Adjustable Piston Rod Assembly for Drug Delivery Device

Solution Overview

Problem

Drug delivery devices often require a priming operation before the first dose, which can be confusing for users and may lead to accidental injection of prime fluid due to mechanical tolerances and lack of accuracy in the first dispensed dose.

Innovation Solution

An assembly for a drug delivery device that adjusts the length of a piston rod to fix its length, allowing for precise dose setting and dispensing without the need for a priming operation, using a mechanism with ratchet teeth or a lead screw to advance the piston rod and ensure accurate delivery of medicinal products.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a priming operation is required before the first dose, then the device can be used, but the usability is reduced and users may accidentally inject prime fluid

Engineering Contradiction:

Improveaccuracy of first dispensed doseVSAvoidusability

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The piston rod is pre-adjusted to a fixed length during manufacturing, establishing the correct initial position before the device is used by the patient. This preliminary action eliminates the need for priming operations and ensures accurate dose delivery from the first use.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the parameter of piston rod length from variable (requiring priming) to fixed (no priming needed). By adjusting the piston rod to a specific fixed length that accounts for mechanical tolerances, the device delivers accurate doses without requiring the user to perform priming operations.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the piston rod length is adjustable, then the device can accommodate tolerances, but the first dispensed dose is inaccurate

Engineering Contradiction:

Improveadjustment of piston rodVSAvoidaccuracy of first dose

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The piston rod is pre-adjusted to a fixed length during manufacturing, establishing the correct initial position before the device is used by the patient. This preliminary action eliminates the need for priming operations and ensures accurate dose delivery from the first use.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the parameter of piston rod length from variable (requiring priming) to fixed (no priming needed). By adjusting the piston rod to a specific fixed length that accounts for mechanical tolerances, the device delivers accurate doses without requiring the user to perform priming operations.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If a priming operation is required, then the device can deliver subsequent doses, but the user may accidentally inject prime fluid

Engineering Contradiction:

Improvedose dispensing capabilityVSAvoidaccidental injection of prime fluid

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The piston rod is pre-adjusted to a fixed length during manufacturing, establishing the correct initial position before the device is used by the patient. This preliminary action eliminates the need for priming operations and ensures accurate dose delivery from the first use.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention converts the potential harm of accidental prime fluid injection into a benefit by designing the piston rod with a fixed length that eliminates the priming step entirely. The mechanical tolerance accommodation is built into the fixed length design, turning a potential source of error into a reliable dosing mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 enhances the usability and accuracy of the first dispensed dose by eliminating the need for priming, ensuring correct volume delivery and preventing accidental injection of prime fluid, applicable to both fixed and variable dose pens.

Implementation Method 1

The second member may comprise ratchet teeth or a lead screw as part of the related drive mechanism. In case of a ratchet teeth based drive mechanism, the piston rod is linearly advanced

Methodology Applied

Scientific EffectRatchet mechanism: Ratchet

Implementation Method 2

The second member may comprise ratchet teeth or a lead screw as part of the related drive mechanism. In case of a lead screw based drive mechanism, the piston rod is rotationally advanced

Methodology Applied

Scientific EffectLead screw mechanism: Screw

Data Source

PatentUS9750890B2Mechanism for a drug delivery device

Publication Date: 2017.09.05 SANOFI AVENTIS DEUT GMBH

AI summary

The present invention relates to an assembly forming a piston rod for advancing a cartridge bung in a drug delivery device, the assembly comprising a first member and a second member wherein in a first state, the first and the second member are moveable with respect to each other to adjust the length of the piston rod and wherein in a second state the first member is locked in position with respect to the second member in order to define a fixed length of the piston rod. Furthermore, it relates to a drug delivery device comprising the assembly and to a method for assembling such a drug delivery device.