Induction heated thermal actuator

Abstract

A thermal actuator includes a piston slidingly disposed within a cylinder. The piston cooperates with the cylinder to define a cavity. The piston also includes a stem extending away from the cavity. A magnetic field generator selectively applies an alternating magnetic field to the cylinder and inductively heats a heating element mounted within the cavity. The cavity also includes a volume of phase change material that is melted by the heating element. The melted phase change material expands to drive the stem from a retracted position to an extended position.

Description

Background Technology

[0001] A thermal actuator (also known as a wax motor) is a linear actuator that converts heat into linear motion using the phase change properties of wax or other materials. When wax changes from a solid to a liquid, its volume increases by approximately 5% to 20%. In a thermal actuator, solid wax is enclosed in a cylinder with a piston. The wax is heated, causing it to melt and expand, thus applying force to the piston to produce linear motion. When the heat source is removed, the wax cools and solidifies. As the wax solidifies, it returns to its original volume, and the piston (usually assisted by a return spring) returns to its original position. High actuation force, simplicity, smooth extension, reliability, and cost make thermal actuators suitable for many different applications.

[0002] U.S. Patent No. 8,567,716, granted to Schmidt et al., is currently assigned to Safran Landing Systems Canada, the disclosure of which is expressly incorporated herein by reference, teaching the use of a thermal actuator to release a latching member of a landing gear locking mechanism. Referring to Figure 1, one such locking assembly 10 is configured for use with an aircraft landing gear and landing gear door. Figure 1 shows the orientation of the landing gear locking assembly 10 when mounted in the landing gear bay. In operation, to lock the landing gear (not shown) in the retracted position during flight, the landing gear retracts into a spring-loaded latch 16, which pivots upward (counterclockwise) about a first pivot point 18. To release the landing gear, a heating mechanism of the thermal actuator 11 heats wax contained within the thermal actuator. Heating the wax causes it to expand in volume, which in turn applies force to the piston 13 of the thermal actuator 11. This force drives piston 13 to extend and causes locking release mechanism 14 to pivot about second pivot point 12. As the wax cools (e.g., heat is dissipated from the wax via a heating mechanism), the volume of wax in the chamber decreases, allowing piston 13 to retract. Once the landing gear is released, tension from a resilient biasing device (e.g., spring 15) returns hook 16 to the unlocked state (and then hook 16 pivots clockwise about first pivot point 18). The landing gear can also be released by pulling a manual cable release device 17 connected to locking release mechanism 4 in the event of an electrical system failure.

[0003] One difficulty known with thermal actuators is transferring heat to melt the wax. Most known thermal actuators provide heat either through the actuator's cylinder or by immersing a heater into the wax. Heating the cylinder is inefficient because the external heater must conduct heat to the cylinder wall and then to the paraffin wax inside. Additionally, heating the cylinder causes it to expand, increasing the actuator's internal volume and reducing the potential work done by the wax expansion.

[0004] Immersing the heater in paraffin wax also presents challenges. The heater's electrical connections must extend through the cylinder, requiring the connection path to be sealed and withstand the actuation pressure generated by the molten wax. Furthermore, the assembly of the actuator, wax, and heater must be free of gas gaps. In some cases, it may not be possible to directly expose the heating element to the wax, which would delay heating time. Additionally, the heater may be located at a distance from the furthest point of the wax, resulting in the need for prolonged heating to melt all the wax.

[0005] Therefore, there is a need for an improved thermal actuator that provides a simple, reliable, and efficient configuration for melting wax within the actuator's cylinder. Summary of the Invention

[0006] A first embodiment of the disclosed thermal actuator includes a cylinder and a piston slidably disposed within the cylinder. The cylinder and piston define a cavity, and the piston includes a rod extending away from the cavity. A phase change material is disposed within the cavity. The thermal actuator also includes a magnetic field generator configured to provide an alternating magnetic field. A conductive element is mounted within the cavity and exposed to the alternating magnetic field. The conductive element heats the phase change material, causing it to expand and drive the rod from a retracted position to an extended position.

[0007] In one embodiment, the phase change material includes wax.

[0008] In one embodiment, the magnetic field generator includes a coil surrounding a cylinder.

[0009] In one embodiment, the coil includes conductive wires.

[0010] In one embodiment, the coil includes a conductive tube configured to receive a flow of cooling fluid.

[0011] In one embodiment, the magnetic field generator further includes a power supply and a controller, the power supply being operatively coupled to the coil, and the controller selectively controlling the supply of alternating current from the power supply to the coil.

[0012] In one embodiment, the controller is a switch.

