Lifting protection method for a double-girder overhead crane with a lifting mode

Abstract

The present invention provides a lifting protection method for a double-girder overhead crane with a lifting mode, including a lifting height protection method: real-time monitoring of the height H3 of the main trolley hook and the height H4 of the auxiliary trolley hook; when the absolute value of H3 - H4 is greater than the allowable height deviation, control the hook with a faster lifting or lowering speed to decelerate or control the hook with a slower lifting or lowering speed to accelerate. The lifting protection method for the double-girder overhead crane with a lifting mode of the present invention, in the lifting mode, adopts the lifting height protection method, by controlling the height difference between the main trolley hook and the auxiliary trolley hook, preventing the lifted item from tilting, with a higher safety factor, and can effectively protect the lifting equipment and the lifted object.

Description

Technical Field

[0001] The present invention relates to the technical field of construction machinery, and particularly relates to a lifting protection method for a double-girder overhead crane with a lifting mode. Background Art

[0002] When a double-girder overhead crane with a lifting mode performs a lifting operation, in order to ensure the safety and efficiency of the operation, the following protection methods are usually adopted: during the lifting process, ensure that the load distribution of the two cranes is uniform to avoid the imbalance or overturning of the crane caused by uneven load. Ensure that the crane is equipped with necessary safety devices, such as height limiters, moment limiters, anti-unhooking devices, etc., to prevent accidents such as overwinding, overloading, and accidental unhooking of the sling.

[0003] Through the comprehensive application of the above measures, the operation safety of the double-girder overhead crane in the lifting mode can be effectively protected, and the risk of accidents can be reduced. However, it is not sufficient to ensure the safety of the hoisting equipment and the hoisted object when the double-girder overhead crane with a lifting mode performs a lifting operation. Summary of the Invention

[0004] The present invention provides a lifting protection method for a double-girder overhead crane with a lifting mode to solve at least one of the above problems.

[0005] According to one aspect of the present invention, there is provided a lifting protection method for a double-girder overhead crane with a lifting mode. The double-girder overhead crane includes a main trolley and a sub-trolley. The method includes a lifting height protection method: continuously monitoring the height H3 of the hook of the main trolley and the height H4 of the hook of the sub-trolley; when the absolute value of H3 - H4 is greater than the allowable height deviation, controlling the hook with a faster lifting or lowering speed to decelerate or controlling the hook with a slower lifting or lowering speed to accelerate.

[0006] The lifting protection method for the double-girder overhead crane with a lifting mode of the present invention adopts the lifting height protection method in the lifting mode. By controlling the height difference between the hooks of the main trolley and the sub-trolley, it can prevent the hoisted item from tilting, has a higher safety factor, and can effectively protect the hoisting equipment and the hoisted object.

[0007] In some embodiments, the present invention further includes a load protection method: the lifting loads of the main trolley and the auxiliary trolley are monitored in real time respectively; the lifting load G1 of the main trolley is compared with the rated load of the main trolley. If the lifting load G1 of the main trolley is greater than the rated load of the main trolley, the hook of the main trolley stops lifting; the lifting load G2 of the auxiliary trolley is compared with the rated load of the auxiliary trolley. If the lifting load G1 of the auxiliary trolley is greater than the rated load of the auxiliary trolley, the hook of the auxiliary trolley stops lifting; the sum of the lifting load G1 of the main trolley and the lifting load G2 of the auxiliary trolley is compared with the rated load of the crane. If G1 + G2 is greater than the rated load of the crane, the hooks of both the main trolley and the auxiliary trolley stop lifting. The load protection method takes into account the loads of the main trolley and the auxiliary trolley respectively, as well as whether the sum of the two exceeds the rated load of the crane, with a higher safety factor.

[0008] In some embodiments, the present invention further includes a lifting speed protection method: controlling the motor speed ratio of the lifting mechanisms of the main trolley and the auxiliary trolley according to formula (1) to keep their lifting speeds consistent;

[0009]

[0010] Where:

[0011] n1 is the rotational speed of the main trolley lifting motor, d1 is the diameter of the main trolley drum, i1 is the speed ratio of the main trolley lifting speed reducer (or including open gear), and m1 is the pulley block ratio of the main trolley lifting;

[0012] n2 is the rotational speed of the auxiliary trolley lifting motor, d2 is the diameter of the auxiliary trolley drum, i2 is the speed ratio of the auxiliary trolley lifting speed reducer (or including open gear), and m2 is the pulley block ratio of the auxiliary trolley lifting.

[0013] During the lifting and walking process, maintaining the lifting speeds of the hooks of the main and auxiliary trolleys within the error range can prevent the lifted item from tilting and causing potential safety hazards.

[0014] In some embodiments, the lifting point distance protection method of the present invention includes monitoring the walking distance S1 of the main trolley and the walking distance S2 of the auxiliary trolley in real time; when the absolute value of S1 - S2 is greater than the allowable distance deviation, controlling the faster trolley to decelerate or controlling the slower trolley to accelerate.

[0015] In some embodiments, the present invention further includes a walking speed protection method: controlling the motor speed ratio of the main and auxiliary trolleys according to formula (2) to keep their walking speeds consistent;

[0016]

[0017] Where:

[0018] Let \(n_1\) be the rotational speed of the main trolley traveling motor, \(d_1\) be the diameter of the main trolley wheels, and \(i_1\) be the speed ratio of the main trolley traveling speed reducer (or including open gearing);

[0019] Let \(n_2\) be the rotational speed of the auxiliary trolley traveling motor, \(d_2\) be the diameter of the auxiliary trolley wheels, and \(i_2\) be the speed ratio of the auxiliary trolley traveling speed reducer (or including open gearing). During the hoisting and traveling process, maintaining the distance between the suspension points of the hooks of the main and auxiliary trolleys within the error range can prevent potential safety hazards caused by excessive deflection angles of the steel ropes.

