Auto-injector Coupling Shroud Prevents Premature Decoupling
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Solution Overview
Problem
Current auto-injectors face challenges such as incomplete dose delivery, high injection forces, and accidental needle stick injuries due to premature decoupling of the plunger and needle shroud, which can lead to discomfort and inefficiency in administering medicaments, especially for elderly or dexterity-impaired users.
Innovation Solution
An auto-injector design featuring a cylindrical chassis with a pre-filled syringe, needle shroud, and drive mechanism that ensures complete medicament expulsion before decoupling, utilizing a coupling shroud and plunger system to prevent premature decoupling and ensure needle safety, along with a single compression spring for efficient operation, and a manually actuatable release element for intuitive use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the plunger and coupling shroud are decoupled early to simplify the mechanism, then device complexity is reduced, but incomplete dose delivery occurs and medicament is wasted
Solution Approach 1:
The coupling catch is designed to engage the plunger shoulder in advance, creating a predetermined decoupling point that ensures complete medicament delivery before separation occurs. This preliminary engagement arrangement prevents premature decoupling and associated medicament waste while maintaining mechanism simplicity.
Solution Approach 2:
The coupling shroud acts as an intermediary element between the drive means and the plunger. It transmits the driving force while controlling the decoupling timing through its interaction with the plunger shoulder, ensuring that separation occurs only after complete dose delivery.
2Object-affected harmful factors
If the needle shroud is made retractable to improve needle safety, then harmful factors are reduced, but device complexity increases
Solution Approach 1:
The needle shroud is merged with the coupling shroud structure, combining two functions into a single component. This integration reduces the number of separate parts while maintaining both the needle safety function and the coupling function, thereby reducing overall device complexity.
Solution Approach 2:
The needle shroud is designed to be dynamically retractable rather than fixed. It can move between extended and retracted positions based on operational needs, providing enhanced needle safety when retracted while maintaining structural simplicity through its integrated design.
3Device complexity
If a single compression spring is used for the drive means to reduce complexity, then device complexity is reduced, but controlling the decoupling point becomes more difficult
Solution Approach 1:
The plunger shoulder is pre-positioned at a specific location that corresponds to the desired decoupling point. This preliminary positioning ensures that when the coupling catch engages the shoulder, separation occurs at the precise moment when complete medicament delivery has been achieved, maintaining manufacturing precision with a single spring system.
Solution Approach 2:
The single compression spring system is designed to automatically control the decoupling timing through the inherent mechanical interaction between the coupling shroud and plunger shoulder. The system self-regulates the decoupling point based on the pre-designed geometric relationships, eliminating the need for additional control mechanisms.
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 auto-injector ensures complete medicament delivery without wasting any dose and provides reliable needle safety features, reducing the risk of accidental injuries and improving user experience by preventing premature decoupling and ensuring proper placement and activation.
Implementation Method 1
a single compression spring for efficient operation
Data Source
AI summary
An auto-injector comprises a chassis to contain a syringe with a, needle and a stopper, a needle shroud slideable within the chassis and adapted to rest on the skin of a patient, a plunger adapted to translate the stopper to expel medicament, a coupling shroud slideable within the chassis and releasably coupled to the plunger and a drive means, the drive means driving the coupling shroud proximally from a first position Proximal movement of the coupling shroud translates the syringe exposing the needle, depresses the plunger to expel medicament and advances the needle shroud to a safe position to surround the needle. The needle shroud arranged to prevent decoupling of plunger and coupling shroud when the needle shroud is in a retracted position, whereas the needle shroud is arranged to allow decoupling of plunger and coupling shroud when the needle shroud is moved towards the safe position.