Self-locking tow hook

Abstract

The invention aims to solve the problems that a locking mechanism in an existing tow hook cannot realize zero load on a motor after being locked, so that the service life of the motor is influenced; according to the self-locking tow hook, a self-locking structure is arranged, after a bent hook is opened, a locking relation is formed among a steel ball, a rotating shaft seat and a sleeve of the bent hook, and therefore force transmitted through the bent hook is transmitted to the rotating shaft seat and a connecting plate fixedly connected with the rotating shaft seat, and a rotating shaft is prevented from being influenced; in addition, through the matching relation of a clamping pin and an unlocking pin, after the hook rotates to the retracting angle, locking is achieved through the clamping pin and a clamping hole in the connecting plate; therefore, zero load of the motor can be kept when the hook is unfolded and folded.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of trailer hooks, in particular to a self-locking trailer hook. BACKGROUND

[0002] The trailer connecting device, also known as a drawbar, a trailer bar, and sometimes directly as a trailer hook, a tow hook, etc., is a device for connecting a vehicle to other vehicles or equipment, mainly used for towing other vehicles or cargo by a car. The installation of the trailer connecting device on the current household vehicle is mainly used for towing a trailer such as a motor home, etc., or installing a bracket to fix luggage or a bicycle, etc., to meet the needs of people on vacation or riding in the suburbs, etc.

[0003] Since the tow hook on the vehicle is usually exposed to the rear of the car in the use state, on the one hand, it is easy to collide with passing objects, and on the other hand, it also affects the overall styling of the vehicle, so a rotating tow hook is used to make it able to be rotated and stored when not in use, such as the content shown in the patent with the application publication number CN120327155A. In the existing rotating tow hook structure, the tow hook is usually controlled to rotate by a motor, and a gear set structure and a locking mechanism are used to achieve locking, however, since it is impossible to achieve zero load on the gear set and the motor after locking, the locking effect and service life of the overall structure will be ultimately affected. Therefore, a self-locking trailer tail hook is needed which can achieve zero load on the motor when locking. SUMMARY

[0004] The purpose of the present application is to solve the deficiencies of the prior art and provide a self-locking trailer hook.

[0005] In order to solve the above problems, the technical scheme adopted by the present application is as follows: The utility model provides a self -locking trailer hook, including connecting plate, rotation power part, hook and self -locking structure, wherein rotation power part is fixedly arranged on the connecting plate, and the connecting plate is used for and the fixed connection of external frame, self -locking structure is rotatably arranged on the connecting plate, and self -locking structure is also transmission connection with rotation power part, hook is arranged on self -locking structure, the self -locking structure includes rotation axis, paddle, pivot seat, axle, steel ball, first pin column and second pin column, wherein, paddle is connected with the output end of rotation power part, and follows rotation power part rotation, paddle is also transmission connection with rotation axis, and drives rotation axis rotation, axle is rotatably connected on the outside of rotation axis, the outside of axle is also provided with pivot seat, and pivot seat is slidingly fitted with axle, pivot seat is provided with a plurality of self -locking holes for embedding steel ball on, and the axis of self -locking hole is along the radial of pivot seat, and self -locking hole penetrates the side wall of pivot seat, pivot seat is also fixedly connected with connecting plate, one end of hook is provided as the sleeve of tubular, and the sleeve is rotatably connected on the outside of pivot seat, steel ball is embedded in the self -locking hole on pivot seat, and steel ball is also in contact with the outer surface of axle in pivot seat, the outside of axle is provided with the ball groove corresponding with steel ball, the sleeve of hook is also provided with the locking groove corresponding with steel ball, paddle is also provided with the undulating rotation drive portion corresponding with axle, and rotation drive portion drive axle slides along the axis direction of rotation axis, and the other side of axle is provided with first spring between the end of rotation axis, and axle is pushed to paddle, and paddle is provided with special spline structure between rotation axis and pivot seat and is matched, and drives rotation axis rotation.

[0006] Further, the rotation axis is also connected with the sleeve of the hook, and drives the sleeve to rotate.

[0007] Further, the sleeve is also provided with a pin, the pin is slidingly embedded in the cylindrical hole on the sleeve, and the second spring is also arranged in the cylindrical hole to push the pin, the connecting plate is provided with the pin hole penetrating the connecting plate corresponding with the pin, the unlocking pin is arranged in the pin hole on the connecting plate, one end of the unlocking pin penetrates the connecting plate and contacts the paddle, the paddle is provided with the rotation inclined surface corresponding with the unlocking pin, and the depth of the unlocking pin in the pin hole is controlled when the paddle rotates, the third spring is also arranged between the unlocking pin and the pin hole to push the unlocking pin to the paddle.

