Abstract:
A slidable trailer hitch apparatus comprises a trailer hitch head operable to receive a cooperating portion of a trailer, the trailer hitch head adapted to be slidable and rotatable relative to the vehicle about an axis of rotation, first and second parallel spaced part guides fixedly located relative to the vehicle, and a body affixed to and rotatable with the trailer hitch head, the body having a center of rotation about the axis and a distal surface adapted to engage either of the first or second guides when the body is rotated relative to the first and second guides. The engagement of the distal surface upon either of the first or second guides displaces the center of the body and the trailer hitch head parallel to the first or second guide when the trailer hitch head is rotated relative to the first and second guides.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a continuation-in-part of U.S. patent application Ser. No. 11/345,998, filed Feb. 1, 2006, which is incorporated herein by reference. 

   BACKGROUND 
   1. Field 
   This disclosure relates to hitches for connecting a trailer to a vehicle, and more particularly, to a method and apparatus for adjustably securing a portion of a trailer to a sliding a fifth-wheel trailer hitch head assembly. 
   2. Description of Related Art 
   Trailers are often secured to a vehicle so as to enable the vehicle to tow a load or a trailer containing recreational living quarters. Various means have been adapted for connecting the trailer to the tow vehicle including what is known in the art as a fifth-wheel trailer hitch. 
   In a fifth-wheel trailer hitch, the trailer includes a forwardly projecting arm which includes a vertical kingpin projecting out of a horizontal portion of the pin box. The kingpin is received within a corresponding slot of a trailer hitch plate located on the tow vehicle. The kingpin is then secured in the slot of the trailer hitch plate so as to enable the tow vehicle to tow the trailer. 
   The fifth-wheel trailer hitch assembly has many advantages that make it attractive for use in towing large trailers. Particularly, the engagement of a pin in a horizontal surface of the trailer hitch assembly allows the trailer hitch of a fifth-wheel hitch assembly to be located at any location on a vehicle desired by a user. Correspondingly, a ball-type trailer hitch assembly is limited to being located at the rear of a vehicle. 
   The ability to locate the trailer hitch assembly at any location desired by the user enables the trailer hitch of fifth-wheel hitch assembly to be located at the center of the vehicle at a point between the two rear wheels above the rear axle. Locating the trailer hitch assembly above the rear axle serves to transfer the portion of the weight of the trailer applied on the trailer arm to a position above the axles rather than at a distance from the axles as in the case of a ball joint. This serves to reduce stresses imparted to the frame and bumper of a tow vehicle. In addition the weight transferred to the rear tires of the tow vehicle is not increased by as great a degree as is the case in a ball hitch where the distance from the ball hitch to the rear axle creates a moment arm thereby increasing the weight applied to the rear tires. 
   A conventional fifth-wheel trailer hitch assembly, however, includes several deficiencies. When the tow vehicle is towing the trailer in a straight line, the front edge of the trailer and the rear edge of the tow vehicle will be in a parallel orientation to each other. As the tow vehicle negotiates a turn, however, the front edge of the trailer will be rotated relative to the rear edge of the tow vehicle. This will bring one corner of the trailer closer to its opposing corner of the tow vehicle. If the trailer arm connecting the trailer to the fifth-wheel hitch is not long enough, when the tow vehicle negotiates a turn, the aforementioned corner of the trailer may become quite close to or even contact its corresponding corner of the tow vehicle. 
   Accordingly, relatively long trailer arms are necessary to provide ample clearance between the trailer and the tow vehicle during all anticipated orientations of the trailer relative to the tow vehicle. Opposing the requirement for longer trailer arms, is the requirement to maintain efficient operation of the vehicle and trailer. In order to maintain efficient operation of the vehicle and trailer, it is desirable to maintain the distance between the trailer and the tow vehicle as low as possible so as to reduce drag and instability. 
   In the past, a balance has been struck when selecting the distance between the trailer and the tow vehicle so as to allow efficient operation while still enabling sufficient range of maneuverability. What is desirable is to provide a fifth-wheel hitch assembly which is able to move rearward while turning to enable ample maneuverability of the tow vehicle and trailer while being able to be subsequently moved forward to an optimal straight line tow position thereby shortening the distance between the tow vehicle and the trailer. 
