TECHNICAL FIELD 
     This invention relates to a vehicle-borne spray boom for wide pattern application of a liquid chemical to the grounds of a golf course or the like. 
     BACKGROUND OF THE INVENTION 
     Vehicle-borne spray booms are commonly used in agricultural and commercial applications for applying liquid chemicals such as fertilizer, herbicide or insecticide over an expansive area such as a field, park, golf course, etc. The liquid chemical is typically stored in a tank carried or towed by the tractor, and is dispense through an array of spray nozzles distributed along the length of the spray boom. The boom is generally is generally provided with a mounting plate at its midpoint, and the boom arms are laterally cantilevered from the mounting plate. Also, the boom arms are commonly divided into sections that are hinged and foldable for ease of transportation and storage. 
     Spray booms of the type described above are obviously best suited for use on relatively flat terrain so that a generally consistent distance is maintained between the ground and the spray nozzles, ensuring even application of the liquid chemical. However, flat terrain is frequently not the norm in parks and golf courses, resulting in uneven application of the liquid chemical, and in some cases, interference between the ground and the boom. These disadvantages can be avoided to some extent by elevating the entire boom, but elevating the boom makes the spray pattern more susceptible to wind effects, and optimal application of a liquid chemical is usually achieved when the spray nozzle is maintained within about 12-24 inches of the ground surface, depending on the nozzle design. Accordingly, what is needed is a spray boom that retains the advantages of currently known devices, but which is capable of maintaining a consistent and optimal distance between the spray nozzles and the ground on hilly and uneven terrain. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an improved vehicle-borne spray boom apparatus having multiple articulated sections that are foldable and individually supported with respect to the ground to maintain a consistent and optimal distance between the boom sections and the ground on hilly and uneven terrain. A center section of the boom is mounted on a forward facing frame element of the vehicle, and boom arms extending from either end of the center section each comprise at least first and second sections, each supported by a ground-engaging wheel. Each first section is coupled at one end to the center section to permit vertical inclination with respect to the center section, and each second section is coupled at one end to a respective first section to permit vertical inclination with respect to such first section. The coupling between the central and first sections additionally permits relative horizontal inclination, and releasable latch mechanisms are triggered upon full horizontal extension of the first sections to maintain a proper alignment between the first and center sections. In a preferred implementation, each of the second sections includes a tip portion (or third section) that is hinged to permit rearward horizontal inclination with respect to the remainder of the second section and a spring coupling for biasing the tip portion into alignment with the second section. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an overhead view of the spray boom of this invention, as mounted on a tractor. 
     FIGS. 2A and 2B are partial top and frontal views of one side of the spray boom of FIG.  1 . 
     FIG. 3 is a partial rear view of a latch mechanism depicted FIG.  2 A. 
     FIG. 4 is a partial frontal view of the tractor and spray boom of FIG. 1, illustrating vertical inclination of first and second boom sections to accommodate hilly terrain. 
     FIGS. 5A and 5B are partial top and frontal views of a coupling between central and first boom sections as depicted in FIG.  4 . 
     FIGS. 6A and 6B are partial top and frontal views of a coupling between first and second boom sections as depicted in FIG.  4 . 
     FIG. 7 is an overhead view of a coupling between second and third sections of the spray boom of FIG. 1, illustrating horizontal inclination of the third section with respect to the second section. 
     FIG. 8 is a frontal view of the tractor and spray boom of FIG. 1, with the spray boom sections folded for transportation. 
     FIG. 9 is a side view of a spray boom bracket depicted in FIGS. 1,  4  and  8 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, and particularly to FIG. 1, the reference numeral  10  generally designates a ground vehicle such as a small commercial or agricultural tractor equipped with soft, high floatation rear and front tires  12 ,  14  that distribute its weight and enable it to be driven over well-groomed sod (such as a golf course fairway or green) without damaging the sod or creating permanent impressions in the underlying soil. The tractor  10  is adapted to tow (via the illustrated single point hitch  16  or a standard three-point hitch) a wheeled trailer  18  supporting a large tank  20  designed to contain liquid fertilizer, herbicide, insecticide, or the like. As with the tractor  10 , the trailer  18  is equipped with soft, high floatation tires  22  that distribute the weight of the trailer  18  and the liquid contained in tank  20 . A spray boom, generally designated by the reference numeral  24 , and mounted on the front of tractor  10 , is equipped with a commercially available spray distribution system  26  that receives pressurized liquid from tank  20  via hose  28 . A plurality of spray nozzles  30  disposed in distributed fashion along the length of spray boom  24  are coupled to the spray distribution system  26  so that liquid from the tank  20  is directed toward the ground in a series of fine spray patterns along the length of boom  24  as shown. Optionally, the lateral ends of the boom  24  may be equipped with a marking device such as a foam dispenser for purposes of visibly identifying the extent of the spray pattern. 
