Touch type trailer follow-up steering system

Abstract

The invention belongs to the technical field of trailer steering systems, and particularly discloses a touch type trailer follow-up steering system which comprises a frame, a suspension system, wheel assemblies, a main beam steering device, an auxiliary beam adjusting device, an auxiliary beam touch device and a trailer arm touch plate. The main beam steering device and the auxiliary beam adjusting device are both movably connected to the frame, a steering pull rod is connected between the two sets of wheel assemblies and the main beam steering device, the auxiliary beam touch device is movably connected to the auxiliary beam adjusting device, and two follow-up steel cables are connected between the auxiliary beam touch device and the main beam steering device. The trailer arm touch panel is movably connected to the frame. The angles of the wheels of the trailer can be adjusted in a follow-up mode along with turning of the trailer head, the turning radius and the occupied area of the trailer pulled by the trailer head are effectively reduced, and the phenomenon that the trailer head and the trailer are bent by 90 degrees during reversing is also avoided.

Description

Technical Field

[0001] This invention belongs to the technical field of trailer steering systems, specifically relating to a touch-sensitive trailer follow-up steering system. Background Technology

[0002] When a tractor unit towing a trailer encounters a bend in the road, the trailer needs a lot of space to turn. In narrow bends, it is necessary to achieve a smooth turn with less space. When reversing, because the trailer has a rigid axle, the tractor unit and trailer are prone to bending at 90 degrees. Therefore, it is crucial to achieve synchronous steering of the trailer wheels and the front wheels of the tractor unit.

[0003] To address the problem of the trailer wheels and the front wheels of the trailer cab not being able to turn synchronously in the existing technology, it is necessary to improve the structure of the trailer steering system to solve the current technical problem. Summary of the Invention

[0004] The purpose of this invention is to provide a touch-sensitive trailer steering system that allows the trailer wheels to adjust their angles as the trailer head turns, enabling the trailer to turn or reverse along the trajectory of the trailer head. This reduces the turning radius and floor space occupied by the trailer head while pulling the trailer, and also prevents the trailer head and trailer from bending at a 90° angle when reversing.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a touch-sensitive trailer follow-up steering system, comprising a frame, a suspension system, wheel assemblies, a main steering device, a secondary steering adjustment device, a secondary steering contact device, and a trailer arm contact plate. Two sets of wheel assemblies are provided, and the two sets of wheel assemblies are movably connected to the frame via the suspension system. The main steering device is rotatably connected to the frame. Steering tie rods connect the two sets of wheel assemblies to the main steering device. The secondary steering adjustment device is slidably connected to the frame. The secondary steering contact device is movably connected to the secondary steering adjustment device. Two follow-up steel cables connect the secondary steering contact device and the main steering device. The trailer arm contact plate is movably connected to the frame.

[0006] To better realize the present invention, the wheel assembly includes a wheel hub, an axle, a hub shaft, and a hub bearing. The hub bearing is fixedly connected to the wheel hub, the hub shaft is connected to the hub bearing, and both ends of the axle are rotatably connected to the hub shaft.

[0007] To better realize the present invention, the suspension system includes a leaf spring, a U-bolt connecting plate, a shock absorber, and a center axle cap. Both ends of the axle are connected to leaf springs through the U-bolt connecting plate. The center axle cap is placed between the U-bolt connecting plate and the top surface of the leaf spring. Both ends of the leaf spring are provided with lug bushings. The frame is provided with a rotating shaft that is rotatably connected to the lug bushings. The shock absorber is connected between the U-bolt connecting plate and the frame.

[0008] To better realize the present invention, the main steering device includes a main steering center shaft and a main steering wheel. The main steering wheel is rotatably connected to the frame through the main steering center shaft. Main steering cable connecting sleeves are movably connected to both sides of the main steering wheel. One end of each of the two follower cables is fixedly connected to the main steering cable connecting sleeve. A forward-extending swing arm is fixedly connected to the hub bearing. A steering tie rod is movably connected between the swing arm and the main steering wheel.

