Ventilator Exhalation Valve Skirt Geometry for Noise Reduction
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Solution Overview
Problem
Existing expiration valves in ventilation devices produce noise due to periodic turbulence and pressure fluctuations during the exhalation process, leading to undesirable acoustic emissions like whistling, which is not effectively mitigated by current designs.
Innovation Solution
The expiration valve incorporates an apron that surrounds the counter surface and end surface, directing the exhalation flow through an annular gap space, stabilizing the flow conditions and reducing noise emissions by guiding the flow along a longer path and using a wavy skirt design to create uniform periodic flow conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plate-shaped valve body is used to control expiration flow, then the valve can effectively block and release respiratory gas flow, but periodic turbulence and pressure fluctuations occur causing noise emissions
Solution Approach 1:
The patent applies curvature by replacing the flat plate-shaped valve body with a dome-shaped valve body. This curved surface design modifies the flow pattern of respiratory gas during expiration, reducing periodic turbulence and pressure fluctuations that cause noise. The dome shape allows smoother flow transition and eliminates the harmful acoustic effects while maintaining effective valve function.
Solution Approach 2:
The patent introduces a vertical dimension by extending the valve body into a dome shape rather than using a flat plate. This three-dimensional configuration creates a more complex flow path that stabilizes pressure and reduces turbulence. The domed structure adds vertical flow components that distribute the respiratory gas more evenly, preventing the periodic pressure fluctuations that generate noise.
2Productivity
If the valve body is moved away from the end surface during expiration, then flow resistance decreases allowing gas to flow away, but this movement creates pressure fluctuations and turbulence
Solution Approach 1:
The dome-shaped valve body modifies the flow dynamics during expiration. As the valve body moves away from the end surface, the curved surface guides the respiratory gas flow more smoothly, reducing sudden pressure changes and turbulence. This curvature ensures that high productivity during expiration does not come at the cost of excessive pressure fluctuations.
3Stress or pressure
If respiratory gas pressure increases on the inflow side during expiration, then the valve body moves away from the end surface, but this creates turbulence and noise in the annular gap
Solution Approach 1:
The dome-shaped valve body design addresses the noise problem caused by pressure increases during expiration. The curved surface distributes the pressure more evenly and guides the flow to avoid sudden changes that create turbulence. This eliminates the whistling and noise that occur in flat plate designs when pressure builds up and the valve moves away from the seat.
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 significantly reduces noise emissions, particularly in the operationally relevant volume flow range of 15 liters per minute, by minimizing pressure fluctuations and eddy formation, resulting in a quieter operation without compromising the valve's performance.
Implementation Method 1
the valve body has an apron which, when viewing the expiration valve in a reference state unstressed by the intended respiratory flow, surrounds the counter surface and the end surface in a circumferential direction and which, in the reference state, protrudes axially away from the counter surface in the direction opposite to the lifting direction
Implementation Method 2
using a wavy skirt design to create uniform periodic flow conditions
Implementation Method 3
Periodic turbulence and local flow separation can occur in the area between the end surface and the valve body, which can cause pressure fluctuations in the expiration valve
Implementation Method 4
directing the exhalation flow through an annular gap space, stabilizing the flow conditions and reducing noise emissions by guiding the flow along a longer path
Data Source
Figure 1
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AI summary
The present invention relates to an exhalation valve (10) for a ventilator apparatus for at least partial instrumental respiratory assistance of a patient, comprising a valve housing (14) with a flow passage (16) which extends along a passage trajectory (D1, D2) defining a local axial, radial and circumferential direction and along which respiratory air can flow through the valve housing (14), wherein the valve housing (14) has a housing-side valve sub-formation with a closed end surface (24) which extends around the passage trajectory (D1) and towards which a mating surface (26) of a valve body (12), movable relative to the valve housing (14) and facing the end surface (24), can be pretensioned by the pretensioning force of a pretensioning device (38) in such a way that the mating surface (26), when subjected to respiratory gas in an exhalation flow direction (E) counter to the pretensioning force of the pretensioning device (38), is removable, with enlargement of an annular gap (42) which is present or can be generated between the end surface (24) and the mating surface (26), from the end surface (24) in a lifting direction (A), such that the flow passage (16) can be flowed through in the exhalation flow direction (E), and flow through the flow passage (16) in a flow direction opposite to the exhalation flow direction (E) can be blocked by the mating surface (26) of the valve body (12) bearing on the end surface (24), wherein the valve body (12) has a skirt (44) which, when viewing the exhalation valve (10) in a reference state not loaded with intended respiratory flow, surrounding the mating surface (26) and the end surface (24), extends in a circumferential direction and, in the reference state, protrudes from the mating surface (26) past the end surface (24) counter to the lifting direction (A), wherein an annular gap space (46) is provided radially between the skirt (44) and an end portion (22) of the valve sub-formation that has the end surface (24).