A battery cell electrode stacking device

Abstract

The present invention discloses a device for stacking battery cell electrodes, comprising a chassis and a stacking platform. The chassis is provided with a movable guide rail on the top, a mechanical claw mounted on the movable guide rail, and an electric telescopic rod, a connecting mechanism, a lifting mechanism, a conveyor belt, and a placement plate. A groove is provided on one side of the chassis, a rotating plate is rotatably mounted within the groove, and a servo motor is fixedly mounted within the chassis for transmission connection with the rotating plate. In the present invention, electrodes are individually placed in the placement groove. After the mechanical claw picks up the electrode, the movable guide rail drives the mechanical claw to move above the stacking platform. After releasing the electrode, the mechanical claw returns to its original position, ensuring that the mechanical claw only picks up one electrode at a time, avoiding adhesion between adjacent electrode sheets, thereby preventing battery failure caused by multiple electrode sheets stacked in the battery cell structure.

Description

Technical Field

[0001] The present invention relates to the technical field of laminating machines, and in particular to a battery cell pole piece laminating device. Background Art

[0002] The common method used in existing lithium battery cell stacking machines for loading is to place multiple electrode sheets in a material box, then use a mechanical claw to pick up the top electrode sheet and place it on the workstation for the next process.

[0003] However, since the electrode sheets are very thin and carry static electricity, the electrode sheets often overlap and stick together, and the mechanical claw picks up multiple electrode sheets at a time. If multiple electrode sheets are stacked in the battery cell structure, serious battery failure will occur. Therefore, the present invention provides a battery cell electrode sheet stacking device that prevents battery cell electrode sheets from sticking together. Summary of the Invention

[0004] In order to solve the problems mentioned in the above background technology, a battery cell electrode stacking device is proposed.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A battery cell electrode stacking device includes a chassis and a stacking platform. A movable guide rail is provided on the top of the chassis, and a mechanical claw is installed on the movable guide rail. The chassis is equipped with an electric telescopic rod, a connecting mechanism, a lifting mechanism, a conveyor belt, and a placement plate. A groove is provided on one side of the chassis, and a rotating plate is rotatably installed in the groove. A servo motor is fixedly installed inside the chassis and is transmission-connected to the rotating plate.

[0007] The placement plate is used to place the pole pieces, and the conveyor belt feeds multiple placement plates to the lifting mechanism in sequence. The lifting mechanism drives the placement plate to rise and fall in the vertical direction to feed the placement plates to the top platform of the chassis in sequence. The connecting mechanism connects the free end of the electric telescopic rod to the placement plate, and the electric telescopic rod pushes the placement plate to move under the mechanical claw. The mechanical claw picks up the pole piece and feeds the pole piece to the stacking table through the movable guide rail.

[0008] As a further description of the above technical solution:

[0009] The connecting mechanism includes a U-shaped plate fixedly mounted on the free end of the electric telescopic rod, a fixed rod fixedly connected between the horizontal ends of the U-shaped plate, sliders slidably connected at both ends of the fixed rod, a pressure rod passing through the horizontal ends of the U-shaped plate, and a fifth connecting rod rotatably connected to the horizontal ends of the U-shaped plate, the two ends of the fifth connecting rod being rotatably connected to the slider and the pressure rod respectively, and a first driving mechanism for driving the sliders to move closer to or away from each other on the fixed rod is provided on the U-shaped plate.

[0010] As a further description of the above technical solution:

[0011] The first driving mechanism includes a worm gear rotatably mounted on the vertical end of the U-shaped plate, and sixth connecting rods are rotatably mounted on both sides of the worm gear at eccentric positions. The free ends of the sixth connecting rods are respectively rotatably connected to the sliders. A first driving motor is fixedly mounted on the U-shaped plate, and the output shaft of the first driving motor is transmission-connected to a worm meshing with the worm gear.

[0012] As a further description of the above technical solution:

[0013] The lifting mechanism includes a fixed plate slidably connected to the chassis, a third connecting rod passes through both ends of the fixed plate, one end of the third connecting rod is rotatably connected to the first connecting rod and the second connecting rod, the free end of the first connecting rod is rotatably connected to the lifting platform, the free end of the second connecting rod is rotatably connected to the chassis, and a second driving mechanism is provided in the chassis to drive the third connecting rod to move in the horizontal direction.

