Abstract:
An extension coupling for releasably interconnecting a trailer to a fifth wheel tow hitch. This extension coupling includes a mount that is secured to the trailer, and an elongated arm that is pivotally secured to the mount and one end. A universal joint with lateral pins is attached to the other end of the arm to mate with the tow hitch. This allows the trailer to be displaced rearwardly of the tow hitch a distance equal to the length of the elongated arm while at the same time maintaining the loading point on a tractor vehicle forward of the rear axle. The assembly allows the trailer to pivot normally, without hitting the cab of short-bed pickup trucks. It also ensures that the weight of the trailer is carried forward of the rear axle for stability.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to travel hitches and particularly to trailer hitches for fifth-wheel type trailers. 
     2. Description of Related Art 
     A fifth-wheel travel trailer is essentially a small, self-contained home that may be towed to a desired location by any suitable tractor vehicle, such as a pick-up truck. The forward portion of the travel trailer has a downwardly depending hitch box and downwardly projecting kingpin. This kingpin is sized and adapted to mate with a standard fifth-wheel hitch that is mounted on the tractor vehicle. Thus, the tractor vehicle supports the travel trailer so that its forward end is elevated above the surface of travel, such as a roadway, while the rear portion of the vehicle is supported on a wheel set so that it may travel over the surface. 
     The substantial weight of the fifth-wheel travel trailer requires proper loading and mounting of the hitch assembly. Where the typical pick-up truck is employed as the tractor vehicle, the fifth-wheel tow hitch receiver is secured in the bed of the pick-up truck above and slightly in front of the rear axle. It is important that the mounting not be located too far forward of the axle to avoid unnecessary bending moments about the axle. Moreover, it is important not to mount the hitch rearwardly of the axle otherwise the tractor vehicle will tend to rear off its front wheels resulting in loss of steering control. 
     When a long-bed truck is employed as the tractor vehicle, relatively few difficulties are encountered in the proper mounting of a hitch receiver for a fifth-wheel trailer. Recently, though, the popularity of the short-bed pick-up truck has grown. These trucks typically have beds that are 6 to 7 feet in length. Consequently, there is a decreased distance between the rear axle of the pick-up truck and the cab. In such cases, as discussed more thoroughly below, the proper mounting of the hitch receiver results in inadequate clearance between the forward portion of the fifth-wheel trailer and the truck cab. FIGS. 1,  2  and  3 , show a typical fifth-wheel trailer  10  attached truck  12 , which is a short bed pick-up truck with a hitch  9 . In order to keep the hitch receiver and axis A forward of the rear axle  200 , as is represented by transverse axis X, a diminished space between the cab  201  of truck  12  and forward portion  11  of the trailer  10  is created. Towing trailer  10  in a straight line causes no problems. However, the turning radius of the combination of truck  12  and trailer  10  is diminished, as is shown in FIG.  3 . As is shown in this figure, when the vehicle is making a turn, the corner  11   a  of forward portion  11  can contact cab  201  which can result in damage to truck  12 , trailer  10  or both. 
     In order to achieve adequate clearance, the tow hitch may be moved rearwardly in the bed, behind the rear axle. However, as noted above, this creates an undesirable and potentially dangerous towing configuration. 
     Another undesirable situation occurs as the tractor and trailer encounter a series of dips or bumps in the road and the rear of the tractor vehicle and the front of the trailer start a pitching or bucking action as one dip in the road is encountered after another. This pitching action is not only bad for the components of the two vehicles; it is dangerous. Accordingly, a need has arisen for alternative mounting assemblies for fifth-wheel trailer vehicles. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a hitch receiver, a hitch extension coupling and a shock absorbing bar to connect a tractor vehicle to a trailer, that allows the trailer to be towed by a short bed type vehicle. 
     A further object of the present invention is to provide a hitch coupling for a trailer that moves the pivot axis of the trailer rearwardly of the tractor vehicle while maintaining the load point of the trailer forward of the tractor vehicle&#39;s rear axles. 
     Another object of the present invention is to provide an extension coupling that allows the towing of a fifth-wheel travel trailer by a short bed pick-up truck in a safe manner. 
     Another object of the present invention is to provide a receiver, an extension coupling and a pitch absorber that allows a short bed pick-up truck to be used to tow a fifth-wheel trailer with diminished risk of damage to either during the towing operation. 
     Another object is to provide an appropriate hitch receiver for the hitch extension coupling. 
