Safety Switch Resonant Circuit for Interlock Contact Detection
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Solution Overview
Problem
Existing safety switches for movable protective equipment in hazardous zones, such as machine doors, lack a reliable and efficient method to detect the safe status of the equipment and ensure secure locking and unlocking, which can lead to unsafe conditions if the door is opened inadvertently.
Innovation Solution
A safety system with a base housing comprising two part members, a signal receiver, and a signal transmitter, utilizing a resonant circuit formed by a coil and capacitor, where a pulse signal is used to evaluate the contact between an electromagnet and a retaining plate, providing a redundant and reliable detection mechanism for the safe status of the equipment, ensuring secure locking and unlocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical principle or RFID technology is used for safety switch detection, then the safety status can be monitored, but the detection reliability and safety integrity level are insufficient to meet SIL3 standards
Solution Approach 1:
The patent replaces traditional mechanical contact detection or RFID technology with an electromagnetic induction-based detection system. The evaluation unit generates a detection signal that induces current in the retaining plate, and the contact state is determined by evaluating the induced current signal. This substitution provides higher detection precision and reliability meeting SIL3 safety standards.
Solution Approach 2:
The patent introduces an electromagnetic field as an intermediary between the evaluation unit and the retaining plate. The evaluation unit generates an alternating detection signal that creates an electromagnetic field, which induces current in the retaining plate when in proximity. This intermediary enables non-contact detection of the contact state with high precision.
2Reliability
If continuous voltage is applied to the electromagnet coil, then the locking function is maintained, but energy consumption increases and the coil may overheat
Solution Approach 1:
The patent applies periodic pulsed voltage to the electromagnet coil instead of continuous voltage. The control unit generates pulse signals at specific intervals to activate the electromagnet only when needed for locking or unlocking operations. This periodic action maintains the locking function reliability while significantly reducing energy consumption and preventing coil overheating.
Solution Approach 2:
The electromagnet system utilizes the residual magnetic field and mechanical momentum to maintain the locked state without continuous power supply. Once the coil is energized to establish the magnetic field and attract the retaining plate, the system maintains the locked position through mechanical self-holding, requiring no continuous energy input.
3Reliability
If the door is locked for trailing movements, then safety is ensured, but the productivity and access efficiency are reduced
Solution Approach 1:
The patent implements dynamic locking control where the lock state is adjusted based on real-time operational conditions. During trailing movements, the system dynamically maintains the locked state for safety. When trailing movements are complete and the zone is safe, the system dynamically transitions to an unlocked state, allowing efficient access. This dynamic adaptation optimizes both safety and productivity.
Solution Approach 2:
The system uses feedback from the detection unit to monitor the safety status and trailing movement conditions. Based on this feedback, the control unit automatically adjusts the lock state - maintaining locked during hazardous trailing movements and unlocking when safe. This feedback-driven control ensures safety during critical operations while enabling efficient access during safe periods.
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
The system provides a high safety integrity level by ensuring accurate detection of the retaining plate's position, allowing for secure operation of the interlocking unit, satisfying safety standards up to SIL3, and preventing unauthorized access to hazardous zones.
Implementation Method 1
a coil of the electromagnet forms a resonant circuit with a capacitor, with the resonant circuit being acted on cyclically by the control and evaluation unit by at least one pulse signal and with the pulse response being evaluated by the control and evaluation unit
Implementation Method 2
an interlocking device having an electromagnet and a retaining plate that is disposed opposite the electromagnet for locking or unlocking the protective equipment
Data Source
AI summary
A safety system having a safety switch for monitoring a safe protective equipment status of movable protective equipment, having a base housing that comprises at least two part members that can be positioned with respect to one another, wherein a signal receiver is provided in one part member and a signal transmitter is provided in the other part member so that a safe state of the protective equipment is detectable by means of a control and evaluation unit, and having an interlocking device having an electromagnet and a retaining plate that is disposed opposite the electromagnet for locking or unlocking the protective equipment, wherein the control and evaluation unit is configured to unlock or lock the interlocking unit after checking and verifying the signal receiver, wherein a coil of the electromagnet forms a resonant circuit with the capacitor, with the control and evaluation unit being configured to control the resonant circuit cyclically by at least one pulse signal, and with the control and evaluation unit being configured to evaluate the pulse response from the resonant circuit and with at least one contact or with no contact between the electromagnet and the retaining plate being detectable by the control and evaluation unit in dependence on the pulse response.