A rebound hammer

Abstract

The present invention relates to a rebound hammer, comprising a rebound hammer bracket and a pendulum. A hook bracket is rotatably mounted on the rebound hammer bracket, a pendulum hook mating portion is provided on the pendulum, a hook mechanism is provided on the hook bracket for hooking and mating with the pendulum hook mating portion, an unlocking trigger device is also provided on the rebound hammer bracket, and a spring device is also provided on the rebound hammer bracket. The spring device has a potential energy trigger portion that is pushed by the pendulum to store energy when the hook mechanism drives the pendulum to rotate in the opposite direction. The spring device is independently provided with the pendulum. When the pendulum collides with an external force, the pendulum and the potential energy trigger portion are spaced apart. The rebound hammer bracket is also provided with a speed detection device for detecting the rotation speed of the pendulum. The present invention solves the technical problem in the prior art that, because the pendulum spring always acts on the pendulum, when the pendulum collides, if the pendulum spring is not in the zero potential energy position, the accuracy of the rebound value characterized by the kinetic energy loss before and after the pendulum collision is affected.

Description

Technical Field

[0001] The invention relates to concrete strength testing equipment, in particular to a rebound tester. Background Art

[0002] A rebound test hammer is a device used to test concrete strength. Its working principle is that a spring-driven hammer strikes the concrete surface through a rod, causing the concrete surface to elastically deform to absorb energy. The hammer then rebounds, and the energy loss is used to characterize the concrete's hardness. The harder the concrete, the less energy it absorbs through elastic deformation, and the less energy is lost during the hammer's impact and rebound.

[0003] The working process of the rebound hammer is as follows Figure 10 As shown: To clearly illustrate the problem, the first, second, third, fourth and fifth states occur in chronological order. During operation, the height of the hammer 21 is first raised and maintained by a hook mechanism (not shown in the figure). As shown in the first state, the hammer spring 22 stores energy, and the end of the hammer rod 20 away from the hammer contacts the concrete surface. Subsequently, the hook mechanism releases the hammer 21, and the hammer moves toward the hammer rod under the guidance of the guide rod 23, as shown in the second state. Subsequently, the lower end face 24 of the hammer strikes the hammer rod 20, and the hammer rod strikes the concrete, as shown in the third state. Immediately afterwards, as shown in the fourth state, the hammer begins to rebound away from the hammer rod. Finally, as shown in the fifth state, the hammer reaches the highest rebound position.

[0004] In the prior art, there are basically two measurement methods to characterize the energy loss of the impact hammer. The first method is to measure the height difference between the impact hammer in the first state and the fifth state, and calculate the rebound value through the change in energy between the two states. The difference between the sum of the gravitational potential energy of the impact hammer in the first state and the elastic potential energy of the spring in the first state and the sum of the gravitational potential energy of the impact hammer in the fifth state and the elastic potential energy of the spring in the fifth state is the change in energy between the two states. This method obviously has the following disadvantages: 1) The change from the first state to the fifth state is not only a change in gravitational potential energy and elastic potential energy. There is sliding friction between the impact hammer and the guide rod. This friction will also cause energy loss. This friction cannot be ignored and will affect the accuracy of the rebound value characterization; 2) Since the gravitational potential energy of the impact hammer must be considered, the impact angle of the impact rod hitting the concrete surface is very critical, and the entire operation process is relatively strict.

[0005] The second method is to measure the impact velocity V0 when the hammer hits the impact rod, and the rebound velocity VR when the hammer just leaves the impact rod. The energy loss of the hammer is characterized by the kinetic energy loss of the hammer before and after the impact, and then the rebound value is calculated. This method has the following disadvantages: the hammer spring 13 is always connected to the hammer 21. 1) Due to the existence of the hammer spring, the kinetic energy loss is not complete in the two states before and after the impact. Only when the elastic potential energy of the hammer spring 22 is at the potential energy zero point at the moment of impact, the kinetic energy loss can accurately characterize the energy loss of the hammer. However, it is difficult to ensure that the spring is at the potential energy zero point at the moment of impact, because the zero potential energy point of the spring is affected by many factors such as gravity, posture, and spring fatigue; 2) The friction between the hammer and the impact rod is still an energy loss factor that cannot be ignored in the energy calculation process.

