. . " of the casing 31.The inflation of the sealing elements by means of a fluid under pressure completes the clamping of the walls 46a and 46b against the outer surface of the wall 31 and closes the chamber 44 in a sealed manner.The flat sealing elements 54'a and 54'b provide the seal between the sectors 49a and 49b, on one hand, and the parts such as 50 on the other hand.As previously described, the" . . .