A centering positioning device

Abstract

The application discloses a centering positioning device, which comprises a mounting plate, four guide sliding grooves arranged on the mounting plate, a two-way screw rod rotatably mounted on the mounting plate through a mounting frame, clamping assemblies symmetrically arranged at the two ends of the two-way screw rod and slidably matched with the guide sliding grooves, a driving mechanism mounted on the mounting frame, a transmission end of the driving mechanism and the two-way screw rod, the driving mechanism comprising a fixed ring cylinder fixedly mounted on the mounting frame and a transmission disc rotatably connected in the fixed ring cylinder, a transmission end of the transmission disc and the two-way screw rod, a plurality of elastic limiting pieces connected on the inner side of the transmission disc, a transmission gear arranged at the center of the transmission disc, and a tooth block matched with the transmission gear and connected on the side of the elastic limiting piece close to the transmission gear. The application can avoid overdrive and clamping too tightly, does not need manual judgment, is not prone to misjudgment and is more convenient and safe to use.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of machining positioning, and particularly relates to a centering positioning device. BACKGROUND

[0002] In automatic production, a PCB (Printed Circuit Board) workpiece to be machined needs to be positioned by a positioning device before being grabbed by a manipulator for machining, so that the manipulator can accurately grab it. The existing positioning device generally uses a cylinder to drive a clamping jaw for centering and fixing, which can only be used for square or circular workpieces. Rectangular workpieces need to be clamped by four cylinders from multiple directions to realize positioning and fixing.

[0003] Chinese Patent Publication No. CN207810610U discloses a centering positioning device for positioning a workpiece, which includes a support plate and a driving member arranged on one side of the support plate. The device further includes a rotating disc arranged on the other side of the support plate and four positioning modules. The driving member is connected to the rotating disc to drive the rotating disc to rotate. The rotating disc is provided with four arc-shaped guide grooves. The four positioning modules are arranged at the four edges of the support plate. Each positioning module includes a sliding plate, a connecting rod, a cam follower, and a positioning member. The sliding plate is slidably arranged on the support plate. One end of the connecting rod is fixedly connected to the sliding plate, and the other end is connected to the cam follower. The cam follower is slidably arranged in the corresponding guide groove. The positioning member is arranged on the sliding plate.

[0004] In the scheme, when the driving member drives the rotating disc to rotate, the cam follower slides in the guide groove, and the connecting rod drives the sliding plate and the positioning member to move towards the center of the support plate to center and position the workpiece. However, the centering and positioning of the workpiece may still be driven after being fixed in place, which may cause damage to the workpiece or may have a certain risk of damage. SUMMARY

[0005] The present application aims to provide a centering positioning device to solve the problems in the background art.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme.

[0007] A centering and positioning device includes a mounting plate with four guide grooves symmetrically distributed in a cross shape on its upper surface. A bidirectional lead screw aligned with the guide grooves is rotatably mounted below the mounting plate via a mounting bracket. Clamping components that slide and adapt to the guide grooves are symmetrically threaded at both ends of the bidirectional lead screw. A driving mechanism is mounted on the mounting bracket and is drivenly connected to the end of the bidirectional lead screw. The driving mechanism includes a fixed ring cylinder fixedly mounted on the mounting bracket and a transmission disk rotatably connected in the fixed ring cylinder. The transmission disk is drivenly connected to the end of the bidirectional lead screw. Multiple sets of elastic limiting members are connected to the inner side of the transmission disk. A transmission gear is provided at the center of the transmission disk, and a tooth block adapted to the transmission gear is connected to the side of the elastic limiting member near the transmission gear.

[0008] As a further aspect of the present invention: four sets of elastic limiting members are connected to the inner wall of the transmission disk, and telescopic rods are symmetrically arranged on both sides of the elastic limiting members. The telescopic rods and the elastic limiting members have the same extension and retraction direction, and the telescopic rods are connected between the tooth block and the inner wall of the transmission disk.

[0009] As a further aspect of the present invention: a limiting component for limiting the elastic limiting member is provided on the periphery of the fixed ring cylinder relative to the transmission disc; a ring cover is assembled and connected on the side of the fixed ring cylinder away from the bidirectional lead screw; the ring cover and the fixed ring cylinder are concentrically arranged; and an elastic pressing ring for driving the limiting component to disengage from the end of the elastic limiting member is elastically connected to the ring cover.

