Brake disk 2 rotates about fixed axis A and is rigidly attached to drum b about which flexible link c is wound in hoisting load d. The brake disk engages round roller 1 which rolls along a fixed circular recess of the base with a working surface along circular arc a-a described from centre 0. The load is hoisted by rotating the disk and drum counterclockwise. Reverse rotation of disk 2 and the drum (and dropping of the load) is prevented by roller 1 which jams between the disk and arc a-a if angle γ has been properly chosen. A ball can be used in place of roller 1.
$3378$SmF,Br$