Locking device of traction seat for semitrailer and using method of locking device

Abstract

The invention relates to the field of semitrailer traction seats, in particular to a locking device of a traction seat for a semitrailer and a use method of the locking device, and aims to solve the problems that automatic compensation is performed by utilizing an inclined plane or wedge-shaped principle, but the structure is generally simple, the compensation force is limited, and a mechanism for automatically converting into a rigid locking state after a gap is eliminated is lacked. According to a traditional rigid adjusting mode, clamping stagnation is easily generated at the adjusting tail section due to part machining errors or poor centering, operation is strenuous, and a new gap generated due to abrasion in the using process cannot be compensated. In the pre-tightening stage, the balls allow elastic receding, after the switching part acts and the elastic pre-tightening force is relieved, the push block body is locked, at the moment, the balls make contact with the end face of the wedge-shaped sliding block in an approximately rigid mode, and therefore switching from an elastic adjustable working mode to a gapless rigid working mode is achieved.

Description

Technical Field

[0001] This invention relates to the field of semi-trailer towing seats, specifically to a locking device for a semi-trailer towing seat and its usage method. Background Technology

[0002] The traction seat, also known as the "saddle," is the core component connecting the semi-trailer and the tractor unit for load transfer. It couples with the towing pin mounted on the semi-trailer via a locking device, forming a hinged connection. The performance of the locking device directly affects the safety, smoothness, and service life of the train. Currently, mainstream traction seat locking mechanisms typically include a rotatable locking hook (or locking tongue). When the towing pin slides into the saddle's positioning hole, the locking hook rotates under the action of a spring or manual lever, engaging the neck of the towing pin to achieve initial locking.

[0003] In practical applications, due to manufacturing tolerances of components, wear caused by long-term use, and slight differences in the size of the traction pin, an unavoidable assembly gap often exists between the meshing surfaces of the locking hook and the traction pin neck after initial locking. This small residual gap can cause impact at the connection point when the vehicle starts or travels on bumpy roads, and may also cause slight relative movement at the hinge point, reducing the rigidity of the connection.

[0004] The following problems exist in the existing technology and have not been adequately resolved:

[0005] 1. Currently, fine-tuning is achieved by setting an adjustable shim on the back of the locking hook or by directly pushing the locking hook with a bolt. However, these methods are cumbersome to adjust and lack holding force after adjustment, making them prone to loosening under vibration.

[0006] 2. There are also automatic compensation methods that use inclined planes or wedges, but these are usually simple in structure, have limited compensation force, and often lack a mechanism to automatically switch to a rigid locking state after eliminating the gap. Traditional rigid adjustment methods are prone to jamming at the end of the adjustment due to part machining errors or poor alignment, which is laborious to operate and cannot compensate for new gaps caused by wear during use. Summary of the Invention

[0007] The purpose of this invention is to provide a locking device for a semi-trailer towing seat and its usage method, to solve the problems mentioned in the background art. To achieve the above objective, this invention provides the following technical solution: A locking device for a semi-trailer towing seat, comprising a saddle, the saddle mainly including a guide connecting unit and a locking unit, a traction adjustment component disposed in the locking unit, the traction adjustment component including an adjusting screw disposed on the side wall of the saddle, and a wedge-shaped slider disposed inside the saddle, the working inclined surface of the wedge-shaped slider cooperating with the corresponding inclined surface on the back of the locking hook, the axial rotational motion of the adjusting screw is converted into the linear displacement of the wedge-shaped slider by the adjusting screw and the wedge-shaped slider, driving the locking hook to produce lateral fine-tuning motion, thereby precisely changing the engagement gap between the locking hook and the neck of the towing pin.

[0008] Preferably, the end of the adjusting screw facing the wedge-shaped slider is connected to a thrust transmission component, which keeps in contact with the end face of the wedge-shaped slider. The thrust transmission component reduces sliding friction during adjustment to ensure smooth operation.

[0009] Preferably, the thrust transmission component includes a drive seat connected to the end of the adjusting screw and sliding along the screw axis. A thrust transmission block is fixedly connected to one end of the drive seat facing the wedge-shaped slider. A guide cavity is provided inside the thrust transmission block, and a push block body is radially slidably disposed in the guide cavity.

