Washing Drum Lifter Layout to Reduce Shear Stress Fatigue
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Solution Overview
Problem
Washing machine drums with protruding structures are prone to plastic deformation and fatigue failure due to concentrated shear stress, especially when formed from thin metal sheets with convex inner and concave outer surfaces, leading to structural vulnerability and reduced durability.
Innovation Solution
The drum is designed with a cylindrical shape formed by joining metal sheets, featuring multiple lifters spaced along the circumference with a phase angle, and reinforcement grooves to disperse shear stress and enhance yield strength and fatigue life, reducing plastic deformation and improving durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a protruding structure is formed by plastic working a metal sheet to create a lifter, then washing force is improved, but shear stress concentrates in the intermediate portion causing plastic deformation and fatigue failure
Solution Approach 1:
The patent applies local quality by forming reinforcement ribs at specific locations (intermediate portions between lifters) where shear stress concentrates. These ribs provide localized structural strengthening without modifying the entire drum structure, thereby preventing plastic deformation at critical stress points while maintaining the washing force generated by the lifters.
Solution Approach 2:
The patent segments the drum structure by dividing it into functional regions: lifters for washing and reinforcement ribs for structural support. This segmentation allows each component to perform its specific function optimally - lifters generate washing force while ribs prevent stress concentration, resolving the contradiction between washing effectiveness and structural integrity.
2Ease of manufacture
If the drum is formed from a thin metal sheet with convex inner and concave outer surfaces, then manufacturing is simplified, but the drum becomes vulnerable to crushing and plastic deformation
Solution Approach 1:
The patent maintains the simple thin metal sheet construction for ease of manufacture but adds localized reinforcement ribs at intermediate portions. This approach preserves the manufacturing simplicity of using thin sheets while providing targeted structural strengthening to prevent crushing and plastic deformation at stress concentration points.
3Productivity
If multiple protruding structures are formed in the circumferential direction, then washing performance is improved, but shear stress concentration increases leading to fatigue failure
Solution Approach 1:
The patent segments the drum into alternating functional zones: lifters for washing performance and reinforcement ribs for structural reliability. This segmentation allows multiple lifters to be arranged in the circumferential direction for improved washing while interspersed ribs prevent shear stress concentration, thereby extending fatigue life and preventing failure.
Solution Approach 2:
The patent applies local quality by placing reinforcement ribs specifically at intermediate portions between lifters where shear stress concentrates. This localized reinforcement prevents fatigue failure at critical points while allowing multiple lifters to maintain high washing performance throughout the drum circumference.
Data Source
AI summary
The present disclosure relates to a washing machine configured to rotate a cylindrical drum formed by processing a metal sheet about a horizontal axis. The drum includes a lifter, formed by processing the metal sheet, respectively provided at a plurality of points spaced along a circumferential direction, when viewed from a front side. The lifter includes a front lifter which is formed by protruding the metal sheet into the drum, and pressurized to be extended in a longitudinal direction of the drum, and a rear lifter disposed in a rear side of the front lifter. The rear lifter is disposed to form a certain phase angle with respect to the front lifter.