ES2724705T3 - Locking mechanism above the landing gear that uses a phase change thermal actuation - Google Patents

Abstract

An upper locking assembly (100) for retaining and releasing landing gear systems, said upper locking assembly being characterized in that it comprises: a thermal actuator (1) comprising: a chamber configured to contain expandable material (15) inside it. ; a heating mechanism coupled to said chamber to heat said expandable material and cause its volumetric expansion; a piston (3) slidably coupled to said chamber and adapted to extend in response to said volumetric expansion; and an up-lock release mechanism (4) releasably applied by said piston when extended, such that said up-applied lock release mechanism causes the release of said landing gear.

Description

DESCRIPTION

Locking mechanism above the landing gear that uses a phase change thermal actuation

Field of the Invention

The present invention relates to landing gear control systems and, in particular, to mechanisms for retaining and releasing the landing gear when in the retracted position.

Background of the invention

The locking mechanisms above the aircraft are designed to lock the landing gear in a retracted position and help load the landing gear weight during the flight. Conventional locking mechanisms above consist of a spring lock that locks the gear in place and a hydraulic cylinder to release the locking mechanism to release the landing gear that must be lowered during landing.

Current aircraft systems often use a multitude of hydraulic subsystems as a source of mechanical energy. The locks above typical of the prior art employ a hydraulic actuator to perform the unlocking function, and often use a manually operated cable system to perform the unlocking in the event of a hydraulic system failure. Other existing blockages employ a secondary hydraulic actuator for an alternative release. Disadvantageously, the hydraulic actuation system is complex and adds an unnecessary additional weight that must be transported by the aircraft.

There has been a trend in the aeronautical industry towards electrical actuation systems. A general reduction in the weight of the aircraft can be observed through the use of electrical systems, rather than hydraulic systems. However, electrical actuation systems are complex to manufacture and are not completely reliable.

To solve the difficulty of releasing a blockage above using electric power, two approaches have been investigated. In the first approach, an electromagnetic solenoid can be used as the main release actuator. Solenoids typically offer a relatively low force per unit mass, but they are simple and reliable. Solenoid systems can be used where the weight of the landing gear can be lifted from the locking hook above before the solenoid is activated. In the event of a fault where the landing gear lifting mechanism becomes inoperable, the weight of the landing gear on the hook is excessive for the solenoid to release. Systems that use solenoids for primary release also have a secondary release mechanism. This release mechanism can be manual, cable operated, but typically an electromechanical actuator is used. An electromechanical actuator uses an electric motor coupled to a gearbox to provide a high force / torque actuation system. Electromechanical actuators have a high level of complexity and several problematic failure modes.

Therefore, there is therefore a need for an aircraft landing gear actuation system that allows the release of the blockages above to avoid or mitigate at least some of the disadvantages set forth above. In addition, there is a need for an actuator that avoids or mitigates at least some of the disadvantages of the actuators presented above.

U.S. Pat. No. 5685149 describes a proportionally controlled thermochemical mechanical actuator where an operator can select an operating characteristic, such as an extension or force degree of an extension member of a thermal actuator, with an input circuit. The input control circuit generates a reference signal. A feedback circuit controls a characteristic of the thermal actuator, such as the temperature of its internal polymer, the extension of the extension member, the force or the like, and generates a corresponding feedback signal. An error circuit compares the reference and feedback signals and generates an error signal according to them. A dither circuit (small oscillation) generates an oscillating dither signal that overlaps one of the control and feedback signals before the comparison made by the error circuit. An energy conversion circuit adjusts an amount of electrical energy supplied to a heating element of the thermal actuator according to the error signal.

WO 2005/005252 A1 describes a lock assembly above to retain and release the landing gear systems.

Compendium of the invention

According to one aspect of the invention, an upper locking assembly is provided comprising at least one of the primary and secondary thermal actuation means for activating the release of an upper locking mechanism coupled thereto. Accordingly, the present invention uses at least one thermal actuator to activate the locking release mechanism.

According to one aspect, the thermal actuator comprises a chamber for containing expandable materials such as paraffin wax or other suitable materials. The thermal actuator further comprises a piston adapted to be extended to apply the lock release mechanism above and have it released. The heating mechanisms are used inside the thermal actuator

paraffin wax (for example, during the phase change from solid to liquid). According to one aspect, the heating mechanism includes, for example, resistive heating elements that are used to melt expandable material contained within the cylindrical chamber to extend the piston and produce a linear action. According to another aspect of the invention, the thermal actuator comprises a Peltier joining device to heat the expandable material in the chamber and cause a linear actuation of the piston for the subsequent release of the landing gear. According to a further aspect of the invention, the thermal actuator comprises a Peltier bonding device and a resistive heating device for cooperatively heating the expandable material.

