Auto-Retracting Syringe Spring-Latch Mechanism
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Manual hypodermic syringes lack an effective mechanism for automatic needle retraction after injection, posing risks of accidental needle exposure and requiring user intervention for safe disposal.
Innovation Solution
A hypodermic syringe design featuring a housing with axially-extending and radially-movable latching arms, a plunger with latch-triggering discs, and a spring mechanism that enables automatic needle retraction into the outer barrel after completion of the injection cycle, utilizing a four-stroke cycle to engage and disengage latches for controlled needle movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual hypodermic syringes are used without automatic retraction mechanism, then device simplicity is maintained, but safety risks increase due to accidental needle exposure
Solution Approach 1:
The syringe automatically retracts the needle into the outer barrel after injection without requiring user intervention. The spring mechanism self-activates when the plunger reaches the end of its stroke, and the latching mechanism automatically secures the needle in the retracted position, eliminating the need for manual disposal operations.
Solution Approach 2:
A latching mechanism acts as an intermediary between the plunger and the needle retraction system. The latch members engage with latch-triggering surfaces on the plunger and control the timing of needle retraction, ensuring that retraction occurs only after injection is complete while preventing premature activation.
2Ease of operation
If latching mechanism is added for controlled needle movement, then needle retraction control is improved, but device complexity increases
Solution Approach 1:
The latching mechanism is segmented into multiple independent components: latch members on the housing, latch-triggering discs on the plunger, and spring mechanisms. Each component has a specific function, and together they create a controlled sequence of operations that manages needle retraction without requiring a single complex mechanism.
3Reliability
If automatic retraction mechanism is implemented, then safety is improved by preventing accidental needle exposure, but manufacturing complexity increases
Solution Approach 1:
The syringe employs a nested structure where the inner barrel containing the needle is housed within an outer barrel. The latch members and spring mechanisms are integrated into the walls of these barrels, with components nested within each other to minimize overall device volume and reduce the number of separate parts that need to be manufactured and assembled.
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 automatic needle retraction, allowing users to control the retraction rate and preventing inadvertent needle exposure, while enabling easy needle attachment and detachment for repeated use.
Implementation Method 1
a spring adapted to exert retraction force against the inner barrel to retract the needle into the housing after usage
Data Source
AI summary
An auto-retracting hypodermic syringe has a housing extending axially to form a collar and housing interacting syringe components, an outer barrel is fixed within or forms part of the housing and an inner barrel is slidably mounted within the outer barrel for rearward movement within the outer barrel, the inner barrel has a mount for mounting a hypodermic needle on it or a needle already within a mount; a plunger has a piston on its distal end for withdrawing liquid dosage into the inner barrel when the plunger is pulled back and for injecting dosage when the plunger is pushed forward; axially-spaced, different-diameter discs on the plunger engage with radially pivoting, hinged latching arms formed on the proximal end of the housing and there are other associated latch members on the inner barrel and the housing which move inwards and outwards in correspondence with forward and rearward movements of the plunger; a coil spring is placed between the housing and inner barrel to exert needle retraction force against the inner barrel to retract it into the housing after completion of injection of syringe contents whereupon a latch locks it into the housing.