Abstract:
One of more cross members of a pickup bed structure include a hole in a flange in a location that is advantageous for installation of aftermarket accessories. The hole does not extend through the floorpan itself. When customers install aftermarket accessories that require holes through the floorpan, the customers are encouraged to align the new holes with the holes in the cross members. Consequently, loads applied by the aftermarket accessories are efficiently transferred to the frame rails.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to the field of pickup truck structures. More particularly, the disclosure pertains to the structure of a pickup bed. 
       BACKGROUND 
       [0002]    Pickup trucks are motor vehicles with a rear open top cargo area often referred to as a bed. Pickup trucks are popular largely because the bed allows them to be utilized in so many different ways, including carrying a variety of types of cargo and towing various types of trailers. Traditionally the majority of body structures on pickup trucks have been formed from steel alloys. Through years of experience, pickup truck designers have learned how to design steel truck body parts that withstand the variety of demanding pickup truck applications. The current regulatory and economic environment have increased the importance of making pickup trucks more fuel efficient as well as functional and durable. One way to reduce the fuel consumption of a vehicle, especially when unloaded, is to reduce vehicle structure weight. 
         [0003]    Aluminum alloys typically have a higher strength to weight ratio than steel alloys. Consequently, replacing steel with aluminum offers the potential for weight reduction. However, the elastic modulus of aluminum is generally lower than the elastic modulus of steel. As well, fabrication techniques and methods of joining parts that work well for steel parts may not work well for the same aluminum part. Due to these and other differences, simple material substitution does not necessarily produce an acceptable design. 
         [0004]    Aluminum alloys are generally identified by a four-digit number, the first digit of which typically identifies the major alloying element. When describing a series of aluminum alloys based on the major alloying element, the first number may be followed by three x&#39;s (upper or lower case) or three zeros. For example, the major alloying element in 6xxx (or 6000) series aluminium alloy is magnesium and silicon, while the major alloying element of 5xxx series is magnesium and for 7xxx series is zinc. Additional numbers represented by the letter ‘x’ (or zeros) in the series designation define the exact aluminum alloy. For example, a 6061 aluminum alloy has a composition of 0.4-0.8% Silicon, 0-0.7% Iron, 0.15-0.4% Copper, 0-0.15% Manganese, 0.8-1.2% Magnesium, 0.04-0.35% Chromium, 0-0.25% Zinc, and 0-0.15% Titanium. Different alloys provide different trade-offs of strength, hardness, workability, and other properties. 
         [0005]    In addition, five basic temper designations may be used for aluminum alloys which are: F—as fabricated, O—annealed, H—strain hardened, T—thermally treated, and W—as quenched (between solution heat treatment and artificial or natural aging). The temper designation may be followed by a single or double digit number for further delineation. For example, aluminum with a T6 temper designation has been solution heat treated and artificially aged, but not cold worked after the solution heat treatment (or such that cold working would not be recognizable in the material properties). 
       SUMMARY 
       [0006]    An aluminum truck bed includes a beaded sheet metal floorpan and at least one cross member. The cross member includes front and rear flanges welded to the floorpan between the beads. One of the flanges defines a hole abutting a flat region of the floorpan between the beads but not extending into the floorpan. In one embodiment, the cross member is fabricated by roll forming which results in a cross member with a constant cross section. In another embodiment, the flange has a variable width to provide increased bearing area for a fastener. The flange may be re-inforced in the vicinity of the hole. A stiffener may be riveted to the cross member to stiffen the cross member near the point at which the cross member is bolted to frame rails. To minimize loads in the cross member, the hole may be located within one bead of the stiffener. 
         [0007]    A pickup truck includes left and right frame rails, a cross member bolted to the frame rails, and a beaded floorpan welded to the cross member. The cross member includes a flange defining a hole. The hole is covered by a flat region of the floorpan. The cross member may include a roll formed channel riveted to a stiffener. The hole may be in either the channel or the stiffener. Instruction may encourage customers to align any hole through the floorpan with the hole in the cross member when installing after-market accessories. 
         [0008]    A method of constructing a truck bed includes roll forming a cross member, stamping a floorpan, and welding the cross member to the underside of the floorpan. The cross member includes a front flange and a rear flange, one of which defines a hole. The hole may be formed into the stock from which the cross member is formed. A bead pattern is stamped into the floorpan. The flanges are welded to flat regions of the floorpan between the beads. The hole in the flange is aligned with a region of the floorpan that does not have a hole. The floorpan and the cross member may be formed from aluminum alloy stock, such as 6xxx. A stiffener may be riveted to the cross member near the hole. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a cut-away pictorial view of a pickup bed. 
           [0010]      FIG. 2  is a bottom pictorial view of a portion of the pickup bed of  FIG. 1 . 
           [0011]      FIG. 3  is a cut-away pictorial view of a pickup bed after installation of an aftermarket accessory. 
           [0012]      FIG. 4  is a bottom pictorial view of the pickup bed of  FIG. 1  adapted to provide a suitable location for installation of aftermarket bed-mounted accessories. 
