Convertible Plunger Segmentation for Syringe Seal and Friction

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Solution Overview

Problem

Existing plungers in drug delivery devices, such as prefilled syringes, face challenges in balancing container closure integrity and gas-tightness with the need for low and consistent plunger force during dispensing, while avoiding the use of flowable lubricants that can interact with the drug product and cause degradation or patient discomfort.

Innovation Solution

A convertible plunger design with a compressible and resilient storage sealing section that transitions from an expanded state for storage mode to a constricted state for dispensing mode, providing a liquid-tight and gas-tight seal without the need for flowable lubricants, and featuring a liquid sealing section with a fluoropolymer film coating for reduced friction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a rubber plunger is used to provide container closure integrity and gas-tightness, then sealing performance is improved, but plunger force required for dispensing increases

Engineering Contradiction:

Improvecontainer closure integrityVSAvoidplunger force

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The plunger is divided into two distinct sections: a rubber sealing section for maintaining container closure integrity and a smooth dispensing section for low-friction operation. This segmentation allows each section to be optimized for its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the plunger are given different surface properties: the sealing section has high friction and compliance for gas-tightness, while the dispensing section has low friction for smooth operation. This local differentiation resolves the contradiction between sealing performance and dispensing ease.

Inventive Principle:

Principle #3Local quality

2Ease of operation

If flowable lubricant is applied to reduce plunger force, then dispensing smoothness is improved, but drug product degradation and patient discomfort risk increases

Engineering Contradiction:

Improveplunger forceVSAvoidlubricant interaction with drug product

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The lubricating function is extracted from the flowable lubricant approach and transferred to a solid, non-interacting coating layer on the plunger surface. This eliminates the harmful interaction between lubricant and drug product while maintaining low friction.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

A inert coating layer serves as an intermediary between the plunger and the drug product, providing the necessary lubrication without allowing direct contact between the lubricant and the drug, thus preventing degradation.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If tight fit between plunger and barrel is increased to maintain gas-tightness, then container closure integrity is improved, but plunger force for initiation and continuation increases

Engineering Contradiction:

Improvegas-tightnessVSAvoidplunger force

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The plunger is segmented into a sealing section that provides gas-tightness through tight fit and a dispensing section that provides low friction. This allows the system to achieve both gas-tightness and low plunger force simultaneously.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The plunger transitions from a static tight-fit state during storage to a dynamic low-friction state during dispensing. The rubber sealing section maintains tight fit for gas-tightness, while the smooth dispensing section reduces friction for easy movement.

Inventive Principle:

Principle #15Dynamics

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 solution enables a low break-loose and glide force, typically below 15 N, ensuring comfortable administration and maintaining drug product integrity by eliminating the risk of lubricant interaction, while maintaining container closure integrity and gas-tightness throughout the product's shelf life.

Implementation Method 1

a compressible and resilient storage sealing section that is maintained in an expanded state by outward radial pressure provided by the internal portion

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

a liquid sealing section with a fluoropolymer film coating for reduced friction

Methodology Applied

Scientific EffectLubrication: Lubrication

Data Source

PatentUS10765812B2Convertible plungers and methods for assembling the same in a medical barrel

Publication Date: 2020.09.08 SIO2 MEDICAL PRODUCTS LLC

AI summary

Disclosed are plunger assemblies including various convertible plungers and methods of making the same. Each plunger assembly is configured for disposition within a barrel of a medical container, e.g., a syringe, and displaced within the barrel from an engagement position to a release position. The engagement position is configured to provide a compression seal between a storage sealing section of the plunger and an inner wall of the syringe barrel. In the release position, the compression seal is reduced or eliminated. Also disclosed are methods for making convertible plungers and as assembling them into syringes, e.g., pre-filled syringes.