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:
Aug. 10, 2004
Filed:
Aug. 30, 2002
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
A differential pressure between a delivery pressure of a fixed displacement hydraulic pump and a maximum load pressure among a plurality of actuators to is maintained at a target differential pressure by an unloading valve . A setting pressure of the unloading valve is changed depending on an engine revolution speed by introducing a differential pressure &Dgr;Pp across a throttle , which is disposed in a delivery line of a fixed pump , to a pressure bearing sector of the unloading valve. With such an arrangement, in a hydraulic drive system including an LS system, it is possible to ensure fine operability based on setting of the engine revolution speed, to perform flow rate control at a good response, and to realize superior operability.