Aerodynamic retraction system for a landing gear with mechanical sequential control and rapid unloading

Abstract

A pneumatic landing gear retraction and extension system with mechanical sequence control and rapid unloading capability includes: a gas supply mechanism, an unloading valve, and a retraction and extension mechanism; the unloading valve has a left-position functional state and a right-position functional state; when the unloading valve is in the left-position functional state, the outlet of the unloading valve is connected to the inlet; when the unloading valve is in the right-position functional state, the outlet of the unloading valve is connected to the exhaust port; when the retraction and extension mechanism needs to be deployed, the unloading valve is in the left-position functional state; the gas supply mechanism supplies gas to the unloading valve, which enters the hatch retraction and extension mechanism and the positioning trigger valve of each retraction and extension mechanism; when the gas drives the hatch retraction and extension mechanism to deploy to the position, the positioning trigger valve switches to the conducting state, delivering gas to the landing gear retraction and extension mechanism to drive it to deploy to the position; when the retraction and extension mechanism is deployed to the position, the unloading valve is in the right-position functional state; the residual gas in the retraction and extension mechanism is discharged to the atmosphere through the exhaust port of the unloading valve, realizing rapid pneumatic unloading.

Description

Technical Field

[0001] This invention relates to a pneumatic landing gear retraction and extension system with mechanical sequence control and rapid unloading, belonging to the field of landing gear pneumatic retraction and extension system design. Background Technology

[0002] Pneumatic landing gear retraction systems are commonly used in aircraft such as drones. In these systems, ensuring that all components deploy in a predetermined sequence and that the mechanism quickly unloads gas after deployment is crucial for safe landing. If components do not deploy in the pre-set order, it can cause jamming or damage to the pneumatic mechanism, potentially preventing the landing gear from deploying properly and posing a significant safety hazard. Furthermore, if the landing gear is deployed without complete gas unloading before landing, it can lead to inaccurate landing gear positioning and structural overload upon impact, also posing serious safety risks. Therefore, aircraft landing gear retraction systems require all components to deploy in a predetermined sequence and ensure rapid gas unloading after deployment.

[0003] However, most existing landing gear aerodynamic retraction systems rely on computer-controlled deployment timing for each component. Computer-controlled deployment is susceptible to electromagnetic interference, easily leading to errors in the deployment timing of components within the system. Furthermore, existing landing gear aerodynamic retraction systems lack rapid unloading capabilities. Most systems only unload after landing, while a smaller number install exhaust valves on each retraction mechanism, controlling all valves to open for unloading once the landing gear is fully deployed. Installing exhaust valves on each mechanism makes valve operation cumbersome and redundant, requiring significant time for valve control and severely impacting overall unloading speed. Additionally, multiple exhaust valves increase aircraft weight, affecting flight performance.

[0004] For example, the patent "A Dual System for Integrated Landing Gear Retraction and Braking of a UAV (CN208544412U)" uses hydraulic drive and pneumatic emergency methods to achieve landing gear retraction and extension, but this method cannot perform pneumatic rapid unloading. The patent "An Energy-Redundant Pneumatic Landing Gear Retraction and Extension System (CN209225390U)" uses a cold air drive and gas energy redundancy scheme for landing gear retraction and extension, but this method also cannot perform pneumatic unloading. The patent "A Cold Air Landing Gear Retraction and Extension System and Its Landing and Landing Method (CN109733594A)" uses cold air as the main energy source for landing gear retraction and extension, controlling the retraction and extension speed through a reverse inflation strategy. However, this method uses electromagnetic reversing valves at the front end of each actuator for sequential control and exhaust of the components of the retraction and extension mechanism. This results in low reliability of sequential operation, a large number of electromagnetic reversing valves, and redundant exhaust schemes, severely affecting exhaust speed and increasing the weight of the aircraft. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a pneumatic landing gear retraction and extension system with mechanical sequence control and rapid unloading. This pneumatic retraction and extension system, through a position trigger valve and an unloading valve, solves the problems of existing systems being susceptible to electromagnetic interference leading to incorrect deployment timing of various components and the inability to achieve rapid exhaust and unloading.

