Quick change structure of angle grinder protective cover

Abstract

The invention provides an angle grinder protective cover quick-change structure which comprises a handle, a transmission shaft rotationally installed at the end of the handle, an angle grinding piece detachably connected to the end of the transmission shaft and a protective cover arranged on the outer side of the angle grinding piece in a covering mode, the inner side of the protective cover is connected with a limiting ring, and the end of the handle is connected with a shell. An annular groove is formed in the shell in the circumferential direction, a plurality of bayonets are formed in the side, close to the protective cover, of the annular groove, and a plurality of clamping blocks matched with the bayonets are arranged on the inner side of the limiting ring, so that when the limiting ring is installed on the shell, the clamping blocks are inserted into the bayonets, and limiting matching is conducted through the clamping blocks and the annular groove; the protective cover is convenient to disassemble, and the cutting depth of the angle abrasive disc cannot be affected.

Description

Technical Field

[0001] The invention relates to the field of angle grinders, and in particular to a quick-change structure for a protective cover of an angle grinder. Background Art

[0002] Angle grinder, also known as grinding machine or disc grinder, is a portable electric grinding tool used for cutting and grinding. It is mainly used for cutting, grinding and brushing metal and stone.

[0003] When the angle grinder is in use, it needs to be installed with an angle grinding disc for cutting and grinding. Since sparks are generated during the processing of the angle grinding disc, the current angle grinders are usually equipped with a protective cover to prevent sparks from flying.

[0004] However, the existing protective cover installation method basically adopts trigger fixing, which has the disadvantage that the trigger will affect the cutting depth of the angle grinder, which is not conducive to the cutting process of the angle grinder at a deeper position, and because the trigger fixing method is difficult to disassemble, the replacement of the existing protective cover is not convenient enough. Summary of the invention

[0005] The object of the present invention is to provide a quick-change structure for an angle grinder protective cover which improves the convenience of disassembly of the protective cover and does not affect the cutting depth of the angle grinding disc.

[0006] In order to solve the above technical problems, the present invention provides a quick-change structure of an angle grinder protective cover, comprising a handle, a transmission shaft rotatably installed on the end of the handle, an angle grinding disc detachably connected to the end of the transmission shaft, and a protective cover arranged on the outside of the angle grinding disc, the inner side of the protective cover is connected to a limiting ring, the end of the handle is connected to a shell, the shell is provided with a ring groove along the circumferential direction, and a plurality of bayonet holes are provided on the side of the ring groove close to the protective cover, the inner side of the limiting ring has a plurality of clamping blocks matching the bayonet holes, so that when the limiting ring is installed on the shell, the clamping block is inserted into the bayonet hole, and the clamping block and the ring groove are limited.

[0007] Furthermore, a lever is rotatably provided on the side of the shell, and a positioning flange is provided at the end of the lever. A plurality of positioning openings are provided at intervals along the circumferential direction on the side of the limiting ring, so that the positioning flange is buckled in one of the positioning openings.

[0008] Furthermore, a rotating shaft is connected between the lever and the housing, a reset member is sleeved on the rotating shaft, and a shifting piece is provided at one end of the lever away from the positioning flange.

[0009] Further, the bayonet includes a first bayonet and a second bayonet, the opening width of the first bayonet is greater than the opening width of the second bayonet, the card block includes a first card block and a second card block, the first card block matches the first bayonet, and the second card block matches the second bayonet.

[0010] Furthermore, a fixed block is fixedly provided at the end of the transmission shaft, a fastener is threadedly provided at the end of the transmission shaft, and the angle grinding disc is located between the fixed block and the fastener, a plurality of adjustment grooves are circumferentially opened inside the fixed block, the adjustment block is movably installed in the adjustment groove, and a through groove is opened on one side of the adjustment groove, and a reducing rod is connected to the side of the adjustment block close to the through groove, so that when the adjustment block moves relative to the adjustment groove, the reducing rod moves along the through groove.

[0011] Furthermore, a driving groove is opened at one end of the adjustment groove, and the driving block is movably installed in the driving groove, and the driving block and the adjustment block are matched with an oblique wedge, so that when the driving block moves along the driving groove, the adjustment block moves along the adjustment groove, and a first elastic member is connected between one end of the driving block and the driving groove, and a second elastic member is connected between one end of the adjustment block and the adjustment groove.

