Elevator Hoistway Access Safety Control
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Solution Overview
Problem
Elevator mechanics face risks during maintenance due to unexpected movement of the elevator car, necessitating a solution to prevent car movement during maintenance operations.
Innovation Solution
An elevator system that includes a method to determine the presence of the elevator car at a specified landing and a hoistway door lock mechanism, which engages an access detection mode to shut down the elevator drive if the car is not present, preventing movement by ensuring the door lock mechanism is engaged for a predetermined duration, typically greater than 4 seconds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the elevator door lock mechanism is engaged for a predetermined duration to ensure safety, then the safety of maintenance personnel is improved, but the time required to perform maintenance operations increases
Solution Approach 1:
The system performs preliminary actions by detecting door lock engagement and verifying car position before allowing maintenance access. The elevator drive is prevented from receiving movement commands until the door lock mechanism has been engaged for the predetermined duration, ensuring safety checks are completed in advance of maintenance operations.
2Reliability
If the elevator drive is prevented from receiving movement commands during access detection mode, then unexpected car movement is prevented, but the productivity of the elevator system decreases
Solution Approach 1:
The system dynamically adjusts its operational state by entering access detection mode when the door lock mechanism is engaged, preventing movement commands during this period. Once the predetermined duration elapses and safety is confirmed, the system transitions back to normal operation, allowing movement commands to be received again, thus balancing safety with productivity.
3Reliability
If the system monitors door lock mechanism engagement duration and car position continuously, then safety monitoring is improved, but the device complexity increases
Solution Approach 1:
The elevator drive receives feedback signals from the door lock mechanism indicating when it has been engaged, and from position switches indicating car position. The controller continuously monitors these feedback signals to determine whether to enter access detection mode and to track the duration of door lock engagement, enabling automated safety monitoring without requiring complex additional hardware.
Data Source
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AI summary
A method of controlling movement of an elevator car including determining whether the elevator car is present at a specified landing, determining a door lock state, and entering an access detection mode based in part on whether the elevator car is present at the specified landing and the door lock state.