Core pressing machine for lithium battery production

Abstract

The invention discloses a core pressing machine for lithium battery production, and relates to the technical field of lithium battery processing and production.The core pressing machine comprises a workbench, two first lower grooves are symmetrically formed in the upper end face of the workbench, an electric guide rail is fixed to the inner bottom of each first lower groove, and an electric sliding block is movably arranged on each electric guide rail; an electric push rod is fixed to the upper end face of each electric sliding block, an abutting assembly is arranged at the tail end of the telescopic end of each electric push rod, a positioning assembly used in cooperation with the abutting assemblies is arranged on the upper end face of the workbench, a hydraulic cylinder is fixedly arranged above the workbench, and a pressing die is fixed to the tail end of the telescopic end of the hydraulic cylinder. Two notches are symmetrically formed in the upper end face of the workbench, and a plurality of rotating rollers are rotationally arranged in each notch. When the battery cell conveying device is used, battery cells can be conveniently conveyed and placed.

Description

Technical Field

[0001] The invention relates to the technical field of lithium battery processing and production, in particular to a core pressing machine for lithium battery production. Background Art

[0002] The patent with application announcement number CN219066906U discloses a core pressing machine for lithium battery production, including: a first conveyor belt, which is arranged horizontally; a core pressing machine body, which is arranged on the output side of the first conveyor belt; and a second conveyor belt, which is arranged horizontally and the input side is located below the core pressing machine body; wherein the core pressing machine body includes: a bracket; a support plate, on which there is an openable and closable core pressing bottom plate; a plurality of movable buffer pad mechanisms, which are spaced apart from each other in the vertical direction and arranged horizontally in the middle section of the bracket, each of which can move up and down along the bracket and can be opened or closed in the horizontal direction; an upper pressure head mechanism, which is arranged at the top of the bracket and is located directly above the core pressing bottom plate. This scheme is provided with a plurality of movable buffer pad mechanisms, which can provide buffering effects on the upper and lower parts of the battery cells to be pressed, so that the surface force is evenly applied, and at the same time, the uppermost and lowermost battery cells can be protected.

[0003] The above-mentioned core pressing machine has certain defects during use. For example, the core pressing machine uses a first conveyor belt to transport the battery cells to be processed, and then receives the battery cells through a core pressing bottom plate. When the battery cells leave the first conveyor belt and fall onto the core pressing bottom plate, the battery cells are easily flipped and displaced due to the action of multiple buffer pad mechanisms, causing the battery cells to deviate from the correct pressing position, which causes problems in the transportation of the battery cells. Summary of the invention

[0004] The purpose of the present invention is to solve the problems existing in the prior art:

[0005] When the existing core pressing machine is in use, there are problems with the transportation of the battery cores.

[0006] The proposed core pressing machine for lithium battery production.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A core pressing machine for lithium battery production includes a workbench, wherein the upper end surface of the workbench is symmetrically provided with two lower grooves, an electric guide rail is fixed to the inner bottom of each lower groove, an electric slider is movably arranged on each electric guide rail, an electric push rod is fixed to the upper end surface of each electric slider, a resistance component is arranged at the end of the telescopic end of each electric push rod, a positioning component used in conjunction with the resistance component is arranged on the upper end surface of the workbench, a hydraulic cylinder is fixedly arranged above the workbench, a pressing die is fixed to the end of the telescopic end of the hydraulic cylinder, and two notches are symmetrically provided on the upper end surface of the workbench, and a plurality of rotating rollers are rotatably arranged in each notch.

[0009] As a further technical solution of the present invention, each of the resistance components includes a connecting plate, which is fixed to the end of the telescopic end of the corresponding electric push rod. The outer surface of each connecting plate is movably provided with a connecting sleeve, an elastic unit is arranged between the connecting sleeve and the connecting plate, and an anti-slip layer is fixed on the side of the connecting sleeve away from the connecting plate.

[0010] As a further technical solution of the present invention, each of the elastic units includes multiple springs, a side groove is opened at one end of the connecting sleeve close to the connecting plate, the connecting plate is movably arranged in the side groove, and the spring is fixed between the connecting plate and the inner wall of the side groove.

