Bar speed changing device

A bar speed changing device (48) comprising a pair of upper rollers (55, 55') and a pair of lower rollers (59, 59'). Said device receives a bar section with the rollers (55, 55', 59, 59') in the open position and rotating at a given speed. Upon leaving the device (48) said sections are fed into axially arranged peripheral seats (58) of rotating drum channels. Control devices calculate the speed at which the bar section must be released, upon completion of the braking action, according to the position that said section must occupy in one of said seats and on the basis of the bar-seat friction coefficient. When the rollers (55, 55', 59, 59') receive the bar, they turn at the calculated release speed. At a predefined moment, such to enable braking in the correct space and time, the four rollers close on the section and exert the braking action, exploiting the dynamic friction between the roller-section.