Self-tensioning box beam hoist capable of adjusting the lifting center of gravity and operation method thereof

Abstract

A self-tensioning box beam hoist with adjustable lifting center of gravity and its operation method, comprising: a main lifting beam assembly, a tensioning beam assembly, a positioning locking screw assembly and a remote control hydraulic station; two sets of tensioning beam assemblies straddle the main lifting beam assembly and can move laterally along the main lifting beam assembly, the positioning locking screw assembly passes through the corresponding circular holes of the tensioning beam assembly and the main lifting beam assembly from both sides, and when the tensioning beam assembly and the main lifting beam assembly are positioned, they can be interlocked and fixed by the positioning locking screw assembly; the remote control hydraulic station is installed on the main lifting beam assembly, and is connected to the adjustment cylinder of the main lifting beam assembly and the tensioning cylinder of the tensioning beam assembly through a hydraulic hose. This hoist uses a spherical hinge and an automatic tensioning mechanism to tightly bind the hoist to the segmental box beam and achieve slope adjustment; a screw adjustment mechanism is used to enable the lifting point to move horizontally steplessly to adapt to the changes in the center of gravity position of the segmental box beam with different configurations; the swing center height is reduced, the number of operating cylinders is reduced, and the operation method is simple.

Description

Technical Field

[0001] The invention belongs to the field of bridge construction engineering, and relates to a heavy object hoisting and installation tool, in particular to a self-tensioning box beam hoist with adjustable hoisting center of gravity and an operation method thereof. Background Art

[0002] At present, in bridge construction, for large prestressed concrete box girder structures, the international community generally adopts the method of segmented prefabrication and on-site assembly for construction. This construction method has also been widely used in China. Usually, when assembling a segmental box girder at the bridge construction site, it is first necessary to use a special hoist to safely lift and accurately position the beam segment according to the design requirements, and then the prestressing of the beam segment can be carried out. Due to the longitudinal and transverse slopes of the bridge, the segmental box girder is usually tilted and lifted at a certain angle. At the same time, in order to meet the structural safety requirements, the connection between the hoist and the segmental beam needs to apply an effective preload. In order to firmly bind the segmental box girder to the lifting attachment, the current hoist must use a movable cylinder to pre-tension the lifting screw separately or use four fixed tensioning cylinders to tension the lifting screws at the same time. The former requires multiple sets of hoists to meet the construction period requirements, while the latter first needs to tighten the nuts of the four lifting screws, then operate the tensioning cylinder to tension the lifting screws, and then lock the tensioning cylinder piston, which is more troublesome. At the same time, due to the need to adjust the transverse and longitudinal slope angles of the segmental box beam, the hoist adopts a layered structure, which makes the swing center (lifting point) of the hoist higher than the center of gravity of the box beam, the eccentric moment when the slope changes is larger, and the force required for slope adjustment is increased. In addition, due to the change of bridge type, the cross-section of the box beam segment will have an asymmetric shape change, so that its center of gravity position will also change. The lifting point of the hoist is difficult to adapt to the offset of its center of gravity, resulting in the use of more cylinders, troublesome adjustment of the lifting point, complex operation and control system, and high cost of the hoist.

[0003] Therefore, it is absolutely necessary to provide a self-tensioning box girder hoist with adjustable lifting center of gravity, which has compact structure, reasonable cost, safe and reliable use, and an operating method thereof. Summary of the invention

[0004] The object of the present invention is to provide a box girder hanger and an operating method thereof, which can utilize the spherical hinge and automatic tensioning mechanism on the box girder hanger to adjust the lifting center of gravity, reduce the height of its swing center when adjusting the slope, and complete the operation safely and reliably.

