Retractable Needle Assembly Single-Handed Lever Mechanism

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Solution Overview

Problem

Existing retractable needle assemblies for injection devices often require two-handed use, increasing the risk of needle stick injury due to the need for twisting actions that expose users to the needle during retraction.

Innovation Solution

A retractable needle assembly with a manually operated lever that allows single-handed use, featuring a deflector element and lever design where the lever intersects the plane perpendicular to the needle axis, providing temporary guarding and allowing the needle to be safely retracted by a simple linear motion without twisting, along with a non-return mechanism to prevent re-extension.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a twist handle is used to rotate the reel for cannula retraction, then the cannula can be drawn into the housing, but the user requires two-handed operation which increases the risk of needle stick injury

Engineering Contradiction:

Improveneedle retraction operationVSAvoidneedle stick injury risk

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

Instead of requiring the user to grasp and rotate a twist handle from the front or side, the invention inverts the interaction by allowing the user to push the deflector lever from the rear side. This reverses the direction of force application and eliminates the need for twisting motions that expose the user to the needle.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The deflector lever acts as an intermediary element between the user's thumb and the needle retraction mechanism. By pushing the lever, the user indirectly actuates the deflector element which then rotates the reel, preventing direct contact with the needle while still enabling retraction.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the deflector lever is positioned to intersect the plane perpendicular to the deflector rotary axis and containing the needle axis, then the lever provides temporary guarding of the user's thumb, but this requires precise geometric alignment

Engineering Contradiction:

Improvethumb protectionVSAvoidlever positioning accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The deflector lever is designed with an asymmetric configuration where it projects from the body portion at a specific angle (at least 90° to the patient end of the needle). This asymmetric positioning naturally achieves the protective geometric relationship without requiring high-precision alignment during assembly.

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentUS10426898B2Retractable needle assemblies

Publication Date: 2019.10.01 OWEN MUMFORD

AI summary

A retractable needle assembly comprises a body portion, a needle having a patient end and being movable between an operational position in which the needle extends along a longitudinal needle axis with the patient end projecting forwardly from said body portion, and a safe position in which said patient end is retracted into said body portion, a deflector element rotatable about a deflector rotary axis generally perpendicular to said needle axis to move the needle to its safe position, and a manually operated deflector lever connected to or forming part of said deflector element, the deflector lever projecting from said body portion and intersecting a plane perpendicular to the deflector rotary axis and containing the needle axis.