a platform approach, with different diameters and/or lengths for different deflections and package constraints can be readily utilized. The aforementioned embodiments additionally allow for a high-temperature thermal actuator with the ability to control where deflection occurs on the surface of a shape, as well as in applications where the actuator deflection must be in a specific direction. Utilizing these embodiments, the location of the deflection can easily be controlled to manage stresses, which are easily held below any applicable limits, such as yield.