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:
Dec. 31, 1985
Filed:
Mar. 02, 1982
Nobuya Okabe, Tsuchiura, JP;
Fumiki Nakagiri, Tsuchiura, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A hydraulic drive system for civil engineering and construction machinery in which at least first and second hydraulic circuits having at least first and second hydraulic pumps, respectively, are provided for driving a plurality of actuators such as left and right travelling actuators, a boom actuator and an arm actuator. The first circuit includes a first travelling directional control valve for one of the left and right travelling actuators located downstream of a first boom directional control valve for the boom actuator and a first arm directional control valve for the arm actuator that the latter to receive a hydraulic fluid supply from the first pump by taking priority over the first travelling valve. The second circuit includes a second travelling directional control valve for the other of the left and right travelling actuators upstream of a second boom directional control valve for the boom actuator and/or a second arm directional control valve for the arm actuator so as to be able to receive hydraulic fluid supply from the second pump by taking priority over the second boom and/or arm valves. A bypass circuit extends between the second pump and the one travelling actuator whereby a hydraulic fluid supply from the second pump can be received by the first travelling valve.