Title:
Agricultural sprayer boom and method of manufacture
Kind Code:
A1


Abstract:
Sprayer boom beam structure includes a girder member having an elongated profiled sheet structure including at least two folds or bends defining three portions in an inverted V- or U- or C-shaped cross-section, i.e. a pair of side or wing walls integrally joined by a top or bridge wall. Triangular orifices are punched out of the side walls, alongside one another in a longitudinal direction, alternating between inverted and upright triangles, leaving inclined strips of sheet material in between, and which absorb and transmit strains and stresses similar to a tubular lattice structure, and having benefits of a spatial lattice-like structure. Complementary beam members include a base plate joining longitudinal edges of sidewalls of the profiled member and close the open face of the profiled member, forming a sturdy box-like structure, and internal cross-platelets joined to inclined strips of the profiled-member sidewalls to further rigidify the beam structure.



Inventors:
Rivas, Alberto (Provincia de Santa Fe, AR)
Badalassi, Gabriel (Provincia de Santa Fe, AR)
Application Number:
11/320838
Publication Date:
09/14/2006
Filing Date:
12/30/2005
Primary Class:
International Classes:
E04H12/34
View Patent Images:



Primary Examiner:
GITLIN, MATTHEW J
Attorney, Agent or Firm:
SHLESINGER, ARKWRIGHT & GARVEY LLP (ALEXANDRIA, VA, US)
Claims:
I claim:

1. A beam structure for a boom elongated in a longitudinal direction, comprising: a) the beam structure including a girder; and b) the girder being an elongated sheet folded into one of a substantially V-, U-, and C-shaped cross-section.

2. A boom beam structure as in claim 1, wherein: a) the elongated sheet of the girder is folded substantially at least twice; b) the girder includes a pair of elongated sidewalls, each sidewall having a top edge, a bottom edge, and a plurality of substantially triangular orifices aligned in the longitudinal direction, the orifices having shapes alternating between upright and inverted triangles, and adjacent orifices are separated by an inclined strip of the sheet; and c) each sidewall further including a lower elongated strip of sheet joined to each of the inclined strips.

3. A boom beam structure as in claim 2, wherein: a) the elongated sidewalls have a height which varies linearly in the longitudinal direction.

4. A boom beam structure as in claim 2, wherein: a) the girder further includes an elongated top wall bridging the sidewalls along the top edges thereof.

5. A boom beam structure as in claim 4, wherein: a) the girder top wall is shaped like an elongated trapeze, wherein the girder sidewalls have a height and the girder top wall has a breadth, the sidewall height and the top wall breadth varying inversely in relation to one another in the longitudinal direction.

6. A boom beam structure as in claim 2, wherein: a) the lower elongated plate includes an elongated bottom edge folded inwards.

7. A boom beam structure as in claim 2, wherein: a) a stabilizer element is provided, the stabilizer element bridges the girder sidewalls by a removable fastener element, the stabilizer element includes a removable elongated baseplate joined to the girder sidewalls along the bottom edges thereof by the removable fastener element.

8. A boom beam structure as in claim 7, wherein: a) the baseplate has a substantially constant breadth throughout the longitudinal direction.

9. A boom beam structure as in claim 2, wherein: a) a reinforcement element bridging the girder sidewalls by a removable fastener element, the reinforcement element includes a plurality of inclined platelets joined to the girder sidewalls at the inclined strips thereof by the removable fastener element, and the removable fastener element including one of bolts, nuts, and rivets.

10. A boom beam structure as in claim 2, wherein: a) the triangles are substantially isosceles.

11. A boom beam structure as in claim 2, wherein: a) the inclined strips have an inclination of around 45°.

12. A boom beam structure as in claim 2, wherein: a) the pair of girder sidewalls are substantially identical.

13. A boom beam structure as in claim 1, wherein: a) the girder includes one of the substantially U- and C-shaped cross-sections; and b) the elongated sheet is folded along parallel fold lines.

14. A boom beam structure as in claim 1, wherein: a) the girder includes a substantially V-shaped cross-section; and b) the elongated sheet is folded along non-parallel fold lines.