[0006] The technical solution of this invention is: A pneumatic landing gear retraction and extension system with mechanical sequence control and rapid unloading includes: an air supply mechanism, an unloading valve, and a retraction and extension mechanism; The unloading valve has an air inlet, an air outlet, and an exhaust outlet, and has a left-position functional state and a right-position functional state. When the unloading valve is in the left-position functional state, the air outlet of the unloading valve is connected to the air inlet. When the unloading valve is in the right-position functional state, the air outlet of the unloading valve is connected to the exhaust outlet. The air inlet of the unloading valve is connected to the air supply mechanism, the air outlet of the unloading valve is connected in parallel with three retraction mechanisms, and the exhaust outlet of the unloading valve is open to the atmosphere. The retraction mechanism includes a door retraction mechanism, a positioning trigger valve, and a landing gear retraction mechanism. When the door retraction mechanism and landing gear retraction mechanism need to be deployed, the unloading valve is in the left-hand functional state; the gas supply mechanism supplies gas to the unloading valve, and the gas enters the door retraction mechanism and the landing gear trigger valve of each retraction mechanism through the gas outlet of the unloading valve; the landing gear trigger valve is in a non-conductive state when the door retraction mechanism is not deployed, and in a conductive state when the door retraction mechanism is deployed; the gas enters the door retraction mechanism and drives the door retraction mechanism to deploy; after the door retraction mechanism is deployed, the landing gear trigger valve is in a conductive state, and delivers gas to the landing gear retraction mechanism to drive the landing gear retraction mechanism to deploy; Once the landing gear retraction mechanism is fully extended, the unloading valve is in the right-hand position. The air supply mechanism stops supplying gas to the unloading valve, and the residual gas in the retraction mechanism is discharged to the atmosphere through the exhaust port of the unloading valve, achieving rapid pneumatic unloading.

[0007] Furthermore, the gas supply mechanism includes: a gas cylinder, a filling valve, a solenoid switch valve, a pressure reducing valve, and a check valve; The inflation valve, gas cylinder, electromagnetic switch valve, pressure reducing valve, and check valve are pneumatically connected in sequence; the outlet of the check valve is connected to the inlet of the unloading valve; the inflation valve is used to inflate the gas cylinder to the rated pressure so that the gas cylinder is filled with gas. When the door retraction mechanism and landing gear retraction mechanism need to be deployed, the electromagnetic switch valve opens, and the gas in the gas cylinder flows through the electromagnetic switch valve, pressure reducing valve and check valve in sequence under the pressure of the rated gas, and finally enters the unloading valve to provide gas to the unloading valve. Once the landing gear retraction mechanism has extended to its position, the electromagnetic switch valve closes, and the gas supply mechanism stops supplying gas to the unloading valve.

[0008] Furthermore, the pneumatic retraction and deployment system also includes a controller; the controller is used to remotely control the opening and closing of the electromagnetic switch valve, and also to remotely control the state switching of the unloading valve.

[0009] Furthermore, the door retraction mechanism includes a door upper lock and a door actuator; the landing gear retraction mechanism includes a landing gear upper lock and a landing gear actuator. The air inlet of the upper door lock is connected to the air outlet of the unloading valve, and the air outlet of the upper door lock is connected to the air inlet of the door actuator; the air inlet of the landing gear trigger valve is connected to the air outlet of the unloading valve, and the air outlet of the landing gear trigger valve is connected to the air inlet of the upper landing gear lock; the air outlet of the upper landing gear lock is connected to the air inlet of the landing gear actuator.

[0010] Furthermore, after the gas enters the hatch retraction mechanism, it first enters the upper lock of the hatch, driving the upper lock of the hatch to unlock. After the upper lock of the hatch is unlocked, the gas enters the hatch actuator, driving the piston rod of the hatch actuator to move to the end position. When the piston rod of the door actuator reaches its end position, the door retraction mechanism extends into place, and the position trigger valve changes from a non-conducting state to a conducting state; the gas in the unloading valve enters the landing gear upper lock through the position trigger valve, driving the landing gear upper lock to unlock into place; after the landing gear upper lock is unlocked, the gas enters the landing gear actuator, driving the piston rod of the landing gear actuator to move to its end position; when the piston rod of the landing gear actuator reaches its end position, the landing gear retraction mechanism extends into place.

