An excitation actuator

Abstract

The application discloses an actuating executor, which comprises a shell, an actuating source, a rotating executor, a cavity arranged in the shell, a first limiting structure arranged in the cavity, the rotating executor rotatably arranged in the cavity, a connecting end arranged on at least one side of the rotating executor, the connecting end arranged towards the outside of the shell so that the connecting end can be connected with at least one driven end outside the shell, the first limiting structure defining an initial position of the rotating executor, the actuating source arranged on the shell, a receiving end of the actuating source receiving a trigger signal and being connectable with the outside of the shell, one end of the actuating source releasing high-pressure gas and being in communication with the cavity where the rotating executor is arranged, and the rotating executor driven by the high-pressure gas released by the actuating source to displace from the initial position to a terminal position against the first limiting structure. The application has the advantages of fast response speed, small volume and simple structure.

Description

Technical Field

[0001] This invention relates to the fields of power control and electric vehicles, and in particular to an excitation actuator for rapidly changing the state of the main circuit. The excitation actuator can drive switching devices to move rapidly, change the switching state, and realize the change of the main circuit state. Background Technology

[0002] Actuators are essential components in automatic control systems, responsible for transmitting power. Their primary function is to receive control signals from the controller, transmit power to change the state of the controlled medium, and drive valves or switches to open, close, or regulate. Currently, mainstream actuators are primarily electric, pneumatic, and hydraulic. Generally, they use a motor to drive a transmission mechanism or pneumatic / hydraulic pressure as the drive source, propelling the device to perform linear, rotary, or helical motions, serving as the drive source for circuit control devices. Due to their inherent structure and power source, different actuator designs often result in complex structures, large sizes, low response speeds, low transmission efficiency, and difficulty in application under specific working environments. Developing a compact actuator with a fast response speed is a pressing technical problem that needs to be solved. Summary of the Invention

[0003] The purpose of this invention is to provide an excitation actuator that releases high-pressure gas as a driving force through an electronic ignition device, drives a rotating actuator to rotate, and provides torque to the driven end as a driving force, thereby changing the state of a switching device.

[0004] To achieve the above objectives, the present invention provides an actuator, comprising a housing, an excitation source, and a rotating actuator. The housing has a cavity, and a first limiting structure is provided within the cavity. The rotating actuator is rotatably disposed within the cavity, and a connecting end is provided on at least one side of the rotating actuator. The side of the rotating actuator with the connecting end is rotatably mounted on the housing wall, and the connecting end faces outward from the housing, allowing it to connect to at least one external driven end. The first limiting structure defines the initial position of the rotating actuator. The excitation source is disposed on the housing, and the receiving end of the excitation source that receives a trigger signal is connected to the outside of the housing. One end of the excitation source that releases high-pressure gas communicates with the cavity where the rotating actuator is located. When the excitation source actuates, the released high-pressure gas drives the rotating actuator to overcome the limitation of the first limiting structure and move from the initial position to the final position.

[0005] Preferably, a second limiting structure is provided in the cavity, which limits the termination position of the rotating actuator when the rotating actuator is displaced to the termination position.

[0006] Preferably, the cavity includes a connected arc-shaped cavity and a fan-shaped cavity; the rotating actuator includes an integrally connected circular portion and a lever portion, the connecting end is disposed on one side of the circular portion, the circular portion is rotatably fitted into the arc-shaped cavity, the lever portion is disposed in the fan-shaped cavity, and the lever portion is in contact with the fan-shaped cavity; the fan-shaped cavity is provided with a first limiting structure and a second limiting structure, which respectively limit the initial position and the final position of the lever portion, the initial position of the lever portion being located near the end of the excitation source that releases high-pressure gas.

[0007] Preferably, a first limiting hole is provided in the lever portion, the first limiting structure is a positioning pin, and the second limiting structure is a limiting protrusion; in the initial position, the positioning pin is located in the first limiting hole, limiting the initial position of the lever portion; when the lever portion overcomes the limitation of the first limiting structure and moves to the termination position, the first limiting hole moves to the limiting protrusion, and the limiting protrusion is nested in the first limiting hole, limiting the termination position of the lever portion.

[0008] Preferably, the edge of the lever portion away from the circular portion has a beveled structure.

[0009] Preferably, the connecting end is a connecting shaft protruding from the side of the rotating actuator or a connecting hole located on the side of the rotating actuator.

