Cable terminal protection device for transformer

Abstract

The utility model discloses a cable terminal protection device for a transformer, and relates to the technical field of transformer protection, the protection device comprises a base and a dragging buffer mechanism, the dragging buffer mechanism is installed on the base through a support, and the dragging buffer mechanism comprises a material returning prevention assembly, a buffer assembly and a dragging material stroking assembly, the material returning prevention assembly is used for preventing a cable in laying from returning, the cable close to the support has the surplus length and is wound and placed on the buffering assembly, the buffering assembly is used for buffering the pulling force borne by the cable close to the support, and the dragging and material stroking assembly is installed on the material returning prevention assembly and is in transmission connection with the buffering assembly. And the dragging and stroking assembly is used for reducing the bending angle of the cable close to the anti-returning assembly. The protection device buffers the tensile force of the cable at the wiring end, so that the cable close to the wiring end is prevented from being deformed due to tightening tensile force, even core wire conductors in the cable are prevented from being broken, and even the cable at the wiring end is prevented from being loosened.

Description

Technical Field

[0001] This utility model belongs to the field of transformer protection technology, specifically relating to a protective device for cable terminals of transformers. Background Technology

[0002] A transformer is an electrical device used to change alternating current voltage (by increasing or decreasing it). It utilizes the principle of electromagnetic induction to achieve the transmission of electrical energy and the conversion of voltage. Transformers are widely used in power transmission, electronic equipment, and industrial production. In the use of transformers, cables are mainly used to connect the various components of the transformer. Cables are typically needed to connect to the power source, load, and other related equipment to ensure the transmission of electricity.

[0003] In the process of power transmission, cable trays are needed to support the cable lines during installation. According to a published Chinese patent application (patent number 202221701256.1) entitled "A Box-Type Transformer for Preventing Cable Sagging," the technical problem is that when the cables inside the transformer extend to the external cable tray, the cables located on the outside are prone to sagging under the influence of gravity, resulting in poor cable installation stability and easy damage to the cables when subjected to sudden pulling. The patent addresses this issue by setting up a cable auxiliary support mechanism on the mounting frame. The cables are electrically connected to both sides of the bottom of the transformer body. The triangular stress formed by the first and second guide rollers can enhance the stability of the cable installation and effectively prevent the cables from sagging.

[0004] However, when the cable outside the transformer is pulled by gravity or external force during installation, the part of the cable near the transformer terminal is always in a taut and stretched state. That is, the cable and the transformer terminal are always in a rigid and taut state. If the external force is too large, it is very easy to cause the cable terminal to loosen or even the core conductor inside the cable to break, affecting the service life of the cable. Utility Model Content

[0005] The purpose of this utility model is to provide a transformer cable terminal protection device with a simple structure and reasonable design in order to solve the above problems.

[0006] This utility model achieves the above objectives through the following technical solutions:

[0007] A cable terminal protection device for transformers, comprising:

[0008] The base is used to fix and install the transformer. A cable tray is fixed on one side of the base. The cable tray is used to lay and support the cables led out from the cable terminals of the transformer.

[0009] A tension buffer mechanism is provided, which is mounted on a base via a support and positioned near the cable terminal of the transformer. The tension buffer mechanism includes an anti-retraction component, a buffer component, and a tension-relieving component. The anti-retraction component prevents the cable from retracting during installation. The buffer component is mounted on the support, which is also mounted on the base near the cable terminal of the transformer. The cable near the support has excess length and is wound around the buffer component. The buffer component buffers the tension force on the cable near the support. The tension-relieving component is mounted on the anti-retraction component and is drively connected to the buffer component. The tension-relieving component reduces the bending angle of the cable near the anti-retraction component.

[0010] As a further optimization of this utility model, a first through hole is provided on the side end of the support, and the first through hole is used to pass through the cable to be laid.

[0011] The buffer assembly includes an outer sleeve, an inner sleeve, a sealing plate, a fixing rod, a sliding sleeve, a first spring, and a slider. The outer sleeve is fixedly installed on a support, and the support communicates with the outer sleeve through a first through hole. The inner sleeve is slidably connected to the outer sleeve. The end of the inner sleeve away from the support is fixedly connected to the sealing plate. A fixing rod is fixedly connected to the support inside the outer sleeve. The outside of the fixing rod is slidably connected to the sliding sleeve. A slider is fixedly connected to the end of the fixing rod away from the support. The slider is located inside the sliding sleeve and is slidably connected to the sliding sleeve. A first spring is sleeved on the circumferential side of the fixing rod inside the sliding sleeve. The end of the sliding sleeve away from the support is fixedly connected to the sealing plate.

