Speed change mechanism for belt driven devices

Claim 1

IN A BELT DRIVEN DEVICE OF THE TYPE HAVING A STEPPED MOTOR PULLEY WITH A PLURALITY OF BELT GROOVES OF DIFFERENT DIAMETERS SPACED ALONG THE AXIS OF SAID PULLEY, A DRIVEN MEMBER, AND AN ENDLESS BELT EXTENDED OVER THE STEPPED MOTOR PULLEY AND DRIVEN MEMBER FOR DRIVING THE LATTER FROM THE MOTOR PULLEY AT A SPEED DETERMINED BY THE DIAMETER OF THE GROOVE IN WHICH THE BELT IS LOCATED, THE IMPROVEMENT COMPRISING SPEED CHANGE MECHANISM INCLUDING, IN COMBINATION, BELT LIFTER MEANS MOVABLE IN A DIRECTION GENERALLY PARALLEL TO SAID MOTOR PULLEY AXIS AND ENGAGEABLE WITH SAID BELT FOR SHIFTING THE SAME FROM ONE OF SAID BELT GROOVES TO ANOTHER, GUIDE MEANS ALONG WHICH SAID BELT LIFTER MEANS IS MOVABLE WHEN SHIFTING SAID BELT, AND MOVABLE CAM MEANS HAVING TWO CAM SURFACE PORTIONS IN ENGAGEMENT WITH SAID BELT LIFTER MEANS AT RESPECTIVE SPACED CONTACT AREAS TO MOVE SAID BELT LIFTER MEANS ALONG SAID GUIDE MEANS AND CONTROL THE ORIENTATION OF SAID BELT LIFTER MEANS, SAID TWO CAM SURFACE PORTIONS HAVING CONFIGURATIONS DIFFERENT FROM ONE ANOTHER TO PROVIDE TILTING OF SAID BELT LIFTER MEANS AS THE LATTER IS MOVED ALONG SAID GUIDE MEANS.