[0009] To better realize the present invention, the auxiliary adjustment device includes a lower connecting frame, the top of which is detachably connected to a front upper cover and a rear upper cover. The front upper cover, the rear upper cover and the lower connecting frame are combined to form a through hole for the frame to slide through. The bottom of the lower connecting frame is provided with a steel cable fixing frame near the rear upper cover, and the follower steel cable is movably connected to the steel cable fixing frame. The top of the front cover is fixedly provided with a grooved cam, the grooved cam is provided with a cross-shaped slot, the top of the frame is provided with a bearing, the bearing passes through the grooved cam and is rotatably connected to a cam, the cam is connected to a cam follower coupled to the cross-shaped slot, the cam is fixedly connected to a handle rod, and the handle rod is provided with a rotating handle.

[0010] To better realize the present invention, the bottom of the lower connecting frame is provided with a sub-bond central shaft near the front upper cover. The sub-bond contact device includes a sub-bond, the sub-bond is provided with a bearing seat, the sub-bond is rotatably connected to the sub-bond central shaft through the bearing seat, and two sub-bond steel cable connecting sleeves are movably connected to both sides of the sub-bond. The other ends of the two follower steel cables are respectively fixedly connected to the sub-bond steel cable connecting sleeves.

[0011] To better realize the present invention, the secondary bond is fixedly connected to two spring sleeves, each of which contains a spring. The springs are coaxially fixedly connected to a secondary bond contact rod. The end of the secondary bond contact rod away from the spring passes through the spring sleeve and is rotatably connected to a pin with a hole. The pin with a hole is fixedly connected to a polyurethane-coated bearing.

[0012] To better realize the present invention, the frame is provided with a spring-loaded latch near the sub-bond. The spring-loaded latch includes a fixed frame fixedly connected to the frame. The fixed frame is provided with a triangular support block near the sub-bond. The triangular support block is rotatably connected to two arc-shaped locking plates. Both arc-shaped locking plates are fixedly connected to a support plate. The two arc-shaped locking plates are combined to form a slot with an opening. The sub-bond is fixedly connected to a ball plug. Both sides of the triangular support block are provided with return springs. The support plate is provided with a limiting rod that is inserted into the return spring.

[0013] To better realize the present invention, the top of the trailer arm touch plate is provided with a trailer ball, the top of the frame is fixedly provided with a trailer cover coupled to the trailer ball, and the frame is provided with a hand-cranked lifting wheel.

[0014] Beneficial effects: This invention connects the trailer arm contact plate to the trailer head via a pin or other components, and then couples the trailer cover to the trailer ball via a hand-cranked lifting wheel, achieving a left-right swing connection between the trailer and the trailer arm contact plate. By rotating the handle of the auxiliary bearing adjustment device, the rubber-coated bearing of the auxiliary bearing contact device is adjusted forward to contact the trailer arm contact plate. This allows the auxiliary bearing to rotate left and right in the same direction as the trailer head when it swings left and right. During the rotation of the auxiliary bearing, the main bearing is driven to rotate in the same direction as the auxiliary bearing via a follower cable. During the rotation of the main bearing, the swing arm is driven to rotate in the opposite direction via a steering tie rod. This allows the trailer wheels to adjust their angles according to the trailer head's turning, enabling the trailer to turn or reverse along the trailer head's trajectory. This reduces the turning radius and floor space required when the trailer is pulling the trailer, and also prevents the trailer head and trailer from bending at a 90° angle during reversing. Attached Figure Description

[0015] Figure 1 This is a three-dimensional structural diagram of the present invention from one perspective; Figure 2 This is a top view of the present invention; Figure 3 This is a bottom view of the present invention; Figure 4 For the present invention Figure 2 OO cross-section diagram; Figure 5 For the present invention Figure 4 Enlarged view of point A; Figure 6 For the present invention Figure 4 Enlarged view of point B; Figure 7 For the present invention Figure 4 Enlarged view of point C; Figure 8 This is a structural diagram of the trailer arm contact plate of the present invention; Figure 9 This is a structural diagram of the sub-bonding adjustment device of the present invention; Figure 10 This is a three-dimensional structural diagram from another perspective of the present invention; Figure 11 For the present invention Figure 10 Enlarged view of point D; Figure 12 For the present invention Figure 10 Enlarged view of point E; Figure 13 For the present invention Figure 3 Enlarged view of point F.