[0020] In some embodiments, the present invention further includes a method for reducing the swing of the hook group: An expansion and contraction rod is provided at the top of the hook group, and the upper part of the expansion and contraction rod is installed on the expansion and contraction rod mounting seat through a spherical roller bearing; the expansion and contraction rod mounting seat is arranged on the trolley frame of the bridge crane; A plurality of displacement sensors are evenly arranged on the circumference with the expansion and contraction rod as the center to detect the position of the expansion and contraction rod, and output the displacement data of the expansion and contraction rod to the control device; The control device determines the swinging direction of the hook group according to the received multiple displacement data and outputs a driving instruction to the driving device; The driving device executes the driving instruction to drive the main or auxiliary trolley of the bridge crane to decelerate or accelerate. The method for reducing the swing of the hook group monitors the swing amplitude of the hook group through multiple displacement sensors, and the control device controls the driving devices of the main or auxiliary trolley in the corresponding direction to decelerate or accelerate according to the swing amplitude of the hook group, which can reduce the swing of the hook group.

[0021] In some embodiments, the expansion and contraction rod of the present invention includes a plurality of telescopic joints sleeved from the outside to the inside. The outermost telescopic joint includes an upper pressure plate, a steel pipe, and a lower pressure plate. Each internal telescopic joint includes an upper pressure plate, a sliding bearing, a connecting shaft, a steel pipe, and a lower pressure plate arranged in sequence from top to bottom; On the same telescopic joint, the steel pipe is fixedly connected to the lower end of the connecting shaft, the sliding bearing is sleeved outside the connecting shaft, and the upper pressure plate is connected to the upper end of the connecting shaft; The outer diameter of the sliding bearing is larger than the outer diameter of the steel pipe; The outer diameter of the upper pressure plate is smaller than the outer diameter of the sliding bearing and larger than the inner diameter of the sliding bearing; The inner diameter of the lower pressure plate is the same as the inner diameter of the steel pipe; A flange ring is connected to the lower part of the lower pressure plate, and the inner diameter of the flange ring is larger than the outer diameter of the steel pipe of the adjacent inner telescopic joint and smaller than the outer diameter of the sliding bearing of the adjacent inner telescopic joint.

[0022] In some embodiments, there is a gap between adjacent telescopic joints of the present invention. The gap between the sliding bearing on the inner telescopic joint and its adjacent outer telescopic joint is smaller than the gap between the steel pipes. When the inner telescopic joint is eccentric or the hook is deflected, the sliding bearing slides in the steel pipe of the adjacent outer telescopic joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of a double-trolley bridge crane with a hoisting mode according to an embodiment of the present invention;

[0024] Figure 2Schematic diagram of the partial structure of a double-girder bridge crane with a lifting mode according to an embodiment of the present invention;

[0025] Figure 3 Schematic diagram of the main hook, movable pulley block, fixed pulley block, balance wheel, and wire rope winding structure of a double-girder bridge crane with a lifting mode according to an embodiment of the present invention;

[0026] Figure 4 For Figure 3 Schematic diagram of the wire rope winding on the main hook group, movable pulley block, fixed pulley block, and balance wheel of the hoisting device of the bridge crane shown;

[0027] Figure 5 Schematic diagram of the anti-overtravel and guiding structure of the lifting protection method of a double-girder bridge crane with a lifting mode according to an embodiment of the present invention;

[0028] Figure 6 For Figure 5 Schematic diagram of the anti-overtravel and guiding structure shown;

[0029] Figure 7 For Figure 6 Schematic diagram of the installation structure of the guide plate shown;

[0030] Figure 8 For Figure 6 Schematic diagram of the precise guiding and anti-overtravel structure shown;

[0031] Figure 9 Schematic diagram of the principle of the hook anti-sway structure of the lifting protection method of a double-girder bridge crane with a lifting mode according to an embodiment of the present invention;

[0032] Figure 10 , Figure 11 And Figure 12 Schematic diagram of the hook group anti-sway structure of the lifting protection method of a double-girder bridge crane with a lifting mode according to another embodiment of the present invention;

[0033] Figure 13 Schematic diagram of the process of the lifting height protection method of the lifting protection method of a double-girder bridge crane with a lifting mode according to an embodiment of the present invention;

[0034] Figure 14 Schematic diagram of the process of the load protection method of the lifting protection method of a double-girder bridge crane with a lifting mode according to an embodiment of the present invention;

[0035] Figure 15 Schematic diagram of the process of the trolley travel distance protection method of the lifting protection method of a double-girder bridge crane with a lifting mode according to an embodiment of the present invention;

[0036] Figures 16 - 18 Schematic diagram of the frame structure of the main trolley of a double-trolley bridge crane according to an embodiment of the present invention. Specific embodiments

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0038] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0039] Finally, it should also be noted that in this text, relational terms such as first and second, counterclockwise and clockwise, positive and negative are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising" and "including" not only include those elements, but also other elements not explicitly listed, or elements inherent to such a process, method, article, or device. Without further limitation, the elements defined by the statement "comprising..." do not exclude the existence of additional identical elements in the process, method, article, or device including the said elements.

[0040] The present invention will be further described in detail below with reference to the accompanying drawings.

[0041] Figures 1 - 4 Schematically shows the structure of a lifting protection method for a double-trolley bridge crane with a lifting mode according to an embodiment of the present invention.

[0042] Reference Figures 1 - 4 As shown, this bridge crane can be used for lifting large-tonnage and large-volume objects, and includes a gantry traveling mechanism 21 and two trolley traveling mechanisms 22 (including a main trolley 221 and a sub-trolley 222).

[0043] The gantry traveling mechanism 21 is integrally in the shape of a long rectangle, and includes two parallel bridge girders 211 and end beams 212 connecting the two ends of the bridge girders 211. The two ends of the bridge girders 211 are slidably connected to the first track 111 provided on the rock anchor beam. Traveling rollers are provided at the bottoms of the two ends of the bridge girders 211 of the gantry traveling mechanism 21, and the traveling rollers are driven by a motor. The gantry traveling mechanism 21 as a whole can reciprocally move along the first track 111.

[0044] The auxiliary trolley 222 is generally rectangular in shape as a whole, including two first main beams 251 and two second main beams 252 arranged in parallel, and two auxiliary beams 254 respectively connecting the first main beam 251 and the second main beam 252 at both ends. The main trolley 221 has an additional support beam 253 parallel to the first main beam 251 and the second main beam 252 on the basis of the auxiliary trolley 222. Both ends of the main trolley 221 and the auxiliary trolley 222 are respectively slidably connected to two bridge frames 211. A second track 112 is provided on the bridge frame 211, and rollers adapted to the second track 112 are provided at the lower part of the auxiliary beam 254. The rollers of the main trolley 221 and the auxiliary trolley 222 are respectively driven by motors, and the main trolley 221 and the auxiliary trolley 222 can reciprocally move along the bridge frame 211 of the gantry traveling mechanism 21 respectively.