15. A boom beam structure as in claim 1, wherein: a) the elongated sheet is folded at least four to six times.

16. A boom beam structure as in claim 1, wherein: a) the girder is made of metal, preferably one of steel and aluminum.

17. A boom beam structure as in claim 1, wherein: a) the girder is made of molded plastic material.

18. A boom beam structure as in claim 1, wherein: a) end caps are mounted to respective ends of the girder by a removable fastener element, the end caps including a hinge element, the removable fastener element being one of bolts and nuts, screws, and rivets.

19. A boom beam structure as in claim 1, wherein: a) the boom beam structure is configured for use as a boom beam structure of an agricultural sprayer machine.

20. A boom comprising an inner beam and an outer beam, the beams being hinged end-to-end to one another, and wherein at least the inner beam includes the girder as in claim 1.

21. A boom comprising at least two beam structures as in claim 1 hinged end-to-end.

22. A boom as in claim 21, wherein: a) the boom has an overall length over 20 meters.

23. A method of manufacturing a beam structure for a boom, the method comprising: a) folding an elongated metal sheet in approximately the transversal direction at least twice into one of a substantially inverted V-, U-, and C-shaped cross-section.

24. A method as in claim 23, further including the steps of: a) providing a first sheet material; b) performing one of cutting, stamping, and laminating in a general trapeze shape on the first sheet material, c) performing one of cutting, punching, and stamping triangular holes arranged in two long slightly unparallel lines and alternating between upright and inverted triangles, leaving inclined strips of sheet material in between, d) performing one of drilling and punching round and oblong holes over the strip material, e) folding the first sheet material into the substantially inverted V- or U- or C-shaped cross-section to form a girder, f) providing a second sheet material, the second sheet material being one of cut, stamped, and laminated in a general rectangular shape, g) folding the second sheet material along parallel longitudinal edges thereof to form a baseplate, and h) placing and removably fastening the base plate inside the girder to form a closed box-like structure.

25. A method as in claim 24, further including the step of: a) performing one of bolting and rivetting the girder to the base plate.

26. A method as in claim 24, further including the step of: a) removably fastening a plurality of inclined platelets to the girder inclined strips.

Description:

CROSS-REFERENCE OF RELATED APPLICATIONS

This application claims priority of Argentine patent application no. P 05 01 00962, filed Jun. 9, 2005, and this application claims priority of Argentine patent application no. P 05 01 00962, filed on Mar. 11, 2005, and each of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention is related in general to farming machinery, more particularly to boom structures on sprayer machines.

BACKGROUND OF THE INVENTION

Sprayer machines carry booms mounting a number of spray nozzles at regular intervals thereon for applying fertilizers, herbicides and the like on crops. The purpose of these beams is proper positioning of the spraying nozzles. Productivity is enhanced using booms on the order of about 25 to 30 meters across, sometimes more for large tracts of farmland. For constructive, operational and practical reasons, the booms are built in sections or modules in the form of beams joined together by hinge elements which enable folding the booms so as to avoid obstacles, like fences and windmills, make a tight turn or put the machine away.

To achieve their purpose, a boom structure must be designed and built to withstand bending-moment strains generated by weight distributed along the length of its structure, including that of its nozzles and accessory elements, without undue vertical or horizontal deformation thereof. A typical 25- or 30-meter boom may be made up of three beams on each side of the machine. The inner beam must be particularly strong enough to withstand the overall weight of its structure and load and that of other beams joined to its distant (outer) end. Hence, structural weight is a major factor in boom design and construction.

As in many fields of engineering, the classical solution to the weight and strength (mechanical resistance) dilemma is tubular spatial-lattice structures. Thus, the beams for sprayer booms currently found on the market comprise spatial (3-dimensional) lattice structures made of tubular steel members having square o rectangular cross-sections, wherein the ends of the members are welded together forming isosceles triangles, with the vertex between like sides pointing downwards. US patent publication No. 2002/0113137 contains an example of this kind of lattice structure.

