Single-Spring Auto-Injector for Complete Dose and Needle Retraction
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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, as well as issues with needle visibility and accidental triggering.
Innovation Solution
An auto-injector design utilizing a single compression spring for needle insertion, dose delivery, and retraction, with a simplified trigger mechanism and safety features to prevent accidental operation, ensuring complete dose delivery and safe needle retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a manual device with button/plunger is used, then the user can control the injection process, but the user must continuously press the button during injection which causes high injection forces and hand shaking
Solution Approach 1:
The device uses a spring mechanism that automatically performs the injection action without requiring continuous user pressing. The spring is compressed during loading and automatically expands to push the plunger, making the system self-actuating and eliminating the need for continuous manual force application during injection.
Solution Approach 2:
The spring-based system provides periodic action where the spring compresses during the loading phase and then expands automatically during the injection phase. This periodic compression-expansion cycle replaces the continuous pressing action, reducing hand shaking and providing smoother injection forces.
2Reliability
If the button/plunger is extended fully to ensure complete dose, then the injection can be completed, but the extension is too great causing inconvenience for users to reach
Solution Approach 1:
The device replaces the manual button-plunger extension mechanism with an automatic spring-driven system. The spring automatically pushes the plunger to the correct position and maintains it there, eliminating the need for users to manually extend and hold a button, thus improving accessibility while ensuring complete dose delivery.
3Reliability
If multiple springs are used for needle insertion and retraction, then the functions are reliable, but the device complexity increases
Solution Approach 1:
The single spring element is designed to perform multiple functions: it compresses during needle insertion, maintains insertion depth, and automatically drives retraction after injection. This multi-functional spring replaces what would traditionally require separate springs for insertion and retraction, reducing component count while maintaining reliability.
Solution Approach 2:
The invention merges the functions of needle insertion spring and retraction spring into a single spring element. The spring is compressed during insertion and then automatically expands to drive retraction, combining two separate mechanical functions into one unified component that reduces overall device complexity.
4Loss of information
If the needle is visible to the user during injection, then the user can monitor the process, but the risk of accidental needle exposure and injury increases
Solution Approach 1:
The device introduces a shield or cover as an intermediary element that hides the needle from view during storage and retraction phases. The shield acts as a mediator between the user and the needle, allowing the user to monitor the injection process through transparent or translucent portions while preventing accidental exposure to the sharp needle tip.
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 minimizes the risk of accidental needle exposure, while reducing part count 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 through the orifice and past the proximal end
Implementation Method 2
spring means capable of, upon activation: operating the syringe to supply the dose of medicament
Implementation Method 3
spring means capable of, upon activation: 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.