A concealed aluminum alloy furniture fastener

Abstract

The present invention discloses a concealed aluminum alloy furniture fastener, which includes a sub-component and a connecting fastener. The sub-component includes mounting ears symmetrically arranged at the left and right ends. Fixed screw holes are provided on the mounting ears. A positioning convex block is arranged between the mounting ears. Three groups of staggered mounting columns are provided at the bottom end of the positioning convex block. Tightening hooks are arranged on the outer sides of the mounting columns. The connecting fastener includes a mounting groove. Fixed strips are symmetrically arranged at the front and rear ends of the mounting groove. A guiding groove is arranged at the middle position of the mounting groove. By providing a connecting fastener adapted to be connected with the sub-component, it helps to enhance the connection tightness of the device between furniture. Moreover, the anti-slip rib system on the outer side of the connecting fastener can effectively enhance the connection tightness between the device and furniture, and it will not loosen even after long-term use, which helps to extend the service life of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of invisible connectors for furniture, and particularly to a concealed aluminum alloy furniture fastener. Background Art

[0002] The three-in-one connector is one of the most commonly used installation methods for panel furniture. The three-in-one connector can be disassembled and assembled multiple times without the use of adhesives. As people's requirements for the aesthetics of customized furniture are getting higher and higher, the requirements for the connectors of customized furniture are also getting higher and higher. Therefore, the demand for invisible connecting mother and son parts is increasing. The so-called invisible connecting mother and son parts mean that when assembling furniture, the connection holes are hidden. There are almost no hole traces on the appearance of the furniture, which is naturally more beautiful. At the same time, the installation of the invisible connecting mother and son parts is also very fast and convenient.

[0003] Currently, a furniture connecting return part appears on the market. By setting a magnetic return part, the stability between the connectors is enhanced, the connection between the furniture is made more stable, the loosening of the connectors caused by external forces is avoided, and the practicability of the device is enhanced. However, it is not suitable for installation on all-aluminum furniture. The product of the present invention is also very suitable for all-aluminum furniture and is the only invisible part used on all-aluminum furniture in the market. Summary of the Invention

[0004] The purpose of the present invention is to provide a concealed aluminum alloy furniture fastener to solve the problems raised in the above background art.

[0005] To achieve the above object, the present invention provides the following technical solution: A concealed aluminum alloy furniture fastener, comprising a sub-component and a connecting fastener. The sub-component includes mounting ears symmetrically arranged at the left and right ends. Fixing screw holes are provided on the mounting ears. A positioning convex block is arranged between the mounting ears. Three groups of staggered mounting posts are arranged at the bottom end of the positioning convex block. Tightening hooks are arranged on the outer sides of the mounting posts. The connecting fastener includes a mounting groove. Fixed strips are symmetrically arranged at the front and rear ends of the mounting groove. A guiding groove is arranged at the middle position of the mounting groove. Guiding inclined surfaces are symmetrically arranged at the front and rear ends of the middle position of the guiding groove. An installation cavity is arranged at the middle position of the bottom end of the connecting fastener. The installation cavity and the guiding groove communicate with each other. Connecting ribs are symmetrically arranged in the front and rear between the installation cavity and the guiding groove. Multiple stabilizing convex blocks adapted to the mounting posts are arranged at the bottom end of the connecting ribs. The mounting posts pass through between the connecting ribs. The tightening hooks are in contact connection with the bottom surface of the connecting ribs. Multiple groups of evenly distributed anti-slip rib systems are arranged on the outer side of the connecting fastener. A return device is arranged in the installation cavity. The return device includes a lower module. The lower module includes a lower plate. Three staggered lower through holes are arranged on the lower plate. Return rods are arranged in the lower through holes. The diameter of the return rods is adapted to the lower through holes. Return springs are arranged on the outer sides of the return rods. Lower connecting plates are symmetrically arranged at the left and right ends of the lower plate. Lower connecting holes are arranged on the lower connecting plates. An upper plate is arranged above the lower plate. Upper through holes adapted to the return rods are arranged on the upper plate. The upper parts of the return rods pass through the upper through holes. Side plates extending downward are symmetrically arranged at the left and right ends of the upper plate. Upper connecting plates are arranged on the outer sides of the side plates. Upper connecting holes corresponding to the lower connecting holes are arranged on the upper connecting plates. Connecting rods are arranged between the upper connecting holes and the lower connecting holes. Connecting springs are arranged on the outer sides of the connecting rods. The return rods are in contact connection with the sides of the mounting posts away from the tightening hooks. Four evenly distributed return device fixing hooks are arranged at the bottom end of the connecting fastener. The bottom ends of the return device fixing hooks are in contact connection with the bottom end of the return device.