   Various attempts have been made to provide a trailer hitch assembly that is moveable with respect to the tow vehicle so as to increase the maneuverability of the tow vehicle and trailer. For example, various attempts have been made to provide a sliding trailer hitch assembly which is lockable at a plurality of positions. In such a trailer hitch assembly, a user may unlock the sliding hitch assembly and slide it to a second position. At the second position, the vehicle and trailer may negotiate a tight turn. Thereafter, the user may unlock the sliding trailer hitch assembly from the second position and slide it back to a first position. Examples of such attempts may be shown in U.S. Pat. No. 6,357,777. 
   Such trailer hitch assemblies having a sliding lockable assembly are not able to automatically move the pivot point of the fifth-wheel hitch assembly rearward when the vehicle begins to negotiate a turn. Rather the entire trailer and tow vehicle must be stopped so that the user may manually reposition the hitch assembly. When the vehicle and trailer have completed the turn, the vehicle must once again be stopped so that the hitch assembly may be moved back to it&#39;s preferred straight line towing position. This is a time consuming process that a user is required to undertake before performing any turns of greater than a given radius. In addition, if the user neglects to perform these activities before negotiating the turn, the aforementioned damage of the trailer impacting the tow vehicle may still occur. 
   In addition, various attempts have been made to provide a pair of substantially perpendicular slots with a common body having a pivot in each of the slots. The body is connected to the trailer wherein the slots are located on a vehicle. When the trailer and thereby the body is rotated relative to the slots and the vehicle, the pivot located in a slot perpendicular to the vehicle is displaced laterally in the vehicle thereby allowing a pivot located in a slot parallel to the vehicle to be displaced longitudinally relative to the vehicle. As the trailer hitch is mounted substantially above the second pivot point, the trailer hitch will accordingly be displaced longitudinally in the vehicle as the vehicle and trailer negotiate a turn. The resulting assembly is highly dependent upon anti-friction means such as grease or bearings. Accordingly, if the assembly is not maintained properly, large angle turns negotiated by the tow vehicle may induce too large a force on the assembly and may therefore jam the assembly. Examples of such a system may be seen in U.S. Pat. No. 6,308,977. 
   Previous pivotable hitches have also suffered from the difficulty of requiring an additional adapting plate to be affixed to the trailer for engaging the pivotable truck mounted hitch. The adapting plate has a shape corresponding to an opening in the pivotable hitch. Such adapting plates, however are time consuming to install and limit the ability of a non-cooperating truck mounted hitch to pull such a trailer. 
   What would be desirable is a method and apparatus for engaging a portion of a trailer to a truck mounted trailer that is readily adaptable to receive trailer portions of varying dimensions without requiring modification to the trailer. 
   What would also be desirable is a simple way of providing a sliding fifth-wheel hitch assembly operable to automatically displace the pivot point of a trailer rearward in the tow vehicle as the tow vehicle and trailer negotiate a turn and thereafter return the pivot point back to the pre-selected straight line towing position when the trailer and tow vehicle complete the turn. 
   SUMMARY 
   Accordingly, the present invention provides an apparatus for displacing a hitch for connecting a trailer to a vehicle, the apparatus comprising:
         a trailer hitch head operable to receive a cooperating portion of a trailer, the trailer hitch head adapted to be slidable and rotatable relative to the vehicle about an axis of rotation;   first and second parallel spaced part guides fixedly located relative to the vehicle; and   a body affixed to and rotatable with said trailer hitch head, the body having a center of rotation about said axis, a first orientation and a distal surface adapted to engage either of said first or second guides when said body is rotated relative to said first and second guides,   whereby said engagement of the distal surface upon either of the first or second guides displaces said center of said body and said trailer hitch head parallel to said first or second guide when said trailer hitch head is rotated relative to said first and second guides.       

   The present invention also provides an apparatus for rotationally fixing a trailer hitch head to a portion of a trailer hitch having a pin and parallel side surfaces, the apparatus comprising a rotatable trailer hitch head having a pair of adjustable opposed spaced apart hitch guides, said trailer hitch head being slidably moveable in response to rotation of said trailer hitch head. 
   The present invention also provides an apparatus for displacing a hitch for connecting a trailer to a vehicle, the apparatus comprising:
         a trailer hitch head operable to receive a cooperating portion of a trailer between an opposed pair of adjustable hitch guides, the trailer hitch head adapted to be slidable and rotatable relative to the vehicle about an axis of rotation;   first and second spaced, parallel displacing guides fixedly located relative to the vehicle; and   a body affixed to and rotatable with said trailer hitch head, the body having a center of rotation about said axis, a first orientation and a distal surface adapted to engage either of said first or second displacing guides when said body is rotated relative to said first and second displacing guides,   whereby said engagement of the distal surface upon either of the first or second displacing guides displaces said center of said body and said trailer hitch head parallel to said first or second displacing guide when said trailer hitch head is rotated relative to said first and second displacing guides.       

