GB713982A - Improvements relating to the manufacture of commutator segments - Google Patents

Abstract

713,982. Commutators for dynamo-electric machines. METRO-CUTANIT, Ltd. March 4, 1953 [March 7, 1952], No. 6013/52. Class 35 [Also in Group XXII] A commutator segment comprises a porous metallic body portion formed by powder metallurgical methods, and a conductor portion consisting of a metal or alloy of good electrical conductivity, e.g. copper or silver, securely bonded to the body portion by infiltration of part of the metal or alloy of the conductor portion into the porous body portion. The body portion is made from iron,. steel, or alloy steel powders by hot or cold pressing or extrusion and subsequent sintering. Examples are given of the grain sizes, pressures, temperatures, specific gravities and porosities for bodies made from iron powder. The bodies are then placed in a mould with a quantity of copper placed on top of them and they are heated in an atmosphere of hydrogen or in a vacuum or inert atmosphere whereby the copper melts and infiltrates into the porous body and also forms the conducting layer thereon. Additional conductor metal may subsequently be cast on to said layer. The bodies may be subjected to centrifugal force during the casting of the copper thereto whereby the density of the finished segments is increased. The segments ate subsequently heated and tempered. This heat treatment tends to precipitate out of the copper any iron which may have dissolved therein, thus increasing the conductivitv of the conductor portion. The segments may also be pressed in or through dies to further increase their density and to harden them. The porous body may be formed with recesses or protrusions to form keys for the conductor portion and the segment itself may have end recesses for interfitting with the usual end rings of the commutator.