Abstract:
The vehicle frame rail in one form has front, middle and rear portions which are seamlessly joined together to form a unitary one-piece monolithic frame rail. The frame rail may be straight with an upper surface of an upper flange of the frame rail being planar. At the transition regions of this form of frame rail form, the lower flange converges toward the upper flange at a transition between the front and middle portion and diverges from the upper flange at a transition from the middle portion to the rear portion. The upper flange of the frame rail may converge toward the lower flange along a rearmost section of the frame rail.

Description:
RELATED APPLICATION DATA  
       [0001]     This application claims priority to co-pending U.S. patent application No. 60/525,064, filed Nov. 24, 2003, entitled, “Vehicle Frame Rail”, by Nicholas Michael Rini and Mark Waitman Pitsenbarger, which is hereby incorporated by reference. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention relates to improved frame rails for vehicles and which have particular applicability to recreational vehicles. The present invention also relates to vehicles which incorporate such frame rails and also chassis constructions which incorporate such frame rails.  
       BACKGROUND  
       [0003]      FIGS. 1 and 2  illustrate one known form of frame rail incorporated into a chassis of a recreational vehicle such as for a Winnebago® motorhome. The construction of  FIGS. 1 and 2  include spaced apart parallel frame rails  10 , 12  which are interconnected by a plurality of cross-members, one being indicated at  14  in  FIG. 2 . A front suspension  16  is coupled to the frame rails  10 , 12  and also to an axle structure  18  which carries first and second wheels and tires  20 , 22 . A rear suspension  24  is coupled to the frame rails  10 , 12  and supports and axle and tandem wheel structure  26  toward the rear of the chassis.  
         [0004]     The frame rails of  FIGS. 1 and 2  are generally of a C-shaped configuration with upper and lower inwardly extending flanges interconnected by an upright or vertical web. The frame rails of  FIGS. 1 and 2  have a height H 1  which in one specific known embodiment is 9 inches. The height H 1  is constant along the full length of each of the frame rails  10 , 12 .  
         [0005]     A clearance C 1  exists between the underside of frame rails  10 , 12  and the ground  30  adjacent to front wheels  18 . In addition, a clearance C 2  exists between the underside of frame rails  10 , 12  and the ground  30  adjacent to the rear wheels  26 . In known constructions, C 2  may be slightly greater than C 1 . The actual clearances C 1  and C 2  vary with the tire size and suspension that is being used. For example, an average clearance in the section between the front and rear wheels  18 , 26  between the underside of the frame rails and ground in one known construction is 25 inches.  
         [0006]     Another form of known chassis and frame rail construction for a recreational vehicle is shown in  FIGS. 3 and 4 . This configuration is known as a stacked rail configuration. Each frame rail  40 , 42  in  FIGS. 3 and 4  is an assembly of three separate rail sections. Thus, frame rail  40  has a first upper or top rail section  44  which extends from a location  46  forwardly of a set of wheels and axle  48  to a location  50  which is rearwardly of a set of rear wheels and axle  52 . At the forward end of the chassis, rail section  44  is stacked on top of a rail section  54  which extends from a location  56  rearwardly of the wheels  48  to a location  58  at the forward end of the chassis. In addition, the frame rail  40  has a lower rear frame rail section  60  which extends from a location  62  forwardly of the wheels  52  to a location  62  at the rear of the chassis. The lower front rail section  54  extends forwardly of the front end of rail section  44  while the rail section  62  extends rearwardly of the rear end  50  of the rail section  44 . In one known construction, the height H 2  of rail section  44  is 9 inches and the height H 3  of each of the rail sections  54 , 60  is also 9 inches. Thus, the overall height H 4  of the rail sections  44 , 54  (and of rail sections  44 , 60 ) is 18 inches. The rail sections  44 , 54  and  60  are also of a generally C-shaped configuration. The lower generally horizontal inwardly extending flange of rail section  44  is secured to the upper generally horizontal inwardly extending flange of rail section  54  and also to the upper generally horizontally inwardly extending flange of the rail section  60 . Rail  42  in  FIG. 4  is the mirror image of rail section  40  and is also a stacked three rail section assembly.  
         [0007]     Assuming the clearance C 4  of the  FIG. 3  embodiment is the same as the clearance C 1  in the  FIG. 1  embodiment, then the average clearance C 5  between the wheels  48  and  52  (and more specifically between ends  56  and  62  of the rail sections  54 , 60 ) is 9 inches greater than the average clearance between the wheels  18 , 26  of the  FIG. 1  configuration. This allows for the positioning of under frame rail storage compartments for convenient storage of articles being transported by a user of the vehicle, such as a recreational vehicle having a body (not shown in these figures) mounted to the chassis depicted therein.  
