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:
Oct. 31, 2006
Filed:
Mar. 15, 2004
Tsuyoshi Nakamura, Ibaraki-ken, JP;
Genroku Sugiyama, Ryuugasaki, JP;
Tsukasa Toyooka, Ibaraki-ken, JP;
Kouji Ishikawa, Ibaraki-ken, JP;
Tsuyoshi Nakamura, Ibaraki-ken, JP;
Genroku Sugiyama, Ryuugasaki, JP;
Tsukasa Toyooka, Ibaraki-ken, JP;
Kouji Ishikawa, Ibaraki-ken, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
A joining directional control valveis disposed to supply, to an arm cylindernot only a hydraulic fluid delivered from a first hydraulic pumpbut also a hydraulic fluid delivered from a second hydraulic pumpwhen an arm directional control valveis driven. Respective delivery pressures of the hydraulic pumpsare detected by pressure sensorsand the opening area of a recovery control valveis controlled depending on a lower one of the detected pressures from the pressure sensorssuch that, even in the combined operation of the arm cylinderand another actuatorthe hydraulic fluid can be recovered for return to the arm cylinderwhen the load pressure of the arm cylinderis low. Thus, by supplying the hydraulic fluids from the two hydraulic pumps to the particular actuator for which the hydraulic fluid is to be recovered, a recovery flow rate is ensured when the load of the particular actuator is low in the combined operation.