[0008] Further, one end of the unlocking pin is provided as the cylinder corresponding with the pin hole, and the other end of the unlocking pin is provided as the mushroom head, the mushroom head is located outside the pin hole, and the third spring is arranged between the mushroom head and the connecting plate.

[0009] Further, the special spline structure includes two lever rods arranged on the paddle and the spline piece fixedly arranged on the rotation axis, the middle part of the spline piece is fixedly connected with the rotation axis, the two sides of the spline piece are provided as the fan-shaped pieces which are centrally symmetrical, the two lever rods on the paddle are centrally symmetrical about the center of the paddle, the fan-shaped pieces on the two sides of the spline piece correspond with the lever rods on the paddle, the spline piece is attached with the lever rod, and the paddle drives the rotation axis to rotate.

[0010] Further, the rotating driving part provided on the dial includes a protruding part which is symmetric about the center of the dial, and a recessed part between the two protruding parts; a stud is provided on the shaft near one end of the dial, and the end of the stud corresponds to the rotating driving part.

[0011] Further, the end of the stud is provided as a ball head.

[0012] Further, one end of the shaft seat is provided with a connecting seat extending radially outward, and the connecting seat is fixedly connected with the connecting plate by bolts; the other end of the shaft seat is rotatably matched with the sleeve on the hook through the connecting plate.

[0013] Further, the dial is also fixedly provided with a cam disc, and the dial rod is fixed between the cam disc and the dial; a circular recessed groove is provided on the connecting seat for embedding the cam disc; a protruding limiting block is provided on the inner edge of the circular recessed groove, and a limiting protrusion corresponding to the limiting block is provided on the edge of the cam disc; the limiting protrusion rotates following the rotation of the cam disc; and the limiting block is on the rotation path of the limiting protrusion.

[0014] Further, the end of the rotating shaft near the hook is provided with a bent plate for clamping the hook; the bent plate is in a U shape as a whole, and the two ends of the bent plate are clamped on one side of the sleeve of the hook.

[0015] The beneficial effects of the present application are: By setting the self-locking structure, a locking relationship is formed between the steel ball, the shaft seat and the sleeve of the hook after the hook is opened, so that the force transmitted through the hook is transmitted to the shaft seat and the connecting plate fixedly connected with the shaft seat, avoiding affecting the rotating shaft and realizing zero load of the motor; By setting the matching relationship of the clamping pin and the unlocking pin, the hook is locked by the clamping pin and the clamping hole on the connecting plate after being rotated to a set angle, realizing zero load of the motor after being folded up; By setting the special-shaped spline structure, the self-locking structure will be unlocked first when controlling the rotation of the hook, on the one hand ensuring that the hook remains stable in the opened and folded states, avoiding the interference of vehicle vibration on the hook, and on the other hand cutting off the direct connection between the rotating shaft and the dial, so as to avoid the transmission of the torsional force of the rotating shaft to the dial and the motor. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of Example 1; Figure 2 It is a schematic diagram of the rotating power member of Example 1; Figure 3 It is an exploded view of the overall structure of Example 1; Figure 4 is a schematic view of the hook of embodiment 1; Figure 5 is a rear view of the hook of embodiment 1; Figure 6 is a schematic view of the shaft seat of embodiment 1; Figure 7 is a schematic view of the shaft center of embodiment 1; Figure 8 is a schematic view of the cooperation between the push piece and the rotating shaft of embodiment 1; Figure 9 is a schematic view of the special spline structure of embodiment 1; Figure 10 is a perspective view of the open state of the hook of embodiment 1; Figure 11 is a perspective view of the rotating state of the hook of embodiment 1; Figure 12 is a perspective view of the folded state of the hook of embodiment 1; Figure 13 is a schematic view of the rotating shaft and the sleeve of embodiment 2.