[0013] In one embodiment, the controller is programmed to selectively control the supply of alternating current from the power source to the coil.

[0014] In one embodiment, the conductive element is a cylinder mounted on one of the piston and the cylinder.

[0015] In one embodiment, the cylinder includes a hollow interior in fluid communication with a cavity.

[0016] In one embodiment, the locking assembly for holding and releasing the landing gear component includes a thermal actuator, wherein when the lever is in an extended position, the lever of the thermal actuator releasably engages a locking release mechanism, and the engagement of the lever with the locking release mechanism releases the landing gear component.

[0017] Another embodiment of the thermal actuator includes a cylinder and a piston slidably disposed within the cylinder, wherein the piston and cylinder define a cavity with a variable volume. Wax is disposed within the cavity, and an induction heater is configured to selectively heat the wax from a solid state to a liquid state. The induction heater includes an alternating magnetic field generator and a conductive target mounted within the cylinder and functioning via an alternating magnetic field generated by the alternating magnetic field generator.

[0018] In one embodiment, the conductive target is a cylinder that extends longitudinally through a portion of the cylinder.

[0019] In one embodiment, the cylinder includes a hollow interior in fluid communication with a cavity.

[0020] In one embodiment, the alternating magnetic field generator includes a conductive coil surrounding at least a portion of the cylinder.

[0021] In one embodiment, the alternating magnetic field generator further includes a power supply configured to selectively supply alternating current to the conductive coil.

[0022] In one embodiment, the locking assembly for holding and releasing the landing gear component includes a thermal actuator, wherein when the lever is in an extended position, the lever releasably engages a locking release mechanism, and engagement of the lever with the locking release mechanism releases the landing gear component.

[0023] This summary is provided to introduce, in a simplified form, selected concepts that will be further described in the detailed embodiments described below. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter. Attached Figure Description

[0024] The foregoing aspects and the many incidental advantages of the disclosed subject matter will become more readily understood and appreciated by referring to the following detailed description in conjunction with the accompanying drawings, in which:

[0025] Figure 1 is a side view of a known landing gear locking assembly with a thermal actuator;

[0026] Figure 2 This is an isometric view of a first representative embodiment of a thermal actuator according to the present disclosure, wherein the thermal actuator is adapted for use with the locking assembly shown in FIG1;

[0027] Figure 3 yes Figure 2The image shows a cross-sectional view of the thermal actuator in its retracted position.

[0028] Figure 4 yes Figure 2 The diagram shows a cross-sectional view of the thermal actuator, with the thermal actuator in its extended position; and

[0029] Figure 5 This is a cross-sectional view of a second representative embodiment of the thermal actuator according to the present disclosure, wherein the thermal actuator is in the retracted position. Detailed Implementation

[0030] The specific embodiments described below with reference to the accompanying drawings (where like reference numerals denote like elements) are intended to describe various embodiments of the disclosed subject matter, and not to represent only embodiments. Each embodiment described in this disclosure is provided by way of example or illustration only and should not be construed as superior to or advantageous to other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the claimed subject matter to the precise forms disclosed.

[0031] Examples of induction-heated thermal actuators are described below based on the techniques and methods of this disclosure. In one embodiment, the thermal actuator includes a cylinder and a piston slidably disposed within the cylinder, the cylinder and piston together defining a cavity to be filled with a phase change material (e.g., wax). In some embodiments, a magnetic field generator is provided that selectively applies an alternating magnetic field to the cylinder. The alternating magnetic field inductively heats a heating element surrounded by the phase change material. The phase change material is melted by the heating element. As the phase change material melts, it expands to drive the piston in a positive linear motion.

[0032] Now for reference Figures 2 to 4 This illustrates a first representative embodiment of a thermal actuator 100 according to the present disclosure. The actuator 100 includes a cylinder 110, the first end 112 of which is coupled to an end cap 120. (As shown...) Figure 3 and Figure 4 As best shown, piston 130 is slidably disposed within cylinder 110. First side 132 of piston 130 mates with inner surface 116 of cylinder 110 and end cap 120 to define cavity 122.

[0033] Rod 136 extends from the second side 134 of piston 130 through a hole 118 formed in the second end 114 of cylinder 110. As piston 130 reciprocates slidably within cylinder 110, rod 136... Figure 3 The retraction position shown and Figure 4The rod reciprocates between the extended positions shown. In the illustrated embodiment, the rod 136 is shown to be integrally formed with the piston 130. However, it will be understood that alternative embodiments may exist in which the rod and piston are separate components, joined together mechanically or by other suitable means. In some embodiments, the cylinder 110, end cap 120, piston 130, and / or rod 136 may optionally be made of a non-conductive material to minimize heating of the induction coil 124 described below.

