Abstract:
A hitch for coupling a trailer to a towing vehicle includes a first hitch member on the trailer and a second hitch member on the towing vehicle. The hitch member on the towing vehicle is mounted on a sliding mount extending across the rear axle of the vehicle. A linkage is responsive to pivoting between the trailer and towing vehicle to move the hitch on the towing vehicle toward the rear of the vehicle when turning is effected and to move the hitch on the towing vehicle just forward of the rear axle during normal longitudinal movement of the truck and trailer.

Description:
This application claims domestic priority based upon U.S., provisional Patent Application Ser. No. 60/047,872 filed May 29, 1997. 
    
    
     The present invention relates generally to a self-adjusting fifth wheel hitch assembly for use on pickup trucks and similar vehicles used to tow fifth wheel trailers. The hitch assembly having the features of the present invention allows fifth wheel trailers to be towed using short bed pickup trucks and other trucks having a relatively short distance between the rear portion of the passenger compartment and the rear axle. 
     BACKGROUND OF THE INVENTION 
     Fifth wheel trailers and tow vehicles for fifth wheel trailers are generally well known in the art. Fifth wheel trailers are much longer, roomier, and heavier than typical tent campers and travel trailers, and thus a fifth wheel trailer typically requires a specially modified, relatively heavy tow vehicle such as a heavy duty pickup truck. The front portion of a fifth wheel trailer extends over the rear portion of the tow vehicle so that a portion of the trailer&#39;s weight is carried directly over the rear axle of the tow vehicle. In order to accommodate the weight of the trailer a special hitch assembly is required. 
     The front portion of the trailer includes a pin box which includes a support plate and a downwardly extending hitch pin. A base plate having an aperture and a latch mechanism is mounted to the tow vehicle, and the support plate carried by the pin box rests on the base plate with the hitch pin secured in the aperture by the latch mechanism. The support plate rotates relative to the base plate with the hitch pin acting as a pivot point. Typically, grease or other lubricant is applied between the support plate and the base plate. The fifth wheel trailer is thus able to pivot relative to the tow vehicle about a vertical axis to facilitate cornering and parking. Normally, the hitch assembly is mounted directly over or a short distance in front of the rear axle of the tow vehicle in order to maintain proper weight distribution. 
     The vehicle most commonly used to tow fifth wheel trailers is a pickup truck having an 8 foot bed length. On such a truck, there is typically at least 53 inches between the centerline of the rear axle and the rear of the cab. The maximum width for a fifth wheel trailer is 102 inches as dictated by federal highway regulations, which amounts to 51 inches on each side of the pivot point. Thus, in order to prevent contact between the trailer and the cab during cornering, there must be at least 51 inches of clearance between the pivot point and the rear of the cab (sometimes more depending on the fore/aft location of the pivot pin relative to the front of the trailer). 
     Recently, there has been a consumer trend towards extended cab pickup trucks, which have longer, roomier cabs. These trucks have greatly expanded interior cargo volume and also have specially designed rear jump seats for accommodating additional passengers. Unfortunately, most of these extended cab pickups are built on a standard wheelbase chassis because consumers prefer the driving characteristics of a shorter truck, and accordingly, the bed of these trucks is typically 6 feet long rather than 8 feet long. Although these shorter bed pickups have the towing capacity to handle fifth wheel trailers, they do not have enough clearance between the axle and the rear of the cab to allow the trailer to pivot to 90 degree angle without contacting the cab, which could damage the truck and severely injure any occupants. In most circumstances, a fifth wheel trailer will contact the cab of a short bed pickup at angles much less than 90 degrees. 
     A number of approaches have been contemplated to adapt fifth wheel trailers to short bed pickup trucks, all of which have their drawbacks. One possible approach is to use a hydraulically operated sliding base to force the hitch assembly, and hence the pivot point, rearward away from the truck cab. Such a system would be expensive, difficult to maintain and would have to be driver actuated. Hence such a system would involve a significant delay or lag time. In an accident such as a jackknife such a system would operate too slowly to prevent the trailer from contacting and most likely damaging the cab. 
