Detachable powered endless-tread unit for vehicles

Claim 1

IN COMBINATION WITH A VEHICLE CHASSIS, HAVING A PAIR OF FRONT STEERABLE WHEELS; AN OPERATING UNIT THEREFOR, COMPRISING: A FRAMEWORK UNDERLYING THE REAR PORTION OF SAID CHASSIS; SPRING MEANS BETWEEN EACH END OF SAID FRAMEWORK AND SAID CHASSIS FOR RESILIENTLY SUPPORTING SAID CHASSIS THEREFROM; A PAIR OF BALANCING BARS, EACH CENTRALLY AND PIVOTALLY MOUNTED ON ONE SIDE OF SAID FRAMEWORK; FOUR GROUND WHEELS, EACH ROTATABLY SUPPORTING ONE OF THE ENDS OF SAID BALANCING BARS; A PAIR OF FURTHER GROUND WHEELS ROTATABLY SUPPORTING SAID FRAMEWORK, ONE ON EACH SIDE THEREOF, AND IN SPACED TANDEM RELATION BEHIND SAID FIRST MENTIONED GROUND WHEELS; A PAIR OF ELEVATED IDLER WHEELS, EACH MOUNTED FOR ADJUSTABLE END-SLIDING MOVEMENT ON ONE OF THE FRONT CORNERS OF SAID FRAMEWORK; A PAIR OF SPROCKETS, EACH ROTATABLY MOUNTED ON A SIDE OF SAID FRAMEWORK, ADJACENT ONE OF THE REAR CORNERS THEREOF; SAID IDLER WHEELS AND SAID SPROCKETS IN ALIGNMENT WITH SAID GROUND WHEELS, ON EACH SIDE OF SAID FRAMEWORK; A MOVABLE TREAD ENCIRCLING SAID WHEELS AND SPROCKET ON EACH SIDE OF SAID FRAMEWORK; SAID TREADS EACH COMPRISING A PAIR OF SPACED ENDLESS BELTS WHICH STRADDLE THEIR RESPECTIVE WHEELS AND SPROCKET, WITH CROSS BARS CONNECTING SAID BELT-PAIRS AT SPACED INTERVALS THEREALONG TO FORM RACKS FOR MESHING WITH SAID SPROCKETS AND PROVIDE TRACKS FOR SAID GROUND WHEELS TO TRAVEL ON; MEANS FOR LOCKING SAID IDLER WHEELS IN TREAD-TIGHTENED POSITIONS ON SAID FRAMEWORK; AND MEANS ON SAID CHASSIS FOR DRIVING SAID SPROCKETS THROUGH A DIFFERENTIAL TRANSMISSION.