Intelligent movable lowering device for bridge crane gantry hook and use method thereof

Abstract

The present invention relates to an intelligent movable lowering device for a gantry hook of a bridge crane and a method for using the device, comprising a base, a roller and a control device, wherein the roller is arranged on the base, the roller is controlled by a driving motor and comprises a first trigger plate and a second trigger plate arranged at both ends of the roller, the control device comprises an electrical control box and a first limit switch and a second limit switch electrically connected to the electrical controller, the first limit switch is a normally open limit switch and is connected to the first trigger plate, the second limit switch is a normally closed limit switch and is connected to the second trigger plate, and the driving motor is electrically connected to the electrical control box. The present invention has a simple and reasonable structure and is easy to operate, and can be applied to different types of gantry hook placement devices, solving the problem that the gantry hook of a bridge crane is difficult to place on the ground, and also solving the problem that the gantry hook can only be placed in a fixed place for maintenance personnel to operate, reducing the operation risk factor and labor intensity, and further improving the work efficiency of maintenance personnel.

Description

Technical Field

[0001] The invention relates to a bridge crane, and more particularly to an intelligent movable lowering device for a gantry hook of a bridge crane and a use method thereof. Background Art

[0002] Bridge cranes are lifting equipment installed above workshops, warehouses and material yards for lifting materials. They are the most widely used and most numerous lifting machinery. The gantry hook of a bridge crane must be inspected after being used for a period of time. Lay the gantry hook flat on the ground, and the maintenance personnel will check, lubricate or replace the bearings, clamps, pulleys, wire ropes and other parts of the gantry hook. There are the following problems in laying the gantry hook flat on the ground: laying the gantry hook flat requires maintenance personnel to command the crane driver to cooperate with the operation on the ground near the gantry hook, which poses a safety risk of injury; when the gantry hook is laid flat on the ground, the bottom of the gantry hook contacts the ground first, and then the crane driver drives the crane to the side where the gantry hook is to be laid down to slowly lay the gantry hook flat on the ground. However, since the crane speed is often too fast or too slow, the crane, wire rope and gantry hook pulley block are not on the same vertical line, which may cause the gantry hook to twist. Due to safety hazards, maintenance personnel are prohibited from working on the twisted gantry hook and can only lay the gantry hook down again; when laying down the gantry hook, if the ground is uneven, it will also cause the front and back of the gantry hook to be unbalanced after being laid down, and maintenance personnel need to use an iron rod to correct it or raise the hook again and lay it down. Therefore, it is necessary to propose a gantry hook laying device. Summary of the invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an intelligent movable lowering device for the gantry hook of a bridge crane which has a simple and reasonable structure and is easy to operate, and a method of using the device, which can be applicable to different types of gantry hook placement devices, and solves the problem that the gantry hook of a bridge crane is difficult to place on the ground. At the same time, it also solves the problem that the gantry hook can only be placed in a fixed place for maintenance personnel to operate, reduces the operation risk factor and labor intensity, and further improves the work efficiency of maintenance personnel.

[0004] The above technical objectives of the present invention are achieved through the following technical solutions:

[0005] An intelligent movable lowering device for a gantry hook of a bridge crane comprises a base, a roller table and a control device, wherein the roller table is arranged on the base, the roller table is driven by a driving motor, a first trigger plate and a second trigger plate are respectively arranged at both ends of the roller table, the control device comprises an electrical control box and a first limit switch and a second limit switch electrically connected to the electrical controller, the first limit switch is a normally open limit switch and is connected to the first trigger plate, the second limit switch is a normally closed limit switch and is connected to the second trigger plate, the driving motor is electrically connected to the electrical control box, the base is moved to the bottom of the gantry hook, and the control device is electrically connected to the electrical control box. The overhead crane lowers the gantry hook, the bottom of the gantry hook contacts the first trigger plate and applies pressure to the first trigger plate to make the first limit switch normally closed, the control circuit of the drive motor is energized, the drive motor controls the rollers of the roller table to rotate, the gantry hook continues to descend, the bottom of the gantry hook contacts the roller table and moves forward with the rotation of the rollers until the gantry hook is completely laid down, when the bottom of the gantry hook moves forward and contacts the second trigger plate and applies pressure to the second trigger plate to make the second limit switch normally open, the control circuit of the drive motor loses power, the rollers of the roller table stop rotating, the gantry hook stops moving forward and lies flat on the roller table.