[0012] Furthermore, a tightening ring is threadedly provided at the end of the transmission shaft, the tightening ring is located on the side of the fastener away from the fixed block, and a connecting ring is rotatably provided on the side of the tightening ring close to the fastener, and a plurality of tightening rods matching the driving block are provided on the side of the connecting ring close to the driving block, so that when the tightening ring rotates along the transmission shaft, the tightening rods drive the driving block to move.

[0013] Furthermore, a guide hole is provided on one side of the driving block close to the clamping rod, and a plurality of arc grooves are provided on the fastener along the circumferential direction so that the clamping rod can pass through the arc groove and then be inserted into the guide hole, and the width of the arc groove is greater than the outer diameter of the clamping rod.

[0014] Furthermore, the end of the reducing rod is detachably connected with a sleeve so that the inner ring of the angle grinding disc abuts against the sleeve.

[0015] Furthermore, the protective cover includes an inner cover and an outer cover, the connection between the inner cover and the outer cover is a stepped structure, and a card plate is connected to the side of the outer cover close to the inner cover, and a buckle matching the card plate is provided on the side of the inner cover close to the outer cover, so that when the outer cover is connected to the inner cover, the card plate is buckled in the buckle; a pressing groove is opened on the side of the buckle, and the pressing groove corresponds to the end of the card plate.

[0016] The beneficial effects of the present invention are as follows: when installing the protective cover, the limit ring is aligned with the outer circumference of the shell and sleeved, and a plurality of card blocks are plugged into a plurality of bayonet ports one by one, so that the plurality of card blocks are snapped into the annular groove, and then the protective cover is controlled to rotate along the shell, so that the limit ring drives the plurality of card blocks to rotate along the annular groove, and then the card blocks and the bayonet ports are staggered with each other, so that the annular groove limits the card blocks, and the installation of the protective cover can be quickly completed. Moreover, since the card blocks, buckles and other structures are all located at the position of the limit ring, the connection structure of the protective cover will not affect the grinding depth of the angle grinder, so as to improve the cutting efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the present invention.

[0018] Figure 2 It is a schematic diagram of the connection between the fixing block and the fastener in the present invention.

[0019] Figure 3 It is a side view of the fastener in the present invention.

[0020] Figure 4 The present invention Figure 3 Section view along line AA.

[0021] Figure 5 The present invention Figure 4 A partial enlarged view of point A in the middle.

[0022] Figure 6 It is a schematic diagram of the connection between the inner cover and the outer cover of the present invention.

[0023] Figure 7 It is an exploded view of the inner cover and the outer cover of the present invention.

[0024] Figure 8 It is a half-section view of the present invention.

[0025] Fig. 9 The present invention Figure 8 A partial enlarged view of point B in the middle.

[0026] Fig.10 It is a schematic diagram of the assembly of the bayonet and the clamping block in the present invention.

[0027] 1. The camshaft is provided with a plurality of locking members, each of which is provided with a plurality of locking members. The camshaft is provided with a plurality of locking members, each of which is provided with a plurality of locking members. The camshaft is provided with a plurality of locking members, each of which is provided with a plurality of locking members. The camshaft is provided with a plurality of locking members, each of which is provided with a plurality of locking members. DETAILED DESCRIPTION

[0028] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0029] Those skilled in the art should understand that, in the disclosure of the present invention, the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0030] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0031] like Figure 1-Figure 10 The present invention provides a quick-change structure for an angle grinder protective cover, comprising a handle 1, a transmission shaft 2 rotatably installed at the end of the handle 1, an angle grinding disc detachably connected to the end of the transmission shaft 2, and a protective cover 4 arranged on the outside of the angle grinding disc, the inner side of the protective cover 4 is connected to a limiting ring 5, the end of the handle 1 is connected to a shell 6, the shell 6 is provided with a ring groove 7 along the circumferential direction, and a plurality of bayonet holes 8 are provided on the side of the ring groove 7 close to the protective cover 4, the inner side of the limiting ring 5 has a plurality of clamping blocks 9 matching the bayonet holes 8, so that when the limiting ring 5 is installed to the shell 6, the clamping block 9 is inserted into the bayonet hole 8, and the clamping block 9 and the ring groove 7 are limited and matched.