     According to the present invention, the boom  24  comprises a central section  32  mounted on tractor  10 , and a pair of boom arms  34  and  36  coupled to the left and right lateral ends of central section  32 , as depicted in FIG.  1 . Each of the boom arms  34 ,  36  comprises first, second and third sections  34   a ,  34   b ,  34   c ;  36   a ,  36   b ,  36   c . In boom arm  34 : the first section  34   a  is coupled to the central section  32  so as to support both horizontal and vertical inclination of the first section  34   a  with respect to the central section  32 , the second section  34   b  is coupled to the first section  34   a  so as to support only vertical inclination of the second section  34   b  with respect to the first section  34   a ; and the third section  34   c  is coupled to the second section  34   b  so as to support only rearward horizontal inclination of the third section  34   c  with respect to the second section  34   b . Likewise in boom  36 : the first section  36   a  is coupled to the central section  32  so as to support both horizontal and vertical inclination of the first section  36   a  with respect to the central section  32 , the second section  36   b  is coupled to the first section  36   a  so as to support only vertical inclination of the second section  36   b  with respect to the first section  36   a ; and the third section  36   c  is coupled to the second section  36   b  so as to support only rearward horizontal inclination of the third section  36   c  with respect to the second section  36   b . Finally, a first pair of wheels  34   d ,  36   d  are mounted on the respective first sections  34   a ,  36   a , and a second pair of wheels  34   e ,  36   e  are mounted on the respective second sections  34   b ,  36   b , such that the wheels engage the ground and support the boom arms  34 ,  36  when the boom arms  34 ,  36  are fully extended as shown in FIG.  1 . 
     The couplings between the central, first, second and third sections  32 ,  36   a ,  36   b ,  36   c  are depicted in detail in the top and frontal views of FIGS. 2A and 2B, respectively, with the spray nozzles  30  and associated hoses being omitted for clarity. Of course, the boom sections  34   a ,  34   b ,  34   c  are the mirror image of the illustrated boom sections  36   a ,  36   b    36   c . Also, it will be noted that he central boom section  32  is formed with a single tubular member, whereas he first, second and third sections  36   a ,  36   b ,  36   c  are formed with a pair of tubular members joined by a number of plates welded therebetween. 
     The coupling between the central and first boom sections  32 ,  36   a  is generally designated by the reference numeral  40 , and as indicated above, supports both horizontal and vertical inclination of the first section  36   a  with respect to the central section  32 . The coupling  40  comprises two hinge pins: vertical hinge pin  42  for enabling the horizontal inclination, and horizontal hinge pin  44  for enabling the vertical inclination. Vertical hinge pin  42  is rotatably captured in a housing  46  that is welded to the central boom section  32 , while the horizontal hinge pin  44  is captured by a pair of brackets  48   a , 48   b  welded to first boom section  36   a . The vertical pin  42 , which is free to rotate in housing  46 , is welded to a sleeve  50  surrounding horizontal pin  44  via intermediate plates  52 ,  54 ,  56 . Although not clearly indicated in FIG. 2A, a limited clearance between the plate  54  and the housing  46  prevents rearward horizontal inclination of the first section  36   a  with respect to the central section  32 . 
