Abstract: A joint device enables to join a brace member, into which regulated pretension is exactly introduced, to unmovable connector nodes, comprising a steel rod 1 having a swelled portion 1A and a threaded connector portion 1B formed on the end thereof, respectively, one sleeve 3 providing an external threaded part 3A joined to one node 2M, which contacts a swelled portion 1A: and another sleeve 4 providing an external threaded part 4A joined to node 2N, which engages threaded connector portion 1B. The length from a node-contact face 3c of sleeve 3 to a node-contact face 4c of sleeve 4 is selected equal to difference of length between both nodes 2, 2 from length for generating a preferable elongation enough to introduce regulated pretension into steel rod 1.

Abstract: An apparatus for manufacturing a core wire for use in laying optical fibers over a long distance produces a plurality of continuous corrugated deep grooves in a wire that are capable of holding therein the optical fibers longitudinally along the peripheral surface of the wire. An endless raw wire material of circular cross section is formed by the apparatus into a wire of square cross section through plastic processing and thereafter the wire is formed into a core wire of a flower patterned cross section with a plurality of petals having corrugated deep grooves in the periphery thereof continuously longitudinally thereof through a rolling device. In addition, the core wire so constructed is formed into a core wire with spiral corrugated deep grooves formed in the peripheral surface thereof. The rolling means has forming rolls equal in number to the number of ridges of the square wire, and each such roll having two perfect corrugated convex portions formed widthwise on the peripheral surface thereof.