Two-Stage Syringe Seal for Freeze-Thaw Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional syringe designs for drug infusion systems fail to maintain a gas-tight seal during the freeze-thaw cycle of products with high water content, leading to air ingress and reduced delivery accuracy due to inadequate sealing and thermal contraction differences between thermoplastic and rubber components.
Innovation Solution
A syringe design featuring a barrel with a first portion of smaller diameter and a second portion of larger diameter, along with a plunger that engages the barrel with varying contact pressures to maintain a gas-tight seal across a temperature range of -25°C to 40°C, and a method for accommodating expansion by using a restraining element that deflects or abuts the plunger to prevent air ingress during freezing and thawing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tight seal is maintained between plunger and barrel during freeze-thaw cycle, then gas-tight sealing is improved, but the force required to move the plunger increases
Solution Approach 1:
The barrel is divided into two portions with different inner diameters: a first portion with a smaller diameter for maintaining gas-tight sealing during freeze-thaw cycles, and a second portion with a larger diameter for reducing friction during product dispensing. The plunger transitions between these two portions, allowing the system to segment the sealing and dispensing functions into distinct spatial zones.
Solution Approach 2:
Different regions of the barrel have different diameters to provide locally optimized properties: the first portion provides high sealing quality with smaller diameter for gas-tightness, while the second portion provides low friction quality with larger diameter for ease of plunger movement during dispensing.
2Reliability
If a tight seal is maintained during freeze-thaw cycle, then air ingress is prevented, but power consumption of the pump increases
Solution Approach 1:
The dispensing process is segmented into two phases: Phase 1 operates in the first portion of the barrel where the plunger maintains gas-tight sealing during freeze-thaw cycles, and Phase 2 transitions to the second portion where larger diameter reduces friction and consequently reduces the power required by the pump to dispense product.
Solution Approach 2:
The system dynamically transitions between two operational modes by moving the plunger between two portions of the barrel. The plunger starts in the first portion for sealing, then transitions to the second portion for low-friction dispensing, allowing the system to adapt its sealing and friction characteristics based on the dispensing phase.
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 syringe design ensures a gas-tight seal throughout the freeze-thaw cycle, reducing air ingress and maintaining delivery accuracy by adjusting contact pressures and using a restraining element to manage expansion, thus extending battery life and improving delivery efficiency.
Implementation Method 1
thermal contraction differences between thermoplastic and rubber components
Implementation Method 2
using a restraining element that deflects or abuts the plunger
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A syringe includes a barrel, a plunger, and a sealing member creating a seal between the plunger and the barrel. The barrel includes a first portion with a first inner diameter and a second portion with a second inner diameter that is larger than the first inner diameter. The sealing member engages the first portion of the barrel to give rise to a first contact pressure when the barrel is filled with product. The first contact pressure is sufficient to maintain a gas-tight seal over the expected temperature ranges -25°C to 40°C. A first force is applied to the plunger to overcome the first contact pressure and move the plunger out of the first portion and into the second portion to dispense product. The sealing member engages the second portion of the barrel to give rise to a second contact pressure that is lower than the first contact pressure. A second force lower than the first force is sufficient to overcome the second contact pressure and move the plunger in the second portion to continue dispensing product. The syringe may include a restraining element for accommodating expansion of the product during freezing.