The above-mentioned triangular lattice structure meets many mechanical requirements such as stability and resistance to the high stresses generated by such boom lengths. However, its construction requires substantial manpower and time. For instance, a typical boom 25 meters long may have between 40 and 100 tubular members, which have to be welded to one another after sawing off the two ends thereof at an angle. Furthermore, because of the weight constraints the walls of the tubular members should be as thin as possible. Welding generates residual strains in the tubular walls which may break during service.

Repair is likewise cumbersome and expensive. Since the beam is a welded unit, in many cases the structure has to be completely replaced even when damage is restricted to just a part thereof.

There are also examples teaching away from the lattice-type structure and therefore less labour-intensive to manufacture. Argentine patent (AR) No. 246,684 also available as Brazilian patent (BR) No. 9500654, to Favot (of Cruz Alta, Córdoba, Argentina) discloses a boom comprising left- and right-hand bar or tubular members spanning 28 meters. The members are of constant section with tubular walls 2 mm thick. The boom weighs about 150 kg resulting in a substantial bending moment at the near end, this being a critical zone where the weld may eventually crystallize, leading to breakage.

OBJECTS AND SUMMARY OF THE INVENTION

An object of the present invention is to facilitate construction of beams for agricultural sprayer booms strong enough to resist strains and stresses to which the structures are subjected during normal operation.

Another object of the present invention is to provide a boom beam structure that is not weakened by welding points. And a related object is to enable a beam to be built using other, unweldable materials.

Yet another object of the present invention is to facilitate repair and maintenance of boom beams.

Yet a further object of the present invention is to enable automation of the construction of boom beams using tools and means available on the market.

The sprayer boom beam structure of the present invention comprises a girder member produced in an elongated profiled sheet structure having at least two folds or bends that define three portions in an inverted V- or U- or C-shaped cross-section, i.e. a pair of side or wing walls integrally joined by a top or bridge wall. Triangular orifices are previously punched out of the side walls, alongside one another in a longitudinal direction and alternating between inverted and upright (non-inverted) triangles so as to leave inclined strips of the sheet material integrated in between which absorb and transmit strains and stresses in a like fashion to the typical tubular lattice structure, thereby maintaining the abovementioned benefits of a spatial lattice-like structure.

Complementary beam members include a base plate joining the longitudinal edges of the sidewalls of the profiled member so as to close the open face of the profiled member and form a sturdy box-like structure, and internal cross-platelets joined to the inclined strips of the profiled-member sidewalls to further stabilize (rigidize) the beam structure. The platelets, being inclined to the longitudinal direction of the boom, become thus a functional part of these strips in transmitting strains and stresses throughout the beam structure resulting from intrinsic (weight and bending moment) and extrinsic (e.g. wind, jerks, collisions, etc.) factors. Removable fastener elements such as bolts and nuts, rivets or screws may be used to join the baseplate and the cross-platelets to the profiled member. This eliminates the need of welding and consequential local weak points in addition to simplifying construction and reducing manpower in relation to the forementioned welded tubular structure.

The height of the side walls advantageously decreases outwardly (i.e. away from the machine) and, likewise, the triangular orifices get gradually smaller. A particular feature of the invention is that the fold lines in the sheet structure are not parallel but slightly offset such that they virtually converge at a point off the beam. This feature facilitates use of a suitable standard folding machine for bending a metal sheet along the fold lines to form the girder of the beam structure. As a result, the shape of the bridge wall is not strictly rectangular but trapeze in fact, gradually broadening in the longitudinal direction away from the machine, i.e. towards the distant end of the beam.

As a member of a multibeam boom, the beam structure is supplemented with removable end caps provided with pivot or hinge elements for connecting outer boom beams to inner beams and the innermost beams to an agricultural machine structure. Preferably, the caps are made of the same metal or plastics material as the other beam components.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-stated and other novel features and aspects of this invention and how it may be reduced to practice may be better understood from the detailed description hereinafter of a preferred embodiment shown in the attached drawings, wherein:

FIG. 1 is a perspective view of a boom for mounting to one side of a sprayer machine and comprising three hinged beams or sections illustrated in a partially folded position.

FIG. 2 is an exploded view of the innermost beam of FIG. 1, according to a preferred embodiment of the present invention.

