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:
Mar. 01, 2011
Filed:
Aug. 05, 2004
Yusuke Kajita, Ushiku, JP;
Kouji Ishikawa, Niihari-gun, JP;
Hideo Karasawa, Tsuchiura, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
A hydraulic drive system is mounted on a hydraulic excavator, and is provided with a directional control valvefor a boom, a directional control valvefor an arm, a boom control devicefor selectively controlling the directional control valvefor the boom, and an arm control devicefor selectively controlling the directional control valvefor the arm. The directional control valvescontrol a boom cylinderand an arm cylinder, respectively, which are driven by pressure oil delivered from a main hydraulic pump. The hydraulic drive system is provided with a communication control unit for communicating a rod chamberof the boom cylinderand a bottom chamberof the arm cylinderwith each other when a stroke of the arm control devicehas become a predetermined amount S or greater.