An automatic centering and gripping device

Abstract

The application provides an automatic centering and clamping device, and belongs to the technical field of clamping devices. The device comprises a fixed mounting seat, a horizontally extending floating guide assembly is arranged on the lower side of the fixed mounting seat, and a horizontal floating seat is slidably arranged on the lower side of the floating guide assembly. Two groups of clamping parts are slidably arranged on the lower side of the horizontal floating seat and are arranged in a horizontal interval. The clamping sides of the two groups of clamping parts are oppositely arranged. A clamping driving assembly is arranged on the horizontal floating seat and is in transmission connection with the two groups of clamping parts. Contact detection assemblies are arranged on the clamping sides of the two groups of clamping parts. A horizontal locking assembly is arranged between the fixed mounting seat and the horizontal floating seat. The horizontal locking assembly locks the horizontal floating seat when the two groups of contact detection assemblies are in a triggered state. The device is used for sliding the horizontal floating seat along the floating guide assembly, so that the two groups of clamping parts horizontally move when contacting the offset workpiece and adapt to the position of the workpiece. After the contact detection assemblies are triggered, the horizontal locking assembly locks the horizontal floating seat, so that the horizontal floating seat is prevented from continuously moving during the carrying.

Description

Technical Field

[0001] This invention belongs to the field of clamping device technology, and in particular to an automatic centering clamping device. Background Technology

[0002] Automatic clamping devices are mechanical actuators used to clamp, transport, or transfer workpieces. Their advantages include automatic clamping, position transfer, and coordination with production line operations. They are also applicable to fields such as automatic assembly, material handling, and workpiece loading and unloading.

[0003] However, at present, automatic clamping devices generally clamp the workpiece from both sides according to the preset clamping center. When there is a lateral deviation in the actual position of the workpiece, it is difficult for the clamping center to form and maintain a stable positional matching relationship with the workpiece. This can easily cause inconsistent contact between the clamping parts on both sides and the workpiece, which is not conducive to the stable clamping of the misaligned workpiece. Improvement is needed. Therefore, it is urgent to propose an automatic centering and clamping device to solve the above problems. Summary of the Invention

[0004] To address the shortcomings of the prior art, the present invention provides an automatic centering clamping device to solve the problem in the prior art that the clamping center is difficult to form and maintain a stable position match with the laterally offset workpiece, resulting in inconsistent contact states of the clamping parts on both sides.

[0005] To achieve the above objectives, the present invention provides the following technical solution: An automatic centering and clamping device includes a fixed mounting base, a laterally extending floating guide assembly on the lower side of the fixed mounting base, and a lateral floating seat slidably mounted on the lower side of the floating guide assembly; two sets of clamping portions arranged laterally at intervals are slidably mounted on the lower side of the lateral floating seat, with the clamping sides of the two sets of clamping portions facing each other; a clamping drive assembly is provided on the lateral floating seat, the clamping drive assembly being operatively connected to the two sets of clamping portions respectively, and each set of clamping portions has a contact detection assembly on its clamping side; a lateral locking assembly is provided between the fixed mounting base and the lateral floating seat, the lateral locking assembly locking the lateral floating seat when both sets of contact detection assemblies are in a triggered state.

[0006] In a further embodiment, the floating guide assembly includes two sets of linear guide rails arranged parallel to each other, both sets of linear guide rails being installed on the lower side of the fixed mounting base; the upper side of the transverse floating base is provided with multiple sets of guide rail sliders corresponding to the two sets of linear guide rails, and the multiple sets of guide rail sliders are slidably connected to the corresponding linear guide rails.

[0007] In a further embodiment, the clamping drive assembly includes a drive motor and a bidirectional lead screw. The bidirectional lead screw is rotatably disposed on the lower side of the transverse floating seat, and the drive motor is fixedly disposed on one side of the transverse floating seat. The output end of the drive motor is connected to one end of the bidirectional lead screw.

[0008] In a further embodiment, the bidirectional lead screw is provided with a first threaded section and a second threaded section with opposite directions of rotation; the two sets of clamping parts respectively include clamping sliders and jaws, the two sets of clamping sliders are respectively threadedly connected to the first threaded section and the second threaded section, and the two sets of jaws are respectively disposed on the lower side of the two sets of clamping sliders.