[0006] In one embodiment, the electrical control box includes a main power switch, a control power switch, a contactor, a PLC control switch and a PLC controller, the main power switch is electrically connected to the control power switch, the control power switch is electrically connected to the contactor, the contactor is electrically connected to the first limit switch, the second limit switch and the PLC control switch respectively, and the PLC control switch and the PLC controller are electrically connected to the drive motor in sequence;

[0007] Close the main power switch, control power switch and PLC control switch. When the first limit switch is in the normally open state, the gantry hook does not apply pressure to the first trigger plate. At this time, the control circuit of the drive motor is in an unpowered state, and the PLC controller is also in an unpowered state, and the drive motor is not started; when the first limit switch is in the normally closed state, the gantry hook applies pressure to the first trigger plate. At this time, the control circuit of the drive motor forms a closed loop, the contactor is energized, the PLC controller is energized, and the PLC controller controls the drive motor to rotate, driving the roller to drive the gantry hook to fall down. When the bottom of the gantry hook applies pressure to the second trigger plate so that the second limit switch is in the normally open state, the control circuit of the drive motor is broken, the contactor loses power, the PLC controller loses power, and the drive motor stops. At this time, the gantry hook is completely flat on the roller.

[0008] In one embodiment, the electrical control box also includes a frequency converter, which is arranged between the PLC controller and the drive motor. The frequency converter is electrically connected to the PLC controller and the drive motor respectively, and the speed of the drive motor is controlled by the frequency converter, and the speed of the roller of the roller table is adjusted according to the speed at which the gantry hook descends.

[0009] In one of the embodiments, a speed sensor is provided on the roller conveyor, and the speed sensor is electrically connected to the PLC controller. The movement speed of the gantry hook on the roller conveyor is detected in real time by the speed sensor, and the detection information is fed back to the PLC controller. The PLC controller controls the rotation speed of the drive motor through the frequency converter according to the detection information, thereby adjusting the movement speed of the gantry hook on the roller conveyor.

[0010] In one embodiment, the control power switch includes a first power switch, a transformer, and a second power switch electrically connected in sequence, the first power switch is electrically connected to the main power switch, and the second power switch is electrically connected to the contactor. When the main power voltage is different from the rated voltage of the drive motor, the voltage needs to be changed through the transformer to match the drive motor.

[0011] In one embodiment, the electrical control box is provided with a start button, a working indicator light, a stop button and a power indicator light. The power indicator light is electrically connected to the main power switch. When the main power switch is closed, the power indicator light is on. The start button and the stop button are electrically connected to the PLC control switch respectively. The working indicator light is electrically connected to the second power switch to display whether the circuit at the front end of the PLC control switch is connected.

[0012] In one of the embodiments, supports for carrying the crossbeam of the gantry hook are respectively provided on both sides of the roller conveyor, and the two supports are located on both sides of the first trigger plate. When the gantry hook is completely laid down on the roller conveyor, the crossbeam of the gantry hook is supported by the two supports.

[0013] In one embodiment, a reducer is provided between the roller and the drive motor, the transmission shaft of the drive motor is connected to the reducer, and the output end of the reducer is connected to the roller. Since the roller needs to have a lower rotation speed and a larger load, adding a reducer is beneficial to slowing down the speed and increasing the output torque.

[0014] In one of the embodiments, the base is provided with lifting ears at four corners, two adjacent lifting ears are fixedly connected with steel wire ropes, and the overhead crane lifts the base to a designated area for planned maintenance.

