Turbine Spirometer Vane Vertical Axis Low Flow Response
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Solution Overview
Problem
Conventional turbine spirometers face limitations in responding to low flow rates due to friction in supporting bearings and imbalances in the vane assembly, leading to insufficient torque and potential cessation of rotation at low flow rates, particularly in diagnosing conditions like COPD where low flow rates are common.
Innovation Solution
The spirometer design features a vane that rotates about a vertical axis, with a breathing tube and mouth piece configuration that diverts air flow by 90° ± 50°, utilizing V-jewel bearings to minimize friction and ensure free rotation, allowing the vane to maintain rotation at low speeds and low flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional horizontal vane mounting with jewel bearings is used, then the device structure is simple, but the response at low flow rates is limited due to friction and imbalance
Solution Approach 1:
The patent changes the mounting orientation of the vane from horizontal to vertical axis, fundamentally altering the dimensional configuration. This allows the vane to rotate about a vertical axis instead of a horizontal one, enabling gravity to assist the rotation at low flow rates and eliminating the friction problems associated with horizontal jewel bearings.
Solution Approach 2:
The patent replaces the conventional mechanical jewel bearing support system with a vertical axis mounting that utilizes gravitational forces. Instead of relying on low-friction mechanical bearings, the system uses the vertical orientation to allow gravity to act on the vane, providing a mechanical advantage at low flow rates without requiring complex bearing support structures.
2Force
If V-jewel bearing is used to reduce friction, then the pivot rolls up the inside cone causing torque loss, but conventional jewel bearing has higher friction
Solution Approach 1:
The patent eliminates the conical V-jewel bearing structure entirely by mounting the vane on a vertical axis. This dimensional change removes the rolling motion that causes torque loss, allowing the vane to rotate freely without the pivot rolling up the inside cone of a V-jewel bearing.
3Reliability
If the vane axis is horizontal for simple mounting, then the air flow path is short and straight, but the low torque at low flow rates cannot overcome bearing friction and imbalance
Solution Approach 1:
The patent reorients the vane axis from horizontal to vertical, fundamentally changing the spatial configuration. This allows the air flow path to be extended vertically while maintaining a compact horizontal profile, enabling the vane to rotate freely at low flow rates without requiring a long horizontal air flow path.
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 design enables the vane to freely rotate at low flow volumes, overcoming the limitations of conventional spirometers by ensuring consistent torque application and maintaining rotation without imbalance issues, enhancing the device's sensitivity and accuracy in measuring low flow rates.
Implementation Method 1
a fixed swirl plate which causes the exhaled air to swirl, twisting the air into a vortex. The angular velocity of the vortex is proportional to the flow rate of air passing through the mouth piece.
Implementation Method 2
The swirled air applies a torque to the vane which rotates at the same angular velocity as the vortex.
Implementation Method 3
V-jewel bearing, which exhibit very low friction. However when these low friction bearings are used in conventional turbine spirometers, the pivot lies against the inside of the conical V and rolls up and down the surface of the bearing radius
Data Source
Figure 1
Figure 2
AI summary
A turbine spirometer (1) comprises a breathing tube (13) into which is subject is to breath and a vane (9) to be driven by the subject's breath. The breathing tube (13) has a first axis A-A at its opening (21) in the direction of air flow and the vane (9) rotates about a second axis B-B, (11). The first A-A and second B-B axes are inclined to one another at angle of around 100 degrees such that in use the axis of rotation B-B is substantially vertical.