A clamping device

Abstract

The application discloses a clamping device suitable for clamping a workpiece to be processed, which comprises a first mounting plate, a second mounting plate, a positioning block and a back plate. The first mounting plate and the second mounting plate are suitable for fixing the workpiece to be processed in a first direction during processing of the workpiece to be processed. The positioning block and the back plate are suitable for fixing the workpiece to be processed in a second direction and a third direction during processing of the workpiece to be processed, the second direction and the third direction are in the same clamping plane, and the first direction is perpendicular to the clamping plane. The positioning block and the back plate are respectively arranged on a first surface of the first mounting plate. The positioning block has an abutting surface which is recessed in a direction away from the back plate and abuts on the workpiece to be processed. The clamping device realizes fixing of the workpiece to be processed and other special-shaped workpieces through cooperation of the first mounting plate and the second mounting plate and cooperation of the positioning block and the back plate, reduces the difficulty in fixing the special-shaped workpieces, and facilitates subsequent machining of the special-shaped workpieces.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of clamps, in particular to a clamping device. BACKGROUND

[0002] A boiler is provided with many pipelines. Among them, part of the pipelines are fixed by pipeline fixing devices. The pipeline fixing device is composed of a suspension pipe and a plurality of blocks. Specifically, the plurality of blocks are distributed along the length direction of the suspension pipe, and the plurality of blocks are respectively welded on the surface of the suspension pipe. One side of the block is provided with a clamping opening for clamping and fixing the pipeline.

[0003] Please refer to Figures 1-2 The specific manufacturing process of the above pipeline fixing device is as follows: laser cutting the profile of the block to obtain a workpiece to be processed 8b (as shown in Figure 1 Fix the workpiece to be processed 8b, and machine the work area 84 of the workpiece to be processed 8b (i.e. groove machining) to obtain a block 8a with a groove (as shown in Figure 2 Weld the groove of the block 8a with the suspension pipe, and then obtain the pipeline fixing device.

[0004] Because the shape of the workpiece to be processed 8b is complex (as shown in Figure 1 When machining the groove, the traditional clamping tool is difficult to fix, such as the vice. The vice can only clamp the two sides of the workpiece to be processed 8b in one direction, but cannot effectively fix the workpiece to be processed 8b in other directions, which may cause the workpiece to be processed 8b to move during subsequent machining of the work area 84 of the workpiece to be processed 8b, increasing the machining difficulty. The existing tooling fixture cannot meet the fixing requirements of the workpiece to be processed 8b and other special-shaped workpieces, and is not convenient for subsequent machining of such special-shaped workpieces. SUMMARY

[0005] The technical problem to be solved by the present application is that the existing special-shaped workpiece is difficult to fix and is not convenient for subsequent machining.

[0006] The clamping device disclosed by the present application is suitable for clamping a workpiece to be processed, and comprises a first mounting plate, a second mounting plate, a positioning block and a back plate.

[0007] The first mounting plate and the second mounting plate are suitable for fixing the workpiece to be processed in a first direction during machining of the workpiece to be processed;

[0008] The positioning block and the back plate are suitable for fixing the workpiece to be processed in a second direction and a third direction during machining of the workpiece to be processed, the second direction and the third direction are in the same clamping plane, and the first direction is perpendicular to the clamping plane.

[0009] The positioning block and the backing plate are respectively disposed on the first surface of the first mounting plate;

[0010] The positioning block has an abutment surface that is recessed away from the backing plate. The abutment surface abuts against the workpiece to be processed. The abutment surface has a first mating surface, a second mating surface, and a third mating surface. The first mating surface and the third mating surface are connected via a second mating surface. The first, second, and third mating surfaces are each in contact with a first surface of the first mounting plate. The angle between the first and second mating surfaces is less than 180°, and the angle between the second and third mating surfaces is also less than 180°. Through the cooperation of the first and second mounting plates and the positioning block and the backing plate, irregularly shaped workpieces with this structure are fixed, reducing the difficulty of fixing irregularly shaped workpieces and facilitating subsequent machining.

