Reversing mechanism of box type four-way shuttle vehicle

Abstract

The utility model discloses a reversing mechanism of a box type four-way shuttle vehicle. The technical problem that a guide mechanism is prone to abrasion in the reversing process is solved. A vehicle body reversing walking driving motor (5) is started, a reversing driving driving gear (17) connected to an output shaft of the vehicle body reversing walking driving motor is meshed with a reversing driving driven gear (8) to drive a reversing driving shaft (7) to rotate, and the reversing driving shaft (7) is driven to rotate through a right side flexible coupler (9) and a left side flexible coupler (29). A first reversing swing shaft (10) and a third reversing swing shaft (30) are synchronously driven to rotate, so that a first reversing roller (12) and a third reversing roller (32) synchronously swing downwards, a second reversing swing shaft (14) is synchronously driven to synchronously rotate through transmission of a right longitudinal gear transmission set (18), and a right longitudinal walking wheel carrier plate (19) is put down by a second reversing roller (16) and the first reversing roller together. And reversing is realized.

Description

Technical Field

[0001] This invention relates to a shuttle, and more particularly to a reversing mechanism for a box-type four-way shuttle. Background Technology

[0002] When in operation, the shuttle car moves either horizontally (lateral) or vertically (forward). It typically changes direction at intersections, switching from straight to lateral travel. The reversing mechanism of a traditional box-type four-way shuttle car generally adopts a one-point lifting and two-point guiding mechanism. This mechanism is usually located in the middle of the car frame. Since single-point lifting is prone to uneven load, and severe uneven load operation will cause severe wear of the guiding mechanism or cause uneven load on the entire car body, affecting the normal operation of the four-way shuttle car. Summary of the Invention

[0003] This invention provides a reversing mechanism for a box-type four-way shuttle, which solves the technical problem of wear on the guide mechanism during the reversing process and realizes balanced reversing of the reversing vehicle.

[0004] The present invention solves the above technical problems through the following technical solutions:

[0005] A reversing mechanism for a box-type four-way shuttle includes a rectangular frame. Lateral travel wheels are mounted on both the front and rear crossbeams of the rectangular frame. A fork assembly is located at the top center of the rectangular frame. A drive motor mounting plate is located to the right of the fork assembly. A reversing drive motor is mounted on the drive motor mounting plate. A reversing drive drive gear is connected to the output shaft of the reversing drive motor. A pair of drive shaft support plates are arranged parallel to each other along the longitudinal direction on the rectangular frame. A reversing drive shaft is located between the pair of drive shaft support plates. A reversing drive driven gear is located on the reversing drive shaft to the right of the pair of drive shaft support plates. A right-end reversing drive shaft support box is connected to the right longitudinal beam of the rectangular frame. A first reversing swing shaft and a second reversing swing shaft are respectively mounted on the right-end reversing drive shaft support box. A right-end reversing drive shaft support box is located between the first and second reversing swing shafts. A right-side longitudinal gear transmission assembly is installed in the support housing. The left end of the first reversing swing shaft is connected to the right end of the reversing drive shaft via a right-side flexible coupling. A first reversing eccentric swing block is connected to the right end of the first reversing swing shaft, and a first reversing roller is installed on the first reversing eccentric swing block. A second reversing eccentric swing block is connected to the right end of the second reversing swing shaft, and a second reversing roller is installed on the second reversing eccentric swing block. A right longitudinal traveling wheel frame plate is movably installed on the right side of the right-side reversing drive shaft support housing. A right longitudinal traveling wheel is installed on the right outer surface of the right longitudinal traveling wheel frame plate. Horizontal first reversing roller embedded in a channel steel and horizontal second reversing roller embedded in a channel steel are respectively installed on the left inner surface of the right longitudinal traveling wheel frame plate. The first reversing roller is movably installed in the first reversing roller embedded in the channel steel, and the second reversing roller is movably installed in the second reversing roller embedded in the channel steel. The reversing drive driving gear and the reversing drive driven gear mesh together.

[0006] A first upper and lower guide rail is provided at the right front end of the rectangular vehicle frame, and a first slider is provided on the first upper and lower guide rail. A first slider connecting seat is provided on the inner side of the front end of the right longitudinal travel wheel frame plate, and the top surface of the first slider is connected to the first slider connecting seat. A second upper and lower guide rail is provided at the right rear end of the rectangular vehicle frame, and a second slider is provided on the second upper and lower guide rail. A second slider connecting seat is provided on the inner side of the rear end of the right longitudinal travel wheel frame plate, and the top surface of the second slider is connected to the second slider connecting seat.