     Vertical inclination of the first boom section  36   a  with respect to the central boom section  32  is illustrated in general in FIG. 4, and in detail in FIGS. 5A and 5B. FIG. 4 depicts the tractor  10  with the spray boom  24  extended as in FIG. 1, but with the tractor  10  positioned above a downward slope in the ground surface, and FIGS. 5A and 5B depict top and frontal views of the coupling  40  under such conditions. Horizontal inclination of the first boom section  36   a  with respect to the central boom section  32  is illustrated in general in FIG. 8, which depicts the tractor  10  with the spray boom  24  folded for transportation or storage. 
     The coupling  40  also comprises a latch mechanism that can be automatically deployed upon full horizontal inclination of the first section  36   a  with respect to central section  32  to maintain the full horizontal inclination. Referring to FIGS. 2A and 3, the latch mechanism is formed by a lateral extension  54   a  of the plate  54  and a hinged bar  60 . The plate  54  is welded to the first section  36   a , as explained above, while the bar  60  is rotatably supported on a pin  62  captured in a pair of plates  64 ,  66  welded to central section  32  on either side of bar  60 . As best seen in the rear view of FIG. 3, the plate extension  54   a  has a tapered leading edge  68 , terminating in a vertical latching edge  70 , so that as the first section  36   a  nears full horizontal inclination with respect to the central section  32 , the tapered leading edge  68  engages and rotates the trailing end of bar  60  upward about pin  62 . As full horizontal inclination is achieved, the vertical edge  70  moves past the bar  60 , allowing the bar  60  to fall to its deployed position as depicted in FIGS. 2A and 3, whereupon interference between bar  60  and vertical edge  70  of plate extension  54   a  maintains the full horizontal inclination. 
     The coupling between the first and second boom sections  36   a ,  36   b  is generally designated by the reference numeral  70 , and as indicated above, supports only vertical inclination of the second section  36   b  with respect to the first section  36   a . For this purpose, the coupling  70  comprises a single horizontal hinge pin  72  that is captured by a pair of brackets  74   a ,  74   b  welded to tubular frame elements of the first boom section  36   a . A plate  76  welded to the inboard ends of the tubular frame elements of the second boom section  36   b  extends upwardly and is welded to a sleeve  78  surrounding horizontal pin  72 . This couples the first and second boom sections  36   a ,  36   b , and permits the aforementioned vertical inclination. 
     Vertical inclination of the second boom section  36   b  with respect to the first boom section  36   a  is illustrated in general in FIGS. 4 and 8, and in detail in FIGS. 6A and 6B. FIG. 4 depicts the tractor  10  positioned above a downward slope in the ground surface with the spray boom  24  extended, as mentioned above, and FIGS. 6A and 6B depict top and frontal views of the coupling  70  under such conditions. FIG. 8, as also mentioned above, depicts the tractor  10  with the spray boom  24  folded for transportation or storage. 
     The coupling between the second and third boom sections  36   b ,  36   c  is generally designated by the reference numeral  80 , and as indicated above, supports only rearward horizontal inclination of the third section  36   c  with respect to the second section  36   b . For this purpose, the coupling  80  comprises a single vertical hinge pin  82  that is captured by a pair of brackets  84   a ,  84   b  welded to rearward face of the tubular frame elements of the second boom section  36   b  via spacer plate  85 . A sleeve  86  surrounding the vertical hinge pin  82  is welded to the rearward frame element of boom section  36   c ; this couples the second and third boom sections  36   b ,  36   c  while permitting the aforementioned rearward horizontal inclination therebetween. An example of such rearward horizontal inclination is depicted in FIG. 7. A stop plate  87  welded to the sleeve  86  limits the degree of permitted horizontal inclination when sleeve  86  is rotated to the point where stop plate  87  contacts the spacer plate  85 . A spring  88  is strung between a vertical post  90  welded to the rearward tubular member of second boom section  36   b  and a vertical post  92  welded to the forward tubular member of third boom section  36   c . The spring  88  therefore stretches across the coupling  80 , and biases the second and third boom sections  36   b ,  36   c  into alignment as shown in FIGS.  1  and  2 A- 2 B, for example. 
