Numerical control vertical lathe with plug pin assembly
By designing the pin assembly and drive assembly, the problem of unstable fixture fixation on CNC vertical lathes was solved, achieving stable workpiece clamping and flexible machining, improving machining accuracy and efficiency, and adapting to the machining needs of different workpieces.
Patent Information
- Application Number
- CN202423098465.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-16
- Publication Date
- 2025-11-21
- Estimated Expiration
- 2034-12-16
AI Technical Summary
The existing CNC vertical lathes have unstable fixture fixation and insufficient clamping accuracy, which makes the workpiece easy to loosen or shift during processing, affecting processing accuracy and product quality.
The system employs a pin assembly and a drive assembly. The pin assembly includes a positioning plate, pins, fixing posts, and a clamping plate. The pins pass through the positioning holes and the clamping plate to limit the position, ensuring stable clamping of the workpiece. The drive assembly uses a motor and a screw to enable flexible lifting and horizontal movement of the processing head.
It improves the machining accuracy and product quality of workpieces, enhances the fixing effect, adapts to workpieces of different sizes and shapes, expands the application range of lathes, and improves machining efficiency and flexibility.
Smart Images

Figure CN223572499U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to numerical control vertical lathe technical field especially, a numerical control vertical lathe with bolt subassembly is provided. BACKGROUND
[0002] Numerical control vertical lathe is a kind of process test instrument for mechanical engineering field, vertical lathe can carry out internal and external cylinder, conical surface, end plane, groove, chamfer processing, and the clamping, correction of workpiece, etc. It is more convenient to operate. In the machining process of numerical control vertical lathe, the accurate positioning and stable clamping of workpiece are crucial. But the existing numerical control vertical lathe still has the following problems when using:
[0003] Traditional numerical control vertical lathe usually uses simple clamp to fix workpiece, however, this clamp often has the problems of unstable fixing effect, insufficient clamping precision, etc., especially when tooling has a certain weight workpiece, the clamping force of clamp is easy to weaken due to the weight of workpiece or vibration in machining process, which leads to workpiece loosening or displacement, thereby affecting machining precision and product quality.
[0004] In view of the above problems, the utility model file proposes a numerical control vertical lathe with bolt subassembly. INVENTION CONTENTS
[0005] The utility model aims at solving the problems of insufficient fixing effect of traditional numerical control vertical lathe clamp on workpiece, insufficient fixing precision, and workpiece moving due to weight or vibration in prior art, and proposes a numerical control vertical lathe with bolt subassembly.
[0006] In order to achieve the above purpose, the utility model adopts the following technical scheme:
[0007] A numerical control vertical lathe with bolt subassembly, comprising:
[0008] A workbench, the top of the workbench is fixedly installed with a support frame, the side of the support frame is slidably connected with a first moving plate, the side of the first moving plate is slidably connected with a second moving plate, the side of the second moving plate is provided with a machining head, and the machining head is used for machining workpiece placed on the workbench;
[0009] Further comprising a driving assembly, the driving assembly is used for completing the lifting and horizontal movement of the machining head;
[0010] Further comprising a fixing assembly, the fixing assembly is used for completing the fixing of workpiece to be machined;
[0011] Further comprising a bolt subassembly, the bolt subassembly is used for further ensuring the fixing effect of the fixing assembly on workpiece.
[0012] In a possible design, the driving assembly comprises a first motor fixedly installed at the top of the support frame, one side of the support frame is rotationally connected with a first screw rod, one end of the output shaft of the first motor is fixedly connected with one end of the first screw rod, the first screw rod is threadedly connected with the first moving plate, and is configured to drive the first moving plate to move up and down; one side of the first moving plate is rotationally connected with a second screw rod, and the first moving plate is fixedly installed with a second motor, one end of the output shaft of the second motor is fixedly connected with one end of the second screw rod, and the second screw rod is threadedly connected with the second moving plate, and is configured to drive the second moving plate to move horizontally.
