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:
Apr. 06, 1999
Filed:
Dec. 26, 1996
Kouji Ishikawa, Tsuchiura, JP;
Toichi Hirata, Ushiku, JP;
Genroku Sugiyama, Ibariki, JP;
Tsukasa Toyooka, Ibariki, JP;
Youichi Kowatari, Ibariki, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
A pilot pressure sensor detects a pilot pressure from an arm operating unit and outputs a pilot pressure signal. A drive signal corresponding to the pilot pressure signal is then outputted from a controller to a solenoid-operated proportional valve. Through the solenoid-operated proportional valve, a pilot pressure is fed to an auxiliary selector valve so that an opening of said auxiliary selector valve becomes greater. Of pressure oil delivered from a first hydraulic pump, a flow rate of the pressure oil to be branched to a side of a by-pass circuit is hence increased. The pressure oil fed through the by-pass circuit passes through a merging directional control valve and is caused to merge with pressure oil fed from a second hydraulic pump. The thus-merged pressure oil is then fed to a hydraulic arm cylinder.