Syringe Reuse Prevention via Indexing Locking Element
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Solution Overview
Problem
Existing single-use syringes often require user intent to render them inoperable, which is ineffective against users intending to reuse them, and there is a need for a mechanism that automatically disables the syringe after a pre-selected number of plunger strokes without interfering with normal use.
Innovation Solution
A syringe assembly with a locking mechanism that includes a stopper and locking element with ramps and recesses, allowing variable dosages and automatic disabling after a specific number of aspirating and dispensing cycles, where the locking element engages with the syringe barrel to prevent further use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking mechanism with ramps and recesses is used to enable automatic disabling after a pre-selected number of strokes, then the syringe can prevent reuse automatically without user intervention, but the device complexity increases
Solution Approach 1:
The locking mechanism is designed to automatically engage after a pre-selected number of plunger strokes without requiring any user action. The ramps and recesses work together to automatically lock the plunger rod in the barrel after the injection is complete, making the system self-servicing in terms of preventing reuse.
Solution Approach 2:
The locking mechanism uses dynamic interaction between moving ramps and recesses that engage only after a specific number of strokes. The ramps allow normal plunger movement during injection but automatically lock when the pre-selected stroke count is reached, providing dynamic control over syringe usability.
2Reliability
If the locking element engages with the barrel to prevent further use, then reuse is prevented, but the ease of operation during normal use is reduced
Solution Approach 1:
The locking mechanism allows partial movement of the plunger rod during normal injection operations by designing the ramps to accommodate the required number of strokes. The locking action only engages after the pre-selected number of strokes, allowing full ease of operation during legitimate use while preventing reuse.
Solution Approach 2:
The interaction between ramps and recesses is segmented into distinct phases: during normal use, the ramps allow smooth plunger movement, and after the pre-selected strokes, the segments engage to lock the plunger. This segmentation separates the operational phase from the locking phase.
3Reliability
If a disabling mechanism is added to the syringe assembly, then reuse prevention is achieved, but the manufacturing cost and complexity increase
Solution Approach 1:
The locking element is integrated into the existing plunger rod structure, and the ramps are formed as part of the stopper or barrel geometry. This merging of the locking mechanism with existing syringe components minimizes additional manufacturing steps and reduces overall production complexity.
Solution Approach 2:
The locking mechanism is designed as a simple, inexpensive additive to the single-use syringe that effectively prevents reuse. The mechanism uses basic geometric features (ramps and recesses) that can be molded or machined into existing components without requiring expensive specialized parts.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A syringe assembly (100) having passive disabling structure includes a barrel (102) and a plunger rod assembly. The plunger rod assembly includes a plunger rod (108) and a stopper (128) connected by an indexing locking element. 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 (130). Upon completion of the final delivery stroke, any attempt to withdraw the plunger rod from the barrel will cause the locking element (130) to engage the barrel and trap the stopper (128) in the barrel preventing further use of the syringe.