[0005] The technical solution adopted by the present invention is: a self-tensioning box beam hoist with adjustable lifting center of gravity, comprising: a main hanging beam assembly, a tensioning beam assembly, a positioning locking screw assembly and a remote control hydraulic station; two sets of tensioning beam assemblies straddle the main hanging beam assembly, and the two sets of tensioning beam assemblies can move laterally along the main hanging beam assembly, and the positioning locking screw assemblies pass through the corresponding circular holes of the tensioning beam assembly and the main hanging beam assembly from both sides. When the tensioning beam assembly and the main hanging beam assembly are positioned, they can be interlocked and fixed with the positioning locking screw assembly; the remote control hydraulic station is installed on the main hanging beam assembly, and is connected to the adjustment cylinder of the main hanging beam assembly and the tensioning cylinder of the tensioning beam assembly through a hydraulic hose.

[0006] The main suspension beam assembly comprises: a suspension rod, a main cross beam, a longitudinal slope adjustment cylinder, a transverse slope adjustment cylinder, a cotter pin and a spherical hinge; the spherical hinge comprises: a split ball socket, a hollow sphere and a first pin shaft; the split ball socket is a split type, with a hollow sphere inside, embedded in the lower pin shaft hole of the suspension rod, clamped by the flange of the lower pin shaft hole and the elastic retaining ring stuck in the elastic retaining ring groove, and load-reducing grooves and pin holes are provided at both ends of the first pin shaft, and the first pin shaft passes through the pin shaft seat hole of the main cross beam and then through the hollow sphere, and is positioned by the cotter pin.

[0007] The suspension rod comprises an upper / lower pin shaft hole and two oil cylinder mounting lugs arranged at 90 degrees. One end of the lower pin shaft hole is provided with a flange, and the other end is provided with an elastic retaining ring groove.

[0008] The main cross beam is welded into a cross-shaped structure by a central pin shaft seat and long wing beams and short wing beams. The hinge seat is an open box type and is located in the center of the cross. A connecting ear seat of the transverse slope adjustment cylinder is welded above the long wing beam on one side, and a connecting ear seat of the longitudinal slope adjustment cylinder is welded above the short wing beam on the front side. A remote control hydraulic station and control system are installed above the short wing beam on the rear side. A through hole is opened in the middle of the short wing beams on the front and rear sides of the main cross beam, and the precision-rolled threaded steel rod in the positioning locking screw assembly passes through the through hole.

[0009] The connecting pin holes at both ends of the longitudinal slope adjustment cylinder and the transverse slope adjustment cylinder are provided with joint bearings. The cylinder end joint bearing of the longitudinal slope adjustment cylinder is connected to the ear seat on the short wing beam on the front side of the main cross beam through a pin shaft; the rod end joint bearing of the longitudinal slope adjustment cylinder is connected to the ear seat in front of the boom through a pin shaft; the cylinder end joint bearing of the transverse slope adjustment cylinder is connected to the ear seat on the long wing beam of the main cross beam through a pin shaft; the rod end joint bearing of the transverse slope adjustment cylinder is connected to the ear seat on the side of the boom through a pin shaft.

[0010] The tensioning beam assembly includes: a tensioning cylinder, a force-enhancing arm, a push rod, a pre-tightening wedge, a tensioning screw, a tensioning nut, an upper plane pad, a lower open pad, a second pin shaft, and an Ω-shaped beam. The force-enhancing arm, the push rod, the pre-tightening wedge, the tensioning screw, the tensioning nut, the upper plane pad, the lower open pad, and the second pin shaft are two pieces each, and are symmetrically arranged in the Ω-shaped beam; the force-enhancing arm is fixed to the pin hole position inside the Ω-shaped beam through the second pin shaft, and its lower end contacts the push rod; the push rod has a bolt welded at one end to connect with the pre-tightening wedge, and the other end is a push-pull groove; the pin holes at both ends of the tensioning cylinder are connected to the upper pin holes of the force-enhancing arms on both sides through the pin shaft; the pre-tightening wedge, the upper plane pad, and the tensioning nut are sequentially stacked on the slide inside the Ω-shaped beam; the tensioning screw passes through their inner holes downward, and the lower end of the tensioning screw is installed with the lower open pad and the tensioning nut.

