Method and apparatus for continuously hot-stretching a steel cable

A method of hot-stretching a cable in which first, second and third capstans of different diameters, having a common rotating shaft, and having grooves on the circumferential surfaces thereof for winding said cable a plurality of turns are provided in parallel between a stranding machine and a winding machine and positioned adjacent to the stranding machine, first and second guide pulleys are provided in parallel and positioned adjacent to the winding machine, a front heat treatment equipment for heating said cable is provided between said first capstan and said second capstan, and a rear heat treatment equipment for heating said cable is provided between said second capstan and said third capstan, said method comprising the steps of

• winding said cable around said winding machine through said first capstan, said first guide pulley, said second capstan, said second guide pulley and said third capstan,
• increasing the operating speed of said stranding machine to a predetermined low speed after starting, and after the predetermined low speed is maintained for a predetermined period of time, gradually increasing the operating speed to a rated operating speed of said stranding machine, and
• selectively operating said front heat treatment equipment and said rear heat treatment equipment, while at the same time selectively subjecting a first part of said cable lying between said first capstan and said second capstan and a second part of said cable lying between said second capstan and said third capstan to a predetermined tension, until the operating speed of said stranding machine reaches said rated operating speed after starting so that the entire length of said stranded cable is continuously and effectively subjected to a hot-stretching treatment.