Prismatic Wash Tub Structure for Higher Rigidity and Lower Vibration

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Solution Overview

Problem

Existing laundry treatment machines, such as washing machines, face challenges with tub rigidity, leading to vibrations, damage, and wear due to insufficient resistance against tensile, bending, and torsional forces, which are not effectively addressed by current designs.

Innovation Solution

A tub design featuring a prism-shaped outer shell with a truncated pyramid end wall and reinforcing ribs, made of high-strength plastic like PVC, providing increased rigidity without additional material costs and allowing for simple manufacturing processes, including injection molding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional cylindrical tub designs are used, then manufacturing is simple, but rigidity against tensile, bending and torsional forces is insufficient

Engineering Contradiction:
ImproverigidityVSAvoidstructural complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The patent applies the opposite principle by using flat planar surfaces instead of curved surfaces. The tub end wall is designed with multiple flat surfaces (at least three) that meet at edges to form a polyhedral or truncated polyhedral shape, replacing the conventional curved cylindrical design. This geometric transformation significantly increases rigidity against tensile, bending and torsional forces while maintaining manufacturability through standard plastic injection molding processes.

Inventive Principle:
Principle #14Spheroidality (Curvature)

2Strength

If additional reinforcing structures are added to increase rigidity, then strength improves, but manufacturing complexity and material costs increase

Engineering Contradiction:
ImproverigidityVSAvoidmanufacturing simplicity
Core Design Contradiction:
StrengthVSEase of manufacture

Solution Approach 1:

The patent merges the structural reinforcement function directly into the tub end wall geometry itself. The flat surfaces and edges forming the polyhedral shape inherently provide the required rigidity without needing separate reinforcing ribs or additional structural components. This integrated design achieves enhanced strength while maintaining simple manufacturing through standard injection molding, eliminating the need for post-molding reinforcement additions.

Inventive Principle:
Principle #5Merging (Combining)

3Strength

If more material is used to strengthen the tub, then rigidity increases, but weight and manufacturing cost increase

Engineering Contradiction:
ImproverigidityVSAvoidtub weight
Core Design Contradiction:
StrengthVSWeight of moving object

Solution Approach 1:

The patent changes the geometric parameters of the tub end wall from a conventional curved cylindrical shape to a polyhedral shape with flat surfaces and edges. This parameter change in geometry fundamentally alters the structural properties, increasing rigidity and strength against various forces. The design achieves this enhanced performance using the same material volume and type, thereby maintaining lightweight construction and cost-effectiveness without requiring additional material.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP2640886B1Wash tub for accommodating a rotatably mounted washing drum, and laundry treatment machine
Publication Date: 2015.06.17 BSH HAUSGERATE GMBH
  • EP2640886B1 patent drawingFigure 1
  • EP2640886B1 patent drawingFigure 2
  • EP2640886B1 patent drawingFigure 3

AI summary

The invention relates to a wash tub (1, 15) for accommodating a rotatably mounted washing drum, having a wash tub casing (2, 16) and having a wash tub end wall (3, 17), and to a laundry treatment machine having such a wash tub. The aim of the invention is to provide a wash tub having increased rigidity. For this purpose the wash tub casing (2, 16) is shaped substantially like the outer surface of a prism and the wash tub end wall (3, 17) has the shape of a truncated pyramid at least in a circumferential partial region (20, 21) extending in the radial direction (22).