Auto-Injector Spring Segmentation for High-Viscosity Delivery
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Solution Overview
Problem
Existing auto-injectors face challenges with high injection forces, discomfort due to hand shaking, and incomplete doses, especially when administering high viscosity medicaments, and often require complex mechanisms for needle insertion and retraction.
Innovation Solution
An auto-injector design with separate drive and control springs, where the drive spring is released only upon reaching the injection depth, ensuring smooth medicament delivery without user impact, and a plunger release mechanism triggers injection reliably, while the control spring manages needle insertion and retraction, allowing for versatile drug delivery.
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 user experiences high impact and discomfort during needle insertion and triggering
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 each spring to be optimized for its specific function, with the drive spring providing sufficient force for high viscosity medicaments without creating excessive impact during needle insertion.
Solution Approach 2:
The patent applies different spring characteristics to different functional zones: the control spring is positioned to manage the insertion phase with appropriate force characteristics, while the drive spring is positioned to deliver the medicament with the required force for high viscosity substances. Each spring has locally optimized properties matching its specific operational requirements.
2Device complexity
If manual button/plunger devices are used for injection, then the device structure is simple, but the user must continuously press the button which causes hand shaking and trembling
Solution Approach 1:
The auto-injector performs the injection function automatically once activated. The control spring automatically advances the needle, and the drive spring automatically delivers the medicament without requiring continuous user input. The user simply activates the device and the system completes the injection sequence autonomously, eliminating hand shaking issues.
3Force
If the drive spring is released early to assist needle insertion, then the insertion force is improved, but the injection timing becomes unreliable and may trigger before reaching injection depth
Solution Approach 1:
The patent separates needle insertion force generation from medicament delivery. The control spring provides the force for reliable needle insertion and positioning, while the drive spring remains locked until the needle reaches the correct depth. This segmentation ensures that insertion force is available when needed without compromising injection timing reliability.
Solution Approach 2:
The control spring performs the preliminary action of advancing the needle to the correct injection depth before the drive spring is released to deliver the medicament. This sequential action ensures proper positioning occurs first, establishing reliable timing for the subsequent injection phase.
4Device complexity
If a single spring system is used for both needle insertion and medicament delivery, then the device complexity is reduced, but the system cannot accommodate different viscosity drugs effectively
Solution Approach 1:
The patent segments the drive mechanism into two independent spring systems that can be independently selected and optimized. Different drive springs with varying force characteristics can be used to accommodate different medicament viscosities, while the control spring remains consistent for needle management. This modular spring selection enables versatile drug delivery across different viscosity ranges.
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 provides a reliable, user-friendly auto-injector that safely delivers high viscosity medicaments with consistent doses, reduces discomfort, and allows for a single platform to accommodate different viscosity drugs by swapping drive springs, enhancing safety and ease of use.
Implementation Method 1
the energy to deliver the fluid is provided by a spring
Implementation Method 2
a control spring, arranged around the carrier and acting between the case and the carrier
Data Source
AI summary
An auto-injector for administering a dose of a liquid medicament includes an elongate tubular case and a carrier subassembly including a tubular carrier slidably arranged inside the case. The carrier is adapted to contain a syringe with a hollow injection needle, 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, wherein the drive spring acts between the carrier and the plunger, wherein the plunger, in an initial state, is locked to the carrier by a ramped engagement to the carrier and by being prevented from rotating out of this ramped engagement, depending on a relative longitudinal position of the carrier in the case, and wherein the plunger is arranged to be released for rotating out of the ramped engagement.