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 causing discomfort to users, as they require strong drive springs that result in high impact and force, leading to issues like wet injection and increased manufacturing costs.
Innovation Solution
The auto-injector employs a dual-spring mechanism with a control spring and a drive spring, where the control spring manages needle extension and retraction without user impact, allowing for efficient delivery of viscous medicaments while preventing wet injection and reducing part count for lower manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a strong drive spring is used to deliver high viscosity medicaments, then the injection force is sufficient, but the impact and force felt by the user increases causing discomfort
Solution Approach 1:
The patent divides the single drive spring into two separate springs: a control spring that manages needle extension and retraction, and a drive spring that powers plunger movement and medicament delivery. This segmentation allows each spring to be optimized for its specific function, enabling the drive spring to generate high force for viscous medicaments while the control spring manages user-interaction phases with reduced impact
2Force
If a strong drive spring is used to deliver high viscosity medicaments, then the injection force is sufficient, but the manufacturing cost increases
Solution Approach 1:
The patent divides the single drive spring into two separate springs: a control spring that manages needle extension and retraction, and a drive spring that powers plunger movement and medicament delivery. This segmentation allows each spring to be optimized for its specific function, enabling the drive spring to generate high force for viscous medicaments while the control spring manages user-interaction phases with reduced impact
Solution Approach 2:
The control spring is designed to be reusable across multiple injection cycles, while the drive spring is consumed with each injection. This allows the system to recover and reuse the control spring mechanism, reducing long-term manufacturing costs despite the initial complexity of having two springs
3Productivity
If the button/plunger extension is made long to ensure full injection, then the injection is complete, but the user experiences trembling and discomfort
Solution Approach 1:
The auto-injector mechanism automatically completes the injection process without requiring continuous manual pressure from the user. The spring-driven system self-regulates the plunger movement, eliminating the need for long button extensions and the associated hand tremors that occur during manual injection
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 reliable and comfortable delivery of high viscosity medicaments, reduces user discomfort, and allows for easy swapping of drive springs for different viscosity fluids, enhancing the auto-injector's versatility and cost-effectiveness.
Implementation Method 1
a control spring arranged around the carrier
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 has 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 adapted to contain a syringe with a hollow injection needle. The injector 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. There is also a trigger button arranged distally or laterally in or on the case, a control spring arranged around the carrier, and a needle extension control mechanism for coupling a proximal end of the control spring to either the carrier for advancing it for needle extension or to the chassis for needle retraction depending on the relative axial position of the carrier and the chassis.