Screw-Coupled Piston Rod Structure for Stable Drug Injection

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Solution Overview

Problem

Existing drug injectors require specialized skills for use and lack user-friendly features for dose setting and delivery confirmation, with a need for improved ease of use, reduced size, and cost-effective manufacturing.

Innovation Solution

A drug injection control device with a rotating rod guide and linearly moving piston rod, utilizing a torsion spring mechanism to set and deliver doses through a dose dial, incorporating a screw coupling between the piston rod and rod guide for stable drug release.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a rotating rod guide and screw-coupled piston rod mechanism is used, then drug delivery stability is improved, but device complexity increases

Engineering Contradiction:

Improvedrug delivery stabilityVSAvoidmechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The piston rod is nested inside the rod guide, with the rod guide rotating externally while the piston rod makes linear motion internally. This nested configuration allows the complex screw coupling mechanism to be compact, improving drug delivery stability while minimizing the increase in overall device complexity.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The screw coupling mechanism between the piston rod and rod guide uses spiral/curved geometries to transform rotational motion into linear motion. This curved mechanical advantage provides stable, controlled drug delivery through the dose dial while maintaining a manageable device structure.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Measurement precision

If specialized subcutaneous injection skills are required, then injection precision is improved, but ease of operation deteriorates

Engineering Contradiction:

Improveinjection precisionVSAvoiduser operation ease

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The device is designed as an autoinjector that performs the injection automatically once activated. The mechanism self-regulates the drug delivery through the screw-coupled piston rod and rod guide, eliminating the need for users to have specialized injection skills while maintaining precise dose delivery through the dose dial setting.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The complex manual injection skill requirement is replaced by an automated mechanical system. The screw coupling mechanism automatically converts the user's simple activation action into precise linear motion of the piston rod, substituting needed mechanical precision for user skill.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If manufacturing and assembly are simplified, then manufacturing cost is reduced, but manufacturing precision may deteriorate

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidassembly precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The device is divided into separable modules including the cartridge holder, rod guide, piston rod, and dose dial. This segmentation allows each component to be manufactured and assembled independently, simplifying manufacturing processes while maintaining precision through standardized coupling interfaces between segments.

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

Enables stable and user-friendly drug injection with dose setting confirmation, reducing manufacturing complexity and cost while ensuring safe and efficient drug delivery.

Implementation Method 1

an injection amount setting module 100 configured to make a rotational motion with the dose dial 20 in the housing 10 to set an amount of the drug to be injected by storing a twisting moment in a torsion spring 140

Methodology Applied

Scientific EffectTorsion spring: Torsion Spring

Implementation Method 2

a piston rod 220 screw-coupled to an outer side of the rod guide 210 to deliver the drug from the cartridge embedded in the cartridge holder 30 by making a linear motion with a rotational motion of the rod guide 210

Methodology Applied

Scientific EffectScrew coupling: Screw

Data Source

PatentUS12623028B2Drug injection control device having cartridge drug release structure through screw coupling between piston rod and rod guide

Publication Date: 2026.05.12 POONGLIM PHARMATECH

AI summary

A drug injection control device allows a structure in which a piston rod moving with a rod guide makes a linear motion to stably inject a drug set through a dose dial. When an injection amount of drug is preset through an injection amount setting module configured to make a rotational motion with the dose dial in a housing to set the amount of drug to be injected by storing the twisting moment in a torsion spring, in actuating a drug delivery module switchably coupled to the injection amount setting module by an injection button on top of the drug injection control device, the rod guide is connected to the inside of the piston rod through a reset tube movably coupled to the injection button to allow a sub-linear motion of the piston rod.