Abstract:
A vehicle frame assembly, including a pair of sidebars, interconnecting crossbars and optional connecting brackets all formed from channel sections, is manufactured using soft adjustable tooling, preferably a roll former, thereby eliminating the need to use hard tooling. The shorter frame assembly components, including the crossbars and optional brackets, are formed as multi-piece gang members. The frame may be assembled with mechanical fasteners (bolts or rivets) or by welding, the latter obviating the need to use brackets. When mechanical fasteners are used, the components are hole-punched, preferably with numerically controlled piercing equipment. When heat treated steel is used, the piercing and cutting operations are preferably performed after heat treating.

Description:
[0001]    This is a continuation-in-part of application No. 10/355,313, filed Jan. 31, 2003. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention pertains to the manufacture of the components for a vehicle frame assembly and, more particularly, to the forming of frame sidebars, crossbar members and optionally, bracket members, all comprising channel sections.  
           [0003]    The present invention relates to the preferred use of a computer controlled roll former and an associated computer controlled hole punching apparatus to form the sidebar components, ganged bracket members, and ganged crossbar members, with the ganged members cut to form individual brackets and crossbars after all the preliminary forming is completed. However, optional forming means may also be used.  
           [0004]    A typical frame member for a vehicle chassis includes a pair of parallel sidebars or side rails connected by transverse crossbars with the connections effected by brackets if the connections are made by bolting or riveting. Welded frames may not require connecting brackets. However, in the heavy truck industry, bolted connections are preferred and predominate. The use of welded frames is generally limited to light trucks.  
           [0005]    For many years, truck fame components were formed primarily by stamping individual pieces utilizing hard tooling designed to form sequentially identical component parts. Truck frame components are typically made of channel members, but within a particular frame assembly, both the size and the gauge of the channels for the respective sidebars, crossbars and brackets may vary. Thus, three or more sets of hard tooling may be required for stamping the components of a typical frame assembly. For a bolted (or riveted) frame assembly, the bolt holes are punched in the individual components after the components are stamped and often prior to final heat treating. Because the bolt holes may be punched with different punching apparatus, there is often a problem of bolt hole match-up at assembly. In addition, heat treating the components after the holes have been punched may result in further changes in bolt hole position and/or size.  
           [0006]    All of the foregoing problems may be compounded where the components are supplied by more than one manufacturer or are made at different locations. In addition, truck manufacturers often desire essentially identical frame members in an order to be provided with varying bolt hole patterns depending on the engine, truck body and other intended uses for a particular frame. This also propounds the problems of bolt hole position and match-up.  
           [0007]    Even in the manufacture of a welded frame assembly, where connecting brackets may not be utilized, there is utility and importance in forming the crossbars as initial ganged crossbar members. Both dimensional accuracy and productivity are enhanced by utilizing ganged crossbar members and, if needed, ganged bracket members as well. Although practice of the present invention lends itself particularly well to formation of the frame members in a continuous roll forming apparatus, ganged members, both crossbars and brackets, may also be formed in more conventional soft-tooled equipment such as a press brake or a universal stamping/forming tool. These machines may be operated either automatically or manually, all while preserving the basic benefits of ganged part formation.  
         SUMMARY OF THE INVENTION  
         [0008]    In accordance with one embodiment of the present invention, a vehicle frame assembly, comprising sidebars, crossbars and connecting brackets, is manufactured using a computer controlled flexible roll former that eliminates the need for hard tooling. The shorter frame assembly components, namely the crossbars and the brackets, are formed as multi-piece gang members that are hole-punched and, if necessary, offset-formed before being cut into respective individual crossbars and brackets.  
           [0009]    In one embodiment of the method of the present invention, the method comprises the steps of (1) forming a steel strip in the roll former to a first channel shape, (2) cutting the first channel shape to provide a sidebar, (3) adjusting the roll former and forming a steel strip to a second channel shape, (4) cutting the second channel shape to provide a multi-bracket gang member, (5) adjusting the roll former and forming a steel strip to a third channel shape, (6) cutting the third channel shape to provide a multi-crossbar gang member, (7) punching a plurality of attachment holes in the sidebars, in the bracket gang member, and in the crossbar gang member, and (8) cutting the bracket gang member and the crossbar gang member to provide respective individual brackets and crossbars.  
