Spring-Biased Axle Actuation Indicator for Wide Tolerance Dose Counting
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Solution Overview
Problem
Existing actuation indicators for pressurized metered dose inhalers (pMDIs) require tight manufacturing tolerances and are costly to produce and assemble, making them unsuitable for use with aerosol canisters or actuators with wide manufacturing tolerances, and they are not easily adaptable to different sizes.
Innovation Solution
The use of a spring-biased axle assembly for rotatable elements, such as indicator wheels, allows for operation with wide tolerances and includes a slipping clutch mechanism with a ratchet pawl and drums sub-assembly for counting doses, which can be easily attached to various valve stem ends using a split-ring collar, enabling cost-effective and versatile manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If tight manufacturing tolerances are used for actuation indicators, then measurement precision and reliability are improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent changes the operational parameters of the dose counter by introducing a spring mechanism that allows the indicator wheel to engage and disengage from the valve stem at different compression levels. This parameter change enables the system to tolerate wider manufacturing variations while maintaining accurate dose counting through the spring's elastic deformation range.
Solution Approach 2:
The patent introduces dynamic elements including a spring-loaded axle assembly that allows the indicator wheel to move axially and rotate. The spring mechanism provides dynamic engagement and disengagement capability, allowing the system to adapt to manufacturing tolerances through controlled movement rather than requiring fixed, precision-matched components.
2Measurement precision
If complex actuation indicator mechanisms are used to achieve accurate dose counting, then measurement precision is improved, but device complexity and assembly difficulty increase
Solution Approach 1:
The patent combines multiple functions into a single integrated spring mechanism that simultaneously provides axial biasing, rotational drive transmission, and engagement control. The spring-loaded axle assembly merges the functions of positioning, driving, and limiting the indicator wheel's movement, reducing the number of separate components needed while maintaining counting accuracy.
Solution Approach 2:
The spring mechanism serves multiple functions: it biases the indicator wheel toward engagement with the valve stem, transmits rotational motion from valve stem compression to the indicator wheel, and provides a controlled disengagement mechanism. This multi-functionality reduces overall device complexity while maintaining accurate dose counting capability.
3Measurement precision
If specialized actuation indicators are designed for specific aerosol canister sizes, then measurement precision is improved, but adaptability decreases
Solution Approach 1:
The spring-loaded indicator mechanism is designed to accommodate different valve stem dimensions and compression characteristics through the spring's adjustable preload and travel range. The elastic mechanism can adapt its engagement force and movement characteristics to work with various aerosol canister and valve stem configurations while maintaining accurate dose counting.
Solution Approach 2:
The patent allows for parameter adjustments in the spring mechanism (such as spring constant, preload force, and free length) to optimize performance for different aerosol canister sizes and valve stem specifications. This parameter variability enables a single indicator design to accurately count doses across multiple canister types and sizes.
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 solution allows for the production of actuation indicators that are inexpensive to manufacture and assemble, capable of operating with wide manufacturing tolerances and adaptable to different aerosol canister sizes, while maintaining accurate dose counting and ease of assembly.
Implementation Method 1
an axle provided by a spring which is adapted in use to bias the rotatable element towards another element with which the rotatable element is engaged
Implementation Method 2
a slipping clutch mechanism with a ratchet pawl and drums sub-assembly for counting doses
Data Source
AI summary
An actuation indicator that includes a drum sub-assembly, which includes a rotatable actuation indicator wheel, a rocking, ratchet pawl for rotating the indicator wheel in a set direction and a rocking mechanism for the pawl driven by a slipping clutch arrangement, is described. The slipping clutch arrangement includes a slipping clutch spring engaged at one end to a pinion of a rack and pinion assembly and at a second end to the ratchet pawl.