Rubber Stopper Geometry for Needle Coring Suppression

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Solution Overview

Problem

Existing rubber stoppers for pharmaceutical containers suffer from insufficient measures against coring, which occurs when a needle is inserted, leading to potential contamination and increased manufacturing costs due to the use of multiple materials or additional components.

Innovation Solution

A rubber stopper design featuring a canopy portion with a tapered base and a leg portion having specific curvature radii and dimensions, along with a recessed center and needle sticking portion, to prevent coring while maintaining stability and reducing component count.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a needle is inserted into a conventional rubber stopper, then drug administration is enabled, but coring occurs causing contamination and quality issues

Engineering Contradiction:

Improveprevention of coringVSAvoidcoring and contamination

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The rubber stopper employs a multi-layer construction where each layer has different hardness properties. The soft layer ( Shore A 20-40) at the needle insertion surface prevents coring by deforming easily, while the hard layer (Shore A 50-90) provides structural support. This local differentiation of material properties solves the contradiction between preventing coring and maintaining stopper integrity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention uses composite rubber materials with different hardness characteristics combined in a single stopper structure. The soft rubber layer and hard rubber layer work together to provide both coring prevention and structural stability, resolving the contradiction between softness needed for needle insertion and hardness needed for support.

Inventive Principle:

Principle #40Composite materials

2Reliability

If multiple materials or additional components are used to prevent coring, then coring is suppressed, but manufacturing costs increase

Engineering Contradiction:

Improveprevention of coringVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention combines multiple material layers into a single integrated rubber stopper component that can be manufactured as one piece using mold co-molding technology. This merging approach achieves coring prevention without requiring separate components or complex assembly, thereby controlling manufacturing costs while improving reliability.

Inventive Principle:

Principle #5Merging (Combining)

3Ease of manufacture

If the rubber stopper structure is simplified to reduce costs, then manufacturing is easier, but coring prevention becomes insufficient

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidcoring suppression

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The invention changes the physical parameters of the rubber material, specifically the hardness (Shore A scale), to create functional differentiation within a simple single-piece structure. By controlling the hardness parameters of different layers during mold co-molding, the invention achieves both manufacturing simplicity and effective coring prevention.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP4268789B1Rubber plug

Publication Date: 2025.12.31 DAIKYO SEIKO LTD

Figure 1A~1B
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Figure 3

AI summary

To provide a rubber stopper capable of suppressing occurrence of coring. Provided is a rubber stopper including a canopy portion having an upper surface and a lower surface, and a leg portion provided on the lower surface of the canopy portion, in which the leg portion has a tapered base portion at the center on a lower surface side of the canopy portion, and a curvature radius R1 of the tapered base portion is 2mm or more and 4mm or less.