[0012] The sealing plate has a second through hole for passing through the cable, and the anti-reverse assembly is installed on the sealing plate near the second through hole.

[0013] As a further optimization of this utility model, the anti-reverse assembly is provided in multiple sets, and the multiple sets of the anti-reverse assembly are installed on the side of the sealing plate near the support, and the multiple sets of the anti-reverse assembly are evenly distributed around the second through hole.

[0014] As a further optimization of this utility model, the anti-return assembly includes a bracket, a first swing rod, a second spring, and a clamping block. The bracket is fixedly mounted on a sealing plate. The first swing rod is rotatably connected to the end of the bracket away from the sealing plate. The clamping block is fixedly connected to the end of the first swing rod near the axis of the second through hole. The clamping block has an arcuate protrusion at the end away from the first swing rod. The second spring is fixedly connected to the side of the end of the first swing rod away from the axis of the second through hole. The end of the second spring away from the first swing rod is fixedly connected to the bracket.

[0015] As a further optimization of this utility model, the material pulling assembly includes a support rod, a protrusion, a second rocker arm, and a third spring. A sliding groove is provided on the sliding sleeve. The support rod is fixedly connected to the side end of the slider. The support rod is slidably connected to the sliding sleeve through the sliding groove. A protrusion is fixedly connected to one end of the support rod that passes through the sliding groove to the outside of the sliding sleeve. A second rocker arm is rotatably connected to the clamping block in a set of anti-reverse material assembly near the sliding sleeve. A third spring is fixedly connected to the side of the second rocker arm facing the first rocker arm. The end of the third spring away from the second rocker arm is fixedly connected to the first rocker arm. The side of the second rocker arm away from the first rocker arm has an arc-shaped protrusion.

[0016] As a further optimization of this utility model, a ball bearing is embedded on one side of the arcuate convex portion of the second rocker arm.

[0017] As a further optimization of this utility model, there are multiple traction buffer mechanisms, and there are multiple first through holes, with each first through hole corresponding to a traction buffer mechanism.

[0018] As a further optimization of this utility model, a support assembly is also provided on the base. The support assembly includes a knob, a screw, and a bracket. The screw is threadedly connected to the base. The knob is fixedly connected to one end of the screw outside the base, and the bracket is rotatably connected to one end of the screw inside the base. The contact surface of the bracket abuts against the outer surface of the support.

[0019] The present invention has at least the following beneficial effects: The present invention device provides a traction buffer mechanism between the transformer and the cable tray, and uses an anti-retraction component to clamp and fix the cable terminal near the transformer, thereby preventing the cable from coming out of the inner sleeve.

[0020] Moreover, the device of this utility model uses a buffer component to buffer the tension on the cable near the transformer. Since the cable is wound with extra length in the inner sleeve, the cable is flexibly distributed between the clamping position and the connection position of the cable terminal, and can be stretched out. This avoids the existing situation where the cable is stretched and straightened, causing the cable terminal to loosen or even the core conductor inside the cable to break.

[0021] In addition, under the pulling of the clamping block on the cable, the second swing arm is swung towards the cable by the contact of the protrusion with the second swing arm, so as to push the cable near the clamping position open, reduce the bending angle of the cable at the clamping position, and reduce the impact of cable bending on the electrical performance of the cable. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0023] Figure 2 This is the utility model Figure 1 Enlarged view of point A in the middle;

[0024] Figure 3 This is a partial cross-sectional structural schematic diagram of the support and traction buffer mechanism in this utility model;

[0025] Figure 4 This is a partial cross-sectional view of the traction buffer mechanism in this utility model;

[0026] Figure 5 This is a utility model Figure 4 Enlarged view of point B in the middle.