           [0013]      FIG. 5  is a bottom pictorial view of the pickup bed of  FIG. 1  with an alternative adaptation to provide a suitable location for installation of aftermarket bed-mounted accessories. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Embodiments of the present disclosure are examples and other embodiments may take various and alternative forms. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to utilize the present invention. Various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. Combinations and modifications of features consistent with the teachings of this disclosure could be used for particular applications or implementations. 
         [0015]      FIG. 1  shows a cut-away view of a pickup truck box and frame rail. The box structure includes a floorpan  10 , left and right sidewalls  12 , and a headboard  14 . The floorpan, sidewalls, and headboard may be formed from sheet metal by a stamping process. A number of cross members  16  are welded to the floorpan  10 . The cross members may be formed from sheet metal using a roll forming process. Parts made from a roll forming process have a constant cross sectional shape. To vary the cross section of a roll formed part, a subsequent operation such as shear cutting must be performed. The floorpan, headboard, sidewalls, and cross members may be made of an aluminum alloy such as 6111. The box structure is bolted to frame rails  18 . 
         [0016]      FIG. 2  shows a bottom view of a portion of the pickup bed near the location at which the floorpan  10  is attached to one of the cross members  16 . Note that a number of longitudinal beads  20  are stamped into the floorpan making some regions higher than other regions. Each cross member  16  has front and rear flanges  22 . These flanges are welded to the flat regions of floorpan  10  at various weld locations  24  between the beads  20 . A stiffener  26  is riveted to the cross member  16  at  28  to add rigidity where cross member  16  is bolted to the frame rails  18 . 
         [0017]    In use, a wide variety of loads may be exerted at various points in the box and in various directions. The box structure is designed to transmit these loads to the frame rails with acceptable levels of deflection and without weakening or loosening any joints or sustaining any permanent deformation. Some aftermarket accessories may be attached to the floorpan  10 . These accessories may exert large concentrated loading at the attachment point.  FIG. 3  shows a salt spreader  30  installed in the bed of a pickup truck. The instructions for installation of this salt spreader, like many other aftermarket accessories, calls for drilling holes in the floorpan and installing fasteners  32  into the holes. Then, straps  34  are tightened around the salt spreader to hold the spreader firmly in place. 
         [0018]    When a vertical force is exerted on floorpan  10  at a location between cross members or aft of the rear cross member, floorpan  10  is loaded in bending. For example, an upward force exerted behind the rear cross member loads the raised portions formed by beads  20  in compression and the non-raised portions in tension. An upward force exerted between cross members loads the raised portions in tension and the non-raised portions in compression. The magnitude of the tension and compression stresses and the deflections increases as the distance between the force and the cross member increases. These loads are conveyed from the floorpan  10  to the frame rails  18  by cross members  16 . The magnitude of the stresses in the cross member and the defections increase as the distance between the load and the frame rail increases. 
         [0019]    Although the truck manufacturer cannot control where end users will elect to attach accessories, users can be encouraged to attach accessories in preferred locations. As shown in  FIG. 4 , a hole  36  is drilled in a flange of cross member  16  near the stiffener  26 . This hole may be formed in the stock from which the cross member is formed. Alternatively, it may be drilled or stamped after the cross member is formed. When the vehicle is produced, the sheet metal floorpan  10  above hole  36  is imperforate. In other words, the floorpan does not have a hole aligned with hole  36 , although the location may be marked on the top surface by a small indentation, for example. A customer installing an accessory that requires a hole is encouraged to drill the hole in this location. For example, text may be placed in the owner&#39;s manual, on an adhesive sticker near the hole, or stamped into the bottom surface of the floorpan  10  indicating that this location is preferred. A load applied through a fastener that extends through this hole will be applied directly to the flange and will not cause stress on the floorpan  10 . Since the load is close to the location at which the cross member  16  bolts to the frame rail  18 , the load is carried efficiently to the frame rail with minimal deflection. Cross member  16  may be reinforced in the vicinity of hole  36  to reduce local stresses and to absorb any crush forces exerted by installation of a fastener  32 . For example, the material may be thicker in that region or an additional stiffener may be adhered to the flange in the vicinity of the hole. The stiffener may extend outwardly from the cross member  16  to provide a larger area for installation of the fastener. 
         [0020]      FIG. 5  illustrates another embodiment. In this embodiment, the stiffener  28  is extended beyond the weld locations  28  and shaped to provide a suitable fastening location. In some embodiments, the stiffener may extend to the raised portion of one or more beads  20 . A hole is drilled through the stiffener to mark the preferred fastener location but the hole does not extend through the floorpan  10 . The end user completes the hole as part of installing an aftermarket accessory. 
         [0021]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation. It is understood that various changes can be made and the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments are described as providing advantages or being preferred over other embodiments or prior art implementations, those of ordinary skill in the art should recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes that depend on the specific application and implementation. Embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.