The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 31, 2005
Filed:
May. 13, 2002
Yusuke Kajita, Ushiku, JP;
Yusuke Kajita, Ushiku, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
A hydraulic driving unit is provided with a directional control valveand directional control valvefor controlling a boom cylinderand arm cylinder, both of which are driven by pressure oil delivered from a main hydraulic pump, respectively, a boom control devicefor selectively controlling the directional control valveand an arm control devicefor selectively controlling the directional control valve, and is mounted on a hydraulic excavator. To permit effective use of pressure oil in a rod chamberof the boom cylinderwhen a bottom pressure of the arm cylinderhas become high while performing a combined operation such that pressure oil is being supplied to bottom chambersof the boom cylinderand arm cylinder, the hydraulic driving unit is provided with a communication controlling means for bringing the rod chamberof the boom cylinderand the bottom chamberof the arm cylinderinto communication with each other when the bottom pressure of the arm cylinderhas increased to a high pressure equal to or higher than a predetermined pressure.