Detachable Needle Syringe Reducing Dead Space via Flat Annular Seals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Syringe assemblies with replaceable needle assemblies face challenges in minimizing dead space and maintaining an effective seal between the syringe barrel and needle assembly, leading to medication loss, especially in high-stakes applications like immunization programs.
Innovation Solution
A syringe and detachable needle assembly design featuring a syringe barrel with a collared distal end and a needle hub with a primary and secondary seal mechanism, including a flat annular surface and an outwardly projecting annular sealing ring, which forms a reliable seal and minimizes dead space through a threaded engagement system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a frusto-conical syringe barrel tip is used to frictionally engage a frusto-conical needle hub passageway, then an excellent seal is provided, but large variations in dead space occur due to tolerance variations in angle and diameter
Solution Approach 1:
The patent changes the geometric parameters of the engagement surfaces from frusto-conical to flat annular surfaces. This parameter change eliminates the sensitivity to angle and diameter tolerances that characterized the frusto-conical design, thereby achieving consistent dead space while maintaining seal effectiveness through the flat surface engagement.
Solution Approach 2:
The patent introduces asymmetry in the sealing mechanism by using a flat annular surface on the syringe barrel that engages with a corresponding flat surface on the needle hub, creating a non-conical engagement geometry. This asymmetric flat-to-flat contact pattern provides tolerance compensation that the symmetric conical design could not achieve.
2Manufacturing precision
If a flat seal perpendicular to the longitudinal axis is used to reduce dead space, then dead space is greatly reduced, but the seal becomes leaky due to imperfections on mating surfaces
Solution Approach 1:
The patent applies beforehand cushioning by incorporating an elastomeric O-ring seal that compensates for surface imperfections before final engagement. The O-ring deforms to accommodate minor irregularities on the flat mating surfaces, preventing leaks while maintaining the dead space reduction benefits of the flat seal geometry.
Solution Approach 2:
The patent uses a flexible elastomeric O-ring as a thin film sealing element that conforms to the flat annular surfaces. This flexible sealing component bridges the gap between the rigid flat surfaces, ensuring leak-free operation even when surface imperfections exist, while the flat geometry itself controls dead space.
3Manufacturing precision
If a threaded engagement system is used to secure the needle assembly, then consistent dead space is achieved, but device complexity increases
Solution Approach 1:
The patent merges the sealing function and the engagement function into a single integrated flat annular surface interface. The flat surfaces provide both the seal and the positioning that controls dead space, while the threaded collar provides only the securing function. This merging reduces complexity compared to having separate sealing and positioning mechanisms.
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
The design consistently reduces dead space and ensures an effective seal, minimizing medication loss and improving efficiency in delivering doses, particularly in multi-patient immunization programs by maintaining a tight seal and reducing variability in assembly tolerances.
Implementation Method 1
The annular sealing ring is resilient enough to deflect upon installation of the needle assembly to the barrel so that the annular sealing ring deflects upon contact with the cylindrically shaped, axially aligned circular sidewall portion of the collar.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A syringe and detachable needle assembly having reduced dead space features includes an elongate syringe barrel having open distal end including a collar and a distally facing annular surface projecting inwardly from the collar. A needle assembly includes a hub having a proximally facing annular surface and an outwardly projecting annular sealing ring positioned distally from the surface. The needle assembly also includes a cannula having a lumen therethrough connected to the distal end of the hub. Structure is provided for engaging the hub to the barrel resulting in the annular surface of the barrel contacting the annular surface of the hub to form a primary seal between said barrel and said hub and the annular sealing ring contacting the collar to form a secondary seal between the barrel and the hub.