Abstract:
Wheels adapted to roll on and across surfaces of fields, for example, as part of irrigation systems of types used in agricultural applications. Such a wheel has an axis of rotation, a center portion comprising a central hub concentrically disposed on the axis of the wheel and multiple spokes radiating from the central hub, and a tread portion circumscribing the center portion. A radially outermost extent of each spoke terminates at a spade that is oriented parallel to the axis of the wheel. The tread portion includes tread plates, each located between and attached to adjacent pairs of the spokes. The spades protrude radially outward between and beyond adjacent pairs of the tread plates.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Patent Application Ser. No. 62/297,263, filed Feb. 19, 2016, the contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention generally relates to wheels configured for propelling objects and structures on the ground, and particularly to wheels suitable for propelling or supporting irrigations systems and other equipment traveling across agricultural fields. 
         [0003]      FIG. 1  schematically represents a nonlimiting example of a portion of a center-pivot irrigation system  10  of a type used in agricultural applications. In  FIG. 1 , structural members of the system  10  can be seen to be equipped with wheels  12  that support the system  10  as it moves across the ground of a field. The wheels  12  are represented as inflated tires, which are prone to puncture hazards in their path. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    The present invention provides wheels adapted to roll on and across surfaces of fields, for example, as part of irrigation systems of types used in agricultural applications. The wheels are suitable for use as replacements for conventional wheels and pneumatic tires commonly used in agricultural irrigation systems. 
         [0005]    According to one aspect of the invention, the wheel has an axis of rotation, a center portion comprising a central hub concentrically disposed on the axis of the wheel and multiple spokes radiating from the central hub, and a tread portion circumscribing the center portion. A radially outermost extent of each spoke terminates at a spade that is oriented parallel to the axis of the wheel. The tread portion includes tread plates each having a tread surface region. Each tread plate is between and attached to adjacent pairs of the spokes, and the spades of the center portion protrude radially outward beyond adjacent pairs of the tread plates. 
         [0006]    According to another aspect of the invention, a method of fabricating a wheel includes providing a one-piece flat pattern having a hub portion from which radiating arms emanate relative to an axis of the flat pattern located within the hub portion. Each radiating arm is twisted to form one spoke of a center portion of the wheel and an outer radial end of the arm forms a spade of the spoke. Tread plates are then individually attached between adjacent pairs of the spades. 
         [0007]    A technical effect of the wheel is that it is not required to be inflated, and therefore is not prone to puncture hazards in its path. The wheel is also not required to be formed of rubber or another pliable material that can be prone to degradation by the weather, for example, as a result of being damaged by ultraviolet rays of the sun. In addition, the wheel does not require moving parts, and can be assembled without the need to interconnect a large number of parts. 
         [0008]    Other aspects and advantages of this invention will be better appreciated from the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  schematically represents a portion of a center-pivot irrigation system of a type used in agricultural applications. 
           [0010]      FIGS. 2, 3 and 4  represent perspective, top and side views of a wheel in accordance with a nonlimiting embodiment of this invention. 
           [0011]      FIG. 5  is a plan view of a flat pattern suitable for fabricating a wheel center portion of the wheel shown in  FIGS. 2, 3 and 4 . 
           [0012]      FIGS. 6, 7 and 8  represent perspective, top and side views of a wheel in accordance with another nonlimiting embodiment of this invention. 
           [0013]      FIG. 9  shows a profile view of a tread plate of the wheel shown in  FIGS. 6, 7, and 8 . 
           [0014]      FIG. 10  shows a profile view of an alternative tread plate for the wheels shown in  FIGS. 1 through 3 and 5 through 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]      FIGS. 2 through 4 and 6 through 8  represent various views of wheels  20  and  60  suitable for propelling an object or structure across a surface. The wheels  20  and  60  are particularly well suited for propelling an irrigation system across the surface of an agricultural field. Although the invention will be described hereinafter in reference to irrigation systems such as that shown in  FIG. 1 , it will be appreciated that the teachings of the invention are more generally applicable to a variety of applications in which a rugged wheel would be beneficial for transporting a structure across uneven ground typically encountered in an agricultural field. 
