Bi-Material Expiratory Valve Structure to Prevent Membrane Sagging
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Solution Overview
Problem
The existing expiratory valves in medical ventilators often suffer from sagging or depression, which prevents the flexible membrane from deforming sufficiently to allow exhaled gases to escape, leading to a blockage known as the 'expiratory brake', hindering the evacuation of CO2-rich gases in patients with respiratory issues.
Innovation Solution
A bi-material deformable valve element is used, comprising a hollow body and annular flange made of a flexible material, with a washer element of greater rigidity arranged on the annular flange, formed from materials like polyamide or polyacetal, to enhance the structural integrity and prevent sagging, ensuring proper gas evacuation during exhalation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the flexible wall forming the membrane is made more flexible to allow sufficient deformation for gas escape, then the expiratory valve can prevent expiratory braking, but the valve element sags or sinks inward toward the rigid valve body due to assembly constraints and patient circuit forces
Solution Approach 1:
The valve element is constructed as a composite structure combining a flexible membrane portion (made of elastomeric material) and a rigid annular collar portion (made of rigid material). This composite design allows the membrane to deform sufficiently for gas escape while the rigid collar prevents sagging and maintains structural stability during operation.
Solution Approach 2:
The valve element is divided into two distinct functional segments: a flexible membrane portion that deforms to control gas flow, and a rigid annular collar portion that provides structural support and prevents inward sagging. This segmentation allows each part to optimize its specific function without compromising the other.
2Stability of the object's composition
If the central body is made more rigid to prevent sagging, then the valve element maintains structural integrity, but the ability to generate desired PEEP through flexibility is reduced
Solution Approach 1:
Different parts of the valve element have different mechanical properties tailored to their specific functions: the membrane portion is made highly flexible to enable PEEP generation through deformation, while the annular collar portion is made rigid to prevent sagging and maintain structural integrity. This local differentiation of material properties resolves the contradiction between rigidity and flexibility.
3Ease of manufacture
If a single piece of flexible material is used for the deformable valve element, then manufacturing is simplified, but the valve element sags under assembly constraints and patient circuit forces, blocking gas passage
Solution Approach 1:
The valve element transitions from a single-material construction to a composite structure with a flexible membrane portion and a rigid annular collar portion. This composite design maintains manufacturing simplicity through techniques like co-molding or adhesive bonding while dramatically improving reliability by preventing sagging that would block the gas passage.
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 the 'expiratory brake' phenomenon by maintaining the structural integrity of the valve, allowing for efficient CO2 evacuation without premature blockage, as demonstrated by comparative pressure curves showing improved gas flow during respiratory cycles.
Implementation Method 1
By varying the pressure within the internal volume of the deformable valve element, the flexible wall forming the membrane more or less obstructs the gas passage through the rigid valve body
Implementation Method 2
The flexible wall forming the membrane can deform under the pressure of the gas exerted within the internal volume of the deformable valve element
Implementation Method 3
a washer element formed of a second material of greater rigidity than the first material is arranged on the annular collar
Implementation Method 4
the flexible membrane of the expiratory valve completely blocks the passage of gas from the rigid valve body, i.e. the expiratory limb, creating a fluid seal with the valve body
Data Source
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AI summary
The invention relates to a medical ventilator (1) comprising a gas circuit (2, 3) with an expiratory valve (10) including a rigid valve body (11) through which a gas passage (12) passes, and a deformable valve element (13) for controlling gas flow. The deformable valve element (13) comprises a hollow body (14) defining an internal volume (15) and including an opening (16), and an annular flange (17) integral with the hollow body (14) and arranged coaxially around the opening (16). The hollow body (14) and the annular flange (17) are formed of a first flexible material, such as an elastomer, for example silicone. A washer element (21) formed of a second material with greater rigidity than the first material, for example a polymer, is arranged on the annular flange (17).