Continuous Ribbed Pipe Molding With a Collapsible Core
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Solution Overview
Problem
Existing methods for injection molding large diameter plastic pipes require complex and expensive machinery with multiple molds, making it difficult to separate the male mold from the formed pipe, leading to inefficiencies and high costs.
Innovation Solution
A method and apparatus that uses a collapsible male mold element and female mold elements to injection mold continuous lengths of pipe, allowing the male mold to be separated from the formed pipe before ejection, reducing the need for multiple molds and enabling easier mold removal with a small draft angle, resulting in improved rib thickness and structural performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional injection molding process is used with a rigid male mold, then the pipe can be formed with proper shape, but the male mold cannot be easily separated from the formed pipe without applying heat to melt the inner surface
Solution Approach 1:
The male mold is designed with collapsible ribs that can change from an expanded state during molding to a collapsed state during ejection. This dynamic transformation allows the male mold to adapt its shape - rigid when needed for forming, and collapsible when needed for easy separation without heat or complex mechanisms
2Manufacturing precision
If multiple molds are used to form large diameter ribbed pipe, then the pipe can be formed with proper rib structure, but the machinery becomes very complicated and expensive
Solution Approach 1:
The male mold ribs are segmented into collapsible sections that can independently change shape. During molding, they expand to form the complete rib structure; during ejection, they collapse to create clearance. This segmentation allows a single mold to perform functions that traditionally required multiple molds
Solution Approach 2:
The geometry of the male mold ribs is changed dynamically between two states: expanded for molding and collapsed for ejection. This parameter change (from expanded to collapsed configuration) enables the single mold system to achieve what previously required multiple static molds
3Ease of operation
If heat is applied to melt the inner surface of the pipe for male mold release, then the pipe can be ejected, but the process becomes ineffective and impractical for continuous production
Solution Approach 1:
The male mold transitions from a static rigid structure to a dynamic collapsible structure. The ribs can be collapsed to create clearance for pipe removal, enabling continuous production without heat treatment or other time-consuming release methods
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 allows for the production of lighter, more structurally efficient pipes with improved rib thickness and shape control, reducing machinery costs by eliminating the need for multiple molds and enabling the use of less expensive materials, while maintaining similar structural performance to corrugated pipes.
Implementation Method 1
collapsing said collapsible male mold element to disengage from said length of pipe
Data Source
Figure 1~2
Figure 3~4
AI summary
A method and apparatus for manufacturing continuous ribbed pipes of thermoplastic resin material comprises the following successive steps. A length of pipe is injection molded in a mold cavity between a collapsible male mold element and female mold elements, the latter being shaped to provide integral ribbing on the outer surface of the pipe. After sufficient setting, the female mold elements are disengaged and the male mold element is collapsed and disengaged. A plunger then pushes the pipe length axially along the male mold element. The female mold elements and the collapsed male mold element are then re-engaged such that the one end of the formed pipe forms a closure for the mold cavity at the downstream end. Further material is again injected into the cavity which fuses with the one pipe end and which forms a further pipe length. These steps are repeated until the desired length of pipe is formed.