JPS634064Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to an improved overload prevention device for a crane. Figure 1 shows the configuration of a conventional device of this type, where 1 is a strain gauge that detects the moment or load of the boom, 2 is an amplifier that amplifies the output voltage of the strain gauge, and 3 is an offset of the strain gauge 1. A variable resistor for adjusting the voltage, 4 a variable resistor for adjusting the gain of the amplifier 2, 5 a potentiometer for detecting the angle of the boom, and 6 an amplifier for amplifying the output voltage of the potentiometer 5. , 7 is a variable resistor for adjusting the offset voltage of the potentiometer 5, 8 is a variable resistor for adjusting the gain of the amplifier 6, 9 is a potentiometer for detecting the length of the boom, 10
11 is a variable resistor for adjusting the offset voltage of potentiometer 9; 12 is an amplifier 10;
This is a variable resistor for adjusting the gain. 1
3 to 15 are analog switches for controlling ON/OFF the detection voltages output from the three detectors 16 to 18; 19 is an arithmetic circuit and controller; 20
21 is a stop lamp, 21 is a warning lamp, 22 is a solenoid, and 23 is a relay contact for operating the hydraulic cylinder of the crane body to stop the crane. In the conventional example configured as described above, the arithmetic circuit and the controller 19 control the analog switches 13 to 15 to control the three detectors 1.
Input the detected voltages output from 6 to 18. Then, the rated characteristic value of the crane is calculated from the angle detection voltage output from the angle detector 17 and the length detection voltage output from the length detector 18,
Voltage and load detector 16 corresponding to its rated characteristic value
Find the ratio with the load detection voltage output from the
When the ratio is 100% or more, the stop lamp 20 is turned on and the solenoid 22 is turned on.
A current is applied to close the relay contact 23 to stop the crane. By the way, in order for the crane overload prevention device to operate accurately as explained above, the amount to be detected and the detection voltage output from the detectors 16 to 18 must have a predetermined correspondence relationship. There must be. However, the strain gauge 1 and potentiometers 5 and 9 have variations in detection sensitivity depending on the parts and change over time, and the amplifier 2,
6 and 10 are variable resistors installed in the detectors 16 to 18 in order to establish a predetermined correspondence between the detected amount and the detected voltage, since the gain varies depending on the components and changes over time. 3,
4, 7, 8, 11, and 12 must be adjusted. Conventionally, such adjustments have been made using a directly readable display (not shown) provided in the arithmetic circuit and controller 19, such as a meter, a digital display, or the like. In the conventional example described above, when adjusting the angle detector 17, the detection end 5a of the potentiometer 5 is set at the 0 degree position (minimum adjustment point) so that the display on the indicator becomes 0 degree. Adjust variable resistor 7. Next, the detection end 5a is set at the maximum angle of 75 degrees (maximum adjustment point), and the variable resistor 8 is adjusted so that the display shows 75 degrees. Load detector 16, length detector 18
Similarly to the adjustment of the angle detector 17, the variable resistors 7, 8, 11, and 12 are sequentially adjusted at the minimum and maximum adjustment points of the detector. As described above, in the conventional example described above, in order to adjust each detector using the arithmetic circuit and the directly readable display provided in the controller 19, the crane overload prevention device becomes larger and The drawback was that production costs were also high. In order to eliminate this drawback, instead of providing a directly readable display, a measuring device such as a digital volt meter should be used at points a to c shown in Figure 1 when adjusting the detector. There is a way to connect and adjust the detector. In this method, the output points (points A to C) of the detector to be adjusted are connected to a digital volt meter using lead wires, and the detector is adjusted while watching the display on the digital volt meter. It is something. In this case, the display on the digital volt meter is the output voltage of the detector, so the person making the adjustment must convert the adjustment range shown in Table 1 into voltage before adjusting the detector. .

