The pump has a rotating part (12) fixed at one end (19) of a hollow elongated drive shaft (20). A motor is coupled to the other end (21) of the shaft. The rotating part is submerged in a liquid and the motor is located outside. The shaft end connected to the rotating part has a conical ferrule (19) which fits in a conical opening in an insert (17) fixed to the rotating part. A locking rod (23) extending axially inside the shaft ensures locking of the ferrule and insert. The locking rod has threaded ends which extend beyond the shaft. The locking rod is screwed at one of its ends (24) to the insert (17) and its opposite end (25) fits in a nut (28) supported on the other shaft end.
