Sealing joint for connecting adjoining duct pieces in an engine exhaust system

1. A sealing joint comprising a one-piece tubular body;

the tubular body having a first axial end portion, a second axial end portion, and a bridge portion extending therebetween;

the first end portion having a coaxially convex outer profile with a maximum outer diameter (OD 1max );

the second end portion having a coaxially convex outer profile with a maximum outer diameter (OD 2max ); and

the bridge portion having a coaxially concave outer profile with a minimum outer diameter (OD Bmin ), this minimum outer diameter (OD Bmin ) being less than the maximum outer diameter (OD 1max ) of the first end portion and less than the maximum outer diameter (OD 2max ) of the second end portion,

wherein the tubular body includes a wear-resistant coating on its outer surface.

2. A sealing joint as set forth in claim 1 , wherein the first end portion has a coaxially concave inner profile with a maximum inner diameter of (ID 1max );

wherein the second end portion has a coaxially concave inner profile with a maximum inner diameter of (ID 2max ); and

wherein the bridge portion has a convex inner profile with a minimum inner diameter (ID Bmin ), this inner diameter (ID Bmin ) being less than the maximum inner diameter (ID 1max ) and less than the maximum inner diameter (ID 2max ).

3. A sealing joint as set forth in claim 1 , wherein the tubular body has substantially the same thickness throughout its portions, whereby the difference between the maximum outer and inner diameters (OD 1max -ID 1max ) of the first end portion, the difference between the maximum outer and inner diameters (OD 2max -ID 2max ) of the second end portion, and the difference between the maximum outer and inner diameters (OD Bmin -ID Bmin ) of the bridge portion are approximately equal.

4. A sealing joint as set forth in claim 1 , wherein the first end portion has a minimum outer diameter (OD 1min ), wherein the second end portion has a minimum outer diameter (OD 2min ), and wherein the minimum outer diameter (OD 1min ) of the first end portion and the minimum outer diameter (OD 2min ) of the second end portion are approximately equal.

5. A sealing joint as set forth in claim 1 , wherein the bridge portion has a minimum outer diameter (OD Bmin ) that is less than the minimum outer diameter (OD 1min ) of the first end portion and/or that is less than the minimum outer diameter (OD 2min ) of the second end portion.

6. A sealing joint as set forth in claim 1 , wherein the end portions are symmetrical relative to each other about the bridge portion.

7. A sealing joint as set forth in claim 1 , wherein the tubular body is symmetrical about a plurality of planes passing through its longitudinal axis.

8. A sealing joint as set forth in claim 1 , wherein the tubular body comprises metal or metal alloy.

9. A sealing joint as set forth in claim 1 , wherein the tubular body has a thickness of about 0.5 mm to about 1.0 mm.

10. A sealing joint as set forth in claim 1 , wherein the coating comprises a matrix phase comprising a metal or a metal alloy; and

MCrAlY particles dispersed in the matrix, wherein M is chosen from nickel, cobalt, iron, or a combination of two or more thereof.

11. A sealing joint as set forth in claim 10 , wherein the matrix phase comprises cobalt, nickel, tin, zinc, copper, iron, tungsten, or a combination of two or more thereof.

12. A sealing joint as set forth in claim 11 , wherein the coating has a thickness of from about 25 μm to about 130 μm.

13. A sealing joint as set forth in claim 1 , wherein:

the first end portion has a coaxially concave inner profile with a maximum inner diameter of (ID 1max ) and a minimum outer diameter (OD 1min );

the second end portion has a coaxially concave inner profile with a maximum inner diameter of (ID 2max ) and a minimum outer diameter (OD 2min );

the bridge portion has a convex inner profile with a minimum inner diameter (ID Bmin ) and a minimum outer diameter (OD Bmin );

the minimum outer diameter (OD 1min ) of the first end portion and the minimum outer diameter (OD 2min ) of the second end portion are approximately equal;

the minimum inner diameter (ID Bmin ) of the bridge portion is less than the maximum inner diameter (ID 1max ) of the first end portion and less than the maximum inner diameter (ID 2max ) of the second end portion; and

the minimum outer diameter (OD Bmin ) of the bridge portion is less than the minimum outer diameter (OD 1min ) of the first end portion and/or that is less than the minimum outer diameter (OD 2min ) of the second end portion.

14. A sealing joint as set forth in claim 13 , wherein the tubular body has substantially the same thickness throughout its portions, whereby the difference between the maximum outer and inner diameters (OD 1max -ID 1max ) of the first end portion, the difference between the maximum outer and inner diameters (OD 2max -ID 2max ) of the second end portion, and the difference between the maximum outer and inner diameters (OD Bmin -ID Bmin ) of the bridge portion are approximately equal.

15. A sealing joint as set forth in claim 14 , wherein the end portions are symmetrical relative to each other about the bridge portion.

16. A sealing joint as set forth in claim 14 , wherein the tubular body is symmetrical about a plurality of planes passing through its longitudinal axis.

17. A sealing joint as set forth in claim 14 , wherein the tubular body comprises metal or metal alloy, and has a thickness of about 0.5 mm to about 1.0 mm.

18. Ductwork comprising a first duct piece, a second duct piece, and the sealing joint set forth in claim 1 interconnecting adjoining ends of the first duct piece and the second duct piece; wherein:

the first duct piece includes a passage for conveying fluid gas and a female recess, coextensive with the passage, on its adjoining end;

the second duct piece includes a passage for conveying combustion gas and a female recess, coextensive with the passage on its adjoining end;

the first end portion of the tubular body is at least partially positioned within the female recess of the first duct piece;

the second end portion of the tubular body is at least partially positioned with the female recess of the second duct piece; and

the bridge portion of the tubular body extends across a gap between the adjoining ends of the duct pieces and/or is positioned partially within the female recesses.

19. An engine exhaust system comprising the ductwork set forth in claim 18 , wherein combustion gas passes through the passage in the first duct piece, through the passage in the tubular body of the sealing joint, and through the passage in the second duct piece.