According to another aspect, the present invention provides an upper locking assembly having a thermal actuator for partially or totally actuating a locking release mechanism above the locking assembly above.

According to one aspect of the invention, the thermal actuator further comprises a first and second dual redundant heating mechanism for heating the expandable material such as paraffin wax. In one aspect, the first heating mechanism comprises a Peltier thermoelectric heat pump to transfer heat to the actuator to melt the wax and transfer heat from the actuator to cool the wax. According to another aspect, the second heating mechanism further comprises a resistive heating element for heating the expandable material.

According to one aspect, a thermal actuator is provided comprising: a chamber configured to contain expandable material inside; a first thermostatic heating device coupled to said chamber and in communication with said material, said first thermostatic heating device is operable to heat and maintain said material at a predetermined temperature; a heating mechanism coupled to said chamber and in communication with said material, said heating mechanism is operable to heat said material once at said predetermined temperature causing its volumetric expansion; and a piston slidably coupled to said chamber and adapted to extend in response to said volumetric expansion.

In one aspect, the predetermined temperature comprises a temperature below the melting temperature of the expandable material.

Brief description of the drawings

Exemplary embodiments of the invention are described below together with the following drawings, in which:

Figure 1 is a side view of an upper locking assembly that includes a thermal actuator according to an embodiment of the invention;

Figure 2 is an isometric view of the thermal lock release actuator above the lock assembly above of Figure 1;

Figure 3 is a side and cross-sectional view of the thermal actuator according to one embodiment;

Figure 4 is a schematic diagram of an implementation of the positive temperature coefficient heater for use with the thermal actuator;

Figure 5 is an isometric view of the lock assembly above according to an alternative embodiment;

Figure 6 is a schematic view illustrating the operation of the control system and the temperature sensor of the thermal actuator according to one embodiment; Y

Figure 7 is a schematic view illustrating the operation of the thermostatic heating device and a heating mechanism of the thermal actuator according to another embodiment.

Detailed description of the preferred embodiments

According to an embodiment illustrated in Figure 1, a lock assembly is provided above 100 comprising a thermal actuator 1 to activate a lock release mechanism above 4 and release a retention hook 6 to release landing gear and / or the gates of an aircraft that are in the closed and retracted position. For example, this may occur to free the landing gear for the grounding of the aircraft. As will be apparent to one skilled in the art, thermal actuators may also be referred to as paraffin actuators or wax actuators.

As described below, the thermal actuator 1 further comprises a substantially closed chamber (for example, cylindrical) configured to contain expandable material 15 (eg, paraffin wax, Figure 3) that undergoes a volumetric change due to a temperature change (such as paraffin wax, or other waxes or materials that expand their volume during a phase change from solid to liquid caused by heating the material). Preferably, the cylindrical chamber is rigid. The thermal actuator 1 further comprises a mechanism of heating coupled to the cylindrical chamber and in communication with the expandable material to heat said expandable material and cause its volumetric expansion (for example, during a change of solid to liquid phase of the material). Referring to Figure 1, the thermal actuator 1 further comprises a piston 3 coupled to the chamber and adapted to apply said lock release mechanism above 4 to release said retention hook 6 in response to said material heating.

The operation of the blockage assembly above 100 is explained below with reference to Figure 1. The blockage assembly above 100 is configured to be used with the aircraft landing gear and the landing gear gates. The orientation of the locking assembly above 100 of the landing gear is illustrated in Figure 1, as it is mounted in the landing gear compartment. In operation, to block the landing gear (not shown) during the flight, the landing gear is retracted on the spring loaded retention hook 6, which pivots upwards (counterclockwise) around a first pivot point 8. In order to release the landing gear, the heating mechanism of the thermal actuator 1 heats said expandable material. As will be apparent, the heating of the expandable material causes the volumetric expansion of the material. The volumetric expansion causes a force against the piston 3 of the thermal actuator 1, so that the piston 3 extends to pivot the locking release mechanism up 4 around a second pivot point 2. On the other hand, once that the material inside the chamber is cooled (for example, by extracting heat from the material through the heating mechanism), this causes the volume of the material inside the chamber to decrease, allowing the piston to retract 3. In Once the gear has been released, the tension of a flexible loading means such as a spring 5 returns the retaining hook 6 to the unlocked state (the capture member 6 then rotates clockwise around the first pivot point 8). According to one embodiment, the gear can also be unlocked if the electrical systems fail to pull a manual release cable 7 coupled to the lock release mechanism above 4.

