Abstract:
A reduced weight fifth wheel generally mountable on a tractor for coupling between a tractor and a trailer, which fifth wheel has the approximately the same bearing surface area, a more continuous surface area by elimination of a lever-bar pin port in the bearing surface, thinner support ribs and smaller fillets, a shorter longitudinal length with a wider kingpin receiving slot for receipt of a trailer kingpin, with a locking-jaw mechanism having a redesigned lever-bar pin and pin-receiving port to enable reduction of the weight and to enhance production casting practices, which fifth wheel further encompasses lateral support ribs at the plate outer perimeter and rearward of the mounting brackets to define support pockets ahead of the engaging ramps to avoid lateral deflection and deformation of the plate at vertical loading.

Description:
The present application is a continuation-in-part of application U.S. Ser. No. 08/771,106 filed on Dec. 20, 1996, now U.S. Pat. No. 5,865,458. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to fifth wheel assemblies generally utilized for tractor-trailer combinations. More specifically, the present invention relates to a fifth-wheel bearing plate with a reduced weight structure providing equivalent bearing plate surface areas to prior similar fifth wheel bearing-plate surfaces from the present applicant for contact with trailer wear plates. However, the bearing plate is shorter in overall length, includes a more ovate shape, wider kingpin receiving slot, a more continuous upper surface, has thinner support ribs and fillets to improve casting practice and lower production costs as well as the weight of the bearing plate. 
     Fifth wheel assemblies on tractors broadly encompass a bearing plate, a coupling mechanism with trailer kingpin guide means, mounting brackets for mating the assembly with the tractor, a jaw-release handle and a locking jaw. The locking jaw is opened to receive and retain a mating kingpin extending from a trailer with a wear plate. After mating of the kingpin and fifth wheel jaw, the jaw mechanism locks to secure the kingpin, and thus the trailer, to the fifth wheel. The trailer wear plate bears against the bearing plate planar surface, which contacting surfaces suffer wear during turning or pivoting. In addition, the fifth wheel jaw must be adjusted, as in present practice, for the kingpin or there will be a resultant slack in the jaw. 
     Fifth wheel assemblies are predominantly utilized on commercial or revenue-generating tractors, although notice is taken of their usage on a limited number of recreational trailer applications. The fifth wheel structures are broadly divided by their weight carrying capacity. As over-the-road tractors generally are susceptible to state imposed weight limitations in their carrying capacity, there is an ongoing effort in the industry to reduce the tractor gross vehicle weight and thus to increase the payload capacity of the tractor-trailer arrangements or increase fuel economy. 
     Reduction in fifth-wheel weight cannot preclude safety and load bearing considerations, which are related to the fifth-wheel physical parameters. The particular style, shape or construction of the fifth wheel may be dependent upon the manufacturer. However, the fifth-wheel performance characteristics and apparatus will include the ability to couple with a kingpin, the strength to bear typical highway service loads, which include longitudinal (both buff and draft) loads, vertical loads, transverse loads and overturning (roll) loads, a locking jaw capable of retaining the kingpin and trailer coupled, and a jaw unlocking mechanism for disengagement of the kingpin and trailer. 
     Efforts have been made to reduce the weight of the fifth wheel, especially on flatbed railcars for piggyback transport, by casting the fifth wheel plate of aluminum for lightweight construction. However, the cast aluminum fifth wheels did not have sufficient physical strength to withstand the stresses normally encountered by fifth wheels. Thus, fifth wheel hitches continue to be primarily manufactured of cast steel or formed structural steel. As noted in U.S. Pat. No. 4,659,101 to Buckley, the weight of the fifth-wheels is not only a drawback on collapsible railroad flatbed stanchions but the fifth wheel weight is a considerable addition to the weight of a conventional truck tractor. This Buckley—&#39;101 patent teaches a forged aluminum bearing plate and depending abutments for the locking jaws. A forged aluminum fifth wheel provides the strength necessary to withstand the normal tractor-trailer service stresses. However, it is known that forged fifth-wheel products are considerably more expensive to produce than are cast fifth-wheel products. This fifth-wheel hitch taught in the Buckley—&#39;101 patent may also be manufactured by steel casting or steel fabrication. Although the focus of this Buckley—&#39;101 patent is primarily directed to the locking jaw mechanism, the disclosure also discusses the concept of mass reduction and the benefits therefrom for a fifth wheel assembly. 
