A very fast retractable single-blade coaxial rotor helicopter

Abstract

To provide a superhigh-speed helicopter for a storage-type single blade coaxial rotary vane.SOLUTION: An airframe of an aircraft is included. A main wing and a tail unit are installed in the airframe. A tail-push propeller is installed at the tail end of the airframe. A rotary vane mechanism is installed at the top of the airframe. The rotary vane mechanism includes a rotary vane. The rotary vane mechanism can drive the rotary vane to be stored in a rotary vane storage chamber of the airframe. When the helicopter flies at a high speed, the rotary vane stops its operation, a propulsion force is provided by the tail-push propeller, and a lift force is provided by the main wing. Thus, a defect of aerodynamic characteristics of the rotary vane during high-speed flying is prevented, the rotary vane can be stored in the airframe, resistance is reduced, and maximum flying speed is increased.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the technical field of aircraft, and in particular to a retractable single-blade coaxial rotor super-high speed helicopter. [Background technology]

[0002] Although helicopters have unique application value in many aspects due to their vertical take-off and landing capability and higher air stationary efficiency, their shortcoming is their low flight speed compared to airplanes.

[0003] The aerodynamic characteristics of the rotor are the main reason for restricting the high-speed flight of a helicopter, that is, during forward flight, as the flight speed increases, shock waves are likely to appear on the advancing blade, which will dramatically increase drag, and the retreating blade is likely to have airflow separation, and as the flight speed increases, the airflow separation area will gradually become wider, and when the blade enters and leaves the area during rotation, the pitch moment will change greatly, which will cause vibration and early structural fatigue failure, and the stable operation characteristics of the helicopter will be poor. In the prior art, it is difficult to solve the effect of the rotor on the high-speed flight of a helicopter. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to solve the problems existing in the prior art and provide a retractable single-blade coaxial rotor ultra-high speed helicopter, in which when the helicopter flies at high speed, the rotor stops working, the tail thrust propeller provides thrust, and the main wing provides lift, thereby avoiding the aerodynamic defects of the rotor during high speed flight; the rotor can also be retracted and stored inside the fuselage, further reducing drag and improving maximum flight speed. [Means for solving the problem]

[0005] In order to achieve the above object, the present invention provides the following solutions: The present invention provides a retractable single-blade coaxial rotor super high-speed helicopter, which includes an airframe, a main wing and a tail wing are respectively installed on the airframe, a tail propeller is installed at the end of the airframe, and after the rotor is stored in a storage compartment, the propulsion of the aircraft is provided by the tail propeller and the lift is provided by the main wing, so that the aircraft changes to a propeller airplane mode to achieve high-speed flight, a rotor mechanism is installed on the top of the airframe, the rotor mechanism includes a rotor, and the rotor mechanism can drive the rotor to store in a rotor storage compartment inside the airframe.

[0006] Optionally, the rotor mechanism includes a rotor storage mechanism and a coaxially contra-rotating propeller mechanism, the rotors are mounted to the coaxially contra-rotating propeller mechanism, the coaxially contra-rotating propeller mechanism is mounted to the rotor storage mechanism, and the rotor storage mechanism can drive the coaxially contra-rotating propeller mechanism and the rotors to rise and fall within the rotor storage chamber.

[0007] Optionally, the rotor housing mechanism includes a base fixedly installed in the rotor housing chamber, two symmetrically arranged rotor housing guide rails are fixedly installed on the base, a coaxial contra-rotating propeller mechanism bracket is installed between the two rotor housing guide rails, both ends of the coaxial contra-rotating propeller mechanism bracket are slidably fitted in the two rotor housing guide rails, a vertically arranged rotor housing rack is installed on one side of the coaxial contra-rotating propeller mechanism bracket, and a rotor housing gear is meshed and connected to the rotor housing rack, the rotor housing gear is attached to the base through a rotor housing gear bracket, a joint is installed on one side of the rotor housing gear bracket remote from the rotor housing rack, an L-shaped groove is opened in the joint, a worm is installed in the L-shaped groove, the worm can be switched from a horizontal state to a vertical state along the L-shaped groove, and the worm is meshed and transmission-connected to the one side of the rotor housing gear remote from the rotor housing rack when switched to the vertical state.

