Composite bath tub and method of manufacture
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bath tubs, particularly those made of cast iron, are heavy and difficult to lift and install, risking injury and damage, while lightweight plastic tubs lack rigidity and require support frames to prevent flexing under water pressure.
Innovation Solution
A composite bath tub design featuring an upper and lower plastic member forming an outer shell with a uniform inner core of filler material, where the filler exhibits non-Newtonian behavior to prevent voids and provide strength, and the members are made of hardwearing materials like acrylic capped ABS for durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cast iron material is used for bath tubs, then strength and rigidity are improved, but weight increases making lifting and installation difficult
Solution Approach 1:
The patent applies composite materials by combining a plastic outer shell with a stone resin or resin-infused core. This composite structure provides the rigidity and strength of traditional cast iron tubs while significantly reducing the weight, making the bath tub easier to lift and install without requiring multiple people.
Solution Approach 2:
The patent changes the material parameters by using a core material with controlled density and rigidity properties. The core is formed with a specific density range (1.8-2.2 g/cm³) and rigidity modulus (3-5 GPa), which optimizes the strength-to-weight ratio, achieving cast iron-like structural performance at a fraction of the weight.
2Weight of moving object
If plastic material is used for bath tubs, then weight is reduced facilitating lifting and installation, but rigidity decreases requiring support frames
Solution Approach 1:
The patent creates a composite structure where a rigid core (stone resin or resin-infused) is enclosed within a plastic outer shell. This composite design eliminates the need for external support frames by providing internal structural rigidity, while maintaining the lightweight advantage of plastic materials.
Solution Approach 2:
The patent uses a nested structure where the rigid core is placed inside the plastic outer shell. The core acts as an internal support structure that prevents flexing under water and user weight, eliminating the need for external support frames while maintaining the lightweight benefit of the plastic shell.
3Ease of manufacture
If filler material viscosity is reduced to enable flow between members, then manufacturing ease is improved, but sedimentation increases causing nonuniform particle distribution
Solution Approach 1:
The patent optimizes the viscosity parameter of the filler material to a specific range (50-200 Pa·s) that balances flowability and sedimentation resistance. This controlled viscosity allows the filler to flow adequately between the outer shell and inner core during manufacturing while maintaining uniform particle distribution without excessive sedimentation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composite tub design balances weight and rigidity, allowing easier installation and providing structural integrity similar to cast iron tubs without the need for support frames, while maintaining a durable and aesthetically appealing surface.
Implementation Method 1
The fillers demonstrate shear-thinning, i.e. a decrease in viscosity with increasing shear. The relatively higher viscosity when the filler material is stationary reduces sedimentation. The relatively lower viscosity when pressure is being applied allows the filler material to flow to take the shape of the inner core, without creating voids.
Implementation Method 2
One or both of the upper and lower members may be an acrylic capped acrylonitrile butadiene styrene (ABS) material. The acrylic material forms the hardwearing, scratch resistant surface of the bath tub
Data Source
Figure 1a~1b
Figure 1c~2a
Figure 2b~2d
AI summary
A bath tub has an upper member of plastics material and a lower member of plastics material that together form an outer shell, and an inner core of filler within the shell. The inner core has a substantially uniform thickness. The ratio of the combined thickness of the upper and lower members to the thickness of the inner core may be approximately 1:1.