GB932963A - Improvements in or relating to handpieces for dental drills or the like - Google Patents

Abstract

932,963. Dental handpieces. SIEMENSREINIGER-WERKE A.G. Oct. 6, 1960 [Oct. 9, 1959], No. 34306/60. Class 81 (2). [Also in Group XXVI] In a dental handpiece having a head housing a compressed air turbine, the turbine shaft 9 is rad ally mounted on both sides of the wheel 8 in axial compressed air bearing gaps 28, 29 which are fed by radial air supply gaps 35 and which merge with radial bearing gaps 42 adjoining end faces of the wheel. Compressed air is conveyed through a conduit 13 and branch conduits 14, 15 in the handpiece to annular grooves 30 in two nozzle rings 20, 21 one on each side of the turbine wheel, the nozzle rings 20, 21 being a suction fit in the turbine housing 7. Air passes from the grooves to the axial bearing gaps 28, 29 by way of radial bores 31 in the nozzle rings and in distribution rings 22, 23 which fit inside the nozzle rings, axial bores 33 in the distribution rings and the radial air supply gaps 35 at each end of the distribution rings. Air from both axial bearing gaps passes towards the wheel to supply the radial bearing gaps 42 which hold the turbine against axial pressure, and along helical grooves 40 in the turbine shaft towards the bases 38 of recesses defining the blades 37 to assist in driving the wheel. Also, air passes forwardly from the front axial bearing gap 28 to atmosphere by way of an annular bearing gap 45 between the shaft and a front housing cover 11 and rearwardly from the rear axial bearing gap 29 to atmosphere by way of an aperture 46 in the rear housing cover 12. The wheel has, on each side of a central rib 36, two rows of blades defined by frusto-conical recesses having an elliptical cross-section. The blades are inclined to the shaft and the central plane of the wheel. Driving air from the annular grooves 30 of the nozzle rings is directed by nozzles 39 in the nozzle rings against the wheel tangentially of the blade recess bases 38 and at an angle less than 90 degrees to the turbine axis. Air is exhausted from the housing through a conduit 16 in the handle. Water under pressure fed to a nozzle 18 may be directed against a tool rotated by the turbine.