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. 10, 2009
Filed:
Aug. 29, 2003
Tsutomu Udagawa, Ibaraki-ken, JP;
Kazuo Takiguchi, Ibaraki-ken, JP;
Masami Ochiai, Atsugi, JP;
Takashi Yagyuu, Ushiku, JP;
Yukihiko Sugiyama, Tsuchiura, JP;
Mitsuo Aihara, Ibaraki-ken, JP;
Tsutomu Udagawa, Ibaraki-ken, JP;
Kazuo Takiguchi, Ibaraki-ken, JP;
Masami Ochiai, Atsugi, JP;
Takashi Yagyuu, Ushiku, JP;
Yukihiko Sugiyama, Tsuchiura, JP;
Mitsuo Aihara, Ibaraki-ken, JP;
Hitachi Constuction Machinery Co., Ltd., Tokyo, JP;
Abstract
A hydraulic drive system comprises directional flow control valves (-) for selectively supplying a hydraulic fluid from a first hydraulic pump (), inflow control valves (-) disposed respectively in branch lines (A-C) branched from a supply line () for supplying a hydraulic fluid delivered from a second hydraulic pump () to rod pushing-side chambers (A,A,A,A) of hydraulic cylinders, a bypass flow control valve () disposed in a line () connecting the supply line () and a reservoir (), and a controller () for computing control variables corresponding to operation command signals from control levers () and controlling the inflow control valves (-) and the bypass flow control valve () in accordance with the computed control variables. Thus, the number of flow control valves and the length of piping required for their connection can be reduced, and a total pressure loss can be further reduced.