Torque responsive automatic bicycle transmission with hold system

An automatic transmission for a cycle having a frame, front and rear wheels wherein one of said wheels is a driven wheel, axial means mounted on said frame for supporting said driven wheel in rotation about a first axis of rotation, a first sprocket mounted to said driven wheel for fixed rotation therewith, a chain wheel mounted to said frame and journalled for rotation about a second axis of rotation, and pedal means for driving said chain wheel in rotation, comprising;

• a transmission mounting bracket having first and second parallel shafts and means for mounting said bracket to said frame;
• a drive pulley and a driven pulley supported by said first and said second shafts respectively and mounted for free relative rotation with respect to said bracket;
• said drive pulley having a hub and a second sprocket drivingly connected to said drive pulley for fixed rotation therewith;
• said driven pulley having a hub and a third sprocket drivingly connected to said driven pulley for fixed rotation therewith;
• each of said pulleys including a plurality of arms having a first end pivotally mounted to the respective one of said hubs, and each of said arms having an annular drive surface portion opposite said first end, each said annular drive surface portion of each of said arms together constituting an annular drive surface for supporting an endless flexible transmission belt passed over said pulleys for transmitting torque from said drive pulley to said driven pulley, and each of said arms having axially opposite surfaces;
• means for varying the diameter of said drive pulley annular drive surface between an expanded position and a plurality of contracted positions including means for constantly biasing said drive pulley toward said expanded position by applying a predetermined biasing torque through said biasing means to each of said arms, and means for contracting said drive pulley to said plurality of contracted positions from said expanded position against said biasing means in response to a torque exceeding said predetermined torque applied to said drive pulley through said second sprocket and transmitted to said driven pulley through the belt;
• means for varying the diameter of said driven pulley annular drive surface between a contracted position and a plurality of expanded positions;
• means for expanding said driven pulley to said plurality of expanded positions in response to a decrease in diameter of said driven pulley;
• a first chain engaging said second sprocket and said chain wheel for transmitting said torque from said chain wheel to said drive pulley;
• a second chain engaging said third sprocket and said first sprocket for transmitting torque from said driven pulley to said driven wheel, whereby the speed ratio between said chain wheel and said driven wheel is automatically varied in response to a torque exceeding said predetermined torque applied to said chain wheel through said pedal means and transmitted to said driven pulley through said first chain;
• and
• said drive pulley having selectively actuatable hold means for holding said driven pulley in one of said contracted positions so that a selected speed ratio is maintained when a torque is applied to said chain wheel that is in excess of the torque applied to said drive pulley through said biasing means and when a torque is applied to said chain wheel that is less than the torque applied to said drive pulley through said biasing means.