JPH0332601Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention consists of a telescoping arm that is rotatably attached to the tip of a boom that is attached to the main body so as to be able to rise and fall freely, and that is rotatable by an arm rotation cylinder and extendable and retractable by an arm telescoping cylinder. This invention relates to a hydraulic circuit for an excavator, in which a telescoping rod is suspended from the tip of the arm, and a hydraulic clam shell is rotatably attached to the tip of the rod.

(Background technology) The first excavator equipped with a hydraulic clam shell.
As shown in the figure and FIG.
A telescoping arm 5 is attached to the tip of the arm 5, which is rotatable by an arm rotation cylinder 4 and extendable by an arm telescoping cylinder 6, and a telescoping rod 8, which is extendable and retractable by a rod telescoping cylinder 10, is suspended from the end of the arm 5. However, there is an excavator in which a hydraulic clam shell 11 is rotatably attached to the tip of the rod 8. The telescoping arm 5 is constructed by slidably fitting an inner arm 5B into a cylindrical outer arm 5A, and the outer arm 5A is attached to the tip of the boom 3 by connecting it with a pin 12. The cylinder 6 is attached by connecting the tube and rod to the outer arm 5A and inner arm 5B using pins 13 and 14, respectively. Also,
The telescoping rod 8 is constructed by slidably fitting a cylindrical inner rod 8B into a cylindrical outer rod 8A, and the outer arm 8A is connected to the tip of the arm 3 by a pin 15 and hangs down. 10 is installed in the rod 8 by connecting the tube and rod to the outer rod 8A and inner rod 8B by pins 16 and 17, respectively.
The hydraulic clam shell 11 is connected to the inner rod 8B by a pin 18 and hangs down so as to be rotatable.
It is opened and closed by an opening/closing cylinder 9.

Excavators with this type of structure have a telescoping rod hanging from the tip of a non-telescopic arm, or a multi-stage telescoping rod rotatably attached to the tip of the boom, as shown in Figure 1. By extending the telescopic arm 5 from the upright position of the boom 3, a high dumping height can be obtained, and by extending both the telescopic arm 5 and the telescopic rod 8 as shown in Fig. This method has the advantage that a sufficient depth of excavation can be obtained.

Conventionally, a circuit shown in FIG. 3 has been used as an operating hydraulic circuit for the arm telescopic cylinder 6 and the rod telescopic cylinder 10 used in this excavator. This circuit has manual switching valves 21A and 21B for controlling the supply of pressure oil from the hydraulic pump 24 and the discharge to the oil tank 22, corresponding to the arm telescoping cylinder 6 and the rod telescoping cylinder 10, respectively. 23 is a relief valve that sets the discharge pressure of the hydraulic pump 24.

In this conventional hydraulic circuit, when extending and contracting the telescoping arm 5 and the telescoping rod 8 to raise and lower the hydraulic clam shell 11, two manual switching valves 21A and 21B must be operated.
In addition, for hole drilling, boom cylinder 2,
Arm rotation cylinder 4 and hydraulic clam shell 1
Since the operation valve of the first open/close cylinder 9 must be operated, there is a drawback that the valve operation becomes complicated. In addition, if you try to realize this excavator by modifying the front of the hydraulic excavator, you will need to use the operating valve for the existing boom cylinder 2, the arm rotation cylinder 4
In addition to the operation valve for rotating the bucket used in the opening/closing cylinder 9 of the clamshell 11, two operation valves for the arm telescopic cylinder 6 and the rod telescoping cylinder 10 must be newly installed. In order to add this, it is necessary to make design changes such as expanding the operator's cab provided in the main body 1, which means that the machine is beyond the scope of modification and becomes an expensive machine. In addition, when extending the arm telescoping cylinder 6 and performing work with a large working radius, forgetting to retract the arm telescoping cylinder 6 and extending the boom cylinder 2, as shown in FIG. If you try to raise the excavator as shown in , the center of gravity of the excavator will move forward, making it unstable, making it more likely to tip over when working on slopes, and causing the tip of the telescoping arm 5 to hit the inner wall of the drilled hole 19. However, the drawback was that the excavator could fall over.

(Purpose of the present invention) In view of the above-mentioned points, the present invention provides an excavator having a telescoping arm, a telescoping rod, and a hydraulic clamshell, which facilitates valve operation during work, provides good stability, and is inexpensive. The purpose is to provide a hydraulic circuit for an excavator that can be used.

(Structure of the present invention) A hydraulic circuit for an excavator according to the present invention will be described below with reference to an embodiment shown in FIG. The fifth hydraulic circuit is
This is a hydraulic circuit used in the excavator shown in FIGS. 1 and 2, and the same reference numerals as in FIGS. 1 to 4 indicate the same parts. In the present invention, a common manual switching valve 21 is provided as a control valve for the arm telescopic cylinder 6 and the rod telescopic cylinder 10. Two secondary pipes 2 of the manual switching valve 21
One of the pipe lines 25 of 5 and 26 connects to the arm telescopic cylinder 6 and the rod telescopic cylinder 1, respectively.
The other pipe line 26 branches into pipe lines 26A and 26B connected to the bottom chambers of the arm telescopic cylinder 6 and the rod telescopic cylinder 10, respectively. . Further, in the pipe line 25B, a relief valve 27a is provided which causes the arm telescopic cylinder 6 to contract before the rod telescopic cylinder 10 when the arm telescopic cylinder 6 and the rod telescopic cylinder 10 are contracted.
and a check valve 27b that forms an oil discharge passage when the rod telescopic cylinder is extended. Relief valve 28 that extends the cylinder 10 in advance of the arm telescopic cylinder 6
An assist valve 28 is provided which includes a check valve 28b which forms an oil discharge passage when the arm telescopic cylinder is contracted.