[0027] In the diagram: 1. Transformer; 11. Base; 12. Cable tray; 121. Conduit; 2. Pulling and buffering mechanism; 21. Buffer assembly; 211. Fixing rod; 212. First spring; 213. Sliding sleeve; 214. Sliding block; 215. Outer sleeve; 216. Inner sleeve; 217. Sealing plate; 2171. Second through hole; 22. Pulling and material-pulling assembly; 221. Support rod; 222. Protrusion; 223. Slide groove; 224. Second swing rod; 225. Third spring; 23. Anti-reverse assembly; 231. Clamping block; 232. First swing rod; 233. Bracket; 234. Second spring; 24. Support; 241. First through hole; 31. Knob; 32. Screw; 33. Support. Detailed Implementation

[0028] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0029] In one embodiment, such as Figure 1 , Figure 2 and Figure 3 As shown, the present invention provides a transformer cable terminal protection device, comprising:

[0030] Base 11, on which transformer 1 is fixedly installed, and a cable tray 12 is fixedly installed on one side of base 11, the cable tray 12 being used to lay and support the cables leading out from the cable terminals of transformer 1; such as Figure 1 and Figure 2 As shown, a conduit 121 is provided at one end of the cable tray 12 near the base 11. The cable terminal first passes through the conduit 121 into the inside of the base 11 and waits to be further pulled to the terminal on the transformer 1 to complete the electrical connection of the cable.

[0031] A traction buffer mechanism 2 is mounted on the base 11 via a support 24, and is positioned near the cable terminal of the transformer 1. The traction buffer mechanism 2 includes an anti-retraction component 23, a buffer component 21, and a traction buffer component 22. The anti-retraction component 23 prevents the cable from retracting during installation. The buffer component 21 is mounted on the support 24, which is mounted on the base 11 and positioned near the cable terminal of the transformer 1. Figure 3 As shown, the support 24 is rotatably connected to the base 11 via a threaded pipe thread, so that the cable connection position of the transformer 1 corresponds to the installation position of the support 24. The cable near the support 24 has a spare length and is wound and placed on the buffer assembly 21. The buffer assembly 21 is used to buffer the tension on the cable near the support 24. The tensioning and smoothing assembly 22 is installed on the anti-retraction assembly 23, and the tensioning and smoothing assembly 22 is connected to the buffer assembly 21. The tensioning and smoothing assembly 22 is used to reduce the bending angle of the cable near the anti-retraction assembly 23.

[0032] It should be noted that multiple traction buffer mechanisms 2 can be set for the multiple terminals on transformer 1 to buffer the multiple cables.

[0033] Continue reading Figure 3 and Figure 4 In one embodiment, the support 24 has a first through hole 241 on its side, which is used to pass through the cable to be laid, such as... Figure 3 The dashed arrow in the middle indicates the cable threading trajectory;

[0034] The buffer assembly 21 includes an outer sleeve 215, an inner sleeve 216, a sealing plate 217, a fixing rod 211, a sliding sleeve 213, a first spring 212, and a slider 214. The outer sleeve 215 is fixedly mounted on a support 24, and the support 24 communicates with the outer sleeve 215 through a first through hole 241. The inner sleeve 216 is slidably connected to the outer sleeve 215, and one end of the inner sleeve 216 away from the support 24 is fixedly connected to the sealing plate 217, located on the outer sleeve 215. A fixing rod 211 is fixedly connected to the support 24 inside 5. The outside of the fixing rod 211 is slidably connected to the sliding sleeve 213. A slider 214 is fixedly connected to the end of the fixing rod 211 away from the support 24. The slider 214 is located inside the sliding sleeve 213 and is slidably connected to the sliding sleeve 213. A first spring 212 is sleeved on the circumferential side of the fixing rod 211 inside the sliding sleeve 213. The end of the sliding sleeve 213 away from the support 24 is fixedly connected to the sealing plate 217.

[0035] The sealing plate 217 has a second through hole 2171 for passing through a cable, and the anti-removal component 23 is installed on the sealing plate 217 near the second through hole 2171.