[0045] An auxiliary hoist drum 233 (abbreviated as auxiliary drum 233) is provided on the first main beam 251 of the auxiliary trolley 222. The auxiliary hoist is used to drive the auxiliary hook 263 to move up and down, and the rated load of the auxiliary hook 263 is 100 tons.

[0046] A main hoist drum 231 (abbreviated as main drum 231) is provided on the first main beam 251 of the main trolley 221. The two fixed pulley sets 241 include a left fixed pulley set 2411 and a right fixed pulley set 2412. The pulley shaft directions of the left fixed pulley set 2411, the right fixed pulley set 2412 and the balance wheel 243 are perpendicular to the first main beam 251 and the second main beam 252. The two ends of the supports of the left fixed pulley set 2411, the right fixed pulley set 2412 and the balance wheel 243 are respectively supported above the first main beam 251 and the second main beam 252. The main hook group includes a left movable pulley set 2421, a right movable pulley set 2422, a hanging plate 270 and a main hook 261. The main hook 261 of the main trolley 221 is connected to the two movable pulley sets 242 (left movable pulley set 2421 and right movable pulley set 2422) through the hanging plate 270, and the rated load of the main hook 261 is 200 tons. The small hoist drum 232 is provided above the support beam 253. The small hoist is used to drive the small hook 262 to move up and down. The small hook 262 is located below the support beam 253, and the rated load is 25 tons.

[0047] Anti-collision devices 352, limit devices 351 and trolley stoppers 361 are provided on both trolleys 22.

[0048] Reference Figure 2 As shown, the left and right movable pulley sets of the main hook group are respectively located below the left and right fixed pulley sets and between the first main beam 251 and the second main beam 252 of the trolley frame. The maximum dimension B of the hanging plate 270 of the main hook group in the direction perpendicular to the first main beam 251 is smaller than the minimum distance Ax between the first main beam 251 and the second main beam 252. During the hoisting process of the main hook group, the hanging plate 270 will rise to the position between the first main beam 251 and the second main beam 252.

[0049] Reference Figure 3 and 6 As shown, both ends of the steel wire rope 271 of the main hoist drum 231 are respectively fixed at both ends of the main hoist drum 231. The middle of the steel wire rope 271 is hung on the balance pulley 243 to form the balance pulley section 543. The left section of the steel wire rope 271 includes a left winding section 541 that bypasses the left section of the main hoist drum, a left fixed pulley section 511 that bypasses the left fixed pulley group 2411, and a left movable pulley section 521 that bypasses the left movable pulley group 2421; the right section of the steel wire rope 271 includes a right movable pulley section 522 that bypasses the right movable pulley group 2422, a right fixed pulley section 512 that bypasses the right fixed pulley group 2412, and a right winding section 542 that bypasses the right section of the main hoist drum. In this embodiment, each movable pulley group 242 has three movable pulleys, and each fixed pulley group 241 has three fixed pulleys. Then, the steel wire rope winds three times between the fixed pulley group 241 and the movable pulley group 242 on the same side.

[0050] Reference Figure 2 As shown, when the main hook 261 is hoisted to the upper limit 2611 position by the main hoist, the lifting plate 270 is located between the first main beam 251 and the second main beam 252. The upper limit 2611 of the main hook 261 is above the rail surface of the first rail 111. The height difference between the upper limit 2611 of the main hook 261 and the rail surface of the first rail 111 is D. In this embodiment, the height difference D is 200 millimeters.

[0051] The trolleys of traditional bridge cranes all adopt a single main beam, and the fixed pulley group and the hook are both located below the main beam. Therefore, the running space of the hook can only be below the main beam. Moreover, in order to achieve sufficient strength, the height of the main beam is relatively large, so that a relatively large space above the bridge frame of the bridge crane is required for the trolley to run, and there is a lot of non-hoisting space below the bridge frame, and the lifting height of the hook is relatively low. The trolley frame of the present invention adopts a double-main-beam structure. On the basis of ensuring the strength of the main beam, the height of the main beam is reduced, which can not only reduce the space above the bridge frame 211 for the trolley to run, but also make the space between the two main beams become the running space of the movable pulley group 242, so that the upper limit 2611 of the main hook 261 can be above the rail surface of the first rail 111, and the lifting height of the main hook 261 is increased.

[0052] Figures 5 - 8 Schematically shows the hook group guiding and anti-overhead structure of the lifting protection method of a double-trolley bridge crane with a lifting mode according to an embodiment of the present invention.

[0053] Reference Figures 5 - 8As shown in the figure, guide plates 323 are provided on the opposite sides of the first main beam 251 and the second main beam 252. The guide plate 323 includes a guide web 3231 and a wing plate 3232. One side of the guide web is welded to the lower part of the opposite sides of the first main beam 251 and the second main beam 252, and the other side is an inclined surface, to which the wing plate 3232 is welded. The distance Az between the upper ends of the left and right wing plates is less than the distance Ad between the lower ends. Az is less than the maximum distance B between the outer sides of the two hanging plates 270, and Ad is greater than the outer distance B between the two hanging plates 270.

[0054] Reference Figure 5 As shown in the figure, the hoisting motor and the reducer 244 drive the main hoist drum 231 to rotate. The main drum 231 winds the wire rope to lift the main hook group upwards. When the main hook group is lifted upwards to a suitable distance close to the bottom of the frame of the main trolley, a deceleration signal is sent to the control system through the height sensor. After receiving the deceleration signal, the control system reduces the input frequency of the hoisting motor, so that the main hook group continues to rise at a low speed. When the hanging plate 270 enters the area between the first main beam 251 and the second main beam 252, due to the blocking of the guide plates 323 on the left and right sides, the hanging plate 270 equipped with two sets of movable pulley blocks 242 and the main hook 261 gradually moves towards the middle of the first main beam 251 and the second main beam 252 during the rising process, which can also prevent the main hook group from colliding with the trolley frame.

