Patent Publication Number: US-9402354-B2

Title: Drive tower for self-propelled irrigation system

Description:
RELATED APPLICATION 
     This application is a divisional of prior application Ser. No. 12/842,309 filed Jul. 23, 2010, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of a center-pivot irrigation system according to the present invention. 
         FIG. 2  is a perspective view of the center-pivot irrigation system according to one embodiment of the invention. 
         FIG. 3  is an elevation view of a drive tower for the center-pivot irrigation system according to one embodiment of the invention. 
         FIGS. 4A-4E  illustrate the drive tower crossing a drainage ditch in an irrigated field. 
         FIG. 5  is a schematic diagram of the drive train for the drive tower. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, a self-propelled irrigation system  10  according 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. 1  illustrates the irrigation system  10  in a field  12  having a series of drainage ditches  14  that extend in parallel across the field  12 .  FIG. 2  illustrates in perspective the main functional components of the irrigation system  10 . The irrigation system  10  includes a center-pivot structure  20 , an irrigation pipeline  30 , and a series of drive towers  40 . The irrigation pipeline  30  extends radially-outward from the center pivot structure  20  and is supported at spaced-apart locations by the drive towers  40 . The drive towers  40  are self-propelled structures that move the irrigation pipeline  30  in a circular path around the center-pivot structure  20  as shown in  FIG. 1 . 
       FIG. 3  illustrates an exemplary drive tower  40  according to one embodiment of the present invention. The drive tower  40  resembles a truss with wheels. The drive tower  40  includes a generally triangular frame  42  supported on wheels  60 ,  62 . The frame  42  comprises a base beam  44  that extends transversely to the irrigation pipeline  30 . Frame members  46  extend upwardly at an angle from respective ends of the base beam  44  and meet at the top of the drive tower  40 . Struts  48 ,  50 , and  52  interconnect the base beam  44  and the frame members  46  at various points to form a truss and to provide strength and rigidity to the frame  42 . Cross members  54  interconnect the frame members  46  to 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 tower  40 , as previously noted, is supported by wheels  60 ,  62  that roll on the ground. More specifically, the drive tower  40  includes a pair of outer wheels disposed at opposing ends of the base beam  44  and a pair of inner wheels  62  that are disposed close to the center of the base beam  44 . As used herein, the term inner wheels refer to the wheels closest to the midpoint of the base beam  44 . Each of the wheels  60 ,  62  mounts to a gear box  64 , which is connected by a drive shaft  65  to a drive motor  66  as shown in  FIG. 5 . As shown in  FIG. 2 , the wheels  60 ,  62  may be mounted to follow a straight line parallel to the base beam  44 . However, in the case of the drive towers  40  closest to the center-pivot structure  12 , the wheels  60 ,  62  and corresponding gear boxes  64  may be mounted at a slight angle to make it easier for the drive tower  40  to 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 wheels  60  and inner wheels  62 . Also, a wheel could be located at the center of the elongated base beam  44 . 
     According to the present invention, the drive tower  40  is configured to give the drive tower  40  the inherent ability to cross over drainage ditches  14  in an irrigated field  12  without the need for bridges spanning the drainage ditches  14 . Drainage ditches  14  in irrigated fields  12  are typically several feet deep and 8 feet or more in width. The drive tower  40  will not always cross the ditch  14  on a perpendicular path. As shown in  FIG. 1 , the drive tower  40  may cross some drainage ditches at a sharp angle (e.g. 60 degrees from perpendicular or more). Therefore, the drive towers  40  need to be able to cross a distance much greater than the width of the drainage ditch  14 . For example, when the drive tower  40  crosses a ditch at an angle of 60 degrees from perpendicular, the actual distance from one side of the ditch  14  at the angle of approach is twice the width of the ditch  14 . If the ditch  14  is 8 foot wide, the distance from one side to the other on the path followed by the drive tower  14  will be 16 feet. 
     The length of the base beam  44  and the spacing of the wheels  60 ,  62  along the base beam  44  are important factors in designing a drive tower  40  with the ability to cross over drainage ditches  14 . The basic idea is to increase the length of the drive tower and increase the distance between each outer wheel and the nearest inner wheel  62  such that the outer wheel  60  and inner wheel  62  may contact the ground on opposing sides of the drainage ditch  14 . 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 frame  42  is at least 3 times the height H, and more preferably at least 3.5 times the height. The distance between the outer wheel  60  and nearest inner wheel is labeled D 1  in  FIG. 3 . The distance D 1  between outer and inner wheels  60 ,  62  is preferably greater than the distance D 2  between the inner wheels. Typically, the distance D 1  is at least twice the distance D 2  and may exceed three times the distance D 2 . The distance D 1  is the maximum distance that the drive tower  40  can cross without a bridge. The length L of the frame  42  enables the drive tower  40  to cantilever over a drainage ditch and the ratio of the length L to the height H reduces the tendency of the drive tower  40  to tip down into the ditch. 
     The present invention enables deployment of self-propelled irrigation systems  10  in 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 tower  40  is approximately 45 feet in length and the distance D 1  between outer and inner wheels  60 ,  62  is approximately 19 feet. The distance D 2  between the inner wheels  62  is approximately 7 feet. With these dimensions, the drive tower  40  is 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 tower  40  may not always cross the drainage ditches  14  on a perpendicular path. For most practical applications, the drive tower  40  needs to span a distance up to twice the width of the drainage ditch  14  in order to cross the drainage ditch at angles of up to 60° from perpendicular. 
       FIGS. 4A-4E  illustrate how the drive tower  40  is able to cross over the drainage ditch  14  in an irrigated field.  FIG. 4A  illustrates the drive tower  40  approaching a drainage ditch  14 . The arrow in  FIG. 4A  illustrates the direction of travel. At this point, all four wheels  60 ,  62  are on the ground on the near side of the drainage ditch  14 . In  FIG. 4B , the drive tower  40  has moved forward so that the outer wheel  60  on the leading end of the drive tower  40  cantilevers over the drainage ditch  14 . It should be noted that, when the outer wheel  60  on the leading end of the drive tower  40  is cantilevered, the remaining three wheels  60 ,  62  remain in contact with the ground on the near side of the drainage ditch  14 .  FIG. 4C  shows the outer wheel  60  on the leading end of the drive tower  40  making contact with the ground on the far side of the drainage ditch  14 . The point to note here is that the inner wheel  62  on the leading side of the drive tower  40  is still in contact with the ground on the near side of the drainage ditch  14 . 
     In this example, it is presumed that the distance D 2  between the inner wheels  62  is less than the width of the drainage ditch  14 . Therefore, the two inner wheels  62  will be suspended over the drainage ditch as shown in  FIG. 4D  as the drive tower  40  continues to move forward. Finally, as shown in  FIG. 4E , when the two inner wheels  62  make contact with the ground on the far side of the drainage ditch  14 , the outer wheel  60  on the trailing end of the drive tower  40  will cantilever over the drainage ditch  14 . During the crossing, at least two wheels  60 ,  62  remain in contact with the ground at all times. The spacing of the wheels  60 ,  62  and the weight distribution prevent the drive tower  40  from tipping into the ditch  14 , as would be the case with conventional drive towers. 
     The drive tower  40  according to the present invention significantly reduces cost of an irrigation system  10  by eliminating the need to install bridges at points where the drive tower  40  crosses over the drainage ditches  14 . Thus, the present invention should facilitate the deployment and use of irrigation systems in fields  12  with drainage ditches  14  or other water courses, which in turn, will result in greater yields.