Large-tonnage double-beam hoist

Abstract

The application discloses a large-tonnage double-beam hoist, which comprises two cross beams and a moving trolley arranged on each cross beam, an annular platform is arranged between the two moving trolleys, and the moving trolleys are used to drive the annular platform to move along the direction of the cross beam; the winding and unwinding of a plurality of lifting ropes is realized by the mutual approach or separation of a plurality of first wire columns, thereby realizing the lifting of the object, the distance between the two first wire columns is calculated, the output length of the lifting rope is directly calculated, the lifting height of the hook and the object is directly calculated, the lifting position of the object is accurately controlled, the error and the labor consumption when the lifting position is observed and evaluated by the human eye are avoided, the lifting mode is simplified, the lifting precision is improved, and the requirement of the equipment on the operator is reduced.

Description

Technical Field

[0001] This invention relates to the technical field of lifting equipment, and in particular to a large-tonnage double-beam hoist. Background Technology

[0002] Double beam hoists are a type of special lifting equipment, mainly installed on overhead cranes and gantry cranes. Compared with single beam hoists, double beam hoists mainly use two crossbeams and two sets of moving trolleys to achieve the movement of equipment and the hoisting and transfer of objects. They have higher stability and can lift greater weight.

[0003] Traditional double-girder hoists lift objects primarily by releasing or rewinding the lifting rope through the rotation of rollers within the equipment. This causes the hook and the object to move up and down, thus achieving the lifting operation. However, with this type of equipment, the diameter of the lifting rope wound on the rollers cannot be accurately calculated, resulting in inaccurate calculation of the rope's length and the lifting height of the object. Workers must visually assess and judge the lifting position of the object and make multiple adjustments to achieve the desired lifting position. This method of lifting is quite cumbersome, and the equipment requires a high level of experience from the operators. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a large-tonnage double-beam hoist.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A large-tonnage double-beam hoist includes two crossbeams and a movable trolley set on each crossbeam. A ring platform is provided between the two movable trolleys. The movable trolleys are used to drive the ring platform to move along the direction of the crossbeams.

[0007] Multiple grooves are provided on the annular platform, with the grooves running along the radial direction of the annular platform. A first slider is slidably installed in the groove, and a first transmission post is fixed on the first slider. A transmission groove is provided on the outer wall of the first transmission post. A suspension rope is fixed to the top of each first transmission post. The suspension rope is wrapped around the outer wall of multiple first transmission posts. The outer end of the suspension rope passes around a first transmission post and passes through the circular hole in the middle of the annular platform to the bottom of the annular platform. The outer ends of the multiple suspension ropes are connected to hooks.

[0008] Furthermore, the top of the annular platform is provided with a plurality of second transmission posts in a ring shape. The second transmission posts are located between two adjacent first transmission posts and are close to the central circular hole of the annular platform. A plurality of first U-shaped wheels are rotatably mounted on the second transmission posts, and the suspension rope passes around the first U-shaped wheels and transports the cable.

[0009] Furthermore, it also includes a telescopic rod, the fixed end of which is rotatably mounted on the top of a first transmission post, and the movable end of which is rotatably mounted on the top of a second transmission post adjacent to the first transmission post. A measuring plate is fixed on the movable end of the telescopic rod, and a laser rangefinder is mounted on the fixed end of the telescopic rod.

[0010] Furthermore, a support ring is provided inside the central circular hole of the annular platform. Multiple second sliders are provided on the outer wall of the support ring, and the support ring slides on the second sliders. A support plate is fixed on the second slider, and the outer end of the support plate is fixed on the inner wall of the central circular hole of the annular platform. Multiple support columns are fixed on the support ring, and a second U-shaped wheel is rotatably provided on the outer wall of the support column. The suspension rope passes around the second U-shaped wheel and is transported downward.

[0011] Furthermore, a base is provided in the middle of the support ring, and multiple fastening groove plates are provided on the outer wall of the base. The fastening groove plates are right-angled and the middle part is arc-shaped. The fastening groove plates are fastened to the outside of the lifting rope on the second U-shaped wheel. Multiple connecting arms are fixed on the outer wall of the base, and the outer ends of the connecting arms are fixed on the inner wall of the support ring.

