Auto-Injector Trigger Mechanism Using One Spring for Full Dose Delivery
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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 underdosing, and complexity in self-administration, particularly for elderly or dexterity-impaired individuals, and issues with needle visibility and accidental reuse.
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 unintentional 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 auto-injector device performs the injection action automatically without requiring continuous user pressure. The spring-loaded mechanism propels the plunger automatically after activation, eliminating the need for the user to continuously press the button during injection, thus reducing injection force and hand-shaking while maintaining user control through the activation mechanism
2Measurement precision
If the button/plunger is extended fully to ensure complete dose delivery, then accurate dosing is achieved, but the extension is too great causing inconvenience for users to reach and potential discomfort
Solution Approach 1:
The device transitions from a static extended button design to a dynamic mechanism where the plunger is propelled automatically by spring force. The button remains compact and accessible while the internal spring mechanism ensures complete dose delivery through automatic plunger extension and retraction, eliminating the need for large external extension
3Extent of automation
If a tension spring is used to provide injection energy, then automatic injection is achieved, but the device complexity increases with multiple springs and mechanisms
Solution Approach 1:
The device merges the functions of injection energy storage and delivery into a single spring-loaded mechanism. The compression spring simultaneously provides the force for needle insertion, medicament delivery, and needle retraction, eliminating the need for separate tension springs and multiple independent mechanisms found in conventional auto-injectors
4Ease of operation
If the needle is left exposed after injection, then easy needle removal is achieved, but the risk of needle exposure and accidental reuse increases
Solution Approach 1:
The auto-injector automatically retracts the needle into the device housing after injection using spring force, eliminating the need for manual needle removal. The needle is shielded by the housing and a protective cap, automatically preventing exposure and accidental reuse while requiring no additional user action beyond the initial activation
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 accurate dose delivery, and minimizes the risk of needle exposure and reuse, providing a reliable and cost-effective auto-injector for self-administration of medications.
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.