Patent ID: 6343417
Filing Date: 2002-02-05
Classification: F01N,Y10T

Abstract:
Process for manufacturing an air-gap-insulated exhaust elbow for an exhaust system of a motor vehicle, comprising:(i) providing a plurality of exhaust pipes, a plurality of entry flanges, and an exit flange, wherein each exhaust pipe is a double pipe comprising an inner pipe and an outer pipe, wherein the inner pipe for each exhaust pipe defines an exhaust pipe internal passageway; (ii) shaping the exhaust pipes into a pipe-bend-shaped exhaust pipe and at least one branched exhaust pipe, forming an air-insulating gap in each exhaust pipe by internal high pressure forming, wherein the at least one branched exhaust pipe includes two non-branched ends and an air-gap-insulated branch with a double-walled end lacking an air-insulated gap; (iii) removing a section of the double-walled end of the branch of the at least one branched exhaust pipe to provide an opening to the exhaust pipe internal passageway without opening the air-insulating gap; (iv) joining together the plurality of air-gap-insulated exhaust pipes to form an exhaust elbow, wherein the exhaust pipes are connected such that an exhaust elbow inner passageway and at least one exhaust elbow air-insulating gap are formed thereby; and (v) connecting the entry flanges and the exit flange to the exhaust elbow to permit connection of the exhaust elbow to a motor vehicle exhaust system.