         [0008]     Although frame rail constructions for vehicles such as recreational vehicles are known, a need exists for improved frame rails for such vehicles and for chassis and vehicles incorporating such frame rails. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a side elevational view of a prior art chassis having straight frame rails.  
         [0010]      FIG. 2  is a top view of the chassis of  FIG. 1 .  
         [0011]      FIG. 3  is a side elevational view of a prior art chassis including plural stacked frame rail sections.  
         [0012]      FIG. 4  is a top view of the chassis of  FIG. 3 .  
         [0013]      FIG. 5  is a perspective view of an embodiment of interconnected frame rails of an improved design.  
         [0014]      FIG. 6  is a side elevational view of a chassis including frame rails of the form shown in  FIG. 5 .  
         [0015]      FIG. 7  is a top view of the chassis of  FIG. 6 .  
         [0016]      FIGS. 8, 8A  and  8 B depict side elevational, top and bottom views of a section of one of the frame rails of  FIG. 6 .  
         [0017]      FIGS. 9, 9A  and  9 B depict side elevational, top and bottom views of a central section of a frame rail of  FIG. 6  adjacent to the section depicted in  FIGS. 8, 8A  and  8 B.  
         [0018]      FIGS. 10, 10A  and  10 B are respective side elevational, top and bottom views of a section of the frame rail of  FIG. 6  adjacent to and rearwardly of the section depicted in  FIGS. 9, 9A  and  9 B.  
         [0019]      FIGS. 11, 11A  and  11 B are respective side elevational, top and bottom views of the rearmost frame rail section of the  FIG. 6  embodiment, which is adjacent to the section depicted in  FIGS. 10, 10A  and  10 B. 
     
    
     DETAILED DESCRIPTION  
       [0020]      FIG. 5  illustrates one embodiment of a frame rail assembly comprised of improved frame rails  100 , 102  interconnected by various cross-members, with some of such cross-members being indicated by the number  104  in  FIG. 5 .  
         [0021]     Desirably, the frame rails  100 , 102  are mirror images of one another. For this reason, the discussion below focuses on frame rail  100 .  
         [0022]     Most desirably, the frame rail  100  is formed of a single monolithic unitary homogeneous durable material, such as ASTM A656 Grade 50 steel. Frame rail  100  is preferably a straight rail, with straight being defined generally to mean substantially straight in a longitudinal direction.  
         [0023]     With reference to  FIG. 7 , a front suspension  106  couples axle supported front wheels  108  to the respective frame rails  100 , 102 . In addition, a rear suspension  110  couples an axle with tandem wheels indicated at  112  to the respective frame rails. The axle/wheel assembly  108  and axle/wheel assembly  112  extend perpendicularly to the respective rails  100 , 102 . The chassis may have more than two axles, such as two rear axles and a front axle. In the chassis of  FIGS. 6 and 7 , the rails  100 , 102  are desirably parallel to one another and are supported at the same elevation. Although other cross-sectional configurations may be employed, desirably the cross-section of the rails  100 , 102  is generally C-shaped with an upper flange  130  ( FIG. 5 ), an upright web  132  and a lower flange  134 . The upper and lower flanges  130 , 134  are desirably parallel to one another and extend generally horizontally when the frame rail is supported on the axles except in transition regions between various front-to-rear sections of the rails.  
         [0024]     With reference to  FIG. 6 , the frame rail  100  comprises a front section  140 , a front intermediate section  142 , a rear intermediate section  144  and a rearmost section  146 . It should be understood that rearmost section  146  optionally may simply be an extension of rear intermediate section  144 . Rail section  140  transitions through a transition region  150  to the section  142 . In addition, rail section  142  transitions through a transition region  152  to the rail section  144 . Also, rail section  144  transitions through a transition region  154  to rail section  146 .  
         [0025]     In the illustrated  FIG. 6  embodiment, although not required, front rail section  140  is of a uniform height leading to the transition region  150  with this height being indicated at H 5 . In addition, transition region  150  may have a generally S-shape along its lower edge portion as shown. The height H 6  of rail section  142  intermediate the transition regions  150 , 152  is desirably less than the height H 5 . Desirably, H 5  is less than two times H 6  and more desirably H 5  is less than 1.5 times H 6 . The transition region  152  may also be generally S-shaped along its lower edge portion. The height H 7  intermediate the transition regions  152 , 154  may be constant and desirably is the same as the height H 5 . Alternatively, H 7  may vary along its length and may be different than H 5  such as somewhat greater than H 5 . At transition region  154 , which may have an upper edge portion which is also of a generally S-shaped configuration, the frame rail transcends to the rearmost section  146 . Section  146 , although not required, may be of a constant height H 8 . H 8  may vary, but in one specific example, is the same as H 6 .  