In this hydraulic circuit, when the manual switching valve 21 is switched to the left position, pressure oil from the hydraulic pump 24 is supplied to the bottom chamber of the rod telescopic cylinder 10 through the pipe line 26, and the telescopic rod 8 is first extended. . If the rod telescopic cylinder 10 extends its full stroke, the pressure in the conduit 26 increases, and when the pressure exceeds the set pressure of the relief valve 28a, the relief valve 28a switches to the communicating position, and the conduit 26A
Pressure oil is supplied to the bottom chamber of the arm telescopic cylinder 6 through the arm telescopic cylinder 6, and the arm telescopic cylinder 6 also extends.
Therefore, when both cylinders 6 and 10 extend, the rod telescopic cylinder 10 first extends, and then the arm telescopic cylinder 6 extends.

On the other hand, when both the telescoping arm 5 and the telescoping rod 8 are to be retracted from the extended state, the manual switching valve 21 is switched to the left position. Then, the pressure oil from the hydraulic pump 24 is supplied to the rod chamber of the arm telescopic cylinder 6 through the conduit 25, and the arm telescopic cylinder 6 is first contracted. When the arm telescopic cylinder 6 contracts through its full stroke, the pressure in the pipe line 25 increases, and when the pressure exceeds the set pressure of the relief valve 27a, the relief valve 27a switches to the communicating position, and the rod expands and contracts via the pipe line 25B. cylinder 1
Pressure oil is supplied to the rod chamber 10, and the rod telescopic cylinder 10 also contracts. Therefore, both cylinders 6, 1
When the 0 is contracted, the arm telescopic cylinder 6 is contracted first, and then the rod telescopic cylinder 10 is contracted.

Note that when the rod telescopic cylinder 10 is contracted, a larger hydraulic pressure is required than when it is extended, so the set pressure of the relief valve 27a is set higher than the set pressure of the relief valve 28a.

With the above configuration, when the hydraulic clam shell 11 is lowered, the telescoping rod 8 extends first, so while the excavation hole is shallow, the hydraulic clam shell 11 can be raised and lowered only by the extension and contraction of the telescoping rod 8. If the excavation hole 19 becomes deep, the telescoping arm 5 can be extended vertically as shown in FIG. 2, thereby making it possible to excavate a deep hole. Furthermore, when retracting the telescoping arm 5 and the telescoping rod 8 after digging a deep hole, the telescoping arm 5 contracts first as shown by the imaginary line a in FIG. 4 to pull up the hydraulic clam shell 11, the tip of the arm can be easily pulled up without colliding with the inner wall of the hole 19, and the working radius is small, making it stable. There is less risk of the excavator falling down due to collision.

(Effects of the present invention) As described above, in the present invention, the telescoping arm and the telescoping rod can be extended and contracted by operating one manual switching valve, which simplifies the operation and allows the operator to The burden of this will be reduced. In addition, the excavator of the present invention can be provided at low cost because it can be realized by attaching one manual switching valve that is shared by the arm telescopic cylinder and the rod telescopic cylinder to the driver's seat of an existing hydraulic excavator. can. In addition, when discharging soil, the telescoping arm is contracted first, so the arm is always in the contracted state when in the soil discharging position where the working radius is large, improving stability and making it easy to operate each cylinder on the front. This further reduces the risk of falling.

[Brief explanation of the drawing]

Figures 1 and 2 are side views showing the excavator to which the present invention is applied in the soil-unloading and digging positions, and Figure 3 shows the arm telescopic cylinder and rod telescopic cylinder conventionally used in the excavator. hydraulic circuit diagram,
FIG. 4 is a side view of an excavator to explain the problems of the prior art, and FIG. 5 is a hydraulic circuit diagram showing an embodiment of the present invention. 1...Main body, 3...Boom, 4...Arm rotating cylinder, 5...Telescopic arm, 6...Arm telescopic cylinder, 8...Telescopic rod, 10...Rod telescopic cylinder, 11...Hydraulic pressure Clamsiel, 2
1...Manual switching valve, 27a, 28a...Relief valve, 27b, 28b...Check valve.

Claims (1)

[Scope of utility model registration request] A telescoping arm that is rotatable by an arm rotation cylinder and extendable by an arm telescoping cylinder is attached to the tip of the boom that is attached to the main body so that it can be raised and lowered freely. In a hydraulic circuit for an excavator in which a rod is suspended and a hydraulic clam shell is rotatably attached to the tip of the rod, a manual switching valve is provided which is commonly used for operating the arm telescoping cylinder and the rod telescoping cylinder, and the manual switching valve is provided. A pipe line connecting the valve and each of the telescopic cylinders,
A hydraulic circuit for an excavator, comprising a valve device that causes a rod telescopic cylinder to extend in advance when both cylinders are extended, and an arm telescopic cylinder to contract in advance when both cylinders contract.