[0007] A left-end reversing drive shaft support housing is connected to the left-end longitudinal beam of the rectangular body frame. A third and fourth reversing swing shaft are respectively installed on the left-end reversing drive shaft support housing. A left-side longitudinal gear transmission assembly is installed in the left-end reversing drive shaft support housing between the third and fourth reversing swing shafts. The right end of the third reversing swing shaft is connected to the left end of the reversing drive shaft via a left-side flexible coupling. A third reversing eccentric swing block is connected to the right end of the third reversing swing shaft, and a third reversing roller is installed on the third reversing eccentric swing block. The fourth reversing swing... The left end of the drive shaft is connected to a fourth reversing eccentric swing block, and a fourth reversing roller is provided on the fourth reversing eccentric swing block; a left longitudinal travel wheel frame plate is movably provided on the left side of the left reversing drive shaft support box, a left longitudinal travel wheel is provided on the left outer facade of the left longitudinal travel wheel frame plate, and a horizontal third reversing roller embedded in a channel steel and a horizontal fourth reversing roller embedded in a channel steel are respectively provided on the right inner facade of the left longitudinal travel wheel frame plate. The third reversing roller is movably provided in the third reversing roller embedded in the channel steel, and the fourth reversing roller is movably provided in the fourth reversing roller embedded in the channel steel.

[0008] A third upper and lower guide rail is provided at the left front end of the rectangular vehicle frame, and a third slider is provided on the third upper and lower guide rail. A third slider connecting seat is provided on the inner side of the front end of the left longitudinal travel wheel frame plate, and the top surface of the third slider is connected to the third slider connecting seat. A fourth upper and lower guide rail is provided at the left rear end of the rectangular vehicle frame, and a fourth slider is provided on the fourth upper and lower guide rail. A fourth slider connecting seat is provided on the inner side of the rear end of the left longitudinal travel wheel frame plate, and the top surface of the fourth slider is connected to the fourth slider connecting seat.

[0009] A reversing method for a box-type four-way shuttle car, wherein when the box-type four-way shuttle car moves left or right, it is achieved by transverse traveling wheels set on the front and rear crossbeams of the rectangular car frame. At this time, the first reversing roller, the second reversing roller, the third reversing roller, and the fourth reversing roller are all in the highest position, and the right longitudinal traveling wheel frame plate and the left longitudinal traveling wheel frame plate are lifted, so that the two right longitudinal traveling wheels and the two left longitudinal traveling wheels are off the ground; characterized in that, if the box-type four-way shuttle car reverses to move in the forward and backward direction, the steps are as follows:

[0010] Step 1: Start the vehicle body reversing travel drive motor. The reversing drive active gear connected to the output shaft of the vehicle body reversing travel drive motor meshes with the reversing drive driven gear, driving the reversing drive shaft to rotate. The reversing drive shaft drives the first reversing swing shaft and the third reversing swing shaft to rotate synchronously through the right flexible coupling and the left flexible coupling, respectively, so that the first reversing roller and the third reversing roller swing downward synchronously.

[0011] At the same time, as the first reversing swing shaft rotates, it drives the second reversing swing shaft to rotate synchronously through the right longitudinal gear transmission group. The second reversing roller and the first reversing roller together lower the right longitudinal traveling wheel frame plate, so that the two right longitudinal traveling wheels can land on the ground.

[0012] At the same time, as the third reversing swing shaft rotates, it drives the fourth reversing swing shaft to rotate synchronously through the left longitudinal gear transmission group. The third and fourth reversing rollers together lower the left longitudinal traveling wheel frame plate, so that the two left longitudinal traveling wheels can land on the ground.

[0013] The second step involves the vehicle body reversing drive motor continuing to rotate, causing the first, second, third, and fourth reversing eccentric blocks to swing synchronously, raising the entire rectangular vehicle body frame and lifting the four lateral travel wheels off the ground, thus completing the reversing.

[0014] When the second reversing roller and the first reversing roller together lower the right longitudinal travel wheel frame plate, the first slider slides along the first upper and lower guide rails, the second slider slides along the second upper and lower guide rails, the third slider slides along the third upper and lower guide rails, and the fourth slider slides along the fourth upper and lower guide rails.

