CN113501425A

CN113501425A - Method for realizing rapid detection and protection of crane hook

Info

Publication number: CN113501425A
Application number: CN202110911602.2A
Authority: CN
Inventors: 王照海; 王照岳
Original assignee: SHANGHAI EECTRL ELECTRIC CO Ltd
Current assignee: SHANGHAI EECTRL ELECTRIC CO Ltd
Priority date: 2021-08-10
Filing date: 2021-08-10
Publication date: 2021-10-15
Anticipated expiration: 2041-08-10
Also published as: CN113501425B

Abstract

The invention discloses a method for realizing quick detection and protection of a crane hook, which comprises the following steps: s1, acquiring the initial braking moment and the preset braking time of the crane hoisting mechanism; s2, collecting a change value delta R of the number of rotation turns of a winding drum of the crane hoisting mechanism in a T time period from the end moment of preset braking time; and S3, comparing the product value of T x Delta R with a preset unhooking judgment threshold value, if the comparison result is that the product value is greater than the unhooking judgment threshold value, judging that unhooking occurs, and immediately starting a motor speed regulator of the crane hoisting mechanism. The method not only can realize the rapid and accurate detection and judgment of the hook slipping, but also can effectively avoid the hook slipping from being enlarged into accidents, is simple to use and easy to realize, can be suitable for various new and old cranes, and has important value and significance for improving the safety of the cranes.

Description

Method for realizing rapid detection and protection of crane hook

Technical Field

The invention relates to a method for realizing quick detection and protection of a crane hook, belonging to the technical field of crane safety control.

Background

The crane is a multi-action crane for vertically lifting and horizontally carrying heavy objects within a certain range, and generally comprises a lifting mechanism, a cart mechanism and a trolley mechanism, wherein the lifting mechanism lifts the heavy objects and then moves the heavy objects to a required position through the cart and the trolley. When the heavy object is moved by the cart and the trolley, the heavy object is stopped in the air at the moment, and the high-speed shaft at the motor side or the low-speed shaft of the speed reducer is braked by the brake so as to ensure that the heavy object cannot slip off the hook. However, in the actual use process, due to an electrical fault, a brake fault or a mechanical fault, etc., the hoisting mechanism of the crane often causes the phenomenon of hook slipping (stalling, slipping, etc.) of the crane, so that heavy objects fall down to the ground, equipment is damaged and smashed, the safety of field personnel is seriously threatened, and disastrous results are caused.

Because modern cranes generally adopt speed regulation equipment such as frequency conversion, stator voltage regulation and the like, when a hoisting mechanism brakes, firstly the speed regulation equipment controls the output torque of a motor, so that the speed of the motor is reduced to be close to zero, and then a brake is closed. If the brake fails (such as adhesion of a contact of a brake contactor or mechanical failure of the brake, and the like), the load drags the motor to accelerate and roll down from a static state or an extremely low speed, because of the resistance of a mechanical mechanism such as a speed reducer and the like, and the brake may have some residual braking force, the speed of the load does not steadily increase or steadily change but suddenly increases or suddenly decreases, sometimes does not exist, so the process of detecting the slide hook by detecting the speed or the acceleration in the prior art usually needs a longer time (more than 500ms), usually, the time from the detection of the slide hook to the response of slide hook protection still needs 500ms or more, however, in most cases, before the slide hook protection response is made, an overspeed switch of a crane hoisting mechanism is already actuated, and the overspeed switch is actuated as a result of closing the brake, but the brake fails to work, thus leading to the load still continuing to fall rapidly out of control, eventually leading to an accident with catastrophic consequences.

Therefore, in order to effectively avoid the hook slipping accident caused by the failure of the brake, the rapid detection of the hook slipping and the starting of the hook slipping protection are required to be completed before the overspeed switch acts, but no relevant effective solution and technical report is found so far.

Disclosure of Invention

In view of the above problems and needs in the prior art, an object of the present invention is to provide a method for quickly detecting and protecting a hook slipping of a crane, so as to quickly detect the hook slipping and start the hook slipping protection before an overspeed switch is operated, thereby effectively preventing the hook slipping from being produced into an accident.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for realizing quick detection and protection of a crane hook comprises the following steps:

s1, acquiring the initial braking moment and the preset braking time of the crane hoisting mechanism;

s2, collecting a change value delta R of the number of rotation turns of a winding drum of the crane hoisting mechanism in a T time period from the end moment of preset braking time;

and S3, comparing the product value of T x Delta R with a preset unhooking judgment threshold value, if the comparison result is that the product value is greater than the unhooking judgment threshold value, judging that unhooking occurs, and immediately starting a motor speed regulator of the crane hoisting mechanism.

In a preferred embodiment, in step S1, the preset braking time can be automatically updated according to the setting value of the normal braking time.

In a preferred embodiment, in step S2, the absolute value encoder disposed on the winding drum is used to acquire the rotation circle value of the winding drum at each time.

In a preferred embodiment, in step S2, the T period is within 0.5 seconds.