         [0016]    To facilitate the description provided below of the embodiments represented in the drawings, relative terms may be used to describe the wheels  20  and  60  and their components, On the basis of coaxial arrangements of certain components of the wheels  20  and  60 , relative terms including but not limited to “axial,” “circumferential,” “radial,” etc., and related forms thereof may also be used to describe the nonlimiting embodiments represented in the drawings. All such relative terms are intended to indicate the construction and relative orientations of components and features of the wheels  20  and  60 , and therefore are intended to indicate the construction, installation and use of the invention and therefore help to define the scope of the invention. 
         [0017]    The wheel  20  depicted in  FIGS. 2 through 4  has an axis  22  of rotation and is rotationally symmetrical about its axis  22 . The wheel  20  has a wheel center portion  24  circumscribed by a tread portion  26 . The center portion  24  comprises multiple spokes  28  radiating from a central hub  30  that is concentrically disposed on the axis  22  of the wheel  20 . The hub  30  is preferably formed to define a central hub opening surrounded by a pattern of holes by which the wheel  20  can be mounted to a section of an irrigation system or other appropriate structure. Each spoke  28  has an approximately ninety-degree twist as a result of its radially innermost extent  31  lying in the plane of the center portion  24  and hub  30  so as to be approximately perpendicular to the axis  22  of the wheel  20 , and its radially outermost extent  32  terminating at a spade  34  (or blade) that is oriented approximately parallel to the wheel axis  22 . With this orientation, the spades  34  have axial widths in the axial direction of the wheel  20 . The hub  30  can be reinforced with a plate as seen in  FIGS. 2 and 4 . 
         [0018]    The tread portion  26  generally defines a cylindrical shape whose axis coincides with the axis  22  of the wheel  20 . As represented in  FIGS. 2 through 4 , the tread portion  26  is constructed of multiple individual tread plates  36 , each attached between an adjacent pair of spades  34  of the spokes  28 . Each tread plate  36  has a width in the axial direction of the wheel  20  and a length in the circumferential direction of the wheel  20 . Each tread plate  36  further defines along its length a radius of curvature having a center of curvature that approximately coincides with the axis  22  of the wheel  20 , resulting in the tread plates  36  defining, in combination, the generally cylindrical shape of the tread portion  26 . The radially outermost extents  32  of the spades  34  radially protrude from the circular shape of the tread portion  26  and generally lie on a circle that is substantially concentric with the cylindrical shape of the tread portion  26  as a result of having a center of curvature that coincides with the axis  22  of the wheel  20 . In the embodiment shown in the Figures, the axial widths of the spades  34  preferably exceed the widths of the tread plates  36  on each axial side of the wheel  20 . 
         [0019]    Each tread plate  36  has a pair of rims or lips  38  projecting radially outward, preferably along the entire length of the plate  36 . Each lip  38  is located along one of the lateral edges of the plate  36  that delimits the width of the plate  36 , and is oriented generally perpendicular to the spades  34  to which the plate  36  is attached. With the spades  34  located at each circumferential end of a tread plate  36 , the lips  38  located along the lateral edges of the plates  36  define a tread surface region  40  surrounded by a substantially continuous wall formed by the spades  34  and lips  38 . The tread surface region  40  is recessed below the continuous wall, and therefore are preferably capable of partially containing soil contacted by the tread plates  36  as the wheel  20  rotates and traverses the soil. As a result, soil traversed by the wheel  20  after being wetted by an irrigation system will remain at least partially contained within the wheel track (rut) created by the continual traversing of the wheel  20  over the same path. 
         [0020]    The tread plates  36  are preferably formed to include an embossed pattern  42  that protrudes radially outward from the tread surface region  40 . The embossed pattern  42  is shown in  FIGS. 2 and 3  as comprising two raised linear portions  42 A that converge to give the pattern  42  an approximate V-shape, which aids in the clean out of soil over which the wheel  20  traverses. 