[0010] As a further aspect of the present invention: the elastic limiting member includes a cylinder fixedly installed on the inner side wall of the transmission disc, a transmission rod is provided through the cylinder, one end of the transmission rod is fixedly connected to the tooth block, and the other end of the transmission rod extends movably into the fixed ring cylinder and is slidably connected, the fixed ring cylinder has an annular inner groove inside, the diameter of the end of the transmission rod matches its width, the limiting component is provided on the side of the annular inner groove, a flange is fixedly sleeved on the outer periphery of the transmission rod, a spring is connected to the flange and the cylinder, the end of the transmission rod extending into the fixed ring cylinder is embedded in a groove facing the limiting component, a limiting protrusion is slidably connected in the groove, and a spring is connected between the limiting protrusion and the groove.

[0011] As a further aspect of the present invention: the limiting component includes an inner ring body embedded in a fixed ring cylinder, the inner ring body and the fixed ring cylinder being concentrically arranged, one side of the inner ring body communicating with the side of the annular inner groove, the other side of the inner ring body being flush with the side of the fixed ring cylinder connected to the ring cover, an annular limiting groove communicating with the side of the inner ring body facing the annular inner groove being embedded, a plurality of insertion holes being provided through the annular limiting groove, a partition being provided between the openings of adjacent insertion holes, and the partition being fixedly connected in the annular limiting groove.

[0012] As a further embodiment of the present invention: a washer is fixedly connected to one side of the elastic pressing ring embedded in the ring cover, a plurality of mounting holes are embedded in the surface of the washer, and a plurality of insert rods corresponding one-to-one with the insertion holes are connected to the surface of the washer, and the insert rods and the insertion holes are slidably adapted.

[0013] As a further embodiment of the present invention: the clamping assembly includes a sliding rod that is slidably fitted in a guide groove, a sleeve block that is fixedly connected to one end of the sliding rod, the sleeve block being threadedly fitted around the bidirectional lead screw, a clamping plate that is fixedly connected to the other end of the sliding rod, the lower surface of the clamping plate slidingly fitting against the upper surface of the mounting plate, rotating shafts that are symmetrically rotatably connected to both sides of the clamping plate, a limiting belt that is fitted around the rotating shafts, and multiple sets of grooves that are laterally embedded on the surface of the limiting belt.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: First, a bidirectional lead screw is driven, so that the two ends of the PCB board to be processed can be fixed by two clamping components, and the synchronously moving clamping components can center the PCB board to be processed in one direction. Then, a bidirectional lead screw in another direction can be driven, so that the PCB board to be processed can be limited by the other two clamping components, and the board can also be centered in the other direction. This setting can facilitate the centering of rectangular PCB boards, and is more flexible and convenient than the traditional claw-type synchronous clamping centering. The transmission gear is driven by a motor. During operation, the transmission gear engages with the toothed block, causing the transmission disc to rotate synchronously. This, in turn, drives the bidirectional lead screw, enabling the clamping components to move closer or further away synchronously, thus centering and fixing the PCB board. During positioning, once the clamping and fixing process is complete and resistance increases, the transmission gear pushes the toothed block away from the transmission gear, gradually disengaging it. At this point, the transmission gear can only rotate freely, and the clamping components stop moving closer or further away. The end of the elastic limiting member away from the toothed block can be inserted into the fixing ring and fixed, thus limiting the relative position of the clamping components and preventing loosening. This design avoids over-driving causing excessive clamping, eliminates the need for manual judgment, reduces the risk of misjudgment, and makes it more convenient and safer to use. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention.

[0016] Figure 2 This is a schematic diagram of the bidirectional lead screw and drive mechanism in this invention.

[0017] Figure 3 for Figure 2 A magnified structural diagram of region A in the middle.

[0018] Figure 4 This is a schematic diagram of the drive mechanism in this invention.

[0019] Figure 5 for Figure 4 A magnified structural diagram of region B in the middle.

[0020] Figure 6 This is a schematic diagram of the elastic limiting member in this invention.

[0021] Figure 7 This is a schematic diagram of the limiting protrusion in the present invention.

[0022] Figure 8 This is a schematic diagram of the limiting component in this invention.