[0055] The main beam of the traditional trolley frame adopts a variable cross-section design of a single main beam to solve the problem of large stress caused by large bending moment in the middle of the main beam, and a large-height cross-section is correspondingly adopted. Reference Figure 7 As shown in the figure, in the present invention, limited by the height of the tunnel, the main hook main beam of the trolley frame in the present invention adopts a double main beam design with an equal cross-section whose height is equal to that of the side beam, which can greatly reduce the height of the trolley without reducing the strength of the main beam of the trolley. The trolley frame includes a first main beam 251 and a second main beam 252 arranged in parallel, and two auxiliary beams 254 arranged in parallel and connecting the two ends of the first main beam 251 and the second main beam 252.

[0056] Reference Figure 8 As shown in the figure, the guiding and anti-overtravel device 32 further includes a balance wheel support 53, a travel switch 321, a guide rod 322 and a guide sleeve 324. A guide sleeve 324 is provided on the top of the hanging plate 270. The guide rod 322 is inserted into the shaft hole of the balance wheel support 53. A pressing plate 3211 is welded to the upper end of the guide rod 322, and the guide rod 322 is slidably connected to the shaft hole. The guide sleeve 324 is connected to the hanging plate 270 by bolts. When the hook group is further lifted, the guide sleeve 324 installed on the hanging plate 270 gradually approaches the guide rod 322, and the guide rod 322 is inserted into the guide sleeve 324, further guiding the hanging plate 270 of the hook group towards the middle of the first main beam 251 and the second main beam 252 during the hoisting process.

[0057] A pressing plate 3211 is welded to the upper end of the guide rod 322. When the hook block has not risen to the height of the main beam of the trolley frame, the pressing plate 3211 on the guide rod 322 presses the contact of the travel switch 321. When the hook block drives the guide sleeve 324 to lift upward, the guide rod 322 is inserted into the guide sleeve 324, and the hook block continues to lift to move the guide rod 322 upward, so that the pressing plate 322 leaves the contact of the travel switch 321. At this time, the control system will cut off the circuit for the hook block to lift, preventing potential safety hazards caused by further lifting of the hook block.

[0058] A camera 31 is also installed below the balance wheel support 53, and the state of the hook block can be monitored through a visualization system. The control system compares the real-time state diagram of the hook block captured by the camera 31 with the pre-stored normal state diagram of the hook block to determine whether to cut off the circuit for the hook to lift. Through the video data collected by the camera 31, the system can sense whether the hook block enters the gap between the first main beam 251 and the second main beam 252 of the trolley. After comparison with the standard picture (a safety state picture conforming to normal operation), if the comparison passes, it indicates that the hook block is in a normal state and the hook block continues to rise; if the comparison fails, it indicates that the hook block is in an abnormal state, and then the control system outputs a signal to stop the hook block from rising, controlling the hook block to stop rising to ensure operation safety.

[0059] Figure 9 Schematically shows the hook block anti-sway structure and principle of a lifting protection method for a double-trolley bridge crane with a lifting mode according to an embodiment of the present invention.

[0060] Reference Figure 9 As shown, both the fixed pulley block 241 and the movable pulley block 242 are arranged in two groups. With this structure, its principle is similar to that of two groups of pulley blocks lifting a hook and a heavy object. When the heavy object does not swing, the distance between the left fixed pulley block 2411 and the left movable pulley block 2421 is equal to the distance between the right fixed pulley block 2412 and the right movable pulley block 2422, both being H1. Assume that when the trolley starts to move backward or accelerates, due to inertia, and the steel wire rope 271 is a flexible element, after the steel wire rope swings, a deflection angle α is generated with the original vertical state. At this time, a height difference will appear between the left movable pulley block 2421 and the right movable pulley block 2422 that were originally at the same height, that is, the connecting line OA of the axles of the originally horizontal left movable pulley block 2421 and right movable pulley block 2422 rotates around point O to OB, making the distance H2 between the right fixed pulley block 2412 and the right movable pulley block 2422 greater than the distance H1 between the left fixed pulley block 2411 and the left movable pulley block 2421, that is, there is an included angle β between OA and OB. Since the steel wire ropes on both sides of the balance wheel 234 are the same steel wire rope, reference Figure 4As shown, and its two sides have equal lengths maintained by the balance wheel 243 in the middle. The frictional force between the wire rope 271 and the fixed pulley block 241 and the movable pulley block 242, as well as the balancing effect of the balance wheel 243, can prevent the phenomenon where H2 is greater than or less than H1. Therefore, this structural design can reduce the sway of the hook block on the trolley during the movement of the trolley traveling mechanism 21.

[0061] The larger the installation spacing S between the two groups of fixed pulley blocks, the greater the height difference between H2 and H1. Therefore, by increasing the value of the installation spacing S between the two groups of fixed pulley blocks and cooperating with a multi-sheave pulley block, the sway reduction effect can be better.

[0062] Figures 10 - 12 Schematically shows the sway reduction structure of the hook block of the lifting protection method of a double-trolley bridge crane with a lifting mode according to another embodiment of the present invention.

[0063] Refer to Figures 10 - 12 As shown, the sway reduction structure of the hook block includes a telescopic rod 348 arranged at the top of the hanging plate 270 of the hook block, and four displacement sensors 340 for detecting the position of the telescopic rod. The lower end of the telescopic rod 348 is connected to the hanging plate 270, and the middle part is installed on the telescopic rod mounting seat 343 through a spherical roller bearing 345. The telescopic rod mounting seat 343 is connected to the first main beam 251 and the second main beam 252 of the trolley (main trolley and auxiliary trolley), and can also be installed on the balance wheel support 53. The telescopic rod 348 can retract as the hook block rises, or extend as the hook block descends.

[0064] The four displacement sensors 340 are installed below the balance wheel support 53, evenly distributed on a circumference with the telescopic rod 348 as the center, and one is arranged in each of the front, rear, left, and right running directions of the crane's trolley traveling mechanism and the crane's main trolley traveling mechanism for detecting the displacement of the telescopic rod 348 in four directions. The displacement sensor 340 can be a proximity switch or other devices that can be used to detect the displacement of an object. In this embodiment, four displacement sensors 340 are used. In other embodiments, the number of displacement sensors 340 can also be set to three, six, or other numbers according to needs.

[0065] The displacement sensor 340 outputs the displacement data of the telescopic rod to the control device.

[0066] The control device 300 is used to determine the sway direction of the hook block according to the received displacement data and output a driving instruction to the driving device.