[0036] In the above embodiment, after the cable terminal enters the base 11 from the conduit 121 and before passing through the first through hole 241, it first passes through the second through hole 2171, and the excess cable length is wound around the sliding sleeve 213, as shown. Figure 3 As shown, the cable is wound three times. In other embodiments, the cable can be wound two times, and the cable is loosely wound on the sleeve 213 rather than tightly wound on the sleeve 213. Moreover, the outer surface of the sleeve 213 is smooth, reducing the friction between the wound cable and the sleeve 213, so as to ensure that the cable can be unwound smoothly during the buffering process. Then the cable is inserted above the base 11 and connected to the terminal of the transformer 1. When the cable is pulled, the anti-retraction component 23 clamps the cable to prevent the cable from coming out of the inner sleeve 216. Under the pull of the cable, the anti-retraction component 23 drives the sleeve 213 along the sealing plate 217. Figure 4 The cable shifts to the right as shown, compressing the first spring 212. At this time, under the clamping of the anti-retraction component 23, the excess cable length extends, greatly reducing the tensile strength of the cable near the terminal. This avoids the existing situation of the cable being pulled and straightened, solving the problem of the existing cable being rigidly pulled in the direction of the axis, causing the core conductor inside the cable to break. It effectively avoids the existing situation of the cable being pulled and straightened, causing the cable terminal to loosen or even the core conductor inside the cable to break. At the same time, it also reduces the rigid pulling strength of the existing cable on the terminal.

[0037] Please continue reading. Figure 3 In one embodiment, multiple sets of the anti-retraction components 23 are provided. The multiple sets of anti-retraction components 23 are installed on the side of the sealing plate 217 near the support 24, and the multiple sets of anti-retraction components 23 are evenly distributed around the second through hole 2171 to achieve multi-point clamping of the cable and good anti-retraction effect.

[0038] For example, see [link to relevant documentation]. Figure 3 , Figure 4 and Figure 5 The anti-return assembly 23 includes a bracket 233, a first swing rod 232, a second spring 234, and a clamping block 231. The bracket 233 is fixedly mounted on the sealing plate 217. The first swing rod 232 is rotatably connected to one end of the bracket 233 away from the sealing plate 217. The clamping block 231 is fixedly connected to one end of the first swing rod 232 near the axis of the second through hole 2171. The clamping block 231 has an arc-shaped protrusion at one end away from the first swing rod 232. The second spring 234 is fixedly connected to the side of one end of the first swing rod 232 away from the axis of the second through hole 2171. The second spring 234 is fixedly connected to the bracket 233 at one end away from the first swing rod 232.

[0039] In the above embodiments, such as Figure 3 As shown, the cables are arranged according to the trajectory of the dashed arrow. For the cable passing through the second through hole 2171, it passes smoothly from right to left. When the cable is pulled to the right due to its laying on the cable tray 12, the arc protrusion of the clamping block 231 rubs against the surface of the cable and uses the friction between the two to clamp and fix the cable, so as to prevent the cable from coming out of the inner sleeve 216. Thus, under the force of the cable being pulled, the sealing plate 217 drives the sliding sleeve 213 to move to the right, so that the buffer assembly 21 can play a buffering role.

[0040] Please continue reading. Figure 4 and Figure 5 In one embodiment, the material pulling assembly 22 includes a support rod 221, a protrusion 222, a second rocker arm 224, and a third spring 225. The sliding sleeve 213 has a groove 223. The side end of the slider 214 is fixedly connected to the support rod 221. The support rod 221 is slidably connected to the sliding sleeve 213 through the groove 223. The support rod 221 passes through the groove 223 and is fixedly connected to the protrusion 222 at one end outside the sliding sleeve 213. The second rocker arm 224 is rotatably connected to the clamping block 231 in a set of anti-reverse material assembly 23 near the sliding sleeve 213. The third spring 225 is fixedly connected to the side of the second rocker arm 224 facing the first rocker arm 232. The end of the third spring 225 away from the second rocker arm 224 is fixedly connected to the first rocker arm 232. The side of the second rocker arm 224 away from the first rocker arm 232 has an arcuate protrusion.

[0041] In the above embodiment, due to the force pulling the cable, the clamping block 231 rubs against and clamps the cable, causing the excess cable to quickly extend when the sliding sleeve 213 moves to the right. This increases the bending angle between the clamping block 231 and the cable clamping position. At this time, the second swing rod 224 is swung towards the cable by the contact of the protrusion 222, so as to push the cable near the clamping position open, reduce the bending angle of the cable at the clamping position, and reduce the impact of cable bending on the electrical performance of the cable.

