Passive Reuse Prevention Syringe with Breakable Plunger Neck
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Solution Overview
Problem
Existing syringe systems fail to effectively prevent reuse without requiring a specific user intent or affirmative action, and they often impose limitations on dosage or increase costs due to automatic locking mechanisms.
Innovation Solution
A syringe design featuring a passive reuse prevention mechanism that locks the plunger assembly through normal use, eliminating the need for a rubber stopper and allowing variable dosing, with a breakable neck portion that separates upon attempted reuse, rendering the syringe disabled.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking mechanism is added to prevent reuse, then reliability of single-use prevention is improved, but device complexity increases
Solution Approach 1:
The plunger assembly is divided into separable components: a plunger body and an extension member connected by a breakable neck portion. The extension member engages with the locking mechanism, and upon reuse attempt, the breakable neck portion fractures to disable the syringe. This segmentation allows the locking function to be achieved through simple geometric features rather than complex mechanical components.
Solution Approach 2:
The breakable neck portion is designed as a disposable, single-use structural element that is intentionally weakened at a specific location. After the first use, this neck portion is meant to break and discard itself, preventing any further operation of the syringe. This approach uses a simple, low-cost structural feature instead of a complex reusable locking mechanism.
2Reliability
If automatic locking mechanism is implemented, then reuse prevention is improved, but loss of time for filling and use increases
Solution Approach 1:
The locking mechanism is pre-configured within the syringe barrel, with the locking surface positioned to automatically engage with the extension member during the normal injection process. As the plunger is pushed forward to deliver the medication, the extension member naturally contacts and engages the locking surface, activating the lock as a byproduct of the intended use rather than requiring a separate action.
Solution Approach 2:
The syringe automatically locks itself through the normal injection motion. The geometry of the extension member and locking surface is designed so that the forward movement of the plunger during medication delivery automatically positions the extension member to engage the locking surface, disabling the syringe after use without requiring user intervention.
3Reliability
If rubber stopper is used for sealing, then sealing reliability is improved, but manufacturing cost increases
Solution Approach 1:
The sealing surface on the plunger body is made from the same material and formed through the same injection molding process as the rest of the plunger assembly. This eliminates the need for separate rubber stopper components and their associated assembly steps, reducing manufacturing complexity and cost while maintaining adequate sealing functionality for single-use applications.
Data Source
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AI summary
Various embodiments of syringe assemblies include a syringe barrel and a substantially conical tip or outlet disposed on the distal end of the barrel. The substantially conical tip includes a locking mechanism that engages an extension of a plunger assembly extending from a distal end of the plunger assembly so as to retain the extension within the substantially conical tip or outlet upon full injection of the contents of the syringe to a patient. According to one embodiment, a plunger head of the plunger assembly is slidably disposed on the extension. According to another embodiment, a separate hub, which holds a needle cannula, is disposed on an outlet at the distal end of the syringe barrel, which contains the locking mechanism. According to a further embodiment, the locking mechanism includes a locking clip disposed within the substantially conical tip of the syringe assembly.