KR20010080785A - Overload Cutoff Device for Hoist and Crane - Google Patents

Abstract

PURPOSE: An overload isolator of a hoist and a crane is provided to protect an equipment from overload by sensing overcurrent flowing through a power wire of a motor in driving a hoist and a crane, displaying the sensed state and isolating operation of a rising switch in a control unit. CONSTITUTION: An overload isolator of a hoist and a crane consists of: a current sensor(2) detecting the electric current state of a motor(11) through a CT(Current Transformer); a comparator(6) converting the analog output of the current sensor into digital data, comparing the digital data with input digital data of a deep switch(8) and a key pad(9), and outputting the corresponding digital data; an alarm unit(7) consisting of an LED(Light Emitting Diode) and a buzzer driven in overload of the output from a switch drive unit(3) and the comparator; a displayer(4) displaying the electric current value in the overload; and a control unit(1) outputting control signals to the switch drive unit, the displayer and the alarm unit. In case of the overload state of a hoist and a crane, the buzzer and the LED are driven. A worker recognizes the overload state of the equipment by referring to the alarm unit and the displayer. Therefore, the worker takes prompt action on the overload to prevent the equipment from damage.

Description

Overload Cutoff Device for Hoist and Crane {Overload Cutoff Device for Hoist and Crane}

The present invention relates to an overload circuit breaker of a hoist and a crane, and in particular, a hoist to turn off the load rise switch of the control unit when an overcurrent flows due to the overload of the motor driving unit during the operation of the hoist and the crane, which are widely used in the construction and manufacturing industries. And it relates to an overload blocking device of the crane.

Representative examples of the conventional hoist and crane overload breaker can be seen by the Republic of Korea Utility Model Publication (Publication No. 1985-1604, designation name: overload protection device of the crane and hoist (hereinafter referred to as "quoting proposal")) have.

According to the description, the cited proposal is to rectify the power supply voltage of the relay controlling the power supply circuit of the motor into a bridge rectification circuit, smoothing it with a smoothing circuit, maintaining a constant voltage with a zener diode, and controlling this power supply circuit as an SCR. In this case, the overload current of the motor is detected as a high-sensitivity CT, divided by a dip switch, amplified by an amplifier, compared as a comparator through a spat, separated and compared by an amplifier, and then the gate of the SCR is connected through a driving circuit connected with a delay circuit. When overload occurs by triggering and conducting, the signal detected by CT is compared with the reference signal which is the voltage set by the variable resistor, and the output signal is generated. After the output signal is amplified again, the trigger signal is applied to the gate of the switching element SCR. It has been proposed to be authorized to control the operation of the motor, On who would by to prevent damage to the Motor due to overcurrent.

This citation is to detect the excessive increase in the current flowing in the motor and to turn off the lift switch on the hoist and crane control to protect the equipment and to prevent human injury. In this case, it is difficult to trust the accuracy because a series of control is performed in an analog manner, and in addition, in the case of this cited proposal, the start time of ignoring a detection signal caused by an inrush current generated at the initial power-up. Overload time, which is regarded as overload if overcurrent persists for more than the set time, reset time, which is the time required to return to the initial state after the alarm when overload occurs, and overcurrent limit value set by the user ( There is a problem that the arbitrary setting of the overcurrent limit is impossible.

In addition, the cited proposal is not able to adjust the conditions as described above to suit the characteristics of the work site and load, which has a problem that can cause damage to the damage of the motor or damage equipment of the related mechanical elements, and the load If it is necessary to change the set value according to the characteristics of the star, there is a problem to design and manufacture a new overload protection device itself.

Accordingly, an object of the present invention is to detect the overcurrent flowing in the power line of the motor when the hoist and the crane are driven and to display the detected state, as well as to block the operation of the lift switch on the operation unit to protect the device from overload and furthermore Is to increase the reliability to use the device with confidence.

1 is a circuit diagram of the overload breaker of the present invention hoist and crane (for Single Speed)

Figure 2 is a circuit diagram of the overload breaker of the present invention hoist and crane (for Dual Speed)

<Description of the symbols for the main parts of the drawings>

1 control unit 2 current detection unit

3: switch drive unit 4: display unit

5: setting unit 6: comparing unit

7: alarm unit 8: dip switch

9: keypad 10: control panel

10: motor

In order to achieve the above object, the present invention provides a current sensing unit for detecting a current state flowing in the power line of the motor when the hoist and the crane are driven;

A comparator whose output is determined by whether or not the signal output from the current sensing unit exceeds a set value, a switch driver for controlling the rising switch of the operation unit by the output of the comparator, and an output of the comparator are regarded as an overload occurrence. In the well-known configuration consisting of an alarm unit that immediately activates the LED and the buzzer,

