Patent Publication Number: US-6991246-B1

Title: Trailer hitch assembly

Description:
FIELD OF THE INVENTION 
   This invention relates to an improved trailer hitch arrangement for attachment to a vehicle to facilitate the attaching and towing of a double caster wheel trailer. 
   BACKGROUND OF THE INVENTION 
   Most two-wheel trailers involve a conventional pivot-type hitch such that the trailer does not identically track with the towing vehicle, particularly when backing up. Nevertheless there have been attempts to provide a two-wheel trailer which will track with the vehicle similar to a single-wheel trailer. For example, U.S. Pat. No. 2,475,174 (Boone), U.S. Pat. No. 3,033,593 (Zaha), U.S. Pat. No. 3,379,452 (Torrisi), U.S. Pat. No. 4,452,465 (Bourke), U.S. Pat. No. 4,305,602 (Ungvari), U.S. Pat. No. 4,512,593 (Ehrhardt) and U.S. Pat. No. 4,076,264 (Chatterley) all disclose two-wheel trailers employing some special arrangement, such as casters, a control linkage between the two caster wheels, and/or a dual or specialized hitch arrangement for effecting a rigid securement of the trailer to the towing vehicle. These latter patents have hence attempted to provide a structure so as to increase the control, and thus the tracking, of the trailer relative to the towing vehicle. These attempts, however, as evidenced by the complexities of the structures disclosed in these patents, and the fact that these structures still have undesirable characteristics, readily indicate the difficulty in providing a two-wheel trailer together with a hitch attachment therefore which will properly track with the vehicle movement, particularly when backing up. 
   More specifically, U.S. Pat. No. 2,475,174 to Boone discloses a trailer having a pair of caster-type wheels, with the trailer having a single central hitch for attachment to the towing vehicle. The trailer also has a pair of separate auxiliary connectors disposed on opposite sides of the hitch adjacent the ends of the vehicle bumper, which auxiliary connectors control a flexible cable linkage, which in turn controls the swivelling of the casters. This patent hence discloses a three-point hitch arrangement, and does not permit free swivelling of the casters, but rather provides a complex arrangement for controlling swivelling of the casters. 
   U.S. Pat. No. 3,033,593 to Zaha as mentioned above, discloses a trailer having a pair of caster-type wheels, a central hitch of conventional configuration, and a pair of sidewardly spaced tie bars so as to create a three-point connection. This hence rigidifies the trailer relative to the vehicle, but the side tie bars must be released when swivelling of the wheels and backing of the trailer is desired. Further, this three-point connection does not permit proper rolling movement of the trailer relative to the vehicle, such as may be necessary to compensate for irregularities in the highway. 
   U.S. Pat. No. 4,305,602 to Ungvari discloses a trailer having caster-type wheels, with the trailer having a dual hitch arrangement so as to rigidify the trailer relative to the vehicle. This double hitch arrangement, however, has several disadvantages. For example, the tow vehicle must be provided with a specialized tow bar which mounts hitch balls thereon. Further, the overall hitch arrangement does not permit or compensate for rolling movement of the trailer relative to the vehicle due to unevenness in the highway. This hitch arrangement also does not permit even weight distribution on the trailer or vehicle wheels. 
   U.S. Pat. No. 4,512,593 to Ehrhardt discloses two caster wheels joined together by drive sprockets and chains so that the caster wheels are constrained for simultaneous movement. The trailer also has two rigid tow bars which couple to sidewardly spaced hitch balls mounted on the tow vehicle. This arrangement possesses the same disadvantages mentioned above, and like Ungvari, does not permit relative roll between the vehicle and trailer. 
   U.S. Pat. No. 4,664,403 to Livingston is directed to a trailer hitch structure for coupling a double caster-type wheel trailer to a towing vehicle having a conventional hitch bar fixed thereto and projecting rearwardly thereof. A rigid vehicle connector has a front portion fixedly connectable to the hitch bar. The front portion connects to a transversely extending rear portion which extends generally parallel to the vehicle bumper. This rear portion mounts adjustable bumper elements adjacent the opposite ends thereof, the bumper elements being adjustable for engagement with the vehicle bumper. A crossbar is positioned adjacent but slightly rearwardly from the rear portion and is coupled thereto through a swivel structure which defines a horizontal roll axis which extends in the longitudinal direction of the vehicle. The crossbar mounts a pair of hitch balls adjacent the opposite ends thereof. The trailer has a tongue structure provided with a pair of sidewardly spaced couplers for releasable engagement with the hitch balls. 