[0023] Figure 9 for Figure 8 A magnified structural diagram of region C in the middle.

[0024] Figure 10 This is a schematic diagram of the elastic pressing ring in this invention.

[0025] Figure 11 This is a schematic diagram of the clamping component in this invention.

[0026] In the diagram: 1-installation plate, 11-mounting bracket, 12-guide slide, 2-double-acting lead screw, 3-clamping assembly, 31-sliding rod, 32-sleeve block, 33-clamping plate, 34-rotating shaft, 35-limiting belt, 4-drive mechanism, 5-fixed ring cylinder, 51-inner ring body, 52-annular limiting groove, 53-insertion hole, 54-partition plate, 6-transmission disc, 61-elastic limiting component, 6101-cylinder body, 6102-transmission rod, 6103-flange, 6104-groove, 6105-limiting protrusion, 62-telescopic rod, 63-tooth block, 7-ring cover, 8-elastic pressing ring, 81-washer ring, 82-mounting hole, 83-insertion rod, 9-transmission gear. Detailed Implementation

[0027] Please see Figures 1-5In this embodiment of the invention, a centering and positioning device includes a mounting plate 1. The upper surface of the mounting plate 1 is symmetrically provided with four guide grooves 12 in a cross shape. A bidirectional lead screw 2 arranged in a cross shape is rotatably mounted on the lower part of the mounting plate 1 via a mounting bracket 11. The bidirectional lead screw 2 and the guide grooves 12 are aligned and the two sets of bidirectional lead screws 2 are overlapped. Therefore, the ends of the four guide grooves 12 that are close to each other are not connected. The two ends of the bidirectional lead screw 2 are symmetrically threaded and fitted with clamping components 3. The clamping components 3 and the guide grooves 12 are slidably adapted. When the bidirectional lead screw 2 is driven, it can drive the two clamping components 3 to move closer or further away synchronously. First, a bidirectional lead screw 2 is driven, which allows the two ends of the PCB board to be processed to be fixed by two clamping components 3. The synchronously moving clamping components 3 can center the PCB board in one direction. Then, the bidirectional lead screw 2 in the other direction can be driven, which allows the other two clamping components 3 to limit the PCB board to be processed and center it in the other direction as well. This setting can facilitate the centering of rectangular PCB boards and is more flexible and convenient than the traditional claw-type synchronous clamping centering. Furthermore, to prevent damage caused by excessive tightness of the clamping assembly 3 when clamping the PCB board, a drive mechanism 4 is installed on the mounting bracket 11. The drive mechanism 4 is connected to the end of the bidirectional lead screw 2. The drive mechanism 4 includes a fixed ring cylinder 5 fixedly installed on the mounting bracket 11 and a transmission disk 6 rotatably connected in the fixed ring cylinder 5. The transmission disk 6 is connected to the end of the bidirectional lead screw 2. Multiple sets of elastic limiting members 61 are connected to the inner side of the transmission disk 6. A transmission gear 9 is provided at the center of the transmission disk 6. A tooth block 63 adapted to the transmission gear 9 is connected to the side of the elastic limiting member 61 near the transmission gear 9. The transmission gear 9 is driven to rotate by a drive motor, preferably a servo motor, which can control the transmission gear 9 to rotate forward or backward. During use, the transmission gear 9 can engage with the toothed block 63 while rotating, thereby driving the transmission disk 6 to rotate synchronously, which in turn drives the bidirectional lead screw 2 to rotate, achieving synchronous approach or departure of the clamping component 3, thus centering and fixing the PCB board. During the positioning process, once the clamping and fixing are completed and the resistance increases, the transmission gear 9 can push the toothed block 63 away from the transmission gear 9, thereby gradually disengaging from the transmission gear 9. At this time, the transmission gear 9 can only rotate freely, and the clamping component 3 will no longer approach or move away. The end of the elastic limiting member 61 away from the toothed block 63 can be inserted into the fixing ring cylinder 5 and fixed, thus limiting the relative position of the clamping component 3 and preventing loosening. This setting can avoid excessive clamping caused by over-drive, does not require manual judgment, is less prone to misjudgment and other problems, and is more convenient and safer to use.

