US Patent 6962222 Mobile agricultural machinery

A mobile agricultural machine, particularly for use as a combine, which demonstrates improved operational movement and travel performance characteristics, and is capable of easily changing direction during operation, includes right and left travel crawlers, supported by drive sprockets and tension rollers, which are installed on right and left track frames through track rollers. Right and left travel frames are capable of being controllably elevated through crawler elevation arms. Tension rollers provide movement to the travel crawlers in a vertical direction, perpendicular to the ground.