Auto-Retractable Syringe Detent and Spring Mechanism
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Solution Overview
Problem
Retractable syringes face issues with liquid leakage and functional reliability, and their complex designs make them difficult and costly to manufacture, while some designs leave dead-zones in the barrel, preventing full fluid dispensing.
Innovation Solution
An auto-retractable syringe design featuring a detent arrangement with inclined claws to securely hold the needle hub, a partially compressed spring for controlled retraction, and a stopper with a partly-spherical surface to enhance manufacturing simplicity and fluid dispensing efficiency, along with an O-ring for effective sealing to prevent leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a spring mechanism is used for automatic needle retraction, then needle safety is improved, but liquid leakage and functional reliability issues occur
Solution Approach 1:
The syringe is divided into distinct functional zones: a sealed injection chamber for fluid delivery, a retraction mechanism chamber for the spring and needle hub, and a detent mechanism for controlled activation. This segmentation isolates the liquid-containing portion from the mechanical retraction components, preventing leakage while maintaining reliable automatic retraction functionality.
2Reliability
If a complex mechanism is used for needle retraction, then retraction reliability is improved, but manufacturing difficulty and cost increase
Solution Approach 1:
Multiple functions are merged into single components to simplify manufacturing: the detent mechanism combines locking and activation functions, the biased member integrates spring-loaded retraction force with hub engagement, and the needle hub serves both as a structural support and as the component that receives the retraction force. This merging reduces part count and assembly complexity while maintaining reliable automatic retraction.
3Ease of manufacture
If the barrel design is simplified, then manufacturing ease is improved, but dead-zones remain preventing full fluid dispensing
Solution Approach 1:
The plunger is designed with dynamic engagement features rather than static sealing: a tapered leading edge that progressively seals against the barrel wall during injection, and a trailing edge with engagement features that interact with the needle hub assembly. This dynamic design allows the plunger to maintain sealing effectiveness throughout its travel while being manufactured with simpler geometry, eliminating dead zones without requiring complex barrel internal features.
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 improves reliability and manufacturing ease, reduces leakage, and allows for complete fluid dispensing by securely engaging and disengaging the needle hub, ensuring safe needle retraction and efficient operation.
Implementation Method 1
a spring acting to bias the hub into the plunger
Implementation Method 2
whereby the spring acts to retract the needle inside the syringe barrel
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An auto-retractable syringe having a barrel and a plunger wherein engagement of said plunger with an otherwise immobilised needle hub allows a biasing member to push the needle hub into a cavity in the plunger.