Apparatus for forming a metallic tape into a tube having an overlapped seam

摘要

The invention relates to the formation of a substantially circular metallic shield (37) about a cable core (32) by wrapping a metallic tape (64) longitudinally about the core with longitudinal edge portions of the tape being overlapped by a forming key (100) to provide a closed seam (38). As the seam is formed, an underlying longitudinal edge portion (48) of the shield is supported while an overlying longitudinal edge portion (45) at the overlap is directed inwardly toward the cable core to preclude its protrusion into a jacket (39) which is subsequently extruded over the shielded cable core. A relatively thin strip (145) of metal attached to an inner surface of the forming key assures formation of the seam before juxtaposing the longitudinal edge portions and the core, and avoids penetration of a priorly formed inner shield by the longitudinal edge of the outer shield to prevent rotation of the inner shield and undesirable alignment of the shield seams. The formation of cable shields in accordance with this invention and the subsequent extrusion of a plastic jacket thereover results in a cable having a substantially monolithic sheath which minimizes slippage of elements of the sheath relative to one another during field cable pulling operations.