Patent ID: 7388312

Claim:
A power tool comprising: a tool bit that performs a predetermined operation and a motor to drive the tool bit, wherein the motor includes an armature having a plurality of slots, a four-pole stator, a commutator that rotates together with the armature, two brushes spaced 90° apart from each other in the direction of sliding contact with the commutator, a plurality of segments provided on the commutator, and a plurality of armature windings, both ends of each winding being connected to the segments, each of the armature windings being defined by coils that are wound between respective pairs of the slots of the armature and wherein each of the armature windings is formed by at least two coils connected in series, wherein: at least one of the coils defining the armature windings has a different number of turns of a wire wound between the associated slots from the other coils in the same armature winding, and the total number of turns of the coils of each of the armature windings is the same, each of the armature windings comprises a first coil and a second coil that are connected in series, the second coil being wound between the slots which are diametrically opposite in the armature with respect to the slots for the first coil, and when one armature winding is connected between an associated pair of the segments and comprises the first coil of m turns and the second coil of n turns, another armature winding is connected between an associated pair of the segments adjacent to the pair of segments for the one armature winding and comprises the first coil of n turns and the second coil of m turns, the difference between m and n being an odd number.