Flight lock, door locking system and method for locking and unlocking a flight lock

Abstract

The present application relates to a flight lock, a cabin door locking system and a method for locking and unlocking the flight lock. The flight lock comprises a housing, a cylindrical linear motor arranged in the housing and comprising a stator and a mover, the stator is fixed to the inner wall of the housing and is provided with a winding, the winding is configured to generate a time-varying magnetic field when energized, the mover is provided with a permanent magnet, the mover is coaxially arranged on the inside of the stator and has a radial air gap with the stator, and the mover is configured to move in the axial direction under the action of the time-varying magnetic field; an extension rod is integrally formed with the mover and extends from the front end of the housing in the axial direction; a spring is arranged in the housing, and the spring is configured to drive the extension rod to reset to the extended position in the power-off state; a first support is arranged in the housing and close to the root of the mover; a second support is arranged at the front end of the housing and located at the output port of the extension rod; the first and second supports are arranged in the axial direction of the extension rod and are spaced apart, and together limit the radial displacement of the extension rod.

Description

Technical Field

[0001] This invention relates to a flight lock for aircraft, and more particularly to a flight lock that uses a cylindrical linear motor as a drive source. Background Technology

[0002] Flight locks are safety actuators in aircraft door systems. During flight, the flight lock must keep the door locking mechanism in the locked position to prevent the door from opening accidentally in the air. Upon landing and power failure or upon receiving an unlocking command, the flight lock must release its lock, allowing the door to open.

[0003] The current mainstream solution for linear flight locks uses a rotary motor as the power unit, which converts rotary motion into linear motion via a lead screw. Upon receiving a locking signal, the rotary motor drives the ball screw to rotate, and the lead screw nut converts the rotary motion into linear motion, causing the output rod to retract and complete the locking process. Upon receiving an unlocking signal or when the flight lock loses power, a spring acts as the power source, pushing the output rod to extend and complete the unlocking process. This solution offers high efficiency and thrust density.

[0004] However, this solution has repeatedly encountered problems such as actuation jamming leading to alarms in practical applications. The main reason is that in the complex mechanical environment of the air, such as vibration and door structure deformation, the flight lock is susceptible to lateral loads. Furthermore, the flight lock operates under low load and short stroke conditions, and due to motor size limitations, the ball screw pair used has a small diameter, making it less able to resist lateral loads. When lateral loads are transmitted to the ball screw pair, the uneven force on the balls between the screw nut and the screw easily leads to jamming.

[0005] To reduce the transmission of lateral loads to the ball screw, a common solution is to provide radial support at multiple points in the drivetrain using bearings and other supporting components. However, the drivetrain of a flight lock is relatively long, consisting of multiple series-connected sections including the extension rod, ball screw, ball screw nut, and motor shaft. Multiple points of support are needed between these sections to ensure coaxiality, making the structure more complex and heavier. Furthermore, ball screw assemblies generally require regular lubrication, resulting in higher maintenance costs.

[0006] In summary, existing linear-actuated flight locks have the following technical defects: First, the lead screw and nut pair is prone to jamming under lateral force; second, the multi-point support transmission chain is long, has high coaxiality requirements, complex structure, and heavy weight; third, the lead screw pair requires regular lubrication, resulting in high maintenance costs. Summary of the Invention

[0007] In view of the technical defects of existing flight locks that use a rotary motor and a lead screw and nut pair as the transmission mechanism, such as the lead screw being prone to jamming under lateral force, the long transmission chain due to multiple support points resulting in complex structure and heavy weight, and the need for regular lubrication of the lead screw pair leading to high maintenance costs, the technical problem to be solved by this invention is: how to simplify the transmission structure of the flight lock, improve its resistance to lateral loads, and reduce the risk of jamming.

[0008] To address the aforementioned technical problems, an embodiment of the present invention provides a flight lock, comprising a housing, a cylindrical linear motor, an extension rod, a spring, a first support member, and a second support member. The cylindrical linear motor is disposed within the housing and includes a stator and a mover. The stator is fixed to the inner wall of the housing and has windings configured to generate a time-varying magnetic field when energized. The mover has a permanent magnet and is coaxially disposed inside the stator with a radial air gap between them. The mover is configured to move axially under the influence of the time-varying magnetic field. The extension rod is integrally formed with the mover and extends axially from the front end of the housing. The spring is disposed within the housing and configured to drive the extension rod to return to its extended position when power is off. The first support member is disposed within the housing and adjacent to the root of the mover, and is configured to provide radial support for the extension rod. The second support member is disposed at the front end of the housing and located at the outlet of the extension rod, and is configured to provide radial support for the extension rod. The first and second support members are spaced apart along the axial direction of the extension rod, jointly restricting the radial displacement of the extension rod.

[0009] By utilizing the aforementioned flight lock, the cylindrical linear motor can directly convert electromagnetic energy into linear mechanical energy, eliminating the rotary-to-linear conversion transmission chain of the rotary motor and lead screw-nut pair, thereby simplifying the flight lock's transmission structure and reducing the number of parts. The integrated design of the mover and extension rod eliminates the multi-segment series connection interfaces found in traditional solutions, reducing transmission links and sources of assembly gaps. The dual-point interval support scheme, with the first support member positioned adjacent to the root of the mover and the second support member located at the output port of the extension rod, replaces the multi-point support of traditional solutions, thus reducing the number of support parts while ensuring coaxiality. Through the synergy of these technical solutions, the flight lock's transmission structure can be simplified, its resistance to lateral loads improved, and the risk of jamming reduced.