[0017] The figure identification explanation: connecting plate 1, clamping hole 11, rotating power piece 2, hook 3, sleeve 31, locking groove 32, end cover 33, self-locking structure 4, rotating shaft 41, push piece 42, rotating shaft seat 43, self-locking hole 431, connecting seat 432, shaft center 44, column head 441, ball groove 442, steel ball 45, rotating driving part 46, first spring 48, special spline structure 49, push rod 491, spline piece 492, sector piece 493, clamping pin 410, second spring 411, unlocking pin 412, third spring 413, cam disc 414, circular groove 415, limiting block 416, limiting protrusion 417, bending plate 418, limiting pin 419, nut cover 420. DETAILED DESCRIPTION

[0018] The embodiments of the present application will be described herein below with specific reference on concrete examples. Those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in the present specification. The present application can also be implemented or applied in different specific embodiments, and the details in the present specification can be modified or changed in different views and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0019] It should be noted that the drawings provided in the following embodiments only schematically illustrate the basic concept of the present application, and only the components related to the present application are shown in the drawings without drawing the number, shape and size of the components in actual implementation. The type, number and proportion of each component in actual implementation can be arbitrarily changed, and the component layout type can also be more complex.

[0020] Example 1: like Figures 1-12 As shown, a fully self-locking trailer hitch includes a connecting plate 1, a rotating power component 2, a hook 3, and a self-locking structure 4. The rotating power component 2 is fixedly mounted on the connecting plate 1. In this example, the rotating power component 2 is a motor, which outputs the torque required for rotation. The connecting plate 1 is used for fixed connection with an external vehicle frame. The self-locking structure 4 is rotatably mounted on the connecting plate 1 and is also connected to the rotating power component 2 via a transmission connection. The hook 3 is mounted on the self-locking structure 4. The self-locking structure 4 includes a rotating shaft 41, a lever 42, a rotating shaft seat 43, a shaft center 44, and steel balls 45. The lever 42 is connected to the output end of the rotating power component 2 and rotates with it. The lever 42 is equipped with... It has a triangular connecting hole for transmission connection with the rotating power component 2; the paddle 42 is also transmission connected to the rotating shaft 41, driving the rotating shaft 41 to rotate; the shaft 44 is rotatably sleeved on the outside of the rotating shaft 41, allowing the rotating shaft 41 to rotate freely within the shaft 44; a rotating shaft seat 43 is also provided on the outside of the shaft 44, the rotating shaft seat 43 slides with the shaft 44, and the rotating shaft seat 43 is provided with several self-locking holes 431 for embedding steel balls 45, the axis of the self-locking holes 431 passes through the side wall of the rotating shaft seat 43 along the radial direction of the rotating shaft seat 43; the rotating shaft seat 43 is also fixedly connected to the connecting plate 1; one end of the hook 3 is set as a tubular sleeve 31, the sleeve 31 rotatably sleeved on the outside of the rotating shaft seat 43; steel The ball 45 is embedded in the self-locking hole 431 on the rotating shaft seat 43, and the ball 45 also contacts the outer surface of the shaft 44 inside the rotating shaft seat 43; the outer side of the shaft 44 is provided with a ball groove 442 corresponding to the ball 45. In this example, the diameters at both ends of the shaft 44 are larger, and the diameter in the middle part is smaller, serving as the ball groove 442; the outer surface of the shaft 44 has a smooth curved transition, allowing the ball 45 to smoothly enter or leave the ball groove 442; the sleeve 31 of the hook 3 is also provided with a locking groove 32 corresponding to the ball 45. It should be noted that only a part of the ball 45 can be embedded in the locking groove 32, and the other part of the ball 45 remains on the rotating shaft seat 43. The hook 3 is locked to the pivot 43 by the locking hole 431, thus preventing the force on the hook 3 from being transmitted to the pivot 41, but instead to the pivot 43 and the connecting plate 1. The lever 42 is also provided with an undulating rotation drive part 46 corresponding to the shaft 44. The rotation drive part 46 drives the shaft 44 to slide along the axis of the pivot 41. A first spring 48 is provided between the other side of the shaft 44 and the end of the pivot 41, which pushes the shaft 44 toward the lever 42. The lever 42 and the pivot 41 are fitted with a special spline structure 49 to drive the pivot 41 to rotate. The pivot 41 is also connected to the sleeve 31 of the hook 3, which drives the sleeve 31 to rotate.

