MULTIPLE-BAR MECHANISM OF A DOUBLE BLOCK BRAKE

Symmetrically arranged angle levers 7 and 6 turn about fixed axes A and B. These levers are turned by levers 5 and 4 which are of the same length and are connected by turning pairs D to lever 1. When force P is applied to lever 1, turning about fixed axis C, motion is transmitted through levers 4, 5, 6 and 7 to shoes a and b mounted on levers 2 and 3. Shoes a and b are pressed with equal force against the rim of rotating pulley 8, thereby braking the pulley.
$874$LW,Br$