JPH05270792A - Automatic stopper circuit for over-winding of crane hook - Google Patents

Abstract

PURPOSE:To provide a hook over-wind auto-stopper circuit for crane, with which a falling accident of hung objects or a hook clan be precluded resulting from misoperation in boom depressing at the time of hook over-winding. CONSTITUTION:An oil-hydraulically driven crane is equipped with a hook over- wind sensing switch 5a mounted near the top of a boom, a relay 20 driven with actuation of the hook over-wind sensing switch 5a, a solenoid-operated selector valve 21 to stop the wind-up rotation of a winch motor 10a with actuation of the relay 20, and a solenoid-operated selector valve 22 to stop the boom depressing motion of a boom rising/falling winch motor 11a in conformity to an over-load signal. The contact of the relay 20 is connected with the selector valve 22, and the hook wind-up motion and boom depressing motion are simultaneously stopped automatically at the time of hook over-winding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hook overwinding automatic stop circuit in a hydraulic drive system crane.

[0002]

2. Description of the Related Art FIG. 2 is a side view showing a state in which a conventional hydraulic crawl crane is performing a lifting work. As shown in FIG. 2, the crane body 1 includes a hook 3 on which a suspended load 4 is suspended.
It has a winch 10 for moving up and down and a winch 11 for hoisting the boom 2. The hoisting rope 6 of the hook 3 is wound around the sheave 3a of the hook 3 through the sheaves 2a and 2b at the tip of the boom 2, and the winch 10 is used to wind the rope. The hook 3 moves up and down by winding or unwinding 6. In addition, the other end of the pendant rope 7 whose one end is connected to the end of the boom 2 is connected to the bridle 9 and is wound around between the bridle 9 and the sheave block 31 on the A frame 30. -The boom 2 is undulated by winding the rope 8 around the winch 11 and winding or unwinding the rope 8 with the winch 11.

In such a crane, an overwinding prevention device 5 for the hook 3 is provided so that the hook 3 will not be overwound during lifting work so as not to damage the boom 2. This overwinding prevention device 5 has a hook overwinding detection switch 5a composed of a micro switch in which a switch operating portion is connected to a weight suspended by a chain near the top of the boom 2, and normally, the chain is suspended by the weight. Although the micro switch 5a is stretched, the micro switch 5a is turned on, but when the hook 3 is overwound, the hook 3 pushes up the weight, and the chain is loosened to turn off the hook overwinding detection switch 5a.

FIG. 3 is a conventional hydraulic circuit diagram for vertically driving the hook 3. 10a is a hydraulic winch motor for driving the hoisting winch 10, and 17 and 18 are the hoisting winch motors 1
0a is a hydraulic pump for supplying hydraulic oil, 14 and 15 are control valves inserted in a line between the hydraulic pumps 17 and 18 and the hoisting winch motor 10a, and 12 is an operation of these control valves 14 and 15. The valve 12a is an operating lever thereof, and an electromagnetic switching valve 21 is inserted in a winding operation pipe line 23 between the operating valve 12 and the operating chambers of the control valves 14 and 15, and a solenoid of the electromagnetic switching valve 21 is inserted. Is connected to the power source 42 via the b contact 40 of the relay 20 which is closed when the hook is overwound.
It is connected to the.

In this circuit, when the hook 3 is overwound and the hook overwinding detection switch 5a is turned off, the b contact 40 of the relay 20 is closed, which causes the electromagnetic switching valve 21.
An electric current is passed to the solenoid of the above, the electromagnetic switching valve 21 is switched to the left position, and the operating oil from the hook 3 up / down operating valve 12 to the control valves 14 and 15 is shut off. In this state, even if the lever 12a of the operation valve 12 is in the raised position, the hoisting control valves 14 and 15 return to the neutral position shown, and hoisting of the hook 3 is automatically stopped. After the automatic stop, the lever 12a is lowered, the rope 6 is drawn out from the winch 10, and the hook 3 is lowered to restore the normal state.

[0006]

However, when the hook 3 is overwound as described above, an inexperienced operator makes a mistake and does not operate the lever 12a for moving the hook 3 up and down. There is a risk of attempting to recover from the overwound state by lowering the boom 2 from "a" to "b" in FIG. 2 by operating the lever for raising and lowering the boom 2. Thus, when the boom 2 is lowered in the direction of the arrow while the hook 3 is overwound, the length of the rope 6 is pulled from L to L1 and the rope 6 is sewn.
It breaks at the time when it comes off the bump 2a or exceeds the elongation limit,
There is a possibility that a large accident may occur in which the suspended load 4 and the hook 3 fall.