[0006] Chinese patent CN2021221258413 discloses a "pendulum rebound tester" that uses a swinging pendulum to achieve impact. The center of gravity of the pendulum is located on the axis of rotation of the pendulum. Therefore, before and after the pendulum impact, the gravitational potential energy does not do work, which reduces the impact of the gravitational potential energy on the pendulum before and after the impact. However, it still has the problem that the pendulum spring is always connected to the pendulum, that is, before and after the impact, the pendulum spring always acts on the pendulum. If you want to use kinetic energy to characterize the impact loss, you still need to find the zero potential energy point of the pendulum spring, which requires an additional indirect impact, which is more cumbersome to use. Summary of the Invention

[0007] The object of the present invention is to provide a rebound hammer to solve the technical problem in the prior art that, because the pendulum spring always acts on the pendulum, if the pendulum spring is not in the zero potential energy position when the pendulum impacts, it will affect the accuracy of the rebound value characterized by the kinetic energy loss before and after the pendulum impact.

[0008] In order to solve the above technical problems, a technical solution of a rebound tester in the present invention is as follows:

[0009] A rebound tester comprises a rebound tester bracket and a pendulum with a rotation axis extending in the front-to-back direction for realizing external impact when rotating forward, the pendulum having a pendulum impact part, a hook bracket rotatably assembled on the rebound tester bracket and arranged coaxially with the pendulum, the hook bracket having a bracket torque input structure for inputting torque to drive the hook bracket to rotate, a pendulum hook matching part is provided on the pendulum, and a hook mechanism for hooking and cooperating with the pendulum hook matching part is provided on the hook bracket, an unlocking trigger device for pushing and cooperating with the hook mechanism to realize unlocking of the hook mechanism and the pendulum hook matching part is also provided on the rebound tester bracket, a spring device is also provided on the rebound tester bracket, the spring device has a potential energy trigger part for being pushed by the pendulum when the hook mechanism drives the pendulum to rotate in the opposite direction to realize energy storage, the spring device and the pendulum are independently arranged, and the pendulum is spaced apart from the potential energy trigger part when the pendulum collides with the outside, and a speed detection device for detecting the rotation speed of the pendulum is also provided on the rebound tester bracket.

[0010] Furthermore, the rebound tester bracket is provided with traveling wheels.

[0011] Furthermore, the center of gravity of the pendulum is located on the rotation axis of the pendulum.

[0012] Furthermore, the hook mechanism includes a hook rod rotatably assembled on the hook bracket, and the rotation axis extends along the front-to-back direction. One end of the hook rod is provided with a hook for hooking with the pendulum hook matching part, and the other end of the hook rod is provided with a pushing head for contacting and pushing with the unlocking trigger device. A hook return spring is provided between the hook rod or the pushing head and the hook bracket.

[0013] Furthermore, the bracket torque input structure includes a transmission shaft whose rotation axis extends in the front-to-back direction, and the rebound hammer bracket is provided with a driving motor for driving the transmission shaft to rotate.

[0014] Furthermore, a fixed shaft with an axis extending in the front-to-back direction is fixed on the bracket. The fixed shaft, pendulum and hook bracket are coaxially arranged. The hook bracket and pendulum are rotatably sleeved on the fixed shaft. The hook bracket is located in front of the pendulum.

[0015] Furthermore, the speed detection device includes a magnetic ring fixed on the pendulum and a magnetic encoder fixed on the rebound tester bracket and used in conjunction with the magnetic ring.

[0016] Furthermore, the pendulum hook matching portion is located on the front side of the pendulum, and at least two of the hook mechanisms are provided on the hook bracket, each hook mechanism is arranged at intervals along the circumferential direction, and the hook bracket drives each hook mechanism to rotate in the opposite direction, and each hook mechanism is hooked and matched with the pendulum hook matching portion in sequence.