     Another approach, which also uses a sliding base, requires the operator to exit the truck, unlock the base, lock the brakes on the trailer and pull the truck forward. This temporarily moves the pivot point rearward so that the trailer can pivot relative to the truck to a certain extent without contacting the cab. However, before resuming driving, the driver must lock the trailer brakes, back the truck towards the trailer, again exit the truck and lock the sliding hitch, and return to the truck. Obviously, such a system is impractical in many situations, such as negotiating sharp turns in traffic, and is practically useless in an emergency. 
     Accordingly, there exists a need for an improved sliding hitch assembly that allows fifth wheel trailers to be towed using short bed pickup trucks, but which prevents contact between the trailer and the truck during normal operations. There also exists a need for a sliding hitch assembly that slides automatically in response to pivoting movement between the trailer and the tow truck and that does not require the expense, maintenance and lag time of hydraulic systems, and does not require the operator to exit the vehicle in order to lock or unlock the hitch assembly. 
     SUMMARY OF THE INVENTION 
     The sliding hitch assembly according to the present invention allows fifth wheel trailers to be towed safely and conveniently using short bed pickup trucks. The present sliding hitch assembly automatically moves rearward away from the truck cab in response to the pivotal movement between the trailer and the truck that typically occurs during normal driving situations such as cornering, parking, etc. The hitch assembly responds almost immediately to any turns, thus substantially eliminating any lag or delay, and no operator input is needed at any time. Thus in normal operating conditions, and even in many jackknife situations, the hitch assembly slides rearward far enough so that the trailer will not contact the truck cab. 
     The present sliding hitch assembly includes a sliding, rotating base plate that is mounted on a pair of rods. A lever arm extends from the base plate, and a cam follower attached to the end of the lever arm engages a stationary slot that extends substantially perpendicular to the rods. Any rotation of the base plate causes the cam follower to move within the slot towards one slot ends, which in turn causes the base plate to slide back and forth along the rods. Thus, as the base plate is rotated the base plate moves between a forward position, in which the cam follower is at the center of the slot, and a rearward position, in which the cam follower is near one of the slot ends. When in the forward position, the hitch pin receiving aperture, and thus the pivot point of the trailer, is directly or slightly in front of the axle centerline. As the base plate rotates relative to the truck, the lever arm mechanism causes the base plate to slide rearwardly on the rods, effectively moving the pivot point of the trailer away from the rear of the truck cab. 
     In order to effectuate this sliding movement, the sliding base plate must pivot relative to the truck in tandem with the trailer, and accordingly the connection between the trailer and the truck must be modified. As in the prior art, the base plate aperture includes a latch mechanism to receive and retain the hitch pin. However, the present base plate includes a rectangular cutout or depression surrounding the base plate aperture. The standard pin box is also modified by adding a rectangular locking plate to the support plate, with the locking plate effectively being concentric with the hitch pin. When the hitch pin is positioned in the base plate aperture according to standard practice, the locking plate on the pin box registers with and locks into the cutout in the base plate. Thus, when the trailer pivots relative to the tow truck during turning, cornering, etc., the support plate carried by the pin box and the base plate locked to the support pivot along with the trailer. Consequently, the lever arm mechanism described above moves the sliding base plate and thus the pivot point back and forth relative to the truck. Thus, no matter what position the trailer is in relative to the truck, the sliding base plate prevents the trailer from contacting the cab. 
     Accordingly, it is an object of this invention to provide an improved fifth wheel hitch assembly that allows fifth wheel trailers to be towed using short bed pickup trucks. 
     It is another object of this invention to provide a sliding fifth wheel hitch assembly that prevents the fifth wheel trailer from contacting the truck cab during normal operations such as turning or cornering. 