[0010] Preferably, the end face of the push block facing the wedge-shaped slider is fitted with, but not limited to, a ball bearing to form rolling friction with the end face of the wedge-shaped slider. The other end face of the push block is an inclined surface, which together with the inner wall of the guide cavity defines a V-shaped cross-sectional groove. A transfer steel ball that can roll freely in the cross-sectional groove is provided.

[0011] Preferably, the drive seat is further provided with an elastic pressure applying part, which continuously applies radial pressure to the transmission steel ball, so that it is pressed tightly against the inclined surface of the V-groove.

[0012] Preferably, the elastic pressure application part includes two guide columns fixedly installed on the drive seat, each guide column is slidably fitted with an adjusting slider, and the adjusting slider is provided with a positioning slot.

[0013] Preferably, a pressure transmission rod extends downward from the bottom of one of the adjusting sliders, the end of which contacts the transmission steel ball to apply radial pressure thereon. A mounting shaft is also fixedly mounted on the drive seat, and a main adjusting lever and a switching lever are respectively hinged on the mounting shaft.

[0014] Preferably, the main adjusting lever has guide grooves corresponding to the positions of the two adjusting sliders, and a transmission link is slidably arranged in each guide groove. The transmission link extends toward the positioning groove of the adjusting slider and can cause the adjusting slider to move radially along the guide column under the drive of the transmission link.

[0015] Preferably, a tension spring is also connected between the main adjusting lever and the switching lever. Under normal conditions, the tension spring drives the switching lever to deflect toward the adjusting slider on the side where the pressure transmission rod is provided, and drives the main adjusting lever to rotate synchronously.

[0016] Preferably, the drive base is further provided with a switching part, the switching part including a switching plate that is slidably mounted on the drive base in the longitudinal direction, the end of the adjusting screw is connected to a linkage block, and the linkage block is provided with a guide roller.

[0017] Preferably, the switching plate is machined with an inclined curved guide groove, the guide roller is embedded in the curved guide groove and can roll along it, and two wedge-shaped trigger blocks are also fixedly arranged on the switching plate, and two trigger rods are staggered on the switching swing arm, the two wedge-shaped trigger blocks correspond to the positions of the two trigger rods on the switching swing arm respectively, and interact with each other under the deflection stroke of the switching swing arm.

[0018] Preferably, the method of using the locking device for the towing seat of a semi-trailer includes the following steps:

[0019] S1. After the traction pin is guided and seated by the guide connection unit, the locking unit drives the locking hook to complete the initial locking;

[0020] S2. Rotate the adjusting screw to drive the wedge slider to move through the thrust transmission component, so that the locking hook is tightened laterally and the assembly gap with the traction pin is eliminated;

[0021] S3. During the gap elimination process, the elastic pressure application part applies an elastic preload to the push block by transmitting the steel ball, allowing radial retraction and avoiding jamming;

[0022] S4. After the gap is completely eliminated, the adjusting screw continues to rotate to trigger the switching unit to operate;

[0023] S5. The switching part releases the elastic preload, so that the push block and the wedge slider become a rigid and stable contact. In subsequent traction operations, the connection is in a firmly locked state without elasticity.

[0024] S6. When it is necessary to loosen, rotate the adjusting screw in the opposite direction to reset the switching part and rebuild the preload, in preparation for the next adjustment.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] In this invention, during the pre-tightening stage, the push block makes point contact with the wedge slider through the ball bearings, and the rear end has adaptive floating support from the cross-sectional groove and steel ball. This allows the push block to move slightly adaptively within a certain angle to compensate for the non-parallelism or slight tilt of the wedge slider end face. This not only avoids jamming but also achieves automatic self-alignment and uniform pressure distribution, ensuring the effective and stable transmission of pre-tightening force.

