Abstract: In an arrangement for connecting tube elements of a ventilation duct system, the inner tube (3) has an abutment (7?) for engagement with a matching abutment (8?) of the outer tube (1). By insertion of the inner tube (3) into the outer tube (1), the abutments (7?, 8?) are brought into engagement in a plane (P) perpendicular to the direction of insertion for providing coupling between the abutments and thereby connection of the tubes (1, 3). The abutment (7?) of the inner tube (3) is continuous along the circumference of the tube (3) and is provided at a distance (d) from a free end (20) of the inner tube (3).

Abstract: In an arrangement for connecting tube elements of a ventilation duct system, the inner tube (3) has an abutment (7) for engagement with a matching abutment (8) of the outer tube (1). By insertion of the inner tube (3) into the outer tube (1) the abutments (7, 8) are brought into engagement in a plane (P) perpendicular to the direction of insertion for providing coupling between the abutments and thereby connection of the tubes (1, 3). The abutment (7) of the inner tube (3) is continuous along the circumference of the tube (3) and formed in a bent end portion (20) of the inner tube (3).

Abstract: A flanged coupling ring for a duct element has a mounting section configured to be mounted or a connection portion of the duct element, and flange means extending outwards from the mounting section. The flange means has, along its periphery, flanged coupling portions for connecting two duct elements, each of which is provided with a coupling ring, by means of external coupling means configured to engage with the flanged coupling portions.

Abstract: In a method of reshaping a tube, an apparatus is used which has a roller nip for rotating the tube, and a shaping roller assembly for altering the cross-section of the tube, for instance from round to oval.