Patent Publication Number: US-8979415-B2

Title: Adhesively bonded joint in agricultural boom structure

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 61/479,941 filed Apr. 28, 2011, entitled “ADHESIVELY BONDED JOINT IN AGRICULTURAL BOOM STRUCTURE”. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates generally to a sprayer boom on a crop sprayer, and more particularly to structural joints joining members of the sprayer boom. 
     2. Description of Related Art 
     The high crop yields of modern agribusiness require application of fertilizers, pesticides, and herbicides. Dispersing these chemicals onto high acreage fields requires specialized machines mounted on or towed by a vehicle. An example of such a machine is the self-propelled crop sprayer. 
     A common design for a self-propelled crop sprayer includes a dedicated chassis with a tank, boom arms, and nozzles connected to the boom arms. The tank contains fluid such as fertilizers, pesticides, and herbicides. Boom arms extend outward from the sides of the dedicated chassis. Boom plumbing contains supply lines and a plurality of nozzles spaced apart along the length of the boom arms at a standard spacing distance which corresponds to the spray pattern of the nozzles. In operation, as the crop sprayer crosses the field, fluid is pumped from the tank through the supply lines along the boom arms, and out through the nozzles. This allows the self-propelled sprayer to distribute the fluid along a relatively wide path. The length of conventional boom arms may vary from, for example, 6 meters (18 feet) up to 46 meters (150 feet), but smaller or longer booms are possible. The boom arms typically swing in for transport and out for operation. 
     Conventionally, the boom arm has many beams, chords and braces and other structural members welded or bolted together to form a lattice structure. If the components are to be welded, the wall thickness and the choice of materials for the components can be limited. Additionally, the time to assemble and the manufacturing costs can be high. 
     Based on the foregoing, it would be desirable to provide a structure or especially joint structure that enhances functionality, durability, flexibility in material choice and simplifies assembly by use of adhesives. 
     OVERVIEW OF THE INVENTION 
     In one embodiment, the invention relates to an adhesively bonded joint in a boom arm of an agricultural sprayer. The joint includes a tee-shaped brace member having a top flange and a stem extending from the top flange. The joint also includes a brace-receiving portion of a structural member of the boom arm. The brace-receiving portion has a slot formed therein that receives the stem of the tee-shaped brace member. The sides of the stem and underside of the top flange are adhesively bonded to facing surfaces of the brace-receiving portion. 
     In one embodiment, the slot is formed with a v-shape, with the mouth of the slot being wider than the width of the distal end of the slot, to provide some flexibility in the angular positioning of the tee-shaped bracing member. The adhesively bonded joint further includes a locking collar around an end of the tee-shaped brace. Opposite sides of the locking collar engage notches on either side of the slot to lock the stem of the tee-shaped brace member in the slot. 
     These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of various example embodiments of the systems and methods according to this invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above mentioned and other features of this invention will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a crop sprayer; 
         FIG. 2  is a perspective view of a portion of a boom arm on the crop sprayer of  FIG. 1  according to an embodiment of the invention; 
         FIG. 3  is an enlarged perspective view of a portion of the boom arm of  FIG. 2 ; 
         FIG. 4  is an exploded view of an embodiment of a joint of the boom arm of  FIG. 2 ; 
         FIG. 5  is an enlarged perspective view of a joint of the boom arm of  FIG. 2 ; 
         FIG. 6  is a perspective view of a portion of a tee-shaped bracing member of the boom arm of  FIG. 2 ; 
         FIG. 7  is a partially exploded perspective view of another embodiment of a joint of the boom arm of  FIG. 2 ; and 
         FIG. 8  is a perspective view of the joint of  FIG. 7 . 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the views of the drawings. 
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     The invention will now be described in the following detailed description with reference to the drawings, wherein preferred embodiments are described in detail to enable practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. But to the contrary, the invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description. 
