JPH0825713B2 - Boom backstop device for crane - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boom backstop device for a crane equipped with a lattice boom, which prevents the boom from being turned backward.

[0002]

Boom back stop devices of this type are
Generally, a tubular backstop body is constructed by incorporating means for generating thrust for pushing the boom forward.

Conventionally, as the above-mentioned thrust generating means, one using a hydraulic cylinder instead of a general spring has been known (see, for example, Japanese Patent Publication No. 55-37480).

A crane using this hydraulic cylinder type boom back stop device is shown in FIG.

To explain this, a boom 2 is attached to an upper swing body 1 of a crane so as to be capable of hoisting by a boom foot pin 3, and the boom 2 is supported by a mast 4, a suspension 5 and a boom hoisting rope 6, and The boom foot pin 3 is used as a center for ups and downs.

The boom backstop device 7 is constructed by connecting a hydraulic cylinder 9 to the lower side of the backstop body 8, and the base end of the hydraulic cylinder 9 is attached to the upper swing body 1 so as to be rotatable about a horizontal axis. ing. Further, the upper end of the backstop body 8 can be brought into contact with and separated from the back surface of the boom, and comes into contact with the back surface of the boom at a predetermined boom angle (ground angle) or more.

[0007] Then, the recoil moment when the suspended load is dropped or the wind from the front causes the boom 2 to fall backward,
That is, when a reversing moment acts, the hydraulic cylinder 9 counteracts this reversing moment and pushes the boom 2 back forward.

[0008]

The reversal of the boom 2 does not occur in a range where the boom angle is small (an angle range in which a sufficiently large forward tilting moment is exerted by the weight of the boom 2 and the suspended load), and the reversal of the boom 2 is not less than a certain angle. Occurs in the range of.

Therefore, conventionally, the pressure of the hydraulic cylinder 9 is controlled according to the boom angle.

However, according to the conventional method in which the cylinder pressure (boom front pushing force) is increased as the boom angle is increased, when the load is hung in a state where the boom angle is large, the hanging load is increased due to the large forward pushing force. A large load acts on the boom 2 due to the forward tilting moment caused by the boom 2,
The suspension 5 and the boom hoisting rope 6 may be damaged.

Therefore, the present invention provides a boom backstop device for a crane, in which unnecessary force is not applied to the boom.

[0012]

According to a first aspect of the present invention, in a boom backstop device for a crane in which a hydraulic cylinder is used as a means for generating thrust for pushing a boom forward, the maximum pressure of the hydraulic cylinder is controlled. A cylinder pressure control valve, a reversing moment detecting means for detecting the reversing moment of the boom, a necessary cylinder pressure is calculated based on the reversing moment detected by the reversing moment detecting means, and the calculated pressure is used as the cylinder pressure. And a control means for instructing the pressure control valve.

According to a second aspect of the present invention, in the configuration of the first aspect, the cylinder pressure control valve is a pilot type relief valve for setting the maximum pressure of the hydraulic cylinder, and the relief valve is set based on a signal from the control means. It is composed of an electromagnetic proportional pressure reducing valve for changing the pressure.

According to a third aspect of the present invention, in the configuration of the first aspect, the cylinder pressure control valve has a high pressure relief valve for setting the maximum pressure of the hydraulic cylinder to a high pressure and a low pressure relief valve for setting the cylinder maximum pressure to a low pressure. And a selection valve that selects one of these relief valves.

[0015]

According to the above construction, the maximum pressure of the hydraulic cylinder (hereinafter referred to as the maximum cylinder pressure) is controlled according to the actually detected reversing moment instead of the boom angle. Therefore, even when the boom angle is large, the reversing moment is large. If is smaller, the maximum cylinder pressure is also lower.

Therefore, even if a load is hung in a large boom angle state, there is no possibility that an unnecessary force will be applied to the boom.

Further, according to the second aspect of the invention, since the relief pressure of the relief valve, that is, the maximum cylinder pressure can be controlled steplessly by the electromagnetic proportional pressure reducing valve, highly accurate control corresponding to the reversing moment can be performed. .