[0011] Optionally, a clearance is provided between the first mating surface and the second mating surface, and / or the clearance is provided between the second mating surface and the third mating surface, the clearance being suitable for avoiding sharp corners on the workpiece to be processed. Using the above solution, burrs and flash at some sharp corners of the workpiece to be processed are effectively avoided.

[0012] Optionally, the workpiece to be processed has a clamping opening; the first mounting plate and / or the second mounting plate has an avoidance groove, the position of which matches the position of the edge of the clamping opening when the workpiece to be processed is fixed on the first mounting plate. Using the above solution, burrs and flash on the edge of the clamping opening are effectively avoided.

[0013] Optionally, the width of the clearance groove is 1mm to 3mm. This groove width can effectively avoid burrs and flash from the edge of the clamping opening, without affecting the fixation of the first mounting plate and the second mounting plate on the workpiece to be processed in the first direction.

[0014] Optionally, the distance between the positioning block and the backing plate is adjustable, and the backing plate is a movable backing plate. Using the above solution, by adjusting the position of the backing plate, the distance between the backing plate and the positioning block can be adjusted, thereby matching workpieces of different specifications to be processed.

[0015] Optionally, the backing plate has a waist-shaped hole extending away from the workpiece to be processed; a fixing bolt is fitted inside the waist-shaped hole, and the fixing bolt is threadedly connected to the first mounting plate. This design allows for adjustment of the backing plate's position.

[0016] Optionally, the clamping device further includes: inserts and clamping bolts;

[0017] The backing plate is slidably disposed on the first surface of the first mounting plate;

[0018] The insert is fixed to the first mounting plate, the insert is located on the first side of the backing plate, and the first side of the backing plate is the side away from the positioning block;

[0019] The clamping bolt extends away from the workpiece and is threaded onto the insert, abutting against the first side of the backing plate. This design effectively prevents accidental slippage of the backing plate.

[0020] Optionally, the clamping device further includes: a nut;

[0021] The nut is screwed onto the clamping bolt and abuts against the insert. This design effectively secures the bolt, preventing it from loosening due to vibration.

[0022] Optionally, the thickness of the positioning block is less than the thickness of the workpiece to be processed. By adopting the above solution, interference between the positioning block and the second mounting plate is effectively prevented, thereby ensuring that the first and second mounting plates effectively fix the workpiece 8b to be processed in the first direction.

[0023] Optionally, the positioning block has a mirror-symmetrical structure; there are two backing plates, which are arranged in a mirror image and distributed on both sides of the positioning block. This design improves the working efficiency of the clamping device.

[0024] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0025] By cooperating with the first mounting plate and the second mounting plate, and with cooperating with the positioning block and the backing plate, the irregular workpiece with this structure to be processed can be fixed, reducing the difficulty of fixing the irregular workpiece, so that the irregular workpiece can be processed in subsequent machining.

[0026] By adjusting the position of the backing plate, the distance between the backing plate and the positioning block can be adjusted to match workpieces of different specifications.

[0027] The above description of the disclosure and the following description of the embodiments are intended to demonstrate and explain the spirit and principles of the present invention, and to provide a further explanation of the scope of the patent application of the present invention. Attached Figure Description

[0028] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0029] Figure 1 This is a schematic diagram of the structure of the workpiece to be processed;

[0030] Figure 2 A schematic diagram of the structure of the workpiece after it has been machined into a support block;

[0031] Figure 3 This is a schematic diagram of the clamping device in this invention;

[0032] Figure 4 This is a three-dimensional structural diagram of the clamping device holding the support block in this invention;

[0033] Figure 5 This is a front view of the clamping device holding the support block in this invention;

[0034] Figure 6 This is a three-dimensional structural diagram of the support block being fixed on the first mounting plate in this invention;

[0035] Figure 7 This is a partial structural diagram of the clamping device in this invention;

[0036] Figure 8 This is a front view of the first mounting plate and positioning block in this invention.