[0015] The lifting mechanism of the present invention is set on both sides of the vehicle frame and adopts a two-point lifting and two-line guiding method to ensure smoothness and non-eccentric load when the vehicle body turns, and overcomes the wear of the guiding mechanism caused by the eccentric load during reversal. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention;

[0017] Figure 2 This is a schematic diagram of the rectangular vehicle frame 1 of the present invention;

[0018] Figure 3 This is a schematic diagram of the structure of the right-end reversing drive shaft support box 13 and the left-end reversing drive shaft support box 33 of the present invention;

[0019] Figure 4 This is a schematic diagram of the structure of the right longitudinal travel wheel frame plate 19 and the left longitudinal travel wheel frame plate 38 of the present invention;

[0020] Figure 5 This is a schematic diagram of the structure of the right longitudinal wheel frame plate 19 and the left longitudinal wheel frame plate 38 of the present invention when viewed from the left front direction. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings:

[0022] In the intelligent warehouse, box-type four-way shuttles are used to complete the transfer of goods. These shuttles travel laterally (left-right) or longitudinally (front-back), with the two directions perpendicular to each other, resulting in a 90-degree reversal. The box-type four-way shuttle has a rectangular box-like shape and forks mounted on the body, which are used to transfer goods from the vehicle to their designated storage locations. The reversing mechanism of the box-type four-way shuttle includes a rectangular frame 1. Two lateral travel wheels 2 are mounted on the front crossbeam and two on the rear crossbeam of the rectangular frame 1. These four lateral travel wheels support the entire rectangular frame 1 and enable the lateral movement of the vehicle. A lateral travel drive motor is mounted on the frame, and the lateral travel drive motor transmits power through the lateral travel... The mechanism drives four lateral travel wheels to move. A fork assembly 3 is located at the top center of the rectangular frame 1. A drive motor mounting plate 4 is located to the right of the fork assembly 3. A vehicle reversing drive motor 5 is mounted on the drive motor mounting plate 4. When the vehicle needs to reverse direction, the vehicle reversing drive motor 5 is activated to complete the reversal between the lateral and longitudinal directions. A reversing drive gear 17 is connected to the output shaft of the vehicle reversing drive motor 5. A pair of drive shaft support plates 6 are arranged parallel to each other along the front-rear direction on the rectangular frame 1. A reversing drive shaft 7 is located between the pair of drive shaft support plates 6. The reversing drive shaft 7 is supported by these two drive shaft support plates and transmits the reversing rotational action to the two longitudinal travel wheel frame plates. On the right side of the drive shaft support plate 6, a reversing drive driven gear 8 is provided on the reversing drive shaft 7. The vehicle body reversing travel drive motor 5 drives the reversing drive shaft 7 to rotate by meshing with the reversing drive driven gear 17 fixed on its output shaft and the reversing drive driven gear 8 to perform the reversing task. A right-end reversing drive shaft support box 13 is connected to the right longitudinal beam of the rectangular vehicle body frame 1. This box serves as the support frame for the two right-side reversing swing shafts and also transmits the reversing rotation action. A first reversing swing shaft 10 and a second reversing swing shaft 14 are respectively provided on the right-end reversing drive shaft support box 13. A right-side longitudinal gear is provided in the right-end reversing drive shaft support box 13 between the first reversing swing shaft 10 and the second reversing swing shaft 14. The transmission group 18 has a set of right longitudinal gear transmission groups 18 that mesh sequentially in the right reversing drive shaft support housing 13. The foremost gear of this group is set on the first reversing swing shaft 10, and the rearmost gear is set on the second reversing swing shaft 14. Multiple intermediate transmission gears are set between these two gears to enable the second reversing swing shaft 14 and the first reversing swing shaft 10 to rotate and swing synchronously. The left end of the first reversing swing shaft 10 is connected to the right end of the reversing drive shaft 7 through the right flexible coupling 9. The right end of the first reversing swing shaft 10 is connected to the first reversing eccentric swing block 11, and the first reversing roller 12 is set on the first reversing eccentric swing block 11 to drive the up and down movement of the right longitudinal traveling wheel frame plate 19.A second reversing eccentric swing block 15 is connected to the right end of the second reversing swing shaft 14, and a second reversing roller 16 is provided on the second reversing eccentric swing block 15; a right longitudinal travel wheel frame plate 19 is movably provided on the right side of the right end reversing drive shaft support box 13, and a right longitudinal travel wheel 20 is provided on the right outer surface of the right longitudinal travel wheel frame plate 19; a horizontal first reversing roller embedded channel steel 21 and a horizontal second reversing roller embedded channel steel 22 are respectively provided on the left inner surface of the right longitudinal travel wheel frame plate 19. 12 is movably disposed in the first reversing roller embedded in the channel steel 21, and the second reversing roller 16 is movably disposed in the second reversing roller embedded in the channel steel 22; the reversing drive driving gear 17 meshes with the reversing drive driven gear 8; by rotating the first reversing swing shaft 10 and the second reversing swing shaft 14 fixedly disposed on the right end reversing drive shaft support housing 13, the first reversing eccentric swing block 11 and the second reversing eccentric swing block 15 are driven to swing, and then the first reversing roller 12 moves in the first reversing roller embedded in the channel steel 21;