[0006] Preferably, the width of the mounting groove is adapted to the width of the sub-component. The inner sides of the fixed strips are clamped with the front and rear ends of the sub-component. Two symmetrically arranged guiding blocks are arranged at the bottom end of the sub-component. The shape and size of the guiding blocks are adapted to the guiding groove.

[0007] Preferably, the outer surface of the anti-slip rib system is treated with glue during installation.

[0008] Preferably, a clamping groove is provided at the lower part of the return rod, a limit washer is arranged in the clamping groove, the outer diameter of the limit washer is larger than the diameter of the return rod, the top end of the limit washer is in contact connection with the bottom end of the lower plate, a limit ring is arranged outside the middle position of the upper part of the return rod, the diameter of the limit ring is larger than that of the return rod, the top end of the limit ring is in contact connection with the bottom end of the upper plate, the top end of the return spring is in contact connection with the bottom end of the limit ring, the bottom end of the return spring is in contact connection with the top end of the lower plate, and the diameter of the return spring is adapted to the diameter of the return rod.

[0009] Preferably, the diameter of the connecting rod is adapted to the upper connecting hole and the lower connecting hole. A connecting rod clamping groove is provided at the lower part of the connecting rod, a connecting rod washer is arranged in the connecting rod clamping groove, the outer diameter of the connecting rod washer is larger than that of the connecting rod, the top end of the connecting rod washer is in contact connection with the bottom end of the lower plate, a limit ring is arranged at the upper part of the connecting rod, the diameter of the limit ring is larger than the diameter of the connecting rod, the top end of the connecting spring is in contact connection with the bottom end of the limit ring, the bottom end of the connecting spring is in contact connection with the top end of the upper connecting plate, and the diameter of the connecting spring is adapted to the diameter of the connecting rod.

[0010] Preferably, the lower module includes a lower plate made of a material that can be attracted by a magnet, and the width of the lower plate is slightly smaller than the width of the upper plate.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0012] 1. By providing a connection fastener adapted to be connected with the sub-component, the user aligns the installation column of the sub-component with the installation groove on the connection fastener and buckles it in. When the installation column touches the guiding inclined surface, it tilts slightly. After being buckled in, the installation column penetrates through the connecting rib, and the fastening hook on the installation column fits against the bottom end of the connecting rib. The aftertaste device is buckled into the installation cavity in the connection fastener, and the return rod is clamped with the end of the installation column away from the fastening hook, achieving a tight connection. This ensures that under long-term use, the fastening hook on the sub-component will not fall off from the connecting rib, preventing loosening of furniture connections and other situations, enhancing the stability between the connecting parts, making the connection between furniture more stable, avoiding loosening of the connecting parts caused by external forces, enhancing the practicality of the device. At the same time, by setting the connection fastener to connect the sub-component and the return device, the overall connectivity and integrity of the device are enhanced, which helps to enhance the connection tightness between furniture. Moreover, the anti-slip ribs on the outer side of the connection fastener can effectively enhance the connection tightness between the device and the furniture, and it will not loosen even after long-term use, contributing to extending the service life of the device. Description of the Drawings

[0013] Figure 1 It is a schematic structural diagram of the sub-component of the present invention.

[0014] Figure 2Schematic diagram of the upper structure of the connecting fastener of the present invention.

[0015] Figure 3 Schematic diagram of the lower structure of the connecting fastener of the present invention.

