Patent ID: 8421303

Claim:
Alternating-current-synchronous-servomotor having a disk-shaped rotor which is located between two stator halves of which each is provided with a bearing for a shaft supporting the rotor and comprise each a magnet iron part having a plurality of radial grooves and an electrical coil having leads inserted in the radial grooves, which rotor comprises an even number of flat permanent magnets pieces having magnet field lines extending parallel to the shaft, which permanent magnet pieces form an annular like series including interstices extending around a hub supported on the shaft and of a magnetically non-conductive material and have flat sides acting as magnetic pole surfaces (N, S) which extend in parallel planes to which the axis of the shaft extend perpendicularly and are serially alternating north and south poles, and whereby the interstices between adjacent permanent magnet pieces diverge radially towards the outside, the outer periphery of the hub comprising planes extending along the sides of a regular polygon and edges located therebetween, and the permanent magnet pieces have limiting surfaces located radially inwards, which are supported each on one of the peripheral planes of the hub, wherein said planes and said limiting surfaces comprise cooperating means extending in a plane perpendicular to said peripheral planes, said cooperating means for fixing said magnet pieces on said hub, wherein said cooperating means engage said magnet pieces against the hub in a plane perpendicular to said peripheral planes.