A tower crane control circuit with a hovering function to prevent misoperation

Abstract

The present invention relates to the technical field of tower cranes, and discloses a control circuit for a tower crane with a hovering function to prevent misoperation, which includes a frequency converter with a hovering function, a control switch, a main contactor, a brake wear relay, a time-delay relay, a main control circuit and an auxiliary control circuit; one end of the control switch is connected to the power supply, and the other end of the control switch is connected to the main contactor; the auxiliary control circuit is connected in parallel with the main contactor; the input end of the frequency converter is connected to the power supply through the main control circuit, and the output end of the frequency converter is connected to the hoisting motor; the time-delay relay is connected to the frequency converter through the brake wear relay, the time-delay relay is connected in parallel with the control switch, the time-delay relay uses the frequency converter to supply power to the time-delay relay, and the brake wear relay is used to control the power supply path of the time-delay relay. The present invention can make the time-delay relay delay power-off in case of a hook-sliding accident, and avoid the hook-sliding protection function from losing its effect due to the driver's misoperation to disconnect the control switch.

Description

Technical Field

[0001] The present invention relates to the technical field of tower cranes, and particularly relates to a control circuit of a tower crane with a hovering function to prevent misoperation. Background Art

[0002] A tower crane is an auxiliary machine used for vertical transportation during the construction process. Its electrical control system technology is innovative, and the use of frequency conversion control has become the mainstream control technology in the current market. In order to prevent the crane from slipping hooks during hoisting, in the electrical control circuit using the closed-loop vector control method or the open-loop vector control method, a hovering function control technology is designed. During the application of this technology, if the frequency converter is in the shutdown state and the brake system of the tower crane wears and a slipping hook accident occurs, the brake failure protection function will be triggered. The frequency converter outputs zero-speed large torque to suspend the heavy object in the air at zero speed, waiting for the operator to operate through the console to lower the heavy object to a safe position on the ground. During this process, it is strictly prohibited for the operator to press the emergency stop button, otherwise the hovering technology will lose its protection function. Sometimes, when the operator encounters a slipping hook accident, in a hurry, he misoperates and presses the emergency stop button, causing the slipping hook protection function to lose its effect. Summary of the Invention

[0003] The object of the present invention is to solve the above problems and provide a control circuit of a tower crane with a hovering function to prevent misoperation, which can delay the power-off of the time-delay relay when a slipping hook accident occurs, avoid the control switch from being disconnected due to the misoperation of the operator, and prevent the slipping hook protection function from losing its effect.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows: A control circuit of a tower crane with a hovering function to prevent misoperation includes a frequency converter with a hovering function, a control switch, a main contactor, a brake wear relay, a time-delay relay, a main control circuit, and an auxiliary control circuit;

[0005] One end of the control switch is connected to the power supply, and the other end of the control switch is connected to the main contactor; the auxiliary control circuit is connected in parallel with the main contactor, and the auxiliary control circuit is used to control the operation of the hoisting motor and send an alarm signal in case of an abnormality;

[0006] The input end of the frequency converter is connected to the power supply through the main control circuit, the main control circuit is used to provide a power control signal for the frequency converter, and the output end of the frequency converter is connected to the hoisting motor; the time-delay relay is connected to the frequency converter through the brake wear relay, the time-delay relay is connected in parallel with the control switch, the time-delay relay uses the frequency converter to supply power to the time-delay relay, and the brake wear relay is used to control the power supply path of the time-delay relay.

[0007] Further, the control switch includes an emergency stop button SA0 and a jog button SA1 connected in series. The input terminal of the coil KT of the time-delay relay is connected to the +24V output terminal of the frequency converter. The normally open auxiliary contact KT of the time-delay relay is connected in parallel between the input terminal of the emergency stop button SA0 and the output terminal of the jog button SA1. The input terminal of the coil 1KA3 of the brake wear relay is connected to the frequency converter, and the normally open auxiliary contact 1KA3 of the brake wear relay is connected in series in the power supply path of the coil KT of the time-delay relay. The auxiliary normally open contact KM of the main contactor is connected in parallel with the jog button SA1. The auxiliary control circuit is connected in parallel with the coil KM of the main contactor.

