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:
Mar. 03, 2026
Filed:
Mar. 18, 2021
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Hiroaki Amano, Tsukuba, JP;
Kento Kumagai, Ami-machi, JP;
Hiroto Oohira, Kasumigaura, JP;
Shinji Nishikawa, Kasumigaura, JP;
Akihiro Narazaki, Tsukuba, JP;
Katsuaki Kodaka, Tsukuba, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
A work machine includes: a main circuit that supplies a working fluid from a pump to an actuator; a pilot circuit that introduces part of the working fluid from the pump, to a pilot pressure receiving section of a control valve; a bleed-off passage that connects the pump and a tank. The pilot circuit is provided with: a first pressure reducing valve that generates a pilot primary pressure; and second and third pressure reducing valves that generate a pilot secondary pressure to be applied to the control valve and a bleed-off valve. A moving area of a spool of the bleed-off valve has a first moving area where an opening area of a restrictor changes stepwise, and a second moving area where the opening area of the restrictor changes continuously. A controller controls the third pressure reducing valve such that the spool is positioned in the first moving area at the time of non-operation of the actuator, and the spool is positioned in the second moving area at the time of operation of the actuator. The restrictor of the bleed-off valve has a restricting hole that gives a resistance to the working fluid passing therethrough in a case the spool is positioned in the first moving area.