Anti-skid cable clamping plate and cable fixing device applied to large-dip-angle working face
The anti-slip cable clamp, which combines magnetic adsorption and mechanical interlocking, solves the problem of locking failure of traditional cable clamps under large inclination angle conditions, achieving stable cable fixation and safe operation, and avoiding cable detachment accidents.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-06
- Publication Date
- 2026-03-24
AI Technical Summary
Traditional cable clamps are prone to locking failure due to vibration under steep inclination conditions. The friction anti-slip design is affected by the environment, resulting in a sharp reduction in anti-slip performance, which leads to frequent cable detachment from the groove, insulation wear and short circuit accidents.
The anti-slip cable clamps use magnetic adsorption. The magnetic attraction between the first magnet on the connecting shaft and the side wall of the cable trough enhances the fit of the clamps. Combined with the mechanical interlock of the guide groove, long-term stable fixation without manual tightening is achieved.
It effectively prevents cable slippage, increases lateral anti-slip resistance, avoids cable derailment, and improves the safety and stability of cables in steep working surfaces. It is easy to operate and has strong environmental adaptability.
Smart Images
Figure CN121726901A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of coal mine electromechanical equipment technology, specifically to an anti-slip cable clamp and cable fixing device for use on steeply inclined working faces. Background Technology
[0002] In fully mechanized coal mining faces, cable clamps are crucial devices for ensuring the orderly arrangement and safe operation of cables. Traditional cable clamps mostly rely on mechanical fixing (such as bolt tightening) or friction anti-slip designs (such as rubber pads and toothed grooves). Fixation is achieved through the interaction of clips and grooves, but under steep angle conditions, vibration can easily cause locking failure. Traditional friction anti-slip designs are affected by coal dust and oil contamination, resulting in a 30%-50% decrease in the coefficient of friction and a sharp reduction in anti-slip performance. These problems lead to frequent cable detachment from grooves, insulation wear, and even short circuits in steep fully mechanized mining faces, seriously threatening production safety. Therefore, there is an urgent need for an anti-slip technology solution that does not rely on manual tightening, is highly adaptable to the environment, and provides long-term stability. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to provide an anti-slip cable clamp and cable fixing device for use on steep angle working surfaces. It can enhance the fit between the clamp and the cable trough through magnetic adsorption, without relying on manual tightening, has strong environmental adaptability, and can produce a long-term and stable anti-slip effect on steep angle working surfaces.
[0004] To address the aforementioned technical problems, this invention provides an anti-slip cable clamp for use on steeply inclined working surfaces, comprising two clamps and two connecting plates. The two clamps are symmetrically spaced apart, and the two connecting plates are located between the two clamps and are also symmetrically spaced apart. Each connecting plate connects to one of the two clamps at both ends to form a protective housing for wrapping cables. Each clamp has a clamping portion and a turning plate at both ends along the front-rear direction. Both the clamping portion and the turning plate have corresponding hinge holes. The clamping portion is adapted to clamp the turning plate of another anti-slip cable clamp to form a series connection between the anti-slip cable clamps. The anti-slip cable clamp also includes a connecting shaft, which is adapted to pass through the hinge hole between the clamping part and the steering plate, and a first magnet is provided at one of the outer ends of the connecting shaft.
[0005] In some specific embodiments, a mounting groove is formed at the outer end of the connecting shaft, and the first magnet is disposed in the mounting groove.
[0006] In some specific embodiments, the outermost end face of the first magnet and the outermost end face of the connecting shaft are on the same plane as the outer surface of the clamping plate.
[0007] In some specific embodiments, the clamping part includes a first clamping part and a second clamping part, and a clamping space for clamping the steering plate is formed between the first clamping part and the second clamping part. The first clamping part is located at the outer end relative to the second clamping part. The connecting shaft passes through the hinge holes on the first clamping part, the steering plate and the second clamping part in sequence from the outside to the inside to connect the anti-slip cable clamp.