[0011] Furthermore, the position trigger valve includes a push rod, a valve core, a spring, and a housing; The upper part of the shell is a cylindrical structure, and the bottom is a truncated conical structure; the shell has an air outlet on the side of the truncated conical bottom, an air inlet on the side of the cylindrical top, and a circular hole on the end face of the flat surface of the truncated conical bottom. The valve core is a stepped cylinder with a larger diameter force-bearing section and a smaller diameter sealing section. The valve core is located inside the housing, the sealing section faces the bottom of the housing, and the axis of the valve core is collinear with the axis of the housing. The force-bearing section has a vent hole along the axial direction, and the vent hole is located on the radial outer side of the sealing section. One end of the push rod is fixed at the center of the bottom surface of the sealing section, and the other end extends out through the round hole on the bottom surface of the housing; the extended end of the push rod is located at the end position that the piston rod of the hatch actuator can reach, and the axis of the push rod is perpendicular to the direction of movement of the piston rod of the hatch actuator. The spring is located inside the housing, with one end fixed to the top surface inside the housing and the other end fixed to the top surface of the valve core's force-bearing section. Under the action of the spring force, the sealing section of the valve core blocks the air passage between the air inlet and the air outlet of the housing, so that the position trigger valve is in a non-conducting state; when the piston rod of the hatch actuator moves to the end position, the piston rod of the hatch actuator provides an upward support force to the top rod, and the air passage between the air inlet and the air outlet is connected, so that the position trigger valve is in a conducting state.

[0012] Furthermore, the diameter of the valve core sealing section is larger than the diameter of the cross-section at the location of the air outlet on the housing, and smaller than the diameter of the cylindrical part of the housing; the diameter of the valve core force-bearing section is directly adapted to the cylindrical part of the housing.

[0013] Furthermore, when the piston rod of the door actuator has not moved to the end position, the spring applies a downward preload to the valve core, causing the valve core sealing section to press against the inner wall of the housing, and the pressing position is located above the air outlet, thereby blocking the air passage between the air outlet and the air inlet, so that the position trigger valve is in a non-conducting state. When the piston rod of the hatch actuator moves to its end position, the outer peripheral wall of the piston rod contacts the bottom end of the push rod and applies an upward thrust to the push rod; the push rod and the valve core move upward together under the thrust, the spring is compressed, and the valve core sealing section disengages from the seal against the inner wall of the housing; at this time, the air inlet and outlet of the position trigger valve are connected to each other through the vent hole on the valve core, so that the position trigger valve is in the conducting state.

[0014] Furthermore, the diameter of the push rod matches the diameter of the bottom circular hole of the housing, thereby preventing gas leakage from the bottom circular hole; The bottom end of the push rod is provided with a hemispherical base, and the spherical surface of the base faces the end position of the piston rod of the hatch actuator, so that the piston rod can smoothly push the push rod upward.

[0015] Furthermore, when the unloading valve is in the right-hand functional state, the residual gas in the upper door lock and the door actuator is discharged to the atmosphere through the exhaust port of the unloading valve; the residual gas in the upper landing gear lock and the landing gear actuator is discharged to the atmosphere in sequence through the position trigger valve and the unloading valve.

[0016] The advantages of this invention compared to the prior art are: (1) After the take-up and release mechanism moves to the position, the present invention enables the take-up and release mechanism to be directly connected to the external atmosphere through the unloading valve, which greatly improves the speed of gas unloading, ensures that the gas inside the take-up and release mechanism can be completely released, and further improves the reliability of the take-up and release mechanism.

[0017] (2) In the process of exhaust and unloading, the present invention only needs to control one unloading valve, and does not need to install an exhaust valve on each retraction mechanism. This simplifies the control sequence of the valves during the exhaust process and achieves rapid exhaust without increasing the weight of the aircraft.

