Metal Pipe Thread Forming with Preforming to Preserve Wall Thickness
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Solution Overview
Problem
The existing method for forming screw threads on metal pipes results in localized thinning, leading to reduced strength and rigidity, particularly in fuel filling pipes where expansion forming is involved.
Innovation Solution
A preforming step is introduced before screw thread formation, using a clamping die and pressing die to create a primary formed portion, followed by alignment with outer and inner forming dies to shape the screw thread, reducing deformation and maintaining plate thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a screw thread is formed directly on the metal pipe using conventional forming methods, then the screw thread can be created efficiently, but the plate thickness is significantly reduced in the formed region, resulting in lower strength and rigidity
Solution Approach 1:
The patent applies preliminary action by performing a preforming step before the actual screw thread forming. In this preforming step, a forming die presses the metal pipe to create a preliminary formed portion that pre-compresses and redistributes the material in the region where the screw thread will subsequently be formed. This preliminary compression prevents excessive plate thickness reduction during the final thread forming operation, thereby maintaining the strength and rigidity of the metal pipe while still enabling efficient screw thread production
2Shape
If expansion forming is performed on the metal pipe before screw thread formation, then the pipe can be shaped as required, but the subsequent screw thread formation causes apparent lowering of rigidity and strength due to reduced plate thickness
Solution Approach 1:
The patent resolves this contradiction by introducing a preforming step that occurs after expansion forming but before screw thread formation. This preforming operation compresses the metal pipe in the intended screw thread region, restoring and maintaining plate thickness before the thread forming process. As a result, even though the pipe undergoes expansion forming, the subsequent screw thread formation does not cause apparent lowering of rigidity and strength because the material has already been pre-compressed to the appropriate thickness
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 minimizes the reduction in rigidity and strength by reducing plate thickness deformation, improving formability and precision, and allowing efficient, low-cost formation of screw threads extending around the metal pipe's circumference.
Implementation Method 1
pressing an end portion of the metal pipe with a pressing die in a direction of the cylinder center line to thereby form a primary formed portion on the metal pipe
Implementation Method 2
pressing the outer circumferential surface of the metal pipe with the outer forming surface by moving the outer forming die toward the cylinder center line, while inserting an inner forming die into the metal pipe and pressing the inner circumferential surface of the metal pipe with the inner forming surface
Data Source
AI summary
After holding a metal pipe 10 using a clamping die 5, a primary formed portion 11a corresponding to the preforming surface portion 5c is formed on the metal pipe 10 by pressing an end portion of the metal pipe 10 with a pressing die 6 in a direction of a cylinder center line C1. A final formed portion 11b is formed on the metal pipe 10 by moving an outer forming die 7 to press an outer circumferential surface of the metal pipe 10 with the outer forming die 7 after aligning a rib portion 7c with the primary formed portion 11a, while moving an inner forming die 8 to press an inner circumferential surface of the metal pipe 10 with the inner forming die 8 after aligning a recessed groove portion 8c with the primary formed portion 11a.