Thermal actuator 7

According to one embodiment, the heating mechanism of the thermal actuator 1 further comprises at least one of a first and a second dual redundant heating mechanism for heating the expandable material such as paraffin wax. In one aspect, the first heating mechanism comprises a Peltier thermoelectric heat pump for both transferring heat to the actuator 1 to melt the expandable material and the wax and to subsequently transfer the heat of the actuator 1 when it is desired to cool the wax more rapidly. . According to another aspect, the second heating mechanism further comprises a resistive heating element for heating the expandable material.

As will be apparent to one skilled in the art, redundancy is the duplication of certain components of a system to provide backup functionality in case one of the components fails or is inactive, which improves the reliability of the system. Therefore, as described below, the first and second heating mechanisms are adapted to provide redundant heating of the expandable material.

According to a preferred embodiment, dual redundant heating mechanisms are provided. Referring to Figure 3, a side view and a cross section of the thermal actuator 1 using both heating mechanisms (Peltier thermoelectric junction heat pump 12 and resistive heating element 13) are shown. Therefore, electric heating methods are used to melt the expandable material (for example, paraffin wax 15) contained within the thermal actuator 1, which causes it to expand and activate the locking release mechanism above 4. Preferably, in order to improve reliability in aircraft applications, dual electric heating methods are used to heat the paraffin 15. In one embodiment of the present invention, a Nichrome resistive heating cable 13 is used in conjunction with a pump Peltier 12 thermal thermoelectric heat. Each heating method can provide enough energy to release the lock release mechanism above 4 independently. That is, when one of the two heating mechanisms (for example, one of the nichrome resistive heating cables 13 or the Peltier 12 thermoelectric heat pump) fails or is inactive, the other of the two heating mechanisms is operable to heat the material 15 and provide sufficient volumetric expansion to cause the extension of the piston 3. Furthermore, when both heating mechanisms are used together (for example, resistive heating 13 and the Peltier 12 thermoelectric junction heat pump), this it allows a faster heating of the material 15 and a faster extension of the piston 3, thus reducing the response time to operate the lock release mechanism above 4.

In addition, the Peltier 12 thermoelectric heat pump is operable to transfer heat to actuator 1 to melt wax 15 and, alternatively, to transfer heat from actuator 1 to cool it more quickly. As mentioned above, the resistive heating element 13 can also be used to heat the material. When the thermal actuator 1 comprises both heating mechanisms as illustrated in Figure 3, the Peltier 12 thermoelectric heat pump is operable to heat the expandable material together with the resistive heating element 13. Thus, the dual redundant heating mechanisms allow faster heating of the expandable material (for example, paraffin 15) to allow the actuation of the piston 3 and the application of the lock-up mechanism 4 to be more instantaneous. In addition, as described above, the Peltier 12 thermoelectric heat pump is operable to transfer heat out of the actuator 1 to allow the expandable material to cool more quickly, which causes the volume of the material to decrease. As mentioned above, the contraction of the volume of the material suppresses the force exerted on the piston 3 allowing the piston 3 to retract.

Consequently, small volumes of paraffin wax 15 or other expandable materials in the melting state, can create high pressures inside the chamber and, therefore, give rise to large actuation forces on the piston 3 that cause the piston 3 to extend. In this way, one or both heating mechanisms (Peltier junction heat pump 12 and resistive heating element 13) can be used to heat the expandable material, such as paraffin 15. In addition, this dual redundant heating mechanism allows that one of the heating mechanisms perform the task of heating the paraffin wax 15 in case of failure of the other of the heating mechanisms. In addition, when the two heating mechanisms are used (Peltier junction heat pump 12 and resistive heating element 13), it is possible for the expandable material 15 to heat and cool more quickly.

Referring to Figure 2, the thermal actuator 1 comprises a connector 9, a thermally conductive end cap 11, a housing 10 for containing the chamber containing the expandable material and a piston 3.

