Syringe Stopper and Plunger Rod Support for Misalignment Sealing
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Solution Overview
Problem
Current syringe designs, particularly those using thermal plastic elastomers, face challenges in high temperature autoclave sterilization due to low resistance to compression set, increased manufacturing costs, and mechanical backlash, leading to leakage and reduced infusion control.
Innovation Solution
A syringe assembly design featuring a stopper and plunger rod arrangement that utilizes thermal plastic elastomer materials with reduced stopper stress concentrations and angular misalignment, incorporating support disks and flexible regions to minimize leakage and improve sealing robustness, while maintaining cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thermal plastic elastomer is used for the stopper instead of vulcanized rubber, then manufacturing cost is reduced, but resistance to high temperature compression set deteriorates
Solution Approach 1:
The patent modifies the geometric parameters of the stopper, specifically designing a curved leading end with a radius of curvature between 0.02 inches and 0.06 inches, and optimizing the thickness of the stopper body. These parameter changes reduce stress concentrations in the thermal plastic elastomer stopper, allowing it to maintain sealing performance during autoclave sterilization despite using a lower-cost material
Solution Approach 2:
The patent employs a composite structure where the stopper is made of thermal plastic elastomer material that combines flexibility with improved high-temperature performance through specific formulation and geometric design, creating a material system that balances cost and reliability
2Reliability
If the stopper is designed with reduced stress concentrations to prevent yielding, then sealing robustness is improved, but contact stress with the barrel is reduced
Solution Approach 1:
The patent optimizes the balance between stress concentration reduction and contact stress maintenance by precisely controlling the radius of curvature of the leading end (0.02-0.06 inches) and the thickness of the stopper body. This creates an optimal geometric configuration that prevents yielding while maintaining adequate sealing force
Solution Approach 2:
The patent designs the stopper with a curved leading end that provides partial stress distribution, where the curvature is sufficient to prevent stress concentration yielding but not so extreme that it eliminates all contact stress, maintaining the necessary sealing function
3Reliability
If multi-part plunger rod design is used to reduce side loading, then stopper stress is reduced, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies parameter changes to the stopper geometry (curved leading end with specific radius, optimized thickness) to inherently reduce stress concentrations, eliminating the need for complex multi-part plunger rod designs while achieving the same stress reduction effect
Solution Approach 2:
The patent extracts the stress reduction function from the plunger rod structure and relocates it to the stopper geometry itself, simplifying the overall system by removing the need for additional plunger rod components
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 enhances sealing performance and reduces material costs by minimizing leakage and mechanical backlash, ensuring reliable operation under high temperature conditions.
Implementation Method 1
a support disk on the plunger rod distal end configured to bear against the protrusion upon misalignment of the plunger rod in the syringe barrel
Implementation Method 2
a flexible region provided between the support disks. The flexible region is configured to flex upon misalignment of the plunger rod in the syringe barrel
Data Source
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AI summary
A syringe assembly includes a substantially cylindrical syringe barrel including a fluid dispensing end, an open end, and at least one protrusion adjacent the open end, the at least one protrusion projecting inwardly from an inner surface of the syringe barrel, a stopper configured to be received within the open end of the syringe barrel, and a plunger rod having a plunger rod body extending along a longitudinal axis from a proximal end to a distal end and at least one support disk provided on the distal end thereof. The support disk on the plunger rod is configured to bear against the protrusion of the syringe barrel upon misalignment of the plunger rod in the syringe barrel.