Gasket Insertion Method for Syringe Outer Cylinder

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Solution Overview

Problem

Conventional gasket insertion methods into syringe outer cylinders often result in gasket inclination, leading to increased frictional resistance and reduced operability, especially in prefilled syringes, which can affect the storage stability of drug solutions.

Innovation Solution

A gasket insertion method utilizing a gasket with a recessed section and circular ribs, combined with a flat-tipped inserter, ensures proper alignment and minimizes inclination by maintaining axial alignment during insertion, using a recessed section with a constant inner diameter and circular ribs spaced apart to reduce frictional resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a conventional sleeve method is used to insert the gasket into the outer cylinder, then the gasket can be mounted inside the outer cylinder, but the gasket axis becomes inclined with respect to the sleeve axis due to increased frictional resistance, especially in small diameter syringes

Engineering Contradiction:

Improvegasket insertion processVSAvoidgasket alignment

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The gasket is divided into multiple sections: a tip end section with a smaller diameter, a base end section with a larger diameter, and an intermediate section connecting them. This segmentation allows the tip end section to be inserted into the sleeve first, establishing proper alignment, while the base end section provides stability and prevents inclination during the insertion process.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The tip end section of the gasket is designed to be inserted into the sleeve before the base end section. This preliminary action of inserting the tip end section first establishes the correct axial alignment between the gasket and sleeve, preventing inclination before the entire gasket is mounted.

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If the gasket is inserted into the outer cylinder in an inclined state, then the gasket can be mounted inside the outer cylinder, but the sliding resistance between the gasket and outer cylinder increases, reducing operability

Engineering Contradiction:

Improvegasket mountingVSAvoidsyringe operability

Core Design Contradiction:

Ease of manufactureVSEase of operation

Solution Approach 1:

The intermediate section of the gasket features a curved surface that transitions smoothly between the tip end and base end sections. This curvature allows the gasket to flex and conform to the cylindrical geometry of the sleeve and outer cylinder during insertion, maintaining axial alignment and reducing sliding resistance during subsequent operation.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Ease of manufacture

If the gasket is inserted in an inclined state, then the gasket can be mounted inside the outer cylinder, but the storage stability of the drug solution is affected

Engineering Contradiction:

Improvegasket insertionVSAvoiddrug solution storage stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

Instead of attempting to insert the entire gasket simultaneously (conventional approach), the invention inverts the insertion sequence by first inserting the tip end section into the sleeve, then followed by the base end section. This reversed sequence ensures proper alignment is established before the full gasket is mounted, preventing inclination that would compromise storage stability.

Inventive Principle:

Principle #13The other way round (Inversion)

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 method effectively suppresses gasket inclination, maintaining proper alignment and reducing sliding resistance, thereby enhancing the operability and storage stability of prefilled syringes.

Implementation Method 1

when the sleeve is moved toward the base end with respect to the outer cylinder, the diameter of the gasket is increased due to elastic restoring force

Methodology Applied

Scientific EffectElastic restoring force: Elasticity

Data Source

PatentUS10030771B2Gasket insertion method for mounting gasket inside outer cylinder of syringe, and gasket for mounting

Publication Date: 2018.07.24 TERUMO KK

AI summary

A gasket insertion method for inserting a gasket into an outer cylinder includes providing an outer cylinder having a base end opening section; providing a gasket having a recessed section that is open at a base end of the gasket and that includes a flat bottom surface; pushing the gasket into a sleeve configured to be inserted into the outer cylinder, by relatively moving an inserter in a tip end direction with respect to the sleeve while a flat tip end surface of a tip end section of the inserter abuts the bottom surface of the recessed section; inserting the sleeve into the outer cylinder through the base end opening section; and arranging the gasket inside the outer cylinder by relatively moving the sleeve in a base end direction with respect to the outer cylinder while maintaining relative axial positions of the outer cylinder, the gasket, and the inserter.