[0018] (3) The present invention uses a position trigger valve to ensure that the air is supplied to the upper landing gear lock and landing gear actuator only after the door actuator has moved to the position. This mechanical structure effectively ensures the sequence of the retraction and extension mechanism, further improving the reliability of the entire system.

[0019] (4) The end of the trigger valve rod of the present invention adopts a round head design, which can effectively prevent the trigger valve rod from jamming due to reasons such as eccentricity of the door actuator piston rod and installation error. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a pneumatic landing gear retraction and extension system with mechanical sequence control and rapid unloading according to the present invention. Figure 2 This is a schematic diagram of the positioning trigger valve structure in a pneumatic landing gear retraction and extension system with mechanical sequence control and rapid unloading, according to the present invention. Detailed Implementation

[0021] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.

[0022] like Figure 1 As shown, the present invention provides a pneumatic retraction and extension system for landing gear with mechanical sequence control and rapid unloading, comprising: an air supply mechanism 12, an unloading valve 6, and a retraction and extension mechanism; The unloading valve 6 has an air inlet, an air outlet, and an exhaust outlet, and has a left-position functional state and a right-position functional state. When the unloading valve 6 is in the left-position functional state, the air outlet of the unloading valve 6 is connected to the air inlet. When the unloading valve 6 is in the right-position functional state, the air outlet of the unloading valve 6 is connected to the exhaust outlet. The air inlet of the unloading valve 6 is connected to the air supply mechanism 12, and the air outlet of the unloading valve 6 is connected in parallel with three retraction mechanisms. The exhaust outlet of the unloading valve 6 is open to the atmosphere. The retraction mechanism includes a door retraction mechanism 13, a positioning trigger valve 9, and a landing gear retraction mechanism 14. When the door retraction mechanism 13 and the landing gear retraction mechanism 14 need to be deployed, the unloading valve 6 is in the left-hand functional state; the gas supply mechanism 12 supplies gas to the unloading valve 6, and the gas enters the door retraction mechanism 13 and the positioning trigger valve 9 of each retraction mechanism through the gas outlet of the unloading valve 6; the positioning trigger valve 9 is in a non-conductive state when the door retraction mechanism 13 is not deployed, and is in a conductive state when the door retraction mechanism 13 is deployed; the gas enters the door retraction mechanism 13 and drives the door retraction mechanism 13 to deploy; after the door retraction mechanism 13 is deployed, the positioning trigger valve 9 is in a conductive state and delivers gas to the landing gear retraction mechanism 14 to drive the landing gear retraction mechanism 14 to deploy; When the landing gear retraction mechanism 14 is deployed, the unloading valve 6 is in the right-hand position; the air supply mechanism 12 stops supplying gas to the unloading valve 6, and the residual gas in the retraction mechanism is discharged to the atmosphere through the exhaust port of the unloading valve 6, thereby achieving rapid pneumatic unloading.

[0023] The non-conducting state of the position trigger valve 9 means that the air inlet and outlet of the position trigger valve 9 are not connected, while the conducting state of the position trigger valve 9 means that the air inlet and outlet of the position trigger valve 9 are connected.

[0024] Furthermore, the gas supply mechanism 12 includes: a gas cylinder 1, a filling valve 2, a solenoid switch valve 3, a pressure reducing valve 4, and a one-way valve 5; The inflation valve 2, gas cylinder 1, electromagnetic switch valve 3, pressure reducing valve 4 and one-way valve 5 are pneumatically connected in sequence; the outlet of the one-way valve 5 is connected to the inlet of the unloading valve 6; the inflation valve 2 is used to inflate the gas cylinder 1 to the rated pressure so that the gas cylinder 1 is filled with gas. When the door retraction mechanism 13 and the landing gear retraction mechanism 14 need to be deployed, the electromagnetic switch valve 3 opens, and the gas in the gas cylinder 1 flows through the electromagnetic switch valve 3, the pressure reducing valve 4 and the one-way valve 5 in sequence under the pressure of the rated gas, and finally enters the unloading valve 6 to provide gas to the unloading valve 6. Once the landing gear retraction mechanism 14 has extended to its position, the electromagnetic switch valve 3 closes, and the gas supply mechanism 12 stops supplying gas to the unloading valve 6.