[0009] In a further embodiment, a sliding groove parallel to the bidirectional lead screw is provided on the lower side of the transverse floating seat, and the upper sides of the two sets of clamping sliders are slidably disposed in the sliding groove.

[0010] In a further embodiment, each group of contact detection components includes a sensor mounting base and a plunger-type contact sensor. The sensor mounting base is disposed on the side of the corresponding gripper away from its clamping surface, and the plunger-type contact sensor is disposed within the sensor mounting base. A plunger clearance hole is provided on the gripper, and the plunger head of the plunger-type contact sensor passes through the plunger clearance hole and protrudes from the gripper clamping surface.

[0011] In a further embodiment, the lateral locking assembly includes two sets of guide rail brakes, both sets of guide rail brakes are disposed on the upper side of the lateral floating seat and are respectively slidably engaged with the two sets of linear guide rails; both sets of guide rail brakes are laterally spaced from the corresponding guide rail sliders.

[0012] In a further embodiment, a fixed spring seat is provided on the lower side of the fixed mounting base at the positions on both sides of the transverse floating base, and a spring abutment is provided on both sides of the transverse floating base. A spring is clamped between the fixed spring seat and the corresponding spring abutment.

[0013] In a further embodiment, the lower side of the fixed mounting base is provided with limiting blocks on both sides of the transverse floating seat. The transverse floating seat is located between the two sets of limiting blocks, and the transverse floating seat has limiting surfaces on both sides that abut against the corresponding limiting blocks.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This device is equipped with a transverse floating seat, two sets of clamping parts, a contact detection component, and a transverse locking component. By utilizing the sliding cooperation between the transverse floating seat and the floating guide component, the two sets of clamping parts can move laterally with the transverse floating seat when they contact the workpiece that is misaligned, so that the clamping center can adapt to the actual position of the workpiece. At this time, the transverse locking component can fix the transverse floating seat by the locking action after both sets of contact detection components are triggered, so as to prevent the overall position from changing during clamping and handling.

[0015] 2. Simultaneously, this device uses a drive motor and a bidirectional lead screw to enable the two sets of clamping parts to move closer or further away synchronously, further ensuring that the forces on both sides of the workpiece are corresponding. Through the cooperation of the guide rail brake and the linear guide rail, the transverse floating seat is kept locked after centering, and the springs on both sides are used to make the transverse floating seat return to the initial position after the lock is released. The limit block limits its transverse movement range. The overall structure takes into account floating centering, synchronous clamping, position locking and reset limit. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the assembled structure of the present invention; Figure 2 This is a schematic diagram of the disassembled structure of the present invention; Figure 3 This is the front view of the present invention; Figure 4 This is a top view of the present invention; Figure 5 This is a cross-sectional view of the present invention; Figure 6 This is a top view of the horizontal floating seat of the present invention.

[0017] In the diagram, the correspondence between component names and drawing numbers is as follows: 11. Fixed mounting base; 12. Lateral floating seat; 13. Linear guide rail; 14. Guide rail slider; 15. Drive motor; 16. Two-way lead screw; 17. First threaded section; 18. Second threaded section; 19. Clamping slider; 21. Gripper; 22. Sliding groove; 23. Sensor mounting base; 24. Plunger-type contact sensor; 25. Plunger clearance hole; 26. Guide rail brake; 27. Fixed spring seat; 28. Spring abutment part; 29. ​​Spring; 31. Limit stop. Detailed Implementation

[0018] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the technical solutions of the present invention, but should not be used to limit the scope of protection of the present invention. Example

[0019] Please see Figure 1-6The present invention discloses an automatic centering and gripping device, comprising a fixed mounting base 11 and a transverse floating base 12 disposed below the fixed mounting base 11; the transverse direction referred to herein refers to the direction in which the two sets of gripping parts move closer or further apart from each other, and is also the direction in which the transverse floating base 12 moves relative to the fixed mounting base 11; the fixed mounting base 11 is used to connect with a robotic arm, a lifting module or a transfer mechanism, and the transverse floating base 12 is used to jointly support the gripping drive assembly, the two sets of gripping parts, the two sets of contact detection assemblies and the transverse locking assembly.