[0010] Preferably, the connecting shaft or connecting hole has a polygonal structure.

[0011] Preferably, the connecting ends are respectively provided on opposite sides of the rotating actuator, the connecting ends are respectively located on opposite sides of the housing, and at least one driven end can be connected to each connecting end.

[0012] Preferably, an indicator that can be displaced to the outside of the housing is provided in the housing. One end of the indicator extends into the cavity and is located at the termination position of the rotating actuator, while the other end is located in the shell wall of the housing. When the rotating actuator moves from the initial position to the termination position, the rotating actuator abuts against the end of the indicator located in the cavity, driving the indicator to move towards the outside of the housing, so that the end of the indicator located in the shell wall of the housing is displaced to the outside of the housing.

[0013] Preferably, a mounting hole is provided on the outer shell wall, the mounting hole connecting the outside of the outer shell to the cavity, a limiting cavity is provided in the mounting hole, the indicator passes through the mounting hole, and a third limiting structure and a fourth limiting structure are provided on the indicator at intervals along its length direction, the third limiting structure and the fourth limiting structure are located in the limiting cavity, the third limiting structure is located at the front end of the limiting cavity in the displacement direction of the indicator, and the fourth limiting structure is located at the rear end in the displacement direction of the indicator; when the indicator is displaced, the third limiting structure is released from limiting; when one end of the indicator located in the outer shell wall is displaced to the outside of the outer shell, the fourth limiting structure is displaced to the front end of the limiting cavity and abuts against the front end of the limiting cavity.

[0014] The excitation actuator of the present invention uses an excitation source as the actuator trigger source, has a fast response speed, and can quickly drive the rotating actuator to rotate, generate torque, and provide driving force to the driven end.

[0015] It can be fixed by sliding rails or bolts and nuts, or both, for easy installation;

[0016] Limiting structures with initial and final positions are designed for the actuator during operation to prevent malfunctions and rebound at the final position.

[0017] The rotating actuator has a connecting end on at least one side, which is fixedly connected to multiple driven ends. It has various connection methods, can drive multiple driven end modules, has high output efficiency, and can realize multi-angle and multi-directional execution actions.

[0018] An indicator is set in the actuator to trigger an alarm after the action is performed.

[0019] It has a simple overall structure, is lightweight, small in size, low in production cost, and highly versatile. It is also easy to install and operates quickly. It can be used to quickly control circuit breakers and other protective devices, providing a rapid response and significantly improving breaking capacity to avoid safety hazards. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention in its initial position.

[0021] Figure 2 yes Figure 1 A side view structural diagram.

[0022] Figure 3 yes Figure 1 A schematic diagram of the structure after the action.

[0023] Figure 4 yes Figure 2 A schematic diagram of the structure after the action.

[0024] Figure 5 This is a schematic diagram of a shell structure with a sliding groove.

[0025] Figure 6 It is a schematic diagram of the housing structure with a sliding groove and a mounting base.

[0026] Figure 7 This is a schematic diagram of the indicator structure.

[0027] Figure 8 These are schematic diagrams and enlarged views of the rotating actuator structure.

[0028] Figure 9 This is a schematic diagram of the structure when the rotating actuator is in its initial position.

[0029] Figure 10 yes Figure 9 AA cross-section view.

[0030] Figure 11 yes Figure 10 A magnified schematic diagram of part B.

[0031] Figure 12 This is a schematic diagram of a rotating actuator with connecting ends on opposite sides.

[0032] Figure Labels

[0033] 1. Indicator; 2. Excitation source; 3. Rotation actuator; 4. Housing; 5. Bolt; 6. Cover plate; 7. Fourth limiting structure 101; 8. Third limiting structure 102; 9. Circular part 301; 10. Lever part 302; 10. Circular boss 303; 10. Connecting end 304; 10. First limiting hole 305; 10. Inclined surface structure 306; 10. First mounting hole 401; 10. Arc-shaped cavity 402; 10. Fan-shaped cavity 403; 10. First limiting structure 404; 10. Second limiting structure 405; 10. Second mounting hole 406; 10. Third mounting hole 407; Limiting cavity 407a; 11. Slide groove structure 408; 12. Mounting base 409. Detailed Implementation

[0034] The actuator of the present invention includes a housing, an excitation source, and a rotating actuator. The housing has a cavity, and a first limiting structure is provided within the cavity. The rotating actuator is rotatably disposed within the cavity, and a connecting end is provided on at least one side of the rotating actuator. The side of the rotating actuator with the connecting end is rotatably mounted on the wall of the housing, with the connecting end facing outwards, allowing it to be connected to at least one external driven end. The first limiting structure defines the initial position of the rotating actuator. The excitation source is disposed on the housing, and a receiving end of the excitation source that receives a trigger signal is connected to the outside of the housing. One end of the excitation source that releases high-pressure gas communicates with the cavity where the rotating actuator is located. When the excitation source actuates, the released high-pressure gas drives the rotating actuator to overcome the limitation of the first limiting structure and move from the initial position to the final position.

