Elevator Tension Ratio Detection for Stuck Car Safety
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Solution Overview
Problem
Elevator systems face challenges in detecting stuck cars or counterweights without compromising performance or increasing costs, as existing solutions like using friction modifiers or adding weight to meet safety codes' traction requirements can adversely affect other parameters.
Innovation Solution
The method involves sensing tensions in car and counterweight suspension members, determining a traction ratio, and stopping the elevator system if the ratio exceeds or falls below predetermined limits, allowing for lightweight cars and eliminating the need for excessive traction limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If friction modifiers are used in the suspension member to meet loss of traction requirements, then safety is improved, but other performance parameters of the suspension member are adversely affected
Solution Approach 1:
The patent replaces the mechanical approach of using friction modifiers in the suspension member with an electrical/electronic detection system. Load sensors (electrical devices) monitor tension forces on both sides of the suspension member, and a controller processes this data to detect stuck conditions. This substitution eliminates the need for friction modifiers that compromised suspension member performance while maintaining safety through electronic monitoring.
2Reliability
If weight is added to the car to pass the loss of traction test, then safety is improved, but cost and performance are limited
Solution Approach 1:
The patent replaces the mechanical solution of adding weight to the car with an electronic detection system. Instead of increasing car mass to prevent stuck conditions, the system uses load sensors to monitor tension ratios and electronically detects when the car or counterweight becomes stuck. This eliminates the need for additional weight while maintaining safety through real-time monitoring.
Solution Approach 2:
The patent introduces load sensors as intermediary devices between the mechanical suspension system and the control system. These sensors measure tension forces and provide data to the controller, which uses this information to detect stuck conditions. This intermediary measurement approach allows safety monitoring without physically modifying the car or suspension member with additional weight or friction modifiers.
3Measurement precision
If load sensors are installed on both sides of the suspension member to detect stuck conditions, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the monitoring function by placing separate load sensors on both sides of the suspension member (car side and counterweight side). This segmentation allows independent measurement of tension forces on each side, enabling the system to detect stuck conditions by comparing the tension ratio between the two sides. The segmentation of measurement points improves detection accuracy while the modular sensor design keeps individual components simple.
Solution Approach 2:
The patent implements a feedback system where load sensors continuously monitor tension forces and provide data to a controller. The controller processes this feedback information, calculates tension ratios, and compares them against predetermined thresholds to detect stuck conditions. This closed-loop feedback mechanism improves detection accuracy by continuously monitoring system state and automatically identifying anomalies without requiring complex mechanical modifications.
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 effectively detects stuck conditions without adding cost or limiting performance, enabling safe operation and reducing the need for costly modifications or additional weight, thus enhancing safety and efficiency.
Implementation Method 1
sensing a car side suspension member tension, T1; sensing a counterweight side suspension member tension, T2
Data Source
AI summary
A method of detecting a stuck car or a stuck counterweight in an elevator system having a machine for imparting motion to the car and counterweight includes sensing a car side suspension member tension, T1; sensing a counterweight side suspension member tension, T2; determining a traction ratio in response to a relationship between T1 and T2; and determining a stuck car or a stuck counterweight if the traction ratio violates a limit.