[0020] The two sets of clamping parts are installed on the same transverse floating seat 12. When the transverse floating seat 12 moves laterally relative to the fixed mounting seat 11, the clamping drive assembly, the two sets of clamping parts and the corresponding contact detection assembly all move together with the transverse floating seat 12. The relative opening and closing relationship between the two sets of clamping parts does not change, thereby avoiding the instability of the clamping center caused by the two sets of clamping parts floating separately.

[0021] A floating guide assembly is provided on the lower side of the fixed mounting base 11. The floating guide assembly includes two sets of linear guide rails 13 arranged parallel to each other. The two sets of linear guide rails 13 are installed laterally on a common reference surface on the lower side of the fixed mounting base 11 and are spaced apart from each other. Multiple sets of guide rail sliders 14 corresponding to the two sets of linear guide rails 13 are fixedly provided on the upper side of the transverse floating base 12. The multiple sets of guide rail sliders 14 are slidably connected to the corresponding linear guide rails 13, so that the transverse floating base 12 can be translated laterally relative to the fixed mounting base 11. The distance between the two sets of linear guide rails 13 can provide distributed support for the transverse floating base 12 to withstand the deflection effect generated by the clamping structure below.

[0022] The transverse floating seat 12 can be an integral plate or a rigid frame structure. Its upper side is used to connect the guide rail slider 14 and the guide rail brake 26, and its lower side is used to install the clamping drive assembly and two sets of clamping parts. Since the drive motor 15, the bidirectional lead screw 16, the two sets of clamping sliders 19 and the two sets of grippers 21 are all mounted on the transverse floating seat 12, the above structures move synchronously when the transverse floating seat 12 moves, and the transmission relationship between the drive motor 15 and the bidirectional lead screw 16 will not be affected. In specific implementations, the cables of the drive motor 15, the signal cables of the plunger-type contact sensor 24 and the control cables or air pipes of the guide rail brake 26 should be reserved with a movement margin corresponding to the transverse floating stroke.

[0023] It should be noted that the drive motor 15 can be a Leadshine 42CM06 miniature short-body closed-loop drive motor to stably drive the two sets of clamping sliders 19 to move synchronously in opposite directions; the plunger contact sensor 24 can be a Medtronic CSP087A-BU-5 plunger direct-entry contact sensor to perform high-precision contact detection of the stroke position of the clamping slider 19, so as to realize the confirmation of the clamping position of the gripper 21 and the limit stroke protection.

[0024] The clamping drive assembly includes a drive motor 15 and a bidirectional lead screw 16. The drive motor 15 is fixedly mounted on one side of the transverse floating seat 12, and the bidirectional lead screw 16 is rotatably mounted on the lower side of the transverse floating seat 12. Both ends of the bidirectional lead screw 16 can be connected to the transverse floating seat 12 through lead screw support seats and bearings, and the output end of the drive motor 15 can be connected to one end of the bidirectional lead screw 16 through a coupling.

[0025] The bidirectional lead screw 16 is provided with a first threaded section 17 and a second threaded section 18 with opposite directions of rotation; the two sets of clamping parts include clamping sliders 19 and jaws 21 respectively. The two sets of clamping sliders 19 are threadedly connected to the first threaded section 17 and the second threaded section 18 respectively. The two sets of jaws 21 are fixed on the lower side of the corresponding clamping sliders 19 respectively, and the clamping surfaces of the two sets of jaws 21 are arranged facing each other; when the drive motor 15 drives the bidirectional lead screw 16 to rotate, the two sets of clamping sliders 19 move closer or further away at the same time, thereby driving the two sets of jaws 21 to complete the action.

[0026] The lower side of the transverse floating seat 12 is provided with a sliding groove 22 parallel to the bidirectional lead screw 16, and the upper sides of the two sets of clamping sliders 19 are slidably disposed in the sliding groove 22; the sliding groove 22 is used to restrict the clamping sliders 19 from rotating with the bidirectional lead screw 16, so that the clamping sliders 19 can only move laterally; in this embodiment, the clamping surface of the gripper 21 can adopt a planar structure adapted to the side of the workpiece.

