Safety Switch Resonant Circuit Sensing for Guard Lock Verification
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Solution Overview
Problem
Existing safety switches for movable protective devices in hazardous machine areas lack reliable and redundant methods to ensure the safe status of protective devices, which can lead to unsafe conditions if the protective devices are not properly locked or monitored.
Innovation Solution
A safety system with a safety switch that utilizes a basic housing with a signal receiver and transmitter, an electromagnet, and a retaining plate, where a coil forms an oscillating circuit with a capacitor, and cyclically applies impulse signals to detect contact or proximity between the electromagnet and the retaining plate, providing a redundant and reliable evaluation of the protective device's status.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical principle or RFID technology is used for safety switch monitoring, then the basic protective device status can be monitored, but the safety integrity level is insufficient and redundant verification is lacking
Solution Approach 1:
The patent replaces traditional mechanical monitoring principles or RFID technology with an electromagnetic oscillating circuit system. The electromagnet generates an oscillating magnetic field that interacts with the retaining plate, providing a more reliable and redundant verification mechanism for safety monitoring, thereby increasing the safety integrity level to SIL3.
Solution Approach 2:
The patent introduces an oscillating magnetic field as an intermediary between the electromagnet and the retaining plate. This magnetic field serves as a mediator to detect the presence and position of the retaining plate, providing redundant verification of the protective device status without direct mechanical contact or complex RFID communication.
2Reliability
If the supply voltage to the coil is continuously applied, then the electromagnet maintains its holding force, but the oscillating circuit cannot be properly evaluated
Solution Approach 1:
The patent applies periodic pulse signals to the oscillating circuit at specific intervals. Between these periodic evaluations, the electromagnet maintains continuous holding force. This periodic action allows the system to evaluate the oscillating circuit's response for safety verification while maintaining the protective device's locked state throughout the cycle.
Solution Approach 2:
The system performs preliminary evaluation of the oscillating circuit response before making safety decisions. By measuring the magnetic field interaction in advance through the oscillating circuit, the system can verify the protective device status proactively, ensuring safety before any potential failure occurs.
3Measurement precision
If a simple mechanical locking mechanism is used, then the device complexity is low, but the ability to detect and verify the safe status of the protective device is insufficient
Solution Approach 1:
The patent changes the detection parameter from simple mechanical position sensing to electromagnetic field interaction measurement. By measuring the oscillating circuit's response to the magnetic field interaction between the electromagnet and retaining plate, the system achieves precise detection of the protective device status with higher measurement accuracy.
Solution Approach 2:
The patent substitutes mechanical position detection with electromagnetic field-based detection. The oscillating magnetic field interacts with the retaining plate to produce a measurable electrical response, replacing complex mechanical sensors and verification mechanisms with a more compact and reliable electromagnetic detection system.
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
Ensures a high safety integrity level by providing diverse and redundant signal evaluation, capable of detecting the safe status of the protective device, meeting safety integrity level requirements up to SIL3, and preventing unauthorized access to hazardous areas.
Implementation Method 1
a coil (13) of the electromagnet (11) forms an oscillating circuit (15) with a capacitor (14), the oscillating circuit (15) being controlled by the control and evaluation unit (9) cyclically supplied with at least one impulse signal
Implementation Method 2
the coil of the electromagnet is electromagnetically influenced by the metal holding plate
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Safety system (1) comprising a safety switch (2) for monitoring a safe protective device state of a movable protective device (3), comprising a basic housing (4) consisting of at least two sub-bodies (5, 6) that can be positioned relative to each other, wherein a signal receiver (7) is provided in one sub-body (5) and a signal transmitter (8) in the other sub-body (6), so that a safe state of the protective device (3) can be detected by means of a control and evaluation unit (9), and a locking unit (10) comprising an electromagnet (11) and a retaining plate (12) opposite the electromagnet (11) for locking or unlocking the protective device (3), wherein the control and evaluation unit (9) is configured to unlock or lock the locking unit (10) after checking and verifying the signal receiver (7), wherein a coil (13) of the electromagnet (11) forms a resonant circuit (15) with a capacitor (14),wherein the control and evaluation unit (9) is configured to cyclically drive the resonant circuit (15) with at least one pulse signal (18) and the control and evaluation unit (9) is configured to evaluate the impulse response (VS) of the resonant circuit (15) and depending on the impulse response (VS) at least one contact or a non-contact between the electromagnet (11) and the holder plate (12) can be detected by the control and evaluation unit (9).