[0008] Optionally, the coaxial contra-rotating propeller mechanism includes two left cranks and two right cranks installed on the coaxial contra-rotating propeller mechanism bracket, the two left cranks and the two right cranks are power-transmitted through a support rod, a worm gear is fixedly connected to the bottom of the two left cranks, and the worm is power-transmitted to the worm gear when it switches to a horizontal state, a first gear is fixedly connected to the top of the two left cranks, and a second gear is meshed with the first gear, the second gear is fixedly fitted on a rotation shaft of a first rotor, a rotation shaft of a second rotor is movably drilled in the rotation shaft of the first rotor, a bottom of the rotation shaft of the second rotor is fixedly connected to the top of the right crank, and the rotors are respectively installed on the rotation shaft of the first rotor and the rotation shaft of the second rotor.

[0009] Optionally, the rotor includes an upper single rotor and a lower single rotor arranged one above the other, each of the upper single rotor and the lower single rotor includes one blade, the upper single rotor is mounted on the rotation shaft of the second rotor via a propeller hub, and the lower single rotor is mounted on the rotation shaft of the first rotor via a propeller hub.

[0010] Optionally, a rotor housing door that can be opened and closed is provided at the top opening of the rotor housing, and the rotor housing door is controlled to be opened and closed, thereby completing the storage and deployment of the rotor.

[0011] Optionally, the main wings are mounted symmetrically on either side of the fuselage, and after the rotors are retracted into the fuselage, lift for the aircraft is provided by the main wings, and secondary wings are mounted on the main wings to provide roll moment for the roll movement of the aircraft.

[0012] Optionally, the tail is a V-tail with a V-shaped structure installed on both sides of the aircraft, and a control surface is installed on the V-tail, and the V-tail is made up of two left and right surfaces to form a "V" shape, and the V-tail can reduce the interference drag between the tails and between the tail and the aircraft with a small total number of parts, and can improve the flight speed of an airplane driven by a propeller. The two V-shaped tail surfaces all have a constant projected area in the top and side views, so they can simultaneously play a role in stabilizing the vertical direction (pitch) and the direction of flight, and the V-tail simultaneously functions as a vertical stabilizer and a horizontal stabilizer, and when both control surfaces are deflected in the same direction, they play the role of an elevator, and when they are deflected in different directions (differential), they play the role of a rudder.

[0013] Optionally, a circular through hole is drilled in the base, the circular through hole is at the bottom of the worm gear, and the inner diameter size of the circular through hole is larger than the outer diameter size of the worm gear. Effect of the Invention

[0014] Compared with the prior art, the present invention achieves the following technical advantages: The retractable single-blade coaxial rotor super-high-speed helicopter provided by the present invention has a rotor that stops working during high-speed flight, a tail thrust propeller provides thrust, and a main wing provides lift, thereby avoiding the aerodynamic defects of rotors during high-speed flight. The rotor can be retracted and stored inside the aircraft, further reducing drag and improving maximum flight speed. The rotation axes of the two-layer blades of the upper single rotor and the lower single rotor are arranged coaxially, and the rotation directions of the two are opposite to each other, which offsets the deflection moment of unidirectional rotation, and then the rotation speed can be reduced when the blade rotates to the forward side, and can be increased when the blade rotates to the retreating side, thereby mitigating the impact of the shock wave on the forward side and the airflow separation on the retreating side to a certain extent. The rotor system is different from the conventional multi-blade rotor system in that there is only one blade on each disk plane, and the two blades are respectively on the planes of two disks with different heights. As a result, the blades on the upper and lower disk planes can rotate simultaneously to the same phase, for example, the upper part of the rotor housing corresponds to the phase, and then drives the rotor to move up and down, thereby completing the storage of the rotor housing into the rotor system. When the rotor system is stored in the aircraft, the flight drag is greatly reduced, thereby greatly improving the flight speed. [Brief description of the drawings]

[0015] In order to more clearly describe the embodiments of the present invention or the technical solutions in the prior art, the drawings necessary to be used in the embodiments are briefly described below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those skilled in the art can further obtain other drawings based on these drawings without creative efforts.