[0008] Further, the control circuit further includes a power switch, and the emergency stop button SA0 is connected to the power supply through the power switch.

[0009] Further, the control circuit further includes an encoder matching the hoisting motor, and the encoder is connected to the frequency converter.

[0010] Further, the control circuit further includes a master controller, and the master controller is connected to the input terminal of the frequency converter and is used to provide gear action control signals of rising, falling, and stopping for the frequency converter to control the hoisting motor to act according to the set gears.

[0011] Due to the adoption of the above technical solutions, the present invention has the following beneficial effects:

[0012] In the present invention, the time-delay relay is connected in parallel with the control switch, and at the same time, the time-delay relay is connected to the frequency converter through the brake wear relay. The frequency converter supplies power to the coil KT of the time-delay relay, and the power supply path of the time-delay relay is controlled by the brake wear relay. When the frequency converter is in the stop state, if a hook slipping accident occurs, the hover function of the frequency converter is activated, and the time-delay relay gets power from the frequency converter through the brake wear relay. At this time, if the driver operates wrongly to disconnect the control switch, but because the time-delay relay gets power, the line where the time-delay relay is connected in parallel with the control switch is connected, so that the main contactor remains energized, and the operator can operate through the master controller to safely place the hoisting hook on the ground, avoiding the operator's wrong operation of the emergency stop button from making the hook slipping protection function ineffective, which has the advantages of safety and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is the principle block diagram of the present invention;

[0014] Figure 2 is the circuit wiring schematic diagram of the present invention;

[0015] Figure 3 is the frequency converter wiring schematic diagram of the present invention;

[0016] Figure 4 is the flowchart of the circuit control principle of the present invention;

[0017] In the figure: 1 - frequency converter, 2 - auxiliary control circuit, 3 - master controller, 4 - encoder, 5 - main control circuit, 6 - hoisting motor, 7 - power supply, 8 - power switch, 9 - brake wear relay, 10 - control switch, 11 - time delay relay, 12 - main contactor. Detailed implementation manners

[0018] In order to enable those skilled in the art of the present technology to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The terms "first", "second", etc. in the specification and claims of the present invention and the above drawings are used to distinguish different objects and are not used to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0019] Referring to "embodiments" herein means that specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of the present invention. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0020] As Figure 1 、 Figure 2 and Figure 3 shown, a tower crane control circuit with a hovering function to prevent misoperation includes a frequency converter 1 with a hovering function, a control switch 10, a main contactor 12, a brake wear relay 9, a time delay relay 11, a main control circuit and an auxiliary control circuit 2. The frequency converter 1 with a hovering control function is a type of frequency converter 1 in the industry and belongs to the prior art.

[0021] One end of the control switch 10 is connected to the power supply 7, and the other end of the control switch 10 is connected to the main contactor 12; the auxiliary control circuit 2 is connected in parallel with the main contactor 12, and the auxiliary control circuit 2 is used to control the hoisting motor 6 to operate and send an alarm signal in case of abnormality. The power supply 7 is a power supply in industrial electricity, and the voltage is adjusted by a transformer for circuit use.

[0022] The input end of the frequency converter is connected to the power supply 7 through the main control circuit 5, and the main control circuit 5 is used to provide a power control signal for the frequency converter. The main control circuit 5 is a three-phase power supply circuit, including the main control contact KM of the contactor and the switch contact QM1. The output ends of the switch contact QM1 are respectively connected to the input ends R, S, T of the frequency converter 1. The output end of the frequency converter 1 is connected to the hoisting motor 6. Specifically, the hoisting motor 6 is connected to the U, V, W ends of the frequency converter 1.

[0023] The time-delay relay 11 is connected to the frequency converter 1 through the brake wear relay 9. The time-delay relay 11 is connected in parallel with the control switch 10. The time-delay relay 11 uses the frequency converter to supply power to the time-delay relay 11, and the brake wear relay 9 is used to control the power supply path of the time-delay relay 11.

