Abstract:
An easily manufactured large boom construction includes a plurality of main tube support sections fabricated from plate material of differing material thickness, grade and section dependent on load. The tube support sections include apertured areas which provide a preliminary snap-fit of the main tubes to significantly reduce need for additional fixturing. The opposite ends of diagonal tubes pass through apertures in the fabricated support sections for accurate tube location without complicated weld fixtures or precise tube length and cut end angle tolerances. The tubes are welded on opposite sides of the sections to eliminate need for tube-to-tube connections or connections wherein a cut end edge has to be precisely placed against a planar surface. An inverted right triangle boom cross section with wing over-top fold configuration ability provides strength, stiffness and infinite nozzle placement possibilities.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to boom structure for agricultural implements such as field sprayers. 
   BACKGROUND OF THE INVENTION 
   The desire to increase productivity and reduce the number of passes over a field, implements with folding booms such as field sprayers have been designed for increased working widths and increased operating speeds. Booms which fold out to define a working width of up to 120 feet or more are now available. As boom size, weight and operating speed increase, large inertial loads are encountered. Building a large boom with reduced weight, easy and repeatable manufacturability and structural soundness and stiffness has become an increasing problem. 
   The wide booms must fold to achieve a narrowed transport width. Horizontal folding reduces fold height requirements but results in extreme torsional stresses on the boom structure. For horizontal folding, the boom depth dimension is usually minimized, which results in reducing the boom strength and stiffness in the fore-and-aft direction. Over-top folding relieves the torsional stress but can result in unacceptable fold heights with large booms. 
   A typical boom construction includes a triangular or L-shaped configuration with the base triangle or the lower leg of the L-shaped configuration at the bottom of the boom. Such structural designs that are wider at the bottom than at the top often interfere with desired spray nozzle positioning. Spray nozzle spacing options are limited or operators have to offset certain nozzles from main plumbing line, and uneven spray patterns often result. In the L-shaped designs, most fore-and-aft loads pass through to the centerframe support assembly through the two main lower beams or tubes which advantageously facilitates mounting of boom fold cylinders and tilt pivot structure at the the bottom with the cylinder located at the top. Attempts at providing alternate configurations have met with difficulties, particularly if in the alternate configuration loading is transferred towards the top of the boom. If the fold cylinder and pivot are moved towards the top of the boom and centerframe support assembly to better align with the boom loading, a large separation between the bottom of the boom and centerframe will occur when the boom section is tilted upwardly, while an overlap occurs when the section is tilted downwardly. This separation and overlap cause significant spray pattern problems. Therefore, providing such alternate boom configurations have met with significant design difficulties caused by the load transfers and tilt and fold requirements. 
   Large booms with tubular designs are often very difficult to manufacture. Individual tube sections can have wide length and angle of cut tolerances. Where tube-to-tube connections are required, such tolerances increase the difficulty and cost of welding tube ends together, and the structural integrity of such tube end weld connections is less than optimum. In addition, conventional tubular boom construction methods require a complex and expensive boom weldment fixture. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide an improved boom structure. It is another object to provide such a structure which overcomes one or more of the aforementioned problems. 
   It is another object of the present invention to provide an improved boom structure which is particularly useful for use with agricultural implements such as self-propelled field sprayers. It is another object to provide such a structure which relatively light and yet is strong and has desired stiffness. It is a further object to provide such a structure which is easy and inexpensive to manufacture. 
   It is still another object of the invention to provide an improved boom structure which reduces the cost of tooling, manufacturing and production. It is a further object to provide such a structure which reduces the amount of fixturing required during manufacture and reduces or eliminates problems associated with cut end joint tolerances and tube to tube end connections. It is another object to provide such a structure having tube support members with optimized weight and strength. 
   It is yet another object of the present invention to provide an improved boom structure which facilitates better nozzle or dispenser and supply tube plumbing placement than at least most conventional boom structures. It is a further object to provide such a structure which is wider at the top than at the bottom and which has improved strength in the fore-and-aft direction. It is another object to provide such a structure which is particularly advantageous for an over-top wing fold configuration and which overcomes design difficulties in boom tilt and fold construction caused by boom design configurations which transfer main loading towards the top of the boom. 
   An easily manufactured boom construction particularly useful for large agricultural folding booms includes a plurality of main tube support sections fabricated from plate material of differing thickness and section dependent on the load to be carried by the material. Thicker, higher strength, or higher grade material is used only in high stress areas so that cost and weight are reduced and weight distribution and strength are improved. The material can be laser cut from steel stock and fitted together with the use of tab-slot locators to create a section substantially more precise than is available using saw-cut pieces. The tube support sections include apertured or slotted areas which provide a preliminary snap-fit of the main tubes to significantly reduce need for additional fixturing so that tooling and manufacturing costs are reduced when compared with at least most conventional boom constructions. The opposite ends of diagonal tubes pass through apertures in the fabricated support sections, rather than mate against the surface of the plates. Therefore the diagonal tubes can be precisely located without the need for expensive and complicated weld fixtures. Diagonal tube length and cut end angle tolerances can be substantially greater than possible with structures which use tube end to flat plate mating surfaces or direct tube end to tube end connections. Since the tube ends actually pass through the support sections, each end can be welded on opposite sides of the sections at conveniently accessed locations. By eliminating most or all tube-to-tube connections and connections wherein a cut end edge has to be precisely placed against a planar surface, welds can be made more quickly, easily and reliably than with at least most previously available conventional boom constructions. By making diagonal tube connections at adjacent support sections, welds at intermediate locations on the diagonal tubes are eliminated. 
