Patent GB-407096-A (GB)
Title: Improvements in electric conductors suitable for high frequency transmission
IPC: H01B13/18
Filed: 1932-09-19
Abstract: 407,096. Cables. BRITISH INSULATED CABLES, Ltd., Prescot, BLAKE, A. L., 9, Valescourt Road, West Derby, Liverpool, and LAUDER, W. R., 20, Wood Lane, Prescot, both in Lancashire. Sept. 19, 1932, Nos. 26044/32, 26801/32, and 11053/33. [Class 36.] In the manufacture of a concentric air-space cable of the kind in which the conductors are separated from each other by insulating beads placed at intervals on the wire forming the inner conductor, the beads are applied by a repetitive sequence of operations which consist in forming a bead in place on the wire from a stock of material fed to the wire and then moving the bead and wire forward through a predetermined interval, the attachment of the bead to the wire being effected either during or subsequently to the formation of the bead. Fig. 1 shows a machine for applying beads 4 to a wire 1, the machine comprising means for feeding bars of insulation 5 towards the wire, a mould 6 adapted to cut off portions from the bars 5 and to mould them into a bead and to attach it to the wire, and means for moving the mould and wire forward through a predetermined travel, after which the mould opens and returns to form another bead. The intermittent motion of the wire 1 is effected by a one-way clutch 3 which is operated, through a bar 9, by a cam 8 mounted on a hollow shaft 2 through which the wire passes. The mould 6 comprises upper and lower parts 14, 15 which are normally drawn together by springs 17 but which are opened during the backward motion of the mould by cams 16, the one for operating the upper part 14 only being shown. A bar 18, which carries the upper part 14 of the mould and which is engaged by the cam 16, is pivoted to one end of a bar 20, the other end of which engages a cam 22 on the shaft 2 whereby the reciprocating motion of the upper part of the mould is effected. The motion of the lower part of the mould is controlled by similar mechanism. The bars of insulation 5, which are fed inter. mittently to the wire 1 by ratchet and link mechanism 25-30 driven by a crank 32 on a shaft 31, may be fed through a heating device 35 to soften the material before moulding. In a modified process, employing apparatus substantially the same as that already described, the stock of insulating material consists of a long tube through which the wire passes and from which the beads are parted off, the upper and lower parts 14, 15 of the mould being replaced by a clamp comprising members adapted to grip the bead as it is parted off and to carry it forward with the wire. The members are associated with means which, at the end of the travel of the clamp, definitely locate the bead on the wire by deforming the latter on both sides of the bead. In another process the stock of insulation consists of bead-shaped pieces 53, Fig. 8, having a radial slot 54, a supply of them being pushed sideways on the wire which passes through a machine similar to that used in the modified process described above, but wherein the tool for parting the beads from the tube is replaced by a device having jaws adapted to close the slot in the bead-shaped piece thereby forming a bead which is then carried forward by the clamp and positively located on the wire. To increase the adhesion between the beads and the wire, the bead-shaped pieces may be heated just prior to entering the jaws, or the wire may be of the stranded type so as to have an irregular surface. In each of the above processes the wire with the attached beads may be passed direct into a machine of the kind described in Specification 401,082 which applies the outer conductor.