The cross-sectional view of Figure 3 shows the expandable material 15 (eg, paraffin) contained within a thermally insulating housing 10 and a thermally conductive end cap 11. To extend the piston 3, an electric current is applied to one or both of the above-mentioned heating mechanisms (Peltier junction heat pump 12 and the resistive heating element 13). The Peltier device 12 passes heat into or out of the paraffin 15 from outside the thermal actuator 1 through the thermally conductive end cap 11. An embodiment of the present invention supplies current to the Nichrome resistive heating cable 13 by means of a tightly sealed connector 9.

When designing a thermal actuator 1, the possibility of ensuring a substantially complete retraction of the piston 3 after each cycle is taken into account. According to one embodiment, to recycle a thermal actuator 1, a spring 17 is embedded in the actuator 1 to help the piston 3 return when the wax 15 cools and solidifies.

As illustrated in Figure 3, the thermal actuator 1 employs the use of the spring 17 to ensure a substantially complete retraction of the piston 3 during solidification of the expandable material 15. According to the present embodiment, the compression spring 17 resists the linear extension of the piston 3, so that during the cooling phase the piston 3 returns to its fully retracted state. The additional geometry of the piston 16 functions as a hard stop to limit the displacement of the pistons 3 between the housing 10 and the mounting cover 20.

Referring again to Figure 3, the thermal actuator 1 further comprises high pressure seals 14 containing the expanding paraffin 15 as it undergoes the phase change during heating. In addition, the thermal actuator 1 comprises environmental seals 18 that ensure that the contaminants do not interfere with the internal movement of the piston 3 or the spring 17. Both the support cover 20 and the end cover 11 are threaded 19 and, therefore, are fixed to the housing 10 when they are screwed into place.

Peltier 12 thermoelectric junction heating pump

The following statement provides a general description of the operation of the Peltier 12 thermoelectric junction heat pump used with the thermal actuator 1, as illustrated in Figure 3. The Peltier 12 thermoelectric junction heat pump is a semiconductor device that induces a flow of thermodynamic energy between its two opposing plates. The amount of heat transferred is proportional to the amount of current that passes through an alternating series of semiconductors type n and type p given by:

Q = 2 • N • {a • ITc - [(I2 • p) / (2 • G)] - kAT-G}

Q: Heat pumped (W)

N: Number of thermocouples

a: Seebeck coefficient (V / K)

I: Current (A)

Tc: Cold side temperature (K)

p: Restivity (Q- cm)

G: Surface / Length of the thermoelectric element (cm)

k: Thermal conductivity (W / cm-K)

AT: Hot side temperature - Cold side temperature (K)

Peltier devices 12 can be used to efficiently heat an object such as paraffin 15 by extracting energy from the environment, as well as supplying heat from its internal resistive energy losses. When the electrical polarity of the Peltier 12 junction is reversed, the object is cooled by pumping heat in the other direction and releasing it to the atmosphere. Thus, according to one embodiment, when the landing gear has been released as a result of the heating of the expandable material 15, the thermal energy of the liquid paraffin 15 can be actively dissipated by reversing the electrical polarity of the Peltier device 12. This combination of heating and cooling using the two-way heat transfer property of the Peltier device 12 is advantageous because it reduces the total time of the actuator cycle and allows faster heating and cooling of the paraffin 15.

The thermal energy transferred through the Peltier device 12 during the cooling phase is dissipated by means of a thermal receiver (not illustrated in the Figures). To reduce the volume of the metal that must be heated during operation, the thermal receiver is kept small and the forced convection of a fan is used to dissipate the necessary thermal energy.

Accommodation 10

The materials surrounding and / or in contact with the paraffin 15 are selected so that they have a low thermal conductivity. This design principle results in a reduction of thermal losses through heat dissipation, greater efficiency and, therefore, a reduction in the times of the operating cycles. As an example, this can be achieved by manufacturing the housing 10 of the actuator 1 (Figures 2 and 3) from a high strength polymer or by using insulated inserts within a metal housing. The possibility of allowing adequate thermal conduction of heat to and from the Peltier device 12 through the end cap 11 should be considered.

As described above, according to one embodiment, a single chamber thermal actuator 1 is used to perform the lock release action above. Dual heat transfer methods (for example, Nichrome resistive cable 13 and Peltier 12 junction heat pump) are used to provide a degree of redundancy.

