Auto-injector Dual Spring Mechanism for Viscous Medicament Delivery
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Solution Overview
Problem
Current auto-injectors face challenges in delivering high viscosity medicaments without high impact on the user, often resulting in uncomfortable injection experiences and the risk of incomplete doses due to the use of strong drive springs, which can lead to wet injections and increased manufacturing costs.
Innovation Solution
The auto-injector employs a separate control spring and drive spring system, where the control spring manages needle insertion and retraction, allowing for the use of a weaker drive spring to deliver viscous medicaments without user impact, and features a mechanism to prevent wet injections by releasing the drive spring upon reaching injection depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If strong drive springs are used to deliver high viscosity medicaments, then the injection force is sufficient, but the impact on the user increases and the injection becomes uncomfortable
Solution Approach 1:
The patent divides the spring system 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, enabling the drive spring to provide sufficient force for high viscosity medicaments without requiring the control spring to generate high impact forces during needle insertion.
2Force
If strong drive springs are used to deliver high viscosity medicaments, then the injection force is sufficient, but the risk of wet injections increases
Solution Approach 1:
The control spring is pre-loaded and ready to act immediately upon trigger activation. When the trigger is pulled, the control spring first drives the needle to the injection depth, then the drive spring is released to deliver the medicament. This preliminary positioning ensures the needle is properly seated before the high force drive spring acts, preventing wet injections.
3Ease of operation
If the control spring is coupled to the carrier for needle insertion, then needle insertion is controlled, but the drive spring cannot be released upon reaching injection depth
Solution Approach 1:
The trigger mechanism acts as an intermediary between the user and the drive spring. When the trigger is pulled, it first allows the control spring to advance the needle. Upon reaching the predetermined injection depth, the trigger mechanism then releases the drive spring to deliver the medicament. This intermediary control ensures both precise needle positioning and timely medicament delivery.
4Device complexity
If a single spring system is used for both needle insertion and medicament delivery, then the device is simpler, but it cannot handle different viscosity and volume medicaments with minimal changes
Solution Approach 1:
By separating the spring system into a control spring and a drive spring, the patent enables independent optimization of each function. The drive spring can be easily exchanged or adjusted to accommodate different medicament viscosities and volumes, while the control spring maintains consistent needle insertion performance. This segmentation provides versatility without significantly increasing overall device complexity.
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
This design ensures a comfortable and reliable injection process, reduces manufacturing costs, and allows for versatility in delivering different viscosity and volume medicaments with minimal component changes, while preventing wet injections and ensuring needle safety.
Implementation Method 1
a control spring arranged around the carrier... a needle insertion control mechanism for coupling a proximal end of the control spring to either the carrier for advancing it for needle insertion or to the chassis
Implementation Method 2
a drive spring and a plunger for forwarding load of the drive spring to a stopper of the syringe
Data Source
AI summary
An auto-injector for administering a dose of a liquid medicament includes a tubular chassis telescopable in an elongate chassis, a carrier subassembly including a tubular carrier slidably arranged partially inside the chassis and inside the case, the carrier adapted to contain a syringe with a hollow injection needle, a drive spring, a plunger for forwarding load of the drive spring to a stopper of the syringe, a control spring arranged around the carrier, a needle insertion control mechanism for coupling a proximal end of the control spring to either the carrier for advancing it for needle insertion or to the chassis, wherein the syringe is lockable for joint axial translation with the carrier, wherein the needle insertion control mechanism includes a first collar biased by the control spring in a proximal direction, and wherein at least one fifth clip is arranged on one of the chassis or the first collar.