[0032] When installing the protective cover 4, the limiting ring 5 is aligned with the outer periphery of the shell 6 and is sleeved, and a plurality of clamping blocks 9 are plugged into a plurality of bayonet ports 8 one by one, so that a plurality of clamping blocks 9 are clamped into the annular groove 7, and then the protective cover 4 is controlled to rotate along the shell 6, so that the limiting ring 5 drives a plurality of clamping blocks 9 to rotate along the annular groove 7, and then the clamping blocks 9 and the bayonet ports 8 are staggered with each other, so that the annular groove 7 limits the clamping blocks 9, and the installation of the protective cover 4 can be quickly completed. Moreover, since the clamping blocks 9, the buckles 44 and other structures are all located at the position of the limiting ring 5, the connection structure of the protective cover 4 will not affect the grinding depth of the angle grinding disc, so as to improve the cutting efficiency.

[0033] Among them, the transmission shaft 2 is controlled by a motor to rotate, so that after the angle grinding disc is installed to the end of the transmission shaft 2, the transmission shaft 2 drives the angle grinding disc to rotate; the protection angle of the protective cover 4 is 180°, so that when the protective cover 4 blocks the sparks of the angle grinding disc, it will not interfere with the processing direction of the angle grinding disc.

[0034] In one embodiment of the present scheme, the bayonet 8 includes a first bayonet and a second bayonet, the opening width of the first bayonet is greater than the opening width of the second bayonet, and the card block 9 includes a first card block and a second card block, the first card block matches the first bayonet, and the second card block matches the second bayonet.

[0035] Specifically, the first card block and the second card block are adapted respectively through the first card slot and the second card slot with different opening widths, so that after the card block 9 passes through the position of the card slot 8, the limit ring 5 rotates circumferentially, and the first card block cannot be detached from the second card slot, so as to ensure the stable connection of the protective cover 4 when it rotates with the limit ring 5.

[0036] Among them, the present solution preferably provides a first bayonet, two second bayonet holes, and a first clamping block, two second clamping blocks, so that the limiting ring 5 and the shell 6 can be limited at three points, thereby improving the installation stability of the limiting ring 5.

[0037] Preferably, a lever 10 is rotatably provided on the side of the housing 6 , and a positioning flange 11 is provided at the end of the lever 10 . A plurality of positioning openings 12 are circumferentially spaced apart on the side of the limiting ring 5 , so that the positioning flange 11 is buckled in one of the positioning openings 12 .

[0038] Specifically, after the protective cover 4 is rotated to a suitable angle, the positioning flange 11 is buckled into the corresponding positioning hole 12, so that the lever 10 can position the limiting ring 5, so that the radial direction of the protective cover 4 is limited by the annular groove 7, and the circumferential direction is limited by the positioning flange 11, thereby increasing the overall stability of the protective cover 4; and because a plurality of positioning holes 12 are opened on the side of the limiting ring 5, the protection angle of the protective cover 4 can be adjusted to multiple angles.

[0039] Preferably, a rotating shaft 13 is connected between the lever 10 and the housing 6 , a reset member 14 is sleeved on the rotating shaft 13 , and a shifting piece 15 is provided at one end of the lever 10 away from the positioning flange 11 .

[0040] Specifically, the rotation stability of the lever 10 is ensured by the rotating shaft 13, and the lever 10 is reset and rotated by the reset member 14 to ensure that the positioning flange 11 can be stably engaged in the positioning hole 12. The setting of the paddle 15 can assist the user in pushing the lever 10 away from the limit ring 5 to facilitate the removal or installation of the protective cover 4.

[0041] The reset member 14 adopts a torsion spring structure.

