Autoinjector Drive Mechanism Linear Release

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Solution Overview

Problem

Existing medicament delivery devices with rotator mechanisms often experience jamming due to friction, causing the holding members to bend and fail to release the plunger rod properly.

Innovation Solution

A medicament delivery device with a drive mechanism that includes a plunger rod, a drive spring, an actuator with holding members, and a rotator that is movable relative to the actuator. The rotator interacts with the holding member to maintain engagement with the plunger rod, and an activator linearly displaces the rotator to release the holding member, avoiding rotational-induced jamming.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the rotator rotates inside the housing to trigger and enable different functions, then the number of components is reduced, but friction between the rotator and holding members causes bending and jamming of the holding members

Engineering Contradiction:

Improvenumber of componentsVSAvoidjamming of holding members

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

Instead of rotating the rotator to release the holding members, the invention inverts the mechanism by using linear movement of the activator to directly push the holding members outward from the plunger rod. This reverses the traditional rotational release mechanism into a linear displacement mechanism, eliminating the friction-induced bending problem while maintaining component integration.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention replaces the rotational mechanical interaction between the rotator and holding members with a linear mechanical system. The activator directly pushes the holding members outward through linear displacement, substituting the complex rotational friction-based mechanism with a simpler linear push mechanism that avoids bending and jamming.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If the rotator rotates to release the holding member, then the plunger rod can be released, but the rotational movement causes friction that bends the holding members

Engineering Contradiction:

Improverelease of plunger rodVSAvoidbending of holding members

Core Design Contradiction:

Ease of operationVSShape

Solution Approach 1:

The invention extracts the rotational movement function from the release mechanism. Instead of using rotation to trigger release, the activator directly pushes the holding members outward in a linear motion, separating the release function from rotational movement and eliminating the friction that causes bending.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention inverts the release mechanism by using direct linear pushing instead of rotational triggering. The activator pushes the holding members outward directly, reversing the traditional approach where rotation caused release, thereby eliminating the shape distortion caused by friction.

Inventive Principle:

Principle #13The other way round (Inversion)

3Stability of the object's composition

If the holding members are kept in engagement with the plunger rod through rotator interaction, then the plunger rod is held in tensioned state, but the friction causes jamming that prevents proper release

Engineering Contradiction:

Improveholding of plunger rod in tensioned stateVSAvoidrelease failure of plunger rod

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The invention replaces the rotational friction-based holding and release mechanism with a linear mechanical system. The activator directly pushes the holding members outward, substituting the rotational interaction that caused jamming with a linear displacement mechanism that reliably releases the plunger rod while maintaining stability during the tensioned state.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 effectively prevents jamming of the holding members by transitioning the rotator's movement from rotational to linear, ensuring proper release of the plunger rod and reliable medicament delivery.

Implementation Method 1

a drive spring operably arranged to plunger rod wherein the plunger rod is arranged to act on a stopper arranged in a medicament container

Methodology Applied

Scientific EffectSpring: Spring

Implementation Method 2

the rotational movement of the rotator has caused a bending of the holding members due to the friction between the rotator and the holding members

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentEP3285832B1Drive mechanism for an autoinjector

Publication Date: 2025.03.05 SHL MEDICAL AG

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Figure 2a~2b
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AI summary

The present invention relates to a drive mechanism for use with a medicament delivery device, comprising a plunger rod (68), a drive spring (72) operably arranged to the plunger rod, an actuator (52) comprising a holding member (60) releasibly engaged to the plunger rod (68) for holding said plunger rod (68) with said drive spring (72) in a tensioned state, a rotator (38) operably connected and movable relative to said actuator (52) and configured to interact with said holding member for holding said holding member in engagement with the plunger rod, an activator (30) operably connected to said rotator (38). The invention is characterized in that the activator (30) is configured to rotate and subsequently linearly displace the rotator (38) in relation to the actuator (52) such that said holding member (60) is released from the plunger rod (68).