Injection Device Piston Rod Segmentation for Controlled Needle Protection

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Solution Overview

Problem

Existing injection devices face issues with automatic needle protection systems activating prematurely or inadvertently, leading to potential accidental pricks and reabsorption of injected medication, especially when the needle is still in the skin, resulting in incomplete dosing and safety risks.

Innovation Solution

The design incorporates a piston rod with a first and second portion that can move independently in the proximal direction, allowing the biasing means to be absorbed by the second portion when the covering element presses against the skin, preventing the piston from returning and enabling controlled activation of the protection mechanism.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If automatic protection means are activated by the piston rod when it reaches the end of travel, then the needle is protected after injection, but the piston rod may rise again in the proximal direction causing reabsorption of injected product

Engineering Contradiction:

Improveneedle protection reliabilityVSAvoidinjected product reabsorption

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The piston rod is divided into a first portion and a second portion that can move independently. The second portion can move in the proximal direction relative to the first portion, allowing the biasing means to be absorbed without causing the piston to return and reabsorb injected product.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second portion of the piston rod acts as an intermediary element between the biasing means and the first portion. It absorbs the biasing means' movement through independent proximal motion, preventing force transmission that would cause piston return and product reabsorption.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the covering element is released and pressed against the skin when the whole dose has not yet been injected, then automatic protection is activated, but the injection is interrupted and dosing is incomplete

Engineering Contradiction:

Improveautomatic protection activationVSAvoidinjection completion

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system allows dynamic control of the covering element's movement. The second portion of the piston rod can move independently to absorb biasing means activation, allowing the covering element to be pressed against the skin without interrupting the injection process, ensuring complete dosing while maintaining protection reliability.

Inventive Principle:

Principle #15Dynamics

3Ease of operation

If intermediate lugs return to their undeflected position when distal pressure is relaxed, then the covering element is released, but the piston rises again causing product reabsorption

Engineering Contradiction:

Improvecovering element releaseVSAvoidinjected product reabsorption

Core Design Contradiction:

Ease of operationVSLoss of substance

Solution Approach 1:

The piston rod is segmented into two portions, allowing the second portion to move independently in the proximal direction. This independent movement absorbs the return force of the intermediate lugs when distal pressure is relaxed, preventing the piston from rising and avoiding product reabsorption while still allowing covering element release.

Inventive Principle:

Principle #1Segmentation

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 solution prevents the reabsorption of injected medication, ensures complete dosing, and provides enhanced safety against accidental pricks by allowing controlled activation of the protection mechanism, while simplifying manufacturing processes.

Implementation Method 1

a spring designed to force the distal movement of the covering element when the needle is to be covered

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

elastically flexible lateral lugs designed to be deflected by the head of the piston rod when the latter arrives at the end of travel

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS10226584B2Injection device preventing the return of the piston when the safety system is deployed

Publication Date: 2019.03.12 BECTON DICKINSON FRANCE SAS

AI summary

The present invention relates to an injection device (1) comprising: —a body (3) designed to receive a product to be injected, furnished at its distal end with an injection needle (7) and receiving a piston (5) capable of being moved between a storage position and an end-of-injection position under the effect of a distal pressure exerted on a piston rod (8) to the distal end of which it is attached, —means of protecting the injection needle (7) capable of adopting an initial position, during which the injection needle (7) is uncovered, and a final position, in which the said injection needle (7) is covered, —biasing means (26) aiming at moving the said covering element (6) from its initial position to its final position, —immobilization means (16, 31) aiming at keeping the said covering element (6) in its initial position, the said injection device (1) being characterized in that: —the said piston rod (8) comprises at least a first portion (9) and at least one second portion (10) coupled to the said piston (8), the said first and second portions (9, 10) being operatively coupled together and selectively movable together in the distal direction, at least one of said first portion (9) and said second portion (10) being movable in the proximal direction separate from said other one of said first portion (9) and said second portion (10).