A high torque dual speed turbine rotor for a lightweight hand held tool for grinding and polishing or for use with a spindle mounted pneumatic machine. The high torque dual speed turbine rotor includes a two-piece shaft with flow control screw disposed within the shaft. The shaft includes a first set of hollow openings, at a first position from one end of the shaft, in fluid communications with a first annular chamber of a rotor. There is also a second set of hollow opening, at a second position from the one end of the shaft, in fluid communications with a second annular chamber of the rotor. The flow control screw moves inside a threaded axial bore of the shaft from an open position inside the axial bore to the closed position corresponding to the second set of hollow openings.

A novel turbine motor spindle assembly for a spindle-mounted pneumatic tool, especially in a live tool environment is described. The novel turbine motor spindle assembly includes a manifold with a front end and a rear end. The manifold includes an air intake passage for receiving pressurized air. The pressurized air is directed axially through a drive shaft rotatably coupled to the front end. The pressurized air drives a turbine motor assembly and a drive shaft. The drive shaft is mounted inside a housing with self-lubricating. The turbine motor assembly includes tangential openings for expelling exhaust air therefrom. The turbine motor housing is mechanically coupled to the front end of the manifold with an exhaust air passage for directing exhaust air from the one or more tangential openings out through the rear end of the manifold. The combined overall length of the turbine motor spindle assembly is no more than 1.76 inches in length for live tooling applications.

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).

A high torque dual speed turbine rotor for a lightweight hand held tool for grinding and polishing or for use with a spindle mounted pneumatic machine. The high torque dual speed turbine rotor includes a two-piece shaft with flow control screw disposed within the shaft. The shaft includes a first set of hollow openings, at a first position from one end of the shaft, in fluid communications with a first annular chamber of a rotor. There is also a second set of hollow opening, at a second position from the one end of the shaft, in fluid communications with a second annular chamber of the rotor. The flow control screw moves inside a threaded axial bore of the shaft from an open position inside the axial bore to the closed position corresponding to the second set of hollow openings.

A novel turbine motor spindle assembly for a spindle-mounted pneumatic tool, especially in a live tool environment is described. The novel turbine motor spindle assembly includes a manifold with a front end and a rear end. The manifold includes an air intake passage for receiving pressurized air. The pressurized air is directed axially through a drive shaft rotatably coupled to the front end. The pressurized air drives a turbine motor assembly and a drive shaft. The drive shaft is mounted inside a housing is self-lubricating. The turbine motor assembly includes tangential openings for expelling exhaust air therefrom. The turbine motor housing is mechanically coupled to the front end of the manifold with an exhaust air passage for directing exhaust air from the one or more tangential openings out through the rear end of the manifold.