[0016] [Figure 1] FIG. 1 is a structural schematic diagram of a retractable single-blade coaxial rotor hyperspeed helicopter according to the present invention. [Diagram 2] FIG. 1 is a front view of a retractable single-blade coaxial rotor hyperspeed helicopter according to the present invention; [Diagram 3]FIG. 1 is a side view of a retractable single-blade coaxial rotor hyperspeed helicopter according to the present invention. [Figure 4] FIG. 1 is a top view of a retractable single blade coaxial rotor hypervelocity helicopter according to the present invention; [Diagram 5] FIG. 2 is a schematic diagram of the rotor of the retractable single-blade coaxial rotor hyper-high speed helicopter according to the present invention after the rotor is retracted into the rotor storage compartment; [Figure 6] 4 is a schematic diagram of a conversion process in which the rotor according to the present invention is stored in the rotor storage chamber and the rotor is deployed. [Figure 7] FIG. 2 is a schematic diagram illustrating the principle of a coaxial counter-rotating propeller mechanism according to the present invention. [Figure 8] 1 is a schematic diagram showing the principle of a rotor housing mechanism according to the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention, and obviously, the described embodiments are only some embodiments of the present invention, not all embodiments, and all other embodiments obtained by those skilled in the art without creative efforts based on the embodiments of the present invention are all within the protection scope of the present invention.

[0018] In order to solve the problems existing in the prior art, the present invention aims to provide a retractable single-blade coaxial rotor ultra-high speed helicopter in which, when the helicopter flies at high speed, the rotor stops working, a tail thrust propeller provides thrust, and the main wing provides lift, thereby avoiding the aerodynamic defects of the rotor during high speed flight, and the rotor can be folded up and stored inside the fuselage, further reducing drag and improving maximum flight speed.

[0019] In order to make the above objects, features and advantages of the present invention more apparent and comprehensible, the present invention will be described in more detail below with reference to the drawings and the description of the preferred embodiment of the invention.

[0020] Helicopters, as a special aircraft, are often irreplaceable due to their vertical take-off and landing capability and higher hovering efficiency. However, traditional helicopters are limited by the aerodynamic characteristics of their rotors, making it difficult to further increase their flight speed, and the lack of speed greatly limits the scope of helicopter use. To solve the above problem, the present invention provides a high-speed helicopter solution with a new configuration of "retractable coaxial single blade + high-lift main wing + tail thrust propeller", which not only makes up for the shortcomings of traditional helicopters in terms of speed, but also retains the advantages of vertical take-off and landing and hovering of helicopters, greatly enriching the mission profile and scope of use of helicopters. Specifically, as shown in Figures 1, 2, 3 and 4, the retractable single-propeller coaxial rotor super-high-speed helicopter provided by the present invention is suitable for super-high-speed flight, and includes an airframe 1, the airframe 1 is provided with a main wing 2 and a tail wing, and the airframe 1 is provided with a retractable single-propeller coaxial rotor. At the end of the fuselage 1, a tail thrust propeller 7 is installed, and after the rotor is stored in the storage compartment, the propulsion force of the helicopter is provided by the tail thrust propeller 7, and the lift force is provided by the main wing 2, so that the helicopter changes to a propeller airplane mode and realizes high-speed flight. A rotor mechanism is installed at the top of the fuselage 1, and the rotor mechanism includes a rotor. As shown in FIG. 5 and FIG. 6, a rotor storage compartment is installed inside the fuselage 1, and the rotor storage compartment door 8 is controlled to be opened and closed, so that the rotor mechanism can drive the rotor to store in the rotor storage compartment inside the fuselage, thereby realizing the storage and deployment of the rotor, that is, a retractable rotor. At the main wings 2 on both sides of the fuselage 1, after the rotor is stored in the fuselage, the lift force of the aircraft is provided by the main wing 2, and the auxiliary wing 3 is installed on the main wing to provide a roll moment for the roll movement of the helicopter. The tail fin installed on the fuselage 1 is a V-shaped tail fin 5, and a control surface 6 is installed on the V-shaped tail fin 5. The V-tail 5 is composed of two wing surfaces, one on the left and one on the right, forming a "V shape." The V-tail 5 can reduce interference drag between the tails and between the tail and the fuselage with a small total number of parts, and can improve the flight speed of a propeller-driven airplane.The two V-shaped tail surfaces all have a constant projected area when viewed from the top and side, so they can simultaneously stabilize the vertical direction (pitch) and the direction of travel. The V-tail simultaneously functions as a vertical stabilizer and a horizontal stabilizer. When both control surfaces are deflected in the same direction, they act as an elevator, and when they are deflected in different directions (differential), they act as a rudder.

