Abstract:
A fabricated vehicle axle is shown to include a main body having an inverted U-shaped configuration. The fabricated vehicle axle further includes a continuous bottom plate welded to the main body. The fabricated axle also includes a first king pin top plate having a reversed curved fork portion welded to the main body at one end thereof. Similarly, the fabricated vehicle axle includes a second king pin top plate having a reversed curved fork portion welded to the main body at an opposite end thereof. Still further, the fabricated vehicle axle includes a first gooseneck part welded to the first king pin top plate and the first end of the bottom plate. Similarly, the fabricated vehicle axle includes a second gooseneck part welded to the second king pin top plate and the second end of the bottom plate. 
     REEXAMINATION RESULTS 
     The questions raised in reexamination request 90/007,703, filed Sep. 1, 2005 have been considered and the results thereof are reflected in this reissue patent which constitutes the reexamination certificate required by 35 U.S.C. 307 as provided in 37 CFR 1.570(e), for ex parte reexaminations, or the reexamination certificate required by 35 U.S.C. 316 as provided in 37 CFR 1.99(e) for inter partes reexaminations.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to axles for vehicles and more particularly to fabricated axles for vehicles. 
     Typical steer axle assemblies for vehicles include a forged I-beam axle, and a pair of steering knuckles pivotally attached to opposite ends of the axle by way of king pins. Although they are generally strong and reliable, such forged I-beam axles are limited in their shape, are relatively heavy, and require a relatively large amount of machining. All of this translates into increased manufacturing and payload costs. 
     In light of the foregoing, fabricated axles have been developed. Such axles are typically manufactured from sheets of steel that are cut and then welded together. Fabricated axles generally weigh less than forged I-beam axles. For example, a typical forged I-beam steering axle for use with the heavy-duty trucks weighs approximately one hundred ninety-five pounds, whereas an equivalent typical fabricated axle weighs approximately one hundred twenty-five pounds. In the case of commercial vehicles, including heavy-duty truck commercial vehicles, this translates into substantially increased payload capacity. 
     Another benefit of fabricated axles is that the material used (e.g., steel) can be spread around for more efficient distribution thereof. This can contribute to making the fabricated axle much lighter, and can even make it stiffer against both bending and torsion stresses. On top of all this, fabricated axles typically require less machining than forged I-beam axles. Accordingly, they are easier and less expensive to manufacture. 
     As implied above, fabricated axles are known in the art. An example of a fabricated axle is shown and described in U.S. Pat. No. 5,810,377, issued to Keeler et al., the disclosure of which is hereby incorporated herein by reference. The fabricated axle disclosed therein and incorporated herein by reference was a marked improvement over what was then the prior art and it is still useful for most purposes. However, it has now been recognized to have certain deficiencies. In particular, that fabricated axle does not utilize material efficiently, causing increased costs in manufacture and material waste. Furthermore, it fails to integrate several of the steering features that can be integrated in a fabricated axle for optimization of design, as demonstrated by the present invention. These and other deficiencies, many of which will be apparent to those skilled in the art, particularly after reading this description, have led to the development of the present invention. 
     Referring briefly to  FIGS. 1-3 , the main body part of the fabricated axle shown and described in U.S. Pat. No. 5,810,377 is illustrated. As shown, a plate  20  of material is used for the main body part of the material of the fabricated axle. A main body blank  22  is cut from plate  20  to form the main body of the fabricated axle. The remainder of plate  20  is waste and left unused. This waste material is identified by reference numeral  23  in FIG.  1 . The main body blank  22  is then bent or folded along lines  24 ,  26  to form the main body of the fabricated axle. The main body blank forms a U-channel configuration at its central portion, as best shown in FIG.  3 . As will be appreciated, the fabricated axle is also formed with additional sheets of metal welded to its main body. Reference can be made to U.S. Pat. No. 5,810,377 for further understanding of this construction. 
     As will be appreciated, a relatively large amount of material is wasted during construction of the fabricated axle shown and described in U.S. Pat. No. 5,810,377. This results in a considerable drawback to the extent that it becomes more expensive to manufacture that fabricated axle. Reasons for this inefficient use of material is that the main body part extends completely along the length of the steering axle such that it has an irregular shape, as shown in FIG.  1 . 
