Autoinjector Needle Shield Triggering Mechanism

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Solution Overview

Problem

Existing autoinjectors face issues with non-optimal performance due to excessive forces in the release mechanism, leading to unsynchronized needle movement feedback, potential sterility breaches, painful insertion, and shallow injection depth, primarily caused by static friction between triggering components.

Innovation Solution

The autoinjector design incorporates a threaded connection between the plunger release element and the base thread component, with a gearing mechanism and inclined sections to overcome static friction, ensuring smooth and controlled needle shield movement, and a releasable retaining mechanism that allows for precise energy transfer from the actuator to the plunger, enabling user control over needle insertion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a lock component is deformed to unlock for releasing energy from the drive spring, then the drive spring energy is released, but the needle shield movement becomes non-optimal due to excessive forces

Engineering Contradiction:

Improvedrive spring energy releaseVSAvoidneedle shield movement performance

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The trigger mechanism is divided into separate functional components: a trigger element that moves linearly and a lock component that rotates independently. This segmentation allows the linear trigger movement to be converted into rotational lock disengagement, separating the energy release function from the shield movement control, thereby reducing excessive forces on the shield mechanism.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of using linear deformation of a lock component to release the drive spring, the invention uses rotational movement of the lock component. The trigger element's linear movement is inverted into rotational movement through a cam or inclined surface, which then rotates the lock component to disengage it from the drive spring plunger, providing smoother force distribution.

Inventive Principle:

Principle #13The other way round (Inversion)

2Extent of automation

If automatic needle insertion is provided, then automation level increases, but user control over insertion is lost leading to user uneasiness

Engineering Contradiction:

Improveautomatic needle insertionVSAvoiduser control over insertion

Core Design Contradiction:

Extent of automationVSEase of operation

Solution Approach 1:

The device provides automatic needle insertion and medicament delivery without requiring user intervention during the injection process. The drive spring automatically drives the plunger, which moves the needle into the skin and delivers the medicament, allowing the device to serve itself once activated, thereby achieving high automation while maintaining simple user interaction.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The drive spring is pre-loaded with energy during device assembly, storing the force required for needle insertion and medicament delivery. This preliminary action allows the device to automatically perform the insertion function upon activation, providing automation while requiring only a simple trigger pull from the user, thus maintaining ease of operation.

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If static friction between triggering components is present, then component simplicity is maintained, but triggering reliability decreases due to potential failure to overcome friction

Engineering Contradiction:

Improvetriggering mechanism simplicityVSAvoidtriggering activation

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The invention extracts and addresses the static friction problem by designing the trigger element and lock component with minimal contact surfaces and optimized geometry. The cam or inclined surface converts linear trigger movement into rotational lock movement, reducing the normal force and thereby reducing static friction between components, ensuring reliable triggering without adding complex mechanisms.

Inventive Principle:

Principle #2Taking out (Extraction)

4Ease of operation

If the shield is retracted slowly to ensure control, then user comfort improves, but needle insertion becomes painful and injection depth is reduced

Engineering Contradiction:

Improveuser comfort during insertionVSAvoidinsertion pain and shallow depth

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The trigger mechanism is designed to allow rapid shield retraction when the user pulls the trigger, converting the stored drive spring energy into quick needle insertion. The dynamic response of the mechanism ensures that the needle penetrates the skin quickly to minimize pain, while the drive spring's controlled energy release ensures adequate insertion depth is achieved without requiring slow, controlled 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

This design enhances user control over needle insertion, prevents sterility breaches, reduces pain during injection, and ensures consistent injection depth by effectively managing static friction and energy release, resulting in improved performance and reduced manufacturing costs.

Implementation Method 1

Methodology Applied

Scientific EffectThreaded connection mechanical advantage: Screw

Implementation Method 2

ensuring smooth and controlled needle shield movement, and a releasable retaining mechanism that allows for precise energy transfer from the actuator to the plunger, enabling user control over needle insertion

Methodology Applied

Scientific EffectStatic friction: Static Friction

Implementation Method 3

Injection devices that provide automatic delivery of the medicament, i.e. auto-injectors, typically use a drive spring as driving force for the injection. Before use, the drive spring will be held in a pre-tensioned position from which it is released upon activation of the device

Methodology Applied

Scientific EffectElastic energy storage and release: Spring

Data Source

PatentUS11260176B2Autoinjector having needle shield triggering

Publication Date: 2022.03.01 NOVO NORDISK AS

AI summary

An autoinjector (100′) for expelling a single dose of a drug from a held cartridge (600) comprising a piston (630). The autoinjector includes a needle shield (350, 380′) axially movable from an initial extended position via a triggering position to a trigger release position. The needle shield (350, 380′) is operatively coupled to a plunger release element (320′, 1320) cooperating with a plunger (310, 400) to define a releasable retaining mechanism that retains the plunger release element (320′, 1320) threadedly engaged with a base thread component (204′, 1204) in a predefined relative rotational and axial position and against rotational bias provided by an actuator (330). The needle shield (350, 380′) is configured for operating the retaining mechanism to release the retaining of the plunger release element (320′, 1320) and the base thread component (204′, 1204) from the predefined relative rotational and axial position upon the needle shield (350, 380′) being moved into the trigger release position.