Espresso Pump Flow Measurement for Pressure-Profiling Extraction
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Solution Overview
Problem
Existing espresso machines lack efficient methods for regulating pressure and volume during the brewing process, particularly in the pre-infusion stage, which affects the quality and consistency of espresso production.
Innovation Solution
A flow measurement apparatus and pump power modification module are integrated into the espresso machine to measure and control the resultant flow, allowing for real-time calculation of the shot dose and enabling pressure profiling, including a controlled low-pressure pre-infusion stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a pump is used to deliver water at high pressure for espresso extraction, then the extraction pressure is sufficient (9-10 bar), but the pre-infusion stage cannot deliver controlled low pressure (1-5 bar) effectively
Solution Approach 1:
The pump operates in two distinct dynamic modes: a first mode during pre-infusion delivering water at controlled low pressure (1-5 bar), and a second mode during extraction delivering water at high pressure (9-10 bar). This dynamic switching of pump operating states enables the system to meet different pressure requirements for different brewing stages without requiring multiple pumps
Solution Approach 2:
The system changes the operating parameters of the pump between stages. During pre-infusion, the pump delivers water at a first flow rate and low pressure; during extraction, it switches to a second flow rate and high pressure. This parameter switching allows a single pump to fulfill multiple pressure delivery requirements
2Measurement precision
If flow meters are installed to measure dose delivery, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The flow measurement function is segmented into two separate flow meters: a first flow meter measuring feed flow into the pump, and a second flow meter measuring return flow from the over-pressure valve. This segmentation allows independent measurement of each flow stream, improving overall measurement accuracy while maintaining manageable system complexity through modular design
Solution Approach 2:
The over-pressure valve acts as an intermediary element that creates a measurable return flow. By routing excess water through the second flow meter before returning it to the reservoir, the system creates a controlled measurement point that enables accurate dose calculation without requiring direct measurement at the extraction point
3Stress or pressure
If an over-pressure valve is used to maintain extraction pressure, then pressure regulation is improved, but the ability to measure resultant flow accurately is reduced
Solution Approach 1:
The system uses feedback from both flow meters to calculate the resultant flow. The first flow meter measures total feed flow, the second flow meter measures return flow through the over-pressure valve, and the controller subtracts the return flow from the feed flow to determine the actual dose delivered. This feedback mechanism compensates for the flow diversion caused by the over-pressure valve, maintaining measurement accuracy
Solution Approach 2:
The system extracts the return flow measurement function from the main feed flow measurement. By separating the measurement of feed flow (first flow meter) from return flow measurement (second flow meter), the system can accurately account for the portion of water diverted by the over-pressure valve, enabling precise calculation of resultant flow despite the pressure regulation mechanism
Data Source
AI summary
A method and apparatus for measuring a resultant flow delivered by a pump coupled to an over pressure valve, the method comprising the steps of: measuring, using a first flow meter, feed flow to the pump; measuring, using a second flow meter, return flow from the over pressure valve; and calculating resultant flow, at least in part, by subtracting measured return flow from measured feed flow. A pump power modification module can further modifying the pump output pressure to enable pressure profiling.