US Patent 7240860 Water distribution plate for rotating sprinklers

A rotor plate for a sprinkler includes a water impingement surface bounded by an annular peripheral wall and having a radial center, and adapted to be impinged upon by a stream emitted from a nozzle. The water impingement surface is formed to include at least one radially extending drive channel having an entrance proximate the radial center and an exit in the peripheral wall, the drive channel curving from entrance to exit in a first direction so as to cause the plate to rotate when the stream exits at an offset from the center of rotation; at least one range channel extending substantially radially with little or no curving, from entrance to exit; and at least one brake channel curving from entrance to exit in a second direction opposite the first direction to thereby resist rotation of the plate caused by at least one drive channel.