Power plants – Pressure fluid source and motor – Condition responsive control of motive fluid flow
Reexamination Certificate
2007-01-30
2007-01-30
Nguyen, Hoang (Department: 3748)
Power plants
Pressure fluid source and motor
Condition responsive control of motive fluid flow
C060S494000
Reexamination Certificate
active
11078425
ABSTRACT:
A hydraulic control device for a working machine includes hydraulic actuators, a hydraulic pump which functions as a hydraulic power source, control valves which control the actuators on the basis of operations by an operating unit, a common bleed-off valve which returns excess oil to a tank via an unload passage on the basis of the operations by the operating unit, and a control unit which controls the common bleed-off valve. The common bleed-off valve is capable of setting a position for closing the unload passage when the common bleed-off valve is in a non-operating state. The control valves have center bypass passages which function as individual bleed-off passages which open when the control valves are in neutral states. Opening characteristics of the control valves are set such that the center bypass passages are closed in initial stroke periods in which the control valves move toward operating positions.
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Patent Abstracts of Japan, JP 10-073101, Mar. 17, 1998.
Oka Hidekazu
Toji Yutaka
Kobelco Construction Machinery Co., Ltd.
Nguyen Hoang
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