[0025] Both the position trigger valve 9 and the solenoid switch valve 3 are two-position two-way structures.

[0026] Furthermore, the pneumatic retraction and extension system also includes a controller; the controller is used to remotely control the opening and closing of the electromagnetic switch valve 3, and at the same time to remotely control the state switching of the unloading valve 6.

[0027] Furthermore, the door retraction mechanism 13 includes a door upper lock 7 and a door actuator 8; the landing gear retraction mechanism 14 includes a landing gear upper lock 10 and a landing gear actuator 11. The air inlet of the upper door lock 7 is connected to the air outlet of the unloading valve 6, and the air outlet of the upper door lock 7 is connected to the air inlet of the door actuator 8; the air inlet of the position trigger valve 9 is connected to the air outlet of the unloading valve 6, and the air outlet of the position trigger valve 9 is connected to the air inlet of the upper landing gear lock 10; the air outlet of the upper landing gear lock 10 is connected to the air inlet of the landing gear actuator 11.

[0028] Furthermore, after the gas enters the hatch retraction mechanism 13, it first enters the hatch upper lock 7, driving the hatch upper lock 7 to unlock into place; after the hatch upper lock 7 is unlocked into place, the gas enters the hatch actuator 8, driving the piston rod of the hatch actuator 8 to move to the end position. When the piston rod of the door actuator 8 moves to the end position, the door retraction mechanism 13 unfolds into place, and the position trigger valve 9 changes from a non-conducting state to a conducting state; the gas in the unloading valve 6 enters the landing gear upper lock 10 through the position trigger valve 9, driving the landing gear upper lock 10 to unlock into place; after the landing gear upper lock 10 is unlocked into place, the gas enters the landing gear actuator 11, driving the piston rod of the landing gear actuator 11 to move to the end position; when the piston rod of the landing gear actuator 11 moves to the end position, the landing gear retraction mechanism 14 unfolds into place.

[0029] Furthermore, such as Figure 2 As shown, the position trigger valve 9 includes a push rod 901, a valve core 902, a spring 903, and a housing 904; The upper part of the housing 904 is a cylindrical structure, and the bottom is a truncated conical structure; the housing 904 has an air outlet on the side of the truncated conical bottom, an air inlet on the side of the cylindrical top, and a circular hole on the end face of the flat surface of the truncated conical bottom. The valve core 902 is a stepped cylinder with a larger diameter force-bearing section and a smaller diameter sealing section. The valve core 902 is located inside the housing 904, with the sealing section facing the bottom of the housing 904, and the axis of the valve core 902 is collinear with the axis of the housing 904. The force-bearing section has a vent hole along the axial direction, and the vent hole is located on the radial outer side of the sealing section. One end of the top rod 901 is fixed at the center of the bottom surface of the sealing section, and the other end extends out through the round hole on the bottom surface of the housing 904; the extended end of the top rod 901 is located at the end position that the piston rod of the door actuator 8 can move to, and the axis of the top rod 901 is perpendicular to the direction of movement of the piston rod of the door actuator 8. The spring 903 is located inside the housing 904. One end of the spring 903 is fixed to the top surface inside the housing 904, and the other end is fixed to the top surface of the force-bearing section of the valve core 902. Under the elastic force of the spring 903, the sealing section of the valve core 902 blocks the air passage between the air inlet and the air outlet of the housing 904, so that the position trigger valve 9 is in a non-conducting state; when the piston rod of the hatch actuator 8 moves to the end position, the piston rod of the hatch actuator 8 provides an upward support force to the top rod 901, and the air passage between the air inlet and the air outlet is connected, so that the position trigger valve 9 is in a conducting state.