[0067] The driving device executes the driving instruction to drive the trolley or the main trolley of the bridge crane to decelerate or accelerate. The driving device can be a motor or other devices that can drive the trolley or the main trolley to move.

[0068] The telescopic rod 348 is composed of four telescopic sections (3481, 3482, 3483, 3484) sleeved from the outside to the inside. The outermost first telescopic section 3481 includes an upper pressure plate 342, a steel pipe 346, and a lower pressure plate 341 connected in sequence from top to bottom. Each of the second telescopic section 3482, the third telescopic section 3483, and the fourth telescopic section 3484 is provided with an upper pressure plate 342, a sliding bearing 349, a connecting shaft 347, a steel pipe 346, and a lower pressure plate 341 in sequence from top to bottom. The steel pipe 346 can be a seamless steel pipe.

[0069] On the same telescopic section, the lower end of the steel pipe 346 is fixedly connected to the lower end of the connecting shaft 347. The sliding bearing 349 is sleeved outside the connecting shaft 347, and the upper pressure plate 342 is connected to the upper end of the connecting shaft 347. The outer diameter of the upper pressure plate 342 is smaller than the outer diameter of the sliding bearing 349 and larger than the inner diameter of the sliding bearing 349. The inner diameter of the lower pressure plate 341 is the same as the inner diameter of the steel pipe 346.

[0070] There is a gap of 2 - 3 millimeters between adjacent telescopic sections, and there is a gap of 1 - 2 millimeters between the sliding bearing 349 and its adjacent outer telescopic section. When the inner telescopic section is eccentric or the hook group deflects, the sliding bearing 349 slides in the steel pipe of the adjacent outer telescopic section, reducing the sliding friction and the processing cost. A lower pressure plate 341 is provided at the bottom of each telescopic section, and the lower pressure plate 341 of the innermost telescopic section is connected to the bottom of the hanging plate by bolts.

[0071] A flange ring 3411 is connected to the lower part of the lower pressure plates 341 of the first telescopic section 3481, the second telescopic section 3482, and the third telescopic section 3483. The inner diameter of the flange ring 3411 is larger than the outer diameter of the steel pipe 346 of the adjacent inner telescopic section and smaller than the outer diameter of the sliding bearing of the adjacent inner telescopic section. The flange ring 3411 can prevent the adjacent inner telescopic sections from coming out.

[0072] A telescopic rod shaft 344 is welded to the outside of the steel pipe 346 of the outermost first telescopic section 3481, and the telescopic rod shaft 344 is installed on the telescopic rod mounting seat 343 through a spherical roller bearing 345.

[0073] When the hook block swings, since the lower end of the telescopic rod 348 is connected to the hanging plate 270 of the hook block by bolts, and the middle part of the telescopic rod 348 is fixed on the telescopic rod mounting seat 343 through a spherical roller bearing 348, the telescopic rod 348 can swing together with the hook block. After swinging, the distance between the telescopic rod 348 swinging to one side and the displacement sensor 340 becomes smaller. The displacement sensor 340 arranged on this side sends an induction signal to the control system, and the control device controls the traveling mechanism to decelerate in the opposite direction or accelerate in the same direction. For example, when the crane starts to move forward, due to inertia, the hook block swings backward, the telescopic rod 348 generates a backward swing angle, the displacement sensor 340 located at the rear side senses the telescopic rod 348 and sends a signal. After the control system receives the signal, the control device controls the traveling mechanism to decelerate forward or accelerate backward. The displacement sensor 340 can be a proximity switch or other devices that can be used to detect the displacement of an object.

[0074] For example, when the displacement sensor 340 detects that the telescopic rod 348 moves backward, the displacement sensor 340 outputs the displacement data of the telescopic rod to the control device 300. The control device determines that the hook block swings backward, indicating that the forward speed of the trolley traveling mechanism 21 is too fast. The control device outputs a deceleration control instruction to the driving device of the trolley traveling mechanism 21, and the driving device of the trolley traveling mechanism 21 drives the trolley traveling mechanism 21 to decelerate, and the swinging amplitude of the hook block backward will be reduced. If the displacement sensor 340 detects that the telescopic rod 348 moves left or right, the trolley traveling mechanism 22 can be controlled to decelerate or accelerate to reduce the swing of the hook block.

[0075] In addition, in this embodiment, the outer diameter of the telescopic rod 348 is 200 mm, which is composed of four telescopic joints, and a sliding mechanism is provided at the tail. The gap between the inner and outer joints in the full length direction is relatively small (2 mm - 3 mm). It is a rigid-flexible structure with a relatively large slenderness ratio, which can withstand a certain bending moment and lateral force. When the hook block or the heavy object deflects, the telescopic rod 348 generates elastic deformation and forms a reverse acting force, which can hinder the swing of the hook block or the heavy object and play a role in reducing the swing of the hook block. In other embodiments, the number of telescopic joints can be adjusted according to the lifting height of the hook block.

[0076] The double-trolley bridge crane with a lifting mode of the present invention has a lifting mode, that is, the main hook of the main trolley (referred to as the main hook 261 for short) and the hook of the auxiliary trolley (referred to as the auxiliary hook 263 for short) lift the same item at the same time. To ensure the safe operation of the lifting mode, a lifting protection system is set up, and the system includes a main trolley load sensor, an auxiliary trolley load sensor, a main trolley wheel encoder, an auxiliary trolley wheel encoder, a hook block height detection device for the main trolley, and a hook block height detection device for the auxiliary trolley.

[0077] The lifting protection method for a double-girder overhead crane with a lifting mode includes a hoisting protection method and a traveling protection method. The hoisting protection method includes a load protection method, a hoisting speed protection method, and a hoisting height protection method. The traveling protection method includes a hook distance protection method and a traveling speed protection method. In actual working conditions, one or a combination of more than one of these protection methods can be adopted.

[0078] The main trolley load sensor is used to detect the load of the main trolley hook, the auxiliary trolley load sensor is used to detect the load of the auxiliary trolley hook, the main trolley wheel encoder is used to detect the traveling distance of the main trolley, the auxiliary trolley wheel encoder is used to detect the traveling distance of the auxiliary trolley, the main trolley height detection device is used to detect the hoisting height of the main trolley hook, and the auxiliary trolley height detection device is used to detect the hoisting height of the auxiliary trolley hook.