[0014] As a further description of the above technical solution:

[0015] The second driving mechanism includes a second driving motor fixedly installed at the bottom of the chassis, the output shaft of the second driving motor is connected to a transmission screw, the outer side of the transmission screw is connected to a screw sleeve through a threaded engagement, the other end of the third connecting rod is rotatably connected to a fourth connecting rod, and the free end of the fourth connecting rod is rotatably connected to the screw sleeve.

[0016] As a further description of the above technical solution:

[0017] A through slot is provided on one side of the chassis, and the conveyor belt passes through the through slot.

[0018] As a further description of the above technical solution:

[0019] A baffle is fixedly connected to one side of the top platform of the chassis.

[0020] As a further description of the above technical solution:

[0021] A discharge port corresponding to the lifting platform and larger in size than the lifting platform is provided on the other side of the top platform of the chassis.

[0022] As a further description of the above technical solution:

[0023] An annular sliding groove is provided on the placement plate, and a rubber ball is rotatably mounted on the free end of the pressure rod and abuts against the annular sliding groove.

[0024] As a further description of the above technical solution:

[0025] The placement plate is provided with a plurality of placement slots for accommodating the pole pieces, and the plurality of placement slots are distributed at equal angles around the central axis of the placement plate.

[0026] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0027] The lifting mechanism is actuated by the lifting device to move the lifting plate upward in the vertical direction to the discharge port, and then, the lifting mechanism drives the lifting plate to move in the direction close to the laminating table by the electric telescopic rod, until one side of the lifting plate contacts the baffle, and at the same time, the lifting plate is located on the rotating plate, and after the mechanical claw picks up the electrode piece, the mechanical claw is driven to move above the laminating table under the action of the moving guide rail. After releasing the electrode piece, the mechanical claw returns to its original position, and at the same time, the servo motor drives the rotating plate to drive the placing plate to rotate, and rotates the next electrode piece to the bottom of the position of the mechanical claw so that the mechanical claw can pick up the electrode piece again, ensuring that the mechanical claw only picks up one electrode piece at a time, avoiding adhesion between adjacent electrode pieces, thereby avoiding battery failure problems caused by multiple electrode pieces stacked in the battery cell structure.

[0028] 2. In the present invention, when the pressure rod is opposite to the annular slide groove, the worm is driven by the first drive motor to drive the worm wheel to rotate clockwise. Under the linkage action of the sixth connecting rod, the sliders at both ends are pushed to move away from each other on the fixed rod. Under the linkage action of the fifth connecting rod, the pressure rod is pushed to move close to the placement plate. Due to the self-locking effect between the worm wheel and the worm, the pressure rods on the upper and lower sides fix the placement plate in the vertical direction, thereby preventing the electric telescopic rod from pushing the placement plate to move and causing the placement plate to deflect, thereby ensuring that the placement plate can move smoothly to the rotating plate.

[0029] 3. In the present invention, an annular groove is provided on the placement plate, and a rubber ball is rotatably installed on the free end of the pressure rod to abut against the annular groove, thereby increasing the friction between the pressure rod and the placement plate and improving the fixing effect of the pressure rod on the placement plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the three-dimensional structure of a connection mechanism of a battery cell electrode stacking device provided in accordance with an embodiment of the present invention is shown;

[0031] Figure 2 A schematic diagram of the internal structure of a battery cell electrode stacking device provided in an embodiment of the present invention is shown;

[0032] Figure 3 A partial cross-sectional schematic diagram of a cell electrode stacking device at a servo motor provided according to an embodiment of the present invention is shown;

[0033] Figure 4 It shows an enlarged schematic diagram of point A of a battery cell electrode stacking device provided in an embodiment of the present invention;

[0034] Figure 5 It shows a partial enlarged schematic diagram of a lifting mechanism of a battery cell electrode stacking device provided in an embodiment of the present invention;

[0035] Figure 6 A schematic diagram of the three-dimensional structure of a lifting mechanism of a battery cell electrode stacking device provided in an embodiment of the present invention is shown;

[0036] Figure 7 A schematic top view of a placement plate of a battery cell electrode stacking device provided according to an embodiment of the present invention is shown.