[0028] like Figures 4-5As shown, four sets of elastic limiting members 61 are connected to the inner wall of the transmission disk 6. Telescopic rods 62 are symmetrically arranged on both sides of each elastic limiting member 61. The telescopic rods 62 and the elastic limiting members 61 extend and retract in the same direction. The telescopic rods 62 connect the toothed block 63 and the inner wall of the transmission disk 6. This arrangement allows the toothed block 63 to move parallel towards or away from the transmission gear 9, and it also maintains the stability of the elastic limiting members 61 during extension and retraction, preventing jamming and deflection of the toothed block 63 during movement. The telescopic rods 62 consist of a sleeve and a slidingly fitted round rod, allowing for extension and retraction during the movement of the toothed block 63.

[0029] like Figures 4-7 As shown, the fixed ring cylinder 5 has a limiting component for restricting the elastic limiting member 61 on its periphery relative to the transmission disk 6. A ring cover 7 is mounted on the side of the fixed ring cylinder 5 away from the bidirectional lead screw 2. The ring cover 7 and the fixed ring cylinder 5 are concentrically arranged, and an elastic pressing ring 8 is elastically connected to the ring cover 7 for driving the limiting component to disengage from the end of the elastic limiting member 61. When the elastic limiting member 61 and the toothed block 63 move away from the transmission gear 9, and the end of the elastic limiting member 61 is restricted by the limiting component, pressing the elastic pressing ring 8 can release the restriction. This design allows the transmission gear 9 to easily push the toothed block 63 and the elastic limiting member 61 away after encountering resistance during driving, and also allows the transmission gear 9 to idle freely after the elastic limiting member 61 is restricted, preventing the clamping component 3 from moving closer or further away. This design effectively avoids over-clamping and damage to the PCB board. The tooth block 63 has an arc-shaped internal tooth groove on the side facing the transmission gear 9. This allows it to both lock and drive the transmission disk 6 and the bidirectional lead screw 2 to rotate synchronously when the transmission gear 9 rotates, and to move away from the transmission gear 9 when subjected to greater force.

[0030] like Figures 6-7As shown, the elastic limiting component 61 includes a cylindrical body 6101 fixedly installed on the inner wall of the transmission disc 6. A transmission rod 6102 is disposed through the cylindrical body 6101. One end of the transmission rod 6102 is fixedly connected to the toothed block 63, and the other end of the transmission rod 6102 extends movably into the fixed ring cylinder 5 and is slidably connected. The fixed ring cylinder 5 has an annular inner groove. The diameter of the end of the transmission rod 6102 matches its width. The limiting component is disposed on the side of the annular inner groove. A flange 6103 is fixedly sleeved around the transmission rod 6102. A spring is connected between the flange 6103 and the cylindrical body 6101. When the spring acts, the end of the transmission rod 6102 extending into the fixed ring cylinder 5 is located below the limiting component. When the toothed block 63 and the transmission rod 6102 move synchronously towards the fixed ring cylinder 5, the end of the transmission rod 6102 gradually... As the stepping limit assembly approaches and aligns with it, the end of the transmission rod 6102 extending into the fixed ring cylinder 5 is embedded in a groove 6104 facing the limit assembly. A limit protrusion 6105 is slidably connected in the groove 6104. A spring connects the limit protrusion 6105 and the groove 6104. The spring causes the limit protrusion 6105 to move away from the groove 6104. When the transmission rod 6102 is not extended to align with the limit assembly, the limit protrusion 6105 is pressed into the groove 6104. At this time, the relative rotation of the transmission disc 6 and the fixed ring cylinder 5 is not affected. However, when the transmission rod 6102 extends to align with the limit assembly, the limit protrusion 6105 pops out and extends into the limit assembly to form a fit, thereby restricting the relative rotation of the transmission disc 6 and the fixed ring cylinder 5, thus limiting the relative position of the clamping assembly 3. By using the elastic pressing ring 8 in conjunction with the limiting component, the limiting protrusion 6105 can be pushed into the groove 6104. At this point, without the continuous force of the transmission gear 9 pushing the toothed block 63, the spring in the cylinder 6101 can push the transmission rod 6102 away from the fixed ring cylinder 5. Thus, the limiting protrusion 6105 remains restricted by the annular inner groove in the fixed ring cylinder 5 and cannot pop out. This combination ensures that the transmission gear 9 no longer transmits power to the rotation of the bidirectional lead screw 2 after encountering resistance, and the rotation of the bidirectional lead screw 2 is restricted, preventing the clamping component 3 from loosening. The annular inner groove faces the transmission disc 6.

