Guidance system for lateral move irrigation machines

Claim 1

In a lateral move irrigation machine having a plurality of mobile support units spaced apart in a substantially straight row, an elongate irrigation boom mounted on said support units at an elevated position above the field to be irrigated, a pair of gound engaging wheels on each support unit spaced apart on opposite sides of the boom and rotatable about axes of rotation located at the centers of the wheels, means for supplying water to said boom, a plurality of outlets spaced along the boom for applying water to the field, and drive means for each support unit for driving same through the field, an improved guidance system comprising: means defining a linear path extending along the field in a preselected direction which the boom is to follow with the boom extending substantially perpendicular to said path; a pair of elongate guide arms; means for coupling both guide arms with an intermediate support unit in a manner permitting the guide arms to pivot relative to said intermediate support unit about generally vertical pivot axes offset from the irrigation boom and spaced apart from one another on opposite sides of the boom at locations more distant from the boom than the axes of rotation of the respective wheels of the intermediate support unit, said guide arms projecting from said axes in opposite directions whereby one guide arm leads the boom during movement of same along the field in one direction and the other guide arm leads the boom during movement of same along the field in the opposite direction; a guide member carried on each guide arm, said guide members being restricted to movement along said path to thereby effect relative pivotal movement between said guide arms and said intermediate support unit upon deviation of said intermediate unit from said preselected direction; means responsive to relative pivotal movement between said one guide arm and said intermediate support unit for controlling the drive means of selected support units on opposite sides of said intermediate unit in a manner to prevent either end of the boom from moving ahead of or behind said intermediate unit when the boom is moving in said one direction; and means responsive to relative pivotal movement between said other guide arm and said intermediate support unit for controlling the drive means of said selected support units in a manner to prevent either end of the boom from moving ahead of or behind said intermediate unit when the boom is moving in said opposite direction, whereby the boom is maintained substantially perpendicular to said path as it is driven through the field.