| 摘要 |
An electric motor for a power tool comprises a stator having separately forming pole pieces 404, return path pieces 706 and field coils 700. The field coils are placed on the poles and retained by snap fitting or staking the pole at 528 and the return path pieces are then affixed to the pole pieces with interengaging structures, the pole portion 516 being deformed to lock the end of the return piece to the pole. With the assembled field coils 700 extending beyond pole tips. The field coils may be insulated by moulding in silicon rubber, projections 624 and ribs 626 ensuring a gripping contact to restrain the assembly. Alternative a pair of insulating sleeves fig 10 may be provided , pockets 1000 receiving pole parts. Or insulating wraps fig 13 having adhesive patches 1304,1308 may be used. Fig 16a (not shown) discloses an alternative wrap with heat curable adhesive (1602). The sleeve/wrap edges may form a cuff. The stator may be of a circular or square configuration (fig 17) and the stator/rotor assembly may be sized so that the armature has an outside diameter of at least 0.625 the outside diameter of the stator. Field coil packing factors and circumferential lengths are disclosed as are frame size and speed power outputs. The arrangement is said to be thermally balanced. |