[0023] The second reversing roller 16 moves within the channel steel 22, simultaneously lowering the right longitudinal travel wheel frame plate 19 to the ground. As the first reversing eccentric swing block 11 and the second reversing eccentric swing block 15 swing, the rectangular vehicle frame 1 is lifted, causing the four transverse travel wheels 2 to leave the ground, thus changing the vehicle body from traveling in the left-right direction to being able to travel in the front-back longitudinal direction.

[0024] A first upper and lower guide rail 25 is provided at the right front end of the rectangular vehicle frame 1, and a first slider 26 is provided on the first upper and lower guide rail 25. A first slider connecting seat 23 is provided on the inner side of the front end of the right longitudinal travel wheel frame plate 19, and the top surface of the first slider 26 is connected to the first slider connecting seat 23. A second upper and lower guide rail 27 is provided at the right rear end of the rectangular vehicle frame 1, and a second slider 28 is provided on the second upper and lower guide rail 27. A second slider connecting seat 24 is provided on the inner side of the rear end of the right longitudinal travel wheel frame plate 19, and the top surface of the second slider 28 is connected to the second slider connecting seat 24. The two guide rails and sliders cooperate to guide the movement of the right longitudinal travel wheel frame plate 19, realizing smooth and stable reversal.

[0025] A left-end reversing drive shaft support housing 33 is connected to the left-end longitudinal beam of the rectangular body frame 1. A third reversing swing shaft 30 and a fourth reversing swing shaft 34 are respectively installed on the left-end reversing drive shaft support housing 33. A left-side longitudinal gear transmission assembly 37 is installed in the left-end reversing drive shaft support housing 33 between the third reversing swing shaft 30 and the fourth reversing swing shaft 34. The right end of the third reversing swing shaft 30 is connected to the left end of the reversing drive shaft 7 through a left-side flexible coupling 29. A third reversing eccentric swing block 31 is connected to the right end of the third reversing swing shaft 30. A third reversing roller 32 is installed on the third reversing eccentric swing block 31. The left end of the drive shaft 34 is connected to a fourth reversing eccentric swing block 35, and a fourth reversing roller 36 is provided on the fourth reversing eccentric swing block 35; a left longitudinal travel wheel frame plate 38 is movably provided on the left side of the left reversing drive shaft support box 33, a left longitudinal travel wheel 39 is provided on the left outer surface of the left longitudinal travel wheel frame plate 38, and a horizontal third reversing roller embedded channel steel 40 and a horizontal fourth reversing roller embedded channel steel 41 are respectively provided on the right inner surface of the left longitudinal travel wheel frame plate 38. The third reversing roller 32 is movably provided in the third reversing roller embedded channel steel 40, and the fourth reversing roller 36 is movably provided in the fourth reversing roller embedded channel steel 41.

[0026] A third upper and lower guide rail 45 is provided at the left front end of the rectangular car frame 1, and a third slider 44 is provided on the third upper and lower guide rail 45. A third slider connecting seat 42 is provided on the inner side of the front end of the left longitudinal travel wheel frame plate 38, and the top surface of the third slider 44 is connected to the third slider connecting seat 42. A fourth upper and lower guide rail 47 is provided at the left rear end of the rectangular car frame 1, and a fourth slider 46 is provided on the fourth upper and lower guide rail 47. A fourth slider connecting seat 43 is provided on the inner side of the rear end of the left longitudinal travel wheel frame plate 38, and the top surface of the fourth slider 46 is connected to the fourth slider connecting seat 43. The reversing mechanism structures on the left and right sides of the rectangular car frame 1 are basically the same.

