Power transmission for self-propelled irrigation system

Claim 1

In a center pivot irrigation system including a plurality of articulated span units each rotating about a center pivot on drive wheels driven by a drive motor through a transmission, the improvement comprising: (a) the transmission comprising a series of individual planetary gear assemblies operationally mounted within a housing and interconnected in series to provide successive steps of torque increase and speed reduction between an input to and an output from the transmission, each of said planetary gear assemblies comprising planet gears of a self-lubricating thermoplastic material mounted on a planetary carrier with an associated sun gear, said planet gears of at least all said assemblies after the first of said series each comprising a plurality of gear segments rotatably mounted on a common shaft carried by said connector whereby the operational loading forces imposed on each of said segmented planet gears is equally proportionally distributed to each of said gear segments, said planet gears of each of said series of assemblies being comprised of a greater number of said segments than the next preceding of said assemblies of said series and all said segments being of substantially the same thickness whereby said planet gears of each of said series of assemblies are provided with an increased surface area as compared to the next preceding of said assemblies of said series; and, (b) means for absorbing misalignment stresses disposed between said input of the transmission and the first of said series of assemblies comprising: (1) a worm driven by said input of the transmission; and, (2) a helical gear driven by said worm and connected to drive the first of said series of assemblies.