[0010] Preferably, the first and second supports are needle roller bearings, each comprising multiple needle rollers spaced apart along the circumference of the extension rod, with the needle rollers forming line contact with the outer circumferential surface of the extension rod. Utilizing the line contact bearing method of the needle rollers, the radial lateral load-bearing capacity is 3 to 5 times that of ball bearings in the same installation space. This makes the flight lock less prone to deformation and crushing when subjected to continuous lateral forces from airflow impacts from the cabin door and airframe vibrations, thereby improving the support's resistance to lateral loads.

[0011] Preferably, the ratio of the axial span between the first and second supports to the cantilever length from the second support to the free end of the extension rod is not less than 5:1. By utilizing this span-to-cantilever length ratio, the maximum bending moment of the extension rod under lateral load is significantly reduced, allowing the radial deformation at the mover position to be controlled at the micrometer level, far smaller than the rated air gap on one side of the motor. This avoids compression between the mover and stator air gaps on one side, suppressing eccentricity from a mechanical perspective and ensuring uniform air gap in the motor.

[0012] Preferably, the ratio of the total axial length of the stator to the effective working axial length of the permanent magnet on the mover is not less than 1.5:1. This axial length ratio design ensures that the permanent magnet completely covers the effective magnetic field range of the stator winding throughout the entire rated working stroke, thereby providing a stable output of rated driving force without any thrust drop.

[0013] Preferably, the stator has magnetic field redundancy sections at both ends in the axial direction. These redundancy sections are configured to counteract local magnetic flux shift when the mover is subjected to lateral loads. By using these magnetic field redundancy sections, local magnetic flux shift can be counteracted when the mover is subjected to lateral loads, weakening the unilateral electromagnetic attraction force, thereby reducing the magnetic attraction force imbalance caused by eccentricity and further stabilizing the motor air gap.

[0014] Preferably, the mover and the extension rod are integrally machined from a single substrate, with the permanent magnet directly fixed to the outer circumferential surface of the mover, and there is no assembly interface between the mover and the extension rod. This seamless, one-piece substrate design ensures high inherent coaxiality between the mover and the extension rod, eliminating secondary eccentricity caused by loose connections in separate structures, thereby further stabilizing the motor air gap.

[0015] Preferably, the radial air gap between the stator and the mover has a safety margin, which is configured such that the minimum single-sided air gap between the mover and the stator remains positive when the extension rod is subjected to a predetermined lateral load. By reserving this air gap safety margin, the minimum single-sided air gap between the mover and the stator can remain positive when the extension rod is subjected to a predetermined lateral load, thereby ensuring that the circumferential electromagnetic attraction remains balanced and eliminating wall-adhesion effects and continuous dry friction.

[0016] Preferably, the spring is a compression spring, which is sleeved on the outer periphery of the extension rod. The first end of the compression spring abuts against a fixed surface on the outer wall of the housing, and the second end abuts against an axial limiting step surface provided on the mover. The compression spring maintains a pre-compressed state when the extension rod is in the retracted position. By utilizing the pre-compression energy stored in the retracted position, the spring can release energy and reliably drive the extension rod to return to the extended position in the event of a power failure, thereby achieving a fault-safe unlocking function and ensuring that the system tends towards a safe direction under any power failure fault mode.

[0017] Preferably, the permanent magnets are surface-mounted to the outer circumferential surface of the mover, and the permanent magnets are arranged along the axial direction of the mover, with the magnetization directions of adjacent permanent magnets alternating. By coupling the alternatingly magnetized permanent magnets with the time-varying magnetic field of the stator winding, the mover can be subjected to a stable axial electromagnetic thrust, thereby realizing the traveling wave magnetic field drive of the linear motor.

[0018] Preferably, the housing includes a front cover and a rear cover. The front cover has a through hole for the extension rod to pass through, and the extension rod has a radially protruding limiting shoulder. The limiting shoulder is configured to abut against the inner end face of the front cover when the extension rod is extended to its maximum extended position to form an extension limit. The rear end face of the mover is configured to abut against the inner end face of the rear cover when the extension rod is retracted to its maximum retracted position to form a retraction limit. By means of the cooperation between the limiting shoulder and the front cover, and the cooperation between the rear end face of the mover and the rear cover, the extension rod can be mechanically limited in both the extended and retracted positions, thereby preventing the extension rod from disengaging or over-retracting.

[0019] An embodiment of the present invention also provides a door locking system, including a door structure and the aforementioned flight lock, wherein the extension rod of the flight lock is connected to a locking interface on the door structure; wherein, when the stator winding of the flight lock is energized, the mover moves axially to retract the extension rod to the retracted position, thereby locking the door structure; when the flight lock is de-energized, a spring drives the extension rod to return to the extended position, thereby unlocking the door structure. By integrating the flight lock into the door locking system, it is possible to achieve flight locking and unlocking functions at the door system level, whereby the extension rod retracts to the retracted position to lock the door structure when the flight lock is energized, and the extension rod returns to the extended position to unlock the door structure when the flight lock is de-energized.

[0020] An embodiment of the present invention also provides a method for locking and unlocking a flight lock, including a locking step, an unlocking step, and a guiding step. In the locking step, energizing the stator winding generates a time-varying magnetic field that drives the mover to retract the extension rod and compress the spring to store energy. In the unlocking step, cutting off the power supply causes the spring to release energy and drive the extension rod to reset. In the guiding step, the extension rod is radially supported by a first support member and a second support member. By utilizing the electromagnetic drive and spring energy storage in the locking step, the passive release of the spring in the unlocking step, and the dual-point support radial limiting in the guiding step, the flight lock can reliably lock when energized and safely unlock when power is off. Furthermore, the air gap between the mover and stator remains uniform throughout the locking and unlocking process, thereby reducing the risk of actuation jamming. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a flight lock according to an embodiment of the present invention.

