Elevator – industrial lift truck – or stationary lift for vehicle – Having specific load support drive-means or its control – Includes control for power source of drive-means
Patent
1995-02-17
1997-06-03
Nappi, Robert
Elevator, industrial lift truck, or stationary lift for vehicle
Having specific load support drive-means or its control
Includes control for power source of drive-means
187285, B66B 134
Patent
active
056356897
ABSTRACT:
A speed command signal is applied to a variable voltage, variable frequency controller for driving a three-phase induction motor that operates a positive displacement pump for supplying fluid to a hydraulic elevator drive cylinder. An accelerometer mounted on the car provides an acceleration-related feedback signal to the car speed command input of the motor control, thereby to dampen low frequency resonant modes of the elevator car. A sensor on a check valve between the hydraulic pump and the hydraulic cylinder provides a signal indicative of when the pump pressure is sufficient to support the car load, and the check valve begins to open; the signal is used to memorize ramped-up motor speed at that point, which equals the motor speed necessary to overcome pump leakage in order to support the car. That speed is added into the car speed command at the input of the motor controller to compensate for pump leakage. The acceleration damping of low frequency resonant modes of the elevator car may be utilized in roped elevator systems.
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Fargo Richard N.
Shepard Mark E.
Terry Harold
Nappi Robert
Otis Elevator Company
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