         [0021]    The center portion  24  of the wheel  20 , including its spokes  28  and hub  30 , can be fabricated from a single piece, for example, from a flat pattern  44  represented in  FIG. 5  as having a central hub portion  46  that defines the hub  30  of the wheel  20  and from which radiating arms  48  emanate, each arm  48  increasing in its width in the radially outward direction. The pattern  44  is depicted as having a central opening  50  within the hub portion  46  that will define the central hub opening of the wheel  20 . The center portion  24  of the wheel  20  can be fabricated from the pattern  44  by twisting each radiating arm  48  to form one of the spokes  28 , so that the outer radial ends  52  of the arms  48  form the spades  34  of the spokes  28 . As such, each radiating arm  48  is preferably twisted until its outer radial end  52  is roughly perpendicular to its original orientation within the pattern  44 , and is parallel to the axis  22  of the hub  30  (wheel). Thereafter, the individual tread plates  36  can be attached between adjacent spades  34  in any suitable manner, such as by welding, bolts, etc. The attachment of the tread plates  36  to the spades  34  confers structural integrity to the wheel  20 . The ability to form the entire center portion  24  of the wheel  20  from a one-piece flat pattern  44  can greatly decrease the fabrication time and costs related to the manufacturing of the wheel  20 . 
         [0022]    The center portion  24  and tread plates  36  of the wheel  20  can be fabricated from various structural materials, nonlimiting examples of which include corrosion-resistant steels, optionally galvanized to further promote corrosion resistance. The wheel  20  can be fabricated in various axial widths and diameters and to have various numbers of spokes  28 . As nonlimiting examples, wheels  20  can be manufactured in different size models for irrigation applications, including diameters of about forty-eight inches (about 1.2 meters) with twelve spokes  28  and sixty inches with fourteen spokes  28  (about 1.5 meters). 
         [0023]    In view of similarities with the first embodiment of  FIGS. 2 through 4 , the following discussion of the wheel  60  depicted in  FIGS. 6 through 8  will focus primarily on aspects of the wheel  60  that differ from the first embodiment in some notable or significant manner. Other aspects of the wheel  60  not discussed in any detail can be, in terms of structure, function, fabrication, materials, etc., essentially as was described for the wheel  20 . For convenience, identical reference numerals are used in  FIGS. 6 through 8  to denote the same or functionally related elements described for the wheel  60  of  FIGS. 6 through 8 . 
         [0024]    The tread plates  36  of the wheel  60  shown in  FIGS. 6, 7 and 8  include an embossed pattern  42  that protrudes radially outward from the tread surface region  40 .  FIG. 9  schematically represents the profile of one of the tread plates  36  of  FIGS. 6, 7 and 8 . The embossed pattern  42  shown in  FIGS. 6, 7 and 9  comprises a central raised linear portion that protrudes radially outward from the tread surface region  40 , onto which are superimposed two raised linear portions  42 A that further protrude radially outward from the tread surface region  40 . The tread surface region  40  has two tapered regions  40 A that slope radially inward in opposite axial directions away from the embossed pattern  42 , so as to be between the pattern  42  and the lateral lips  38  of the tread plate  36 . The raised linear portions  42 A are parallel to each other instead of converging, and are believed to offer certain advantages over the embossed pattern  42  shown in  FIGS. 2 and 3 . 
         [0025]      FIG. 10  schematically represents the profile of an alternative tread plate  36  also formed to include an embossed pattern  42 . In the embodiment of  FIG. 10 , the pattern  42  comprises two centrally-located raised linear portions  42 A that are parallel to each other and protrude radially outward from the tread surface region  40 . The tread surface region  40  has three regions  40 A that are flat when viewed in profile and separate the raised linear portions  42 A from each other and from the lateral lips  38  of the tread plate  36 . The embossed pattern  42  of  FIG. 10  is believed to offer certain performance advantages similar to the embossed pattern  42  of  FIGS. 6, 7 and 8 . 
         [0026]    While the invention has been described in terms of a specific embodiment, it is apparent that other forms could be adopted by one skilled in the art. For example, the wheel center portion  24 , tread portion  26 , and patterns  44  from which they are fabricated could differ in appearance and construction from what is shown in the drawings, the functions of certain components could be performed by components of different construction but capable of a similar (though not necessarily equivalent) function, and various materials could be used in the construction of the wheel  20 . Accordingly, it should be understood that the invention is not limited to the specific embodiment illustrated in the drawings. It should also be understood that the phraseology and terminology employed above are for the purpose of disclosing the illustrated embodiment, and do not necessarily serve as limitations to the scope of the invention. Therefore, the scope of the invention is to be limited only by the following claims.