[0012] Furthermore, crossbars are provided on both sides of the second U-shaped wheel, and the crossbars are fixed on the support ring. A U-shaped frame is provided between the two crossbars. The U-shaped frame is vertically slidably installed on the crossbars. The top of the U-shaped frame is set in a groove shape. A push plate is fixed on the inner side wall of the U-shaped frame. A slide block is fixed on the outer side wall of the second U-shaped wheel. A slide plate is slidably mounted on the slide block, and the sliding direction of the slide plate is along the radial direction of the second U-shaped wheel. A first leaf spring connects the slide plate and the slide block.

[0013] Furthermore, a right-angle support plate is provided at the bottom of the crossbar, and the bottom of the right-angle support plate contacts the bottom of the U-shaped frame. A second leaf spring connects the U-shaped frame and the crossbar.

[0014] Furthermore, a gear ring is rotatably mounted on the top of the annular platform, and a gear meshes on the gear ring. A motor is mounted on the gear and fixed on the annular platform. Multiple first push-pull plates are rotatably mounted on the outer circumference of the gear ring. Second push-pull plates are rotatably mounted on the outer ends of the first push-pull plates. One end of the second push-pull plate is rotatably mounted on the side wall of the first slider, and the other end of the second push-pull plate is mounted on a support plate. The second push-pull plate passes through the support plate and slides relative to it. The support plate is rotatably mounted on the annular platform.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: by using multiple first transmission posts to move closer or further apart from each other, the lifting and unloading of multiple lifting ropes is achieved, thereby realizing the lifting of objects. Furthermore, by calculating the distance between two first transmission posts, the output length of the lifting rope can be directly calculated, thereby directly calculating the lifting height of the hook and the object. This facilitates accurate control of the object's lifting position, avoids errors and manpower consumption when using human eyes to observe and evaluate the lifting position, simplifies the lifting method, improves lifting accuracy, and reduces the requirements of the equipment on operators. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of the present invention;

[0018] Figure 2 yes Figure 1 Enlarged schematic diagram of the central ring platform;

[0019] Figure 3 yes Figure 2 Cross-sectional structural diagram of the top structure of the central ring platform;

[0020] Figure 4 yes Figure 2 Enlarged schematic diagram of the central support ring structure;

[0021] Figure 5 yes Figure 4 A schematic diagram of the structure after removing the retaining plate;

[0022] Figure 6 yes Figure 4 Enlarged structural diagram of the central groove plate;

[0023] Figure 7 yes Figure 5 A magnified oblique view of the second U-shaped wheel in the middle;

[0024] The following are labels in the attached diagram: 1. Crossbeam; 2. Moving trolley; 3. Circular platform; 4. Slide groove; 5. First slider; 6. First cable feed post; 7. Suspension rope; 8. Hook; 9. Second cable feed post; 10. First U-shaped wheel; 11. Telescopic rod; 12. Measuring plate; 13. Laser rangefinder; 14. Support ring; 15. Second slider; 16. Support plate; 17. Support column; 18. Second U-shaped wheel; 19. Base; 20. Clip plate; 21. Connecting arm; 22. Crossbar; 23. U-shaped frame; 24. Push plate; 25. Slide seat; 26. Slide plate; 27. First leaf spring; 28. Right-angle support plate; 29. ​​Second leaf spring; 30. Gear ring; 31. Gear; 32. Motor; 33. First push-pull plate; 34. Second push-pull plate; 35. Support plate. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0026] In the description of this invention, it should be noted that the orientations or positional relationships indicated by terms such as "center", "up", "down", "left", "right", "vertical", "horizontal", "inner", and "outer" are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. This embodiment is written in a progressive manner.

[0028] like Figures 1 to 4 As shown, a large-tonnage double-beam hoist of the present invention includes two crossbeams 1 and a movable trolley 2 disposed on each crossbeam 1. An annular platform 3 is disposed between the two movable trolleys 2. The movable trolley 2 is used to drive the annular platform 3 to move along the crossbeam 1.