[0021] Specifically, the rotor mechanism includes a rotor storage mechanism and a coaxially contra-rotating propeller mechanism, and as shown in Figs. 7 and 8, the rotor is installed in the coaxially contra-rotating propeller mechanism, and the coaxially contra-rotating propeller mechanism is installed in the rotor storage mechanism, and the rotor storage mechanism can drive the coaxially contra-rotating propeller mechanism and the rotor to move up and down in the rotor storage chamber. The rotor storage mechanism includes a base 11 fixedly installed in the rotor storage chamber, and two symmetrically arranged rotor storage guide rails 13 are fixedly installed on the base 11, and a coaxially contra-rotating propeller mechanism bracket 14 is installed between the two rotor storage guide rails 13, and both ends of the coaxially contra-rotating propeller mechanism bracket 14 are slidably mounted on the two rotor storage guide rails 13, and the coaxially contra-rotating propeller mechanism can move up and down along the rotor storage guide rails 13, and a vertically arranged rotor storage rack 18 is installed on one side of the coaxially contra-rotating propeller mechanism bracket 14, and the rotor storage rack 18 is provided with a rotor storage rack 18. The rotor housing gear 17 is meshed and connected, the rotor housing gear 17 is attached to the base 11 via the rotor housing gear bracket 12, a joint 25 is installed on one side of the rotor housing gear bracket 12 remote from the rotor housing rack 18, an L-shaped groove is opened in the joint 25, a worm 15 is installed in the L-shaped groove, a power system is externally connected to the worm 15, which can be switched from a horizontal state to a vertical state along the L-shaped groove as a power input end, and when the worm 15 is switched to the vertical state, it is meshed and transmitted to the one side of the rotor housing gear 17 remote from the rotor housing rack 18. When the rotor is stored, the worm 15 is in a vertical state. At this time, the worm 15 rotates to drive the rotor storage gear 17 to rotate, and the rotor storage gear 17 meshes with the rotor storage rack 18. The rotor storage rack 18, as a driving force input point, drives the entire coaxial contra-rotating propeller mechanism to move up and down along the rotor storage guide rail 13, thereby completing the storage and deployment of the rotor system.

[0022] The coaxial contra-rotating propeller mechanism includes two left cranks 24 and two right cranks 26 mounted on the coaxial contra-rotating propeller mechanism bracket 14, and is power-transmitted between the two left cranks 24 and the two right cranks 26 via the support rods 21. The worm gear 16 is fixedly connected to the bottom of the two left cranks 24, and is power-transmitted to the worm gear 16 when the worm 15 is switched to the horizontal state. A circular through-hole is drilled in the base 11, and the circular through-hole is located at the bottom of the worm gear 16. When the rotor is stored, the worm gear 16 can easily move downward from within the circular through-hole, and the inner diameter size of the circular through-hole is adjusted so that the rotor can be stored in the rotor storage chamber without colliding with or interfering with the base 11. The diameter of the left crank 24 is larger than the outer diameter of the worm gear 16. The first gear 19 is fixedly connected to the top of the two left cranks 24. The second gear 20 is meshed with the first gear 19. The second gear 20 is fixedly fitted to the rotation shaft 22 of the first rotor. The rotation shaft 23 of the second rotor is movably drilled into the rotation shaft 22 of the first rotor. The two are arranged coaxially to realize the coaxiality of the two rotors. The bottom of the rotation shaft 23 of the second rotor is fixedly connected to the top of the right crank 26. When the coaxial contra-rotating propeller mechanism is operating, the worm 15 is in a horizontal state. At this time, the worm 15 rotates to drive the worm gear 16 to rotate. The worm gear 16 is fixedly connected to the left crank 24 and the first gear 19, and the three rotation directions are the same. There are four cranks in each of the four, and the two upper and lower cranks on the same side form one set, and the left and right cranks form two sets, i.e., the two cranks in one set are called left cranks, and the two cranks in the other set are called right cranks. The two sets are connected by a support rod 21, and the right crank is driven by the left crank through the support rod, so that the steering of the two sets of cranks coincides. At the same time, the right crank 26 is fixedly connected to the rotating shaft 23 of the second rotor, and the two rotation directions coincide, that is, the steering of the two sets of cranks, the rotating shaft 23 of the second rotor, the worm gear 16, and the first gear 19 coincides. The first gear 19 meshes with the second gear 20 to drive it to rotate, and the second gear 20 rotates in the opposite direction to the first gear 19. The second gear 20 is fixedly connected to the rotating shaft 22 of the first rotor, so that the steering of the two sets of cranks coincides.Therefore, the steering of the second gear 20 and the first rotor shaft 22 is opposite to the steering of the two sets of cranks, the second rotor shaft 23, the worm gear 16 and the first gear 19, i.e. the steering of the second rotor shaft 23 is opposite to the steering of the first rotor shaft 22, and the steering of the rotors respectively installed on both are opposite, thereby realizing a coaxial contra-rotating propeller.

