You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
TECHNICAL FIELD  
         [0001]    This invention relates generally to a structural member of a work machine and, more particularly, to a particular structure of the structural member.  
         BACKGROUND  
         [0002]    In work machines, such as backhoe loaders, skid steer loaders, and excavators, substantial forces are transmitted through a member that connects an implement to a frame of the work machine. The member typically includes a boom and a stick, the stick being pivotally attached with the boom. During operation of the work machine, the member experiences heavy forces as the implement penetrates the ground to dig, carries heavy loads from one location to another, or pushes or pulls material. The member, therefore, must be able to endure such heavy forces. The member, however, must also be sufficiently light to prevent the work machine from using most of its available power to manipulate the member. The member, therefore, must have a structural design that combines a heavy-duty construction along with being relatively light weight.  
           [0003]    One known boom design is disclosed in U.S. Pat. No. 6,158,949 issued to Walth et. al. on Dec. 12, 2000. It discloses a boom design having a top boom support structure, a bottom boom support structure, a first lateral boom support structure, and a second lateral boom support structure, which cooperate with each other to define a boom void therein. This boom design requires the attachment of four supporting structures, which creates a heavier boom, increases fatigue due to the additional welding required to manufacture, and is more time consuming to manufacture. This creates a boom design that is expensive to operate due to the additional energy required to manipulate the heavy boom and is more expensive to manufacture due to the additional structures and the additional welding required.  
           [0004]    The present invention is directed to overcoming one or more of the problems as set forth above.  
         SUMMARY OF THE INVENTION  
         [0005]    In one aspect of the present invention, a structural member of a work machine has first and second-end portions, and comprises, a body having a top portion, a bottom portion, and a middle portion. The top and bottom portions have longitudinal centerlines. The middle portion is positioned between and substantially perpendicular with the top and bottom portions and positioned substantially at the longitudinal centerline of at least one of the top and bottom portions. The structural member further comprises a primary coupling formed with the body at the first-end portion of the structural member and extends from at least one of the top, bottom, and middle portions.  
           [0006]    In another aspect of the present invention, a work machine comprises a frame, a first member, a second member, a primary coupling, and a secondary coupling. The first member has first and second end portions, a top portion having a longitudinal centerline, a bottom portion having a longitudinal centerline, and a middle portion. The middle portion is positioned between and substantially perpendicular with the top and bottom portions and positioned substantially at the longitudinal centerline of at least one of the top and bottom portions. The primary coupling is defined at the first-end portion of the first member for pivotable attachment with the frame, and the secondary coupling is defined at the second-end portion of the first member for pivotable attachment with the second member.  
           [0007]    The present invention is a structural member of a work machine that has first and second-end portions, and comprises, a body having a top portion, a bottom portion, and a middle portion. The top and bottom portions have longitudinal centerlines. The middle portion is positioned between and substantially perpendicular with the top and bottom portions substantially at the longitudinal centerline of at least one of the top and bottom portions. The structural member further comprises a primary coupling formed with the body at the first-end portion of the structural member and extends from at least one of the top, bottom, and middle portions. The positioning of the middle portion between and substantially perpendicular with the top and bottom portions provides sufficient support for the compressive and tensional forces applied to the structural member during normal operation by distributing such forces throughout the structural member. The structural member, therefore, is able to handle heavy-duty applications with a reduced weight configuration. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a side view of a work machine, such as a backhoe loader, incorporating a boom of the present invention;  
         [0009]    [0009]FIG. 2 is a perspective view of the boom of FIG. 1 fabricated as a unitary casting; and  
         [0010]    [0010]FIG. 3 is an exploded view of an alternate embodiment of the boom of FIG. 1 manufactured from various components. 
     
    
     DETAILED DESCRIPTION  
       [0011]    While the invention is open to various modifications and alternative forms, a specific embodiment thereof has been shown by way of example in the drawings and will herein be described in detail. There is, however, no intent to limit the invention to the particular form disclosed.  
         [0012]    Referring to the drawings, FIG. 1 is a work machine  1 , such as a backhoe loader, skid steer loader, or excavator, that has a frame  10 , a plurality of wheels  20  supporting the frame  10  against the ground, and an operator&#39;s compartment  30  supported on the frame  10  and positioned substantially above the wheels  20  on the rear-end portion of the work machine  1 . The work machine  1  further includes a front member  40  and a rear member  50  pivotally attached with the front and rear-end portions of the frame  10 , respectively. The front member  40  includes a multi-bar linkage  60  pivotally attached with the front-end portion of the frame  10  and a front implement  70  pivotally attached with the multi-bar linkage  60 . The front implement  70  may be a loader bucket, brush, auger, or other suitable worktool. The rear member  50  includes a boom  80  pivotally attached with the rear-end portion of the frame  10 , a stick  90  pivotally attached with the boom  80 , and a rear implement  100  pivotally attached with the stick  90 . The rear implement  100  may be a bucket, a grapple, or any other suitable worktool. The work machine  1  also includes a first hydraulic cylinder  110  that has a first-end portion attached with the boom  80  and a second-end portion attached with the stick  90 . A second hydraulic cylinder  120  has a first-end portion attached with the boom  80  and a second-end portion attached with the rear-end portion of the frame  10 . It should be understood that the work machine  1  could be of any suitable type that utilizes a boom and not just those enumerated above or the backhoe loader depicted in FIG. 1.  
