Patent ID: 11951669
Assignee: BODO RICHTER
Field: Other special machines (Mechanical engineering)
Classification: CPC B | IPC B

Claim 2:
3. a. A method for producing a triple-walled tubular body in which a first preform is output and is expanded by a first expanding mandrel with smooth expanding elements,
b. afterwards, a second preform is output concentrically to the first preform and is expanded by a second expanding mandrel with one of corrugated or cup-shaped expanding elements so far that it welds to the still warm first preform at contact points,
c. and afterwards, a third preform is output concentrically to the second preform and is expanded by a third expanding mandrel with smooth expanding elements so far that it welds to the still warm second preform at contact points, and in which the three preforms are cooled off,
d. wherein the third preform is pressed against one of a corrugated profile or a cup-shaped profile of the second preform and the third preform adopts the shape of one of the corrugated profile or the cup profile by applying one of a vacuum to the hollow mold or compressed air to the third expanding mandrel.