[0029] Multiple sliding grooves 4 are provided on the annular platform 3. The sliding grooves 4 are along the radial direction of the annular platform 3. A first slider 5 is slidably provided in the sliding groove 4. A first wire feeding post 6 is fixed on the first slider 5. A wire feeding groove is provided on the outer wall of the first wire feeding post 6. A suspension rope 7 is fixed to the top of each first wire feeding post 6. The suspension rope 7 is wrapped around the outer wall of multiple first wire feeding posts 6. The outer end of the suspension rope 7 passes around a first wire feeding post 6 and passes through the circular hole in the middle of the annular platform 3 to the bottom of the annular platform 3. The outer ends of multiple suspension ropes 7 are connected to hooks 8.

[0030] Specifically, the lifting rope 7 on each first transmission post 6 is wound around the outer wall of multiple first transmission posts 6. The multiple lifting ropes 7 are wound sequentially in the transmission groove on the outer wall of all first transmission posts 6. The outer end of the lifting rope 7 can bypass the outer wall of the first transmission post 6 that fixes the lifting rope 7 and pass through the central circular hole of the annular platform 3 to be transported downward. The multiple lifting ropes 7 are simultaneously used to lift and connect the hook 8. By adopting the structure of multiple lifting ropes 7, it is convenient to balance the force on the hook 8 and avoid the risk of the hook 8 swinging randomly when lifting objects, thus improving the stability of the lifting operation.

[0031] When an object needs to be lifted by the hook 8, multiple first sliders 5 are simultaneously pushed to move within multiple slide grooves 4. The multiple first sliders 5 drive multiple first feeder posts 6 to move closer or further away from each other simultaneously. When multiple first feeder posts 6 move closer to each other simultaneously, the length of the lifting rope 7 between two adjacent first feeder posts 6 is shortened. The lifting rope 7 passes through the central hole of the annular platform 3 and is conveyed downwards. Multiple lifting ropes 7 are conveyed simultaneously, thereby causing the hook 8 to move downwards and closer to the object. When multiple first feeder posts 6 move further away from each other simultaneously, the length of the lifting rope 7 between two adjacent first feeder posts 6 is increased. The lifting rope 7 slides on the first feeder post 6. Multiple lifting ropes 7 simultaneously drive the hook 8 and the object on the hook 8 to move upwards, thereby realizing the lifting operation.

[0032] By calculating the distance between the two first transmission posts 6, the output length of the lifting rope 7 can be directly calculated, thereby calculating the lifting height of the hook 8 and the object.

[0033] By using multiple first transmission posts 6 to move closer or further apart, the lifting ropes 7 can be extended and retracted, thus enabling the lifting of objects. Furthermore, by calculating the distance between two first transmission posts 6, the output length of the lifting rope 7 can be directly calculated, thereby directly calculating the lifting height of the hook 8 and the object. This facilitates accurate control of the object's lifting position, avoids errors and manpower consumption when using human observation to assess the lifting position, simplifies the lifting method, improves lifting accuracy, and reduces the equipment's requirements for operators.

[0034] like Figure 2As shown, in a preferred embodiment, the top of the annular platform 3 is provided with a plurality of second transmission posts 9 in an annular shape. The second transmission posts 9 are located between two adjacent first transmission posts 6. The second transmission posts 9 are close to the central circular hole of the annular platform 3. A plurality of first U-shaped wheels 10 are rotatably arranged on the second transmission posts 9. The suspension rope 7 passes around the first U-shaped wheels 10 and transports the cable.

[0035] Specifically, when multiple first transmission posts 6 are far apart from each other, the distance between the first transmission post 6 and the second transmission post 9 increases. The second transmission post 9 and its multiple first U-shaped wheels 10 can block and bend the suspension rope 7, thereby increasing the length variation of the suspension rope 7 between the two first transmission posts 6, which facilitates further expansion of the range of the conveying length of the suspension rope 7 and the lifting height of the object.

