US Patent 7366443 Constant-velocity joint and image-forming device

A constant-velocity joint includes an outer ring formed with an annular space therein having an opening at one end thereof. The annular space is defined by a radially outer wall and a radially inner wall. One of the radially inner and outer walls is formed with three axially extending track grooves circumferentially spaced apart from each other by 120 degrees. A cage is inserted in the annular space with one end thereof protruding from the opening of the annular space. A second shaft is provided on the one end of the cage. Balls are retained by the cage and adapted to roll in the track grooves. At least one of the outer ring and the cage is formed of a synthetic resin.