Single-Spring Auto-Injector for Dose Delivery and Needle Retraction
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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 self-administered therapies like diabetes and hormone treatments.
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-loaded mechanism that automatically delivers the injection without requiring continuous user pressure. The spring is pre-loaded and automatically propels the plunger to deliver the full dose, making the system self-servicing and eliminating the need for continuous manual pressure application.
Solution Approach 2:
The spring is pre-loaded during device assembly or storage, storing mechanical energy in advance. When the device is activated, this pre-stored energy automatically propels the plunger to deliver the injection, eliminating the need for continuous user pressure during the actual injection process.
2Reliability
If the button/plunger is extended fully to ensure complete dose, then the injection force is sufficient, but the extension is too great causing inconvenience for the user to reach
Solution Approach 1:
The spring-loaded mechanism automatically extends the plunger to its full position and maintains it there during injection, eliminating the need for the user to manually extend and hold the button. The system self-manages the extension and retraction, providing reliable complete dose delivery without excessive user effort.
3Reliability
If multiple springs are used for needle insertion and retraction, then the functions are reliable, but the part count and manufacturing complexity increase
Solution Approach 1:
A single spring element is designed to perform multiple functions: it provides the force for needle insertion, maintains the needle in the inserted position during injection, and automatically retracts the needle after the injection is complete. This multi-functional spring eliminates the need for separate springs for each function, reducing part count while maintaining reliability.
Solution Approach 2:
The invention combines the functions of needle insertion, position maintenance, and needle retraction into a single spring-loaded mechanism. By merging these functions into one component system, the design reduces the total number of parts while ensuring reliable performance of each function.
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 injection, 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.