     Another object is to provide a pitch-absorbing bar to restrict extreme movement of the vehicles. 
     To accomplish these objects an extension coupling is provided that is adapted to releasably interconnect the trailer to a tow hitch that is located on the tractor vehicle. This extension coupling includes a mount that is adapted to be secured to the trailer, and an elongated arm that has a proximal end portion pivotally secured to the mount, and a distal end portion opposite the proximal end portion. A universal joint with lateral pins is attached to the distal end portion and is adapted to releasably mate with the tow hitch. This allows the trailer to be displaced rearwardly of the tow hitch a distance equal to the length of the elongated arm while at the same time maintaining the loading point on a tractor vehicle forward of the rear axle. 
     A mount is adapted to be secured to a hitch connecting station on the receiver that has a base plate and a pair of opposed side plates, which are oriented to be fastened to mounting plates that depend downwardly from the front of the trailer. Two cylinders extend down from the base plate of the inner cylinder. They are rigidly secured to the mount. The elongated arm includes a receiver adapted to rotatably receive the truck-mounted hitch. The arm may be structured as a housing, which includes a top wall, a bottom wall opposed to the top wall, and a surrounding sidewall. The arm may be telescoping to adjust the length of the arm. 
     A universal joint assembly is also provided with the hitch on the towed vehicle. The universal joint assembly engages the tow vehicle receiver when the trailer is attached and is used to resist rotation of the arm relative to the receiver on the tow vehicle. The fore and aft arms of the universal joint connect to the hitch assembly by means of sleeves, which allow the universal joint to pivot on an axis parallel to the tow vehicle. The tow arms perpendicular to the parallel arms seat in the hitch receiver create a perpendicular axis to the parallel axis. 
     Attached to the truck is a hitch receiver that is a box-like structure with the top and back end removed, The sides of the structure guide the hitch as the receiver is backed under the hitch. Inside the receiver is a pair of “U” shaped blocks machined to receive the vertical ends of the universal joint. The “U” shaped blocks receive the universal joint appendages as the fifth wheel hitch is lowered onto the hitch receiver. A pair of blocking plates on either side of the receiver swing in over the universal joint appendages securing the universal joint in the “U” shaped blocks. A rod passing through a slot in the locking plates moves the locking plates in or out of locking position. A spring-loaded plate engages the rod to secure it in the desired position. 
     An arm extends rearwardly from the extension coupling to engage the pitch dampener. A pitch dampener is used to reduce the pitching, or up and down bouncing movement, on the rear springs of the tractor vehicle when a series of depressions in the road are encountered. 
     These and other objects of the present invention will become more readily appreciated and understood from a consideration of the following detailed description of the exemplary embodiment when taken together with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view in elevation of a fifth-wheel travel trailer being towed by a tractor vehicle having a short box bed according to prior art. 
     FIG. 2 is a top plan view of the prior art truck and trailer combination of the trailer being towed in a straight line. 
     FIG. 3 is a top plan view of the prior art truck and trailer combination showing its reduced turning radius. 
     FIG. 4 is a side view in elevation showing the use of the extension coupling of the present invention with a truck and trailer combination. 
     FIG. 5 is a side view of the extension-coupling hitch according to the present invention. 
     FIG. 6 is a side view in cross-section of the extension coupling hitch according to the present invention that is shown in FIG.  5 . 
     FIG. 7 is a perspective of the extension coupling including offset view of the universal joint. 
     FIG. 8 is a perspective of the hitch receiver attached to the tow vehicle. 
     FIG. 8 a  is a detail view of the receiver blocks and the locking plates of the hitch receiver. 
     FIG. 9 is a partial side view in elevation showing parts in relationship to axis S. 
     FIG. 10 is a side view in elevation of the present invention showing the pitch dampener bar installed on a vehicle. 
     FIG. 11 a  is the side view of a trailer using the present invention with the pitch a damper bar installed showing the damper fully compressed. 
     FIG. 11 b  is the side view of a trailer using the present invention with the pitch damper bar installed showing the damper fully extended. 
     FIG. 12A shows a plan view of an alternate configuration of the U-joint shown in FIG.  7 . 
     FIG. 12B is a side view of the alternate configuration of the U Joint of FIG. 12A mounted in the receiver. 
