GB913106A - Improvements in or relating to dental handpieces having an air turbine for driving adental tool - Google Patents

Abstract

913,106. Dental handpieces. SIEMENSREINIGER-WERKE A.G. Sept. 22, 1959 [Sept. 24, 1958], No. 32269/59. Class 81 (2). [Also in Group XXVI] In a dental handpieee having an air turbine 7 for driving a tool 2, the turbine rotor 8 is mounted at each end in ball bearings 11, 12 and the driving air which impinges on the rotor tangentially is discharged through the ball bearings, the rotor blades presenting concave guide surfaces 23 to the impinging air stream, the ends of the guide surfaces forming an acute angle with the ends of the rotor. The blades are formed by recesses 21 in the rotor which widen in the direction of the surface of the rotor, each recess having a wall 22 which is parallel to the rotor axis and makes an angle of 45 degrees with the concave wall 23 which is a portion of the surface of a cone, the line 24 along which the walls join being arcuate. The width of each recess in the axial direction of the rotor is less than the width of the rotor there being outlet apertures between the recess and the ends of the rotor. Alternatively, each recess intersects the ends of the rotor to form outlet apertures defined by edges 37, 38 of the recess walls (Fig. 6) the recesses being so dimensioned that air, which contains oil mist and leaves the rotor after a deflection of 120-140 degrees, impinges on the outer bearing races 13, 14. The outer bearing races are secured to end caps 15, 16 of the rotor housing, there being a clearance between the rotor and the housing. The width 28 of the clearance is 5-10% of the diameter of the rotor. The inner bearing races 17, 18 are secured to the rotor shaft 9, 10 which is shouldered to maintain a clearance between the bearings and the rotor. Discharged air leaves the head of the handpiece through channels 29, 30, a pipe through the handpiece and a hose. The rotor may be mounted eccentrically in the housing.