Auto-Injector Mechanism Using One Spring for Dosing and 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 insulin and GLP-1 drugs, with manual devices requiring continuous user effort and auto-injectors often needing multiple springs for needle insertion, retraction, and dose delivery.
Innovation Solution
An auto-injector design utilizing a single compression spring for needle insertion, dose delivery, and retraction, with a simplified mechanism that includes a retraction sleeve and decoupling arms, ensuring complete dose delivery and safe needle retraction, and incorporating 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 increases and manufacturing costs rise
Solution Approach 1:
The patent combines multiple functions (needle insertion, dose delivery, and needle retraction) into a single spring mechanism. The compression spring is configured to perform all three functions sequentially through a unified mechanical linkage system, eliminating the need for separate springs for each function and thereby reducing device complexity while maintaining automation.
Solution Approach 2:
The single compression spring is designed as a universal driving element that performs multiple functions: it drives needle insertion, delivers the medicament dose, and retracts the needle after injection. This multi-functional design reduces the overall component count and simplifies the mechanical structure while achieving complete automation.
2Device complexity
If a single spring is used for all functions, then device complexity and manufacturing costs are reduced, but ensuring complete dose delivery and safe retraction becomes more difficult
Solution Approach 1:
The patent segments the single spring's action into distinct phases through a multi-component linkage system. The compression spring is divided into functional segments that sequentially perform needle insertion, dose delivery, and needle retraction. This segmentation ensures that each function is completed reliably while using a single spring source, maintaining both simplicity and reliability.
Solution Approach 2:
The patent introduces intermediary components (such as linkages, levers, and control mechanisms) that mediate between the single spring and the various functions it must perform. These intermediaries ensure that the spring's energy is transferred reliably to accomplish needle insertion, complete dose delivery, and safe needle retraction, thereby maintaining high reliability despite the simplified single-spring design.
3Manufacturing precision
If injection force is high to ensure complete dose delivery, then the medicament is delivered accurately, but user discomfort increases and hand-shaking occurs
Solution Approach 1:
The patent employs a dynamic spring mechanism that adjusts the force delivery over time. The compression spring releases energy in controlled stages: initial low force for needle insertion, followed by controlled force for dose delivery, and then retraction. This dynamic force management ensures complete dose delivery while minimizing user discomfort and preventing hand-shaking by avoiding sudden high-force shocks.
Solution Approach 2:
The patent performs preliminary actions through the spring mechanism to prepare for the main injection force. The spring first pre-loads the system, then releases energy in a controlled sequence that includes preliminary needle insertion and positioning before delivering the main medicament dose. This preliminary action sequence ensures accurate dose delivery while managing force application to reduce user discomfort and hand-shaking.
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 simplifies operation with a low part count, reducing manufacturing costs and weight, while enhancing safety and reliability.
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: pushing the needle from a covered position inside the housing into an advanced position through the orifice and past the proximal end, operating the syringe to supply the dose of medicament
Implementation Method 3
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, operating the syringe to supply the dose of medicament, and 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.