Medication Pen Drive Mechanism for Accurate Dose Setting
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Solution Overview
Problem
Medication delivery devices often face challenges in achieving accurate dose delivery due to unintentional movement of the piston rod during dose setting, which can lead to inconsistencies in the amount of medication dispensed.
Innovation Solution
A drive mechanism with a rotation member, drive member, and stop member that prevents rotational movement during dose setting, converting rotational movement into distal movement of the piston rod during delivery, ensuring accurate dose delivery by preventing proximal movement of the piston rod.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the drive member is allowed to rotate freely during dose setting, then the device structure is simpler, but the piston rod moves unintentionally in the proximal direction causing dose inaccuracy
Solution Approach 1:
The stop member acts as an intermediary element between the drive member and the housing. It selectively prevents rotational movement of the drive member in the first direction (during dose setting) while allowing rotation in the second direction (during dose delivery). This mediator component resolves the contradiction by controlling when the drive member can rotate, thereby preventing unintended piston rod movement during dose setting without overly complicating the overall mechanism.
Solution Approach 2:
The drive mechanism transitions from a static constraint system to a dynamic one where the stop member selectively engages based on rotation direction. During dose setting, the stop member prevents rotation; during delivery, it allows rotation. This dynamic behavior enables the system to adapt its constraints based on operational phase, improving dose accuracy while maintaining operational simplicity.
2Ease of operation
If the drive member rotates during dose setting, then the device is easier to operate, but the piston rod moves in the proximal direction reducing dose accuracy
Solution Approach 1:
The stop member serves as a directional mediator that selectively permits or prevents rotation based on the operational phase. During dose setting, it blocks rotation to prevent piston rod movement; during delivery, it allows rotation for proper mechanism operation. This selective mediation maintains ease of operation while ensuring dose accuracy.
3Manufacturing precision
If the stop member prevents rotation of the drive member during dose setting, then dose accuracy is improved, but the device complexity increases
Solution Approach 1:
The stop member is a simple intermediary component that provides directional constraint. Rather than complex control systems or multiple actuators, a single stop member selectively engages to prevent rotation in the wrong direction. This minimalistic approach to mediation achieves dose accuracy improvement with minimal increase in device complexity.
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 enhances dose accuracy by preventing unintentional proximal movement of the piston rod during dose setting, ensuring that the actual delivered dose matches the set dose, thereby improving the reliability of medication delivery devices.
Implementation Method 1
the rotational movement of the drive member in the second direction is converted into movement of the piston rod in the distal direction with respect to the housing
Data Source
AI summary
A drive mechanism for a medication delivery device containing a resilient member and having a rotation member configured to be rotated in a first direction during setting of a dose of a medication and to be rotated in a second direction during delivery of the dose, where the rotation member is coupled to a drive member that is coupled to a piston rod such that on dose delivery the piston rod is displaced in a distal direction to dispense a medicament and where the resilient member prevents movement of the drive member and the piston rod during dose setting.