[0008] In some specific embodiments, the connecting shaft includes a first shaft and a second shaft arranged from the outside to the inside. The diameter of the first shaft is larger than the diameter of the second shaft. The hinge hole of the first clamping part is a first stepped hole. The first shaft is clamped on the first stepped hole. The end of the second shaft away from the first shaft extends out from the hinge hole of the second clamping part to connect the locking member.
[0009] In some specific embodiments, the connecting shaft further includes an intermediate shaft located between the first shaft and the second shaft. The diameter of the intermediate shaft is smaller than the diameter of the first shaft and larger than the diameter of the second shaft. The hinge hole of the steering plate is a second stepped hole. The end of the intermediate shaft near the first shaft is located in the first stepped hole, and the end face of the intermediate shaft near the second shaft is held in the second stepped hole.
[0010] In some specific embodiments, a second magnet is provided on the end face of the intermediate shaft that is held in the second stepped hole, and the second magnet is adapted to attract the steering plate.
[0011] The present invention also provides a cable fixing device, including a cable trough and the above-mentioned anti-slip cable clamps applied to a large-angle working surface, wherein the two clamps of the anti-slip cable clamps are magnetically attracted and attached to the opposite side walls of the cable trough by their respective first magnets.
[0012] In some specific embodiments, the first magnet can be slidably installed in the mounting groove of the connecting shaft, and a guide groove is provided on the side wall of the cable groove corresponding to the connecting shaft. When the anti-slip cable clamp is installed in the cable groove, the first magnet is adapted to extend outward into the guide groove under the action of magnetic attraction, so as to magnetically attract and fit the bottom of the guide groove.
[0013] In some specific embodiments, a limiting groove is formed on the side wall of the first magnet, and a limiting protrusion corresponding to the limiting groove is formed on the side wall of the mounting groove. The limiting groove and the limiting protrusion cooperate to limit the movement range of the first magnet, and an elastic element is provided between the bottom of the mounting groove and the first magnet.
[0014] The beneficial effects of the present invention through the above solution are as follows: The present invention has a first magnet on the outer side of the two clamps. When the cable clamps are installed in the cable trough, the magnetic attraction enhances the fit between the clamps and the cable trough, effectively preventing coal dust intrusion and effectively resisting the sliding force caused by gravity and vibration, so that the clamps are tightly attached to the cable trough and the risk of slippage is reduced.
[0015] The first magnet is slidably installed in the mounting groove of the connecting shaft, and a guide groove is provided on the side wall of the cable trough corresponding to the connecting shaft. When the anti-slip cable clamp is installed in the cable trough, the first magnet is adapted to extend outward into the guide groove under the action of magnetic attraction, so as to magnetically attract and fit the bottom of the guide groove, thereby forming a mechanical interlock. Combined with the improved fit between the clamp and the cable trough brought about by magnetic attraction, the lateral anti-slip resistance is further improved, and the cable is prevented from sliding off the trough on the large-angle composite working surface.
[0016] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description
[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of a specific embodiment of the anti-slip cable clamp of the present invention applied to a large-angle working surface; Figure 2 This is an exploded view of a specific embodiment of the anti-slip cable clamp of the present invention applied to a large-angle working surface; Figure 3 This is a structural schematic diagram of a specific embodiment of the cable fixing device of the present invention; Figure 4 This is a cross-sectional view of the connection point of the anti-slip cable clamps in series configuration; Figure 5 It is a cross-sectional view of the connection between the first magnet and the guide groove in the retracted state; Figure 6 It is a cross-sectional view of the connection between the first magnet and the guide groove when the magnet is in the extended state.
[0018] Explanation of reference numerals in the attached figures 1. Clamping plate; 2. Connecting plate; 3. Clamping part; 301. First clamping part; 302. Second clamping part; 4. Turning plate; 5. Connecting shaft; 501. First shaft body; 502. Second shaft body; 503. Intermediate shaft body; 504. Mounting groove; 504-1. Limiting protrusion; 6. First magnet; 601. Limiting groove; 7. Locking element; 8. Second magnet; 9. Cable groove; 901. Guide groove; 10. Elastic element; 11. Shaft pin; 1101. Bending section. Detailed Implementation
[0019] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention, and the scope of protection of the present invention is not limited to the specific embodiments described below.
