Separate-Spring Auto-Injector for High-Viscosity Injection
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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 they often require complex mechanisms that can lead to user confusion and safety hazards.
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 handles medicament delivery, ensuring a smooth and controlled injection process without high impact forces, and featuring a sequential operation to prevent user errors and enhance safety.
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 and the force during triggering become excessively high causing discomfort and safety hazards
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 handles medicament delivery. 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 forces during triggering, as the control spring manages the insertion/retraction sequence separately.
2Device complexity
If manual button/plunger devices are used, then the device complexity is low, but the user must continuously press the button causing hand shaking and risk of incomplete doses
Solution Approach 1:
The auto-injector device performs the injection process automatically once triggered. The control spring and drive spring work in sequence without requiring continuous user input. The device self-regulates the needle insertion, medicament delivery, and needle retraction processes, eliminating hand shaking and the risk of incomplete doses while maintaining relatively simple device structure.
3Force
If the button extension is made long to ensure full plunger compression, then the injection force can be sufficient, but the button becomes difficult to reach and operate
Solution Approach 1:
The patent extracts the force generation function from the user's manual button pressing action and transfers it to the spring mechanism. The control spring and drive spring are pre-loaded to provide the necessary injection force, eliminating the need for a long button extension. The user only needs to trigger the sequence, and the springs automatically provide the full force required for medicament delivery.
4Reliability
If complex mechanisms are added to improve safety and prevent user errors, then the reliability increases, but the device complexity increases leading to user confusion
Solution Approach 1:
The patent uses a dynamic sequential operation mechanism where the control spring and drive spring are engaged in a specific sequence. The control spring first inserts the needle, then the drive spring delivers the medicament, and finally the control spring retracts the needle. This dynamic sequencing ensures safety and dose accuracy without requiring complex additional mechanisms, as the springs naturally follow their engagement sequence based on the mechanical design.
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 medicaments, including high viscosity fluids, with reduced user discomfort and improved safety features, such as needle safety and tactile feedback, while being cost-effective and adaptable for various medicament types.
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 adapted to deliver a dose of medicament from 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.