Hydraulic driving unit
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United States of America Patent
Stats
-
May 31, 2005
Grant Date -
Apr 15, 2004
app pub date -
May 13, 2002
filing date -
May 17, 2001
priority date (Note) -
In Force
status (Latency Note)
Importance
Abstract
A hydraulic driving unit is provided with a directional control valve 23 and directional control valve 24 for controlling a boom cylinder 6 and arm cylinder 7, both of which are driven by pressure oil delivered from a main hydraulic pump, respectively, a boom control device 25 for selectively controlling the directional control valve 23 and an arm control device 26 for selectively controlling the directional control valve 24, and is mounted on a hydraulic excavator. To permit effective use of pressure oil in a rod chamber 6a of the boom cylinder 6 when a bottom pressure of the arm cylinder 7 has become high while performing a combined operation such that pressure oil is being supplied to bottom chambers 6a,7a of the boom cylinder 6 and arm cylinder 7, the hydraulic driving unit is provided with a communication controlling means for bringing the rod chamber 6b of the boom cylinder 6 and the bottom chamber 7a of the arm cylinder 7 into communication with each other when the bottom pressure of the arm cylinder 7 has increased to a high pressure equal to or higher than a predetermined pressure.
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