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:
Sep. 28, 1982
Hiroshi Watanabe, Ibaraki, JP;
Eiki Izumi, Ibaraki, JP;
Yukio Aoyagi, Ibaraki, JP;
Kazuo Honma, Ibaraki, JP;
Kichio Nakajima, Ibaraki, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A control system for a hydraulic circuit having at least first and second hydraulic pumps of the variable displacement type, a first hydraulic actuator arranged for hydraulic connection with the first pump through first valve to be driven thereby, and a second hydraulic actuator arranged for selective hydraulic connection with said first and second pumps through second and third valve respectively to be driven thereby. The order of priority for hydraulic connection is preset so that, when an operation signal for the second actuator is received while the first pump is inoperative, the first pump takes priority over the second pump, and when an operation signal for the first actuator is received while the first pump is in hydraulic connection with the second actuator, the first actuator takes priority over the second actuator and the second actuator is brought into hydraulic connection with the second pump, and the displacement volume of the first pump and switching of the second valve means are controlled such that, when the first pump which is, in hydraulic connection with the second actuator, is to be brought into hydraulic connection with the first actuator, the displacement volume of the first pump is returned to zero before changing of the hydraulic connection. The control system includes a first judging device for determining if the first pump is in hydraulic connection with the second actuator when the operation signal for the first actuator is received, and for generating a command for backing up reduction in the supply of hydraulic fluid into the second actuator simultaneously when the displacement volume of the first pump begins to returns to zero. When judged that the first pump is in hydraulic connection with the second actuator, a command signal switches a third valve to an open position in accordance with the backup command. A command for initiating a displacement of the second pump is generated in accordance with the backup command.