           [0010]    In one variation of the foregoing method, each of the forming steps is performed on the same strip. The method may also include the step of heat treating the sidebars, the bracket gang member, and the crossbar gang member before punching. Preferably, the method comprises cutting the first channel shape to provide a plurality of pairs of sidebars, cutting the second channel shape to provide a plurality of bracket gang members, and cutting the third channel shape to provide a plurality of crossbar gang members.  
           [0011]    In a further variation of the present invention, vehicle frame assemblies each including a pair of sidebars, a plurality of crossbars for interconnecting the sidebar pair, and a plurality of connection brackets, all formed of channel sections, are manufactured by a method comprising the steps of (1) forming sidebars, ganged bracket members, and ganged crossbar members utilizing an adjustable computer controlled roll former, (2) heat treating, if necessary, the sidebars, bracket members and crossbar members, (3) punching connection holes in the sidebars, bracket members and crossbar members utilizing a computer controlled punch, and (4) cutting the bracket members and crossbar members to form individual brackets and crossbars.  
           [0012]    This variant method may also include the step of, prior to cutting the crossbar members, forming offset portions at selected positions of the crossbar members. The offset portions are preferably formed at crossbar end positions defined by the subsequent cutting step. The offset forming step may comprise vertical offsetting or horizontal offsetting.  
           [0013]    A further embodiment of the method of the present invention comprises manufacturing a plurality of vehicle frame assemblies, each including a pair of sidebars, a plurality of crossbars and a plurality of brackets, including the steps of (1) forming the sidebars to individual cut lengths, (2) forming the crossbars and the brackets, respectively, in initial ganged crossbar members and ganged bracket members, (3) punching the sidebars, crossbar members, and bracket members in a computer controlled punch device to form connection holes, and (4) cutting the crossbar members and the bracket members to form individual crossbars and brackets.  
           [0014]    Preferably, the forming step of the foregoing method comprises roll forming. The roll forming step preferably utilizes a computer-controlled adjustable roll former. The method may also include the step of heat treating the sidebars, crossbar members and bracket members prior to punching. The heat treating step is preferably performed after the roll forming step.  
           [0015]    In accordance with the basic method of the present invention, a vehicle frame assembly, comprising sidebars and crossbars, is manufactured using gang forming for at least some of the components. The shorter frame assembly components, namely the crossbars, are formed as multi-piece ganged members and, if necessary, offset-formed before being cut into individual crossbars. The basic method comprises the steps of (1) forming the sidebars to individual cut lengths, (2) forming the crossbars in initial ganged crossbar members, (3) cutting the crossbar members to form individual crossbars, and (4) connecting the sidebars with the crossbars.  
           [0016]    If the frame assemblies utilize mechanical fasteners and brackets to provide the component interconnections, the method may also include the steps of (1) forming the brackets in initial ganged bracket members, (2) forming connection holes in the sidebars, crossbar members and bracket members, (3) cutting the bracket members to form individual brackets, and (4) utilizing the brackets to connect the sidebars to the crossbars. Preferably, the connection holes are formed by punching and the brackets are utilized to connect the sidebars to the crossbars with bolted connections.  
           [0017]    The forming step preferably comprises roll forming, and the method may also include the step of heat treating the sidebars, crossbar members and bracket members prior to forming the connection holes.  
           [0018]    In a variant of the basic method wherein the frame assembly includes a plurality of brackets, the method includes the steps of (1) forming the brackets in initial ganged bracket members, (2) forming connection holes in the sidebars, crossbar members and bracket members, (3) cutting the bracket members to form individual brackets, and (4) utilizing the brackets to connect the sidebars to the crossbars. The step of forming connection holes may comprise any one of the steps of punching, drilling, and thermal cutting. The method for utilizing the brackets to connect the sidebars to the crossbars preferably comprises bolting or riveting.  
           [0019]    The basic method of the present invention may alternately utilize the connecting step of welding. In this case, the forming step also preferably comprises roll forming. In a variation of the basic method to provide a welded frame assembly, a plurality of second crossbars are used and combined with the initial crossbars to form composite box-like crossbars. In particular, the method includes the additional steps of (1) forming the sidebars, the ganged crossbar members, and second ganged crossbar members in the shape of channel sections, the channel sections of the crossbar members being larger in cross-sectional size than the second crossbar members, (2) cutting the second ganged crossbar members to form individual second crossbars, (3) forming a composite crossbar of a second crossbar within a crossbar, and (4) connecting the composite crossbar to the sidebars by welding. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 is a side elevation view of a vehicle frame sidebar, bracket gang member, and crossbar gang member formed in accordance with the method of the present invention.  
