Patent ID: 7204302

Claim:
An exhaust gas heat exchanger comprising: a tank; a plurality of generally rectangular tubes disposed within said tank, said plurality of generally rectangular tubes being parallel with one another; a first core plate attached to a first side of said tank and to a first side of said plurality of generally rectangular tubes, each of said plurality of generally rectangular tubes extending through said first core plate; a second core plate attached to a second side of said tank and to a second side of said plurality of generally rectangular tubes, each of said plurality of generally rectangular tubes extending through said second core plate; a first bonnet attached to said first side of said tank; a second bonnet attached to said second side of said tank; wherein each of said generally rectangular tubes comprises a first plate and a second plate, each plate having a substantially U-shaped configuration to define a first and a second arm, said first arm of said first and second plate each forming an inwardly stepped portion, said inwardly stepped portion of said first arm of said first plate mating with said second arm of said second plate and said inwardly stepped portion of said first arm of said second plate mating with said second arm of said first plate to form said tube having a substantially level outer surface, the inwardly stepped portion is formed on a surface extending generally perpendicular to a longer side of the generally rectangular tube.