[0037] Explanation of icon numbers:

[0038] 1. First mounting plate; 11. Clearance groove; 2. Second mounting plate; 3. Positioning block; 31. First mating surface; 32. Second mating surface; 33. Third mating surface; 34. Clearance opening; 4. Backing plate; 41. Waist-shaped hole; 42. Fixing bolt; 5. Insert; 6. Tightening bolt; 7. Nut; 8a. Support block; 8b. Workpiece to be processed; 81. First connecting surface; 82. Second connecting surface; 83. Clamping opening; 84. Processing area. Detailed Implementation

[0039] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention is presented in conjunction with preferred embodiments, this does not mean that the features of the invention are limited to these embodiments. On the contrary, the purpose of describing the invention in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of the present invention. To provide a deep understanding of the invention, many specific details will be included in the following description. The invention may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of the invention, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0040] In the description of this embodiment, it should be noted that the terms "upper", "lower", "inner", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the product of the invention is usually placed in during use. They 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, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0041] The terms “first”, “second”, etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0042] In the description of this embodiment, it should also be noted that, unless otherwise explicitly specified and limited, the terms "provided with," "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment based on the specific circumstances.

[0043] This application discloses a clamping device suitable for clamping a workpiece 8b to be processed.

[0044] In this embodiment, please refer to Figures 1-2 As shown, the workpiece 8b to be processed has a first side and a second side, as well as a third side and a fourth side. The second side of the workpiece 8b has a first connecting surface 81, a second connecting surface 82, and a clamping opening 83. The first connecting surface 81 is close to the third side of the workpiece 8b. The second connecting surface 82 is close to the fourth side of the workpiece 8b. The clamping opening 83 is located between the first connecting surface 81 and the second connecting surface 82 and is used to fix the outer wall of the pipe. The included angle between the first connecting surface 81 and the second connecting surface 82 is less than 180°. The third side of the workpiece 8b is the processing area 84, used for beveling. After beveling the processing area 84 of the workpiece 8b, the support block 8a is obtained. A sharp corner is provided between the third side of the workpiece 8b and the second connecting surface 82.

[0045] Please see Figures 3-5 As shown, the clamping device includes a first mounting plate 1, a second mounting plate 2, a positioning block 3, and a backing plate 4. The first mounting plate 1 and the second mounting plate 2 are adapted to fix the workpiece 8b to be processed in a first direction during the processing of the workpiece 8b. The positioning block 3 and the backing plate 4 are adapted to fix the workpiece 8b to be processed in a second direction and a third direction during the processing of the workpiece 8b. The second direction and the third direction are on the same clamping plane. The first direction is perpendicular to the clamping plane.

[0046] In this embodiment, the thickness direction of the first mounting plate 1 is taken as the first direction, the length direction of the first mounting plate 1 is taken as the second direction, and the height direction of the first mounting plate 1 is taken as the third direction.

[0047] In this embodiment, the clamping device is mounted on a bench vise. Specifically, the bench vise includes a first jaw and a second jaw, with a mounting plate jaw formed between the first jaw and the second jaw. The first mounting plate 1 is disposed on the side of the first jaw facing the second jaw. The second mounting plate 2 is disposed on the side of the second jaw facing the first jaw. The clamping device opens and closes the second mounting plate 2 and the first mounting plate 1 by opening and closing the first jaw and the second jaw.

[0048] Please see Figures 6-8 As shown, the positioning block 3 and the abutment plate 4 are respectively disposed on the first surface of the first mounting plate 1. The positioning block 3 and the abutment plate 4 are distributed on the first side and the second side of the workpiece 8b to be processed. The positioning block 3 has an abutment surface. The abutment surface is recessed in the direction away from the abutment plate 4. The abutment surface abuts against the workpiece 8b to be processed. The abutment surface has a first mating surface 31, a second mating surface 32, and a third mating surface 33. The first mating surface 31 and the third mating surface 33 are connected through the second mating surface 32. The first mating surface 31, the second mating surface 32, and the third mating surface 33 are in contact with the first surface of the first mounting plate 1. The included angle between the first mating surface 31 and the second mating surface 32 is less than 180°. The included angle between the second mating surface 32 and the third mating surface 33 is less than 180°.

