Brake torque monitoring and health assessment

Patent metadata

Field	Value
Publication number	US-9791009-B2
Application number	US-201114355128-A
Country	US
Kind code	B2
Filing date	Nov 2, 2011
Priority date	Nov 2, 2011
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

A method for monitoring brake torque of an elevator having a motor is provided. The method may engage an elevator brake for a predefined duration, determine a displacement of an output shaft of the motor during the predefined duration, and generate an alert if the displacement exceeds a predefined threshold.

First claim

What is claimed is:

1. A method for monitoring brake torque of an elevator having a motor, the method comprising:
engaging an elevator brake;
determining a minimum motor current required to drive an output shaft of the motor through the brake while engaging the brake;
computing a baseline brake torque based at least partially on the minimum motor current;
periodically monitoring the brake torque for any significant decrease as compared with the baseline brake torque; and
generating an alert if a subsequently computed brake torque is determined to be less than a predefined fraction of the baseline brake torque.

2. The method of claim 1 , wherein the elevator brake is a machine brake.

3. The method of claim 1 , wherein an elevator car of the elevator is raised to an uppermost landing prior to engaging the brake.

4. A method for monitoring at least one brake of an elevator having a motor, the method comprising:
during a brake calibration, engaging the brake and determining a minimum motor current required to drive an output shaft of the motor through the engaged brake;
during a brake test, applying a test motor current to the motor while engaging the brake, the test motor current being a fraction of the minimum motor current;
determining a displacement of the output shaft; and
generating an alert if the displacement exceeds a predefined threshold.

5. The method of claim 4 , wherein the elevator includes a machine brake and an emergency brake, the brake calibration and the brake test being performed for each of the machine brake and the emergency brake of the elevator.

6. The method of claim 4 , wherein an elevator car of the elevator is raised to an uppermost landing prior to performing the brake calibration and the brake test.

7. The method of claim 4 , wherein the brake test is performed at predefined intervals.

8. The method of claim 4 further comprising:
computing a baseline brake torque based at least partially on the minimum motor current;
periodically monitoring the brake torque for any significant decrease as compared with the baseline brake torque; and
generating an alert if a subsequently computed brake torque is determined to be less than a predefined fraction of the baseline brake torque.

9. A brake monitoring system for an elevator, the brake monitoring system comprising:
a motor having an output shaft;
an encoder configured to detect displacement of the output shaft;
at least one brake configured to selectively engage the output shaft;
a controller in communication with each of the motor, the encoder, and the brake, the controller configured to engage the brake and determine a minimum motor current required to drive the output shaft through the engaged brake during a brake calibration, apply a test motor current being a fraction of the minimum motor current to the motor during a brake test, monitor the encoder for any displacement of the output shaft, and generate an alert if the displacement exceeds a predefined threshold.

10. The system of claim 9 , wherein the elevator includes a machine brake and an emergency brake, the controller being configured to perform the brake calibration and the brake test for each of the machine brake and the emergency brake.

11. A brake monitoring system for an elevator, comprising:
a motor having an output shaft;
an encoder configured to detect displacement of the output shaft;
at least one brake configured to selectively engage the output shaft;
a controller in communication with each of the motor, the encoder, and the brake, the controller configured to engage the brake and determine a minimum motor current required to drive the output shaft through the engaged brake during a brake calibration, apply a test motor current being a fraction of the minimum motor current to the motor during a brake test, monitor the encoder for any displacement of the output shaft, and generate an alert if the displacement exceeds a predefined threshold;
wherein the controller computes a baseline brake torque based at least partially on the minimum motor current, and periodically monitors the brake torque for any significant decrease as compared with the baseline brake torque.

12. The system of claim 11 , wherein the controller generates an alert if a subsequently computed brake torque is determined to be less than a predefined fraction of the baseline brake torque.

13. The system of claim 11 , wherein the controller periodically communicates the baseline brake torque and subsequently computed brake torques to a remote monitoring facility.

14. The system of claim 11 , wherein the controller computes the baseline brake torque further based on parameters associated with one or more of duty load, counterweight, tensile members' traction sheave and the motor.

15. The system of claim 9 , wherein the controller repeats each brake test two or more times in order to confirm a passed or a failed brake test.

16. The system of claim 9 , wherein the controller resumes normal operation when no alerts are generated and ceases normal operation when at least one alert is generated.

17. The system of claim 9 , wherein the controller generates the alert using one or more of an audible alarm, a visual alarm, and an electronic error message.

Assignees

• Hubbard James L
• Garfinkel Michael
• Illan Juan Antonio
• Shepherd Robert D
• Otis Elevator Co

Inventors

• Hubbard James L
• Garfinkel Michael
• Illan Juan Antonio
• Shepherd Robert D

Classifications

• F16D2066/005

  Force, torque, stress or strain · CPC title

• B60T7/18

  operated by wayside apparatus · CPC title

• B66B5/0037 Primary

  Performance analysers · CPC title

• G01L5/28

  for testing brakes · CPC title

• B66B5/00

  Applications of checking, fault-correcting, or safety devices in elevators · CPC title