Protective Field Bridging for Light Curtain Shutdown Avoidance
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Solution Overview
Problem
Existing monitoring devices in security technology, such as light grids, often unnecessarily shut down systems when non-safety-critical objects like workpieces enter the danger area, leading to unnecessary downtime and inefficiency.
Innovation Solution
A monitoring device with a bridging unit that evaluates signals from detection means at multiple points to distinguish between safety-critical and non-safety-critical objects, temporarily bridging the protective field to allow non-hazardous objects to pass without triggering the safety function, ensuring the system remains operational.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light curtain is used to monitor the danger zone, then safety function is improved by detecting objects, but unnecessary shutdowns occur when non-safety-critical objects like workpieces enter the zone
Solution Approach 1:
The protective field is divided into multiple independently monitorable areas (first protective field and second protective field). Each area can be monitored separately, allowing the system to distinguish between objects in different zones and apply appropriate responses without triggering unnecessary shutdowns of the entire system.
Solution Approach 2:
Different evaluation rules are applied to different areas of the protective field. The first protective field (entry zone) triggers shutdown only when specific conditions are met, while the second protective field (processing zone) allows workpiece presence without triggering shutdown. This local differentiation enables selective monitoring that maintains safety while preventing unnecessary productivity loss.
2Productivity
If muting sensors are added to differentiate between safety-critical and non-safety-critical objects, then unnecessary shutdowns are reduced, but device complexity increases
Solution Approach 1:
The single safety sensor performs multiple functions by monitoring different protective fields with different evaluation criteria. The same sensor unit can detect both safety-critical objects (persons) and non-safety-critical objects (workpieces) and apply context-appropriate responses, eliminating the need for separate muting sensors while maintaining system availability.
Solution Approach 2:
The monitoring system dynamically adjusts its response based on the detected object type and location. The evaluation unit can switch between different monitoring modes (strict safety monitoring vs. permissive workpiece monitoring) depending on which protective field is affected and what object is detected, providing adaptive behavior without additional hardware complexity.
3Reliability
If the safety sensor monitors all objects in the danger zone uniformly, then safety is ensured, but operational efficiency decreases due to frequent shutdowns
Solution Approach 1:
The monitoring zone is segmented into distinct protective fields with different safety requirements. By dividing the monitoring area, the system can apply differentiated monitoring strategies that ensure safety in critical zones while allowing operational flexibility in non-critical zones, thereby reducing unnecessary shutdowns and time loss.
Solution Approach 2:
Different safety monitoring strictness is applied to different locations within the danger zone. The first protective field employs stricter monitoring rules compared to the second protective field, allowing the system to maintain high safety standards where needed while minimizing disruptions in areas where workpiece presence is expected and non-hazardous.
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
This solution prevents unnecessary system shutdowns by accurately differentiating between hazardous and non-hazardous objects, allowing safe passage of permissible objects while maintaining system functionality, thus reducing downtime and improving operational efficiency.
Implementation Method 1
a sensor unit with at least one light-emitting transmitter (4) and one light-receiving receiver (6) for monitoring a protective field (2)
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention comprises a monitoring device (20) with a safety sensor by means of which objects within a protective field (2) can be detected. In normal operation, the safety sensor triggers a safety function when it registers an object encroaching within the protective field (2). A bridging unit (24) and detection means are provided, by means of which an object moving towards the safety sensor can be detected successively at at least two detection points (27a, 27b). At least one area of the protective field (2) of the safety sensor is bridged by the bridging unit (24) only if an object encroachment is registered at the detection points (27a, 27b) within a predetermined time interval, whereby the safety sensor does not trigger a safety function if an object encroachment occurs within the bridged area of the protective field (2).