Dual-Contact Key Switch for Safety-Critical Machine Control
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Solution Overview
Problem
Existing machine control panels require additional I/O units and switches to comply with safety standards, leading to increased complexity and variability in operability.
Innovation Solution
A machine control panel design featuring key switches with dual contacts connected to independent communication circuits and transmission lines, allowing signals to be categorized into two systems without the need for additional I/O units or switches, ensuring compliance with safety standards while maintaining operability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional I/O units and switches are provided to comply with safety standards, then safety compliance is improved, but device complexity increases
Solution Approach 1:
The patent combines the safety-related signal transmission function into the existing communication circuits of the I/O units, merging the safety system with the control system. The key switches are connected to both communication circuits within the same I/O unit, eliminating the need for separate safety I/O units while maintaining safety compliance through dual-system signal categorization.
Solution Approach 2:
The communication circuits in the I/O units are designed to handle both control signals and safety-related signals universally. The same communication infrastructure serves multiple functions: transmitting normal control commands and transmitting safety-critical signals, thereby reducing the need for dedicated safety hardware while ensuring safety standard compliance.
2Reliability
If additional I/O units and switches are provided to comply with safety standards, then safety compliance is improved, but the number of components increases
Solution Approach 1:
The patent merges safety signal transmission capabilities into existing I/O units by connecting key switches to multiple communication circuits within the same unit. This consolidation reduces the total number of components while maintaining the dual-system signal categorization required for safety compliance.
Solution Approach 2:
Existing I/O units are made multi-functional by enabling their communication circuits to handle both control and safety signals. This universality eliminates the need for separate safety-specific components, reducing overall component quantity while ensuring safety standards are met.
3Reliability
If enable switch and key switches are used in combination, then safety compliance is improved, but operability varies
Solution Approach 1:
The patent combines the functionality of enable switches and key switches into a unified key switch design where each key switch directly provides both enable and command functions through its multiple contacts. This merging maintains consistent operability across all switches while ensuring safety compliance through dual-system signal categorization.
Solution Approach 2:
Each key switch is designed as a multi-functional component that simultaneously provides enable signals and command signals through its different contacts. This universal design eliminates the need for separate enable switches, maintaining uniform operability characteristics across all switches while meeting safety requirements.
Data Source
AI summary
A key switch on a machine control panel is provided with two contacts such that the machine control panel can include two independent communication circuits. Signals from a double-contact key switch are received by the two communication circuits, and safety-related signals are transmitted from the communication circuits to a numerical controller through a bus. The signals received by the numerical controller are compared with each other so that they can be made to comply with the safety standards by monitoring the integrity of the safety function.