[0015] The method for using the intelligent movable lowering device for the gantry hook of a bridge crane comprises the following steps:

[0016] The overhead crane lifts the wire ropes between the adjacent lifting ears, lifts the base to the designated area for maintenance, starts the electrical control box, and puts the roller table in a state of preparation for work;

[0017] The overhead crane controls the gantry hook to be lowered, and the bottom of the gantry hook contacts the first trigger plate. The gantry hook applies pressure to the first trigger plate, and the first limit switch connected to the first trigger plate is normally closed. The control circuit of the drive motor forms a closed loop, and the electrical control box controls the drive motor to rotate. The gantry hook continues to descend and contacts the roller of the roller table. The bottom of the gantry hook moves forward as the roller rotates. The gantry hook gradually tilts and the bottom continues to contact the roller table. When the gantry hook is completely laid down on the roller table, the gantry hook continues to move forward until the bottom of the gantry hook contacts the second trigger plate. The bottom of the gantry hook applies pressure to the second trigger plate so that the second limit device is normally open, and the control circuit of the drive motor is disconnected. The electrical control box controls the drive motor to stop rotating, and the maintenance personnel can safely and conveniently inspect, refuel, lubricate or replace the parts of the gantry hook;

[0018] After the maintenance is completed, the overhead crane gradually lifts the gantry hook. Since the control circuit of the drive motor is still in an open state at this time, the drive motor is in a stopped state when the gantry hook is lifted. The overhead crane continues to lift the gantry hook until the gantry hook leaves the roller table.

[0019] The present invention has the following beneficial effects:

[0020] The invention realizes the laying down operation of the gantry hook by driving the gantry hook to move through the roller way, and has the advantages of stability and safety. The invention respectively arranges a first trigger plate and a second trigger plate at both ends of the roller way, and the first trigger plate and the second trigger plate are respectively connected to the first limit switch and the second limit switch, and the first limit switch and the second limit switch are both electrically connected to the electrical control box, and the electrical control box is electrically connected to the driving motor. The driving motor is controlled to rotate by closing the first limit switch in contact with the gantry hook, and the roller way drives the gantry hook to move so as to gradually and steadily lay down the gantry hook, and then the driving motor is controlled to stop by disconnecting the second limit switch in contact with the gantry hook, and the gantry hook is smoothly laid down on the roller way, which is convenient for maintenance personnel to repair the gantry hook. The invention has a high safety factor, can realize automatic laying down of the gantry hook, has a high degree of intelligence, solves the problem that the gantry hook of the bridge crane is difficult to lay down on the ground, and also solves the problem that the gantry hook can only be placed in a fixed place for maintenance personnel to operate, reduces the operation risk factor and labor intensity, and improves maintenance efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of the present invention;

[0022] Figure 2 It is a front view schematic diagram of the gantry hook and a corresponding side view schematic diagram;

[0023] Figure 3 is a schematic diagram of the interior of the electrical control box of the present invention;

[0024] Figure 4is a schematic diagram of the outer surface of the electrical control box of the present invention;

[0025] Figure 5 It is a schematic diagram of the support of the present invention.

[0026] In the figure: 1-base, 11-drive motor, 12-reducer, 13-support, 14-lifting ear, 15-wire rope, 2-roller, 21-first trigger plate, 22-second trigger plate, 23-first limit switch, 24-second limit switch, 3-electrical control box, 301-second power switch, 302-PLC control switch, 303-transformer, 304-PLC controller, 305-inductor connector, 306-limit switch first connector, 307-limit switch second connector, 308-motor connector, 309-frequency converter, 310-contactor, 311-main power switch, 312-first power switch, 313-working indicator light, 314-stop button, 315-power indicator light, 316-start button, 4-plate hook, 5-crossbeam. DETAILED DESCRIPTION

[0027] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0028] It is worth noting that the directional words such as "upper" and "lower" involved in this article are all relative to the viewing angle of the drawings and are only for the convenience of description and cannot be understood as limitations on the technical solution.

[0029] like Figure 1-5 shown.

