Abstract:
A vehicle frame component, such as a siderail or a cross member, is formed with a generally C-shaped cross section in which the vertical web member has a greatly reduced mass, as compared to a comparable C-channel section of uniform construction. The reduced mass web member has a corresponding reduced effective cross section to substantially reduce the component weight without adversely affecting its vertical stiffness.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority to and the benefit of U.S. Provisional Application Nos. 60/792,268, filed Apr. 14, 2006; 60/792,267, filed Apr. 14, 2006; and 60/792,269, filed Apr. 14, 2006. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to frames for vehicle chassis and, more particularly, to weight saving siderail components for heavy truck frames. Methods of making such frame components are also disclosed.  
         [0003]     In order to meet federally mandated vehicle emission requirements, truck manufacturers have had to use larger cooling packages and exhaust systems. In addition to the added cost, these changes also add significantly to the vehicle weight and, as a result, to reduced fuel efficiency. Therefore, there is great emphasis on weight reduction in all vehicle components.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention is directed to weight reduction in the main frame members of heavy duty trucks by eliminating material in areas having little effect on frame strength and durability. In particular, the siderail of heavy truck frames are typically made from C-section steel channel members, either heat treated steel or high strength low alloy (HSLA) steel. The sections are typically used for the main siderail pair, but may also function as the connecting cross members and connecting brackets (if used). The siderail flanges provide most of the siderail stiffness in the vertical direction, which stiffness is the primary strength requirement in truck frames. Because the web which connects the flanges has little effect on vertical stiffness, it is believed that removal of material from the web can be undertaken without significant decrease in vertical stiffness.  
         [0005]     In accordance with one embodiment of the present invention, a sheet steel blank is provided, in a center region, with a series of strategically placed longitudinal slits along its full length. The blank is then stretched transversely to open the slit web to its final desired width. Two variant methods are disclosed for this embodiment, the result of which is the fabrication of siderails of substantially reduced weight, but only a nominal reduction in vertical stiffness. The method is also applicable to the manufacture of frame cross members.  
         [0006]     In accordance with another embodiment of the present invention, a steel C-section channel preform with a narrow web is cut longitudinally to provide upper and lower angle sections that are spaced apart to provide the upper and lower flanges of a siderail and short upper and lower web portions. The angle sections are spaced to the desired siderail height and connected to the common end of a cross member. The resulting siderail has very little WEB material, resulting in a siderail of substantially reduced weight, but only a nominal reduction in vertical stiffness.  
         [0007]     In accordance with a further embodiment of the present invention, a structural channel for the siderail of a heavy truck frame is fabricated from a pair of heavy gauge angle members for the upper and lower flanges and a lighter gauge web section interconnecting the flange angles. The web section is formed with a number of offsets to provide added stiffness. The overall assembly provides a significant reduction in weight as compared to a unitary channel member made of the same heavy gauge steel. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a perspective view of a heavy duty truck frame utilizing expanded metal siderails and expanded metal cross members made in accordance with methods of the present invention.  
         [0009]      FIG. 2  is a process flow diagram showing schematically two methods for making expanded metal frame components.  
         [0010]      FIG. 3  is a perspective view of a heavy duty truck frame utilizing the “webless” siderails made in accordance with another method of the present invention.  
         [0011]      FIGS. 4 and 5  are perspective views of alternate truck frames embodying deeper siderails, but made in accordance with the method of the  FIG. 6  embodiment of the present invention.  
         [0012]      FIG. 6  is a process flow diagram showing schematically the method for making webless siderails in accordance with this embodiment of the present invention.  
         [0013]      FIG. 7  is a vertical section through a fabricated channel member of a further embodiment of the present invention.  
         [0014]      FIG. 8  is a flow chart of the process for making the fabricated siderail member of  FIG. 7 .  
         [0015]      FIG. 9  is a perspective view of a partially assembled heavy truck frame utilizing the fabricated siderail of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     The truck frame  10  shown in  FIG. 1  includes, as its main components, a pair of spaced parallel siderails  11  which are interconnected by a series of cross members  12 , all in a manner well known in the industry. Each of the siderails  11  comprises a C-section channel member having a vertically disposed intermediate web  13  that interconnects upper and lower flanges  14 . Similarly, at least some of the cross members  12  comprise C-section channel members, each having an intermediate web  15  and integrally formed upper and lower flanges  16 . The cross members  12  may be attached to the siderails  11  by welding or bolted connections, also in a manner well known in the industry.  
         [0017]     Referring also to  FIG. 2 , there are shown two slightly different processes for making expanded metal frame components in accordance with the present invention. In the upper Process A, a flat sheet  17  of steel may be provided as either a blank or cut from a coil. The flat sheet  17  is provided with a series of staggered slits  18  along its length in a center region  20  which will become the web of a C-section channel member. The slit sheet  17  is then formed into a channel preform  21  by bending the opposite lateral edges to form preform flanges  22  with an intermediate preform web  23 . It should be noted that the preform web  23  has a height (distance between preform flanges  22 ) substantially less than the width of the web  12  in the completed siderail  11 . The channel preform  21  may be conveniently formed by roll forming or press forming in a known manner.  
