Power plants – Pressure fluid source and motor – With control means for structure storing work driving energy
Reexamination Certificate
2005-05-31
2005-05-31
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
With control means for structure storing work driving energy
C060S424000, C091S452000
Reexamination Certificate
active
06898932
ABSTRACT:
A hydraulic driving unit is provided with a directional control valve23and directional control valve24for controlling a boom cylinder6and arm cylinder7, both of which are driven by pressure oil delivered from a main hydraulic pump, respectively, a boom control device25for selectively controlling the directional control valve23and an arm control device26for selectively controlling the directional control valve24, and is mounted on a hydraulic excavator. To permit effective use of pressure oil in a rod chamber6aof the boom cylinder6when a bottom pressure of the arm cylinder7has become high while performing a combined operation such that pressure oil is being supplied to bottom chambers6a,7aof the boom cylinder6and arm cylinder7, the hydraulic driving unit is provided with a communication controlling means for bringing the rod chamber6bof the boom cylinder6and the bottom chamber7aof the arm cylinder7into communication with each other when the bottom pressure of the arm cylinder7has increased to a high pressure equal to or higher than a predetermined pressure.
REFERENCES:
patent: 5323687 (1994-06-01), Zenker et al.
patent: 5797310 (1998-08-01), Casey et al.
patent: 48-11803 (1973-02-01), None
patent: 50-8881 (1975-03-01), None
patent: 55-119838 (1980-09-01), None
Crowell & Moring LLP
Hitachi Construction Machinery Co. Ltd.
Leslie Michael
Look Edward K.
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