Patent GB-1126276-A (GB)
Title: Dental handpiece with compressed-air turbine drive
IPC: A61C1/05
Filed: 1966-04-06
Abstract: 1,126,276. Bearings. SIEMENS-REINIGERWERKE A.G. 6 April, 1966 [10 April, 1965; 29 March, 1966], No. 15399/66. Heading F2A. [Also in Divisions A5 and F1] In a dental handpiece comprising an air turbine the rotor of which incorporates at least one turbine wheel and is supported by air bearings, the bearing system comprises an axially-extending cylindrical bearing gap bounded by the cylindrical surface of the rotor and by the internal cylindrical surface of a single bearing bushing, two radially-extending bearing gaps bounded by surface portions of the rotor and by surfaces of associated bearing parts, which surfaces are parallel to the surface portions of the rotor, at least one ring of radially-extending nozzles formed in the bearing bushing and arranged to feed air to the axially-extending bearing gap, and a plurality of axially-extending nozzles formed in the bearing parts which bound the two radiallyextending bearing gaps and arranged to feed air to the two radially-extending bearing gaps. As illustrated in Fig. 2, the head part 4 of a dental handpiece comprises a cylindrical housing 7 and end covers 8 and 9. Mounted within the housing is a turbine comprising a cylindrical bearing bushing 10 and a rotor-shaft 18 which has butt ends 18a on each of which is mounted a turbine wheel 21. Fitted in annular grooves in the outer face of the bearing bushing are elastic rings 11 and 12 which support the turbine in the housing. Compressed air for the bearing system is supplied via conduit 13 and a ring of bores 14 to annular conduit 15 formed in the bearing bushing and passes either via three rings of radially-extending nozzles 16 to axially-extending bearing gap 17, which is bounded by the opposed cylindrical faces of the rotor and of the bearing bushing, or via axially-extending nozzles 19 to radially-extending bearing gaps 20, each of which is bounded by a face of an annular disc 24 which covers an end face of a turbine wheel and by the opposed and parallel end face of the bearing bushing, before exhausting to atmosphere via openings 25 and 26 formed in the end covers. Compressed air for driving the turbine is supplied via conduit 23 to impinge on oblique transverse grooves 22 formed on the periphery of each turbine wheel. Four further constructions of dental handpiece are described and illustrated in the Specification, each construction comprising a turbine the rotor of which incorporates a single turbine wheel having pocket-like blades. As illustrated in Fig. 5 (not shown), the pocketlike blades of the turbine wheel are formed in the axially central portion of the rotor shaft, the axially-extending bearing gap being bounded by the opposed cylindrical surfaces of the rotorshaft and of a single bearing bushing surrounding the rotor-shaft. Alternatively, the single turbine wheel having pocket-like blades is mounted at one end of the rotor-shaft, Fig. 4 (not shown), illustrating a construction in which each of the two radially-extending bearing gaps is bounded by an end face of the turbine wheel, Fig. 3 (not shown), illustrating a construction in which an annular flange having a diameter equal to the diameter of the turbine wheel is mounted on the other end of the rotorshaft, and Figs. 6 and 7 (not shown), illustrating a similar construction in which at least those surfaces of the rotor which bound the bearing gaps are made of steel and in which those portions of the bearing bushing which bound the bearing gaps are made of carbon.