     In light of the foregoing, it is desirable to provide for a fabricated vehicle axle that has substantially high material utilization. 
     It is also desirable to provide for a fabricated vehicle axle offering increased strength to bending and torsion stresses. 
     It is further desirable to provide for a fabricated vehicle axle that is less expensive to manufacture. 
     It is still further desirable to provide for a fabricated vehicle axle that integrates several of the steering system component functions. 
     These and other benefits of the preferred form of the invention will become apparent from the following description. It will be understood, however, that an apparatus could still appropriate the invention claimed herein without accomplishing each and every one of these benefits, including those gleaned from the following description. The appended claims, not the above listed benefits, define the subject matter of this invention. Any and all benefits are derived from the preferred form of the invention, not necessarily the invention in general. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is directed to a fabricated vehicle axle that includes a main body having an inverted U-shaped configuration. The fabricated vehicle axle further includes a continuous bottom plate welded to the main body. The continuous bottom plate has a first end with a first king pin bore extending through it and a second end with a second king pin bore extending through it. The fabricated vehicle axle also includes a first king pin top plate welded to the main body. The first king pin top plate has a third king pin bore extending through it in substantial alignment with the first king pin bore. Similarly, the fabricated vehicle axle includes a second king pin top plate welded to the main body. The second king pin top plate has a fourth king pin bore extending through it in substantial alignment with the second king pin bore. Still further, the fabricated vehicle axle includes a first gooseneck part welded to the first king pin top plate and the first end of the bottom plate. Similarly, the fabricated vehicle axle includes a second gooseneck part welded to the second king pin top plate and the second end of the bottom plate. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       In the following detailed description, reference has been and will frequently be made to the following views of the drawing, in which like reference numerals refer to like components, and in which: 
         FIG. 1  is a top plan view of the main body part of a prior art fabricated vehicle axle, depicting the inefficient material utilization for construction of same; 
         FIG. 2  is a front elevational view of the main body part of the prior art fabricated vehicle axle shown in  FIG. 1 ; 
         FIG. 3  is a sectional view of the main body part of the prior art fabricated vehicle axle taken along line  3 — 3  of  FIG. 2 ; 
         FIG. 4  is a front elevational view of a fabricated vehicle axle constructed in accordance with the principles of the present invention; 
         FIG. 5  is a top plan view of the fabricated vehicle axle shown in  FIG. 4 ; 
         FIG. 6  is a top plan view of the main body of the fabricated vehicle axle shown in  FIG. 4 ; 
         FIG. 7  is a front elevational view of the main body of the fabricated vehicle axle shown in  FIG. 4 ; 
         FIG. 8  is a sectional view of the main body of the fabricated vehicle axle shown in  FIG. 7  taken along line  8 — 8  thereof; 
         FIG. 9  is a top plan view of the bottom plate used in the fabricated vehicle axle shown in  FIG. 4 ; 
         FIG. 10  is a sectional view of the bottom plate shown in  FIG. 9  taken along line  9 — 9  thereof; 
         FIG. 11  is a front elevational view of the bottom plate used in the fabricated vehicle axle shown in  FIG. 4 ; 
         FIG. 12  is a detailed view of the head area included at each end of the bottom plate shown in  FIG. 9 ; 
         FIG. 13  is a diagrammatic view of a symmetric section, depicting the tension stress associated therewith; 
         FIG. 14  is a diagrammatic view of the section formed by a fabricated vehicle axle constructed in accordance with the principles of the present invention, depicting the tension stress associated therewith; 
         FIG. 15  is a top plan view of a top plate used in the fabricated vehicle axle shown in  FIG. 4 ; 
         FIG. 16  is a front elevational view of a top plate used in the fabricated vehicle axle shown in  FIG. 4 ; 
         FIG. 17  is a fragmentary section view of the fabricated vehicle axle shown in  FIG. 5  taken along lines  17 — 17  thereof; 
         FIG. 18  is a sectional view of the fabricated vehicle axle shown in  FIG. 5  taken along lines  18 — 18  thereof; and 
         FIG. 19  is a broken away elevational view of the fabricated vehicle axle shown in  FIG. 4  depicting features of the welding used to construct the axle. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 4 and 5  illustrate a fabricated vehicle axle generally designated  40  constructed in accordance with the principles of the present invention. Fabricated axle  40  generally includes a main body  42 , a bottom plate  44 , two top king pin plates  46 ,  48  positioned on opposite ends of the axle, and two gooseneck parts  50 ,  52  also positioned on opposite ends of the axle. As will be appreciated, each of the parts for fabricated axle  40  are welded together along their respective points and lines of intersection. Also shown welded to main body  42  are suspension seat areas  54 ,  56 . 