     A further object of this invention is to provide a sliding fifth wheel hitch assembly that moves automatically in response to pivotal movement of the trailer relative to the tow vehicle. 
     A still further object of this invention is to provide a sliding fifth wheel hitch assembly that requires no driver intervention and that does not have a delay or lag time. 
     These and other objects of the invention will become readily apparent to those skilled in the art upon a reading of the following description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary view in perspective of the sliding trailer hitch assembly according to the present invention shown installed in the bed of a pickup truck; 
     FIG. 2 is an exploded view in perspective illustrating the locking plate that secures the pin box to the base plate and also showing the lever arm assembly; 
     FIG. 3 is an elevational view in section taken substantially along line  3 — 3  of FIG. 1; 
     FIG. 4 is an elevational view in section taken substantially along line  4 — 4  of FIG. 1 showing the sliding support assembly, the support rods and the lever arm; 
     FIG. 5 is a fragmentary top plan view taken from above showing a fifth wheel trailer attached to a pickup truck using the sliding base plate body support assembly according to the present invention, in which the fifth wheel trailer is aligned with the pickup truck; 
     FIG. 6 is a top plan view similar to that shown in FIG. 5, but shown with the fifth wheel trailer turned relative to the pickup truck and illustrating the movement of the pivot point away from the rear of the cab; 
     FIG. 7 is a top plan view similar to that shown in FIGS. 5 and 6, in which the trailer is oriented at 90° relative to the pickup truck, and the pivot point is moved the maximum distance rearward away from the cab; 
     FIG. 8 is a fragmentary top plan view of the hitch assembly as it would be situated with the trailer in the position of FIG. 5; 
     FIG. 9 is a fragmentary top plan view similar to that shown in FIG. 8 but illustrating the configuration of the hitch assembly when the trailer is in the position of FIG. 6; 
     FIG. 10 is a top plan view similar to FIGS. 8 and 9, but showing the configuration of the hitch assembly when the trailer is in the position shown in FIG. 7; 
     FIG. 11 is an enlarged fragmentary view in perspective of the pin box to base plate connection shown in FIGS. 3 and 4, but with portions of the pin box cut away to reveal the support plate carried by the pin box interlocking with the cutout in the base plate; 
     FIG. 12 is an enlarged view in section of the pin box to base plate connection shown in FIG. 11; 
     FIG. 13 is a fragmentary view in perspective of a sliding trailer hitch according to a second embodiment of the present invention, illustrated installed in the bed of a pickup truck; 
     FIG. 14 is a detailed view of a portion of the hitch illustrated in FIG. 13, shown with the floor of the bed of the pickup truck broken away to illustrate the manner in which the hitch is secured to the truck; 
     FIG. 15 is an exploded view in perspective of the sliding trailer hitch illustrated in FIGS. 13 and 14; and 
     FIG. 16 is a top plan view of a portion of the hitch illustrated in FIGS. 13,  15 , and illustrating the manner in which the hitch members on the pickup truck and on the trailer are coupled together. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiment herein described does not intend to be exhaustive or to limit the invention to the precise form disclosed. It has been chosen and described to explain the principles of the invention and its application and practical use to best enable others skilled in the art to follow its teachings. 
     Referring now to the drawings, a sliding fifth wheel hitch assembly according to the present invention is generally indicated by the reference numeral  10 . Hitch assembly  10  is shown attached to the bed  12  of a pickup truck  14  according to common industry practice. Preferably, hitch assembly  10  is secured to the frame  13 . As shown in FIGS. 5-7, hitch assembly  10  is adapted to secure a fifth wheel trailer  16  to pickup truck  14  so that trailer  16  can pivot relative to pickup truck  14  about a pivot point  18 . A sliding hitch assembly  10  according to the present invention allows the pivot point  18  to slide in a rearward direction away from cab  20  and rearward from reference line “A” which is typically directly over, or in some circumstances slightly in front of, the center line of the truck axle (not shown), so that during all normal operating conditions the trailer  16  is prevented from contacting cab  20  of pickup truck  14 . 
