JPS5838059Y2 - Overload prevention hydraulic circuit for continuous trench excavator - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an overload prevention hydraulic circuit for a continuous excavator equipped with an excavator operated by a hydraulic cylinder.

FIG. 1 shows a continuous trench excavator in which an arm 2 attached to the main body M supports a digging plate 1 operated by a hydraulic cylinder 3, and FIG. 1 shows a continuous trench excavator supporting an excavation cutter 4 operated by a cylinder 3;

To excavate a trench in the ground G, the excavation plate 1 or the excavation cutter 4 is inserted into the ground to a certain depth by the force of the hydraulic cylinder 3, and the main body M is driven by itself or pulled by another vehicle in the direction of the arrow. Let it run.

During this excavation work, if the excavation plate 1 or excavation cutter 4 hits an obstacle in the soil, remove the excavation plate 1 or excavation cutter 4 to protect the excavation mechanism, peripheral equipment, and main body M. Must be relieved by overload prevention hydraulic circuit.

Next, a conventional general overload prevention hydraulic circuit will be explained with reference to FIG.

The switching valve 7 is connected to the hydraulic power source 6 and the oil tank 11, as well as to the head chamber (high pressure side chamber) 8 and rod chamber 9 of the hydraulic cylinder 3.

On the other hand, the head chamber 8 is connected to the oil tank 11 via a conduit 13, a relief valve 12, and a conduit 16, and the rod chamber 9 is connected to a conduit 17 and a non-return check that allows flow to the rod chamber 9 side. It is connected to the oil tank 11 via a valve 14, a pipe line 15, and a pipe line 16.

During excavation, high pressure oil from the hydraulic source 6 enters the head chamber 8 by switching the switching valve 7, and the rod 1 of the hydraulic cylinder 3 enters the head chamber 8.
0 is pushed out and the excavation plate 1 or excavation cutter 4 is pushed into the soil.

When the excavation plate 1 or the excavation cutter 4 hits an obstacle during excavation, the hydraulic cylinder 3 receives a reaction force R, and the oil pressure in the head chamber 8 becomes abnormally high.

When the oil pressure becomes higher than the set pressure of the relief valve 12, the relief valve 12 opens and the pressure oil in the head chamber 8 is released from the pipe line 13.
, the oil flows to the oil tank 11 via the relief valve 12 and the pipe line 16.

As a result, the rod 10 of the hydraulic cylinder 3 is retracted by the reaction force R of the obstacle, and at the same time, the excavation plate 1 or the excavation cutter 4 escapes.

At this time, oil from the oil tank 11 flows into the rod chamber 9 of the hydraulic cylinder 3 via the pipe line 17.

In this overload prevention hydraulic circuit, the pressure oil in the head chamber 8 escapes only by the relief operation of the relief valve 12, so a force equivalent to the relief pressure of the linenoff valve 12 is always applied to the hydraulic cylinder 3 and the excavation mechanism. Drilling to continue
There is a drawback that the mechanism (particularly the excavation plate 1 or the excavation cutter 4) has a slow escape operation.

This idea eliminates most of the hydraulic pressure that pushes the excavation plate or cutter into the soil when the excavation plate or cutter hits an obstacle during excavation, making it easier for the excavation mechanism to escape. The object of the present invention is to provide an overload prevention hydraulic circuit that can be used to prevent overloads.

First, one embodiment of this invention shown in FIG. 4 will be explained.

In this figure, the same reference numerals as in FIG. 3 represent the same parts.

A pipe line 1 is connected to the load side oil chamber (head chamber) 8 of the hydraulic cylinder 3.
The primary side of the IJ-F valve 12 is connected through 3,
The secondary side of the relief valve 12 is a conduit 16 provided with a throttle valve 18.
It is connected to the oil tank 11 via.

The primary side of the hydraulic pilot-operated switching valve 19 is connected to the pipe line 13 via a pipe line 21, and the secondary side is connected to the pipe line 16 between the relief valve 12 and the throttle valve 18 via a pipe line 22. The pilot oil pressure receiver is connected via a pilot line 20 to the line 16 between the relief valve 12 and the throttle valve 18, as well as the line 22.

Other details are the same as those in Figure 3. When the excavation plate 1 or the excavation cutter 4 hits an obstacle during excavation work, the pressure in the load-side hydraulic pressure 8 increases due to the reaction force R of the rod 10.

The pressure is sensed by the relief valve 12 via the conduit 13.

At this time, if the pressure in the oil chamber 8 is higher than the set pressure of the relief valve 12, the relief valve 12 opens and the pressure oil flows to the secondary side of the relief valve 12.

Oil coming out from the secondary side of the relief valve 12 is throttled by the throttle valve 18 and flows into the oil tank 11.

Therefore, pressure is generated in the section of the pipe line 16 upstream of the throttle valve 18.