       FIGS. 6-8  illustrate the main body  42  of fabricated axle  40 . Referring first to  FIG. 6 , a rectangular strip of material  60  is utilized to form a main body blank  62 . Main body blank  62  is cut from strip  60  using one of several conventional techniques known in the art, leaving minimal amounts of waste material  64 . As shown, no portion of the finished main body exceeds the envelope of strip  60 . This solution offers much better material utilization than the prior art. The cuts form tapering edges at the opposite ends of main body blank  62  in order to permit accommodation of the transition zones for the bottom plate  44  of fabricated axle  40 , as further described below with reference to FIG.  10 . 
     As best shown in  FIG. 7 , the main body blank is formed to make the main body  42  of fabricated axle  40 . The cross-section of main body  42  is an inverted U-shaped configuration, as shown in FIG.  8 . 
     Alternatively, a roll formed channel having a U-shaped cross-section could be used to form the main body directly. In that case, it would be unnecessary to manufacture a main body blank and form the main body for fabricated axle. 
     In view of the foregoing, it will be appreciated that main body  42  can be constructed from strip or a roll formed channel. The strip or roll formed channel is cut to its desired length and shape with a small trim on the ends, resulting in minimal waste. In turn, this translates into reduced manufacturing costs. 
       FIGS. 9-12  illustrate the bottom plate  44  of fabricated axle  40 . Referring first to  FIG. 9 , a rectangular strip of material  70  is utilized to form a bottom plate blank  72 . Bottom plant blank  72  is cut from strip  70  using one of several conventional techniques known in the art, leaving minimal amounts of waste material  74 . The end details for bottom plate  44  are cut by robotic plasma cutting or blanking dies. As shown, no portion of the finished bottom plate exceeds the envelope of strip  70 . This solution offers much better material utilization than the prior art. 
     In one construction technique, this removal of the waste material  74  from bottom plate blank  72  during construction of bottom plate  44  occurs prior to welding of bottom plate  44  to other components to construct axle  40 . In an alternative construction technique, bottom plate blank  72  is formed and then welded to other components. Thereafter, the waste material  74  is removed. 
     A preferred feature of the strip  70  from which the bottom plate is made is its section profile illustrated in FIG.  10 . Strip  70  is preferably rolled such that its top  76  is flat to permit optimum weld land during construction of the fabricated axle, while its corners  78  are slightly rounded to provide an accommodating interface with attaching components. In this construction, attaching components do not bear on a sharp edge, which could create a notch, potentially reducing the fatigue life of the fabricated axle. 
     As shown in  FIG. 11 , after being cut from strip  70 , the bottom plate blank  72  is bent to form the bottom plate  44  of fabricated axle  40 . Bottom plate  44  includes a head portion  80  positioned at one end thereof, a transition zone portion  82  extending from head portion  80  at a bend  84 , a body portion  86  extending from transition zone portion  82  at a bend  88 , a transition zone portion  90  extending from body portion  86  at a bend  92 , and a head portion  94  extending from transition zone portion  90  at a bend  96  and positioned on the other end of the bottom plate. 
     In a preferred arrangement, before machining, bottom plate  44  extends approximately 1,860 millimeters in length from its end at head portion  80  to its end at head portion  94  (most preferably 1,860.42 millimeters). As shown, bottom plate  44  is continuous with no seams or joints along its length. This characteristic increases the useful life of the fabricated axle in that the risk of cracking due to vertical loading is minimized. 
     In a preferred construction, bottom plate  44  is of constant thickness and has a constant section to provide adequate structural integrity in the king pin areas positioned in the head portions  80 ,  94 . The preferred thickness ranges from twelve to sixteen millimeters, which takes into consideration optimum robustness and weight. The robust thickness across the full width of bottom plate  44  allows the vehicle to be jacked up at any point along the length of body portion  86 , without risk of damage. The robust thickness of bottom plate  44  also provides foreign object protection so that the axle is not bent or damaged due to rock, debris and the like. It also provides a tie down for decking during transport. 
