Single-Spring Auto-Injector for Complete Dose Delivery
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Solution Overview
Problem
Existing auto-injectors face challenges such as user discomfort due to injection force and hand shaking, risk of incomplete doses, and complexity in operation, particularly for elderly or dexterity-impaired individuals, and often require multiple springs for needle insertion, retraction, and dose delivery.
Innovation Solution
An auto-injector design utilizing a single compression spring for needle insertion, dose delivery, and retraction, with a simplified trigger mechanism and a delay box to ensure complete dose delivery and safe needle retraction, featuring a low part count and reduced manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple springs are used for needle insertion, retraction, and dose delivery, then the functions are reliable, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple spring functions (needle insertion, dose delivery, and retraction) into a single compression spring system. The spring is configured to perform these different functions sequentially during operation, eliminating the need for separate springs for each function and thereby reducing device complexity while maintaining reliability.
Solution Approach 2:
The single compression spring is designed to serve multiple purposes: it drives needle insertion, delivers the medicament dose, and retracts the needle after injection. This multi-functional design reduces the number of components needed while ensuring all critical functions are performed reliably.
2Device complexity
If a single compression spring is used for all functions, then device complexity is reduced, but ensuring complete dose delivery and safe retraction becomes more difficult
Solution Approach 1:
The patent segments the single compression spring's operation into distinct phases: compression phase for needle insertion, injection phase for dose delivery, and retraction phase for needle withdrawal. This temporal segmentation allows one spring to perform multiple functions reliably by controlling when each function is activated during the injection cycle.
Solution Approach 2:
The spring system is designed with dynamic characteristics that automatically transition between different operational modes. The spring's compression, expansion, and locking mechanisms dynamically adapt to ensure complete dose delivery and safe retraction without requiring complex control systems.
3Measurement precision
If injection force is increased to ensure complete dose delivery, then dosing accuracy improves, but user discomfort and hand shaking increase
Solution Approach 1:
The patent replaces manual mechanical injection force with an automated compression spring mechanism. The spring provides controlled, consistent force throughout the injection cycle, eliminating the need for the user to exert high forces while reducing hand shaking and discomfort. The mechanical system automatically ensures complete dose delivery.
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 ensures reliable, complete dose delivery with reduced user discomfort and operational complexity, minimizing the risk of incomplete doses and needle injuries, while reducing material and manufacturing costs.
Implementation Method 1
spring means capable of, upon activation: pushing the needle from a covered position inside the housing into an advanced position
Implementation Method 2
retracting the syringe with the needle into the covered position after delivering the medicament
Data Source
AI summary
An auto-injector for administering a dose of a liquid medicament includes an elongate housing arranged to contain a syringe with a hollow needle and a stopper for sealing the syringe and displacing the medicament, the housing having a distal end and a proximal end with an orifice intended to be applied against an injection site. The syringe is slidably arranged with respect to the housing. A spring capable of, upon activation: pushing the needle from a covered position inside the housing into an advanced position through the orifice and past the proximal end (P), operating the syringe to supply the dose of medicament (M), and retracting the syringe with the needle into the covered position. After delivering the medicament, an activator arranged to lock the spring in a pressurized state prior to manual operation and capable of, upon manual operation, releasing the spring for injection.