Auto-Injector Re-Cocking Lock for Controlled Injection Force
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Solution Overview
Problem
Existing autoinjectors face issues such as variable spring forces leading to painful injections, inability to test functionality before use, complex design with metal parts causing recycling difficulties, and lack of modulated force profiles for different fluid viscosities.
Innovation Solution
An autoinjector design comprising a reservoir module, driver module, and interface module, with a piston rod, injection spring, and a lock mechanism that allows for a predetermined force profile and reusability, using a thread and winder wheel system to control force variation and a reusable design without metal parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a spring is used to provide injection force, then the injection function is achieved, but the force varies during injection causing pain and reliability issues
Solution Approach 1:
The patent replaces the static spring force system with a dynamic cam mechanism that actively modulates the injection force throughout the piston stroke. The cam profile is specifically designed to provide a predetermined force profile that maintains constant force during injection, compensating for pressure build-up and fluid viscosity effects, thereby ensuring reliable and consistent injection performance.
Solution Approach 2:
The invention changes the force parameter from a naturally decaying spring force to a controlled force profile through the cam mechanism. By varying the cam profile geometry, the system can adjust the force applied at different stages of injection, ensuring optimal force delivery that adapts to changing injection conditions and fluid properties.
2Productivity
If a spring provides high initial thrust to ensure full injection, then injection completeness is improved, but the beginning of injection becomes painful
Solution Approach 1:
The cam mechanism dynamically adjusts the force application during injection, providing high force when needed to ensure complete injection while reducing force at the beginning and end of the stroke to minimize pain. This dynamic control allows the system to optimize both injection completeness and patient comfort, unlike a spring that provides maximum force at the start regardless of pain considerations.
Solution Approach 2:
The invention uses the cam profile to change the force parameter throughout the injection process, specifically designing the profile to limit peak forces that cause pain while maintaining sufficient force to complete the injection. This parameter modulation allows separation of injection effectiveness from pain induction.
3Reliability
If complex metal parts are used in autoinjector design, then device functionality is improved, but recycling becomes difficult
Solution Approach 1:
The patent divides the autoinjector into distinct functional modules: a reusable driver module containing the cam mechanism and injection spring, and a disposable reservoir module containing the syringe and fluid. This segmentation allows the complex metal cam mechanism to be reused multiple times while the disposable portion handles clinical waste, significantly improving recycling ease without sacrificing device functionality.
Solution Approach 2:
The invention applies the disposable principle to the reservoir module, which contains the syringe, piston, and fluid. This module is designed for single use and then discarded according to clinical waste regulations, while the expensive metal cam mechanism in the driver module is reused. This approach resolves the contradiction by isolating the recyclable component from the disposable component.
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
Ensures reliable, safe, and efficient fluid delivery with adjustable force control, allows pre-testing, and facilitates recycling by separating reusable and disposable components.
Implementation Method 1
an injection spring for urging said piston rod towards its injection position
Data Source
AI summary
An autoinjector having a reservoir (110); a piston (111); a needle (112); a driver module having a body (201); a piston rod (210) movable between rest position and injection positions; an injection spring (220); and a lock that blocks the piston rod in its rest position. The lock ha a thread (230) connected to the piston rod and to a toothed winder wheel (240), a locking member (260) co-operating with a tooth (241) of the toothed winder wheel, the locking member (260) movable between a blocking position preventing the winder wheel from turning in the direction of actuation force (Fa) exerted by the injection spring, and an actuated position allowing turning of the winder wheel. The autoinjector includes a re-cocking mechanism (400) for rewinding the thread on the winder wheel by turning the winder wheel in the opposite direction to its direction during the injection stage.