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:
Feb. 18, 2014
Filed:
Sep. 01, 2010
Yasuo Okano, Tsuchiura, JP;
Tsuyoshi Nakamura, Tsuchiura, JP;
Kouji Ishikawa, Tsuchiura, JP;
Kensuke Sato, Tsuchiura, JP;
Naoki Hagiwara, Tsuchiura, JP;
Yasuo Okano, Tsuchiura, JP;
Tsuyoshi Nakamura, Tsuchiura, JP;
Kouji Ishikawa, Tsuchiura, JP;
Kensuke Sato, Tsuchiura, JP;
Naoki Hagiwara, Tsuchiura, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
A hydraulic drive system realizes a jack-up operation without arrangement of a flow rate control valve and center bypass selector valve. The hydraulic drive system has first and second hydraulic pumps, first and second directional control valves for controlling boom cylinders, a third directional control valve for controlling the boom cylinders, and a third hydraulic pump for feeding pressure oil to the third directional control valve. A jack-up selector valve has a second select position where, when a pressure in bottom chambers of the boom cylinders is not higher than a predetermined pressure, feeding of pressure oil, which is delivered from the first hydraulic pump and second hydraulic pump, to rod chambers of the boom cylinders, is held permissible in association with switching of the second directional control valve and third directional control valve by a manipulation of a control device.