[0035] The following describes preferred embodiments in detail with reference to the accompanying drawings. The directional terms used are for reference only and do not constitute a limitation on the technical solution of this invention.

[0036] Excitation actuator, see Figures 1 to 12 It includes a housing, an indicator 1, an excitation source 2, and a rotary actuator 3. The housing includes a casing 4 and a cover plate 6.

[0037] Casing 4, see Figure 5 and Figure 6 Its shape can be designed as square, round, or according to requirements. In this embodiment, it is designed as square. On opposite sides of the housing 4: one side is open, and the other side has a first mounting hole 401 for mounting the rotating actuator 3. The cover plate 6 is located on the open side of the housing 4 and closes the open side of the housing 4. The housing 4 and the cover plate 6 are fixedly connected by bolts 5.

[0038] An arc-shaped cavity 402 and a fan-shaped cavity 403 are provided on the side of the housing 4 facing the cover plate 6. The arc-shaped cavity 402 and the fan-shaped cavity 403 are adjacent and connected. A first mounting hole 401 is located in the arc-shaped cavity 402. A first limiting structure 404 and a second limiting structure 405 are respectively provided at both ends of the arc-shaped structure of the fan-shaped cavity 403. In this embodiment, the first limiting structure 404 is a positioning pin structure, and the second limiting structure 405 is a limiting protrusion structure. A second mounting hole 406 for mounting the excitation source 2 is opened on the housing 4 at one end of the arc-shaped structure of the fan-shaped cavity 403, and a third mounting hole 407 for mounting the indicator 1 is opened on the housing 4 at the other end. One end of the second mounting hole 406 and the third mounting hole 407 are connected to the fan-shaped cavity 403, and the other end is connected to the outside of the housing 4.

[0039] A limiting cavity 407a is provided in the third mounting hole 407, and the inner diameter of the limiting cavity 407a is larger than the inner diameter of the portion of the third mounting hole 407 that communicates with it and is located at both ends thereon.

[0040] The actuator can be installed using a sliding rail or by bolt fixing. For sliding rail installation, see [link / reference]. Figure 5 A sliding groove structure 408 is provided on the bottom outer side of the housing 4. During installation, the sliding groove structure 408 can be slidably mounted on the sliding guide rail to achieve the installation of the housing 4. Alternatively, a mounting base 409 and the sliding groove structure 408 can be provided on the bottom of the housing 4. (See reference...) Figure 6 This allows the housing 4 to be connected and fixed to the mounting base 409 with the external installation location by bolts, or it can be installed by sliding guide rail via the sliding groove structure 408.

[0041] Indicator 1, see Figure 7 The indicator 1 has a rod-shaped structure, and is generally red or another bright color. A fourth limiting structure 101 is provided on the outer periphery of the rod between the two ends of the indicator 1. The shape of the fourth limiting structure 101 matches the inner wall shape of the limiting cavity 407a of the third mounting hole 407, and the limiting cavity 407a retains space for the fourth limiting structure 101 to move. A third limiting structure 102 is also provided on the indicator 1. The third limiting structure 102 is a protrusion on the outer periphery of the rod of the indicator 1. The third limiting structure 102 and the fourth limiting structure 101 are spaced apart along the length of the indicator. When indicator 1 is installed in the third mounting hole 407, the third limiting structure 102 and the fourth limiting structure 101 of indicator 1 are respectively located in the limiting cavity 407a. The third limiting structure 102 and the fourth limiting structure 101 abut against the two ends of the limiting cavity 407a. The third limiting structure 102 abuts against the end of the limiting cavity 407a facing the outside of the housing 4, and the fourth limiting structure 101 abuts against the end of the limiting cavity 407a facing the fan-shaped cavity 403. The end facing the limiting indicator 1 extends out of the third mounting hole and is located in the fan-shaped cavity 403, while the other end is close to the outside of the housing 4 and is located inside the housing 4. The third limiting structure 102 prevents indicator 1 from malfunctioning and extending outside the housing 4.

