Proximity Sensor Plunger Position Detection Auto-Injector

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Solution Overview

Problem

Manual injection devices require continuous user effort, leading to potential underdosing and discomfort due to high injection forces and extended button activation, while auto-injectors face challenges in accurately determining the plunger position within drug cartridges for proper priming and dosing.

Innovation Solution

An arrangement using a proximity sensor to detect the position of a plunger relative to a bung in a drug cartridge, which includes an imaging or light-based system to determine contact and position the plunger for accurate priming and dosing, integrated with an electromechanical drive for automatic operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a manual injection device is used, then the user can control the injection process, but the user experiences high injection forces and extended button activation leading to discomfort and potential underdosing

Engineering Contradiction:

Improveuser effortVSAvoiddosing accuracy

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The injection device is designed to perform the injection automatically without requiring continuous user effort. The spring mechanism self-activates when the trigger is pulled, and the plunger automatically pushes the bung to deliver the full dose without needing user intervention throughout the process.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The manual mechanical system requiring continuous user pressure is replaced with a spring-driven mechanical system. The spring stores energy and automatically converts it to linear motion of the plunger, eliminating the need for sustained user force while ensuring complete dose delivery.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If the button extension is made long to ensure full activation, then the plunger can reach its end position, but it becomes inconvenient for users to reach and causes hand trembling

Engineering Contradiction:

Improveplunger position accuracyVSAvoidbutton accessibility

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The long button extension mechanical system is replaced with a trigger mechanism that activates a spring. The trigger requires minimal user input to initiate the spring's automatic action, eliminating the need for users to reach or hold extended buttons while maintaining precise plunger positioning through the spring's controlled expansion.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If an electromechanical drive is used to automatically displace the plunger, then user effort is reduced, but the device complexity increases with additional electronic components

Engineering Contradiction:

Improveautomation levelVSAvoidcomponent count

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The electromechanical drive system with motors and electronic controls is replaced with a purely mechanical spring-driven system. The spring provides the driving force automatically when triggered, achieving automation without requiring electronic components, thereby reducing device complexity while maintaining ease of operation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Measurement precision

If a proximity sensor is added to detect plunger position, then dosing accuracy is improved, but the device complexity increases

Engineering Contradiction:

Improveplunger position detectionVSAvoidsensor integration

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The electronic proximity sensor system is replaced with a simple optical detection system using a light source and light sensor. This optical system detects the plunger position by monitoring light reflection or transmission changes, achieving precise measurement without the complexity of electronic proximity sensors while maintaining automation capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Enables accurate positioning of the plunger within the drug cartridge for automatic priming and dosing, reducing user effort and the risk of underdosing, while enhancing the reliability of auto-injector devices by ensuring proper contact and fluid delivery.

Implementation Method 1

a proximity sensor located close to a distal end of the plunger facing the bung and aligned to receive light reflected by the bung

Methodology Applied

Scientific EffectLight reflection: Reflection

Data Source

PatentUS11786657B2Arrangement for detecting a position of a plunger

Publication Date: 2023.10.17 SANOFI AVENTIS DEUT GMBH

AI summary

The invention relates to an arrangement for detecting a position of a plunger (4) relative to a bung (3) in a drug cartridge (1), comprising a proximity sensor (5) located close to a distal end (6) of the plunger (4) facing the bung (3) and aligned to receive light reflected by the bung (3).