A device for locking a dental instrument, of the type comprising the dental instrument comprising a body accommodates accommodating motorization elements and/or movement-transmitting elements, and a tool-holder head, said device comprising:
- a rotary spindle being comprised of a hollow spindle adapted to mesh with the movement-transmitting elements and being traversed longitudinally by an open central bore receiving the dental instrument, said a hollow spindle carrying a pinion perpendicular to a central axis of said hollow spindle, said pinion adapted to mesh in a conventional manner with the movement-transmitting elements;
- a locking spring being comprised of a lower ring positioned around said hollow spindle and continued on a common side by a plurality of elastic arms, each arm being provided with a pin and having a rest position, said pin engaging an annular groove on the dental instrument, each arm having a spaced-apart position, said pin being moved away from said central axis for release of said hollow spindle;
- and
- a cap-shaped push-button comprising, on an underside thereof, a central and conical pressure head with an external slope radially spacing the arms of the locking spring apart and releasing pins from the annular groove of the dental instrument, when the push-button presses in a direction toward the dental instrument, wherein
- said hollow spindle, comprises a cylindrical sleeve on an underside of said pinion, said cylindrical sleeve being cooperative with a bearing,
- wherein said hollow spindle comprises a cylindrical lower part above said pinion, a central part being positioned on top of the lower part and having smaller diameter than a diameter of the lower part said central part forming a first peripheral shoulder on the lower part, and a cylindrical upper part of being positioned on top of said central part and having a smaller diameter than a diameter of said central part, said upper part forming a second peripheral shoulder on said central part,
- the wherein said hollow spindle comprises at least one slot being located on said upper part and said central parts, said slot diametrically crossing said upper part and said central bore and opening outward on each side, said slot being continued downward by two cuttings opening outwardly along an entire width of said central part, said two cuttings having a width identical to said slot and a concavely curved profile, and
- wherein each arm of said locking spring comprises a central segment inclined in a direction of said central axis, and by an upper segment parallel to said central axis, said central segment extending from said lower ring to said upper segment, each segment having an internal slope inclined by an angle toward a top end thereof.