[0042] In one embodiment, a ball bearing is embedded on one side of the arcuate protrusion of the second rocker arm 224. There are multiple balls bearings, and the spherical surface of the balls protrudes from the arcuate surface of the arcuate protrusion of the second rocker arm 224. This reduces friction on the cable when the second rocker arm 224 swings to push the cable, making it easier to push the cable out.

[0043] In one embodiment, there are multiple tension buffer mechanisms 2, and multiple first through holes 241, with each first through hole 241 corresponding to a tension buffer mechanism 2. The number of tension buffer mechanisms 2 can be adapted to the number of cables required for electrical connections to equipment at the construction site.

[0044] For example, see [link to relevant documentation]. Figure 2 and Figure 3 The base 11 is also provided with a support assembly, which includes a knob 31, a screw 32 and a bracket 33. The screw 32 is threadedly connected to the base 11. The knob 31 is fixedly connected to one end of the screw 32 outside the base 11, and the bracket 33 is rotatably connected to the other end of the screw 32 inside the base 11. The contact surface of the bracket 33 abuts against the outer surface of the support 24 to provide auxiliary support for the support 24.

[0045] It should be noted that, when using the cable terminal protection device for this transformer, first install the support 24 threaded onto the base 11, and then pass the cable terminal from the support side of the cable tray 12 through the conduit 121 into the inner side of the base 11. Next, pass the cable terminal sequentially through the second through hole 2171 and the first through hole 241, with the excess cable length wound around the sliding sleeve 213. Hold the sealing plate 217 and insert the anti-retraction component 23 into the inner sleeve 216. Rotate the sealing plate 217 until the second swing rod 224 is located to the left of the protrusion 222 (e.g., Figure 5 (as shown in the diagram), and fix the sealing plate 217 to the sliding sleeve 213 with fastening screws, and fix the sealing plate 217 to the inner sleeve 216 with fastening screws, while the cable terminals pass through the support 24 and the base 11 in sequence and are electrically connected to the transformer 1.

[0046] When workers pull the cable on the cable tray 12 to lay and fix it, the cable near the cable terminal is subjected to rigid tension due to the dragging of the workers. Under the clamping action of the clamping block 231, the cable will not come out of the inner sleeve 216. The anti-retraction component 23 drives the sealing plate 217 to move to the right, thereby driving the sliding sleeve 213 to compress the first spring 212. The elastic deformation of the first spring 212 is used to buffer the tension force on the cable. Moreover, since the cable is wound with extra length in the inner sleeve 216, the cable is flexibly distributed between the clamping position and the cable terminal connection position, and can be stretched out. This avoids the existing situation where the cable is stretched and straightened, causing the cable terminal to loosen or even the core conductor inside the cable to break.

[0047] Moreover, when the cable is pulled by force, as the sliding sleeve 213 moves to the right, the excess cable quickly extends. Through the contact of the protrusion 222 with the second swing rod 224, the second swing rod 224 swings towards the cable, thereby pushing the cable near the clamping position open, reducing the bending angle of the cable at the clamping position, and reducing the impact of cable bending on the electrical performance of the cable.

[0048] The embodiments described above are merely examples of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these modifications and improvements all fall within the protection scope of this utility model.

Claims

1. A cable terminal protection device for transformers, characterized in that, include: The base (11) is used to fix and install the transformer (1). A cable tray (12) is fixedly installed on one side of the base (11). The cable tray (12) is used to lay and support the cables led out from the cable terminals of the transformer (1). A traction buffer mechanism (2) is mounted on a base (11) via a support (24) and is located on the side adjacent to the cable terminal of the transformer (1). The traction buffer mechanism (2) includes an anti-retraction component (23), a buffer component (21), and a traction buffer component (22). The anti-retraction component (23) is used to prevent the cable from retracting during installation. The buffer component (21) is mounted on the support (24), and the support (24) is mounted on the base (11). The cable terminal near the transformer (1) is located on the support (24) and has a spare length and is wrapped around the buffer assembly (21). The buffer assembly (21) is used to buffer the tension on the cable near the support (24). The tensioning assembly (22) is installed on the anti-retraction assembly (23) and is connected to the buffer assembly (21). The tensioning assembly (22) is used to reduce the bending angle of the cable near the anti-retraction assembly (23).