FIG. 3 is a side view, broken in the middle, of the girder member of the beam of FIG. 2, according to a preferred embodiment of the present invention.

FIG. 4A is a cross-section through the middle of the beam of FIG. 2. FIGS. 4B, 4C and 4D are cross-sections analogous to FIG. 4A but illustrating alternative beam embodiments.

FIG. 5 is a top plan view of the base plate of the beam of FIG. 2.

FIG. 6 is a plan view of a steel sheet prior to holding to make the folded girder member of FIG. 3.

FIG. 7 is an elevational view of the base plate of FIG. 5 showing some of the sprayer units and piping mounted thereon.

FIG. 8A is a plan view of and FIG. 8B a medial cross-section through an internal cross-platelet used for reinforcing the beam of FIG. 2.

FIGS. 9A and 9B are enlarged, respective side-elevation and top-plan views of the articulation in FIG. 1 between the end-caps of the middle and inner boom beams in an extended position. The end-cap of the inner boom beam is partially cut away in FIG. 9A to show part of the mechanism for folding the middle and outer boom beams. FIG. 9C is an end view of the articulation of FIGS. 9A and 9B in a fully folded or non-operational position.

FIGS. 9A and 9B are enlarged, respective side-elevation and top-plan views of the articulation in FIG. 1 between the end-caps of the middle and inner boom beams in an extended position. The end-cap of the inner boom beam is partially cut away in FIG. 9A to show part of the mechanism for folding the inner and middle boom beams. FIG. 9C is an end view of the articulation of FIGS. 9A and 9B in a fully folded or non-operational position.

FIG. 10A is an enlarged view of the articulation in FIG. 1 between the end-caps of the middle and outer boom beams. FIG. 10B is a view from below of the articulation of FIG. 10A in a slightly yielding position.

FIG. 11 is a perspective view of the boom end mounted to a tractor.

Like numerals in different figures refer to like or equivalent elements.

DETAILED DESCRIPTION OF THE INVENTION

A boom according to a preferred embodiment of the invention is illustrated in FIG. 1. Two such booms are mounted, one to each side, of a sprayer machine (not illustrated) having an overall operational spray width of 25 meters and carrying a tank for 3,200 liters of spray solution. The boom comprises three beams 10-10′-10″ extending end to end in a longitudinal direction X (the longitudinal direction X of the boom corresponds to the cross-machine direction of the sprayer machine) when the boom is in its unfolded position (which is not the case in FIG. 1). The two innermost beams 10-10′ comprise elongated structures according to the present invention, although the dimensions of the middle beam 10′ are on a reduced scale in relation to the innermost beam 10 of the two. An inner cap 12 is mounted to the near end of the innermost beam 10 and is provided with hinge element 14 for mounting the boom to the sprayer machine. An outer cap 16 is mounted to the distant end of the innermost beam 10 and is provided with hinge element 18 described in further detail hereinafter for attachment to an end cap 12′ of the middle beam 10′ in order to pivotably connect the two innermost beams 10-10′. Finally, the middle beam 10′ has an outer cap 16′ mounted to its distant end for pivotably attaching the outermost beam 10″ of the boom via a fifth cap 12″ as also described in further detail hereinafter.

The outermost beam 10″ need not have a lattice-like structure as the two innermost beams 10-10′ since its load is obviously on a much lesser scale. In the preferred embodiment, the innermost beam 10 weighs about 120 kg in all, the middle beam 10′ about 30 kg and the outermost beam 10″ around 18 kg.

The entire structure of the innermost beam 10 is illustrated in FIG. 2. The main structural member or girder of the beam 10 is an elongated sheet structure 20 illustrated in FIG. 3 with main fold lines 22 having a tall trapeze-like cross-section resembling a “V” shape as illustrated in FIG. 4A, with a pair of generally identical front and rear (in relation to the machine travel direction) sidewalls 24 depending downwards from a narrow horizontal top wall or spine 26. In the preferred embodiment, the top fold 22 is a little less than a right-angle, opening gradually down along the beam, and each sidewall 24 has a complementary, much slighter fold 28 such that the overall fold 22-28 on to each side is 90°. The open side or bottom of the girder structure 20 is closed by a base plate 30 illustrated in FIG. 5, thereby forming a closed box-like structure 20-30 conveying structural stability to the boom beam 10.