     In an alternative preferred construction, bottom plate  44  has a tapered construction, as desired. In this construction, the bottom plate is still continuous, but is taper rolled or machined such that it has optimum, varying thickness at all locations. 
     Another feature of bottom plate  44  is that the angle formed at bends  88 ,  92  for transition zone portions  82 ,  90 , respectively, is sufficiently large enough to permit those bends to be positioned as far outboard as possible in order to reduce stresses due to vertical axle loading. Preferably, the angle (alpha) formed by bends  88 ,  92  is within the range of forty degrees to fifty degrees, most preferably equal to forty-five degrees. Smaller angles provide inadequate life in the welds at bends  88 ,  92 , while larger angles make it impractical to package the tie rod arm components (not shown) for the vehicle. 
       FIG. 12  illustrates a detailed view of the head portion and transition zone portion for bottom plate  44  at one end thereof. In particular, head portion  80  and transition zone portion  82  are illustrated in FIG.  12 . It will be appreciated that the description regarding  FIG. 12  applies equally to head portion  94  and transition zone portion  90  of bottom plate  44 . 
     As shown, transition zone portion  82  includes a tie rod clearance region  98 , preferably configured in a waist-like shape. Tie rod clearance region  98  is formed when the bottom plate blank  72  is cut from the strip of material  70  (see FIG.  9 ). Tie rod clearance region  98  provides for tie rod and arm packaging, thereby allowing for high angle wheel cut. 
     With respect to head portion  80 , a steering axis or king pin bore construction hole  100  is machined through it. King pin bore construction hole  100  is formed when the bottom plate blank  72  is cut from the strip of material  70  (see FIG.  9 ). This king pin bore construction hole is then machined preferably after construction of axle  40  to form a king pin bore. The construction of bottom plate  44  is such that the material around the king pin bore  100  in  FIG. 18  has been made as large as reasonably possible to provide maximum structural integrity. In a preferred embodiment, the minimum distance from the center of king pin bore  100  to the edge of material is at least forty millimeters, and most preferably approximately forty-five millimeters. This construction provides increased fatigue life in braking and side loading. 
     Further regarding head portion  80 , a steering stop  102  is integrally formed therewith when the bottom plate blank  72  is cut from the strip of material  70  (see FIG.  9 ). Steering stop  102  provides a contact zone for the steering stop bolt incorporated in steering systems utilized in vehicles. The integration of steering stop  102  into the construction of bottom plate  44  eliminates the need to weld additional components to fabricated axle  40  with that functionality. 
     Another feature of bottom plate  44  is that it is thick and heavy relative to main body  42  of fabricated axle  40 . This moves the neutral axis of the section of fabricated axle  40  along the length of the body portion  86  of bottom plate  44  lower, which reduces tension stresses in the bottom plate and thereby extends its fatigue life. In all, an optimized, lighter section is formed. 
     Referring to  FIG. 13 , a symmetric section  110  is shown, such as would be the case if main body  42  and bottom plate  44  were formed to have identical thickness and weight characteristics. Under these circumstances, the neutral axis  112  would be positioned at a distance equal to half the height of section  110  from the bottom leg of the section. 
     Referring to  FIG. 14 , the asymmetric section  114  formed by the main body  42  and bottom plate  44  of fabricated axle  40  is shown. Because bottom plate  44  is thick and heavy relative to main body  42 , the neutral axis  116  of fabricated axle  40  is positioned lower than half the height of the section from the bottom plate. This reduces tension stresses in bottom plate  44  and extends its fatigue life. As a result, a robust, lighter section is formed. 
       FIGS. 15-17  illustrate one of the top king pin plates  46 ,  48  for fabricated vehicle axle  40 . King pin plate  46  is shown, but it will be appreciated that this description applies equally to king pin plate  48 . 