[0024] In this embodiment, the control switch 10 includes an emergency stop button SA0 and a jog button SA1 connected in series. The input end of the coil KT of the time-delay relay 11 is connected to the +24V output end of the frequency converter. The normally open auxiliary contact KT of the time-delay relay 11 is connected in parallel between the input end of the emergency stop button SA0 and the output end of the jog button SA1; the input end of the coil 1KA3 of the brake wear relay 9 is connected to the frequency converter 1, and the normally open auxiliary contact 1KA3 of the brake wear relay 9 is connected in series in the power supply path of the coil KT of the time-delay relay 11; the auxiliary normally open contact KM of the main contactor 12 is connected in parallel with the jog button SA1. When the coil 1KA3 of the brake wear relay 9 is energized, the normally open auxiliary contact 1KA3 of the brake wear relay 9 closes, the power supply path of the input end of the coil KT of the time-delay relay 11 is connected, the coil KT of the time-delay relay 11 is powered on, and after being energized, the normally open auxiliary contact KT of the time-delay relay 11 closes, connecting the coil KM of the main contactor 12. The time-delay relay 11 is powered by the +24v output power supply of the frequency converter 1, and the auxiliary normally open contact 1KA3 of the brake wear relay 9 is used as the switching-on switch.

[0025] The control circuit further includes a power switch 8, and the emergency stop button SA0 is connected to the power supply through the power switch 8. The power switch 8 is a circuit breaker switch QF2.

[0026] The control circuit further includes an encoder 4 that matches the hoisting motor 6. The encoder 4 is connected to the frequency converter 1. In this embodiment, the encoder 4 is a Tofino encoder. The Tofino encoder is connected to the PE, +15V, OV, A-, and B- terminals of the frequency converter 1. The frequency converter 1 forms a closed-loop control of the hoisting motor 6 through the encoder 4, with high speed control accuracy and a large speed regulation range.

[0027] The control circuit further includes a master controller 3. The master controller 3 is connected to the input terminal of the frequency converter 1 and is used to provide gear action control signals for rising, falling, and stopping to the frequency converter, so as to control the hoisting motor 6 to act according to the set gears. In this embodiment, the master controller 3 is connected to the DI3, DI4, DI5, and DI6 points at the input terminal of the frequency converter 1.

[0028] The working principle of the present invention is as follows:

[0029] As Figure 4 shown, when the tower crane is in the working state and the driver returns the gear of the master controller 3 to the zero position, the encoder 4 will detect an abnormal rotation signal, that is, when the feedback speed of the encoder 4 is greater than the speed detection threshold and the duration exceeds the detection time, the frequency converter 1 determines that the hook has slipped. Then the hover function of the frequency converter 1 is started, and the alarm in the auxiliary control circuit 2 is triggered. The frequency converter 1 outputs voltage to the coil 1KA3 of the brake wear relay 9. The normally open auxiliary contact 1KA3 of the brake wear relay 9 closes, and the coil KT of the time delay relay 11 is energized. The auxiliary contact KT of the time delay relay 11 is closed, waiting for the driver to operate the master controller 3 to place the item on the hook in a safe area. If the driver does not accidentally press the emergency stop button SA0 at this time, the driver can operate the master controller 3 to place the lifted object in a safe area. If the driver accidentally presses the emergency stop button SA0 at this time, the emergency stop button SA0 is disconnected. When there is no auxiliary contact KT of the time delay relay 11 in the circuit, the main contact KM of the main contactor 12 will be disconnected, and the input terminal of the frequency converter 1 will be powered off, and the driver cannot operate the master controller to place the lifted object in a safe area. When the time delay relay 11 is added, even if the emergency stop button SA0 is pressed to make the emergency stop button SA0 disconnected, since the coil KT of the time delay relay 11 is energized from the frequency converter 1, the auxiliary contact KT of the time delay relay 11 is closed, so that the coil KM of the main contactor 12 continues to be energized, ensuring that the power supply at the input terminal of the frequency converter 1 is continuously connected, and the driver can operate the master controller 3 to place the lifted object in a safe area.

