Combination spindle-drive system for high precision machining

Claim 1

A combination spindle-drive for a precision machining lathe comprising: a spindle having a rotatably disposed shaft adapted to carry a workpiece at one end of said shaft; a cup-shaped rotor supported in cantilever arrangement from the opposite end of said shaft by affixing the base of said cup-shaped rotor concentrically to the said opposite end of said shaft so that the walls of said cup-shaped rotor extend axially from said opposite end of said shaft, said rotor composed of an electrically conductive, non-magnetic material; a stator disposed coaxially about the walls of said cup-shaped rotor in an adjacent spaced relationship from said rotor, to form air gaps along the outer and inner walls of the said cup-shaped rotor, said stator having an outer core member disposed adjacent the outer wall of said cup and provided with a poly-phase AC winding for applying a rotating magnetic field to said rotor and an inner core member disposed adjacent the inner wall of said cup-shaped rotor, said inner core member magnetically coupled to said outer core member so that the magnetic flux produced by said winding circulates through the walls of said cup-shaped rotor to produce torque on said rotor due to the reaction of eddy currents induced in said rotor by said rotating magnetic field.