초록 ▼

A method for manufacturing an air-gap-insulated exhaust pipe having a branch stub, as well as an exhaust pipe produced according to such a method and a tool for forming such an exhaust pipe. Two tubes are inserted into one another to form a double tube. The double tube is placed in a first internal

A method for manufacturing an air-gap-insulated exhaust pipe having a branch stub, as well as an exhaust pipe produced according to such a method and a tool for forming such an exhaust pipe. Two tubes are inserted into one another to form a double tube. The double tube is placed in a first internal high-pressure shaping tool, and exposed to internal high pressure fluid such that it expands to match the contours of the engraving of the first shaping tool, and a double-walled branch stub is blown out of the double tube. The partially formed double tube is then placed in a second internal high-pressure shaping tool, with the double tube being surrounded, between the two ends including the branch stub, circumferentially and throughout by a corresponding design of the engraving, by an expansion chamber. The outer tube is expanded between the outer tube and inner tube under high pressure up to a precise fit with the engraving of the second shaping tool to form an insulating air gap, with the end of the branch stub being supported externally without yielding via a second counterpunch. The finished double tube is removed from the second shaping tool and a cap area of the branch stub, containing the end, is cut off to form a through opening between the interior of the inner tube and the ambient environment outside the air-gap-insulated exhaust pipe.

대표청구항 ▼

1. A modular, air-gap-insulated exhaust pipe with an air-gap insulated branch stub for a vehicle exhaust line having an inner tube with a branch for carrying exhaust surrounded at a distance by an outer jacket to form an insulating air gap manufactured by the process comprising:providing two tubes h

1. A modular, air-gap-insulated exhaust pipe with an air-gap insulated branch stub for a vehicle exhaust line having an inner tube with a branch for carrying exhaust surrounded at a distance by an outer jacket to form an insulating air gap manufactured by the process comprising:providing two tubes having a corresponding shape, inserting said tubes into one another with limited play to form a double tube, placing said double tube in a first internal high-pressure shaping tool having a first engraving including a branch, sealing off both ends of said double tube to be tight to a high-pressure fluid, closing the first shaping tool and introducing a pressure fluid into an interior of the inner tube of the double tube such that the double tube expands to match the contours of the first engraving to form a shaped double tube including a double-walled branch stub blown out of the double tube into the branch, relieving the pressure fluid in the first shaping tool, removing the shaped double tube from the first shaping tool, placing the shaped double tube in a second internal high-pressure shaping tool having a second engraving which holds the shaped double tube at axial end areas in a fit with play, the second engraving being spaced apart from the shaped double tube between the axial end areas including the branch stub to define an expansion chamber, closing the second shaping tool and introducing a pressure fluid between the two tubes that form the shaped double tube and simultaneously into the interior of the inner tube, such that the outer tube expands into said expansion chamber and engages said second engraving of the second shaping tool to define an insulating air gap between the outer tube and the inner tube, an end of the branch stub facing away from the rest of the double tube being externally supported without yielding via a second tool counterpunch located in a branch of said second engraving, relieving the pressure fluid in the second shaping tool, removing the finished double tube from the second shaping tool, and cutting off a cap area at the end of the branch stub to form a through opening between the interior of the inner tube and the outside of the air-gap-insulated exhaust pipe.