[0042] Preferably, a fixing block 16 is fixedly provided at the end of the transmission shaft 2, a fastener 17 is threadedly provided at the end of the transmission shaft 2, and the angle grinding disc is located between the fixing block 16 and the fastener 17, a plurality of adjustment grooves 18 are circumferentially opened inside the fixing block 16, an adjustment block 19 is movably installed in the adjustment groove 18, and a through groove 20 is opened on one side of the adjustment groove 18, a reducing rod 21 is connected to the side of the adjustment block 19 close to the through groove 20, so that when the adjustment block 19 moves relative to the adjustment groove 18, the reducing rod 21 moves along the through groove 20.

[0043] Specifically, when installing the angle grinding disc, the inner hole of the angle grinding disc is sleeved onto the end of the transmission shaft 2, and then one side of the angle grinding disc is pressed against the fixing block 16, so that the fastener 17 rotates along the transmission shaft 2 and clamps the other side of the angle grinding disc.

[0044] At the same time, since angle grinding discs of different sizes have different inner hole sizes, in order to ensure the adaptability to the inner holes of various angle grinding discs, the present solution provides a reducing rod 21. After the angle grinding disc is placed on one side of the fixed block 16, the adjusting block 19 is first moved to move the reducing rod 21 along the through groove 20, so that several reducing rods 21 are synchronously against the inner hole position of the angle grinding disc to ensure the supporting effect of several reducing rods 21 on the inner hole of the angle grinding disc, thereby improving the adaptability to the inner holes of different angle grinding discs, and then tightening the fasteners 17 to limit the two sides of the angle grinding disc to ensure the stability of the center position of the angle grinding disc.

[0045] The through groove 20 is opened along the radial direction of the transmission shaft 2 to ensure that the diameter-changing rod 21 moves along the radial direction of the transmission shaft 2, thereby stably adapting to the inner hole of the angle grinding disc.

[0046] Preferably, a driving groove 22 is opened at one end of the adjustment groove 18, and a driving block 23 is movably installed in the driving groove 22, and the driving block 23 and the adjustment block 19 are matched in an oblique wedge, so that when the driving block 23 moves along the driving groove 22, the adjustment block 19 moves along the adjustment groove 18, and a first elastic member 24 is connected between one end of the driving block 23 and the driving groove 22, and a second elastic member 25 is connected between one end of the adjustment block 19 and the adjustment groove 18.

[0047] Specifically, through the wedge cooperation between the driving block 23 and the adjusting block 19, when the driving block 23 moves along the driving groove 22, the adjusting block 19 can be driven to move by the driving block 23 to ensure the stable use of the variable diameter rod 21. At the same time, the driving block 23 and the adjusting block 19 are reset and adjusted respectively by the first elastic member 24 and the second elastic member 25 to ensure the subsequent stable reset of the variable diameter rod 21.

[0048] The first elastic member 24 and the second elastic member 25 may be spring structures.

[0049] Preferably, a tightening ring 26 is threadedly provided at the end of the transmission shaft 2, and the tightening ring 26 is located on the side of the fastener 17 away from the fixed block 16, and a connecting ring 27 is rotatably provided on the side of the tightening ring 26 close to the fastener 17, and a plurality of tightening rods 28 matching the driving block 23 are provided on the side of the connecting ring 27 close to the driving block 23, so that when the tightening ring 26 rotates along the transmission shaft 2, the tightening rods 28 drive the driving block 23 to move.

[0050] Specifically, after the angle grinding disc is placed between the fixing block 16 and the fastener 17, the angle grinding disc is initially positioned by the fastener 17. At this time, the fastener 17 is not in a tightened state, so that the angle grinding disc can be adjusted to a certain extent along the radial direction of the transmission shaft 2, and then a plurality of tightening rods 28 are inserted one by one to align with the position of the driving block 23 until the end of the tightening rod 28 is against the driving block 23, and then the tightening ring 26 is matched with the thread of the transmission shaft 2, so that the tightening ring 26 drives the connecting rod to move toward the fastener 17, and pushes the driving block 23 through the tightening rod 28, so that the reducing rod 21 moves to adapt to the inner hole size of the angle grinding disc, and due to the connection and cooperation between the tightening ring 26 and the connecting ring 27, when the tightening ring 26 rotates, it will not drive the connecting ring 27 to rotate, so as to ensure the stability of the axial movement process of the tightening rod 28.

