Drug Delivery Cap Assembly With Multi-Slope Twist Release
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Solution Overview
Problem
Drug delivery devices require high forces to remove the cap, which can be difficult for infirm patients, especially at low temperatures, due to frictional interfaces and material properties.
Innovation Solution
A cap assembly with a mechanical interface that converts rotational movement into axial movement using guide tracks with varying sloped regions, adjusting force transfer to facilitate easier cap removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cap is secured to the housing with a frictional interface, then the cap remains securely attached during storage and transport, but a high force is required to remove the cap
Solution Approach 1:
The guide track is divided into multiple sloped regions with different slopes, segmenting the cap removal process into stages. Each region handles a specific portion of the removal force requirement, allowing the cap to be securely attached during storage while enabling easier removal through a multi-stage unlocking process
Solution Approach 2:
The mechanical interface transitions from a static frictional connection to a dynamic multi-stage release mechanism. The guide track with varying sloped regions allows the interface to adapt during removal, initially requiring high force to overcome the frictional lock, then progressively reducing force requirements as the cap moves through different sloped regions
2Strength
If the frictional interface between the needle shield and syringe is increased, then the cap remains firmly attached, but the force required to remove the cap increases
Solution Approach 1:
The guide track is divided into multiple sloped regions with different slopes, segmenting the cap removal process into stages. Each region handles a specific portion of the removal force requirement, allowing the cap to be securely attached during storage while enabling easier removal through a multi-stage unlocking process
Solution Approach 2:
The slope parameter of the guide track regions is varied to change the mechanical advantage at different stages of cap removal. Steeper slopes require higher force but provide shorter travel, while shallower slopes reduce required force over longer travel, allowing optimization of both attachment strength and removal ease
3Device complexity
If the cap removal mechanism uses a simple axial pull, then the mechanism is simple, but high forces must be exerted by the user
Solution Approach 1:
The cap removal mechanism transitions from a one-dimensional axial pull to a two-dimensional rotational and axial movement. The guide track with sloped regions converts rotational movement of the cap into axial displacement, providing mechanical advantage and reducing the force the user must exert while adding only moderate complexity to the mechanism
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
Reduces the force required to remove the cap, providing a user-friendly and efficient mechanism that adapts to varying forces needed during the removal process.
Implementation Method 1
the guide track has at least a first sloped region and a second sloped region, wherein, when the assembly is switched from the capped state to the uncapped state, the first sloped region guides the movement of the outer member before the second sloped region guides the movement of the outer member
Implementation Method 2
The force required to remove the cap from the housing can be relatively high which can be due to the frictional interface between the needle shield and the syringe
Data Source
AI summary
An assembly for a drug delivery device is provided, the assembly comprising: a housing for receiving a reservoir, and a cap releasable with respect to the housing, wherein the assembly has a capped state and an uncapped state, wherein the cap comprises a member to be gripped by a user for releasing the cap from the housing, wherein the member is rotatable to release the cap from the housing, wherein the assembly comprises an interface to convert rotational movement of the member into axial movement of the member, the interface comprising a track configured to guide movement of the member, wherein the track has a first region and a second region, wherein, when the first region guides the movement, the member is displaced from the housing by a first distance, and when the second region guides the movement, the member is displaced from the housing by a second distance.