[0049] In this embodiment, the abutting surface abuts against the second and fourth sides of the workpiece 8b to be processed. The backing plate 4 has a first side and a second side facing each other. The first side of the backing plate 4 is the side away from the positioning block 3. After the clamping device clamps and fixes the workpiece 8b to be processed, the first mating surface 31 abuts against the first connecting surface 81; the second mating surface 32 abuts against the second connecting surface 82; the third mating surface 33 abuts against the fourth side of the workpiece 8b to be processed; and the second side of the backing plate 4 abuts against the first side of the workpiece 8b to be processed.

[0050] Further, in this embodiment, the included angle between the first mating surface 31 and the second mating surface 32 is 150° to 170°, and the included angle between the second mating surface 32 and the third mating surface 33 is 80° to 100°. The included angle between the second side of the backing plate 4 and the horizontal direction is 60° to 80°. Preferably, the included angle between the first mating surface 31 and the second mating surface 32 is 160°, and the included angle between the second mating surface 32 and the third mating surface 33 is 90°. The included angle between the second side of the backing plate 4 and the horizontal direction is 70°.

[0051] Furthermore, in order to ensure that the first mounting plate 1 and the second mounting plate 2 effectively fix the workpiece 8b to be processed in the first direction, the thickness of the positioning block 3 is less than the thickness of the workpiece 8b to be processed, that is, there will be no interference between the positioning block 3 and the second mounting plate 2.

[0052] In this embodiment, the outline of the workpiece 8b to be processed is formed by laser cutting. Workpieces formed by laser cutting may have burrs on one side, so the outline of one side of the workpiece 8b may have burrs and flash. The workpiece 8b to be processed has sharp corners, and these sharp corners may have a large number of burrs, which will affect the fixing of the positioning block 3 and the backing plate 4 to the workpiece 8b, and cannot guarantee that the abutment surface of the positioning block 3 effectively fits the side wall of the workpiece 8b.

[0053] Therefore, please refer to Figures 7-8 As shown, in order to effectively avoid burrs and flash at some sharp corners of the workpiece 8b to be processed, a clearance opening 34 is provided on the abutment surface. The distribution of the clearance opening 34 includes three cases: Case 1, the clearance opening 34 is located between the first mating surface 31 and the second mating surface 32; Case 2, the clearance opening 34 is located between the second mating surface 32 and the third mating surface 33; Case 3, there are two clearance openings 34, one clearance opening 34 is located between the first mating surface 31 and the second mating surface 32, and the other clearance opening 34 is located between the second mating surface 32 and the third mating surface 33.

[0054] In this embodiment, the clearance 34 is provided between the second mating surface 32 and the third mating surface 33 to avoid the sharp corner between the third side of the workpiece 8b to be processed and the second connecting surface 82, effectively preventing burrs at the sharp corner from interfering with the clamping device's fixation of the workpiece 8b to be processed.

[0055] In this embodiment, the clamping opening 83 of the workpiece 8b to be processed is an arc-shaped opening. The edge of the clamping opening 83 may have burrs, which may affect the fixation of the first mounting plate 1 and the second mounting plate 2 on the workpiece 8b to be processed in the first direction.

[0056] Therefore, in order to effectively avoid burrs and flash on the edge of the clamping opening 83, a clearance groove 11 is provided on the clamping device. The position of the clearance groove 11 matches the position of the edge of the clamping opening 83 when the workpiece 8b to be processed is fixed on the first mounting plate 1. The distribution of the clearance groove 11 includes three cases: Case 1, the clearance groove 11 is only provided on the first surface of the first mounting plate 1; Case 2, the clearance groove 11 is only provided on the second surface of the second mounting plate 2; Case 3, there are two clearance grooves 11, one on the first surface of the first mounting plate 1 and the other on the second surface of the second mounting plate 2.

[0057] In this embodiment, the clearance groove 11 is only formed on the first surface of the first mounting plate 1.