         [0021]    [0021]FIG. 2 is a perspective view of a portion of a vehicle frame assembled with the components formed in accordance with the present invention.  
         [0022]    [0022]FIG. 3 is an enlarged sectional detail taken on line  3 - 3  of FIG. 2.  
         [0023]    [0023]FIG. 4 is an enlarged sectional detail taken on line  4 - 4  of FIG. 2.  
         [0024]    [0024]FIG. 5 is a schematic process flow diagram for the manufacture of a frame assembly in accordance with the present invention.  
         [0025]    [0025]FIG. 6 is a perspective view of a frame assembled with the components made in accordance with the process of FIG. 5.  
         [0026]    [0026]FIG. 7 is a side elevation view of a vehicle frame sidebar, a larger section crossbar gang member, and a smaller section crossbar gang member formed in accordance with a further embodiment of the present invention.  
         [0027]    [0027]FIG. 8 is a side elevation detail, partly in section, showing a welded construction utilizing crossbars cut from one of the crossbar members of FIG. 7.  
         [0028]    [0028]FIG. 9 is a sectional detail taken on line  9 - 9  of FIG. 8.  
         [0029]    [0029]FIG. 10 is a side elevation detail, partly in section, showing a further embodiment of a welded construction utilizing crossbars cut from both of the crossbar members of FIG. 7.  
         [0030]    [0030]FIG. 11 is a section taken on line  11 - 11  of FIG. 10.  
         [0031]    [0031]FIG. 12 is a perspective view of a vehicle frame utilizing the crossbar construction of FIGS. 10 and 11. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]    In a roll former, structural shapes may be formed from rolls of flat strip steel or other metals by moving the strip through progressive tooling to change the shape of the strip to, for example, a channel shape. Channel members so formed may be continuously produced and cut to length with a flying shear, all in a manner known in the art. In accordance with the method of the present invention, to be described in detail hereinafter, an automated flexible roll forming system, of the type made, for example, by Stam Spa (Italy) is used to form three different channel member components for a vehicle frame assembly and is combined with a computer controlled punch or piercing apparatus, and optimally other offsetting devices, to form the frame components in an extremely accurate and cost effective way.  
         [0033]    [0033]FIG. 1 shows the three master components of a vehicle frame assembly after they have been initially roll formed, heat treated if necessary, and pierced to form the holes for bolts or rivets used to assemble the frame. Each of the elements shown in FIG. 1 comprises a channel member. One component comprises a sidebar  10  of a conventional channel section, including a central web  11  and opposite end flanges  12 . To produce a complete frame  13 , as shown in part in FIG. 2, two sidebars  10  are required. The sidebars are individually cut to length as they exit the roll former, preferably utilizing a flying shear as indicated above. The lower component in FIG. 1 is a crossbar gang member  14  which is formed similarly to the sidebar  10  but may have different dimensions for its web  15  and flanges  16 , and may be formed from a different gauge steel strip. The crossbar gang member  14  is formed to any convenient length in the roll former, resulting in multiple crossbars  17  subsequently provided in a cutting operation which will be described below. Although a crossbar gang member  14  having three potential crossbars  17  is shown in FIG. 1, a roll former may be capable of producing a member having a length, for example, of about 40 feet from which up to 16 crossbars  17  may be subsequently cut.  
         [0034]    The middle member in FIG. 1 comprises a bracket gang member  18  which, like the sidebar  10  and crossbar gang member  14 , is roll formed to a channel section including a web  20  and flanges  21 . The bracket gang member  18  may be heat treated after forming, if necessary, hole punched in a computer controlled piercing apparatus and subsequently cut to short lengths to form connecting brackets  22  utilized to attach the crossbars  17  to the sidebars  10  in the assembly of the frame  13 .  
         [0035]    [0035]FIGS. 3 and 4 show how flange head bolts  23  and related flange head nuts  24  are used to connect the crossbars  17  to the sidebars  10 , utilizing brackets  22 . Specifically, the frame  13  is assembled with the following bolted connections, as shown in FIGS. 3 and 4. A pair of crossbars  17  is bolted back-to-back with bolted connections  29   a . This crossbar subassembly is connected to a bracket  22  by bolted connections  29   b  interconnecting the crossbar flanges  16  to the bracket flanges  21 . Finally, the brackets are bolted to the sidebars  10  with bolted connections  29   c  attaching their respective webs  20  and  11 . In these figures, it will be noted that the web  11  of the sidebar  10  has the greatest width, the web  14  of the crossbar  17  has the smallest width, and the web  20  of the bracket  18  has an intermediate width. Other frame assemblies may use channel components with web (and flange) dimensions that are relatively different.  
