Asymmetric Doctor Blade for Fiber Web Machine
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Solution Overview
Problem
Conventional doctor blades for fiber web machines are limited by the need for multiple blade types and are prone to bending, especially when used with soft-surfaced rolls or belts, leading to uneven contact profiles and web breaks, which shortens fabric life and requires more equipment.
Innovation Solution
A doctor blade with an asymmetric blade section and a symmetric fastening detent section, allowing installation in two opposite positions for dual functions, reducing the need for multiple blade types and adapting to various blade holders, while maintaining a stable and wear-resistant design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple different doctor blades are used for different positions, then each position can have optimized performance, but the device complexity and inventory requirements increase
Solution Approach 1:
The doctor blade is designed with an asymmetric blade section that can function in multiple positions. The blade section has a first side for doctoring rolls and a second side for doctoring belts, allowing a single blade design to serve multiple functions in the fiber web machine
Solution Approach 2:
The blade section is designed with asymmetric geometry where the first side has different characteristics than the second side. This asymmetry allows the blade to be optimized for both roll doctoring and belt doctoring applications while maintaining a single unified blade design
2Adaptability or versatility
If plastic blades are used for soft-surfaced rolls or belts, then the blades can adapt to soft surfaces, but the blades bend easily and become swaged during operation
Solution Approach 1:
The doctor blade employs a composite structure combining a plastic blade section with a metal fastening detent section. The plastic portion provides adaptability to soft surfaces while the metal fastening section provides structural stability and resistance to swaging and bending
3Adaptability or versatility
If plastic blades are used, then they can be used for soft-surfaced rolls or belts, but the blades bend during storage and transport
Solution Approach 1:
The hybrid composite design with metal fastening detent provides structural rigidity during storage and transport while maintaining the plastic blade section's ability to adapt to soft surfaces during operation. The metal portion acts as a structural reinforcement that prevents unwanted bending
4Manufacturing precision
If the blade section becomes swaged or bent, then adaptation to the roll surface becomes incomplete, but this causes unevenness in contact profile and web breaks
Solution Approach 1:
The metal fastening detent section provides structural reinforcement that prevents swaging and bending of the blade section, maintaining consistent contact profile and preventing web breaks caused by blade deformation
Solution Approach 2:
The blade section features a curved lower surface that conforms to the roll surface geometry. This curved design, combined with the structural support from the metal fastening section, ensures uniform contact pressure and prevents uneven wear and web breaks
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
The invention relates to a doctor blade for a fiber web machine. The doctor blade (10) includes a blade section (11) and a fastening detent sect ion (12). In the cross-sectional plane, the blade section (11) is asymmetric while the fastening detent section (12) is substantially symmetric so that the doctor blade (10) can be installed in two opposite positions for providing two different functions. The invention also relates to a doctor arrangement in a fiber web machine.