Patent ID: 7334334

Claim:
A method of producing a catalytic converter for an internal combustion engine exhaust system, the converter having interior and exterior surfaces said catalytic converter comprising: a. a single-piece, seamless metallic housing; b. a tubulated gas inlet port in said housing through which exhaust gas is introduced; c. a tubulated gas outlet port in said through which the exhaust gas is discharged; d. a tubulated intermediate section of said housing connecting said gas inlet port and said gas outlet port said intermediate section having a plurality of rib-like indentations which are axially elongated along said intermediate section; e. an inlet transition section connecting said inlet port and said inlet end of said intermediate section; f. an outlet transition section connecting said outlet end of said intermediate section and said outlet port; and g. a catalytic element contained within said intermediate section and through which said exhaust gas passes when flowing between said gas inlet port and said gas outlet port; and the interior surfaces of said intermediate section said inlet and outlet transition sections and said gas inlet and outlet ports having been swaged and being smooth and substantially free from ridges thereon; and said method comprises: i. providing a seamless metallic tube preform having a first end and a second end, said perform being adapted to be formed into said housing; ii. inserting said catalytic element in said tube preform; iii. gripping said tube preform; iv. swaging said first end to form said gas inlet port and said inlet transition section; v. swaging said second end to form said gas outlet port and said outlet transition section; vi swaging said intermediate section to a reduced diameter; vii swaging of said first and second ends of said tube preform is carried out in a plurality of graduated swaging steps using a plurality of dies to form each end of said housing.