| 摘要 |
1,122,506. Dental handpieces. E. MAVERNA. 25 May, 1966 [5 June, 1965], No. 23399/66 Heading ASR. [Also in Divisions F1 and F2] In a pressure-fluid-driven rotary tool, which tool may for example form part of a dental handpiece which includes a drill adapted to be driven by an air turbine, comprising a casing, a shaft located within the casing and journalled in two spaced-apart ball bearings, and a vaned rotor adapted to be driven by pressure fluid and mounted on the shaft between the two bearings, the outer race of one bearing is rigidly secured to the casing while the outer, race of the other bearing is fixed to a member slidably mounted within the casing, the arrangement being such that, in operation, fluid pressure causes the member to move axially relative to the casing thereby to effect relative movement between the outer races of the bearings to eliminate axial and/or radial free play in the bearings As illustrated in Figure 1, turbine rotor 1 comprises a set of vanes 2 keyed to a rotatable shaft 3 which, is adapted to carry a drill 3'. The rotor, which is enclosed in cylindrical casing 5, is adapted to be rotated by compressed air supplied through duct 4 and exhausting through a second duct (not shown), the two ducts being enclosed by handle 7. The shaft is mounted on two ball bearings 8 and 9, the inner races 10 and 11, respectively, of which are fastened to the shaft. The outer race 12 of bearing 9 is fixed to the casing; the outer race 13 of bearing 8 is fixed to piston member 14 which is non- rotatably mounted as a close fit within the casing to be slidable in an axial direction. The shaft has enlarged portions 15 and 16 which are enclosed by a chamber 17 bounded in part by portion 18 of the casing and portion 19 of the piston member; the surface 14 of the piston member upon which the pressure fluid acts thus defines one wall of the space between the two bearings and is exposed to the same pressure as the rotor, the speed of rotation of the rotor and the relative movement between the outer races of the bearings being functionally related at all times. To allow axial movement between the inner race and outer race of each bearing, an annular groove preferably is provided adjacent at least one radial end surface of the inner race of each hearing; as illustrated, grooves a and b are formed in respective surfaces of the casing and of the slidable member which abut the inner races of the bearings. A further similar annular groove c may be provided in the surface of the slidable member. |
