JP3742720B2 - Excavator with offset boom - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic excavator provided with an offset boom, and more particularly, to a hydraulic excavator that prevents expansion and contraction of an offset boom after completion of work or when work is temporarily stopped.
[0002]
[Prior art]
Conventionally, in excavation work such as water and sewage pipes, hydraulic excavators equipped with a side ditching front (offset front) are used to excavate narrow grooves on the side of the road. In recent years, a hydraulic excavator called a small swivel type has been frequently used. As conventional excavators for side trench excavations, Japanese Patent Laid-Open Nos. 6-220885 and 6-240703 are known.
[0003]
An example of a conventional small turning hydraulic excavator is shown in FIGS.
[0004]
4A is a side view of the small turning hydraulic excavator, and FIG. 4B is a rear view of the small turning hydraulic excavator.
[0005]
As shown in these drawings, the small swivel excavator is configured such that a side groove front 2 is rotatably attached to a main body 1 and is moved up and down by a boom cylinder 10. The side groove digging front 2 forms a parallel link with the lower boom 3, the upper boom 4, the cylinder stay 5, and the stay 6, and strokes the offset cylinder 7, so that the tip of the stay cylinder 11 (arm 8, bucket 9 and bucket cylinder 12 ) With respect to the center line of the lower boom 3.
[0006]
FIG. 5 is a view showing a part of the hydraulic circuit of the small turning type hydraulic excavator shown in FIG.
[0007]
As shown in FIG. 5, the pressure oil discharged from the pilot pump 22 and pressurized by the pilot relief valve 24 is supplied to the manually operated pressure reducing valves 13, 14, 15, and 16. By operating the operation levers 131, 141, 151, 161, the manually operated pressure reducing valves 13, 14, 15, 16 are depressurized, and the direction switching valves 17, 18, 19, 20 are switched to desired amounts, and the main pump The pressure oil from 21 is supplied to each cylinder 7, 10, 11, 12 to cause the side groove front 2 to expand and contract.
[0008]
Further, when the operator gets on and off the hydraulic excavator, the pilot pump 22 and the manually operated pressure reducing valves 13, 14, 15, and 16 are communicated with each other in order to prevent the front from moving by touching the operation levers 131, 141, 151, and 161. A lock valve 23 is installed between the circuits. By manually operating the lock valve 23, pressure oil is not supplied to the manually operated pressure reducing valves 13, 14, 15, and 16, and the switching valves 13, 14 are moved even if the operation levers 131, 141, 151, and 161 are moved. , 15 and 16 do not operate.
[0009]
[Problems to be solved by the invention]
By the way, in the small turning type hydraulic excavator, as shown in FIG. 4A, in order to reduce the turning radius, the raising amount of the boom 3 is increased upward as compared with a standard hydraulic excavator. . Therefore, at the end of raising the boom, the front center of gravity 29 in the front retracting position is located behind the boom foot pin 30. For this reason, even when the boom is held in the air, the boom 3 is not lowered, so that the storage space can be reduced even when the machine is stored.
[0010]
However, if the small swivel excavator is left in the state where the boom is lifted with the front retracted posture as described above, the holding pressure of the offset cylinder 7 increases due to the front weight (from the upper boom 4), and the offset cylinder 7 Leakage will increase. As a result, as shown by the arrow in FIG. 4 (b), the offset cylinder 7 extends, and the front (from the upper boom 4) jumps out of the vehicle body width of the small turning excavator. There is a risk of colliding with surrounding objects such as buildings.
[0011]
In view of the above-described problems, an object of the present invention is to provide a hydraulic excavator equipped with an offset boom such as a small swing type hydraulic excavator, and the extension cylinder can be extended and contracted even in a boom raising end state in a front winding position such as when the machine is stored. It is an object of the present invention to provide a hydraulic excavator that can prevent a collision with another object.
[0012]
[Means for Solving the Invention]
In order to achieve the above object, the present invention employs the following means.
[0013]
In addition, a lower boom connected to the upper swing body so as to be pivotable in the vertical direction, an upper boom attached to the tip of the lower boom so as to be pivotable in the left-right direction, and attached to the tip of the upper boom so as to be pivotable in the left-right direction. A cylinder stay, a stay rotatably supported by the lower boom and the cylinder stay in parallel with the upper boom, an offset cylinder for extending and retracting by switching a direction switching valve, and a pressure from a pilot pump Pressure oil flows into the variable control valve from the pilot pump, which is interposed between a variable control valve that is supplied with oil and controls the direction switching valve and a circuit that communicates the pilot pump and the variable control valve. A hydraulic excavator provided with an offset boom comprising: Between the circuit communicating the direction switching valve and the offset cylinder, characterized in that interposed a check valve for detecting and controls the opening and closing of the pressurized oil between the circuits that communicates with said locking valve and the variable control valve .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
First, a reference example in which the present inventors have devised be described with reference to FIGS.
[0015]
FIG. 2A is a side view of the small turning hydraulic excavator, and FIG. 2B is a rear view of the small turning hydraulic excavator.
[0016]
The configuration shown in FIGS. 2A and 2B is substantially the same as the configuration shown in FIGS. 4A and 4B described as the prior art, so the same reference numerals are given and description thereof is omitted. .
[0017]
FIG. 1 is a diagram showing a part of a hydraulic circuit of a small turning hydraulic excavator according to a reference example devised by the present inventor.
[0018]
In this figure, 31 is a pilot operated check valve that constitutes the load hold circuit, 32 is a conduit that transmits a signal pressure to the pilot operated check valve 31. Since other configurations are substantially the same as the configuration shown in FIG. 5 described as the prior art, the same reference numerals are given and description thereof is omitted.