According to an alternative embodiment, a second thermal actuator 1 (not shown) is provided in the same lock assembly above 100 to function as the secondary release system of the first thermal actuator 1 described herein. This second actuator 1 operates with an independent power supply to function as a redundant actuation source. As will be apparent, if one of the first and second thermal actuators 1 fails, the other of the first and second thermal actuators 1 is used as a backup to activate the lock release mechanism above 4 and cause the release of the retention hook 6 and of the landing gear. Either one or the other (or both) of the heating methods (for example, the nichrome resistive cable 13, the Peltier 12 heat pump or other heating mechanisms, as will be apparent to one skilled in the art) can be implemented to melt the paraffin 15 of this secondary actuator and cause the landing gear to release.

Advantageously, the thermal actuator 1 generates a relatively large force for a small unit of mass. In general, thermal actuators have homogeneous operating characteristics and can be used in closed circuit feedback systems. A disadvantage of the known thermal actuators is the cycle time. Because the heating system must be heated so that the wax melts; The acting process is not instantaneous. According to one embodiment, the actuation time can be reduced by minimizing the volume of wax 15 in the cylindrical chamber of the housing 10, thus minimizing thermal conduction through the actuator body and maximizing energy input.

Temperature sensor 602 and control system 604

According to one embodiment, the thermal actuator 1 further comprises a temperature sensor 602 and a control system 604, as illustrated in Figure 6. The temperature sensor 602 is operable to detect a temperature reading of the expandable material (e.g., paraffin 15) while the control system 604 is operable to receive the temperature reading and to continuously monitor the temperature of the material according to the temperature reading.

For example, the temperature sensor 602 is embedded within the paraffin 15 of the thermal actuator 1. As illustrated in Figure 6, the temperature data of the paraffin 15 can be fed back to a control system 604 that is operable to maintain the temperature of paraffin 15 just below the melting point. At this point, once the temperature of the paraffin 15 is just below the melting point 604, the heating devices 603 (for example, the nichrome resistive cable 13 and / or the Peltier 12 junction heat pump or other heating mechanisms) only need to supply enough energy to overcome the latent heat of fusion and melt the paraffin 15 to cause the expansion of the volume of the paraffin 15 and the extension of the piston 3. Consequently, this implementation reduces the response time of the thermal actuator 1 since the expandable material 15 is already at a predetermined temperature below the melting temperature and the nichrome resistive cable 13 and / or the Peltier 12 heat pump bond provide sufficient energy to melt the expandable material 15 In addition, as a person skilled in the art will understand, the temperature sensor 602 and the control system 604 can be similarly implemented in the case of the second thermal actuator (not shown).

According to one embodiment, the thermal actuator 1 further comprises a pressure sensor coupled to the expandable material and to the control system 604. The pressure sensor is adapted to monitor the pressure of the expandable material and provide a reading of its pressure. In one aspect, the control system 604 is operable to receive the pressure reading and to control the pressure of the expandable material to a predetermined amount. The control system is also operable to determine if a fault has occurred in the thermal actuator 1 due to an excessive pressure reading.

As described herein, it is advantageous to keep the expandable material 15 at a predetermined temperature just below the melting point of the expandable material 15 so that only sufficient energy is provided to overcome the latent heat of fusion to cause extension of the piston 3. In the embodiment described above, an active control system 604 is used to maintain the temperature at a desired temperature with feedback from the temperature sensors 602. According to another embodiment, the thermal actuator 1 has a cycle time improved by maintaining the temperature of the expandable material 15 at a first predetermined threshold, passively by means of a thermostatic heating device 702.

702 thermostatic heating device

According to the present embodiment illustrated in Figure 7, the thermal actuator 1 comprises a first thermostatic heating device 702 coupled to the chamber and in communication with the material 15, so that the first thermostatic heating device 702 is operable to heat said material 15 at a first predetermined temperature and to maintain said material 15 at the first predetermined temperature (for example, slightly below the melting temperature of the expandable material).

According to the present embodiment, the thermal actuator 1 further comprises a second heating mechanism 704 coupled to the chamber and in communication with the material 15 so that the second heating mechanism 704 is operable to heat the expandable material 15 from the first predetermined temperature up to a second predetermined temperature. A person skilled in the art will understand that the first and second predetermined temperatures may include a range of desirable temperatures.

