Automated Extreme Limit Switch Testing for Elevator Safety
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Solution Overview
Problem
Existing elevator systems face challenges in testing and ensuring the correct operation of extreme limit switches, which are crucial for safety, due to difficulties in manual positioning and the need for precise measurement of the operating point, often requiring manual intervention and multiple attempts, and can lead to incorrect positioning or failure in stopping the elevator car at the extreme limit, potentially causing collisions.
Innovation Solution
An automated testing apparatus that uses a wireless connection between a sensor and actuator to verify the correct operation of the extreme limit switch, allowing for automatic measurement of the operating point and preventing normal operation if the switch does not function correctly, ensuring the elevator system is safely removed from service and only returned to service after successful testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual positioning of the elevator at the extreme limit switch is performed using the emergency drive apparatus, then the operating point of the extreme limit switch can be tested, but the testing process becomes difficult and time-consuming due to lack of direct visual contact and narrow stopping area requiring multiple attempts
Solution Approach 1:
The system performs self-testing of the extreme limit switch by automatically driving the elevator car to the terminal floor and measuring the operating point distance, eliminating the need for manual positioning by servicemen. The control unit automatically controls the drive apparatus to position the elevator and the measuring device automatically measures the distance.
Solution Approach 2:
The patent replaces manual mechanical positioning with an automated control system that uses the existing drive apparatus under control unit supervision. The measuring function is also automated using a measuring device that automatically determines the distance between the elevator car and the extreme limit switch operating point.
2Reliability
If the operating point of the extreme limit switch is positioned too close to the terminal floor, then the elevator stops correctly, but the elevator car remains jammed at the terminal floor requiring serviceman intervention
Solution Approach 1:
The control unit receives the measured distance value from the measuring device and compares it against predetermined acceptable ranges. Based on this feedback, the control unit automatically determines whether the operating point is correctly positioned or if adjustment is needed, and can prevent elevator operation until the correct positioning is achieved.
Solution Approach 2:
The system performs the measurement and evaluation of the operating point distance before allowing normal elevator operation to commence. This preliminary check ensures that the extreme limit switch is correctly positioned to prevent both jamming and failure to stop, eliminating the need for serviceman intervention during normal operation.
3Adaptability or versatility
If the operating point of the extreme limit switch is positioned too far from the terminal floor, then the elevator can operate freely, but the extreme limit switch may not function correctly after rope stretching causing potential collision
Solution Approach 1:
The control unit uses feedback from the measuring device to determine whether the measured distance falls within the acceptable range that ensures both operational flexibility and safety. If the distance is too large, the system can alert operators or prevent operation until corrected, ensuring the extreme limit switch will function reliably even after rope stretching.
Solution Approach 2:
The system performs a preliminary measurement and verification of the operating point distance before allowing the elevator to enter service. This ensures that the extreme limit switch is positioned correctly to maintain safety functionality after normal operational variations such as rope stretching, preventing potential collisions.
4Reliability
If conventional manual testing methods are used for extreme limit switches, then safety devices can be tested, but the process requires serviceman visits and multiple attempts increasing time and cost
Solution Approach 1:
The elevator system performs self-testing of its extreme limit switches as part of normal operation or maintenance routines, eliminating the need for external serviceman visits. The automated measurement and evaluation process can be completed in a single operation, significantly reducing the time and cost associated with safety device testing.
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
The invention relates to a safety arrangement and also a testing apparatus (2, 3, 9, 45) for testing the operation of an extreme limit switch (5, 45) in a conveying system, which can be removed from service on the basis of a signal to be received from the extreme limit switch (5, 45). The testing apparatus (2, 3, 9, 45) comprises a microprocessor and a memory, in which is recorded a testing program to be run with the microprocessor, which testing program comprises instructions for preventing removal of the conveying system from service occurring on the basis of a signal from an extreme limit switch (5, 45) as well as for testing the operation of the extreme limit switch (5, 45) when removal of the conveying system from service has been prevented.