In view of the above problems, it is an object of the present invention to provide an automatic hook-over-winding stop circuit for a crane, which can prevent a hanging load or a hook falling accident due to an erroneous operation.

[0008]

In order to achieve the above object, the present invention provides a hook overwinding detection switch mounted near the top of a boom and a relay driven by the operation of the hook overwinding detection switch. -, And an electromagnetic directional switching valve that stops the hoisting and rotating operation of the hoisting winch motor by the operation of the relay, and an electromagnetic directional switching valve that stops the operation of the boom up-and-down winch motor in the boom lowering direction by an overload signal. The hydraulically driven crane has a feature that when the hook is overwound, the hook hoisting operation and the boom lowering operation are automatically stopped at the same time.

[0009]

Since the present invention has the above circuit, when the hook overwinding detection switch is actuated by the hook overwinding, not only the hook hoisting but also the boom lowering operation cannot be performed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a hook over-winding automatic stop circuit for a crane according to the present invention. This circuit is based on the conventional circuit shown in FIG. 2 and has one synchronous contact of the relay 20.
The number of added contacts is two, and the added contact b 41 is connected to the hydraulic circuit of the winch 11 for raising and lowering the boom 2. 1
1a is a hydraulic boom hoisting winch motor for driving the winch 11, 19 is a hydraulic pump for driving the motor 11a, 16
Is a control valve for the winch motor 11a. As shown in FIG. 1, the b-contact 41 of the relay 20 is a lowering position for supplying operating oil when the boom is lowered between the boom hoisting control valve 16 and the boom 2 hoisting operation valve 13. It is connected to the solenoid of the electromagnetic switching valve 22 inserted in the side operation pipe line 24.

When the hook 3 is overwound in this circuit,
The hook 3 is the overwinding detection switch 5 of the overwinding prevention device 5.
The weight of a is pushed up to turn off the hook overwinding detection switch 5a. When the hook overwinding detection switch 5a is turned off,
The b-contacts 40, 41 of the relay 20 are closed, whereby current from the power source 42 is passed through the solenoids of the electromagnetic switching valves 21, 22 to change the respective valves to the left position, and the operation valve 12 and the hoisting control valve 14 are closed. , 15 and the boom lowering operation pipe line 24 between the operation valve 13 and the boom hoisting control valve 16 are shut off.

As described above, by shutting off the operation pipe lines 23 and 24, the hoisting control valves 14 and 15 are set to the neutral position shown in the drawing even if the operation lever 12a of the operation valve 12 is on the winding side. At the same time, the winding of the hook 3 is automatically stopped, and at the same time, the operation of lowering the boom 2 cannot be performed.

[0013]

According to the present invention, when the overwinding prevention device for the hook operates and the winding of the hook is stopped, the operation for raising and lowering the boom cannot be performed. Even if an attempt is made to lower the boom to recover from the winding state, the boom does not work, and the hoisting rope that may have occurred when the boom started to come off the sheave, Or prevent accidents such as hanging loads or hooks falling due to breakage, and
Operation can be performed safely.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of a hook overwinding automatic stop circuit for a crane according to the present invention.

FIG. 2 is a side view of a crane provided with a conventional hook overwinding automatic stop device for a crane.

FIG. 3 is a circuit diagram showing a conventional hook overwinding automatic stop circuit for a crane.

[Explanation of symbols]

 1 Crane Main Body 2 Boom 3 Hook 4 Suspended Load 5 Overwinding Prevention Device 5a Hook Overwinding Detection Switch 6 Rope 10 Winding Winch 10a Winch Motor 11 Boom Raising Winch 11a Winch Motor 12, 13 Operation Valve 14 -16 Control valve 17-19 Hydraulic pump 20 Relay 21, 22 Switching valve 23 Winding upper side operation pipe 24 Boom lowering side operation pipe 40, 41 Contacts

Claims (1)

[Claims] 1. A hook overwinding detection switch mounted near the top of a boom, a relay driven by the operation of the hook overwinding detection switch, and a hoisting winch motor winding by the operation of the relay. In a hydraulically driven crane having an electromagnetic directional control valve for stopping the upper rotation operation and an electromagnetic directional control valve for stopping the operation of the boom hoisting winch motor in the boom lowering direction by an overload signal, the relay contacts are boomed. The crane is characterized in that it is connected to an electromagnetic directional control valve that stops the operation of the hoisting winch motor in the lowering direction and automatically stops the hook hoisting operation and the boom lowering operation simultaneously when the hook is overwound. Over-winding hook automatic stop circuit.