Rotational Molded Pipe Fitting Rib Profile Design

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Solution Overview

Problem

The HDPE corrugated pipe industry faces challenges in manufacturing large-diameter pipe fittings with smooth interiors and corrugated exteriors due to high mold and material costs, design difficulties, and inconsistencies in hand-fabricated fittings, which compromise watertight integrity and structural performance.

Innovation Solution

A rotationally molded large-diameter pipe fitting with a smooth interior and exterior ribs, designed with specific dimensional ratios and angles to ensure structural stability and watertight integrity, allowing for cost-effective production and enhanced performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If hand-fabricated fittings are used to reduce mold and material costs, then manufacturing cost is reduced, but watertight integrity and structural performance deteriorate

Engineering Contradiction:

Improvemanufacturing costVSAvoidwatertight integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent combines multiple fitting components (pipe sections, elbows, tees, wyes) into a single rotationally molded unit, eliminating the need for hand fabrication and welding. This integrated approach ensures watertight integrity while maintaining cost-effectiveness through automated manufacturing.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent replaces the mechanical welding process with rotational molding, substituting a complex multi-step fabrication process with a single automated molding operation. This eliminates welding-related defects and ensures consistent watertight seals.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of manufacture

If hand-fabricated fittings are used to reduce mold and material costs, then manufacturing cost is reduced, but structural performance deteriorates

Engineering Contradiction:

Improvemanufacturing costVSAvoidstructural performance

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If rotational molding is used to manufacture large-diameter pipe fittings, then manufacturing consistency and watertight integrity are improved, but mold costs and design complexity increase

Engineering Contradiction:

Improvewatertight integrityVSAvoiddesign difficulty

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies specific dimensional ratios (rib height-to-pitch ratio of 0.2-0.4, rib base thickness-to-crown thickness ratio of 1.5-3.0) to optimize the fitting design for rotational molding. These parameter specifications enable consistent manufacturing while maintaining structural integrity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent segments the fitting design into distinct functional zones (smooth interior surface for flow, corrugated exterior for structural support, ribs for reinforcement) that can be independently optimized while being manufactured as a unified piece through rotational molding.

Inventive Principle:

Principle #1Segmentation

4Productivity

If a smooth interior surface is used to improve fluid flow, then fluid flow capacity is improved, but structural strength deteriorates

Engineering Contradiction:

Improvefluid flow capacityVSAvoidstructural strength

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The patent applies different surface qualities to different regions of the fitting: a smooth interior surface (without corrugations) to maximize fluid flow capacity, and a corrugated exterior surface with ribs to provide structural strength and buckling resistance. This local differentiation resolves the contradiction between flow efficiency and structural integrity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent moves the corrugation structure from the interior dimension (which would impede flow) to the exterior dimension, where it provides structural reinforcement without affecting fluid flow. The smooth interior maintains hydraulic efficiency while the corrugated exterior delivers structural strength.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS9815229B2Method of rotational molding rib profile for large diameter pipe fittings

Publication Date: 2017.11.14 PRINSCO INC

AI summary

A method of rotationally molding a large-diameter pipe fitting, the wall structure of which is characterized as having a generally smooth interior surface and an exterior surface that is defined by a plurality of axially-spaced circumferentially extending ribs which are monolithically formed and homogeneous with the smooth interior surface of the fitting. The fitting is seamless and modularly designed with integral coupling elements at each terminal end, and with a ribbed wall structure profile capable of withstanding the loads typically found in buried applications with watertight performance requirements, where such ribbed wall structure meets the following dimensions and dimensional ratios: Rib Sidewall Angle (95-105 degrees); Bottom/Top Rib Thickness Ratio (1.80-2.80); Pitch/Rib Height Ratio (1.50-1.95); Rib Height/Fitting Diameter Ratio (0.04-0.09); and Avg. Rib Thickness/Rib Height Ratio (0.28-0.40).