       FIG. 1  shows a crop sprayer  10  used to deliver chemicals to agricultural crops in a field. Crop sprayer  10  includes a chassis  12  and a cab  14  mounted on the chassis  12 . Cab  14  may houses an operator and a number of controls for the crop sprayer  10 . An engine  16  may be mounted on a forward portion of chassis  12  in front of cab  14  or may be mounted on a rearward portion of the chassis  12  behind the cab  14 . The engine  16  may be commercially available from a variety of sources and may comprise, for example, a diesel engine or a gasoline powered internal combustion engine. The engine  16  provides energy to propel crop sprayer  10  and also may provide energy used to spray fluids from the crop sprayer  10 . 
     The crop sprayer  10  further includes a storage tank  18  used to store a fluid to be sprayed on the field. The fluid may include chemicals, such as but not limited to, herbicides, pesticides, and/or fertilizers. Storage tank  18  may be mounted on chassis  12 , either in front of or behind cab  14 . Crop sprayer  10  may include more than one storage tank  18  to store different chemicals to be sprayed on the field. The stored chemicals may be dispersed by crop sprayer  10  one at a time or different chemicals may be mixed and dispersed together in a variety of mixtures. 
     Boom arms  20  extending from each side of the crop sprayer  10  are used to distribute the fluid from the tank  18  over a wide swath as the crop sprayer  10  is driven through the field. The fluid is conveyed by a fluid supply system and various spray nozzles (not shown) spaced along the boom arms  20 . As is known in the art, a pump (not shown) pumps fluid from the tank  18  through the spray nozzles. An operator of the crop sprayer  10  may use controls (not shown) located in the cab  14  to control movement of the boom arm  20  and to turn on and to shut off the fluid flow to the plurality of spray nozzles. The boom arms  20  extending from either side of the crop sprayer  10  are desirably substantially identical but mirror images of each other, so only one boom arm  20  will be discussed herein. 
     Turning to  FIG. 2 , the boom arm  20  is a truss structure having three chords  30 A,  30 B and  30 C arranged in a triangular formation extending outward from the crop sprayer  10 . At periodic intervals, cross-sectional frame members  34  connect the three chords  30 A,  30 B,  30 C to provide structural integrity. Looking at the embodiment of the boom arm  20  from the frame of reference shown in  FIG. 2 , each cross-sectional frame member  34  includes a generally horizontal component  36  and a generally vertical component  38  meeting at a cross-sectional junction  40 . In one example embodiment, the boom arm  20  is mounted on the crop sprayer  10  such that the horizontal and vertical components  36 ,  38  of the cross-sectional frame members  34  are generally horizontal and vertical with respect to the surface of the ground when the crop sprayer  10  is in use. However, one skilled in the art will understand that the boom arm  20  may be mounted on the crop sprayer  10  in other orientations such that the horizontal and vertical components  36 ,  38  are not respectively parallel and perpendicular with the general surface of the ground. 
     In the illustrated embodiment, each cross-sectional frame member  34  has three legs  42 A,  42 B,  42 C extending from the interior junction  40 . First leg  42 A of cross-sectional frame member  34  extends toward chord  30 A, second leg  42 B extends toward chord  30 B and third leg  42 C extends toward chord  30 C such that the three legs  42 A,  42 B,  42 C of the cross-sectional frame member form a tee shape. In the tee-shaped embodiment illustrated in  FIG. 2 , the frame member  34  desirably has one or more diagonals  41  connecting two of the legs, such as the end of leg  42 A with the end of leg  42 C as in the illustrated embodiment. In another embodiment of the cross-sectional frame member  34 , the three legs  42 A,  42 B and  42 C are arranged in a triangular formation with the three chords  30 A,  30 B and  30 C connecting at or near the corners of the triangular formation. Cross-sectional frame members  34  may be formed from two or more castings or welded parts or may be of one piece constructions. Differing requirements for size of boom arm  20  may be met by selecting the size and shape of cross-sectional frame members  34  using sound engineering judgment. 
