Patent ID: 7878429

Claim:
In an irrigation system having a liquid conduit that spans mobile towers, each of the mobile towers including at least one ground-engaging wheel, the improvement comprising: a solar panel having a collecting surface, said solar panel operable to collect light energy from the sun and convert the light energy into electrical energy; an electrical charge source in electrical communication with the solar panel, said electrical charge source receiving the electrical energy from the solar panel; a motor in electrical communication with the electrical charge source, said motor receiving the electrical energy from the electrical charge source, said motor driving the ground-engaging wheel, said irrigation system comprising a center pivot system, wherein the liquid conduit extends radially outwardly from a central pivot; a rotation assembly, said solar panel being attached to the rotation assembly, said rotation assembly being rotatable about a vertical axis, such that the collecting surface of the solar panel can turn to face the sun as the irrigation system rotates about the pivot; and a direction control system, the relative angular position of said rotation assembly being controlled by the direction control system, said rotation assembly comprising a platform raised above the top of the liquid conduit by supporting members and a rotating element coupled to the platform for relative rotation therewith, said rotating element including an arcuate periphery, said direction control system comprising a fixed element with an arcuate periphery on the central pivot and an endless member wrapped around the periphery of the fixed element and also around the periphery of the rotating element of the rotation assembly, said endless member interconnecting the fixed element and the rotating element such that as the irrigation machine rotates about the central pivot, the endless member causes the rotation assembly to rotate relative to the mobile tower such that the facing direction of the collecting surface of the solar panel remains constant.