Abstract: A commutator includes a cylindrical insulator and commutator pieces, which are formed on the outer circumferential surface of the insulator and arranged side by side in the circumferential direction of the insulator. The commutator pieces are each composed of a conductive plate material, and each includes a connection claw and an engagement claw. The connection claw extends outward in the radial direction of the insulator while being configured to electrically being connected to an armature coil. The engagement claw extends inward in the radial direction of the insulator and engages with the insulator. The commutator pieces each include a recess portion with an undercut formed in a surface facing inward in the radial direction of the insulator.

Abstract: A commutator includes a cylindrical insulator and commutator pieces, which are formed on the outer circumferential surface of the insulator and arranged side by side in the circumferential direction of the insulator. The commutator pieces are each composed of a conductive plate material, and each includes a connection claw and an engagement claw. The connection claw extends outward in the radial direction of the insulator while being configured to electrically being connected to an armature coil. The engagement claw extends inward in the radial direction of the insulator and engages with the insulator. The commutator pieces each include a recess portion with an undercut formed in a surface facing inward in the radial direction of the insulator.

Abstract: A commutator includes a cylindrical insulator and commutator pieces, which are formed on the outer circumferential surface of the insulator and arranged side by side in the circumferential direction of the insulator. The commutator pieces are each composed of a conductive plate material, and each includes a connection claw and an engagement claw. The connection claw extends outward in the radial direction of the insulator while being configured to electrically being connected to an armature coil. The engagement claw extends inward in the radial direction of the insulator and engages with the insulator. The commutator pieces each include a recess portion with an undercut formed in a surface facing inward in the radial direction of the insulator.

Abstract: There is described a method for controlling the profile of a workpiece on a rolling mill, wherein the workpiece is imparted with a predetermined profile in the roughing stage which is suitable for further control in the following finishing stage. In the finishing stage, the desired profile of the workpiece is attained by controlling the temperature of the workpiece at inlet position of the second finishing stage and/or controlling the thickness of the workpiece at outlet position of the first roughing stage. To determine the temperature and/or the thickness of the workpiece at inlet position of the second finishing stage a crown model formula is utilized. The crown model formula includes some constants, and variables which represent the mean temperature of the workpiece in the second finishing stage, and the thickness of the workpiece at the outlet of the first roughing stage.