[0030] Furthermore, the diameter of the sealing section of the valve core 902 is larger than the diameter of the cross-section at the location of the air outlet on the housing 904, and smaller than the diameter of the cylindrical part of the housing 904; the diameter of the force-bearing section of the valve core 902 is directly adapted to the cylindrical part of the housing 904.

[0031] Furthermore, when the piston rod of the door actuator 8 has not moved to the end position, the spring 903 applies a downward preload to the valve core 902, causing the sealing section of the valve core 902 to press against the inner wall of the housing 904, and the pressing position is located above the air outlet, thereby blocking the air passage between the air outlet and the air inlet, so that the position trigger valve 9 is in a non-conducting state. When the piston rod of the hatch actuator 8 moves to its end position, the outer peripheral wall of the piston rod contacts the bottom end of the push rod 901 and applies an upward thrust to the push rod 901; the push rod 901 and the valve core 902 move upward together under the action of the thrust, the spring 903 is compressed, and the sealing section of the valve core 902 disengages from the sealing contact with the inner wall of the housing 904; at this time, the air inlet and air outlet of the position trigger valve 9 are connected to each other through the vent hole on the valve core 902, so that the position trigger valve 9 is in the conducting state.

[0032] Furthermore, the diameter of the push rod 901 matches the diameter of the bottom circular hole of the housing 904, thereby preventing gas leakage from the bottom circular hole; The bottom end of the push rod 901 is provided with a hemispherical base, and the spherical surface of the base faces the end position of the piston rod of the door actuator 8, so that the piston rod can smoothly push the push rod 901 upward. The end of the position trigger valve push rod of the present invention adopts a round head design, which can effectively prevent the position trigger valve push rod from jamming due to the eccentricity of the piston rod of the door actuator, installation error, etc.

[0033] Furthermore, when the unloading valve 6 is in the right-hand functional state, the residual gas in the upper door lock 7 and the door actuator 8 is discharged to the atmosphere through the exhaust port of the unloading valve 6; the residual gas in the upper landing gear lock 10 and the landing gear actuator 11 is discharged to the atmosphere in sequence through the position trigger valve 9 and the unloading valve 6.

[0034] In summary, after the retraction mechanism has reached its designated position, this invention uses an unloading valve to directly connect the retraction mechanism to the external atmosphere, accelerating the gas unloading speed and ensuring the complete release of gas inside the retraction mechanism, thus further improving its reliability. Simultaneously, during exhaust unloading, this invention only requires controlling one unloading valve, eliminating the need for an exhaust valve on each retraction mechanism, simplifying the valve control sequence during exhaust and achieving rapid exhaust without increasing the aircraft's weight. Furthermore, this invention uses a position trigger valve to ensure that gas is only supplied to the landing gear upper lock and landing gear actuator after the door actuator has reached its designated position, effectively guaranteeing the sequence of retraction mechanism actions through mechanical structure, further enhancing the reliability of the entire system.

[0035] The parts of this invention not described in detail are common knowledge to those skilled in the art.

Claims

1. A pneumatic retraction and extension system for landing gear with mechanical sequence control and rapid unloading capability, characterized in that, include: Gas supply mechanism (12), unloading valve (6) and retraction mechanism; The unloading valve (6) has an air inlet, an air outlet and an exhaust outlet, and has a left-position functional state and a right-position functional state; when the unloading valve (6) is in the left-position functional state, the air outlet of the unloading valve (6) is connected to the air inlet; when the unloading valve (6) is in the right-position functional state, the air outlet of the unloading valve (6) is connected to the exhaust outlet; the air inlet of the unloading valve (6) is connected to the air supply mechanism (12), the air outlet of the unloading valve (6) is connected to three retraction mechanisms in parallel, and the exhaust outlet of the unloading valve (6) is connected to the atmosphere; The retraction mechanism includes a door retraction mechanism (13), a positioning trigger valve (9), and a landing gear retraction mechanism (14). When the door retraction mechanism (13) and landing gear retraction mechanism (14) need to be deployed, the unloading valve (6) is in the left-hand functional state; the gas supply mechanism (12) supplies gas to the unloading valve (6), and the gas enters the door retraction mechanism (13) and the position trigger valve (9) of each retraction mechanism through the outlet of the unloading valve (6), driving the door retraction mechanism (13) to deploy; after the door retraction mechanism (13) is deployed to the position, the position trigger valve (9) is turned on, and the gas is delivered to the landing gear retraction mechanism (14), driving the landing gear retraction mechanism (14) to deploy; When the landing gear retraction mechanism (14) is deployed, the unloading valve (6) switches to the right position; the air supply mechanism (12) stops supplying gas to the unloading valve (6), and the residual gas in the retraction mechanism is discharged to the atmosphere through the exhaust port of the unloading valve (6), thus achieving rapid pneumatic unloading.