[0011] As a further technical solution of the present invention, guide seats are fixed on both sides of each electric push rod, and two guide rods are symmetrically fixed on one side of the connecting plate away from the connecting sleeve, and each guide rod movably passes through the guide seat.

[0012] As a further technical solution of the present invention, two limit sliding blocks are symmetrically fixed to the lower end surface of each electric push rod, and a plurality of limit sliding grooves used in conjunction with the limit sliding blocks are provided on the upper end surface of the workbench.

[0013] As a further technical solution of the present invention, a lower groove 2 is opened on the upper end surface of the workbench, a lifting block is movably arranged in the lower groove 2, a contact sensor 1 is fixed on the side of each connecting sleeve close to the lifting block, and a control box is arranged in the workbench.

[0014] As a further technical solution of the present invention, a cylinder is fixed to the inner bottom of the second lower groove, and the end of the telescopic end of the cylinder is fixedly connected to the lower end surface of the lifting block.

[0015] As a further technical solution of the present invention, a mounting top seat is arranged above the workbench, a plurality of support columns are fixed between the mounting top seat and the upper end surface of the workbench, and the hydraulic cylinder is fixedly passed through the mounting top seat.

[0016] As a further technical solution of the present invention, a connecting seat is fixed on one side of the die, a lifting rod is movably provided on the upper end surface of the connecting seat, mounting blocks are fixed on both sides of the lifting rod, two contact sensors are fixed on the upper end surface of each mounting block, and a buffer assembly is provided between the lifting rod and the connecting seat.

[0017] As a further technical solution of the present invention, the buffer assembly includes an upper top plate fixed to the upper end surface of the lifting rod, and two springs 2 are symmetrically fixed between the lower end surface of the upper top plate and the connecting seat.

[0018] Beneficial effects of the present invention:

[0019] 1. When in use, the processed battery cells are transported through the production line conveyor 1. When the battery cells leave the production line conveyor 1, they move to the surface of the rotating roller under the action of inertia. At this time, the telescopic ends of the two electric push rods extend, pushing the corresponding abutment components close to the battery cells until the two abutment components abut on both sides of the battery cells. Then the electric guide rail drives the electric slider to move, thereby driving the electric push rod, the abutment components and the battery cells to move (in this process, there is sliding friction between the battery cells and the upper end surface of the workbench). The abutment components are positioned by the provided positioning components. At this time, the electric slider stops moving, and then the telescopic ends of the two electric push rods retract. When the battery cell is located below the die, the telescopic end of the hydraulic cylinder extends to push the die to press the battery cell (the specific working principle is the prior art). After the pressing is completed, the telescopic end of the hydraulic cylinder contracts to drive the die to move upward to the initial position, and then the telescopic ends of the two electric push rods extend again to push the abutment assembly to abut against the side wall of the battery cell. Then the electric guide rail drives the electric slider to move again, thereby driving the battery cell to move. When it is almost moved to the end of the workbench, the telescopic ends of the two electric push rods contract. At this time, the battery cell slides horizontally to the surface of the second conveyor of the production line under the action of inertia force, and then the battery cell is transported and transferred, which is convenient to use.

[0020] 2. In the initial state, the telescopic end of the cylinder is in an extended state. At this time, the upper end of the lifting block extends from the lower groove 2. When the connecting sleeve moves with the battery cell, the contact sensor on the connecting sleeve will contact the side wall of the lifting block. At this time, the contact sensor sends an electrical signal, and the control box controls the electric slider to stop moving. When the telescopic end of the hydraulic cylinder extends and pushes the die to press the battery cell, the telescopic end of the cylinder contracts, driving the lifting block back to the lower groove 2 to avoid affecting the pressing of the battery cell and subsequent conveying and transfer. When the pressing is completed and the die moves upward, the control box controls the electric slider to continue moving, and the two connecting sleeves continue to move and transfer with the pressed battery cell. When the battery cell leaves the workbench, the electric slider returns to the initial position with the electric push rod and the connecting sleeve. At this time, the telescopic end of the cylinder extends again, pushing the lifting block upward, preparing to cooperate with the next round of processing, and the battery cell can be conveniently positioned. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0022] Figure 2 It is a schematic diagram of the connection between the electric slider and the electric push rod in the present invention;

[0023] Figure 3 It is a schematic diagram of the internal structure of the side groove in the present invention;

[0024] Figure 4 It is a schematic diagram of the connection between the electric push rod and the guide seat in the present invention;

[0025] Figure 5 It is a schematic diagram of the internal structure of the lower groove 2 in the present invention;

[0026] Figure 6 It is a schematic diagram of the connection between the pressing die and the connecting seat in the present invention.