[0013] In a possible design, the fixing assembly comprises a fixing plate fixedly installed at the top of the workbench, a bottom plate fixedly installed at the top of the fixing plate, four fixing blocks fixedly installed at the top of the bottom plate, two fixing blocks in each of the two groups, and the two groups of fixing blocks are located at positions close to the two sides of the bottom plate, a first clamping plate and a second clamping plate slidingly connected to the top of the bottom plate, a clamping groove formed in the side of each of the first clamping plate and the second clamping plate, the first clamping plate and the second clamping plate cooperating with each other to clamp and fix the workpiece, recesses formed in the bottom of the first clamping plate and the second clamping plate, two fixed rods fixedly installed on the inner wall of one side of the recess, one end of each of the two fixed rods slidingly penetrating through the adjacent fixing block, springs sleeved on the outer wall of each of the plurality of fixed rods, one end of each of the plurality of springs fixedly connected with the inner wall of one side of the corresponding recess, and the other end of each of the plurality of springs fixedly connected with one side of the adjacent fixing block, and the plurality of springs configured to ensure that the first clamping plate and the second clamping plate can be continuously kept close.
[0014] In a possible design, the latch assembly comprises two positioning plates fixedly installed at one side of the first clamping plate and the second clamping plate respectively, the two positioning plates slidingly cooperating and moving relative to each other, a plurality of through holes formed in the interior of each of the two positioning plates, the plurality of through holes in different positioning plates cooperating with each other, a latch penetrating through the corresponding two through holes, a positioning hole formed in the fixing plate, one end of the latch penetrating through the positioning hole, and the latch configured to position the first clamping plate and the second clamping plate to ensure the continuous and stable clamping of the workpiece.
[0015] In a possible design, the latch assembly further comprises two fixed columns fixedly installed on one side of the two positioning plates respectively, a mounting block threadedly connected to the top end of the latch, a mounting rack sleeved on the outer wall of the latch, the mounting block fixedly connected to the top of the mounting rack, a double-threaded screw rod rotatably connected to the top of the mounting rack, the double-threaded screw rod rotatably penetrating through the mounting block, two clamping plates slidably connected to the top of the mounting rack and located on the two sides of the mounting block respectively, the two clamping plates threadedly connected to the double-threaded screw rod, the two clamping plates located on opposite threads of the double-threaded screw rod respectively, and clamping grooves formed in the bottom of the two clamping plates, the two fixed columns matched with the inner walls of the corresponding clamping grooves, and used for more accurate limiting of the gap between the first clamping plate and the second clamping plate.
[0016] In a possible design, the interior of each of the two positioning plates is provided with a sliding groove, one side of each of the two positioning plates is fixedly installed with a limiting rod, the limiting rods are slidably connected to the inner walls of the adjacent sliding grooves, and the other ends of the limiting rods are threadedly sleeved with nuts matched with the adjacent positioning plates, and used for adjusting the moving friction between the first clamping plate and the second clamping plate.
[0017] In the application, when used, the user can place the workpiece to be processed between the first clamping plate and the second clamping plate, and the clamping groove on one side of the first clamping plate and the second clamping plate can place and clamp the workpiece; after the workpiece is placed, under the action of the two springs, the first clamping plate and the second clamping plate can continuously approach and complete clamping and fixing of the workpiece; at this time, since the positioning plate on one side of the first clamping plate and the second clamping plate can move synchronously, if there are two aligned through holes, one end of the bolt can be directly penetrated through the two through holes and inserted into the corresponding positioning hole below, so that the first clamping plate and the second clamping plate can be limited, and the continuous clamping and fixing of the workpiece can be ensured; if there are no two aligned through holes, the user can rotate the bolt and take it off from the bottom of the mounting block, then the user can rotate the double-threaded screw rod to adjust the position of the two clamping plates, so that the two fixing columns can be clamped into the corresponding clamping grooves at the same time, after adjustment, the mounting frame can be placed vertically on the two positioning plates, at this time, the two clamping plates can limit the two fixing columns through the clamping grooves, and the user can rotate the double-threaded screw rod again to drive the two fixing columns to be extruded, so as to ensure that the distance between the first clamping plate and the second clamping plate can be limited, and the clamping effect of the workpiece is better; after the workpiece is installed, the user can start the numerical control vertical lathe, the first motor and the second motor can drive the machining head, and then the workpiece on the workbench can be processed; after processing, no matter which positioning method is used, the user only needs to lift the mounting block upward, so that the bolt or the clamping plate is away from the positioning plate, then the workpiece can be taken out from between the first clamping plate and the second clamping plate, and a new workpiece can be replaced for the next processing.