[0022] Figure 2This is a schematic diagram of a flight lock in the locked state according to an embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram of a flight lock in the unlocked state according to an embodiment of the present invention.

[0024] List of reference numerals in the attached diagram: 1. Shell 2. Front cover 3. Rear end cover 4. Stator 6 moving parts 7 permanent magnets 8. Extend the rod 9 Springs 10 First support component 11 Second support component 13 Limit shoulder 17 Circuit Components Detailed Implementation

[0025] The following describes specific embodiments of the present invention. It should be noted that, in order to provide a concise description, this specification cannot exhaustively describe all features of the actual embodiments. It should be understood that, in the actual implementation of any embodiment, just as in any engineering or design project, various specific decisions are often made to achieve the developer's specific goals and to meet system-related or business-related constraints, and this can change from one embodiment to another. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this invention, some design, manufacturing, or production modifications based on the technical content disclosed herein are merely conventional technical means and should not be construed as insufficient content of this disclosure.

[0026] Unless otherwise defined, the technical or scientific terms used in the claims and description shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in the patent application description and claims of this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising" or "including" and similar terms mean that the element or object preceding "comprising" or "including" encompasses the element or object listed following "comprising" or "including" and its equivalents, and do not exclude other elements or objects. The terms "connected" or "linked" and similar terms are not limited to physical or mechanical connections, nor are they limited to direct or indirect connections.

[0027] It is worth noting that although the following description uses an aircraft cabin door flight lock as an example, the flight lock based on an embodiment of the present invention can also be applied to other devices or systems in fields that require linear actuation locking, such as cargo hold locks, landing gear door locks, thrust reverser locks, spacecraft cabin door locks, and rail transit door locks, as long as these devices or systems require reliable locking and unlocking under lateral loads.

[0028] In this invention, the term "cylindrical linear motor" refers to a motor in which both the stator and mover have a cylindrical rotary structure, and electromagnetic energy is directly converted into axial linear motion without passing through a rotary-linear conversion mechanism. The stator is equipped with windings, and the mover is equipped with permanent magnets. When the windings are energized, they generate a time-varying magnetic field, which acts on the permanent magnets to cause the mover to move axially. This term is not limited to a specific number of phases or winding configuration.

[0029] In this invention, the term "flight lock" refers to an electromechanical actuation device installed in the aircraft door system that locks and unlocks the door through the linear movement of an extended rod. The flight lock remains locked when powered on and is reset to the unlocked state by a spring when powered off, i.e., a fail-safe mode of "locked when powered on, unlocked when powered off".

[0030] In this invention, the term "extend rod" refers to a component in the flight lock that extends axially from the front end of the housing, connects to the door locking interface, and outputs linear motion. In this invention, the extend rod is integrally formed with the mover.

[0031] In this invention, the term "first support member" refers to a component disposed immediately adjacent to the root of the mover and providing radial support for the extended rod.

[0032] In this invention, the term "second support" refers to a component located at the outlet of the extension rod at the front end of the housing, which provides radial support for the extension rod.

[0033] In this invention, the term "radial air gap" refers to the annular gap between the inner wall of the mover and the outer peripheral surface of the mover, which is the physical space for electromagnetic energy transfer.

[0034] In this invention, the term "retracted position" refers to the position where the extension rod is retracted to the maximum depth inside the housing by the passive actuator, corresponding to the locked state of the flight lock.

[0035] In this invention, the term "extended position" refers to the position where the extension rod extends to its maximum extension under the action of the spring, corresponding to the unlocked state of the flight lock.

[0036] like Figure 1 As shown, a flight lock according to an embodiment of the present invention mainly includes a housing 1, a cylindrical linear motor, an extension rod 8, a spring 9, a first support member 10, a second support member 11, and a circuit assembly 17.

[0037] A cylindrical linear motor is housed within a housing 1, comprising a stator 4 and a mover 6. The stator 4 is fixed to the inner wall of the housing 1 and has windings. The mover 6 has a permanent magnet 7 and is coaxially positioned inside the stator 4, with a radial air gap between them. An extension rod 8 is integrally formed with the mover 6 and extends axially from the front end of the housing 1. A spring 9 is located within the housing 1 and is used to drive the extension rod 8 back to its extended position when power is off. A first support member 10 is located within the housing 1 and adjacent to the root of the mover 6, providing radial support for the extension rod 8. A second support member 11 is located at the front end of the housing 1 and at the outlet of the extension rod 8, providing radial support for the extension rod 8. The first support member 10 and the second support member 11 are spaced apart axially along the extension rod 8, together limiting the radial displacement of the extension rod 8. A circuit assembly 17 provides drive current to the windings.

[0038] It is understood that the flight lock according to an embodiment of the present invention may also include other devices or components besides those described above, such as position sensors, status indicator switches, etc. Since these are not the focus of the present invention, they will not be described in detail herein.

[0039] (a) Shell 1

[0040] The housing 1 is a cylindrical structure of revolution. The housing 1 includes a front cover 2 and a rear cover 3. The front cover 2 has a through hole for the extension rod 8 to pass through. The front cover 2 and the rear cover 3 are respectively connected to both ends of the housing 1. The connection method can be integral forming, welding, bolting, etc., but this is not limiting. The stator 4 is fixed to the inner wall of the housing 1, and can be fixed by interference fit press fitting.