[Table] Such adjustments must be made by an experienced person.
Also, this cannot be done in places without a digital volt meter. Therefore, there is a drawback that the detector cannot be adjusted at any time and it is difficult to maintain the device in a highly accurate state. In order to eliminate the drawbacks of the conventional example, the present invention provides a reference voltage generator that outputs a reference voltage consisting of two voltages that determine the permissible range of output voltage at the adjustment point of each detector, and a detector output voltage. By providing a comparator that compares the voltage with a reference voltage and a lamp that displays the result, the detector can be adjusted easily and at any time, and the accuracy of the device can be maintained at a high level of accuracy. An object of the present invention is to provide an overload prevention device for a crane, which allows the device to be downsized and to reduce the production cost of the device. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 shows the configuration of an embodiment of the present invention, in which the same reference numerals as in FIG. 1 indicate the same components, and 24a outputs the upper limit reference voltage at each adjustment point. A reference voltage generator 24b outputs a lower limit reference voltage at each adjustment point, and 25 to 36 are analog switches. 37 is a comparator that compares the upper limit reference voltage outputted from the reference voltage generator 24a and the output voltage of the detector; 38 is the reference voltage generator 24b
A comparator 39 is an exclusive OR gate that compares the lower limit reference voltage output from the detector with the output voltage of the detector, and comparators 37 and 3
8 and the exclusive OR gate 39 constitute a window comparator 40. 41 to 43 are amplifiers that amplify the output of the window comparator 40; 44 is an LED that displays High when the output voltage of the detector is higher than the upper limit reference voltage;
5 is an LED that displays OK when the output voltage of the detector is between the upper limit reference voltage and the lower limit reference voltage;
46 is an LED that displays LOW when the output voltage of the detector is lower than the lower limit reference voltage. here,
The reference voltage generators 24a and 25b divide the voltage with resistors to determine each adjustment point (minimum adjustment point,
The reference voltage at the maximum adjustment point) is output.
The reference voltages for the upper and lower limits at each adjustment point should be the values when converting the adjustment range in Table 2, for example, when the load detector is 0%, the upper limit is 0.4% and the lower limit is 0.2%. is set to . 4
7 is deco

【table】

[Table] Under normal conditions, switch 48 is connected to terminal a, and decoder 47 is controlled by the output of the arithmetic circuit and controller 19. During detector adjustment, switch 48 is connected to terminal b. The decoder 47 is controlled by the output of the counter 49. The counter 49 counts the pulses output from the pulse generator 51 by the push button switch 50 and outputs the result to the decoder 47. The decoder 47 selects one of the six output lines 52 to 57 based on the output of the counter 49, and makes the analog switch connected to that line conductive. That is, the decoder 47
The reference voltage input to the window comparator 40 and the output voltage of the detector can be simultaneously switched in conjunction with the output of the window comparator 40. 58 to 63
is used to display which output line the analog switch connected to is in a conductive state.
The LEDs 58 to 63 indicate which variable resistor of which detector should be adjusted by the user. In this embodiment configured as described above, the switch 48 is normally connected to the terminal a, and the arithmetic circuit and controller 19 lights up the alarm lamp 21 based on the outputs of the detectors 16 to 18. Alternatively, a current is applied to the solenoid 22 to close the relay contact 23 to stop the crane and turn on the stop lamp 20. When adjusting the detectors 16 to 18, the user first
Connect the switch 48 to terminal b, operate the push button switch 50 while looking at the display on the LEDs 58 to 63, and select the variable resistor you wish to adjust. For example, when adjusting the variable resistor 7 of the angle detector 17, the user operates the push button switch 50.
Turn on LED60. In this state where the LED 60 is lit, the analog switches 14, 27 and 33 connected to the output line 54 are in a conductive state, and the comparator 3 is in a conductive state.
The output voltage of the angle detector 17 and the voltage corresponding to 0.4 degree output from the reference voltage generator 24a are input to the comparator 7, and the output voltage of the angle detector 17 and the voltage corresponding to 0.4 degrees output from the reference voltage generator 24a are input to the comparator 38.
The voltage corresponding to 0.2 degrees output from 4b is input. Next, the user sets the detection end 5a of the angle detector 17 to the 0 degree position (minimum output point),
While watching LEDs 44 to 46, adjust variable resistor 7 so that LED 45 (OK display) lights up.
As described above, variable resistors 3, 4, 7, 8,
11 and 12 can be adjusted sequentially. The configuration of the invention described above is suitable for configuration using a microcomputer, and when configured based on a microcomputer, it is best to configure the reference voltage generators 24a and 24b with P-ROM. Can be constructed economically. In this case, in order to make the reference voltage respond flexibly to model changes, the reference voltage is configured as model-specific data separate from the overall system program, for example, in the same package as the rated characteristic data. By converting two P-ROMs, it is possible to easily change the model, and even when setting values differ depending on the model, setting errors can be prevented. FIG. 3 shows the configuration of another embodiment of the present invention in which a stop lamp 20, a warning lamp 21, and a pilot lamp of a crane overload prevention device are used as adjustment indicators when adjusting a detector. The same reference numerals as in Fig. 2 indicate the same parts, and 64 is the pilot lamp of the crane overload prevention device, and 65 is the one to which an "L" level signal is input during normal times and is detected. 66 is an inverter, 67 to 72 are analog switches, and 73 to 75 are amplifiers. Next, the operation of this embodiment configured as above will be explained. In normal times, since an "L" level signal is input to the signal input terminal 65, the analog switches 67 to 69 are in a conductive state, and the analog switches 70 to 72 are in a non-conductive state. . Therefore, the stop lamp 20, the alarm lamp 21, and the pilot lamp 64 are controlled by the output of the arithmetic circuit and the controller 19, and each performs normal operation (in this case, the stop lamp 21
0 and the alarm lamp 21 shall blink during operation). Next, when adjusting the detector, an "H" level signal is input to the signal input terminal 65, so the analog switches 67 to 69 become non-conductive, and the analog switch 70
to 72 become conductive. Therefore, the stop lamp 20, the warning lamp 21, and the pilot lamp 64 operate according to the output of the window comparator 40. That is, the stop lamp 20 lights up when the output voltage of the detector is higher than the upper limit reference voltage.
The alarm lamp 21 lights up to indicate OK when the output voltage of the detector is between the upper limit reference voltage and the lower limit reference voltage, and the pilot lamp 64 indicates that the output voltage of the detector is at the lower limit. Lights up and displays LOW when the voltage is lower than the reference voltage. As described above, in this embodiment, the stop lamp 20, alarm lamp 21, and pilot lamp 64 are used as indicators for adjusting the detector, so that the configuration of the apparatus can be simplified. In addition, it is possible to reduce the production cost of the device. As explained above, according to the present invention, the detector can be adjusted easily and at any time, the accuracy of the device can always be maintained at a high level, and the device can be made smaller. Therefore, there is an advantage not found in the conventional example in that the production cost of the device can be reduced.