[0030] like Figure 1As shown, the intelligent movable lowering device for the gantry hook of the bridge crane includes a base 1, a roller 2 and a control device. The roller 2 is arranged on the base 1, and the roller 2 is driven by a driving motor 11. The first trigger plate 21 and the second trigger plate 22 are respectively arranged at both ends of the roller 2. The control device includes an electrical control box 3 and a first limit switch 23 and a second limit switch 24 electrically connected to the electrical controller. The first limit switch 23 is a normally open limit switch and is connected to the first trigger plate 21. The second limit switch 24 is a normally closed limit switch and is connected to the second trigger plate 22. The driving motor 11 is electrically connected to the electrical control box 3, and the base 1 is moved to the bottom of the gantry hook, and the gantry hook is lowered by the overhead crane. The bottom of the gantry hook contacts the first trigger plate 21. And apply pressure to the first trigger plate 21 so that the first limit switch 23 is normally closed, the control circuit of the drive motor 11 is energized, the drive motor 11 controls the rollers of the roller table 2 to rotate, the gantry hook continues to descend, the bottom of the gantry hook contacts the roller table 2 and moves forward with the rotation of the rollers until the gantry hook is completely laid down, when the bottom of the gantry hook moves forward and contacts the second trigger plate 22 and applies pressure to the second trigger plate 22 so that the second limit switch 24 is normally open, the control circuit of the drive motor 11 loses power, the rollers of the roller table 2 stop rotating, the gantry hook stops moving forward and lies flat on the roller table 2, the four corners of the base 1 are respectively provided with lifting ears 14, and two adjacent lifting ears 14 are fixedly connected with wire ropes 15, and the overhead crane lifts the base 1 to the designated area for planned maintenance.

[0031] Preferably, the first trigger plate 21 is arranged on the roller conveyor through an elastic mechanism. When the gantry hook descends and applies pressure to the first trigger plate, the first trigger plate 21 moves downward to close the first limit switch 23. Even in subsequent operations, the gantry hook does not contact the first trigger plate 21, and the first limit switch 23 is still in a normally closed state. When the first trigger plate 21 does not contact the gantry hook, the first trigger plate 21 is reset under the action of the elastic mechanism. After completing the operation of inspecting the gantry hook, the first limit switch 23 can be reset.

[0032] Preferably, the second trigger plate 22 is inclined to the roller 2, for example, the angle between the second trigger plate 22 and the roller 2 is 45°, and the second trigger plate 22 is connected to the elastic mechanism. When the gantry hook moves to the second trigger plate 22 driven by the roller 2, the bottom of the gantry hook applies pressure to the second trigger plate 22, and the second trigger plate 22 rotates so that the second limit switch 24 is normally open. When the gantry hook is not in contact with the second trigger plate 22, the second trigger plate 22 is reset under the action of the elastic mechanism, and the gantry hook is not in contact with the second trigger plate 22. The second limit switch 24 is still in the normally open state. After completing the operation of inspecting the gantry hook, the second limit switch 24 can be reset.

[0033] In addition, the connection relationship between the second trigger plate 22 and the roller 2 is not limited to the above-mentioned manner. For example, the second trigger plate 22 can also be arranged vertically with the roller 2, and the second trigger plate 22 is also connected to the elastic mechanism. When the gantry hook moves to the second trigger plate 22 driven by the roller 2, the bottom of the gantry hook applies pressure to the second trigger plate 22, and the second trigger plate 22 moves backward to make the second limit switch 24 normally open. When the gantry hook does not contact the second trigger plate 22, the second trigger plate 22 is reset under the action of the elastic mechanism, the gantry hook does not contact the second trigger plate 22, and the second limit switch 24 is still in a normally open state. After completing the operation of repairing the gantry hook, the second limit switch 24 can be reset. Preferably, a reducer 12 is provided between the roller 2 and the drive motor 11, the transmission shaft of the drive motor 11 is connected to the reducer 12, and the output end of the reducer 12 is connected to the roller 2. Since the speed of the roller 2 needs to be low and the load is large, adding a reducer 12 is conducive to slowing down the speed and increasing the output torque.

