Abstract:
A fifth-wheel hitch system is described including: (a) a framework having an upright support; wherein the framework is adapted to be secured to a towing vehicle; (b) a support plate member secured to the top of the support member; wherein the plate member preferably includes a raised central portion and lower side portions; (c) a yoke member attached to the support plate member with fasteners which allow the yoke to be tilted away from the raised central portion of the plate member and then biased back to a central position; and (d) a receiver member attached to the yoke member for receiving and releasably connecting to the king pin of a trailer to be towed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon, and claims priority from, my Provisional Application No. 61/853,269, filed Apr. 1, 2013. 
     FIELD OF THE INVENTION 
     This invention relates to hitch systems used for pulling or towing fifth-wheel type trailers with a towing vehicle (e.g. a truck). More particularly, this invention relates to improvements in the construction and utilization of fifth-wheel hitch systems. 
     BACKGROUND OF THE PRIOR ART 
     Conventional fifth-wheel hitch systems involve use of a king pin secured to the underside portion of the forward end of a trailer to be towed, e.g. a camper trailer. The truck used for towing the trailer has a receiver portion mounted to it which is adapted to receive and releasably connect to the king pin. Normally the receiver portion is secured to a framework in the bed of the truck with a plurality of bolts which extend downwardly through the bed and are fastened to the truck frame. The receiver portion (a receiver plate) may be attached to the hitch framework by means of a yoke member which allows the receiver plate to tilt or rotate about a horizontal plane which is perpendicular to the longitudinal axis of the truck. This feature allows the receiver plate to tilt forwardly or rearwardly, for example, relative to the hitch framework when the towing truck goes over inclines or sloping terrain where the rear wheels of the truck become raised (or lowered) relative to the front of the truck. 
     However, in certain towing situations the trailer is subjected to various twisting forces, e.g. when the towing vehicle is tipped to one side or the other relative to the trailer, such as when the towing vehicle turns onto or off from a roadway which is lower or higher than its current path. In those situations one side of the towing vehicle becomes higher that the other side while the trailer is still in the original plane. This twisting action also can occur when only one side of the towing vehicle travels over a bump (or through a hole). These twisting forces are very undesirable. They place further burdens on the hitch system itself, and the trailer frame can be twisted or otherwise damaged. 
     A prior art method for alleviating the problem of twisting forces in the fifth-wheel hitch involves the use of a universal joint in which there are two axis of rotation at 90° to each other. This necessarily requires maintenance of two joints and also adds to the overall weight and cost of the hitch system. 
     There has not heretofore been provided a fifth-wheel hitch system having the advantages and features of the present invention. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides an improved fifth-wheel hitch system comprising: 
     (a) a framework system comprising an upright support member; wherein the framework system is adapted to be secured to a towing vehicle; 
     (b) a support plate secured to the top of the support member; wherein the support plate member preferably includes a raised central portion and lower side portions; 
     (c) a yoke member attached to the plate member by means of fasteners which allow the yoke member to be tilted away from the central portion of the plate member and then biased back to a central position; and 
     (d) a receiver portion attached to the yoke member for receiving and releasably connecting to the king pin of a trailer to be towed. 
     The improved fifth-wheel hitch system enables the receiver portion of the hitch to tilt either to the left or to the right of the longitudinal centerline of the towing vehicle, as needed in order to accommodate left and right tilting of the trailer being towed as the trailer travels over uneven ground. This avoids twisting of the trailer frame. In one embodiment the fifth-wheel hitch system can be easily secured to a conventional ball-type hitch in the bed of a truck. The hitch system of the invention can be easily disconnected from the ball-type hitch when the fifth-wheel hitch is no longer needed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates one embodiment of a fifth-wheel type hitch system of the present invention that is suitable for use in towing fifth-wheel type trailers with a vehicle such as a truck. 
         FIG. 2  is an elevational view of another configuration of a fifth-wheel hitch system of the invention. 
         FIG. 3  is an elevational view of yet another configuration of a hitch system of the present invention that is suitable for use with a ball type of hitch located in the bed of a truck. 
         FIGS. 4A and 4B  are elevational views of two different types of support plates that are useful in the hitch systems of the invention. 
         FIGS. 5A and 5B  are elevational views of two different embodiments of yoke members which are useful in the present invention. 
         FIG. 6  illustrates one embodiment of bracing which may be used in conjunction with one type of hitch system of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     One embodiment of the hitch system  10  of the present invention is illustrated in  FIG. 1 . The hitch system includes an upright support member  12  having a plate member  14  secured to its upper end. Attached to the plate member is a yoke  16  having a relative flat base  17  and outwardly protruding shafts or fingers  18  (one extending outwardly from each side of the yoke, as shown). The yoke is attached (by means of fingers  18 ) to the legs  32  of a receiver  30 . The receiver includes a pathway  34  for guiding the king pin  42  of trailer  40  to a lockable (i.e. latch) position in the receiver where latch  36  captures the king pin. Lever  37  enables the user to unlatch the king pin when desiring to unhook the trailer from the towing vehicle. Because the receiver is attached to the yoke solely by means of the fingers on the sides, the yoke allows for pivoting action of the receiver in the longitudinal direction but not in a side-to-side or lateral direction 
     The yoke is attached at the center of its base to the central portion of the support plate  14  by means of bolts  20  which extend through corresponding holes in the yoke base and the plate  14 . A spring  21  encircles the bolt and provides a biasing action when yoke  16  is tilted to one side or the other away from the center of the support plate. The tension on the spring can be increased (or decreased) by means of tightening or loosening nut  22  on the upper end of bolt  20 . 