[0016] Figure 4 Schematic diagram of the upper structure of the connection between the sub-component and the connecting fastener of the present invention.

[0017] Figure 5 Schematic diagram of the lower structure of the connection between the sub-component and the connecting fastener of the present invention.

[0018] Figure 6 Schematic diagram of the lower module structure of the present invention.

[0019] Figure 7 Schematic diagram of the disassembled structure of the return device of the present invention.

[0020] Figure 8 Schematic diagram of the overall structure of the return device of the present invention.

[0021] Figure 9 Schematic diagram of the semi-sectional structure of the overall assembly of the present invention.

[0022] Figure 10 Schematic diagram of the connection structure between the sub-component and the board of the present invention.

[0023] Figure 11 Schematic diagram of the connection structure between the whole and the board of the present invention.

[0024] In the figure: 1. Sub-component, 11. Installation ear, 111. Fixed screw hole, 12. Positioning convex block, 13. Guide block, 14. Installation column, 141. Fastening hook, 2. Connecting fastener, 21. Installation groove, 211. Fixed strip, 22. Guide groove, 221. Guide inclined plane, 23. Anti-slip rib system, 24. Connecting rib, 241. Stabilizing convex block, 25. Installation cavity, 26. Fixed hook for return device, 3. Return device, 31. Lower module, 311. Lower plate, 3111. Lower through hole, 312. Lower connecting plate, 3121. Lower connecting hole, 32. Return rod, 321. Card slot, 322. Limit ring, 33. Return spring, 34. Limit washer, 35. Upper plate, 351. Upper through hole, 352. Side plate, 353. Upper connecting plate, 3531. Upper connecting hole, 36. Connecting rod, 361. Connecting rod limit ring, 362. Connecting rod card slot, 37. Connecting spring, 38. Connecting rod washer. Detailed implementation manners

[0025] To make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific implementation manners.