   In the embodiment shown, the cross section of the boom is in the shape of an inverted right triangle with the base of the triangle at an uppermost portion of the boom. The apex of the triangular cross section is located at a lowermost portion of the boom, and the forwardly facing portion of the boom lies generally in an upright plane. The inverted construction provides improved nozzle and plumbing, much of which can be outside the boom cross section, and better facilitates over-top folding of a boom section compared to most previous boom designs. A unique torque-tube inner hinge design helps facilitate the inverted section and permits the boom fold cylinder and tilt pivot structure to be located near the bottom of the boom with the tilt cylinder near the top of the boom to avoid spray pattern overlaps or gaps with boom tilting. The wider upper base of the triangular cross section improves boom strength and stiffness and allows steel to be utilized throughout the boom if desired rather than more expensive, lighter materials which often increase joint fabrication difficulties. An outer wing over-top fold configuration allows for the maximum depth dimension of the wing structure and maximized strength of the structure in the fore-aft direction. 
   These and other objects, features and advantages of the present invention will become apparent from the detailed description which follows taken in view of the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a rear perspective view of a portion of a wide folding boom structure. 
       FIG. 2  is an enlarged perspective view of the inner boom section of the structure of  FIG. 1 . 
       FIG. 3  is an enlarged rear perspective view of a portion of the inner boom of  FIG. 2 . 
       FIG. 4  is a front view of the portion of the inner boom shown in  FIG. 3 . 
       FIG. 5  is a left side end view of the boom portion shown in  FIG. 4 . 
       FIG. 6  is a rear view of the boom portion shown in  FIG. 3 . 
       FIG. 7  is a top view of the boom portion shown in  FIG. 6 . 
       FIG. 8  is an right side end view of the portion shown in  FIG. 6 . 
       FIG. 9  is a bottom view of the portion shown in  FIG. 6 . 
       FIG. 10  is a perspective view of one of the fabricated tube-receiving sections for the inner boom of  FIG. 2 . 
       FIG. 11  is an enlarged perspective view of the inner hinge area of the boom section of  FIG. 2  showing the torque tube hinge construction 
       FIG. 12  is an end view, partially in section, of the hinge area of  FIG. 11 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to  FIG. 1 , therein is shown a portion of an agricultural implement  10  such as a large field sprayer adapter for forward movement (F) over a field to be sprayed. The implement  10  includes right- and left-hand boom assemblies  14  and  16  supported on a vehicle or trailer (not shown) by a lift frame support or centerframe assembly  18 . The boom assemblies  14  and  16  are similar in construction and, as shown, include an inner boom section  20  connected to the support assembly  18  for pivoting about an upright axis  22   a  by a structural hinge  22  for movement between an extended field working position (shown) and a forwardly folded position wherein the section  20  extends forwardly from the support assembly  18 . An intermediate boom section  24  is connected by hinge structure  26  to the outer end of the section  20  for pivoting between an outwardly extended field working position and a transport position overlying the section  20  against a stop  27  on the top of the section  20 . An outermost boom section  28  is pivotally connected to the outer end of the intermediate boom section  24  by a tip breakaway hinge structure  30  for folding about an axis to a transport position adjacent the aft side of the section  24 . The integrated breakaway of the structure  30  allows the tip of the boom assembly to move rearwardly against a spring bias upon encountering an obstacle. The tip to tip width of the structure shown in  FIG. 1  can be up to 120 feet or more. 
   Hydraulic boom fold cylinders  32 ,  36  and  40  are connected at the hinge locations  22 ,  26  and  30  to effect the positioning of the boom sections relative to each other and to the support assembly  18 . Boom attitude or tilt control cylinders  44  and  46  extend between the assembly  18  and the upper portions of the structural hinges  22  connecting the boom assemblies  14  and  16  to the assembly  18 . The structural hinge  22  provides joint structure at location  22   b  about which the boom section both  20  tilts and folds. The location  22   b  is near the bottom of the hinge and centerframe and facilitates a boom tilt of approximately 15 degrees about a tilt axis which extends horizontally in the fore-and-aft direction when the boom is in the field working position. The structural hinge  22  also provides approximately 90 degrees of fold so the boom extends transversely in the field working position and fore-and-aft in a forwardly folded transport position. Although a three section boom assembly  14  is shown, the boom construction described below for the inner boom section  20  may be utilized with other types of boom assemblies. 
