Method of making an intermediate stage, intermediate blank for a dynamo

Abstract

To form a commutator segmental ring, an intermediate stage commutator ring (4) is formed from a flat strip (1) of commutator material which is bent into essentially cylindrical tubular shape to form a blank (2) having a gap or crack (3) adjacent the ends of the strip. The commutator ring, upon forming of the commutator, is severed into commutator segments. The gap or crack of the blank is aligned with a ridge or rib in a forming punch press to form a groove within the essentially cylindrical tubular blank (2) so that, when the intermediate stage commutator ring (4) is made, a cylindrical portion (5) already dimensioned for the intermediate segmental ring and a flange portion (6) are made, with a groove in alignment with the gap or crack obtained during cold-flowing of the metal in the press by the guidance afforded by the rib or ridge in the gap or crack of the cylindrical tubular blank. Preferably, the ridge or rib, defining the groove, extends in a plane which passes through the axis of the cylindrical portion (5) of the intermediate commutator ring (4) and extends radially therefrom through the center line of the groove. The apparatus includes multiple concentric punch, stamp and die elements to permit cold-flowing of the cylindrical tubular blank upon compression of the commutator metal which, typically, is copper.