Bicycle hub unit with bearing-receivers for mounting a cylinder drive in a hub shell thereof

A bicycle hub unit including:

• a hub shell having an axial bore with a first axial end portion and a second axial end portion opposite to said first axial end portion;
• a first bearing mounted in said first axial end portion;
• a cylinder drive having an externally threaded end portion, a head portion which is spacedly axially from said threaded end portion, and a plurality of ratchet pawls mounted on an outer circumferential surface between said head portion and said threaded end portion, said head portion of said cylinder drive being secured partially in said second axial end portion of said axial bore, said ratchet pawls and said threaded end portion being disposed exteriorly from said second axial end portion, a sprocket carrier supported around an enlarged portion of said head portion, said ratchet pawls and said threaded end portion and engaging said ratchet pawls for rotation in only one direction;
• and a second bearing disposed within said sprocket carrier;
• wherein the improvement comprises:
• said axial bore of said hub shell being defined by an internal wall which is divided into a first section adjacent to said first axial end portion, and a second section adjacent to said second axial end portion and narrower than said first section, thereby forming an annular shoulder between said first and second sections;
• a first bearing-receiver disposed in said first axial end portion of said axial bore and having an enlarged head receiving said first bearing therein and an internally threaded connecting tube extending into said first section of said axial bore;
• a second bearing-receiver disposed in said sprocket carrier, said second bearing-receiver receiving said second bearing therein and having an internally threaded portion engaging said externally threaded end portion of said cylinder drive;
• and
• said head portion of said cylinder drive further having an externally threaded and axially extending tube extension projecting into said first section of said axial bore and engaging said internally threaded connecting tube of said first bearing-receiver, thereby securing said cylinder drive on said hub shell.