   The construction of the inner boom section  20  ( FIGS. 2–12 ) provides an inverted triangle cross section. As best seen in  FIGS. 5 and 8  two main upper beams or tubes  51  and  52  define the base of the triangle and a main lower beam or tube  53  defining the inverted apex of the triangle. The beams  51 – 53  extend transversely between the hinge  22  and hinge structure  26 . As shown, the cross section is in the form of a right triangle with the upper beams  51  and  52  lying generally in a horizontal plane P 1  and with the lower beam  53  and upper beam  51  defining an upright plane P 2 . The upright plane P 2  faces the forward direction (F) or direction of travel of the machine when the boom sections are in the unfolded field working position. The triangular cross section provides a substantially unencumbered space indicated generally at  54  behind the lower beam  53  and below the beams  51  and  52  for supporting supply lines or other plumbing and material dispensers in one of a possibly infinite number of patterns. 
   The construction of the section  20  includes a plurality beam or tube spacing members  71 – 79  ( FIG. 1 ), each of similar construction but decreasing in dimensions from the member  71  outwardly to the member  79 . Each of the spacing members  71 – 79  is fabricated as a subweldment  80  including a top web  81 , a bottom web  83 , a rear flange piece  84 , a front flange piece  85 , a central connecting piece  86 , and a top flange piece  87 . The weldment is in the form of an I-beam section which is narrow at the bottom extremity and wide at the top extremity. Laser cut tab and slot combinations with a slight interference fit at locations indicated at  90  accurately center the tab in the slot to assembly the subweldment  80 . The top and bottom webs  81  and  83  include accurately cut apertures or slots  101 ,  102  and  103  conforming to a portion of the outer surface of the main beams or tubes  51 ,  52  and  53 , respectively. After the flange pieces  84 ,  85  and  87  are welded to the webs  81  and  83 , the slots  101 – 103  along with the slightly flared ends of the flanges define openings slightly smaller than the cross sectional dimension of the tubes  51 – 53  so that the tubes are snapped into place on the tube spacing members  71 – 79  during assembly of the section  20  and then welded to the subweldment  80 . Therefore, the amount and complexity of the weld fixturing necessary for fabrication is substantially reduced compared to most conventional boom fabrication methods. In addition, the material thickness, material grade and/or strength of each of the pieces of the subweldment  80  can be varied according to the loads encountered at the piece so that cost, weight and total area of the subweldment can be optimized. By way of example only without limitation, the top and bottom webs  81  and  83  which receive heavy loads from the main tubes  51 – 53  can be fabricated from grade 80 steel of 0.088 inch thickness while the flange pieces  84 ,  85  and  87  and the connecting piece  86 , which carry much lighter loads, can be fabricated from a lower grade, thinner material such as 0.075 inch thick grade 50 steel. 
   The upper and lower webs  81  and  83  include apertures or slots  111  and  113  for receiving diagonal tubes or brace members  121 ,  122  and  123  extending between the subweldments  80  of adjacent beam spacing members. The brace members  121 – 123  extend through the apertures  111 – 113  and are fixed to the webs  81  and  83  by welds which extend partially around the circumference of the brace member ends on both sides of the webs. The brace members  121 – 123  can be precisely located without weld fixtures and without precise tube end and tube length cuts. Since the tube ends actually pass through the webs  81 – 83 , each end can be welded on opposite sides of the webs at conveniently accessed locations. Tube-to-tube connections and connections wherein a cut end edge has to be precisely placed against a planar surface can be eliminated using the above-described configuration. 
   As shown in  FIGS. 2 and 3 , a truss construction is provided with the upper brace member  122  having an outer end connected to the web  81  next to the rear upper tube  52  and an inner end connected to the next adjacent web  81  next to the front upper tube  51 . The upper innermost end of the diagonal brace member  123  is connected to the web  81  adjacent the outer end of the upper brace member  122 . Each front diagonal brace  121  has an outermost upper end connected to the web  81  adjacent the innermost end of the upper brace member  122 , and a lower innermost end connected to the web  83  adjacent the lower outermost end of the diagonal brace member  123  which extends between the lower tubes  53  and the upper front tube  51 . As shown, the diagonal brace members  121 – 123  extend between adjacent tube spacing members, and no welds are required at central locations on the brace members. End-to-end welds of the diagonal brace members  121 – 123  and direct welds of the brace members to the main tubes  51 ,  52  and  53  can be eliminated. 
   The inner structural hinge  22  transfers loading from the upper portion of the boom section  20  towards the bottom of the boom section at the hinge area and thereby permits the pivot and fold structure to remain near the bottom of the boom and the centerframe assembly  18  to avoid the problems of gapping and overlap as the boom is tilted about a fore-and-aft axis during field working operations. The outer hinge structure  26  advantageously provides hinge pivot locations  26   b  which are aligned with the upper tubes  51  and  52  for providing a sturdy pivot area for upward and over center folding of the boom section  24  about the axis  26   a.  As shown, the structural hinge  22  and the hinge structure  26  also use a tab and slot construction to facilitate assembly with a minimum of additional fixturing. 
   Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.