Flow Sensor Double Obstruction Low Flow Sensitivity
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Solution Overview
Problem
Existing flow sensors, such as pneumotachographs, face challenges in sensitivity, especially at low flows, and are prone to secretion accumulation and vibration issues, which affect their performance during continuous monitoring in medical applications like lung ventilators and anesthesia devices.
Innovation Solution
A flow sensor with a combination of a fixed and variable obstruction in a single body, where the fixed obstruction is a rigid semi-ring orifice and the variable obstruction is a flexible semi-ring disc, both mounted crosswise to the flow passage, providing a linear relationship between flow and pressure drop, thus enhancing sensitivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed obstruction is used in the flow sensor, then the sensor structure is simple and easy to manufacture, but the sensitivity at low flows is reduced
Solution Approach 1:
The flow sensor is segmented into two distinct obstruction elements: a fixed obstruction and a variable obstruction. Each obstruction serves a specific function - the fixed obstruction provides structural simplicity while the variable obstruction enhances sensitivity at low flows by adjusting its position based on flow conditions. This segmentation allows the system to combine the advantages of both fixed and variable designs.
Solution Approach 2:
The patent introduces a variable obstruction that can dynamically adjust its position in response to flow conditions. This dynamic element complements the static fixed obstruction, allowing the sensor to maintain high sensitivity across a wide range of flow rates while preserving the manufacturing simplicity of fixed obstruction designs.
2Reliability
If a screen obstruction is used (Fleisch type), then the response is linear, but secretions accumulate on the screen making it inadequate for continuous monitoring
Solution Approach 1:
The patent extracts the screening function from a traditional Fleisch-type screen and replaces it with a controlled variable obstruction mechanism. This eliminates the problem of secretion accumulation on screens while preserving the linear response characteristic through proper design of the variable obstruction's movement and positioning.
Solution Approach 2:
The variable obstruction is implemented using flexible materials that can deform and adjust to flow conditions without providing a large surface area for secretion accumulation. The flexible thin film approach maintains linear response while minimizing the harmful effect of secretion buildup.
3Device complexity
If the obstruction intersects with tube walls, then the structure is compact, but secretions accumulate in the low speed region favoring adherence during continued use
Solution Approach 1:
The patent employs asymmetric positioning of the obstructions within the tube, ensuring that the fixed and variable obstructions are arranged to minimize dead zones and low-speed regions where secretions could accumulate. The asymmetric design maintains compactness while promoting uniform flow distribution that reduces secretion adherence.
Solution Approach 2:
The variable obstruction dynamically adjusts its position to prevent the formation of stagnant low-speed regions where secretions would accumulate. This dynamic adjustment maintains compact structure while actively preventing secretion adherence throughout continuous operation.
4Measurement precision
If a variable area sensor is used, then sensitivity to low flows is improved, but the structure becomes more complex and fragile
Solution Approach 1:
The patent merges a fixed obstruction and a variable obstruction into a single integrated sensor structure. The fixed obstruction provides structural stability and simplicity, while the variable obstruction contributes enhanced sensitivity to low flows. This combination achieves the desired sensitivity without the excessive complexity and fragility of purely variable area sensors.
Solution Approach 2:
Different regions of the sensor have different qualities - the fixed obstruction region provides structural stability while the variable obstruction region provides sensitivity. This local differentiation allows the overall structure to achieve high sensitivity to low flows while maintaining structural robustness and reducing complexity.
Data Source
AI summary
The present invention refers to a flow sensor with double obstruction disclosing a simple and innovative structure, able to promote a series of advantages and new technical effects from the combination of fixed and variable obstruction elements. More particularly, the present invention comprises a front main body (12) and a main body (40) fitted to each other so to press two obstruction elements, the first one being fixed (30) and the second being variable (50), so to increase sensitivity and reduce the annoying noise, being especially useful to monitor patients for long periods.