Patent ID: 8246010

Claim:
A hoist brake mechanism for a hoist including a hoist shaft rotationally mounted on a hoist frame to lift a load on a cable by rotation of the shaft in a lift direction or to lower said load in an opposite lowering direction of shaft rotation, said mechanism comprising: (a) an outer hub fixed to said hoist frame in surrounding relation to said shaft; (b) a main brake positioned within said outer hub and engaged between said outer hub and said shaft, said main brake including main brake members which retard rotation of said shaft upon axial engagement of said main brake members and which enable substantially free rotation of said shaft upon axial disengagement of said main brake members; (c) an actuator hub helically engaged with said outer hub in such a manner as to axially advance toward said main brake to cause said axial engagement of said main brake members upon rotation of said actuator hub in said lowering direction of said shaft and to axially retract from said main brake upon rotation of said actuator hub in said lift direction to cause axial disengagement of said main brake members; (d) a fluid shear actuator assembly engaged between said actuator hub and said shaft in such a manner that fluid shear caused by rotation of said shaft in said lowering direction urges said actuator hub to rotate in said lowering direction and fluid shear caused by rotation of said shaft in said lift direction urges said actuator hub to rotate in said lift direction; and (e) a liquid fluid positioned within said fluid shear actuator assembly and generating said fluid shear therein in response to rotation of said shaft.