2. The pneumatic retraction and extension system for landing gear with mechanical sequence control and rapid unloading as described in claim 1, characterized in that: The gas supply mechanism (12) includes: a gas cylinder (1), a filling valve (2), a solenoid switch valve (3), a pressure reducing valve (4), and a one-way valve (5); The inflation valve (2), gas cylinder (1), electromagnetic switch valve (3), pressure reducing valve (4) and one-way valve (5) are pneumatically connected in sequence; the outlet of the one-way valve (5) is connected to the inlet of the unloading valve (6); the inflation valve (2) is used to inflate the gas cylinder (1) to the rated pressure so that the gas cylinder (1) is filled with gas. When the door retraction mechanism (13) and landing gear retraction mechanism (14) need to be deployed, the electromagnetic switch valve (3) opens, and the gas in the gas cylinder (1) flows through the electromagnetic switch valve (3), pressure reducing valve (4) and check valve (5) in sequence under the pressure of rated gas, and finally enters the unloading valve (6) to provide gas to the unloading valve (6); When the landing gear retraction mechanism (14) is deployed, the electromagnetic switch valve (3) closes and the gas supply mechanism (12) stops supplying gas to the unloading valve (6).

3. The pneumatic retraction and extension system for landing gear with mechanical sequence control and rapid unloading as described in claim 2, characterized in that: The pneumatic take-up and release system also includes a controller; the controller is used to remotely control the opening and closing of the electromagnetic switch valve (3), and at the same time to remotely control the state switching of the unloading valve (6).

4. The pneumatic retraction and extension system for landing gear with mechanical sequence control and rapid unloading as described in claim 1, characterized in that: The door retraction mechanism (13) includes a door upper lock (7) and a door actuator (8); the landing gear retraction mechanism (14) includes a landing gear upper lock (10) and a landing gear actuator (11). The air inlet of the upper door lock (7) is connected to the air outlet of the unloading valve (6), and the air outlet of the upper door lock (7) is connected to the air inlet of the door actuator (8); the air inlet of the position trigger valve (9) is connected to the air outlet of the unloading valve (6), and the air outlet of the position trigger valve (9) is connected to the air inlet of the upper landing gear lock (10); the air outlet of the upper landing gear lock (10) is connected to the air inlet of the landing gear actuator (11).

5. A pneumatic retraction and extension system for landing gear with mechanical sequence control and rapid unloading as described in claim 4, characterized in that: After the gas enters the hatch retraction mechanism (13), it first enters the hatch upper lock (7) and drives the hatch upper lock (7) to unlock. After the hatch upper lock (7) is unlocked, the gas enters the hatch actuator (8) and drives the piston rod of the hatch actuator (8) to move to the end position. When the piston rod of the door actuator (8) moves to the end position, the door retraction mechanism (13) unfolds into place, and the position trigger valve (9) changes from a non-conducting state to a conducting state; the gas in the unloading valve (6) enters the landing gear upper lock (10) through the position trigger valve (9), driving the landing gear upper lock (10) to unlock into place; after the landing gear upper lock (10) is unlocked into place, the gas enters the landing gear actuator (11), driving the piston rod of the landing gear actuator (11) to move to the end position; when the piston rod of the landing gear actuator (11) moves to the end position, the landing gear retraction mechanism (14) unfolds into place.