     Referring now to FIGS. 1-4, hitch assembly  10  includes a base plate  22  having an aperture  23  therein for accommodating the hitch pin  24  which is attached to the pin box  26  of trailer  16 . Hitch pin  24  corresponds with pivot point  18  as will be discussed in greater detail below. Base plate  22  includes a mounting slot  28  which is oriented towards the rear of the truck as shown in FIG.  1  and which is used to guide hitch pin  24  into aperture  23  when mounting the trailer  16  to pickup truck  14 . Base plate  22  also includes a pair of internal latch members  30 ,  32  which are actuated by release lever  34  in a manner commonly employed in the industry in order to secure hitch pin  24  firmly to base plate  22  thus securing trailer  16  to pickup truck  14 . A variety of readily available latching mechanisms as are well known in the art may be substituted for the mechanism shown. As shown in FIGS. 2,  11  and  12 , base plate  22  includes a rectangular depression or cutout  25 . A support plate  27  mounted to the underside of pin box  26  fits into the cutout  25 , which effectively prevents relative rotation between pin box  26  and base plate  22 , the purpose of which is described in greater detail below. Base plate  22  also includes a top surface  36  and a pair of pivot rods  38 ,  40  that extend from the sidewalls  39  which extend downwardly from top surface  36 . Pivot rods  38 ,  40  enable base plate  22  to be pivotally mounted to first intermediate support member  42 . First intermediate support member  42  includes a pair of support slots  44 ,  46  which accommodate pivot rods  38 ,  40  respectively, so that support base plate  22  can pivot relative to first intermediate support member  42  about the axis of pivot rods  38 ,  40  in response to angular changes between trailer  16  and pickup truck  14 . Each slot  44 ,  46  includes a pair of retention tabs  48 , and each tab  48  has a bore  50  therethrough for accommodating a cotter pin  52 , which is used to secure base plate  22  to first intermediate support member  42  by locking pivot rods  38 ,  40  within their respective support slots  44 ,  46 . 
     First intermediate support member  42  includes a front wall  51  and a rear wall  53 , each of which includes a bore  54  which extends perpendicular to support slots  44 ,  46 . First intermediate support member  42  is in turn pivotally mounted to a second intermediate support member  56 . Second intermediate support member  56  includes a pair of vertical supports  58 ,  60  mounted to a base member  62 . Vertical supports  58 ,  60  each include a bore  64  therethrough for accommodating a threaded pivot bolt  66 . First intermediate support member  42  is received in the gap between plates supports  58  and  60 , and support member  42  is secured to second intermediate support member  56  by pivot bolt  66 . Pivot bolt  66  extends through  54  and  64  so that first intermediate support  42  is pivotable relative to second intermediate support  56  about the axis of bolt  66 . Bolt  66  is secured within bores  54 ,  64  by threaded nut  68 . Accordingly, hitch pin  24  and hence trailer  16  is rotatable about mutually orthogonal axes in response to angular changes between trailer  16  and pickup truck  14 . 
     As shown in FIGS. 2 and 4, a pivot pin  70  connects second intermediate support  56  to a lever arm  72  which is slidably mounted within guide box  100  as discussed in greater detail below. The top end  74  of pivot pin  70  is welded or otherwise secured to the bottom face of base member  62 , while the bottom end  76  of pivot pin  70  is welded or otherwise secured to the pivot end  73  of lever arm  72 . Accordingly, any rotation of base member  56  produces a corresponding rotation in lever arm  72 . Slide plate  78  fits between lever arm  72  and second intermediate support  56 . Slide plate  78  includes a top surface  80  and a pair of downwardly depending endwalls  82 ,  84 . Top surface  80  includes a hole  86 , which is sized to accommodate pivot pin  70  and bushing  88  which is provided to prevent binding between pivot pin  70  and slide plate  78 . Sidewalls  82 ,  84  each include a pair of guide bores  90  which engage guide rods  92  to guide slide plate  78  back and forth as is discussed in greater detail below. 