[0011] The pre-tightening wedge block has a double-layer structure, the bevel angle of the pre-tightening wedge block is smaller than the friction angle of its material, and a circular hole matching the tensioning screw is provided in the middle of the upper wedge body of the pre-tightening wedge block; an oblong hole is provided in the middle of the lower wedge body of the pre-tightening wedge block, and its thick end is connected to the push rod by a thread, and can move horizontally left and right.

[0012] The positioning locking screw assembly is composed of two groups, including: precision-rolled threaded steel rods, precision-rolled locking nuts, and locking washers; the precision-rolled threaded steel rods pass through the corresponding through holes on the Ω-shaped beam and the short arm of the main crossbeam at the same time, and there is a set of precision-rolled locking nuts and locking washers on both sides of the short wing beam of the main crossbeam, and a pair of precision-rolled locking nuts on both sides of the Ω-shaped beam.

[0013] The remote-controlled hydraulic station comprises: a hydraulic station, a manual / electromagnetic multi-way valve group, a balancing valve, a PLC control system, and a remote controller; the input end of the manual / electromagnetic multi-way valve group is connected to the hydraulic station through a hydraulic pipeline, wherein two outputs are connected to two balancing valves, and the balancing valves are respectively installed on two longitudinal slope adjustment cylinders and a transverse slope adjustment cylinder.

[0014] The operation method of a self-tensioning box girder lifting device with adjustable lifting center of gravity is as follows: [1] The lifting device is lifted onto the upper surface of the segment box girder to be lifted, a lifting tensioning screw is inserted from the top downward into the lifting hole of the segment box girder, a tensioning nut is screwed on from the bottom, a lower opening spacer corresponding to the position is inserted, and the tensioning nut is tightened;

[0015] [2] Install and fix the four lifting tensioning screws in sequence;

[0016] [3] Press the "lock" button on the remote control to retract the tension cylinder, which pushes the push rods on both sides through the force-enhancing arm, causing the preload wedge to move to both sides to lift up the upper plane pad on it, and pull the tension screw until the tension force of the tension screw is balanced with the set tension force of the tension cylinder; the set working tension of the tension cylinder is calculated according to the tension force to be applied;

[0017] [4] Lift the segmental box girder to the splicing position;

[0018] [5] Press any of the “Longitudinal Slope +” and “Longitudinal Slope -” buttons on the remote control to adjust the longitudinal slope angle of the segmental box girder;

[0019] [6] Press any of the “Cross Slope +” and “Cross Slope -” buttons on the remote control to adjust the transverse slope angle of the segmental box girder;

[0020] [7] Complete the splicing process;

[0021] [8] Press the crane down button to release the hoisting device. After checking that the segmental box girder is correct, press the release button again. The tensioning cylinder extends and the push rod is pulled to move the pre-tightening wedge inward, thereby releasing the tensioning force of the lifting tensioning screw.

[0022] [9] Loosen the lower tension nuts one by one, remove the lower opening spacer, and then unscrew all the tension nuts;

[0023]

[10] Press the crane up button to release the lifting device from the fixed segment box girder and start the installation of the next segment.

[0024] The present invention can achieve the following positive effects after adopting the above technical solution: the present invention has a compact structure, reasonable cost, and safe and reliable use. It uses a spherical hinge and an automatic tensioning mechanism to tightly bind the sling to the segmental box beam and achieve slope adjustment; a simple screw adjustment mechanism is used to enable the lifting point to move horizontally steplessly to adapt to the changes in the center of gravity position of the segmental box beam with different configurations; thereby reducing the height of the swing center, reducing the number of operating cylinders, and making the operation easier. The spherical hinge and automatic tensioning mechanism on the box beam sling can be used to adjust the lifting center of gravity and reduce the height of the swing center during slope adjustment. The operation method is simple and the operation can be completed safely and reliably. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall structure of a self-tensioning box beam hoist with adjustable lifting center of gravity according to the present invention;

