Drug Delivery Assembly Dose Locking Mechanism
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Solution Overview
Problem
Existing drug delivery devices often lack high dose accuracy and safety features, allowing users to set doses that exceed the available quantity of medication, which can lead to underdosing or overdosing, potentially causing fatal consequences.
Innovation Solution
An assembly for a drug delivery device featuring a drive mechanism with a stop member and interaction member that switch from a non-locking to a locking mode when the maximum settable dose exceeds the available medication, preventing further dose setting and ensuring accurate dispensing of the remaining quantity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a drive mechanism allows continuous dose setting without restrictions, then ease of operation is improved, but dose accuracy and user safety deteriorate due to inability to prevent exceeding available medication
Solution Approach 1:
The system dynamically transitions between two operational states: a non-locking mode during normal dose setting where the drive member can move freely relative to the piston rod, and a locking mode when the maximum dose is reached. The stop member radially moves between positions to enable or prevent mechanical cooperation with the interaction member, allowing the system to adapt its constraints based on the dosing state
Solution Approach 2:
The assembly incorporates a feedback mechanism where the axial distance between the stop member and interaction member changes in response to drive member movement. When the dosing distance equals the axial distance, the system detects the maximum dose condition and automatically activates the locking mode, providing real-time feedback on medication availability and preventing further dose setting
2Reliability
If a locking mechanism is added to prevent exceeding maximum dose, then dose accuracy and safety are improved, but device complexity increases
Solution Approach 1:
The locking mechanism is integrated into the existing drive mechanism components. The stop member is provided on one of the piston rod or drive member, and the interaction member on the other, combining the locking function with the dose setting structure. The same axial movement that sets the dose also controls the locking state, merging two functions into a unified mechanism
Solution Approach 2:
The assembly automatically locks when the maximum dose is reached without requiring external intervention or complex control systems. The radial bias of the stop member and the axial distance reduction self-activate the mechanical cooperation between the stop member and interaction member, allowing the system to self-regulate its operation
Data Source
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Figure 8A~8B
AI summary
An assembly for a drug delivery device (1), comprising: a housing (2) having a distal end and a proximal end, a piston rod (14), a drive member (21), the drive member (21) being moveable in a proximal direction with respect to the housing (2) and with respect to the piston rod (14) for setting a dose of a drug (12), at least one stop member (18) which is provided on one of the piston rod (14) and the drive member (21) and which is radially moveable with respect to the one of the piston rod (14) and the drive member (21) on which it is provided, and at least one interaction member (19) which is provided on the other one of the piston rod (14) and the drive member (21). Furthermore, a piston rod (14) for a drug delivery device is provided.