[0018] Beneficial effects: in the numerical control vertical lathe with the bolt assembly, the driving assembly is arranged, the lifting and horizontal movement of the machining head are realized, the numerical control vertical lathe can flexibly process the workpiece, and the processing efficiency and flexibility are improved.
[0019] In the numerical control vertical lathe with the bolt assembly, the first clamping plate and the second clamping plate are matched with each other, and the elastic effect of the spring is used, so that the workpiece can be stably clamped, the workpiece can be quickly installed and taken out conveniently, and the processing efficiency of the workpiece is improved.
[0020] The utility model discloses a numerical control vertical lathe with bolt assembly, through the setting of bolt assembly, can further enhance the fixed assembly's fixed effect to work piece, through the bolt through positioning hole, has realized the accurate positioning between first clamping plate and second clamping plate, has guaranteed the sustained stable clamping of work piece in the processing, avoided the problem that work piece is loose or displacement because of dead weight or vibration, improved the processing accuracy and product quality, simultaneously, the flexible design of bolt assembly can adapt to work piece of different size and shape, has expanded the application scope of lathe.
[0021] The utility model discloses a numerical control vertical lathe with bolt assembly, bolt assembly still includes double -threaded screw rod and card board etc. structure, through the cooperation relation of adjusting card board and fixed column, can realize more accurate limit between first clamping plate and second clamping plate, further improved the installation stability and processing accuracy of work piece.
[0022] The utility model discloses a numerical control vertical lathe with bolt assembly, through the setting of bolt assembly, can further enhance the fixed assembly's fixed effect to work piece, through the bolt through positioning hole, has realized the accurate positioning between first clamping plate and second clamping plate, has guaranteed the sustained stable clamping of work piece in the processing, avoided the problem that work piece is loose or displacement because of dead weight or vibration, improved the processing accuracy and product quality, simultaneously, the flexible design of bolt assembly can adapt to work piece of different size and shape, has expanded the application scope of lathe. ACCURACY
[0023] Figure 1 A three-dimensional structure schematic view of the numerical control vertical lathe with bolt assembly is provided for the utility model;
[0024] Figure 2 Another three-dimensional structure schematic view of the numerical control vertical lathe with bolt assembly is provided for the utility model;
[0025] Figure 3 A fixed assembly structure schematic view of the numerical control vertical lathe with bolt assembly is provided for the utility model;
[0026] Figure 4 A fixed assembly split structure schematic view of the numerical control vertical lathe with bolt assembly is provided for the utility model;
[0027] Figure 5 A clamping plate bottom structure schematic view of the numerical control vertical lathe with bolt assembly is provided for the utility model;
[0028] Figure 6 A bolt assembly structure schematic view of the numerical control vertical lathe with bolt assembly is provided for the utility model.
[0029] In the figure: 1, workbench; 2, support frame; 3, first motor; 4, first screw rod; 5, first moving plate; 6, second moving plate; 7, machining head; 8, second motor; 9, second screw rod; 10, fixed plate; 11, bottom plate; 12, first clamping plate; 13, second clamping plate; 14, clamping groove; 15, positioning hole; 16, fixed block; 17, bolt; 18, groove; 19, fixed rod; 20, spring; 21, positioning plate; 22, through hole; 23, sliding groove; 24, limiting rod; 25, fixed column; 26, mounting frame; 27, clamping plate; 28, clamping groove; 29, double-thread screw rod; 30, mounting block. DETAILED DESCRIPTION
[0030] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all the embodiments.
[0031] Embodiment 1: refer to Figures 1-6 A numerical control vertical lathe, comprising:
[0032] The workbench 1 is fixedly installed with the support frame 2 on the top, the first moving plate 5 is slidably connected to one side of the support frame 2, the second moving plate 6 is slidably connected to one side of the first moving plate 5, and the machining head 7 is arranged on one side of the second moving plate 6, and the machining head 7 is used for machining the workpiece placed on the workbench 1.
