Plunger Form Fit Structure Resolves Stopper Deformation

Solution Overview

Problem

Existing medical delivery devices face challenges in achieving both sufficient tightness and dosing accuracy due to the conflicting requirements of stopper flexibility and strength, which can lead to impaired function and deformation during use.

Innovation Solution

A plunger design featuring a rod element with a first form fit structure and a stopper with a second form fit structure, securely interlocking to provide a strong and stable connection that resists operational forces without deforming, using materials like ABS for the rod and TPE for the stopper, with anchor portions and stabilization elements to prevent axial and radial movement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the stopper is made soft and flexible to achieve tightness in the chamber, then the chamber can be tightly closed, but the stopper deforms under friction and pressure forces during movement

Engineering Contradiction:

ImprovetightnessVSAvoidstopper deformation

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The stopper is divided into two distinct parts: a soft stopper body for achieving tightness in the chamber, and a rigid stabilization element for maintaining structural integrity. This segmentation allows each part to fulfill its specific function without compromise - the soft body conforms to the chamber wall while the rigid element resists deformation from operational forces.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The stopper combines two materials with different mechanical properties: a soft, elastic material (such as medical-grade silicone or rubber) for the stopper body to ensure tight sealing, and a rigid material (such as medical-grade plastic or metal) for the stabilization element to prevent deformation. This composite structure resolves the contradiction between needing softness for tightness and rigidity for stability.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If the stopper is made stiff to resist deformation during operation, then dosing accuracy is maintained, but the stopper cannot tightly fit into the chamber

Engineering Contradiction:

Improvestopper deformationVSAvoidtightness

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The stopper is divided into two distinct parts: a soft stopper body for achieving tightness in the chamber, and a rigid stabilization element for maintaining structural integrity. This segmentation allows each part to fulfill its specific function without compromise - the soft body conforms to the chamber wall while the rigid element resists deformation from operational forces.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The stopper combines two materials with different mechanical properties: a soft, elastic material (such as medical-grade silicone or rubber) for the stopper body to ensure tight sealing, and a rigid material (such as medical-grade plastic or metal) for the stabilization element to prevent deformation. This composite structure resolves the contradiction between needing softness for tightness and rigidity for stability.

Inventive Principle:

Principle #40Composite materials

3Reliability

If adhesive or snapping methods are used to connect stopper to rod, then the connection may fail under operational forces, but more complex connection methods increase device complexity

Engineering Contradiction:

Improveconnection strengthVSAvoidconnection structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The stabilization element is extracted as a separate, integrated component that provides mechanical reinforcement to the stopper-rod connection. Instead of relying solely on adhesive or snapping methods, the rigid stabilization element acts as an internal reinforcement structure that distributes and resists operational forces, thereby strengthening the connection without requiring additional external components or complex assembly procedures.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The stopper combines two materials with different mechanical properties: a soft, elastic material (such as medical-grade silicone or rubber) for the stopper body to ensure tight sealing, and a rigid material (such as medical-grade plastic or metal) for the stabilization element to prevent deformation. This composite structure resolves the contradiction between needing softness for tightness and rigidity for stability.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS11577027B2Plunger and method of manufacturing a plunger

Publication Date: 2023.02.14 F HOFFMANN LA ROCHE INC

AI summary

A plunger (1) for a medical delivery device comprises: a rod element (2) having a distal end (22) and a proximal end, and a stopper (3) mounted to the rod element (2) at its distal end (22). The rod element (2) has a first form fit structure (24) and the stopper (3) has a second form fit structure (31). The stopper (3) is locked to the rod element (2) by the first form fit structure (24) of the rod element (2) and the second form fit structure (31) of the stopper (3) engaging each other.