Patent ID: 7350883
Filing Date: 2008-04-01
Classification: B66B

Abstract:
1. A method of checking for excessive drag in an elevator system having a car moveable in a hoistway, characterized by: initially, establishing baseline currents while the elevator car is operating properly with no drag, by: (a) with the car either empty or carrying a load which is a small fraction of rated load, recording ( (b) with the car carrying a load which is either 100% or a high fraction of rated load, recording ( then, during normal operation of the elevator car over time, during at least some normal runs of the elevator car, comparing the motor current used to operate the car with motor current predicted to be required to move the car under its present load, direction and position in the hoistway, by: (c) when the doors are closed ( (d) recording ( (e) if said actual motor current exceeds a predicted motor current by a tolerance value (