[0079] Using the above detection devices and other measuring tools, through the control of the control device, the following method can be used to protect the lifting operation of the double-girder overhead crane with a lifting mode.

[0080] Figure 13 Schematically shows the flow of the hoisting height protection method of the lifting protection method for a double-girder overhead crane with a lifting mode according to an embodiment of the present invention. The hoisting height protection method includes real-time monitoring of the height H3 of the main hook 261 of the main trolley and the height H4 of the auxiliary hook 263 of the auxiliary trolley.

[0081] When the absolute value of H3 - H4 is greater than the allowable deviation of the height system, the hook with a faster hoisting or lowering speed is controlled to decelerate or the hook with a slower hoisting or lowering speed is controlled to accelerate. In this embodiment, the absolute value of H3 - H4 being greater than the allowable deviation of the height system is 10 millimeters.

[0082] Angle sensors 33 are respectively arranged beside the drums of the hoisting devices of the main and auxiliary trolleys. Refer to Figure 13 As shown, the two angle sensors respectively monitor the number of rotations (n3, n4) of the drums of the main and auxiliary trolleys in real time. The angle sensors of the main and auxiliary trolleys output 4 - 20 mA analog signals to the control device 300. The control device respectively calculates the hoisting heights (H3, H4) of the hooks of the main and auxiliary trolleys, and then calculates the absolute value of H3 - H4. The control device compares the absolute value of H3 - H4 with the allowable deviation of the system hoisting height. If the absolute value of H3 - H4 is greater than the allowable deviation of the system hoisting height, the control device issues a hoisting control instruction to the main hoisting mechanism or the auxiliary hoisting mechanism. The main hoisting mechanism or the auxiliary hoisting mechanism executes the hoisting control instruction, driving the hook with a faster hoisting or lowering speed to decelerate or driving the hook with a slower hoisting or lowering speed to accelerate. If the absolute value of H3 - H4 is less than the allowable deviation of the system, the control device 300 allows the hooks of the main and auxiliary trolleys to continue to hoist or lower.

[0083] The main hoisting mechanism drives the hook of the main trolley to move up and down, and the auxiliary hoisting mechanism drives the hook of the auxiliary trolley to move up and down. In this embodiment, both the main hoisting mechanism and the auxiliary hoisting mechanism are winches.

[0084] The lifting height protection method prevents the lifted item from tilting by controlling the height difference between the hooks of the main trolley and the auxiliary trolley, with a higher safety factor. In this embodiment, the main lifting height monitoring device is an angle sensor installed beside the main drum 231 of the main trolley, and the auxiliary lifting height monitoring device is an angle sensor installed beside the auxiliary drum 233 of the auxiliary trolley. The lifting heights of the main and auxiliary trolley hooks are obtained by the control device through converting the monitored values of the angle sensors on the main and auxiliary trolleys to the lifting heights (H3, H4) of the hooks of the main and auxiliary trolleys. In other embodiments, the height change values of the hooks measured directly by height sensors can also be used to monitor the lifting heights (H3, H4) of the hooks of the main and auxiliary trolleys.

[0085] Figure 14 Schematically shows the flow of the load protection method of the lifting protection method of a double-trolley bridge crane with a lifting mode according to an embodiment of the present invention.

[0086] The load protection method includes the following steps:

[0087] Real-time monitor the lifting loads of the main trolley and the auxiliary trolley respectively;

[0088] Compare the lifting load G1 of the main trolley with the rated load of the main trolley. If the lifting load G1 of the main trolley is greater than the rated load of the main trolley, the main trolley stops lifting; compare the lifting load G2 of the auxiliary trolley with the rated load of the auxiliary trolley. If the lifting load G1 of the auxiliary trolley is greater than the rated load of the auxiliary trolley, the auxiliary trolley stops lifting;

[0089] Compare the sum of the lifting load G1 of the main trolley and the lifting load G2 of the auxiliary trolley with the rated load of the crane. If G1 + G2 is greater than the rated load of the crane, both the main trolley and the auxiliary trolley stop lifting. The load protection method takes into account both the respective loads of the main trolley and the auxiliary trolley, as well as whether the sum of the two exceeds the rated load of the crane, with a higher safety factor.

[0090] Reference Figure 14As shown, load sensors are respectively arranged on the main and auxiliary trolleys. The main load sensor is used to monitor the lifting load of the main trolley in real time and output the measured lifting load value G1 of the main trolley to the control device; the auxiliary load sensor is used to monitor the lifting load of the main trolley in real time and output the measured lifting load value G2 of the auxiliary trolley to the control device. The load sensors of the main and auxiliary trolleys output 4 - 20 mAn analog signals to the control device, and the control device converts the analog signals into digital signals and compares them with the rated loads of the main and auxiliary trolleys respectively. When G1 is greater than the rated load of the main trolley, the hook of the main trolley stops lifting; when G2 is greater than the rated load of the auxiliary trolley, the hook of the auxiliary trolley stops lifting; when G1 + G2 is greater than the rated load of the crane, the hooks of both the main and auxiliary trolleys stop lifting; when G1 is less than the rated load of the main trolley, G2 is less than the rated load of the auxiliary trolley, and G1 + G2 is less than the rated load of the crane, the hooks of both the main and auxiliary trolleys continue to lift.

[0091] When G1 is greater than the rated load of the main trolley and G2 is less than the rated load of the auxiliary trolley, the hook of the main trolley stops lifting and the hook of the auxiliary trolley continues to lift. When G1 is less than the rated load of the main trolley and G2 is greater than the rated load of the auxiliary trolley, the hook of the main trolley continues to lift and the hook of the auxiliary trolley stops lifting. This situation is applicable when the lifted item is being flipped.

[0092] Figure 15 Schematically shows the flow of the lifting point distance protection method of the lifting protection method of a double - trolley bridge crane with a lifting mode according to an embodiment of the present invention.

[0093] The lifting point distance protection method includes monitoring the traveling distance S1 of the main trolley and the traveling distance S2 of the auxiliary trolley in real time; when the absolute value of S1 - S2 is greater than the allowable deviation of the distance, the trolley with a faster speed is controlled to decelerate or the trolley with a slower speed is controlled to accelerate.

