Auto-injector Drive Spring Grounding Switch
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Solution Overview
Problem
Current auto-injectors for administering liquid medicaments face challenges such as complex handling requirements, high injection forces, and difficulties in ensuring complete dose delivery due to the need for precise operation of small buttons, which can be problematic for users with dexterity issues and may result in incomplete or inconsistent dosing.
Innovation Solution
An auto-injector design utilizing a single drive spring for both needle insertion and syringe operation, with a wrap-over sleeve trigger button that allows whole-hand operation and a mechanism to ensure reliable retraction of the needle only after complete delivery of the medicament, reducing the complexity and physical demands of the injection process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single drive spring is used for both needle insertion and syringe operation, then device complexity is reduced, but injection force requirements increase
Solution Approach 1:
The drive spring dynamically switches its grounding point from the distal end to the proximal end during operation. Initially grounded at the distal end for needle insertion, it then switches to proximal end grounding for syringe operation, allowing a single spring to adaptively provide appropriate force for each phase without requiring multiple springs or complex mechanisms
Solution Approach 2:
The single drive spring performs multiple functions: it drives needle insertion when grounded at the distal end, and drives syringe operation when grounded at the proximal end. This multi-functionality eliminates the need for separate springs for each function, reducing overall device complexity while maintaining adequate force delivery
2Ease of operation
If a wrap-over sleeve trigger button is used for whole-hand operation, then ease of operation is improved, but device complexity increases
Solution Approach 1:
The wrap-over sleeve trigger button is designed to be operated by the whole hand in a natural gripping motion, allowing the user's hand to serve the device rather than requiring precise finger dexterity. The sleeve's geometry guides the hand into the correct operating position, making the activation process intuitive and self-explanatory
Solution Approach 2:
Instead of requiring precise finger manipulation of a small button, the design inverts the approach by providing a large sleeve that accommodates the entire hand. The operation shifts from fine motor control to gross motor movement, benefiting users with dexterity limitations while the sleeve structure itself manages the complexity of force transmission
3Manufacturing precision
If needle retraction is delayed until complete medicament delivery, then dose accuracy is improved, but injection time increases
Solution Approach 1:
The system incorporates feedback through the drive spring's grounding mechanism that monitors medicament delivery status. When the syringe reaches its retracted position, the grounding automatically switches from distal to proximal end, triggering needle retraction. This feedback-based control ensures complete dose delivery before retraction while using automatic timing rather than manual intervention
Solution Approach 2:
The grounding switch mechanism is pre-configured to automatically trigger needle retraction at the precise moment when syringe retraction is complete. This preliminary setup ensures that retraction timing is predetermined and automatic, eliminating delays caused by manual judgment while maintaining accurate dose delivery
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 simplifies handling, reduces the physical effort required for injection, and ensures complete and reliable delivery of the medicament dose, particularly benefiting users with dexterity problems by eliminating the need for precise finger operation and ensuring full dose administration.
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
Data Source
AI summary
An auto-injector for administering a dose of a liquid medicament (M) is presented comprising an elongate housing arranged to contain a syringe with a hollow needle and a stopper for sealing the syringe and displacing the medicament (M), the housing having a distal end (D) and a proximal end (P) with an orifice intended to be applied against an injection site, wherein the syringe is slidably arranged with respect to the housing. The auto-injector contains a 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 (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 (M). There is also an activating means arranged to lock the spring means in a pressurized state prior to manual operation.