[0026] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "front end", "rear end", "both ends", "one end", "the other end", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0027] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] Please refer to Figures 1-9, an embodiment provided by the present invention: a concealed aluminum alloy furniture fastener, including a sub-component 1 and a connecting fastener 2. The sub-component 1 includes mounting ears 11 symmetrically arranged at the left and right ends. Fixed screw holes 111 are provided on the mounting ears 11 for fixed connection with the board. A positioning convex block 12 is arranged between the mounting ears 11 for embedding into the board positioning groove to position the sub-component 1. At the bottom end of the positioning convex block 12, three groups of staggered mounting posts 14 are provided. Fastening hooks 141 are arranged on the outer sides of the mounting posts 14. The connecting fastener 2 includes a mounting groove 21. The width of the mounting groove 21 is adapted to the width of the sub-component 1. The inner sides of the fixed strips 211 are clamped with the front and rear ends of the sub-component 1. At the bottom end of the sub-component 1, two symmetrically arranged guide blocks 13 are provided. The shape and size of the guide blocks 13 are adapted to the guide grooves 22. Fixed strips 211 are symmetrically arranged at the front and rear ends of the mounting groove 21. A guide groove 22 is arranged at the middle position of the mounting groove 21. Guide inclined surfaces 221 are symmetrically arranged at the front and rear ends of the middle position of the guide groove 22. At the middle position of the bottom end of the connecting fastener 2, a mounting cavity 25 is provided. The mounting cavity 25 and the guide groove 22 communicate with each other. Connecting ribs 24 are symmetrically arranged in the front and rear between the mounting cavity 25 and the guide groove 22. At the bottom end of the connecting ribs 24, a plurality of stabilizing convex blocks 241 adapted to the mounting posts 14 are provided. The mounting posts 14 pass through between the connecting ribs 24. The fastening hooks 141 are in contact connection with the bottom surface of the connecting ribs 24. A plurality of groups of uniformly distributed anti-slip ribs 23 are arranged on the outer side of the connecting fastener 2. The outer surface of the anti-slip ribs 23 is coated with glue during installation to enhance the connection tightness between the connecting fastener 2 and the board, prevent loosening between the connecting fastener 2 and the board, and affect the service life of the connecting fastener 2. A return device 3 is arranged in the mounting cavity 25. The return device 3 includes a lower module 31. The lower module 31 includes a lower plate 311. Three staggered lower through holes 3111 are provided on the lower plate 311. Return rods 32 are arranged in the lower through holes 3111. A clamping groove 321 is provided at the lower part of the return rod 32. A limit washer 34 is arranged in the clamping groove 321. The outer diameter of the limit washer 34 is greater than the diameter of the return rod 32. The top end of the limit washer 34 is in contact connection with the bottom end of the lower plate 311. A limit ring 322 is arranged on the outer side of the middle position of the upper part of the return rod 32. The diameter of the limit ring 322 is greater than that of the return rod 32. The top end of the limit ring 322 is in contact connection with the bottom end of the upper plate 35. The diameter of the return rod 32 is adapted to the lower through holes 3111. A return spring 33 is arranged on the outer side of the return rod 32. The top end of the return spring 33 is in contact connection with the bottom end of the limit ring 322. The bottom end of the return spring 33 is in contact connection with the top end of the lower plate 311. The diameter of the return spring 33 is adapted to the diameter of the return rod 32. Lower connecting plates 312 are symmetrically arranged at the left and right ends of the lower plate 311. Lower connecting holes 3121 are provided on the lower connecting plates 312. An upper plate 35 is arranged above the lower plate 311. The lower module 31 includes a lower plate 311 made of a material that can be attracted by a magnet, which is convenient for later disassembly by magnet attraction.The width of the lower plate 311 of the lower module 31 is slightly smaller than the width of the upper plate 35. An upper through hole 351 adapted to the return rod 32 is provided on the upper plate 35. The upper part of the return rod 32 passes through the upper through hole 351. Side plates 352 extending downward are symmetrically arranged at the left and right ends of the upper plate 35. Upper connecting plates 353 are arranged on the outer sides of the side plates 352. Upper connecting holes 3531 corresponding to the lower connecting holes 3121 are provided on the upper connecting plates 353. A connecting rod 36 is arranged between the upper connecting hole 3531 and the lower connecting hole 3121. The diameter of the connecting rod 36 is adapted to the upper connecting hole 3531 and the lower connecting hole 3121. A connecting rod slot 362 is provided at the lower part of the connecting rod 36. A connecting rod washer 38 is arranged in the connecting rod slot 362. The outer diameter of the connecting rod washer 38 is larger than that of the connecting rod 36. The top end of the connecting rod washer 38 is in contact connection with the bottom end of the lower plate 311. A limiting ring 322 is provided at the upper part of the connecting rod 36. The diameter of the limiting ring 322 is larger than the diameter of the connecting rod 36. A connecting spring 37 is arranged on the outer side of the connecting rod 36. The top end of the connecting spring 37 is in contact connection with the bottom end of the limiting ring 322. The bottom end of the connecting spring 37 is in contact connection with the top end of the upper connecting plate 353. The diameter of the connecting spring 37 is adapted to the diameter of the connecting rod 36. The return rod 32 is in contact connection with the side of the mounting post 14 away from the fastening hook 141. Four uniformly distributed return device fixing hooks 26 are provided at the bottom end of the connecting fastener 2. The bottom end of the return device fixing hook 26 is in contact connection with the bottom end of the return device 3. In the present invention, a connecting fastener 2 adapted to be connected with the sub-component 1 is provided. The user aligns the mounting post 14 of the sub-component 1 with the mounting slot 21 on the connecting fastener 2 and buckles it in. When the mounting post 14 touches the guiding inclined surface 221, it tilts slightly. After being buckled in, the mounting post 14 penetrates through the connecting rib 24. The fastening hook 141 on the mounting post 14 fits against the bottom end of the connecting rib 24. The return device 3 is buckled into the mounting cavity 25 in the connecting fastener 2. The return rod 32 is clamped with the end of the mounting post 14 away from the fastening hook 141, and is tightly connected, ensuring that under long-term use, the fastening hook 141 on the sub-component 1 will not fall off from the connecting rib 24, causing loosening of furniture connection and other situations, enhancing the stability between the connecting parts, making the connection between furniture more stable, avoiding loosening of the connecting parts caused by external force, enhancing the practicability of the device. At the same time, by setting the connecting fastener 2 to connect the sub-component 1 and the return device 3, the overall connectivity and integrity of the device are enhanced, which helps to enhance the connection tightness of the device between furniture. And the anti-slip ribs 23 on the outer side of the connecting fastener 2 can effectively enhance the connection tightness between the device and furniture, and will not loosen after long-term use, which helps to extend the service life of the device.,