     In the example embodiment illustrated in  FIG. 2 , the boom arm  20  has a tapered shape such that the distance between chord  30 A and chords  30 B and  30 C decreases along the boom arm  20  from its proximal end  43  closest the chassis  12  of the crop sprayer  10  out toward its distal end  44 . Each cross-sectional frame member  34  is configured to receive an extension member  46  that extends between a distal end  48  of leg  42 A and a connector  50 A mounted on chord  30 A. As can be seen in  FIG. 2 , the length of extension member  46  depends on the location of the cross-sectional frame member  34  on the boom arm  20 . Extension members  46  are longer on the inner portions of the boom arm  20  closest to the chassis  12  of the crop sprayer  10  and decrease in length out towards the distal end  44  of the boom arm  20  as the boom arm  20  tapers. Thus, cross-sectional frame member  34  at the distal end  44  of the boom arm  20  may have a short extension member  46  or may not have an extension member  46  at all. In the illustrated embodiment, each extension member  46  is a generally rectangular beam received in a pocket  52  at the distal end  48  of leg  42 A. However, one skilled in the art will understand that extension member  46  may have any other shape that is suitable to provide the requisite strength, such as U-shaped, H-shaped or I-shaped, and may connect with the end of leg  42 A by any means using sound engineering judgment. In this example embodiment, the tapered boom arm  20  is made with cross-sectional frame members  34  having a uniform design and the taper of the boom arm  20  is accounted for using extension members  46  extending from leg  42 A having progressively shorter lengths. Of course, one skilled in the art will understand that boom arm  20  may be constructed without a tapered shape such that cross-sectional frame members  34  and extension members  46 , if any, are identical throughout the boom arm  20 . 
     Joints of the boom arm  20  have connectors  50 A,  50 B,  50 C that connect the cross-sectional frame member  34  to chords  30 A,  30 B,  30 C. In one embodiment as best seen in  FIG. 3 , connectors  50 B and  50 C are integral with the legs  42 B,  42 C respectively of the cross-sectional frame member  34  and desirably formed by casting. Alternately, connectors  50 B and  50 C may be fastened to the end of legs  42 B and  42 C, respectively, of the cross-sectional frame members  34  with any means using sound engineering judgment. In the illustrated embodiment, connector  50 A is attached at the end of the extension member  46  on leg  42 A of the cross-sectional frame member  34 . In one embodiment, connectors  50 A,  50 B,  50 C have an enclosed shape that fits around chords  30 A,  30 B,  30 C and may be fastened to the chords by welding or with suitable fasteners. However, any means to attach connectors  50 A,  50 B,  50 C to the chords  30 A,  30 B,  30 C may be used without departing from the scope of the invention. 
     As best seen in  FIGS. 3 and 4 , the cross-sectional frame members  34  and the connectors  50 A,  50 B,  50 C are cast or welded with brace-receiving portions  60  configured to receive tee-shaped brace members  70 . The brace receiving portion  60  may be formed as a lobe, flange or other extension of the connectors  50 A,  50 B,  50 C and cross-sectional frame member  34 . In the illustrated embodiment, the cross-sectional frame members  34  have brace-receiving portions  60  extending from each side near the junction  40  of the three legs  42 A,  42 B,  42 C and near the connectors  50 A,  50 B,  50 C. The brace-receiving portions  60  may be formed by casting or by plate welding. Brace-receiving portions  60  have a slot  62  formed therein configured to receive tee-shaped brace members  70  as will be explained below. 
     Tee-shaped brace member  70  is desirably extruded with a top flange  72  with a stem  74  extending therefrom to form the tee-shape.  FIGS. 4 and 5  best show that the stem  74  of the tee-shaped brace member  70  fits into the slot  62  of the slotted brace-receiving portions  60 . In the illustrated embodiment, the tee-shaped brace member  70  has a tee-shape along its entire length. However, one skilled in the art will understand that the tee-shape brace member  70  can have a tee-shape at its ends that join with the slotted receiving member  60  and have any other suitable shape at other points along its length. 