[0021] The sleeve 31 is further provided with a latch 410 which is slidingly embedded in a cylindrical hole on the sleeve 31, and the cylindrical hole is further provided with a second spring 411 which abuts against the latch 410; the connecting plate 1 is provided with a latch hole 11 which penetrates the connecting plate 1 and corresponds to the latch 410; the latch hole 11 on the connecting plate 1 is provided with an unlocking pin 412; one end of the unlocking pin 412 penetrates the connecting plate 1 and contacts the push piece 42; the push piece 42 is provided with a rotating inclined surface which corresponds to the unlocking pin 412, and when the push piece 42 rotates, the rotating inclined surface controls the depth of the unlocking pin 412 in the latch hole 11, and further controls the distance between the other end of the unlocking pin 412 and the end of the latch hole 11, so that the unlocking pin 412 can push the latch 410 out of the latch hole 11 or leave space for the latch 410 to enter the latch hole 11; the third spring 413 is further provided between the unlocking pin 412 and the latch hole 11 to push the unlocking pin 412 towards the push piece 42, so that the unlocking pin 412 can be kept against the push piece 42. It should be noted that in this example, the length of the rotating inclined surface only accounts for a part of the edge length of the push piece 42, that is, in the remaining part of the time, the unlocking pin 412 is always deep into the latch hole 11 and keeps the other end of the latch hole 11 blocked.

[0022] One end of the rotating shaft seat 43 is provided with a connecting seat 432 which extends radially outward, and the connecting seat 432 is fixedly connected with the connecting plate 1 by bolts; the other end of the rotating shaft seat 43 penetrates the connecting plate 1 and is rotationally matched with the sleeve 31 on the hook 3.

[0023] One end of the unlocking pin 412 is provided in a cylindrical shape corresponding to the latch hole 11, and the other end of the unlocking pin 412 is provided in a mushroom head which is located outside the latch hole 11, and the third spring 413 is provided between the mushroom head and the connecting plate 1; in this example, the mushroom head part on the unlocking pin 412 is slidingly embedded in a through hole on the connecting seat 432 of the rotating shaft seat, and the third spring 413 is further provided in the through hole.

[0024] The special-shaped spline structure 49 includes two push rods 491 provided on the push piece 42 and a spline piece 492 fixedly provided on the rotating shaft 41; the middle part of the spline piece 492 is fixedly connected with the rotating shaft 41, and the two sides of the spline piece 492 are provided in a center-symmetric fan-shaped piece 493; the two push rods 491 on the push piece 42 are symmetrically arranged about the center of the push piece 42; the fan-shaped pieces 493 on the two sides of the spline piece 492 correspond to the push rods 491 on the push piece 42, and when the spline piece 492 is in contact with the push rods 491, the push piece 42 drives the rotating shaft 41 to rotate, while when the spline piece 492 is not in contact with the push rods 491, the rotation of the push piece 42 will not drive the spline piece 492 to rotate, that is, the rotating shaft 41 will not rotate, so that a unlocking movement interval is left, on the one hand to avoid the influence of factors such as vibration and affect the locking effect, and on the other hand to avoid transmitting the force on the hook 3 to the motor.

[0025] The rotating driving part 46 arranged on the dial 42 includes protruding parts which are symmetric about the center of the dial 42, and a recessed part between the two protruding parts; a stud 441 corresponding to the rotating driving part 46 is arranged on the shaft 44 near one end of the dial 42, and the end of the stud 441 corresponds to the rotating driving part 46; the end of the stud 441 is arranged as a ball head, so that the stud 441 and the rotating driving part 46 keep a small contact surface, reducing the resistance when sliding. A platform is arranged at the limit position of the protruding part and the recessed part, so that when the dial 42 rotates, the distance between the shaft 44 and the dial 42 does not change, facilitating the locking or unlocking of the steel ball 45. It should be noted that the angle of the protruding part between the rotating driving part 46 corresponds to the angle of the dial lever 491 on the dial 42.

[0026] The cam disc 414 is further fixedly arranged on the dial 42, and the dial lever 491 is fixed between the cam disc 414 and the dial 42; a circular recess 415 into which the cam disc 414 is embedded is arranged on the connecting seat 432; a protruding limiting block 416 is arranged on the inner edge of the circular recess 415, and a limiting protrusion 417 corresponding to the limiting block 416 is arranged on the edge of the cam disc 414; the limiting protrusion 417 rotates following the rotation of the cam disc 414; the limiting block 416 is on the rotating movement path of the limiting protrusion 417, and is used to limit the rotation angle range of the cam disc 414 in the clockwise and counterclockwise directions, thereby controlling the rotation of the dial 42. It should be noted that in this example, the dial 42 and the cam disc 414 are spaced apart by a certain distance, and the spline piece 492 is clamped between the dial 42 and the cam disc 414. It should be noted that in this example, the cam disc 414 is integrally formed with the rotating driving part 46.