   OBJECTS OF THE INVENTION 
   It is an object of the present invention to provide an improved hitch arrangement specifically for cooperation between a towing vehicle and a trailer of the type employing plural caster-type wheels. 
   Another object of the present invention is to provide such a hitch arrangement provides improved tracking of the trailer in both a forward direction and a rearward direction. 
   A further object of the present invention is to provide such a hitch arrangement which facilitates coupling and decoupling of a trailer from a towing vehicle. 
   Yet another object of the present invention is to provide such a hitch arrangement that automatically converts between a forward motion mode of operation and a rearward motion mode of operation. 
   These and other objects of the present invention will be apparent from the drawings and description herein. Although every object of the invention is believed to be attained by at least one embodiment of the invention, there is not necessarily any single embodiment that achieves all of the objects of the invention. 
   SUMMARY OF THE INVENTION 
   A trailer hitch assembly in accordance with the present invention comprises a trailer having a plurality of wheels each rotatable about a first axis oriented parallel to an underlying ground surface and a second axis oriented substantially perpendicularly to such ground surface. The hitch assembly further comprises coupling elements on the trailer for fixedly engaging the trailer to a towing vehicle in a horizontal plane parallel to the ground surface during a rearward motion of the vehicle and the trailer and for pivotably linking the trailer to the vehicle in the horizontal plane during a forward motion of the vehicle and the trailer. Locking components are operatively connected to the coupling elements for preventing rotation of the wheels about the respective second axes during the forward motion of the trailer and the vehicle and for enabling rotation of the wheels about the respective second axes during the rearward motion of the trailer and the vehicle. 
   In accordance with another feature of the present invention, the coupling elements include a first bar rigidly secured to the trailer in the horizontal plane perpendicularly to a longitudinal axis of the trailer. The coupling elements further include a second bar rigidly securable to the vehicle in the horizontal plane perpendicularly to a longitudinal axis of the vehicle. The first bar and the second bar are positioned to be in contact with one another during the rearward motion of the trailer and the vehicle. 
   In accordance with another feature of the present invention, the coupling elements also include a third bar slidably connected to the trailer and pivotably connectable to the vehicle. The locking components are operatively linked to the third bar. 
   In accordance with further features of the present invention, the locking components include a spring loaded latching mechanism operatively connected to the third bar, an elongate tensile member extending from the spring loaded latching mechanism to the third bar, a pair of locking rods extending substantially perpendicularly to the longitudinal axis of the trailer, and a rotatable disk connected to the rods and the tensile member, the disk being spring biased to pivot about a substantially vertical axis oriented perpendicularly to the ground surface. 
   In accordance with additional features of the present invention, the coupling elements further include links for connecting the second bar to the vehicle at exactly two locations on the vehicle. The links include a U-shaped clamping member extendable around and engageable with a bumper or an axle of the vehicle and further include a screw adjustment for modifying a length of the clamp. The links may further includes a fastener for tying the second bar to a trailer post on the vehicle. 
   In accordance with more specific features of the present invention, the first bar and the second bar have mutually engageable planar faces, while the third bar is constrained to one degree of freedom of motion relative to the trailer. 
   Another embodiment of a trailer hitch assembly in accordance with the present invention comprises a trailer having a plurality of castor-type wheels, a front side and a back side and a longitudinal axis oriented perpendicularly to the front side and the back side. A first bar is attached to the trailer at the front side, the bar extending substantially perpendicularly to the axis and substantially parallel to a ground surface. Coupling elements are provided for securing a second bar to a rear side of a towing vehicle at exactly two locations on the towing vehicle. The coupling elements include a fastener for coupling the second bar to a trailer post on the vehicle and further include a clamp connected to the second bar at a position spaced from the fastener for coupling the second bar to a bumper bar of the vehicle. A connector is provided for at least indirectly connecting the first bar to the second bar at exactly one location. 