[0030] Working principle: When the present invention is in use, it is necessary to have a simple understanding of the structure of the present invention. Align the positioning bump 12 on the sub-component 1 with the positioning groove on the plate A and embed it. Align the bolt with the fixing screw hole 111 on the mounting ear 11 to fix the sub-component 1 on the plate A. Align the mounting groove 21 on the connecting fastener 2 with the guiding block 13 on the sub-component 1 and snap it in. When the mounting post 14 touches the guiding inclined surface 221, it tilts slightly. After snapping in, the mounting post 14 penetrates through the connecting rib 24, and the fastening hook 141 on the mounting post 14 fits against the bottom end of the connecting rib 24. Align the return device 3 with the mounting cavity 25 on the connecting fastener 2 and snap it in. The fixed hook 26 of the return device hooks tightly to the bottom end of the return device 3, and the return rod 32 is clamped with the end of the mounting post 14 away from the fastening hook 141, tightly connected, ensuring that under long-term use, the fastening hook 141 on the sub-component 1 will not fall off from the connecting rib 24, causing loosening of furniture connections and other situations, enhancing the stability between the connecting parts, making the connection between furniture more stable, avoiding loosening of the connecting parts caused by external forces, and enhancing the practicality of the device. At the same time, by setting the connecting fastener 2 to connect the sub-component 1 and the return device 3, the overall connectivity and integrity of the device are enhanced, which helps to enhance the connection tightness of the device for furniture. Apply glue on the outside of the anti-slip rib system 23 on the outside of the connecting fastener 2 and snap the device into the mounting groove in the plate B. The present invention can effectively enhance the connection tightness between the device and furniture and will not loosen after long-term use, which helps to extend the service life of the device. When disassembling, place a magnet on the top or back of the lower plate 311. According to the principle of magnetic attraction, move it backward. The magnet will attract the lower plate 311 to slide backward, and at the same time drive the return rod 32 to move downward until the return rod 32 completely disengages from one side of the mounting post 14. Under the condition of applying an external pulling force, the sub-component 1 and the mother component 2 can be separated well to ensure the practicality of the present device and better meet the market demand.

[0031] The above are only the embodiments of the present invention. Specific structures and common knowledge such as well-known characteristics in the solution are not described in detail here. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

