Abstract:
An anti-sway device for conventional trailers, which essentially takes the place of the shank member of a conventional trailer hitch, is described. The shank assembly is comprised of an elongate square member coupled to a conventional hitch receiver of a tow vehicle. Attached to the rearward end of the square member is a pivot member with rearward diverging links connecting it to another somewhat wider pivot member to which a conventional ball mount is attached. The ball mount is further linked to the towed trailer such that the tongue of the trailer is fixed to the ball mount about a vertical axis. This arrangement results in the trailer pivoting about the resulting center of rotation of the converging links, which is substantially forward of the ball of the trailer hitch. Moving the pivot point forward, such as that found on a fifth wheel trailer, reduces sway and enhances the stability of the coupled trailer and tow vehicle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of PPA 60/636,125 dated Dec. 15, 2004 and PPA 60/680,802 dated May 14, 2005. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to anti-sway devices for conventional trailers. Conventional trailers are coupled at the extreme rear of the tow vehicle. Lateral forces encountered by the trailer due to wind, road conditions or uneven loading are transmitted to the tow vehicle through the hitch. The distance between the ball connection of the trailer and the rear axle of the tow vehicle determines by how much leverage the trailer applies these lateral forces to the tow vehicle. Longer distances between the ball connection and the rear axle result in less stability of the trailer and tow vehicle combination. In the case of fifth wheel trailers, where the pivot point is directly over the rear axle of the tow vehicle, the lateral forces are minimized and the coupled trailer and tow vehicle is stable. Effectively moving the pivot point of a conventional trailer and tow vehicle combination closer to the rear axle of the tow vehicle, thereby reducing sway and improving stability, is achieved by this invention by utilizing a four link mechanism as described herein. 
     2. Prior Art 
     Previously, shifting the pivot point of a towed trailer forward was accomplished as described in U.S. Pat. Nos. 4,019,754 4,722,542, 5,660,409, and 6,851,696. The device described in U.S. Pat. No. 4,019,754 solved the sway problem, but would not accommodate sharp turns. The device described in U.S. Pat. No. 4,722,542 solved the sway problem and allowed for sharp turns, but required a specialized structure and was not readily adaptable to the conventional components of an equalizing trailer hitch. It also had tongue weight limitations due to the vertical height of the converging links. The device described in U.S. Pat. No. 6,851,696 uses a similar structure as U.S. Pat. No. 4,772,542 with additional strut assemblies for transferring weight off of the converging links. The device described in U.S. Pat. No. 5,660,409 used a similar structure as U.S. Pat. No. 4,722,542 applied to a special braking system. 
     3. Objects and Advantages 
     The objects and advantages of the present invention are:
     (a) To provide an anti-sway device that shifts the pivot point of a towed trailer forward thereby increasing stability.   (b) To provide an anti-sway device that is readily adaptable to standard equalizing hitch components.   (c) To provide an anti-sway device that allows height adjustment to level the trailer and tow vehicle when hitched.   (d) To provide an anti-sway device that can be inverted about its horizontal centerline, providing additional height adjustment.   (e) To provide an anti-sway device that during the hitching process, allows lateral movement of the hitch ball, thereby speeding up the hitching process.   (f) To provide an anti-sway device that can accommodate larger tongue weight loads without additional support means.
 
Further objects and advantages of my invention will become apparent from a consideration of the drawings and the ensuing description.
   

     SUMMARY OF THE INVENTION 
     The present invention is directed to an effective anti-sway device that is easily installed and, in one embodiment, is adaptable to standard equalizing hitch components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of the adjustable link assembly of the anti-sway device. 
         FIG. 2  is a top view of the adjustable link assembly of the anti-sway device. 
         FIG. 3  is a side view of the anti-sway hitch bar assembly of the anti-sway device. 
         FIG. 4  is a top view of the anti-sway hitch bar assembly of the anti-sway device. 
         FIG. 5  is a side view of both assemblies of the anti-sway device, shown installed. 
         FIG. 6  is a top view of both assemblies of the anti-sway device, shown installed. 
         FIG. 7  is a sectional view of the first pivot member and associated links, pins and bearings. 
         FIG. 8  is a sectional view of the second pivot member and associated links, pins and bearings. 
         FIG. 9  is a sectional view of first and second pivot members, connecting links and associated pins. 
         FIG. 10  shows top and side views of the anti-sway device, with a tool used for initial setup. 
         FIG. 11  is a top view of the anti-sway device, shown at the beginning of a turn of the tow vehicle and trailer. 
         FIG. 12  is a top view of the anti-sway device, shown in a partial turn of the tow vehicle and trailer 
         FIG. 13  is a top view of the anti-sway device, shown in a full turn of the tow vehicle and trailer. 
