Pharmaceutical Container Stopper Geometry for Sealing and Glide Control
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Solution Overview
Problem
Existing pharmaceutical containers face challenges in achieving balanced break loose and glide forces (BLF/GF) while ensuring adequate sealing, leading to potential leakage and user discomfort, with prior solutions involving plasma treatment or autoclaving increasing production costs and risks.
Innovation Solution
The design incorporates annular protrusions on the stopper with controlled angles and surface roughness, along with a balanced ratio of break loose force to glide force (BLF/GF ≤ 2) and total glide force variation (TGFV < 2 N), using materials with specific water contact angles and surface energies to enhance sealing and control force distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the stopper's outer diameter is made very small relative to the container's inner diameter, then the break loose force and glide force are reduced, but the sealing performance deteriorates causing leakage
Solution Approach 1:
The stopper is segmented with multiple annular protrusions (first, second, and third protrusions) at different positions along its length. Each protrusion contacts the inner surface of the container at different locations, distributing the sealing function across multiple points rather than relying on a single large-diameter contact surface. This allows the stopper to maintain small overall diameter while achieving adequate sealing through distributed contact points.
Solution Approach 2:
The invention transitions from relying solely on radial dimension (stopper diameter vs. container diameter) to achieve sealing, to utilizing the axial dimension by positioning multiple annular protrusions at different heights along the stopper. This dimensional shift allows sealing to be achieved through the combination of multiple smaller contact rings distributed axially, rather than requiring a single large radial contact surface.
2Reliability
If the stopper's outer diameter is increased relative to the container's inner diameter, then sealing performance is improved, but the break loose force and glide force increase making operation difficult
Solution Approach 1:
The sealing function is segmented into multiple annular protrusions distributed along the stopper length. Each protrusion provides a portion of the total sealing contact, allowing the use of smaller individual protrusions rather than one large contact surface. This segmentation reduces the total friction area while maintaining sealing integrity, thereby reducing break loose and glide forces.
Solution Approach 2:
Different regions of the stopper are given different functions through the annular protrusions. The protrusions are positioned to contact the inner surface at specific locations optimized for sealing, while other regions of the stopper maintain smaller diameters to reduce friction. This local differentiation allows sealing to be concentrated at specific points without requiring the entire stopper to have a large diameter.
3Force
If plasma treatment or autoclaving is applied to achieve adequate break loose and glide forces, then the force parameters are improved, but production costs increase
Solution Approach 1:
The stopper's geometry itself (the annular protrusions with specific angle ratios) provides the mechanism to control break loose and glide forces, eliminating the need for additional plasma treatment or autoclaving processes. The structural design inherently creates the desired force characteristics through the contact geometry between the protrusions and container inner surface, making the stopper self-regulating regarding force parameters.
Solution Approach 2:
The invention extracts and eliminates the need for costly post-processing steps (plasma treatment, autoclaving) by incorporating the force-control function directly into the stopper's geometric design. The angle ratio of the annular protrusions is designed to naturally produce the desired break loose and glide force characteristics without requiring external treatment processes.
4Reliability
If strong compression is applied to set the stopper into the container, then sealing is improved, but the risk of tilting the stopper increases interrupting production
Solution Approach 1:
The stopper insertion and sealing process is segmented into multiple contact points along the stopper length. The multiple annular protrusions distribute the compression force across different axial positions, preventing concentration of force at a single point that could cause tilting. This distributed contact approach allows gradual, controlled insertion without the stopper binding or tilting during compression.
Solution Approach 2:
The annular protrusions are designed with specific angle ratios that create a self-aligning effect during insertion. The geometry of the protrusions anticipates potential tilting by providing contact surfaces that guide the stopper into proper alignment as it is compressed into the container, cushioning against misalignment before it can cause production interruptions.
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 design ensures controlled drug delivery with reduced leakage risk, maintaining consistent force ratios and variations, even after storage, thus improving user experience and container integrity.
Implementation Method 1
The stopper having one or more annular protrusions contacting the inner surface of the barrel when the stopper moves in distal direction
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
The present invention is concerned with pharmaceutical containers for drug delivery having a barrel configured to slidably receive a stopper. For eluting the contents of the container through an outlet, the stopper must slide within the container. For smooth action adequate break loose and glide forces have to be achieved. The inventive containers achieve these forces by a certain ratio of angels of the most proximal and most distal annular protrusions of the stopper, a certain maximum break loose force to glide force ratio and a certain total glide force variation value.