Dentistry – Apparatus – Having motor or means to transmit motion from motor to tool
Patent
1999-08-09
2000-11-28
Lewis, Ralph A.
Dentistry
Apparatus
Having motor or means to transmit motion from motor to tool
415904, A61C 105, F01D 1506
Patent
active
06152736&
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a dental turbine. Such dental turbines are basically known and have a bladed wheel as a rotor, onto which propellant air emerging from the outlet opening flows tangentially. In this way the rotor is made to rotate and drives a drill bit which can be secured to the rotor.
DISCUSSION OF THE PRIOR ART
In the known dental turbines which are operated with a supply pressure of about 5 bar and have a speed of rotation of the order of magnitude of 250,000 rpm, the generally known noise of the dentist's drill arises in operation, which--as a result of its high intensity and its frequency--can be heard even through closed doors. This noise not only disturbs the patients treated and the patients in the waiting room but can also cause hearing damage to the dentists, since they are exposed to this noise daily. As a remedy it has already been suggested that ear protection should be worn during the treatment.
Since the blades of the rotor are loaded tangentially by compressed air in the known dental turbines, a transverse force arises when the dental turbine is switched on and is disturbing for the dentist carrying out the treatment, because the drill is displaced sideways by it. Accordingly, it would be desirable if the drill were not to exhibit any displacement which has to be compensated for by the dentist.
In the known apparatus it is furthermore disadvantageous that on interruption of the propellant air within the turbine housing, a reverse suction effect occurs, since the rotor, which continues to run, generates a vacuum as a result of the switched off propellant air, whereby aerosols which contain bacteria and the like can be sucked out of the oral cavity of the patient into the rotor housing. On subsequent switching on again of the propellant air, the aerosol components are conveyed out of the turbine space again, which is unhygienic and involves the danger of transfer of pathogens when patients change. In order to avoid these effects, various solutions have been proposed in the prior art; however, these were always complicated design-wise.
SUMMARY OF THE INVENTION
It is the problem (object) underlying the invention to provided a dental turbine which overcomes the above described problems.
This object is satisfied in particular in that the rotor has a flow passage, the outlet opening of which imposes a tangential component on the outflowing propellant air. In this way the rotor does not rotate with the flow which impinges on it but rather a reaction is generated within the flow passage which sets the rotor rotating. At the same time, the spacing between the outlet opening and the surface of the rotor onto which flow takes place remains substantially constant during a rotation and the surface of the rotor, on which the flow impinges, does not undergo any change in shape.
It has namely been found that the disturbing whistling noise in the operation of customary dental turbines is not produced by the bearings or the like but is rather produced by the propellant air at the outer periphery of the rotor been "chopped" by the individual blades. Since a new turbine blade continually enters into the propellant air stream in customary rotors, the shape of the surface, on which the flow impinges, continuously changes as does the spacing of the surface, on which the flow impinges, from the outlet opening. Through the design of the rotor in accordance with the invention it is, however, ensured that even with a rotation of the rotor the outflowing propellant air always encounters a constant surface at a constant spacing from the outflow opening, whereby the disturbing noise is fully removed.
Advantageous embodiments of the invention are described in the description, in the drawings, and also in the subordinate claims.
In accordance with an advantageous embodiment of the invention, the outlet opening can be arranged substantially concentric to the axis of rotation of the rotor. In this embodiment the additional advantage results that on loading of the rotor with pro
REFERENCES:
patent: 3141650 (1964-07-01), Saffir
patent: 3147951 (1964-09-01), Cain, Jr. et al.
patent: 3786875 (1974-01-01), Merle
patent: 4203222 (1980-05-01), Mattchen
Biebl Herbert L.
Schmidinger Frank
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