The cross-section of the girder member 20 illustrated in FIG. 4A is not constant over the entire length of the member 20 but rather continuously varies in size and in its aspect ratios (i.e. minor-base:major-base and height:major-base) along the longitudinal direction X, increasing very gradually breadthwise along the top 26 and decreasing in height at a somewhat greater rate from the inner end (i.e. nearest to the sprayer machine) to the outer or distant end of the beam 10, the major base of the cross-section remaining constant throughout the longitudinal direction X. In other words, the sidewalls 24 are tallest and the spine 26 narrowest at the inner edge. In the preferred embodiment, the sheet is 2½ millimeters thick and the girder 20 is about 6½ meters long, 50 centimeters high at the inner end and 36 centimeters high at the outer end. The decrease in height is an obvious design choice to reduce overall weight since section weight and bending moment loads decrease towards the distant end of the boom away from the sprayer machine but the simultaneous increase in width down along the longitudinal direction X has to do with the folding process when manufacturing the girder member 20 as described further on herein. Referring back to FIGS. 2 and 4A, the bottom edges 24 of the girder sheet 20 are again folded inwards along longitudinal fold lines 32, providing ledges 24 for the baseplate 30 to bear on and to reinforce these edges 24 against collisions against external objects.

Referring now to FIG. 6, the girder member 20 is manufactured from a flat sheet 20′. Because of the just described cross-section variations, the starting shape of the sheet 20′ is not a rectangle but an irregular pentagon resembling the shape of an approximately isosceles trapeze with an indented major base 34. The steel sheet is cut by die-cutting, guillotine, plasma, laser or waterjet into the starting shape 20′. Before folding, triangular orifices 36 are punched out of the side walls of the sheet 20′ one after the other leaving inclined strips 38 in between. The triangles 36 are isosceles right-angled triangles such that the strips 38 are inclined at 45° to the longitudinal edges 24 of the girder 20. The sheet 20′ is then folded twice along lines 32 to form the inturned edges 24, then slightly along lines 28 and finally along the inner lines 22 to form the top wall 26 of the girder 20. The top pair of fold lines 22 converge on an imaginary point on the axis of symmetry X way off the major base of the sheet 20′ (corresponding to the inner or near end of the beam 10) and the remaining pairs of fold lines 28 and 32 converge on an opposite imaginary point off the minor base of the sheet 20′ (corresponding to the distant end of the beam 10).

The baseplate 30 is manufactured from a flat rectangular sheet in which rectangular orifices 40 are punched alongside one another in the longitudinal direction X leaving bridges 42 of sheet material in between. Both the triangular orifices 36 in the girder member 20 of FIG. 3 and the rectangular orifices 40 in the baseplate 30 of FIG. 5 serve to lighten the beam structure 20 and will later resemble the lattice-like structure apparent in FIG. 2. The starting sheet for the baseplate 30 is then folded six times along parallel fold lines 44, 46 and 48 extending in the longitudinal direction X so as to nestle inside the bottom portion of the girder member 20, as illustrated in FIG. 4A.

In addition to structurally strengthening and stabilizing the girder structure 20, the base plate 30 also serves to support thirteen nozzle holders 50 along the boom and to carry plastic piping 52 for supplying liquid fertilizers, herbicides, insecticides and the like to the nozzle holders 50. The sprayers are preferably three-nozzle ¼″ (one-quarter inch) diameter nozzle holders 50 which are placed through the baseplate orifices 40 as shown in FIG. 7. Supports 54 are affixed to the bridges 42 for mounting the pipes 52.

A salient feature of the invention is that the structural members 20 and 30 are mounted to one another using bolts and nuts or other removable securing elements such as rivets for instance. To this end, round holes 56 are drilled or otherwise punched out at predetermined positions on the members 20, 30 prior to the folding process thereof. Some of the round holds 56 may be circular and others oblong-shaped in order to ease mating holes matching each other and passing the bolts 58 or rivets therethrough.

