Variable-Gap Nozzle Coating for Fibrous Webs Without Machine Shutdown
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing coating devices for fibrous material webs, such as paper or cardboard, face limitations in varying the application amount of coating mediums like starch solutions without shutting down the machine, and suffer from high wear and maintenance issues, particularly with doctor blade metering systems and spray nozzles.
Innovation Solution
An application device with a variable outlet gap in the nozzle and a control unit to adjust the application amount based on fibrous web strength characteristics, allowing for a wide range of variation without machine shutdown, using actuators and a control unit to adjust gap width and internal pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If doctor blade metering systems are used to apply coating medium, then the application amount can be controlled, but the machine must be shut down to change the application amount
Solution Approach 1:
The patent implements a variable geometry outlet gap in the application nozzle that can be dynamically adjusted during machine operation. The gap width between the nozzle components is made variable, allowing continuous adjustment of the coating medium flow rate without stopping the machine, thus resolving the contradiction between precise control and operational continuity
Solution Approach 2:
The invention changes the geometric parameters of the outlet gap (width, shape) to control the application amount. By varying the gap dimension as a controllable parameter, the system achieves flexible adjustment of coating medium delivery while maintaining continuous operation, eliminating the need for shutdowns required by fixed-geometry doctor blade systems
2Productivity
If spray nozzles are used to apply coating medium, then the machine does not need to be shut down to change application amount, but the application amount can be varied only within relatively small limits
Solution Approach 1:
The patent employs a dynamically adjustable outlet gap mechanism that allows large-range variation in gap width. This dynamic geometry adjustment enables the system to achieve both continuous operation (like spray nozzles) and wide application amount variation (unlike conventional spray systems), as the gap can be opened wider or narrowed more extensively than spray nozzle flow rates can be adjusted
3Manufacturing precision
If transfer rolls with very hard surfaces are used, then the starch can penetrate the fibrous web better, but the doctor blades become very rapidly worn
Solution Approach 1:
The invention extracts and eliminates the doctor blade component from the system by using an outlet gap-based metering mechanism. The coating medium is precisely controlled through the variable gap geometry itself, removing the need for doctor blades that would rapidly wear against hard transfer roll surfaces, thus solving the wear problem while maintaining precise application control
Solution Approach 2:
The patent replaces the mechanical doctor blade scraping system with a fluid dynamic control system based on outlet gap geometry. The precise metering is achieved through the controlled flow through the variable gap rather than mechanical removal of excess coating, eliminating the harmful mechanical contact that causes rapid blade wear
Data Source
AI summary
An application device and method for coating a fibrous material web, such as a paper web, a web of packaging material, or a web of cardboard. The application device has an application nozzle for applying a coating medium, in particular a starch solution, to a moving surface, and the application nozzle has an outlet gap that produces a film of coating medium or a curtain of coating medium. A device is provided for varying the application amount and the variation is based on a strength variable.