[0023] In addition, preferably, the rotor includes an upper single rotor 9 and a lower single rotor 4 arranged one above the other, and the upper single rotor 9 and the lower single rotor 4 each include one blade, and have a single-blade structure, thereby realizing a single-blade coaxial rotor, that is, the upper single rotor 9 is mounted on the rotation shaft 23 of the second rotor through the propeller hub 10, and the lower single rotor 4 is mounted on the rotation shaft 22 of the first rotor through the propeller hub 10, and the rotation directions of the two are opposite to each other, and the deflection moment of unidirectional rotation is offset (here, the technique of the conventional coaxial contra-rotating propeller helicopter is used). The rotor blades are arranged in two layers, one above the other, so that the entire rotor system can be housed within the aircraft body, greatly reducing flight drag and further improving the ultimate flight speed, enabling high-speed or ultra-high-speed flight. This helicopter combines the vertical take-off and landing capabilities of a helicopter, efficient hovering in the air, and the high-speed cruising capabilities of a propeller aircraft.

[0024] The operation process of the present invention includes: (1) Vertical takeoff phase: The helicopter can take off vertically from a ship's deck or an airport and ascend to a cruising altitude using the lift provided by its single-bladed coaxial rotor. (2) Vertical takeoff to high speed cruising phase: After ascending vertically to cruising altitude, the tail thrust propeller 7 activates to provide thrust, the rotor well door 8 opens, the single-blade coaxial rotor rotates upward into the rotor well and stops, the lift-up propeller hub drives the single-blade coaxial rotor downward until the rotor is stowed within the rotor well, the rotor well door immediately closes and the flight mode conversion is completed to enter high speed cruising mode. (3) High-speed cruise phase: The helicopter provides thrust through the tail thrust propeller 7 and lift through the wings 2, with the rotors retracted within the fuselage, providing high-speed, highly efficient cruising in the form of a propeller aircraft. (4) Operational phase of performing hovering at a fixed altitude: The helicopter approaches the destination in a high-speed, highly efficient cruising state, the rotor well door opens, the liftable propeller hub drives the rotors to extend outside the well, the rotor well door 8 closes, the rotors start to rotate as the helicopter enters helicopter mode and flies forward at a slow speed above the target to perform the hovering operation.

[0025] In describing the present invention, it is necessary to explain that the directions or positional relationships indicated by the terms "center", "top", "bottom", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are directions or positional relationships based on the drawings, and are merely for the purpose of facilitating and simplifying the description of the present invention, and do not indicate or imply that devices or elements must have a particular orientation or be constructed and operated in a particular orientation, and therefore cannot be understood as limitations on the present invention. Also, the terms "first" and "second" are for the purpose of description only, and cannot be understood as indicating or implying a relative importance.

