Patent ID: 7948344

Claim:
An electrically insulating coil bobbin comprising a cylindrical portion around which an electrically conductive coil winding is to be wound, said coil bobbin configured to be sandwiched between magnetic core members in a direction of a center axis of the cylindrical portion, wherein the coil winding is comprised of a plurality of coil members of an end-defined ring shape coupled so as to be continuous in a predetermined winding direction, wherein each of the plurality of coil members has a plurality of indentations indented outwardly in parts of an inner periphery thereof, the plurality of indentations are separated from each other along a circumferential direction of an opening of the coil winding, the plurality of indentations are positioned at respective positions along the circumferential direction of the opening without rotational symmetry, and circumferential positions of the indentations of the respective coil members are coincident, wherein a plurality of first insulating portions protruding outwardly relative to the center axis of the cylindrical portion are integrally provided at a first end of the cylindrical portion, the plurality of first insulating portions being separated from each other in a circumferential direction of the cylindrical portion, wherein a second insulating portion protruding outwardly relative to the center axis of the cylindrical portion is integrally provided at a second end of the cylindrical portion opposite the first end of the cylindrical portion, wherein the cylindrical portion is configured to be inserted into openings of the coil members along the direction of the center axis so that the plurality of first insulating portions pass through the plurality of indentations, and wherein in a state in which the plurality of first insulating portions are located out of an outermost coil member, the cylindrical portion is to be rotated relative to the coil winding whereby the coil winding is interposed between the plurality of first insulating portions and the second insulating portion.