Tubular medical instrument having a flexible sheath driven by a plurality of cuffs

Claim 1

A tubular medical instrument comprising: a flexible sheath to be inserted into a human body cavity, at least one flexible tubular propellent cuff having end portions, said end portions being mounted on the outer surface of said sheath and adapted to contain a fluid, means for supplying fluid to said propellent cuff, tubular drive cuff disposed adjacent to said propellent cuff on the outer surface of said sheath, a tubular return cuff disposed adjacent to said propellent cuff and opposite to said drive cuff with respect to said propellent cuff, said drive and return cuffs being adapted alternately to have a fluid supplied thereinto to expand radially and drawn therefrom to be flattened, means for supplying and withdrawing fluid from said drive and return cuffs, and said propellent cuff having a width greater than the distance between said mounted end portions such that said propellent cuff is normally folded along a circular line over a flattened one of said drive and return cuffs with a folded back portion of said propellent cuff lying on said flattened one of said drive and return cuffs, said propellent cuff being progressively deformed toward the other of said drive and return cuffs with the outer surface of said propellent cuff kept in contact with the inner surface of said human body cavity as fluid is introduced into said one of said drive and return cuffs and drawn from said other of said drive and return cuffs, and being finally folded along another circular line over said other of said drive and return cuffs with a newly folded back portion lying on said other drive and return cuffs now flattened, said propellent cuff being adapted to move said tubular instrument in said human body cavity in the opposite direction to the direction in which said propellent cuff is deformed progressively.