Safety Syringe Plunger Trigger Gap and Spring Sheath
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Solution Overview
Problem
Existing safety syringes often fail to completely expel air from the barrel prior to aspirating fluid, leading to premature triggering of safety mechanisms, which frustrates healthcare workers and renders the syringe ineffective.
Innovation Solution
A syringe assembly design featuring a plunger with three distinct positions and a sheath unit with a compressed spring mechanism, allowing for the complete expulsion of air without triggering the safety mechanism, and a telescopic sheath cover with a trigger lever system for safe needle retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a safety mechanism with a spring-loaded protective element is added to the syringe, then needle safety is improved, but the plunger triggers the safety mechanism prematurely during air expulsion
Solution Approach 1:
The patent introduces a trigger gap parameter between the plunger and the protective element that changes the activation conditions of the safety mechanism. By defining specific distance parameters (trigger gap, engagement position), the system allows full plunger travel for air expulsion without triggering, while still activating safety coverage when the needle needs protection
Solution Approach 2:
The patent positions the protective element and spring mechanism in advance within the barrel, pre-configured to respond only to specific plunger positions. The spring is pre-compressed and the protective element is pre-positioned to cover the needle, creating a ready-state safety system that activates only under the correct conditions (when fluid is present and injection is complete)
2Productivity
If the plunger is designed to travel the full length of the barrel for complete air expulsion, then air removal is improved, but the safety mechanism is triggered prematurely
Solution Approach 1:
The patent defines specific parameter thresholds: a trigger gap distance that allows full air expulsion travel, and an engagement position where the protective element activates. The plunger can travel the full barrel length for air removal because the protective element is positioned beyond the full travel range, creating a parameter-based distinction between operational travel and safety activation
3Object-affected harmful factors
If a telescopic sheath cover with detent engagement is used for needle retraction, then needle protection is improved, but device complexity increases
Solution Approach 1:
The patent implements a nested structure where the sheath cover telescopes over the inner shell, and the plunger assembly is nested within the barrel. The detent mechanism uses nested engagement surfaces on the inner shell and corresponding features on the sheath cover, creating a compact multi-layered protection system that maintains needle coverage during retraction
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
Enables the syringe to be used effectively by allowing complete fluid aspiration without triggering the safety mechanism, ensuring safe and efficient operation by preventing accidental needle exposure.
Implementation Method 1
a spring compressed by a shoulder on the sheath cover and a shoulder on the inner shell
Data Source
AI summary
Syringes are disclosed herein incorporating a variety of safety mechanisms for protecting the users from accidental needle stick. In certain embodiments, the syringes incorporate retractable carriages that can be retracted into the syringe barrels by engaging with the plungers. The carriages are configured to receive different needle hubs having any number of needle sizes. In certain other embodiments, the carriages are spring loaded so that as the plungers disengage the carriages from the syringe barrels, the springs automatically retract the needles into the barrels. Still in certain other embodiments, needle hubs with spring loaded needles are used with the syringes. The needles are retracted into the barrels when the plungers activate certain mechanisms incorporated into the hubs to thereby release the needles. Still yet in certain other embodiments, sheaths are used to cover needle tips.