[Brief explanation of drawings]

Figure 1 is a diagram showing the configuration of a conventional crane overload prevention device, Figure 2 is a diagram showing the configuration of one embodiment of the present invention, and Figure 3 is a diagram showing the configuration of another embodiment of the present invention. It is. 1...Strain gauge, 3, 4, 7, 8, 1
1, 12... Variable resistor, 5, 9... Potentiometer, 16... Load detector, 17... Angle detector, 18... Length detector, 19... Arithmetic circuit and controller, 20 ... Stop lamp, 21 ... Alarm lamp, 22 ... Solenoid, 23 ... Relay contact, 24a, 24b ... Reference voltage generator, 37,
38...Comparator, 39...Exclusive OR gate, 40...Window comparator, 44 to 46, 58 to 63...LED,
47...decoder, 49...counter, 50...
Push button switch, 51... Pulse generator, 64...
pilot lamp.

Claims (1)

[Scope of claim for utility model registration] (1) A load detector that outputs a load detection voltage corresponding to the boom moment or load, an angle detector that outputs an angle detection voltage corresponding to the boom angle, and the length of the boom. a length detector that outputs a length detection voltage corresponding to the angle detection voltage, a rated characteristic value of the crane is calculated from the angle detection voltage and the length detection voltage, and a voltage corresponding to the rated characteristic value and the load detection voltage are calculated. An overload prevention device for a crane that is equipped with an arithmetic circuit and a controller that determines the ratio between the voltage and the voltage and lights up a warning lamp or stops the crane and lights up a stop lamp depending on the value of the ratio. a reference voltage generator that outputs a reference voltage consisting of an upper limit reference voltage and a lower limit reference voltage for adjusting the detector according to the detector; a switch that selects a reference voltage and outputs it to a comparator; a first lamp that lights up when the detected voltage is higher than the upper limit reference voltage; and a switch that selects a reference voltage and outputs it to the comparator; An adjustment indicator is provided, which includes a second lamp that lights up when the voltage is between the upper limit reference voltage and a third lamp that lights up when the detected voltage is lower than the lower limit voltage. Features: Overload prevention device for cranes. (2) The reference voltage generator outputs a maximum reference voltage corresponding to a maximum adjustment point (100%) and a minimum reference voltage corresponding to a minimum adjustment point (0%) for each of the detectors. An overload prevention device for a crane as set forth in claim (1) of the utility model registration claim. (3) The switching device interlocks and simultaneously switches the maximum reference voltage or the minimum reference voltage and the output voltage of the detector and outputs the same to the comparator. Overload prevention device for cranes as described in 2). (4) Each of the detectors is provided with two regulators, and the switch selects one output voltage from among the output voltages of each of the detectors and adjusts the output voltage corresponding to that output voltage. Utility model registration Claim No. (2) characterized in that the utility model is provided with a display that selects the maximum reference voltage or the minimum reference voltage and outputs it to the comparator and identifies the type of detector and the size of the adjustment point. Overload prevention device for cranes as described in . (5) The overload prevention device for a crane according to claim (4), wherein the switching device is operated by a pulse generated by a push button switch. (6) The switching device interlocks and simultaneously switches the maximum reference voltage or the minimum reference voltage and the output voltage of the detector and outputs the same to the comparator. Overload prevention device for cranes as described in 4). (7) The alarm lamp and the stop lamp are used as two lamps among the first, second, and third lamps of the adjustment indicator when adjusting the detector. An overload prevention device for a crane as set forth in claim (1) of the utility model registration. (8) The warning lamp, the stop lamp, and the pilot lamp of the crane overload prevention device are:
The overload prevention device for a crane according to claim 1, wherein a lamp of the adjustment indicator is used when adjusting the detector.