[0051] Preferably, a guide hole 29 is formed on one side of the driving block 23 close to the clamping rod 28, and a plurality of arc grooves 30 are formed circumferentially on the fastener 17 so that the clamping rod 28 can be inserted into the guide hole 29 after passing through the arc groove 30, and the width of the arc groove 30 is greater than the outer diameter of the clamping rod 28.

[0052] Specifically, the end of the clamping rod 28 is guided and limited by the guide hole 29 to improve the pushing effect of the clamping rod 28 on the driving block 23. At the same time, due to the setting of the plurality of arc grooves 30, when the clamping rod 28 completes the pushing of the driving block 23, the radial direction of the angle grinding disc is limited. At this time, because the fastener 17 has not completely clamped the side of the angle grinding disc, the fastener 17 still needs to be tightened. Through the setting of the arc groove 30, during the tightening process of the fastener 17, the clamping rod 28 is within the range of the arc groove 30. Therefore, the rotation of the fastener 17 will not affect the clamping rod 28, and will only cause the clamping rod 28 and the arc groove 30 to move relative to each other.

[0053] Preferably, the end of the reducing rod 21 is detachably connected with a sleeve 31 so that the inner ring of the angle grinding disc abuts against the sleeve 31 .

[0054] Specifically, the outer periphery of the reducer rod 21 is protected by the sleeve 31 to prevent the outer periphery of the reducer rod 21 from being worn and causing unstable use of the reducer rod 21. At the same time, since the sleeve 31 is detachable, the sleeve 31 can be replaced regularly to ensure the service life of the reducer rod 21.

[0055] Preferably, the protective cover 4 includes an inner cover 41 and an outer cover 42, the connection between the inner cover 41 and the outer cover 42 is in a stepped structure, and a clamping plate 43 is connected to the side of the outer cover 42 close to the inner cover 41, and a buckle 44 matching the buckle 43 is provided on the side of the inner cover 41 close to the outer cover 42, so that when the outer cover 42 is connected to the inner cover 41, the buckle 43 is buckled in the buckle 44; a pressing groove 45 is opened on the side of the buckle 44, and the pressing groove 45 corresponds to the end of the clamping plate 43.

[0056] Specifically, the inner hole sizes of angle grinding discs are different, and the outer diameters of angle grinding discs also have a variety of specifications. In order to ensure that the protective cover can adapt to angle grinding discs with different outer diameters, so as to avoid the protective cover 4 being too large to affect cutting, or the protective cover 4 being too small to cause sparks to fly, etc., the present scheme arranges an inner cover 41 and an outer cover 42. The inner cover 41 is first fixed to the angle grinder through a limiting ring 5. Then the user selects the appropriate size of the outer cover 42 according to the required outer diameter of the angle grinding disc, and aligns the clamping plate 43 of the outer cover 42 with the position of the buckle 44 for clamping. Since the connection between the inner cover 41 and the outer cover 42 is a stepped structure, after the outer cover 42 is clamped, its two sides are respectively limited by the stepped structure and the buckle 44 to ensure the stable use of the protective cover 4.

[0057] At the same time, due to the setting of the pressing groove 45, when the outer cover 42 is disassembled, the clamping plate 43 at the pressing groove 45 can be pushed to make the clamping plate 43 more easily detached from the position of the buckle 44, thereby facilitating the replacement of the outer cover 42.

[0058] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. A quick-change structure for an angle grinder protective cover, characterized in that: The invention comprises a handle (1), a transmission shaft (2) rotatably mounted on the end of the handle (1), an angle grinding disc detachably connected to the end of the transmission shaft (2), and a protective cover (4) arranged on the outside of the angle grinding disc, wherein a limiting ring (5) is connected to the inner side of the protective cover (4), a housing (6) is connected to the end of the handle (1), a ring groove (7) is provided on the housing (6) along the circumferential direction, and a plurality of bayonet holes (8) are provided on the side of the ring groove (7) close to the protective cover (4), and the inner side of the limiting ring (5) has a A plurality of clamping blocks (9) are matched with the bayonet (8), so that when the limiting ring (5) is installed on the shell (6), the clamping block (9) is inserted into the bayonet (8), and the clamping block (9) and the ring groove (7) are limited and matched; a lever (10) is rotatably arranged on the side of the shell (1), and a positioning flange (11) is provided at the end of the lever (10); a plurality of positioning openings (12) are spaced apart along the circumferential direction on the side of the limiting ring (5), so that the positioning flange (11) is buckled in one of the positioning openings (12).

