Constant length chain adjustable roller drive

Claim 1

A MECHANICAL SYSTEM OF THE TYPE DESCRIBED, COMPRISING A FRAME INCLUDING A STATIONARY FIRST SUPPORT AND A MOVABLE SECOND SUPPORT, MEANS FOR ADJUSTING THE ELEVATION OF THE SECOND SUPPORT WITH RESPECT TO THE FIRST SUPPORT IN SAID FRAME, FIRST AND SECOND SPACED SPROCKET MEMBERS ROTATABLY CARRIED BY THE FIRST SUPPORT, A FIRST ROLLER ROTATABLY CARRIED BY THE FIRST SUPPORT, SAID ROLLER BEING OPERATIVELY CONNECTED TO AND DRIVEN BY SAID FIRST SPROCKET MEMBER, MOTOR MEANS FOR DRIVING EITHER ONE OF SAID SPROCKET MEMBERS, A THIRD SPROCKET MEMBER ROTATABLY CARRIED BY THE MOVABLE SECOND SUPPORT AND DISPOSED NEAR THE FIRST SPROCKET MEMBER, A SECOND ROLLER ROTATABLY CARRIED BY THE SECOND SUPPORT, THE FIRST AND SECOND ROLLERS BEING DISPOSED AXIALLY PARALLEL TO EACH OTHER AND SPACED A VARIABLE LATERAL DISTANCE APART AS THE SECOND SUPPORT IS MOVED WITH RESPECT TO THE FIRST SUPPORT, A FOURTH SPROCKET MEMBER ROTATABLY CARRIED BY THE SECOND SUPPORT AND SPACED FROM THE OTHER THREE SPROCKET MEMBERS, AND AN ENDLESS CHAIN MEMBER HAVING FOUR LOOPS RESPECTIVELY ENTRAINED AROUND THE FOUR SPROCKET MEMBERS IN A REENTRANT CONFIGURATION WITH ONE SIDE OF THE CHAIN MEMBER FACING AND ENGAGED ON ONLY THE FIRST SPROCKET MEMBER AT ONE OF THE LOOPS, AND WITH AN OPPOSITE SIDE FACING AND ENGAGED ON THE OTHER THREE SPROCKET MEMBERS AT THE OTHER THREE LOOPS, WHEREBY MOVEMENT OF SAID SECOND SUPPORT WITH RESPECT TO THE FIRST SUPPORT SIMULTANEOUSLY MOVES THE THIRD AND FOURTH SPROCKET MEMBERS AND THE SECOND ROLLER TO CHANGE THE LATERAL SPACING OF THE SECOND ROLLER FROM THE FIRST ROLLER, WHILE THE OVERALL LENGTH OF THE CHAIN MEMBER REMAINS SUBSTANTIALLY UNCHANGED AT THE RELATIVE SPEED OF SURFACE TRAVEL OF THE FIRST AND SECOND ROLLERS REMAINS SUBSTANTIALLY CONSTANT.