         [0018]     In the next process step, the channel preform  21  is stretched in a direction transverse to the preform flanges  22  causing the preform web  23  to open and expand in width to the final desired dimension for the siderail  11 . The resulting openings  24  in the web  13  result in a significantly reduced effective vertical cross section and provide a substantial reduction in weight, for example, 20%-25%. The stretching step may also be accomplished using conventional roll forming or press forming techniques and equipment.  
         [0019]     If the siderail  11  is made from a low yield strength steel (30,000-50,000 psi), it is next subjected to heat treating steps  25  which typically comprises austenitizing, quenching and tempering to increase the yield strength to, for example, 100,000 psi. However, if the steel sheet  17  from which the siderail  11  is formed is made from a high strength low alloy steel (HSLA), the heat treating steps  25  are eliminated.  
         [0020]     The final processing of the siderail  11 , prior to fabrication into the frame  10 , may include piercing of connecting holes  26 , sandblasting and painting, all of which are schematically represented as station  27 .  
         [0021]     The foregoing method may be applied as well to the manufacture of expanded cross members  12 . The method disclosed herein is particularly attractive because it results in very little waste material.  
         [0022]     In the alternate Process B shown in  FIG. 2 , a flat blank sheet  17  is provided with slits  18  in the same manner described with respect to Process A. In the next step, however, slit sheet  17  is stretched laterally in its flat condition to expand the blank to provide the openings  24  and a final desired width of the flange  14 . In the following step, the final shape of the siderail  11  is provided by roll forming or press forming the flanges  14 . In Process B, there is, therefore, no channel preform  21  as there is in Process A.  
         [0023]     The siderail  11  is thereafter subjected to heat treating  25 , if required, and the final finishing steps at  27 .  
         [0024]     It is anticipated that a weight reduction in the range of about 15% in siderails made in accordance with this invention will result in only a nominal decrease in vertical stiffness, such that vertical stiffness up to 95% of a comparable solid channel member would be retained. The weight saving, however, is extremely significant for the reasons set forth above.  
         [0025]     In the following Table 1, the mass or weight of the baseline frame and component siderail are compared to the siderail and frame of  FIG. 1 . The numbers in the row for the  FIG. 1  construction indicate the percent reduction from the base line frame and siderail. Similarly, vertical stiffness and torsional stiffness of the baseline frame are compared to the expanded metal frame of  FIG. 1  in terms of the percent reduction in these stiffness measurements. With respect to vertical stiffness, the 5% reduction in the  FIG. 1  frame can be attributed primarily (about 95%) to the siderails  11 .  
                                                                                         TABLE 1                                       Mass, (lbs)   Stiffness, %                % base   Vertical,   Torsional            Frame Type   Siderail   Frame   (lbs/in)   (ft-lb/deg)                    Baseline   902   1268   15,423   252       Expanded Metal   −15   −13   −5   −10       ( FIG. 1 )                  
 
         [0026]     Referring initially to  FIG. 3 , a truck frame  38  includes a pair of laterally spaced parallel siderails  39 , interconnected at various points along their lengths by cross members  40 . As contrasted to more conventional siderails, however, each of the siderails  39  comprises a pair of upper and lower angle sections  41  instead of a single C-section channel member. Thus, much of the space occupied by the web of a conventional C-section channel member is eliminated in the siderails  39 .  
         [0027]     Referring also to  FIG. 6 , each siderail  39 , comprising upper and lower angle sections  41  is formed from a steel sheet blank  42 . In a forming step  43 , the lateral edges of the blank  42  are turned about 90° to form the flanges  44 , interconnected by a web  45 , of a C-section channel preform  46 . If the channel preform  46  is made from a low yield strength steel having a yield strength in the range of 30,000-50,000 psi, the preform is next subjected to a heat treating operation  48  including, for example, the steps of austenitizing, quenching and tempering, all in a well known manner. However, if the preform is made with HSLA steel, the heat treating operation is eliminated.  
         [0028]     The channel preform  46  is then subjected to a piercing step  49  to provide the bolt holes  50  for assembly of the frame or for the connection of other frame parts.  
         [0029]     In a subsequent cutting step  57 , the web  45  of the preform is cut or sheared longitudinally on its centerline  52  to form the two angle sections  41 . Although the angle sections are identical in the process thus far described, the channel preform  46  could be cut on a line offset from the centerline  52  to provide upper and lower siderails pieces of slightly different size and shape.  
         [0030]     In a final processing step  53 , angle sections  41  may be completed by sandblasting and painting, after which they are ready for assembly into a frame  38 .  
         [0031]     Referring again to  FIG. 3 , a cross member assembly  54  is used to interconnect each upper and lower pair of angle sections  41  and to interconnect spaced pairs of webless siderails  39 . The cross member assembly  54  may include channel, angle, box or other section cross member pieces  55  and end brackets  56  for effecting direct connection to the web portions  58  of the angle sections  41 . The upper and lower flanges  44  remain fully intact and provide most of the vertical stiffness of the section. The large open space between the opposed edges of the upper and lower web portions  58  illustrates the great saving in weight provided by the method and assembly of the present invention. A weight reduction in excess of 20%, as compared to a siderail having a full web, may be effected in accordance with the present invention. On the other hand, decrease in vertical stiffness of only about 15% can be attained in a frame utilizing these webless siderails.  
