Gravimetric Bulk Solids Metering with Mass Flow Feedback
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Solution Overview
Problem
Conventional loss-in-weight scales face challenges in accurately determining the conveying rate of bulk materials due to refilling uncertainties and measurement errors, especially with sticky or fine-grained materials, leading to errors in mass flow regulation and requiring low-pass filters that reduce correction speed.
Innovation Solution
A method and scale design that incorporates a weight detection unit, differential filter, and a mass flow measuring device to calculate and control the mass flow, allowing for closed-loop regulation of bulk material flow and rapid adjustments, even during refilling, by processing signals from the weight detection unit and mass flow measuring device to generate control signals for the conveyor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low-pass filter with low cut-off frequency is used to suppress measurement errors, then measurement precision is improved, but correction speed for rapid changes in bulk material density is reduced
Solution Approach 1:
The patent implements feedback by measuring the actual mass flow with a mass flow measuring device and comparing it to the target mass flow, then using this feedback information to adjust the conveying rate. This closed-loop control allows the system to rapidly correct deviations without relying on low-pass filtering, thus maintaining both measurement precision and correction speed.
Solution Approach 2:
The patent replaces the mechanical signal filtering approach (low-pass filter) with a direct measurement approach using a mass flow measuring device. Instead of filtering the weight signal to extract mass flow information, the system directly measures the mass flow and uses this measurement for control, eliminating the trade-off between filtering and response speed.
2Device complexity
If conventional loss-in-weight scales are used without mass flow measurement, then device complexity is reduced, but measurement precision deteriorates due to refilling uncertainties and variable bulk material density
Solution Approach 1:
The patent introduces a mass flow measuring device as an intermediary between the container and the control system. This device directly measures the mass flow of bulk material, providing accurate feedback information that eliminates measurement errors caused by refilling uncertainties and variable bulk material density, while maintaining relatively simple device architecture.
3Measurement precision
If high-accuracy mass flow measuring devices are used to eliminate measurement errors, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the measurement parameter from indirect weight-based calculation to direct mass flow measurement. By measuring the actual mass flow parameter directly and using it for control, the system achieves high measurement precision without requiring expensive high-accuracy mass flow measuring devices, as the control is based on actual measurement rather than calculated inference.
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 approach reduces measurement errors and allows for precise control of mass flow, maintaining accuracy and speed even with variable bulk material densities, significantly improving dosing consistency and reducing the need for costly high-accuracy mass flow measuring devices.
Implementation Method 1
a signal is determined which represents the total weight of a unit formed from the container and the bulk material contained therein
Implementation Method 2
The signal is then processed specifically for the system and/or bulk material, in particular differentiated and filtered in order to calculate a first signal representing the mass flow
Implementation Method 3
after the mass flow has left the conveyor, a second signal representing the mass flow is measured
Data Source
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AI summary
The invention relates to a method for the gravimetric mass metering of bulk solids by means of a container (1) with the bulk solid to be metered and a volumetric conveying device (2), by means of which the bulk solid coming from the container with a mass flow (F), which chronologically follows a target value (W) for a target feed rate, is conveyed, and a differential metering scale suitable for such purpose. The method is characterised in that the bulk solid, after leaving the conveying device (2) can pass through a mass flow measuring device (11) and the mass flow measuring device (11) calculates a second signal (Fm) representing the mass flow, and based on the second signal (Fm) representing the mass flow and the first control signal (Y), a second control device (12) calculates a second signal (Y2) and delivers said signal to a drive (7) of the conveying device (2) for controlling the conveying device (2).