Duct jointing system

A connection means for connecting adjacent ends of rectangular sheet metal ducts, comprising:

• a plurality of elongated hollow flange members each having a channel portion with a mouth opening to receive therein an end face of a wall of said sheet metal duct and to extend along a major part of the length thereof, and a transverse hollow portion upstanding from the channel portion, said transverse portion having a generally planar upstanding outer side face;
• the channel portion extending beyond the plane of said outer face;
• the transverse portion having openings at each longitudinal end thereof;
• a substantially planar, generally L-shaped corner connecting piece, having co-planar limbs, said limbs being adapted to be received in the openings in the longitudinal ends of adjacent ones of said hollow flange members so as to link a pair of flange members together in mutually right angular disposed relationship with said planar outer side faces substantially in a common plane;
• said corner connecting piece having a first laterally offset portion at its radially inner central corner section and a second laterally offset portion at its radially outer central corner section, the first and second offset portions being offset in opposite directions from one another;
• said corner connecting piece being adapted to be assembled with a pair of said flange members with said first laterally offset portion being offset in the direction away from the planar outer side faces thereof;
• a gasket adapted to be placed in sealing engagement with the planar upstanding outer side faces of an adjacent pair of said flange members;
• the channel portions of said profile members extending beyond the plane of said outer face so as to form protuberances extending toward each other in the assembled joint, to grip the gasket in tight sealing engagement between opposed pairs of said flange members;
• each of the first and second offset portions of the corner connecting piece being offset from the main plane thereof sufficiently to protrude a distance of about one wall thickness of the flange member said first offset portion thus constituting means permitting end faces of said walls of the duct in the region of said first offset to project beyond the plane of said first offset portion towards said outer side face to grip said gasket in sealing engagement between opposed such regions of said end faces of opposed ducts.