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:
Mar. 08, 2005
Filed:
Apr. 13, 2001
Michael B. Bishop, Madison, WI (US);
Roger R. Pili, Madison, WI (US);
Bruce E. Knuth, Marshall, WI (US);
Moe K. Barani, Radford, VA (US);
Ron Flanary, Blacksburg, VA (US);
Laurentius A. G. Mentink, Haaksbergen, NL;
George R. Steber, Mequon, WI (US);
Martin Piedl, Blacksburg, VA (US);
Michael B. Bishop, Madison, WI (US);
Roger R. Pili, Madison, WI (US);
Bruce E. Knuth, Marshall, WI (US);
Moe K. Barani, Radford, VA (US);
Ron Flanary, Blacksburg, VA (US);
Laurentius A. G. Mentink, Haaksbergen, NL;
George R. Steber, Mequon, WI (US);
Martin Piedl, Blacksburg, VA (US);
Actuant Corporation, Milwaukee, WI (US);
Abstract
The invention provides a variable speed hydraulic pump designed to operate at a maximum horsepower throughout its pressure range by adjusting motor speed according to motor load parameters. In particular, the variable speed hydraulic pump includes a hydraulic pump unit coupled to a variable speed electric motor by a drive unit and to a hydraulic fluid tank for pressurizing and pumping hydraulic fluid when operated by the motor. A motor controller is electrically connected to the motor to supply drive signals to the motor based on electrical characteristics of the drive signals which are dependent on the load exerted on the motor. Suction from the load is provided by both the main pump and a bidirectional supercharging pump by reversing the direction of the motor and shifting a 4/3 valve to connect the main pump inlet to the load and its outlet to tank. In addition, the controller reduces the motor speed at the maximum rated pressure to just maintain the pressure, to reduce the amount of fluid pumped through the maximum pressure relief valve.