A setting unit having a dip switch or a keypad for converting the output of the current sensing unit into a digital value to set an overcurrent limit value and a start time to a digital value, and converting the output of the current sensing unit into a digital value and converting the output into a digital value. A comparison unit for determining an output in comparison with the control unit, and controlling the setting unit and the comparison unit according to a program to turn off the rise switch when an overcurrent occurs and to operate the alarm unit for a set time, and to display a current value when an overcurrent occurs. An overcurrent interruption device for cranes and hoists consisting of display units is proposed.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit diagram of an overload circuit breaker of a hoist and a crane of the present invention, and a current sensing unit 2 for detecting a current state flowing in a motor 11 through a current transformer and an output value and a setting unit of the current sensing unit 2. Comparing unit (6) in which the output is determined in comparison with the set value of (5), and switch driving unit (3) and comparator (6) to control the rising switch of the operation unit (10) by the output of the comparing unit (6) In the well-known configuration consisting of an alarm unit 7 composed of an LED and a buzzer which is operated when the output of the overload state is high, the output of the current sensing unit 2 is converted from analog to digital, which is a dip switch 8 or a keypad. A comparison unit 6 for outputting a corresponding digital value in comparison with the digital value inputted to (9), a display unit 4 for displaying a current value in case of overload, and a memory in which a CPU and a program are built-in. Electric switch drive unit (3), display unit (4), alarm unit (7), switch The drive unit 3 is composed of control unit 1, which so as to output a predetermined control signal.

Referring to the effects of the present invention configured as described above are as follows.

First, the present invention must enter conditions for optimal operation prior to operation. To this end, in the present invention, a start time for ignoring a detection signal caused by an inrush current generated when power is applied initially, an overload time regarded as an overload when an overcurrent is maintained for a set time or more, and an overload occurs. The reset time, which is the time taken to return to the initial state after the alarm is set, and the overcurrent limit set by the user should be arbitrarily set. For this purpose, the dip switch 8 of the setting unit 5 is set. Alternatively, the keypad 9 or a combination thereof can be used.

After completing the input of the operating conditions in this way, the load on the hoist or crane is loaded, and then the lift switch of the operation unit 10 is turned on. Accordingly, power is applied to the motor 11 so that a current flows. At this time, generation of an inrush current is inevitable at the initial time of applying the power. Since the inrush current is very large, it is necessary to stop a series of overload detection operations at the beginning of the inrush current flow.

To this end, in the present invention, since the start time is set in the above-described process, the detection operation is stopped during the initial operation time to enable smooth operation. After the initial start time has elapsed, the current flowing through the motor 11 is sensed by the current sensing unit 2, and in the normal operating state, the current value flowing through the motor 11 Since it is a normal level, the output value of the current detection part 2 will be below the overcurrent limit value set by the setting part 5. Therefore, at this time, the output value of the comparator 6 becomes a level at which the switch control unit 1 is not driven. Therefore, the operator normally operates the operation unit 10 to operate the lift switch to lift the load. You can do it.

On the other hand, if the load is very large, the motor 11 may not rotate normally, and thus the current flowing through the motor 11 may abnormally increase. This overcurrent damages the motor 11 and may cause stress to related equipment, and may lead to accidents that may damage human life as well as mechanical failure and fire. Therefore, in this case, in the present invention, the overcurrent flowing in the motor 11 is induced through the current transformer to invert the output of the current sensing unit 2.

The output of the current sensing unit 2 is converted into a digital signal while being applied to the control unit 1, and the converted digital signal is inverted from the setting of the setting unit 5 to invert the output of the comparing unit 6. Let's do it. The control unit 1 counts the time for which the inverted state is different from the normal state. In this way, when the inverted state is maintained, i.e., when the overload time exceeds the set value, the control unit 1 immediately returns to the overload state. In this regard, the switch driving unit 3 is controlled to turn off the rising switch of the operation unit 10.

The reason for waiting until the overload condition exceeds the set time is to prevent unnecessary overload response operation because the overload will be restored to the normal state immediately when it is caused by external transient shock or external noise. In addition, when the switch drive unit 3 is operated by the output of the comparator 6, the rise of the load is stopped, and in the present invention, the alarm unit 7 is activated to flash the red LED, and the buzzer is operated to indicate that the operator is overloaded. In this case, the current value is displayed on the display unit 4 by converting the output value of the comparison unit 6.

Therefore, the operator can accurately understand the current state and take appropriate measures to solve the cause of the overload.

