Abstract: A method for producing a strip of material having a non-uniform cross section is carried out by passing a strip of material in the longitudinal direction through a first set of working rolls, at least one of which is provided with an annular slot intermediate the ends thereof so that a reducing force is applied only to those portions of the strip engaging said roll on opposite sides of the slot whereby the excess material flows toward that portion of the strip opposed to the slot to cause the strip to buckle outwardly into the slot. The strip is subsequently passed through a set of smooth rolls to flatten the buckled portion. This procedure is repeated any desired number of times with the width of the slot becoming progressively smaller. The strip may then be passed through one or more sets of finishing rolls and a heating and annealing operation can take place before each passage through a set of finishing rolls.

Abstract: An apparatus for producing a foamed plastic insulating coating in a wire. A gaseous foaming agent is mixed with a resin and passed through a high pressure narrow passage and then through a lower pressure wide passage.The release of pressure, when the resin enters the wide passage, results in a foaming of the resin. The foamed resin is thereafter extruded through an orifice onto a wire. In one embodiment a chemical is added to serve as a nuclei for the gas bubbles formed during foaming. In a second embodiment, a second chemical is added to provide a smoother extruded surface. In still a further embodiment, the pressure in the wide passage is automatically controlled to remain at a predetermined preferred pressure.