6. A pneumatic landing gear retraction and extension system with mechanical sequence control and rapid unloading as described in claim 4, characterized in that: The position trigger valve (9) includes a push rod (901), a valve core (902), a spring (903), and a housing (904). The upper part of the shell (904) is a cylindrical structure, and the bottom is a truncated conical structure; the shell (904) has an air outlet on the side of the truncated conical bottom, an air inlet on the side of the cylindrical top, and a circular hole on the end face of the truncated conical bottom. The valve core (902) is a stepped cylinder with a larger diameter force-bearing section and a smaller diameter sealing section. The valve core (902) is located inside the housing (904), with the sealing section facing the bottom of the housing (904), and the axis of the valve core (902) is collinear with the axis of the housing (904). The force-bearing section has a vent hole along the axial direction, and the vent hole is located on the radial outer side of the sealing section. One end of the top rod (901) is fixed at the center of the bottom surface of the sealing section, and the other end extends out through the round hole on the bottom surface of the housing (904); the extended end of the top rod (901) is located at the end position that the piston rod of the door actuator (8) can reach, and the axial direction of the top rod (901) is perpendicular to the direction of movement of the piston rod of the door actuator (8). The spring (903) is located inside the housing (904). One end of the spring (903) is fixed to the top surface inside the housing (904), and the other end is fixed to the top surface of the force-bearing section of the valve core (902). Under the elastic force of the spring (903), the sealing section of the valve core (902) blocks the air passage between the air inlet and the air outlet of the housing (904), so that the position trigger valve (9) is in a non-conducting state; when the piston rod of the hatch actuator (8) moves to the end position, the piston rod of the hatch actuator (8) provides an upward support force to the top rod (901), and the air passage between the air inlet and the air outlet is connected, so that the position trigger valve (9) is in a conducting state.

7. A pneumatic landing gear retraction and extension system with mechanical sequence control and rapid unloading as described in claim 6, characterized in that: The diameter of the sealing section of the valve core (902) is greater than the diameter of the cross section at the location of the air outlet on the housing (904) and smaller than the diameter of the cylindrical part of the housing (904); the diameter of the force-bearing section of the valve core (902) is directly adapted to the cylindrical part of the housing (904).

8. A pneumatic landing gear retraction and extension system with mechanical sequence control and rapid unloading as described in claim 7, characterized in that: When the piston rod of the hatch actuator (8) has not moved to the end position, the spring (903) applies a downward preload to the valve core (902), causing the valve core (902) to press against the inner wall of the housing (904), and the pressing position is located above the air outlet, thereby blocking the air passage between the air outlet and the air inlet, so that the position trigger valve (9) is in a non-conducting state; When the piston rod of the hatch actuator (8) moves to the end position, the outer peripheral wall of the piston rod contacts the bottom end of the push rod (901) and applies an upward thrust to the push rod (901); the push rod (901) and the valve core (902) move upward together under the action of the thrust, the spring (903) is compressed, and the sealing section of the valve core (902) disengages from the seal against the inner wall of the housing (904); at this time, the air inlet and outlet of the position trigger valve (9) are connected to each other through the vent hole on the valve core (902), so that the position trigger valve (9) is in the conducting state.

9. A pneumatic landing gear retraction and extension system with mechanical sequence control and rapid unloading as described in claim 6, characterized in that: The diameter of the top rod (901) matches the diameter of the bottom circular hole of the housing (904), thereby preventing gas from leaking from the bottom circular hole; The bottom end of the push rod (901) is provided with a hemispherical base, and the spherical surface of the base faces the end position of the piston rod of the door actuator (8), so that the piston rod can smoothly push the push rod (901) upward.

10. A pneumatic landing gear retraction and extension system with mechanical sequence control and rapid unloading as described in claim 4, characterized in that: When the unloading valve (6) is in the right-hand functional state, the residual gas in the upper door lock (7) and the door actuator (8) is discharged to the atmosphere through the exhaust port of the unloading valve (6); the residual gas in the upper landing gear lock (10) and the landing gear actuator (11) is discharged to the atmosphere through the position trigger valve (9) and the unloading valve (6) in sequence.

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