Watertight disc coaxial cables

A watertight disc coaxial cable including in combination a center conductor having a circumferential surface, dielectric spacer discs firmly secured to the center conductor at spaced loactions along the length of said conductor and each having a substantially cylindrical circumferential surface and a tubular outer conductor surrounding the discs and exerting radial pressure on the circumferential surfaces of the discs, said discs being of progressively greater axial thickness as they extend from their circumferences toward the inner conductor and being imperforate between the inner and outer conductors and adhered to the inner and outer conductors so as to divide the interior of the coaxial cable into watertight compartments, the center conductor being of less diameter around its entire circumference, where it passes through each disc, than it is along the length of said inner conductor between the discs, the lesser diameter being progressively deeper as the inner conductor extends further into the portions of each disc that are of progressively greater axial thickness, and the outer conductor being of uniform diameter at the circumference of the discs and between said discs.

A coaxial cable including in combination a center conductor, a tubular outer conductor, discs of dielectric material on the center conductor and extending outward therefrom to maintain the center conductor spaced from the outer conductor and coaxial therewith, the discs being spaced form one another lengthwise of the cable and enclosing air chambers between them, the cross-section of the inner conductor having grooves that reduce the cross-section of the inner conductor at the discs to less than that of the inner conductor in the spaces between the successive discs, the grooves being of an axial length substantially equal to the axial width of the disc structure and of progressively less radial depth toward the ends thereof, the discs fitting snugly around and filling the grooves of the center conductor and held thereby against axial movement along the length of the center conductor, and the grooves extending circumferentially around the inner conductor so as to maintain the impedance uniform around the circumference of the center conductor.

A watertight disc coaxial cable including in combination a center conductor having a circumferential surface, a continuous coating of other material that surrounds and hugs the circumferential surface of the center conductor for improving the bonding of spacer discs to the center conductor structure, dielectric spacer discs firmly secured to the center conductor at spaced locations along the length of said conductor, and by the intervening coating of said other material, and a tubular outer conductor surrounding the discs and exerting radial pressure on the discs, said discs being imperforate and adhered to the inner and outer conductors so as to divide the interior of the coaxial cable into watertight compartments, and characterized by the continuous coating that hugs the center conductor being made of regular polyethylene and extending continuously lengthwise along the center conductor and through successive discs of the cable, and the discs being made of adhesive polyethylene having a dissipation factor higher than that of the regular polyethylene.

The method of making a coaxial cable having a center conductor held coaxial with an outer tubular conductor by dielectric discs carried at spaced locations along the length of the inner conductor, characterized by pre-treating the inner conductor in a chromate bath to reduce a copper surface of the inner conductor and apply a conversion coating of a chromate salt layer on the surface of the inner conductor to more securely bond polyolefin discs to the inner conductor, applying non-adhesive dielectric spacer discs to the inner conductor at spaced locations therealong, forming the outer tubular conductor as an oversize outer tube around the outside of the discs, swedging the tube to a smaller diameter that causes the outside tube to grip tightly the circumferences of the discs and to put them under substantial radial compression.

The method of making a coaxial cable having a center conductor held coaxial with an outer tubular conductor by dielectric discs carried at spaced locations along the length of the inner conductor, applying a coating to the inner conductor to provide stronger adhesion of spaced discs to the inner conductor, applying non-adhesive dielectric spacer discs to the inner conductor at spaced locations therealong, forming an oversize outer tube around the outside of the discs, swedging the tube to a smaller diameter that causes the outside tube to grip tightly the circumferences of the discs and to put them under substantial radial compression, characterized by stretching the inner conductor to reduce the diameter of the inner conductor where it passes through the successive discs and while the discs are in subtantially molten condition and maintaining the inner conductor at high temperature where it passes through the discs to localize the stretching of the inner conductor to the regions in the discs, forming the respective discs with inner diameters that fit snugly around the reduced diameter portions of the inner conductor to hold the discs against axial movement along the inner conductor by the fuller diameter portions of the inner conductor between the discs.