[0036] like Figure 3 As shown, as a preferred embodiment of the above, it also includes a telescopic rod 11. The fixed end of the telescopic rod 11 is rotatably mounted on the top of a first transmission post 6, and the movable end of the telescopic rod 11 is rotatably mounted on the top of a second transmission post 9 adjacent to the first transmission post 6. A measuring plate 12 is fixed on the movable end of the telescopic rod 11, and a laser rangefinder 13 is mounted on the fixed end of the telescopic rod 11.

[0037] Specifically, the distance between the laser rangefinder 13 and the measuring plate 12 is measured, thereby measuring the distance between the first transmission post 6 and the second transmission post 9. This facilitates the quick and accurate calculation of the length of the suspension rope 7. By adopting the structure of the telescopic rod 11, the line connecting the measuring plate 12 and the laser rangefinder 13 can be kept on the line connecting the first transmission post 6 and the second transmission post 9. This allows the orientation of the measuring plate 12 and the laser rangefinder 13 to be adjusted in real time as the first transmission post 6 moves, improving the accuracy of the measurement.

[0038] like Figures 4 to 5 As shown, in a preferred embodiment, a support ring 14 is provided in the central circular hole of the annular platform 3. A plurality of second sliders 15 are provided on the outer side wall of the support ring 14, and the support ring 14 slides on the second sliders 15. A support plate 16 is fixed on the second sliders 15, and the outer end of the support plate 16 is fixed on the inner wall of the central circular hole of the annular platform 3. A plurality of support columns 17 are fixed on the support ring 14, and a second U-shaped wheel 18 is rotatably provided on the outer wall of the support column 17. The suspension rope 7 passes around the second U-shaped wheel 18 and is transported downward.

[0039] Specifically, by setting the second U-shaped wheel 18, the lifting rope 7 can be easily guided and supported, the positions of the multiple lifting ropes 7 can be kept fixed, the tension generated by the lifting rope 7 on the hook 8 can be kept vertical, and the forces exerted by the multiple lifting ropes 7 on the hook 8 are parallel to each other, thereby improving the balance of the force on the hook 8 and the smoothness of its movement.

[0040] When the first feed post 6 moves, the first feed post 6 synchronously feeds the suspension rope 7. At this time, since one end of the suspension rope 7 is the tangent point between the outer wall of the first feed post 6 and the outer wall of the suspension rope 7, the feeding direction of the suspension rope 7 is constantly changing slightly. Due to the change in the feeding direction of the suspension rope 7, the suspension rope 7 can push the support ring 14 to rotate on the second slider 15 through the second U-shaped wheel 18 and the support column 17, so that the second U-shaped wheel 18 and the support column 17 move synchronously with the suspension rope 7, so that it can always meet the requirement of smooth feeding of the suspension rope 7. The rotation direction of the second U-shaped wheel 18 is always consistent with the feeding direction of the suspension rope 7. When the suspension rope 7 is feeding, the suspension rope 7 drives the second U-shaped wheel 18 to rotate.

[0041] like Figure 6 As shown, in a preferred embodiment, a base 19 is provided in the middle of the support ring 14, and a plurality of fastening plates 20 are provided on the outer wall of the base 19. The fastening plates 20 are right-angled and the middle part is arc-shaped. The fastening plates 20 are fastened to the outside of the suspension rope 7 on the second U-shaped wheel 18. A plurality of connecting arms 21 are fixed on the outer wall of the base 19, and the outer ends of the connecting arms 21 are fixed on the inner wall of the support ring 14.

[0042] Specifically, by setting the groove plate 20, the lifting rope 7 on the second U-shaped wheel 18 can be easily blocked and limited, preventing the lifting rope 7 from detaching from the second U-shaped wheel 18 and ensuring that the lifting rope 7 is transported smoothly on the second U-shaped wheel 18. The base 19 and the connecting arm 21 can support the groove plate 20, and when the support ring 14 rotates, it can drive the base 19, the groove plate 20 and the connecting arm 21 to rotate synchronously.

