Bell Cup Curved Surface Design for Uniform Electrostatic Coating
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Solution Overview
Problem
The existing bell cups in rotary atomizing electrostatic coating apparatuses produce coating materials with large standard deviation in particle diameter distribution, leading to diminished orientation of lustrous pigments during high ejection rate/wide pattern coating.
Innovation Solution
The bell cup's coating material diffusion surface is designed with a convex curved surface at the proximal end and a concave curved surface at the distal end, equalizing forces to promote uniform diffusion and minimize flow patterns like spiral flow or fingering, resulting in smaller average particle diameter and reduced standard deviation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the bell cup uses a convex curved surface at the proximal end and concave curved surface at the distal end, then the standard deviation of particle diameter distribution is reduced, but the device complexity increases
Solution Approach 1:
The bell cup surface is divided into two distinct zones with different geometric properties: a convex curved surface at the proximal end for uniform diffusion and a concave curved surface at the distal end for force equalization. This local differentiation allows each zone to perform its specific function optimally, reducing particle diameter distribution standard deviation while maintaining overall system efficiency.
Solution Approach 2:
The invention employs curved surfaces (both convex and concave) instead of flat surfaces on the bell cup. The convex curved surface at the proximal end promotes uniform coating material diffusion, while the concave curved surface at the distal end equalizes forces acting on the liquid film, thereby reducing particle diameter variation and improving coating quality.
2Manufacturing precision
If the bell cup uses a convex curved surface at the proximal end and concave curved surface at the distal end, then the average particle diameter is reduced, but the manufacturing cost increases
Solution Approach 1:
The bell cup incorporates localized geometric features (convex and concave curved surfaces) in specific regions rather than uniform complexity throughout. This allows the complex surfaces to be manufactured using standard CNC machining or molding techniques, reducing overall manufacturing cost while achieving the desired particle diameter reduction.
Solution Approach 2:
The convex and concave curved surfaces can be efficiently manufactured using conventional machining methods such as CNC turning or molding. The curved geometries, while functionally complex, represent standard manufacturing features that do not require advanced or expensive fabrication processes, thereby maintaining cost-effectiveness.
3Manufacturing precision
If the coating material liquid film is uniformly diffused by equalizing forces, then the particle diameter distribution uniformity is improved, but the flow pattern control complexity increases
Solution Approach 1:
The bell cup geometry itself performs the flow control function through its convex and concave curved surfaces. The shapes naturally guide the coating material liquid film to diffuse uniformly and equalize forces without requiring external control mechanisms, sensors, or active regulation systems. The structure is self-regulating based on the physical properties of the coating material.
Solution Approach 2:
The invention changes the geometric parameters of the bell cup surface (convex and concave curvatures) to optimize flow patterns. By carefully selecting the curvature radii and transition zones, the design achieves uniform particle diameter distribution through passive geometric control rather than active flow management.
Data Source
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AI summary
Provided is a bell cup (11) installed on a rotation axis (CL) of a rotary atomizing electrostatic coating apparatus (1), a coating material diffusion surface (111) on an inner surface of the bell cup being supplied with a coating material, a first range (114) extending from an end part (117) of the coating material diffusion surface to a center part (116) of the coating material diffusion surface, the end part (117) being disposed toward the proximal end of the bell cup, is constituted by a convex curved surface facing towards the rotation axis; and a second range (115) extending from the center part (116) to the distal end edge (113) of the bell cup is constituted by a concave curved surface facing towards the rotation axis.