[0034] Preferably, if Figure 5 As shown, supports 13 for carrying the gantry hook crossbeam are respectively provided on both sides of the roller conveyor 2, and the two supports 13 are located on both sides of the first trigger plate 21. When the gantry hook is completely laid down on the roller conveyor, the crossbeam 5 of the gantry hook is supported by the two supports 13.

[0035] like Figure 2 As shown, the gantry hook comprises a cross beam 5 and a plate hook 4 , and the plate hook 4 is rotatably connected to the cross beam 5 .

[0036] like Figure 3 As shown, the electrical control box 3 includes a main power switch 311, a control power switch, a contactor 310, a PLC control switch 302 and a PLC controller 304, wherein the main power switch 311 is electrically connected to the control power switch, the control power switch is electrically connected to the contactor 310, the contactor 310 is electrically connected to the first limit switch 23, the second limit switch 24 and the PLC control switch 302 respectively, and the PLC control switch 302 and the PLC controller 304 are electrically connected to the drive motor 11 in sequence;

[0037] A frequency converter 309 is provided between the PLC controller 304 and the drive motor 11. The frequency converter 309 is electrically connected to the PLC controller 304 and the drive motor 11 respectively. The speed of the drive motor 11 is controlled by the frequency converter 309, and the speed of the roller of the roller table 2 is adjusted according to the speed at which the gantry hook descends.

[0038] The main power switch 311, the control power switch and the PLC control switch 302 are closed. When the first limit switch 23 is in the normally open state, the gantry hook does not apply pressure to the first trigger plate 21. At this time, the control circuit of the drive motor 11 is in an unpowered state, and the PLC controller 304 is also in an unpowered state, and the drive motor 11 is not started; when the first limit switch 23 is in the normally closed state, the gantry hook applies pressure to the first trigger plate 21. At this time, the control circuit of the drive motor 11 forms a closed loop, the contactor 310 is energized, the PLC controller 304 is energized, and the PLC controller 304 controls the drive motor 11 to rotate, driving the roller 2 to drive the gantry hook to fall down. When the bottom of the gantry hook applies pressure to the second trigger plate 22 so that the second limit switch 24 is in the normally open state, the control circuit of the drive motor 11 is disconnected, the contactor 310 loses power, the PLC controller 304 loses power, and the drive motor 11 stops. At this time, the gantry hook is completely flat on the roller 2.

[0039] Preferably, a speed sensor is provided on the roller 2, and the speed sensor is electrically connected to the PLC controller 304. The movement speed of the gantry hook on the roller 2 is detected in real time by the speed sensor, and the detection information is fed back to the PLC controller 304. The PLC controller 304 controls the rotation speed of the drive motor 11 through the frequency converter 309 according to the detection information, thereby adjusting the movement speed of the gantry hook on the roller 2.

[0040] Preferably, the control power switch includes a first power switch 312, a transformer 303 and a second power switch 301 which are electrically connected in sequence. The first power switch 312 is electrically connected to the main power switch 311, and the second power switch 301 is electrically connected to the contactor 310. The total power supply voltage is 380V, which is different from the rated voltage of 220V of the drive motor 11. The voltage needs to be changed by a 380V / 220V transformer 303 to match the drive motor 11.

[0041] The electrical control box 3 is provided with a motor connector 308 electrically connected to the drive motor 11, a limit switch first connector 306 electrically connected to the first limit switch 23, a limit switch second connector 307 electrically connected to the second limit switch 24, and an inductor connector 305 electrically connected to the speed sensor. The contactor 310 is electrically connected to the first limit switch 23 and the second limit switch 24 respectively through the limit switch first connector 306 and the limit switch second connector 307. The PLC controller 304 is electrically connected to the speed sensor through the inductor connector 305. The frequency converter 309 is electrically connected to the drive motor 11 through the motor connector 308.

[0042] Preferably, the PLC controller 304 is a Siemens s7-300 editable controller, the speed sensor is a TRANS-TEK100 series linear speed sensor, the total power supply is 380V AC, and the contactor 310 is a three-phase AC contactor 310 .