[0058] Furthermore, the width of the clearance groove 11 is 1mm to 3mm. Preferably, the width of the clearance groove 11 is 2mm. This groove width can effectively avoid burrs and flash on the edge of the clamping opening 83, and will not affect the fixation of the first mounting plate 1 and the second mounting plate 2 on the workpiece 8b to be processed in the first direction.

[0059] Please see Figures 5-6 As shown, the distance between the positioning block 3 and the backing plate 4 is adjustable. The positioning block 3 and the first mounting plate 1 are either integrally formed or separate structures. In this embodiment, the positioning block 3 and the first mounting plate 1 are integrally formed. The backing plate 4 is a movable backing plate. By adjusting the position of the backing plate 4, the distance between the backing plate 4 and the positioning block 3 can be adjusted, thereby matching workpieces 8b of different specifications to be processed.

[0060] Furthermore, the backing plate 4 has a waist-shaped hole 41. The waist-shaped hole 41 extends in a direction away from the workpiece 8b to be processed. A fixing bolt 42 is fitted inside the waist-shaped hole 41. The fixing bolt 42 is threadedly connected to the first mounting plate 1. In this embodiment, the waist-shaped hole 41 extends in a second direction. In addition, a washer is provided between the fixing bolt 42 and the backing plate 4 to increase the friction between the fixing bolt 42 and the backing plate 4, thereby preventing the fixing bolt 42 from loosening due to vibration.

[0061] Furthermore, the clamping device also includes an insert 5 and a clamping bolt 6. The abutment plate 4 is slidably disposed on the first surface of the first mounting plate 1. The insert 5 is fixed to the first mounting plate 1. The insert 5 is located on the first side of the abutment plate 4. The clamping bolt 6 extends in a direction away from the workpiece 8b to be processed. The clamping bolt 6 is threaded onto the insert 5 and abuts against the first side of the abutment plate 4 to prevent accidental slippage of the abutment plate 4. In this embodiment, the clamping bolt 6 extends in a second direction.

[0062] Furthermore, the clamping device also includes a nut 7. The nut 7 is screwed onto the clamping bolt 6 and abuts against the insert 5. In this embodiment, the nut 7 is located on the first side of the insert 5. The first side of the insert 5 is the side away from the backing plate 4. Since one end of the clamping bolt 6 abuts against the first side of the backing plate 4, and the other end of the clamping bolt 6 abuts against the first side of the insert 5 through the nut 7, the clamping bolt 6 is effectively fixed, thereby preventing the clamping bolt 6 from loosening due to vibration.

[0063] Furthermore, to improve the working efficiency of the clamping device, the clamping device is arranged in a mirror image. Specifically, the positioning block 3 has a mirror-symmetrical structure. There are two abutment plates 4. The two abutment plates 4 are arranged in a mirror image and distributed on both sides of the positioning block 3. Each side of the positioning block 3 is provided with an abutment surface to cooperate with the corresponding abutment plate 4, thereby enabling the clamping device to clamp two workpieces 8b to be processed simultaneously.

[0064] In this embodiment, the specific working principle of the present invention is as follows:

[0065] The workpiece 8b to be processed is placed on the abutting surface of the positioning block 3, and the processing area 84 of the workpiece 8b is exposed to the clamping device.

[0066] According to the specifications of the workpiece 8b to be processed, rotate the clamping bolt 6 to adjust the relative position of the clamping bolt 6 and the insert 5, and then adjust the position of the backing plate 4 so that the positioning block 3 and the backing plate 4 fix the workpiece 8b to be processed in the second direction and the third direction. Then tighten the fixing bolt 42. After tightening the fixing bolt 42, tighten the nut 7 so that the nut 7 abuts against the insert 5.

[0067] The first mounting plate 1 and the second mounting plate 2 are closed by driving the bench vise, so that the first mounting plate 1 and the second mounting plate 2 fix the workpiece 8b to be processed in the first direction.

[0068] The machining equipment performs beveling on the processing area 84 of the workpiece 8b to be processed.