[0031] The end of the limiting protrusion 6105 and the surface of the transmission rod 6102 have the same curvature, so that the end of the transmission rod 6102 that extends into the fixed ring cylinder 5 will not be affected in sliding within the fixed ring cylinder 5, and thus the relative rotation of the transmission disc 6 and the fixed ring cylinder 5 will not be restricted.

[0032] like Figures 8-9As shown, the limiting component includes an inner ring body 51 embedded in a fixed ring cylinder 5. The inner ring body 51 and the fixed ring cylinder 5 are concentrically arranged. One side of the inner ring body 51 is connected to the side of the annular inner groove, and the other side of the inner ring body 51 is flush with the side of the fixed ring cylinder 5 connected to the ring cover 7. An annular limiting groove 52 is embedded in the side of the inner ring body 51 facing the annular inner groove and is connected thereto. A plurality of insertion holes 53 are provided through the annular limiting groove 52. A partition 54 is provided between the openings of adjacent insertion holes 53. The partition 54 is fixedly connected in the annular limiting groove 52. Preferably, the sides of two adjacent insertion holes 53 are both inclined surfaces, and the distance between two adjacent partitions 54 is slightly larger than the width of the end of the limiting protrusion 6105. When the end of the transmission rod 6102 extends into the annular inner groove and the opening of the groove 6104 gradually aligns with the annular limiting groove 52, the end of the limiting protrusion 6105 will be inserted into the annular limiting groove 52 and between the two partitions 54. The elastic pressing ring 8 can pass through the insertion hole 53 and push the end of the limiting protrusion 6105 back into the groove 6104.

[0033] like Figure 10 As shown, a washer 81 is fixedly connected to one side of the elastic pressing ring 8 embedded in the ring cover 7. The function of the washer 81 is to facilitate the sliding of the elastic pressing ring 8 relative to the ring cover 7 and to prevent the elastic pressing ring 8 from falling off. Multiple sets of mounting holes 82 are embedded in the surface of the washer 81. The mounting holes 82 are used to install springs. The other end of the spring can abut against the ring cover 7 or the fixed ring cylinder 5. This arrangement allows the elastic pressing ring 8 to return to its original state under the action of the spring when it is no longer pressed. Multiple insertion rods 83 are connected to the surface of the washer 81, which correspond one-to-one with the insertion holes 53. The insertion rods 83 and the insertion holes 53 are slidably adapted. Pushing the elastic pressing ring 8 can push the limiting protrusion 6105 that extends between the adjacent partitions 54 back into the groove 6104 through the insertion rods 83, thereby releasing the restriction on the relative rotation between the transmission disc 6 and the fixed ring cylinder 5. Then the rotation of the transmission gear 9 can continue to drive the transmission disc 6 to rotate synchronously.

[0034] To improve the flexibility of positioning, such as Figure 1 and Figure 11As shown, the clamping assembly 3 includes a sliding rod 31 slidably fitted in the guide groove 12. One end of the sliding rod 31 is fixedly connected to a sleeve block 32, which is threaded onto the periphery of the bidirectional lead screw 2. The other end of the sliding rod 31 is fixedly connected to a clamping plate 33. The lower surface of the clamping plate 33 slidably fits against the upper surface of the mounting plate 1. Rotating shafts 34 are symmetrically rotatably connected to both sides of the clamping plate 33. A limiting belt 35 is fitted around the periphery of the rotating shafts 34. Multiple sets of grooves are laterally embedded on the surface of the limiting belt 35. The limiting belt 35 is preferably made of rubber, and its movement direction is laterally. A pad (not shown in the figure) is fixedly connected between the upper and lower ends of the clamping plate 33. The pad is located between the two rotating shafts 34, and its two sides are slidably fitted against the limiting belt 35. When the PCB board is fixed and clamped by two opposing limiting belts 35, it can be fixed in the vertical direction and in the direction of relative movement of the two limiting belts 35, while it can continue to move in the horizontal direction. This makes it convenient for the limiting belts 35 in the other two directions to clamp and position. This makes positioning of rectangular PCB boards convenient and safer.

