Dual-Material Bung for Drug Delivery Cartridge Dose Accuracy
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Solution Overview
Problem
Drug delivery devices face challenges in ensuring dose accuracy, particularly when dispensing the last dose from drug-containing cartridges, due to inaccuracy issues.
Innovation Solution
A bung for drug-containing cartridges is designed with a dual-material structure, featuring a softer rubber material covering the lateral and distal end faces for adaptability and sealing, and a harder material, such as metal or ceramic, inside for resistance, allowing for precise dose dispensing by adapting to the cartridge's shape and limiting axial compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-material bung is used, then the manufacturing process is simple, but the dose accuracy is insufficient particularly for the last dose dispensing
Solution Approach 1:
The bung is constructed with a core-shell structure where the core is made of a harder material (metal, ceramic, or polymer matrix) and the shell is made of a softer, more compressible material (rubber or elastomer). This composite structure allows the bung to maintain its shape and resist excessive compression while still adapting to the cartridge body, thereby improving dose accuracy for the last dose without significantly complicating the manufacturing process.
Solution Approach 2:
Different regions of the bung have different material properties: the core provides structural integrity and resistance to compression, while the outer shell provides adaptability and sealing. This local differentiation of material properties allows each part of the bung to perform its specific function optimally, resolving the contradiction between precision and complexity.
2Adaptability or versatility
If a softer material is used for the bung, then the bung can adapt to the cartridge shape, but the bung cannot resist axial compression effectively
Solution Approach 1:
The core-shell structure combines a hard core that resists axial compression with a soft outer shell that adapts to the cartridge shape. The hard core (metal, ceramic, or rigid polymer) maintains the bung's structural integrity under compression, while the soft shell (rubber or elastomer) conforms to the cartridge body, simultaneously achieving both adaptability and compression resistance.
Solution Approach 2:
The bung's core region is designed with high strength to resist compression, while the outer region is designed with high elasticity to adapt to the cartridge. This spatial differentiation of material properties resolves the contradiction between adaptability and strength.
3Strength
If a harder material is used for the bung, then the bung can resist compression, but the bung cannot adapt to the cartridge shape and increases retention time
Solution Approach 1:
The core-shell structure with a hard core and soft shell allows the bung to resist compression while adapting to the cartridge shape. The soft outer layer ensures proper sealing and adaptability, preventing the retention time issue that would occur with a purely hard material.
4Ease of operation
If the bung material is highly compressible, then the bung can be easily driven by the piston, but the bung deforms excessively during dispensing
Solution Approach 1:
The soft outer shell allows easy compression by the piston for driving the bung, while the hard core prevents excessive deformation during dispensing. This composite structure balances ease of operation with shape stability.
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
The dual-material bung enhances dose accuracy and reduces retention time, enabling more precise dispensing of the last dose of the medicinal product by maintaining a consistent compression and preventing deformation during dispensing.
Implementation Method 1
the first material comprises rubber and has a larger compressibility than the second material
Implementation Method 2
due to the relatively high compressibility of the first material the bung is able to adapt its shape to the shape of the main body portion of the cartridge
Implementation Method 3
the second material which is at least partly arranged inside the bung, wherein the second material provides a rigid core to resist or at least to limit axial compression of the bung while a piston is pressed onto the bung
Data Source
Figure 1~2
AI summary
The present invention relates to a bung (20) for drug containing cartridges (10) for use in drug delivery devices wherein the bung (20) has a distal end face (22), a proximal end face (24) and a lateral area (26), wherein the bung (20) comprises at least two different materials, a first material (30) covering the whole lateral area (26) of the bung (20) and a second material (32) which is at least partly arranged inside the bung (20), wherein the first material(30) has a larger compressibility than the second material (32) and wherein the whole lateral area (26) has a flat surface. Furthermore, it relates to a cartridge (10) and to a drug delivery device comprising a bung (20) as claimed.