     U.S. Pat. No. 4,221,397 to Holt teaches a trailer hitch head with jaws to bear all kingpin wear. However, the illustrated top or bearing plate is shown with a generally rectangular configuration demonstrating that bearing plate shape is not limited to an oval, elliptical or circular shape. One of the problems to be overcome with any of the disclosed fifth-wheel structures is excessive top plate wear and avoidance of this wear reduces repair, renovation or replacement of the top plate and trailer wear plate prior to their expected life cycle. The Holt—&#39;397 disclosure alludes to flatcar service, but the teaching of the fifth wheel structure is not limited to such flatcar service. 
     A second aluminum fifth wheel structure is shown in U.S. Pat. No. 4,208,062 to Maassen, and this fifth-wheel structure is fabricated to be a high-strength, low-weight assembly. However, it is implied in the description that the top bearing plate and the bottom plate are cast aluminum with vertical frames, which top and bottom plates are subsequently bolted together to reduce the total mass of the assembly. The total weight of a given assembly or a percentage reduction in weight is not noted in the disclosure. 
     Other illustrations of fifth wheel shapes, locking mechanisms and mounting apparatus are shown in the following U.S. Pat. Nos.: 2,621,056; 2,640,707; 2,648,544; 4,946,183; 4,477,100; 4,333,666; 3,813,114; 3,578,357; 3,013,815; 3,640,549; 2,861,818; and 2,581,254. All of these patented apparatus are cast or formed steel and iron components, which iron-based structures have an inherent weight problem related to the physical weight to strength relationship of the material. That is, the density of the iron is relativiely large, thus, manufacture of a component with a fixed surface area and thickness requisite for a specified strength characteristic results in a heavy structure. The mass of a fifth-wheel necessary to carry both the static vertical load and the trailing load adds to the gross vehicle weight and consequently reduces the payload carrying capacity or the fuel economy of the tractor-trailer combination. Therefore, it is an ongoing effort to reduce the mass of the fifth wheel while maintaining its strength and load-bearing capacity. 
     SUMMARY OF THE INVENTION 
     A reduced weight fifth wheel for tractors with the maximum allowable weight-bearing capacity for the highway systems in the United States is provided in the present invention. This fifth wheel structure, relative to its predecessors, reduced the center recess area, shortened the longitudinal length, widened the outer ramp where the slope of the ramp begins, widened the kingpin receiving groove, shortened the grease groove as the ramp tips were shortened, narrowed the support ribs and reduced the fillets, while maintaining the bearing plate surface contact area requisite for the load-bearing capacity. Maintaining the bearing-plate surface area permits reduced wear between the bearing plate and the trailer wear plate in a lighter fifth wheel. Adequate fifth-wheel, load-bearing strength is maintained in the disclosed structure, as is the provision for communication of grease to the plate surface, while the weight of the fifth wheel assembly is reduced by about twenty percent from its previous design weight. Thus, the fifth wheel is provided with a wider ramping area for receipt of the trailer kingpin and wear plate, and the kingpin receiving groove has been widened to provide a larger target area for the kingpin, which will assist the tractor driver in the coupling of the tractor with the trailer kingpin. Along with the reduction in the fifth-wheel weight, the present lever-bar-pin access hole in the extant fifth-wheel bearing plate surface has been eliminated from the bearing plate, which provides economic manufacturing improvements by reducing the raw material and labor costs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the figures of the Drawing, like reference numerals identify line components, and in the drawing: 
     FIG. 1 is a plan view of a fifth wheel assembly; 
     FIG. 2 is an elevational view in cross-section taken along the line  2 — 2  in FIG. 1; 
     FIG. 3 is an elevational view in cross-section taken along the line  3 — 3  in FIG. 1; 
     FIG. 4 is a bottom plan view of the fifth wheel assembly in FIG. 1; 
     FIG. 4A is a bottom plan view of the fifth wheel assembly in FIG. 4 noting the potential deformation of a load bearing fifth wheel; 
     FIG. 5 is a sectional view of a support rib taken along the line  5 — 5  in FIG. 4; 
     FIG. 6 is a sectional view of the lever-bar pin bracket taken along the line  6 — 6  in FIG. 4; 
     FIG. 6A is a cross-sectional plan view of the lever-bar pin bracket in FIG. 6; 
     FIG. 6B is a cross-sectional view of one of the fifth-wheel end ramps with the lever-bar pin bracket in phantom outline; 
     FIG. 7 is a side elevational view of the fifth wheel assembly in FIG. 1; 
     FIG. 8 is a plan view of a prior art fifth wheel assembly; 
     FIG. 8A is a plan view of a prior art fifth wheel assembly with the potential deformation from a vertical load; 
     FIG. 9 is an elevational view of the mating ends of a trailer and a tractor during coupling; 
     FIG. 10 is a partially exploded, oblique sectional view of a fifth wheel and its locking mechanism; and, 
     FIG. 11 is an enlarged and upright elevational view in partial section of the button-shaped pin and port of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A fifth wheel assembly  10 , and more specifically top bearing plate  12 , is shown in plan view in FIG.  1 . Assembly  10  in FIG. 9 is generally mounted on tractor  21  for mating with kingpin  23  of trailer  25 , which provides a tandem arrangement for over-the-road transport of goods. In addition, fifth wheel assemblies  10  are utilized on stanchions of flatbed railcars for transport of trailer assemblies and also have been utilized for towing recreational vehicles. However, the predominant use of fifth wheels  10  is as a coupling apparatus on tractors  21  for towing cargo bearing trailers  23 . 