[0016] In the diagram: 1. Frame; 2. Suspension system; 21. Leaf spring; 22. U-bolt connecting plate; 23. Shock absorber; 24. Lug bushing; 25. Shaft; 3. Wheel assembly; 31. Wheel hub; 32. Wheel hub bearing; 33. Wheel hub axle; 34. Control arm; 35. Axle; 4. Main steering gear; 41. Main steering center shaft; 42. Main steering gear; 43. Main steering cable connecting sleeve; 5. Sub-bond adjustment device; 51. Lower connecting frame; 52. Front upper cover; 53. Rear upper cover; 54. Through hole; 55. Steel cable fixing frame; 56. Groove cam; 57. Cross-shaped slot; 58. Bearing; 59. Cam; 591. Cam follower; 592. Handle rod; 593. Rotary handle; 6. Sub-bond contact device; 61. Sub-bond central shaft; 62. Sub-bond; 63. Sub-bond steel cable connecting sleeve; 64. Spring sleeve; 65. Spring; 66. Sub-bond contact rod; 67. Pin with hole; 68. Rubber-coated bearing; 7. Trailer arm touch plate; 71. Trailer ball; 72. Trailer cover; 73. Hand-cranked lifting wheel; 8. Follow-up steel cable; 9. Steering tie rod; 10. Spring-loaded latch; 101. Fixing bracket; 102. Triangular support block; 103. Arc-shaped locking plate; 104. Support plate; 105. Slot; 106. Ball plug; 107. Return spring; 108. Limiting rod. Detailed Implementation

[0017] 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.

[0018] Example like Figure 1 - Figure 13 As shown, the touch-sensitive trailer follow-up steering system includes a frame 1, a suspension system 2, wheel assembly 3, main steering device 4, auxiliary steering adjustment device 5, auxiliary steering contact device 6, and trailer arm contact plate 7.

[0019] The wheel assembly 3 includes a wheel hub 31, an axle 35, a wheel hub 32, a wheel hub axle 33, and a wheel hub bearing 32. The wheel hub bearing 32 is fixedly connected to the wheel hub 31, and the wheel hub axle 33 is connected to the wheel hub bearing 32. Both ends of the axle 35 are rotatably connected to the wheel hub axle 33. There are two sets of wheel assemblies 3, and the two sets of wheel assemblies 3 are movably connected to the frame 1 through the suspension system 2.

[0020] The suspension system 2 includes leaf springs 21, U-bolt connecting plates 22, shock absorbers 23, and center axle caps 26. Both ends of the axle 35 are connected to leaf springs 21 via U-bolt connecting plates 22. A center axle cap 26 is placed between the top surface of the U-bolt connecting plates 22 and the leaf springs 21. The center axle cap 26 can prevent stress concentration of the leaf springs 21 at the connection point of the U-bolt connecting plates 22, reducing the risk of leaf springs 21 breaking due to stress concentration. Both ends of the leaf springs 21 are provided with lug bushings 24. The frame 1 is provided with a rotating shaft 25 that can be rotatably connected to the lug bushings 24. A shock absorber 23 is connected between the U-bolt connecting plates 22 and the frame 1.

[0021] Two sets of wheel assemblies 3 are connected to the main steering device 4 by a steering tie rod 9. The main steering device 4 is rotatably connected to the frame 1. The auxiliary steering device 5 is slidably connected to the frame 1. The auxiliary steering contact device 6 is movably connected to the auxiliary steering device 5. Two follower steel cables 8 are connected between the auxiliary steering contact device 6 and the main steering device 4. The trailer arm contact plate 7 is movably connected to the frame 1.

[0022] The main steering device 4 includes a main steering center shaft 41 and a main steering wheel 42. The main steering wheel 42 is rotatably connected to the frame 1 through the main steering center shaft 41. Main steering cable connecting sleeves 43 are movably connected to both sides of the main steering wheel 42. One end of each of the two follower cables 8 is fixedly connected to the main steering cable connecting sleeves 43. A forward-extending swing arm 34 is fixedly connected to the hub bearing 32. A steering tie rod 9 is movably connected between the swing arm 34 and the main steering wheel 42.