[0041] The housing 1 adopts a rotating cylindrical structure with a uniform outer diameter and no lateral protrusions. It can be axially nested and integrated into the hatch lock housing, minimizing lateral space occupation and adapting to the narrow installation cavity of the hatch lock. The material of the housing 1 can be aluminum alloy, titanium alloy, or other materials that combine lightweight and structural strength requirements, but these are not necessary choices for the solution of this invention.

[0042] (ii) Stator 4 and windings

[0043] The stator 4 is a cylindrical rotating structure, fixed to the inner wall of the housing 1. The stator 4 is equipped with windings that are wound along the toothed grooves of the stator core. When the circuit assembly 17 supplies alternating current to the windings, the windings generate a time-varying magnetic field. The total axial length of the stator 4 is greater than the effective working axial length of the permanent magnet 7 on the mover 6.

[0044] In one specific embodiment, the total axial length of the stator 4 is 42mm, and the effective working axial length of the permanent magnet 7 on the mover 6 is 27mm. The ratio of the total axial length of the stator 4 to the effective working axial length of the permanent magnet 7 is 1.56:1. The inventors have discovered that when the ratio of the total axial length of the stator 4 to the effective working axial length of the permanent magnet 7 is not less than 1.5:1, it can be guaranteed that the permanent magnet 7 always completely covers the effective magnetic field range of the stator 4 winding throughout the entire rated working stroke of the mover 6, thereby ensuring a stable output of rated driving force throughout the entire stroke without any thrust drop.

[0045] The physical basis for this ratio is that the theoretical condition for ensuring full coverage is that the stator length minus the permanent magnet length is not less than the stroke, i.e., the ratio is not less than 1 plus the ratio of the stroke to the permanent magnet length. Taking a stroke of 13.5mm and a permanent magnet length of 27mm as an example, the theoretical minimum ratio is 1 plus 13.5 divided by 27, which equals 1.5. This invention does not exclude implementations where the ratio is greater than 1.5:1.

[0046] The stator 4 has magnetic field redundancy sections at both ends in the axial direction. The inventors noted that during flight, the flight lock extension rod 8 continuously bears radial lateral force. When the external mechanical lateral force causes a slight eccentricity in the mover 6, the circumferential air gap becomes asymmetrical, disrupting the previously balanced magnetic pull and generating a net attraction force pointing towards the smaller air gap. The magnetic field redundancy sections at both ends of the stator 4 can counteract local magnetic flux shifts when the mover 6 is subjected to lateral loads, weakening the unilateral electromagnetic attraction force and thus mitigating the magnetic attraction imbalance caused by eccentricity.

[0047] (III) Motor 6 and permanent magnet 7

[0048] The mover 6 is a cylindrical rotating structure, coaxially mounted inside the stator 4. A radial air gap exists between the mover 6 and the stator 4. Permanent magnets 7 are mounted on the mover 6. The permanent magnets 7 are surface-mounted to the outer circumference of the mover 6, arranged along the axial direction of the mover 6, with adjacent permanent magnets 7 alternating in magnetization direction (N pole and S pole alternate). When the winding is energized to generate a time-varying magnetic field, the time-varying magnetic field interacts with the alternately magnetized permanent magnets 7, applying an axial thrust to the mover 6, driving the mover 6 to move axially.

[0049] The permanent magnet 7 can be made of rare-earth permanent magnet materials such as neodymium iron boron or samarium cobalt. In high-temperature applications in aircraft, samarium cobalt permanent magnets have higher Curie temperatures and temperature stability, making them a preferred choice. However, this is not limiting for the present invention, and other permanent magnet materials are also within the scope of protection of this invention.

[0050] The mover 6 and the extension rod 8 are integrally machined from a single substrate, with the permanent magnet 7 directly fixed to the outer circumferential surface of the mover 6. There is no assembly interface between the mover 6 and the extension rod 8. In a specific embodiment, the base of the mover 6 and the extension rod 8 are integrally precision machined from a single stainless steel or titanium alloy substrate, without any separate threaded, pin, or flanged splicing structures. The inventors have creatively discovered that the integrated base has no assembly gaps, and the inherent coaxiality of the mover 6 and the extension rod 8 is high, eliminating the secondary eccentricity caused by loose connections in separate structures, and further stabilizing the motor air gap. This is significantly different from the traditional solution where the separate mover and output rod are connected by couplings or flanges, and the assembly gaps amplify the eccentricity.

[0051] The radial air gap between stator 4 and mover 6 has a safety margin. The inventors discovered that by reserving a safety margin for the air gap during the design phase, the minimum single-sided air gap between mover 6 and stator 4 remains positive when the extension rod 8 is subjected to a predetermined lateral load, meaning that mover 6 will not contact the inner wall of stator 4. This ensures that the circumferential electromagnetic attraction remains balanced, eliminating the wall-adhesion effect and continuous dry friction caused by the air gap approaching zero.

