JPH04202920A - Boom height limiting device - Google Patents

Abstract

PURPOSE:To automatically limit the height of a boom by providing an electromagnetic switching valve between a boom oscillating cylinder and a cylinder control valve, and disposing an on/off switch for operating the switching valve and a boom angle detecting switch in a series in an electric circuit from a power supply of the electromagnetic switching valve. CONSTITUTION:A cam piece 21 for operating a limit switch 20 is fitted to a boom 5 by a bolt 23 in such a manner as to freely change the position thereof, and the boom height detecting position is changed by varying the fitting position. When an on/off switch 19 is turned on, and the boom 5 is raised to a designated position, the cam piece 21 pushes a contact 22 of the limit switch (angle detecting switch) 20 to turn off the limit switch 20, and an electromagnetic switching valve keeps off-state, so that the boom 5 is raised. When the boom is raised more than a designated position, the contact 22 is separated from the cam piece 21 to turn on the limit switch 20 and turn on the electromagnetic switching valve, so that the supply of operating oil to the cylinder 7 is cut off to stop raising the boom 5. Thus, the height of the boom can be limited.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a boom height limiting device that prevents the height of a boom of a front loader or the like from rising above a predetermined position.

(Prior Art) A front loader in which the boom automatically stops rising when the boom rises to a predetermined height is disclosed, for example, in the specification and drawings of Japanese Patent Application No. 171594/1982. ing.

In the conventional system, the cylinder for raising and lowering the boom is operated by an electromagnetic control valve, and a switch for detecting a boom swing angle is provided, and when the switch detects a predetermined rising angle of the boom, the solenoid control valve is operated. This was to turn off the cylinder, stop the supply of hydraulic oil to the cylinder, and stop the boom from rising.

(Problems to be Solved by the Invention) In the above-mentioned conventional device, a solenoid valve had to be used as a control valve for controlling the cylinder for raising and lowering the boom.

Front loaders require delicate operations such as high-speed, low-speed, and minute movements to raise and lower the boom, and if such operations were to be performed using a solenoid valve, the control device would be extremely expensive. It had become.

Therefore, normally, a manually operated valve is used as the control valve.

However, in the conventional boom height limiting device, the control valve must be a solenoid valve, which increases the cost.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a boom height limiting device that can limit the height of a boom even if the control valve is a conventional manual valve.

(Means for Solving the Problems) In order to achieve the above object, the present invention takes the following measures. That is, the features of the present invention include a boom that is pivotably supported on a vehicle body so as to be able to swing vertically and that has a working tool attached to its tip, a cylinder that swings the boom, and a control that controls the cylinder. a valve, an electromagnetic on-off valve interposed in a pipe connecting the control valve and the cylinder, an on/off switch for operating the electromagnetic on-off valve, and an on/off switch that is electrically connected in series with the switch, and the boom is set at a predetermined angle. The main feature is that it is equipped with an angle detection switch that is activated when the camera moves.

(Function) According to the present invention, an electromagnetic on-off valve is provided in the piping between the boom rocking cylinder and the control valve that controls the cylinder, and an on/off switch that operates the on-off valve and the boom An angle detection switch that detects a predetermined angle is installed in series, so turn the on/off switch to "off" and turn the electromagnetic on-off valve to "
When left open, hydraulic oil from the control valve is supplied to the cylinder and the boom swings freely.

At this time, even if the angle detection switch is activated, the on/off switch is turned off, so the electromagnetic on-off valve is not activated.

Next, turn the on/off switch to “on”. At this time, unless the angle detection switch is activated, the electromagnetic on-off valve will not close, so the hydraulic oil from the control valve is supplied to the cylinder until the angle detection switch is activated. If the boom is raised from a low position, when the boom reaches a predetermined angle, the angle detection switch will turn on, and since the on/off switch is connected in series with the on/off switch, the solenoid on-off valve will be closed. j to cut off the hydraulic oil from the control valve.

Therefore, the boom is stopped from rising and the height of the boom is limited.

According to the present invention, the height of the boom can be limited without using a solenoid valve as the control valve, so the control valve can be manually operated as in the past.

(Example) Embodiments of the present invention will be described below based on the drawings.

What is shown in FIG. 2 is a tractor-mounted front loader, in which a mounting frame 2 is fixed to a tractor body 1, and a support 3 is removably erected on the mounting frame 2.

A boom 5 is supported at the top of the support column 3 via a pivot shaft 4 so as to be swingable in the vertical direction. A packet, which is a working tool 6, is rotatably supported at the tip of the boom 5.

The boom 5 can be raised and lowered by a boom cylinder 7 interposed between the boom 5 and the support column 3, and the packet 6 is moved up and down by a packet cylinder 8 interposed between the packet 6 and the boom 5.
It can be rotated freely.

FIG. 1 shows the boom cylinder 7 and the heget cylinder 8.
The control circuit is shown. The boom cylinder 7 is connected to a boom cylinder manual control valve 9 through oil passages 10 and 11, and the bucket cylinder 8 is connected to a bucket cylinder manual control valve 12 through oil passages 13 and 14. There is.

