Pipe coupling structure

A coupling structure for first and second cylindrically shaped air conducting duct bodies, each of the cylindrically shaped duct bodies having an inner and outer cylindrical wall surface, the coupling structure comprising:

• a first duct engagement portion extending outwardly from the outer wall surface of the first duct body, wherein the first duct engagement portion has a cross-sectional shape that includes:
• a first wall portion extending from a first wall portion first end in a direction approximately perpendicular to the outer wall surface;
• and
• a second curved wall section extending from the outer wall surface to a first wall portion second end;
• and
• a second duct engagement portion extending inwardly from the inner wall surface of the second duct body, wherein the second duct engagement portion has a cross-sectional shape that includes:
• a third wall portion extending from a third wall portion first end in a direction approximately perpendicular to the inner wall surface;
• and
• a fourth curved wall section extending from the inner wall surface to a third wall portion second end,
• wherein the first duct engagement portion extends about the entire circumference of the outer cylindrical wall surface of the first duct body.

A coupling structure for first and second cylindrically shaped air conducting duct bodies, each of the cylindrically shaped duct bodies having an inner and outer cylindrical wall surface, the coupling structure comprising:

• a first duct engagement portion extending outwardly from the outer wall surface of the first duct body, wherein the first duct engagement portion has a cross-sectional shape that includes:
• a first wall portion extending from a first wall portion first end in a direction approximately perpendicular to the outer wall surface;
• and
• a second curved wall section extending from the outer wall surface to a first wall portion second end;
• and
• a second duct engagement portion extending inwardly from the inner wall surface of the second duct body, wherein the second duct engagement portion has a cross-sectional shape that includes:
• a third wall portion extending from a third wall portion first end in a direction approximately perpendicular to the inner wall surface;
• and
• a fourth curved wall section extending from the inner wall surface to a third wall portion second end, wherein the second duct body comprises a spirally-wrapped strip.

A coupling structure for first and second cylindrically shaped air conducting duct bodies, each of the cylindrically shaped duct bodies having an inner and outer cylindrical wall surface, the coupling structure comprising:

• a first duct engagement portion extending outwardly from the outer wall surface of the first duct body, wherein the first duct engagement portion has a cross-sectional shape that includes:
• a first wall portion extending from a first wall portion first end in a direction approximately perpendicular to the outer wall surface;
• and
• a second curved wall section extending from the outer wall surface to a first wall portion second end;
• and
• a second duct engagement portion extending inwardly from the inner wall surface of the second duct body, wherein the second duct engagement portion has a cross-sectional shape that includes:
• a third wall portion extending from a third wall portion first end in a direction approximately perpendicular to the inner wall surface;
• and
• a fourth curved wall section extending from the inner wall surface to a third wall portion second end, wherein the outer wall surface of the first duct body has no communicating opening to the inside of the first duct body.