The degree of throttling of the throttle valve 18 is adjusted to the pressure at which the hydraulic pilot-operated switching valve 19 opens.

When the switching valve 19 is opened by the pressure oil generated in the pipe line 16, the pressure oil in the oil chamber 8 is transferred to the pipe line 13, pipe line 21, . The oil flows to the oil tank 11 via the switching valve 19, the pipe line 22, and the throttle valve 18.

At this time as well, the pressure oil passes through the throttle valve 18, so the relief valve 1
2 and the throttle valve 18, pressure is generated in the section of the pipe line 16, which keeps the switching valve 19 open.

Furthermore, even if the switching valve 19 opens and the pressure oil in the oil chamber 8 of the hydraulic cylinder 3 flows out through the switching valve 19, the oil pressure in the oil chamber 8 decreases and the relief valve 12 closes, the switching valve 1
9 is open, pressure oil flows out into the oil tank 11 through the switching valve 19.

The pressure from the throttle valve 18 is then present, and the switching valve 19 remains open.

Therefore, the rod 10 is easily pushed back by the reaction force R from the obstacle, and the escape operation of the excavating plate 1 or the excavating cutter 4 is easily performed.

When the rod 10 is pushed back, oil from the oil tank 11 is replenished into the oil chamber (rod chamber) 9 via the pipe 15, check valve 14, and pipe 17.

When the overload condition is removed and the reaction force from the excavation mechanism on the rod 10 disappears, the rod 10 stops moving and the oil is transferred from the oil chamber 8 of the hydraulic cylinder 3 to the oil tank 1 via the switching valve 19.
1 is stopped, the oil pressure generated by the throttle valve 18 disappears, and the oil pressure in the pipe line 16 and the pilot line 20 becomes equal to the pressure in the oil tank 11.

Therefore, the switching valve 19 closes and the overload prevention hydraulic circuit returns to its normal state.

In place of the hydraulic pilot operated switching valve 19 in the embodiment shown in FIG. 4, a hydraulic pilot operated check valve 23 may be provided as shown in FIG.

Also, instead of the throttle valve 18 in the embodiment of FIG.
If the variable throttle valve 24 is provided as shown in FIG.
The hydraulic pressure generated within the 6th part can be adjusted and the responsiveness of the system can be changed.

4 and 5 show an embodiment in which an overload prevention hydraulic circuit according to this invention is installed in one oil chamber 8 of the reciprocating cylinder 3, but the same effect can be achieved even if it is installed in the other oil chamber 9. There is.

As shown in FIG. 6, both oil chambers 8 of the hydraulic cylinder 3,
If an overload prevention hydraulic circuit of this invention is installed in each of the excavating plate 1 or the excavating cutter 4, no matter whether the excavating plate 1 or the excavating cutter 4 is overloaded in either the forward or backward direction (no matter whether the continuous trench excavator runs forward or backward), ) Overload can be prevented.

Note that in FIGS. 5 and 6, the same reference numerals as in FIG. 4 represent the same components.

As explained above, according to this invention, when the excavating tool hits an obstacle during the excavation operation of the continuous trench excavator, it is possible to quickly and reliably escape from the overloaded state.

[Brief explanation of the drawing]

Figures 1 and 2 are side views showing a general continuous trench excavator;
Fig. 3 is a system diagram showing a general overload prevention hydraulic circuit of a conventional continuous trench excavator, and Figs. 4 to 6 are system diagrams showing different embodiments of the overload prevention hydraulic circuit according to this invention. . M...Body, 1...Drilling plate, 3...
... Hydraulic cylinder, 4 ... Excavation cutter, 8
...Head chamber, 9...Rod chamber 1.1
1...Oil tank, 12...Relief valve, 13...Pipe line, 14...Check valve, 1
5...Pipe line, 16...Pipe line, 17...
... Pipe line, 18 ... Throttle valve, 19 ...
...Hydraulic pilot operated switching valve, 20...Pilot conduit, 21...Pipe line, 22...
・Pipe line, 23...Hydraulic pilot type check valve, 2
4...Variable throttle valve.

Claims (2)

[Scope of utility model registration request] (1) In a continuous trench excavator equipped with a digging tool operated by a hydraulic cylinder, the load side oil chamber of the hydraulic cylinder is
It is connected to the oil tank via a pipe line provided with a relief valve and a throttle valve located on the secondary side of the relief valve.The primary side is connected to the load side chamber of the hydraulic cylinder via the pipe line, and the secondary side In addition, the hydraulic receiver section is equipped with a hydraulic pilot-operated on-off valve connected between the relief valve and the throttle valve via a conduit, and also connects the low-pressure side chamber of the hydraulic cylinder to the inflow of oil into that chamber. An overload prevention hydraulic circuit characterized in that it is connected to an oil tank via a conduit provided with a check valve that allows for. (2) The overload prevention hydraulic circuit according to claim (1) of the registered utility model, in which the throttle valve is of a variable type.