They comprise jaw means (70) mounted on a rotating body (60), first and second means (100, 200) for transmitting movement of jaw means (70) and the rotating body (60), respectively, comprising respectively at least one tendon (300, 350, 400) consisting of several cables (500) arranged so that the cross-section of at least one tendon (300, 350) associated with the first means (100) for transmitting movement has a variable geometry (A, B, C) therealong formed by a first arrangement (A) in which cables (500) are arranged, in cross-section, with their longitudinal axes in a radial distribution (A), a second arrangement (B) in which said axes are arranged in a first orientation, and a third arrangement (C) in which said axes are arranged in a second orientation, perpendicular to the first orientation.