[0034] A compression spring 138 is disposed within the cylinder 110, between the second side 134 of the piston 130 and the second end 114 of the cylinder. When the rod 136 and piston 130 move from the retracted position to the extended position, the spring compresses and applies a biasing force that pushes the rod and piston back to the retracted position. When the rod 136 and piston 130 are in the retracted position, the spring 138 may be in a neutral state (i.e., uncompressed), or alternatively, the spring may be preloaded.

[0035] Still referencing Figure 3 and Figure 4 A heating element 142 (at least a portion of which is conductive) is disposed within the cavity 122. In the illustrated embodiment, the heating element 142 is an elongated cylinder threaded to a second side 134 of the piston 130 and has an axis substantially aligned with the axis of the cylinder. It should be understood that alternative embodiments of the heating element may exist, wherein the shape, position, mounting, and / or material differ from the illustrated embodiment, and these variations should be considered within the scope of this disclosure.

[0036] Cavity 122 also includes a volume of phase change material 140. In some embodiments, phase change material 140 is of the type that melts and solidifies over a narrow temperature range, and the volume of this type of phase change material also expands by approximately 5% to 20% when it changes from a solid to a liquid state (i.e., when the phase change material melts). When in a solid state, in some embodiments, this volume of phase change material 140 fills cavity 122 when rod 136 is in the retracted position. In some embodiments, phase change material 140 comprises wax, polymeric material, or other materials known to be used in thermal actuators. In one embodiment, the phase change material is paraffin wax. However, it should be understood that other waxes and other materials having similar thermal and phase change properties can be used.

[0037] The thermal actuator 100 also includes a magnetic field generator. In the illustrated embodiment, the magnetic field generator includes an induction coil 124 wound around the outer surface of the cylinder 110. The induction coil 124 is made of a conductive material, such as copper wire or Litz wire. The magnetic field generator also includes a power supply 150 and a controller 160, which is operatively coupled to the induction coil 124 and configured to selectively supply alternating current (AC) to the induction coil.

[0038] Controller 160 is configured to receive an activation signal from a sensor (not shown) or another input device, indicating that the actuator will be activated. Controller 160 is programmed to control power supply 150 to provide AC current to induction coil 124 in response to the actuation signal. Using the AC current supplied to induction coil 124, the induction coil generates a rapidly changing magnetic field concentrated along the center of the coil. Controller 160 is also configured to receive a deactivation signal from a sensor or another input device, indicating that the actuator will be deactivated. Controller 160 is also programmed to control power supply 150 to stop the flow of AC current to induction coil 124. It should be understood that the deactivation signal can be active (i.e., a positive signal) or passive (i.e., the actuation signal stops).

[0039] To activate actuator 100, an activation signal is sent to controller 160, which controls power supply 150 to provide AC current to induction coil 124. The AC current causes induction coil 124 to generate an electromagnetic field, the strength of which varies due to the constantly changing current in the induction coil. As the changing magnetic field penetrates heating element 142, the temperature of the heating element rises due to hysteresis and / or eddy current losses generated within it. The increased temperature of heating element 142, contained within cavity 122 and in thermal communication (e.g., indirect or direct contact) with phase change material 140, melts the phase change material. As phase change material 140 melts, its volume increases, and the expanding phase change material exerts an actuating force on piston 130. This actuating force drives piston 130 and thus moves rod 136 from... Figure 3 The retraction position is driven to Figure 4 The extended position.

[0040] To deactivate actuator 100, a deactivation signal is sent to controller 160, which controls power supply 150 to stop supplying AC current to induction coil 124. With the cessation of AC current, the presence of the electromagnetic field and induction heating of heating element 142 also cease. Without heat from heating element 142, phase change material 140 cools and solidifies. In some embodiments, a thermoelectric cooler, such as a Peltier cooler, or other known cooling configuration may be added to reduce the solidification time of phase change material 140. As phase change material 140 solidifies and returns to its original volume, piston 130 and rod 136 return to their original position with the assistance of force provided by spring 138. Figure 3 The retracted position.

[0041] refer to Figure 5 A second embodiment of the actuator 200 according to this disclosure is shown. The actuator 200 shown is similar to... Figure 2 and Figure 3The actuator 100 shown above, wherein the components of actuator 200 identified by reference numeral 2XX correspond to similar components of actuator 100 identified by reference numeral 1XX. For the sake of brevity, similar components will not be described further except to distinguish the various features of the described embodiments.

