Composite Toilet Flush Tank Joint Design for Pressure-Cycle Reliability
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Solution Overview
Problem
Plastic tanks for pressure assist toilet flush systems experience frequent failures at the joint due to stress from expansion and contraction during flush cycles, leading to potential leakage and reduced lifespan.
Innovation Solution
A two-piece tank design with a tongue-and-groove joint and internal reinforcing structures, including cross-ribs and sidewall ribs, made from a composite material with short fiber reinforcement, is used to enhance strength and durability, along with RF welding for a watertight connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a two-piece tank design is used, then manufacturing ease and assembly flexibility are improved, but the joint between pieces becomes a weak point susceptible to failure under pressure cycles
Solution Approach 1:
The tank is divided into two separate pieces (base and cover) that can be manufactured independently and then assembled, improving manufacturing ease while the segmentation allows for a designed joint interface
Solution Approach 2:
The base and cover are joined through welding to form a unified pressure-containing structure, merging the two separate pieces into a functionally integrated tank that resists pressure cycles
2Strength
If internal reinforcing structures are added, then resistance to bulging and warpage is improved, but device complexity increases
Solution Approach 1:
Ribs are strategically positioned at specific locations within the tank base where stress concentration occurs during pressure cycles, providing localized reinforcement exactly where needed to prevent bulging and warpage
Solution Approach 2:
The tank incorporates ribs as structural elements integrated with the base material, creating a composite structure that combines the base material with reinforcing geometric features to achieve enhanced strength-to-weight ratio
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 design significantly improves the tank's resistance to bulging and warpage, reduces residual stresses, and enhances the weld quality, resulting in a longer product life and reduced risk of catastrophic failure, with up to a 10-20 times increase in average lifetime.
Implementation Method 1
The cover and the base are connected by a tongue-and-groove joint that extends around the upper end of the base
Implementation Method 2
RF welding for a watertight connection
Data Source
AI summary
A tank for a pressure-assist toilet flush system includes a base and a cover formed of a composite material including a polymer matrix of a crystalline polymer material, with a short fiber reinforcement material having a fiber length of 0.125 inch to 0.177 inch dispersed therein at a fill ratio of 25-35%. The base has a bottom wall and a plurality of base sidewalls extending upward from the bottom wall to an upper end of the base, with an outlet defined in the bottom wall. The cover has an inlet for receiving water into the tank and includes a top wall and a plurality of cover sidewalls extending downward from the top wall to a lower end of the cover. The inlet is defined in the top wall, and the lower end of the cover is connected to the upper end of the base.