[0042] Excitation source 2, a gas generating device, activates upon receiving a trigger signal, releasing high-pressure gas as driving force. It is fixedly installed in the second mounting hole 406. The excitation source 2 can be fixed by interference fit, adhesive bonding, or injection molding, ensuring a sealed contact between the excitation source 2 and the second mounting hole. In this example, excitation source 2 uses interference fit. The end of excitation source 2 that receives the trigger signal faces outwards from the housing 4 and can be connected to an external control system or control circuit that sends the trigger signal via a connector. The end of excitation source 2 that releases high-pressure gas faces the fan-shaped cavity 403, and the released high-pressure gas enters the fan-shaped cavity 403 through the second mounting hole.

[0043] The rotating actuator 3 includes an integrally connected circular portion 301 and a lever portion 302. The circular portion 301 is a circular structure with a certain thickness, and the lever portion 302 is a rod-shaped structure integrally formed on the outer circumferential surface of the circular portion 301. The circular portion 301 is rotatably mounted in an arc-shaped cavity, and the lever portion 302 is also displaceable in a fan-shaped cavity. The cover plate 6 and the housing 4 define the relative positions of the rotating actuator 3 on both sides, so that when the rotating actuator 3 rotates in the circular portion 301, it moves the lever portion 302 along the fan-shaped cavity, from one end of the fan-shaped cavity near the excitation source 2 to the other end near the indicator 1. To prevent the high-pressure gas released by the excitation source 2 from leaking to the outside of the housing 4, the contact surface between the housing 4 and the cover plate 6 is sealed. The sealing method can be achieved by setting a sealing ring or a mechanical seal structure. The housing 4 and the cover plate 6 are connected, fixed and sealed by threaded connection or riveting to ensure internal sealing and prevent the high temperature and high pressure gas from the excitation source from being ejected from the gaps in the housing. At the same time, it can limit the extra degrees of freedom of the rotating lever 3 to ensure normal rotation in the arc-shaped cavity and the fan-shaped cavity. In this example, four bolts 5 or rivets are used for fixed connection.

[0044] Specific structure and configuration of rotating actuator 3:

[0045] The circular portion 301 of the rotating actuator 3 matches the shape of the arc-shaped cavity 402. A circular boss 303 protruding from the end face of the circular portion 301 is provided on the side of the circular portion 301 facing the first mounting hole 401. The outer diameter of the circular boss 303 is smaller than the outer diameter of the circular portion 301, forming a limiting step structure at the end face of the circular portion 301 located on the outer periphery of the circular boss 304. The circular portion 301 of the rotating actuator 3 is located in the arc-shaped cavity 402, and the circular boss 303 on it is rotatably installed in the first mounting hole 401. The outer peripheral surface of the circular portion 301 is rotatably fitted with the inner wall of the arc-shaped cavity 402. The limiting step structure of the circular portion 301 prevents the circular portion 301 from falling out of the first mounting hole 401. A connecting end 304 is provided on the side of the circular boss 301 facing the outside of the housing 4. The connecting end 304 can be a polygonal columnar structure or a polygonal hole structure to facilitate connection with the external driven end. And through the polygonal structure, relative rotation is prevented after connection.

[0046] In this embodiment, the connecting end is set as a connecting shaft, which connects to the driven end outside the actuator. The output torque, through the rotation of the actuator 3, drives the driven end located outside the housing 4 to rotate. The connecting shaft is a polygonal columnar structure, such as a regular square column or a regular hexagonal column.

[0047] The lever portion 302 is located in the fan-shaped cavity 403, and its initial position is located at the end of the fan-shaped cavity 403 adjacent to the second mounting hole 406. A first limiting hole 305 is provided on the lever portion 302 at the position corresponding to the first limiting structure 404. In the initial position, refer to… Figures 9 to 11 The first limiting structure 404 is inserted into the first limiting hole 305 of the lever portion 302 to limit the initial position of the lever portion 302 of the rotating actuator 3. The length of the first limiting structure 404 inserted into the first limiting hole 305 is less than the depth of the first limiting hole 305 to ensure that when the lever portion 302 is displaced to the termination position, the second limiting structure 405 can be nested at the opening end of the first limiting hole 305. When the high-pressure gas released by the excitation source 2 acts on the rotating actuator 3, the first limiting structure 404 is disengaged, releasing the limitation on the initial position of the lever portion 302 of the rotating actuator 3.