[0043] like Figure 7 As shown, in a preferred embodiment, the second U-shaped wheel 18 is provided with crossbars 22 on both sides, the crossbars 22 are fixed on the support ring 14, and a U-shaped frame 23 is provided between the two crossbars 22. The U-shaped frame 23 is vertically slidably mounted on the crossbars 22. The top of the U-shaped frame 23 is set in a groove shape. A push plate 24 is fixed on the inner side wall of the U-shaped frame 23. A slide block 25 is fixed on the outer side wall of the second U-shaped wheel 18. A slide plate 26 is slidably disposed on the slide block 25, and the sliding direction of the slide plate 26 is along the radial direction of the second U-shaped wheel 18. A first leaf spring 27 is connected between the slide plate 26 and the slide block 25.

[0044] Specifically, when the lifting rope 7 is normally conveying, it drives the second U-shaped wheel 18 to rotate. The second U-shaped wheel 18 drives the slide block 25, the slide plate 26, and the first leaf spring 27 to rotate smoothly. The slide plate 26 is separated from the push plate 24. When the lifting rope 7 breaks, it quickly moves downward and drives the second U-shaped wheel 18 to rotate rapidly. At this time, the slide plate 26 undergoes centrifugal motion and its radius of rotation increases. The slide plate 26 overcomes the elastic tension of the first leaf spring 27. After the slide plate 26 slides outward on the slide block 25 to a specified distance, it can contact the push plate 24. When the sliding plate 26 pushes the push plate 24 upward, the push plate 24 can push the U-shaped frame 23 upward. The groove at the top of the U-shaped frame 23 can squeeze the outer wall of the hoisting rope 7 and squeeze the hoisting rope 7 onto the buckle plate 20, thereby achieving the clamping and locking of the hoisting rope 7, thus preventing the hook 8 from falling freely and causing injury to workers or equipment. When the sliding plate 26 contacts the push plate 24, due to the friction between them and the rotational inertia of the sliding plate 26, the sliding plate 26 can directly push the push plate 24 to move, and the sliding plate 26 always maintains the pushing action on the push plate 24.

[0045] like Figure 7 As shown, in a preferred embodiment, the bottom of the crossbar 22 is provided with a right-angle support plate 28, the bottom of the right-angle support plate 28 is in contact with the bottom of the U-shaped frame 23, and a second leaf spring 29 is connected between the U-shaped frame 23 and the crossbar 22.

[0046] Specifically, the second leaf spring 29 generates a downward elastic thrust on the U-shaped frame 23, and the right-angle support plate 28 limits the position of the U-shaped frame 23, thereby preventing the U-shaped frame 23 from sliding freely on the crossbar 22 during equipment operation.

[0047] like Figure 3 As shown, in a preferred embodiment, a gear ring 30 is rotatably mounted on the top of the annular platform 3, a gear 31 is meshed on the gear ring 30, a motor 32 is mounted on the gear 31, and the motor 32 is fixed on the annular platform 3. A plurality of first push-pull plates 33 are rotatably mounted on the outer circumference of the gear ring 30, and a second push-pull plate 34 is rotatably mounted on the outer end of the first push-pull plate 33. One end of the second push-pull plate 34 is rotatably mounted on the side wall of the first slider 5, and the other end of the second push-pull plate 34 is provided with a support plate 35. The second push-pull plate 34 passes through the support plate 35 and slides relative to it. The support plate 35 is rotatably mounted on the annular platform 3.