It is acknowledged that the baseplate would optimize rigidity and stability if it were mounted upside-down from the position illustrated in FIG. 4A, however the illustrated mounting is preferred since the nozzle holders 50, particularly the active nozzles thereof, are protected in this way by the lower strip 64 of the girder sidewall 24 and the inturned edge 32. In order to compensate for this protective arrangement and at the same time enhance rigidity and stability, bar-shaped spacer units 62 straddle the lower strips 64, 66 of the girder and baseplate members 20-30. Threaded holes 68 are drilled at each end of the spacers for affixing in place using the same bolts 58 as for joining the latter members 20-30. More particularly, the spacers 62 are omitted at the positions of the nozzle holders 50, preferably alternating two spacers 62 to a nozzle holder 50.

Stability of the inner beam 10 is further supplemented by a plurality of cross-platelet members 70 illustrated in FIGS. 8A and 8B, mounted at regular intervals (coinciding with the girder strips 38) inside the girder member 20. As in the cases of the elongated girder members 20 and 30, the cross-platelets 70 are folded sheet parts, generally trapeze-shaped and dimensioned to fit snugly inside the girder cross-section. The side edges 72 thereof are folded back at right-angles to provide ear surfaces for joining to the girder member 20. The sizes of the platelet members 70 differ from one another, the larger of the platelets 70 being mounted to the sidewalls 24 towards the inner end of the girder 20 and the shorter platelets 70 towards the outer end thereof. Oval-shaped holes 74 are punched out to lessen the weight contribution, at least in the larger platelets 70. Round circular and matching oblong holes 56 are drilled or punched out of the folded-back edges 72 of the platelets 70 and the inclined strips 38 of the girder sidewall 24 for bolting 58 the platelets 70 to the sidewalls 24. Finally, the top and bottom ends of the platelet are recessed inwards 78 to make room for the passage of piping 52 and assorted wiring and the like.

The middle boom beam 10′ is designed with the same structure as the above-described inner beam 10 except on a smaller scale with otherwise similar girder and baseplate members since the bending moment load is much less. For this reason, sheet only 1/16′ thick is used and the cross-platelets 70 in the larger beam 10 may be left out of the middle beam 10′. On the other hand, as illustrated in FIG. 1, the outermost beam 10″ may be manufactured in a more simplified folded-sheet structure.

All the end-caps 12, 12′, 16, 16′ are also manufactured by folded metal sheets. Sheet 3/16″ thick is used for the pair of caps 12, 16 on the inner beam 10 and ⅛″ thick for the caps 12′, 16′ on the middle beam 10′. Round and oblong holes 56 for bolts 58 are drilled or punched out at predetermined positions on the members 12, 16, 12′ and 16′ prior to the folding process thereof. Generally conventional articulations on the end-caps allow the outstanding boom section or beam to be purposely pulled up to fold the boom, such as when the sprayer machine is taken out of service for instance or, as the case may be, to yield and be automatically pushed back by an obstacle encountered in operation, such as when turning around near a fence for instance, to avoid damaging the boom. In the illustrated embodiment, the articulation 12′-16 between the larger beams 10, 10′ folds up and back vertically whereas the articulation 16′-12″ yields backwards horizontally.

FIGS. 9A, 9B and 9C illustrate two articulated end-caps 16 and 12′ which are mounted to the outer and inner ends, respectively of the inner and middle beam beams 10-10′. The end-caps 16 and 12′ are interconnected via a pull-up articulation consisting of a metal shaft 80 extending through respective pairs of ears 82, 82′ projecting from the tops of each beam 10-10′. The articulation shaft may comprise a bolt 80 passing through the inner and the outer ears 82-82′ and secured by a nut 84 in a way in which the ears 82-82′ pivot when the middle beam 10′ is turned upwards by a partially toothed gear-wheel 86 mounted on the same shaft 80 driven by a toothed rack 88 extending lengthwise inside the girder 20. The rack 88 may be remotely driven by a hydraulic cylinder 90 mounted inside the girder 20 and connected to further piping (not illustrated) extending inside the top of the inner beam 10.