Claims

1. A centering and positioning device, comprising a mounting plate, wherein four guide grooves are symmetrically distributed in a cross shape on the upper surface of the mounting plate; a bidirectional lead screw aligned with the guide grooves is rotatably mounted below the mounting plate via a mounting bracket; clamping assemblies that are symmetrically threaded at both ends of the bidirectional lead screw and slidably adapted to the guide grooves are provided; a driving mechanism is mounted on the mounting bracket; the driving mechanism is drively connected to the end of the bidirectional lead screw, characterized in that... The driving mechanism includes a fixed ring cylinder fixedly mounted on a mounting frame and a transmission disc rotatably connected in the fixed ring cylinder. The transmission disc and the end of the bidirectional lead screw are connected in a transmission connection. Multiple sets of elastic limiting members are connected and arranged on the inner side of the transmission disc. A transmission gear is provided at the center of the transmission disc. A tooth block adapted to the transmission gear is connected and arranged on the side of the elastic limiting member near the transmission gear.

2. The centering and positioning device according to claim 1, characterized in that, The inner wall of the transmission disc is connected with four sets of elastic limiting members. The fixed ring cylinder is provided with a limiting component for limiting the elastic limiting members relative to the outer periphery of the transmission disc. A ring cover is assembled and connected on the side of the fixed ring cylinder away from the bidirectional lead screw. The ring cover and the fixed ring cylinder are concentrically arranged, and an elastic pressing ring for driving the limiting component to disengage from the end of the elastic limiting member is elastically connected to the ring cover.

3. The centering and positioning device according to claim 2, characterized in that, The elastic limiting member is also symmetrically provided with telescopic rods on both sides. The telescopic rods and the elastic limiting member have the same extension and retraction direction. The telescopic rods are connected between the tooth block and the inner wall of the transmission disc.

4. The centering and positioning device according to claim 2, characterized in that, The elastic limiting component includes a cylinder fixedly installed on the inner wall of the transmission disc. A transmission rod is provided through the cylinder. One end of the transmission rod is fixedly connected to the toothed block, and the other end of the transmission rod extends movably into the fixed ring cylinder and is slidably connected.

5. The centering and positioning device according to claim 4, characterized in that, The fixed ring cylinder has an annular inner groove inside, and the diameter of the end of the transmission rod matches its width. The limiting component is set on the side of the annular inner groove. A flange is fixedly sleeved on the outer periphery of the transmission rod. A spring is connected between the flange and the cylinder body. The end of the transmission rod that extends into the fixed ring cylinder is embedded in a groove facing the limiting component. A limiting protrusion is slidably connected in the groove. A spring is connected between the limiting protrusion and the groove.

6. The centering and positioning device according to claim 5, characterized in that, The limiting component includes an inner ring body embedded in a fixed ring cylinder. An annular limiting groove is embedded on the side of the inner ring body facing the annular inner groove and communicates with it. Multiple insertion holes are provided through the annular limiting groove. A partition is provided between the openings of adjacent insertion holes. The partition is fixedly connected in the annular limiting groove.

7. A centering and positioning device according to claim 6, characterized in that, The inner ring body and the fixed ring cylinder are concentrically arranged. One side of the inner ring body is connected to the side of the annular inner groove, and the other side of the inner ring body is flush with the side of the fixed ring cylinder that is connected to the ring cover.

8. A centering and positioning device according to claim 6, characterized in that, A washer is fixedly connected to one side of the elastic pressing ring embedded in the ring cover. Multiple sets of mounting holes are embedded in the surface of the washer, and multiple insertion rods corresponding to the insertion holes are connected to the surface of the washer. The insertion rods and the insertion holes are slidably adapted to each other.

9. A centering and positioning device according to claim 1, characterized in that, The clamping assembly includes a sliding rod that is slidably fitted in a guide groove. A sleeve block is fixedly connected to one end of the sliding rod. The sleeve block is threaded onto the periphery of the bidirectional lead screw. A clamping plate is fixedly connected to the other end of the sliding rod. The lower surface of the clamping plate slidably fits against the upper surface of the mounting plate.

10. A centering and positioning device according to claim 9, characterized in that, The clamp is symmetrically and rotatably connected to the two sides of the clamp, and a limiting belt is sleeved around the outer periphery of the rotating shaft. Multiple sets of grooves are horizontally embedded on the surface of the limiting belt.

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