[0017] Furthermore, the spring device includes a disc spring having one end fixed on a fixed shaft and the other end connected to a barrier rod, the barrier rod constituting the potential energy triggering part, the length of the barrier rod extending in the front-to-back direction, the axis of the disc spring coaxially arranged with the rotation axis of the pendulum, the disc spring located at the front or rear side of the pendulum, and the barrier rod located at the upper side of the pendulum.

[0018] The beneficial effects of the present invention are as follows: when in use, the hook mechanism is hooked and matched with the pendulum hook matching part on the pendulum, the hook bracket rotates, and the hook mechanism rotates the pendulum in the opposite direction through the hook matching part. After the pendulum rotates to a certain angle, the pendulum contacts the potential energy triggering part of the spring device and compresses the spring device, and the spring device begins to store energy. As the hook bracket continues to rotate in the opposite direction, when the hook mechanism triggers the reverse unlocking trigger device, the hook mechanism releases the hook with the pendulum hook matching part, the spring device releases energy, and the pendulum rotates forward. After the pendulum is separated from the potential energy triggering part of the spring device, the pendulum impact part of the pendulum will impact outward. The speed detection device detects the speed of the inverted pendulum before and after the impact, and calculates the energy loss caused by the impact through the change in kinetic energy to characterize the hardness of the corresponding concrete. In the present invention, the pendulum will not impact outward until it is separated from the spring device. Therefore, at the moment of impact, the spring device and the pendulum are separated. At the moment of impact, the potential energy of the spring will not act on the pendulum. The speed change before and after the impact can accurately reflect the energy loss caused by the impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present disclosure are shown in an illustrative and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0020] Figure 1 1 is a structural diagram of a rebound hammer according to embodiment 1 of the present invention;

[0021] Figure 2 yes Figure 1 A top view of

[0022] Figure 3 This is a schematic diagram of the state when the hook bracket in Example 1 rotates in the opposite direction with the pendulum through the hook mechanism.

[0023] Figure 4 is a schematic diagram of the state after the hook mechanism and the unlocking trigger device are in contact in Example 1;

[0024] Figure 5 yes Figure 1 Schematic diagram of the structure of the pendulum;

[0025] Figure 6 yes Figure 1 A magnified view of point A in the figure;

[0026] Figure 7 1 is a structural diagram of a rebound hammer according to a second embodiment of the present invention;

[0027] Figure 8 Schematic diagram of the cooperation between the impact wheel and the rebound tester bracket in Example 2;

[0028] Figure 9 1 is a schematic structural diagram of a rebound hammer according to a third embodiment of the present invention;

[0029] Figure 10 It is a schematic diagram of the use principle of the rebound hammer in the background technology of the present invention;

[0030] Explanation of the accompanying reference numerals: 1. pendulum; 1-1. pendulum hook fitting part; 2. hook mechanism; 2-1. hook rod; 2-2. hook; 3. spring device; 3-1. coil spring; 3-2. blocking rod; 4. unlocking trigger device; 5. magnetic ring; 6. magnetic encoder; 7. driving motor; 8. walking wheel; 9. rebound tester bracket; 10. fixed shaft; 11. pendulum impact part; 12. surface of the object to be tested; 13. transmission shaft; 14. hook bracket; 15. hook reset spring; 16. pushing head; 17. striking wheel; 18. striking wheel axle; 19. axle reset spring; 20. striking rod; 21. striking hammer; 22. striking hammer spring; 23. guide rod; 24. lower end face of the striking hammer. DETAILED DESCRIPTION

[0031] To facilitate understanding of the present invention, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments. Preferred embodiments of the present invention are shown in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0032] It should be noted that, unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0033] Embodiment 1 of a rebound tester in the present invention is as follows Figures 1 to 6 As shown in the figure, it includes a rebound hammer bracket 9, which is a shell structure. The rebound hammer bracket 9 is not completely drawn in the figure. A running wheel 8 is provided at the bottom of the rebound hammer bracket 9. The running wheel 8 may not have a power source. When in use, the staff pushes the rebound hammer bracket to move it by hand, or a running wheel driving motor is provided to drive the running wheel, and the rebound hammer bracket is moved by electric drive.