[0037] Legend:

[0038] 1. Chassis; 2. Electric telescopic rod; 3. Moving guide rail; 4. Discharge port; 5. Connecting mechanism; 51. U-shaped plate; 52. Fixed rod; 53. Fifth connecting rod; 54. Pressure rod; 55. Slider; 56. Sixth connecting rod; 57. Worm gear; 58. Worm; 59. First drive motor; 6. Mechanical claw; 7. Stacking table; 8. Lifting mechanism; 81. Lifting table; 82. First connecting rod; 83. Second connecting rod; 84. Fixed plate; 85. Third connecting rod; 86. Fourth connecting rod; 87. Second drive motor; 88. Screw sleeve; 89. Drive screw; 9. Conveyor belt; 10. Placement plate; 11. Through groove; 12. Rotating plate; 13. Baffle; 14. Groove; 15. Servo motor; 16. Annular slide; 17. Placement groove; 18. Rubber ball. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0040] Example 1

[0041] See also Figure 1-7The present invention provides a technical solution: a battery cell electrode stacking device, comprising a chassis 1 and a stacking table 7, a movable guide rail 3 is provided on the top of the chassis 1, a mechanical claw 6 is installed on the movable guide rail 3, an electric telescopic rod 2, a connecting mechanism 5, a lifting mechanism 8, a conveyor belt 9 and a placement plate 10 are provided on the chassis 1, a groove 14 is provided on one side of the chassis 1, a rotating plate 12 is rotatably installed in the groove 14, a servo motor 15 is fixedly installed inside the chassis 1 and is transmission-connected to the rotating plate 12, a plurality of placement grooves 17 for accommodating electrode sheets are provided on the placement plate 10, and the plurality of placement grooves 17 are distributed at equal angles around the central axis of the placement plate 10, a through slot 11 is provided on one side of the chassis 1, and the conveyor belt 9 passes through the through slot 11;

[0042] The placement plate 10 is used to place the electrode. The conveyor belt 9 feeds multiple placement plates 10 to the lifting mechanism 8 in sequence. The lifting mechanism 8 drives the placement plates 10 to rise and fall in the vertical direction to feed the placement plates 10 to the top platform of the chassis 1 in sequence. The connecting mechanism 5 connects the free end of the electric telescopic rod 2 to the placement plate 10. The electric telescopic rod 2 pushes the placement plate 10 to move under the mechanical claw 6. The mechanical claw 6 picks up the electrode and feeds the electrode to the stacking table 7 through the movable guide rail 3.

[0043] The pole piece is placed separately in the placement groove 17, and the placement plate 10 is placed on the conveyor belt 9. The placement plate 10 is fed to the lifting platform 81 through the conveyor belt 9. Then, the placement plate 10 is driven by the lifting mechanism 8 to move upward in the vertical direction to the discharge port 4. Then, the connecting mechanism 5 is pushed to the position adapted to the placement plate 10 by the electric telescopic rod 2, so that the connecting mechanism 5 is connected to the placement plate 10. Then, the placement plate 10 is pushed to move toward the direction close to the lamination platform 7 by the electric telescopic rod 2 until one side of the placement plate 10 contacts the baffle 13. At the same time, the placement plate 10 is placed. The plate 10 is located on the rotating plate 12. After the mechanical claw 6 picks up the pole piece, the mechanical claw 6 is driven to move above the stacking table 7 under the action of the moving guide rail 3. After releasing the pole piece, the mechanical claw 6 returns to its original position. At the same time, the servo motor 15 drives the rotating plate 12 to drive the placement plate 10 to rotate, and rotates the next pole piece to the bottom of the position of the mechanical claw 6 so that the mechanical claw 6 can pick up the pole piece again, ensuring that the mechanical claw 6 only picks up one pole piece each time, avoiding adhesion between adjacent pole pieces, thereby avoiding battery failure problems caused by multiple pole pieces stacked in the battery cell structure.

