JPH0757678B2 - Hydraulic circuit for hoisting machine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydraulically driven hoisting machine, and more particularly to a hydraulic circuit suitable for a two-division drive system.

[Conventional technology]

In order to prevent the wire rope from digging in and the winding wire rope from becoming uneven, the drive unit and the wire rope, which receive tension, have a constant tension. There is a split type hydraulically driven hoisting machine that has a winding section that winds up on a drum.

In this conventional example, the wire rope is unwound by driving the drum by a load. Therefore, when the load is light, it is difficult to unwind the wire rope.

FIG. 2 shows the mechanism of a conventional two-division drive type hoisting machine. FIG. 3 shows the hydraulic circuit.

In this hoisting machine, the wire rope 13 is wound onto the drum by driving the hydraulic motor 16. The hydraulic motor 16 is driven with a constant torque in order to wind the wire rope in an orderly manner without digging into the drum. A torque setting valve 24 is provided in the hydraulic circuit to give a constant torque. Therefore, at the time of winding, the hydraulic motor 16 acts so as to always wind up the wire rope 13. The drive assists the drum 14 in winding the wire rope 13 by taking up most of the load.

When the wire rope 13 is unwound in the reverse direction, the drum is rotated in the unwinding direction by the wire rope 13 and the hydraulic motor 16 is driven. In this case, the circuit of the operation flight 22 is switched to the circuit 22C, and the oil from the hydraulic pressure source 21 receives the oil from the hydraulic motor 1.
Supplying low pressure to 6. The pressure on the supply side is set by the check valve 25 so that the hydraulic motor does not cause cavitation. When the hydraulic motor 16 is driven from the drum 14 in this state, the oil discharged from the hydraulic motor 16 is discharged from the torque setting valve 24.
And returned to the oil tank. Since the torque setting valve 24 is set to the specified pressure, the driving torque commensurate with the specified pressure is required to drive the hydraulic motor 16. The torque setting valve 24 needs to be set to a certain specified pressure from the required tension at the time of winding. Therefore, in the unwinding operation, the wire rope 13 is unwound by the load. Therefore, there is a problem that the unwinding operation is difficult to perform when the load is light.

Examples of devices related to this type include, for example, JP-A-53-4949 and JP-A-54-88763.

[Problems to be Solved by the Invention]

The above-mentioned prior art has a mechanism for performing the lowering operation by the load acting on the hoisting machine, so that there is a problem in the lowering operation under a light load.

It is an object of the present invention to obtain a hoisting machine hydraulic circuit that can be easily operated even at a light load during a hoisting operation.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present invention is a two-part system comprising a drive unit having a sheave and taking up most of the load required to wind the wire, and a winding unit for winding the wire on a drum with a constant tension. The hoisting machine includes a drive unit having a hydraulic motor, a hydraulic power source, an operation valve, and an oil tank, and the winding unit has a hydraulic motor,
In a hydraulic circuit for a hoisting machine having a hydraulic pressure source, an operation valve, a torque setting valve that keeps the hydraulic pressure constant, and an oil tank, an external pilot line is provided in the torque setting valve and is connected to the oil tank of the winding section. The present invention is characterized in that a pipe and means for opening and closing the flow path are provided between the pipe and the external pilot line.

[Action]

For the torque setting valve provided in the hydraulic circuit of the winding section, a pressure control valve equipped with an external pilot line is used.When the load is normal, the external pilot line is shut off to set a high torque, and when the load is light, Set low torque by connecting the external pilot line to the oil tank.

As a result, when the wire rope is unwound by the load, the torque setting valve can be set to a low torque, so it is not necessary to apply tension for pulling the wire rope, and the unwinding operation can be easily performed even with a light load.

〔Example〕

FIG. 1 shows a hydraulic circuit diagram of an embodiment of the present invention. The torque setting valve 24 shown in the figure is held at the initially set pressure because the circuit of the means (solenoid valve or manual switching valve) 28 for opening and closing the flow path provided in the external pilot line 29 is switched to the circuit 28A. Therefore, the hydraulic motor 16 is driven with a constant torque commensurate with this pressure. When the wire rope 13 is unwound, the wire rope 13 is unwound with a load having a driving torque commensurate with the pressure of the torque setting valve 24. When the load exceeds the set pressure, the torque setting valve 24 opens and allows the oil supplied from the hydraulic pressure source 21 to escape to the oil tank 26.

However, when the load is small, the set pressure of the torque setting valve 24 is not reached, so the hydraulic motor 16 is stopped and the lowering operation is disabled. In order to carry out the unwinding operation from this state, it is necessary to apply a tension for pulling out the wire rope 13.

When the circuit of the solenoid valve or the manual switching valve is switched to the circuit 28B, the set pressure of the torque setting valve 24 becomes almost zero. Therefore, when performing the lowering operation under a light load, it can be easily performed by selecting this circuit (28B). That is, since the set value of the torque setting valve 24 is low, the hydraulic motor 16 can be driven even with a light load, and the wire rope 13 can be unwound.

〔The invention's effect〕

Since the torque setting valve can be set to a low torque when the wire rope is unwound by the load, it is not necessary to apply tension to pull out the wire rope, and the unwinding operation can be easily performed even under a light load.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention. FIG. 2 is a mechanical diagram of a conventional two-division hoisting machine, and FIG. 3 is a hydraulic circuit diagram of FIG. 5 ... drive hydraulic motor, 6 ... reducer, 7-9 ... gear, 10-11 ... sheave, 12 ... roller, 13 ... wire rope, 14 ... drum, 15 ... reducer , 16 …… hydraulic motor, 17 …… hydraulic power source, 18 …… operating valve, 19 …… limit switch, 20 …… counter balance valve, 21 …… hydraulic power source, 22…
… Operating valve, 23 …… Check valve, 24 …… Torque setting valve, 25
...... Check valve, 26 ...... oil tank, 28 ...... solenoid valve or manual switching valve, 29 ...... pilot line.

Claims (1)

[Claims] 1. A two-division type hoisting machine comprising a drive section having a sheave, which bears most of the load required to wind the wire, and a winding section which winds the wire around a drum at a constant tension. The drive unit has a hydraulic motor, a hydraulic pressure source, an operation valve, and an oil tank, and the winding unit has a hydraulic motor, a hydraulic pressure source, an operation valve, a torque setting valve that keeps the hydraulic pressure constant, and a hydraulic circuit for a hoisting machine. In the above, the torque setting valve is provided with an external pilot line, a pipe connected to the oil tank of the winding section, and means (28) for opening and closing a flow path between the pipe and the external pilot line are provided. A hydraulic circuit for hoisting machines, which is characterized in that