[0027] In this invention, during the pre-tightening stage, the ball is allowed to elastically retract. When the switching part moves and the elastic pre-tightening force is released, the push block is locked. At this time, the ball and the end face of the wedge slider become approximately rigidly contacted, thereby realizing the switching from an elastically adjustable to a backlash-free rigid working mode. Attached Figure Description

[0028] Figure 1 This is a three-dimensional structural diagram of the saddle in the traction seat locking device of the present invention;

[0029] Figure 2 for Figure 1 Top view of the internal structure of the middle saddle;

[0030] Figure 3 This is a three-dimensional structural diagram of the internal structure of the saddle in this invention;

[0031] Figure 4 This is a three-dimensional structural diagram of the traction adjustment component in this invention;

[0032] Figure 5 This is a three-dimensional structural diagram of the wedge-shaped slider and the thrust transmission component in this invention;

[0033] Figure 6 This is a side view of the thrust transmission component in this invention;

[0034] Figure 7 This is a three-dimensional cross-sectional view of the thrust transmission component in this invention;

[0035] Figure 8 This is a cross-sectional view of the thrust transmission component in this invention;

[0036] Figure 9 This is a front view of the elastic pressure application part in the present invention;

[0037] Figure 10 A perspective view of the elastic pressure applying part in its first working state (applying preload);

[0038] Figure 11 A perspective view of the elastic pressure application part in its second working state (releasing preload);

[0039] Figure 12 This is a partial three-dimensional structural diagram of the switching part in this invention.

[0040] In the diagram: 1. Saddle; 11. Guide connection unit; 12. Locking unit; 2. Traction adjustment assembly; 21. Adjusting screw; 22. Wedge slider; 3. Thrust transmission component; 31. Drive seat; 32. Thrust transmission block; 33. Guide cavity; 34. Push block body; 35. Ball bearing; 36. Section groove; 37. Transmission steel ball; 4. Elastic pressure application part; 41. Guide column; 42. Adjusting slider; 43. Positioning slot; 44. Pressure transmission rod; 45. Mounting shaft; 46. Main adjusting rocker arm; 47. Guide slide; 48. Transmission link; 49. Switching rocker arm; 410. Tension spring; 5. Switching part; 51. Switching plate; 52. Linkage block; 53. Guide roller; 54. Curved guide groove; 55. Wedge trigger block; 56. Trigger rod. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Example 1

[0043] Please see Figures 1 to 12 The present invention provides a technical solution: a locking device for a semi-trailer traction seat, including a traction adjustment component 2, which is suitable for actively eliminating the assembly gap between the locking hook and the traction pin after the initial locking is completed, thereby improving the connection rigidity and stability.

[0044] For example, the traction adjustment component 2 can be integrated into the saddle 1. The saddle 1 mainly includes a guide connection unit 11 and a locking unit 12. The traction adjustment component 2 is set in the locking unit 12. The guide connection unit 11 is used to guide the traction pin to slide into the center positioning hole of the saddle 1 along the guide rail. When the traction pin is in place and sits stably, its neck is exactly in the locking position of the locking hook, and the locking unit 12 completes the locking.

[0045] Specifically, in order to adjust the engagement gap between the traction pin and the locking hook after locking, the traction adjustment assembly 2 includes an adjustment screw 21 disposed on the side wall of the saddle 1. The saddle 1 is also provided with a wedge-shaped slider 22. The working inclined surface of the wedge-shaped slider 22 cooperates with the corresponding inclined surface on the back of the locking hook. By adjusting the screw 21 and the wedge-shaped slider 22, the axial rotational motion of the adjustment screw 21 is converted into the linear displacement of the wedge-shaped slider 22, driving the locking hook to produce a lateral fine-tuning motion, thereby precisely changing the engagement gap between the locking hook and the neck of the traction pin.

[0046] The end of the adjusting screw 21 facing the wedge slider 22 is connected to a thrust transmission component 3. The thrust transmission component 3 keeps in contact with the end face of the wedge slider 22. The thrust transmission component 3 reduces sliding friction during the adjustment process to ensure smooth operation. After eliminating the gap, it achieves rigid contact with the wedge slider 22.

[0047] After the locking hook and the traction pin are initially locked, the operator rotates the adjusting screw 21. The axial feed of the adjusting screw 21 pushes the wedge slider 22 to move in the set direction through the thrust transmission component 3. The inclined surface of the wedge slider 22 interacts with the inclined surface on the back of the locking hook, converting the linear motion of the slider into a lateral tightening displacement of the locking hook perpendicular to the axis of the traction pin. Through fine adjustment, the remaining gap between the locking hook and the traction pin caused by manufacturing tolerances and component wear is actively eliminated, so that the two form a tight, gapless fit.

