Safety Interface Unit for Conveying Systems
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Solution Overview
Problem
The complexity of electronic safety circuits in conveying systems, such as elevators, increases the risk of connection errors and wiring issues, necessitating simpler and more reliable diagnostics to maintain safety integrity levels like SIL 2 or SIL 3 without duplicating components.
Innovation Solution
An interface unit for the safety circuit that disconnects and tests the signal determining the system's safety, allowing for monitoring without affecting the signal, and includes duplicated signal paths for redundancy, enabling central and simultaneous condition assessment, and communication of fault information via a bus for improved diagnostics and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If components and data transfer channels are duplicated to achieve SIL 3 safety level, then safety integrity level is improved, but device complexity and amount of components increase
Solution Approach 1:
The patent uses functional copying through software-based redundancy instead of physical component duplication. The interface unit implements duplicate signal processing paths and monitoring functions in software, achieving SIL 3 safety integrity without requiring duplicate physical sensors, cables, or processing units. This allows the system to meet safety requirements while reducing hardware complexity.
2Measurement precision
If more sensors and data bus connections are added to monitor safety-critical properties, then measurement capability is improved, but device complexity and wiring complexity increase
Solution Approach 1:
The interface unit is designed as a multi-functional device that can monitor multiple safety-critical properties through a single data bus connection. It implements universal monitoring capabilities for various sensors (door sensors, overload sensors, speed sensors) without requiring separate dedicated wiring for each sensor type, thereby reducing wiring complexity while maintaining comprehensive monitoring capability.
Solution Approach 2:
The patent combines multiple monitoring functions and sensor interfaces into a single interface unit that communicates through one data bus. This merging of functions reduces the overall wiring complexity compared to having separate monitoring circuits for each sensor, while still providing comprehensive safety monitoring through centralized processing.
3Productivity
If testing is performed while safety signal is active, then system operation is maintained, but testing accuracy is affected by the safety signal
Solution Approach 1:
The interface unit performs preliminary testing of signal paths and components before actual safety-critical operation. It includes self-test functions that activate during system initialization or maintenance modes, allowing comprehensive testing of monitoring paths without interference from active safety signals. This ensures testing accuracy while maintaining continuous safety monitoring during normal operation.
Data Source
Figure 1
Figure 2
AI summary
The invention relates to an interface unit, (1), a conveying system and a method. The interface unit (1) comprises an input circuit (2) for the signal (3a, 3b) determining the safety of the conveying system. The interface unit (1) further comprises means (4a, 4b, 5a, 5b, 6) for testing the operating condition of the input circuit (2).