Auto-Injector Single-Spring Mechanism 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, hand trembling, and the risk of incomplete doses, particularly in manual devices, while auto-injectors often require multiple springs for needle insertion, retraction, and dose delivery, increasing complexity and cost.
Innovation Solution
An auto-injector design utilizing a single compression spring for both needle insertion and dose delivery, with a simplified mechanism that includes a retraction sleeve and a decoupling system to ensure complete dose delivery and safe needle retraction, featuring a safety button to prevent accidental operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If multiple springs are used for needle insertion, retraction, and dose delivery, then the auto-injector can perform all functions automatically, but the device complexity and manufacturing cost increase
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. The spring is first compressed to store energy for needle insertion, then automatically repositions to deliver the dose, and finally retracts the needle, eliminating the need for separate springs for each function.
Solution Approach 2:
The single compression spring is designed to serve multiple functions: it acts as the driving force for needle insertion, then as the piston for dose delivery, and finally as the retraction mechanism. This multi-functional component reduces the overall part count while maintaining automatic operation capability.
2Device complexity
If a single compression spring is used for all functions, then device complexity and cost are reduced, but ensuring complete dose delivery and safe retraction becomes more challenging
Solution Approach 1:
The system uses dynamic repositioning of the compression spring through a cam mechanism that automatically changes the spring's position and orientation during operation. The spring transitions from a compressed state for insertion to an extended state for dose delivery, then to a retraction phase, with each phase controlled by the cam's geometric profile ensuring reliable function completion.
Solution Approach 2:
A cam mechanism serves as an intermediary between the compression spring and the injection system components. The cam converts the spring's linear compression motion into the sequential rotational and linear motions required for needle insertion, dose delivery, and retraction, ensuring proper timing and reliability of each function.
3Device complexity
If manual devices are used, then device complexity is low, but user discomfort from high injection forces and hand trembling occurs
Solution Approach 1:
The auto-injector performs all injection functions automatically without requiring continuous user input. The user simply activates the device, and the system autonomously handles needle insertion, dose delivery, and needle retraction, eliminating the need for the user to manually apply injection force and reducing hand trembling issues.
4Manufacturing precision
If the button/plunger extension is great to ensure complete dose, then injection completeness is improved, but user convenience deteriorates due to difficulty in reaching and operating the extended button
Solution Approach 1:
The patent replaces the manual button/plunger activation mechanism with an automatic trigger system. The user activates the device by pressing a trigger, which automatically initiates the complete injection sequence including needle insertion, dose delivery, and needle retraction, eliminating the need for the user to manually extend and operate a long plunger.
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 lowers manufacturing costs by using fewer parts, while preventing accidental triggering and ensuring safe needle retraction.
Implementation Method 1
spring means 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
Implementation Method 2
a single compression spring arranged to be grounded at a distal end in the housing for advancing the needle and for injecting the dose of medicament
Implementation Method 3
The content of the ampoule is thereafter expelled by the tension spring forcing a piston forward inside the ampoule
Implementation Method 4
pushing the needle from a covered position inside the housing into an advanced position through the orifice and past the proximal end
Implementation Method 5
retracting the syringe with the needle into the covered position after delivering the medicament
Implementation Method 6
torsion stored in the tension spring is released and the injection needle is automatically retracted back to its original storage position
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.