[0048] When the lever portion 302 rotates with the rotating actuator 3 to the end adjacent to the sector cavity 403 and the third mounting hole 407, that is, at the termination position of the lever portion 302, the second limiting structure 405 is nested into the opening end of the first limiting hole 305 of the lever portion 302. (See figure) Figure 4The termination position of the lever portion 302 is limited to prevent it from rebounding. In order to allow the second limiting structure 405 to be smoothly nested into the limiting hole 305, a sloped structure 306 is provided at the edge of the lever portion 302 on the front side of the displacement direction of the first limiting hole 305. This ensures that when the lever portion 302 is displaced, the sloped structure 306 can easily pass over the second limiting structure 405, making it easier for the second limiting structure 405 to be nested into the first limiting hole 305.

[0049] The lever portion 302 is fitted to the housing 4 and cover plate 6 on opposite sides of the fan-shaped cavity 403. When the excitation source 2 releases high-pressure gas, the high-pressure gas acts directly on the lever portion 302, driving the lever portion 302 to rotate along with the circular portion 301, causing the lever portion 302 to move along the arc trajectory of the fan-shaped cavity 403. When the lever portion 302 moves to the end position, the lever portion 302 abuts against one end located in the fan-shaped cavity 403, driving the indicator 1 to move along the third mounting hole 407 toward the outside of the housing 4, so that the end of the indicator 1 facing the outside of the housing 4 extends out of the housing 4.

[0050] In this embodiment, the indicator 1 is set horizontally, and the lever portion 302 rotates from the horizontal position to the vertical position by a 90-degree angle.

[0051] Working principle:

[0052] The actuator is connected and fixed to the driven end outside the actuator via the connection end 304.

[0053] When action is required, the excitation source 2 activates according to the received trigger signal, releasing high-pressure gas into the sector-shaped cavity 403. The high-pressure gas acts on the lever portion 302, driving the rotating actuator 3 to rotate within the circular portion 301 and the sector-shaped cavity 302. This first causes the first limiting structure 404, i.e., the positioning pin, to disengage, releasing the initial position limitation of the rotating actuator 3 by the first limiting structure 404. Then, the lever portion 302 of the rotating actuator 3 rotates along the arc trajectory of the sector-shaped cavity 302, driving the indicator 1 to move along the third mounting hole 407, first overcoming the limitation of the third limiting structure 102. The indicator 1 moves outward along the third mounting hole 407 toward the outside of the housing 4, so that the end of the indicator 1 facing the outside of the housing 4 protrudes outside the housing 4 to provide a warning. At the same time, the fourth limiting structure 101 is engaged in the limiting cavity 407a at the end facing the outside of the housing 4 to prevent the indicator 1 from falling out of the third mounting hole 407. When the lever part 302 moves to the end position near the indicator 1, the second limiting structure 405 is nested into the first limiting hole 305 of the rotating actuator 3 to limit the end position of the rotating actuator, prevent it from rebounding, and abut against the indicator 1 to keep it in the position of protruding from the housing 4.

[0054] After the rotating actuator 3 is moved to the termination position, the cavity between the housing and the cover plate can remain sealed due to the position limitation of the second limiting structure 405. The high-pressure gas exerts a certain force on the lever part to ensure that the rotating actuator 3 is in the termination position. Alternatively, after the rotating actuator 3 is moved to the termination position, the air can be vented. Due to the position limitation of the second limiting structure, the lever part will not rebound.

[0055] In other embodiments, connecting ends 304 are respectively provided on opposite sides of the circular portion 301 of the rotating actuator 3, see reference. Figure 12 That is, a fourth mounting hole is also provided on the cover plate 6. Circular bosses are provided on opposite sides of the circular part 301 of the rotating actuator 3. Connecting ends 304 are provided on the circular bosses respectively. The circular bosses on opposite sides of the rotating actuator 3 are installed in the first mounting hole 401 on the housing 4 and the fourth mounting hole on the cover plate 6 respectively, so that the connecting ends 304 on opposite sides of the rotating actuator 3 are located on opposite sides of the excitation actuator. The connecting ends 304 on opposite sides of the excitation actuator can be connected to the external driving end, so as to simultaneously drive at least two driven ends to move.

