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 high injection forces 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 both needle insertion and dose delivery, with a simplified trigger mechanism and a retraction sleeve, featuring a delay box to ensure complete dose delivery and safe needle retraction, and a safety button to prevent accidental operation.
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 increases
Solution Approach 1:
The patent combines multiple spring functions into a single compression spring that performs needle insertion, dose delivery, and retraction through sequential activation phases. The single spring is activated in three stages: first for needle insertion, then for dose delivery, and finally for retraction, eliminating the need for multiple separate springs while maintaining all required functions.
Solution Approach 2:
The single compression spring is designed to serve multiple functions throughout its activation cycle. It acts as the driving force for needle insertion, then continues to drive the syringe plunger for dose delivery, and finally retracts the needle, making one component perform the work of what would traditionally require multiple specialized springs.
2Device complexity
If a single compression spring is used for all functions, then device complexity is reduced, but ensuring complete dose delivery becomes challenging
Solution Approach 1:
The single compression spring's activation is segmented into three distinct phases: needle insertion phase, dose delivery phase, and retraction phase. This segmentation allows the spring to be activated in controlled stages, ensuring that the full dose is delivered while maintaining simple device architecture.
Solution Approach 2:
The delay box mechanism provides a time delay between the activation of the spring and the release of the syringe plunger. This preliminary delay ensures that the spring has fully activated and the needle is properly positioned before the dose delivery begins, preventing incomplete dosing while keeping the mechanism simple.
3Measurement precision
If injection forces are high to ensure complete dose delivery, then dosing accuracy improves, but user discomfort and hand shaking increase
Solution Approach 1:
The delay box creates a time delay that separates the high-force injection phase from the user's perception of discomfort. The spring activates with sufficient force to deliver the complete dose, but the delay box modulates the delivery timing to reduce sudden force spikes and hand shaking, making the injection more comfortable for the user.
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 reduces user discomfort, ensures complete dose delivery, and simplifies operation, while reducing material and manufacturing costs, with enhanced safety features to prevent accidental use and improve reliability.
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.