Elevator Brake Failure Detection via Torque Imbalance
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Solution Overview
Problem
Current elevator systems face challenges in ensuring safety against free fall due to potential brake failures, despite existing redundancies, as new building codes require additional safeguards against such hazards.
Innovation Solution
The elevator system includes methods to recognize brake failures by temporarily hovering the car to allow evacuation, controllably moving it based on weight and torque imbalances, and confirming brake functionality through tests, allowing safe placement back in service or controlled descent if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundancy is built into electro-mechanical brakes to prevent free fall, then safety against free fall is improved, but device complexity increases
Solution Approach 1:
The system performs preliminary brake verification by temporarily hovering the elevator car after brake activation to confirm proper brake engagement before allowing normal operation to continue. This preliminary check prevents undetected brake failures from causing free fall incidents.
Solution Approach 2:
The system implements feedback by monitoring whether the elevator car remains stationary after brake activation. If the car moves when it should be held stationary, the system detects brake failure and triggers appropriate safety responses, including preventing door opening and alerting maintenance personnel.
2Reliability
If the elevator car is temporarily hovered in place to allow evacuation, then passenger safety is improved, but loss of time increases
Solution Approach 1:
The system performs preliminary verification of brake failure by hovering the car temporarily to confirm the brake cannot hold the car stationary. Only after confirming actual brake failure does the system initiate evacuation procedures, avoiding unnecessary evacuations for minor issues while ensuring safety when truly needed.
Solution Approach 2:
The system automatically manages the hover and evacuation process without requiring manual intervention. The controller autonomously determines when brake failure is confirmed, initiates the hover sequence, and manages evacuation, reducing both time loss and human error.
3Measurement precision
If the elevator car is controllably moved to top or bottom of hoistway, then brake failure confirmation is improved, but device complexity increases
Solution Approach 1:
The system utilizes the existing counterweight mechanism to controllably move the elevator car to the top or bottom of the hoistway for brake verification. By leveraging the counterweight system already present in the elevator, no additional complex positioning equipment is needed, maintaining simplicity while achieving precise verification.
Solution Approach 2:
The elevator car's own drive system and counterweight mechanism perform the verification movement autonomously under controller direction. The system uses its existing components to execute the verification sequence, eliminating the need for external testing equipment or complex additional mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances safety by ensuring brakes function correctly, meeting new building code requirements without the need for additional hardware, thus being cost-effective and ensuring passenger safety in case of brake failures.
Implementation Method 1
torque applied to the elevator car for driving the elevator car upwardly or downwardly
Implementation Method 2
electro-mechanical brakes
Implementation Method 3
hydraulic-mechanical brakes
Implementation Method 4
relative weights of the elevator car and a counter-weight
Data Source
AI summary
A method of operating an elevator system is provided and includes recognizing that brakes of an elevator car fail to drop upon brake power being removed, temporarily hovering the elevator car in place to allow the elevator car to be emptied, controllably moving the elevator car in a direction of imbalance, which is defined in terms of relative weights of the elevator car and a counter-weight and torque applied to the elevator car for driving the elevator car upwardly or downwardly, to either a top or a bottom of a hoistway and confirming that the brakes are failing to drop or provide sufficient holding torque.