[0033] In the embodiment, the driving assembly is further included, and the driving assembly is used for completing the lifting and horizontal movement of the machining head 7. The driving assembly comprises the first motor 3 fixedly installed on the top of the support frame 2, the first screw rod 4 rotatably connected to one side of the support frame 2, the output shaft of the first motor 3 fixedly connected to one end of the first screw rod 4, the first screw rod 4 threadedly connected to the first moving plate 5, and the first moving plate 5 driven to lift up and down. The second screw rod 9 is rotatably connected to one side of the first moving plate 5, the second motor 8 is fixedly installed on one side of the first moving plate 5, the output shaft of the second motor 8 is fixedly connected to one end of the second screw rod 9, the second screw rod 9 is threadedly connected to the second moving plate 6, and the second moving plate 6 is driven to move horizontally.
[0034] The embodiment also includes a fixing assembly for fixing the workpiece to be processed. The fixing assembly includes a fixing plate 10 fixedly installed on the top of the workbench 1, a bottom plate 11 fixedly installed on the top of the fixing plate 10, four fixing blocks 16 fixedly installed on the top of the bottom plate 11, two groups of the four fixing blocks 16, and the two groups of the fixing blocks 16 located near the two sides of the bottom plate 11, respectively. The top of the bottom plate 11 is slidably connected with a first clamping plate 12 and a second clamping plate 13, and the first clamping plate 12 and the second clamping plate 13 are both provided with a clamping groove 14 on the side close to each other. The first clamping plate 12 and the second clamping plate 13 are matched with each other to clamp and fix the workpiece. The bottom of the first clamping plate 12 and the second clamping plate 13 is provided with a recess 18, and two fixed rods 19 are fixedly installed on the inner wall of one side of the recess 18. One end of the two fixed rods 19 is slidably penetrated through the adjacent fixing block 16. The outer wall of the plurality of fixed rods 19 is sleeved with a spring 20. One end of the plurality of springs 20 is fixedly connected with the inner wall of one side of the corresponding recess 18. The other end of the plurality of springs 20 is fixedly connected with one side of the adjacent fixing block 16. The plurality of springs 20 ensures that the first clamping plate 12 and the second clamping plate 13 can be continuously kept close.
[0035] The embodiment also includes a latch assembly for further ensuring the fixing effect of the fixing assembly on the workpiece. The latch assembly includes two positioning plates 21 fixedly installed on one side of the first clamping plate 12 and the second clamping plate 13, respectively, and slidably matched and relatively moved between the two positioning plates 21. The interior of the two positioning plates 21 is provided with a plurality of through holes 22. The plurality of through holes 22 in the different positioning plates 21 are matched with each other. The corresponding two through holes 22 are penetrated by a latch 17. The fixing plate 10 is provided with a positioning hole 15. One end of the latch 17 is penetrated through the positioning hole 15. The latch 17 is used for positioning between the first clamping plate 12 and the second clamping plate 13 to ensure the continuous and stable clamping of the workpiece.
[0036] Further, the embodiment also includes two fixed columns 25 fixedly installed on one side of the two positioning plates 21. The top of the latch 17 is threadedly connected with a mounting block 30. The outer wall of the latch 17 is sleeved with a mounting bracket 26. The mounting block 30 is fixedly connected with the top of the mounting bracket 26. The top of the mounting bracket 26 is rotatably connected with a double-threaded screw rod 29. One end of the double-threaded screw rod 29 is rotatably penetrated through the mounting block 30. The top of the mounting bracket 26 is slidably connected with two clamping plates 27, and the two clamping plates 27 are located on the two sides of the mounting block 30, respectively. The two clamping plates 27 are threadedly connected with the double-threaded screw rod 29, and the two clamping plates 27 are located on the two opposite threads of the double-threaded screw rod 29, respectively. The bottom of the two clamping plates 27 is provided with a clamping groove 28. The two fixed columns 25 are matched with the inner wall of the corresponding clamping groove 28 to more accurately limit the gap between the first clamping plate 12 and the second clamping plate 13.
[0037] The application can be used in the technical field of numerical control vertical lathe, and can also be used in other fields applicable to the application.