   In a further aspect, the present invention provides a method of displacing a hitch for connecting a trailer to a vehicle, the method comprising:
         providing a trailer hitch head adapted to be slidably and rotatably connected about an axis to the vehicle, the trailer hitch head being adapted to fixably engage the trailer; and rotating a body having a distal surface with said trailer hitch head, the body being affixed to and coaxial with said trailer hitch head so as to engage said distal surface on either of a pair of spaced apart guides such that the axis of the body and trailer hitch head are displaced relative to said guides when said trailer hitch head is rotated with the trailer.       

   In a further aspect, there is provided a method of displacing a hitch for connecting a trailer to a vehicle, the method comprising:
         providing a trailer hitch head adapted to be slidably and rotatably connected about an axis to the vehicle, the trailer hitch head being adapted to fixably engage a cooperating portion of the trailer between an opposed pair of adjustable hitch guides; and   rotating a body having a distal surface with said trailer hitch head, the body being affixed to and coaxial with said trailer hitch head so as to engage said distal surface on either of a pair of spaced apart displacing guides such that the axis of the body and trailer hitch head are displaced relative to said displacing guides when said trailer hitch head is rotated with the trailer.       

   In a still further aspect, the present invention provides a method of rotationally fixing a rotatable trailer hitch head to a portion of a trailer hitch, the method comprising:
         providing a vehicle mounted rotatable trailer hitch head having a pair of adjustable opposed spaced apart hitch guides;   locating a pin attached to the portion of the trailer within a slot of said trailer hitch head, the portion having parallel side surfaces; securing said pin within said slot; and   positionally securing said hitch guides to said trailer hitch head adjacent to said side surfaces to prevent rotation between said trailer portion and said trailer hitch head.       

   The apparatus and method of the present invention allow for automatic displacement of the pivot point of a trailer rearward in the tow vehicle as the tow vehicle and trailer negotiate a turn, and thereafter automatic return of the pivot point to the straight line towing position when the trailer and tow vehicle complete the turn. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Aspects of the present invention are illustrated, merely by way of example, in the accompanying drawings: 
       FIG. 1  is a perspective view of the sliding fifth-wheel trailer hitch according to a first embodiment of the present invention. 
       FIG. 2  is a perspective view of the slide assembly, bottom guides and toothed guides of the sliding fifth-wheel trailer hitch of  FIG. 1 . 
       FIG. 2A  is a perspective view of an alternative arrangement of the trailer hitch using an elongated bridging plate. 
       FIG. 3  is a cross sectional view of the sliding fifth-wheel trailer hitch of  FIG. 1  taken along line  3 - 3  of  FIG. 1 . 
       FIG. 3A  is a cross sectional view of the alternative arrangement of  FIG. 2A . 
       FIGS. 4   a - 4   c  are process diagrams showing successive stages in the operation of the sliding fifth-wheel trailer hitch of  FIG. 1 . 
       FIGS. 4   d - 4   f  are process diagrams showing successive stages in the operation of the sliding fifth-wheel trailer hitch according to the alternative embodiment of  FIGS. 2A and 3A . 
       FIG. 5  is a perspective view of a trailer hitch head of the sliding fifth-wheel trailer hitch of  FIG. 1  having adjustable trailer hitch guides. 
       FIG. 6  is a bottom view of the trailer hitch head of  FIG. 5  showing the underside of the adjustable trailer hitch guides. 
       FIG. 7  is an exploded view of the trailer hitch head of  FIG. 5   
   

   DETAILED DESCRIPTION 
   Referring to  FIG. 1 , a trailer hitch according to a first embodiment of the invention is shown generally at  10 . The trailer hitch comprises a frame  20  mountable to a bed of a vehicle (not shown), a slide assembly shown generally at  60 , and a trailer hitch head assembly  100 . The frame is mounted longitudinally in the bed of the vehicle wherein the longitudinal direction of the vehicle is shown generally at  24 . The slide assembly is slidably and rotatably received within a top slot  26  in the frame  20  and supports the trailer hitch head assembly  100 . 
