Claims
- 1. A method of manufacturing a corrugated metallic pipe having a predetermined corrugation, comprising the steps of:
- providing a plurality of first mandrels having each an axially extending corrugation having a predetermined shape and height, with the heights of the first mandrels progressively increasing from one first mandrel to another first mandrel but with a length of a corrugation protrusion of each of the first mandrels exceeding the height of each of the first mandrel in several times;
- inserting one after another in a predetermined sequence each of the plurality of the first mandrels into a smooth cylindrical metallic pipe, radially expanding an inserted first mandrel against exchangeable complementary cheek means and displacing the complementary cheek means, which surrounds the pipe and has a corrugation at least approximately corresponding to the corrugation of the inserted first mandrel, radially inwardly into the pipe to provide a first preformed corrugation different from the predetermined corrugation of the pipe and having corrugation protrusions a length of which exceeds a height thereof in several times;
- thereafter, inserting into the pipe, having the first preformed corrugation, a second mandrel having an outer diameter corresponding to an inner diameter of the first preformed corrugation;
- thereafter, radially displacing into first corrugation hollows disc-shaped, axially spaced from each other, jaws which surround the pipe; and
- axially displacing the jaws toward each other, effecting folding up of the first, preformed corrugation to obtain the predetermined corrugation of the pipe, with a ratio of a length of a corrugation protrusion of the predetermined corrugation of the pipe to a corrugation protrusion height of the predetermined corrugation being about 1:1.
- 2. A method as set forth in claim 1, wherein a length of a corrugation hollow of the first preformed corrugation measured at a half of a corrugation height equals a fraction of a length of a corrugation crest of the first preformed corrugation.
- 3. A method as set forth in claim 1, wherein the length of the corrugation hollow equals from 0.3 to 0.6 of the length of the corrugation crest.
- 4. A method as set forth in claim 3, wherein the corrugation hollow has a flank angle of at least 45.degree..
- 5. A method as set forth in claim 4, wherein the flank angle is 65.degree..
RELATED APPLICATIONS
This application is a continuation-in-part of application Ser. No. 08/694,018 filed Aug. 8, 1996, now abandoned.
US Referenced Citations (4)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
694018 |
Aug 1996 |
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