[0023] The auxiliary adjustment device 5 includes a lower connecting frame 51. The top of the lower connecting frame 51 is detachably connected to a front upper cover 52 and a rear upper cover 53. The front upper cover 52, the rear upper cover 53 and the lower connecting frame 51 are combined to form a through hole 54 for the frame 1 to slide through. The bottom of the lower connecting frame 51 is provided with a steel cable fixing frame 55 near the rear upper cover 53. The follower steel cable 8 is movably connected to the steel cable fixing frame 55. The top of the front cover 52 is fixedly provided with a grooved cam 56, the grooved cam 56 is provided with a cross-shaped slot 57, the top of the frame 1 is provided with a bearing 58, the bearing 58 passes through the grooved cam 56 and is rotatably connected to a cam 59, the cam 59 is connected to a cam follower 591, the cam 59 is fixedly connected to a handle rod 592, and the handle rod 592 is provided with a rotating handle 593.

[0024] The bottom of the lower connecting frame 51 is provided with a secondary hub central shaft 61 near the front upper cover 52. The secondary hub contact device 6 includes a secondary hub 62, which is provided with a bearing 58 seat. The secondary hub 62 is rotatably connected to the secondary hub central shaft 61 through the bearing 58 seat. Two secondary hub steel cable connecting sleeves 63 are movably connected to both sides of the secondary hub 62. The other ends of the two follower steel cables 8 are respectively fixedly connected to the secondary hub steel cable connecting sleeves 63.

[0025] The secondary bond 62 is fixedly connected to two spring sleeves 64, each of which contains a spring 65. The spring 65 is coaxially fixedly connected to a secondary bond contact rod 66. The end of the secondary bond contact rod 66 away from the spring 65 passes through the spring sleeve 64 and is rotatably connected to a perforated pin 67. The perforated pin 67 is fixedly connected to a polyurethane-coated bearing 68.

[0026] The frame 1 is provided with a spring-loaded latch 10 near the sub-plate 62. The spring-loaded latch 10 includes a fixed frame 101 fixedly connected to the frame 1. The fixed frame 101 is provided with a triangular support block 102 near the sub-plate 62. The triangular support block 102 is rotatably connected to two arc-shaped locking plates 103. Both arc-shaped locking plates 103 are fixedly connected to a support plate 104. The two arc-shaped locking plates 103 are combined to form a slot 105 with an opening. The sub-plate 62 is fixedly connected to a ball plug 106. Both sides of the triangular support block 102 are provided with return springs 107. The support plate 104 is provided with a limiting rod 108 inserted into the return spring 107.

[0027] The movement of the secondary plug 62 is controlled by the secondary plug adjustment device 5 to control the insertion or disengagement of the ball plug 106 into or out of the slot 105. Specifically, rotating the rotary handle 593 causes the cam 59 to rotate under the transmission of the handle rod 592. The cam follower 591 moves within the cross-shaped slot 57 as the cam 59 rotates, pushing the grooved cam 56 to move. Since the grooved cam 56 is fixedly connected to the front upper cover 52, and the front upper cover 52 is connected to the lower connecting bracket 51, while the secondary plug 62... The sub-bonded connector 62 is connected to the lower connecting frame 51 via the central axis 61. Therefore, the sub-bonded connector 62 will be moved, thereby driving the ball plug 106 to move. When the ball plug 106 approaches the slot 105, the two arc-shaped locking plates 103 rotate to the sides to widen the opening. When the ball plug 106 is fully inserted into the slot 105, the two arc-shaped locking plates 103 will be reset under the elastic force of the return spring 107 and lock the ball plug 106. At this time, the sub-bonded connector 62 can no longer rotate around the central axis 61.

[0028] When the ball plug 106 disengages from the slot 105, the secondary bridge 62 and the primary bridge 42 are unlocked. Conversely, when the ball plug 106 is inserted into the slot 105, the secondary bridge 62 and the primary bridge 42 are locked, the steering system is locked, and the vehicle becomes a rigid axle trailer, which is convenient for driving on straight roads or roads with sharp turns.

[0029] The top of the trailer arm touch plate 7 is provided with a trailer ball 71, the top of the frame 1 is fixedly provided with a trailer cover 72 coupled to the trailer ball 71, and the frame 1 is provided with a hand-cranked lifting wheel 73.