[0052] The inventors noted that the underlying reason why cylindrical linear motors were not successfully applied to flight locks before was that the industry generally believed that the 360-degree radial magnetic pull of cylindrical linear motors canceled each other out, with no static inherent off-center load, thus solving the lateral load problem. However, this view ignores a key premise: magnetic self-balancing only applies to the ideal state where the mover is completely coaxial. Once an external mechanical lateral force causes a slight eccentricity and the circumferential air gap becomes asymmetrical, the originally balanced magnetic pull will break the equilibrium, generating a net attraction force pointing towards the side with the smaller air gap. The smaller the air gap, the greater the local electromagnetic attraction force becomes exponentially larger. The magnetic pull force on the side with the smaller air gap continuously attracts the mover to the inner wall of the stator, generating continuous dry friction, which leads to thrust attenuation and actuation jamming after long-term operation. One embodiment of the present invention overcomes this obstacle through the integrated structure of the mover 6 and the extension rod 8, the dual-point interval support scheme, the preferred axial length ratio design of the stator 4 and the permanent magnet 7, the magnetic field redundancy sections at both ends of the stator 4, and the air gap safety margin design.

[0053] (iv) Extending rod 8

[0054] The extendable rod 8 is integrally formed with the mover 6, extending axially from the front end of the housing 1. The free end of the extendable rod 8 is connected to the locking interface on the hatch structure. When the stator winding is energized, the mover 6 moves axially under the action of a time-varying magnetic field, causing the extendable rod 8 to retract from the extended position to the retracted position, thus locking the hatch structure. When the flight lock is de-energized, the spring 9 drives the extendable rod 8 to reset from the retracted position to the extended position, thus unlocking the hatch structure.

[0055] In one specific embodiment, the rated working stroke of the extender 8 is 13.5 mm.

[0056] (V) Spring 9

[0057] Spring 9 is a compression spring, sleeved on the outer periphery of the extension rod 8. The first end of spring 9 abuts against a fixed surface on the outer wall of housing 1, and the second end of spring 9 abuts against an axial limiting step surface provided on the mover 6. Spring 9 remains in a pre-compressed state when the extension rod 8 is in the retracted position, storing elastic potential energy.

[0058] During locking, the stator winding is energized, and the mover 6 drives the extension rod 8 to retract from the extended position to the retracted position. The spring 9 is further compressed and stores energy during the retraction of the extension rod 8. During unlocking, the power supply to the stator winding is cut off, and the spring 9 releases the stored energy and drives the extension rod 8 to return to the extended position from the retracted position. The spring 9 maintains residual pre-compression force when the extension rod 8 is in the extended position, ensuring that the extension rod 8 remains stably in the extended position, thus achieving the unlocking holding function.

[0059] This fail-safe design of "locking on power and unlocking off power" means that in any power failure mode, including power outage, signal loss, open circuit or short circuit in the motor windings, spring 9 can drive the extension rod 8 back to the unlocked position, and the system tends towards a safe direction. Spring 9 can adopt a single spring structure or a double spring symmetrical arrangement structure. The latter can provide redundancy protection, but it is not a necessary choice for this invention.

[0060] (vi) First support member 10 and second support member 11

[0061] The first support member 10 is disposed inside the housing 1 and adjacent to the root of the mover 6, and is used to provide radial support for the extension rod 8, directly constraining the radial sway of the root of the mover 6. The second support member 11 is disposed at the front end of the housing 1 and located at the output port of the extension rod 8, close to the end where the lateral load is applied. The first support member 10 and the second support member 11 are arranged axially spaced along the extension rod 8, and together restrict the radial displacement of the extension rod 8, forming a simply supported double support structure.

[0062] In one specific embodiment, the first support 10 and the second support 11 are needle roller bearings. Each needle roller bearing includes multiple needle rollers spaced apart along the circumferential direction of the extension rod 8. The needle rollers form line contact with the outer circumferential surface of the extension rod 8. The multiple needle rollers are evenly distributed along the circumferential direction of the extension rod 8, providing radial guidance when the extension rod 8 moves axially, constraining the radial offset of the extension rod 8 in all directions, and stabilizing the circumferential air gap between the mover 6 and the stator 4.

[0063] The inventors discovered that using needle roller bearings as support components offers the following advantages: First, strong lateral load-bearing capacity. Needle rollers provide line contact load bearing, resulting in a radial lateral load-bearing capacity 3 to 5 times that of ball bearings within the same installation space, capable of withstanding the impact of airflow from the cabin door and the continuous lateral forces caused by aircraft vibration. Second, suppression of stator-mover eccentricity. Multiple needle rollers are evenly arranged along the circumference, comprehensively constraining the radial offset of the extension rod, stabilizing the motor's circumferential air gap, and avoiding magnetic force imbalance caused by eccentricity. Third, stable frictional resistance. Pure rolling friction results in a low coefficient of friction, preventing jamming under high and low temperature and high-altitude environments. Fourth, compact structure. The small radial thickness of the needle roller bearing eliminates the need to increase the motor's outer diameter, making it suitable for the narrow installation cavity of the cabin door lock. Fifth, resistance to aircraft vibration fatigue. Load is evenly distributed, eliminating the risk of ball pitting and bushing wear failure.

[0064] The ratio of the axial span between the first support member 10 and the second support member 11 to the cantilever length from the second support member 11 to the free end of the extension rod 8 is not less than 5:1. In a specific embodiment, the axial span L1 between the centers of the double support bearings is 100 mm, the cantilever length L2 from the distal support point to the force-bearing end face of the extension rod is 20 mm, and the ratio of the span to the cantilever length is 5:1.

[0065] The inventors creatively discovered that the mechanical model of the extension rod 8 is a double-point simply supported beam with a front cantilever, where all lateral loads are applied to the cantilever end. The larger the span and the shorter the cantilever, the significantly reduced the maximum bending moment of the rod. In one embodiment of this invention, the 5:1 span-to-cantilever length ratio, considering a maximum radial load of 15N, can control the radial deformation at the mover 6 position to the micrometer level, a magnitude far smaller than the rated air gap on one side of the motor, thus avoiding compression between the mover 6 and the air gap on one side of the stator 4. Compared to the traditional single-point support structure, the bending deformation of the rod under the same lateral force is more than five times that of this embodiment, making it highly prone to friction between the mover and the inner wall of the stator. This embodiment of the invention, with its large span double-point support, suppresses eccentricity from a mechanical perspective, ensuring a uniform air gap in the motor.