[0048] In this embodiment, the thrust transmission component 3 includes a drive seat 31 connected to the end of the adjusting screw 21 and sliding along the screw axis. A thrust transmission block 32 is fixedly connected to one end of the drive seat 31 facing the wedge-shaped slider 22. A guide cavity 33 is opened inside the thrust transmission block 32, and a push block body 34 is radially slidably arranged inside the guide cavity 33.

[0049] The push block 34 has a ball 35 embedded on its end face facing the wedge slider 22 to form rolling friction with the end face of the wedge slider 22. The other end face of the push block 34 is an inclined surface. The inclined surface and the inner wall of the guide cavity 33 together define a V-shaped cross-sectional groove 36. A transfer steel ball 37 that can roll freely in the cross-sectional groove 36 is provided in the cross-sectional groove 36.

[0050] The drive seat 31 is also provided with an elastic pressure application part 4, which continuously applies radial pressure to the transmission steel ball 37, so that it is pressed tightly against the inclined surface of the V-shaped groove.

[0051] When the rotating adjusting screw 21 drives the sliding seat forward, the thrust is transmitted to the wedge slider 22 through the push block 34 inside the thrust transmission block 32. The ball 35 at the front end of the push block 34 contacts the end face of the wedge slider 22 for rolling friction, which reduces the frictional resistance during the movement of the adjusting wedge slider 22 and makes the adjustment action easy and smooth.

[0052] During this process, the elastic pressure application part 4 applies an elastic preload to the push block 34 through the transmission steel ball 37. When the wedge slider 22 is slightly skewed or has movement resistance due to manufacturing errors or uneven surface, the push block 34 can produce radial elastic relief under the cooperation of the cross-sectional groove 36 and the transmission steel ball 37, avoiding rigid jamming and eliminating the backlash phenomenon caused by wear at the end of the adjusting screw 21 or the end of the wedge slider 22 in traditional rigid connections.

[0053] In this embodiment, the elastic pressure application part 4 includes two guide columns 41 fixedly installed on the drive seat 31. Each guide column 41 is slidably fitted with an adjustment slider 42, and the adjustment slider 42 is provided with a positioning slot 43.

[0054] One of the adjusting sliders 42 extends downward from its bottom to form a pressure transmission rod 44. The end of the pressure transmission rod 44 contacts the transmission steel ball 37 to apply radial pressure to it. The drive seat 31 is also fixedly provided with a mounting shaft 45, on which a main adjusting lever 46 and a switching lever 49 are respectively hinged.

[0055] The main adjusting lever 46 is provided with guide grooves 47 corresponding to the positions of the two adjusting sliders 42. A transmission link 48 is slidably arranged in each guide groove 47. The transmission link 48 extends toward the positioning slot 43 of the adjusting slider 42 and can cause the adjusting slider 42 to move radially along the guide post 41 under the drive of the transmission link 48.

[0056] A tension spring 410 is also connected between the main adjusting lever 46 and the switching lever 49. Under normal conditions, the tension spring 410 drives the switching lever 49 to deflect toward the adjusting slider 42 on the side where the pressure transmission rod 44 is provided, and drives the main adjusting lever 46 to rotate synchronously.

[0057] When the tension spring 410 pulls the switching lever 49 and the main adjusting lever 46 to deflect in the direction of the pressure transmission rod 44, the rotation of the main adjusting lever 46 drives the corresponding transmission link 48 to move downward through the guide groove 47 on it. The transmission link 48 pushes the adjusting slider 42 with the pressure transmission rod 44 to slide downward along the guide post 41 through the positioning slot 43.

[0058] The downward movement of the pressure transmission rod 44 applies radial pressure to the transmission steel ball 37. The pressure acts on the V-shaped cross-sectional groove 36 through the steel ball, and is converted into an elastic preload force on the push block 34. The tension of the tension spring 410 directly determines the initial value of this preload force.

[0059] In this embodiment, the drive base 31 is also provided with a switching part 5. The switching part 5 includes a switching plate 51 that is longitudinally slidably mounted on the drive base 31. The end of the adjusting screw 21 is connected to a linkage block 52. The linkage block 52 is provided with a guide roller 53.