[0026] Figure 2 It is a schematic diagram of the main lifting beam assembly of a self-tensioning box beam sling with adjustable lifting center of gravity according to the present invention;

[0027] Figure 3 It is a left-side structural schematic diagram of a main lifting beam assembly of a self-tensioning box beam hanger with adjustable lifting center of gravity according to the present invention;

[0028] Figure 4 It is a schematic diagram of the main structure of a tensioning beam assembly of a self-tensioning box beam hoist with adjustable lifting center of gravity according to the present invention;

[0029] Figure 5It is a schematic diagram of the top view of the structure of a tensioning beam assembly of a self-tensioning box beam hoist with adjustable lifting center of gravity according to the present invention;

[0030] Figure 6 It is a schematic diagram of the hydraulic control principle of a remote-controlled hydraulic station of a self-tensioning box beam hoist with adjustable lifting center of gravity according to the present invention;

[0031] In the figure: 1. Main suspension beam assembly, 2. Tensioning beam assembly, 3. Positioning locking screw assembly, 4. Remote control hydraulic station, 5. Suspension rod, 6. Main cross beam, 7. Longitudinal slope adjustment cylinder, 8. Cross slope adjustment cylinder, 9. Split ball socket, 10. Hollow sphere, 11. First pin shaft, 12. Split pin, 13. Tensioning cylinder, 14. Force-enhancing arm, 15. Push rod, 16. Preload wedge, 17. Tensioning screw, 18. Tensioning nut, 19. Upper plane pad, 20. Lower open pad, 21. Second pin shaft, 22. Ω-shaped beam, 23. Finished rolling locking nut, 24. Locking washer, 25. Finished rolling threaded steel rod, 26. Hydraulic station, 27. Multi-way valve group, 28. Balance valve. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings. Figure 1 As shown in Figure 6, a self-tensioning box girder sling with adjustable lifting center of gravity and its operation method mainly include: the sling is composed of a main lifting beam assembly 1 with two degrees of freedom, two sets of tensioning beam assemblies 2, a positioning locking screw assembly 3 and a remote control hydraulic station 4; the main lifting beam assembly 1 is connected to the lifting mechanism hook and has two rotational degrees of freedom to adjust the longitudinal and transverse slopes of the segmental box girder. The two sets of tensioning beam assemblies 2 straddle the main lifting beam assembly 1, and the sling is tightly fixed on the segmental box girder to prevent relative sliding and shearing of the lifting tensioning screw 17. The two sets of tensioning beam assemblies 2 can move laterally along the main lifting beam assembly 1 to adapt to the lateral offset of the center of gravity of segmental box girders of different structural types. After the tensioning beam assembly 2 and the main lifting beam assembly 1 are positioned, they can be interlocked and fixed with the positioning locking screw assembly 3. During lifting, the main lifting beam assembly 1 lifts the tensioning beam assemblies 2 on both sides to a certain height, and then adjusts the longitudinal slope angle and transverse slope angle of the segmental box beam as required.

[0033] The main suspension beam assembly 1 includes: a suspension rod 5, a main cross beam 6, a longitudinal slope adjustment cylinder 7, a transverse slope adjustment cylinder 8, a cotter pin 12, and a spherical hinge A.

[0034] The suspension rod 5 comprises an upper / lower pin hole and two cylinder mounting lugs arranged at 90 degrees. One end of the lower pin hole has a flange and the other end has an elastic retaining ring groove.

[0035] The spherical hinge A comprises: a split ball socket 9, a hollow sphere 10, and a first pin 11; the split ball socket 9 is a split type, and after the hollow sphere 10 is installed inside, it is embedded in the lower pin hole of the suspension rod 5, and is clamped by the flange of the lower pin hole and the elastic retaining ring stuck in the elastic retaining ring groove. The first pin 11 passes through the pin seat hole of the main crossbeam 6 and then passes through the hollow sphere 10, and is blocked and positioned by the split pin 12. The first pin 11 is provided with a load-reducing groove and a pin hole at both ends.