         [0036]    It is important to note, however, that regardless of variations in the sizes of the webs, the heights of the flanges, or the gauge of the material strip from which the channel pieces are formed, each of the profiles for the sidebars  10 , crossbar gang members  14 , and bracket gang members  18  can be programmed into the computer controlled roll former to automatically provide the desired shape and size. No custom hard tooling is required and, consequently, once programmed, there is no tooling changeover required when going from one shape to another. Instead, the computer controlled roll former permits on-the-fly change from one roll-formed shape to the next, thereby permitting the continuous manufacturer of an order of any desired size of sidebars  10 , crossbar gang members  14  and bracket gang members  18 .  
         [0037]    The roll forming process may utilize ultra high strength low alloy steel (UHSLA), such as that having a yield strength in excess of 100 ksi. Preferably, however, lower yield strength steel, in the range of 30-50 ksi, is used. After various channel members  10 ,  14  and  18  are formed, they are heat treated to raise the yield to, for example, in excess of 100 ksi, using a conventional heat treating process, including austinitizing and quenching. One such heat treating process is described in U.S. Pat. No. 6,488,791. After heat treat, the component pieces  10 ,  14  and  18  are punched to form connecting bolt holes in a computer controlled piercing apparatus of the mechanical type made, for example, by Beatty Machine Co. (US) or the hydraulic type made, for example, by Soenen (Belgium). The piercing or punching operation provides accurate control of the hole locations and permits ready changes in bolt hole locations for special customized order criteria. Forming the bolt holes after heat treat avoids the possibility of bolt hole location or size deviations as the result of growth in heat treating. Bolt hole accuracy and alignment, and ease of fit-up, are all enhanced as a result of this process.  
         [0038]    Referring again to FIG. 1, after the bolt holes have been formed, both the crossbar gang members  14  and the bracket gang members  18  are cut on the respective cut lines  25  and  26  form the final crossbars  17  and brackets  22 . Cutting may be provided by conventional sawing devices, by plasma or laser cutting, or some other method. The component pieces  10 ,  17  and  22  are ready for assembly using the bolted connectors  23  and  24  as shown in FIGS.  2 - 4 .  
         [0039]    Referring now to FIG. 5, there is shown a process flow for a somewhat more complex frame manufacturing process and, in FIG. 6, there is shown a truck frame assembled from the components of the FIG. 5 process. The computer controlled roll former is set and operated to roll form the sidebars  27 , the crossbar gang members  28  and the bracket gang members  30  all in a manner similar to that described above. If desired, each of the members  27 ,  28  and  30  may be heat treated. The front edge of the sidebars  27  may be trimmed, as with a trim cut  31 , depending on the truck manufacturer&#39;s requirements. The bolt holes are then punched in the web of the sidebars  27 , leaving them ready for assembly into the frame  32  shown in FIG. 6. With reference to FIG. 6, the frame  32  includes three different types of crossbars, namely, straight crossbars  33 , vertically offset crossbars  34  and horizontally offset crossbars  35 . Such various crossbars may be required to meet a truck manufacturer&#39;s particular requirements for strength, engine position, and other requirements. The vertically offset ends  36  in crossbars  34  and the horizontally offset ends  37  in crossbars  35  are formed in the ganged configuration of member  28 . This offsetting process may be performed without the use of special hard tooling and dies in a computer controlled forming apparatus, such as a hydraulic offsetting press made, for example, by Stenhoj A/S (Denmark). The offsetting steps may also be performed after the connecting holes have been punched in the crossbars without loss of accuracy in bolt hole position.  
         [0040]    The assembled truck frame  32 , shown in FIG. 6, includes a pair of sidebars  27  each having a trim cut  31  on the front edge, immediately to the rear of which are attached a pair of vertically offset crossbars  34 . The crossbars  34  are attached at their offset ends  36  to the sidebars  27  by the use of brackets  38  cut from the bracket gang members  30  in the same manner previously described. Near the center of the frame  32 , a pair of back-to-back horizontally offset crossbars  35  are attached by their offset ends  37  to the sidebars  27 , using brackets  38 . Finally, at the rear of the frame, two longitudinally spaced pairs of straight crossbars  33  are attached at their opposite ends between the sidebars  27 , again utilizing connecting brackets  38 . All of the foregoing connections are preferably effected with the same type of bolt and nut assemblies  23 ,  24  described above. Riveted connections may also be used.  
