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. 02, 1991
Filed:
Jul. 12, 1989
Takashi Kanai, Kashiwa, JP;
Masami Ochiai, Chiyoda, JP;
Morio Oshina, Shimoinayoshi, JP;
Mitsuo Sonoda, Shimoinayoshi, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
A hydraulic drive system is equipped with an engine, a plurality of hydraulic pumps adapted to be driven by the engine and including a variable displacement hydraulic pump provided with a displacement varying mechanism, a hydraulic motor connected to the variable displacement pump, a hydraulic actuator for actuating the displacement varying mechanism of the variable displacement hydraulic pump, a working fluid feeding means for feeding the hydraulic actuator with a hydraulic fluid of a pressure according to the degree of control of an accelerator lever which is adapted to instruct a target revolution number of the engine, and a low-pressure circuit for allowing the hydraulic fluid to be discharged therethrough from the hydraulic actuator. The system is provided with a maximum pressure limiting means for guiding the hydraulic fluid of the hydraulic fluid feeding means to the low-pressure circuit depending on the degree of control of the accelerator lever, thereby limiting the maximum pressure of the hydraulic fluid and a means for selectively actuating the maximum pressure limiting means.