[0036] The main cross beam 6 is welded into a cross-shaped structure by a central pin shaft seat and a long wing beam and a short wing beam. The hinge seat is an open box type and is located in the center of the cross. The connecting lugs of the longitudinal slope adjustment cylinder 7 and the transverse slope adjustment cylinder 8 are welded above the long wing beam and the short wing beam, and the remote control hydraulic station 4 and the control system can be installed on the other end of the short wing beam. The middle part of the short wing beams on both sides of the main cross beam 6 is opened with a through hole for the precision rolled threaded steel rod 25 in the positioning locking screw assembly 3 to pass through.

[0037] The connecting pin holes at both ends of the longitudinal slope adjustment cylinder 7 and the transverse slope adjustment cylinder 8 are provided with articulated bearings.

[0038] The tension beam assembly 2 includes: a tensioning cylinder 13, a force-enhancing arm 14, a push rod 15, a pre-tightening wedge 16, a tensioning screw 17, a tensioning nut 18, an upper plane pad 19, a lower opening pad 20, and a second pin 21. The force-enhancing arm 14, the push rod 15, the pre-tightening wedge 16, the tensioning screw 17, the tensioning nut 18, the upper plane pad 19, the lower opening pad 20, and the second pin 21, and the Ω-shaped beam 22 are symmetrically arranged in the Ω-shaped beam 22, and the force-enhancing arm 14 is fixed inside the Ω-shaped beam 22 through the pin 21, and is operated by the tensioning cylinder 13 to be mutually linked.

[0039] The push rod 15 has a bolt welded on one end to connect with the pre-tightening wedge 16, and a push-pull groove on the other end. The pre-tightening wedge 16 is a double-layer structure, and the bevel angle of the pre-tightening wedge 16 is smaller than the friction angle of its material, and the friction force of its dual surface can ensure that it does not slide along the bevel. A circular hole matching the tensioning screw is opened in the middle of the upper wedge of the pre-tightening wedge 16, and it can only move up and down due to the constraint of the Ω-shaped beam 22; the lower wedge is connected to the push rod 15 by a thread, and can move horizontally left and right.

[0040] The positioning locking screw assembly 3 includes: a precision-rolled threaded steel rod 25, a precision-rolled locking nut 23, and a locking washer 24. The precision-rolled threaded steel rod 25 passes through the corresponding through holes on the Ω-shaped beam 22 and the short wing beam of the main cross beam 6 at the same time, and there is a set of precision-rolled locking nuts 23 and locking washers 24 on both sides of the short arm of the main cross beam 6, and a pair of precision-rolled locking nuts 23 on both sides of the Ω-shaped beam 22.

[0041] The remote-controlled hydraulic station 4 includes: a hydraulic station 26, a manual / electromagnetic multi-way valve group 27, a balancing valve 28, a PLC control system, and a remote controller; the input end of the manual / electromagnetic multi-way valve group 27 is connected to the hydraulic station 26 through a hydraulic pipeline, wherein the two outputs are connected to two balancing valves 28, and the balancing valves 28 are respectively installed on two longitudinal slope adjustment cylinders 7 and transverse slope adjustment cylinders 8.

[0042] At the construction site, loosen the front / rear / left / right positioning finishing lock nuts 23 of any set of tension beam assemblies 2, adjust the distance between the two sets of tension beam assemblies 2 according to the lifting hole spacing of the box beam to be lifted, and then lock the front / rear / left / right positioning finishing lock nuts 23. Adjust the distance from the center of the spherical hinge of the main crossbeam 6 to a set of tension beam assemblies 2 to meet the center offset of the segment box beam to be lifted, and then press the finishing lock nuts 23 on both sides of the lock washers 24.

[0043] The specific operation method of the present invention is as follows: 1. Lift the lifting device to the upper surface of the segment box girder to be lifted, insert the lifting tensioning screw 17 from top to bottom into the lifting hole of the segment box girder, screw on the tensioning nut 18 to a certain position from below, then insert the lower opening pad 20 corresponding to this position, and then tighten the tensioning nut 18.

