Patent GB-1428430-A (GB)
Title: Method of and apparatus for insulating a thin conductor
IPC: B29C48/15
Filed: 1973-06-15
Abstract: 1428430 Coating electrical conductors NOKIA AB OY 15 June 1973 [16 June 1972] 28697/73 Heading B5A [Also in Division G3] A telephone cable conductor, of a diameter down to 0À32 mm., is coated with plastics insulation in passage through an extrusion head, e.g. at speed of 2,500 metres/min., the wire being delivered to, and drawn from the head, by devices each operated at a different constant wire speed to ensure a constant elongation of the wire therebetween. The coating apparatus comprises a wire reel device 1; pre-annealing device 2 including means delivering the wire at constant speed; extrusion coating head 11; apparatus controls 6; cooling channel 7; wire pulling device 12 pulling the wire at a higher constant speed; and an insulated wire reeling device 9. Reference is made to the prior art, Figs. 1 and 2 (not shown) in which the annealing device (2) delivers to a wire reservoir (3) in which the wire passes around a wheel system (4) which is vertically displaceable in dependency upon differences in speed of the wire being delivered to, and pulled from the reservoir. The prior art pulling device (12) operates at constant wire speed, and the vertical displacement of the wheel system actuates a potentiometer which controls the speed of the motor of a drive delivering the wire from the annealer to the reservoir, to maintain the wheel system at a constant height, and hence a constant speed of wire delivery to and from the reservoir. The prior art reeling device (9) operates similarly, at the same speed as the pulling device (12) via a wire reservoir (15) but having horizontally displaceable wheels. In the Fig. 3 and 4 embodiment of the present invention the prior art reservoir (4) is omitted, and the drive delivering from the annealing device 2, and the pulling device 12, operate at the different constant speeds to ensure the constant wire elongation therebetween. In the Figs. 5 and 6 embodiment of the present invention (not shown) the pulling device (8) is incorporated within the cooling channel (7) through which the wire makes a plurality of passes. When the wire speed is accelerating at the commencement of extrusion, the relative speeds may be maintained by driving both the drive delivering from the annealing device, and that of the pulling device, from a common shaft. Alternatively, the Fig. 7 control may be utilized in which motors 10, and 23 or 19, respectively drive the pre-heater 2 and pulling device 12 or 8, the relative speeds of which motors are maintained constant by controls 21, 25 which act by comparison of a desired speed of motor 10, set at a source 22, with the signal respectively from devices 20, 24 measuring the speeds of motors 10, and 23 or 19. The signal from source 22 to device 25 is modified by a further signal through a potentiometer 26 and series resistance 27. Movement of the potentiometer slide from a zero position, increases the speed of motor 23 or 19 with respect to motor 10, and the relative speeds remain constant for changing values of the speed set at 22. A plurality of pulling devices may be employed operating at progressively increasing constant speeds.