[0027] In the figure: 1. workbench; 2. electric guide rail; 3. electric slider; 4. electric push rod; 5. hydraulic cylinder; 6. die; 7. missing groove; 8. rotating roller; 9. connecting plate; 10. connecting sleeve; 11. spring 1; 12. side groove; 13. guide seat; 14. guide rod; 15. limit slider; 16. limit slide groove; 17. lower groove 2; 18. lifting block; 19. contact sensor 1; 20. cylinder; 21. mounting top seat; 22. support column; 23. connecting seat; 24. lifting rod; 25. mounting block; 26. contact sensor 2; 27. upper top plate; 28. spring 2. DETAILED DESCRIPTION

[0028] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation mode, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0029] Reference Figure 1-Figure 6 A core pressing machine for lithium battery production comprises a workbench 1, the upper end surface of the workbench 1 is symmetrically provided with two lower grooves 1, an electric guide rail 2 is fixed to the inner bottom of each lower groove 1, an electric slider 3 is movably arranged on each electric guide rail 2, an electric push rod 4 is fixed to the upper end surface of each electric slider 3, a resistance component is arranged at the end of the telescopic end of each electric push rod 4, a positioning component used in conjunction with the resistance component is arranged on the upper end surface of the workbench 1, a hydraulic cylinder 5 is fixedly arranged above the workbench 1, a pressing die 6 is fixed to the end of the telescopic end of the hydraulic cylinder 5, two notches 7 are symmetrically provided on the upper end surface of the workbench 1, and a plurality of rotating rollers 8 are rotatably arranged in each notch 7.

[0030] A core pressing base can be provided on the workbench 1 as required to cooperate in pressing the battery core. The specific pressing principle is a conventional technical means in the art.

[0031] The core pressing machine is placed at one end of an external production line conveyor 1 (one end of the workbench 1 provided with an electric push rod 4 is connected to the end of the production line conveyor 1), and an external production line conveyor 2 is arranged on the other side of the core pressing machine. The production line conveyor 1 and the production line conveyor 2 rotate intermittently, and cooperate with the core pressing machine to press the lithium battery cells.

[0032] When in use, the processed battery cells are transported through the production line conveyor 1. When the battery cells leave the production line conveyor 1, they move to the surface of the rotating roller 8 under the action of inertia. At this time, the telescopic ends of the two electric push rods 4 extend, pushing the corresponding interference components close to the battery cells until the two interference components interfere with each other on both sides of the battery cells. Then the electric guide rail 2 drives the electric slider 3 to move, thereby driving the electric push rod 4, the interference component and the battery cells to move (in this process, there is sliding friction between the battery cells and the upper end surface of the workbench 1). The interference component is positioned by the provided positioning component. At this time, the electric slider 3 stops moving, and then the telescopic ends of the two electric push rods 4 contract. The core is located below the die 6, and then the telescopic end of the hydraulic cylinder 5 extends to push the die 6 to press the battery cell (the specific working principle is the prior art). After the pressing is completed, the telescopic end of the hydraulic cylinder 5 contracts to drive the die 6 to move upward to the initial position, and then the telescopic ends of the two electric push rods 4 extend again to push the abutment assembly to abut against the side wall of the battery cell, and then the electric guide rail 2 drives the electric slider 3 to move again, thereby driving the battery cell to move. When it is almost moved to the end of the workbench 1, the telescopic ends of the two electric push rods 4 contract. At this time, the battery cell slides horizontally to the surface of the second conveyor of the production line under the action of inertia, and then the battery cell is transported and transferred, which is convenient to use.