[0027] A reversing method for a box-type four-way shuttle: When the box-type four-way shuttle moves left or right, it is achieved by transverse traveling wheels 2 installed on the front and rear crossbeams of the rectangular frame 1. At this time, the first reversing roller 12, the second reversing roller 16, the third reversing roller 32, and the fourth reversing roller 36 are all in their highest positions, and the right longitudinal traveling wheel frame plate 19 and the left longitudinal traveling wheel frame plate 38 are lifted, causing the two right longitudinal traveling wheels 20 and the two left longitudinal traveling wheels 39 to leave the ground. The shuttle body is supported on the ground by the four transverse traveling wheels 2 and completes the left and right movement. If the box-type four-way shuttle reverses to move in the forward or backward direction, the steps are as follows:

[0028] Step 1: Start the vehicle body reversing travel drive motor 5. The reversing drive active gear 17 connected to the output shaft of the vehicle body reversing travel drive motor 5 meshes with the reversing drive driven gear 8, driving the reversing drive shaft 7 to rotate. The reversing drive shaft 7 drives the first reversing swing shaft 10 and the third reversing swing shaft 30 to rotate synchronously through the right flexible coupling 9 and the left flexible coupling 29, respectively, so that the first reversing roller 12 and the third reversing roller 32 swing downward synchronously.

[0029] At the same time, as the first reversing swing shaft 10 rotates, it drives the second reversing swing shaft 14 to rotate synchronously through the right longitudinal gear transmission group 18. The second reversing roller 16 and the first reversing roller 12 together lower the right longitudinal traveling wheel frame plate 19, so that the two right longitudinal traveling wheels 20 land on the ground.

[0030] At the same time, as the third reversing swing shaft 30 rotates, it drives the fourth reversing swing shaft 34 to rotate synchronously through the left longitudinal gear transmission group 37. The third reversing roller 32 and the fourth reversing roller 36 together lower the left longitudinal traveling wheel frame plate 38, so that the two left longitudinal traveling wheels 39 land on the ground.

[0031] The second step involves the vehicle body reversing drive motor 5 continuing to rotate, causing the first reversing eccentric swing block 11, the second reversing eccentric swing block 15, the third reversing eccentric swing block 31, and the fourth reversing eccentric swing block 35 to swing synchronously at the same angle, thereby raising the entire rectangular vehicle body frame 1 and lifting the four transverse traveling wheels 2 off the ground, thus completing the reversing.

[0032] When the second reversing roller 16 and the first reversing roller 12 together lower the right longitudinal travel wheel frame plate 19, the first slider 26 slides along the first upper and lower guide rail 25, the second slider 28 slides along the second upper and lower guide rail 27; the third slider 44 slides along the third upper and lower guide rail 45, and the fourth slider 46 slides along the fourth upper and lower guide rail 47.

Claims

1. A reversing mechanism for a box-type four-way shuttle, comprising a rectangular frame (1), with transverse travel wheels (2) provided on both the front and rear crossbeams of the rectangular frame (1), a fork assembly (3) provided at the top center of the rectangular frame (1), a drive motor mounting plate (4) provided on the right side of the fork assembly (3), a reversing drive motor (5) provided on the drive motor mounting plate (4), and a reversing drive active gear (17) connected to the output shaft of the reversing drive motor (5), characterized in that, On the rectangular car frame (1), a pair of drive shaft support plates (6) are arranged parallel to each other along the front-rear direction. A reversing drive shaft (7) is arranged between the pair of drive shaft support plates (6). A reversing drive driven gear (8) is arranged on the reversing drive shaft (7) on the right side of the pair of drive shaft support plates (6). A right reversing drive shaft support box (13) is connected to the right longitudinal beam of the rectangular car frame (1). A first reversing swing shaft (10) and a second reversing swing shaft (14) are respectively arranged on the right reversing drive shaft support box (13). A right longitudinal gear transmission group (18) is arranged in the right reversing drive shaft support box (13) between the first reversing swing shaft (10) and the second reversing swing shaft (14). The left end of the first reversing swing shaft (10) is connected to the right end of the reversing drive shaft (7) through a right flexible coupling (9). A first reversing eccentric swing block is connected to the right end of the first reversing swing shaft (10). 11) A first reversing roller (12) is provided on the first reversing eccentric swing block (11); a second reversing eccentric swing block (15) is connected to the right end of the second reversing swing shaft (14), and a second reversing roller (16) is provided on the second reversing eccentric swing block (15); a right longitudinal travel wheel frame plate (19) is movably provided on the right side of the right end reversing drive shaft support box (13), and a right longitudinal travel wheel is provided on the right outer surface of the right longitudinal travel wheel frame plate (19). (20) On the left inner surface of the right longitudinal travel wheel frame plate (19), there are horizontal first reversing roller embedded in channel steel (21) and horizontal second reversing roller embedded in channel steel (22). The first reversing roller (12) is movably disposed in the first reversing roller embedded in channel steel (21), and the second reversing roller (16) is movably disposed in the second reversing roller embedded in channel steel (22). The reversing drive active gear (17) meshes with the reversing drive driven gear (8).