The ears 82′ of the end-cap 12′ of the middle beam 10′ are placed inwards of the pair of ears 82 of the end-cap 12 of the inner beam 10. A tubular sleeve 92 is mounted coaxial to the shaft 80 and welded to the toothed wheel 86 and, at each end thereof to the pair of ears 82′ so that the latter is turned upwards when the rack 88 is pushed outwards by an increase in hydraulic pressure in the cylinder 90, thereby folding the middle beam 10′ about the shaft 80, together with the outer beam 10″ at the end thereof, to lie on top of the inner beam 10′, in the position shown in FIG. 9C. Conversely, when the rack 88 is pulled back towards the cylinder 90, the wheel 86 is turned the other way and the middle and outer beams 10′-10″ unfold back into their extended operational positions. Stops 94, 94′ are welded at the bottom of each cap 12′, 16 in order abut when the boom is in its fully extended, operational position. Respective rubber caps 96 cover the ends of the stops 94, 94′ to dampen contact and noise when they come together.

FIGS. 10A and 10B illustrate two end-caps 16′ and 12″ which are mounted to the outer and inner ends, respectively, of the middle and outer boom beams 10′-10″. The push-back articulation is a ball 98 and socket 100 joint mounted at the bottom of the respective beam ends. A spring 102 projecting half-way up from the inner beam 10 returns the outer beam(s) to the normal extended position once it has been released by the obstacle. A stub 104 extends inside the spring and abuts against a stop 94″ when the boom is fully extended and operational.

The innermost end-cap 12 illustrated in FIGS. 1 and 2 serves to mount the boom to the front of the sprayer machine in a generally conventional fashion. As illustrated in FIG. 11, the end-cap 12 includes a cross-arm 106 having a proximal pivot 14 mounted to the tractor vehicle chassis (not illustrated) in a conventional fashion and distant offset pivot 108 articulated to the piston shaft 110 of a hydraulic cylinder 112 for moving the boom about the hinge 14 between its respective operative and folded-back positions.

All girder 20, baseplate 30, cross-platelet 70 and end-cap 12, 12′, 16, 16′ members of both beam beams 10-10′ are manufactured from SAE 1010. The members 12, 16, 20, 30 and 70 may be painted or subjected to other surface treatment processes, such as steel galvanization for example, prior to mounting.

Of course, changes, variations and aggregations may be made to any of the above-detailed embodiments, without departing from the scope of the invention. The same has been described by way of preferred embodiments, however those skilled in the art may suit it to other applications or introduce modifications without departing from the purview of the invention as set forth in the appended claims. For instance, while steel sheets are used in the preferred embodiment, the teachings herein may be adapted and applied to other materials, such as fiberglass or carbon reinforced plastics and the like, for which other cross-sections may be suitable. Another possible material is aluminum or an alloy thereof; the reason aluminum is not used typically for boom structures is its unsuitability for welding, however the present invention does away with practically all welding and aluminum is light, thereby relaxing bending moment loads along the cross-sections of the structure and stresses on the sprayer machine.

Furthermore, FIGS. 4B, 4C and 4D illustrate alternative “U”-shaped cross sections and FIG. 4E a “C”-shaped cross-section for embodying the girder and baseplate members 20, 30 with folded sheet structures. In FIG. 4B the sidewall 24′ is formed by a single, rounded 90° fold 22′. FIG. 4C illustrates an open girder structure 20″ made from thicker sheet material with no baseplate, wherein the sprayers may be mounted depending from the underside of the top wall 26′. Whereas the fold lines 22 and 28 are not parallel in the V-shaped girder member 20 only illustrated in FIG. 4A as specified hereinbefore, parallel fold lines would be provided for alternative booms having a U- or a C-shaped cross-section of FIGS. 4B to 4E.

While this invention has been described as having a preferred design, it is understood that it is capable of further modifications, and uses and/or adaptations of the invention and following in general the principle of the invention and including such departures from the present disclosure as come within the known or customary practice in the art to which the invention pertains, and as may be applied to the central features hereinbefore set forth, and fall within the scope of the invention or limits of the claims appended hereto.