Syringe Assembly Seal Compression for Uniform Pressure Limits
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Solution Overview
Problem
The compression of the seal member in syringe assemblies is non-uniform in the circumferential direction, leading to variations in the internal pressure limit, resulting in potential liquid leakage and reduced sealing performance.
Innovation Solution
A syringe assembly design featuring a cap with a pressing surface that uniformly presses a seal member against a distal nozzle portion, utilizing a ring-shaped protrusion on the sealing surface to maintain consistent compressive load, and a gasket that is slidable within the syringe, along with a drive mechanism to administer liquid medicine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the cap is assembled by fitting it toward the distal nozzle portion using a mounting device, then the assembly process is simplified, but the axis of the cap becomes inclined with respect to the axis of the syringe, causing non-uniform compression of the seal member and variation in pressure limit
Solution Approach 1:
The cap is pre-formed with a pressing surface that has a specific geometric shape designed to compensate for assembly misalignment. This preliminary design feature ensures that even when the cap is assembled with some inclination, the pressing surface distributes the compressive load uniformly across the seal member, thereby maintaining consistent pressure limits without requiring high-precision alignment during assembly.
2Reliability
If the seal member is compressed between the cap and distal nozzle portion, then the distal opening is sealed, but the compression becomes non-uniform in the circumferential direction, causing variation in pressure limit and potential liquid leakage
Solution Approach 1:
The pressing surface of the cap is designed with non-uniform geometric features that create localized variations in pressing force. These local quality variations are specifically engineered to compensate for the non-uniform compression of the seal member, ensuring that the overall compressive load distribution becomes uniform across the circumferential direction. This results in consistent pressure limits and reliable sealing performance.
3Reliability
If the cap is designed with a pressing surface that presses the seal member uniformly, then the pressure limit variation is suppressed, but the cap structure becomes more complex
Solution Approach 1:
The pressing surface of the cap incorporates geometric parameters such as curvature radius, surface inclination angle, and local protrusion dimensions that are optimized to distribute compressive force uniformly. By carefully selecting and adjusting these geometric parameters, the cap achieves uniform seal member compression and consistent pressure limits while maintaining a relatively simple overall structure that does not significantly increase device complexity.
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 ensures uniform compressive load on the seal member, suppressing variations in pressure limits and minimizing liquid leakage, thereby enhancing sealing performance and reliability.
Implementation Method 1
a seal member arranged between the cap and the distal nozzle portion and made of an elastic body that seals the distal nozzle portion
Data Source
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AI summary
Provided are a syringe assembly (12A) and a liquid-medicine administration device (10) capable of suppressing a variation in a pressure limit of a seal member (46). In the syringe assembly (12A), the seal member (46) is pressed and held between a pressing surface (48) of a cap (44) and a sealing surface (60) of a distal nozzle portion (56) of a syringe (24). The seal member (46) is pressed and held in the axial direction in a pressing space (64) over the whole region of an opposing portion between the pressing surface (48) and the sealing surface (60), and a gap between the pressing surface (48) and the sealing surface (60) in the pressing space (64) is narrowest on the inner peripheral side.