         [0032]     The following Table 2 is similar to Table 1 and shows the percent reduction in frame and siderail weight of the  FIG. 3  frame as compared to the baseline frame made with conventional full section siderails.  
                                                                                                         TABLE 2                                       Mass, (lbs)   Stiffness, %                    % base       Vertical,   Torsional                Frame Type   Siderail   Frame   (lbs/in)   (ft-lb/deg)                            Baseline   902   1268   15,423   252           Webless   −20   −10   −15   −10           ( FIG. 3 )                      
 
         [0033]     Referring now to  FIG. 4 , a modified frame  59  is shown which has siderails  60  comprising upper and lower angle sections  41  cut from a channel preform  46  in the manner previously described. However, because the siderails  60  are substantially deeper vertically than the siderails  39  of the  FIG. 3  embodiment, it may be desirable to connect the upper and lower angle sections  41  with web members  61  as in a conventional truss or with open truss-like plates  62  spaced along the length of the angles, or a combination of both.  
         [0034]     In  FIG. 5 , there is shown a further modified frame  63  that utilizes somewhat longer web members  64  and truss-like plates  65  of a somewhat different construction from the plates  62  of the  FIG. 4  embodiment.  
         [0035]     A fabricated siderail  66  of the further embodiment of the invention is shown in vertical section in  FIG. 7 . The siderail  66  includes upper and lower angle sections  67  of a heavy gauge steel and an intermediate connecting web section  68  of a lighter gauge steel. In the section shown, the angle sections  67  are attached to the intermediate web section  68  with rivets  69 . However, bolted connections may also be used.  
         [0036]     The web section  68  is formed with three longitudinally extending offset sections  70 , including two wider outside offsets  71  and a somewhat narrower center offset  72 . The section thus takes on a wave-like or corrugated appearance. The effect of the wavy or corrugated section is to increase the stiffness and other strength characteristics of the web  68  to compensate for the substantial decrease in gauge of the material used. For example, the gauge of the web section  68  may be 0.157 inch (4 mm), whereas the gauge of the angle sections  67  is 0.315 inch (8 mm).  
         [0037]     Referring to  FIG. 8 , the upper and lower angle sections  73  and  74  are formed in a conventional manner using either a roll forming process or stamping in a press brake or the like. Each of the angle sections includes a full heavy gauge flange  77  and leg  75 . An offset  76  on the leg  75  accommodates connection to a lateral edge  78  of the web section  68 , as best seen in  FIG. 7 . In a subsequent step, connecting holes  79  are formed in the web legs by piercing, cutting or punching in a known manner.  
         [0038]     The web section  68  is similarly formed by roll forming or pressing to form the corrugated or wavy cross section described above and shown in  FIG. 7 . The lateral edges  78  of the web section  68  are subsequently pierced to form connecting holes  80  to compliment the connecting holes  79  in the angle sections  67 .  
         [0039]     The composite siderail  6  is then assembled by riveting or bolting or welding the angle sections  67  to the opposite lateral edges of the web section  68 . The fabricated siderail is then subjected to a piercing step to provide holes  81  in the web section  68  and, if necessary, in the flanges  77  as well to facilitate assembly into the truck frame or for the connection of other components or equipment.  
         [0040]     In  FIG. 9 , there is shown a partial heavy truck frame  82  including one siderail  66  of the present invention. The other siderail is not shown, but is, of course, of an identical construction. The two siderails  66  are connected by a series of cross members  83  in a conventional manner using riveted, bolted or welded connections.  
         [0041]     The siderail  66  made in accordance with the method of the present invention and utilizing the lighter gauge steel for the web section  68  will provide a vertical stiffness equivalent to the vertical stiffness of a unitary siderail channel of conventional construction using the heavier gauge material of the flange angle sections  67 . However, the siderail  66  of the present invention can provide an overall siderail weight reduction of 10%-20% as compared to the unitary heavy gauge construction of the prior art.  
         [0042]     Table 3, which follows, shows the weight reductions in the siderail and the frame incorporating these siderails as shown in  FIG. 9 . As can be seen, the siderail is 19% lighter than the full section siderail of the baseline frame and the frame as a whole is 17% lighter. The vertical stiffness in the  FIG. 9  frame (95% of which may be attributed to the siderails  66 ) is only 7%. The calculated reduction in torsional stiffness of the  FIG. 9  frame as compared to the baseline frame is also shown, but this is not a critical property. Vertical stiffness, however, is extremely important and the indicated reduction of only about 7% is quite significant.  
                                                                                                             TABLE 3                                       Mass, (lbs)       Stiffness, %                    % base       Vertical,   Torsional                Model   Siderail   Frame   (lbs/in)   (ft-lb/deg)                            Baseline   902   1268   15,423   252           Wave   −19   −17   −7   10           ( FIG. 9 )