   The frame comprises a body having first and second sides  28  and  30 , a front and a rear end  32  and  34  respectively and a top  36 . The top includes first and second parallel spaced apart top guides  38  and  40  wherein the first and second top guides define a longitudinal top slot  26  therebetween. The first and second top guides  38  and  40  comprise elongated raised portions extending from the top  36  of the frame between the front end and the rear ends  32  and  34  respectively. The first and second top guides  38  and  40  further include top surfaces  42  and  44  operable to support the slide assembly  60 . 
   Turning now to  FIG. 2 , a slide assembly is shown generally at  60 . The slide assembly  60  is comprised of a toothed gear portion  62  mounted on a shaft  64  having an axis  65 . The shaft  64  further supports first and second bearings  66  and  68  (not shown in  FIG. 2 ) about axis  65  and a trailer hitch head mounting assembly  70  at a top end of the shaft. The first bearing  66  is adapted to be slidingly received between first and second top guides  38  and  40  of the frame. The second bearing  68  is adapted be slidingly received between first and second bottom guides  46  and  48  respectively wherein the bottom guides  46  and  48  are attached to a bottom portion of the frame  20 . The bottom guides  46  and  48  form a bottom slot  50  therebetween in which the second bearing  68  is received. 
   As shown in  FIG. 2 , first and second toothed displacing guides  52  and  54  are located in parallel spaced apart positions with the toothed gear portion therebetween. The first and second toothed displacing guides  52  and  54  are connected to the frame  20  so as to be fixably located relative to the frame. The first and second toothed displacing guides  52  and  54  include a plurality of teeth  56  and  58  oriented along displacing surfaces  57  and  59 , respectively, operable to engage the gear teeth  72  of the gear portion  62 . 
   The first and second bottom guides  46  and  48  further includes a bridging plate  74  bridging bottom slot  50  between the first and second bottom guides  46  and  48 . The bridging plate  74  includes a first end and side surfaces  77  and  79  wherein a bearing  78  is secured to the first end  76  of the bridging plate  74  by a bolt  80 . The bearing  78  further includes an external circular bearing surface  82 . 
   The slide assembly further includes a gear bar  84 . The gear bar extends radially away from the shaft  64  and includes a distal end  86  having an external bearing surface  88 . As shown in  FIG. 2 , the gear bar is connected to the gear portion  62 , however, the gear bar may also be coaxially connected to the shaft  64 . In addition, the slide assembly further includes a support plate  90  having a bottom surface  92  adapted to slidingly engage the top surfaces  42  and  44  of the first and second top guides  38  and  40  respectively. The trailer hitch head mounting assembly  70  further includes a means for securing the trailer hitch head assembly. As shown in  FIG. 2 , the means for mounting the trailer hitch head assembly may comprise a pair of spaced apart uprights  93  and  95  having respective bores  94  and  96  adapted to receive bolts or a pin connected to the trailer hitch head assembly. 
   The trailer hitch head assembly includes a hitch plate  104  wherein the hitch plate  104  includes a U-shaped slot  106  adapted to receive a corresponding pin on a trailer. The hitch plate  104  includes first and second sides  108  and  110  respectively and a front edge and a rear edge  112  and  114  respectively. The rear edge  114  may include a downwardly inclined portion  116  so as to assist in the engagement of a trailer to the trailer hitch assembly. The trailer hitch head assembly further includes first and second parallel spaced apart hitch guides  118  and  120  respectively located adjacent to the first and second sides  108  and  110  respectively of the hitch plate  104 . The first and second parallel spaced apart hitch guides  118  and  120  comprise an upstanding member having a length substantially parallel to the trailer hitch plate. The first and second spaced apart hitch guides  118  and  120  may further include an outwardly angled portions  122  and  124  respectively so as to assist in guiding the trailer hitch portion into the slot of the trailer hitch head. 
   Turning now to  FIG. 3 , a side view of an assembled sliding trailer hitch assembly is shown according to a first embodiment of the present invention. As shown in  FIG. 3 , the trailer hitch head assembly  100  is attached to the trailer hitch head mounting assembly  70  by passing a pin  102  connected to the trailer hitch head assembly through bores  94  and  96 . As shown in  FIG. 3 , the slide assembly  60  is received in the frame  20  wherein the support plate  90  rests on the top surfaces  42  and  44  of the first and second top guides  38  and  40 . The first bearing  66  is received between the first and second top guides  38  and  40  wherein the second bearing  68  is received between the first and second bottom guides  46  and  48 . The gear portion  62  is received between the first and second toothed displacing guides  52  and  54  while the gear bar  84  extends radially from the gear portion so as to engage upon the bearing  78 . 
