Reverse-flow brake for rotors in dental preparation instruments

Patent metadata

Field	Value
Publication number	US-12201487-B2
Application number	US-201917297511-A
Country	US
Kind code	B2
Filing date	Nov 27, 2019
Priority date	Nov 27, 2018
Publication date	Jan 21, 2025
Grant date	Jan 21, 2025

Abstract

The invention relates to a rotor ( 1 ) having a turbine wheel ( 3 ) driven by propellant (TG) in a turbine housing ( 2 ), a dental preparation instrument ( 20 ) having such a rotor ( 1 ) and a method ( 100 ) for operating such a preparation instrument ( 20 ), wherein at least one part of the propellant (TG) flows back to the gas outlet opening ( 51 ) in an inner wall ( 21 ) radially orbiting the turbine wheel ( 3 ) through a return flow channel ( 6 ) after impinging on at least one of the drive blades ( 31 ) of the turbine wheel ( 3 ) counter to the direction of rotation (DR) of the turbine wheel ( 3 ), the inner wall ( 21 ) in the segment of a circle (KS) comprises at least one return flow channel ( 6 ) extending at least from the gas inlet opening ( 41 ) as far as the gas outlet opening ( 51 ), which allows at least one part of the propellant (TG) to flow back to the gas outlet opening ( 51 ) through the return flow channel ( 6 ) after impinging on at least one of the drive blades ( 31 ) counter to the direction of rotation (DR) of the turbine wheel ( 3 ), wherein, in axial direction (AR), the turbine housing ( 2 ) has at least one cross-sectional extension ( 8 ) of a surface between drive blades ( 31 ) and inner wall ( 21 ) as far as the return flow channel ( 6 ).

First claim

The invention claimed is:

1. A rotor for driving an implement of a dental preparation instrument, having
a turbine wheel mounted in a turbine housing of the dental preparation instrument, which turbine wheel has a plurality of drive blades,
wherein the turbine housing is formed from an inner wall radially orbiting the turbine wheel, and cover surfaces enclosing the inner wall above and below,
at least one gas inlet channel with a gas inlet opening for admitting a propellant into the turbine housing for driving the turbine wheel and
at least one gas outlet channel with a gas outlet opening for leading the propellant away from the turbine housing once the turbine wheel has been driven,
wherein the gas inlet opening and the gas outlet opening are arranged in the inner wall within a segment of a circle of a maximum of 180°,
wherein the inner wall in the segment of the circle comprises at least one return flow channel extending at least partially from the gas inlet opening as far as the gas outlet opening,
wherein the return flow channel allows at least one part of the propellant to flow back to the gas outlet opening through the return flow channel after impinging on at least one of the drive blades counter to the direction of rotation of the turbine wheel, and
wherein, in the axial direction, the turbine housing has at least one cross-sectional extension between the drive blades and one of the cover surfaces, which is formed by a recess in one of the cover surfaces, with a first distance in the axial direction between the drive blades and the cover surface, which extends at least over a first region of the return flow channel viewed in the direction of the propellant flowing in the return flow channel at least as far as an outer end of the gas outlet opening in the direction of the returning propellant, and with at least one second distance in the axial direction between the drive blades and the cover surface in a region of the return flow channel different from the first region, wherein the second distance is shorter than the first distance.

2. The rotor according to claim 1 , characterized in that the return flow channel orbits the turbine wheel at the same axial height relative to the axis of rotation of the turbine wheel.

3. The rotor according to claim 1 , characterized in that the gas inlet opening and/or the gas outlet opening are arranged, relative to the return flow channel, above or below one another, viewed in the direction of the axis of rotation of the turbine wheel.

4. The rotor according to claim 3 , characterized in that the return flow channel is guided in the inner wall of the turbine housing with a cross-sectional surface parallel to the radial direction of the turbine wheel such that at least the centre of the cross-sectional surface lies further away from the turbine wheel in a radial direction than the gas inlet opening and/or the gas outlet opening.

5. The rotor according to claim 1 , characterized in that the cross-sectional extension extends to below the turbine wheel.

6. The rotor according to claim 2 , characterized in that the gas inlet and gas outlet openings each possesses centres which are arranged at the same axial height relative to the axis of rotation of the turbine wheel.

7. The rotor according to claim 1 , characterized in that the segment of a circle with gas inlet and gas outlet openings is arrangeable on one hand side of the dental preparation instrument.

8. The rotor according to claim 1 , characterized in that a contour of the drive blades is formed such that the propellant is deflected in its propagation direction by 90° to 175°.

9. The rotor according to claim 1 , characterized in that the cover surface passes from the first distance to the second distance to the turbine wheel in a curved contour.

10. The rotor according to claim 1 , characterized in that the gas inlet channel is shaped as a nozzle at least in the region of the gas inlet opening, in order to steer the propellant onto the drive blades in a directed manner.

11. The rotor according to any one of the preceding claims , characterized in that a ratio between the first and second distances forces an eddy which redirects the propellant returning through the return flow channel against a region of the drive blade facing the eddy, at least the region facing the eddy has an alignment which causes the returning propellant to strike the region at an angle of 80° to 100°.

12. The rotor according to claim 1 , characterized by a second return flow channel, wherein the gas inlet and gas outlet openings are arranged between the two return flow channels in orbiting direction in the inner wall relative to the axis of rotation of the turbine wheel, wherein the other cover surface of the turbine housing also has, same as said at least one cross-sectional extension, another cross-sectional extension, formed by a recess therein, with the result that two separate eddies are generated, and propellant returning therethrough is in each case deflected from above and below onto the drive blades of the turbine wheel.

13. The rotor according to claim 1 , characterized in that at least one further opening for guiding through a further component is arranged in the inner wall.

14. A dental preparation instrument having a rotor according to claim 1 arranged in a head part, which, by means of a propellant supplied by a hand part, drives an implement.

15. A method for operating a dental preparation instrument having a rotor arranged in a head part, for driving an implement with a turbine wheel mounted in a turbine housing, wherein the turbine housing is formed from an inner wall radially orbiting the turbine wheel and cover surfaces enclosing the inner wall above and below, comprising the following steps: admitting a propellant which is supplied by a hand part via a gas inlet channel through a gas inlet opening into the turbine housing for driving the turbine wheel with a plurality of drive blades; reversing the flow at least of one part of the propellant, after impingement on at least one of the drive blades counter to the direction of rotation of the turbine wheel, through a return flow channel to a gas outlet opening, wherein the gas inlet opening and the gas outlet opening are arranged in the inner wall of the turbine housing within a segment of a circle of a maximum of 180° and the return flow channel extends at least partially from the gas inlet opening as far as a gas outlet opening in the segment of a circle; generating an eddy in the propellant by the turbine housing having, in an axial direction, at least one cross-sectional extension of a surface between the drive blades and one of the cover surfaces;
generating a rotation speed-dependent braking force on the turbine wheel by at least one part of the propellant returning along the return flow channel, which gas is deflected, by the eddy, onto the drive blades, counter to the direction of rotation of the turbine wheel; and leading the returning propellant away via the gas outlet opening through at least one gas outlet channel.

Assignees

• Dentsply Sirona Inc

Inventors

• Goisser Siegfried
• Göbel Stefan
• Ertugrul Metin

Classifications

• F01D15/065

  with pressure-velocity transformation exclusively in rotor · CPC title

• F01D15/062

  Controlling means specially adapted therefor · CPC title

• A61C1/05 Primary

  with turbine drive · CPC title