Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Patent
1990-02-14
1992-01-28
Look, Edward K.
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
60422, 60427, 60428, 60429, 60430, 60486, 91436, 91513, F16D 3102
Patent
active
050834282
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to fluid control systems for civil engineering working machines, especially for power shovels for use in excavation and like work, and more particularly to a fluid control system for causing a power shovel to efficiently perform work by traveling the body of the machine and effecting a single movement or two or more simultaneous movements of the working device.
BACKGROUND ART
Generally, fluid control systems for power shovels are adapted to control the running of the machine body and the pivotal movement and swiveling of the boom, arm and bucket by supplying a pressure fluid from two main pumps to actuators, such as a pair of running motors, boom cylinder, arm cylinder and swivel motor, via opposite running control valves and working device control valves for the boom, arm, bucket and swivel body. These control valves are divided into two groups so as to be easily operable at the same time.
Since power shovels are used for work on large and small scales as working machines in place of manual work, they are operated in a wider variety of modes. The operations of the power shovel include, for example, running only, a single movement of the boom, arm, bucket or swivel body with the machine body in a fixed position, and horizontal excavation or work on slopes wherein the forward end of the shovel is moved along a horizontal surface or the slope through two or more simultaneous operations. In any of these cases, it is required to operate the power shovel efficiently. Further with the power shovel, the working device, especially the boom and the arm, must be moved powerfully and rapidly, so that when the boom or the arm is to be moved, the fluid discharged from the two main pumps needs to be supplied as a confluent flow to the actuator concerned. Further when the working device is to be operated during running, the machine body must be made to run straight.
To fulfill these requirements, Unexamined Japanese Patent Publication SHO 62-107124 discloses a fluid control system, which comprises a first boom control valve for supplying the pressure fluid from one of two main pumps to the boom cylinder, and a second boom control valve for supplying the pressure fluid from the other main pump, as joined with the fluid from the first-mentioned pump, to the boom cylinder. Similarly, the system includes a first arm control valve and a second arm control valve for the arm cylinder. One of two running control valves, the first boom control valve, a bucket control valve and the second arm control valve form a control valve group, and the other running control valve, the first arm control valve and the second boom control valve form another control valve group. Further to enable the machine body to run straight, a flow-dividing selector valve (pilot directional control valve) is provided between the two main pumps and the two control valve groups.
When the power shovel having the conventional fluid control system described is caused to run only, the pressure fluid discharged from the main pumps is supplied to the running control valves independently of each other by the flow-dividing selector valve. When one of the working device actuators is to be operated simultaneously with running, the pressure fluid is supplied from one of the main pumps to the opposite running control valves, and the pressure fluid from the other main pump is supplied to the control valve for the actuator, whereby the power shovel is maintained in straight travel. When the boom cylinder is to be moved, the first and second two boom control valves are operated, such that the pressure fluid flows from the two main pumps are passed through the two boom control valves and supplied as joined together to the boom cylinder. Thus, the boom cylinder, i.e., the boom, is operated powerfully and rapidly. The arm is moved also in the same manner.
With the conventional fluid control system, however, the first and second two control valves are necessary for the boom cylinder, as well as for the arm cylinder. Each of thes
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Doi Kazuyuki
Kubomoto Wataru
Kabushiki Kaisha Kobe Seiko Sho
Look Edward K.
Mattingly Todd
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