         FIG. 14  is a side view of the anti-sway hitch bar assembly, shown in an alternate embodiment that allows for height adjustment between the tow vehicle and trailer. 
         FIG. 15  is a side view of the anti-sway hitch bar assembly, shown inverted in an alternate embodiment that allows for height adjustment between the tow vehicle and trailer. 
         FIG. 16  is a side view of an alternate embodiment of the anti-sway hitch bar assembly. 
         FIG. 17  is a top view of an alternate embodiment of the anti-sway hitch bar assembly. 
         FIG. 18  is a sectional view of an alternate embodiment of the anti-sway hitch bar assembly. 
         FIG. 19  is a second sectional view of an alternate embodiment of the anti-sway hitch bar assembly. 
         FIG. 20  is a third sectional view of an alternate embodiment of the anti-sway hitch bar assembly. 
         FIG. 21  is a side view of the anti-sway hitch bar assembly, shown in an alternate embodiment that allows for height adjustment between the tow vehicle and trailer. 
         FIG. 22  is a sectional view of the anti-sway hitch bar assembly, shown in an alternate embodiment that allows for height adjustment between the tow vehicle and trailer. 
         FIG. 23  is a side view of the anti-sway hitch bar assembly, shown in an alternate embodiment that allows for height adjustment between the tow vehicle and trailer. 
         FIG. 24  is a sectional view of the anti-sway hitch bar assembly, shown in an alternate embodiment that allows for height adjustment between the tow vehicle and trailer. 
         FIG. 25  is a side view of the anti-sway hitch bar assembly, shown in an alternate embodiment that allows for height adjustment between the tow vehicle and trailer. 
         FIG. 26  is a sectional view of the anti-sway hitch bar assembly, shown in an alternate embodiment that allows for height adjustment between the tow vehicle and trailer. 
         FIG. 27  is a sectional view of the anti-sway hitch bar assembly, shown in an alternate embodiment that allows for height adjustment between the tow vehicle and trailer. 
         FIG. 28  is a side view of an alternate embodiment of the adjustable link assembly of the anti-sway device. 
         FIG. 29  is a top view of an alternate embodiment of the adjustable link assembly of the anti-sway device. 
         FIG. 30  is a transverse sectional view of an alternate embodiment of the adjustable link assembly of the anti-sway device. 
         FIG. 31  is a longitudinal sectional view of an alternate embodiment of the adjustable link assembly of the anti-sway device. 
         FIG. 32  is a first end view of an alternate embodiment of the adjustable link assembly including engaging tool. 
         FIG. 33  is a second end view of an alternate embodiment of the adjustable link assembly including engaging tool. 
     
    
    
     DETAILED DESCRIPTION 
     This invention relates to conventional weight distributing trailer hitches that have friction type sway controls. In its preferred embodiment, the invention consists of two assemblies which are; an adjustable link assembly  10 , and an anti-sway hitch bar assembly  12 . These assemblies install in place of the friction type sway control and hitch bar elements of a conventional weight distributing hitch. The hitch created by this combination of the two assemblies of the invention and conventional equalizing hitch components, shifts the pivot point of the trailer/tow vehicle combination forward, thereby reducing sway.  FIGS. 1 through 4  show side and top views of the adjustable link assembly  10  and anti-sway hitch bar assembly  12 .  FIGS. 5 and 6  show side and top views of the invention as installed to the hitch receiver of a tow vehicle  14 , and a conventional trailer tongue  16 . The other standard parts of this hitch are; a standard ball mount  18  with a hitch ball  20  and a sway control mounting ball  22 , a separate rear sway control mounting ball  24  attached to the tongue of the trailer  16 , spring bars  26  and  28 , and snap-up brackets  30  and  32 . 
     The first of two assemblies of the invention is the adjustable link  10 . This assembly performs two functions. The first function of the adjustable link is to connect the sway control mounting ball  22  of the ball mount  18  to a rear sway control mounting ball  24 , thereby eliminating rotational movement between the ball mount  18  and the tongue of the trailer  16 . The second function of the adjustable link is to be adjustable in length so as to allow for alignment of the longitudinal centerline of the trailer  34  parallel to the longitudinal centerline  36  of the second pivot member  68  of the hitch bar assembly  12  (see  FIG. 6 ). The adjustable link  10  consists of a front section  38 , a center section  40 , and a back section  42 . Both ends of the adjustable link have sockets  162  and  164  that snugly fit over the respective mounting balls  22  and  24  and are retained in place by clips  44  and  46 . The back end  42  of the adjustable link  10  is threaded into the center section  40  using right handed threads and locked in position by a clamp  48 . The front end  38  of the adjustable link  10  is threaded into the center section  40  using left handed threads and locked in position by a clamp  50 . The length of the adjustable link  10  is varied by loosening the clamps  48  and  50 , rotating the center section  40  relative to the ends  38  and  42  to achieve the desired length and re-tightening clamps  48  and  50 . 