   Referring back to  FIG. 1 , the frame may includes a plurality of mounting holes  140  located on the first and second sides  28  and  30  of the frame  20 . The frame  20  may be secured to the bed of a vehicle by means of attaching brackets  142  to the mounting holes  140  by way of bolts  144  as shown in  FIG. 4   c . The mounting bracket  142  may then be secured to a rail system (not shown) by bolts  146  wherein the rail system is thereby secured to the bed of a vehicle. The rail system may thereafter permit the frame to be located at a plurality of positions within the bed of the vehicle. The frame  20  may also be secured to the bed of a vehicle by means of a load distributing bar  148 . The load distributing bar  148  is secured to the bed of a vehicle and is attached to the frame  20  by means of bolts  150  and  152  as shown in  FIG. 1 . It will be appreciated that when the trailer hitch head assembly and slide assembly are at a rear-most position as shown in  FIG. 4   c , additional loads and torques may be applied to the bolts  146  and  144  on the mounting brackets  142  due to the longitudinal distance between the applied load at the trailer hitch head assembly and the location of bolts  144  and  146 . Load distributing bar  148  may reduce these loads and torques by providing an additional support point closer to the applied load when the trailer hitch head assembly is at a rearmost location. 
     FIGS. 2A and 3A  show an alternative embodiment of the trailer hitch which employs an alternative arrangement for controlling the movement of gear bar  84 . In  FIGS. 2A and 3A , similar parts have the same reference number. The embodiment of  FIGS. 2A and 3A  employs a transition bar to guide the movement of gear bar  84 . The transition bar includes an elongated bridging plate  74  for bridging bottom slot  50  between the first and second bottom guides  46  and  48 . The elongated bridging plate  74  includes elongated side surfaces  77  and  79  which extend adjacent the toothed displacing guides  52  and  54 . A first end  76  of elongated bridging plate  74  defines a bearing surface to engage with the bearing surface  88  of gear bar  84 . This alternative arrangement avoids the use of a bearing  78 , while elongated surfaces  77  and  79  act to provide additional control over the movement of gear bar  84 . Otherwise, transition bar  76  functions in a similar manner to the arrangement shown in  FIGS. 2 and 3 . 
   Referring to  FIG. 5 , another embodiment of the trailer hitch head assembly  100  is shown having adjustable trailer hitch guides  160 . Adjustable trailer hitch guides  160  include securing portions  164  which are parallel to a top plate  168  of the trailer hitch support  170 . The adjustable trailer hitch guides  160  may be secured to the trailer hitch support  170  by securing bolts  172  or other suitable means. The trailer hitch support  170  may include slots (shown as  190  in  FIG. 6 ) through which the securing bolts  172  pass so as to enable the adjustable trailer hitch guides  160  to be secured to the trailer hitch support  170  at a plurality of positions as indicated by arrows  174 . The trailer hitch head assembly may also include adjusting bolts  178  for facilitating positioning of the adjustable trailer hitch guides  160  at a desired location as will be described in greater detail below. 
   Referring now to  FIG. 6 , a bottom view of the adjustable trailer hitch head assembly is provided showing the underside of one of the adjustable trailer hitch guides  160 . As illustrated, the adjustable trailer hitch guides  160  may include a backing plate  180  which is operably connected to the securing portions  164  of the adjustable trailer hitch guides  160  with the top plate  168  of the trailer hitch support  170  therebetween. The backing plate  180  and the securing portions  164  may be connected by passing securing bolts  172  therethrough which may be threaded into nuts  182  below the backing plate  180  so as to retain the backing plate  180  and securing portion  164  together on opposed sides of the top plate  168 . The backing plate  180  may include a downturned portion  184  adapted to be engaged by the adjusting bolts  178 . 
   As shown in  FIG. 6 , the adjusting bolts  178  may be secured to the trailer hitch support  170  by securing brackets  186 . The adjusting bolts  178  may be threadably secured within the securing brackets  186  or threaded through backing nuts  179  which are secured to the securing brackets  186 . The adjusting bolts  178  include distal ends  181  which bear against the downturned portion  184  of the backing plates  180 . The adjusting bolts  178  may optionally be longitudinally fixed and freely rotatable relative to the securing bracket  186 . In this optional arrangement which is not shown, the distal ends of the adjusting bolts may be threaded into the downturned portion  184  of the backing plates  180 . 
