Metered Dose Inhaler Valve with Elastomeric Retention Element
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Solution Overview
Problem
Pressure-actuated metered dose inhaler (pMDI) devices experience dose variations due to turbophoresis, where particles migrate in and out of the pre-metering region, leading to incorrect medicament doses for patients.
Innovation Solution
Incorporating a first and second dose retention element, specifically an elastomeric disc with re-sealable slits, at the inlet and outlet of the pre-metering region to trap and isolate active particles, preventing migration and ensuring consistent doses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a valve metering chamber is closed off when the pMDI device is at rest, then dose enrichment or dose depletion effects into or out of the metering chamber are prevented, but dose enrichment or dose depletion effects in the pre-metering region are not addressed
Solution Approach 1:
The valve is divided into distinct functional regions: a closed metering chamber and an open pre-metering region. The dose retention element segments the pre-metering region to control particle migration, allowing the metering chamber to remain sealed while addressing turbulence effects in the pre-metering region through localized structural features.
Solution Approach 2:
A dose retention element is introduced as an intermediary component within the pre-metering region. This element acts as a mediator that controls particle migration by creating a dose retention zone, preventing both dose enrichment and dose depletion without requiring the entire valve structure to be complex.
2Ease of manufacture
If the pre-metering region is left open to bulk formulation, then device operation is simple, but particles migrate in and out of the pre-metering region causing dose variations
Solution Approach 1:
The pre-metering region is given local quality through the dose retention element, which creates a specific zone with different flow characteristics. This localized modification allows the rest of the valve to remain simple while the pre-metering region specifically addresses particle migration to ensure dose consistency.
Solution Approach 2:
The dose retention element performs preliminary action by trapping and holding the correct dose of medicament in the pre-metering region before actuation. This preliminary dosing action ensures that when the valve is activated, the correct amount of medicament is already positioned for delivery, preventing dose variations.
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
Substantially reduces turbophoresis effects, ensuring accurate and consistent medicament dosing by trapping particles within the pre-metering and metering chambers, thereby preventing dose enrichment or depletion.
Implementation Method 1
particles in the suspension migrate in the direction of decreasing fluid turbulence (which can be into or out of the metering chamber), resulting in variations in the actual dose of the medicament dispensed to the patient. This migration is a phenomenon known as turbophoresis.
Implementation Method 2
a first dose retention element positioned in an inlet path to the pre-metering region and being operable for retaining a measured dose within the pre-metering region
Data Source
AI summary
The present invention addresses the problem of turbophoresis and provides a relatively simple and low cost solution for a metered dose inhaler, in particular, a pressure-actuated metered dose inhaler. A metering valve (100) comprises a valve body (110), a valve stem (130) mounted within the valve body (110) and a spring element (140) for biasing the valve stem (130) in an “at rest” position. A pre-metering region (170) is formed in the valve stem (130) which is provided with a miniature valve seal (210) at its inlet (180). The miniature valve seal (210) effectively isolates the pre-metering region (170) from surrounding bulk formulation (4) within a canister (1) in which the metering valve (100) is mounted when the valve stem (130) is in the “at rest” position.