[0034] A fixed shaft 10 with an axis extending in the front-to-back direction is fixed to the rebound tester bracket. A coaxial rotating sleeve is connected to the fixed shaft 10 for realizing external impact when rotating in the forward direction. The center of gravity of the pendulum 1 is located on the axis of rotation of the pendulum. Therefore, during the reciprocating swing of the pendulum, the gravity in the pendulum does not do work. The pendulum has a pendulum impact part 11 for impacting the surface of the object to be tested 12. The pendulum impact part 11 is a ball head structure, so the pendulum impact part is in point contact with the surface of the object to be tested. The forward and reverse directions in the present invention are relative, that is, when the pendulum rotates, the rotation in one direction is forward, and the rotation in the other direction is reverse. In this embodiment, Figure 1 Viewing angle, counterclockwise rotation becomes positive, clockwise rotation becomes negative.

[0035] The front end of the fixed shaft is also coaxially rotatably sleeved with a hook bracket 14, on which a transmission shaft 13 is fixed, which is sleeved on the front end of the fixed shaft. The transmission shaft constitutes a bracket torque input structure for inputting torque to drive the hook bracket to rotate. In this embodiment, a drive motor 7 for driving the transmission shaft to rotate is provided on the rebound tester bracket.

[0036] The hook bracket is a rod-shaped structure whose length extends radially along the fixed axis. A hook mechanism 2 is provided at both ends of the hook bracket. A pendulum hook matching part 1-1 for matching with the hook of the hook mechanism is provided on the pendulum 1. The hook matching part includes a hook matching groove. The hook matching groove is located on the front side of the pendulum. The hook mechanism 2 is located on the front side of the pendulum 1. The hook mechanism includes a hook rod 2-1 that is rotatably mounted on the hook bracket and extends along the front-to-back direction along the rotation axis. One end of the hook rod 2-1 is provided with a hook 2-2 for matching with the hook. The other end of the hook rod is provided with a pushing head 16. A hook return spring 15 is provided between the pushing head 16 and the hook bracket 14. The hook spring is used to apply force to the pushing head so that the hook rod has a clockwise rotation tendency.

[0037] The rebound tester bracket is also provided with an unlocking trigger device 4 for cooperating with the hook mechanism to push and unlock the hook mechanism and the pendulum hook matching part. In this embodiment, the unlocking trigger device is a fixed block fixed to the rebound tester bracket. When the hook bracket rotates clockwise, the pushing head touches the unlocking trigger device, the hook rod rotates counterclockwise, and the hook 2-2 can be disengaged from the hook matching groove. At the same time, as the hook bracket 14 continues to rotate clockwise, the pushing head 16 can pass over the unlocking trigger device. In this way, the hook bracket only needs to maintain clockwise unidirectional rotation, and each hook mechanism 2 can cooperate with the hook matching part in sequence. The hook bracket does not need to rotate back and forth, and the control is simpler.

[0038] A spring device 3 is also provided on the rebound hammer bracket. The spring device 3 has a potential energy trigger part that is pushed by the pendulum to store energy when the hook mechanism drives the pendulum to rotate in the opposite direction. The spring device and the pendulum are independently arranged. When the pendulum collides with the outside, the pendulum and the potential energy trigger part are spaced apart. A speed detection device for detecting the rotation speed of the pendulum is also provided on the rebound hammer bracket.

[0039] In this embodiment, the speed detection device includes a magnetic ring 5 fixed on the pendulum and a magnetic encoder 6 fixed on the rebound hammer bracket and used in conjunction with the magnetic ring. The magnetic encoder can measure the rotational angular velocity of the pendulum.

[0040] The spring device 3 includes a disc spring 3-1 whose inner end is fixed on a fixed shaft and whose outer end is connected to a barrier rod 3-2. The barrier rod 3-2 constitutes a potential energy trigger part. The length of the barrier rod is extended in the front-to-back direction. The axis of the disc spring is coaxial with the rotation axis of the pendulum. The disc spring 3-1 is located between the pendulum 1 and the hook bracket 14, and the barrier rod is located on the upper side of the pendulum.