On the other hand, according to the third aspect of the present invention, only switching between high pressure and low pressure is required, so that control is easy and the hydraulic circuit configuration is simple.

[0019]

Embodiments of the present invention will be described with reference to the drawings.

First Embodiment (See FIGS. 1, 2 and 4) An electromagnetic switching valve 11 is provided between a hydraulic cylinder 9 of a boom back stop device 7 and a hydraulic pump 10 as a hydraulic pressure source. A pressure switch 13 for detecting the cylinder pressure is connected to a pressure oil supply line 12 that connects the electromagnetic switching valve 11 and the cylinder 9.

This pressure switch 13 is turned on at the lower limit value of the preset pressure range, and this ON signal causes
The electromagnetic switching valve 11 is switched from the off position (b) to the on position (b), and the oil discharged from the pump 10 is supplied to the cylinder 9.
Then, when the cylinder pressure reaches the upper limit value of the set pressure range, the pressure switch 13 is turned off, the off signal causes the electromagnetic switching valve 11 to return to the off position b, and the oil supply to the cylinder 9 is stopped.

By this action, the minimum pressure of the cylinder 9 is kept constant.

The boom back stop device 7 shown in FIG.
Are usually provided on both the left and right sides, but here, for convenience of explanation, only one side is shown and only one cylinder 9 is shown in FIG.

A cylinder pressure control valve 14 for controlling the cylinder pressure is connected to the pressure oil supply line 12.

The cylinder pressure control valve 14 comprises a hydraulic pilot type relief valve 15 and an electromagnetic proportional pressure reducing valve 16 connected to the vent line of the relief valve 15. The secondary pressure of the electromagnetic proportional pressure reducing valve 16 is increased. The set pressure of the relief valve 15 is controlled by this set pressure (relief pressure).
Is the force that pushes the boom 2 forward when the maximum cylinder pressure, that is, the reversal moment acts. Reference numeral 17 is a primary pressure source of the electromagnetic proportional pressure reducing valve 16.

The secondary pressure of the electromagnetic proportional pressure reducing valve 16 is controlled by the valve controller 18 shown in FIG. 2, which is based on the signal from the load detector 19 shown in FIGS. It is controlled by the unit 20.

The load detector 19 detects the tension acting on the boom hoisting rope 6 (it becomes smaller as the reversing moment of the boom 2 becomes larger), and this detection signal is inputted to the controller 20.

The control unit 20 includes a calculation unit 21 and an output unit 22.
First, the calculating unit 21 calculates the reversing moment of the boom 2 from the detected rope tension, and from the obtained reversing moment, calculates the cylinder pressure that can oppose the moment.

The cylinder pressure obtained by this calculation is converted into an electric signal at the output section 22 and sent to the valve controller 18 as a secondary pressure command signal for the electromagnetic proportional pressure reducing valve 16.

As a result, when a reversing moment acts on the boom 2, the set pressure (maximum cylinder pressure) of the relief valve 15 is automatically controlled to a value according to the magnitude of the reversing moment.

As described above, since the maximum cylinder pressure is controlled according to the reversing moment that actually acts instead of the boom angle, if the reversing moment does not act even when a load is hung when the boom angle is large, Since the maximum cylinder pressure is kept at the minimum set pressure of the relief valve 15, there is no fear that the boom 2 will be subjected to an unnecessary forward pushing force.

It should be noted that the boom 2 may be reversed when a crane operation is stopped (including when the engine is stopped) due to a strong wind from the front.

Therefore, as shown in FIG. 1, on the upstream side of the cylinder pressure control valve 14, an electromagnetic opening / closing valve 23 (which is turned on by operating a remote control valve for crane work) is turned off except during crane work. Provided,
In the pressure oil supply line 12, the set pressure is the cylinder pressure control valve 14
The maximum pressure setting relief valve 24 that is larger than the maximum pressure is provided, and the cylinder pressure is set to the set pressure of the relief valve 24 except when the crane operation is performed, and the reversal of the boom 2 is prevented.