2. The reversing mechanism of a box-type four-way shuttle car according to claim 1, characterized in that, A first upper and lower guide rail (25) is provided at the right front end of the rectangular vehicle frame (1), and a first slider (26) is provided on the first upper and lower guide rail (25). A first slider connecting seat (23) is provided on the inner side of the front end of the right longitudinal travel wheel frame plate (19), and the top surface of the first slider (26) is connected to the first slider connecting seat (23). A second upper and lower guide rail (27) is provided at the right rear end of the rectangular vehicle frame (1), and a second slider (28) is provided on the second upper and lower guide rail (27). A second slider connecting seat (24) is provided on the inner side of the rear end of the right longitudinal travel wheel frame plate (19), and the top surface of the second slider (28) is connected to the second slider connecting seat (24).

3. The reversing mechanism of a box-type four-way shuttle car according to claim 1 or 2, characterized in that, A left-end reversing drive shaft support box (33) is connected to the left-end longitudinal beam of the rectangular body frame (1). A third reversing swing shaft (30) and a fourth reversing swing shaft (34) are respectively provided on the left-end reversing drive shaft support box (33). A left-side longitudinal gear transmission group (37) is provided in the left-end reversing drive shaft support box (33) between the third reversing swing shaft (30) and the fourth reversing swing shaft (34). The right end of the third reversing swing shaft (30) is connected to the left end of the reversing drive shaft (7) through a left-side flexible coupling (29). A third reversing eccentric swing block (31) is connected to the right end of the third reversing swing shaft (30). A third reversing roller (32) is provided on the third reversing eccentric swing block (31). The left end of the swing shaft (34) is connected to the fourth reversing eccentric swing block (35), and the fourth reversing roller (36) is provided on the fourth reversing eccentric swing block (35); the left longitudinal travel wheel frame plate (38) is movably provided on the left side of the left reversing drive shaft support box (33), the left longitudinal travel wheel (39) is provided on the left outer facade of the left longitudinal travel wheel frame plate (38), and the right inner facade of the left longitudinal travel wheel frame plate (38) is provided with the horizontal third reversing roller embedded channel steel (40) and the horizontal fourth reversing roller embedded channel steel (41), respectively. The third reversing roller (32) is movably provided in the third reversing roller embedded channel steel (40), and the fourth reversing roller (36) is movably provided in the fourth reversing roller embedded channel steel (41).

4. The reversing mechanism of a box-type four-way shuttle car according to claim 3, characterized in that, A third upper and lower guide rail (45) is provided at the left front end of the rectangular vehicle frame (1), and a third slider (44) is provided on the third upper and lower guide rail (45). A third slider connecting seat (42) is provided on the inner side of the front end of the left longitudinal travel wheel frame plate (38), and the top surface of the third slider (44) is connected to the third slider connecting seat (42). A fourth upper and lower guide rail (47) is provided at the left rear end of the rectangular vehicle frame (1), and a fourth slider (46) is provided on the fourth upper and lower guide rail (47). A fourth slider connecting seat (43) is provided on the inner side of the rear end of the left longitudinal travel wheel frame plate (38), and the top surface of the fourth slider (46) is connected to the fourth slider connecting seat (43).

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