[0044] See also Figure 1-4The connecting mechanism 5 includes a U-shaped plate 51 fixedly mounted on the free end of the electric telescopic rod 2, a fixed rod 52 is fixedly connected between the horizontal ends of the U-shaped plate 51, and sliders 55 are slidably connected at both ends of the fixed rod 52. The horizontal ends of the U-shaped plate 51 are penetrated by a pressure rod 54, and the horizontal ends of the U-shaped plate 51 are rotatably connected to a fifth connecting rod 53. The two ends of the fifth connecting rod 53 are rotatably connected to the slider 55 and the pressure rod 54 respectively. The U-shaped plate 51 is provided with a first driving mechanism that drives the sliders 55 to move closer to or away from each other on the fixed rod 52;

[0045] The first drive mechanism includes a worm gear 57 rotatably mounted on the vertical end of the U-shaped plate 51. Sixth connecting rods 56 are rotatably mounted at eccentric positions on both sides of the worm gear 57. The free ends of the sixth connecting rods 56 are respectively rotatably connected to the sliders 55. A first drive motor 59 is fixedly mounted on the U-shaped plate 51. The output shaft of the first drive motor 59 is drivingly connected to a worm 58 meshing with the worm gear 57.

[0046] When the pressure rod 54 is opposite to the annular slide groove 16, the worm 58 is driven by the first drive motor 59 to drive the worm wheel 57 to rotate clockwise. Under the linkage action of the sixth connecting rod 56, the sliders 55 at both ends are pushed to move away from each other on the fixed rod 52. Under the linkage action of the fifth connecting rod 53, the pressure rod 54 is pushed to move closer to the placement plate 10. Due to the self-locking effect between the worm wheel 57 and the worm 58, the pressure rods 54 on the upper and lower sides fix the placement plate 10 in the vertical direction, thereby preventing the electric telescopic rod 2 from pushing the placement plate 10 to move and causing the placement plate 10 to deflect, ensuring that the placement plate 10 can move smoothly to the rotating plate 12.

[0047] Similarly, by controlling the first drive motor 59 to reverse, the pressure rod 54 is moved away from the placement plate 10, does not interfere with the rotation of the placement plate 10 with the rotating plate 12, and the connecting mechanism 5 is reset along with the electric telescopic rod 2 to continue to fix the next placement plate 10.

[0048] See also Figure 1 、 Figure 5 and Figure 6 The lifting mechanism 8 includes a fixed plate 84 slidably connected to the chassis 1, with guide blocks fixedly connected at both ends of the fixed plate 84. Guide grooves slidably connected to the guide blocks are provided on both sides of the chassis 1. A third connecting rod 85 passes through both ends of the fixed plate 84, and one end of the third connecting rod 85 is rotatably connected to the first connecting rod 82 and the second connecting rod 83. The free end of the first connecting rod 82 is rotatably connected to the lifting platform 81, and the free end of the second connecting rod 83 is rotatably connected to the chassis 1. A second driving mechanism for driving the third connecting rod 85 to move in the horizontal direction is provided in the chassis 1;

[0049] The second driving mechanism includes a second driving motor 87 fixedly mounted on the bottom of the chassis 1, the output shaft of the second driving motor 87 is connected to a transmission screw 89, the outer side of the transmission screw 89 is screwed to a screw sleeve 88 by a thread, the other end of the third connecting rod 85 is rotatably connected to a fourth connecting rod 86, and the free end of the fourth connecting rod 86 is rotatably connected to the screw sleeve 88;

[0050] A discharge port 4 is provided on the other side of the top platform of the chassis 1, which corresponds to the lifting platform 81 and is larger in size than the lifting platform 81;

[0051] The transmission screw 89 is driven to rotate forward by the second drive motor 87. According to the principle of thread transmission, the drive screw sleeve 88 is driven to move upward in the vertical direction. Under the linkage action of the fourth connecting rod 86, the third connecting rods 85 on both sides are pushed to move away from each other in the horizontal direction. Under the linkage action of the first connecting rod 82 and the second connecting rod 83, the lifting platform 81 is driven to drive the placement plate 10 to move close to the discharge port 4 to feed the placement plate 10 to the electric telescopic rod 2. Similarly, by controlling the second drive motor 87 to reverse, the lifting platform 81 is lowered to a position level with the conveyor belt 9, so that the upper and lower placement plates 10 on the conveyor belt 9 can be smoothly fed to the lifting platform 81.