[0033] Each resistance assembly includes a connecting plate 9, which is fixed to the end of the telescopic end of the corresponding electric push rod 4. The outer surface of each connecting plate 9 is movably covered with a connecting sleeve 10, an elastic unit is arranged between the connecting sleeve 10 and the connecting plate 9, and an anti-slip layer is fixed to the side of the connecting sleeve 10 away from the connecting plate 9.

[0034] Each elastic unit includes a plurality of springs 11 . A side groove 12 is formed at one end of the connecting sleeve 10 close to the connecting plate 9 . The connecting plate 9 is movably arranged in the side groove 12 . The springs 11 are fixed between the connecting plate 9 and the inner wall of the side groove 12 .

[0035] When the telescopic end of the electric push rod 4 is extended, the connecting plate 9, the spring 11 and the connecting sleeve 10 are pushed close to the battery cell until the electric push rod 4 reaches the set extension amount. At this time, the battery cell is clamped between the two connecting sleeves 10 with anti-slip layers.

[0036] The spring 11 is provided to buffer the force when the connecting sleeve 10 contacts the battery cell, thereby avoiding deformation of the battery cell.

[0037] Guide seats 13 are fixed on both sides of each electric push rod 4 , and two guide rods 14 are symmetrically fixed on one side of the connecting plate 9 away from the connecting sleeve 10 , and each guide rod 14 movably passes through the guide seat 13 .

[0038] The cooperation between the guide seat 13 and the guide rod 14 can avoid the problem of shaking of the connecting plate 9 and the connecting sleeve 10 during use.

[0039] Two limit slide blocks 15 are symmetrically fixed to the lower end surface of each electric push rod 4 , and a plurality of limit slide grooves 16 used in conjunction with the limit slide blocks 15 are provided on the upper end surface of the workbench 1 .

[0040] The cooperation between the limiting sliding block 15 and the limiting sliding groove 16 can avoid the problem of shaking of the electric push rod 4 during the translation process.

[0041] A lower groove 17 is provided on the upper end surface of the workbench 1, and a lifting block 18 is movably provided in the lower groove 17. A contact sensor 19 is fixed on one side of each connecting sleeve 10 close to the lifting block 18. A control box is provided in the workbench 1. The control box is of prior art and is electrically connected to the contact sensor 19.

[0042] A cylinder 20 is fixed to the inner bottom of the lower groove 17 , and the end of the telescopic end of the cylinder 20 is fixedly connected to the lower end surface of the lifting block 18 .

[0043] In the initial state, the telescopic end of the cylinder 20 is in an extended state. At this time, the upper end of the lifting block 18 extends from the lower groove 17. When the connecting sleeve 10 moves with the battery cell, the contact sensor 19 on the connecting sleeve 10 will contact the side wall of the lifting block 18. At this time, the contact sensor 19 sends an electrical signal, and the control box controls the electric slider 3 to stop moving. When the telescopic end of the hydraulic cylinder 5 extends and pushes the die 6 to press the battery cell, the telescopic end of the cylinder 20 contracts, driving the lifting block 18 back to the lower groove 17 to avoid affecting the pressing of the battery cell and subsequent conveying and transfer. When the pressing is completed and the die 6 moves upward, the control box controls the electric slider 3 to continue to move, and the two connecting sleeves 10 continue to move and transfer with the pressed battery cell. When the battery cell leaves the workbench 1, the electric slider 3 returns to the initial position with the electric push rod 4 and the connecting sleeve 10. At this time, the telescopic end of the cylinder 20 extends again, pushing the lifting block 18 upward, preparing to cooperate with the next round of processing, and the battery cell can be conveniently positioned.

[0044] A mounting top seat 21 is arranged above the workbench 1 , a plurality of support columns 22 are fixed between the mounting top seat 21 and the upper end surface of the workbench 1 , and the hydraulic cylinder 5 is fixedly passed through the mounting top seat 21 .

[0045] A connecting seat 23 is fixed on one side of the die 6, and a lifting rod 24 is movably provided on the upper end surface of the connecting seat 23. Mounting blocks 25 are fixed on both sides of the lifting rod 24. A contact sensor 26 is fixed on the upper end surface of each mounting block 25. A buffer assembly is provided between the lifting rod 24 and the connecting seat 23.

