Patent US 4,129,742

A vertical shaft furnace for continuously melting metal materials, such as scrap, copper cathode pieces and the like is disclosed. The furnace comprises an elongated cylindrical melting chamber having an opening in the upper portion thereof for intermittently gravity-charging the furnace with metal pieces, which form a descending metal column in the melting chamber. A plurality of plasma arc generators is mounted in the sidewalls of the melting chamber extending inwardly thereof in a downwardly inclined attitude. The plasma arc torches are arranged in upper and lower vertically spaced planes for respectively preheating and melting the metal charged to the furnace. Protective refractory shrouds are provided which extend inwardly from the inside wall of the melting chamber and at least partly surround the plasma arc torches to substantially prevent damage to the torches by the descending or dropped metal charge.