In FIG. 1, I5 is a pump circuit, and 1G is a tank circuit.

The boom cylinder control valve 9 is a control valve that has four positions from the left side in FIG. 1: floating, rising, stopping, and lowering. The bucket cylinder control valve 12 is also a three-position control valve with scoop, stop, and dump positions from the left side.

An electromagnetic on-off valve 17 is interposed in the oil passage 10.11 between the boom cylinder control valve 9 and the boom cylinder 7.

This on-off valve 17 operates in each oil passage 10 when the current is "off".
Let's open 11. When "on", both oil passages 10.
11 to cut off the hydraulic oil supplied to the cylinder 7.

In the middle of the electric circuit from the power supply 18 of the electromagnetic on-off valve 17,
When both of the nine switches 19 and 20, in which the on/off switch 19 and the angle detection switch 20 are arranged in series, are "on",
The electromagnetic on-off valve 17 is turned on.

As shown in FIG. 3, the on/off switch 19 is connected to the boom cylinder manual control valve 1 provided on the support column
2. Also, the angle detection switch 2
0 consists of a limit switch notch provided on the support column 3 near the pivot shaft 4. A cam piece 21 for operating this limit switch 20 is attached to the boom 5. The contact 2 of the limit switch 20 is attached to this cam piece 21.
2 is pressed, the limit switch 20 is "off"
This is the "on" state where the cam piece 21 separates from the cam piece 21. This cam piece 21 is attached with a bolt 23 so that its position can be changed, and by changing the attachment position, the detection position of the boom height can be changed.

According to the embodiment with the above configuration, the on/5/off switch 19 is kept in the "off" state during normal work. In this state, regardless of the operation of the limit switch 20, the electromagnetic on-off valve 17 is always in the "off" state, and the boom cylinder 7
is moved up and down over the entire range by operating the boom cylinder control valve 9.

When the height of the boom 5 is limited, such as when working indoors, the position of the cam piece 21 is adjusted and the on/off switch 19 is turned on. In this state, while the boom 5 is rising to a predetermined position, the cam piece 21 is pushing the contact 22 of the limit switch, so the limit switch 20 is in the "cut" state and the electromagnetic on-off valve 17 is "off". ” and the boom 5 rises.

When the boom 5 rises above a predetermined position, the contact 22 separates from the cam piece 21, the limit switch 20 is turned on, the electromagnetic on-off valve 17 is turned on, and the cylinder 7 is turned on.
Hydraulic oil supply to the boom 5 is cut off, and the boom 5 stops rising.

The one shown in FIG. 4 connects the cylinder supply side oil passage 10 to the tank circuit 16 when the electromagnetic on-off valve 24 is turned on.

In the one shown in FIG. 5, an electromagnetic on-off valve 25 is interposed only in the hydraulic oil supply line 10 for lifting the boom cylinder, and when the electromagnetic on-off valve 25 is turned on, the supply of hydraulic oil is stopped. It is something.

The one shown in FIG. 6.7 is equipped with a snow blower as the working tool 6 instead of the bucket.

That is, a snow blower chain fitting 26 is attached to the tip of the boom 5, and an on/off switch 19 is provided on the coupling fitting 26. This on/off switch 19 can be turned on by attaching the snow blower 6 to the coupling fitting 26. ” state.

Therefore, when the snow blower 6 is attached, the on/off switch 19 automatically changes to the "man" position, and when the angle detection switch 20 is activated, the boom 5 is stopped from rising.

Note that the present invention is not limited to the above embodiments.

(Effects of the Invention) According to the present invention, the height of the boom can be limited without using a solenoid valve for the boom cylinder control control valve, so the cost is lower than that using the N1tfl valve. Become.

[Brief explanation of the drawing]

Fig. 1 is a hydraulic/electrical circuit diagram showing an embodiment of the present invention;
The figure is a side view of the front loader, FIG. 3 is a partially enlarged view showing the angle detection switch, FIG. 4 is a circuit diagram showing another embodiment of the electromagnetic on-off valve, and FIG. 5 is another embodiment of the present invention. FIG. 6 is a side view of a tractor equipped with a snow blower as a working implement, and FIG. 7 is a plan view showing the connection relationship between the snow blow and the boom. 5-boom, 7-boom cylinder, 9-control valve, 10.
11-Overnight passage (piping), 17-Solenoid on-off valve, 19-On/off switch, 20-Angle detection switch 7, 24.25-
Solenoid on-off valve.

Claims (1)

[Claims] (1) A boom that is pivotably supported on a vehicle body so as to be able to swing vertically and has a working tool attached to its tip; a cylinder that swings the boom; a control valve that controls the cylinder; An electromagnetic on-off valve interposed in the piping connecting the cylinder,
A boom height limiting device comprising: an on/off switch for operating the electromagnetic on-off valve; and an angle detection switch electrically connected in series with the switch and activated when the boom reaches a predetermined angle.