Compression-Spring Auto-Injector for Complete Dose Delivery
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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, and often require 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 trigger mechanism and safety features to prevent accidental operation, ensuring complete dose delivery and safe needle retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple springs are used for needle insertion, retraction, and dose delivery, then the injection functions are reliable, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple spring functions (needle insertion, dose delivery, and needle retraction) into a single compression spring system. The compression spring is configured to perform all three functions sequentially through its compression and expansion cycles, eliminating the need for separate springs for each function and thereby reducing device complexity while maintaining reliability
Solution Approach 2:
The single compression spring is designed with multi-functionality, serving as the driving mechanism for needle insertion, medicament delivery, and needle retraction. This universal spring component replaces what would traditionally require multiple specialized springs, simplifying the overall device structure
2Device complexity
If a single compression spring is used for all functions, then the device complexity is reduced, but the force requirements for needle insertion and retraction may be insufficient
Solution Approach 1:
The compression spring is designed with variable force characteristics throughout its compression and expansion cycle. The spring provides high force during the initial compression phase for needle insertion, maintains appropriate force during the dosing phase, and generates sufficient retraction force when released. This dynamic force delivery is achieved through the natural mechanical properties of the spring rather than requiring multiple springs
3Measurement precision
If the button/plunger extension is increased to ensure complete dose delivery, then the dosing accuracy improves, but the user comfort decreases due to hand shaking and discomfort
Solution Approach 1:
The auto-injector system performs the injection action automatically without requiring continuous user pressure on a plunger. The compression spring automatically drives the needle insertion and medicament delivery, while the system self-regulates the injection process. This eliminates the need for extended button pressure and associated hand shaking, providing both accurate dosing and user comfort
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 manufacturing costs by using fewer parts, while providing a reliable and safe injection experience.
Implementation Method 1
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. The force of the compression spring is forwarded to the needle and/or the syringe via a plunger
Implementation Method 2
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
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.