[0019]
The pilot operated check valve 31 is provided in a circuit that communicates the offset cylinder 7 and the direction switching valve 20. When the pilot operation check valve 31 is opened, when the operation lever 161 is operated from the neutral position shown in FIG. 1 to the left side while the lock valve 23 is operated to the (B) side, the pilot is checked via the lock valve 23. The pressure oil from the pump 22 is supplied to the manually operated pressure reducing valve 16 for offset, and the signal pressure is transmitted to the pilot operated check valve 31 via the pipe line 32 to open the valve.
[0020]
When the operation is finished or the operation is temporarily stopped, the operation lever 161 is held in the neutral position, so that the signal pressure is not supplied to the pilot operated check valve 31 via the pipe line 32. The pilot operated check valve 31 is closed. For this reason, even if the holding pressure of the offset cylinder 7 increases due to the weight of the front (from the upper boom 4), the leakage from the offset cylinder 7 stops and the front can be prevented from being offset.
[0021]
Next, an embodiment of the present invention will be described with reference to FIG.
[0022]
FIG. 3 is a diagram showing a part of a hydraulic circuit of the small turning excavator according to the present embodiment.
[0023]
In this figure, 33 is a conduit for transmitting a signal pressure to the pilot operated check valve 31.
[0024]
Compared with the reference example described above , the present embodiment takes a signal pressure for opening the pilot operated check valve 31 from the manually operated pressure reducing valve 16 in the reference example described above. 23 and the manually operated pressure reducing valves 13, 14, 15, and 16 are different from each other in that they are taken from a pipeline 26, but other configurations are not different.
[0025]
In this embodiment configured as described above, when the pilot pump 22 is operated by operating the small swing type hydraulic excavator, a pressure is generated in the pipe line 25 connecting the pilot pump 22 and the lock valve 23 by the pilot relief valve 26. . When the operator operates the lock valve 23 to start the operation and is switched from (A) to (B), pressure is generated in the pipe line 26, and the signal pressure is supplied to the pilot operated check valve 31 through the pipe line 33. The valve is transmitted to open the valve, and the offset cylinder 7 can expand and contract.
[0026]
When the work is to be ended or temporarily stopped without stopping the small swing excavator (engine) during the work, the operator operates the lock valve 23 to switch from (B) to (B). As a result, the pressure in the pipe line 26 is lowered, the signal pressure in the pipe line 33 is also lowered, and the pilot operated check valve 31 is closed. As a result, similar to the above-described reference example , even when the holding pressure of the offset cylinder 7 increases due to the front weight (from the upper boom 4), the leakage from the offset cylinder 7 is suppressed and the front is offset. Can be prevented.
[0027]
As described above, in the present embodiment, the front offset can be prevented when the lock valve 23 is in the locked state regardless of the operation or stoppage of the small swing excavator (engine).
[0028]
Incidentally, in the above you facilities embodiment, the pilot-operated check valve 31, the example to set between the rod side oil chamber and the directional control valve 20 of the offset cylinder 7, and the bottom-side oil chamber of the offset cylinder 7 It may be installed between the direction switching valve 20 or both.
[0029]
【The invention's effect】
As described above, according to the present invention, the check valve for detecting the pressure oil between the circuits communicating the lock valve and the variable control valve is interposed between the circuits communicating the direction switching valve and the offset cylinder. Therefore, the expansion and contraction of the offset boom can be prevented after the work is completed or when the work is temporarily stopped.
[Brief description of the drawings]
FIG. 1 is a diagram showing a part of a hydraulic circuit of a small turning hydraulic excavator according to a reference example devised by the present inventor.
FIGS. 2A and 2B are a side view and a rear view of a small turning hydraulic excavator according to a first embodiment of a reference example devised by the present inventor.
FIG. 3 is a diagram showing a part of a hydraulic circuit of a small turning hydraulic excavator according to an embodiment of the present invention.
FIGS. 4A and 4B are a side view and a rear view of a small swivel excavator according to the related art.
FIG. 5 is a view showing a part of a hydraulic circuit of a small turning type hydraulic excavator according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Small turning type hydraulic excavator main body 2 Side grooved front 3 Lower boom 4 Upper boom 5 Cylinder stay 6 Stay 7 Offset cylinder 8 Arm 9 Bucket 10 Boom cylinder 11 Arm cylinder 12 Bucket cylinder 13, 14, 15, 16 Manually operated pressure reducing valve 131 , 141, 151, 161 Operation lever 17, 18, 19, 20 Switching valve 22 Pilot pump 23 Lock valve 25, 26 Pipe line 30 Boom foot pin 31 Pilot operated check valve
3 3 pipeline

Claims (1)

A lower boom coupled to the upper swing body so as to be vertically rotatable;
An upper boom attached to the tip of the lower boom so as to be rotatable in the left-right direction;
A cylinder stay attached to the tip of the upper boom so as to be rotatable in the left-right direction;
In parallel with the upper boom, a stay rotatably supported by the lower boom and the cylinder stay,
An offset cylinder for extending and retracting by rotating the direction switching valve to rotate the upper boom;
A variable control valve that is supplied with pressure oil from a pilot pump and controls the direction switching valve;
A lock valve that is interposed between circuits that communicate the pilot pump and the variable control valve, and controls inflow of pressure oil from the pilot pump to the variable control valve;
Hydraulic excavator with an offset boom composed of
And wherein the directional control valve and the said offset cylinder between circuit communicating, was interposed a check valve for detecting and controls the opening and closing of the pressurized oil between the circuits that communicates with said locking valve and the variable control valve Hydraulic excavator with offset boom.

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