JPH0251012B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a loading shovel with automatic horizontal extrusion function of bucket.

A loading shovel with a bucket automatic horizontal extrusion function is already known, and has a construction as shown in FIG. 1 is a lower traveling body, 2 is an upper rotating body, 3 is a boom, 4 is an arm, 5 is a bucket, 6 is a boom cylinder, 7 is an arm cylinder,
8 is a bucket cylinder, and 9 is a level cylinder. The hydraulic circuit is shown in FIG. The rod side oil chamber 9A of the level cylinder 9 is communicated with the rod side oil chamber 6A of the boom cylinder 6 through a pipe 10, and the bottom side oil chamber 9B of the level cylinder 9 is communicated with the bottom side oil chamber 6B of the boom cylinder 6 through a pipe 11. will be communicated to. The main pumps 12, 13 are the directional valves 14A to 14D, 15A of the directional valve groups 14, 15.
Pressure oil is supplied to the arm cylinder 7, boom cylinder 6, bucket cylinder 8, and other actuators (not shown) through 15D, and the return oil is discharged to the tank 16. The pilot pump 17 includes an arm pilot valve 18 and a boom pilot valve 1.
9 and the pilot valve 20 for the bucket. The output ports of each pilot valve 18 to 20 are connected to the directional control valve 1 by pilot pressure signal circuits a to f.
They are connected to pressure receiving parts 4B, 14D, 15A, and 15C, respectively. 21 is a relief valve.

When the arm pilot valve 18 is operated and a pilot pressure signal is sent to the directional switching valve 14B via the pilot pressure signal circuit a, the pressure oil of the main pump 12 is transferred to the bottom side oil chamber 7B of the arm cylinder 7 by the directional switching valve 14B. As a result, the rod of the arm cylinder 7 is extended and the arm 4 is rotated forward. Along with this, the rod of the level cylinder 9 also extends, oil is sent from the rod side oil chamber 9A to the rod side oil chamber 6A of the boom cylinder 6, the rod of the boom cylinder 6 contracts, and the boom 3 lowers. Therefore, only by operating the arm pilot valve 18, the bucket 5 moves horizontally along the ground surface.

In this way, when the arm cylinder 7 is operated, the boom cylinder 6 is also necessarily operated, so the arm cylinder 7 cannot be operated independently. Depending on the excavation site, independent operation of the arm cylinder 7 may be required. For example, if there is a sloped concrete surface on the other side of the accumulated earth and sand, it is better to move the bucket 5 in an arc from bottom to top instead of pushing it out horizontally. For such requests,
The conventional device shown in FIG. 2 cannot cope with this problem.

An object of the present invention is to solve the above-mentioned problems and provide a hydraulic circuit for a loading shovel that can select between horizontal movement and circular arc movement of the bucket.

In order to achieve this object, the present invention opens the pipe line that communicates the level cylinder and the boom cylinder when the horizontal movement of the bucket is selected, and when the arcuate movement of the bucket is selected, the pipe is opened. In addition to closing the passage, a switching valve is provided to communicate the rod-side oil chamber of the level cylinder with the rod-side oil chamber of the arm cylinder, and the bottom-side oil chamber of the level cylinder with the bottom-side oil chamber of the arm cylinder. Features.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments. Components similar to those in FIG. 2 are designated by the same reference numerals. A switching valve 22 is provided in the middle of a pipe 10 that communicates between the rod side oil chamber 9A of the level cylinder 9 and the rod side oil chamber 6A of the boom cylinder 6.
A switching valve 23 is provided in the middle of the pipe line 11 that communicates with the bottom side oil chamber 6B. Switching valves 22, 23
opens the pipes 10 and 11 at the return position x, closes the pipes 10 and 11 at the switching position y, and
The rod side oil chamber 9A of the level cylinder 9 is connected to the pipe 10.
The rod side oil chamber 7A of the arm cylinder 7 is communicated with the rod side oil chamber 7A through a part of the pipe line 11 and the pipe line 24, and the bottom side oil chamber 9B is communicated with the bottom side oil chamber 7B through a part of the pipe line 11 and the pipe line 25. be. Switching valves 22, 23
A pilot pressure signal that simultaneously switches and drives the directional control valve 26 is generated by the switching valve 26. The switching valve 26 does not generate a pilot pressure signal in switching position m, but generates a pilot pressure signal in switching position n.