[0046] The buffer assembly includes an upper top plate 27 fixed to the upper end surface of the lifting rod 24 , and two springs 28 are symmetrically fixed between the lower end surface of the upper top plate 27 and the connecting seat 23 .

[0047] When the telescopic end of the hydraulic cylinder 5 extends and pushes the die 6 to move downward, it will also drive the connecting seat 23, the lifting rod 24 and the mounting block 25 to move downward together. During this process, the lifting rod 24 will contact the upper end surface of the workbench 1. At this time, the telescopic end of the hydraulic cylinder 5 continues to extend, pushing the die 6 and the connecting seat 23 to continue to move downward until the contact sensor 2 26 on the upper end surface of the mounting block 25 hits the lower end surface of the connecting seat 23. At this time, the telescopic end of the hydraulic cylinder 5 no longer extends, and the die 6 has pressed the battery cell to a specified thickness (the sum of the heights of the mounting block 25 and the contact sensor 2 26 is the required thickness of the battery cell). Then the telescopic end of the hydraulic cylinder 5 contracts, driving the die 6 to move upward to the initial height.

[0048] When the present invention is in use, the core pressing machine is placed at one end of an external production line conveyor 1 (one end of the workbench 1 provided with an electric push rod 4 is connected to the end of the production line conveyor 1), and an external production line conveyor 2 is arranged on the other side of the core pressing machine. The production line conveyor 1 and the production line conveyor 2 rotate intermittently, and cooperate with the core pressing machine to press the lithium battery cell;

[0049] When in use, the processed battery cells are transported through the production line conveyor 1. When the battery cells leave the production line conveyor 1, they move to the surface of the rotating roller 8 under the action of inertia. At this time, the telescopic ends of the two electric push rods 4 extend, pushing the corresponding interference components close to the battery cells until the two interference components interfere with each other on both sides of the battery cells. Then the electric guide rail 2 drives the electric slider 3 to move, thereby driving the electric push rod 4, the interference component and the battery cells to move (in this process, there is sliding friction between the battery cells and the upper end surface of the workbench 1). The interference component is positioned by the provided positioning component. At this time, the electric slider 3 stops moving, and then the telescopic ends of the two electric push rods 4 contract. The core is located below the die 6, and then the telescopic end of the hydraulic cylinder 5 extends to push the die 6 to press the battery core (the specific working principle is the existing technology). After the pressing is completed, the telescopic end of the hydraulic cylinder 5 contracts, driving the die 6 to move upward to the initial position, and then the telescopic ends of the two electric push rods 4 extend again, pushing the abutment assembly to abut against the side wall of the battery core, and then the electric guide rail 2 drives the electric slider 3 to move again, thereby driving the battery core to move. When it is almost moved to the end of the workbench 1, the telescopic ends of the two electric push rods 4 contract. At this time, the battery core slides horizontally to the surface of the second conveyor of the production line under the action of inertia, and then the battery core is transported and transferred, which is convenient to use;

[0050] When the telescopic end of the electric push rod 4 is extended, the connecting plate 9, the spring 11 and the connecting sleeve 10 are pushed close to the battery cell until the electric push rod 4 reaches the set extension amount, at which time the battery cell is clamped between the two connecting sleeves 10 with anti-slip layers;

[0051] In the initial state, the telescopic end of the cylinder 20 is in an extended state. At this time, the upper end of the lifting block 18 extends from the lower groove 17. When the connecting sleeve 10 translates with the battery cell, the contact sensor 19 on the connecting sleeve 10 will contact the side wall of the lifting block 18. At this time, the contact sensor 19 sends an electrical signal, and the control box controls the electric slider 3 to stop moving. When the telescopic end of the hydraulic cylinder 5 extends and pushes the die 6 to press the battery cell, the telescopic end of the cylinder 20 contracts, driving the lifting block 18 back to the lower groove 17 to avoid affecting the pressing of the battery cell and subsequent conveying and transfer. When the pressing is completed and the die 6 moves upward, the control box controls the electric slider 3 to continue to move, and the two connecting sleeves 10 continue to move and transfer with the pressed battery cell. When the battery cell leaves the workbench 1, the electric slider 3 returns to the initial position with the electric push rod 4 and the connecting sleeve 10. At this time, the telescopic end of the cylinder 20 extends again, pushing the lifting block 18 upward, preparing to cooperate with the next round of processing, and the battery cell can be conveniently positioned.