[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "forming," "having," "setting," and "connecting," etc., should be interpreted broadly. For example, a connection can be a direct connection or an indirect connection through an intermediate medium; it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate connector; it can be the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0021] In this invention, unless otherwise specified, the directional terms "up," "down," "left," "right," "counterclockwise," etc., used to indicate the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. The directional terms of this invention should be understood in conjunction with the actual installation state.
[0022] This invention provides an anti-slip cable clamp for use on steeply inclined working surfaces, see [link / reference]. Figures 1 to 6 In a specific embodiment of the anti-slip cable clamp of the present invention, the cable clamp includes two clamping plates 1 and two connecting plates 2. The two clamping plates 1 are symmetrically arranged at intervals, and the two connecting plates 2 are located between the two clamping plates 1 and are also symmetrically arranged at intervals. The two ends of the connecting plates 2 are respectively connected to the two clamping plates 1 to form a surrounding shell for wrapping the cable. The clamping plates 1 are respectively provided with clamping parts 3 and turning plates 4 at both ends along the front-back direction. Both clamping parts 3 and turning plates 4 are provided with corresponding hinge holes. The clamping parts 3 are adapted to clamp the turning plates 4 of another anti-slip cable clamp to form a series connection of the anti-slip cable clamps. The anti-slip cable clamp also includes a connecting shaft 5, which is adapted to pass through the hinge holes on the clamping parts 3 and the turning plates 4. A first magnet 6 is provided at one of the outer ends of the connecting shaft 5.
[0023] Based on the above basic embodiments, see Figure 3The cable is wrapped inside the housing by the clamping parts 3 and the turning plate 4 of different anti-slip cable clamps, forming a complete power supply line. The power supply line is laid in the cable trough 9. The connecting shaft 5 connects the cable clamps in series, and adjacent cable clamps can rotate around the connecting shaft 5 to adjust the direction of the power supply line to meet the requirements of the laying route. The connecting shaft 5 is provided with a first magnet 6 on the outer side. When the cable clamp is installed in the cable trough 9, the magnetic attraction enhances the fit between the clamp 1 and the cable trough, effectively preventing coal dust intrusion and resisting the sliding force caused by gravity and vibration, so that the clamp is tightly attached to the cable trough and the risk of slippage is reduced.
[0024] It should be noted that both ends of the connecting plate 2 can be inserted into the grooves of the corresponding clamping plate 1, and a pin 11 is provided inside the connecting plate 2. Both ends of the pin 11 extend from the grooves of the corresponding clamping plate 1, forming bent sections 1101. These bent sections 1101 are engaged in the grooves on the outer side of the corresponding clamping plate 1. The interaction of the bent sections 1101 at both ends of the pin 11 holds the connecting plate 2 and the clamping plates 1 together. It should be understood that the above-described embodiment, which uses the pin 11 to create a holding force to connect the connecting plate 2 and the clamping plate 1, is not a limitation on the scope of protection of this invention. Various methods can be used to connect the connecting plate 2 to the clamping plates 1 at both ends, including but not limited to threaded connections, snap-fit connections, and integral injection molding.
[0025] In a specific embodiment, the connecting shaft 5 can be made of high-strength composite steel to give it high structural strength. See also Figure 2 , Figures 4 to 6 A mounting groove 504 is formed at one outer end of the connecting shaft 5, and a first magnet 6 is disposed in the mounting groove 504. The first magnet 6 is preferably a neodymium iron boron magnet. The size and number of the first magnet 6 disposed in the mounting groove 504 can be designed according to actual needs. Specifically, during the pre-processing of the connecting shaft 5, epoxy resin can be applied to the mounting groove 504, and permanent magnets can be embedded in an alternating N and N pole arrangement to ensure that the direction of the magnetic field lines is perpendicular to the mating surface of the cable groove 9.
