Cartridge Holder Stiffness and Asymmetric Coding for Drug Delivery
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Solution Overview
Problem
Drug delivery devices face risks due to the potential for incorrect drug cartridges being inserted, and existing cartridges are prone to damage, especially when they are glass and sold separately.
Innovation Solution
A cartridge fixing system is designed with a region of reduced mechanical stiffness integrated into the cartridge holder, which alters the load path to prevent radial deflection and securely fix the cartridge, using a fixing feature that flexes inwardly to enhance stability and prevent removal attempts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a cartridge holder is designed to allow easy cartridge replacement, then ease of operation is improved, but reliability deteriorates due to risk of incorrect cartridge insertion
Solution Approach 1:
The cartridge holder and cartridge are designed with asymmetric coding features including a coding element on the cartridge holder and a corresponding coding feature on the cartridge. These features create a unique geometric configuration that allows only compatible cartridges to be inserted in the correct orientation, preventing incorrect cartridge insertion while maintaining ease of operation through intuitive alignment.
Solution Approach 2:
Interface features act as intermediaries between the cartridge holder and cartridge. These include an interface element on the cartridge holder and a corresponding interface feature on the cartridge that must engage properly for the cartridge to be securely retained. This intermediary mechanism ensures compatibility verification during the insertion process.
2Reliability
If a fixing feature is made rigid to prevent cartridge removal, then reliability is improved, but ease of operation deteriorates due to difficulty in cartridge assembly
Solution Approach 1:
The fixing feature is designed with dynamic characteristics, being flexible rather than rigid. The fixing feature can deflect radially outward to accommodate the cartridge head portion during assembly, then returns to its original position to secure the cartridge. This dynamic behavior allows easy cartridge assembly while maintaining reliable cartridge retention during use.
Solution Approach 2:
The mechanical properties of the fixing feature are optimized by changing its flexibility parameter. The fixing feature is made sufficiently flexible to allow radial deflection during cartridge insertion, yet maintains enough stiffness to provide secure retention during drug delivery. This parameter optimization resolves the contradiction between assembly ease and retention reliability.
3Reliability
If the cartridge holder structure is reinforced to prevent radial deflection, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
Instead of uniformly reinforcing the entire cartridge holder structure, the design applies local quality by providing a reinforcement section only in the specific region where radial deflection occurs during cartridge insertion. This localized reinforcement maintains structural stability while minimizing manufacturing complexity and material usage.
Solution Approach 2:
The cartridge holder is segmented into different functional regions with different structural characteristics. The reinforcement section is separated from other regions, allowing each segment to be optimized for its specific function. This segmentation enables simplified manufacturing while achieving the required structural stability in the critical area.
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
The system securely retains the cartridge, reducing the risk of incorrect insertion and damage, while allowing easy assembly and reliable operation, enhancing user safety and device stability.
Implementation Method 1
a region with reduced mechanical stiffness compared to the stiffness of the main body region... such that when the cartridge is moved in the proximal direction an emerging load is transferred from the cartridge to the fixing feature
Data Source
AI summary
The disclosure relates to a cartridge assembly for a drug delivery device, the cartridge assembly comprising a cartridge containing a drug; a cartridge holder, the cartridge holder defining an interior cartridge holding section, where the cartridge is arranged within the cartridge holding section, wherein the cartridge holder comprises a distal region with a needle connector arranged at a distal end of the distal region and a main body region; a fixing feature which is arranged at the distal region; and a region with reduced mechanical stiffness compared to the stiffness of the main body region, the region with reduced mechanical stiffness being integrated into the distal region and arranged between the needle connector and the fixing feature, such that when the cartridge is moved in a proximal direction, an emerging load is transferred from the cartridge to the fixing feature and to the main body region in the proximal direction.