   Referring now to  FIG. 7 , an exploded view of the adjustable trailer hitch head assembly is shown. As shown in  FIG. 7 , the top plate  168  of the trailer hitch support  170  includes slots  190  through which the securing bolts  172  may pass. The securing bolts  172  may be slidably located to a desired location within the slots  190  and thereafter tightened with the nuts  182  so as to secure the adjustable trailer hitch guides  160  at the desired location. Adjusting bolts  178  may also assist in urging the adjustable trailer hitch guides towards a portion of the trailer (not shown) so as to ensure the adjustable trailer hitch guides  160  closely engage the trailer. 
   Operation 
   In operation, a pin and support plate of a trailer may be received in the U-shaped slot  106  of the trailer hitch between first and second parallel spaced apart hitch guides  118  and  120 . First and second spaced apart hitch guides  118  and  120  engage upon corresponding side surfaces of the trailer arm pin box thereby serving to align the trailer hitch head assembly  100  with the trailer. As shown in  FIGS. 1 ,  2  and  3 , the trailer hitch head assembly  100  is positioned longitudinally aligned to the frame  20  and the vehicle to which the frame is attached. In this orientation, when a trailer is mounted to the trailer hitch head assembly  100 , the trailer and the tow vehicle will accordingly be in longitudinal alignment with each other. As the tow vehicle negotiates a turn, the tow vehicle and the trailer will move out of linear alignment with each other and there will therefore exist an angle between their respective longitudinal lengths. Due to the engagement of the first and second parallel spaced apart hitch guides  118  and  120  on the corresponding side surfaces of the pin box, the trailer hitch head assembly  100  will remain longitudinally aligned with the trailer thereby moving the trailer hitch head assembly  100  out of linear alignment with the frame  20  and the tow vehicle to which the trailer is attached. 
   Now referring to  FIG. 4   a  to  4   c , the sliding fifth-wheel hitch is shown in a series of three orientations. As shown in  FIG. 4   a , the sliding fifth-wheel hitch is shown according to the orientation shown in  FIGS. 1 through 3  wherein the trailer, the tow vehicle and trailer hitch head assembly  100  are aligned with each other. As shown in  FIG. 4   a , the gear bar  84  aligns with and abuts against the bearing  78 . In addition, the gear teeth  72  of gear portion  62  do not engage upon the teeth  56  or  58  of the first or second toothed displacing guides  52  and  54 . In this orientation, sliding of the slide assembly  60  is resisted solely by the gear bar  84  bearing upon the bearing  78 . 
   Now referring to  FIG. 4   b , the trailer hitch head assembly  100  is shown oriented in a second orientation in which the tow vehicle is negotiating a turn to the right. According to the second orientation shown in  FIG. 4   b , as the tow vehicle negotiates a turn to the right, the orientation of the tow vehicle relative to the trailer will be changed in a clockwise direction. Accordingly, the trailer hitch head assembly  100  will remain oriented with the trailer whereby the trailer hitch head assembly  100  is rotated counter-clockwise relative to the frame  20 . As the trailer hitch head assembly  100  is rotated counter-clockwise, the slide assembly  60  is rotated clockwise by an equal amount thereby rotating the gear bar  84  out of alignment with the bearing  78 . In addition, the gear teeth  72  of the gear portion  62  will be rotated into contact with the teeth  56  of the first toothed displacing guide  52 . As the gear portion  62  is rotated relative to the first toothed displacing guide  52 , the slide assembly  60  will be displaced laterally within the top slot  26  towards the rear of the tow vehicle. 
   Now referring to  FIG. 4   c , the tow vehicle and trailer have been oriented at 90° to each other such that the trailer hitch head assembly  100  has been equally rotated 90° relative to the frame  20 . As shown in  FIG. 4   c , the gear teeth  72  have engaged upon the teeth  56  of the first toothed displacing guide  52  and rotated relative thereto. The slide assembly  60  has been accordingly laterally displaced within the top and bottom slots  26  and  50  respectively. The trailer hitch head assembly  100  has been displaced towards the rear of a vehicle with the slide assembly  60 . It will be appreciated that although the rotation of the sliding trailer hitch assembly as shown in  FIGS. 4   a  through  4   c  is shown wherein the tow vehicle is negotiating a turn to the right, the slide assembly may also be rotated in a direction clockwise relative to the frame assembly wherein the tow vehicle is negotiating a turn to the left. This will correspondingly cause the gear teeth  72  of the gear portion  62  to engage upon the teeth  58  of the second toothed displacing guide  54 . 