         [0026]     Thus, in the illustrated frame rail construction, the upper surface or upper flange  130  of rail  100  is at a constant elevation throughout frame rails sections  140 , 142  and  144  until the transition region  154 , at which point the elevation of the upper flange of the frame rail is reduced. In addition, the elevation of the lower flange of the frame rail may be constant throughout the entire length of the frame rail except from transition region  150  along section  142  and along transition region  152 . Intermediate frame rail section  142  is thus stepped up relative to the end frame rail sections. That is, the clearance C 6  is less than the clearance C 7 .  
         [0027]     As a specific example, H 5  may be 13 inches, H 6  may be 9 inches, H 7  may be 13 inches, and H 8  may be 9 inches. Thus, with this specific example, the clearance C 7  is 4 inches greater than the clearance C 6  assuming the frame rail  100  is positioned with its longitudinal axis in a horizontal plane. The upper surface of frame rail sections  140 , 142  and  144  may be raised, such as 4 inches to increase the height of the vehicle floor a corresponding amount. This would place the vehicle floor at a higher elevation than in the  FIG. 1  construction but would also make C 6  and C 1  the same. However, the elevation of the upper surface of frame rail sections  140 , 142  and  144  is at a lower elevation than the elevation of the upper surface of frame rail section  44  in  FIG. 3  if C 4  in  FIG. 3  is the same as C 1  in  FIG. 2 . The elevation of the stacked rail sections  44  and  54  of  FIG. 3  have a height H 4  of 18 inches in comparison to H 5  of 13 inches in the  FIG. 6 . Therefore, the floor height (to of upper rail sections) in  FIG. 3  would be 5 inches higher than in  FIG. 6  if C 1 , C 4  and C 6  is the same. This can make it harder to egress and ingress a vehicle of the  FIG. 3  construction because additional height needs to be negotiated. With this specific configuration, C 7  in  FIG. 6  would thus be 4 inches greater than C 6  but where the elevation of the floor (top of the rail) is raised 4″, C 7  is 8 inches greater than C 1 . In comparison, C 5  would be 9 inches greater than C 1 . In the  FIGS. 6 and 7  constructions, added space for storage is thus provided between the respective wheels  108 , 112  of the chassis (in comparison to the straight rail embodiment of  FIG. 1 ) while not requiring the floor of the vehicle to be raised as much as in the case of the stacked rail design of  FIGS. 3 and 4 .  
         [0028]     The resistance to bending moment of the  FIGS. 6 and 7  constructions is greater than that of specifically known embodiments of the  FIGS. 1 and 3  constructions of a frame rail. This is computed below for specific exemplary embodiments of these three types of frame rails.  
         [0029]     Definitions: 
        Iy−y=Moment of Inertia (in {circumflex over ( )}4)     H=Rail Height (in)     Z=Frame Section Modulus=I/H (in {circumflex over ( )}3)     S=Yield stress of rail material (psi)     RBM=Resistance Bending moment (industry standard for rating a rail&#39;s strength/stiffness)=Z×S (S=50,000 psi in all cases)     Straight Rail: Z=8.25 in {circumflex over ( )}3; RBM=412,500 in-lb (9″×2.8″×0.25 in thk)     Stacked Rail: Z(avg)=0.34(23.5 in {circumflex over ( )}3)+0.66(8.25 in {circumflex over ( )}3)=13.44 in {circumflex over ( )}3; RBM=672,000 in-lb (18″−9″−18″×2.8″×0.25 in thk) stacked     Formed Rail: Z(avg)=0.54(18.04 in {circumflex over ( )}3)+0.42(10.45 in {circumflex over ( )}3)+0.04(13.92 in {circumflex over ( )}3)=14.7 in{circumflex over ( )}3; RBM=735,500 in-lb (13.062−9″−13.062″×3.0″×0.313″ thk)     *Note-because the section modulus is not continuous in the stacked and formed rail applications, a weighted average of the section modulus for a 267″ wheelbase was used to determine the overall RBM in those cases.        