     As shown in FIGS. 2,  3  and  4 , the entire structure consisting of base plate  22 , first and second intermediate supports  42  and  56 , slide plate  78  and lever arm  72  are supported by guide box  100 . Guide box  100  is bolted, welded or otherwise secured to frame  13  of pickup truck  14  by drilling holes (not shown  0  through bed  12 . Guide box  100  includes a bottom surface  102 , front and rear walls  104 ,  106 , and left and right side walls  108 ,  110 , having sloped portions  109 ,  111 , respectively. Front and rear walls  104 ,  106  each include a pair of holes  112  which support guide rods  92 , so that guide rods  92  extend through the interior of guide box  100 . A shear pin  114  at each end of guide rods  92  maintain rods  92  in guide box  100 , and enable rods  92  to be removed during assembly or disassembly or during servicing of hitch assembly  10 . Bottom surface  102  of box  100  includes a transverse slot  116  which extends generally perpendicular to guide rods  92 . Slot  116  includes a left and right ends  118 ,  120 , and further includes a front edge  122  and a rear edge  124 . Lever arm  72  includes a cam roller  126  attached to cam end  127  of lever arm  72  through mounting bore  128 . Cam roller  126  engages slot  116  and cams against the edges  122 ,  124  of slot  116  upon pivotal movement of lever arm  72 , which occurs upon rotation of pin box  26  and base plate  22 , thus causing slide plate  78  to slide back and forth along guide rods  92 . Accordingly, slide plate  78  is shiftable between a forward position in which plate  78  is disposed adjacent front wall  104 , and a rearward position in which plate  78  is disposed adjacent rear wall  106  of guide box  100 . When in the rearward position, cam roller  126  may be disposed adjacent either end  118  or  120  of slot  116  depending on the direction of rotation of lever arm  72 , which is dictated by the direction of rotation of trailer  16  relative to truck  14 . A pair of adjustment bolts  130  mounted through front wall  104  abut slide plate  78  when the plate is in the forward position. When slide plate  78  is in the forward position adjustment bolts  130  prevent inadvertent fore/aft movement of slide plate  78 . 
     In operation, with latch members  30  and  32  in an open position, a trailer  16  is mounted to pickup truck  14  according to standard practice by backing the pickup truck towards the trailer until the hitch pin  24  slides though slot  28  and into aperture  23 . In the process, support plate  27  slides into cutout  25  in base plate  22 . Upon actuation of lever  34 , latch members  30 ,  32  close about hitch pin  24 , thus securing hitch pin  24  in aperture  23  and also securing pin box  26  to base plate  22 . At this point any relative rotation between pin box  26  and base plate  22  is prevented. The trailer  16  may then be towed in the normal manner by pickup truck  14 . When pickup truck  14  and trailer  16  encounter a turn in the road, trailer  16  pivots relative to pickup  14  and guide box  100  about a vertical axis which coincides with hitch pin  24  and pivot point  18 . When the trailer  16  turns relative to the truck  14  as shown in FIGS. 6 or  7 , base plate  22 , first and second intermediate supports  46  and  56 , and lever arm  72  also turn relative to pickup truck  14 . As shown in FIG. 9, rotation of trailer  16  relative to guide box  100 , which is fixed in the bed  12  of pickup  14 , causes cam end  127  of lever  72  to slide towards one of ends  118 ,  120  of slot  116 . In the process, cam  126  presses against edge  122  of slot  116  causing a moment which draws slide plate  78  away from front wall  104  along guide rods  92 . In the process, the hitch pin  24  carried by base plate  22  move in a rearward direction away from the cab  20  of pickup  14 , thereby providing enough room for trailer  16  to pivot without contacting cab  20  of pickup truck  14 . When the truck/trailer combination straightens out and returns from the turned position shown in FIG. 6 or  7  to the straight position of FIG. 5, cam  126  presses against edge  124  of slot  116 , again creating a moment that urges slide plate  78  in a forward direction guided by rods  92  back towards front wall  104 . 
