Single-Spring Auto-Injector for Low-Force Complete Dosing
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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-loaded mechanism that automatically generates and maintains the injection force without requiring continuous user pressure. The spring is pre-loaded to provide the necessary force throughout the injection cycle, allowing the user to simply activate the trigger while the system self-regulates the force application.
Solution Approach 2:
The spring-loaded system provides periodic force delivery in controlled increments. As the spring releases its stored energy during the injection cycle, it delivers force in a controlled manner that prevents sudden spikes in injection force, reducing hand shaking and improving comfort.
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 the user to reach
Solution Approach 1:
The device employs a dynamic needle and plunger retraction system that automatically returns components to their starting positions after injection. The spring mechanism dynamically adjusts the positions of the needle and plunger, ensuring they are retracted to safe, accessible lengths while maintaining the ability to deliver the complete dose when activated.
3Extent of automation
If a spring-loaded auto-injector is used, then injection forces are reduced and automation is improved, but the device complexity increases with multiple components
Solution Approach 1:
The spring-loaded mechanism serves multiple functions simultaneously: it provides the injection force, automatically retracts the needle and plunger, and maintains the device in a ready state for subsequent use. By making the spring system multi-functional, the design reduces the need for separate mechanisms for each function, thereby limiting the increase in 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 needle may cause accidental injury or health risk
Solution Approach 1:
The device uses a shield or cover as an intermediary element that obscures the needle from the user's view during storage and transport. This shield can be automatically positioned to block the needle while allowing the injection process to proceed normally, eliminating the risk of accidental injury while maintaining user awareness through other feedback mechanisms.
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
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 compression spring is arranged to have its ground in the housing switched to its proximal end for retracting the syringe when the injection of the medicament is at least nearly finished
Implementation Method 4
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
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.