[0069] In summary, the clamping device provided in this application achieves the fixation of irregularly shaped workpieces with structures such as the workpiece to be processed through the cooperation of the first mounting plate and the second mounting plate, and the cooperation of the positioning block and the backing plate, thereby reducing the difficulty of fixing irregularly shaped workpieces, so that the bench vise can fix irregularly shaped workpieces for subsequent beveling; by adjusting the position of the backing plate, the distance between the backing plate and the positioning block can be adjusted, thereby matching workpieces of different specifications.

[0070] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A clamping device suitable for clamping a workpiece (8b) to be machined, characterized in that, The clamping device comprises a first mounting plate (1), a second mounting plate (2), a locating block (3) and a back plate (4); The first mounting plate (1) and the second mounting plate (2) are adapted to fix the workpiece (8b) in a first direction during machining of the workpiece (8b); The locating block (3) and the back plate (4) are adapted to fix the workpiece (8b) in a second direction and a third direction during machining of the workpiece (8b), the second direction and the third direction being in the same clamping plane, and the first direction being perpendicular to the clamping plane; The locating block (3) and the back plate (4) are respectively arranged on a first surface of the first mounting plate (1); The locating block (3) has an abutting surface which is recessed away from the back plate (4), the abutting surface abutting against the workpiece (8b), the abutting surface having a first matching surface (31), a second matching surface (32) and a third matching surface (33), the first matching surface (31) being connected with the third matching surface (33) through the second matching surface (32), the first matching surface (31), the second matching surface (32) and the third matching surface (33) respectively contacting the first surface of the first mounting plate (1), the angle between the first matching surface (31) and the second matching surface (32) being less than 180°, and the angle between the second matching surface (32) and the third matching surface (33) being less than 180°.

2. The clamping device of claim 1, wherein An avoiding opening (34) is arranged between the first matching surface (31) and the second matching surface (32), and / or an avoiding opening (34) is arranged between the second matching surface (32) and the third matching surface (33), the avoiding opening (34) being adapted to avoid a sharp corner on the workpiece (8b).

3. The clamping device of claim 1, wherein A clamping opening (83) is arranged on the workpiece (8b), and an avoiding groove (11) is arranged on the first mounting plate (1) and / or the second mounting plate (2), the position of the avoiding groove (11) matching the position of the edge of the clamping opening (83) when the workpiece (8b) is fixed on the first mounting plate (1).

4. The clamping device of claim 3, wherein The width of the avoiding groove (11) is 1mm-3mm.

5. The clamping device of claim 1, wherein The distance between the locating block (3) and the back plate (4) is adjustable, and the back plate (4) is a movable back plate.

6. The clamping device of claim 5, wherein A waist-shaped hole (41) is arranged on the back plate (4), the waist-shaped hole (41) extending away from the workpiece (8b), a fixing bolt (42) being sleeved in the waist-shaped hole (41), and the fixing bolt (42) being threadedly connected with the first mounting plate (1).

7. The clamping device of claim 5, wherein Further comprising: an inlay block (5) and a pressing bolt (6); The back plate (4) is slidably arranged on the first surface of the first mounting plate (1); The inlay block (5) is fixed on the first mounting plate (1), and the inlay block (5) is located on a first side of the back plate (4), the first side of the back plate (4) being a side away from the locating block (3); The abutting bolt (6) extends away from the workpiece (8b) to be processed, is threadedly connected to the insert block (5), and abuts against the first side of the back plate (4).

8. The clamping device of claim 7, wherein Further comprising: A nut (7); The nut (7) is screwed on the abutting bolt (6) and abuts against the insert block (5).

9. The holding device according to claim 1, characterized in that The thickness of the positioning block (3) is less than the thickness of the workpiece (8b) to be processed.

10. The clamping device of claim 1, wherein The positioning block (3) is a mirror-symmetrical structure; the back plate (4) is two, and the two back plates (4) are mirror-symmetrically arranged and distributed on both sides of the positioning block (3).

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