[0030] The driver operates the master controller 3. When the hook has a downward hook operation, the alarm in the auxiliary control circuit 2 is released, and the delay relay 11 starts timing. The driver operates to lower the lifted object to a safe area. After the lifted object is placed in the safe area, the timing of the delay relay 11 ends, and the delay relay 11 returns to the standby state. If the lifted object has not been placed in the safe area, after the timing of the delay relay 11 ends and the emergency stop button SA0 is not reset, the delay relay 11 disconnects, the circuit loses power, the encoder 4 detects abnormal rotation, and the entire circuit enters a cyclic state where the hover function of the frequency converter 1 is started.

[0031] In the present invention, the delay relay 11 is connected in parallel with the control switch 10, and at the same time, the delay relay 11 is connected to the frequency converter 1 through the brake wear relay 9. The frequency converter 1 supplies power to the coil KT of the delay relay 11, and the power supply path of the delay relay 11 is controlled by the brake wear relay 9. When the frequency converter 1 is in the shutdown state, if a hook slipping accident occurs, the hover function of the frequency converter 1 is started, and the delay relay 11 is powered by the frequency converter 1 through the brake wear relay 9. At this time, if the driver operates incorrectly and disconnects the control switch 10, since the delay relay 11 is powered, the line connecting the delay relay 11 and the control switch 10 is connected, so that the main contactor 12 remains energized, and the operator can operate through the master controller 3 to safely place the lifting hook on the ground, preventing the driver from operating the control switch 10 incorrectly and causing the hook slipping protection function to fail, which has the advantages of safety and reliability.

[0032] The above has generally described the present invention in detail. However, based on the present invention, some modifications or improvements can be made, which are obvious to those of ordinary skill in the technical field. Therefore, modifications or improvements made without departing from the spirit and idea of the present invention are within the protection scope of the present invention.

Claims

1. A tower crane control circuit with a hovering function to prevent misoperation, characterized in that: it includes a frequency converter with a hovering function, a control switch, a main contactor, a brake wear relay, a time-delay relay, a main control circuit and an auxiliary control circuit; one end of the control switch is connected to the power supply, and the other end of the control switch is connected to the main contactor; the auxiliary control circuit is connected in parallel with the main contactor, and the auxiliary control circuit is used to control the hoisting motor to act and send an alarm signal in case of abnormality; the input end of the frequency converter is connected to the power supply through the main control circuit, the main control circuit is used to provide a power control signal for the frequency converter, and the output end of the frequency converter is connected to the hoisting motor; the time-delay relay is connected to the frequency converter through the brake wear relay, the time-delay relay is connected in parallel with the control switch, the time-delay relay uses the frequency converter to supply power to the time-delay relay, and the brake wear relay is used to control the power supply path of the time-delay relay; the control switch includes an emergency stop button SA0 and a jogging button SA1 connected in series, the input end of the coil KT of the time-delay relay is connected to the +24V output end of the frequency converter, and the normally open auxiliary contact KT of the time-delay relay is connected in parallel between the input end of the emergency stop button SA0 and the output end of the jogging button SA1; the input end of the coil 1KA3 of the brake wear relay is connected to the frequency converter, and the normally open auxiliary contact 1KA3 of the brake wear relay is connected in series in the power supply path of the coil KT of the time-delay relay; the auxiliary normally open contact KM of the main contactor is connected in parallel with the jogging button SA1; the auxiliary control circuit is connected in parallel with the coil KM of the main contactor; the control circuit further includes an encoder matched with the hoisting motor, and the encoder is connected to the frequency converter.

2. The tower crane control circuit with a hovering function to prevent misoperation according to claim 1, characterized in that: the control circuit further includes a power switch, and the emergency stop button SA0 is connected to the power supply through the power switch.

3. The tower crane control circuit with a hovering function to prevent misoperation according to claim 1, characterized in that: the control circuit further includes a master controller, and the master controller is connected to the input end of the frequency converter and is used to provide gear action control signals for rising, falling and stopping for the frequency converter to control the hoisting motor to act according to the set gears.

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