Drug Injection Dose Setting Limiter Mechanism
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Solution Overview
Problem
Existing drug delivery devices, particularly pen-type injectors, face challenges in being intuitive for users with impaired vision due to small dose indicating numbers and lack of effective last dose limiting mechanisms, which can lead to incorrect dose settings and potential overdose.
Innovation Solution
A drive mechanism with a rotatable drive sleeve and dose limiting member that engages with the piston rod, allowing for easy dose setting and dispensing while preventing over-dosing by locking at maximum capacity, and featuring a large-scale dose indicating display for improved readability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact design is used for the drug delivery device, then the device size is reduced and portability is improved, but the dose indicating numbers become small and difficult to read for visually impaired users
Solution Approach 1:
The patent implements a nested dose indication system where multiple dose wheels (first dose wheel and second dose wheel) are arranged coaxially and nested within each other. The first dose wheel displays units digits while the second dose wheel displays tens digits, allowing both to be contained within the compact device housing while providing large, readable numerals that address the readability issue for visually impaired users.
2Reliability
If a last dose limiting mechanism is added to prevent over-dosing, then user safety is improved, but the device complexity increases
Solution Approach 1:
The patent combines the last dose limiting function with the existing dose setting mechanism by integrating a limit wheel that interacts with the dose wheels through shared mechanical elements (teeth, latches, springs). The limit wheel is positioned coaxially with the dose wheels and uses the same rotational direction and mechanical interaction principles, merging the safety function into the existing structure rather than adding a separate independent mechanism.
Solution Approach 2:
The dose limiting mechanism operates automatically through mechanical interaction between the limit wheel teeth and the latch element. When the maximum dose is reached, the mechanical configuration self-locks to prevent further rotation, providing automatic safety without requiring additional active control or complex electronic systems.
3Loss of information
If the dose indicating numbers are enlarged for better readability, then visibility for impaired users is improved, but the device dimensions increase
Solution Approach 1:
The patent resolves the space constraint by transitioning from a single-plane display to a multi-dimensional nested arrangement. Multiple dose wheels are stacked coaxially along the longitudinal axis, utilizing the third dimension (depth) to accommodate large numeral displays while maintaining a compact external footprint. This allows large readable numerals without increasing the device's width or height significantly.
Data Source
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AI summary
The present invention relates to a drive mechanism of a drug delivery device for dispensing of a dose of a medicament, the mechanism comprising: - a housing (20), - a piston rod (120) extending in an axial direction (1, 2) to operably engage with a piston (14) of a cartridge (12), - a drive sleeve (90) rotatably supported in the housing (20), at least partially enclosing the piston rod (120), the drive sleeve (90) is operably releasable from the piston rod (120) for setting of a dose and the drive sleeve (90) is operably engageable with the piston rod (120) for dispensing of the dose, -a dose limiting member (130) threadedly engaged with the drive sleeve (90), rotatably locked to the housing (20) and being displaceable in axial direction (1, 2) in response to a rotation of the drive sleeve (90) relative to the piston rod (120), - at least one stop member (124) provided on the piston rod (120) to engage with the dose limiting member (130) for impeding a further displacement of the drive sleeve (90) relative to the piston rod (120), when a maximum dose configuration has been reached.