         [0041]    [0041]FIG. 7 shows the three master components of another vehicle frame assembly after they have been initially formed and heat treated, if necessary, prior to assembly by welding. Although the method of the present invention preferably utilizes roll forming to form the various channel members, it is to be understood that the invention encompasses the use of any type of soft-tooled arrangement, i.e. adjustable tooling which does not require a specific set of hard tools for each of the frame members, including the ganged members as will be described. Thus, in addition to roll forming, ganged frame members may also be formed in a press brake or a universal stamping/forming tool of a type well known in the industry.  
         [0042]    The FIG. 7 components include a sidebar  40  of a conventional channel section, including a central web  41  and opposite end flanges  42 . The sidebar  40  is the largest of the three sections shown in FIG. 7. The components also include a first larger ganged crossbar member  43 , used by itself to form the crossbars  44  for the welded assembly shown in FIGS. 8 and 9, and a second smaller ganged crossbar member  45  used to produce the crossbars  46  which are combined with crossbars  44  to form composite box crossbars  47  used in the welded frame assembly shown in FIGS. 10 and 11.  
         [0043]    In a manner similar to that described with respect to the FIG. 1 embodiment, each of the sidebars  40  is individually cut to length as it exits the roll former or other soft-tooled forming machine. The larger ganged crossbar member  43  is formed to any convenient length in the roll former, resulting in a member from which three crossbars  44  may be subsequently cut. Similarly, the smaller ganged crossbar member  45  is also formed to any convenient length resulting in a member having multiple crossbars  46  of which there are three in the example shown in FIG. 7. As with the previously described embodiment, a roll former may be capable of producing a ganged crossbar member  43  or  45  having a length, for example, of about 40 feet (about 16 m) from which 15 or more crossbars  44  or  46  may be subsequently cut.  
         [0044]    Referring also to FIGS. 8 and 9, a detail of a welded frame assembly is shown that utilizes sidebars  40  and crossbars  44 . Each crossbar  44  is butt welded at opposite ends to the central webs  41  of a pair of parallel sidebars  40  (a part of only one of which is shown in the drawings). The weld  50  is preferably continuous, following the entire section of the crossbar  44 . Any convenient thermal joining technique may be used, including MIG, TIG, arc-welding, STIR-welding or a chemical joining technique.  
         [0045]    In FIGS. 10 and 11 there is shown a detail of another welded frame assembly  51  which uses composite box crossbars  47 , also welded between a pair of parallel sidebars  40 , only one of which is shown. The smaller ganged crossbar member  45  is formed with a section small enough such that the end flanges  52  of the smaller crossbar  46  fits snuggly within the end flanges  53  of the larger crossbar  44  to form the box-like crossbar  47 . The central web  41  of the sidebar  40  is cut to form a rectangular opening  54  (see FIG. 7) just large enough to provide clearance for the box crossbar  47 . The crossbar  47  is then securely fastened to the web  41  of the sidebar  40  with outer and inner perimeter welds  55  and  56 . In FIG. 12, there is shown a vehicle frame assembly  57  utilizing a pair of box crossbars  47  of the type shown in FIGS. 10 and 11 and described above. The box crossbars  47  are welded to the sidebars  40  and the remainder of the frame assembly includes a pair of vertically offset crossbars  34  and a pair of horizontally offset crossbars  35 , all of which are welded to the sidebars  40 . The frame assembly  57  is thus very similar to that shown in the FIG. 6 embodiment, but the bolted connections have been replaced with welds.  
         [0046]    The roll forming apparatus described herein can form various size channel members from steel strip to provide sidebars, crossbar gang members and bracket gang members with web widths in a range of about 5 inches to 13 inches, and with flange heights in the range of about 2 inches to 4½ inches. Steel strip with gauges varying from {fraction (3/16)} inch to {fraction (7/16)} inch may be processed. The aforementioned dimensional ranges are typical, although if the application requires may extend beyond these ranges. The soft tooling used in the computer controlled roll former permits on-the-fly changes from one channel size to another and, if a gauge change is required for a channel size change, the strip roll change may be effected simply and in a short time. The customer does not have to purchase custom hard tooling nor is there the customary hard tooling change over required when changing channel sizes as would be required in a conventional stamping operating. The entire process is extremely flexible, accurate, fast and cost-effective.