Optical Leak Detection for Sealed Packages
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Solution Overview
Problem
Current leak testing methods for gas-filled containers are unable to achieve 100% testing of individual packages at full production line speeds, as they are limited by the response time of hydrogen sensors and the diffusion of tracer gases through packaging materials, leading to incomplete detection of leaks and reduced production efficiency.
Innovation Solution
A novel leak detection arrangement using a test gas with a gas sensor that evaluates the instantaneous slope of gas concentration changes, combined with an open hood or flow guide and mechanical pressure to enhance gas flow, allowing for faster detection and higher production speeds by synchronizing signal changes with sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydrogen sensors are used for leak detection, then the testing speed can be increased, but the response time of the sensor becomes too long for high speed leak testing
Solution Approach 1:
The patent replaces the mechanical/chemical hydrogen sensor system with an optical detection system using a laser and photo detector. This substitution enables instantaneous detection of tracer gas concentration changes without the 1-10 second response delay inherent in hydrogen sensors, thereby resolving the contradiction between testing speed and response time.
Solution Approach 2:
The patent changes the detection parameter from hydrogen concentration measurement (which requires slow sensor response) to optical absorption measurement at specific wavelengths. By using a laser tuned to the absorption wavelength of the tracer gas and detecting the attenuation of light, the system achieves rapid response times compatible with high-speed production lines.
2Reliability
If tracer gas diffusion through packaging materials is considered, then false positive leak detections occur, but shortening the time between filling and testing is required
Solution Approach 1:
The patent introduces a specific tracer gas (such as sulfur hexafluoride or perfluorocarbon) as an intermediary substance that has distinct optical absorption characteristics not present in common packaging materials. This allows differentiation between actual leaks and diffusion through the package barrier, maintaining reliability even when testing occurs after a longer time interval.
Solution Approach 2:
The patent utilizes optical absorption (analogous to color changes in spectroscopy) at specific wavelengths to detect the presence of tracer gas. By monitoring the attenuation of laser light at the characteristic absorption wavelength of the tracer gas, the system can distinguish leaked tracer gas from the packaging material itself, preventing false positives regardless of diffusion effects.
3Productivity
If parallel testing arrangements are provided to increase testing capacity, then the collective testing speed matches production line speed, but the device complexity increases
Solution Approach 1:
The patent replaces multiple parallel mechanical testing arrangements with a single optical testing station. The optical system can rapidly switch between packages or use multiple sensors in a single station, achieving the same collective testing capacity without the mechanical complexity of multiple parallel systems.
Solution Approach 2:
The optical detection system is designed to be universal and adaptable, capable of testing multiple packages in sequence or parallel within a single station. The system can detect leaks in various package types and configurations using the same fundamental optical principle, eliminating the need for specialized parallel testing arrangements for different package types.
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
Enables testing of at least four packages per second with improved accuracy for larger leaks, reducing unnecessary product scrapping and providing immediate feedback for production optimization, while maintaining high production uptime.
Implementation Method 1
Hydrogen and helium are commonly used as tracer gases for leak testing. One problem with these gases is their relatively high diffusion rate through the thin polymer films and other packaging materials used as gas barriers in packaging materials.
Implementation Method 2
The arrangement further comprises means for applying a predetermined pressure on the package
Implementation Method 3
The arrangement may further comprise a suction means for drawing ambient air past a seal on a packet to be tested and a gas sensor in the flow of ambient air drawn off by the suction means
Data Source
Figure 1
Figure 2A~2B
Figure 2C
AI summary
The invention relates to a method and an arrangement for detecting a leak in a sealed package containing a product in the form of a foodstuff or a pharmaceutical. The leak detecting arrangement comprises a testing station, in which a package is placed by the transporting means and a pressure applying means arranged to apply a predetermined amount of pressure on the package located in the testing station. The arrangement further comprises a continuously operated suction means arranged to draw ambient air past a seal on the packet to be tested and a gas sensor located in the flow of ambient air drawn off by the suction means and arranged to transmit a signal dependent on the test gas concentration detected in the ambient air.