Brevet US3797517 - SELF-PROPELLED IRRIGATION APPARATUS

PATENTEOHAR191974 3,797,517

SHEET k OF 6

FIG. 7

PATENTED WAR 191974 3J97',517

SHEET 6 OF 6

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1 2

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

field, j3 should vary from 90° (at a = 0°) to its maximum when a = 45° and back to 90° when a = 90°. This pattern repeats for each of the successive quadrants in the case of a square field. For purposes of mechanical stability, it is generally desirable that the maximum value 5 of j8 be less than 180°, for example, 140°.

As noted previously, the main extension arm consists of a series of sections 12A,B. . .N, which are joined at flexible joints. In prior art constructions, where there is no extension, the driving motor for the outermost sup- 10 port tower 18N is driven continuously. A microswitch is placed at the joint between the outermost section 12N and the next adjacent section. When the microswitch is actuated because of stress at the joint caused by movement of the outermost section 12N, the motor 15 for this next section is actuated.

Similarly, movement of the second section actuates a microswitch at the junction of the second and third sections to operate the driving motor for the third section, and so forth for each of the remaining sections. ^° Each of the motors drives its associated support wheels at the same rate of speed and, consequently, since the outermost section 12N travels at the highest rate of speed, the inner sections would be operated intermit- 25 tently with the innermost section operating over the shortest periods. The system is relatively simple and inexpensive since constantspeed motors, all of which are the same, can be used and special gear reduction units are not required for the individual sections. 30

According to the preferred embodiments of the invention, the system is controlled by movement of the extension arm rather than the outermost section of the main arm. The drive motor for tower 18N is not continuously operated, but instead, is controlled by a stress 35 switch shown diagrammatically at 29 in FIG. 1.

A position angle encoder 30 is located at the base 10 for the main extension arm 12. The encoder 30 may be an analog to-digital device which coverts the angle a to a five-bit digital signal. A similar position angle encoder 40 31 is physically located at the support tower 22Y for the steering wheels 24Y, and also produces a five-bit digital signal representing the position angle of the steering wheels of the extension arm with respect to an arbitrarily selected reference angle (e.g. perpendicular 45 to arm 16).

The two digital signals from the encoders 3® and 31 are coupled to an electrical comparator 32 which produces an electrical control signal when the two digital signals are not equal (or have any other preselected re- 50 lationship). This electrical signal is coupled to the steering motor 26 which causes the wheels 24Y (and 24X) to turn until the encoded digital output representing the steering wheel position is equal (or otherwise corresponds) to the output from the main arm position 55 angle encoder 30. At this position, the steering motor 26 is deactivated and the extension arm continues to rotate with the steering wheels in a fixed position.

As the extension arm 16 rotates, a position is reached where the stress on the main extension arm section 12N causes the stress switch 29 to be actuated. When switch 29 is actuated, it energizes the driving motor for the wheels on the main section 12N which then causes this section of the main extension arm to start moving. In 65 a similar way, as described in the foregoing, the movement of this outer main section successively operates the drive motors associated with the remaining interior

sections so that the main extension arm sweeps across the field.

In this particular system, it is necessary to determine the direction in which the steering wheels must be aligned for each discreet position of the main arm assembly. This can be done mathematically if the lengths of the respective assemblies and their relative velocities are known. The direction of the extension arm steering wheels 24Y for each discreet position (a) of the main arm is in the same direction as the velocity vector required for the outer point of the extension arm 16 relative to the base 10. Hence, this velocity vector is computed for each discreet main arm position and then the encoder wheels (which produce a different digital signal for each main arm position) are properly positioned so as to cause the required control of the steering wheels. By way of example, FIG. 3 shows a workable relationship between the position angle a of the main arm and the steering wheel position angle <p as indicated in FIG. 2.

It may appear from FIG. 3 that unusually abrupt changes in steering wheel position are required between a = 40° and a = 60° in view of the movement of the main arm assembly; however, the linear velocity of the outer section of the main arm 12 is very low, for example, in the order of 300 feet per hour. Therefore, for all intents and purposes, the turning of the steering wheels 22Y may be considered to be instantaneous in the sense that the steering wheels are positioned very quickly with respect to the linear velocity of the assembly.

FIGS. 4A, 4B, 5 and 6, show certain mechanical features of a system incorporating the basic invention. The parts illustrated in these figures have been numbered to correspond with FIG. 1. Inasmuch as the construction of the main arm assembly is known, an extended discussion of the physical structure of the system is not included.

Sections 12A.12B. . .N of the main arm assembly are shown as consisting of hollow conduits through which water is applied to sprinklers 40 spaced along the individual sections. (Alternatively, a separate conduit for the water may be supported in conventional fashion onthese sections.) Drive motors 42A, 42B. . ,N are mounted on respective support towers 18A,18B.. .N to drive the wheels 20A,20B. . .N which rotate the main arm assembly. As mentioned above, the manner in which these motors are controlled is standard, except that operation of motor 42N is determined by the stress of the section 12N caused by rotation of the extension arm 16.

The outermost main arm section 12N may be coupled to the inner extension arm section 16A by a flexible hose 43 which will permit the required pivoting of extension arm 16 while supplying water to the extension arm sprinklers 44. Support tower 22X for the extension arm section 16X may include a plate 45 in which a pin 46 extending downwardly from section 12N is suitably journaled. Obviously, numerous other satisfactory arrangements can be used to provide the required pivotable movement between these two parts.

The steering arrangement for the steering wheels 24B is shown most clearly in FIGS. 5 and 6. The steering motor 26 is physically supported on support tower 22Y above the wheels. Motor 26 is a constant speed electrical motor which is turned on and off upon receipt of signals from comparator 34, as described above with

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SELF-PROPELLED IRRIGATION APPARATUS