Elevator – industrial lift truck – or stationary lift for vehicle – Stationary lift for roadway vehicle or required component... – Having specific drive means for support
Patent
1991-10-15
1993-09-07
Stephan, Steven L.
Elevator, industrial lift truck, or stationary lift for vehicle
Stationary lift for roadway vehicle or required component...
Having specific drive means for support
187110, 187 292, B66B 104
Patent
active
052431541
ABSTRACT:
An apparatus for controlling a car of a hydraulic elevator by variable-speed-driving an electric motor directly coupled to a hydraulic pump so as to adjust the rate at which oil is supplied from the hydraulic pump to a hydraulic jack system, the apparatus having a speed controller for variable-speed-driving the electric motor, a first detector for detecting the speed of the car, a second detector for detecting the rotational speed of the electric motor, a third detector for detecting a pressure in the hydraulic jack system, a feedback circuit for returning a control signal for limiting vibration of the car as a feedback signal to the speed controller. The feedback circuit forms the control signal from a differential signal representing the difference between a car speed value converted from the rotational speed of the electric motor detected by the second detector and the car speed detected by the first detector and a pressure signal representing the pressure detected by the third detector.
REFERENCES:
patent: 3977497 (1976-08-01), McMurray
patent: 4593792 (1986-06-01), Yamamoto
patent: 4775031 (1988-10-01), Nakamura et al.
patent: 4967128 (1990-10-01), Sawai et al.
patent: 5099957 (1992-03-01), Eriksson
patent: 5131507 (1992-07-01), Watanabe
Kubota Takehiko
Tomisawa Masao
Dougherty Thomas M.
Mitsubishi Denki & Kabushiki Kaisha
Stephan Steven L.
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