         [0013]    In FIG. 2, the boom  80  of the work machine  1  is shown in more detail. The boom  80  is made from a unitary casting and includes a body  124  that has a top portion  130 , a bottom portion  140 , and a middle portion  150 . The middle portion  150  is positioned between and substantially perpendicular with a longitudinal centerline  160 ,  170  of the top and bottom portions  130 ,  140  to define a substantially I-shaped beam. It should be understood that the middle portion  150  could a variety of other shapes, such as V, W, M, or any other shape so long as the middle portion  150  is located substantially along the longitudinal centerline  160 ,  170  of at least one of the top and bottom portions  130 ,  140 . The boom  80  also includes a primary coupling  180  at a first-end portion  190  of the boom  80  and a secondary coupling  200  at a second-end portion  210  of the boom  80 . The primary coupling  180  includes a boss  220  that is formed as an integral part of the boom  80  and is positioned between the top and bottom portions  130 ,  140 , adjacent with the middle portion  150 . The boss  220  allows for the attachment of the boom  80  with the rear-end portion of the frame  10 . The secondary coupling  200  includes bifurcated legs  230 ,  240 , a first boss  250 , and a second boss  260 , all of which are formed as an integral part of the boom  80 . The first boss  250  is positioned at the second-end portion  210  of the boom  80  adjacent to one of the bifurcated legs  230  of the boom  80  and the second boss  260  is positioned at the second-end portion  210  of the boom  80  adjacent to the other bifurcated leg  240 . The first and second bosses  250 ,  260  allow for the attachment of the boom  80  with the stick  90 .  
         [0014]    Further, the boom  80  includes top and bottom mounts  270 ,  280  formed as an integral part of the boom  80 . The top mount  270  includes a top flange  290  positioned on the top portion  130  and a boss  300  formed on the top flange  290 . The top mount  270  is positioned between a midpoint  310  of the boom  80  and the second-end portion  210 . The bottom mount  280  includes a bottom flange  320  positioned on the bottom portion  140  and a boss  330  formed on the bottom flange  320 . The bottom mount  280  is positioned so that the boss  330  is positioned near the midpoint  310  of the boom  80 .  
         [0015]    Finally, the body  124  of the boom  80  includes a curvilinear portion  340  positioned between the midpoint  310  of the boom  80  and the first-end portion  190 . The curvilinear portion  340  is usually positioned a predetermined distance D 1  from the first-end portion  190  and a predetermined distance D 2  from the second-end portion  210  wherein the distance D 2  is greater than D 1 . Alternatively, the curvilinear portion  340  could be positioned so that the distance D 1 is greater than the distance D 2 . The curvilinear portion  340  is formed to position the first-end portion  190  at an inclination of between 20 and 90 degrees with respect to the second-end portion  210  as shown at  350 . It should be understood that the angle of inclination  350  of the first end portion  190  with respect to the second-end portion  210  could be different depending upon the particular work machine on which the boom  80  is attached and the ranges referenced above are not meant to limit the angle of inclination of the first-end portion with respect to the second-end portion.  
         [0016]    An alternative embodiment is depicted in FIG. 3 with reference numbers of previous Figures being used to identify similar components therein. The boom  80  is manufactured from various components through an assembly process and has a first-end portion  400  and a second-end portion  410 . The boom  80  includes top and bottom plates  420 ,  430 , and a middle plate  440  welded between and substantially perpendicular with longitudinal centerlines  450 ,  460  of the top and bottom plates  420 ,  430 , to define a body  124  similar to that of FIG. 2. The top and bottom plates  420 ,  430  each include bifurcated legs  470 ,  480 ,  490 ,  500  positioned at the second-end portion  410 . The boom  80  also includes a primary coupling  510  defined at the first-end portion  400  and a secondary coupling  520  defined at the second-end portion  410  of the boom  80 .  
         [0017]    The primary coupling  510  is formed by welding a boss  530  between and with the top and bottom plates  420 ,  430  and with the middle plate  440 . When the middle plate  440  is welded with the top and bottom plates  420 ,  430 , the top and bottom plates  420 ,  430  are longer than the middle plate  440  and extend beyond the middle plate  440  at the first-end portion  400  thus creating a pocket  540 . The boss  530  fits into the pocket  540  and is welded with the top, bottom, and middle plates  420 ,  430 ,  440 . The primary coupling  510  pivotally attaches the boom  80  with the rear-end portion of the frame  10 .  