In addition, the present invention is to maintain the alarm state for a time that can be fully recognized by the operator after starting to generate an overload alarm, and after the reset time has elapsed, the operation of the alarm unit 7 is stopped and returned to the initial state By doing so, reoperation is possible.

In this way, the present invention allows the lowering switch for lowering the load to be turned on and the rising switch to be in the off state.

In addition, when the operator operates the lowering switch and the load is lowered by the rising amount, the automatic return is made to be turned on.

In addition, in the present invention, when a separate reset switch is operated in an overload state, the control unit 1 recognizes this and operates the down switch in a state in which the up switch is turned off so that the load can be lowered and the home position is lowered.

In addition, the present invention is also applicable to the case of the two-speed (high speed, low speed) type hoist and crane as shown in FIG. This state is shown in FIG.

This includes the start time for stopping operation during the overcurrent occurrence time due to the inrush current, the overcurrent limit set by the user, and the set time for overload alarm if the overcurrent limit value is kept above the set time. The overload time and the reset time, which is the time it takes to return to the initial state after the alarm in case of an overload, must be set. These values must be changed in the case of high speed and low speed. In the speed embodiment, the setting operation should be repeated twice. For this purpose, the keypad 9 or the dip switch 8 can be used.

In the case of the two-speed type hose and crane, when the operator sets the speed to the high speed or the low speed by operating the motor 11 control unit 1, current flows in the high speed phase or the low speed phase. An electric current flows in either. Accordingly, by looking at which current transformer is first generated a current signal, the control unit 1 recognizes the high speed phase and the low speed phase and applies the input value set by the operator to perform the operation as described above.

That is, such a two-speed hoist or crane, when the high speed switch is pressed on the operation unit 10, the motor control unit 12 connects the motor 11 to the high speed to rotate at a high speed, and the operation unit 10 Pressing the low speed switch in the motor control unit 12 to connect the motor 11 to the low speed to operate at a low speed. As described above, when the motor 11 is driven, the current sensing unit 2 detects a current state detected by a current transformer installed at a low speed phase and a high speed phase, and when current is detected at the low speed phase, the current value of the low speed phase is transmitted to the controller 1. If the current is detected first in the high speed phase, the current value of the low speed phase is sent to the controller 1, and the current value is a low speed or a high speed phase limit value corresponding to the low speed or high speed phase. It is compared and output by the comparator 6 by a high-speed overcurrent limit.

When the detected current value and the low speed or high speed phase limit value are exceeded and the set value is exceeded, it is determined as overload to control the switch driver 3, and the output of the switch control unit 1 as described above is as described above. Opening and closing the upswitch will operate the LED and the buzzer of the alarm unit (7).

In addition, the display unit 4 displays the current value at this time so that the operator can accurately grasp the current situation, and this state is maintained for the reset time.

In this way, the present invention is to be able to perform the correct operation under the conditions set by the operator in relation to the overload condition that occurs unexpectedly when using the hoist and crane, the operator can quickly refer to the alarm unit 7 and the display unit 4 Being able to make good judgment and take action not only provides the effect of resolving problems such as equipment damage and other human injury caused by the overload, but also the start time, overcurrent limit value and load as described above. It is possible to operate more conveniently by setting the time, reset time, etc. to the optimum conditions according to various situations such as the field or work type.

Claims (3)

A current sensing unit 2 for detecting a current state flowing in the motor 11 through a current transformer, and a comparison unit in which an output is determined by comparing an output value of the current sensing unit 2 and a setting value of the setting unit 5 ( 6) and an alarm unit comprising an LED and a buzzer which are operated when the output of the comparison unit 6 and the switch driver 3 and the output unit of the comparison unit 6 to control the rising switch of the operation unit 10 by the output of the comparison unit 6. In the known configuration consisting of (7), the output of the current sensing unit 2 is converted from analog to digital, and the corresponding digital value is compared with the digital value input to the dip switch 8 and the keypad 9. An electric switch driving unit 3, a display unit 4, and an alarm unit 7 by means of a comparator 6 for outputting, a display unit 4 for displaying a current value in case of overload, and a memory in which a CPU and a program are built in. The control unit 1 is configured to output a predetermined control signal to the switch driver 3. Hoist and crane overload prevention device characterized in that. 2. The overload protection device of a hoist and a crane according to claim 1, wherein a start time, an overcurrent limit value, a load time, and a reset time of the setting unit (5) are set by a dip switch (8). 2. The overload protection device of a hoist and a crane according to claim 1, wherein a start time, an overcurrent limit value, a load time, and a reset time of the setting unit (5) are set by the keypad (9).