Capacitive Measurement for Paper Container Moisture and Thickness
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Solution Overview
Problem
Existing methods for determining properties of pulp-based containers, such as residual moisture and wall thickness, are inadequate as they often require contact measurements that can disrupt production processes and struggle to accurately differentiate between these parameters, especially when using visible light, which pulp containers do not transmit.
Innovation Solution
A capacitive measurement method using electrodes to determine electrical parameters characteristic of the container's electrical field, allowing for non-contact assessment of residual moisture and wall thickness, particularly suitable for pulp-based containers, by applying an alternating electric field and measuring at different frequencies to distinguish between water content and wall thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contact measurement methods (e.g., hygrometer with sword sensor) are used to determine residual moisture, then measurement can be performed, but production performance is significantly impacted and measurement time increases
Solution Approach 1:
The patent replaces contact-based mechanical measurement systems (hygrometer with sword sensor requiring physical contact and stable positioning) with a non-contact electrical field-based measurement system. electrodes generate an electrical field that penetrates the container wall to measure residual moisture without mechanical contact, thereby maintaining production speed while achieving accurate measurements
Solution Approach 2:
The measurement system is integrated into the production line such that residual moisture measurement is performed automatically during the drying process before the container leaves the production area. This preliminary action eliminates the need for separate post-production measurement steps, maintaining continuous production flow
2Measurement precision
If optical measuring devices using visible light are used, then container properties can be determined, but pulp containers cannot be inspected because they do not transmit visible light
Solution Approach 1:
The patent changes the physical parameter used for measurement from optical properties (visible light transmission) to electrical properties (electrical field penetration). Since electrical fields can penetrate pulp material while visible light cannot, this parameter change enables measurement of pulp containers without requiring material transparency
Solution Approach 2:
The patent substitutes optical measurement systems with electrical field-based measurement systems. electrodes generate an electrical field that interacts with the container material's dielectric properties, enabling measurement of pulp containers that are opaque to visible light
3Measurement precision
If radiometric absorption measurement or weighing methods are used to determine residual moisture, then measurement can be performed, but these methods are slow, complex or expensive
Solution Approach 1:
The patent replaces complex radiometric absorption measurement systems or precision weighing systems with a simpler electrical field-based measurement system. electrodes generate an electrical field whose interaction with the container material provides direct information about residual moisture content through dielectric property changes, eliminating the need for complex radiation sources, detectors, or precision mass measurement equipment
Solution Approach 2:
The measurement system uses simple electrodes that can be easily manufactured and replaced if needed, rather than expensive radiometric equipment or precision weighing systems. The electrical field measurement approach requires minimal infrastructure while providing sufficient measurement accuracy for production control
4Productivity
If electrical field measurement is used to determine both residual moisture and wall thickness, then both parameters can be measured simultaneously, but accurate differentiation between the two parameters is challenging
Solution Approach 1:
The patent employs periodic action by using alternating electrical fields at multiple different frequencies. Different frequencies penetrate the container wall to different extents and interact differently with water content versus wall thickness. By measuring at multiple frequencies and analyzing the frequency-dependent response, the system can mathematically differentiate between residual moisture and wall thickness contributions to the overall electrical field interaction
Solution Approach 2:
The patent changes the frequency parameter of the electrical field to differentiate between measurement targets. By varying frequency, the measurement system exploits the different dielectric properties and frequency responses of water (residual moisture) versus dry paper/cardboard material (wall thickness), enabling separation of these two parameters through frequency-dependent measurement analysis
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 precise, non-contact quality control of pulp containers during production, allowing for closed-loop control of material input and drying processes without impacting production output, and can measure these parameters simultaneously over the entire container surface.
Implementation Method 1
at least one wall of the container is arranged between two electrodes, and an electrical voltage or an alternating electrical field is applied to the electrodes
Implementation Method 2
an electrical voltage or an alternating electrical field is applied to the electrodes, and at least one electrical parameter is determined which is characteristic of an electrical field which is built up between these electrodes
Implementation Method 3
a further approach to the examination was also identified-namely, the above-mentioned possibility of measuring an electric field, and therefore a capacitive measurement
Data Source
AI summary
A method for determining container properties, wherein a container to be examined is transported along a predetermined transport path, and this container has a bottom region, a main body which serves to receive a filling material, and an mouth region, and wherein this container is formed at least in part of a material containing paper or cardboard. At least one wall of the container is arranged between two electrodes, and an electrical voltage or an alternating electrical field is applied to the electrodes, and at least one electrical parameter is determined which is characteristic of an electrical field which is built up between electrodes, and from this electrical parameter, at least one parameter characteristic of the container is determined.