Drive tower for self-propelled irrigation system

A self-propelled irrigation system includes a drive tower configured to cross over a drainage ditch or other watercourse in an irrigated field without the use of a bridge or other support structure to support the load of the drive tower.

BACKGROUND

The present invention relates generally to agricultural irrigation systems and, more particularly, to an improved drive tower for self-propelled irrigation systems.

Self-propelled irrigation systems are commonly used for irrigation of agricultural lands. Self-propelled irrigation systems typically comprise an elongated pipeline supported by a plurality of spaced-apart drive towers. Sprinklers spaced along the irrigation pipeline spray water as the drive towers move the irrigation pipeline over the land. In center-pivot irrigation systems, the irrigation pipeline extends radially from a center pivot, and the drive towers move in a circle about the center pivot. In lateral move irrigation systems, the drive towers move in a straight line in a direction lateral to the irrigation pipeline.

The drive towers for self-propelled irrigation systems typically comprise a generally-triangular frame with an elongated base beam extending transverse to the irrigation pipeline. In the most common designs, wheels are disposed at opposite ends of the base beam. In some designs, additional wheels may be disposed between the ends of the base beam. To prevent the drive tower from tipping over or getting stuck, the path traveled by the drive tower needs to be relatively uniform.

On some farms, the fields being irrigated may be traversed by one or more drainage ditches, irrigation ditches, streams, or water courses. The ditches may be too wide for a traditional drive tower to cross. Consequently, bridges or culverts may need to be installed at points where the drive towers cross the ditches. In some installations, hundreds of bridges may be needed for irrigation of a single field. The cost of the bridges adds significantly to the cost of the irrigation system, which is an impediment to the adoption of self-propelled irrigation systems. Also, the bridges can interfere with tractors, other equipment, and drainage.

SUMMARY

The present invention relates to an improved drive tower for a self-propelled irrigation system having the ability to cross drainage ditches without the need for bridges. The drive tower comprises a frame with an elongated base beam extending in a direction transverse to the irrigation pipeline. The elongated beam is typically several times longer than the beams in conventional drive towers and is designed to cantilever over ditches as the drive tower crosses the ditches. A pair of outer wheels are disposed at opposing ends of the base beam. A pair of inner wheels are disposed in a center portion of the base beam between the outer wheels. Each outer wheel is spaced from the nearest inner wheel so that the outer wheel can make contact with the ground on one side of the drainage ditch while the nearest inner wheel remains in contact with the ground on the opposite side of the drainage ditch. In one exemplary embodiment, the distance between the outer wheels and the nearest inner wheel is greater than the distance between the inner wheels. For crossing large drainage ditches, the distance from the outer wheels to the nearest inner wheels is preferably more than twice the distance between the inner wheels, and in some embodiments may be more than 3 times the distance between the inner wheels.

When the drive tower crosses a ditch, the outer wheel on the leading end of the drive tower will initially cantilever over the ditch until the wheel contacts the ground on the opposite side of the ditch. While the leading wheel is cantilevered, the weight of the drive tower is supported by the other three wheels. As the drive tower continues to move forward, the inner wheels pass over the top of the ditch, while the outer wheels remain in contact with the ground on opposing sides of the ditch. When the inner wheels have reached the opposing side of the ditch, the outer wheel on the trailing end of the drive tower will then cantilever over the ditch with the weight of the drive tower supported by the other three wheels. Thus, the drive tower will always be supported by two or three wheels during the crossing. The spacing of the wheels and the weight distribution of the drive tower prevents the leading and/or trailing ends of the drive tower from tipping down into the ditch during the crossing.

DETAILED DESCRIPTION

Referring now to the drawings, a self-propelled irrigation system10according to one embodiment of the present invention is illustrated. While the illustrated embodiment is a center-pivot irrigation system, those skilled in the art would well appreciate that the present invention may also be applied to a lateral-move irrigation system or other type of self-propelled irrigation system.

FIG. 1illustrates the irrigation system10in a field12having a series of drainage ditches14that extend in parallel across the field12.FIG. 2illustrates in perspective the main functional components of the irrigation system10. The irrigation system10includes a center-pivot structure20, an irrigation pipeline30, and a series of drive towers40. The irrigation pipeline30extends radially-outward from the center pivot structure20and is supported at spaced-apart locations by the drive towers40. The drive towers40are self-propelled structures that move the irrigation pipeline30in a circular path around the center-pivot structure20as shown inFIG. 1.

FIG. 3illustrates an exemplary drive tower40according to one embodiment of the present invention. The drive tower40resembles a truss with wheels. The drive tower40includes a generally triangular frame42supported on wheels60,62. The frame42comprises a base beam44that extends transversely to the irrigation pipeline30. Frame members46extend upwardly at an angle from respective ends of the base beam44and meet at the top of the drive tower40. Struts48,50, and52interconnect the base beam44and the frame members46at various points to form a truss and to provide strength and rigidity to the frame42. Cross members54interconnect the frame members46to provide lateral stability. Other frame members (not shown) may be used as needed to provide strength and rigidity for crossing ditches as will be hereinafter described.

