Dental handpiece and axial groove ball bearing
The dental handpiece consists of a housing with a handle and a turbine that can be operated with compressed gas or compressed air. The rotational movement of the turbine driven by compressed gas is transmitted to the dental tool via a rotor shaft and a chuck. The rotor shaft is rotatably supported by at least one axial groove ball bearing. The radial rigidity required for operating a dental handpiece is achieved by axially preloading the ball bearings. Projections on the housing and the shaft disc of the at least one axial groove ball bearing allow the axial groove ball bearing to be used as radial groove ball bearings. The proposed design of the dental handpiece exhibits little power loss or frictional loss in comparison to dental handpieces with radial groove ball bearings, and slip and drilling friction components can be virtually completely prevented in particular.
1 . A dental handpiece for rotating a rotating dental tool, comprising:
a housing that has a handle and a chuck for receiving the dental tool in the dental handpiece;
a turbine which can be driven by compressed gas and/or compressed air and has a turbine wheel and a rotor shaft connected to the turbine wheel; wherein the rotor shaft is connected to the chuck to transmit the rotation of the turbine wheel to the chuck; and
two axial groove ball bearings, which are arranged on an upper area and a lower area of the rotor shaft, wherein each axial groove ball bearing comprises a shaft disc, a housing disc, and a single row of rolling elements, the shaft disc and the housing disc are spaced apart in an axial direction of the rotor shaft and define opposing bearing surfaces that overlap in the axial direction of the rotor shaft, and the rolling elements are arranged between the shaft disc and the housing disc in the axial direction of the rotor shaft in contact with the opposing bearing surfaces;
wherein the shaft disc of each axial groove ball bearing acts on the rotor shaft or is integrated with the turbine wheel;
wherein the housing disc of each axial groove ball bearing is mounted in the housing;
wherein the housing disc of each axial groove ball bearing has a projection extending in the axial direction, and the projection covers the rolling elements of each axial groove ball bearing on the outside;
wherein a groove is defined on the inside of the projection and a step is defined on the outside of the shaft disc in the region of the groove; and
wherein each axial groove ball bearing further comprises a snap ring configured to snap into the groove and engage with the step to retain the rolling elements between the shaft disc and the housing disc.
2 . The dental handpiece according to claim 1 , wherein each axial groove ball bearing is preloaded in the axial direction with a force greater than or equal to 3 N and less than or equal to 8 N.
3 . The dental handpiece according to claim 1 , wherein the turbine wheel and/or the rotor shaft and/or the shaft disc of each axial groove ball bearing are made in one piece.