     Assembly  10  has pivot bracket pockets  14  and  16  on top plate under-surface  18 , which pivot bracket pockets  14 , 16  are shown in FIGS.  2 , 3 , 4  and  7 , on diametrically opposed sides  20  and  22  of plate  12 . Pivot bracket pockets  14  and  16  are matable with tractor mounting brackets  27  on tractor frame  29  in FIG. 9, and bracket pockets  14  and  16  are secured thereto by a pin extending through port  15  and matable with ports in mounting brackets  27  for pivoting of plate  10 . In FIG. 4, transverse cross-ribs  24  and  26 , which are transverse to longitudinal axis  28 , extend between bracket pockets  14  and  16  along under-surface  18 . Bracket pockets  14  and  16  are generally parallel to each other, and to longitudinal axis  28 . Support ribs  30  and  32  in FIG. 4 generally extend longitudinally forward and parallel to axis  28 , from bracket pockets  14  and  16 , respectively, to forward rim  34  of top plate  12 . Similarly, support ribs  36  and  38  longitudinally extend from transverse cross-rib  26 , which is forward of jaw opening  56 , forward to rim  34  on either side transverse of longitudinal axis  28 . 
     As shown in FIG. 8, prior art fifth wheel  50  has a generally ovate top plate  52  with a forward longitudinal arc surface having a first arc radius  55  smaller than the arc radius of forward rim  34  of fifth wheel  10 . Longitudinal axis  28  and transverse axis  70  in FIG. 8 intersect at radius center point  51  of kingpin throat or jaw opening  56 . In this prior fifth wheel configuration, inner recess area  54  is approximately a complete circle with centrally positioned locking jaw opening  56  for mating with kingpin  23 . Slot  58  extends between opening  56  and vee-groove  60 , which groove  60  is provided between first ramp  62  and second ramp  64 . Ramps  62  and  64  downwardly slope from the plane of top plate  52 , and begin to slope down from a reference line  66  in FIG.  8 . Plate transverse axis  70  is about parallel to and forwardly displaced from line  66  at a distance ‘X’ in FIG. 8, which is about one-third of the overall length ‘Y’ of fifth wheel  50 . Grease grooves  72  are provided on plate or bearing face  74 , which grooves  72  generally surround recess  54 . Grooves  72  provide a method for transfer of grease to lubricate surface  74  and thus to reduce wear with a contacting trailer wear plate  31  on the lower surface of trailer  25  in FIG.  9 . 
     Lever-bar, pin hole or passage  76  in plate bearing surface  74  of fifth-wheel top plate  52  provides access to lower or under surface  18  of plate  52  and to lever-bar pin  73  for lever bar  75  of locking mechanism  77  in FIG.  10 . Passage  76  is requisite for maintenance of a lever-bar pin in pin port  73  beneath extant fifth wheel  50 , which lever-bar pin would otherwise be inaccessible except by removal of fifth wheel  50  from tractor mounting brackets  27 . 
     The mass and large dimensions of extant fifth wheels  50  have required larger support ribs and fillets for added strength than support ribs  80  and fillets  82  of fifth wheel  10 , which are illustrated in FIG. 5, as well as a larger recess area  54 . These previous support ribs and fillets were usually developed to provide an excess of load-bearing strength based upon historical experience or empirical data and to avoid manufacturing problems, such as hot tears. Both extant fifth wheel  50  and the present invention include jaw pins  86 , locking mechanisms  77 , operating rods  81  for locking jaws  79  and related components. 