[0094] The crane is also provided with a main displacement detection device and an auxiliary displacement detection device, as well as a main traveling mechanism for driving the main trolley to travel and an auxiliary traveling mechanism for driving the auxiliary trolley to travel. The main displacement detection device is used to monitor the traveling distance of the main trolley and output the detected displacement value S1 to the control device; the auxiliary displacement detection device is used to monitor the traveling distance of the auxiliary trolley and output the detected displacement value S2 to the control device. The control device is used to compare the absolute value of S1 - S2 received with the allowable deviation of the traveling distance. If the absolute value of S1 - S2 is greater than the allowable deviation, a traveling control instruction is sent to the main traveling mechanism or the auxiliary traveling mechanism; the main traveling mechanism or the auxiliary traveling mechanism executes the traveling control instruction to drive the trolley with a faster speed to decelerate or control the trolley with a slower speed to accelerate.

[0095] In this embodiment, both the main displacement detection device and the secondary displacement detection device adopt encoders. In other embodiments, the main displacement detection device and the secondary displacement detection device may also adopt other devices such as displacement sensors that can measure the displacement of an object.

[0096] The main traveling mechanism includes a main traveling motor, and the secondary traveling mechanism includes a secondary traveling motor.

[0097] Reference Figure 15 As shown, the main trolley encoder measures the number of rotations n1 of the main trolley traveling roller, and the secondary trolley encoder measures the number of rotations n2 of the secondary trolley traveling roller. The main trolley encoder and the secondary trolley encoder respectively output an analog quantity of ~20 mA to the control device. The control device respectively calculates the traveling distances (S1, S2) of the main and secondary trolleys, and calculates the absolute value of S1 - S2. The control device compares the absolute value of S1 - S2 with the system allowable deviation. If the absolute value of S1 - S2 is greater than the system allowable deviation, the control device controls the trolley with a faster speed to decelerate or controls the trolley with a slower speed to accelerate; if the absolute value of S1 - S2 is less than the system allowable deviation, both the main and secondary trolleys continue to travel. During the lifting and traveling process, maintaining the deviation of the lifting points of the main and secondary trolleys within the allowable range can prevent potential safety hazards caused by excessive deflection of the steel wire rope.

[0098] The main trolley hoisting mechanism includes a main hoisting motor and a main drum 231, and the secondary trolley hoisting mechanism includes a secondary hoisting motor and a secondary drum 233.

[0099] The hoisting speed protection method includes controlling the motor speed ratio of the main hoisting motor and the secondary hoisting motor according to formula (1) to keep their hoisting speeds consistent;

[0100]

[0101] Where:

[0102] n1 is the rotational speed of the main trolley hoisting motor, d1 is the diameter of the main trolley drum, i1 is the speed ratio of the main trolley hoisting speed reducer (or including open gearing), and m1 is the pulley block ratio of the main trolley hoisting;

[0103] n2 is the rotational speed of the secondary trolley hoisting motor, d2 is the diameter of the secondary trolley drum, i2 is the speed ratio of the secondary trolley hoisting speed reducer (or including open gearing), and m2 is the pulley block ratio of the secondary trolley hoisting.

[0104] During the lifting and traveling process, maintaining the hoisting speed difference of the hooks of the main and secondary trolleys within the error range can prevent the lifted item from tilting and causing potential safety hazards.

[0105] The lifting height protection method also includes the upper and lower limit protection of the hook. When the hook descends to the lower limit, the control system cuts off the descending circuit of the hook group; when the hook ascends to the upper limit, the control system cuts off the lifting circuit of the hook group.

[0106] The control device is also used to control the speed ratio of the main traveling motor and the auxiliary traveling motor, so that the traveling speeds of the main trolley and the auxiliary trolley are the same.

[0107] The traveling speed protection method includes controlling the speed ratio of the main traveling motor and the auxiliary traveling motor according to formula (2) to keep their traveling speeds consistent;

[0108]

[0109] Where:

[0110] n1 is the rotational speed of the main trolley traveling motor, d1 is the diameter of the main trolley wheels, and i1 is the speed ratio of the main trolley traveling speed reducer (or including open gearing);

[0111] n2 is the rotational speed of the auxiliary trolley traveling motor, d2 is the diameter of the auxiliary trolley wheels, and i2 is the speed ratio of the auxiliary trolley traveling speed reducer (or including open gearing).

[0112] During the lifting and traveling process, maintaining the traveling speeds of the main and auxiliary trolleys within the error range can prevent potential safety hazards caused by excessive wire rope deflection angles.

[0113] For shield construction in the middle of the tunnel, two shield machines need to be installed in the shield machine installation room. The directions of these two shield machines are opposite, so the positions and placement directions of the two trolleys of the bridge crane used to install these two shield machines can be adjusted. The customized cost of a large-tonnage bridge crane is very high. If it is only used for installing shield machines, it will cause waste of resources. After the tunnel construction is completed, the large-tonnage bridge crane used for this construction needs to be converted into a lifting equipment for production. When this large-tonnage bridge crane is used as a tunnel construction equipment, it is restricted by many factors such as spatial layout and tunnel limit dimensions. Therefore, this large-tonnage bridge crane must have a flexible functional conversion design in structure to meet the usage requirements in different time states such as shield machine hoisting construction, segment hoisting, and production hoisting in two directions of the tunnel.

[0114] Figures 16 - 18 Schematically shows the frame structure of the main trolley of a large-tonnage crane according to an embodiment of the present invention.

[0115] Reference Figures 16 - 18As shown in the figure, the main trolley 221 includes a first main beam 251, a second main beam 252, and a support beam 253 that are parallel to each other, and two auxiliary beams 254 that connect the first main beam 251, the second main beam 252, and the support beam 253. A guardrail 74 is provided on the outer edge of the upper end of the first main beam 251. There is a certain gap between the first main beam 251 and the second main beam 252 for the wire rope or the hook block to pass through. A first through hole 2511 that penetrates up and down is provided in the middle of the first main beam 251 for the wire rope of the main hoist of the crane in the production state to pass through.

[0116] On the side of the second main beam 252 close to the first main beam 251, a retractable guardrail 70 is provided. The retractable guardrail 70 is integrally L-shaped and includes a handrail 71 and a retractable seat. The retractable seat includes a bottom rod 72 connected to the handrail 71 and a base 73 provided on the second main beam 252. The base 73 is hollow, and the bottom rod 72 is inserted into the base 73. Refer to Figure 16 As shown in the figure, when the crane is in the construction state, the main hoisting device is installed at the first installation position, and the bottom rod 72 can be pulled out from the base 73 in the direction of the first main beam 251. Refer to Figure 17 As shown in the figure, when the crane is in the production state, the main hoisting device is installed at the second installation position, and the bottom rod 72 can be pushed in the direction of the second main beam 252, so that the handrail 71 of the retractable guardrail 70 will not interfere with the main drum 231.

