Safety Switch Circuit Redundancy for Escalator Drive Control
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Solution Overview
Problem
Current safety systems for escalators and passenger conveyance systems require extensive wiring and lack a cost-effective mechanism to determine the operability of safety system detectors and their circuitry, necessitating a more efficient solution.
Innovation Solution
A safety circuit with controllable switches and a controller that monitors switch output signals, utilizing a redundant interrupt switch to ensure the drive system is safely disabled upon detection of malfunctions, reducing the need for multiple wires and enhancing reliability through series connections and redundant components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional safety systems with multiple switches and extensive wiring are used, then safety coverage is comprehensive, but material and labor costs increase significantly
Solution Approach 1:
The patent combines multiple safety switch functions into a single integrated circuit board. The circuit board receives signals from multiple functional units (step detection, handrail speed detection, foreign object detection) and processes them centrally, eliminating the need for separate wiring for each switch while maintaining comprehensive safety coverage.
Solution Approach 2:
The interrupt circuit is designed to handle multiple types of safety signals through a single unified interface. The circuit board can process different functional unit signals (step presence, handrail speed, foreign objects) through the same interrupt mechanism, making the system multi-functional while reducing overall complexity.
2Reliability
If redundant safety components are added to ensure safe shutdown, then system reliability improves, but device complexity and cost increase
Solution Approach 1:
The circuit board continuously monitors signals from all functional units before initiating shutdown. By detecting malfunctions in advance and preparing the interrupt signal beforehand, the system ensures safe shutdown without needing multiple redundant physical switches, as the monitoring and decision-making occurs proactively through the intelligent circuit.
Solution Approach 2:
The circuit board acts as an intermediary between multiple functional units and the drive system. It consolidates signals from various sensors and functional units, processes them centrally, and generates a single interrupt signal to the drive system, eliminating the need for multiple direct connections while maintaining reliable shutdown capability.
3Reliability
If extensive wiring is used to connect multiple switches and safety components, then safety signal transmission is reliable, but installation time and labor costs increase
Solution Approach 1:
Multiple signal transmission paths are merged into a single circuit board interface. Instead of running separate wires from each functional unit to the drive system, all signals are consolidated at the circuit board level, dramatically reducing installation time while maintaining signal integrity through centralized processing.
Data Source
AI summary
An apparatus and method of disabling a drive system of a passenger conveying system is provided. The passenger conveying system is monitored with switches each arranged to detect a respective malfunction of the passenger conveying system. A shutdown signal is produced by a respective one of the switches detecting the respective malfunction and is coupled to a corresponding shutdown contact and to a controller. The corresponding shutdown contact operates to interrupt a drive enabling signal of the drive system in response to receipt of the shutdown signal. The controller monitors the shutdown signals from the switches and the drive enabling signal. The controller sends a signal to open a redundant contact to interrupt the drive enabling signal if the shutdown signal is detected and the drive system remains enabled.