[0066] In other embodiments, the first support 10 and the second support 11 may also be sliding bushings. The sliding bushings form a sliding fit with the outer peripheral surface of the extension rod 8, i.e., surface contact. Although the load-bearing capacity of the sliding bushing is not as high as that of the line contact of the needle roller bearing, it has the advantages of simpler structure and easier assembly in low-cost and low-load scenarios. The present invention does not exclude the use of alternative support solutions such as sliding bushings, but the needle roller bearing is the preferred embodiment.

[0067] (vii) Mechanical limiting structure

[0068] like Figure 1 As shown, the housing 1 includes a front cover 2 and a rear cover 3. The front cover 2 has a through hole for the extension rod 8 to pass through. The extension rod 8 has a radially protruding limiting shoulder 13.

[0069] When the extension rod 8 extends to its maximum extension position, the limiting shoulder 13 abuts against the inner end face of the front cover 2, forming an extension limit, i.e., an unlocking limit, to prevent the extension rod 8 from dislodging from the housing 1. When the extension rod 8 retracts to its maximum retracted position, the rear end face of the mover 6 abuts against the inner end face of the rear end cover 3, forming a retraction limit, i.e., a locking limit, to prevent the extension rod 8 from retracting excessively. The two sets of limiting surfaces are located at the two ends of the movement stroke, forming a bidirectional mechanical limit.

[0070] It should be noted that mechanical limiting is achieved through the engagement of the limiting shoulder 13 with the front end cover 2 and the engagement of the rear end face of the mover 6 with the rear end cover 3. The function of the needle roller is to provide radial guidance and load bearing, and it does not undertake axial limiting function.

[0071] (viii) Sealing structure

[0072] A sealing element is provided at the through hole of the front cover 2. The sealing element is fitted around the outer periphery of the extension rod 8 and forms a sealing contact with the outer peripheral surface of the extension rod 8. Since the housing 1 is a rotating cylindrical structure, the sealing element only needs to be installed at the circular through hole of the front cover 2, resulting in a short sealing path and a small number of sealing elements. The sealing element can be an O-ring, a dust ring, or a combination thereof, to achieve a fully enclosed seal that is dustproof, waterproof, and oil-proof. The flight lock is installed inside the interior panel of the aircraft door. At high altitudes, there are conditions such as condensation, dust, and low temperatures. The sealing advantage of the rotating structure can meet the airworthiness and durability requirements of the aircraft.

[0073] (ix) Circuit components 17

[0074] Circuit assembly 17 includes a motor controller and a drive circuit for providing drive current to the stator windings. Circuit assembly 17 can be integrated into the cavity of the rear end cover 3 of the lock body or externally mounted outside the flight lock housing. When alternating current is supplied to the windings by circuit assembly 17, the windings generate a time-varying magnetic field that drives the mover 6 to move axially. When the power supply is cut off, the magnetic field of the windings disappears, and the spring 9 drives the extension rod 8 to reset. The specific implementation of circuit assembly 17 is known to those skilled in the art, and this invention does not specifically limit it.

[0075] Combination Figure 2 and Figure 3 The working process of the flight lock according to an embodiment of the present invention is as follows: Locking process ( Figure 2 After the flight lock is powered on and receives a locking enable signal, circuit component 17 supplies alternating current to the stator winding, generating a time-varying magnetic field. Under the influence of this time-varying magnetic field, the permanent magnet 7 on the mover 6 experiences axial electromagnetic thrust, causing the extension rod 8 to move from its extended position (…). Figure 3 As shown, it retracts axially to the retracted position. Figure 2 (As shown). During the retraction process, the spring 9 is further compressed and stores energy. When the rear end face of the mover 6 abuts against the inner end face of the rear end cover 3, the extension rod 8 reaches the maximum retraction position, forming a retraction limit, and the hatch structure is in the locked state.

[0076] Unlocking process ( Figure 3 (If no lock enable signal is received or the power is off, circuit assembly 17 cuts off the power supply to the stator winding, and the time-varying magnetic field of the winding disappears. Spring 9 releases its stored elastic potential energy, driving the extension rod 8 to return axially from the retracted position to the extended position. When the limiting shoulder 13 on the extension rod 8 abuts against the inner end face of the front cover 2, the extension rod 8 reaches the maximum extended position, forming an extension limit, and the hatch structure is in the unlocked state. Spring 9 still maintains residual pre-compression force in the extended position, keeping the extension rod 8 stably in the unlocked position.)

[0077] During the locking and unlocking processes, the first support member 10 and the second support member 11 always provide radial support to the extension rod 8, limiting the radial displacement of the extension rod 8 and ensuring that the circumferential air gap between the mover 6 and the stator 4 is uniform.