[0027] Each contact detection assembly includes a sensor mounting base 23 and a plunger-type contact sensor 24. The sensor mounting base 23 is fixed on the side of the corresponding gripper 21 away from its clamping surface, and the sensor body of the plunger-type contact sensor 24 is installed in the sensor mounting base 23. A plunger clearance hole 25 is provided on the gripper 21. The plunger clearance hole 25 is only used for the plunger head of the plunger-type contact sensor 24 to pass through and retract. The plunger head protrudes from the clamping surface of the gripper 21 in the initial state.

[0028] When the gripper 21 approaches the workpiece, the plunger head first contacts the side of the workpiece. After being pressed, the plunger head retracts into the plunger-type contact sensor 24 and outputs a contact signal. After the plunger head continues to retract, the clamping surface of the gripper 21 contacts the side of the workpiece, and the actual clamping force is borne by the gripper 21 body. The plunger-type contact sensor 24 is not used to bear clamping force for a long time. The two sets of plunger heads should be set at the position where the two sets of grippers 21 first contact the workpiece to avoid the edge of the gripper 21 or the sensor mounting base 23 contacting the workpiece before the plunger head.

[0029] The lateral locking assembly includes two sets of guide rail brakes 26, both of which are fixed on the upper side of the lateral floating seat 12 and slide in cooperation with two sets of linear guide rails 13 respectively; each set of guide rail brakes 26 and the corresponding guide rail slider 14 are arranged laterally at intervals, the guide rail slider 14 is used for sliding guidance, and the guide rail brake 26 is used for position locking.

[0030] When the guide rail brake 26 is in the released state, its internal braking part releases the clamping of the linear guide rail 13, allowing the transverse floating seat 12 to move along the linear guide rail 13; when the guide rail brake 26 is in the locked state, its internal braking part clamps the linear guide rail 13, keeping the transverse floating seat 12 in its current transverse position; the two sets of guide rail brakes 26 act synchronously, jointly locking the same transverse floating seat 12.

[0031] In practical implementation, this device can be connected to an external control unit; two sets of plunger-type contact sensors 24 output contact signals to the external control unit respectively, and the external control unit controls the two sets of guide rail brakes 26 to switch synchronously according to the two sets of signals; when only one set of plunger-type contact sensors 24 is triggered, both sets of guide rail brakes 26 continue to remain in the released state; when both sets of plunger-type contact sensors 24 are triggered, the external control unit controls the two sets of guide rail brakes 26 to lock synchronously; the plunger-type contact sensors 24 do not directly control the single-sided guide rail brake 26.

[0032] Fixed spring seats 27 are provided on the lower side of the fixed mounting base 11 at the positions on both sides of the transverse floating base 12. Spring abutment portions 28 are provided on both sides of the transverse floating base 12. Springs 29 are respectively sandwiched between the fixed spring seats 27 and the corresponding spring abutment portions 28. In this embodiment, the springs 29 are compression springs. When the transverse floating base 12 is located in the transverse middle of the fixed mounting base 11, both sets of springs 29 have a preload.

[0033] When the transverse floating seat 12 moves to one side, the compression of the spring 29 on that side increases, and the compression of the spring 29 on the other side decreases. Within the allowable range of movement of the transverse floating seat 12, the spring 29 on the side with reduced compression still remains in contact with the fixed spring seat 27 and the spring abutment 28. The two sets of springs 29 are used to return the transverse floating seat 12 to the middle position after the guide rail brake 26 is released, and are not used to maintain the position of the transverse floating seat 12 during workpiece handling.

[0034] Limiting blocks 31 are also provided on the lower side of the fixed mounting base 11, located on both sides of the transverse floating base 12. The transverse floating base 12 is located between the two sets of limiting blocks 31, and its transverse sides form limiting surfaces that abut against the corresponding limiting blocks 31. When the transverse floating base 12 moves to the maximum allowable position, the corresponding limiting surface abuts against the limiting block 31, thereby restricting the transverse floating base 12 from continuing to move and preventing the guide rail slider 14 from overtravel, the spring 29 from disengaging, and the cable or air pipe from being excessively stretched. The fixed spring seat 27 and the limiting blocks 31 can be staggered in the front-back direction.

