Abstract: A coming off preventing device is provided for a joining part of an air supply and exhaust pipe which joins two pipes by inserting an entry of one air supply and exhaust pipe into a socket of another air supply and exhaust pipe. A cut out window is provided at the socket side, and a metal stopper is equipped on the outer side of the cut out window, wherein the metal stopper has a lock unit which includes a push part on an upper surface of one end, a rectangular shaped lock part on a lower surface of another end and a bearing part on an upper surface of a center part. Further, the lock unit has a lower surface to which one end of a plate spring is welded wherein the plate spring is bent to have an obtuse angle. A joint cover covers said lock unit and fixes said lock unit axially. Further to the entry side, a circumferential groove is engraved to the opposite direction to the entry with a gradient, and an entry stopper.

Abstract: The present invention is a coming off preventing device of joining part of an air supply and exhaust pipe which joins by inserting an entry 3 of the air supply and exhaust pipe into a socket 2 of the air supply and exhaust pipe which comprises, providing a cut out window 9 at said socket side, a metal stopper 4 is equipped at the outer side of the cut out window, said metal stopper 4 forms a push part 5 on an upper surface of one end, a rectangular shape lock part 12 on a lower surface of another end and a bearing 13 on an upper surface of center part, further a lock parts 10 to lower surface of which one end of a plate spring 14 bended to have obtuse angle is welded, a joint cover 11 which covers said lock parts 10 and fixes said lock parts by axial, further, to the entry side, a circumferential groove 7 which stops coming off by fitting the rectangular shape lock part of said lock parts in it is engraved to the opposite direction to the entry with gradient, and an entry stopper 8.