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. 25, 2012
Filed:
Apr. 22, 2009
Toshihiro Abe, Osaka, JP;
Yusuke Kajita, Ushiku, JP;
Kazunori Nakamura, Tsuchiura, JP;
Kouji Ishikawa, Niihari-gun, JP;
Hideo Karasawa, Tsuchiura, JP;
Toshihiro Abe, Osaka, JP;
Yusuke Kajita, Ushiku, JP;
Kazunori Nakamura, Tsuchiura, JP;
Kouji Ishikawa, Niihari-gun, JP;
Hideo Karasawa, Tsuchiura, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
A hydraulic circuit for a hydraulic working machine is composed of a main pump, a boom cylinderarranged for extension or contraction by pressure oil from the main pump, a directional control valvefor controlling flows of pressure oil to be fed from the main pumpto a bottom chamberand rod chamberof the boom cylinder, a control unitfor performing a change-over control of the directional control valve, a pilot pump, a jack-up selector valvefor controlling a flow of pressure oil delivered from the pilot pump, a flow control valveconnected on an upstream side of the directional control valveto a meter-in port of the directional control valvesuch that the flow control valvecan be changed over by the jack-up selector valve, and a center bypass selector valveconnected on a downstream side of the directional control valveto a center bypass port of the directional control valvesuch that the center bypass selector valvecan be changed over by the jack-up selector valve. The hydraulic circuit performs a change-over of the jack-up selector valvein accordance with a bottom pressure on the boom cylinder