Coating Device Impact Surface Uniform Flow
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Solution Overview
Problem
Prior art coating devices for fiber webs suffer from non-uniform coating profiles due to variations in shearing rates through small feed holes, leading to inhomogeneous viscosity and uneven distribution of coating color, resulting in streaks and stripes on the fiber web.
Innovation Solution
A coating device with an impact surface at the outlet of the feed hole directs the coating color flow into an equalizing chamber, shifting the dominant flow resistance from friction to kinetic energy, ensuring uniform distribution regardless of viscosity inhomogeneities, with features like a cup-like impact surface and specific dimensions to maintain high kinetic energy and avoid shear thickening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If small feed holes are used to supply coating color to the nozzle slot, then the coating color flow is constrained and directed, but variations in shearing rates cause inhomogeneous viscosity and non-uniform coating distribution
Solution Approach 1:
An equalizing chamber is introduced as an intermediary between the feed hole and the nozzle slot. This chamber allows the coating color flow to expand and mix, equalizing viscosity variations before the coating is applied to the substrate. The chamber acts as a buffer that decouples the high-shear feed hole from the application point, preventing viscosity inhomogeneity from translating into coating defects.
Solution Approach 2:
The invention changes the flow parameters by providing a sufficiently large equalizing chamber volume and appropriate dimensions. This allows the flow to transition from a constrained, high-shear state in the feed hole to a more uniform, expanded state in the chamber, thereby equalizing viscosity before application.
2Quantity of substance
If the feed hole area is reduced to control coating color flow, then flow rate is controlled, but shearing rate variations increase leading to worse viscosity inhomogeneity
Solution Approach 1:
The equalizing chamber serves as a mediator that decouples flow rate control from uniformity. The feed hole can be small for precise flow control, while the chamber provides the space needed to equalize viscosity variations, allowing both control and uniformity to be achieved separately.
3Device complexity
If coating color is supplied through feed holes directly to the nozzle slot, then the structure is simple, but the coating profile becomes non-uniform due to viscosity variations
Solution Approach 1:
The equalizing chamber is a relatively simple structural addition that acts as an intermediary between the feed hole and nozzle slot. It provides the necessary function of viscosity equalization without requiring complex mechanisms, maintaining ease of construction while improving coating uniformity.
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 solution ensures uniform coating distribution, minimizing the impact of viscosity inhomogeneities and preventing streaks and stripes on the fiber web, thereby enhancing coating quality.
Implementation Method 1
shifting the dominant flow resistance from friction to kinetic energy
Implementation Method 2
shifting the dominant flow resistance from friction to kinetic energy
Implementation Method 3
variations in shearing rates through small feed holes, leading to inhomogeneous viscosity
Implementation Method 4
specific dimensions to maintain high kinetic energy and avoid shear thickening
Data Source
Figure 1~2
Figure 3A~3C
AI summary
The invention relates to a coating device for applying coating color onto a fiber web, which device comprises a nozzle unit with at least one nozzle part (10) comprising a feeding chamber (11) and at least one equalizing chamber (13; 13'), a feed hole (12) between the feeding chamber (11) and the first equalizing chamber (13) and a nozzle slot (14'), from which the coating color discharged through outlet opening (15) of the nozzle slot (14'). At outlet area of the feed hole (12) to the equalizing chamber (13) an impact surface (20) is arranged, which functions as means for distributing uniformly the inhomogeneous coating color flow entering the equalizing chamber (13) from the feed hole (12). The invention also relates to a method for coating of a fiber web, in which method the coating color is applied by a coating device comprising a nozzle unit with at least one nozzle part (10), in which the coating color is fed to a feeding chamber (11) and therefrom to at least one equalizing chamber (13; 13') through a feed hole (12) between the feeding chamber (11) and the first equalizing chamber (13) and then to a nozzle slot (14'), from which the coating color is discharged through outlet opening (15) of the nozzle slot (14'). In the method flow of the coating color at outlet area of the feed hole (12) to the equalizing chamber (13) is directed to an impact surface (20), which distributes uniformly the coating color flow entering the equalizing chamber (13) from the feed hole (12).