[0041] When used, in the initial state, such as Figure 2 As shown, the pendulum impact part of the pendulum contacts the surface of the tested object, the hook of the hook mechanism hooks and cooperates with the pendulum hook matching part on the pendulum, the coil spring of the spring device is in a free state (zero potential energy state), and the pendulum and the blocking rod of the spring device are spaced apart in the circumferential direction; the driving motor drives the hook bracket to rotate clockwise, and the hook bracket rotates clockwise with the pendulum through the hook mechanism. When the pendulum contacts the blocking rod, as shown in FIG. Figure 3 As shown, the coil spring of the spring device begins to store energy. As the hook bracket and the pendulum continue to rotate clockwise, the pushing head of the hook mechanism contacts the unlocking trigger device on the rebound tester bracket, the hook rod of the hook mechanism rotates counterclockwise, the hook of the hook mechanism disengages from the pendulum hook matching part, and the coil spring begins to release energy. Under the action of the coil spring, the pendulum rotates counterclockwise, that is, forward. When the pendulum is disengaged from the blocking rod, the pendulum impact part does not contact the surface of the tested object. As the pendulum continues to rotate counterclockwise, the pendulum impact part of the pendulum contacts and collides with the surface of the tested object. After the collision, the pendulum rebounds, and the magnetic encoder measures the speed of the pendulum before and after the collision. The speed directions of the pendulum before and after the collision are opposite, so this speed is easy to measure. The kinetic energy loss before and after the collision is calculated based on the speed before and after the collision. Since in the present invention, the pendulum is disengaged from the spring device during the collision, the spring device does not act on the pendulum at the moment of collision. The kinetic energy loss before and after the collision is the total energy loss, which can accurately characterize the absorbed energy of the surface of the tested object, thereby accurately judging the hardness of the surface of the tested object.

[0042] When continuous impact testing is required, the hook bracket continues to rotate clockwise, and the other hook mechanism cooperates with the pendulum hook matching part.

[0043] In other embodiments of the present invention, there may be only one hook mechanism. In this case, the hook bracket may swing back and forth to achieve multiple impacts on the surface of the object being tested. The spring device may be a coil spring. The coil spring may be arc-shaped or linear, as long as the coil spring can be compressed to store energy during the reverse rotation of the pendulum.

[0044] A rebound tester embodiment 2 is as follows Figures 7 and 8 As shown: Example 2 is different from Example 1 in that, in this embodiment, the pendulum impact part 11 of the pendulum does not directly impact the surface 12 of the tested object, but the pendulum impacts the surface of the tested object through the impact wheel 17. The outer peripheral surface of the impact wheel is spherical, and the impact wheel axle 18 of the impact wheel is guided and moved in the up and down directions and assembled on the rebound tester bracket 9. A bearing is sleeved on the impact wheel axle of the impact wheel, and an axle reset spring 19 is provided between the upper end of the bearing and the rebound tester bracket. The axle reset spring ensures that the impact wheel is always in contact with the surface of the tested object.

[0045] A rebound tester embodiment 3 is as follows Figure 9 As shown: Example 3 is different from Example 1 in that, in this embodiment, the pendulum impact part 11 of the pendulum does not directly impact the surface 12 of the object to be tested, but the pendulum impacts the surface 12 of the object to be tested through the impact rod 20, and the impact rod is guided and moved in the up and down directions and assembled on the rebound tester bracket 9, and the lower end surface of the impact rod is a spherical surface.