[0042] To efficiently facilitate heat transfer from heating element 242 to phase change material 240, it is beneficial to increase the surface area of ​​the heating element in contact with the phase change material. To provide this increased surface area, the heating element 242 is formed as a hollow cylinder. A portion of the phase change material 240 surrounds a portion of the heating element 242 and contacts and is heated by the outer surface of the heating element. Another portion of the phase change material 240 is contained within a cavity 244 of the heating element 242 and is heated by the inner surface of the heating element.

[0043] It will be appreciated that other heating element 242 configurations with increased surface area are possible. In one embodiment, the heating element has a square, star-shaped, or any other shaped cross-section. In other considered embodiments, the heating element 242 includes one or more fins extending outwardly from the heating element. The fins may extend circumferentially around the heating element 242 or longitudinally along the heating element 242. These features, individually or in combination with other features suitable for increasing heat transfer from the heating element 242 to the wax 240, are considered and should be considered within the scope of this disclosure.

[0044] While increasing heat transfer between heating element 242 and phase change material 240 is desirable, minimizing heating of cylinder 210 and piston 230 is preferred. As previously mentioned, in some embodiments, cylinder 210 and piston 230 are made of non-conductive materials to prevent or minimize inductive heating of induction coil 224. To further prevent heating of cylinder 210, a portion of the inner surface 216 of the cylinder may optionally be coated with a non-conductive heat-insulating coating 228, which not only prevents heating by induction heating but also provides insulation to prevent or reduce heat transfer from phase change material 240 to cylinder. Similarly, a gasket 246 or similar device may be located abutting against a first side 232 of piston 230 within cavity 222 to minimize heat transfer from phase change material 240 to piston. Similar to the coating 228 on the cylinder wall, in some embodiments, gasket 246 is formed of a non-conductive material (e.g., ceramic or thermoplastic) to prevent inductive heating of induction coil 224.

[0045] Still referencing Figure 5 The induction coil 224 shown is a tube formed of a conductive material (e.g., copper). This tube is capable of conducting AC current from a power source (not shown) to generate an alternating magnetic field. The tube also allows the flow of coolant 226, which minimizes the impact of I... 2Undesirable heating of cylinder 210 and coil 224 caused by R-loss. When actuator 200 is deactivated, the cooling fluid also enhances the cooling of wax 240, thereby reducing the time required for actuator 200 to return to its retracted position. It should be appreciated that other embodiments may include pipes that do not use cooling fluid in order to reduce weight. Other embodiments are also contemplated, wherein the induction coil 224 is a solid wire formed of a conductive material.

[0046] Figure 5 The actuator 200 also includes an end cap 220 located at a second end 214 (instead of the first end 212) of the cylinder 210. The cylinder 210 also includes a recess formed in its outer surface such that the induction coil 224 is flush with the outer surface of the actuator 200. In one considered embodiment, a protective sleeve is positioned around the recessed induction coil 224 such that the induction coil is not exposed to the operating environment of the actuator 200. These and other variations of the cylinder configuration should be considered, and they should be considered within the scope of this disclosure.

[0047] While many embodiments of the above-described technology may relate to controllers or describe methods performed by a programmable computer or controller, those skilled in the art will understand that the technology and methods can be practiced on computer / controller systems other than those shown and described above. In embodiments of this disclosure, the functionality of controller 160 and / or controller 160 can be implemented in software or hardware, or a combination of software and hardware. For example, in some embodiments, the technology may be embodied in a dedicated computer, application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), controller, or data processor specifically programmed, configured, or constructed to perform the functions described above.

[0048] In one embodiment, controller 160 may include a hardware circuit implementation (e.g., an implementation in analog circuitry, an implementation in digital circuitry, etc., and combinations thereof) for implementing the functions described herein. In another embodiment, controller 160 herein includes a combination of circuitry and a computer program product having software or firmware instructions stored on one or more computer-readable storage media, which work together to cause a device to perform one or more methods or techniques described herein.

[0049] In one embodiment, controller 160 may include one or more processors, memory, and I / O interfaces, which are suitably interconnected via one or more communication lines or buses. Memory may include read-only memory (ROM), random access memory (RAM), and storage memory such as solid-state hard drives, flash memory, etc. Examples of computer-readable media may be volatile and non-volatile, as well as removable and non-removable memories, implemented using any method or technology capable of storing information (e.g., computer-readable instructions, data structures, programs, or other data) for the implementation of aspects of this disclosure. As used herein, the term processor is not limited to integrated circuits referred to in the art as computers, but broadly relates to microcontrollers, microcomputers, microprocessors, programmable logic controllers, application-specific integrated circuits, and other programmable circuits.

