Drug Delivery Plunger Rod With Nonuniform Stopper Interface
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing drug delivery devices face challenges with high break-loose forces due to piston adherence to reservoir material, leading to jerky motion and uneven drug delivery, especially in dual chamber systems, and require powerful springs that increase device weight and cost.
Innovation Solution
A drug delivery device with a plunger rod structure featuring a distal end face with a first force transferring portion that initially applies pressure to a peripheral portion of the stopper, reducing static friction by sequentially detaching the stopper from the reservoir wall, allowing for a more uniform piston displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional plunger rod with uniform force distribution is used, then the structure is simple and manufacturing is easy, but the break-loose force is high causing jerky motion and requiring powerful springs
Solution Approach 1:
The plunger rod's distal end face is designed with non-uniform force distribution, concentrating force at a peripheral region rather than distributing it uniformly across the entire surface. This local quality change allows the stopper to detach sequentially from the reservoir wall, reducing break-loose force and eliminating jerky motion during piston displacement.
2Reliability
If powerful springs are used to overcome high break-loose forces, then reliable drug expulsion is achieved, but device weight and cost increase
Solution Approach 1:
The plunger rod structure performs a preliminary action by concentrating force at the peripheral region of the stopper interface, which initiates sequential detachment of the stopper from the reservoir wall. This preliminary localized force application reduces the overall break-loose force required, allowing lighter springs to reliably expel the drug without increasing device weight.
3Productivity
If uniform force is applied across the stopper surface, then manufacturing is simple, but static friction is high causing uneven drug delivery
Solution Approach 1:
The distal end face of the plunger rod features a peripheral force concentrating region with a different geometric profile than the central region. This local quality differentiation creates non-uniform force distribution during stopper interface, enabling sequential detachment and more uniform drug delivery while maintaining manufacturability through straightforward geometric modifications.
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
Reduces the break-loose force required for drug expulsion, ensuring smoother delivery and reducing the need for powerful springs, thus minimizing device weight and cost while maintaining uniform force throughout the process.
Implementation Method 1
reducing static friction by sequentially detaching the stopper from the reservoir wall
Data Source
AI summary
The present invention provides a drug delivery device (1) comprising: a drug reservoir (20) comprising a reservoir body (21) extending along a reference axis and an elastomeric stopper (30) arranged in the reservoir body (21), the elastomeric stopper (30) comprising a stopper body (31) extending between a front stopper end (32) and a rear stopper end (34) and having a plurality of axially spaced apart circumferential ribs (33) for sealing interaction with an interior wall (22) of the reservoir body (21), and a plunger rod structure (10) for displacing the elastomeric stopper (30) relative to the interior wall (22), the plunger rod structure (10) extending along the reference axis and comprising a distal end face (12, 14) adapted to interface with the rear stopper end (34). The distal end face (12, 14) comprises a first force transferring portion (14) and a second force transferring portion (12), the first force transferring portion (14) axially leading the second force transferring portion (12) and being adapted to interact with a peripheral portion of the rear stopper end (34).