GB950741A - Extruding apparatus - Google Patents

Abstract

950,741. Extruding wire coatings. WHITNEY BLAKE CO. June 17, 1960 [June 17, 1959], No. 21386/60. Heading B5A. Extruding apparatus for applying insulating coatings of thermoplastic material to a pair of moving wires comprises means for applying a primary coating of thermoplastic material to each wire, a die assembly which receives the coated wires whilst the primary coatings are still in a plastic condition, a secondary coating chamber in the die assembly for applying a secondary coating of thermoplastic material, and land means in the secondary coating chamber arranged to surround one wire only or to surround one wire and partially surround the other, whereby a secondary coating is applied only to the primary coating of the other wire at least over a portion of its periphery. The secondary coating may be of a different colour to the primary coating and may be in the form of strips or bands for identification purposes. In the embodiment shown in Figs. 1 and 2, wires 10, 12 pass through a mandrel 19 and forwardly extending guide members 40, 42 to a die member 20 where they receive a preliminary coating of a coloured thermoplastic material, e.g. polyethylene, in the chamber 22. A supplementary die assembly 26 is mounted in front of the die member 20 and comprises an extrusion device 28 for extruding the secondary coating, which may be of another thermoplastic material such as coloured polyvinyl chloride, to the wires 10, 12. This secondary thermoplastic material is forced through the feeding tube 30 to a circular chamber 34 which surrounds an inner applying chamber 36 (Fig. 2). A land 38 surrounds the wire 10 while it passes through the chamber 36 and seals it from the coating material. To ensure that the wires 10, 12 leave the die assembly 26 with coatings of the same diameter, the exit apertures 58, 60 are of the same diameter. In an alternative embodiment (Fig. 6), insulated wires with one or more identifying stripes are formed using a supplementary die assembly in which a land 81 seals off both wires from the coating material in the circular chamber 80 with the exception of one or more triangular shaped channels 82 leading to one of the two wires passing through the die assembly. In a further embodiment (Fig. 9), a pair of insulated wires having an inner connecting web and one of the wires being provided with a secondary coating is produced, the supplementary die assembly being modified to provide a channel 104 interconnecting the die chambers 88, 90 to form the web 100 which connects the wires 92, 94, and the secondary coating material being fed via the chamber 80 through a channel 106 so as to cover the entire circumference of the primary coating 98 of the wire 94.