[0035] When this device performs floating centering, taking the workpiece shifting to one side as an example, the plunger head on the set of jaws 21 closest to the workpiece first contacts the workpiece, and the workpiece generates a reaction force on the jaws 21; this reaction force is transmitted to the transverse floating seat 12 through the jaws 21, the clamping sliders 19, the threaded engagement position of the bidirectional lead screw 16, the lead screw support structure, and the sliding groove 22; since the guide rail brake 26 is in the released state at this time, the transverse floating seat 12 can move along the linear guide rail 13 in the direction of workpiece shift, and the other set of jaws 21 moves closer to the workpiece as a whole with the transverse floating seat 12, while the two sets of clamping sliders 19 continue to move towards each other until the other set of plunger-type contact sensors 24 is also triggered.

[0036] To ensure that the lateral floating seat 12 moves preferentially rather than pushing the workpiece laterally, the resistance that the lateral floating seat 12 needs to overcome to move along the linear guide rail 13 and the differential force generated by the two sets of springs 29 should be less than the force required to push the workpiece laterally. This device is more suitable for workstations where the workpiece has pallet limiting, bearing friction, or lateral constraints. When the workpiece is freely placed on a low-friction bearing surface, the output torque of the drive motor 15 during the centering stage can be reduced to decrease the situation where the gripper 21 pushes the workpiece.

[0037] The working principle of this invention is: In this embodiment, during operation, in the initial state, the two sets of clamping parts are open, the transverse floating seat 12 is located in the transverse middle of the fixed mounting seat 11, and the two sets of guide rail brakes 26 are in a locked state; the device is driven to the workpiece by a robotic arm, lifting module or transfer mechanism, and then lowered to the clamping position.

[0038] After reaching the clamping position, the two sets of guide rail brakes 26 are simultaneously released, and the transverse floating seat 12 enters a state where it can move laterally; the drive motor 15 drives the bidirectional lead screw 16 to rotate, and the two sets of clamping sliders 19 move closer to each other, causing the two sets of grippers 21 to move to both sides of the workpiece.

[0039] When the workpiece is laterally offset, the plunger head on the side closest to the workpiece contacts the workpiece first, and the corresponding plunger contact sensor 24 outputs a contact signal; at this time, the other set of plunger contact sensors 24 has not yet been triggered, and the guide rail brake 26 continues to remain in the released state; after the set of grippers 21 that first contacts the workpiece is subjected to the reaction force, the lateral floating seat 12 moves in the direction of workpiece offset until the other set of plunger heads also contacts the workpiece.

[0040] When both sets of plunger-type contact sensors 24 are in the triggered state, the two sets of guide rail brakes 26 simultaneously clamp the two sets of linear guide rails 13, locking the transverse floating seat 12 at the current offset position; then the drive motor 15 continues to drive the two sets of clamping sliders 19 to move closer, the plunger head further retracts, and the clamping surfaces of the two sets of grippers 21 clamp the two sides of the workpiece respectively; after clamping is completed, the device moves up and transports the workpiece, and the guide rail brakes 26 remain locked during the transport process.

[0041] During material feeding, the guide rail brake 26 remains locked, and the drive motor 15 drives the two sets of grippers 21 to open and completely detach from the workpiece; then the two sets of guide rail brakes 26 are released, and the two sets of springs 29 push the transverse floating seat 12 back to the center position; after the transverse floating seat 12 returns to the center, the guide rail brake 26 is locked again, so that the device returns to the initial state.

[0042] In practice, the drive motor 15 can use a lower output torque during the floating centering phase. After both sets of contact detection components are triggered and the transverse floating seat 12 is locked, the output torque is increased to complete the formal clamping. This control method does not require additional mechanical switching components.

[0043] This device is suitable for situations where the lateral offset of the workpiece is within the allowable movement range of the lateral floating seat 12 and the width of the workpiece is within the opening and closing stroke range of the two sets of clamping parts. This device mainly compensates for the lateral translation deviation of the workpiece and cannot rely on the existing structure to compensate for the workpiece's angular deviation, vertical height deviation, or lateral offset exceeding the limit range of the limit stop 31.

[0044] With the above structure, the two sets of clamping parts move together with the transverse floating seat 12; when one side of the clamping jaw 21 contacts the misaligned workpiece first, the transverse floating seat 12 moves in the direction of workpiece offset under the reaction force; after both sets of contact detection components are triggered, the guide rail brake 26 locks the transverse floating seat 12, and then the two sets of clamping jaws 21 complete the formal clamping; thus, the device can first adapt to the actual transverse position of the workpiece, and then maintain the clamping position after centering for transportation.

