Auto-Injector Dual-Spring Architecture for Viscous Medicament Delivery
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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, especially when administering high viscosity medicaments, and often require complex manual operation.
Innovation Solution
An auto-injector design with separate control and drive springs, where the control spring manages needle insertion and retraction, allowing for a weaker drive spring to deliver viscous medicaments without user impact, ensuring consistent injection depth and preventing wet injections.
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 user experiences high impact during needle insertion and high forces during triggering
Solution Approach 1:
The patent divides the spring system into two separate springs: a control spring that the user interacts with for triggering, and a drive spring that actually delivers the medicament. The control spring is configured to provide manageable triggering forces, while the drive spring is configured to provide sufficient injection force for high viscosity medicaments. This segmentation allows each spring to be optimized for its specific function without compromising the other.
2Device complexity
If manual devices are used, then the device complexity is low, but the user must continuously press the button/plunger which can cause incomplete doses and hand shaking
Solution Approach 1:
The auto-injector is designed to perform the injection process automatically once triggered. The control spring automatically drives the plunger to complete the injection without requiring continuous user input. The system self-regulates the injection process, ensuring complete dose delivery while eliminating hand shaking issues associated with manual continuous pressing.
3Force
If the button/plunger extension is made long to ensure full depression, then the injection force can be adequate, but it becomes inconvenient for users to reach and causes hand shaking
Solution Approach 1:
The patent separates the force generation function from the user interface element. The control spring provides the necessary injection force through a compact mechanism, eliminating the need for a long button extension. Users only need to press the trigger button a short distance to release the control spring, which then automatically provides the full injection force needed for viscous medicaments.
4Device complexity
If a single spring system is used for both control and drive functions, then the device complexity is reduced, but it cannot simultaneously provide manageable triggering forces and sufficient injection forces for high viscosity medicaments
Solution Approach 1:
The patent employs two separate spring systems with distinct functions: the control spring manages the triggering mechanism with optimized force characteristics for user comfort, while the drive spring is specifically designed to deliver high forces required for injecting high viscosity medicaments. This dual-spring architecture enables the device to handle a wide range of medicament viscosities while maintaining ease of operation.
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 safe, reliable, and efficient injection process with reduced user discomfort, consistent injection depth, and the ability to deliver different medicament viscosities using a single platform, while minimizing manufacturing costs.
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 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 (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.