[0043] like Figure 4 As shown, the electrical control box 3 is provided with a start button 316, a working indicator light 313, a stop button 314 and a power indicator light 315. The power indicator light 315 is electrically connected to the main power switch 311. When the main power switch 311 is closed, the power indicator light 315 lights up, the start button 316 and the stop button 314 are electrically connected to the PLC control switch 302 respectively, and the working indicator light 313 is electrically connected to the second power switch 301, indicating whether the circuit at the front end of the PLC control switch 302 is connected.

[0044] Preferably, a plurality of jacks are provided between the base 1 and the roller 2, and the plurality of jacks are respectively arranged at the four corners of the roller 2. Even if the ground has a slope with a small inclination angle, the roller 2 can be placed in a horizontal plane by adjusting the jacks at the four corners of the roller 2, thereby preventing the gantry hook from sliding due to the inclination of the roller 2.

[0045] In combination with the above-mentioned embodiment, the method for using the intelligent movable lowering device for the gantry hook of the bridge crane comprises the following steps:

[0046] The overhead crane lifts the wire rope 15 between the adjacent lifting ears 14, lifts the base 1 to the designated area for maintenance, closes the main power switch 311, the first power switch 312, the second power switch 301 and the PLC switch, the working indicator light 313 and the power indicator light 315 are on, and the roller table 2 is in a state of preparation for work;

[0047] The overhead crane controls the gantry hook to be lowered, and the gantry hook first descends rapidly until the bottom of the plate hook 4 of the gantry hook is about to contact the first trigger plate 21. When the distance to the roller 2 is 0.5m, the gantry hook descends at a low speed, so that the bottom of the plate hook 4 slowly descends to the first trigger plate 21 connected to the first limit switch 23. The plate hook 4 of the gantry hook applies pressure to the first trigger plate 21 to make the first trigger plate 21 move downward, so that the first limit switch 23 connected to the first trigger plate 21 is normally closed, and the three-phase main contacts of the contactor 310 are closed, and the control circuit of the drive motor 11 forms a closed loop. The PLC controller 304 controls the drive motor 11 to rotate, and the gantry hook continues to descend under the guidance of the first trigger plate 21 to make the plate hook 4 contact with the roller of the roller 2. The bottom of the plate hook 4 moves forward as the roller rotates, and the plate hook 4 of the gantry hook gradually tilts and the bottom continues to contact with the roller 2. The speed sensor continuously detects the movement speed of the plate hook 4 and feeds back the speed information to the PLC controller 304. The PLC controller 304 sends instructions to the frequency converter 309 according to the speed information of the plate hook 4 to maintain or change the speed of the drive motor 11, so as to change the movement speed of the plate hook 4 on the roller 2. When the gantry hook is completely laid down on the roller 2, the gantry hook continues to move forward until the bottom of the plate hook 4 of the gantry hook contacts the second trigger plate 22. The bottom of the plate hook 4 applies pressure to the second trigger plate 22 to make the second limit device normally open, the three-phase main contacts of the contactor 310 are disconnected, the control circuit of the drive motor 11 is broken, the PCL controller loses power, and the drive motor 11 stops rotating. At this time, the crossbeam 5 of the gantry hook is supported by two supports 13, and the maintenance personnel can safely and conveniently check, lubricate or replace the parts of the gantry hook;

[0048] After the maintenance is completed, the overhead crane gradually lifts the gantry hook. Since the three-phase main contacts of the contactor 310 are disconnected at this time, the control circuit of the drive motor 11 is still in an open circuit state. Therefore, when the gantry hook is lifted, the drive motor 11 is in a stopped state, and the overhead crane continues to lift the gantry hook until the gantry hook leaves the roller table 2.