[0052] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A core pressing machine for lithium battery production, comprising a workbench (1), characterized in that: The upper end surface of the workbench (1) is symmetrically provided with two lower grooves, the inner bottom of each lower groove is fixed with an electric guide rail (2), each electric guide rail (2) is movably provided with an electric slider (3), the upper end surface of each electric slider (3) is fixed with an electric push rod (4), the end of the telescopic end of each electric push rod (4) is provided with a resistance component, the upper end surface of the workbench (1) is provided with a positioning component used in conjunction with the resistance component, a hydraulic cylinder (5) is fixedly provided above the workbench (1), a die (6) is fixed at the end of the telescopic end of the hydraulic cylinder (5), and the upper end surface of the workbench (1) is symmetrically provided with two notches (7), and a plurality of rotating rollers (8) are rotatably provided in each notch (7).

2. The core pressing machine for lithium battery production according to claim 1, characterized in that: Each of the abutment components comprises a connecting plate (9), which is fixed to the end of the telescopic end of the corresponding electric push rod (4), and a connecting sleeve (10) is movably sleeved on the outer surface of each connecting plate (9), an elastic unit is arranged between the connecting sleeve (10) and the connecting plate (9), and an anti-slip layer is fixed on the side of the connecting sleeve (10) away from the connecting plate (9).

3. The core pressing machine for lithium battery production according to claim 2, characterized in that: Each of the elastic units comprises a plurality of springs (11); a side groove (12) is provided at one end of the connecting sleeve (10) close to the connecting plate (9); the connecting plate (9) is movably arranged in the side groove (12); and the springs (11) are fixed between the connecting plate (9) and the inner wall of the side groove (12).

4. The core pressing machine for lithium battery production according to claim 1, characterized in that: A guide seat (13) is fixed on both sides of each electric push rod (4), and two guide rods (14) are symmetrically fixed on one side of the connecting plate (9) away from the connecting sleeve (10), and each guide rod (14) movably passes through the guide seat (13).

5. The core pressing machine for lithium battery production according to claim 1, characterized in that: Two limit slide blocks (15) are symmetrically fixed on the lower end surface of each electric push rod (4), and a plurality of limit slide grooves (16) used in conjunction with the limit slide blocks (15) are provided on the upper end surface of the workbench (1).

6. The core pressing machine for lithium battery production according to claim 2, characterized in that: The upper end surface of the workbench (1) is provided with a lower groove 2 (17), a lifting block (18) is movably arranged in the lower groove 2 (17), a contact sensor 1 (19) is fixed on one side of each connecting sleeve (10) close to the lifting block (18), and a control box is arranged in the workbench (1).

7. The core pressing machine for lithium battery production according to claim 6, characterized in that: A cylinder (20) is fixed to the inner bottom of the second lower groove (17), and the end of the telescopic end of the cylinder (20) is fixedly connected to the lower end surface of the lifting stopper (18).

8. The core pressing machine for lithium battery production according to claim 1, characterized in that: A mounting top seat (21) is arranged above the workbench (1), a plurality of support columns (22) are fixed between the mounting top seat (21) and the upper end surface of the workbench (1), and a hydraulic cylinder (5) is fixedly passed through the mounting top seat (21).

9. The core pressing machine for lithium battery production according to claim 6, characterized in that: A connecting seat (23) is fixed on one side of the die (6); a lifting rod (24) is movably provided on the upper end surface of the connecting seat (23); mounting blocks (25) are fixed on both sides of the lifting rod (24); a contact sensor 2 (26) is fixed on the upper end surface of each mounting block (25); and a buffer assembly is provided between the lifting rod (24) and the connecting seat (23).

10. The core pressing machine for lithium battery production according to claim 9, characterized in that: The buffer assembly comprises an upper top plate (27) fixed to the upper end surface of the lifting rod (24), and two springs (28) are symmetrically fixed between the lower end surface of the upper top plate (27) and the connecting seat (23).

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