     In the present invention shown in FIG. 1, bearing or upper plate surface  90  has about the same width B and total surface area as upper surface  74  of extant fifth wheel  50 . However, longitudinal length A is approximately 7.4 inches shorter in length for an equivalent fifth wheel used on DOT Class-8 tractors. It is noted that fifth wheels are provided in different sizes based upon their intended service use. Maintenance of the bearing area requirement for the load bearing characteristics of fifth wheel  10  while significantly reducing the length and weight of extant fifth wheel  50  is accommodated by selectively increasing the ovate shape of the plate plan view, increasing the radius of curvature  91  of front edge  34  of fifth wheel  10 , reducing the surface area of inner recess  96 . The contact area of upper surface  90  has been increased by eliminating lever-bar, pin port  76 , which is provided in fifth-wheel  50  of FIG. 8, and thereby providing a smooth transition surface for trailer kingpin  23  to smoothly slide without snagging and causing damage to either trailer  25  or tractor  21 . 
     Removal of the lever-bar pin in fifth wheel  10  is accommodated by utilization of portal  100  on undersurface  18  of fifth wheel  10 , which is noted in FIGS. 4,  6 ,  6 A,  6 B,  11  and in outline in FIG.  1 . In FIG. 6, portal  100  is in the inverted position with fifth wheel upper surface  90  at the bottom of the figure, however, this is merely provided for illustration. Plate  102  with gap  104  is positioned in passage  106  of portal  100  and is generally parallel to surface  90 , which position of plate  102  creates first subpassage  108  and second subpassage  110 . Port  112  in lower wall  114  provides access to lever bar  75  to release button-shaped, lever-bar pin  116  in passage  106 , as noted in FIG.  11 . In FIG. 6A, gap  104  provides access for lever-bar pin  116 . Pin  116  slides rearward to mate with lever-bar port and port  112  in lower wall  114 . The button-shaped pin head  119  is longitudinally constrained by recess  117 . Port  112  and button-shaped pin  116  are shown in an enlarged and upright view in FIG.  11 . Recess  117  in portal  100  is operable to nest the head of the lever-bar pin and to secure it against longitudinal movement. 
     Grease groove  118  and its related side pockets  120 , which are similar to grease groove  72  and its grease pockets  93  in fifth wheel  50 , as well as jaw pin  86 , are also found in upper surface  90  of fifth wheel  10 . 
     Front length ‘L’ of fifth wheel  50  in FIG. 8 is measured from radius center point  51  of kingpin throat  56 , which length ‘L’ is noted in this figure. Reduction of front length ‘L’ of fifth wheel  50  allows a reduction in the thickness of ribs  80  and fillets  82  on the underside of fifth wheel  10 , which reductions in length and thickness reduce the weight of fifth wheel  10 . In addition, rear length ‘X’ of fifth wheel  50  in FIG. 8 is measured from radius center point  51  of kingpin throat  56 , and a reduction of length ‘X’ also contributes to the reduction in the weight of fifth wheel  10 . The overall weight reduction of fifth wheel  10  is approximately twelve and one-half (12.5%) percent less than the weight of an extant fifth wheel  50 . 
     The primary improvement and benefit of fifth wheel  10  over extant fifth wheel  50  is the total reduction in the weight of fifth-wheel  10  while maintaining the present load-bearing capacity, which weight reduction permits larger revenue load carriage, and a reduction in cost of raw materials, without sacrificing any measure of safety in operating conditions. The underside lever-bar  75  and lever-bar pin  116  arrangement removed the necessity for casting pin-access port  76  through bearing plate  12 , thus avoiding the discontinuity in plate surface  90  as well as the necessity for providing access-port inserts into the manufacturing casting mold or dye. This latter feature further eliminated multiple casting cores utilized in the prior production methods. There has been no loss in the ability to lubricate surface  90 , as grease groove  72  with its grease pockets  93  has been reconfigured as groove  118  with grease pockets  120  to the planar arrangement of bearing surface  90 . Finally, fifth wheel  10  has utilized the available space provided by inner recess area  54  without jeopardizing safety or load-bearing parameters for fifth-wheels  10 . 