[0056] Each side of the rotating actuator 3 can be connected to at least one driven end. When there are two or more driven ends, the multiple driven ends can be set at the same angle or connected to the connecting ends of the rotating actuator 3 at different angles. When both sides of the rotating actuator 3 are set as connecting ends, at least two driven ends can be connected. By rotating the rotating actuator 3, the driven ends on one or both sides of the rotating actuator can be rotated.

Claims

1. An actuator, characterized in that, The device includes a housing, an excitation source, and a rotating actuator. The housing has a cavity, and a first limiting structure is provided within the cavity. The rotating actuator is rotatably disposed within the cavity, and a connecting end is provided on at least one side of the actuator. The side of the actuator with the connecting end is rotatably mounted on the housing wall, and the connecting end faces outwards from the housing, allowing it to connect to at least one external driven end. The first limiting structure defines the initial position of the rotating actuator. The excitation source is disposed on the housing, and a receiving end of the excitation source that receives a trigger signal can be connected to the outside of the housing. One end of the excitation source that releases high-pressure gas communicates with the cavity containing the rotating actuator. When the excitation source actuates, the released high-pressure gas drives the rotating actuator to overcome the limitation of the first limiting structure and move from the initial position to a final position.

2. The actuator according to claim 1, characterized in that, A second limiting structure is provided in the cavity. When the rotating actuator is displaced to the termination position, the second limiting structure limits the termination position of the rotating actuator.

3. The actuator according to claim 2, characterized in that, The cavity includes a connected arc-shaped cavity and a fan-shaped cavity; the rotating actuator includes an integrally connected circular portion and a lever portion, the connecting end is disposed on one side of the circular portion, the circular portion is rotatably fitted into the arc-shaped cavity, the lever portion is disposed in the fan-shaped cavity, and the lever portion is in contact with the fan-shaped cavity; the fan-shaped cavity is provided with a first limiting structure and a second limiting structure, which respectively limit the initial position and the final position of the lever portion, the initial position of the lever portion being located near the end of the excitation source that releases high-pressure gas.

4. The actuator according to claim 3, characterized in that, A first limiting hole is provided in the lever portion, the first limiting structure is a positioning pin, and the second limiting structure is a limiting protrusion. In the initial position, the positioning pin is located in the first limiting hole, limiting the initial position of the lever portion. When the lever portion overcomes the limitation of the first limiting structure and moves to the termination position, the first limiting hole moves to the limiting protrusion, and the limiting protrusion is nested in the first limiting hole, limiting the termination position of the lever portion.

5. The actuator according to claim 4, characterized in that, The edge of the lever portion away from the circular portion has a beveled structure.

6. The actuator according to claim 1, characterized in that, The connecting end is a connecting shaft protruding from the side of the rotating actuator or a connecting hole located on the side of the rotating actuator.

7. The actuator according to claim 6, characterized in that, The connecting shaft or connecting hole has a polygonal structure.

8. The actuator according to claim 1, characterized in that, The connecting ends are respectively provided on opposite sides of the rotating actuator. The connecting ends are located on opposite sides of the housing, and at least one driven end can be connected to each connecting end.

9. The actuator according to any one of claims 1 to 8, characterized in that, An indicator that can be displaced to the outside of the housing is provided in the housing. One end of the indicator extends into the cavity and is located at the termination position of the rotating actuator, while the other end is located in the shell wall of the housing. When the rotating actuator moves from the initial position to the final position, the rotating actuator abuts against one end of the indicator located in the cavity, driving the indicator to move toward the outside of the housing, so that one end of the indicator located in the housing wall moves to the outside of the housing.

10. The actuator according to claim 9, characterized in that, A mounting hole is provided on the outer shell wall, the mounting hole connecting the outside of the outer shell to the cavity. A limiting cavity is provided in the mounting hole, and the indicator passes through the mounting hole. A third limiting structure and a fourth limiting structure are provided on the indicator at intervals along its length direction. The third limiting structure and the fourth limiting structure are located in the limiting cavity. The third limiting structure is located at the front end of the limiting cavity in the displacement direction of the indicator, and the fourth limiting structure is located at the rear end in the displacement direction of the indicator. When the indicator is displaced, the third limiting structure is released from its limiting position. When one end of the indicator located in the outer shell wall is displaced to the outside of the outer shell, the fourth limiting structure is displaced to the front end of the limiting cavity and abuts against the front end of the limiting cavity.

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