To select horizontal movement of the bucket 5, the switching valve 26 is switched to the switching position m. Since no pilot pressure signal is generated at the switching position m, the switching valves 22 and 23 are held at the return position x, and between the rod side oil chambers 9A and 6A of the level cylinder 9 and the boom cylinder 6, and between the bottom side oil chambers 9B and 6A. 6B are communicated with each other. Therefore, when the arm cylinder 7 moves in the direction of rod extension by operating the arm pilot valve 18 and the arm 4 rotates forward, the rod of the level cylinder 9 also extends and the oil on that rod side is released. The hydraulic pressure generated in the chamber 9A is transmitted to the rod-side oil chamber 6A of the boom cylinder 6, thereby retracting the rod of the boom cylinder 6. Therefore, the boom 3 is lowered and the bucket 5 moves forward horizontally, as in the conventional case. When the arm cylinder 7 moves in the rod retraction direction, the arm 4 is pulled back, the boom 3 is raised, and the bucket 5 is horizontally retreated.

In order to select an arcuate movement of the bucket 5, the switching valve 26 is switched to switching position n. At switching position n, a pilot pressure signal is generated and the switching valve 2
2 and 23, the switching valves 22 and 23 are simultaneously switched to the switching position y. As a result, the pipes 10 and 11 are closed, and the level cylinder 9 and arm cylinder 7 are connected in parallel to the directional control valve 14B. Therefore, by operating the arm pilot valve 18, the arm cylinder 7 and the level cylinder 9 move in the same direction, and the arm 4 is strongly rotated forward or pulled backward.
At this time, the boom cylinder 6 does not operate, so the boom 3 does not move, so the tip of the arm 4, that is, the bucket 5 moves forward or backward in an arc.

Although the switching valves 22 and 23 are shown as separate pieces in FIG. 3, they may be integrated. Switching valve 2
A switching valve 26 is used as a means for switching between 2 and 23.
is used, but is not limited to this, and can be performed by mechanical means, electrical means, or the like. Further, the switching valve 26 is not limited to a manual type, but may be one that detects resistance to horizontal excavation and automatically switches to arc excavation, for example.

As explained above, according to the present invention, when the horizontal movement of the bucket is selected, the switching valve opens the pipe that communicates the level cylinder and the boom cylinder, and when the circular movement of the bucket is selected, the switching valve opens the pipe that communicates with the level cylinder and the boom cylinder. By closing the bucket, you can choose between horizontal movement and arc movement of the bucket. When arc movement is selected, the rod side oil chamber of the level cylinder is communicated with the rod side oil chamber of the arm cylinder, and the bottom side oil chamber of the level cylinder is communicated with the bottom side oil chamber of the arm cylinder. The driving force for forward rotation and rearward retraction of the arm during movement can be made stronger by applying the force of the level cylinder.

[Brief explanation of the drawing]

FIG. 1 is a side view of a conventional loading shovel, FIG. 2 is a hydraulic circuit diagram of a conventional loading shovel, and FIG. 3 is a hydraulic circuit diagram of an embodiment of the present invention. 3...Boom, 4...Arm, 5...Bucket, 6...Boom cylinder, 7...Arm cylinder, 8...Bucket cylinder, 9...Level cylinder, 6A, 7A, 9A...Rod side oil room, 6
B, 7B, 9B...Bottom side oil chamber, 10, 11...
...Pipeline, 22, 23...Switching valve, 26...Switching valve.

Claims (1)

[Claims] 1.Equipped with a boom cylinder, an arm cylinder, and a bucket cylinder that drive the boom, arm, and bucket, respectively, and a level cylinder installed between the boom and the arm, and between the rod side oil chambers of the level cylinder and the boom cylinder, In the hydraulic circuit of the loading shovel that communicates between the bottom side oil chambers and the bottom side oil chambers, in the middle of the pipe line that communicates the level cylinder and the boom cylinder, when horizontal movement of the bucket is selected, the pipe line is opened,
When selecting the circular movement of the bucket, the pipe is closed, and the rod-side oil chamber of the level cylinder is connected to the rod-side oil chamber of the arm cylinder, and the bottom-side oil chamber of the level cylinder is connected to the bottom-side oil chamber of the arm cylinder. A hydraulic circuit for a loading shovel characterized by being provided with a switching valve for communication.