[0048] Specifically, the motor 32 can drive the gear ring 30 to rotate via the gear 31. The gear ring 30 can push the second push-pull plate 34 to tilt and rotate on the support plate 35 via the first push-pull plate 33. The second push-pull plate 34 drives the first slider 5 to move, thereby driving the first feed post 6 to move. At this time, the second push-pull plate 34 can drive the support plate 35 to rotate, and the second push-pull plate 34 can slide through the support plate 35.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A large-tonnage double-beam hoist, characterized in that, It includes two crossbeams (1) and a moving trolley (2) set on each crossbeam (1). A ring platform (3) is provided between the two moving trolleys (2). The moving trolleys (2) are used to drive the ring platform (3) to move along the direction of the crossbeams (1). Multiple grooves (4) are provided on the annular platform (3). The grooves (4) are along the radial direction of the annular platform (3). A first slider (5) is slidably provided in the groove (4). A first wire feed post (6) is fixed on the first slider (5). A wire feed groove is provided on the outer wall of the first wire feed post (6). A suspension rope (7) is fixed to the top of each first wire feed post (6). The suspension rope (7) is wrapped around the outer wall of multiple first wire feed posts (6). The outer end of the suspension rope (7) passes around a first wire feed post (6) and passes through the central hole of the annular platform (3) to the bottom of the annular platform (3). The outer ends of multiple suspension ropes (7) are connected to hooks (8). The top of the ring platform (3) is provided with multiple second transmission posts (9) in a ring shape. The second transmission posts (9) are located between two adjacent first transmission posts (6). The second transmission posts (9) are close to the central circular hole of the ring platform (3). Multiple first U-shaped wheels (10) are rotatably arranged on the second transmission posts (9). The suspension rope (7) passes around the first U-shaped wheels (10) and transports the material. It also includes a telescopic rod (11), the fixed end of which is rotatably mounted on the top of a first transmission post (6), the movable end of which is rotatably mounted on the top of a second transmission post (9) adjacent to the first transmission post (6), a measuring plate (12) is fixed on the movable end of the telescopic rod (11), and a laser rangefinder (13) is mounted on the fixed end of the telescopic rod (11). A support ring (14) is provided in the middle circular hole of the annular platform (3). Multiple second sliders (15) are provided on the outer side wall of the support ring (14), and the support ring (14) slides on the second sliders (15). A support plate (16) is fixed on the second sliders (15). The outer end of the support plate (16) is fixed on the inner wall of the middle circular hole of the annular platform (3). Multiple support columns (17) are fixed on the support ring (14). A second U-shaped wheel (18) is rotatably provided on the outer wall of the support column (17). The suspension rope (7) passes around the second U-shaped wheel (18) and is transported downward. A toothed ring (30) is rotatably mounted on the top of the annular platform (3). A gear (31) is meshed on the toothed ring (30). A motor (32) is mounted on the gear (31). The motor (32) is fixed on the annular platform (3). Multiple first push-pull plates (33) are rotatably mounted on the outer circumference of the toothed ring (30). A second push-pull plate (34) is rotatably mounted on the outer end of the first push-pull plate (33). One end of the second push-pull plate (34) is rotatably mounted on the side wall of the first slider (5). A support plate (35) is mounted on the other end of the second push-pull plate (34). The second push-pull plate (34) passes through the support plate (35) and slides relative to it. The support plate (35) is rotatably mounted on the annular platform (3).

2. A large tonnage double beam jib as claimed in claim 1, characterized in that, A base (19) is provided in the middle of the support ring (14). Multiple fastening plates (20) are provided on the outer wall of the base (19). The fastening plates (20) are right-angled and the middle part is arc-shaped. The fastening plates (20) are fastened to the outside of the suspension rope (7) on the second U-shaped wheel (18). Multiple connecting arms (21) are fixed on the outer wall of the base (19). The outer end of the connecting arm (21) is fixed on the inner wall of the support ring (14).

3. A large tonnage double beam jib as claimed in claim 2, characterised in that, The second U-shaped wheel (18) has crossbars (22) on both sides. The crossbars (22) are fixed on the support ring (14). A U-shaped frame (23) is provided between the two crossbars (22). The U-shaped frame (23) is vertically slidably installed on the crossbars (22). The top of the U-shaped frame (23) is set in a groove shape. A push plate (24) is fixed on the inner side wall of the U-shaped frame (23). A slide block (25) is fixed on the outer side wall of the second U-shaped wheel (18). A slide plate (26) is slidably installed on the slide block (25). The sliding direction of the slide plate (26) is along the radial direction of the second U-shaped wheel (18). A first leaf spring (27) is connected between the slide plate (26) and the slide block (25).

4. A large tonnage double beam jib as claimed in claim 3 wherein, The bottom of the crossbar (22) is provided with a right-angle support plate (28), the bottom of the right-angle support plate (28) is in contact with the bottom of the U-shaped frame (23), and a second leaf spring (29) is connected between the U-shaped frame (23) and the crossbar (22).

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