[0078] Addressing the challenges of confined spaces in aircraft door flight locks, harsh high-altitude environments, and high-frequency vibration conditions, the inventors discovered through analysis that cylindrical linear motors offer the following unique advantages compared to flat and curved linear motors: (1) Radial magnetic pull is naturally self-balancing. A flat linear motor has a single-sided stator magnetic field, and the mover continuously bears a unidirectional vertical magnetic pull, lacking self-balancing ability. Even slight lateral forces combined with the electromagnetic pull can easily cause jamming. An arc-shaped motor has only a local circumferential magnetic field, and the radial magnetic pull cannot be completely canceled out, resulting in a fixed off-center load. A cylindrical linear motor has a 360-degree annular winding plus annular permanent magnet structure. The radial magnetic pulls are equal in magnitude and opposite in direction, canceling each other out, and there is no inherent unidirectional electromagnetic off-center load. Only when a slight deviation occurs due to external mechanical lateral forces can the eccentricity be suppressed by the dual-point support of one embodiment of this invention. Flat and arc-shaped motors do not possess this characteristic.

[0079] (2) The rotating body has a compact structure. The installation envelope size of the aircraft door flight lock is strictly limited. The cylindrical motor is a standard rotating body with a uniform outer diameter. It does not have the lateral protrusion of the stator of the flat motor or the additional arc base of the arc motor. It can be axially nested and integrated into the lock housing, and occupies the least lateral space.

[0080] (3) The sealing structure is simple and reliable. The flight lock is installed inside the interior panel of the aircraft door, where there are conditions such as condensation, dust, and low temperature at high altitudes. The cylindrical rotating structure only has seals on the circular end faces at both ends, and a full seal can be achieved using standard O-rings and dust rings. The number of seals is small and the sealing path is short, resulting in better dustproof, waterproof, and oil-proof performance.

[0081] (4) Excellent machining and assembly processability. Stator 4, mover 6, and support sleeve are all rotating parts. Roundness and coaxiality can be stably controlled by precision machining on a lathe, resulting in low machining costs and good dimensional consistency. Assembly only requires axial insertion of the mover and needle roller bearings, without the need for complex alignment tooling. After assembly, the air gap around the entire circumference is naturally uniform, eliminating the need for separate correction of single-sided gaps and reducing the risk of eccentricity caused by assembly errors.

[0082] The inventors verified the technical effects of one embodiment of the present invention through experiments and reliability analysis: (1) Simplified Structure and Weight Reduction. In one embodiment of the present invention, the mechanical transmission chain such as the lead screw and lead screw nut is eliminated, reducing the number of supporting parts such as bearings. The original design had 17 parts per lock, with a total weight of 0.63 kg. The present design has 15 parts per lock, with a total weight of 0.58 kg, achieving a weight reduction of 0.05 kg per flight lock. Based on 8 flight locks per aircraft, the weight reduction per aircraft is 0.4 kg.

[0083] (2) Improved reliability. By eliminating the lead screw and other mechanical transmission chains, the structure is simplified and the reliability is relatively high. The mean time between failures (MTBF) of the original scheme was 102,085 flight hours, while that of this scheme is 104,089 flight hours, which is expected to increase by 2,000 flight hours.

[0084] (3) Improved transmission efficiency. In one embodiment of the present invention, a cylindrical linear motor is used to directly convert electromagnetic energy into mechanical energy for linear motion. The electromagnetic force is transmitted between the mover 6 and the stator 4 through a radial air gap, without mechanical contact or wear. Compared with the prior art scheme of indirect transmission of rotary motor through lead screw and nut pair, the transmission efficiency is significantly improved.

[0085] (4) No lubrication required. In one embodiment of the present invention, the ball screw pair is eliminated, and the needle roller bearing 12 operates on pure rolling friction, requiring no periodic lubrication. Compared with the maintenance requirement of periodic lubrication for the screw pair in the original solution, this solution offers better maintainability and reduces maintenance costs.

[0086] (5) Reduce the risk of jamming. In one embodiment of the present invention, four technical means are used in combination: optimization of the dual-point support position and span, matching design of high load-bearing needle roller bearings, air gap safety margin design and integrated coaxial structure of mover and extension rod. This suppresses mover eccentricity and wall friction from both mechanical and electromagnetic design perspectives, thereby reducing the risk of flight lock jamming.

[0087] (6) Dynamic response characteristics. The linear motor directly outputs linear motion without going through the rotation-linear conversion stage, resulting in good dynamic response characteristics and easy reduction of actuation time.

[0088] In the above embodiments, the first support 10 and the second support 11 are illustrated using a needle roller bearing as an example. However, the present invention does not exclude the use of other types of support members, such as linear ball bearings, sliding bushings, etc. Those skilled in the art can select these based on load rating and installation space, but they are not necessary choices for the solution of the present invention.

[0089] In the above embodiments, the permanent magnet 7 is surface-mounted to the outer peripheral surface of the mover 6. However, the present invention does not exclude the use of other permanent magnet arrangements, such as embedded or Halbach arrays. This can be selected by those skilled in the art based on thrust requirements and air gap uniformity requirements.

[0090] In the above embodiments, spring 9 was described as a compression spring. However, the present invention does not exclude the use of tension springs, symmetrically arranged double springs, or other elastic reset mechanisms. Those skilled in the art can choose according to the installation space and reset force requirements.

[0091] In the above embodiments, the ratio of the total axial length of the stator 4 to the effective working axial length of the permanent magnet 7 is illustrated using 1.56:1 as an example. However, this ratio is not limited to this specific value; as long as it is not less than 1.5:1, the technical effect of stable output of rated driving force throughout the entire process can be achieved.

[0092] In the above embodiments, the ratio of the double support span to the cantilever length is illustrated using 5:1 as an example. However, this ratio is not limited to this specific value; a ratio of not less than 5:1 can achieve the technical effect of controlling the radial deformation of the mover position to the micrometer level.