     As shown in  FIG. 1 , the support plate may have a central portion  15  which is raised relative to the rest of the support plate. This may be by means of a crease in the plate or by means of an arc in the plate. In either event, a gap  24  is created between each side portion of the plate and the base of the yoke. The gap is preferably at least about 0.5 inch but could larger (e.g. about 1 inch). The gap on each side of the plate enables the yoke  16  to be tilted either to the right or to the left (e.g. when the trailer or the towing truck go over bumps or holes in the roadway, or when the truck turns off from one road onto another and the roadways are at different elevations). This avoids harmful twisting of the trailer while towing. 
       FIG. 2  is an elevational view (partially cut-away) of another embodiment of hitch system of the invention where the upright support member  50  is bolted to the frame  60  below bed  62  of a towing vehicle by means of bolts  52 . The support member  50  includes a plate  54  to which the yoke member  16  is attached by means of bolts  20 . A gap  24  is shown between the side portions of the support plate  54  and the yoke member  16 . 
       FIG. 3  is an elevational view (partially cut-away) showing another embodiment  70  of hitch system of the invention. In this embodiment the lower end of the upright support member  72  is releasably connected to a conventional ball  80  secured in the bed  82  of a towing vehicle. The connection is made by means of locking pins  71  which are adapted to move in separate guideways  71 A between retracted and extended positions to lock the support member to the ball  80 . The locking pins are located on opposite sides of the ball, as shown. Rotatable cam members (which are pivotably mounted to ears  75 ) are caused to push the locking pins upwardly against the ball by means of threaded screws  74 . A support plate  76  is secured to the upper end of the support member  72 , and yoke  16  is attached to the support plate by means of bolts  20  (as described in connection with  FIG. 1 ). A gap  24  is shown between the side portions of the plate  76  and the yoke  16 . The receiver  32  for the hitch system is attached to the ears  18  of the yoke, as described in connection with  FIG. 1 . 
     The embodiment shown in  FIG. 3  is especially useful when it is desired to use the existing ball-type hitch in a towing vehicle in order to tow a trailer which has a fifth-wheel type hitch. Thus, it is not necessary to purchase a relatively heavy and expensive framework for a conventional fifth-wheel hitch arrangement. Also, with the embodiment shown in  FIG. 3 , the upright support member can be easily and quickly detached from the ball hitch so that the towing vehicle can use the ball hitch for towing gooseneck trailers. 
       FIGS. 4A and 4B  are elevational views illustrating two different manners in which the side portions of the support plate are lower than the central portion of the plate. In  FIG. 4A  the support plate  14  is curved so that the outer portions of the plate form a gap  24  on each side, as shown. Preferably the gap is in the range of about 0.5 to 1 inch. In  FIG. 4B  the support plate  14 A includes a central ridge  15 A (with the ridge extending along the center of the plate in a longitudinal direction of the towing vehicle). Gap  24  is therefore provided between the outer portions of the support plate and the yoke  16 . The extent of the crease forming the ridge may vary, but typically a crease of about 5 degrees is sufficient to provide the desired gap on each side. As previously stated, the presence of the gaps on the sides of the plate enable the yoke (and, thus, the trailer) to rock or tilt to one side or the other when the trailer and towing vehicle go over bumps or uneven ground. 
       FIGS. 5A and 5B  illustrate other embodiments of the hitch system wherein the support plate  11  is planar, and the yoke member has been modified so that a gap  25  is defined at each side edge between the yoke and the support plate. In  FIG. 5A  the yoke  32 A is provided with a slightly rounded or curved bottom surface, as shown. In  FIG. 5B  the yoke  32 B has been provided with a creased bottom, as shown, with the crease running in the longitudinal direction. 
       FIG. 6  illustrates one type of bracing which may be used in conjunction with the hitch system which is connected to a conventional ball-type hitch in a towing vehicle. The bracing includes elongated base member  100  having a central opening  101  to accommodate the ball  80  secured in truck bed  82 . The base member  100  lies on the bed of the truck and may include elongated leg extension members  92  positioned on opposite sides of the base member and bolted thereto by means of bolts  103 , for example. Brace members  93  are positioned forwardly and rearwardly of the upright support member  12 . The lower end  93 A of each brace is secured to the base member  100  with bolts  96  which extend through the lower end of the brace and through elongated slots  102  in the base. The upper ends  93 B of the braces are positioned, respectively, against the forward and rearward sides of the upright support member  12  beneath stop members  95  (which may be, for example, metal bars welded or otherwise secured to the support post  12  on the forward and rearward surfaces, as shown). Turnbuckles  94  are attached at opposite ends thereof to the two braces  93 . When the turnbuckles are tightened, the upper ends  93 B of braces  93  are drawn upwardly against stop members  95 , and the lower ends  93 A are pulled toward the support post  12  (sliding the bolts  96  in the slots  102 ) to complete triangular bracing of the support post. In this manner, the support post is very rigidly held in a straight upright position during use. It is very easy to remove the bracing when it is necessary to remove the hitch system from the truck bed. 
     Other variants are possible without departing from the scope of this invention.