GB591995A - Improvements in the slitting of insulating material - Google Patents

Abstract

591,995. Dielectric heating. BRITISH INSULATED CABLES, Ltd., QUAYLE, J. C., JONES, P., and BAYLES, R. July 24, 1944, No. 14086. [Class 39 (iii)] [Also in Groups VIII and XXXVI] A length of flexible electric insulating material of heat - softenable nature, e.g. a sheet or cable is slit by moving it through a high - frequency electric field to heat and soften the material along a narrow line and then tearing it on this line as it leaves the field. Circular or annular electrodes 1, 2 preferably spaced by insulating material 5 are mounted to rotate on opposite sides of the sheet to be slit, the discs 1 being attached to a source of high frequency and the discs 2 being earthed. A cable 10 is stripped of insulating material in passing over pulleys 11, 12 from a drum 13. The pulley 11 comprises a thin central metal disc 22 and two insulating side flanges 21 to locate the cable so that it touches the edge of the disc, which is connected to a source of high frequency, the other terminal of which is connected to the metal surface of the pulley wheel 12 making connection with the conductor of the cable. The cable covering .is thus weakened on a radius and on rotation of the pulleys is torn from the cable conductor and passes over a pulley 16 to a driven reel 17. The cable conductor is wound on a driven reel 14. Helical springs 24 on screws 23 space a disc 22 between the insulating flanges 21 of the pulley 11, which has an axial flange 26 rotating on a metal sleeve 27 on an insulating support 28. Current is supplied to the hub of the disc by a sleeve 29 with a flexible end contacting the sleeve 27 connected to a lead 30. The cable may be weakened across a diameter and the covering torn off in two strips which are separately reeled. In an annular recess 37 in each insulating flange 32 of a pulley 11 is inserted a ring electrode 39 with a blunt edge 40 pressed against the cable by springs 43 on adjustable screw plugs 44 connected by radial strips 45 to the supply leads 30 connected to opposite ends of a centre-earthed secondary of a high-frequency transformer. In order that current may be supplied only when the pulleys are moving, contacts 54 from the supply 53 to the motor 52 driving the reels 14, 17 are closed on completion of a contactor control circuit 55 by a relay 56, the supply to which is obtained from a rectifier 57 whose anode is connected to a loop 58 energized by a coil 59 in the supply line from the oscillator 51 to the electrode pulley 11. The rectifier 57 may be energized from the primary of a coupling transformer.