Flexible Element Cartridge Holder for Drug Delivery Dosing Accuracy
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Solution Overview
Problem
Existing pen-type drug delivery devices face challenges in dosing accuracy due to dimensional tolerances in components, which can lead to unintended movement of cartridges and reduced precision in medication delivery, especially in reusable devices.
Innovation Solution
The assembly incorporates a flexible element that axially fixes the cartridge within the cartridge holder, compensating for production tolerances and preventing unintended movement, thereby enhancing dosing accuracy. This flexible element is clamped between the cartridge and guiding elements, ensuring precise engagement and movement of the piston rod during dosing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rigid fixing mechanism is used to secure the cartridge and guiding element, then positional stability is improved, but manufacturing complexity and tolerance accumulation increase
Solution Approach 1:
The patent changes the mechanical parameter of the fixing mechanism from rigid to flexible. The flexible element (spring or elastic component) is introduced to replace rigid fixing elements, allowing the system to maintain positional stability while accommodating manufacturing tolerances. This parameter change transforms the fixing mechanism into a compliance-based system that absorbs dimensional variations without requiring high-precision manufacturing.
Solution Approach 2:
The patent employs a flexible element (spring or elastic component) as the fixing mechanism. This flexible element can deform elastically to accommodate tolerance variations in the cartridge and guiding element positions, while still maintaining sufficient constraint to prevent unintended movement. The flexibility allows the system to achieve reliable positioning without complex rigid fixing structures.
2Adaptability or versatility
If multiple separate components are used to fix the cartridge and guiding element, then adaptability is improved, but the number of components and assembly complexity increase
Solution Approach 1:
The patent merges the functions of cartridge fixation and guiding element fixation into a single flexible element. This flexible element simultaneously contacts and constrains both the cartridge and the guiding element, eliminating the need for separate fixing components. The merged solution reduces the total number of parts while maintaining adaptability to tolerance variations through the elastic deformation capability of the flexible element.
3Manufacturing precision
If tight tolerances are enforced on all components, then dosing accuracy is improved, but manufacturing cost and difficulty increase
Solution Approach 1:
The patent introduces a flexible element that acts as a cushioning mechanism before tolerance accumulation can affect dosing accuracy. The elastic element pre-absorbs dimensional variations and misalignments that would otherwise propagate through the mechanism and compromise the precision of the piston rod positioning. By cushioning against tolerance effects in advance, the system achieves accurate dosing with relaxed manufacturing tolerances.
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 solution significantly improves dosing accuracy by compensating for component tolerances and preventing axial movement of the guiding element, allowing for precise and reliable medication delivery, particularly in reusable devices.
Implementation Method 1
The flexible element is configured to axially fix the cartridge in the cartridge holder when the cartridge holder is attached to the housing
Implementation Method 2
The flexible element is configured to fix the guiding element with respect to a housing of the drug delivery device when the cartridge holder is attached to the housing
Data Source
Figure 1
AI summary
An assembly (2) for use in a drug delivery device (1) is provided, the assembly comprising a cartridge (14), a housing (7) and a cartridge holder (15), wherein the cartridge holder (15) is releasably attached to the housing (7). The assembly (2) further comprises a piston rod (3) which is configured to be moved from a start position to an end position in order to dispense a dose of medication when the cartridge holder (15) is attached to the housing (7), and wherein the piston rod (3) is configured to be reset to the start position when the cartridge holder (15) is detached from the housing (7). The assembly (2) further comprises a flexible element (30), wherein the flexible element (30) is configured to axially fix the cartridge in the cartridge holder (15) when the cartridge holder (15) is attached to the housing (7). Furthermore, the assembly comprises a guiding element (8) which is in threaded engagement with the piston rod (3), wherein the flexible element (30) is configured to fix the guiding element (8) with respect to a housing (7) of the drug delivery device (1) when the cartridge holder (15) is attached to the housing (7).