     FIG. 13 is a detail view of the locking system for the alternate configuration of the U joint system. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 4 shows a fifth wheel trailer  10  that is adapted to be towed by a tractor vehicle, such as a short bed pick-up truck  12  so that it may be moved along a transport surface such as a roadway. In the preferred embodiment, hitch receiver  14  must be mounted as close to the rear axle of truck  12  as possible, to allow the weight of trailer  10  to be supported directly above the axle. It is desirable, though, that the hitch receiver  14  be mounted slightly forward of the rear axle, in order to reduce the possibility that truck  12  will “rear” onto its back tires with the front tires having diminished contact with the roadway or other support surface. The tendency of the vehicle to rear under heavy loads is substantially increased if hitch receiver  14  is mounted either directly above or rearwardly of the rear axle of truck  12 . As shown in FIG. 4, an extension coupling  20  is used to interconnect the trailer  10  with the hitch receiver to maintain the load point of trailer  10  forwardly of the rear axle of the truck while at the same time keeping the trailer  10  a measured distance rearwardly of truck  12 . Moreover, the present invention maintains the pivot axis for trailer  10  at the existing connector box attachment, all as described more thoroughly below. 
     FIGS. 5,  6  and  7  show that extension coupling  20  includes a mount  21  that is adapted to be secured to the trailer by mounting plates  22  which downwardly depend from the front portion  11  of the trailer  10 . Mount  21  includes a base plate  23  from which a pair of opposed, parallel side plates  24  extends upwardly. Mounting holes  25  are formed in side plate  24  and are positioned to engage plates as shown. Mount  21  may be secured to plates  22  by means of nut and bolt sets in mounting holes  25 . 
     FIG. 5 shows an elongated arm  30  that has a proximal end portion  31 , which is secured to a cylinder  40 . Cylinder  40  protrudes downward through cylinder  41  as shown. The rotation of cylinder  40  within cylinder  41  provides a pivot for axis P. Plate  23  and plate  26  provide a turntable for the pivoting on axis P. Plate  26  is attached to cylinder  41 . Cylinder  40  is attached to base plate  23 . 
     FIG. 7 shows distal end  32  secured to proximal end  31  by a bolt  35 . The ends  31  and  32  are four-sided rectangular tubes. The end  31  is designed to be telescoping within end  32 . The length of arm  30  can be adjusted by selecting one of the holes  36 , through which bolts  35  can be placed. 
     FIG. 5 shows that distal end  32  of arm  30  is firmly attached to a cylinder  50  within which cylinder  51  passes through. The turning of cylinder  51  within cylinder  50  is the pivoting point for axis S. 
     Sectional view FIG. 6 shows the hitch on the towed vehicle and the receiver hitch on the tow vehicle mated together and ready for transport on the roadway. Pin  55  is shown in place. Pin  55  locks cylinder  50  to cylinder  51 , thereby stopping the rotation on axis S. 
     FIG. 9 shows pin  55  removed from hole  53  in cylinder  50  and hole  54  in cylinder  51 . Now, cylinder  50  and cylinder  51  are no longer locked together and cylinder  50  may pivot on cylinder  51 . It must be noted that the amount of pivot on axis S for cylinder  51  and cylinder  50  is limited. Notched end  60  on cylinder  50  engages protruding end  61  on cylinder  62 , which is firmly attached to cylinder  51 . As cylinder  50  and cylinder  51  rotate on axis S, cylinder  50  is lifted up until cylinder  50  is pressed against the protruding end  61  of cylinder  62 . As cylinder  50  presses against the protruding end  61  of cylinder  62 , rotation between cylinder  50 , cylinder  51  and cylinder  62  on axis S is terminated. 
     FIG. 7 shows a universal joint  70  having arm  71  with ends  71 A and  71 B. Perpendicular to arm  71  is arm  74 , having two ends  74 A and  74 B. End  71 A is inserted into  72 A as end  71 B is inserted into cylinder  72 B. Cylinders  72 A and  72 B are attached to cylinder  75 . Arm  71  is free to pivot within cylinder  72  on axis X. FIG. 7 also shows guide plate  80 , which is attached to cylinder  75 . Guide plates  82 A and  82 B are laterally attached to either side of the receiver hitch on the tow vehicle as shown. FIG. 7 also shows the receiver on the tow vehicle being backed under the towed vehicle hitch. If the hitch is not centered on the hitch receiver as the tow vehicle backs up, arm  74  on universal joint  70  engages either guide plate  82 A or  82 B on the hitch receiver. This contact then forces the arm  74  to become aligned automatically with the receiver. 