[0027] The end of the rotating shaft 41 near the hook 3 is clamped and provided with a bent plate 418 for clamping the hook 3; in this example, the end of the rotating shaft 41 is arranged in a quadrangular prism shape, and a through hole corresponding to the bent plate 418 is arranged on the bent plate 418 to form a clamping connection; the bent plate 418 is in a U shape as a whole, and the two ends of the bent plate 418 are arranged as protruding clamping heads clamped on one side of the sleeve 31 of the hook 3, forming a transmission connection relationship between the rotating shaft 41 and the sleeve 31; in this example, one end of the first spring 48 abuts against the bent plate 418, and the other end abuts against the shaft 44.

[0028] The shaft 44 and the rotating shaft seat 43 are further provided with a limiting pin 419 clamped between the groove on the outer side of the shaft 44 and the groove on the inner side of the rotating shaft seat 43; the axis direction of the limiting pin 419 is parallel to the axis direction of the rotating shaft 41, limiting the rotation of the shaft 44 relative to the rotating shaft seat 43, so that the shaft 44 can only slide along the axis of the limiting pin 419, thereby stabilizing the movement trajectory of the shaft 44.

[0029] In this case, the end of the rotating shaft seat 43 is also screwed with a nut cover 420, which is located inside the bent plate 418; an end cover 33 is also arranged on the sleeve 31, which is fixedly connected with one side of the sleeve 31, and covers the outside of the bent plate 418, so as to wrap the self-locking structure 4 in the sleeve 31, and form a sealed protection.

[0030] When the bending hook 3 is driven to rotate, there are two states, including the opening of the bending hook 3 and the folding of the bending hook 3. In the state of the opening of the bending hook 3, since the shaft center 44 corresponds to the recessed part on the shaft center 44 driving part, at this time, the shaft center 44 is subjected to the action of the first spring 48 between the shaft center 44 and the rotating shaft 41, and the shaft center 44 is pressed towards the connecting plate 1, at this time, the steel ball 45 in the self-locking hole 431 on the rotating shaft seat 43 is driven by the shaft center 44, and is separated from the ball groove 442 on the shaft center 44, and is away from the rotating shaft 41, and is against the sleeve 31 of the bending hook 3 outside the rotating shaft seat 43; in this case, the locking groove 32 on the sleeve 31 of the bending hook 3 corresponds to the self-locking hole 431 on the rotating shaft seat 43 when the bending hook 3 is opened, that is, when the bending hook 3 is opened, part of the steel ball 45 enters the locking groove 32, and the other part of the steel ball 45 is located in the rotating shaft seat 43, so as to realize the locking of the bending hook 3. In the folding state of the bending hook 3, the steel ball 45 corresponds to the ball groove 442 outside the shaft center 44, at this time, the steel ball 45 is retracted into the self-locking hole 431, and the bending hook 3 is unlocked; in addition, the end of the unlocking pin 412 is against the part far away from the connecting plate 1 on the rotating slope of the tab 42, that is, the unlocking pin 412 is stretched out of the clamping hole 11, and there is a space for inserting the clamping pin 410 on the other side of the clamping hole 11; the clamping pin 410 on the sleeve 31 of the bending hook 3 is embedded into the clamping hole 11 to form the locking. When the bending hook 3 is converted from the opening state to the folding state, due to the special-shaped spline structure 49 between the tab 42 and the rotating shaft 41, the tab 42 does not drive the rotating shaft 41 to rotate at the initial stage of the rotation of the tab 42, but first unlocks the shaft center 44, and pushes the shaft center 44 away from the connecting plate 1, so that the steel ball 45 falls into the ball groove 442 on the shaft center 44, and the bending hook 3 is unlocked, and then the rotating shaft 41 and the bending hook 3 are driven to rotate, in the process, since the locking groove 32 on the sleeve 31 of the bending hook 3 deviates from the self-locking hole 431 on the rotating shaft seat 43, the steel ball 45 cannot be separated from the ball groove 442, so the steel ball 45 reversely locks the shaft center 44, so that the bending hook 3 can normally rotate, until the clamping pin 410 on the bending hook 3 corresponds to the clamping hole 11 on the connecting plate 1, and then the clamping pin 410 is locked; in the reverse action of the bending hook 3, the tab 42 is also driven by the special-shaped spline structure 49, first pushes the unlocking pin 412 to push the clamping pin 410 out of the clamping hole 11, and then drives the bending hook 3 to rotate after the unlocking is completed, until the steel ball 45 is locked.

