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:
Oct. 14, 2008
Filed:
Apr. 16, 2004
Kouji Ishikawa, Niihari-gun, JP;
Yusuke Kajita, Ushiku, JP;
Kazunori Nakamura, Tsuchiura, JP;
Genroku Sugiyama, Ryugasaki, JP;
Hideo Karasawa, Tsuchiura, JP;
Kouji Ishikawa, Niihari-gun, JP;
Yusuke Kajita, Ushiku, JP;
Kazunori Nakamura, Tsuchiura, JP;
Genroku Sugiyama, Ryugasaki, JP;
Hideo Karasawa, Tsuchiura, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
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 pump, a boom cylinderand an arm cylinder, a directional control valvefor a boom and a directional control valvefor an arm, and a boom control deviceand an arm control device. The hydraulic drive system is also provided with a pressure oil feed means for feeding pressure oil in a rod chamberof the boom cylinderto an upstream side of the directional control valvefor the arm when a bottom pressure of the arm cylinderhas increased to a high pressure equal to or higher than a predetermined pressure. This pressure oil feed means includes a flow combiner valvearranged in a reservoir linewhich can communicate to the rod chamberof the boom cylinder. When the bottom pressure of the arm cylinderis the predetermined pressure or higher, the flow combiner valvemaintains a communication line, which communicates the reservoir lineand the upstream side of the directional control valvefor the arm with each other, in a state that pressure oil can be fed to the upstream side of the directional control valvefor the arm.