Auto-Injector Spring Segmentation for Viscous Medicament Delivery
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Solution Overview
Problem
Existing auto-injectors face challenges such as high injection forces, discomfort due to hand shaking, and the risk of incomplete doses, particularly when administering high viscosity medicaments, and often require complex mechanisms for needle insertion and retraction.
Innovation Solution
An auto-injector design with separate control and drive springs, where the control spring manages needle insertion and retraction, allowing for a weaker drive spring to deliver viscous medicaments without user impact, ensuring consistent injection depth and preventing wet injections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a strong drive spring is used to expel high viscosity medicaments, then the injection force is sufficient, but the user experiences high impact during needle insertion and high forces during triggering
Solution Approach 1:
The patent divides the spring system into two separate springs: a control spring that the user interacts with for triggering, and a drive spring that actually delivers the medicament. The control spring is weaker and provides a manageable triggering force, while the drive spring is stronger and can handle high viscosity medicaments without affecting user comfort during activation.
Solution Approach 2:
The control spring acts as an intermediary between the user and the drive spring. It translates the user's gentle triggering action into the activation of the stronger drive spring, which then expels the medicament. This intermediary mechanism allows the user to trigger the device without experiencing the high forces required to expel viscous medicaments directly.
2Ease of operation
If manual devices are used, then the user can control the injection process, but the user must continuously press the button/plunger which requires sustained force and can cause hand shaking
Solution Approach 1:
The auto-injector performs the injection function automatically after a simple trigger action. Once activated, the drive spring automatically expels the medicament without requiring the user to maintain pressure. The device serves itself by using the stored energy in the drive spring to complete the injection process, eliminating the need for sustained user force.
3Device complexity
If a single spring system is used, then the device is simpler, but it cannot provide both consistent needle insertion force and controlled medicament expulsion
Solution Approach 1:
The patent segments the spring system into two specialized springs: the control spring manages needle insertion and triggering with consistent, controlled force, while the drive spring handles medicament expulsion with appropriate force for the specific medicament viscosity. This segmentation allows each spring to be optimized for its specific function, improving overall injection reliability.
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 provides a safe, reliable, and cost-effective auto-injector that maintains consistent injection depth, reduces user discomfort, and prevents medicament leakage, suitable for various medicament viscosities and volumes with a simplified mechanism.
Implementation Method 1
a control spring arranged around the carrier for translating the carrier in a proximal direction for insertion of the needle through the chassis into an injection site
Implementation Method 2
a drive spring and a plunger for forwarding load of the drive spring to a stopper of the syringe
Data Source
AI summary
An auto-injector for administering a dose of a liquid medicament (M) is present having a tubular chassis telescopable in a tubular case, a carrier subassembly comprising a tubular carrier slidably arranged relative to the chassis inside the case, where the carrier is adapted to contain a syringe with a hollow injection needle. The injector also has a drive spring and a plunger for forwarding load of the drive spring to a stopper of the syringe, wherein the syringe is lockable for joint axial translation with the carrier. A control spring is arranged around the carrier for translating the carrier in a proximal direction (P) for insertion of the needle through the chassis into an injection site.