Pulleys 1 and 6 rotate about fixed axes A and B. Flexible link 2 runs over pulleys 1 and 6. Lever 5 turns about fixed axis C and carries idler pulley 3 which is held in constant contact with flexible link 2. Weight 4 can be adjusted along axis D of lever 5 and clamped in the required position to obtain the necessary tension of link 2.
$3486$SFL,4L$