     Finally, FIG. 9 depicts a side view of a bracket  100  welded to the central boom section  32 . The bracket  100  has several features, including a rearwardly extending mounting plate  102  for attachment of the spray boom  24  to the tractor  10 , a vertical mounting plate  104  for attachment of the spray distribution system  26 , and forwardly extending arms  106  and  108  for supporting the boom arms  34 ,  36  when in a folded state as depicted in FIG.  8 . With the boom arms  34 ,  36  are so positioned, the vertical plates  110  and  112  retain the boom arms  34 ,  36  in position during operation of the tractor  10 . 
     The aforementioned features cooperate to provide a spray boom that is inexpensive, easy to use, and capable of maintaining a consistent and optimal distance between the spray nozzles  30  and the ground on hilly and uneven terrain of the sort commonly encountered on golf courses and parks. Being mounted on the front of the tractor  10 , the spray boom  24  is easy to see for purposes of controlling the extent of the spray pattern and maneuvering around obstacles such as trees. Additionally, the boom  24  may be conveniently stored in the folded position with a pair of simple stands (not shown) having posts adapted to be received in corresponding tube members welded to the central boom section  32 , one such tube member  33  being shown in FIG.  2 A. 
     To mount the spray boom  24  on tractor  10 , the operator merely drives the tractor up to the stored folded spray boom, transfers the boom  24  from the stands to a horizontal mounting plate on the tractor, and bolts the boom  24  to the tractor mounting plate via mounting plate  102  of bracket  100 . A central pin (not shown) extending downward from the plate  102  and adapted to be received in a corresponding opening in the tractor mounting plate may be provided to facilitate centering of the spray boom  24  with respect to the tractor  10 . After coupling the hose  28  and an electrical connector (not shown) to the spray distribution system  26 , the operator drives the tractor  10  with attached spray boom  24  to a desired location, and manually extends the boom arms  34  and  36 . The same procedure is used to extend each of the boom arms  34  and  36 , with the forward-most boom arm being extended first. The procedure is simply as follows: (1) lift the respective boom arm off bracket  100 , (2) rotate the boom arm forward and lower it until the respective wheel  34   d ,  36   d  engages the ground, (3) rotate the boom arm about the respective hinge pin  42  until the latching mechanism (plate  54 +bar  60 ) locks the boom arm in place, and (4) rotate the second boom section about the respective hinge pin  72  until the respective wheel  34   e ,  36   e  engages the ground. When both boom arms  34 ,  36  have been so deployed, the operator is ready to begin spraying the intended area. If the end of either boom arm  34 ,  36  contacts an obstacle such as a tree or post, the coupling  80  permits temporary rearward inclination of the respective third boom section  34   c ,  36   c  to prevent damage to the spray boom  24 , whereafter the spring  88  returns the respective third boom section  34   c ,  36   c  to its normal position. When finished spraying, the operator stops the tractor  10 , releases the latching mechanisms by rotating the respective bars  60  upward, reverses the aforementioned procedure for each of the boom arms  34 ,  36  (conveniently, either arm  34 ,  36  may be folded first), and drives the tractor  10  with attached spray boom  24  to another location. To dismount and store the spray boom, the mounting procedure explained above is simply reversed. 
     In summary, the present invention provides an easily operated vehicle-borne spray boom having multiple articulated sections that are conveniently foldable for storage or transportation, with the sections being individually supported with respect to the ground to maintain a consistent and optimal distance between the boom sections and the ground on hilly and uneven terrain. While described in reference to the illustrated embodiment, it is expected that various modifications in addition to those mentioned above will occur to those skilled in the art. Thus, it will be understood that spray booms incorporating these and other modifications may fall within the scope of this invention, which is defined by the appended claims.
A vehicle-borne spray boom apparatus has multiple articulated sections that are foldable and individually supported with respect to the ground to maintain a consistent and optimal distance between the boom sections and the ground on hilly and uneven terrain. A center section of the boom is mounted on a forward facing frame element of the vehicle, and boom arms extending from either end of the center section each comprise at least first and second sections, each supported by a ground-engaging wheel. Each first section is coupled at one end to the center section to permit vertical inclination with respect to the center section, and each second section is coupled at one end to a respective first section to permit vertical inclination with respect to such first section. The coupling between the central and first sections additionally permits relative horizontal inclination, and releasable latch mechanisms are triggered upon full horizontal extension of the first sections to maintain proper alignment between the first and center sections.