[0093] In the above embodiments, the material of the shell 1 is illustrated using aluminum alloy as an example. However, the present invention does not exclude the use of titanium alloy or other materials that combine lightweight and structural strength requirements.

[0094] Although various embodiments of the invention have been described in the accompanying drawings with reference to examples of structures based on aircraft door flight locks, it should be understood that the embodiments within the scope of the invention can be applied to devices or systems such as cargo hold locks, landing gear door locks, thrust reverser locks, spacecraft door locks, and rail transit door locks, which have similar structures and / or functions. In these applications, those skilled in the art can adjust the component parameters according to specific load, travel, and environmental requirements without requiring inventive effort.

[0095] The foregoing description has already given numerous features and advantages, including various alternative implementations, as well as details of the structure and function of the apparatus and method. The intent of this document is exemplary and not exhaustive or limiting. It will be apparent to those skilled in the art that various modifications can be made within the full scope indicated by the broad superordinate meaning of the terms expressed in the appended claims, particularly in terms of structure, materials, elements, components, shapes, dimensions, and arrangement of components, including combinations of these aspects within the scope of the principles described herein. Such various modifications are intended to be included herein without departing from the spirit and scope of the appended claims.

Claims

1. A flight lock, comprising: case; A cylindrical linear motor is disposed within the housing. The cylindrical linear motor includes a stator and a mover. The stator is fixed to the inner wall of the housing and has windings configured to generate a time-varying magnetic field when energized. The mover has permanent magnets and is coaxially disposed inside the stator with a radial air gap between them. The mover is configured to move axially under the action of the time-varying magnetic field. An extension rod, integrally formed with the moving part, extends axially from the front end of the housing; A spring is disposed within the housing, and the spring is configured to drive the extension rod to return to the extended position in the power-off state; A first support member, disposed within the housing and adjacent to the root of the mover, is configured to provide radial support for the extension rod; The second support member is disposed at the front end of the housing and located at the output port of the extension rod, and is configured to provide radial support for the extension rod; The first support member and the second support member are arranged at an axial interval along the extension rod, and together restrict the radial displacement of the extension rod.

2. The flight lock according to claim 1, characterized in that, The first support member and the second support member are both needle roller bearings. Each needle roller bearing includes multiple needle rollers arranged at intervals along the circumferential direction of the extension rod. The needle rollers form line contact with the outer circumferential surface of the extension rod.

3. The flight lock according to claim 2, characterized in that, The ratio of the axial span between the first support member and the second support member to the cantilever length from the second support member to the free end of the extension rod is not less than 5:

1.

4. The flight lock according to claim 1, characterized in that, The ratio of the total axial length of the stator to the effective working axial length of the permanent magnet on the mover is not less than 1.5:

1.

5. The flight lock according to claim 4, characterized in that, The stator has magnetic field redundancy sections at both ends in the axial direction. The magnetic field redundancy sections are configured to counteract local magnetic flux shift when the mover is subjected to lateral load.

6. The flight lock according to claim 1, characterized in that, The moving element and the extending rod are integrally formed from a single base material, and the permanent magnet is directly fixed to the outer peripheral surface of the moving element. There is no assembly interface between the moving element and the extending rod.

7. The flight lock according to claim 1, characterized in that, The radial air gap between the stator and the mover has a safety margin, which is configured such that when the extension rod is subjected to a predetermined lateral load, the minimum single-sided air gap between the mover and the stator remains positive.

8. The flight lock according to claim 1, characterized in that, The spring is a compression spring, which is sleeved on the outer periphery of the extension rod. The first end of the compression spring abuts against the fixed surface on the outer wall of the housing, and the second end of the compression spring abuts against the axial limiting step surface provided on the mover. The compression spring is kept in a pre-compressed state when the extension rod is in the retracted position.

9. The flight lock according to claim 1, characterized in that, The permanent magnets are fixed to the outer peripheral surface of the mover by surface mounting. The permanent magnets are arranged along the axial direction of the mover, and the magnetization directions of adjacent permanent magnets are alternately arranged.

10. The flight lock according to claim 1, characterized in that, The housing includes a front cover and a rear cover. The front cover has a through hole for the extension rod to pass through. The extension rod has a radially outwardly protruding limiting shoulder. The limiting shoulder is configured to abut against the inner end face of the front cover when the extension rod is extended to the maximum extension position to form an extension limit. The rear end face of the mover is configured to abut against the inner end face of the rear cover when the extension rod is retracted to the maximum retracted position to form a retraction limit.

11. A hatch locking system, comprising: A hatch structure, wherein the hatch structure is provided with a locking interface; The flight lock as described in any one of claims 1-10, wherein the extension rod of the flight lock is connected to the locking interface; When the stator winding of the flight lock is energized, the mover moves axially to retract the extension rod to the retracted position, thus locking the door structure. When the flight lock is de-energized, the spring drives the extension rod to return to the extended position, thus unlocking the door structure.

12. A method for locking and unlocking a flight lock, wherein, The flight lock is the flight lock as described in any one of claims 1-10, and the method includes: In the locking step, the stator winding is energized to generate a time-varying magnetic field. The mover moves axially under the action of the time-varying magnetic field and drives the extension rod to retract from the extended position to the retracted position. The spring is compressed and stores energy during the retraction of the extension rod. In the unlocking step, the power supply to the stator winding is cut off, the spring releases the stored energy and drives the extension rod to return from the retracted position to the extended position; In the guiding step, during the execution of the locking and unlocking steps, the protruding rod is radially supported by the first support member and the second support member to limit the radial displacement of the protruding rod.

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