In a preferable embodiment, in step S3, the threshold value for determining slipping-off is 0.01.

In a preferred embodiment, in step S3, the motor governor executes a quick start procedure, that is: neglecting the detection and judgment process of non-key faults, such as the detection and judgment of abnormal master commands, limit protection and other problems, and not executing a series of detection processes of normal starting, but directly determining whether to start the motor according to the existence of the maintaining signal so as to enable the motor to work by power.

Compared with the prior art, the invention has the following beneficial technical effects:

because the brake is the last safety measure of the hoisting mechanism, if the brake fails, the load is out of control and rapidly drops, namely the hook slipping happens, and the prior art either starts the frequency converter after detecting the hook slipping or triggers the overspeed switch to act, because the control objects of the frequency converter and the overspeed switch are both brakes, and the brake at the moment actually fails and cannot act, the prior art can not fundamentally solve the hook slipping accident caused by the failure of the brake; the invention quickly detects whether the hook slips and immediately quickly starts the speed regulator of the motor to enable the motor to be electrified to work after the hook slips, and the motor is electrified to output a certain torque to maintain the slow descending or hovering of the load, thereby effectively avoiding the hook slipping from being expanded into accidents; particularly, the invention carries out detection and judgment on the hook slipping through a mode of acquiring the change value delta R of the number of rotation turns generated in the T time period from the end moment of the preset braking time of the winding drum of the crane hoisting mechanism by using the absolute value encoder arranged on the winding drum, not only can realize quick detection of the hook slipping, but also has high detection precision and good stability, does not need to add any hardware facilities, can be suitable for various new and old cranes, obviously improves the safety of the cranes and has obvious practical value.

Drawings

Fig. 1 is a flow chart of a quick start executed by a motor governor provided by an embodiment.

Detailed Description

The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and examples.

Examples

The method for realizing the rapid detection and protection of the crane hook comprises the following steps:

s2, collecting a change value delta R of the number of rotation turns of a winding drum of the crane hoisting mechanism in a T time period from the end moment of preset braking time; the method comprises the steps of acquiring the rotating circle value of a winding drum at each moment by using an absolute value encoder arranged on the winding drum; the T time period is preferably within 0.5 second, so that the hook slipping detection can be ensured to be completed before the overspeed switch acts;

and S3, comparing the multiplied value of T x Delta R with a preset unhooking judgment threshold value (set to be 0.01 in the embodiment), if the comparison result is that the multiplied value is greater than the unhooking judgment threshold value, judging that unhooking occurs, and immediately starting the motor speed regulator of the crane hoisting mechanism.

In a preferred embodiment, in step S1, the preset braking time can be automatically updated according to the setting value of the normal braking time. The setting refers to averaging actual normal braking time data recorded in a period of time, and the obtained average value is the setting value of the normal braking time.

In a preferred embodiment, in step S3, the motor governor executes a quick start procedure, that is: ignoring the detection and determination processes of non-critical faults, such as the detection and determination of abnormal master commands, limit protection and other problems, and not executing a series of detection processes of normal starting, it is directly determined whether to start the motor to make it work electrically according to the existence of the maintaining signal, as shown in detail in fig. 1.

Because the diameters of winding drums, the diameters of steel wire ropes and the multiplying power of pulley blocks of hoisting mechanisms of different cranes are different, a method for monitoring the descending distance L of a load after the preset normal braking time is finished to judge whether to slip a hook or not is adopted in the prior art, and the fixed standard of a slip hook judging threshold value is difficult to provide due to the difference of L values, so that the accurate monitoring and judgment of the slip hook cannot be realized in practical application. For a hoisting mechanism, the height change value of the load is fixed every time the winding drum rotates for one circle, so that the quick and accurate detection and judgment of the slip hook are realized by skillfully utilizing the characteristic, and the hoisting mechanism is simple to use and easy to realize; in addition, the invention quickly detects whether the hook slips and immediately quickly starts the speed regulator of the motor to enable the motor to be electrified to work after the hook slips are detected, and enables the motor to be electrified to output a certain torque so as to maintain the slow descending or hovering of the load, thereby effectively avoiding the hook slipping from being expanded into accidents and being suitable for various new and old cranes; therefore, compared with the prior art, the crane safety protection device has obvious practical value and has important value and significance for improving the safety of the crane.

It is finally necessary to point out here: the above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims

1. A method for realizing quick detection and protection of a crane hook is characterized by comprising the following steps:

2. The method of claim 1, wherein: in step S1, the preset braking time can be automatically updated according to the setting value of the normal braking time.

3. The method of claim 1, wherein: in step S2, the absolute value encoder provided on the roll collects the number of revolutions of the roll at each time.

4. The method of claim 1, wherein: in step S2, the T period is within 0.5 seconds.

5. The method of claim 1, wherein: in step S3, the hook slipping determination threshold is 0.01.

6. The method of claim 1, wherein: in step S3, the motor speed governor executes a quick start process, that is: the motor is directly started or not according to the existence or nonexistence of the maintaining signal so as to enable the motor to work electrically.