 
         [0039]     In the above example, it is assumed that the yield stress of the rail material is the same in all cases (50,000 psi) based on the assumption that each of the rails is made of the same steel. If different materials are used, the calculations would be altered accordingly.  
         [0040]      FIG. 8  is a side elevation view of a portion of the frame rail section  140 .  FIG. 8A  shows a portion of the top flange  130  of this frame rail portion.  FIG. 8B  shows a portion of the bottom flange  132  of this frame rail portion. Line A-A in this figure illustrates where this frame rail portion connects with the next frame rail portion shown in  FIGS. 9, 9A  and  9 B. As a specific example, and although variable, the length of the frame rail portion depicted in  FIG. 8  from the front end of the frame portion depicted in this figure to line A-A, is 104 inches.  
         [0041]      FIG. 9  depicts a portion of the frame rail  100  commencing from line A-A to a line B-B. In  FIG. 9 , a rear portion of front section  140  is depicted, the transition region  150  is depicted and a portion of the intermediate rail section  142  is shown. Although transition  150  may take other configurations, desirably the lower edge portion of region  150  follows an S-shaped transition. The S-shaped transition is defined by bending radii R 1  and R 2 , which may be the same or different. A specific example of R 1  and R 2  is 10 inches. The corresponding portion of the upper flange  130  of the frame rail is shown in  FIG. 9A  and of the lower flange is shown in  FIG. 9B . Various openings are shown through these frame rail sections for mounting components thereto. The positioning and number of these openings may be varied. In one specific example, the length of the frame rail section shown in  FIG. 9  from line A-A to line B-B is 115 inches.  
         [0042]      FIG. 10  shows a portion of the frame rail  100  commencing from line B-B (see also  FIG. 9 ) and ending at line C-C.  FIG. 10  illustrates a portion of rail section  142 , the transition region  152  and a portion of rail section  144 . The transition region  152  may take other configurations but desirably has an S-shaped lower edge portion such as shown in  FIG. 10 . This transition is defined by radii R 3  and R 4 , which may be the same or different, and may also be 10 inches as a specific example.  FIG. 10A  depicts a portion of the upper flange  130  while  FIG. 10B  depicts a portion of the lower flange  132 . The length of the rail portion depicted in  FIG. 10  from line B-B to line C-C in the specific example under discussion is 109 inches.  
         [0043]      FIG. 11  depicts a portion of frame rail  100  at a rear section thereof. In particular,  FIG. 11  depicts a rearmost portion of frame rail section  144 , the transition region  154  and the rear rail section  146 . The transition region  154  may also have an S-shaped upper edge portion, although this may be varied. This transition region is defined by radii, R 5  and R 6 , which may be the same or different, such as 11.5 inches and 10 inches. As can be seen in  FIGS. 11A and 11B , the respective flanges  130 , 134  may optionally be narrowed at  130 N,  134 N. This provides clearance for equipment mounted thereto. A transition  160  is located between the full width flange  130  and the narrow width flange  130 N. In addition, transition region  162  is positioned between the full width flange section  134  and the narrow width flange section  134 N. As mentioned previously, the height of rail section  146  may be the same as the height of rail section  144 . However, in the construction illustrated, the transition region  154  is used to reduce the height of the upper portion of rail section  146 . The length of the portion of the rail depicted in  FIG. 11  from line C-C to the end of the rail is 133 inches in the specific example shown.  
         [0044]     Thus, the overall length of the exemplary frame rail  100  shown in  FIGS. 8, 9 ,  10  and  11  is 461 inches.  
         [0045]     Alternative rear frame rail configurations may be used.  FIG. 12  shows one such alternative. In the  FIG. 12  version, the top edge portion of the rail comprises a second downwardly extending transition region  164 , that may also be S-shaped with radii R 7  and R 8 , prior to the rear end of the frame rail. In addition, the lower edge portion of the frame rail  134  may also have a downwardly extending transition region  168 , that may also be S-shaped with radii R 9  and R 10 . In this example, the height H 7 ′ of the frame rail section between transition regions  164  and  168  may be the same as H 7 , for example thirteen inches, although this may be varied. Also, the steps X, Y and Z and the respective transition sections  154 ,  164  and  168  may each be the same, such as four inches, although this may be varied.  
         [0046]     Having illustrated and described the principles of our invention with reference to several embodiments, it should be apparent to those of ordinary skill in the art that such arrangements may be modified without departing from the principles of our invention. We claim all such modifications. More specifically, we claim all novel and non-obvious features of a frame rail depicted herein both alone and in various combinations and subcombinations with one another.