   As discussed above, the clamp may include a U-shaped clamping member extendable around and engageable with a bumper bar or an axle of the vehicle and further include a screw adjustment for modifying a length of the clamp. The connector may include a pin. 
   In another embodiment of the present invention, a trailer hitch assembly comprises a trailer having a plurality of wheels each rotatable about a first axis parallel to an underlying ground surface and about a second axis substantially perpendicular to the ground surface. The hitch assembly further comprises a first horizontal bar mounted to the trailer perpendicularly to a longitudinal axis of the trailer, a second bar, two fasteners for connecting the second bar to a rear side of a vehicle, and a trailer hitch member of variable effective length mounted to the trailer and connectable to the vehicle. The first bar and the second bar are engaged with one another during a rearward motion of the vehicle and the trailer and are spaced from one another during a forward motion of the vehicle and the trailer. The hitch assembly further includes a locking mechanism mounted to the trailer and operatively connected to the trailer hitch member and the wheels to alternately permit and disable rotation of the wheels about the respective second axes in accordance with the instantaneous effective length of the trailer hitch member. 
   The present invention provides a hitch arrangement that offers improved tracking of the trailer in both a forward direction and a rearward direction. The present hitch arrangement facilitates coupling and decoupling of a trailer from a towing vehicle. Conversion between a forward motion mode of operation and a rearward motion mode of operation is automatic. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic bottom plan view of a trailer hitch assembly in accordance with the present invention. 
       FIG. 2  is a schematic perspective view of the trailer hitch assembly of  FIG. 1 . 
       FIG. 3  is a schematic perspective view of a portion of a trailer including a castor-type wheel, shown in  FIGS. 1 and 2 . 
       FIG. 4  is a schematic top plan view of the clamp of  FIG. 3 , showing the clamp in an assembled configuration. 
       FIG. 5  is a schematic exploded perspective view, on a larger scale, of a clamp included in the trailer hitch assembly of  FIGS. 1 and 2 . 
       FIG. 6  is a schematic perspective view of another trailer hitch assembly in accordance with the present invention. 
       FIG. 7  is a schematic perspective view of a portion of a trailer including a castor-type wheel, shown in  FIG. 6 . 
   

   DEFINITIONS 
   The term “longitudinal axis” when applied herein to a vehicle or a trailer means a line extending perpendicular to an axle of the vehicle and parallel to a ground surface. 
   The term “castor-type wheel” is used herein to denote a wheel that is rotatable about two axes, namely, a horizontal axis extending along a wheel axle and a vertical axis, so that the wheel is responsive to forces acting thereon to roll in any direction along a ground or floor surface. 
   The word “bar” as used herein refers to an elongate rigid member. The rigid member can have any cross section. However, certain kinds of bars as that term is used herein preferably have a cross-section with at least one flat face. Thus, a bar attached to a front end of a trailer perpendicular to a longitudinal axis of the trailer as described herein has a planar face extending generally perpendicularly to an underlying ground surface, that planar face being engageable with a generally vertical planar surface of another bar attached to a towing vehicle. When these two bars are in this engagement, the trailer becomes rigid with the vehicle and the trailer&#39;s wheels pivot about in accordance with the direction of steering of the vehicle. 
   The term “ground surface” or “ground” is used herein to denote any generally horizontal surface over which a vehicle with a trailer may be impelled. Thus, a ground surface may be a road surface, a field, a lot, a floor surface, a lawn, a garden, etc. 
   The term “effective length” as used herein describes an elongate member extending between two locations, for example, between a point on a towing vehicle and a point on a trailer, and that moves or deforms to accommodate different distances between the two points. The “effective length” of the elongate member is variable because the distance between the two points is variable. Where an elongate member is a slidable bar, the effective length extends from one of the bar attached, for instance to a towing vehicle, and a bearing point of the slidable bar on the trailer. The bearing point may be an end of a sleeve through which the slidable bar extends. Alternatively, a linking member with a variable effective length may take the form of a telescoping tube, or a helical spring. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As illustrated in  FIGS. 1 and 2 , a trailer hitch assembly comprises a trailer  10  having a pair of castor-type wheels  12  and  14 . Wheel  12  is rotatable about a horizontal axis  16  oriented parallel to an underlying ground surface and a vertical axis  18  oriented substantially perpendicularly to such ground surface. Similarly, wheel  14  is rotatable about a horizontal axis  20  and a vertical axis  22 . 