In one aspect, the first thermostatic heating device comprises a positive temperature coefficient (PTC) heater adapted to heat and maintain a desired threshold temperature of the expandable material 15. The second heating mechanism comprises a heating mechanism such as a heating element. resistive heating or Peltier thermoelectric heat pump to transfer heat to the expandable material 15. As stated, the second heating mechanism 704 is adapted to heat the expandable material from the first temperature reached by means of the thermostatic heating device 702 to the second predetermined temperature (for example, the melting temperature of the expandable material). That is, the second heating mechanism 704 is adapted to heat the expandable material to a point that causes the material 15 to melt and causes its volume to increase, in order to provide enough energy to make the piston 3 extend.

As described above, according to a preferred embodiment, the thermal actuator 1 provides dual redundant heating mechanisms, so that if one of the heating mechanisms fails or is in some way inactive, the other heating mechanism is operable to heat the Expandable material 15 sufficiently to cause the extension of the piston 3. In addition, the double redundant heating mechanism allows the two heating mechanisms to work together to cause faster heating of the expandable material 15 and further reduce the cycle time.

According to the present embodiment, the second heating mechanism 704 includes a dual redundant heating mechanism. In this case, the dual redundant heating mechanism is operable to heat said expandable material 15 together with the thermostatic heating device. That is, the thermostatic heating device 702 can maintain the temperature of the expandable material 15 at a predefined threshold (for example, the first predetermined temperature below the temperature of the melting point of the material 15) before actuation. Each of said dual redundant heating mechanisms can independently provide sufficient energy to melt the expandable material 15 when acting, or both heating mechanisms can be used in parallel to allow faster heating of the expandable material 15 when acting.

In one aspect, the dual redundant heating mechanism comprises a first heating mechanism such as a Peltier 12 thermoelectric heat pump and a second heating mechanism such as a resistive heating element 13. The dual redundant heating mechanism is operable to cooperate with heating the expandable material 15 with the thermostatic heating mechanism 702 and comprises a positive temperature coefficient heater.

As one skilled in the art will understand, other combinations of dual redundant heating mechanisms can be contemplated. For example, the dual redundant heating mechanism may include two Peltier 12 thermoelectric heat pumps in communication with the expandable material 15 and operable to cooperate with the thermostatic heating device to heat the expandable material 15 from the first predetermined temperature (for example, just below the melting point temperature) to a second predetermined temperature that causes the volume expansion of the material 15 and results in the extension of the piston 3.

Preferably, in one aspect, the thermal actuator 1 employs a positive temperature coefficient (PTC) heater in combination with a Peltier 12 thermoelectric heat pump, both devices are configured to heat the expandable material 15. In operation, the Positive temperature coefficient heater is activated to transfer heat to the expandable material and to keep the material at a predetermined first temperature. While the PTC heater is transferring heat to the expandable material, the Peltier thermoelectric heat pump is deactivated until the actuation of the piston 3 is desired. Since the positive temperature coefficient of the heater can function as a thermostat, it is self-regulating at a temperature Critical designed (for example, the first predetermined temperature) and reach a steady state temperature. Said designed critical temperature can be selected during the formation of the positive temperature coefficient of the heater so that it has a predefined temperature such that at said predefined temperature, the expandable material is maintained below its melting point. Once the actuation of the piston 3 is desired, the Peltier 12 thermoelectric heat pump is activated to provide energy to overcome the latent heat of fusion of the expandable material 15, thereby melting the material 15 (for example, reaching the second predetermined temperature) and operating the actuator 1. In retraction, the operation of the thermoelectric heat pump of the Peltier 12 junction is reversed to eliminate the energy of the material to solidify the material 15. Upon reaching a predefined temperature, the heat pump thermoelectric of the Peltier 12 junction is deactivated and the positive temperature coefficient of the heater is operable to bring the material 15 to a stable temperature at the designed critical temperature (for example, the first predetermined temperature).

Alternatively, the embodiment described hereinbefore may be configured with a nichrome resistive heater 13 instead of a Peltier thermoelectric heat pump 12 so that the nichrome resistive heater 13 is configured to melt the material 15 once the operation of the piston 3 is desired.

