Plunger Rod Release Mechanism for Drug Delivery Device

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Solution Overview

Problem

Current drug delivery devices, such as auto-injectors, face challenges in ensuring reliable and safe medicament delivery due to accidental release of the plunger rod, which can lead to unintended dosing. Existing designs often require complex mechanisms and protrusions on the plunger rod, limiting the axial extension of the reservoir without increasing device length.

Innovation Solution

The proposed drug delivery device incorporates a drive arrangement with a plunger rod release member, including a collar and collar beam, which engages a notch on the plunger rod, allowing controlled axial and rotational movement to prevent accidental release. This design ensures the plunger rod is securely locked until a deliberate user-initiated movement, utilizing a drive unit to facilitate safe and reliable medicament delivery.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a complex mechanism with protrusions on the plunger rod is used to prevent accidental release, then reliability is improved, but device complexity increases and axial extension of the reservoir is limited

Engineering Contradiction:

Improveprevention of accidental plunger rod releaseVSAvoidcomplexity of release mechanism

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent inverts the conventional approach by making the plunger rod release member (collar) movable relative to the housing, while the plunger rod itself remains simple without protrusions. The release mechanism is transferred from the plunger rod to the collar, which rotates to engage or disengage retention features on the housing, thereby simplifying the plunger rod design while maintaining reliability

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The release mechanism is segmented into distinct functional components: the movable collar as release member, retention features on the housing, and a simple plunger rod. This segmentation allows each component to have a specific function, reducing overall complexity while ensuring reliable operation through dedicated engagement and disengagement features

Inventive Principle:

Principle #1Segmentation

2Reliability

If protrusions are added to the plunger rod to prevent accidental release, then reliability is improved, but the axial extension of the reservoir cannot be increased without increasing device length

Engineering Contradiction:

Improvecontrolled release of plunger rodVSAvoidaxial extension of reservoir

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

Instead of adding features to the plunger rod, the patent places the release control features on the movable collar that interacts with the housing. This inversion allows the reservoir to extend axially without requiring additional length for plunger rod features, as the control mechanism is distributed around the circumference of the collar rather than extending axially

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The release mechanism transitions from an axial arrangement (protrusions on plunger rod) to a rotational arrangement (collar rotating to engage/disengage retention features). This dimensional change from axial to rotational control allows the reservoir to achieve full axial extension without compromising release control, as the mechanism operates in the circumferential direction

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Device complexity

If a simple plunger rod design without protrusions is used, then device complexity is reduced and reservoir axial extension is increased, but reliability of preventing accidental release deteriorates

Engineering Contradiction:

Improvesimplicity of plunger rod designVSAvoidprevention of unintended dosing

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The movable collar serves as an intermediary between the user's rotational input and the plunger rod's axial movement. This intermediary component provides the necessary control and reliability features without requiring them to be on the plunger rod itself, maintaining simplicity while ensuring safe operation through a dedicated release mechanism

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent inverts the conventional design by placing all release control features on the movable collar rather than the plunger rod. This allows the plunger rod to remain simple and smooth, while the collar provides the complex engagement and disengagement functionality through rotational movement, thereby maintaining both simplicity and reliability

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS20230285673A1Drive arrangement for a drug delivery device

Publication Date: 2023.09.14 SANOFI SA(FR)

AI summary

The disclosure refers to a drive arrangement for a drug delivery device including a housing having a proximal end and a distal end, a longitudinal axis extending between the proximal end and the distal end, a plunger rod movable relative to the housing, a drive unit arranged to bias the plunger rod in the distal direction, a plunger rod release member, which includes at least one plunger rod release feature, wherein the plunger rod release member is movable relative to the housing from a first position into a second position, wherein, in the first position, the plunger rod release feature engages the retention feature such that the plunger rod is prevented from moving relative to the plunger rod release member, and wherein, in the second position, the plunger rod release feature is disengaged from the retention feature, thereby allowing the plunger rod to move in the distal direction.