Western Electric Company, Inc.

William Robert Lockhart

William C Vesperman

Max K Wilson

William M Kanotz

George F Piper

An insulation comprising a polyether polyester thermoplastic copolymer obtained by reacting 1,4 butane diol terephthalate with terephthalate esters of polytetramethylene glycol is coated over an irregularly configured conductor, such as for example, a tinsel conductor, suitable for use in telecommunications cordage by moving the copolymer through an extruder and along a flow path formed between a core tube and wall of a die cavity. The die cavity adjacent to the throat of the die has a frustoconical portion formed with an approach angle of sufficient magnitude to minimize the pressure drop through the extruder to extrude the copolymer at a temperature slightly above the melting point of the copolymer. The copolymer is insulation tubed over the tinsel conductor with a gas at a controlled volume rate of flow being moved through the core tube along with the tinsel conductor to expand the copolymer extrudate as it flows out of the die opening to cool the extrudate and to facilitate advantageously oriented crystalline growth of the copolymer. Subsequently, the insulation is drawn down about the tinsel conductor with a slight spacing therefrom while treating the insulation with water at a predetermined temperature to anneal the insulation in a predetermined manner. A plurality of the insulated tinsel conductors are enclosed in a jacket which comprises a plasticized polyvinyl chloride composition.

Apparatus for insulating flexible conductors

An insulation comprising a polyether polyester thermoplastic copolymer obtained by reacting 1, 4 butane diol terephthalate with terepthalate esters of polytetramethylene glycol is coated over an irregularly configured conductor, such as for example, a tinsel conductor, suitable for use in telecommunications cordage by moving the copolymer through an extruder and along a flow path formed between a core tube and wall of a die cavity. The die cavity adjacent to the throat of the die has a frustoconical portion formed with an approach angle of sufficient magnitude to minimize the pressure drop through the extruder to extrude the copolymer at a temperature slightly above the melting point of the copolymer. The copolymer insulation is tubed over the tinsel conductor with a gas at a controlled volume rate of flow being moved through the core tube along with the tinsel conductor to expand the copolymer extrudate as it flows out of the die opening to cool the extrudate and to facilitate advantageously oriented crystalline growth of the copolymer. Subsequently, the insulation is drawn down about the tinsel conductor with a slight spacing therefrom while treating the insulation with water at a predetermined temperature to anneal the insulation in a predetermined manner. A plurality of the insulated tinsel conductors are enclosed in a jacket which comprises a plasticized polyvinyl chloride composition.

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Baltimore, MD, United States of America

William Robert Lockhart