[0038] Embodiment 2: Reference Figure 5 On the basis of Embodiment 1, an improvement is made: a numerical control vertical lathe with a latch assembly, which is applied to the technical field of numerical control vertical lathe;
[0039] In this embodiment, the inner part of each positioning plate 21 is provided with a sliding groove 23, and the side of each positioning plate 21 close to each other is fixedly installed with a limiting rod 24, the limiting rod 24 is in sliding connection with the inner wall of the adjacent sliding groove 23, and the other end of the limiting rod 24 is threadedly sleeved with a nut matched with the adjacent positioning plate 21, for adjusting the moving friction force between the first clamping plate 12 and the second clamping plate 13.
[0040] In this embodiment, the inner part of each through hole 22 is provided with a certain space for giving way, so that the latch 17 can be partially movable in the corresponding through hole 22, and ensure that after the latch 17 is limited, the first clamping plate 12 and the second clamping plate 13 can still have a continuous close effect under the action of the spring 20.
[0041] However, as known to those skilled in the art, the working principle and wiring method of the first motor 3 and the second motor 8 are common, which belong to conventional means or common knowledge, and will not be described here. Those skilled in the art can make any selection according to their needs or convenience.
[0042] The working principle and use process of the technical solution are as follows: when in use, the user can place the workpiece to be processed between the first clamping plate 12 and the second clamping plate 13, and the clamping groove 14 on one side of the first clamping plate 12 and the second clamping plate 13 can place and clamp the workpiece; after the workpiece is placed, under the action of the two springs 20, the first clamping plate 12 and the second clamping plate 13 can continuously approach and complete clamping and fixing of the workpiece; at this time, since the positioning plate 21 on one side of the first clamping plate 12 and the second clamping plate 13 can move synchronously, if there are two aligned through holes 22, the one end of the bolt 17 can be directly penetrated through the two through holes 22 and inserted into the corresponding positioning hole 15 below, so that the first clamping plate 12 and the second clamping plate 13 can be limited, and the continuous clamping and fixing of the workpiece can be ensured; if there are no two aligned through holes 22, at this time, the user can rotate the bolt 17 and take it off from the bottom of the mounting block 30, then the user can rotate the double-threaded screw rod 29 to adjust the position of the two clamping plates 27, so that the two fixing columns 25 can be clamped into the corresponding clamping grooves 28 at the same time, after adjustment, the mounting frame 26 can be placed vertically and placed on the two positioning plates 21, at this time, the two clamping plates 27 can limit the two fixing columns 25 through the clamping grooves 28, and the user can rotate the double-threaded screw rod 29 again to drive the two fixing columns 25 to be extruded, so that the distance between the first clamping plate 12 and the second clamping plate 13 can be limited, and the clamping effect of the workpiece can be ensured; after the workpiece is installed, the user can start the numerical control vertical machine tool, the first motor 3 and the second motor 8 can drive the machining head 7, and then the workpiece on the workbench 1 can be processed; after processing, no matter which positioning mode is used, the user only needs to lift the mounting block 30 upward, so that the bolt 17 or the clamping plate 27 is away from the positioning plate 21, then the workpiece can be taken out from between the first clamping plate 12 and the second clamping plate 13, and a new workpiece can be replaced for the next round of processing.
[0043] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.
Claims
1. A CNC vertical lathe having a latch assembly, characterized by, Include: Workbench (1), the top of the workbench (1) is fixedly installed with a support frame (2), one side of the support frame (2) is slidably connected with a first moving plate (5), one side of the first moving plate (5) is slidably connected with a second moving plate (6), one side of the second moving plate (6) is provided with a machining head (7), and the machining head (7) is used for machining workpieces placed on the workbench (1); Further comprising a driving assembly, the driving assembly is used for completing the lifting and horizontal movement of the machining head (7); Further comprising a fixing assembly, the fixing assembly is used for completing the fixing of the workpiece to be machined; Further comprising a latch assembly, the latch assembly is used for further ensuring that the fixing assembly has good fixing effect on the workpiece.
2. The CNC vertical lathe having a latch assembly according to claim 1, wherein, The driving assembly comprises a first motor (3) fixedly installed on the top of the support frame (2), a first screw rod (4) rotatably connected with one side of the support frame (2), and the output shaft of the first motor (3) is fixedly connected with one end of the first screw rod (4). The first screw rod (4) is threadedly connected with the first moving plate (5) and is used for driving the first moving plate (5) to move up and down. One side of the first moving plate (5) is rotatably connected with a second screw rod (9), and a second motor (8) is fixedly installed on one side of the first moving plate (5). One end of the output shaft of the second motor (8) is fixedly connected with one end of the second screw rod (9), and the second screw rod (9) is threadedly connected with the second moving plate (6) and is used for driving the second moving plate (6) to move horizontally.