Claims

1. A concealed aluminum alloy furniture fastener, comprising a sub-component (1) and a connecting fastener (2), characterized in that: The sub-component (1) includes mounting ears (11) symmetrically arranged at both the left and right ends. Fixing screw holes (111) are provided on the mounting ears (11). A positioning convex block (12) is arranged between the mounting ears (11). At the bottom end of the positioning convex block (12), three groups of staggered mounting posts (14) are provided. Fastening hooks (141) are arranged on the outer sides of the mounting posts (14). The connecting fastener (2) includes a mounting groove (21). Fixed bars (211) are symmetrically arranged at the front and rear ends of the mounting groove (21). A guiding groove (22) is arranged at the middle position of the mounting groove (21). Guiding inclined surfaces (221) are symmetrically arranged at the front and rear ends at the middle position of the guiding groove (22). At the middle position of the bottom end of the connecting fastener (2), a mounting cavity (25) is provided. The mounting cavity (25) and the guiding groove (22) are interconnected. Connecting rib strips (24) are symmetrically arranged in the front and rear between the mounting cavity (25) and the guiding groove (22). At the bottom end of the connecting rib strips (24), a plurality of stabilizing convex blocks (241) adapted to the mounting posts (14) are provided. The mounting posts (14) pass through between the connecting rib strips (24). The fastening hooks (141) are in contact connection with the bottom surface of the connecting rib strips (24). A plurality of groups of uniformly distributed anti-slip rib systems (23) are arranged on the outer side of the connecting fastener (2). A return device (3) is arranged in the mounting cavity (25). The return device (3) includes a lower module (31). The lower module (31) includes a lower plate (311). Three staggered lower through holes (3111) are provided on the lower plate (311). Return rods (32) are arranged in the lower through holes (3111). The diameter of the return rods (32) is adapted to the lower through holes (3111). Return springs (33) are arranged on the outer sides of the return rods (32). Lower connecting plates (312) are symmetrically arranged at the left and right ends of the lower plate (311). Lower connecting holes (3121) are provided on the lower connecting plates (312). An upper plate (35) is arranged above the lower plate (311). Upper through holes (351) adapted to the return rods (32) are provided on the upper plate (35). The upper parts of the return rods (32) pass through the upper through holes (351). Side plates (352) extending downward are symmetrically arranged at the left and right ends of the upper plate (35). Upper connecting plates (353) are arranged on the outer sides of the side plates (352). Upper connecting holes (3531) corresponding to the lower connecting holes (3121) are provided on the upper connecting plates (353). Connecting rods (36) are arranged between the upper connecting holes (3531) and the lower connecting holes (3121). Connecting springs (37) are arranged on the outer sides of the connecting rods (36). The return rods (32) are in contact connection with the sides of the mounting posts (14) away from the fastening hooks (141). Four uniformly distributed return device fixing hooks (26) are arranged at the bottom end of the connecting fastener (2).The bottom end of the fixing hook (26) of the return device is in contact connection with the bottom end of the return device (3). The width of the installation groove (21) is adapted to the width of the sub-component (1). The inner sides of the fixing strips (211) are clamped to the front and rear ends of the sub-component (1). Two symmetrically arranged guiding blocks (13) are provided at the bottom end of the sub-component (1). The shape and size of the guiding blocks (13) are adapted to the guiding grooves (22). The outer surface of the anti-slip rib system (23) is treated with glue during installation. A clamping groove (321) is provided at the lower part of the return rod (32). A limit washer (34) is arranged in the clamping groove (321). The outer diameter of the limit washer (34) is larger than the diameter of the return rod (32). The top end of the limit washer (34) is in contact connection with the bottom end of the lower plate (311). A limit ring (322) is arranged on the outer side of the middle position of the upper part of the return rod (32). The diameter of the limit ring (322) is larger than that of the return rod (32). The top end of the limit ring (322) is in contact connection with the bottom end of the upper plate (35). The top end of the return spring (33) is in contact connection with the bottom end of the limit ring (322). The bottom end of the return spring (33) is in contact connection with the top end of the lower plate (311). The diameter of the return spring (33) is adapted to the diameter of the return rod (32). The diameter of the connecting rod (36) is adapted to the upper connecting hole (3531) and the lower connecting hole (3121). A connecting rod clamping groove (362) is provided at the lower part of the connecting rod (36). A connecting rod washer (38) is arranged in the connecting rod clamping groove (362). The outer diameter of the connecting rod washer (38) is larger than that of the connecting rod (36). The top end of the connecting rod washer (38) is in contact connection with the bottom end of the lower plate (311). A limit ring (322) is arranged at the upper part of the connecting rod (36). The diameter of the limit ring (322) is larger than the diameter of the connecting rod (36). The top end of the connecting spring (37) is in contact connection with the bottom end of the limit ring (322). The bottom end of the connecting spring (37) is in contact connection with the top end of the upper connecting plate (353). The diameter of the connecting spring (37) is adapted to the diameter of the connecting rod (36). The lower module (31) includes a lower plate (311) made of a material that can be attracted by a magnet. The width of the lower plate (311) of the lower module (31) is slightly smaller than the width of the upper plate (35).

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