Cylindrical Carbonaceous Heat Source Inner Coating via Adhesion
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Solution Overview
Problem
Existing methods for applying a thin, uniform coating to the inner surfaces of cylindrical carbonaceous heat sources with longitudinal air flow channels face challenges such as non-uniformity, absorption of coating material into the carbonaceous material, and mechanical pressure-induced imperfections, especially when dealing with low viscosity coatings or hard particles, leading to issues like blockages and abrasion.
Innovation Solution
A process involving the extrusion of a carbonaceous material through a die with mandrels to form air flow channels, where a fluid coating compound is applied downstream, utilizing thermodynamic forces for adhesion and spreading, eliminating the need for mechanical pressure and allowing for low viscosity coatings, thus ensuring a uniform and stable coating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If co-extrusion is used to apply a coating layer to the inner surfaces of extruded tubes, then the coating layer can be applied during the extrusion process, but the die orifice becomes too narrow for coating layers thinner than about 1mm, requiring high viscosity feedstocks that create large shear forces and high pressures
Solution Approach 1:
The patent divides the coating application process into two separate stages: first applying the coating to the outer surface of the extruded tube using conventional coating techniques, then applying a second coating layer to the inner surface through longitudinal channels. This segmentation allows each coating layer to be optimized independently, avoiding the narrow orifice problem of co-extrusion for thin coatings.
Solution Approach 2:
The patent applies the first coating layer to the outer surface before applying the second coating layer to the inner surface. This preliminary action establishes a base coating that can then be followed by the inner surface coating through the longitudinal channels, allowing thin coatings to be applied without requiring narrow die orifices during the extrusion process itself.
2Stability of the object's composition
If high viscosity feedstock is used in extrusion to obtain mechanical stability, then the extruded articles do not deform under gravity, but forcing the feedstock through a narrow orifice creates large shear forces and high pressures
Solution Approach 1:
The patent separates the extrusion process from the coating application process. The extrusion of the carbonaceous material can use high viscosity feedstock for stability, while the coating materials are applied separately through different mechanisms (conventional coating for outer surface, and through longitudinal channels for inner surface), avoiding the need to force high viscosity material through narrow orifices during extrusion.
3Ease of manufacture
If conventional coating techniques such as spraying and dipping are used to apply coating layer to outer surfaces, then the coating application is simple, but applying coating layer to interior surfaces is more difficult
Solution Approach 1:
The patent applies the first coating layer to the outer surface using simple conventional techniques before addressing the inner surface. This preliminary outer coating simplifies the overall process by establishing a base layer that can then be followed by the inner surface coating through the longitudinal channels, making the complex inner coating task more manageable.
Solution Approach 2:
The patent divides the coating application into two separate operations: outer surface coating using conventional simple techniques, and inner surface coating through longitudinal channels. This segmentation allows each coating to be optimized for its specific requirements, with the outer coating being simple and the inner coating addressing the difficulty of interior surface access.
4Manufacturing precision
If the die orifice and flow channels are made smaller to apply thinner coating layers, then the coating thickness can be reduced below 1mm, but the die becomes harder to manufacture and operate and blockage and abrasion occur
Solution Approach 1:
The patent separates the coating application process from the extrusion die design. The extrusion die can have standard-sized orifices for stable material flow, while the coating layers are applied separately through different mechanisms, allowing thin coatings to be applied without requiring proportionally small die orifices that would cause manufacturing and operational difficulties.
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 process achieves a homogeneous, smooth, and well-defined coating with good adhesion, reducing defects and optimizing the performance of the heat source by simplifying the apparatus and reducing precision requirements, while allowing for thinner coatings without increasing shear stress or abrasion issues.
Implementation Method 1
the coating compound wets the inner surface of the air flow channel as a result of forces of adhesion between the coating compound and the inner surface
Data Source
Figure 1~2
AI summary
A process for the production of a cylindrical, carbonaceous heat source (4) for a heated smoking article, the heat source having a longitudinal air flow channel extending therethrough, the inner surface of which is covered with a coating layer (22) comprises the steps of: (a) forming the cylindrical heat source (4) by extrusion of a carbonaceous material through a die (6) comprising an orifice (8) with a mandrel (10) mounted therein to form the air flow channel; and (b) applying a fluid coating compound (16) to the inner surface of the air flow channel downstream of the mandrel. The coating compound (16) is fed through a feed passageway (12) extending longitudinally through the mandrel (10) and having an outlet in the end thereof. The coating compound (16) wets the inner surface of the longitudinal channel as a result of forces of adhesion between the coating compound and the inner surface, thereby forming the coating layer (22) as the cylindrical article (4) is extruded.