   Trailer  10  has a front side  24  and a back side  26  and a longitudinal axis  28  oriented perpendicularly to the front side and the back side, as well as to an axle  30  extending between wheels  12  and  14 . A bar  32  in the exemplary form of an angle beam or a channel member is attached to trailer  10  at front side  24 . Bar  32  extends substantially perpendicularly to axis  28  and substantially parallel to the ground. A set of coupling elements  34  are provided for securing a second angle or channel bar  36  to a rear side  38  of a towing vehicle  40  (ATV, lawn tractor, etc.) at exactly two locations on the towing vehicle. 
   Coupling element set  34  includes a fastener  42  such as a perforated tab for receiving a fastener  43  to couple second bar  36  to a trailer post  44  on vehicle  40  and further includes a clamp  46  connected to the second bar at a position spaced from fastener  42  for coupling the second bar to a bumper bar or axle  48  of the vehicle. A connector  50  such as a pin or bolt is provided for connecting bar  32  and thus trailer  10  to bar  36  at exactly one location. Connector pin or bolt  50  extends through a hole  52  in a substantially rigid metal strip  54  forms part of a supporting trusswork  56  for bar  32 . Connector pin or bolt  50  also extends through a hole (not separately labeled) in bar  36  that is aligned with hole  52 . 
   As depicted in  FIGS. 4 and 5 , clamp  46  includes a U-shaped clamping member  58  with legs  60  that are insertable through respective apertures  62  in a clamping bracket  64 . Nuts  66  secure U-shaped clamping member  58  to bracket  64 . Bracket  64  is in turn connected to bar  36  via a threaded bolt  68  that screwingly traverses an internally threaded aperture  70  in a tab  72  on bar  36  so as to enable an adjustment or modification of the length of clamp  46  and concomitantly of the distance between bar  36  and bumper or axle  48  of towing vehicle  40 . Clamping member  58  is positionable around and in engagement with bumper bar or axle  48  of vehicle  40 . 
   Bar  36  is mounted to vehicle  40  by fastener  42  and clamp  46 . Bolt  68  is turned to adjust the effective length of the bolt, i.e., the distance between bar  36  (or, more specifically, tab  72 ) and bumper or axle  48 . This adjustment ensures that bar  36  is oriented perpendicularly to the longitudinal axis of the vehicle  40 . 
   It is contemplated that bar  36  remains fixed to towing vehicle  40  for an extended period, while trailer  10  may be successively coupled to and decoupled from vehicle  40  several times. Connector  50  is preferably of a quick-connect or quick-release type, such as a bolt or pin that is merely inserted from above, without a nut. 
   As illustrated in  FIGS. 6 and 7 , a trailer hitch assembly comprises a trailer  110  having a pair of castor-type wheels  112 . Wheels  112  are rotatable about respective horizontal axes  116  oriented parallel to an underlying ground surface and respective vertical axes  118  oriented substantially perpendicularly to such ground surface. The hitch assembly further comprises a co-functioning group of coupling elements  124  on trailer  110  for fixedly engaging the trailer to a towing vehicle (not shown) in a horizontal plane parallel to the ground surface during a rearward motion of the vehicle and the trailer (arrow  126 ) and for pivotably linking the trailer to the vehicle in the horizontal plane during a forward motion of the vehicle and the trailer (arrow  128 ). A locking mechanism  130  is operatively connected to the coupling elements  124  for preventing rotation of wheels  112  about the respective vertical axes  118  during forward motion of trailer  110  and the towing vehicle and for enabling rotation of wheels  112  about axes  118  during rearward motion of the trailer and the vehicle. 