   The rotation of the trailer hitch head assembly  100  relative to the frame causes the gear bar  84  to move out of alignment with the bearing  78  as well as cause the gear teeth  72  of the gear portion  62  to engage upon corresponding teeth  56  or  58  of one of the first or second toothed displacing guides  52  or  54 . Accordingly, further rotation of the trailer hitch head assembly  100  relative to the frame causes the gear teeth  72  of the gear portion  62  to displace the slide assembly  60  and trailer hitch head assembly  100  relative to the frame  20  within the top and bottom slots  26  and  50  towards the rear of the vehicle. 
     FIGS. 4   d  to  4   f  show the operation of the alternative embodiment of the sliding fifth-wheel hitch illustrated in  FIGS. 2A and 3A . As with the previously described embodiment, rotation of the trailer hitch head assembly  100  relative to the frame causes the gear bar  84  to move out of alignment with the first end  76  of elongated bridging plate  74  so that gear bar  84  engages with one of side surfaces  77  or  79  which guide and control the movement of the gear bar. At the same time, gear teeth  72  of the gear portion  62  engage upon corresponding teeth  56  or  58  of one of the first or second toothed displacing guides  52  or  54 . Accordingly, further rotation of the trailer hitch head assembly  100  relative to the frame causes the gear teeth  72  of the gear portion  62  to displace the slide assembly  60  and trailer hitch head assembly  100  relative to the frame  20  within the top and bottom slots  26  and  50  towards the rear of the vehicle. 
   The displacement of the trailer hitch head assembly  100  relative to the frame  20  and thereby relative to the vehicle in a longitudinal direction serves to move the pivot point of the trailer relative to the tow vehicle towards the rear of the tow vehicle. The movement of the pivot point of the trailer relative to the tow vehicle towards the rear of the vehicle will serve to increase the distance between the front edge of the tow vehicle of the trailer and the rear of the tow vehicle thereby enabling greater maneuverability of the tow vehicle and trailer. 
   According to another embodiment of the trailer hitch as shown in  FIGS. 5-7 , the adjustable trailer hitch guides  160  may accept support plates of trailers of differing sizes. In operation, the adjustable trailer hitch guides  160  may be spread apart by a sufficient distance to accommodate the width of the support plate of the trailer. After the pin and support plate of the trailer are located within the U-shaped slot  106  and between the adjustable trailer hitch guides  160 , respectively, the adjustable trailer hitch guides  160  may be adjusted so as to closely engage the support plate therebetween. The adjustable trailer hitch guides  160  may be so adjusted by slidably moving the securing bolts  172  within the slots  190  when loosened from their corresponding nuts  182 . Once positioned at the desired locations, the adjustable trailer hitch guides  160  may be secured in place by tightening the nuts  182  upon the securing bolts  172  until backing plate  180  and the securing portion  164  securely retain the top portion  168  of the trailer hitch support  170  therebetween. 
   Optionally, the adjusting bolts  178  may be used to urge the adjustable trailer hitch guides  160  into close engagement with the support plate. The adjusting bolts  178  may be rotated within the backing nuts  179  or corresponding threading of the securing bracket  186  as illustrated in  FIG. 6 . Such rotation will longitudinally displace the adjusting bolts  178  and cause the distal ends  181  of the adjusting bolts  178  to bear against the downturned portions  184  of the backing plate  180 . Further rotation will urge the backing plate  180  as well as the adjustable trailer hitch guides  160  to which they are connected through the securing bolts  172  in the direction of the support plate of the trailer. In an alternative optional arrangement, the adjusting bolts  178  may be freely rotatable within the securing bracket  186  wherein rotation of the adjusting bolts  178  threadably displaces the downturned portions  184  of the backing plates  180  into which the adjusting bolts are threaded. 
   It will be appreciated that the adjusting bolts  178  will also serve to retain the adjustable trailer hitch guides  160  against the support portion of the trailer during operation of the trailer hitch. As set out above the adjusting bolts  178  and their corresponding nuts  182  may also be tightened together to retain the adjustable trailer hitch guides  160  at the desired position. 
   While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.