Front-Shoulder Syringe Support to Reduce Autoinjector Breakage

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Solution Overview

Problem

Existing autoinjectors using standard pre-filled syringes face issues with syringe breakage due to excessive forces during viscous medicament delivery, risking glass fragments and needle exposure, especially when the needle sheath is not properly maintained, and require complex assembly processes.

Innovation Solution

An autoinjector design with a syringe support mechanism that holds the syringe barrel at its front shoulder, using radially flexible fingers with inward protrusions to apply compressive force, minimizing assembly risks and preventing syringe breakage by absorbing shock, while ensuring needle sterility and easy assembly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the syringe is held at the rear flange during injection, then the assembly is simple, but the syringe is placed in tension which increases breakage risk especially with viscous medicaments

Engineering Contradiction:

Improveassembly complexityVSAvoidsyringe breakage risk

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

Instead of holding the syringe at the rear flange (conventional approach), the invention inverts the support location to the front shoulder of the barrel. This inversion changes the force distribution from tensile to compressive, preventing syringe breakage while maintaining assembly simplicity through the self-retaining flexible fingers.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention changes the mechanical parameter of force direction from tension to compression by relocating the support point. The flexible fingers are designed to apply compressive force on the front shoulder of the barrel, which fundamentally alters the stress state of the syringe during injection, especially beneficial for viscous medicaments requiring higher injection forces.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the flexible fingers are constrained to prevent radial movement, then the syringe is securely held, but the needle cover cannot pass during assembly

Engineering Contradiction:

Improvesyringe holding securityVSAvoidassembly ease

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The flexible fingers are designed with dynamic characteristics, allowing radial movement during assembly when the needle cover passes. After assembly, the fingers return to their constrained position to securely hold the syringe. This dynamic behavior resolves the contradiction between security during operation and ease of assembly.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The flexible fingers provide a cushioning effect during assembly by allowing radial displacement. This beforehand flexibility accommodates the needle cover passage without damage, while the subsequent return to constrained position ensures secure syringe holding during injection.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Productivity

If higher forces are applied to deliver viscous medicament quickly, then the injection speed increases, but the syringe breakage risk increases

Engineering Contradiction:

Improveinjection speedVSAvoidsyringe breakage risk

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention changes the stress parameter from tensile to compressive by supporting the syringe at the front shoulder. This allows higher injection forces to be applied for viscous medicaments without increasing breakage risk, as the compressive support prevents the tensile stresses that lead to failure at the rear flange.

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 design reduces syringe breakage risks, maintains needle sterility, and allows for easy assembly, making it suitable for emergency use and self-administration, particularly effective for viscous drugs.

Implementation Method 1

radially flexible fingers having free ends extending in a rearward direction, wherein the front portion is of narrower diameter than the intermediate portion, the plurality of radially flexible fingers comprising one or more inwardly-directed protrusions

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentEP1998831B2Improved autoinjector supporting the syringe at the front

Publication Date: 2025.10.22 SHL MEDICAL AG

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AI summary

An autoinjector comprising a housing in which can be mounted a syringe comprising a barrel for holding a volume of medicament, a needle at one end of the barrel in fluid communication with the medicament and a plunger axially-moveable in the barrel to a forwardmost position, the autoinjector further comprising a syringe support means for supporting the barrel at an axial location at or forward of the forwardmost position of the plunger and having a reaction surface for the syringe, whereby in use said reaction surface (109) provides an axial compressive force on said barrel when a forward axial force is applied to the plunger.