SELF-PROPELLED IRRIGATION APPARATUS The extension arm is moved by steerable wheels oper
ated by a reversible motor under the control of an elec
This invention relates generally to irrigation appara- tro-mechanical switching circuit which compares the tus, and, more particularly, to self-propelled irrigation angle of the main arm with the position of the steerable apparatus of the center pivot type. 5 wheels.
One popular manner of irrigating crops is through The invention is described in detail below with refersprinkler irrigation. Of the various types of sprinkler ence to the annexed drawings, wherein: apparatus, it has been found that the self-propelled, FIG. 1 is a diagrammatic illustration of the basic syscenter pivot irrigation apparatus is the most effective tern as disclosed in Application No. 306545; type for irrigating large sections of land economically 10 FIG. 2 shows diagrammatically the relative positions and in a uniform manner. Self-propelled irrigation ap- of the main arm assembly and extension arm for a repparatus of the center pivot type comprises an elongated resentative scan of one quadrant of a field; main arm assembly, usually including several sections FIG. 3 is a graph showing steering wheel position as connected at their ends, supported at intervals by self- a function of the angle of the main arm assembly; propelling wheeled support towers. The main arm as- 15 FIGS. 4A and 4B are front views of the main arm assembly supports, or may itself constitute, a fluid carry- sembly and extension arm assembly, according to Aping conduit and includes a large number of sprinklers plication No.;
or nozzles spaced along its length. One end of the as- FIG. 5 is a plan view of the main and extension arm sembly is pivotally coupled to a base and water sup- assemblies of Application No. 306545; plied to the conduit is discharged from the sprinklers as 20 FIG. 6 is a sectional view along the line 6—6 of FIG. the assembly rotates around the base, thereby uni- 5;
formly irrigating a section of land. FIG. 7 shows one of the encoding wheels used in the
One problem inherent in the use of such devices is embodiment disclosed in Application No. 306545; and that the irrigated section necessarily takes the form of FIGS. 8A and 8B show the preferred embodiment of a circle (with the arm as its radius). Thus, the use of 25 this invention.
center pivot type irrigation apparatus within a square The basic operation of the system is explained with section of land will result in a substantia] portion of the reference to FIG. 1. The main arm assembly, shown land (outside that circle) remaining un-irrigated. It has generally at 12, includes a plurality of separate sections been estimated that such systems fail to cover 21.4 per- 12A.12B.. .N, which are colineariy aligned. The extencent of the potentially agriculturally productive area of 30 sion arm is shown at 16 and, for example, may include a square field. two sections 16X and 16Y. The extension arm section
One method of attacking this problem has been to 16X is pivotally mounted at 17 to the outer or free exprovide fluid discharge means, such as a water gun at tremity of the main arm section 12N. the end of the arm assembly facing radially outwardly. Each of the main arm sections 12A,B. . .N is supWater is discharged through this gun when it faces the 35 ported on a respective support tower 18A,B. . .N, on un-irrigated portions of the land. Such systems have not which pairs of wheels 20A,B. . .N are mounted. The exproved to be entirely adequate, however, since only a tension arm sections 16X and 16Y are supported on relatively narrow additional arc of land can be irri- towers 22X and 22Y which contain respective pairs of gated, and, moreover, these water-guns expel large wheels 24 X and 24Y. The constructions of the support droplets of water which can cause damage to delicate 40 towers 18 and 22 are identical except that the wheels crops. 24X and 24Y are steerable. In practice, a single steer
U.S. Patent Application Ser. No. 306545, filed on ing motor shown diagrammatically at 26 may be used Nov. 15, 1972, in the names of David Seckler and to control the wheels 24Y with the wheels 24X being David Porat, and entitled "Irrigating Apparatus", dis- allowed to follow the wheels 24Y either passively or closes irrigating apparatus capable of irrigating sections 45 with a power assist.
of a field outside the circular area traversed by the Water is supplied to the main arm assembly 12 and main arm assembly of a center pivot irrigating appara- the extension arm assembly 16 both of which include tus. That invention avoids, or substantially minimizes, sprinkler devices to distribute the water over the length the drawbacks associated with known water-gun sys- ^ of these arms. The main arm assembly may, for examtems for accomplishing this objective, yet it is simple pie, be 1,200 feet in length and require anywhere from and relatively inexpensive. A particular advantage of 24 to 72 hours to rotate 360°.
that invention is that it may be readily incorporated Obviously, the main arm assembly 12, which may be into existing center pivot irrigation systems so that re- considered to be fixed in length, is only capable of covplacement of these costly systems is not required. 55 ering a circular area of the field. The extension arm as
The present invention is an improvement over the sembly 16, when pivoted about point 17, permits irrigabasic invention of Application No. 306545, in that it tion of a section of the field outside of this circular provides a control system for the extension arm assem- area. By controlling the position of the arm 16 with rebly which is simpler and more reliable in operation spect to the main arm 12 (represented by the angle /J), under the field conditions which the system is likely to 6Q it is possible to irrigate non-circular areas so that in encounter. many cases an entire field can be fully irrigated.
Briefly, in accordance with the invention, an exten- Conventionally, irrigating apparatus of the type dission arm is mounted at the free end of a main arm as- closed is self-propelled in the sense that each pair of sembly which rotates about a center pivot. The exten- wheels 20A, 20B . . .N, is driven by a motor (not shown sion arm carries sprinklers which irrigate areas outside 65 in FIG. 1), for example, a constant speed electric moof the circular area covered by the main arm assembly, tor. For purposes of explanation, the angular position and rotates with respect to the main arm assembly to of the main arm assembly 12 may be represented by the control the areas which it (the extension arm) covers. angle a (FIG. 1). !f it is desired to irrigate a square