PTC heater operation

A general description of the operation of a positive temperature coefficient heater is described herein. Preferably, said heater is formed from a ceramic material having a positive temperature coefficient, so that the strongly non-linear thermal response results in a sudden increase in the resistivity of the material beyond a certain critical temperature. Typical materials that have this characteristic are barium titanate and lead titanate compounds. By using this material, the heater can act as its own thermostat and control the temperature of the heater passively. As current is applied to the heater, the resistivity is relatively low and, therefore, the temperature increases due to resistance heating. However, as the temperature increases beyond the designed critical temperature, the resistivity increases significantly and reduces the current flow and, in turn, the resistive heating. This results in a stable state with the heater temperature at the critical temperature (for example, the first predetermined temperature).

In another embodiment illustrated in Figure 4, a positive temperature coefficient resistor is arranged in series with a resistive heating element so that the PTC resistor acts by regulating the flow of current through the heating element and maintaining a temperature of stable state. Since the two resistors are in series, they share the same current flow. By virtue of the relationship between resistivity and temperature in a pTc heater, the increase in resistance reduces the general current flowing through the branch as the temperature increases. When additional heating is required, the PTC resistor can be derived at 0 ohms through the use of a switching mechanism, which allows the full flow of current through the heating element.

Redundancy - Dual

As briefly described herein, the use of a multitude of heating mechanisms to drive the thermal actuator 1 provides redundancy. According to an embodiment illustrated in Figure 3, a side view and a cross-section of the thermal actuator 1 using both heating mechanisms (Peltier thermoelectric junction heat pump 12 and resistive heating element 13) are shown. Furthermore, as described above, according to one embodiment, the Peltier 12 thermoelectric heat pump operates as a primary heating mechanism while the resistive heating element 13 operates as a secondary heating mechanism, thus providing redundant heating in case of Failure or heating the expandable material more quickly (when the Peltier thermoelectric junction heat pump 12 and the resistive heating element 13 operate in parallel).

In one operation, the primary heating mechanism is activated to heat the expandable material when it is desirable to release the lock assembly above, or according to an embodiment of the invention, it is activated to keep the expandable material at a predefined temperature point. In addition, both the primary and secondary heating mechanism can be configured to heat the expandable material together, as described in an embodiment of the invention. The redundancy provided by the secondary heating mechanism it allows said secondary heating mechanism to carry out the task of activating the locking mechanism in the event of a failure of the primary heating mechanism. Such failure modes of the primary heating mechanism may include, but are not limited to, power supply failures and unexpected temperature readings. In such cases, the control system 604 of the thermal actuator 1 can control the temperature of the expandable material so that, for example, extended disparities between the actual temperature and the desired temperature of the expandable material may indicate a failure of the heating mechanism. The operation of the primary and secondary heating mechanisms has been previously described herein.

The thermal actuator 1 shown in Figure 3 is configured to act only on the lock release mechanism above 4. According to an alternative embodiment, the thermal actuator 1 is operable to operate in a hybrid configuration, whereby the thermal actuator 1 acts as a first actuator and a second alternative actuator acts as a secondary actuator. Said second alternative actuator includes, for example, an electric motor actuator, a hydraulic actuator, an electric solenoid actuator and other actuators of this type, as described in the prior art, or combinations thereof. Each of the first and second actuators can be configured to fully activate the locking mechanism above, thus providing another degree of redundancy. This dual redundancy allows one of the actuators to perform the task of unlocking the locking mechanism above in case the other actuator fails. Alternatively, the first and the second actuator may be configured to partially activate the locking mechanism above. In addition, the first and second actuators are operable to actuate the release mechanism together.

Referring to Figure 5, an isometric view of the lock assembly 100 above showing two actuators is shown. In this embodiment, the upper lock assembly 100 comprises a first thermal actuator 1 and a second hydraulic actuator 21. In this configuration, both actuators (1 and 21) can drive the lock release mechanism above 4. The piston 3 of the actuator The thermal actuator and the piston 22 of the hydraulic actuator may be in contact with the locking mechanism above to activate the locking mechanism above 100 in the manner described in the configuration of a single actuator.

As described hereinbefore, the two actuators 1, 21 can be operated to provide dual redundancy by operating the lock release mechanism above. According to an aspect illustrated in Figure 5, the thermal actuator 1 acts as the primary actuator and the hydraulic actuator 21 acts as the secondary actuator. In the event that the thermal actuator 1 shows a fault behavior, the thermal actuator 1 is deactivated (for example, it is inactive) and the hydraulic actuator 21 assumes the role of the primary actuator (for example, it is still active). Such failure behavior may include but not be limited to heater failure (primary and secondary heating mechanisms) or to a lack of action after a predefined time. In such cases, the locking system processing system above 100 can monitor the position of the locking release mechanism above 4 and determine the time elapsed between the desired performance and the actual performance. For example, an unacceptable elapsed time may demonstrate a failure of the locking actuator above and, therefore, instructs the secondary actuator to assume the function of the primary actuator (for example, to be activated) and to deactivate the primary actuator (for example , become inactive).