[0060] The switching plate 51 is machined with an inclined curved guide groove 54. The guide roller 53 is embedded in the curved guide groove 54 and can roll along it. Two wedge-shaped trigger blocks 55 are also fixedly installed on the switching plate 51. Two trigger rods 56 are staggered on the switching swing rod 49. The two wedge-shaped trigger blocks 55 correspond to the positions of the two trigger rods 56 on the switching swing rod 49 respectively, and interact with each other under the deflection stroke of the switching swing rod 49.

[0061] In the first stage, the elastic preload adjustment and gap elimination are achieved by rotating the adjusting screw 21 to push it towards the wedge slider 22. The linkage block 52, through the cooperation of the guide roller 53 and the curved guide groove 54, drives the entire drive seat 31 and the thrust transmission component 3 to move forward synchronously. The thrust is transmitted to the wedge slider 22 through the push block 34 with elastic preload to eliminate the gap between the locking hook and the traction pin.

[0062] In the second stage, after the gap is eliminated, the mode switching occurs. When the gap is completely eliminated and the wedge slider 22 reaches the mechanical limit and can no longer move, the drive seat 31 stops. If the adjusting screw 21 continues to rotate, it will only drive the linkage block 52 to move forward relative to the stopped drive seat 31. The guide roller 53 on the linkage block 52 moves relative to the curved guide groove 54, which is converted into the longitudinal sliding of the switching plate 51 on the drive seat 31.

[0063] The switching plate 51 makes a wedge-shaped trigger block 55 on it contact the corresponding trigger rod 56 on the switching lever 49. Under the action of the wedge-shaped inclined surface, the trigger rod 56 is pushed, forcing the switching lever 49 to overcome the tension of the tension spring 410 and deflect away from the pressure transmission rod 44. This deflection releases the downward pressure on the pressure transmission rod 44 through the main adjusting lever 46 and the transmission connecting rod 48, thereby causing the transmission steel ball 37 to lose radial preload. The push block 34 and the rear end face of the wedge-shaped slider 22 become direct rigid and stable contact, ensuring that the connection is in a firm locking state without elasticity during subsequent traction operations.

[0064] In the third stage, the reset and preload reconstruction occurs. When it is necessary to loosen or readjust, the adjusting screw 21 is rotated in the opposite direction to retract it. The initial linkage block 52 drives the switching plate 51 to move upward and reset. At the end of this reset stroke, another wedge-shaped trigger block 55 on the switching plate 51 contacts another trigger rod 56 on the switching lever 49, pushing the switching lever 49 to deflect back towards the pressure transmission rod 44. The tension spring 410 is then stretched and stored, and preload is applied to the pressure transmission rod 44 again, preparing for the next adjustment.

[0065] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A locking device for a fifth wheel hitch, comprising a saddle (1) having a guide connecting unit (11) and a locking unit (12) inside; a hitch adjusting assembly (2) arranged in the locking unit (12); an adjusting screw rod (21) arranged on a side wall of the saddle (1); and a wedge-shaped slider (22) arranged inside the saddle (1) and having a working inclined surface matched with an inclined surface of a back part of a locking hook; characterized in that a thrust transmission component (3) is connected to one end of the adjusting screw rod (21) towards the wedge-shaped slider (22) and in contact with an end surface of the wedge-shaped slider (22); and the rotation of the adjusting screw rod (21) drives the wedge-shaped slider (22) to move linearly through the thrust transmission component (3), so that the locking hook is tightened transversely to eliminate the gap with a hitch pin.

2. The locking device for the fifth wheel hitch according to claim 1, characterized in that the thrust transmission component (3) comprises a driving seat (31) connected to an end of the adjusting screw rod (21) to slide along an axis; a thrust transmission block (32) fixedly connected to one end of the driving seat (31) towards the wedge-shaped slider (22); a guide cavity (33) opened in the inside of the thrust transmission block (32); a thrust block body (34) radially slidingly arranged in the guide cavity (33) and having a ball (35) embedded towards the end surface of the wedge-shaped slider (22); a cross-section groove (36) arranged in a V shape and defined by the other end inclined surface of the thrust block body (34) and the inner wall of the guide cavity (33); a transmission steel ball (37) rollingly embedded in the cross-section groove (36); and an elastic pressure applying part (4) arranged on the driving seat (31) to continuously apply radial pressure to the transmission steel ball (37).

