Elevator leveling control
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United States of America Patent
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Jun 14, 1988
Grant Date -
N/A
app pub date -
Jun 8, 1987
filing date -
Jun 8, 1987
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
An elevator leveling control for a system described in U.S. Pat. No. 3,056,469, includes a leveling cylinder and piston arrangement responding to less pressure than the main control cylinder and piston, so that during the operation of the main cylinder and piston, the leveling piston is always in its uppermost position, and a leveling cam, carried by the leveling cylinder-piston arrangement produces the minimum resistance in a rheostat electrically connected to the control field of a generator supplying power to the elevator motor. Through the travel of the elevator in high speed, the leveling rheostat is disconnected from the control field and the main rheostat is connected. At a given distance from the floor at which the elevator is to stop, a valve in the hydraulic system is energized to close, holding the main rheostat from dropping farther, the main rheostat is disconnected and the leveling rheostat is electrically connected to the generator control field. The leveling cam then acts to increase the resistance in the control field of the generator to bring the car smoothly and accurately to its rest position.
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