   The coupling elements  124  include a trailer hitch member  132  of variable effective length mounted to trailer  110  and connectable to the towing vehicle. Trailer hitch member  132  takes the form of a cylindrical bar or rod  134  provided at a forward end with a coupling tongue in the form of a pair of parallel plates  136  having bolt-receiving apertures  138 . Bar or rod  134  is provided at a rearward end with a stop disk  140 . Bar or rod  134  slidably traverses a cylindrical bearing  142  welded to a trusswork  144  on the forward side of trailer  110 . 
   Coupling elements  124  additionally include a bar  146  attached to trusswork  144  so as to extend substantially perpendicularly to a longitudinal axis (not shown) of trailer  110  in a horizontal plane, i.e., substantially parallel to the ground surface. Bar  146  may take the form of an angle beam or a channel member. 
   Coupling elements  124  also include a second angle or channel bar  148  connectable to a rear side of a towing vehicle (not shown) at exactly two locations on the towing vehicle, by means of a trailer-post fastener  150  and a clamp  152 . Clamp  152  has a structure and function identical to clamp  46  discussed hereinabove with reference to  FIGS. 4 and 5 . A connector  154  such as a pin or bolt is provided for connecting bar  146  and thus trailer  110  to bar  148  at exactly one location. 
   Bars  146  and  148  are engaged with one another during a rearward motion of the towing vehicle and trailer  110  and are spaced from one another during a forward motion of the vehicle and the trailer. Because trailer hitch member  132  is constrained to a single degree of freedom of motion, i.e., because trailer hitch member  132  can only translate in a single direction, generally but not necessarily substantially parallel to the longitudinal axis of trailer  110 , bar  146  is constrained to remain in contact with and parallel to bar  148 , thus forcing wheels  112  to pivot about vertical axes  118  when the towing vehicle turns during rearward travel. 
   Locking mechanism  130  includes a spring loaded disk  156  ( FIG. 7 ) operatively connected to trailer hitch member  132 , an elongate tensile member  158  extending from the spring loaded disk  156  to trailer hitch member  132 , and a pair of locking rods  160  and  162  extending substant/lly perpendicularly to the longitudinal axis of trailer  110 . Rods  160  and  162  are pivotably connected to disk  156  and to tensile member  158 . Disk  156  is spring biased to pivot about a substantially vertical axis oriented perpendicularly to the ground surface. 
   Tensile member  158  is connected at a forward end to stop disk  140  of trailer hitch member  132  and at a rearward end to an edge of spring loaded disk  156 . Tensile member  158  may include rigid portions, such as rods (not separately illustrated), or may be made entirely of a flexible material such as cable or cord. Pulleys  168 ,  170  may be provided for changing the angle of inclination of tensile member  158  at different points along its transit from stop disk  156  to spring loaded disk  156 . 
   Upon a rearward motion of a towing vehicle, bringing bars  146  and  148  into contact with one another, trailer hitch member  132  slides so as to decrease tension on tensile member  158 , allowing spring-loaded disk  156  to automatically rotate and pull rods  160  and  162  inwardly, out or engagement with holes or recesses  164  in vertical wheel tubes  166 . Wheels  112  are thus free to pivot about vertical axes  118 , in accordance with the direction of rearward motion of the towing vehicle. 
   Upon a subsequent forward motion of the towing vehicle, bars  146  and  148  separate from one another while trailer hitch member  132  slides forward, pulling tensile member  158  and consequently forcing a rotation of spring loaded disk  156  so as to allow rods  160  and  162  to shift outwardly, into potential engagement with holes or recesses  164  in vertical wheel tubes  166 . Upon an engagement of stop disk  140  with a rear end of cylindrical bearing  142 , trailer  110  is entrained into forward motion. Wheels  112  pivot about vertical axes  118  until rods  160  and  162  insert into holes or recesses  164 , thereby locking the wheels against further rotation about axes  118 . Trailer  110  follows the towing vehicle, pivoting with respect to the towing vehicle, the pivoting occurring about connector pin or bolt  154 . 
   Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. For example, the tensile member of the locking mechanism may extend at the leading or forward end from a point on the trailer hitch assembly closed to the vehicle, for instance, from the hitch bar on the vehicle. In any case, the tensile element is responsive to varying distance between the trailer and the towing vehicle to induce a locking of the trailer wheels during forward motion of the vehicle and the trailer. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.