Syringe Stopper with Convex Head for Anti-Sticking
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Solution Overview
Problem
Existing syringe stoppers tend to stick together during storage and assembly due to close contact and external forces, leading to processing issues and scrap. The sticking problem is exacerbated by the use of silicone coatings, which while reducing rubber-to-rubber sticking, can also cause stopper heads to adhere to each other.
Innovation Solution
The development of a syringe stopper with a convex outer surface on its head and optional anti-sticking features such as protrusions or annular protrusions. These features reduce the contact area between stopper heads, minimizing sticking during storage and assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a silicone layer is applied on the stopper head to reduce rubber-to-rubber sticking, then rubber-to-rubber sticking is reduced, but stopper head to stopper head sticking increases due to capillary bridges
Solution Approach 1:
The stopper head is given a convex curved surface instead of a flat surface. This curvature reduces the apparent contact area between stopper heads when they are in contact, thereby minimizing capillary bridge formation and reducing stopper head to stopper head sticking, while preserving the silicone coating for rubber-to-rubber sticking prevention
Solution Approach 2:
Anti-sticking features (protrusions or grooves) are added to specific locations on the stopper head surface. These localized features create air gaps or reduce contact areas at critical zones, preventing capillary bridge formation while maintaining silicone coating coverage in other areas for lubrication and sticking prevention
2Ease of manufacture
If the outer surface of the stopper head is made flat, then manufacturing is simplified, but the large contact area facilitates sticking between stoppers
Solution Approach 1:
The stopper head outer surface is designed with a convex curvature instead of being flat. This geometric change reduces the contact area between adjacent stopper heads, minimizing sticking while remaining compatible with standard manufacturing processes for molded stoppers
3Quantity of substance
If stoppers are packaged in evacuated plastic bags to increase packaging density, then storage space is optimized, but external force increases causing stopper heads to stick together
Solution Approach 1:
The convex curved surface of the stopper head reduces the apparent contact area under external compression forces. When stoppers are stacked in evacuated bags, the curved surfaces minimize the contact zone, reducing capillary bridge formation and sticking even under high compression
4Object-affected harmful factors
If the amount of silicone on the stopper surface is increased to prevent rubber-to-rubber sticking, then rubber-to-rubber sticking is reduced, but stopper head to stopper head sticking increases
Solution Approach 1:
The convex curved surface geometry reduces the apparent contact area between stopper heads, which counteracts the increased sticking tendency from higher silicone amounts. This allows the use of adequate silicone for rubber-to-rubber sticking prevention without exacerbating head-to-head sticking
Solution Approach 2:
Anti-sticking features are strategically positioned on the stopper head to create localized air gaps or reduced contact zones. This allows higher silicone coverage in areas needing lubrication while preventing capillary bridge formation in critical contact zones
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 convex outer surface and anti-sticking features effectively reduce the sticking of stopper heads to each other, enhancing processability and reducing scrap. Additionally, the design minimizes dead space in the syringe chamber and reduces the amount of pharmaceutical residue after injection.
Implementation Method 1
For coated stoppers, where a silicone layer and/or a film such as for example polytetrafluoroethylene (PTFE) or ethylene tetrafluoroethylene (ETFE) are applied on the head of the stopper, it is postulated that sticking of stoppers to one another occurs by capillary bridges.
Implementation Method 2
the outer surface of the head of one stopper can become stuck to the outer surface of the head of another stopper
Data Source
AI summary
A stopper for a syringe including a body having a tail adapted for attachment to a plunger of the syringe, and a head, the head having a outer surface that is convex, such that the outer surface is curved with an apex of the curvature extending away from a plane orthogonal to the longitudinal axis of the stopper and comprising an outer perimeter of the outer surface and the apex of the outer surface of the head is higher than the outer perimeter of the outer surface when the stopper is viewed from a side in a direction perpendicular to the longitudinal axis of the stopper. The stopper may optionally include a plurality of protrusions extending from an outer surface of the head. Also, a syringe including such a stopper.