Metered-Dose Inhaler Counter with Magnetic Coupling
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Solution Overview
Problem
Existing dose counters for metered-dose inhalers face challenges in reliably tracking the release of medicament doses due to manufacturing tolerances, leading to potential over- or under-counting, which can result in premature discarding or misuse of the device.
Innovation Solution
A counter mechanism featuring a first ring member with radial indicia and a limiting mechanism, including an engaging portion and guide arm, that ensures accurate rotation and prevents over-rotation, combined with a second ring member for increased count registration, utilizing a pawl-and-teeth mechanism for drive operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mechanical counter mechanism is used to track doses dispensed, then the number of doses can be registered, but manufacturing tolerances cause unreliable operation leading to over- or under-counting
Solution Approach 1:
The counter mechanism transitions from a static mechanical linkage system to a dynamic magnetic coupling system where the drive magnet and follower magnet interact through magnetic fields. This allows the follower ring to be driven accurately by the drive ring without direct mechanical contact, eliminating tolerance accumulation issues while maintaining reliable dose counting functionality.
2Ease of manufacture
If the container length varies due to manufacturing tolerances, then production flexibility is improved, but the counter mechanism cannot reliably track the position and movement
Solution Approach 1:
The patent replaces the mechanical linkage system with a magnetic coupling system. The drive magnet attached to the moveable component and the follower magnet on the follower ring interact through magnetic fields rather than direct mechanical contact. This substitution allows the system to accommodate variations in container length and manufacturing tolerances while maintaining accurate position tracking and dose counting.
3Measurement precision
If a complex limiting mechanism is added to prevent over-rotation, then rotation accuracy is improved, but device complexity increases
Solution Approach 1:
The patent controls the rotation increment accuracy by optimizing magnetic field parameters rather than adding complex mechanical limiting mechanisms. By adjusting the strength and configuration of the magnetic coupling between the drive magnet and follower magnet, the system achieves precise incremental rotation control. The magnetic interaction naturally limits over-rotation through field strength thresholds, simplifying the overall mechanism while maintaining measurement precision.
Data Source
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AI summary
This invention generally relates to counters and in particular to counters for use with dispensers and to dispensers comprising said counters. More particularly the present invention relates to counters for use with metered-dose dispensers, such as metered-dose inhalers (MDIs). In particular, the present invention provides a counter comprising: a first ring member having a first indicia and being rotatable in increments about an axis, the first indicia indicating a count; a limiting member comprising a limiting mechanism, wherein the limiting mechanism comprises an engaging portion arranged to act radially with respect to the first ring member to contact the first ring member to limit free rotation of the first ring member relative to the limiting member about the axis.