Bell Socket Plastic Pipe Manufacturing with Segmented Mandrel
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Solution Overview
Problem
The existing methods for manufacturing thermoplastic pipes with a bell socket end and gasket cavity require expensive expandable mandrels, making the process costly and inefficient.
Innovation Solution
A method using non-expandable mandrels with Rieber and dummy gaskets to form a bell socket end with a gasket cavity, allowing for the formation of airtight and watertight seals, where the gaskets can be replaced or used to create varying levels of joint restraint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If expandable mandrels are used to form bell socket end with gasket cavity, then the manufacturing precision and quality of the bell socket are improved, but the manufacturing cost and device complexity increase significantly
Solution Approach 1:
The mandrel is divided into multiple cylindrical sections with different diameters, each corresponding to a specific portion of the bell socket. This segmentation allows the formation of the bell socket profile without requiring the mandrel to expand, simplifying the mandrel design while maintaining manufacturing precision.
Solution Approach 2:
The gasket cavity is formed by pre-attaching gasket-forming elements to the mandrel surface before insertion into the pipe. This preliminary action ensures the cavity is created during the forming process itself, eliminating the need for complex expandable mechanisms while achieving the required geometric precision.
2Manufacturing precision
If expandable mandrels are used to form bell socket end with gasket cavity, then the bell socket geometry is achieved, but the production cost increases
Solution Approach 1:
The patent employs simple, non-expandable mandrels that can be easily manufactured and replaced at low cost. These mandrels perform their function in a single use and are discarded or reused after minimal maintenance, significantly reducing production costs compared to expensive expandable mandrels.
Solution Approach 2:
The mandrel dimensions are specifically designed with a length-to-diameter ratio that allows it to be inserted and withdrawn without expansion. The parameters of the mandrel (length, diameter segments) are optimized to create the bell socket geometry through simple insertion and withdrawal actions, eliminating the need for expensive expandable mechanisms.
3Ease of manufacture
If non-expandable mandrels are used, then the manufacturing cost is reduced, but the ability to form differential internal diameters of bell socket is compromised
Solution Approach 1:
The mandrel consists of multiple cylindrical sections with progressively different diameters. Each section corresponds to a specific zone of the bell socket, allowing the creation of differential internal diameters through the segmented structure rather than through expansion.
Solution Approach 2:
Instead of achieving differential diameters through radial expansion in one dimension, the patent uses axial segmentation of the mandrel with different diameter sections along its length. This dimensional approach allows simple non-expandable mandrels to create complex bell socket geometries.
4Reliability
If gasket cavity is formed using conventional methods, then the seal quality is improved, but the device complexity and cost increase
Solution Approach 1:
Gasket-forming elements are attached to the mandrel surface before insertion into the pipe. These elements create the gasket cavity during the forming process itself, ensuring proper seal geometry is achieved without requiring complex post-processing or specialized expandable mechanisms.
Solution Approach 2:
The gasket-forming elements act as intermediaries between the mandrel and the pipe material. These elements transfer the mandrel's geometric profile to the softened pipe material, creating the gasket cavity and ensuring seal quality without requiring the mandrel itself to have complex features.
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
This method reduces production costs by using less expensive mandrels while maintaining a secure seal, even under high pressure, and allows for the use of unrestrained joints where necessary.
Implementation Method 1
heating a first plastic pipe having an inner diameter that is less the outer diameter of the mandrel
Data Source
AI summary
The present disclosure generally pertains to methods for manufacturing an improved plastic pipe. One method includes the steps of: providing a plastic pipe; heating a plastic pipe; inserting a mandrel into the heated plastic pipe to form a bell socket end, wherein the mandrel includes a Rieber gasket and a dummy gasket spanning the outer surface of the mandrel; cooling the plastic pipe; and removing the mandrel from the plastic pipe, wherein the Rieber gasket and dummy gasket remain within a gasket cavity formed in the newly-formed bell socket end of the plastic pipe. The method results in the bell socket end of the pipe having an interior diameter greater than the exterior diameter of the opposing, spigot end of the pipe, wherein the bell socket end further includes a gasket cavity with a greater diameter than the remainder of the bell socket end.