[0026] In order to improve the fit between the clamping plate 1 and the cable trough 9, and thus increase the static friction between them, the outer end face of the first magnet 6 and the outer end face of the connecting shaft 5 are on the same plane as the outer side of the clamping plate 1.
[0027] In some specific embodiments, the surface of the first magnet 6 can be nickel-plated to prevent corrosion, and the surface of the first magnet 6 used to fit the cable trough 9 can be provided with a wear-resistant rubber layer to effectively prevent coal dust intrusion or mechanical impact damage, greatly improving the reliability of the first magnet 6 and extending its service life. The thickness range of the wear-resistant rubber layer is preferably 1mm-3mm.
[0028] In some specific implementations, see Figure 1 , Figure 2 and Figure 4 The clamping part 3 includes a first clamping part 301 and a second clamping part 302. A clamping space for clamping the steering plate 4 is formed between the first clamping part 301 and the second clamping part 302. The first clamping part 301 is located at the outer end relative to the second clamping part 302. The connecting shaft 5 passes through the hinge holes on the first clamping part 301, the steering plate 4, and the second clamping part 302 in sequence from the outside to the inside to connect the anti-slip cable clamp. By providing the first clamping part 301 and the second clamping part 302 on both sides of the steering plate 4, the connection strength between the clamping part 3 and the steering plate 4 is improved. The height of the clamping space matches the thickness of the steering plate 4 to prevent wobbling between the clamping part 3 and the steering plate 4.
[0029] Further, see Figure 2 and Figure 4 The connecting shaft 5 includes a first shaft body 501 and a second shaft body 502 arranged from the outside to the inside. The diameter of the first shaft body 501 is larger than the diameter of the second shaft body 502. The hinge hole of the first clamping part 301 is a first stepped hole. The first shaft body 501 is clamped in the first stepped hole. The end of the second shaft body 502 away from the first shaft body 501 extends out from the hinge hole of the second clamping part 302 to connect the locking member 7. The locking member 7 is preferably a bolt. The extended end of the second shaft body 502 is provided with an external thread for the bolt to make a threaded connection, thereby cooperating with the first shaft body 501 to realize the fastening connection between the clamping part 3 and the steering plate 4 and prevent the two from loosening.
[0030] Furthermore, the connecting shaft 5 also includes an intermediate shaft 503 located between the first shaft 501 and the second shaft 502. The diameter of the intermediate shaft 503 is smaller than the diameter of the first shaft 501 but larger than the diameter of the second shaft 502. The hinge hole of the steering plate 4 is a second stepped hole. The end of the intermediate shaft 503 near the first shaft 501 is located in the first stepped hole, and the end face of the intermediate shaft 503 near the second shaft 502 is engaged in the second stepped hole. A second magnet 8 is provided on the end face of the intermediate shaft 503 engaged in the second stepped hole. The second magnet 8 is suitable for attracting the steering plate 4. During long-term use, even if the locking part 7 becomes loose, the second magnet 8 firmly attracts the steering plate 4 through magnetic attraction, preventing loosening at the connection of adjacent cable clamps and ensuring connection reliability.
[0031] The present invention also provides a cable fixing device, see below. Figure 3 The cable fixing device includes a cable trough 9 and the anti-slip cable clamps applied to the steep angle working surface. Multiple anti-slip cable clamps are connected together as a whole and installed in the cable trough 9. The two clamps 1 of the anti-slip cable clamps are magnetically attracted and attached to the opposite side walls of the cable trough 9 by their respective first magnets 6.
[0032] In a preferred embodiment, see Figure 2 , Figures 4 to 6 The first magnet 6 is slidably installed in the mounting groove 504 of the connecting shaft 5. The side wall of the cable trough 9 is provided with a guide groove 901 corresponding to the connecting shaft 5. When the anti-slip cable clamp is installed in the cable trough 9, the first magnet 6 is adapted to extend outward into the guide groove 901 under the action of magnetic attraction, so as to magnetically attract and fit the bottom of the guide groove 901. The size of the first magnet 6 matches the width of the guide groove 901 so that the first magnet 6 can only slide along the length extension direction of the guide groove 901. The two side walls of the guide groove 901 can effectively restrict the first magnet 6 from falling off, thereby preventing the anti-slip cable clamp from falling off the guide groove 901. The guide groove 901 and the extended first magnet 6 form a mechanical interlock. Combined with the improved fit between the clamp and the cable trough 9 brought about by magnetic attraction, the lateral anti-slip resistance is further improved, and the cable is prevented from sliding off the groove on the large-angle composite working surface.
