Power plants – Pressure fluid source and motor – Unsafeness – unreadiness or disarray prevent manual change or...
Reexamination Certificate
1999-07-07
2001-08-07
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Unsafeness, unreadiness or disarray prevent manual change or...
C060S427000, C091S461000
Reexamination Certificate
active
06269637
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a technical field of a hydraulic control circuit for working machines, such as hydraulic shovels.
2. Description of Related Art
In some working machines, such as hydraulic shovels, an offset-type working implement capable of swinging to the left and right is attached to a machine body. Generally, such working machines accompany a risk that when the working implement is moved, it may contact, or interfere, with an operator's seat portion. In such working machines, therefore, consideration must be paid to avoiding contact between the working implement and the operator's seat portion.
To that end, there has hitherto been proposed a working machine having attitude detecting means for detecting an attitude of a working implement, and a control unit for determining based on a detection signal from the attitude detecting means whether the working implement comes within a predetermined zone around the operator's seat portion. When it is determined that the working implement comes within the predetermined zone around the operator's seat portion, the control unit outputs a control command to a hydraulic circuit, for a hydraulic actuator associated with the working implement, so that the working implement is stopped.
One known example of such a related art device is shown in FIG.
9
. In the example, solenoid proportional pressure reducing valves
49
A,
49
B, which operate in accordance with a command from a control unit, are provided between a pilot-operated control valve
46
for controlling the supply of pressurized oil to a hydraulic actuator
45
, e.g., a boom cylinder, and pilot valves
48
A,
48
B for delivering pilot pressurized oil upon manipulation of a control member
47
. When the working implement is positioned away from the operator's seat portion, the solenoid proportional pressure reducing valves
49
A,
49
B are opened to allow the supply of the pilot pressurized oil to the control valve
46
. On the contrary, when the working implement comes close to the operator's seat portion, the solenoid proportional pressure reducing valves
49
A,
49
B are closed to cut off the supply of the pilot pressurized oil to the control valve
46
, thereby stopping the working implement.
The above prior art however has a problem. Because the solenoid proportional pressure reducing valves are closed to stop the working implement when the working implement comes close to the operator's seat portion, as described above, the working implement is stopped during the operation and the working efficiency is reduced. The invention intends to overcome such a problem.
SUMMARY OF THE INVENTION
In view of the state of art set forth above, the invention has been made with the object of solving the above problem. In a hydraulic control circuit for a working machine, comprising a hydraulic actuator operated to move a working implement, and a pilot-operated control valve for controlling the supply of pressurized oil to the hydraulic actuator, the hydraulic control circuit includes a control valve for controlling the supply of pilot pressurized oil to the pilot-operated control valve in accordance with a command from a control unit, a pilot valve for delivering the pilot pressurized oil to the control valve in accordance with manipulation of a control member, a pilot pump oil line capable of supplying the pilot pressurized oil to the control valve from a pilot oil pressure source without passing the pilot valve, and a selector valve for supplying the pilot pressurized oil delivered from the pilot valve to the control valve when the control member is manipulated, and supplying the pilot pressurized oil from the pilot pump oil line to the control valve when the control member is not manipulated, the control unit including determining means for determining whether the working implement has entered a preset interference prevention area based on input signals from attitude detecting means for detecting an attitude of the working implement, and interference prevention control means for outputting a control command to the control valve, causing the pilot pressurized oil to be supplied to the pilot-operated control valve in the direction to move the working implement away from the interference prevention area, when the determining means determines that the working implement has entered the preset interference prevention area.
In the above hydraulic control circuit, the hydraulic actuator for moving the working implement comprises a boom up-and-down moving cylinder for vertically swinging an offset type boom which is swingable in the up-and-down and left-and-right directions, a boom left-and-right moving cylinder for swinging the boom to the left and right, and a stick cylinder for swinging a stick back and forth which is supported to a fore end of the boom to be swingable in the back-and-forth direction; the control valve, the pilot valve, the pilot pump oil line and the selector valve are provided in an oil line for supplying the pilot pressurized oil to the pilot-operated control valve for the stick cylinder in the direction to move the stick away from the interference prevention area; and the control valve and the pilot valve are provided in each oil line for supplying the pilot pressurized oil to each of the pilot-operated control valves for the boom up-and-down moving cylinder, the boom left-and-right moving cylinder, and the stick cylinder in the direction to move the boom or the stick closer toward the interference prevention area.
Also, according to a second aspect of the invention, in a hydraulic control circuit for a working machine comprising first and second hydraulic actuators for operating a working implement, and first and second pilot-operated control valves for respectively controlling supply of pressurized oil to the hydraulic actuators, the hydraulic control circuit includes interference prevention control means for preventing the working implement from entering a interference prevention area set in advance to avoid interference between a body of the working machine and the working implement; and the interference prevention control means includes a mechanism for operating the first hydraulic actuator in the direction away from the interference prevention area, thereby continuing operation of the second hydraulic actuator while the working implement is prevented from entering the interference prevention area, when it is determined at least in a state of the second hydraulic actuator being operated that the working implement has reached the interference prevention area, the mechanism including valve means for switching over the circuit such that pilot pressurized oil for operating the second hydraulic actuator is also supplied to a pilot oil line for operating the first hydraulic actuator in the direction away from the interference prevention area.
In the above hydraulic control circuit, the hydraulic control circuit may include first and second approaching-side pilot oil lines for supplying the pilot pressurized oil respectively to the first and second pilot-operated control valves in the direction of moving the working implement to approach the interference prevention area, first and second away-side pilot oil lines for supplying the pilot pressurized oil respectively to the first and second pilot-operated control valves in the direction of moving the working implement away from the interference prevention area, and first and second approaching- and away-side pilot valves for outputting the pilot pressurized oil respectively to the first and second approaching- and away-side pilot oil lines in accordance with manipulation of first and second control members, and a control valve for opening and closing one of the pilot oil lines in accordance with a command from the interference prevention control means may be provided at least in the first approaching-side pilot line.
In the above hydraulic control circuit, when the second hydraulic actuator is provided as plurality of facilitators, a s
Motomura Hidetake
Tada Hiroaki
Leslie Michael
Look Edward K.
Oliff & Berridg,e PLC
Shin Caterpillar Mitsubishi Ltd.
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