Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Reexamination Certificate
2004-04-16
2008-10-14
Leslie, Michael (Department: 3745)
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
C060S413000, C091S452000, C091S517000, C091S520000
Reexamination Certificate
active
07434394
ABSTRACT:
To permit using hold-side pressure oil in a first hydraulic cylinder for the acceleration of a second hydraulic cylinder upon performing a combined operation of the first and second hydraulic cylinders, a hydraulic drive system is provided with a main hydraulic pump21, a boom cylinder6and an arm cylinder7, a directional control valve23for a boom and a directional control valve24for an arm, and a boom control device25and an arm control device26. The hydraulic drive system is also provided with a pressure oil feed means for feeding pressure oil in a rod chamber6bof the boom cylinder6to an upstream side of the directional control valve24for the arm when a bottom pressure of the arm cylinder7has increased to a high pressure equal to or higher than a predetermined pressure. This pressure oil feed means includes a flow combiner valve44arranged in a reservoir line42which can communicate to the rod chamber6bof the boom cylinder6. When the bottom pressure of the arm cylinder7is the predetermined pressure or higher, the flow combiner valve44maintains a communication line40, which communicates the reservoir line42and the upstream side of the directional control valve24for the arm with each other, in a state that pressure oil can be fed to the upstream side of the directional control valve24for the arm.
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Ishikawa Kouji
Kajita Yusuke
Karasawa Hideo
Nakamura Kazunori
Sugiyama Genroku
Crowell & Moring LLP
Hitachi Construction Machinery Co. Ltd.
Leslie Michael
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