[0031] Embodiment 2: As Figure 13As shown, the embodiment is a kind of semi-automatic locking trailer hook structure; The difference between the embodiment and embodiment 1 is that the rotating shaft 41 and the sleeve 31 of the hook 3 are not connected with each other, that is, the rotation of the rotating shaft 41 does not drive the sleeve 31 to rotate; It can be seen from the content described in embodiment 1 that the rotation of the rotating shaft 41 can drive other structures in the self-locking structure 4 to move, so as to realize the state of waiting for locking. For example, in one of the cases, the rotating power piece 2 rotates, drives the push piece 42 to rotate, and controls the unlocking pin 412 in the clamping hole 11 of the connecting plate 1 to pop up, at this time, the clamping pin 410 in the sleeve 31 is still resisted on the connecting plate 1, is not embedded in the clamping hole 11, so it is in the state of waiting for locking. With the intervention of external force, the hook 3 is rotated until the clamping pin 410 in the sleeve 31 is popped into the clamping hole 11, and the locking state of one kind is realized. Similarly, in another case, the rotating power piece 2 rotates, drives the rotating driving part 46 to rotate, and the rotation of the rotating driving part 46 drives the shaft 44 to move, realizes pressing the shaft 44 or releasing the shaft 44; After releasing the shaft 44, since the steel ball 45 has not been embedded in the locking groove 32 in the inner wall of the sleeve 31, at this time, the shaft 44 will not be completely popped up, but there is a certain gap between the rotating driving part 46; With the intervention of external force, the hook 3 is rotated until the steel ball 45 is popped up and embedded in the locking groove 32 in the sleeve 31, clamping the sleeve 31, and with the steel ball 45 being pushed out, the shaft 44 is subjected to the elastic force of the first spring 48, slides towards the rotating driving part 46 until abutting against the rotating driving part 46, controls the steel ball 45 to be separated from the ball groove 442 outside the shaft, so that the steel ball 45 is stably embedded in the locking groove 32, realizes the locking of another state.

[0032] The above description is only a specific example of the present application and does not constitute any limitation on the present application. Obviously, for those skilled in the art, after understanding the content and principle of the present application, various modifications and changes in form and detail can be made without departing from the principle and structure of the present application, but these modifications and changes based on the idea of the present application are still within the protection scope of the claims of the present application.

Claims

1. A self-locking trailer hook, comprising a connecting plate (1), a rotating power element (2), a hook (3) and a self-locking structure (4); wherein the rotating power element (2) is fixedly arranged on the connecting plate (1), the connecting plate (1) is used for fixedly connecting with an external frame; the self-locking structure (4) is rotatably arranged on the connecting plate (1), the self-locking structure (4) is further in transmission connection with the rotating power element (2); the hook (3) is arranged on the self-locking structure (4); characterized in that, The self-locking structure (4) comprises a rotating shaft (41), a dial piece (42), a rotating shaft seat (43), a shaft center (44) and a steel ball (45); the dial piece (42) is connected with the output end of the rotating power element (2) and rotates with the rotating power element (2); the dial piece (42) is also in transmission connection with the rotating shaft (41) and drives the rotating shaft (41) to rotate; the shaft center (44) is rotatably sleeved outside the rotating shaft (41); the outside of the shaft center (44) is also provided with the rotating shaft seat (43) which is in sliding fit with the shaft center (44); a plurality of self-locking holes (431) for embedding the steel ball (45) are arranged on the rotating shaft seat (43); the axis of the self-locking hole (431) is along the radial direction of the rotating shaft seat (43); the self-locking hole (431) penetrates the side wall of the rotating shaft seat (43); the rotating shaft seat (43) is fixedly connected with the connecting plate (1); one end of the hook (3) is provided with a sleeve (31) which is rotatably sleeved outside the rotating shaft seat (43); the steel ball (45) is embedded in the self-locking hole (431) on the rotating shaft seat (43) and is in contact with the outer surface of the shaft center (44) in the rotating shaft seat (43); the outside of the shaft center (44) is provided with a ball groove corresponding to the steel ball (45); the sleeve (31) of the hook (3) is also provided with a locking groove (32) corresponding to the steel ball (45); the dial piece (42) is also provided with a wavy rotating driving part (46) corresponding to the shaft center (44); the rotating driving part (46) drives the shaft center (44) to slide along the axis direction of the rotating shaft (41); a first spring (48) is arranged between the other side of the shaft center (44) and the end of the rotating shaft (41) and pushes the shaft center (44) towards the dial piece (42); a special-shaped spline structure (49) is arranged between the dial piece (42) and the rotating shaft (41) to drive the rotating shaft (41) to rotate.

