Elastomeric Stopper with Trim Edge Channel for Drug Reservoir

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Solution Overview

Problem

Dual chamber reservoir devices face issues with residual substance in the bypass channel due to deformable trim edges from batch-produced stoppers, which can obstruct fluid flow when the bypass channel is low, leading to device malfunction and wasted drug volume.

Innovation Solution

An elastomeric stopper design with a convex circumferential rib for sealing and a concave trim edge with a channel structure allowing fluid flow through the trim edge, ensuring that even if the trim edge deforms into the bypass channel, the liquid substance can still pass through to the front chamber, minimizing dead space and preventing malfunction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of substance

If the bypass channel is designed with low radial height to minimize dead space, then drug wastage is reduced, but the trim edge of batch-produced stoppers can easily deform into the bypass channel and obstruct fluid flow

Engineering Contradiction:

Improvedrug wastageVSAvoidfluid flow through bypass channel

Core Design Contradiction:

Loss of substanceVSReliability

Solution Approach 1:

The stopper is designed with different local properties: the circumferential rib has high structural resistance for sealing, while the trim edge portion is made with lower resistance to allow controlled deformation. This local differentiation ensures that under pressure, the trim edge deforms in a controlled manner to open the bypass channel rather than obstruct it, resolving the contradiction between minimizing dead space and ensuring reliable fluid flow.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of designing the trim edge to remain rigid and prevent deformation, the invention inverts the approach by allowing the trim edge to deform controllably. The trim edge portion is designed with lower structural resistance so that it deforms under pressure to create an open path for fluid flow through the bypass channel, transforming the potential defect into a functional feature that ensures reliable flow while minimizing dead space.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If conventional stoppers with circumferential sealing ribs are used, then sealing performance is achieved, but the trim edge created during batch production poses a risk of deforming into the bypass channel and preventing fluid flow

Engineering Contradiction:

Improvesealing performanceVSAvoidtrim edge deformation into bypass channel

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention converts the potentially harmful trim edge deformation into a beneficial feature. By designing the trim edge portion with lower structural resistance, the deformation that would normally be considered a defect is instead harnessed to create an open path for fluid flow through the bypass channel, transforming the harmful factor into a useful function that ensures reliable flow.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Device complexity

If the bypass channel radial height is minimized to reduce dead space, then device complexity is reduced, but manufacturing precision requirements increase due to the sensitivity of low-height channels to trim edge deformation

Engineering Contradiction:

Improvebypass channel structureVSAvoidbypass channel dimensional control

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The invention changes the structural parameters of the stopper by creating an annular recess in the trim edge portion with specific dimensional characteristics. This recess creates a controlled deformation zone that allows the trim edge to deform in a predictable manner under pressure, reducing the sensitivity of the low-height bypass channel to manufacturing variations and maintaining fluid flow reliability without requiring extremely tight manufacturing tolerances.

Inventive Principle:

Principle #35Parameter changes

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 fail-safe transfer of liquid substances from the rear to the front chamber, even with low bypass channels, reducing the risk of device malfunction and minimizing drug wastage by maintaining fluid flow regardless of the bypass channel height.

Implementation Method 1

an elastomeric stopper for a drug reservoir. The elastomeric stopper comprises a stopper body which extends along a reference axis between a leading end surface and a trailing end surface and which has a generally cylindrical sidewall with an outer body diameter

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

a channel structure enabling fluid flow from the trailing end surface to the annular recess through the trim edge portion

Methodology Applied

Scientific EffectFluid flow through pressure gradient: Pressure Gradient

Data Source

PatentUS20220218911A1Dual chamber drug reservoir and stopper therefor

Publication Date: 2022.07.14 NOVO NORDISK AS

AI summary

The present invention concerns an elastomeric stopper (18, 28, 38) for a drug reservoir, comprising: a stopper body (18.1, 28.1, 38.1) extending along a reference axis between a leading end surface (18.2, 28.2, 38.2) and a trailing end surface (18.3, 28.3, 38.3) and having a generally cylindrical sidewall with an outer body diameter, a circumferential convex rib (18.6, 28.6, 38.6) extending radially outwardly from the sidewall, a non-convex trim edge portion (18.7, 28.7, 38.7) at the trailing end surface (18.3, 28.3, 38.3), the non-convex trim edge portion (18.7, 28.7, 38.7) having an outer trim edge diameter which is greater than the outer body diameter and being axially spaced apart from the circumferential convex rib (18.6, 28.6, 38.6), providing an annular recess (18.9, 28.9, 38.9) therebetween. The elastomeric stopper (18, 28, 38) further comprises a channel structure (18.10, 28.10, 38.10) enabling fluid flow from the trailing end surface (18.3, 28.3, 38.3) to the annular recess (18.9, 28.9, 38.9) through the non-convex trim edge portion (18.7, 28.7, 38.7).