Safety Interlock Switch with Dual Anti-Tamper Coding
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Solution Overview
Problem
Actuator operated interlock switches are vulnerable to tampering, allowing personnel to bypass safety features by inserting foreign objects, leading to potential unsafe machine access without proper shutdown.
Innovation Solution
A safety interlock switch incorporating a dual-coded system, combining a coded cam mechanism with a non-contact RFID sensor, requiring both codes to be correctly applied in a specific sequence to enable power, with a microprocessor monitoring contact sequences and detecting faults to prevent activation if conditions are not met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single coded mechanical interlock is used, then tamper resistance is improved, but reliability against determined attacks deteriorates
Solution Approach 1:
The patent combines two different coded interlock technologies (mechanical cam code and electronic RFID code) into a single integrated safety switch system. Both codes must be satisfied simultaneously for the safety output to enable, creating a layered security approach where the mechanical cam provides physical coding and the RFID sensor provides electronic coding, thereby significantly improving tamper resistance without requiring an excessively complex single system
2Ease of manufacture
If mechanical coding is used, then ease of manufacture is improved, but detectability of failure deteriorates
Solution Approach 1:
The patent introduces an electronic RFID sensor as an intermediary verification layer that non-contactly reads the mechanical cam code and independently verifies it against the RFID code. This intermediary electronic system provides easy manufacturing through standard RFID components while simultaneously improving failure detection, as the electronic verification can identify when the mechanical cam is in an incorrect or tampered position without requiring complex mechanical sensors
3Reliability
If dual coded interlocking is implemented, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent segments the dual-coded interlock system into distinct functional modules: the mechanical cam mechanism with its coded slots, the RFID sensor for electronic coding, and the control circuitry that processes both codes independently. This segmentation allows each component to be optimized and manufactured separately, then integrated together, reducing overall system complexity while maintaining the reliability benefits of dual verification
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
Enhances tamper resistance and detects mechanical failures, ensuring the machine remains in a safe state by requiring both coded technologies to concur for operation, preventing unauthorized power-up and ensuring safety contacts are correctly engaged.
Implementation Method 1
The other of the coded technologies may be electronic and may include a non-contact coded RFID sensor. A coded RFID actuator of the sensor may be mounted on the coded tongue
Data Source
AI summary
A safety interlock switch with coded interlocking to provide tamper resistance, the coded interlocking having two differently coded technologies 8,10; 16,18. In a preferred embodiment one technology is mechanical in the form of a coded-cam system operated by a coded-tongue 8, the other is electronic comprising a non-contact coded RFID sensor 16,18, and wherein the switch is only enabled when the two different codes have been correctly applied.