| 摘要 |
637,647. Electric cables. ROBERTS, E. G. L. Oct. 24, 1946, No. 31655. [Class 36] Metal clad, mineral insulated cables are manufactured by the reduction of an initial workpiece by rolling, the workpiece consisting of a metal tube 1 having a closed end 2, into which tube the dielectric material 5 is introduced in granular form and consolidated by sustained pressure. Conductor rods 3, threaded at one end, screw into tapped holes in the end closure 2. A ram 6 with a die 7 is used to consolidate the insulating material. When the tube 1 is filled to the depth required, Fig. 4, a disc 8 is placed in the open end thereof, and the ends 4 of the tube 1 are turned over by means of a suitable die 9, thus locking the disc in position. The workpiece may be drilled with small holes at both ends, and then heated to expel any water vapour and occluded gases that may be present before the reducing operation, which may be carried out either by hot or cold rolling. If it is desired to make a tubular conductor the rods 3 are omitted from the workpiece. The dielectric material used is an isotropic and amorphous substance possessing plastic and flowing properties, e.g. gamma alumina or other crypto-crystalline material that does not chemically hydrate. |
