Syringe Assembly Passive Disabling Mechanism
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Solution Overview
Problem
Existing syringe assemblies intended for single-use often fail to automatically disable after use, allowing for potential reuse and contributing to the spread of diseases and drug abuse, as they require a specific user action to render them inoperable.
Innovation Solution
A syringe assembly with a structure controlling the free axial motion of the stopper with respect to the plunger rod, utilizing inwardly directed projections and recesses on the secondary post to prevent accidental movement and ensure automatic disabling after a predetermined number of strokes, thereby preventing unintended reuse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking element is positioned in the syringe barrel to prevent proximal motion of the plunger rod, then the syringe becomes inoperable after use, but the device requires specific user intent and action to activate the disabling mechanism
Solution Approach 1:
The locking element is pre-positioned within the syringe barrel but remains inactive during normal use. The frangible connection is pre-established between the plunger rod and stopper. When the plunger rod is pulled proximally after use, the frangible connection breaks automatically, causing the locking element to engage with the barrel wall and disable the syringe without requiring any additional user action.
Solution Approach 2:
The syringe assembly performs the disabling action automatically through its own structural features. The frangible connection and locking element work together as a self-activating system that responds to the natural motion of plunger withdrawal, eliminating the need for external activation mechanisms or user intervention beyond the normal reuse attempt.
2Adaptability or versatility
If the syringe allows multiple plunger rod strokes for complete injection process, then the syringe can perform diluent dispensing and medication delivery, but the disabling mechanism must not prevent filling or use under normal conditions
Solution Approach 1:
The frangible connection is located specifically at the interface between the plunger rod and stopper, affecting only the proximal motion after use. During normal injection strokes, the plunger rod moves distally to deliver medication, which does not engage the frangible connection. The local placement of the frangible feature ensures it only activates when the plunger rod is pulled proximally after the injection is complete.
Solution Approach 2:
The system transitions from a flexible state during normal use to a locked state after use. During injection, the plunger rod can move freely in the distal direction to deliver multiple strokes of medication. After use, when the plunger rod is pulled proximally, the frangible connection breaks and the locking element engages, dynamically changing the system from operational to disabled state.
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 solution effectively prevents accidental or unintended reuse of the syringe by requiring a greater force to move the stopper beyond its designated positions, ensuring the syringe is disabled after the intended use, thus addressing the issue of multiple use and disease transmission.
Implementation Method 1
the inwardly directed projection on the plunger rod having a free end frictionally contacting the outside surface of the secondary post increasing the force required to move the stopper with respect to the plunger rod
Data Source
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AI summary
A syringe assembly (20) having passive disabling structure includes a barrel (21) and a plunger rod assembly (43, 81, 71). The plunger rod (43) assembly includes a plunger rod and a stopper (81) connected by an indexing locking element (71). The number of strokes of the syringe plunger before the stopper, is locked into the barrel rendering the syringe assembly unusable is determined by the number of detents on the plunger rod and stopper which engage the locking mechanism. Upon completion of the final delivery stroke, any attempt to withdraw the plunger rod from the barrel will cause the locking element to engage the barrel and trap the stopper in the barrel preventing further use of the syringe.