[0046] In the foregoing description of this specification, unless otherwise expressly specified or limited, terms such as "fixed," "mounted," "connected," or "connected" should be understood broadly. For example, the term "connected" can refer to a fixed connection, a removable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediary; or the internal connection between two components or the interaction between two components. Therefore, unless otherwise expressly defined in this specification, those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0047] According to the above description of this specification, those skilled in the art may also understand that the terms used below, such as "up", "down", "front", "back", "left", "right", "length", "width", "thickness", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential", "center", "longitudinal", "transverse", "clockwise" or "counterclockwise", etc., which indicate orientation or positional relationships, are based on the orientation or positional relationships shown in the drawings of this specification, and are only for the purpose of facilitating the explanation of the scheme of the present invention and simplifying the description, rather than explicitly or implicitly indicating that the device or element involved must have the specific orientation, be constructed and operate in a specific orientation. Therefore, the above-mentioned orientation or positional relationship terms cannot be understood or interpreted as limitations on the scheme of the present invention.

[0048] In addition, the terms "first" or "second" used in this specification to refer to numbers or ordinal numbers are used for descriptive purposes only and should not be understood as explicitly or implicitly indicating relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this specification, "plurality" means at least two, such as two, three or more, etc., unless otherwise clearly specified.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A rebound hammer, comprising a rebound hammer support and a pendulum with a rotation axis extending in the front-to-back direction for achieving external impact when rotating in the forward direction, the pendulum having a pendulum impact portion, characterized in that: A hook bracket coaxially arranged with the pendulum is rotatably assembled on the rebound hammer bracket, the hook bracket has a bracket torque input structure for torque input to drive the hook bracket to rotate, a pendulum hook matching portion is provided on the pendulum, and a hook mechanism for hooking and cooperating with the pendulum hook matching portion is provided on the hook bracket. The rebound hammer bracket is also provided with an unlocking trigger device for pushing and cooperating with the hook mechanism to unlock the hook mechanism and the pendulum hook matching portion. The rebound hammer bracket is also provided with a spring device, the spring device has a potential energy trigger portion for being pushed by the pendulum when the hook mechanism drives the pendulum to rotate in the opposite direction to realize energy storage. The spring device is independently provided with the pendulum. When the pendulum collides with the outside, the pendulum The rebound hammer bracket is arranged at a distance from the potential energy trigger part. A speed detection device for detecting the rotation speed of the pendulum is also provided on the rebound hammer bracket. A fixed shaft with an axis extending in the front-to-back direction is fixed on the rebound hammer bracket. The fixed shaft, the pendulum and the hook bracket are arranged coaxially. The hook bracket and the pendulum are connected to the fixed shaft through a rotating sleeve. The hook bracket is located on the front side of the pendulum. The spring device includes a disc spring with one end fixed on the fixed shaft and the other end connected to a baffle. The baffle constitutes the potential energy trigger part. The length of the baffle extends in the front-to-back direction. The axis of the disc spring is coaxial with the rotation axis of the pendulum. The disc spring is located on the front or rear side of the pendulum. The baffle is located on the upper side of the pendulum. The rebound hammer bracket is provided with a walking wheel.

2. The rebound hammer according to claim 1, characterized in that: The center of gravity of the pendulum is located on the axis of rotation of the pendulum.

3. The rebound hammer according to claim 1, wherein: The hook mechanism includes a hook rod rotatably assembled on the hook bracket and extending along the front-to-back direction along the rotation axis. One end of the hook rod is provided with a hook for hooking with the pendulum hook matching part, and the other end of the hook rod is provided with a pushing head for contacting and pushing with the unlocking trigger device. A hook return spring is provided between the hook rod or the pushing head and the hook bracket.

4. The rebound hammer according to claim 1, wherein: The bracket torque input structure includes a transmission shaft whose rotation axis extends in the front-to-back direction. The rebound hammer bracket is provided with a driving motor for driving the transmission shaft to rotate.

5. The rebound hammer according to claim 1, wherein: The speed detection device comprises a magnetic ring fixed on the pendulum and a magnetic encoder fixed on the rebound tester bracket and used in conjunction with the magnetic ring.

6. The rebound hammer according to claim 1, characterized in that: The pendulum hook matching part is located on the front side of the pendulum, and at least two hook mechanisms are provided on the hook bracket. Each hook mechanism is arranged at intervals along the circumferential direction. The hook bracket rotates in the opposite direction with each hook mechanism, and each hook mechanism is hooked and matched with the pendulum hook matching part in sequence.

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