Coffee Pad Exit Filter Design to Reduce Bypass and Oil Extraction
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Solution Overview
Problem
Existing coffee pads face issues with non-homogeneous coffee grind distribution leading to internal bypass, increased coffee oil extraction, and clogging, which affects the quality and dry matter content of beverages, especially in high dry matter brewing methods like Senseo.
Innovation Solution
A flexible coffee pad with a bed of coffee particles between porous sheets, where the exit filter has a higher fluid flow resistance than the inlet, utilizing a Herzberg water permeability to increase downstream flow resistance without altering the exit filter itself, and a particle size distribution that allows for finer grinds while minimizing bypass and oil extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a finer grind size is used to increase flow resistance, then flow resistance is improved, but the risk of coffee particles forming agglomerates increases leading to internal bypass
Solution Approach 1:
The patent applies local quality by differentiating the pore size between the inlet filter and exit filter. The inlet filter has larger pores (10-50 micrometers) to accommodate finer coffee grind without immediate clogging, while the exit filter has smaller pores (1-10 micrometers) to prevent bypass and retain fine particles. This localized differentiation of filter properties resolves the contradiction between using fine grind for flow resistance and preventing agglomerate formation that causes bypass.
2Stress or pressure
If a finer grind size is used to increase flow resistance, then flow resistance is improved, but coffee oils are extracted at unacceptable levels
Solution Approach 1:
The patent uses local quality by positioning the finer pore size filter (exit filter with 1-10 micrometer pores) specifically at the exit side where oil extraction occurs. This localized filtering approach allows the use of finer coffee grind throughout the bed for increased flow resistance and better extraction, while the exit filter specifically captures excess oils and fine particles, preventing unacceptable oil levels in the final beverage.
3Stress or pressure
If higher doses of coffee powder are used to achieve additional flow resistance, then flow resistance is improved, but non-homogeneities increase leading to clogging
Solution Approach 1:
The patent applies parameter changes by specifying optimal coffee particle size ranges (10-500 micrometers with preferred ranges of 50-200 micrometers) and controlling the distribution of particle sizes. Rather than simply increasing dose, the invention changes the particle size parameters to achieve the desired flow resistance while maintaining bed homogeneity. The dual-filter system with specific pore size ratios further stabilizes the system against clogging by providing graduated filtration.
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 solution enhances the extraction of high dry matter beverages with reduced oil content and improved flow homogeneity, preventing clogging and maintaining filter performance under varying pressures, resulting in a more concentrated and high-quality coffee brew.
Implementation Method 1
the exit filter has a second fluid flow resistance that exceeds the first fluid flow resistance of the bed of coffee particles. The exit filter is selected to possess a Herzberg water permeability of 300 - 3500 seconds per 100 ml per 10 cm 2
Implementation Method 2
Resistance against a flow is measured in pressure drop. In particular when high dry matter beverages, having a small brewing volume, are desired non-homogeneities in the coffee bed will have a strong impact on the final product in terms of internal bypass
Data Source
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AI summary
Pad for use in a beverage preparing device comprising an at least partly porous first sheet of flexible material, an at least partly porous second sheet of flexible material, and a bed of coffee particles provided between the first and second sheet. The first sheet forms an inlet sheet at a water receiving side of the pad. The second sheet forms an exit filter at an outlet side of the pad, wherein the bed of coffee particles has a first fluid flow resistance. The exit filter has a second fluid flow resistance that exceeds the first fluid flow resistance. The exit filter is selected to possess a Herzberg water permeability of 300 - 3500 seconds per 100 ml per 10 cm2 at a pressure head of 50 mm Hg for generating a third fluid flow resistance, in the presence of coffee particles, which exceeds the first fluid flow resistance.