[0052] See also Figure 3 A baffle 13 is fixedly connected to one side of the top platform of the chassis 1, and the electric telescopic rod 2 is positioned to push the mobile terminal placed on the plate 10 to move.

[0053] See also Figure 4 and Figure 7 An annular groove 16 is provided on the placement plate 10, and a rubber ball 18 is rotatably installed on the free end of the pressure rod 54 to abut against the annular groove 16, thereby increasing the friction between the pressure rod 54 and the placement plate 10 and improving the fixing effect of the pressure rod 54 on the placement plate 10.

[0054] Working principle: When in use, first, the pole piece is placed separately in the placement groove 17, and the placement plate 10 is placed on the conveyor belt 9. The placement plate 10 is fed to the lifting platform 81 through the conveyor belt 9. Then, the transmission screw 89 is driven to rotate forward by the second drive motor 87. According to the principle of thread transmission, the screw sleeve 88 is driven to move upward in the vertical direction. Under the linkage action of the fourth connecting rod 86, the third connecting rods 85 on both sides are pushed to move away from each other in the horizontal direction. Under the linkage action of the first connecting rod 82 and the second connecting rod 83, the lifting platform 81 is driven to drive the placement plate 10 to move close to the discharge port 4 to feed the placement plate 10 to the electric telescopic rod 2. Then, the electric telescopic rod 2 pushes the connecting rod 86 to move away from each other. When the connecting mechanism 5 reaches the position adapted to the placement plate 10 and the pressure rod 54 is opposite to the annular slide groove 16, the first drive motor 59 drives the worm 58 to drive the worm wheel 57 to rotate clockwise. Under the linkage action of the sixth connecting rod 56, the sliders 55 at both ends are pushed to move away from each other on the fixed rod 52. Under the linkage action of the fifth connecting rod 53, the pressure rod 54 is pushed to move closer to the placement plate 10. Due to the self-locking effect between the worm wheel 57 and the worm 58, the pressure rods 54 on the upper and lower sides fix the placement plate 10 in the vertical direction, thereby preventing the electric telescopic rod 2 from pushing the placement plate 10 to move and the placement plate 10 from deflecting, ensuring that the placement plate 10 can move smoothly to the rotating plate 12.

[0055] At the same time, by controlling the second drive motor 87 to reverse, the lifting platform 81 is lowered to a position level with the conveyor belt 9, so that the upper and lower placing plates 10 on the conveyor belt 9 can be smoothly fed onto the lifting platform 81;

[0056] Next, after the pole piece is picked up by the mechanical claw 6, the movable guide rail 3 drives the mechanical claw 6 to move above the lamination table 7. After releasing the pole piece, the mechanical claw 6 returns to its original position.

[0057] At the same time, by controlling the first drive motor 59 to rotate in the reverse direction, the pressing rod 54 is moved away from the placement plate 10 so as not to interfere with the rotation of the placement plate 10 along with the rotation plate 12, and the connecting mechanism 5 is reset along with the electric telescopic rod 2 so as to continue to fix the next placement plate 10;

[0058] Finally, the servo motor 15 drives the rotating plate 12 to drive the placement plate 10 to rotate, and rotates the next pole piece to the bottom of the position of the mechanical claw 6 so that the mechanical claw 6 can pick up the pole piece again, ensuring that the mechanical claw 6 only picks up one pole piece each time, avoiding adhesion between adjacent pole pieces, thereby avoiding battery failure problems caused by multiple pole pieces stacked in the battery cell structure.

