Patent ID: 8393985

Claim:
Variable-speed drive unit, comprising: a first pulley and a second pulley ( 1 , 11 ), each of the two pulleys mounted on a corresponding pulley-support shaft ( 2 , 12 ), each of the two pulleys ( 1 , 11 ) comprising a pair of variably-spaced flanges ( 4 , 5 ; 14 , 15 ); and at least one transmission belt ( 9 ) between the two pulleys ( 1 , 11 ), the two pulleys further comprising a first loading device and a second loading device respectively equipping a first flange ( 4 , 14 ) of each pair of flanges, each of the first and second loading devices tending to exert, in a permanent manner and in the active state of the transmission, an axial effort in the direction causing the flanges ( 4 , 5 ; 14 , 15 ) to move inwardly to clamp the belt ( 9 ) between said flanges ( 4 , 5 ; 14 , 15 ), wherein the first loading device exerts a lesser axial effort than an axial force exerted by the second loading device; and one of the two pulleys also comprises a manual control element ( 19 ) for, independently of the corresponding loading device, drawing together or separating the flanges of the one pulley by exerting, on the first flange of the one pulley, a slight control effort corresponding essentially to a power difference of the first and second loading devices.