Dose Setting Mechanism with Linear Stop for Overdose Prevention
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Solution Overview
Problem
Existing medicament delivery devices lack effective mechanisms to prevent users from setting doses larger than the available amount of medication, potentially leading to over-dosing.
Innovation Solution
A dose setting mechanism featuring a tubular member with a longitudinal track and a dose drum that is axially and rotationally movable, where the stop member is locked in an axially slaved connection, preventing further rotation once the predetermined length is reached, thus limiting the maximum dose that can be set.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rotational block with first and second rotational stoppers is used to prevent further rotation, then the maximum dose can be limited, but the device complexity increases
Solution Approach 1:
The invention extracts the dose limiting function from a complex rotational block mechanism with multiple stoppers and isolates it into a simple linear stop member that axially blocks the plunger rod. This stop member is positioned to contact the plunger rod and prevent further axial movement when the predetermined dose is reached, eliminating the need for rotational blocks, multiple stoppers, and complex rotational mechanisms while maintaining reliable over-dose prevention
Solution Approach 2:
Instead of using a rotational block that prevents rotation (as in prior art), the invention inverts the approach by using a linear stop member that prevents axial movement of the plunger rod. The stop member moves axially along with the plunger rod and contacts it directly to limit dose delivery, transforming the control mechanism from rotational to linear and significantly simplifying the overall device structure
2Device complexity
If a linear stop member axially movable but rotationally locked is used, then the device complexity is reduced, but the precision of dose limitation may be affected
Solution Approach 1:
The invention incorporates a dosing indicator that provides visual feedback to the user during dose setting and delivery. The indicator shows the user when the maximum predetermined dose has been reached by displaying a specific pattern or position, ensuring precise dose limitation despite the mechanical simplicity of the linear stop member. This feedback mechanism compensates for any potential imprecision in the mechanical stop position
Solution Approach 2:
The stop member is pre-positioned at a predetermined location along the axial path of the plunger rod during device assembly. This preliminary positioning ensures that the maximum dose limit is precisely defined before use, and the stop member will automatically engage at the correct position to prevent over-dosing without requiring complex adjustment mechanisms during operation
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
Ensures that users cannot set a dose larger than the predetermined amount, preventing over-dosing and ensuring the entire medication content is utilized without waste.
Implementation Method 1
the stop member comprises a track follower in engagement with the longitudinal track, such that rotational movement of the dose drum relative to the tubular member may cause a maximum axial displacement of said dose drum and said stop member, relative to the tubular member, corresponding to said predetermined length
Data Source
AI summary
A dose setting mechanism for a medicament delivery device, which dose setting mechanism comprises, a tubular member 10 having a longitudinal track 18 of a predetermined length; a dose drum 40, coaxial with the tubular member 10, and being axially and rotationally movable relative to the tubular member 10; a stop member 90, axially movable but rotationally locked relative to the tubular member 10, and further being in an axially slaved connection with the dose drum 40; wherein said stop member 90 comprises a track follower 98 in engagement with the longitudinal track 18, such that rotational movement of the dose drum 40 relative to the tubular member 10 may cause a maximum axial displacement of said dose drum 40 and said stop member 90, relative to the tubular member 10, corresponding to said predetermined length.