     In the hitching mode, cylinder  75  and the universal joint  70 , attached to cylinder  75 , are free to pivot on axis S to a limited degree. Should the hitch be off center of the receiver as the receiver is backed under the hitch, and arm  74  engages guide plate  82 , the universal joint assembly pivots on axis S giving arm  74  a sufficient angle in relation to guide plate  82  to slide to the center of the receiver. As the receiver advances, the hitch plate  80  engages guide plate  82 A or  82 B on either the left or the right side of the hitch receiver to square up universal joint  70  with hitch receiver  14  on the tow vehicle. As the hitch receiver continues to move under the hitch, plate  80  engages guide  82 A or  82 B on either side of the hitch receiver to position arm  74  perpendicular to guide  82 . As the tow vehicle and hitch receiver  14  continues toward the towed vehicle, the movement of the tow vehicle and the hitch receiver  14  are stopped as the leading arm  71  comes in contact with guide  82  of hitch receiver  14 . The trailer is then in position to be lowered and the hitch to be attached to receiver  14 . 
     FIGS. 8 and 8 a  show hitch receiver  14  resembling a box having sides  82 A, and  82 B, a front  83  and a bottom  84 . Attached to side  82 A and bottom  84  is receiver block  90 A. See FIG. 8 a  for details of the block. Attached to side  82 B and bottom  84  is receiver block  90 B. Receiver blocks  90 A and  90 B receive arms  74 A and  74 B of the hitch. Locking plates  91 A and  91 B are shown in a position where they lock hitch part  74 A and  74 B in the cradle of receiver blocks  90 A and  90 B. 
     A control rod  95  is shown extending through slots  96 A and  96 B, where it is attached to side  82 A and  82 B by pins  98 A and  98 B. Arm  99  is spring activated by spring  100  and has a lower notch  99 B to restrict control rod  95  at the bottom of slots  96 A and  96 B. Plates  91 A and  91 B are in a locked position-securing arm  74 . Arm  95  has an upper notch  99 A that retains control rod  95  in the upper end of slot  96 , which releases hitch part  74  by retracting locking plates  91 A and  91 B. See also FIGS. 5 and 10. 
     FIGS. 8 and 8 a  also show that in the hitching mode, control rod  95  will be in notch  99   b  of arm  99 . Plate  91  is retracted to clear receiver blocks  90 A and  90 B to receive arms  74 A and  74 B of universal joint  70 . Arm  74  of universal joint  70  is lowered into the recess of receiving blocks  90 A and  90 B. Control rod  95  is lowered to the bottom notch  99   b  of arm  99 . Simultaneously control rod  95  moves downwardly in slots  96 A and  96 B. Locking plates  91 A and  91 B are then positioned inwardly over the upper portion of arms  74 A and  74 B of universal joint  70 . Plates  91 A and  91 B are then in position to prevent any possibility of arms  74 A and  74 B from lifting away from blocks  90 A and  90 B. 
     Referring now again to FIG. 6, at this point the weight of the towed vehicle on notched end  60  of cylinder  50  and the protruding end  61  of cylinder  62 , lines hitch  20  up with receiver hitch  14 . Once these parts are aligned, pin  55  can be inserted, effectively eliminating pivoting on axis S. 
     FIG. 4, shows that, by using the extension coupling  20 , the forward weight of trailer  10  is supported by tow hitch  14  forward of rear axle  200 , while at the same time the extension arm  30  displaces the position of trailer  10  rearwardly. This allows a greater clearance between the truck cab  201  and front portion  11  of the trailer so that the turning angle between truck  12  and trailer  10  may be increased without risking damage to either trailer  10  or the truck cab  201 . At the same time, trailer  10  may pivot during turning about spindle axis S in a standard manner since arm  30  does not pivot significantly with respect to tow vehicle  12 . 
     FIGS. 10,  11   a  and  11   b  show an optional resistance dampening system  120 . FIG. 10 shows a side view of the system installed on a vehicle. As shown in FIG. 10, the system has an extension arm  121 , which is attached to cylinder  41 . Resistance arm  122  is pivotably attached to the end of the extension arm  121  as shown. The resistance arm  122  extends downward into a four-sided, generally rectangular receiver  123 . The receiver  123  is attached to the vehicle  12  in a regular towing hitch  127 . Resistance arm  122  is sized to fit within the receiver  123 . A plate  124  is attached to the top of the receiver  123  as shown. The plate has two “U” bolts  125  attached to it to hold the extension arm  122  against plate  124 . Resistance to movement is produced by arm  122  rubbing against plate  124 . The resistance can be adjusted by tightening or loosening the bolts  125 . Of course, more sophisticated dampers, such as shock absorbers or springs systems may be substituted for the resistance arm and tube assembly discussed above. In the preferred embodiment, the extension arm  121  is further supported by a brace  126  a that runs diagonally as shown as is also connected to cylinder  41 . 
