Needle Guard Triggering Mechanism for Prefilled Syringe Safety
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Solution Overview
Problem
Existing needle safety devices for prefilled syringes face challenges in accommodating plunger rod travel variance due to syringe and stopper tolerances, making it difficult to trigger the safety mechanism independently of these geometries, and often require full plunger rod depression, which can lead to increased risk of needle stick injuries, especially during sudden patient movements.
Innovation Solution
A needle guard system with a triggering mechanism that is independent of syringe and stopper tolerances, where the needle guard body is displaced proximally relative to the device as the needle is inserted, locking out contemporaneously with needle removal from the patient, reducing the risk of needle stick injuries by shielding the needle tip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the safety device is triggered toward the end of administration of the drug near the end of the plunger rod travel, then the safety mechanism can be activated, but the stack up of worst-case tolerances (syringe inside length, syringe flange thickness, and stopper length) can put the required plunger rod travel variance at +/â1.5 mm, making it difficult to accommodate the 3 mm plunger rod position variance
Solution Approach 1:
The safety device is divided into separate functional components: a syringe-mounted body, a needle guard body, and a trigger mechanism. The needle guard body is separate from the syringe assembly, allowing it to move independently and be triggered by needle insertion depth rather than plunger rod position, thereby eliminating the tolerance stack-up problem.
Solution Approach 2:
The needle guard body acts as an intermediary element between the needle and the trigger mechanism. It translates the mechanical action of needle insertion into trigger activation, providing a direct link that bypasses the complex tolerance relationships between syringe components.
2Reliability
If the safety device requires the plunger rod to be fully depressed in order to activate the safety mechanism, then the safety mechanism can be activated, but it increases the risk of needle stick injuries when a patient suddenly jerks or flinches causing the needle to come out of the patient unexpectedly
Solution Approach 1:
The safety mechanism is triggered by needle insertion depth rather than requiring full plunger rod depression. The needle guard body moves proximally as the needle is inserted, activating the trigger early in the injection process, before any sudden patient movements can occur.
Solution Approach 2:
The needle guard body automatically triggers the safety mechanism based on its own displacement during needle insertion, eliminating the need for manual plunger rod manipulation to activate safety features.
3Adaptability or versatility
If the needle guard body is displaced proximally relative to the device as the needle is inserted, then the triggering mechanism can be activated independently of syringe and stopper tolerances, but the device must accommodate the movement and locking mechanism
Solution Approach 1:
The needle guard body is designed to move dynamically during needle insertion, translating proximal displacement into trigger activation. The groove and protrusion mechanism provides a simple, dynamic locking system that engages automatically when the needle guard body reaches its final position, eliminating complex mechanical assemblies.
Data Source
AI summary
A device that is used in conjunction with a needle-based medication injection device (e.g. a prefilled syringe) that prevents needle stick injuries. The used needle is shielded by a needle guard that surrounds and extends beyond the needle tip. In a preferred embodiment, before the needle is inserted into the patient, the needle guard projects forward to substantially hide visibility of the needle for safety and to reduce patient anxiety.