In FIG. 1, 25 is a check valve provided in the pressure oil supply conduit 12, and 26 is an accumulator for stabilizing the pressure in the conduit 12.

Second Embodiment (see FIG. 3) Only differences from the first embodiment will be described.

In the second embodiment, the cylinder pressure control valve 27 includes a low pressure relief valve 28 and a high pressure relief valve 29.
And one of these relief valves 28, 29 is selected 3
It is constituted by a position electromagnetic switching type selection valve 30.

The selection valve 30 is switched and operated by a control signal from a valve controller (none of which is shown) based on a command signal from a control unit corresponding to the control unit 20 of the first embodiment, and the reversing moment is previously set. When it is less than the set reference value, it is set to the low pressure selection position a, when it is more than the reference value, it is set to the high pressure selection position b, and when it is not during crane work, it is set to the neutral position c.

The low pressure relief valve 28 is selected at the low pressure selection position B and the high pressure relief valve 29 is selected at the high pressure setting position B, and the maximum cylinder pressure is controlled to the set pressure of the selected relief valve 28 or 29. It

Further, at the neutral position c, the maximum cylinder pressure becomes the set pressure of the maximum pressure setting relief valve 24 as in the second embodiment.

[0040]

As described above, according to the present invention, since the reversing moment acting on the boom is detected and the maximum cylinder pressure is controlled according to the detected reversing moment, the boom angle is large. However, if the reversal moment is small, the maximum cylinder pressure will also be low.

Therefore, even if a load is hung in a state where the boom angle is large, unnecessary force does not act on the boom, and there is no risk of damaging the boom, suspension, boom hoisting rope, or the like.

According to the second aspect of the present invention, since the relief pressure of the relief valve, that is, the maximum cylinder pressure can be controlled steplessly by the electromagnetic proportional pressure reducing valve, highly accurate control corresponding to the reversing moment can be performed. .

On the other hand, according to the third aspect of the invention, only switching between high pressure and low pressure is required, so control is easy and the hydraulic circuit configuration is simple.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a control block configuration diagram of the embodiment.

FIG. 3 is a hydraulic circuit diagram showing a second embodiment of the present invention.

FIG. 4 is a schematic side view of a crane incorporating the boom backstop device according to both embodiments.

[Explanation of Codes] 2 Boom 7 Boom backstop device 8 Backstop body 9 Hydraulic cylinder 14 Cylinder pressure control valve 15 Relief valve that constitutes the cylinder pressure control valve 16 Electromagnetic proportional pressure reducing valve that changes the set pressure of the relief valve 19 Reversal Load detector 20 for obtaining moment 20 Control unit that also serves as reversing moment detecting means and control means 21 Control section computing section 22 Control section output section 27 Cylinder pressure control valve 28 Low pressure relief valve constituting cylinder pressure control valve 29 Same high pressure relief valve 30 Same selection valve

Claims (3)

[Claims] 1. A boom back stop device for a crane, wherein a hydraulic cylinder is used as a means for generating thrust for pushing a boom forward, and a cylinder pressure control valve for controlling the maximum pressure of said hydraulic cylinder and a reversing moment of said boom. And a control means for calculating a necessary cylinder pressure based on the reversing moment detected by the reversing moment detecting means and instructing the calculated pressure to the cylinder pressure control valve. Boom back stop device for cranes characterized by 2. The boom backstop device for a crane according to claim 1, wherein the cylinder pressure control valve is a pilot type relief valve for setting the maximum pressure of the hydraulic linder,
A boom back stop device for a crane, comprising: an electromagnetic proportional pressure reducing valve that changes a set pressure of the relief valve based on a signal from a control means. 3. The boom backstop device for a crane according to claim 1, wherein the cylinder pressure control valve sets a maximum pressure of the hydraulic cylinder to a high pressure, and a high pressure relief valve.
A boom back stop device for a crane, comprising: a low pressure relief valve that sets the maximum cylinder pressure to a low pressure and a selection valve that selects one of the two relief valves.