[0050] In other embodiments considered, controller 160 may include a switch or contactor that connects the magnetic field generator directly to a power source. In some embodiments, the power source is an existing 120 / 208VAC power source typically available on aircraft. In other embodiments, the switch includes a thermal shut-off device configured to disconnect the magnetic field generator from the power source when a predetermined temperature is exceeded.

[0051] This application may refer to quantities and numbers. Unless otherwise stated, these quantities and numbers should not be considered limiting, but rather examples of possible quantities or numbers relevant to this application. Also in this respect, this application may use the term "multiple" to refer to quantities or numbers. In this respect, the term "multiple" means any number greater than one, such as two, three, four, five, etc. The terms "approximately," "about," "close to," etc., indicate plus or minus 5% of a given value. For the purposes of this disclosure, the phrase "at least one of A, B, and C" refers, for example, to (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C), including all further possible permutations when more than three elements are listed.

[0052] The principles, representative embodiments, and modes of operation of the present invention have been described in the foregoing description. However, the aspects of the invention intended to be protected should not be construed as limited to the specific embodiments disclosed. Furthermore, the embodiments described herein are considered illustrative rather than restrictive. It should be understood that changes and modifications, as well as equivalents, can be made by others without departing from the spirit of the invention. Therefore, it is expressly stated that all such changes, modifications, and equivalents fall within the spirit and scope of the invention as claimed.

Claims

1. A thermal actuator, comprising: cylinder; A piston, which is slidably disposed within the cylinder, the cylinder and the piston defining a cavity, the piston including a rod extending away from the cavity; A phase change material is disposed within the cavity; A magnetic field generator configured to provide an alternating magnetic field includes a conductive tube forming a coil around the cylinder, the conductive tube being configured to receive a flow of cooling fluid that minimizes undesirable heating of the cylinder and enhances cooling of the phase change material within the cavity when the actuator is deactivated. as well as A conductive heating element is installed inside the cavity and exposed to the alternating magnetic field. The heating element heats the phase change material, which expands to drive the rod from a retracted position to an extended position.

2. The thermal actuator according to claim 1, characterized in that, The phase change material includes wax.

3. The thermal actuator according to claim 1, characterized in that, The magnetic field generator also includes: A power source, operably connected to the coil; and A controller that selectively controls the supply of alternating current from the power source to the coil.

4. The thermal actuator according to any one of claims 1 to 3, characterized in that, The heating element is a cylinder mounted on one of the piston and the cylinder.

5. The thermal actuator according to claim 4, characterized in that, The cylinder includes a hollow interior that is in fluid communication with the cavity.

6. A locking assembly for holding and releasing a landing gear component, the locking assembly comprising a thermal actuator according to any one of claims 1 to 3, wherein, When the rod is in the extended position, the rod releasably engages the locking release mechanism, and the engagement of the rod with the locking release mechanism releases the landing gear component.

7. A thermal actuator, comprising: cylinder; A piston, which is slidably disposed within the cylinder, the piston and the cylinder defining a cavity with a variable volume, the piston including a rod extending away from the cavity; Wax, which is disposed within the cavity; as well as An induction heater configured to selectively heat the wax from a solid state to a liquid state, the induction heater comprising: An alternating magnetic field generator includes a conductive tube forming a coil around the cylinder, the conductive tube being configured to receive a flow of cooling fluid that minimizes undesirable heating of the cylinder and enhances cooling of the wax within the cavity when the actuator is deactivated. as well as A conductive heating element is installed inside the cylinder and functions by an alternating magnetic field generated by the alternating magnetic field generator.

8. The thermal actuator according to claim 7, characterized in that, The conductive heating element is a cylinder that extends longitudinally through a portion of the cylinder.

9. The thermal actuator according to claim 8, characterized in that, The cylinder includes a hollow interior that is in fluid communication with the cavity.

10. The thermal actuator according to any one of claims 7 to 9, characterized in that, The alternating magnetic field generator includes a conductive coil surrounding at least a portion of the cylinder.

11. The thermal actuator according to claim 10, characterized in that, The alternating magnetic field generator also includes a power supply configured to selectively supply alternating current to the conductive coil.

12. A locking assembly for holding and releasing a landing gear component, the locking assembly comprising a thermal actuator according to any one of claims 7 to 9, wherein, When the lever is in the extended position, the lever releasably engages the locking release mechanism, and the engagement of the lever with the locking release mechanism releases the landing gear component.

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