     Referring now to the alternate embodiment of FIGS. 13-16, elements the same or substantially the same as in the embodiments of FIGS. 1-12 retain the same reference character. Referring to FIGS. 13 and 14, the guide box  100  is secured to the bed of a pickup truck through ears  130  that extend from side walls  108 ,  110  of the guide box  100 . Conventional angle brackets  132  are secured to side frame members  134  of the pickup truck that supports the bed  12  thereof. Conventionally, a pair of side frame members  134  extend substantially parallel to each other and support the truck bed  10  and are a part of the overall vehicle frame. As illustrated in FIG. 14, two angle brackets are secured to each of the side frame members  134  and are attached thereto by conventional fasteners  136 . Conventional fasteners  138  extend through apertures  140  on the ears  130  to secure the ears  130  to the brackets  132 . Clearly, if it is desired to remove the hitch  10  from the bed of the pickup truck, the fasteners  138  are removed and the hitch  10  can then easily be removed, leaving the substantially flat bed. 
     The pivot pin  70  in sleeve  88  illustrated in FIG. 2 is replaced in the embodiment of FIGS. 13-16 with an enlarged cylindrical boss  140  on the lever  72 . The boss  140  extends through a correspondingly sized aperture  142  in the slide plate  78  and is connected to second support member  56  by conventional fasteners  144 . The lever  72  includes a step-down portion  146  and an end portion  148  upon which cam roller  150  is rotatably mounted. The cam roller  150  engages and is guided by a track  152  which extends between the side walls  108 ,  110 . The track guides the cam roller  150  as the second support member  56  is rotated by pivoting of the trailer with respect to the pickup truck to thereby move the slide plate  178  along the rods  92  in the same way as in the embodiment of FIGS. 1-12. 
     A modified support plate  154  is secured by conventional fasteners  156  to the bottom of pin box  26  which carries the king pin  24 . The hitch pin  24  extends through aperture  158  in support plate  154  and through mounting slot  28  and aperture  23  when the trailer is coupled to the truck. The support plate  158  includes a cutout notch  160  which is adapted to receive a projection  162  on a lever  164  when the trailer is coupled to the truck and the hitch pin  24  is received in aperture  23 . When this occurs, the support plate  154  is engaged with the top surface  36  of base plate  22 . The lever  164  is pivotally mounted on the base plate  22  by a pivot connection  165 . 
     The base plate  22  is provided with notches  166 ,  168 . The handle  164  is provided with a rod  170  slideably mounted for movement within ears  172  extending from the lever  164  and is spring loaded toward the pivot  165  by a spring  174 . A lever  176  extends through elongated aperture  178  in lever  164 . Accordingly, the member  170  is urged into latching engagement with one of the slots  166 ,  168  when the lever  164  is brought into either of the latching positions illustrated in solid and dotted lines in FIG.  16 . The member  170  may be withdrawn from its notch for movement toward the other notch by moving the member  176  toward handle  180  on lever  164 . When in the latched position with the member  170  engaged with the notch  166  and with the hitch pin  24  coupled in the aperture  23 , the projection  162  engages the notched recess  160  in support plate  154  to thereby prevent relative rotation between the hitch box  26  and the base plate  22 . However, when the lever  164  is moved to the dotted line position in FIG.  16  and with the member  170  engaged with the notch  168 , the projection  162  is moved out of the notched recess  160 , thereby permitting relative movement between the hitch box  26  and the base plate  22 , such as upon coupling and uncoupling the trailer. 
     It will be appreciated that the foregoing is presented by way of illustration only, and not by way of any limitation, and that various alternatives and modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention.