JPH0348287Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field This invention is a work equipment such as a bucket, a fork, etc. attached to a poom that swings up and down with a boom cylinder of a tractor shovel, a power shovel, etc. so that it can rotate up and down with the work equipment cylinder. The present invention relates to a hydraulic circuit for a working device.

Prior Art As shown in FIG.
A tractor shovel is known in which a bucket belt 4 is pivotally attached to the tip of the bucket belt so as to be vertically rotatable, and a bucket belt cylinder 5 is pivotally connected to the bucket belt 4 via a bell crank 6.

In such a tractor shovel, when the bucket cylinder 5 is reduced, the bucket 4 dumps (tilts forward) via the bell crank 6 to discharge soil, but in order to improve soil removal from the bucket 4, the dump stopper 7 is used. When dumping, the bell crank 6 collides with the dump stopper 7 and the bucket 4
It is designed to impart an impact force to the

However, with this structure, in order to raise the boom 2 using the boom cylinder 3, the pressure oil in the bucket cylinder is discharged from the overload relief valve to the drain by the boom cylinder force, and the bucket cylinder 5 is extended. It is necessary to raise the boom 2 while tilting the bucket 4.

For this reason, if the boom 2 is raised with the bell crank 6 in contact with the dump stopper 7, the bucket cylinder 5 will become a hindrance to the raising of the boom 2. Hereinafter, this phenomenon will be referred to as lockup.

In other words, in order to raise the boom 2 with the dump stopper 7 in contact with the bell clamp 6 as shown in Fig. 2, it is necessary to move the connecting part A between the bucket cylinder 5 and the bell clamp 6 along the trajectory B. However, if the length of the bucket cylinder 5 is constant, it will move along the trajectory C, so the bucket cylinder 5 must be extended.

Therefore, conventionally, as shown in FIG. 3, an overload relief valve 9 is provided in the conduit 8 connected to the reduction chamber 5a of the bucket cylinder 5, and this overload relief valve 9 is used to release the pressure oil in the reduction chamber 5a. The water is allowed to flow out into the drain. In FIG. 3, 10 is a bucket operating valve, and 11 is a boom operating valve.

However, with this hydraulic circuit, the thrust of the boom cylinder 3 is used to raise the pressure oil in the reduction chamber 5a of the bucket cylinder 5 to the relief pressure of the overload relief valve 9, and to raise the boom 2. cannot be used effectively.

In order to prevent this, the relief pressure of the overload relief valve 9 can be lowered, but in this case, as shown in Fig. 4, the tip 4a of the bucket 4 is grounded and the vehicle is moved backwards to perform the ground leveling work. (hereinafter referred to as back grading work), the bucket cart 4 tends to tilt, resulting in a problem that the performance of the back grading work is poor.

Also, as shown in Figure 5, at the tip of the boom 2,
Even if a fork in which a movable fork 13 is pivotally connected to the fork claw cylinder 14 so as to be movable up and down is attached to the fork claw 12, the same effect as described above is obtained, but when this fork is attached, the above-mentioned bucket is attached. The force for raising the boom 2 becomes larger than that, and the ability of the fork claws 12 to pull in materials such as logs becomes inferior.

Purpose of the invention: When the boom is raised with the bell crank in contact with the dump stopper, the thrust of the boom cylinder can be used effectively without the work equipment cylinder interfering with the boom rising, and it can also be used for back grading work and load pulling work. The purpose is to prevent performance deterioration.

Structure of the invention: A work machine operating valve that supplies pressure oil to a work machine cylinder is provided with a floating position that communicates the contraction chamber of the work machine cylinder with a drain via a throttle and closes the extension chamber.

Embodiment FIG. 6 is a hydraulic circuit diagram of the working device equipped with the bucket shown in FIG.
The reduction chamber 5a is connected to the first and second outlet ports 10 ₁ and 10 ₂ of the bucket operation valve 10, which is the working machine operation valve according to the present invention, through the first and second pipe lines 20 and 21, and The first pipe line 20 and the second pipe line 21 are the first and second pipe lines.
Relief valves (that is, first and second overload relief valves) 22, 23 and first and second check valves 2
4, 25 to the first and second drain passages 26, 2.
7 are connected to each other.

The bucket operation valve 10 has a third outlet port 1
0 ₃ and the inlet port 10 ₄ , a floating position where the second outlet port 10 ₁ and the main inlet port 10 ₅ are disconnected, and a floating position where the second outlet port 10 ₂ and the drain port 10 ₆ are communicated, the third outlet port 10 ₃ and inlet port 10 ₄
A dump position where the main inlet port 10 ₅ and the second outlet port 10 ₂ communicate with each other, a dump position where the first outlet port 10 ₁ and the drain port 10 ₆ communicate with each other, and a dump position where the third outlet port 10 ₃ and the inlet port 10 ₄ communicate with each other. A holding position where the main inlet port 10 ₅ and drain port 10 ₆ and the first and second outlet ports 10 ₁ and 10 ₂ are respectively blocked, and the third outlet port 10 ₃ and the inlet port 1 are in communication with each other.
The main inlet port ₁₀₅ and the first outlet port ₁₀₁ are communicated with each other, and the second outlet port _{102 and} the drain port ₁₀₆ are communicated with each other. The second outlet port 10 ₂ and the drain port 10 ₆ are communicated via a restriction 28 .

Therefore, when the bucket operation valve 10 is set to the floating position, the discharge pressure oil of the pump is supplied to the boom operation valve 11, and the extension chamber 5b of the bucket cylinder 5
is closed, and the reduction chamber 5a is connected to the drain via the throttle 28.

For this reason, the pressure oil in the reduction chamber 5a reaches a pressure corresponding to the restriction 28 (that is, the restriction 28 is such that it generates back pressure in the reduction chamber 5a of the bucket cylinder 5), and the boom cylinder 3 When the boom 2 is extended and the boom 2 is raised, the bucket cylinder 5 is extended by a small thrust of the boom cylinder 3, so that the thrust of the boom cylinder 3 can be effectively used.

In addition, if the bucket operation valve 10 is held in the holding position, the extension chamber 5b and the contraction chamber 5a of the bucket cylinder 5 are
is closed, and the discharge pressure oil of the pump can be supplied to the boom operation valve 11. Therefore, during grading work or load pulling work, the pressure in the reduction chamber 5a of the bucket cylinder 5 is relieved by the second relief valve 23. It can rise to high pressures without degrading its performance.

Effects of the invention When the boom cylinder 3 raises the boom 2, the pressure oil in the reduction chamber 5a of the work equipment cylinder 5 can flow out to the drain via the throttle 28, so the thrust of the boom cylinder 3 can be used effectively. Since the boom 2 can be raised by the operator and the contraction chamber 5a can be closed during grading work and load pulling work, the performance of the work will not be degraded.

[Brief explanation of the drawing]

Figure 1 is a top view of the work equipment equipped with a bucket belt, Figure 2 is a diagram explaining its malfunctions, Figure 3 is a conventional hydraulic circuit diagram, Figure 4 is an illustration of back grading work, and Figure 5 is a forklift. FIG. 6 is a hydraulic circuit diagram showing an embodiment of the hydraulic circuit of the present invention. 2 is a boom, 3 is a boom cylinder, 4 is a work machine (bucket, fork), 5 is a work machine cylinder (bucket cylinder), 5a is a contraction chamber, 5b is an extension chamber,
10 is a working machine cylinder (bucket cylinder).

Claims (1)

[Scope of utility model registration request] A working device in which a working machine 4 is mounted on a boom 2 which is vertically swung by a boom cylinder 3 so as to be movable up and down by a bell crank 6 and a working machine cylinder 5,
The work equipment operating valve 10 that supplies pressure oil to the work equipment cylinder 5 is set to the tilt position, dump position, extension chamber 5b, and contraction chamber that supplies pressure oil to the extension chamber 5b and contraction chamber 5a of the work equipment cylinder 5. holding position to occlude 5a,
The expansion chamber 5b is closed and the contraction chamber 5a is squeezed 28
A hydraulic circuit for a working device, characterized in that it has a floating position connected to a drain via a hydraulic circuit.