Hub brake for bicycles

A hub brake for bicycles comprising:

• a cylindrical hub in which is fitted a screw rod extending therethrough, said hub being formed at an end with a conical recess;
• driving means including a driving screw, a bearing, an adjusting nut and an arm, said driving screw being a tubular member provided with a threaded portion at a first end and a plurality of notches at a second end, said arm being formed at an end with an opening having a plurality of internal teeth and at another end with a hole adapted to connect with a cable, said arm being connected to said second end of said driving screw with said teeth engaged with said notches, said adjusting nut being fitted within said hole and having a longitudinal internal threaded hole and a flange at an intermediate portion thereof, said bearing being fitted over an end of said adjusting nut and bearing against said flange;
• recovering means including a torsion spring, a helical spring and a nut, said torsion spring being provided with a hook portion at both ends thereof bearing against said arm, said helical spring being fitted over said screw rod and disposed within said conical recess, said nut being engaged with said screw rod to prevent said helical spring from detaching from said screw rod;
• braking means including a brake block and a positioning plate, said brake block being slidably mounted within said positioning plate, said brake block being in the shape of a frustum shaped cone adapted to be fitted into said conical recess and having a longitudinal threaded hole engageable with said threaded portion;
• and
• a cover fixedly mounted on said positioning plate and having a center hole for passage of said screw rod.