[0033] See Figure 2 , Figures 4 to 6 A limiting groove 601 is formed on the side wall of the first magnet 6, and a limiting protrusion 504-1 corresponding to the limiting groove 601 is formed on the side wall of the mounting groove 504. The limiting groove 601 and the limiting protrusion 504-1 cooperate to limit the movement range of the first magnet 6, and guide the first magnet 6 through the cooperation of the limiting groove 601 and the limiting protrusion 504-1, so that it moves perpendicular to the contact surface of the cable groove 9, ensuring that the direction of the magnetic field lines is perpendicular to the contact surface of the cable groove 9. An elastic element 10 is provided between the bottom of the mounting groove 504-1 and the first magnet 6. The elastic element 10 is preferably a spring, so that during the assembly of the anti-slip cable clamp and the cable groove 9, the elastic force provided by the elastic element 10 can effectively drive the first magnet 6 to move towards the bottom of the guide groove 901, so that the magnetic attraction between the two can effectively guide the first magnet 6 to move to the bottom of the groove, forming an effective and complete fit.
[0034] To better understand the technical solution of the present invention, its working principle is explained below in conjunction with preferred technical features.
[0035] See Figures 1 to 6Different anti-slip cable clamps are connected end-to-end through clamping part 3 and turning plate 4. When the hinge holes of clamping part 3 and turning plate 4 are adjusted to correspond, connecting shaft 5 is inserted to connect clamping part 3 and turning plate 4, and the cable is wrapped in the enclosure, so that the cable and cable clamps form a complete power supply line. The power supply line is laid in cable trough 9, which has a guide groove 901. When clamp 1 is installed in place, the mounting groove 504 on connecting shaft 5 is aligned with the guide groove 901. The guide groove 901 forms an outward movement space for the first magnet 6. Under the elastic force of elastic member 10, the first magnet 6 moves along the direction perpendicular to the bottom of the guide groove 901. The distance between the first magnet 6 and the bottom of the groove is small, thus the first magnet 6 moves towards the bottom of the groove. Under the magnetic force, the first magnet 6 is completely attached to the bottom of the guide groove 901. The size of the first magnet 6 matches the width of the guide groove 901. The side walls of the guide groove 901 can effectively limit the first magnet 6 from falling off, thereby preventing the anti-slip cable clamp from falling off the guide groove 901. The guide groove 901 and the extended first magnet 6 form a mechanical interlock. Combined with the improved fit between the clamp and the cable groove 9 due to magnetic adsorption, it effectively prevents coal dust from entering and has high lateral anti-slip resistance, which can effectively resist the downward force caused by gravity and vibration, allowing the clamp to be tightly adsorbed on the cable groove, avoiding the phenomenon of cable sliding off the groove on the large-angle integrated working surface. At the same time, the automatic magnetic adsorption positioning method is more convenient to operate and more adaptable to the environment than the previous manual fastening method.
[0036] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.
[0037] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.
[0038] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.
Claims
1. A non-slip cable clamp for use on steeply inclined working surfaces, characterized in that, It includes two clamping plates (1) and two connecting plates (2). The two clamping plates (1) are symmetrically arranged at intervals, and the two connecting plates (2) are located between the two clamping plates (1) and are symmetrically arranged at intervals. The two ends of the connecting plates (2) are respectively connected to the two clamping plates (1) to form a surrounding shell for wrapping the cable. The clamping plates (1) are respectively provided with clamping parts (3) and turning plates (4) at both ends along the front-back direction. The clamping parts (3) and the turning plates (4) are provided with corresponding hinge holes. The clamping parts (3) are adapted to clamp the turning plate (4) of another anti-slip cable clamping plate to form the mutual connection of the anti-slip cable clamping plates. The anti-slip cable clamp also includes a connecting shaft (5), which is adapted to pass through the hinge hole on the clamping part (3) and the turning plate (4). A first magnet (6) is provided on the outer end of the connecting shaft (5).
