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:
Sep. 24, 2002
Filed:
Dec. 04, 2001
Kinya Takahashi, Tsuchiura, JP;
Yoshizumi Nishimura, Tsuchiura, JP;
Yusaku Nozawa, Higashiibaraki-gun, JP;
Mitsuhisa Tougasaki, Niihari-gun, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
To permit forcedly stopping combining flows of pressure fluid from two hydraulic pumps when a load pressure on a combined-flow-driven actuator in which the flows of pressure fluid are combined together exceeds a predetermined pressure and hence to permit driving the combined-flow-driven actuator with the pressure fluid from only one of the hydraulic pumps, a hydraulic drive system is provided with a flow-combining valve connected to a directional control valve in a first group of directional control valves via a center bypass passage , a flow-combining circuit communicating the flow-combining valve and a supply port of a flow-combining directional control valve with each other, and a combined-flow-driven actuator controlled by the flow-combining directional control valve and performs overall power control such that a total value of input torques to the two hydraulic pumps does not exceed an output torque from an engine The hydraulic drive system is provided with a canceling valve to cancel the combination of flows by the flow-combining valve when a load pressure on the combined-flow-driven actuator becomes higher than a predetermined pressure.