Automatic Injector Needle Shield Trigger for Safe Needle Retraction
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Solution Overview
Problem
Existing automatic injectors face challenges in ensuring the needle is protected at all times before, during, and after injection, and there is a need for a mechanism that prevents accidental needle exposure.
Innovation Solution
An automatic injection device with a housing, plunger rod, needle shield, and trigger element that allows for controlled axial displacement of the needle shield to expose or cover the needle, utilizing resilient elements and a trigger mechanism to ensure safe needle protection and provide audible feedback on injection completion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a needle shield is made movable for needle exposure and protection, then needle safety is improved, but device complexity increases
Solution Approach 1:
The needle shield is nested within the housing structure, with the resilient element nested within the trigger element. This nesting arrangement allows multiple protective and actuating functions to be integrated into a compact form, reducing overall device complexity while maintaining needle safety through the movable shield mechanism.
Solution Approach 2:
The resilient element automatically returns the needle shield to its protective forward position after injection, and the trigger element automatically disengages to allow plunger rod movement. This self-service mechanism reduces the need for additional control components, simplifying the device while ensuring continuous needle protection.
2Ease of operation
If a trigger element is added to control plunger rod displacement, then injection control is improved, but device complexity increases
Solution Approach 1:
The trigger element combines multiple functions: it blocks the plunger rod during storage, transfers force to return the needle shield to protective position, and provides audible feedback. By merging these functions into a single component that interacts with existing structures (housing, needle shield, plunger rod), the device achieves improved injection control without proportionally increasing complexity.
Solution Approach 2:
The trigger element serves multiple purposes: as a safety block during storage, as a force transfer mechanism for needle shield retraction, and as an audible indication source. This multi-functionality allows a single component to address multiple operational requirements, improving ease of use while minimizing the addition of separate control mechanisms.
3Reliability
If the needle shield is prevented from forward displacement by resilient needle shield portion engagement, then needle protection is improved, but device complexity increases
Solution Approach 1:
The resilient needle shield portion is pre-configured with engagement protrusions that automatically engage with corresponding features on the housing during assembly. This preliminary positioning ensures the needle shield is held in its protective forward position without requiring additional active control mechanisms, maintaining needle protection while avoiding increased 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
Ensures safe and reliable needle protection throughout the injection process, preventing accidental exposure and providing clear auditory confirmation of injection completion.
Implementation Method 1
at least one resilient element arranged to forwardly bias the plunger rod relative to the syringe
Implementation Method 2
a needle shield adapted for selectable axial displacement with respect to the housing along the longitudinal axis, whereas rearward displacement of the needle shield exposes the needle and forward displacement of the needle shield covers the needle
Implementation Method 3
a trigger element configured to be axially rearwardly displaced upon rearward displacement of the needle shield relative to the housing and thereby allow forward displacement of the plunger rod relative to the syringe under the urge of the at least one resilient element
Implementation Method 4
the trigger element radially supports the housing portion
Data Source
AI summary
An automatic injection device, including a housing arranged along a longitudinal axis and having a forward end and a rearward end, the housing is configured to receive a syringe including at least one syringe piston and a needle coupled to a forward end thereof; a plunger rod adapted to be retained with respect to the housing in an initial operative orientation; at least one resilient element arranged to forwardly bias the plunger rod relative to the syringe; a needle shield adapted for selectable axial displacement with respect to the housing along the longitudinal axis, whereas rearward displacement of the needle shield exposes the needle and forward displacement of the needle shield covers the needle; and a trigger element configured to be axially rearwardly displaced upon rearward displacement of the needle shield relative to the housing and thereby allow forward displacement of the plunger rod relative to the syringe under the urge of the at least one resilient element.