Vent pipe coupling

Claim 1

A one-piece flexible vent pipe coupling having a single-ply wall comprised of an elastic plastic material of substantially uniform thickness, the wall comprising a cylindrical socket end receiving a first short connection pipe section of a roof vent inserted into the socket end, another cylindrical end connected to a second pipe section of the roof vent and a central compressible bellows portion between the ends, the central bellows portion being comprised of a series of folds including an inwardly projecting end fold adjacent the socket end, the folds of the bellows portion in the relaxed condition thereof defining an inner diameter of the bellows portion which is substantially equal to the outer diameter of the short connection pipe section, the inwardly projecting end fold of the central bellows portion being constricted under compression upon insertion of the short connection pipe section of the roof vent into the socket end and the constricted end fold forming an abutment for the inserted connection pipe section, the elastic plastic material of the cylindrical wall of the socket end of the vent pipe coupling being deformed by depressing the wall material to form an inwardly directed circumferential arcuate protrusion pressing against, and sealingly retaining, the inserted first short connection pipe section, the depression of the wall material forming a circumferentially extending annular groove.