Needle-Assisted Injector Trigger and Guard Against Accidental Firing
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Solution Overview
Problem
Existing injectors face issues with accidental firing due to mishandling, constrained design, and friction between components, which can lead to unsafe medicament expulsion and needle penetration, particularly in needle-assisted jet injectors.
Innovation Solution
A needle-assisted jet injector with a cap that detachably couples to the housing, featuring a ram assembly, needle guard, and trigger mechanism that moves between configurations to prevent accidental firing, ensuring safe and controlled medicament expulsion, and includes a needle shield that extends past the cap for protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a needle-assisted jet injector uses high pressure to expel medicament through the skin, then injection speed and penetration depth are improved, but the risk of accidental firing and harmful effects increases
Solution Approach 1:
The needle is extended and positioned to penetrate the skin before the high-pressure medicament expulsion is initiated. The trigger mechanism ensures the needle is in place and the guard is in the pre-injection position before releasing the stored energy to expel medicament, preventing accidental firing during shipping or handling
Solution Approach 2:
A trigger mechanism acts as an intermediary between the user and the high-pressure expulsion system. The trigger member must be deliberately actuated to release the stored energy in the ram assembly, providing a controlled interface that prevents unintended activation while allowing rapid medicament delivery when intended
2Force
If the injector uses a trigger mechanism with stored kinetic energy to drive injection, then injection force is improved, but the device complexity and ease of operation worsen due to friction and binding
Solution Approach 1:
The camming surfaces are designed with specific geometric parameters (angles, radii, profiles) that optimize the conversion of rotational motion to linear ram displacement. The cam profile is shaped to provide smooth acceleration and deceleration of the ram, reducing binding and friction while maintaining high injection force
Solution Approach 2:
The trigger mechanism is divided into separate functional components: the trigger member for user input, the camming surfaces for motion conversion, the ram assembly for force generation, and the energy source for power storage. This segmentation allows each component to be optimized independently and simplifies manufacturing and assembly
3Ease of operation
If the needle guard moves from storage to pre-injection position when cap is detached, then ease of operation is improved, but the device complexity increases
Solution Approach 1:
The needle guard is designed to automatically move from the storage position to the pre-injection position through the mechanical action of cap removal itself. The cap and guard are mechanically coupled such that detaching the cap provides the force to move the guard, eliminating the need for separate actuation mechanisms
Solution Approach 2:
The cap removal action is merged with the needle guard positioning function. The same mechanical motion that removes the cap also advances the guard to the correct position, combining two operations into one simple user action that reduces overall device complexity
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 injector provides safe, controlled medicament delivery with reduced risk of accidental firing and needle exposure, ensuring user safety and effective medicament administration.
Implementation Method 1
The injection mechanism can be structured to pressurize the container. The pressure applied to the medicament within the injector can be less than that of a traditional jet injector
Implementation Method 2
Once the skin is penetrated with the needle, a jet mechanism is activated, causing the medicament containing liquid within the injector to be pressurized and expelled through the needle and into the skin
Data Source
AI summary
An injector including: a housing, a cap detachably coupled to the housing, a ram assembly having a ram configured to pressurize a medicament container for expelling a medicament therefrom, the ram assembly including a trigger engagement member, an energy source associated with the ram for powering the ram to expel medicament from the medicament container, a trigger member disposed about an axis, the trigger member moveable between a pre-firing configuration and a firing configuration, wherein medicament is expelled from the medicament container when the trigger member is in the firing configuration, a needle guard moveably coupled to the housing, the needle guard movable between a storage position and a pre-injection position, wherein the needle guard moves from the storage position to the pre-injection position as the cap is detached from the housing.