2. A self-locking trailer hitch according to claim 1, wherein, The rotating shaft (41) is also connected with the sleeve (31) of the hook (3) and drives the sleeve (31) to rotate.

3. A self-locking trailer hitch according to claim 1 or 2, characterised in that The sleeve (31) is also provided with a pin (410) which is slidably embedded in a cylindrical hole on the sleeve (31); a second spring (411) is arranged in the cylindrical hole to abut against the pin (410); a clamping hole (11) is arranged on the connecting plate (1) and penetrates the connecting plate (1) and corresponds to the pin (410); an unlocking pin (412) is arranged in the clamping hole (11) on the connecting plate (1); one end of the unlocking pin (412) penetrates the connecting plate (1) and is in contact with the dial piece (42); a rotating inclined surface corresponding to the unlocking pin (412) is arranged on the dial piece (42); when the dial piece (42) rotates, the depth of the unlocking pin (412) in the clamping hole (11) is controlled; a third spring (413) is arranged between the unlocking pin (412) and the clamping hole (11) and pushes the unlocking pin (412) towards the dial piece (42).

4. A self-locking trailer hitch according to claim 3, wherein, One end of the unlocking pin (412) is provided as a cylinder corresponding to the card hole (11), and the other end of the unlocking pin (412) is provided as a mushroom head located outside the card hole (11), and a third spring (413) is arranged between the mushroom head and the connecting plate (1).

5. A self-locking trailer hitch according to claim 1 or 2, wherein, The special-shaped spline structure (49) comprises two lever rods (491) arranged on the dial piece (42) and a spline piece (492) fixedly arranged on the rotating shaft (41); the middle part of the spline piece (492) is fixedly connected with the rotating shaft (41), and the two sides of the spline piece (492) are provided as center-symmetric fan-shaped pieces (493); the two lever rods (491) on the dial piece (42) are arranged in a center-symmetric manner about the center of the dial piece (42); the fan-shaped pieces (493) on the two sides of the spline piece (492) correspond to the lever rods (491) on the dial piece (42), and when the spline piece (492) is attached to the lever rod (491), the dial piece (42) drives the rotating shaft (41) to rotate.

6. A self-locking trailer hitch according to claim 5, wherein, The rotating driving part (46) arranged on the dial piece (42) comprises a protruding part arranged in a center-symmetric manner about the center of the dial piece (42) and a recessed part located between the two protruding parts; a stud (441) corresponding to the rotating driving part (46) is arranged on the shaft center (44) close to one end of the dial piece (42), and the end of the stud (441) corresponds to the rotating driving part (46).

7. A self-locking trailer hitch according to claim 6, wherein, The end of the stud (441) is provided as a ball head.

8. A self-locking trailer hitch according to claim 5, wherein, One end of the rotating shaft seat (43) is provided with a connecting seat extending radially outward, and the connecting seat is fixedly connected with the connecting plate (1) through bolts; the other end of the rotating shaft seat (43) penetrates through the connecting plate (1) and is rotationally matched with the sleeve (31) on the hook (3).

9. A self-locking trailer hitch according to claim 8, wherein, The dial piece (42) is further provided with a cam disc (414) fixedly arranged thereon, and the lever rod (491) is fixed between the cam disc (414) and the dial piece (42); a circular recess (415) into which the cam disc (414) is embedded is arranged on the connecting seat; a protruding limiting block (416) is arranged on the inner edge of the circular recess (415), and a limiting protrusion (417) corresponding to the limiting block (416) is arranged on the edge of the cam disc (414); the limiting protrusion (417) rotates following the rotation of the cam disc (414); and the limiting block (416) is on the rotation path of the limiting protrusion (417).

10. A self-locking trailer hitch according to claim 2, wherein, The end of the rotating shaft (41) close to the hook (3) is provided with a bent plate (418) for clamping the hook (3); the bent plate (418) is in a U shape, and the two ends of the bent plate (418) are clamped on one side of the sleeve (31) of the hook (3).

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