         [0018]    The secondary coupling  520  is formed by positioning a curved, outwardly extending intermediate plate  550  between the bifurcated legs  470 ,  480 ,  490 ,  500  and welding it thereto. A first boss  560  is welded between one of the bifurcated legs  470 ,  490  of the top and bottom plates  420 ,  430  and with the intermediate plate  550 , and a second boss  570  is welded between the other bifurcated legs  480 ,  500  of the top and bottom plates  420 ,  430  and with the intermediate plate  550 . The secondary coupling  520  pivotally attaches the boom  80  with the stick  90 .  
         [0019]    The boom  80  further includes a top mount  580  and a bottom mount  600 . The top mount  580  is welded with the top plate  420  and is positioned between a midpoint  590  of the boom  80  and the second-end portion  410 . The bottom mount  600  is welded with the bottom plate  430  and is positioned substantially at the midpoint  590  of the boom  80 . The top and bottom mounts  580 ,  600  include top and bottom flanges  610 ,  620  that are welded with the top and bottom plates  420 ,  430 , respectively. Each of the top and bottom flanges  610 ,  620  include apertures (not shown) therethrough, and each such aperture has a boss  630 ,  635 ,  640 ,  645  welded to each side thereof.  
         [0020]    Finally, the boom  80  includes a curvilinear portion  650  that is similar to the curvilinear portion  340  in FIG. 2. The curvilinear portion  650  is formed before welding of the components by bending the top, bottom, and middle plates  420 ,  430 ,  440  and then welding them together. Further, although welding is mentioned as the means for attaching the various components of the boom  80  together in FIG. 3, it should be understood that any suitable means, such as bonding or the like, may be used to achieve similar results.  
       INDUSTRIAL APPLICABILITY  
       [0021]    During normal operation, the implement  100 , stick  90 , and boom  80  work in unison to effectively perform work functions, such as digging a hole or moving large amounts of material. During this sort of operation, forces are transmitted through the implement  100  to the stick  90 , to the boom  80 , and ultimately to the frame  10 .  
         [0022]    In the embodiment depicted in FIG. 2, the boom  80  is manufactured so that the top, bottom, and middle portions  130 ,  140 ,  150  form the body  124  as a unitary member. Additionally, the primary and secondary couplings  180 ,  200  and the top and bottom mounts  270 ,  280  are manufactured as part of the unitary boom  80 . The manufacturing can be accomplished by casting the boom  80 , or another suitable manufacturing process. The casting process reduces the requirement of assembling and attaching four supporting structures required for the box boom, reducing the time and cost required to manufacture the boom  80 . The reduction of the four supporting structures also reduces the overall weight of the boom  80 . Further, the reduction of welding reduces weld-induced stress and fatigue concerns. Finally, the boom  80  of FIG. 2 has a cross sectional I-shape that provides sufficient support for the compressive and tensional forces applied to the boom  80  during normal operation by distributing such forces throughout the boom  80  structure. The boom  80 , therefore, is able to handle heavy-duty applications with a reduced weight configuration.  
         [0023]    Alternatively, as depicted in FIG. 3, the boom  80  can be manufactured from various components while having the same I-shape structure as that in FIG. 2. The middle plate  440  is welded to the top and bottom plates  420 ,  430  along the longitudinal centerline of the top and bottom plates  450 ,  460 . The primary coupling  510  is assembled and welded to the first-end portion  400 , and the secondary coupling  520  is assembled and welded to the second-end portion  410 . Finally, the top and bottom mounts  580 ,  600  are welded to the top and bottom plates  420 ,  430 , respectively. Even though there are more components than the design in FIG. 2, the manufacture of the boom  80  still reduces the time and cost because it has fewer components to assemble than other boom designs. Further, because there are fewer components to assemble and attach there is less welding required, therefore, the weld-induced stress and fatigue concerns are reduced. Again, as with the boom  80  of FIG. 2, heavy-duty applications are achieved with a reduced weight configuration.  
         [0024]    As can be see from the descriptions above, the boom  80  can be manufactured as a unitary member or with fewer components that the box boom design requiring four supporting structures. This causes the boom  80  to be less expensive to manufacture, less expensive to operate, and reduces stress and fatigue thereof. Further, the general I-shape structure provides a stronger boom  80  with a reduced weight for increased operational advantages.  
         [0025]    Other aspects, objects and advantages of the invention can be obtained from a study of the drawings, the disclosure and the appended claims.

Summary:
Structural members of work machines experience heavy forces and the structural member must be able to endure such heavy forces, but must also be sufficiently light to prevent the work machine from using most of its available power to manipulate the structural member. The present apparatus facilitates the heavy-duty construction along with a reduced weight by comprising top and bottom portions, a middle portion attached between and substantially perpendicular with the top and bottom portions, and a primary coupling formed at a first-end portion of the structural member and extending from at least one of the top, bottom, and middle portions to define a substantially I-shaped structural member.