Handpiece with continuous shaft and bell rotor

A surgical bone operation instrument with a straight shaft arranged coaxially in relation to the longitudinal axis of the instrument, which instrument is provided at the one end of a hand piece with a working unit and at the other end of the hand piece with a driving assembly, the driving assembly and the hand piece each having a tube-shaped shaft piece forming a part of said shaft, which shaft pieces are arranged coaxially with respect to the longitudinal axis of the tool and behind one another, and with their neighboring ends are coupled together, forming over their entire length including their ends a continuous channel which serves for the guidance of a means utilized in the operation of the instrument, said driving assembly being a bell-type electrical motor with the stator enclosed within the bell-shaped rotor, the latter comprising windings of lacquered wire embedded in a plastic material, said windings further being wound to form a hollow cylinder of relatively thin wall thickness to form a part of the bell-shaped rotor, the mechanical structure thereof being furthermore reinforced by glass fibers.