[0045] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

Claims

1. An automatic centering and clamping device, comprising a fixed mounting base (11), characterized in that: The fixed mounting base (11) is provided with a horizontally extending floating guide assembly on its lower side, and a horizontal floating seat (12) is slidably provided on the lower side of the floating guide assembly; two sets of clamping parts are slidably provided on the lower side of the horizontal floating seat (12) and are arranged at a horizontal interval, with the clamping sides of the two sets of clamping parts facing each other; a clamping drive assembly is provided on the horizontal floating seat (12), and the clamping drive assembly is respectively connected to the two sets of clamping parts, and a contact detection assembly is provided on the clamping side of the two sets of clamping parts; a horizontal locking assembly is provided between the fixed mounting base (11) and the horizontal floating seat (12), and the horizontal locking assembly locks the horizontal floating seat (12) when both sets of contact detection assemblies are in the triggered state.

2. The automatic centering and gripping device according to claim 1, characterized in that: The floating guide assembly includes two sets of parallel linear guide rails (13), both sets of linear guide rails (13) are mounted on the lower side of the fixed mounting base (11); the upper side of the transverse floating base (12) is provided with multiple sets of guide rail sliders (14) corresponding to the two sets of linear guide rails (13), and the multiple sets of guide rail sliders (14) are slidably connected to the corresponding linear guide rails (13).

3. The automatic centering and gripping device according to claim 1, characterized in that: The clamping drive assembly includes a drive motor (15) and a bidirectional lead screw (16). The bidirectional lead screw (16) is rotatably disposed on the lower side of the transverse floating seat (12). The drive motor (15) is fixedly disposed on one side of the transverse floating seat (12), and the output end of the drive motor (15) is connected to one end of the bidirectional lead screw (16) for transmission.

4. The automatic centering and gripping device according to claim 3, characterized in that: The bidirectional lead screw (16) is provided with a first threaded section (17) and a second threaded section (18) with opposite directions of rotation; the two sets of clamping parts include clamping sliders (19) and jaws (21), the two sets of clamping sliders (19) are threadedly connected to the first threaded section (17) and the second threaded section (18) respectively, and the two sets of jaws (21) are respectively arranged on the lower side of the two sets of clamping sliders (19).

5. An automatic centering and gripping device according to claim 4, characterized in that: The lower side of the transverse floating seat (12) is provided with a sliding groove (22) parallel to the bidirectional lead screw (16), and the upper sides of the two sets of clamping sliders (19) are slidably disposed in the sliding groove (22).

6. The automatic centering and gripping device according to claim 4, characterized in that: Each of the contact detection components includes a sensor mounting base (23) and a plunger-type contact sensor (24). The sensor mounting base (23) is located on the side of the corresponding gripper (21) away from its clamping surface. The plunger-type contact sensor (24) is located inside the sensor mounting base (23). A plunger clearance hole (25) is provided on the gripper (21). The plunger head of the plunger-type contact sensor (24) passes through the plunger clearance hole (25) and protrudes from the clamping surface of the gripper (21).

7. An automatic centering and gripping device according to claim 2, characterized in that: The lateral locking assembly includes two sets of guide rail brakes (26), both sets of guide rail brakes (26) are disposed on the upper side of the lateral floating seat (12) and are respectively slidably engaged with the two sets of linear guide rails (13); both sets of guide rail brakes (26) are arranged laterally at intervals with the corresponding guide rail sliders (14).

8. The automatic centering and gripping device according to claim 1, characterized in that: Fixed spring seats (27) are provided on the lower side of the fixed mounting base (11) at the positions on both sides of the transverse floating base (12). Spring abutment portions (28) are provided on both sides of the transverse floating base (12). Springs (29) are clamped between the fixed spring seats (27) and the corresponding spring abutment portions (28).

9. An automatic centering and gripping device according to claim 1, characterized in that: The fixed mounting base (11) is provided with limiting blocks (31) on the lower side of the horizontal floating base (12) on both sides. The horizontal floating base (12) is located between the two sets of limiting blocks (31), and the horizontal floating base (12) has limiting surfaces that abut against the corresponding limiting blocks (31) on both sides.

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