Bell Joint Injection System for Plastic Pipe
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current injection systems for forming bell joints in plastic pipes, particularly for large diameters, suffer from uneven pressure and temperature distribution, leading to internal stresses and deformation, and inadequate adhesion due to differential cooling and material properties like plastic memory in polyolefin materials.
Innovation Solution
A multiple casting injection technique with equally spaced radial channels along the mould's circumferential face ensures consistent pressure and temperature conditions across the joint, maintaining a circular shape and enhancing adhesion by orienting the injection flow axially along the mould length to the adhesion area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a radial injection channel is used to inject material laterally into the mould, then the injection system can form bell joints in plastic pipes, but uneven pressure and temperature distribution occurs leading to internal stresses and deformation
Solution Approach 1:
The single radial injection channel is segmented into multiple radial channels distributed around the circumference of the mould. This segmentation allows material to be injected at multiple locations simultaneously, creating a more uniform pressure and temperature distribution throughout the bell joint, thereby preventing internal stresses and deformation while maintaining manufacturing capability
Solution Approach 2:
The injection system transitions from a single centralized injection point to multiple distributed injection points around the mould circumference. This local quality change ensures that each region of the bell joint receives material under similar pressure and temperature conditions, eliminating the uneven distribution that caused deformation while preserving the overall injection manufacturing process
2Productivity
If material is injected laterally from the top into the mould, then the bell joint can be formed, but differential cooling creates internal stresses and loss of circular shape
Solution Approach 1:
The single top-down lateral injection is segmented into multiple simultaneous injections from different circumferential locations. This allows the material to cool uniformly across all sections of the bell joint, preventing differential cooling stresses that would otherwise cause the circular cross-section to deform while maintaining production efficiency
Solution Approach 2:
The multiple radial channels create equipotential conditions for pressure and temperature distribution around the mould circumference. By ensuring all regions experience similar injection conditions, the system prevents the potential differences (uneven cooling rates) that lead to internal stresses and shape loss, maintaining circular integrity throughout the cooling process
3Ease of manufacture
If pressure and temperature are higher in top mould areas and lower in bottom areas, then material can be injected into the mould, but adhesion quality becomes unacceptable in certain areas
Solution Approach 1:
The injection process is segmented from a single top-down approach into multiple simultaneous injections from different circumferential positions. This segmentation equalizes the pressure and temperature conditions across all adhesion areas between the bell joint and pipe, ensuring consistent adhesion quality throughout the entire connection rather than having acceptable areas only in certain regions
Solution Approach 2:
The injection system applies local quality changes by distributing injection points around the circumference, ensuring that each local adhesion area experiences optimal and uniform pressure and temperature conditions. This eliminates the variability in adhesion quality that occurs with single-point injection, making the connection reliable across the entire bell joint-to-pipe interface
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 approach prevents internal stress and deformation, ensuring homogeneous material conditions and improved adhesion quality across the joint, maintaining the original shape and functionality of the bell joint.
Implementation Method 1
a bell joint is injected at the end of a pipe, coaxially and materially integral with it
Implementation Method 2
The formation of bells is normally obtained by plastic deformation of a pipe end, previously heated to the correct temperature
Implementation Method 3
polyolefin-type plastic materials (polypropylene and polyethylene) have a plastic memory which tends to cause the materials to revert to their original extrusion shape
Implementation Method 4
the material, on entering the mould internal space, is routed along two semi-circumferential strips... during the process, however, it will become progressively cooler creating inner stresses along the different circumferential sections
Data Source
Figure 1
Figure 1a
Figure 2
AI summary
The invention refers to an injection system for a bell joint (2), applied to the axial end of a polyolefin-type plastic material pipe (1), such joint having to be integral with the pipe, coaxial with the pipe itself and having a suitable inside diameter in relation to its connection and tightness functions in the pipe line; also, this system is to include multiple injection nozzles (10), arranged frontally with respect to the joint in its circumferential thickness area, preferably at the same distance one from the other, over a cross-section perpendicular to the pipe and joint common axis, on the opposite side to the pipe-to-joint junction; also, these nozzles are to be arranged in an axial direction with respect to the joint so as to generate a flow of injected material directed to the inside of the joint mould, also in a generally axial direction and directed towards the pipe end sealed to the joint.