Auto-Injector Spring Segmentation for High-Viscosity Dosing
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Solution Overview
Problem
Existing auto-injectors face challenges such as high injection forces, discomfort due to hand shaking, and the risk of incomplete doses, particularly when administering high viscosity medicaments, and often require complex mechanisms for needle insertion and retraction.
Innovation Solution
An auto-injector design with separate control and drive springs, where the control spring manages needle insertion and retraction, while the drive spring delivers the medicament, ensuring a smooth and controlled injection process without high impact forces on the user.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a single strong drive spring is used to deliver high viscosity medicaments, then the injection force is sufficient, but the impact force on the user during needle insertion becomes too high
Solution Approach 1:
The patent divides the single drive spring function into two separate springs: a control spring that manages needle insertion and retraction, and a drive spring that delivers the medicament. This segmentation allows the drive spring to provide sufficient force for high viscosity medicaments without the control spring transmitting high impact forces to the user during needle insertion.
2Device complexity
If manual button/plunger devices are used, then device complexity is reduced, but the user cannot deliver complete doses due to inability to maintain continuous pressure
Solution Approach 1:
The auto-injector performs the injection function automatically after initial activation. The drive spring self-actuates to push the plunger and deliver the medicament without requiring the user to maintain continuous pressure, ensuring complete dose delivery while maintaining simple device operation.
3Reliability
If the button/plunger extension is made long to ensure full depression, then complete dose delivery is possible, but hand shaking and user discomfort increase
Solution Approach 1:
The patent extracts the force generation function from the user's hand action and transfers it to the drive spring mechanism. The user only needs to activate the device, after which the drive spring provides the necessary force for complete dose delivery without requiring long button extensions or sustained manual pressure, thereby reducing hand shaking and discomfort.
4Reliability
If complex mechanisms are used to manage needle insertion and retraction, then needle safety is improved, but device complexity increases
Solution Approach 1:
The patent combines needle insertion and retraction functions into a single control spring mechanism. The control spring automatically manages both the insertion of the needle into the patient and the subsequent retraction, eliminating the need for separate complex mechanisms for each function while maintaining needle safety.
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 design allows for reliable, safe, and efficient delivery of high viscosity medicaments with reduced user discomfort and improved reliability, minimizing the risk of incomplete doses and needle exposure, while being adaptable for different viscosity drugs and volumes.
Implementation Method 1
a control spring arranged around the carrier for translating the carrier in a proximal direction for insertion of the needle through the chassis into an injection site
Implementation Method 2
a drive spring arranged inside the carrier, the drive spring pushable by a trigger button arranged on the case
Data Source
AI summary
An auto-injector for administering a dose of a liquid medicament (M) is present having a tubular chassis telescopable in a tubular case, a carrier subassembly comprising a tubular carrier slidably arranged relative to the chassis inside the case, where the carrier is adapted to contain a syringe with a hollow injection needle. The injector also has a drive spring and a plunger for forwarding load of the drive spring to a stopper of the syringe, wherein the syringe is lockable for joint axial translation with the carrier. A control spring is arranged around the carrier for translating the carrier in a proximal direction (P) for insertion of the needle through the chassis into an injection site.