[0044] 2. Complete the installation and fixation of four lifting finishing screws 17 in sequence.

[0045] 3. Press the "Start" button on the remote control, and the PLC control system starts the hydraulic station 26.

[0046] 4. Press the "lock" button on the remote control, and the PLC control system operates the reversing valve of the tensioning cylinder 13 of the left and right tensioning assemblies 2 in the manual / electromagnetic multi-way valve group 27 to shrink the tensioning cylinder 13. The tensioning cylinder 13 pushes the push rods 15 on both sides through the booster arm 14, so that the lower wedge of the pre-tightening wedge 16 moves to both sides to lift up its upper wedge, and pulls the tensioning screw 17 until the tensioning force of the tensioning screw 17 is balanced with the set tension of the cylinder. After that, since the angle of the inclined wedge is smaller than its friction angle, the pre-tightening wedge 16 will not relax even if the hydraulic pressure of the cylinder decreases. The set working tension of the tensioning cylinder 13 is calculated according to the tensioning force to be applied.

[0047] 5. Lift the segmental box girder to the splicing position.

[0048] 6. Press the "Longitudinal Slope +" or "Longitudinal Slope -" button on the remote control. The PLC control system receives the signal and manipulates the reversing valve of the longitudinal slope adjustment cylinder 7 of the main suspension beam assembly 1 in the manual / electromagnetic multi-way valve group 27 to extend or retract the longitudinal slope adjustment cylinder 7, thereby adjusting the longitudinal slope angle of the segmental box beam to the assembly angle and being locked by its balance valve 28.

[0049] 7. Press the "cross slope +" or "cross slope -" button on the remote control, the PLC control system receives the signal, and operates the reversing valve of the cross slope adjustment cylinder 8 of the main suspension beam assembly 1 in the manual / electromagnetic multi-way valve group 27 to extend or retract the cross slope adjustment cylinder 8, thereby adjusting the transverse slope angle of the segmental box beam to the assembly angle, and locked by its balance valve 28.

[0050] 8. Complete the splicing process.

[0051] 9. Press the "down" button on the remote control to loosen the hoist slightly. After checking that the segment box girder is correct, proceed to the next step.

[0052] 10. Press the "Relax" button on the remote control. The PLC control system receives the signal and operates the reversing valve in the manual / electromagnetic multi-way valve group 27 that controls the tensioning cylinder 13 of the left and right tensioning assemblies 2, so that the tensioning cylinder 13 of the left and right tensioning assemblies 2 extends, which pulls the push rod 15 to move the lower wedge of the pre-tightening wedge block 16 inward and the upper wedge descends, thereby releasing the tensioning force of the finishing tensioning screw 17 for lifting.

[0053] 11. Loosen the lower tension nuts 18 one by one, remove the lower opening spacer 20, and then unscrew all the lower tension nuts 18.

[0054] ] 12. Press the "horizontal slope +" or "horizontal slope -" button and the "longitudinal slope +" or "longitudinal slope -" button on the remote control to return the horizontal slope adjustment cylinder 8 and the longitudinal slope adjustment cylinder 7 to their normal positions.

[0055] 13. Press the "Stop" button on the remote control and the hydraulic station 26 stops working.

[0056] 14. Press the "up" button on the remote control to separate the hoist from the fixed segment box girder and start the installation operation of the next section.

[0057] Parts not described in detail in this specification are all known technologies.

[0058] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiment, it is still possible for a person skilled in the art to make formal modifications to the technical solutions described in the aforementioned embodiment, or to make equivalent replacements for some of the technical features. Therefore, any modifications, equivalent replacements, etc. that are not substantial differences made within the scope of the present invention should be included in the scope of protection of the present invention.

