Auto-injector Sheath Deployment for Needle Safety

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Solution Overview

Problem

Existing safety syringes and auto-injectors face issues such as needle exposure risks for healthcare workers, patient discomfort from spring-loaded mechanisms, and increased operational complexity, particularly in high-stress situations.

Innovation Solution

A kit of parts comprising an auto-injector apparatus and a pre-filled safety syringe with a deployable sheath, allowing for automatic needle coverage and reusability, featuring a syringe housing, plunger housing, and a biasing mechanism to actuate the sheath, along with a locking mechanism to secure the sheath in the closed position.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a spring-loaded safety mechanism is used to cover the needle after injection, then healthcare workers are protected from needle stick injuries, but the spring mechanism causes discomfort and bruising to patients when activated

Engineering Contradiction:

Improveneedle protectionVSAvoidpatient discomfort

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The harmful spring-loaded mechanism is removed from the safety syringe design. Instead, a passive sheath cover is used that moves without spring force, eliminating the source of patient discomfort while maintaining needle protection functionality

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

A sheath cover acts as an intermediary element between the needle and the external environment. This sheath can be passively deployed to cover the needle after injection without requiring forceful mechanical action that would cause patient discomfort

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If the needle is removed before engaging the safety mechanism, then patient discomfort is avoided, but healthcare workers are exposed to the needle after use and blood splatter occurs

Engineering Contradiction:

Improvepatient comfortVSAvoidhealthcare worker safety

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The sheath cover is designed to be deployed after injection but before needle removal. This preliminary action of covering the needle ensures healthcare worker safety is established before the needle is extracted from the patient's body

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The sheath cover serves as an intermediary protective barrier that can be placed over the needle while it is still in the patient's body, providing safety for healthcare workers without requiring needle removal first

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If a rigid needle shield is used to cover the needle, then needle protection is improved, but the sheath cannot be retracted to allow needle access for injection

Engineering Contradiction:

Improveneedle protectionVSAvoidneedle accessibility

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The sheath cover is designed with dynamic movement capability - it can be retracted to allow needle access for injection and then deployed to cover the needle after injection. This dynamic behavior resolves the contradiction between protection and accessibility

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Instead of a rigid shield, a flexible sheath cover is used that can easily move between retracted and deployed positions. This flexibility enables both needle access during injection and needle coverage after injection without mechanical complexity

Inventive Principle:

Principle #30Flexible shells and thin films

4Reliability

If the safety syringe is integrated permanently into the auto-injector, then device reliability is improved, but the auto-injector cannot be reused and operational complexity increases

Engineering Contradiction:

Improvedevice performanceVSAvoidoperational complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The auto-injector system is segmented into separate components - the reusable auto-injector mechanism and the disposable safety syringe. This segmentation allows the expensive mechanism to be reused while the disposable component maintains reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The safety syringe is designed as a disposable component that is discarded after single use. This eliminates the need for complex cleaning and sterilization procedures, reducing operational complexity while maintaining device reliability for each use

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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

Ensures safe and intuitive operation with automatic needle coverage, reducing the risk of needle exposure and discomfort, while allowing for reusability and effective delivery of medications, including large drug masses with controlled force application.

Implementation Method 1

the biasing means comprises one of a compression spring and a rotary spring

Methodology Applied

Scientific EffectSpring mechanism: Spring

Data Source

PatentEP3405234B1Auto-injector apparatus

Publication Date: 2026.03.11 OWEN MUMFORD

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Figure 3

AI summary

An auto-injector apparatus (100) for receiving a safety syringe, the safety syringe comprising a sheath (212) deployable on actuation of a plunger (206; 210) to a position at least partially covering a needle (202) of the syringe, wherein the apparatus is configured to allow movement of the sheath to a closed position that substantially covers the needle.