Auto-Injector Cap Assembly With Single-Spring 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 both needle insertion and dose delivery, with a simplified trigger mechanism and a delay box to ensure complete dose delivery and safe needle retraction, featuring a safety button to prevent accidental operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple springs are used for needle insertion, retraction, and dose delivery, then the functions are reliable, but the device complexity increases
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 coupled to both the needle assembly and the syringe plunger, allowing one spring to perform multiple functions that traditionally required separate springs, thereby reducing device complexity while maintaining reliability
Solution Approach 2:
The single compression spring is designed to serve multiple purposes: it drives needle insertion, delivers the medicament dose, and enables needle retraction. This multi-functional spring 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 device complexity is reduced, but the force control for injection may be insufficient
Solution Approach 1:
The patent segments the force delivery process into distinct phases through a delay mechanism. The compression spring applies force in a controlled sequence: first for needle insertion, then for dose delivery after a delay period, and finally for needle retraction. This temporal segmentation allows a single spring to provide appropriate force control for each phase
Solution Approach 2:
The delay mechanism performs a preliminary action by waiting for the needle to be fully inserted and the injection site to be prepared before activating the dose delivery phase. This preliminary delay ensures that the full compression spring force is available for dose delivery without compromising needle insertion or causing premature injection
3Measurement precision
If injection force is increased to ensure complete dose delivery, then dosing accuracy improves, but user discomfort and hand shaking increase
Solution Approach 1:
The delay mechanism performs a preliminary action by maintaining the needle in place and allowing the user to prepare for injection before activating the full compression spring force. This preliminary phase reduces sudden force application and associated discomfort, while still ensuring complete dose delivery when the spring activates
Solution Approach 2:
The patent implements periodic action through the delay mechanism, which creates a timed sequence of events: needle insertion phase, delay period, dose delivery phase, and retraction phase. This periodic control allows the system to apply full spring force during the appropriate phase while maintaining user comfort during transition periods
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, and is suitable for administering medications like insulin and GLP-1 drugs.
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.