     FIG  11   a  shows the resistance arm  122  in a compressed mode as the trailer  10  and truck  12  hinge due to road conditions. FIG. 11 b  shows the resistance arm  122  in an expanded position. In both cases, the hinging action is resisted between the truck  122  and trailer  10  by the resistance arm. The resistance arm system  120  acts like a shock absorber when a bouncing effect occurs on the rear springs due to up and down road conditions. 
     Referring now to FIGS. 12A,  12 B and  13 , an alternate configuration of the U-joint found in FIG. 7 is shown. FIG. 12 A shows a plan view of this system. In this system, the universal joint of the previous embodiment is replaced by a pair of rocking platforms. This platform provides the same type of movement that the universal joint provides, using a simpler structure. The system has two brackets  160  that are secured to the bed of the vehicle  12 . A lower box unit  161  is attached to the brackets  160  by a bolt system  162  that allows the box  161  to pivot about the bolt systems  162 . The lower box unit  161  has four walls, but is open in the center. A hitch receiver platform  163  is positioned within the lower box unit  161 . The hitch receiver platform  163  is an inverted box that has a top  164  and two side walls  165 . The side walls have holes  166  for mounting a shaft  167 . The shaft  167  is pivotably secured to the lower box unit as shown. This allows the hitch receiver platform  163  to pivot orthogonally to the pivoting motion of the lower box unit  161 . As shown in FIGS. 12A and 12B, the hitch receiver platform has a latch arm  168  attached at a pivot point  169 . A receiver keyway  170  is also formed in the top of the hitch receiver platform to receive the locking flange  178  from the hitch, as described below. Extending upward from the top of the hitch receiver platform  163  are two guide plates  171 . As shown in FIG.,  12 A, the guide plates form a “V” shape. 
     The use of the double pivot points on these two assemblies replaces the universal joints used in the first embodiment. 
     In this embodiment, the lower portion of the hitch has been modified to accommodate the new system. FIG. 13 shows cylinder  175  extending down from the extension arm, (not shown in this view). Within cylinder  175  is cylinder  176 , which is fixedly attached to cylinder  175 . As shown in FIG. 13, cylinder  176  extends out of cylinder  175  for some distance. Cylinder  176  has a narrow neck  177  and a flange  178 , which is used as a locking flange. Around the lower portion of cylinder  176  is cylinder  180 , which is firmly attached to plate  181 . Plate  181  is triangular and is designed to fit into the “V” shaped space formed by the guide plates  171 . It has a rear lip  189  for strength. The cylinder  180  and plate  181  combination is designed to rest on locking flange  178 . In this way, cylinder  180  and plate  181  are free to revolve around the neck  177  of cylinder  176 . This provides another range of movement for the system that better allows the hitch plate  181  to align with the receiver and its guide plates during the hitching process. 
     To restrict the amount of movement of the hitch plate  181  and to lock the cylinder  180  to cylinder  175  for transport, ramps  183 A and  183 B are formed onto the cylinders as shown. When separated, the ramps allow cylinder  180  and plate  181  to pivot during the mating period. After the hitch is aligned in the receiver, the towed vehicle weight is lowered onto the hitch. As the hitch is lowered, ramps  183 A and  183 B come together. Once the ramps are together, plate  181  can no longer rotate. 
     The locking flange  178  is lowered through the keyway  170  in platform  163  and can be locked in place by activating latch arm  168  until the locking jaws  185  are secured around the locking flange  178 . At this point, the trailer fully hitched. Once the leveling equipment has been removed, the trailer is ready to haul. 
     The present disclosure should not be construed in any limited sense other than that limited by the scope of the claims having regard to the teachings herein and the prior art being apparent with the preferred form of the invention disclosed herein and which reveals details of structure of a preferred form necessary for a better understanding of the invention and may be subject to change by skilled persons within the scope of the invention without departing from the concept thereof.