Light Curtain Muting With Taught Blanking Pattern
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Solution Overview
Problem
Existing light grid systems for securing danger zones around machines often result in unnecessary shutdowns when non-safety-critical objects, such as workpieces, are detected, and the current muting mechanisms can be manipulated to compromise safety by allowing unauthorized access due to long muting intervals or operational disruptions.
Innovation Solution
A light curtain device with a muting control unit and a teaching mechanism that learns the current status of beam axes to generate a safety signal only when deviations from a taught blanking pattern occur, ensuring that non-critical objects can pass through without triggering a shutdown and preventing unauthorized access by monitoring beam axis interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a long muting time interval is used to prevent unnecessary shutdowns when permissible objects remain in the light curtain area, then the machine availability is improved, but the safety risk increases due to potential manipulation by operating personnel
Solution Approach 1:
The system performs preliminary teaching of the blanking pattern during commissioning or setup, storing the legitimate interruption pattern before normal operation begins. This preliminary action establishes a reference state that prevents future manipulation while allowing legitimate objects to pass through during extended muting intervals.
Solution Approach 2:
The system continuously monitors beam axis interruptions and compares them against the stored blanking pattern in real-time. When a deviation is detected (indicating potential manipulation), the system immediately generates a safety signal and shuts down the machine, providing continuous feedback to maintain safety despite long muting intervals.
2Reliability
If the light curtain generates a safety signal when any beam axis is interrupted, then the safety function is improved, but unnecessary machine shutdowns occur when permissible objects are detected
Solution Approach 1:
The system applies different evaluation criteria to different beam axes based on their interruption patterns. Beam axes that match the stored blanking pattern are treated as legitimate interruptions by permissible objects and ignored, while deviations from the pattern trigger safety signals. This local differentiation allows the system to maintain high safety standards while avoiding unnecessary shutdowns.
Solution Approach 2:
The system changes the evaluation parameter from a binary interrupted/not-interrupted state to a pattern-matching evaluation that compares current interruptions against the stored blanking pattern. This parameter transformation enables the system to distinguish between legitimate permissible objects and potential safety threats, reducing false shutdowns while maintaining safety.
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 effectively prevents unnecessary machine shutdowns and ensures safety by maintaining the light curtain's monitoring function even during operational disruptions, while also preventing manipulation attempts by detecting deviations from the learned pattern, thus enhancing safety and availability.
Implementation Method 1
transmitters (13) which emit light beams (12) and receivers (16) for receiving the light beams (12)
Data Source
Figure 1
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AI summary
The invention relates to a device (1) for securing a danger zone (2) with a light curtain (9). It comprises a number of transmitter-receiver pairs forming beam axes, each with a light-emitting transmitter (13) and a light-receiving receiver (16), as well as an evaluation unit (17). In this unit, a safety signal can be generated if at least one beam axis is interrupted. The device includes a muting control unit (19) by means of which the light curtain (9) can be muted such that, during a muting time interval specified by a muting timer, a permissible object (7a, 7b) can pass through the light curtain (9) without it generating the safety signal.Furthermore, control means are provided by means of which a control signal can be generated, by means of which the muting timer is stopped and by means of which a blanking pattern is taught in the light curtain (9), which indicates the current status for all beam axes, whether they are interrupted or not. Subsequently, a safety signal is generated in the light curtain (9) if a deviation from the blanking pattern is registered for at least one beam axis.