[0059] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A battery cell electrode lamination device, comprising a chassis (1) and a lamination platform (7), wherein a movable guide rail (3) is provided on the top of the chassis (1), and a mechanical claw (6) is installed on the movable guide rail (3), characterized in that: The chassis (1) is provided with an electric telescopic rod (2), a connecting mechanism (5), a lifting mechanism (8), a conveyor belt (9) and a placement plate (10); a groove (14) is provided on one side of the chassis (1); a rotating plate (12) is rotatably mounted in the groove (14); and a servo motor (15) is fixedly mounted inside the chassis (1) and is transmission-connected to the rotating plate (12); The placement plate (10) is used to place the pole piece, the conveyor belt (9) sequentially feeds the plurality of placement plates (10) to the lifting mechanism (8), the lifting mechanism (8) drives the placement plate (10) to rise and fall in the vertical direction, so as to sequentially feed the placement plates (10) to the top platform of the chassis (1), the connecting mechanism (5) connects the free end of the electric telescopic rod (2) to the placement plate (10), the electric telescopic rod (2) pushes the placement plate (10) to move to the bottom of the mechanical claw (6), the mechanical claw (6) picks up the pole piece, and feeds the pole piece to the stacking table (7) through the movable guide rail (3); The placement plate (10) is provided with a plurality of placement grooves (17) for accommodating pole pieces. The plurality of placement grooves (17) are distributed at equal angles around the central axis of the placement plate (10). The placement plate (10) can be pushed onto the rotating plate (12).

2. The battery cell electrode stacking device according to claim 1, characterized in that: The connecting mechanism (5) comprises a U-shaped plate (51) fixedly mounted on the free end of the electric telescopic rod (2), a fixed rod (52) fixedly connected between the horizontal ends of the U-shaped plate (51), sliders (55) slidably connected to the two ends of the fixed rod (52), a pressure rod (54) passing through the horizontal ends of the U-shaped plate (51), a fifth connecting rod (53) rotatably connected to the horizontal ends of the U-shaped plate (51), the two ends of the fifth connecting rod (53) being rotatably connected to the slider (55) and the pressure rod (54) respectively, and a first driving mechanism for driving the sliders (55) to move closer to or farther away from each other on the fixed rod (52) is provided on the U-shaped plate (51).

3. The battery cell electrode stacking device according to claim 2, characterized in that: The first driving mechanism comprises a worm gear (57) rotatably mounted on a vertical end of a U-shaped plate (51), sixth connecting rods (56) rotatably mounted on both sides of the worm gear (57) at eccentric positions, free ends of the sixth connecting rods (56) being rotatably connected to sliders (55), a first driving motor (59) being fixedly mounted on the U-shaped plate (51), and an output shaft of the first driving motor (59) being transmission-connected to a worm (58) meshing with the worm gear (57).

4. The battery cell electrode stacking device according to claim 1, characterized in that: The lifting mechanism (8) includes a fixed plate (84) slidably connected to the chassis (1), a third connecting rod (85) passing through both ends of the fixed plate (84), one end of the third connecting rod (85) is rotatably connected to the first connecting rod (82) and the second connecting rod (83), the free end of the first connecting rod (82) is rotatably connected to the lifting platform (81), the free end of the second connecting rod (83) is rotatably connected to the chassis (1), and a second driving mechanism for driving the third connecting rod (85) to move in the horizontal direction is provided in the chassis (1).

5. The battery cell electrode stacking device according to claim 4, characterized in that: The second driving mechanism comprises a second driving motor (87) fixedly mounted on the bottom of the chassis (1); the output shaft of the second driving motor (87) is connected to a transmission screw (89); the outer side of the transmission screw (89) is connected to a screw sleeve (88) by screw thread engagement; the other end of the third connecting rod (85) is connected to a fourth connecting rod (86) in rotation; the free end of the fourth connecting rod (86) is connected to the screw sleeve (88) in rotation.

6. The battery cell electrode stacking device according to claim 1, characterized in that: A through slot (11) is provided on one side of the chassis (1), and the conveyor belt (9) passes through the through slot (11).

7. The battery cell electrode stacking device according to claim 1, characterized in that: A baffle (13) is fixedly connected to one side of the top platform of the chassis (1).

8. The battery cell electrode stacking device according to claim 5, characterized in that: A discharge port (4) corresponding to the lifting platform (81) and having a larger size than the lifting platform (81) is provided on the other side of the top platform of the chassis (1).

9. The battery cell electrode stacking device according to claim 2, characterized in that: An annular sliding groove (16) is provided on the placement plate (10), and a rubber ball (18) is rotatably mounted on the free end of the pressure rod (54) and is in contact with the annular sliding groove (16).

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