Switch Device Synchronizing Dual Safety Signals
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Solution Overview
Problem
Existing switch devices with dual ON/OFF signal generation units can erroneously determine that a machine tool's safety function is abnormal due to varying response times between safety input signals, leading to incorrect safety monitoring.
Innovation Solution
A switch device with dual ON/OFF signal generation units, including detection units, determination units, monitoring units, and output units, that output ON or OFF signals based on the state of the switch operation unit, ensuring that the numerical control device receives matching signals to accurately monitor the machine tool's safety function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual safety input signals are generated using a press button switch with two contact points, then the safety function can be monitored through signal comparison, but the response time difference between the two signals may cause erroneous determination of machine tool abnormality
Solution Approach 1:
The patent merges the determination logic of both contact points within a single control unit. The control unit receives detection signals from both contact points, determines the pressed state based on both signals, and generates a single unified output signal. This eliminates the response time difference between dual signals while maintaining safety monitoring functionality through signal comparison.
2Reliability
If a permissible time is set to allow mismatch between safety input signals, then erroneous determination can be prevented, but the safety response may be delayed
Solution Approach 1:
The control unit performs preliminary determination of the pressed state by evaluating both detection signals before generating the output signal. By pre-processing both contact point signals and determining the pressed state in advance, the system eliminates the need for permissible time settings while maintaining fast safety response through unified signal generation.
Data Source
AI summary
A switch device includes a switch operation unit, two detection units which convert the amount of press of the switch operation unit into detection signals, determination units which determine the pressed state of the switch operation unit, monitoring units which monitor the determination states of the determination units, and output units, each of which outputs an ON signal when the determination unit determines that a full pressed state is maintained, and when, upon determination that a half pressed state is maintained, the detection signal is equal to or larger than an ON threshold and the monitoring result indicates a full pressed state, and outputs an OFF signal when the determination unit determines that a non-pressed state is maintained, and when, upon determination that a half pressed state is maintained, the detection signal is equal to or smaller than an OFF threshold and the monitoring result indicates a non-pressed state.