     Fifth wheels and fifth wheel assemblies  10  are further known to utilize pocket-like structures in proximity to their mounting brackets and ramps. However, in a known case the pocket structure provides only minimal support against deformation and is primarily intended to inhibit ramp tipping or tilting during the coupling of the fifth wheel to a trailer. In a second structure, the pocket-like structure is, or serves as, the outer perimeter of the fifth wheel and adds only nominal, if any, apparent reinforcement to the plate and ramp structure. This latter structure extends from the backside of the mounting bracket and intersects the outer extremity of the transverse rib with the nominal, if any, apparent support to or interaction with the ramp. 
     In fifth wheel assembly  50  of FIGS. 4A and 8A, the effect of a vertical load, and more specifically the effect of vertical loading, on fifth wheel  50  during coupling to a trailer is reflected in the dashed outline of projected deformation at the merger of ramps  62  and  64  with plate upper surface  90 . The referenced vertical loading induces a deflection or deformation of plate  12  as illustrated in FIG. 8A, which deformation may be characterized as a bowing effect approximately at the intersection of ramps  62  and  64  with plate  12 . More specifically, the bowing occurs at the outer perimeter  158  of plate  12 . This bowing or deflection has been an accepted effect in fifth wheels and fifth wheel assemblies  10 , however, it is not a desirable effect and may be a source of damage or requisite early maintenance of fifth wheel plate  12 . 
     In FIG. 4A, reinforcing ribs  150  and  151  are noted along perimeter  158  of fifth wheel  50  and blend in with perimeter  158  at mergers  156 ,  159  between mounting brackets  14  and  16  and ramps  62  and  64 , respectively. Longitudinal support ribs  152  and  154  respectively extend from the intersections  155 ,  157  of transverse rib  24  with pivot bracket pockets  14  and  16 , and are displaced from outer plate perimeter  158  a predetermined distance ‘c’. Ribs  152 ,  154  tangentially blend with outer perimeters  160  and  162  of ramps  62  and  64 , respectively. As noted in FIG. 4A, ribs  24 ,  150  and  152  cooperate to provide first deflection pocket  166  rearward of pivot bracket pocket  14 . Similarly ribs  24 ,  151  and  154  cooperate to provide second deflection pocket  168  rearward of pivot bracket pocket  16 . 
     Reinforcing ribs  150  and  151  support outer plate-perimeter  158  against deflection and deformation at vertical loading between plate  12  and, ramps  62  and  64 , respectively. In this structure, fifth wheel perimeter  158  at its intersections  161 ,  163  with ramp perimeters  160  and  162  is supported or buttressed against outward deflection of longitudinal ribs  152 ,  154  by reinforcing ribs  150 ,  151 , respectively, which laterally support perimeter  158  at the site of plate deformation and inhibit undue deflection at vertical loading of plate  12 . In this configuration, ribs  150  and  151  appear as an adjunct or extension to longitudinal ribs  152 ,  154  with a generally level lower surface  153  in FIG. 7A about parallel to the plane of plate upper surface  90 . Reinforcing ribs  150 ,  151  blend or appear to be tangential to perimeter  158  at its intersection with transverse rib  24 , and similarly blend or become tangent with ramp perimeters  160  and  162  rearward of the ramp intersection with plate  12 . Initially any vertical load positioned on plate surface  90  will continue to act downward and generally induce the same deformation or deflection load on the ribs and plate. However, the outward support from reinforcing ribs  150  and  151  acts to resist the deformation from the vertical load, and to transfer the load or deformation forces along perimeters  158 ,  160  and  162  without deformation to ribs  152  and  154 , which previously would have constituted the outer wall or perimeter of plate  12  between the plate surface  90  and ramps  62  and  64 . Avoidance of deformation of ribs  152  and  154  as well as the sidewall perimeter of plate  90  is an inhibition to fatigue, cracking and other potential structural failures associated with undesirable deflection and deformation in fifth wheels  50 . In FIG. 7A, plate  12  is at an unloaded and reference state with the distance from plate centerline  140  and the intersection of forward edge of one of ribs  150  and  151  indicated by letter ‘a’, and the backward intersection from centerline  140  of ribs  150 ,  151  with respective ramp perimeters  160 ,  162  noted by letter ‘b’. As an example in a preferred embodiment, a equals 4.06 inches and b is 8.56 inches. 
     While only a specific embodiment of the invention has been described and shown, it is apparent that various alterations and modifications can be made therein. It is, therefore, the intention in the appended claims to cover all such modifications and alterations as may fall within the scope and spirit of the invention.