2. The quick-change structure for the angle grinder protective cover according to claim 1 is characterized in that: A rotating shaft (13) is connected between the lever (10) and the housing (6), a reset member (14) is sleeved on the rotating shaft (13), and a shifting piece (15) is provided at one end of the lever (10) away from the positioning flange (11).

3. The quick-change structure for the angle grinder protective cover according to claim 1 is characterized in that: The bayonet (8) comprises a first bayonet and a second bayonet, the opening width of the first bayonet is greater than the opening width of the second bayonet, the card block (9) comprises a first card block and a second card block, the first card block matches the first bayonet, and the second card block matches the second bayonet.

4. The quick-change structure for the angle grinder protective cover according to claim 1, characterized in that: A fixing block (16) is fixedly arranged at the end of the transmission shaft (2), a fastener (17) is threadedly arranged at the end of the transmission shaft (2), and the angle grinding disc is located between the fixing block (16) and the fastener (17). A plurality of adjustment slots (18) are circumferentially provided inside the fixing block (16), an adjustment block (19) is movably installed in the adjustment slot (18), and a through slot (20) is provided on one side of the adjustment slot (18). A diameter reducing rod (21) is connected to a side of the adjustment block (19) close to the through slot (20), so that when the adjustment block (19) moves relative to the adjustment slot (18), the diameter reducing rod (21) moves along the through slot (20).

5. The quick-change structure for the angle grinder protective cover according to claim 4 is characterized in that: A driving groove (22) is formed at one end of the adjusting groove (18), and a driving block (23) is movably mounted in the driving groove (22). The driving block (23) and the adjusting block (19) are matched with each other in an oblique wedge manner, so that when the driving block (23) moves along the driving groove (22), the adjusting block (19) moves along the adjusting groove (18). A first elastic member (24) is connected between one end of the driving block (23) and the driving groove (22), and a second elastic member (25) is connected between one end of the adjusting block (19) and the adjusting groove (18).

6. The quick-change structure for the angle grinder protective cover according to claim 5, characterized in that: The end of the transmission shaft (2) is threadedly provided with a tightening ring (26), the tightening ring (26) is located on a side of the fastener (17) away from the fixed block (16), and a connecting ring (27) is rotatably provided on a side of the tightening ring (26) close to the fastener (17), and a plurality of tightening rods (28) matching the driving block (23) are provided on a side of the connecting ring (27) close to the driving block (23), so that when the tightening ring (26) rotates along the transmission shaft (2), the tightening rods (28) drive the driving block (23) to move.

7. The quick-change structure for the angle grinder protective cover according to claim 6, characterized in that: A guide hole (29) is provided on one side of the driving block (23) close to the tension rod (28), and a plurality of arc grooves (30) are provided on the fastener (17) along the circumferential direction so that the tension rod (28) can be inserted into the guide hole (29) after passing through the arc groove (30), and the width of the arc groove (30) is greater than the outer diameter of the tension rod (28).

8. The quick-change structure for the angle grinder protective cover according to claim 4, characterized in that: The end of the reducing rod (21) is detachably connected to a sleeve (31) so that the inner ring of the angle grinding disc abuts against the sleeve (31).

9. The quick-change structure for the angle grinder protective cover according to claim 1, characterized in that: The protective cover (4) comprises an inner cover (41) and an outer cover (42); the connection between the inner cover (41) and the outer cover (42) is in a stepped structure; a clamping plate (43) is connected to a side of the outer cover (42) close to the inner cover (41); a buckle (44) matching the clamping plate (43) is provided on a side of the inner cover (41) close to the outer cover (42), so that when the outer cover (42) and the inner cover (41) are connected, the clamping plate (43) is buckled in the buckle (44); a pressing groove (45) is provided on the side of the buckle (44), and the pressing groove (45) corresponds to the end of the clamping plate (43).

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