Patent ID: 8104774

Claim:
A hand-held instrument, for dental or surgical use, intended to rotate, at high speed, a detachable rectilinear tool whereof the end constitutes a bur or similar member, wherein said instrument comprises: a tubular sheath having a longitudinal axis, a first hollow shaft, having the same axis, mounted to rotate inside said tubular sheath, the first hollow shaft comprising: an upstream part of the first hollow shaft, and a downstream part of the first hollow shaft, the downstream part of the shaft itself comprising i) an upstream part partially clasping the upstream part of the first hollow shaft and ii) a downstream part whereof the internal diameter corresponds substantially to an external diameter of the tool, a clamp integral in rotation with said first hollow shaft but movable along said axis and arranged inside the upstream part of the first hollow shaft, concentrically to the first hollow shaft, said clamp existing, in its an upstream part, in the form of a second hollow shaft having an internal diameter corresponding substantially to the external diameter of the tool and which, beyond this, is extended by several elastically deformable jaws designed to grip the tool, and means for moving said clamp longitudinally in the upstream direction such that its jaws penetrate under the upstream part of the first hollow shaft and thus ensure gripping of the tool, and in the downstream direction such that the jaws escape said upstream part and thus ensure releasing of the tool, wherein the end of said jaws constitutes a wedge having a conical profile whereof the thickness increases in the downstream direction and wherein the upstream part of the first hollow shaft is extended, without being part of it, by an independent ring ensuring gripping of the clamp, said ring having a conical internal profile which corresponds to the conical profile of the wedges, a constant external diameter of said ring being slightly smaller than an external diameter of the upstream part of the first hollow shaft so as to offer it a clearance which causes it to float between the wedges and the upstream part of the downstream part of the first hollow shaft, wherein upstream designates an end of the instrument from which the tool is driven in rotation and downstream designates an end bearing the operative tip of the tool.