2. The transformer cable terminal protection device according to claim 1, characterized in that, The support (24) has a first through hole (241) on its side end, and the first through hole (241) is used to pass through the cable to be laid. The buffer assembly (21) includes an outer sleeve (215), an inner sleeve (216), a sealing plate (217), a fixing rod (211), a sliding sleeve (213), a first spring (212), and a slider (214). The outer sleeve (215) is fixedly mounted on a support (24), and the support (24) communicates with the outer sleeve (215) through a first through hole (241). The inner sleeve (216) is slidably connected to the outer sleeve (215), and one end of the inner sleeve (216) away from the support (24) is fixedly connected to the sealing plate (217). The inner sleeve (216) is located on the outer sleeve (215). A fixing rod (211) is fixedly connected to the support (24) inside 215. The outside of the fixing rod (211) is slidably connected to the sliding sleeve (213). A slider (214) is fixedly connected to the end of the fixing rod (211) away from the support (24). The slider (214) is located inside the sliding sleeve (213) and is slidably connected to the sliding sleeve (213). A first spring (212) is sleeved on the circumferential side of the fixing rod (211) inside the sliding sleeve (213). The end of the sliding sleeve (213) away from the support (24) is fixedly connected to the sealing plate (217). The sealing plate (217) has a second through hole (2171) for passing through a cable. The anti-reverse assembly (23) is installed on the sealing plate (217) near the second through hole (2171).

3. A cable terminal protection device for a transformer according to claim 2, characterized in that, The anti-retraction assembly (23) is provided in multiple sets. The multiple sets of the anti-retraction assembly (23) are installed on the side of the sealing plate (217) near the support (24), and the multiple sets of the anti-retraction assembly (23) are evenly distributed around the second through hole (2171).

4. A cable terminal protection device for a transformer according to claim 3, characterized in that, The anti-return assembly (23) includes a bracket (233), a first swing rod (232), a second spring (234), and a clamping block (231). The bracket (233) is fixedly mounted on the sealing plate (217). The first swing rod (232) is rotatably connected to one end of the bracket (233) away from the sealing plate (217). The clamping block (231) is fixedly connected to one end of the first swing rod (232) near the axis of the second through hole (2171). The clamping block (231) has an arc-shaped protrusion at one end away from the first swing rod (232). The second spring (234) is fixedly connected to the side of one end of the first swing rod (232) away from the axis of the second through hole (2171). The second spring (234) is fixedly connected to the bracket (233) at one end away from the first swing rod (232).

5. A cable terminal protection device for a transformer according to claim 4, characterized in that, The tensioning assembly (22) includes a support rod (221), a protrusion (222), a second rocker arm (224), and a third spring (225). A groove (223) is provided on the sliding sleeve (213). The support rod (221) is fixedly connected to the side end of the slider (214). The support rod (221) is slidably connected to the sliding sleeve (213) through the groove (223). The support rod (221) passes through the groove (223) and is fixedly connected to one end of the outer side of the sliding sleeve (213). The second rocker arm (224) is rotatably connected to the clamping block (231) of the anti-reverse assembly (23) near the slide sleeve (213). The second rocker arm (224) is fixedly connected to the side of the first rocker arm (232) facing the first rocker arm (232). The end of the third spring (225) away from the second rocker arm (224) is fixedly connected to the first rocker arm (232). The side of the second rocker arm (224) away from the first rocker arm (232) has an arc-shaped protrusion.

6. A cable terminal protection device for a transformer according to claim 5, characterized in that, A ball bearing is embedded on one side of the arcuate protrusion of the second rocker arm (224).

7. A transformer cable terminal protection device according to claim 5, characterized in that, There are multiple traction buffer mechanisms (2), and there are multiple first through holes (241), with each first through hole (241) corresponding to a traction buffer mechanism (2).

8. A transformer cable terminal protection device according to claim 6 or 7, characterized in that, The base (11) is also provided with a support assembly, which includes a knob (31), a screw (32) and a bracket (33). The screw (32) is threadedly connected to the base (11). The end of the screw (32) located outside the base (11) is fixedly connected to the knob (31), and the end of the screw (32) located inside the base (11) is rotatably connected to the bracket (33). The contact surface of the bracket (33) abuts against the outer surface of the support (24).

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