[0026] In the present invention, specific examples are used to explain the principles and embodiments of the present invention, and the above description of the examples is only used to help understand the method and core idea of ​​the present invention, and at the same time, for those skilled in the art, there are all changes in the form for implementing the invention and the scope of application according to the idea of ​​the present invention. Therefore, the contents of this specification should not be understood as limitations on the present invention. [Explanation of symbols]

[0027] 1-Aircraft 2- Main wing 3-Secondary wing 4-Lower single rotor 5-V type tail 6-Control surface 7-Tail-pushing propeller 8-Rotor compartment door 9-Upper single rotor 10-Propeller Hub 11-Base 12-Rotor housing gear bracket 13-Rotor storage guide rail 14-Coaxial Contra-rotating Propeller Mechanism Bracket 15-Warm 16-Worm Gear 17-Rotor housing gear 18-Rotor Storage Rack 19-1st Gear 20-2nd Gear 21-Support Rod 22-First rotor shaft 23-2nd rotor shaft 24-Left crank 25-Joint 26-Right Crank

Claims

1. A retractable single-blade coaxial rotor super-high speed helicopter, comprising an airframe, a main wing and a tail wing respectively installed on the airframe, a tail-pushing propeller installed at the end of the airframe, and a rotor mechanism installed at the top of the airframe, the rotor mechanism including rotors, the rotor mechanism being capable of driving the rotors to be stored in a rotor housing of the airframe, the rotor mechanism including a rotor housing mechanism and a coaxially contra-rotating propeller mechanism, the rotors being installed in the coaxially contra-rotating propeller mechanism, the coaxially contra-rotating propeller mechanism being installed in the rotor housing mechanism, the rotor housing mechanism being capable of driving the coaxially contra-rotating propeller mechanism and the rotors to be raised and lowered in the rotor housing mechanism, the rotor housing mechanism including a base fixedly installed in the rotor housing mechanism, two symmetrically arranged rotor housing guide rails being fixedly installed on the base, and a rotor housing member having a rotor housing member and a rotor housing member being fixedly installed between the two rotor housing guide rails. a rotor storage rack disposed vertically on one side of the coaxial propeller mechanism bracket, the rotor storage rack having a rotor storage gear meshed therewith; the rotor storage gear being attached to the base through a rotor storage gear bracket; a joint disposed on one side of the rotor storage gear bracket remote from the rotor storage rack, the joint having an L-shaped groove, a worm disposed in the L-shaped groove, the worm being capable of switching from a horizontal state to a vertical state along the L-shaped groove, the worm being meshed with the rotor storage gear at the vertical state, the worm being connected to the rotor storage gear at the vertical state.

2. 2. The retractable single-blade coaxial rotor super high-speed helicopter of claim 1, wherein the coaxial contra-rotating propeller mechanism includes two left cranks and two right cranks mounted on the coaxial contra-rotating propeller mechanism bracket, the two left cranks and the two right cranks are power-transmitted between them through a support rod, a worm gear is fixedly connected to the bottom of the two left cranks, and the worm is power-transmitted to the worm gear when it switches to a horizontal state, a first gear is fixedly connected to the top of the two left cranks, and a second gear is meshed with the first gear, the second gear is fixedly mounted on a rotation shaft of a first rotor, a rotation shaft of a second rotor is movably mounted within the rotation shaft of the first rotor, a bottom of the rotation shaft of the second rotor is fixedly connected to the top of the right crank, and the rotors are respectively mounted on the rotation shaft of the first rotor and the rotation shaft of the second rotor.

3. 3. The retractable single-blade coaxial rotor hyperspeed helicopter of claim 2, wherein the rotor comprises an upper single rotor and a lower single rotor arranged one above the other, the upper single rotor is mounted on a rotation shaft of the second rotor via a propeller hub, and the lower single rotor is mounted on a rotation shaft of the first rotor via a propeller hub.

4. 2. The retractable single-blade coaxial rotor super high speed helicopter according to claim 1, wherein a rotor bay door that can be opened and closed is provided at the top opening of the rotor bay.

5. 2. The retractable single-blade coaxial rotor super high speed helicopter according to claim 1, wherein the main wings are symmetrically installed on both sides of the fuselage, and auxiliary wings are installed on the main wings.

6. 2. The retractable single-blade coaxial rotor super high speed helicopter according to claim 1, wherein the tail is a V-tail installed on both sides of the fuselage in a V-shape, and a control surface is installed on the V-tail.

7. 3. The retractable single-blade coaxial rotor super high speed helicopter as claimed in claim 2, wherein the base is provided with a circular through hole, the circular through hole is located at the bottom of the worm gear, and the inner diameter of the circular through hole is larger than the outer diameter of the worm gear.

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