     As shown, top king pin plate  46  includes a head portion  120 , a body portion  122  and a curved fork portion  124 . A king pin bore  126  is machined through head portion  120  at a position where it is designed to align substantially with the king pin bore construction hole  100  machined through bottom plate  44  (see FIG.  12 ). Curved fork portion  124  is formed by two legs  128 ,  130 , which are separated by a region defined by weld surfaces  132 ,  134 ,  136 . Weld termination points  138 ,  140  are positioned at the edges of weld surfaces  132 ,  136 , respectively. As shown in  FIG. 17 , top king pin plate  46  is welded to main body  42  by a weld line  142  that extends from weld termination point  138  to weld termination point  140 , along weld surfaces  132 ,  134  and  136 . 
       FIG. 16  shows that head portion  120  and body portion  122  are separated by a bend  144 . A bend  146  is also incorporated into curved fork portions  124  to cause the fork portion to form a reversed curved fork portion. Bend  146  preferably forms a ninety degree angle relative to a straight fork configuration. The preferred construction of top king pin plate  46  is such that the distance L 1  shown in  FIG. 16  for the curved fork portion is approximately equal to three hundred thirty millimeters. For a straight fork portion, the distance L 2  would be approximately four hundred fifty millimeters. This feature increases the useful life for axle  40  by reducing stresses during longitudinal loading. 
     In addition, the curved fork portion  124  of top king plate  146  is such that the weld ends are positioned above the vertical loading neutral axis. Most preferably the weld ends are positioned at or above half the section height, ensuring that they are above the vertical loading neutral axis. This helps prevent cracks during vertical loading. 
     In view of the foregoing, the weld line ends positioned in weld termination points  138 ,  140  are positioned in low stress regions for bending stresses about the vertical axis, and stresses resulting from longitudinal forces at the vehicle wheel creating bending moment about the vertical axis. 
       FIG. 18  illustrates a sectional view of one end of the fabricated axle  40 . As shown, a machining datum  150  is included in bottom plate  44  in order to aid during the fabrication process for axle  40 . Another machining datum is similarly positioned at the other end of bottom plate  44 . The drop of axle from machining datum  150  to suspension seat area  56  (see  FIG. 4 ) is controlled during the fabrication process. The flat for the thrust washer is then machined relative to machining datum  150  to ensure that only approximately one millimeter of material must be removed to provide a flat surface. This ensures adequate thickness of the bottom plate  44 , which enhances structural integrity in the head portion  94  of the bottom plate. 
     As further shown in  FIG. 18 , king pin bore  100  is offset to the rear of the axle, providing for additional tie rod clearance. In an alternative construction, the head portion  94  of bottom plate  44  could be constructed such that a large offset, typically within the range of zero to seventy millimeters, could be designed to provide even further steering and brake clearance. 
       FIG. 19  illustrates certain of the weld features for fabricated axle  40 . As shown, a three pass weld is formed at each end of the fabricated axle. In particular, a root pass  160  begins outboard of king pin bore  100  and extends without stop to a point  162 , which is preferably positioned between seventy-five millimeters and one hundred twenty-five millimeters inboard of bend  88 . A second pass  164  also begins outboard of king pin bore  100  and extends without stop to a point  166  positioned inboard of point  162 , preferably between ten and thirty millimeters inboard of point  162 . In this arrangement, second pass  164  obliterates the weld stop created by root pass  160  at point  162 . A final pass  168  also begins outboard of king pin bore  100  and extends without stop to a point positioned on the opposite end of fabricated axle  40 , which is positioned outboard of the king pin bore  100  positioned at that opposite end of the axle. In this arrangement, final pass  168  obliterates the weld stop created by second pass  164  at point  166 . At bend  88 , main body  42  can be weld prepped for approximately fifty millimeters on each side of the bend center for bend  88  so that a full penetration weld can be achieved. 
     In view of the foregoing weld features, a three pass weld is formed at each end of axle  40 , which provides for fatigue resistance in brake and vertical loading. All passes start at a point outboard of king pin bore  100  so that a stress riser is not created. The obliteration of the weld stops for the first (root) and second passes enhances fatigue life due to vertical loading. 
     While this invention has been described with reference to certain illustrative aspects, it will be understood that this description shall not be construed in a limiting sense. Rather, various changes and modifications can be made to the illustrative embodiments without departing from the true spirit and scope of the invention, as defined by the following claims. 
     Furthermore, it will be appreciated that any such changes and modifications will be recognized by those skilled in the art as an equivalent to one or more elements of the following claims, and shall be covered by such claims to the fullest extent permitted by law.