PURPOSE: To promote the easiness in a device adjusting its braking force and setting its rotary speed by constituting the device of a brake shoe resiliently supported in the diametric direction of a shaft, brake ring enveloping this brake shoe with the same tapered surface to the brake shoe being locked in the peripheral direction of a fixed outer cylinder and screw thread adjusting the axial direction of the brake ring.

CONSTITUTION: Supporting a tapered flange 3 to a shaft 1 through a key 2 and providing four blade plates in a rotary inner cylinder 4 fixed to this tapered flange 3, a brake shoe 5 with its periphery in a tapered surface is mounted through a leaf spring 6. While a brake ring 9, which surrounds the brake shoe 5 having an internal peripheral surface 9a with the same tapered surface to the brake shoe, is slidably supported into a fixed outer cylinder 7 through a key 10. Further an adjusting screw thread 11, screwed to the brake ring 9, is provided in an end plate of the fixed outer cylinder 7. Accordingly, in the time of initialization setting, the brake shoe, when it is worn, can be easily and promptly adjusted in its braking force and set in its operating rotary speed.