Pumps – Condition responsive control of pump drive motor – By control of electric or magnetic drive motor
Reexamination Certificate
2005-03-08
2005-03-08
Freay, Charles G. (Department: 3746)
Pumps
Condition responsive control of pump drive motor
By control of electric or magnetic drive motor
C417S044100, C417S042000, C417S280000, C417S476000, C092S072000
Reexamination Certificate
active
06863502
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.
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International Search Report issued in connection with International Patent Application PCT/US01/12221, under date of mailing of Nov. 26, 2001.
Barani Moe K.
Bishop Michael B.
Flanary Ron
Knuth Bruce E.
Mentink Laurentius A. G.
Actuant Corporation
Freay Charles G.
Quarles & Brady LLP
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