     As best seen in  FIG. 6 , in one embodiment the underside of the top flange  72  and sides of the stem  74  desirably have offsets  76  that form channels  78  configured to receive an adhesive (not shown). Adhesive or bonding material such as epoxy resins, hot melt adhesives, or other customary permanent adhesives that will adhere or bond similar or non-similar materials together, may be applied in the channels  78 . Desirably, the size of the offsets  76  depend on what type of adhesives are used. One skilled in the art will understand that these offsets  76  are optional to get as much strength out of a certain bonding area, but are not mandatory. With the offsets the strength of a joint is more predictable. Additionally, a spacing between tee-shaped brace member  70  and the slotted brace-receiving portion  60  could also be achieved by other means without departing from the scope of the invention such as with a plastic insert that keeps tee-shaped brace member  70  and the slotted brace-receiving portion  60  apart from each other. One suitable example adhesive is Scotch-Weld™ Epoxy Adhesive DP920 available from 3M™ of St. Paul, Minn. Alternatively, offsets  76  may be formed in the inner and outer surfaces of the slotted receiving portion  60  that are adjacent the installed tee-shaped brace member  70  without departing from the scope of the invention and the adhesive or bonding material may be applied to these channels. For this adhesive, it has been determined that a height of between about 0.3 and 0.5 mm for the offsets  76  provides suitable channels  78  for the adhesive. Other heights, such as between about 0.2 and 1.0 mm may also be suitable for other adhesives. Because the joint is bonded by adhesives, the material for the tee-shaped brace member  70  and the brace-receiving portion  60  may be made from different material. The tee-shaped brace member  70  and the brace-receiving portion  60  may be made from aluminum or any other suitable material used in lattice-type structures. One skilled in the art will understand that offsets  76  may be used with all receiving pockets and structural parts in the boom arm  20  to form adhesive holding pockets such that the entire structure may be adhesively bonded. Other ways to create a distance between the surfaces such as tight positioning control, plastic insert may be used without departing from the scope of the invention. Additionally, in some instances no offsets may be necessary. 
     Turning now to  FIGS. 7 and 8 , in one embodiment the slotted receiving member  60  has a slot  62  with a v-shape. As best seen in  FIG. 7 , the mouth  64  of the slot  62  has a larger width than the distal end  66  of the slot  62 . In some situations, such as with some brace members  70  in a tapered boom arm  20 , it is desirably to have some flexibility in the angle that the brace member  70  extends from the receiving member  60 . However, the adhesion between the stem  74  of the tee-shaped brace member  70  and the slotted receiving portion  60  is not optimal as forces applied by moving and twisting of the boom arm  20  may cause peel forces on the top flange  72  of the tee-shaped brace member  70 . A locking collar  80  is used to lock the tee-shaped brace member  70  in the slot  60  and keep the top flange  72  of the tee-shaped brace member  70  flat against the slotted receiving portion  60 . In the illustrated embodiment, the slotted receiving portion  60  has notches  82  on either side of the slot  62  and sides  84  of the collar  80  are received in the notches  82  to lock the tee-shaped member  70  in the slot  62 . Top portion  85  of the locking collar  80  presses against the top flange  72  of the tee-shaped brace member to keep the stem  74  in the slot  62 . Locking collar  80  may be adhesively bonded, and therefore may require offsets in the notches  82  of the slotted receiving portion  60  as well to hold the adhesive. Construction of the boom arm  20  is facilitated as the joints can be successively assembled. In a three dimensional lattice structure held together by adhesives, it can be difficult to mount everything because of inserts that require room to slide into another part. Furthermore, the cut length of a part often determines the distance between two joints. With the tee-shape brace member and slotted receiving portion, it is possible to connect two structural joints by adhesive bonding in a part as if welding the two components. 
     An advantage of the boom arm  20  design illustrated herein is it is possible to use different materials throughout the boom arm  20 . Exotic or common materials can be used, depending on demand and requirements. The wall thickness of material can be varied depending on local stresses throughout the structure, depending on plumbing and durability requirements. Thin wall stock or custom material can be used where welding would be difficult or detrimental to the properties of the material. Where high strength materials become available and welding would be more difficult, lighter boom arms  20  may be constructing as shown herein. It is believed that durability of the boom arm is improved because of the reduced number of weld spots at joints. 
     While this invention has been described in conjunction with the specific embodiments described above, it is evident that many alternatives, combinations, modifications and variations are apparent to those skilled in the art. Accordingly, the preferred embodiments of this invention, as set forth above are intended to be illustrative only, and not in a limiting sense. Various changes can be made without departing from the spirit and scope of this invention.