Intravenous Flow Meter Using U-Shaped Passage for Accurate Low-Flow Measurement
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Solution Overview
Problem
Conventional intravenous flow meters are either inaccurate due to variable drop sizes or expensive to manufacture, with existing designs being complex and requiring high tolerances, making them time-consuming and costly to produce.
Innovation Solution
A flow meter device featuring a vertical liquid inlet passage with a 'U'-shaped flow-resistant liquid passage and an indicating chamber, allowing liquid level to rise proportionally with flow rate, marked with calibrated scales for accurate measurement, and manufactured using standard injection molding tolerances, preventing dry-out and solid deposits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rotameter design with a ball or float in a tapered tube is used, then flow rate measurement accuracy is improved, but manufacturing cost increases due to high tolerances and complex assembly
Solution Approach 1:
The device divides the flow measurement function into separate components: a flow-resistant passage for creating pressure differential, an indicating chamber for visual display, and a scale for measurement. This segmentation allows each component to be manufactured independently with standard tolerances rather than requiring high-precision assembly of moving parts.
Solution Approach 2:
The invention extracts the flow resistance function from a separate moving component (ball/float) and integrates it into a fixed flow-resistant passage. This eliminates the need for precision-machined tapered tubes and moving parts, allowing manufacturing with standard injection molding tolerances.
2Device complexity
If a bent tube with orifice design is used, then manufacturing complexity is reduced, but accuracy at low flow rates deteriorates
Solution Approach 1:
The flow-resistant passage is designed with specific local geometric features (narrow section, bends, chamfers) that create consistent flow resistance characteristics. This localized design ensures accurate pressure differential generation even at low flow rates, while the overall device remains simple to manufacture.
Solution Approach 2:
The invention changes the geometric parameters of the flow-resistant passage (length, cross-section, bend radius, chamfer angles) to optimize flow resistance characteristics across the entire flow range, particularly improving performance at low flow rates while maintaining manufacturing simplicity.
3Reliability
If orifice disks of minimal thickness are used, then temperature and viscosity effects are minimized, but manufacturing cost increases due to complex assembly of small parts
Solution Approach 1:
The invention merges the orifice function with the flow-resistant passage into a single integrated component. The flow-resistant passage incorporates the flow restriction geometry directly into the molded structure, eliminating the need for separate orifice disks and their complex assembly, while maintaining reliability under varying conditions.
4Device complexity
If drop counting method is used, then no additional components are needed, but time consumption and measurement accuracy worsen
Solution Approach 1:
The invention introduces an indicating chamber as an intermediary that translates flow rate into a visual liquid level height. This mediator provides direct visual measurement of flow rate, eliminating the need for time-consuming drop counting and calculations, while the overall device remains relatively simple.
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 device provides improved accuracy and consistency at low flow rates, is easier and quicker to use, and comparable in cost to standard administration sets, with the 'U'-shaped passage and chamfered inlet and outlet ensuring reliable readings and preventing errors.
Implementation Method 1
Liquid flowing in the liquid inlet passage will encounter resistance due to the flow-resistant liquid passage (6)
Implementation Method 2
The 'U' shape, along with the chamfered inlet and outlet, also provides that, when flow is stopped by the operator, the flow-resistant liquid passage does not dry out and remains wet
Data Source
AI summary
A flow meter for intravenous liquids comprising a vertical inlet passage (2), a parallel indicating chamber (9), a ‘U’ shaped flow-resistant liquid passage (6), and an exit chamber (11). Liquid to be dispensed enters the inlet passage (2) via inlet (5) and moves down the passage to a junction with both the ‘U’ shaped flow-resistant passage (6), and the indicator passage. From the junction, the liquid rises up the indicator passage to a height proportional to the flow rate set by an external flow meter, and also through the flow resistant passage, which has an outlet (8) that delivers the liquid to the exit chamber (11) and from there to a patient through an outlet (12). The meter may be formed by an assembly of two injection molded components, thus reducing manufacturing costs.