2. The anti-slip cable clamp for use on steeply inclined working surfaces according to claim 1, characterized in that, The connecting shaft (5) has an installation groove (504) formed on one of its outer ends, and the first magnet (6) is disposed in the installation groove (504).
3. The anti-slip cable clamp for use on a steeply inclined working surface according to claim 2, characterized in that, The outer end face of the first magnet (6) and the outer end face of the connecting shaft (5) are on the same plane as the outer surface of the clamp (1).
4. The anti-slip cable clamp for use on steeply inclined working surfaces according to claim 1, characterized in that, The clamping part (3) includes a first clamping part (301) and a second clamping part (302). A clamping space for clamping the steering plate (4) is formed between the first clamping part (301) and the second clamping part (302). The first clamping part (301) is located at the outer end relative to the second clamping part (302). The connecting shaft (5) passes through the hinge holes on the first clamping part (301), the steering plate (4) and the second clamping part (302) from the outside to the inside in sequence to connect the anti-slip cable clamp.
5. The anti-slip cable clamp for use on steeply inclined working surfaces according to claim 4, characterized in that, The connecting shaft (5) includes a first shaft body (501) and a second shaft body (502) arranged from the outside to the inside. The diameter of the first shaft body (501) is larger than the diameter of the second shaft body (502). The hinge hole of the first clamping part (301) is a first stepped hole. The first shaft body (501) is clamped on the first stepped hole. The end of the second shaft body (502) away from the first shaft body (501) extends out from the hinge hole of the second clamping part (302) to connect the locking member (7).
6. The anti-slip cable clamp for use on a steeply inclined working surface according to claim 5, characterized in that, The connecting shaft (5) also includes an intermediate shaft (503) located between the first shaft (501) and the second shaft (502). The diameter of the intermediate shaft (503) is smaller than the diameter of the first shaft (501) and larger than the diameter of the second shaft (502). The hinge hole of the steering plate (4) is a second stepped hole. The end of the intermediate shaft (503) near the first shaft (501) is located in the first stepped hole, and the end face of the intermediate shaft (503) near the second shaft (502) is held in the second stepped hole.
7. The anti-slip cable clamp for use on a steeply inclined working surface according to claim 6, characterized in that, The intermediate shaft (503) is held in place by a second magnet (8) on the end face of the second stepped hole. The second magnet (8) is adapted to attract the steering plate (4).
8. A cable fixing device, characterized in that, Includes a cable trough (9) and an anti-slip cable clamp as described in any one of claims 1 to 7 for use on a large-angle working surface, wherein the two clamps (1) of the anti-slip cable clamp are magnetically attracted and attached to the opposite side walls of the cable trough (9) by their respective first magnets (6).
9. The cable fixing device according to claim 8, characterized in that, The first magnet (6) is slidably installed in the mounting groove (504) of the connecting shaft (5). A guide groove (901) is provided on the side wall of the cable groove (9) corresponding to the connecting shaft (5). When the anti-slip cable clamp is installed in the cable groove (9), the first magnet (6) is adapted to extend outward into the guide groove (901) under the action of magnetic attraction, so as to magnetically attract and fit the bottom of the guide groove (901).
10. The cable fixing device according to claim 9, characterized in that, The first magnet (6) has a limiting groove (601) formed on its side wall. The mounting groove (504) has a limiting protrusion (504-1) corresponding to the limiting groove (601) formed on its side wall. The limiting groove (601) and the limiting protrusion (504-1) cooperate to limit the movement range of the first magnet (6). An elastic element (10) is provided between the bottom of the mounting groove (504-1) and the first magnet (6).