Dentistry – Apparatus – Having motor or means to transmit motion from motor to tool
Patent
1982-06-10
1984-03-06
Peshock, Robert
Dentistry
Apparatus
Having motor or means to transmit motion from motor to tool
A61C 105
Patent
active
044351615
DESCRIPTION:
BRIEF SUMMARY
FIELD AND BACKGROUND OF THE INVENTION
A rotor of an air turbine for dental drills comprises a shaft mounted in ball bearings or in one or more air bearings. The shaft is provided with a chamber accommodating a mechanism for fixing the burr. The nose of the turbine, of course, is bored to receive a shaft passing therethrough.
In the head of the turbine, the rotor is suspended from rings of soft material or O-rings which thus support the turbine, particularly laterally. This means that the rotor may be displaced laterally upon a pressure exerted on the turbine head. In consequence, the diameter of the bore provided in the turbine nose must be much larger than that of the shaft, in order to prevent the rotating shaft from butting against and produce friction at the bore wall. A gap is therefore left between the shaft and the bore in the turbine nose through which dentine, powdered enamel, blood, filling residues, and other waste might infiltrate during the operation of the turbine. Such waste is projected up to the inside ball bearing, or the air bearing and the air inlets which thus become fouled and clogged. This strongly affects the reliability of dental turbines. Their ball bearings or air bearings and air inlets must periodically be cleaned or even replaced. Further, waste of any kind accumulating in the interior of the turbines may become a non-negligible source of infection.
SUMMARY OF THE INVENTION
The present invention is directed to a ball bearing or air cushion mounted dental turbine of such design that the various wastes which might penetrate therein in the way described in the foregoing is prevented from reaching the vital parts of the rotor, i.e. either the lower ball bearing or the air bearing and air inlets.
The inventive turbine is characterized by a protective sleeve which is fitted to the outer ring of the lower ball bearing or to the outside wall of the air bearing, and extends below the bearing and then along the shaft up to the gap between the shaft and the bore of the turbine nose. Further, a ring of soft material is received in compressed state between the outer surface of the lower portion of the protective sleeve and the inner surface of the turbine head.
DESCRIPTION OF THE PREFERRED EMBODIMENT
One embodiment of the invention is shown by way of example in the accompanying drawings.
FIG. 1 is a sectional view of the turbine head;
FIG. 2 is a partial sectional view of the protective sleeve mounted in place.
The protective sleeve 1 made in a single piece comprises an upper portion 9, an intermediate portion 17, and a lower portion 14. Upper portion 9 is fitted by its inner surface onto the outer ring 2 of the ball bearing. Protective sleeve 9 extends by its intermediate portion 17 below the ball bearing and, by its lower portion 14, along shaft 4 into space 5 formed between the shaft and the bore 6 provided in nose 7 of the turbine. The sleeve thus completely surrounds the outer ring 2 of the ball bearing, the bottom surface of this bearing, and the lower portion of shaft 4. The sleeve firmly fits the outer ring 2 of the ball bearing and, consequently, follows any lateral movement of the rotor assembly. The O-ring 8 providing suspension applies against the outer surface of the upper portion 9 of protective sleeve 1. A gap 10 must be provided between shaft 4 and the inner surface of lower portion 14 of protective sleeve 1, to avoid any friction between these elements during the rotation of shaft 4. A minute gap 10 may be provided, however, since protective sleeve 1 is firmly fitted to the rotor assembly.
Further, to insure that the rotor will remain virtually suspended from O-rings 8 and 11, a satisfactory gap 12 must be provided between the outer surface of lower portion 14 of protective sleeve 1 and bore 6 of nose 7 of the turbine.
With the turbine in operation, waste of any kind might penetrate therein, through gap 10 between shaft 4 and the inner surface of lower portion 14 of protective sleeve 1, or through gap 12 between the outer surface of lower portion 14 of protective sl
REFERENCES:
patent: 3955284 (1976-05-01), Baison
patent: 4225308 (1980-09-01), Lohn
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