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 user intervention to render them inoperable.
Innovation Solution
A syringe assembly with a passive disabling mechanism that includes a plunger rod with detents and a stopper connected by a frangible connection, allowing for a predetermined number of aspirating and dispensing cycles before automatically disabling, preventing further use by engaging the locking element with the barrel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking element with cantilevered legs is used to engage the barrel interior surface to prevent proximal movement of the stopper, then the syringe assembly is rendered inoperable for reuse, but the complexity of the disabling mechanism increases
Solution Approach 1:
The locking element is designed to automatically engage the barrel interior surface when the plunger rod is pulled proximally after use. The cantilevered legs with sharp-free ends self-activate to engage the barrel wall, rendering the syringe inoperable without requiring additional user actions or complex external disabling mechanisms. This self-service approach prevents reuse while maintaining relatively simple overall device structure.
2Adaptability or versatility
If a frangible connection is used to connect the retaining element to the stopper, then the stopper can be released from the plunger rod after a predetermined number of strokes, but the manufacturing precision requirements increase
Solution Approach 1:
The frangible connection is pre-configured during manufacturing with specific weak points that are designed to break after a predetermined number of plunger rod strokes. The retaining element is initially connected to the stopper via this frangible connection, allowing the stopper to remain engaged during normal use cycles. After the predetermined number of strokes, the frangible connection automatically breaks, releasing the stopper from the plunger rod. This preliminary action enables controlled multi-stroke functionality while the manufacturing precision is managed through deliberate design of the frangible connection geometry and material properties.
3Length of moving object
If the positioning lug is not on a secondary distal post that increases the axial length of the stopper, then the axial length of the stopper is reduced, but the positioning accuracy of the plunger rod may be compromised
Solution Approach 1:
Instead of extending the axial length of the stopper with a secondary distal post to position the positioning lug, the invention positions the positioning lug on the plunger rod in a different configuration. The positioning lug is located such that it engages with the retaining element without requiring increased axial length of the stopper. This dimensional reconfiguration maintains positioning accuracy while reducing the overall axial length of the stopper component, simplifying the device structure and reducing material usage.
Data Source
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AI summary
A syringe assembly having passive disabling structure includes a barrel (202) and a plunger rod assembly. The plunger rod assembly includes a plunger rod (204) and a stopper (228) connected by an indexing locking element (190). 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 (130) to engage the barrel and trap the stopper in the barrel preventing further use of the syringe.