Claims

1. A self-tensioning box girder hoist with adjustable lifting center of gravity, comprising: A main suspension beam assembly (1), a tensioning beam assembly (2), a positioning locking screw assembly (3) and a remote control hydraulic station (4); the characteristics are: two sets of tensioning beam assemblies (2) straddle the main suspension beam assembly (1), the two sets of tensioning beam assemblies (2) can move laterally along the main suspension beam assembly (1), the positioning locking screw assembly (3) passes through the corresponding circular holes of the tensioning beam assembly (2) and the main suspension beam assembly (1) from both sides, and when the tensioning beam assembly (2) and the main suspension beam assembly (1) are positioned, they can be locked and fixed by the positioning locking screw assembly (3); the remote control hydraulic station (4) is installed On the main suspension beam assembly (1), a hydraulic hose is connected to the adjustment cylinder for controlling the main suspension beam assembly (1) and the tensioning cylinder of the tensioning beam assembly (2); the main suspension beam assembly (1) comprises: a suspension rod (5), a main cross beam (6), a longitudinal slope adjustment cylinder (7), a transverse slope adjustment cylinder (8), a cotter pin (12) and a spherical hinge (A); the spherical hinge (A) comprises: a split ball socket (9), a hollow sphere (10), and a first pin shaft (11); the suspension rod (5) comprises an upper / lower pin shaft hole and two cylinder mounting ear seats arranged at 90 degrees, a split ball socket (9) The invention is a split type, with a hollow sphere (10) embedded in the lower pin hole of the suspension rod (5). The lower pin hole has a flange at one end and an elastic retaining ring groove at the other end. The hollow sphere (10) is clamped by the flange of the lower pin hole and the elastic retaining ring stuck in the elastic retaining ring groove. The first pin (11) is provided with a load-reducing groove and a pin hole at both ends. The first pin (11) passes through the pin seat hole of the main crossbeam (6) and then passes through the hollow sphere (10), and is positioned by a cotter pin (12). The main cross beam (6) is welded into a cross-shaped structure by a central pin shaft seat and a long wing beam and a short wing beam. The hinge seat is an open box type and is located in the center of the cross. A connecting ear seat of a transverse slope adjustment cylinder (8) is welded above the long wing beam on one side, and a connecting ear seat of a longitudinal slope adjustment cylinder (7) is welded above the short wing beam on the front side. A remote control hydraulic station (4) and a control system are installed above the short wing beam on the rear side. Through holes are opened in the middle of the short wing beams on the front and rear sides of the main cross beam (6) to position the locking screw assembly (3). The finely rolled threaded steel rod (25) passes through the through hole; the connecting pin holes at both ends of the longitudinal slope adjustment cylinder (7) and the transverse slope adjustment cylinder (8) are provided with joint bearings, and the cylinder end joint bearing of the longitudinal slope adjustment cylinder (7) is connected to the ear seat on the short wing beam on the front side of the main cross beam (6) through a pin shaft; the rod end joint bearing of the longitudinal slope adjustment cylinder (7) is connected to the ear seat in front of the suspension rod (5) through a pin shaft; the cylinder end joint bearing of the transverse slope adjustment cylinder (8) is connected to the main cross beam through a pin shaft. The beam (6) is connected to the ear seat on the long wing beam; the rod end joint bearing of the slope adjustment cylinder (8) is connected to the ear seat on the side of the suspension rod (5) through a pin shaft; the tensioning beam assembly (2) comprises: a tensioning cylinder (13), a force increasing arm (14), a push rod (15), a pre-tightening wedge block (16), a tensioning screw (17), a tensioning nut (18), an upper plane pad (19), a lower opening pad (20), a second pin shaft (21), and an Ω-shaped beam (22);The force-enhancing arm (14), the push rod (15), the preload wedge (16), the tensioning screw (17), the tensioning nut (18), the upper plane pad (19), the lower opening pad (20), and the second pin shaft (21) are two pieces each and are symmetrically arranged in the Ω-shaped beam (22); the force-enhancing arm (14) is fixed to the pin hole position inside the Ω-shaped beam (22) through the second pin shaft (21), and its