Two identical conical pulleys I and 2 rotate about fixed axes A and B. Belt 6 runs over pulleys 1 and 2, and over two pairs of identical guide rollers 4 and 5 rotating about axes D and C of carriage 7 which can slide along fixed guides a-a. The belt is shifted by fork c, engaging pin b of carriage 7, when lever 3 is turned about fixed axis E. The transmission ratio between pulleys 1 and 2 depends upon the position of belt 6 on pulleys 1 and 2. These pulleys rotate in opposite directions.
$3514$SFL,BD$