Although the thermal actuator 1 illustrated in Figure 3 has dual redundant heating mechanisms (for example, the nichrome resistive cable 13 and the Peltier 12 junction heat pump) that can operate in parallel or individually have been described in this memory for use with a lock assembly above 100, one skilled in the art will understand that other uses and applications for the thermal actuator 1 can be contemplated.

Although this invention has been described with reference to illustrative embodiments and examples, the description is not intended to be construed in a limiting sense. Therefore, various modifications of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to those skilled in the art who refer to this description. Therefore, it is contemplated that the appended claims cover said modifications or embodiments.

Although preferred embodiments of the invention have been described herein, those skilled in the art will understand that variations can be made thereto without departing from the scope of the appended claims.

Claims (10)

1. An upper locking assembly (100) for retaining and releasing landing gear systems, said upper locking assembly being characterized in that it comprises: a thermal actuator (1) comprising: a chamber configured to contain expandable material (15) inside; a heating mechanism coupled to said chamber to heat said expandable material and cause its volumetric expansion; a piston (3) slidably coupled to said chamber and adapted to extend in response to said volumetric expansion; Y an upper lock release mechanism (4) releasably applied by said piston when it is extended, such that said applied top lock release mechanism causes the release of said landing gear. 2. An overhead lock assembly (100) according to claim 1 wherein said heating mechanism further comprises a first resistive heating device (13) operable to heat said expandable material (15) and a second Peltier joint device (12) operable to heat and cool said expandable material alternately, said heating and cooling causing the actuation of said piston (3). 3. A top lock assembly (100) according to claim 1 or claim 2, wherein said thermal actuator (1) further comprises a temperature sensor (602) located within said chamber and operable to measure said temperature of said material expandable (15). 4. An upper lock assembly (100) according to any one of claims 1 to 3, further comprising a control system (604) in communication with said temperature sensor (602), said control system being operable to receive said temperature measured and to maintain said temperature within a predetermined range below a predefined threshold. 5. An upper lock assembly (100) according to any one of claims 1 to 4, further comprising a second actuator selected from the group consisting of: a second thermal actuator, an electric motor actuator, a hydraulic actuator (21) and an electric solenoid actuator, wherein said second actuator is active and operable to apply said lock release mechanism (4) when said thermal actuator is inactive. 6. A top lock assembly (100) according to any one of claims 1 to 5, further comprising a first thermostatic heating device (702) coupled to said chamber and in communication with said material (15), said first device being thermostatic heating operable to heat and maintain said material at a predetermined temperature, wherein said heating mechanism is operable to heat said material once at said predetermined temperature to a second temperature that causes the volumetric expansion of said expandable material. 7. A locking assembly above any one of claims 2 to 6, wherein the first resistive heating device (13) and the second Peltier joint device (12) are each operable to independently cause volumetric expansion of said sufficient material to extend said piston. 8. A locking assembly above according to claim 7 to provide redundancy when another of said resistive heating device and the second Peltier joint device is inactive. 9. A locking assembly above any one of claims 1 to 6, wherein the heating mechanism comprises: a first thermostatic heating device (702) coupled to said chamber and in communication with said material, said first thermostatic heating device being operable to heat and maintain said material at a predetermined temperature; a resistive heating element coupled to said chamber and in communication with said material, said resistive heating element being connected in series to the first thermostatic heating device and operable to heat said material once at said predetermined temperature causing its volumetric expansion; and a switch coupled to the first thermostatic heating device, the switch being operable to reduce the resistance of the first thermostatic heating device to increase the flow of current through the resistive heating element, thereby heating said material once at said temperature default 10. A method for activating a locking mechanism by means of a thermal actuator to release a retaining member that retains a landing gear, the method comprising: heating the expandable material located within a chamber of said thermal actuator, said expandable material experiencing heated a volumetric expansion during the phase change from solid to liquid and causing the actuation of a piston of said thermal actuator coupled to said chamber; Y in response to said action, apply said locking mechanism above to cause the release of said capture member elastically coupled thereto.