The drive tower40, as previously noted, is supported by wheels60,62that roll on the ground. More specifically, the drive tower40includes a pair of outer wheels disposed at opposing ends of the base beam44and a pair of inner wheels62that are disposed close to the center of the base beam44. As used herein, the term inner wheels refer to the wheels closest to the midpoint of the base beam44. Each of the wheels60,62mounts to a gear box64, which is connected by a drive shaft (not shown) to a drive motor66. As shown inFIG. 2, the wheels60,62may be mounted to follow a straight line parallel to the base beam44. However, in the case of the drive towers40closest to the center-pivot structure12, the wheels60,62and corresponding gear boxes64may be mounted at a slight angle to make it easier for the drive tower40to follow a tighter circle. Those skilled in the art will appreciate that the drive tower could include additional wheels (not shown) and is not limited to four wheels. For example, another pair of wheels could be placed between the outer wheels60and inner wheels62. Also, a wheel could be located at the center of the elongated base beam44.

According to the present invention, the drive tower40is configured to give the drive tower40the inherent ability to cross over drainage ditches14in an irrigated field12without the need for bridges spanning the drainage ditches14. Drainage ditches14in irrigated fields12are typically several feet deep and 8 feet or more in width. The drive tower40will not always cross the ditch14on a perpendicular path. As shown inFIG. 1, the drive tower40may cross some drainage ditches at a sharp angle (e.g. 60 degrees from perpendicular or more). Therefore, the drive towers40need to be able to cross a distance much greater than the width of the drainage ditch14. For example, when the drive tower40crosses a ditch at an angle of 60 degrees from perpendicular, the actual distance from one side of the ditch14at the angle of approach is twice the width of the ditch14. If the ditch14is 8 foot wide, the distance from one side to the other on the path followed by the drive tower14will be 16 feet.

The length of the base beam44and the spacing of the wheels60,62along the base beam44are important factors in designing a drive tower40with the ability to cross over drainage ditches14. The basic idea is to increase the length of the drive tower and increase the distance between each outer wheel and the nearest inner wheel62such that the outer wheel60and inner wheel62may contact the ground on opposing sides of the drainage ditch14. In one exemplary embodiment, the overall length L of the frame is several times greater than the height H. In a preferred embodiment, the length L of the frame42is at least 3 times the height H, and more preferably at least 3.5 times the height. The distance between the outer wheel60and nearest inner wheel is labeled D1inFIG. 3. The distance D1between outer and inner wheels60,62is preferably greater than the distance D2between the inner wheels. Typically, the distance D1is at least twice the distance D2and may exceed three times the distance D2. The distance D1is the maximum distance that the drive tower40can cross without a bridge. The length L of the frame42enables the drive tower40to cantilever over a drainage ditch and the ratio of the length L to the height H reduces the tendency of the drive tower40to tip down into the ditch.

The present invention enables deployment of self-propelled irrigation systems10in fields having drainage ditches of up to 19 feet in width or more. In one exemplary embodiment of the invention, the base beam of the drive tower40is approximately 45 feet in length and the distance D1between outer and inner wheels60,62is approximately 19 feet. The distance D2between the inner wheels62is approximately 7 feet. With these dimensions, the drive tower40is able to cross a drainage ditch approximately 9½ feet wide at an angle of up to approximately 60° from perpendicular. It will be appreciated by those skilled in the art that the ability to cross distances greater than the width of the ditch is necessary because the drive tower40may not always cross the drainage ditches14on a perpendicular path. For most practical applications, the drive tower40needs to span a distance up to twice the width of the drainage ditch14in order to cross the drainage ditch at angles of up to 60° from perpendicular.

FIGS. 4A-4Eillustrate how the drive tower40is able to cross over the drainage ditch14in an irrigated field.FIG. 4Aillustrates the drive tower40approaching a drainage ditch14. The arrow inFIG. 4Aillustrates the direction of travel. At this point, all four wheels60,62are on the ground on the near side of the drainage ditch14. InFIG. 4B, the drive tower40has moved forward so that the outer wheel60on the leading end of the drive tower40cantilevers over the drainage ditch14. It should be noted that, when the outer wheel60on the leading end of the drive tower40is cantilevered, the remaining three wheels60,62remain in contact with the ground on the near side of the drainage ditch14.FIG. 4Cshows the outer wheel60on the leading end of the drive tower40making contact with the ground on the far side of the drainage ditch14. The point to note here is that the inner wheel62on the leading side of the drive tower40is still in contact with the ground on the near side of the drainage ditch14.

In this example, it is presumed that the distance D2between the inner wheels62is less than the width of the drainage ditch14. Therefore, the two inner wheels62will be suspended over the drainage ditch as shown inFIG. 4Das the drive tower40continues to move forward. Finally, as shown inFIG. 4E, when the two inner wheels62make contact with the ground on the far side of the drainage ditch14, the outer wheel60on the trailing end of the drive tower40will cantilever over the drainage ditch14. During the crossing, at least two wheels60,62remain in contact with the ground at all times. The spacing of the wheels60,62and the weight distribution prevent the drive tower40from tipping into the ditch14, as would be the case with conventional drive towers.

The drive tower40according to the present invention significantly reduces cost of an irrigation system10by eliminating the need to install bridges at points where the drive tower40crosses over the drainage ditches14. Thus, the present invention should facilitate the deployment and use of irrigation systems in fields12with drainage ditches14or other water courses, which in turn, will result in greater yields.