[0030] The working principle of this invention can be summarized as follows: This embodiment Figure 2 and Figure 3 This diagram illustrates the overall movement of the trailer when the tractor unit turns clockwise. The specific structure and connection relationships of each component are shown in the attached diagram. Figure 1 , Figures 4 to 12 .

[0031] First, the trailer arm touch plate 7 is connected to the trailer head via components such as pins. Then, the trailer cover 72 is coupled to the trailer ball 71 via the hand-cranked lifting wheel 73, realizing the left-right swing connection between the trailer and the trailer arm touch plate 7. By rotating the handle 593 of the auxiliary bearing adjustment device 5, the rubber-coated bearing 68 of the auxiliary bearing contact device 6 is adjusted forward to touch the trailer arm touch plate 7. The ball plug 106 disengages from the slot 105, and the auxiliary bearing 62 and the main bearing 42 are unlocked, so that the auxiliary bearing 62 rotates left and right as the trailer arm touch plate 7 swings left and right.

[0032] When the trailer arm touch plate 7 turns clockwise, the rubber-coated bearing 68 on the right side will be pushed backward by the trailer arm touch plate 7 (it should be noted that the directional terms such as left, right, front, and rear mentioned in this application are based on the forward direction of the trailer). The rubber-coated bearing 68 on the right side being pushed backward will cause the auxiliary bearing 62 to rotate clockwise around the auxiliary bearing central axis 61. During the rotation of the auxiliary bearing 62, the follower cable 8 on the left side is pulled by the auxiliary bearing 62, and the follower cable 8 on the right side is pushed backward by the auxiliary bearing 62.

[0033] Subsequently, the main steering lever 42 rotates clockwise under the action of the two follower steel cables 8. During the rotation of the main steering lever 42, the right steering lever 9 is pulled to the left by the main steering lever 42, and the left steering push lever is pushed to the left by the main steering lever 42.

[0034] Next, the right steering tie rod 9 pulls the swing arm 34 in the right wheel assembly 3. Since the swing arm 34 is fixedly connected to the wheel hub bearing 32, and the wheel hub bearing 32 is fixedly connected to the wheel hub 31, the right wheel hub 31 will rotate counterclockwise around the wheel hub axle 33 under the pulling action of the right steering tie rod 9. The left steering tie rod 9 pushes against the swing arm 34 in the left wheel assembly 3. Since the swing arm 34 is fixedly connected to the wheel hub bearing 32, and the wheel hub bearing 32 is fixedly connected to the wheel hub 31, the left wheel hub 31 will rotate counterclockwise around the wheel hub axle 33 under the pushing action of the left steering tie rod 9.

[0035] In this way, the wheel hubs 31 of the trailer can adjust their angles as the tractor turns, allowing the trailer to turn along the trajectory of the tractor and reducing the footprint of the trailer during turning.

[0036] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A touch-sensitive trailer steering system, characterized in that, The system includes a frame (1), a suspension system (2), wheel assemblies (3), a main steering device (4), a secondary steering adjustment device (5), a secondary steering contact device (6), and a trailer arm contact plate (7). The wheel assemblies (3) are provided in two sets, and the two sets of wheel assemblies (3) are movably connected to the frame (1) through the suspension system (2). The main steering device (4) is rotatably connected to the frame (1). A steering tie rod (9) is connected between the two sets of wheel assemblies (3) and the main steering device (4). The secondary steering adjustment device (5) is slidably connected to the frame (1). The secondary steering contact device (6) is movably connected to the secondary steering adjustment device (5). Two follower steel cables (8) are connected between the secondary steering contact device (6) and the main steering device (4). The trailer arm contact plate (7) is movably connected to the frame (1).

2. The touch-sensitive trailer steering system according to claim 1, characterized in that, The wheel assembly (3) includes a wheel hub (31), a hub bearing (32), a hub axle (33), and an axle (35). The hub bearing (32) is fixedly connected to the wheel hub (31), the hub axle (33) is connected to the hub bearing (32), and both ends of the axle (35) are rotatably connected to the hub axle (33).

