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. 30, 2014
Filed:
Feb. 09, 2011
Naoki Hagiwara, Tsuchiura, JP;
Yasuo Okano, Tsuchiura, JP;
Tsuyoshi Nakamura, Tsuchiura, JP;
Kouji Ishikawa, Tsuchiura, JP;
Kazunori Nakamura, Tsuchiura, JP;
Naoki Hagiwara, Tsuchiura, JP;
Yasuo Okano, Tsuchiura, JP;
Tsuyoshi Nakamura, Tsuchiura, JP;
Kouji Ishikawa, Tsuchiura, JP;
Kazunori Nakamura, Tsuchiura, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
The operability when performing a combined arm-crowd and bucket operation can be improved. A hydraulic drive device for a hydraulic excavator includes: a bucket directional control valve and a second arm directional control valve, which are connected in parallel tandem with a first hydraulic pump; a first arm directional control valve that is connected to a second hydraulic pump; and a flow rate restriction device that restricts the flow rate of pressure oil supplied to the second arm directional control valve, during crowd operation of a bucket. This flow rate restriction device includes a variable throttle whose opening is controlled so as to become smaller as a bucket operating device is operated to the crowd side, the variable throttle being provided in a bypass path connecting to the supply port of the second arm directional control valve.