[0049] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. Intelligent movable lowering device for bridge crane gantry hook, characterized in that: The invention comprises a base (1), a roller conveyor (2) and a control device, wherein the roller conveyor (2) is arranged on the base (1), the roller conveyor (2) is driven by a drive motor (11), a first trigger plate (21) and a second trigger plate (22) are respectively arranged at two ends of the roller conveyor (2), the control device comprises an electrical control box (3) and a first limit switch (23) and a second limit switch (24) electrically connected to the electrical controller, the first limit switch (23) is a normally open limit switch and is connected to the first trigger plate (21), the second limit switch (24) is a normally closed limit switch and is connected to the second trigger plate (22), and the drive motor (11) is electrically connected to the electrical control box (3); The electrical control box (3) comprises a main power switch (311), a control power switch, a contactor (310) and a PLC controller (304); the main power switch (311) is electrically connected to the control power switch; the control power switch is electrically connected to the contactor (310); the contactor (310) is electrically connected to the first limit switch (23), the second limit switch (24) and the PLC controller (304) respectively; and the PLC controller (304) is electrically connected to the drive motor (11); A speed sensor is provided on the roller table (2), and the speed sensor is electrically connected to the PLC controller (304); The control power switch comprises a first power switch (312), a transformer (303) and a second power switch (301) which are electrically connected in sequence, the first power switch (312) being electrically connected to the main power switch (311), and the second power switch (301) being electrically connected to the contactor (310); The electrical control box (3) is provided with a start button (316), a working indicator light (313), a stop button (314) and a power indicator light (315); the power indicator light (315) is electrically connected to the main power switch (311); the start button (316) and the stop button (314) are electrically connected to the PLC control switch (302), respectively; and the working indicator light (313) is electrically connected to the second power switch (301); Supports (13) for carrying the gantry hook crossbeam are respectively provided on both sides of the roller conveyor (2), and the two supports (13) are located on both sides of the first trigger plate (21); The base (1) is provided with lifting ears (14) at four corners, respectively, and two adjacent lifting ears (14) are fixedly connected with steel wire ropes (15).

2. The intelligent movable lowering device for the gantry hook of a bridge crane according to claim 1, characterized in that: The electrical control box (3) further comprises a frequency converter (309), wherein the frequency converter (309) is arranged between the PLC controller (304) and the drive motor (11), and the frequency converter (309) is electrically connected to the PLC controller (304) and the drive motor (11), respectively.

3. The intelligent movable lowering device for the gantry hook of a bridge crane according to claim 1, characterized in that: A reducer (12) is provided between the roller conveyor (2) and the drive motor (11), a transmission shaft of the drive motor (11) is connected to the reducer (12), and an output end of the reducer (12) is connected to the roller conveyor (2).

4. The method for using the intelligent movable lowering device for the gantry hook of a bridge crane is characterized in that: Using the intelligent movable lowering device for the gantry hook of a bridge crane as described in any one of claims 1 to 3 comprises the following steps: The overhead crane lifts the steel wire rope (15) between the adjacent lifting lugs (14), lifts the base (1) to a designated area for maintenance, and starts the electrical control box (3) to put the roller table (2) in a state of preparation for work; The overhead crane controls the gantry hook to be lowered, and the bottom of the gantry hook contacts the first trigger plate (21). The gantry hook applies pressure to the first trigger plate (21), and the first limit switch (23) connected to the first trigger plate (21) is normally closed. The control circuit of the drive motor (11) forms a closed loop. The electrical control box (3) controls the drive motor (11) to rotate, and the gantry hook continues to descend and contacts the roller of the roller conveyor (2). The bottom of the gantry hook moves forward as the roller rotates. The gantry hook gradually tilts and the bottom continues to contact the roller conveyor (2). When the gantry hook is completely laid down on the roller conveyor (2), the gantry hook continues to move forward until the bottom of the gantry hook contacts the second trigger plate (22). The bottom of the gantry hook applies pressure to the second trigger plate (22) so that the second limit device is normally open, and the control circuit of the drive motor (11) is disconnected. The electrical control box (3) controls the drive motor (11) to stop rotating, and the maintenance personnel can safely and conveniently inspect, lubricate or replace the parts of the gantry hook. After the maintenance is completed, the overhead crane gradually lifts the gantry hook until the gantry hook leaves the roller table (2).

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