MDI Valve Sealing Structure for Hard-Seal Propellant Compatibility
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Solution Overview
Problem
Existing metered dose inhaler (MDI) sealing arrangements are inadequate for high hardness materials, leading to inefficiencies and compatibility issues with various propellants, including HFA and CO2, and result in high leachable/extractables profiles.
Innovation Solution
A metering valve with a resilient return member and high-hardness seals, such as Shore D 80, that dynamically stretch to form a seal with the metering valve stem, allowing compatibility with a broader range of propellants and reducing leaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sealing arrangements are used with softer materials, then ease of manufacture and assembly are improved, but sealing performance deteriorates with high hardness materials leading to leaks and high leachable/extractables
Solution Approach 1:
The patent changes the hardness parameter of the sealing material from traditional softer materials to high hardness materials (Shore D 80 or higher). This parameter change improves sealing performance by reducing leachable/extractables and preventing propellant degradation, while the dynamic stretching mechanism accommodates the manufacturing challenges of working with harder materials.
Solution Approach 2:
The patent introduces a dynamic sealing mechanism where the seal opening is adapted to be stretched wider by the metering valve stem passing through it than it would be absent the valve stem. This dynamic adjustment allows the high hardness seal material to conform to the stem during operation, maintaining effective sealing while simplifying the static manufacturing process.
2Reliability
If high hardness seal materials are used, then leachable/extractables are reduced and propellant compatibility is improved, but sealing arrangement complexity increases
Solution Approach 1:
The patent designs a universal sealing arrangement that works with multiple propellant types (HFA 134a, 152a, 1234ze, and CO2) using the same high hardness seal material and dynamic stretching mechanism. This multi-functional design improves propellant compatibility across different MDI formulations while avoiding the need for separate sealing arrangements for each propellant type.
Solution Approach 2:
By changing the material hardness parameter to Shore D 80 or higher, the patent achieves improved compatibility with various propellants including HFA and CO2. The high hardness material resists degradation from different propellants and maintains sealing effectiveness across varying pressure conditions, eliminating the need for propellant-specific seal designs.
3Reliability
If the seal opening is stretched wider by the metering valve stem, then dynamic sealing is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs a dynamic sealing mechanism where the seal opening is intentionally designed to be stretchable. The metering valve stem passes through the opening and stretches it wider during operation, creating an effective dynamic seal. This dynamic approach compensates for manufacturing variations in the initial opening dimensions, reducing the need for extremely tight manufacturing tolerances while ensuring reliable sealing during use.
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 provides improved sealing performance, reduced leachable/extractables, and enhanced compatibility with HFA and CO2 propellants, ensuring effective and reliable operation of MDIs.
Implementation Method 1
a resilient return member urging the metering valve stem from the second position to the first position
Implementation Method 2
the metering valve stem seal opening is adapted to be stretched wider by the metering valve stem passing through it than it would be absent the metering valve stem
Data Source
AI summary
A metered dose inhaler valve (26) has a reservoir portion (37) for assembly with a canister (14) for receiving a pressurised formulation of medicament and propellant, a metering valve body (96) defining a metering chamber, and a metering valve stem (24) having an outlet (56) and being axially moveable within the body. The stem moves between a first position in which the chamber is in fluid communication with the canister, and a second position in which the chamber is in fluid communication with the valve stem outlet. A metering valve seal is defined by the valve body and includes an opening through which the stem passes to form a dynamic seal between the stem and at least one of the outside atmosphere and the pressurized canister, where the opening is adapted to be stretched wider by the stem passing through it than it would be absent the valve stem.