Auto-injector Pressure Chamber Uniform Force Distribution
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Solution Overview
Problem
Auto-injectors face reliability issues due to primary container materials being limited by chemical inertness, which does not provide robust physical properties to withstand the stresses from large forces during activation, leading to potential mechanical failure and incomplete injections.
Innovation Solution
The auto-injector design includes a primary container with a sidewall disposed within a pressure chamber, where the pressure is applied uniformly to both the interior and exterior surfaces, reducing the pressure differential and minimizing stresses on the sidewall, allowing for reliable expulsion of the beneficial agent without subjecting the container to excessive forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional chemically inert materials (glass or polymer) are used for the primary container, then chemical stability is maintained, but the container cannot withstand the large forces during activation, leading to mechanical failure
Solution Approach 1:
The system is divided into two functional parts: the primary container (barrel) that maintains chemical inertness and the pressure chamber that provides mechanical strength. The barrel is disposed within the pressure chamber, separating the chemical containment function from the force-withstanding function.
Solution Approach 2:
The pressure chamber acts as an intermediary structure between the energy source and the primary container. It transmits the activating force to the stopper while protecting the barrel from direct exposure to large forces, thus preventing mechanical failure of the chemically inert container.
2Productivity
If pressure is applied to expel the beneficial agent, then injection is achieved, but large forces act on the primary container causing potential mechanical failure
Solution Approach 1:
The pressure chamber serves as a mediator that applies pressure to expel the beneficial agent while isolating the primary container from the full magnitude of activating forces. The barrel experiences reduced stress because it is not directly exposed to the large forces generated during activation.
Solution Approach 2:
The pressure chamber provides a protective environment for the primary container before and during activation. By disposing the barrel within the pressure chamber, the design preemptively protects the container from mechanical failure caused by large forces during injection.
3Power
If the primary container forms part of the pressure chamber boundary, then force application is direct, but the container experiences large forces that may cause mechanical failure
Solution Approach 1:
The system segments the force transmission path from the container structure. The pressure chamber wall transmits force to the stopper, while the barrel remains separate and experiences minimal stress. This separates the power transmission function from the chemical containment function.
Solution Approach 2:
The pressure chamber acts as an intermediary that enables force application to the stopper without requiring the primary container to form part of its boundary. This allows efficient force transmission while protecting the barrel from large forces.
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
This design enhances the reliability of auto-injectors by reducing the risk of mechanical failure and ensuring complete injection, while using traditional chemically inert materials, thus maintaining economic viability and chemical stability.
Implementation Method 1
an increase in pressure within the pressure chamber relative to an exterior environment of the auto-injector in order to develop a pressure differential that drives the injection
Data Source
AI summary
Parenteral delivery of a beneficial agent using an auto-injector configured for reduction of forces acting on a primary container for the beneficial agent during activation of the auto-injector. The primary container may be disposed within a pressure chamber of the auto-injector such that an increased pressure within the pressure chamber during activation is applied to a stopper of the primary container and an external surface of a sidewall of the primary container. In turn, a pressure differential between a containment volume of the primary container and the pressure chamber may be reduced or eliminated. In turn, forces acing on the primary container in response to the pressure increase in the pressure container may be reduced or eliminated. Configurations are also provided for improved relative movement between a stopper and a sidewall of the primary container for more reliable injection.