3. The CNC vertical lathe having a latch assembly as claimed in claim 1 wherein, The fixing assembly comprises a fixing plate (10) fixedly installed on the top of the workbench (1), a bottom plate (11) fixedly installed on the top of the fixing plate (10), four fixing blocks (16) fixedly installed on the top of the bottom plate (11), two of the four fixing blocks (16) being arranged in each group, and the two groups of fixing blocks (16) being located at positions close to the two sides of the bottom plate (11), respectively. The top of the bottom plate (11) is slidably connected with a first clamping plate (12) and a second clamping plate (13), the first clamping plate (12) and the second clamping plate (13) are provided with clamping grooves (14) on the sides close to each other, the first clamping plate (12) and the second clamping plate (13) are matched with each other, and are used for clamping and fixing the workpiece. The bottom of the first clamping plate (12) and the second clamping plate (13) is provided with a recess (18), two fixed rods (19) are fixedly installed on the inner wall of one side of the recess (18), one end of each of the two fixed rods (19) slidably penetrates through the adjacent fixing block (16), the outer wall of each of the plurality of fixed rods (19) is sleeved with a spring (20), one end of each of the plurality of springs (20) is fixedly connected with the inner wall of one side of the corresponding recess (18), the other end of each of the plurality of springs (20) is fixedly connected with one side of the adjacent fixing block (16), and the plurality of springs (20) are used to ensure that the first clamping plate (12) and the second clamping plate (13) can continuously keep close.
4. The CNC vertical lathe having a latch assembly according to claim 3, wherein, The latch assembly comprises two positioning plates (21) fixedly installed on one side of the first clamping plate (12) and the second clamping plate (13) respectively, the two positioning plates (21) are in sliding fit and relative movement between them, a plurality of through holes (22) are formed in the interiors of the two positioning plates (21), the through holes (22) in different positioning plates (21) are matched with each other, a latch (17) is arranged in penetration between the corresponding two through holes (22), a positioning hole (15) is formed in the fixed plate (10), one end of the latch (17) penetrates the positioning hole (15), and the latch (17) is used for completing the positioning between the first clamping plate (12) and the second clamping plate (13), so as to ensure the continuous and stable clamping of the workpiece.
5. The CNC vertical lathe having a latch assembly as claimed in claim 4 wherein, The latch assembly further comprises two fixed columns (25) fixedly installed on one side of the two positioning plates (21) respectively, a mounting block (30) is threadedly connected to the top end of the latch (17), an installation rack (26) is sleeved on the outer wall of the latch (17), the mounting block (30) is fixedly connected with the top of the installation rack (26), a double-threaded screw rod (29) is rotatably connected to the top of the installation rack (26), one end of the double-threaded screw rod (29) rotatably penetrates the mounting block (30), two clamping plates (27) are slidably connected to the top of the installation rack (26), and the two clamping plates (27) are located on the two sides of the mounting block (30) respectively, the two clamping plates (27) are threadedly connected with the double-threaded screw rod (29), and the two clamping plates (27) are located on the opposite threads of the two sections of the double-threaded screw rod (29) respectively, clamping grooves (28) are formed in the bottoms of the two clamping plates (27), and the two fixed columns (25) are matched with the inner walls of the corresponding clamping grooves (28), so as to more accurately limit the gap between the first clamping plate (12) and the second clamping plate (13).
6. The CNC vertical lathe having a latch assembly according to claim 5, wherein, Sliding grooves (23) are formed in the interiors of the two positioning plates (21), limit rods (24) are fixedly installed on the sides of the two positioning plates (21) close to each other, the two limit rods (24) are slidably connected with the inner walls of the adjacent sliding grooves (23), and nuts matched with the adjacent positioning plates (21) are threadedly sleeved on the other ends of the two limit rods (24), so as to adjust the moving friction between the first clamping plate (12) and the second clamping plate (13).