lower end is in contact with the push rod (15); the push rod (15) has a bolt welded at one end so as to be connected to the preload wedge (16), and the other end is a push-pull groove; the tensioning cylinder (13) The pin holes at both ends are connected to the upper pin holes of the force-enhancing arms (14) on both sides through the pin shafts. The pre-tightening wedge block (16), the upper plane pad block (19), and the tensioning nut (18) are sequentially stacked on the slide table inside the Ω-shaped beam (22). The tensioning screw (17) passes downward through their inner holes. The lower end of the tensioning screw (17) is installed with the lower opening pad block (20) and the tensioning nut (18). The pre-tightening wedge block (16) is a double-layer structure. The bevel angle of the pre-tightening wedge block (16) is smaller than the friction angle of its material. A circular hole matching the tensioning screw (17) is provided in the middle of the upper wedge body of the pre-tightening wedge block (16). The lower wedge of the preload wedge (16) has an oblong hole in the middle, and its thick end is connected to the push rod (15) by threading, so that it can move horizontally left and right; the positioning locking screw assembly (3) is composed of two groups, including: a precision-rolled threaded steel rod (25), a precision-rolled locking nut (23), and a locking washer (24); the precision-rolled threaded steel rod (25) passes through the corresponding through holes on the Ω-shaped beam (22) and the short arm of the main cross beam (6), and there is a set of precision-rolled locking nuts (23) and locking washers (24) on both sides of the short wing beam of the main cross beam (6). ), a pair of precision-rolled locking nuts (23) are provided on both sides of the Ω-shaped beam (22): the remote control hydraulic station (4) comprises: a hydraulic station (26), a manual / electromagnetic multi-way valve group (27), a balancing valve (28), a PLC control system, and a remote controller; the input end of the manual / electromagnetic multi-way valve group (27) is connected to the hydraulic station (26) through a hydraulic pipeline, wherein the two outputs are connected to two balancing valves (28), and the balancing valves (28) are respectively installed on two longitudinal slope adjustment cylinders (7) and transverse slope adjustment cylinders (8). ; 2. The self-tensioning box beam sling with adjustable lifting center of gravity according to claim 1, characterized in that: The operation steps are as follows: [1] Place the lifting device on the upper surface of the segmental box girder to be lifted, insert the lifting tensioning screw (17) from the top to the lifting hole of the segmental box girder, tighten the tensioning nut (18) from the bottom, then insert the lower opening spacer (20) corresponding to this position, and then tighten the tensioning nut (18); [2] Install and fix four lifting tensioning screws (17) in sequence; [3] Press the "lock" button on the remote control, the tensioning cylinder (13) contracts, and pushes the push rods (15) on both sides through the force-increasing arm (14), so that the pre-tightening wedge (16) moves to both sides to lift the upper plane pad (19) above it, and pulls the tensioning screw (17) until the tensioning force of the tensioning screw (17) is balanced with the set tensioning force of the tensioning cylinder (13); the set working tensioning force of the tensioning cylinder (13) is calculated according to the tensioning force to be applied; [4] Lift the segmental box girder to the splicing position; [5] Press any of the "Longitudinal Slope +" and "Longitudinal Slope -" buttons on the remote control to adjust the longitudinal slope angle of the segmental box girder; [6] Press any of the "Cross Slope +" and "Cross Slope -" buttons on the remote control to adjust the transverse slope angle of the segmental box girder; [7] Complete the splicing process; [8] Press the crane down button to release the hoisting device. After checking that the segment box girder is correct, press the release button again. The tensioning cylinder (13) extends and pulls the push rod (15) to move the pre-tightening wedge (16) inward, thereby releasing the tensioning force of the lifting tensioning screw (17). [9] Loosen the lower tension nuts (18) in sequence, remove the lower opening spacer (20), and then unscrew all the tension nuts (18); [10] Press the crane up button to release the lifting device from the fixed segment box girder and start the installation of the next segment.

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