[0117] The support beam 253 abuts against the second main beam 252, and a second through hole 2531 that penetrates up and down is provided on the support beam 253 for the wire rope of the small hoist to pass through.

[0118] At both ends of the main beam of the traditional trolley frame, they are lapped on the upper end of the auxiliary beam, so that the overall height of the trolley frame will be relatively high. Due to the size limitation of the use scenario of the bridge crane of the present invention in the tunnel, the height of the trolley frame needs to be minimized as much as possible. Refer to Figure 18 As shown in the figure, at both ends of the first main beam 251 and the second main beam 252 of the main trolley of the bridge crane of the present invention, they are inserted into the auxiliary beam 254 and welded to the auxiliary beam 254. In this way, the height of the trolley frame of the present invention is reduced by half compared with the height of the traditional trolley frame.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present application.

Claims

1. Lifting protection method for a double-girder overhead crane with a lifting mode, the double trolleys including a main trolley and a secondary trolley, wherein, Including the lifting height protection method: Real-time monitor the height H3 of the main trolley hook and the height H4 of the auxiliary trolley hook; When the absolute value of H3 - H4 is greater than the allowable deviation, control the hook with a faster lifting or lowering speed to decelerate or control the hook with a slower lifting or lowering speed to accelerate; Also including the anti-sway method for the hook block: Set a telescopic rod at the top of the hook block, and the upper part of the telescopic rod is installed on the telescopic rod mounting seat through a spherical roller bearing; Set the telescopic rod mounting seat on the trolley frame of the bridge crane; Uniformly set a plurality of displacement sensors on the circumference with the telescopic rod as the center, detect the position of the telescopic rod, and output the displacement data of the telescopic rod to the control device; The control device determines the swing direction of the hook block according to the received multiple displacement data and outputs a driving instruction to the driving device; The driving device executes the driving instruction and drives the bridge crane's trolley or cart to decelerate or accelerate; The telescopic rod includes a plurality of telescopic sections sleeved from the outside to the inside. The outermost telescopic section includes an upper pressing plate, a steel pipe and a lower pressing plate. Each internal telescopic section includes an upper pressing plate, a sliding bearing, a connecting shaft, a steel pipe and a lower pressing plate arranged in sequence from top to bottom; On the same telescopic section, the steel pipe is fixedly connected to the lower end of the connecting shaft, the sliding bearing is sleeved outside the connecting shaft, and the upper pressing plate is connected to the upper end of the connecting shaft; the outer diameter of the sliding bearing is greater than the outer diameter of the steel pipe; the outer diameter of the upper pressing plate is less than the outer diameter of the sliding bearing and greater than the inner diameter of the sliding bearing; the inner diameter of the lower pressing plate is consistent with the inner diameter of the steel pipe; a flange ring is connected to the lower part of the lower pressing plate, and the inner diameter of the flange ring is greater than the outer diameter of the steel pipe of the adjacent inner telescopic section and less than the outer diameter of the sliding bearing of the adjacent inner telescopic section; there is a gap between adjacent telescopic sections, and the gap between the sliding bearing on the inner telescopic section and its adjacent outer telescopic section is less than the gap between the steel pipes. When the inner telescopic section is eccentric or the hook is swayed, the sliding bearing slides in the steel pipe of the adjacent outer telescopic section.

2. The lifting protection method according to claim 1, wherein, Also including the load protection method: Real-time monitor the lifting loads of the main trolley and the auxiliary trolley of the bridge crane respectively; Compare the lifting load G1 of the main trolley with the rated load of the main trolley. If the lifting load G1 of the main trolley is greater than the rated load of the main trolley, the main trolley hook stops lifting; compare the lifting load G2 of the auxiliary trolley with the rated load of the auxiliary trolley. If the lifting load G1 of the auxiliary trolley is greater than the rated load of the auxiliary trolley, the auxiliary trolley hook stops lifting; Compare the sum of the lifting load G1 of the main trolley and the lifting load G2 of the auxiliary trolley with the rated load of the crane. If G1 + G2 is greater than the rated load of the crane, both the main trolley hook and the auxiliary trolley hook stop lifting.

3. The lifting protection method according to claim 1, wherein, Also including the lifting speed protection method: Control the motor speed ratio of the lifting mechanisms of the main trolley and the auxiliary trolley according to formula (1) to make their lifting speeds consistent; Where: n1 is the rotational speed of the main trolley lifting motor, d1 is the diameter of the main trolley drum, i1 is the speed ratio of the main trolley lifting reducer (or including open gearing), m1 is the pulley block ratio of the main trolley lifting; n2 is the rotational speed of the auxiliary trolley lifting motor, d2 is the diameter of the auxiliary trolley drum, i2 is the speed ratio of the auxiliary trolley lifting reducer (or including open gearing), m2 is the pulley block ratio of the auxiliary trolley lifting.

4. The lifting protection method according to claim 1, wherein, It also includes the suspension point distance protection method: the traveling distance S1 of the main trolley and the traveling distance S2 of the auxiliary trolley are monitored in real time; When the absolute value of S1 - S2 is greater than the allowable deviation of the traveling distances of the main trolley and the auxiliary trolley, the trolley with a faster speed is controlled to decelerate or the trolley with a slower speed is controlled to accelerate.

5. The lifting protection method according to claim 1, wherein, It also includes the traveling speed protection method: the rotation speed ratio of the traveling motors of the main trolley and the auxiliary trolley is controlled according to formula (2) to make their traveling speeds consistent; Where: n1 is the rotation speed of the traveling motor of the main trolley, d1 is the wheel diameter of the main trolley, and i1 is the speed ratio of the traveling speed reducer (or including open gearing) of the main trolley; n2 is the rotation speed of the traveling motor of the auxiliary trolley, d2 is the wheel diameter of the auxiliary trolley, and i2 is the speed ratio of the traveling speed reducer (or including open gearing) of the auxiliary trolley.

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