Drug Delivery Drive Assembly for Accurate Dose Setting
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Solution Overview
Problem
Existing drug delivery devices face challenges in ensuring accurate and reliable administration of doses due to unintentional rotational movements of the piston rod during dose setting, which can lead to decreased dose accuracy.
Innovation Solution
A drive assembly with a housing, rotation member, drive component, and stop member is designed to prevent rotational movement in one direction while allowing axial movement, converting rotational motion into linear motion for precise dose delivery, using a uni-directional friction clutch mechanism and biasing member to maintain engagement between drive parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the drive component is allowed to rotate freely during dose setting, then the device is easier to operate, but dose accuracy decreases due to unintentional proximal movement of the piston rod
Solution Approach 1:
The drive component is designed with dynamic rotational constraints that adapt to different operational phases. During dose setting, the stop member prevents rotation in the proximal direction while allowing distal rotation. During dose delivery, the stop member permits rotation in both directions. This dynamic constraint system resolves the contradiction by providing directional control during setup while maintaining operational flexibility during delivery.
Solution Approach 2:
The stop member acts as an intermediary element between the drive component and the housing. It selectively permits or prevents rotational movement based on the operational phase, mediating between the user's setting actions and the piston rod position. This intermediary mechanism ensures dose accuracy during setting while allowing smooth operation during delivery.
2Measurement precision
If the stop member prevents rotational movement in the first direction, then dose accuracy is improved, but device complexity increases
Solution Approach 1:
The drive component is segmented into a first drive part and a second drive part that can rotate relative to each other. The stop member engages with the second drive part to prevent unwanted rotation. This segmentation allows the complexity to be localized to specific components rather than the entire drive assembly, making the added complexity manageable and targeted.
Solution Approach 2:
Instead of preventing rotation during dose delivery, the stop member is designed to prevent rotation during dose setting. This inverted approach focuses the constraint mechanism on the phase where accuracy is most critical, rather than restricting movement during the delivery phase where flexibility is more important.
3Measurement precision
If the first and second drive parts are rigidly coupled, then rotational movement is more precise, but axial movement freedom is lost
Solution Approach 1:
The coupling between the first and second drive parts is designed to be dynamically selective. The parts are rigidly coupled against relative rotation to maintain precise rotational positioning, while simultaneously allowing relative axial movement. This dynamic coupling特性 enables the system to maintain rotational precision while adapting to axial displacement requirements during different operational phases.
Solution Approach 2:
The coupling between drive parts exhibits different mechanical properties in different directions. In the rotational direction, the coupling is rigid to ensure precise angular positioning. In the axial direction, the coupling is flexible to allow relative movement. This anisotropic coupling quality resolves the contradiction by providing direction-specific mechanical characteristics.
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 design enhances dose accuracy by preventing unintentional proximal movement of the piston rod, ensuring consistent and reliable drug administration.
Implementation Method 1
a biasing member adapted to provide a force on the first and second drive parts
Implementation Method 2
a uni-directional friction clutch mechanism
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A drive assembly (70) for a drug delivery device (1) comprises a rotation member (21) being configured to be rotated in a first direction (44) during setting of a dose of a drug and to be rotated in a second direction (47) during delivery of the dose, a drive component (20) being configured to follow rotational movement of the rotation member (21) in the second direction (47) during delivery of the dose and a stop member (26) being configured to prevent rotational movement of the drive component (20) in the first direction (44). The drive component (20) comprises a first drive part (71) and a second drive part (72), coupled to each other such that relative rotational movement of the first and second drive parts (71, 72) is prevented and relative axial movement is permitted.