3. The touch-sensitive trailer steering system according to claim 2, characterized in that, The suspension system (2) includes a leaf spring (21), a U-bolt connecting plate (22), a shock absorber (23), and a center axle cap (26). Both ends of the axle (35) are connected to the leaf spring (21) through the U-bolt connecting plate (22). The center axle cap (26) is placed between the top surface of the U-bolt connecting plate (22) and the leaf spring (21). Both ends of the leaf spring (21) are provided with a lug bushing (24). The frame (1) is provided with a rotating shaft (25) that can be rotatably connected to the lug bushing (24). The shock absorber (23) is connected between the U-bolt connecting plate (22) and the frame (1).

4. The touch-sensitive trailer steering system according to claim 3, characterized in that, The main steering device (4) includes a main steering center shaft (41) and a main steering wheel (42). The main steering wheel (42) is rotatably connected to the frame (1) through the main steering center shaft (41). Main steering cable connecting sleeves (43) are movably connected to both sides of the main steering wheel (42). One end of each of the two follower cables (8) is fixedly connected to the main steering cable connecting sleeves (43). The wheel hub bearing (32) is fixedly connected to a forward-extending swing arm (34). A steering tie rod (9) is movably connected between the swing arm (34) and the main steering wheel (42).

5. The touch-sensitive trailer steering system according to claim 4, characterized in that, The auxiliary adjustment device (5) includes a lower connecting frame (51). The top of the lower connecting frame (51) is detachably connected to a front upper cover (52) and a rear upper cover (53). The front upper cover (52), the rear upper cover (53) and the lower connecting frame (51) are combined to form a through hole (54) for the frame (1) to slide through. The bottom of the lower connecting frame (51) is provided with a steel cable fixing frame (55) near the rear upper cover (53). The follower steel cable (8) is movably connected to the steel cable fixing frame (55). The top of the front cover (52) is fixedly provided with a grooved cam (56), the grooved cam (56) is provided with a cross-shaped slot (57), the top of the frame (1) is provided with a bearing (58), the bearing (58) passes through the grooved cam (56) and is rotatably connected to a cam (59), the cam (59) is connected to a cam follower (591) coupled to the cross-shaped slot (57), the cam (59) is fixedly connected to a handle rod (592), and the handle rod (592) is provided with a rotating handle (593).

6. The touch-sensitive trailer steering system according to claim 5, characterized in that, The bottom of the lower connecting frame (51) is provided with a sub-bond center shaft (61) near the front upper cover (52). The sub-bond contact device (6) includes a sub-bond (62). The sub-bond (62) is provided with a bearing (58) seat. The sub-bond (62) is rotatably connected to the sub-bond center shaft (61) through the bearing (58) seat. Two sub-bond steel cable connecting sleeves (63) are movably connected to both sides of the sub-bond (62). The other ends of the two follower steel cables (8) are respectively fixedly connected to the sub-bond steel cable connecting sleeves (63).

7. The touch-sensitive trailer steering system according to claim 6, characterized in that, The sub-bond (62) is fixedly connected to two spring sleeves (64), and each of the two spring sleeves (64) is provided with a spring (65). The spring (65) is coaxially fixedly connected to a sub-bond contact rod (66). The end of the sub-bond contact rod (66) away from the spring (65) passes through the spring sleeve (64) and is rotatably connected to a pin with a hole (67). The pin with a hole (67) is fixedly connected to a rubber-coated bearing (68).

8. The touch-sensitive trailer steering system according to claim 7, characterized in that, The frame (1) is provided with a spring-loaded latch (10) near the sub-bond (62). The spring-loaded latch (10) includes a fixed frame (101) fixedly connected to the frame (1). The fixed frame (101) is provided with a triangular support block (102) near the sub-bond (62). The triangular support block (102) is rotatably connected to two arc-shaped locking plates (103). Both arc-shaped locking plates (103) are fixedly connected to a support plate (104). The two arc-shaped locking plates (103) are combined to form a slot (105) with an opening. The sub-bond (62) is fixedly connected to a ball plug (106). Both sides of the triangular support block (102) are provided with a return spring (107). The support plate (104) is provided with a limiting rod (108) inserted into the return spring (107).

9. The touch-sensitive trailer steering system according to claim 1, characterized in that, The top of the trailer arm touch plate (7) is provided with a trailer ball (71), and the top of the frame (1) is fixedly provided with a trailer cover (72) coupled to the trailer ball (71). The frame (1) is provided with a hand-cranked lifting wheel (73).

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