3. The locking device for the fifth wheel hitch according to claim 2, characterized in that the elastic pressure applying part (4) comprises two guide columns (41) fixedly installed on the driving seat (31); two adjusting sliders (42) slidingly sleeved on the guide columns (41) and having positioning clamping grooves (43) opened; a pressure transmission rod (44) downwardly extended from the bottom of one of the adjusting sliders (42) and having an end in contact with the transmission steel ball (37); a mounting pivot (45) fixedly arranged on the driving seat (31); a main adjusting swing rod (46) hingedly connected to the mounting pivot (45) and having a guide sliding groove (47) opened; a transmission connecting rod (48) slidingly arranged in the guide sliding groove (47) and extending towards the positioning clamping groove (43) of the adjusting slider (42); a switching swing rod (49) hingedly connected to the mounting pivot (45); and a tension spring (410) connected to the main adjusting swing rod (46) and the switching swing rod (49) to drive the switching swing rod (49) to deflect to one side of the pressure transmission rod (44).

4. The locking device for the fifth wheel hitch according to claim 3, characterized in that it further comprises a switching part (5) arranged on the driving seat (31); the switching part (5) comprises a switching plate (51) longitudinally slidingly installed on the driving seat (31); a linkage block (52) connected to an end of the adjusting screw rod (21); and a guide roller (53) arranged on the linkage block (52). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ A curve guide groove (54) is obliquely arranged on the switching plate (51) and is in rolling cooperation with the guide roller (53); Two wedge-shaped trigger blocks (55) are fixedly arranged on the switching plate (51); Two trigger rods (56) are arranged on the switching swing rod (49) in an interlaced manner and are in position correspondence with the wedge-shaped trigger blocks (55).

5. The locking device of the hitch seat of the semitrailer according to claim 1, characterized in that: the guide connecting unit (11) is used for guiding the hitch pin to slide into the center positioning hole of the saddle (1) along the guide track; the locking unit (12) is used for driving the locking hook to complete locking after the hitch pin is in place.

6. The locking device of the hitch seat of the semitrailer according to claim 5, characterized in that: the rolling friction between the ball (35) and the end face of the wedge-shaped sliding block (22) reduces the adjusting resistance; the cooperation between the transmission steel ball (37) and the V-shaped cross-section groove (36) allows the push block body (34) to produce radial elastic retreat; the elastic retreat avoids forming rigid jamming and eliminates the idle stroke phenomenon.

7. The locking device of the hitch seat of the semitrailer according to claim 6, characterized in that: when the adjusting screw (21) rotates, the linkage block (52) drives the switching plate (51) to longitudinally slide through the cooperation between the guide roller (53) and the curve guide groove (54); the sliding of the switching plate (51) drives the switching swing rod (49) to deflect through the interaction between the wedge-shaped trigger block (55) and the trigger rod (56), thereby realizing mode switching.

8. A method of using a locking device for a fifth wheel hitch of a semi-trailer, using a locking device for a fifth wheel hitch of a semi-trailer according to any one of claims 1-7, characterized in that, The method comprises the following steps: S1. After the hitch pin is guided into and seated through the guide connecting unit (11), the locking hook is driven by the locking unit (12) to complete preliminary locking; S2. The adjusting screw (21) is rotated, the wedge-shaped sliding block (22) is driven to move through the push force transmission component (3), the locking hook is transversely tightened, and the assembly gap with the hitch pin is eliminated; S3. During the gap elimination process, the elastic pressure applying part (4) applies elastic pre-tightening force to the push block body (34) through the transmission steel ball (37), allowing radial retreat to avoid jamming; S4. After the gap is completely eliminated, the adjusting screw (21) continues to rotate to trigger the switching part (5) to act; S5. The switching part (5) releases the elastic pre-tightening force, so that the push block body (34) and the wedge-shaped sliding block (22) are changed into rigid stable contact, and in subsequent traction operation, the connection is in a firm locking state without elastic retreat; S6. When it is needed to be loosened, the adjusting screw (21) is reversely rotated, the switching part (5) is reset and the pre-tightening force is rebuilt, thereby preparing for the next adjustment.

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