Metering Pump Unit Variable Stroke Rate Gas Bubble Expulsion
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Solution Overview
Problem
Metering pump units face issues with gas bubble accumulation in the metering chamber, leading to reduced metering accuracy and potential blockage due to compressible gas bubbles, especially when shut down, which can result in failure to aspirate liquid.
Innovation Solution
A metering pump unit with a detection system for gas bubbles and a controller that adjusts the positive-displacement drive's stroke rate, starting at a lower rate and increasing to an elevated rate towards the end of the stroke, ensuring efficient expulsion of gas bubbles and maintaining a favorable liquid/air ratio, thereby preventing metering failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump operates at a constant high stroke rate to maintain productivity, then productivity is improved, but gas bubbles accumulate in the metering chamber causing metering failure
Solution Approach 1:
The pump operates with variable stroke rates that dynamically adjust based on operational phase: high stroke rates during normal operation for productivity, and reduced stroke rates during gas bubble expulsion phases for reliability. The controller modifies stroke rate in response to gas detection signals, transforming a static operation mode into a dynamic adaptive system.
Solution Approach 2:
The pump implements periodic gas bubble expulsion cycles interrupting normal high-speed operation. During these periodic intervals, the stroke rate is reduced to allow gas bubbles to rise and be expelled from the metering chamber, then returns to high speed for productive operation. This periodic alternation prevents gas accumulation while maintaining overall productivity.
2Reliability
If the pump reduces stroke rate to expel gas bubbles, then metering reliability is improved, but productivity decreases
Solution Approach 1:
The pump applies partial reduction of stroke rate only during specific phases when gas bubble expulsion is needed, rather than maintaining reduced speed continuously. The controller implements selective stroke rate modification based on gas detection, applying the speed reduction partially in time and space to achieve reliability improvement with minimal impact on overall productivity.
3Productivity
If the pump operates continuously without stroke rate variation, then productivity is maintained, but gas bubbles accumulate causing airlocking
Solution Approach 1:
The pump maintains continuous operation without complete stoppages by implementing continuous variable stroke rate control. Rather than stopping to expel gas, the system continuously adjusts stroke rate between high and low levels, ensuring unbroken liquid flow while periodically creating conditions favorable for gas bubble expulsion. This continuous adaptive action eliminates airlocking while maintaining productivity.
4Loss of time
If the pump increases stroke rate to expel gas bubbles quickly, then gas removal speed is improved, but liquid/air ratio deteriorates
Solution Approach 1:
The pump performs preliminary gas bubble expulsion at reduced stroke rates before returning to high-speed operation. By first creating favorable conditions for gas removal through slower operation, the system ensures gas bubbles are expelled before high-speed operation begins, preventing gas accumulation that would deteriorate the liquid/air ratio during productive phases.
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 effectively prevents metering failures by ensuring a higher liquid percentage in the metering chamber, expelling gas bubbles efficiently, and maintaining operational security against airlocking, while ensuring the desired setpoint flow is achieved.
Implementation Method 1
a metering chamber (6), a positive-displacement body (8) that adjoins the metering chamber and can be moved by a positive-displacement drive
Implementation Method 2
Gas bubbles can form in the metering chamber... gas bubbles take up a portion of the volume of liquid to be metered... the gas bubbles are expelled faster from the metering chamber
Data Source
AI summary
A metering pump unit with a metering chamber (6), a positive-displacement body that adjoins the latter and can be moved by a positive-displacement drive (22), as well as a controller (30) for actuating the positive-displacement drive (22). The controller (30) is designed to actuate the positive-displacement drive (22) at least in a specific operating state in such a way that a stroke, in particular a pressure stroke, of the positive-displacement body is started at a first, lower stroke rate, and the stroke rate is increased to a second, elevated stroke rate as the pressure stroke (36) continues. A method is provided for controlling the positive-displacement drive (22) of such a metering pump unit.