     The second of two assemblies of the invention is the anti-sway hitch bar  12 . The function of this assembly is, by the geometry of its linkage, in conjunction with the elimination of rotation between the ball mount  18  and the trailer tongue  16 , to shift the pivot point of the hitched trailer forward, closer to the rear axle of the tow vehicle. Starting at the front end ( FIGS. 3 and 4 ), the anti-sway hitch bar  12  consists of a square shank section  52  integral with a first pivot member  54 . The longitudinal axis of the shank  52  is perpendicular to the longitudinal axis of the rigidly connected first pivot member  54 . As shown in  FIG. 7 , the first pivot member  54  is of a generally symmetrical H-shape with vertically oriented pairs of bearing bores  56 ,  58 , and  60 ,  62  at the left and right corners. Bearing bores  56  and  58  are coaxial, as are bearing bores  60  and  62 . The centerlines of the bearing bore pairs are parallel to each other and are perpendicular to and equally spaced from the horizontal centerline  108  of the shank  52 .  FIG. 7  also shows first pivot member bearings  110 ,  112 ,  114  and  116  inserted in the bearing bores with the shoulders  118  of the bearings facing toward the horizontal centerline  108  of the first pivot member  54 . Left and right pairs of pivot pins  120 ,  122 ,  124  and  126  are inserted through the respective left and right pairs of bearings  110 ,  112  and  114 ,  116  and press fitted into the frontward bored surfaces  76 ,  76 A,  78  and  78 A of the two connecting links  64  and  66  ( FIGS. 3 and 4 ), which are pivotally connected to the first pivot member  54 . The links are equal in length and the distance between the front bores  76  and  78  and back bores  132  and  136  (see  FIG. 8 ) are longer than one half the distance between the bores  56  and  60  of the first pivot member  54 . 
     Pivotally connected to the back ends of the connecting links  64 ,  66  is the second pivot member  68 , which lies in the same plane as the first pivot member  54 .  FIG. 8  is a sectional view of the second pivot member  68  which is V-shaped ( FIG. 4 ) and symmetrical about its vertical centerline  128 . The rearward end of the connecting left and right links  64  and  66  are connected to the respective left and right front ends  130 A and  130 B of the V-shaped pivot member  68 , using left and right pairs of pivot pins  86 ,  88  and  90 ,  92  which are secured to the connecting links by press fitting in to rearward bored surfaces  132 ,  134 ,  136  and  138 . The pivot pins are inserted through respective bearings  140 ,  142 ,  144 , and  146  received in the bearing bores  70 ,  72 ,  74 , and  76  of the V-shaped pivot member  68 . The right pair of bearing bores of the V-shaped pivot member  70  and  72  are coaxial as are the left pair of bearing bores  74  and  76 . The centerlines of the bearing bores  70  and  74  are parallel to each other and are equally spaced on opposite sides of the centerline  128  of the V-shaped pivot member  68 . The distance between the bores  70  and  74  of the second, V-shaped pivot member  68  is longer than the distance between the bores  56  and  60  of the first, H-shaped pivot member  54 . 
     The vertical distance between the upper and lower pivot bores of the first and second pivot members  54  and  68  ( FIG. 3 ) along with the vertical height of the connecting links  64  and  66  form four parallel couple joints for carrying the axial and bending loads of the hitched trailer. 
     As shown in  FIGS. 3 and 4 , integral to the V-shaped pivot member  68  are two rearward flanges  94  and  96  which each have vertically oriented mounting holes  98  and  100  for bolting a conventional ball mount  18 . The bolts  102  and  104  are secured with nuts  106 . 
     When the trailer/tow vehicle is beginning a turn, the effective pivot point of the hitch is shifted forward to the intersection of the centerline of the trailer  34  and the centerline of the tow vehicle  80 . This is indicated by point  170  on  FIG. 11 . As the turn sharpens (see  FIGS. 12 and 13 ), one side of the front pivot member, the left side in this case, rotates into a position where one set of the first pivot member pivot pins,  120 ,  124  in this case, passes in between the sets of left and right pivot pins  90 ,  92  and  86 ,  88  of the rear V-shaped pivot member. At the same time, the second V-shaped pivot member  68  allows clearance for the first pivot member to rotate into a sharp turn. Also, the vertical distance between short pivot pins  86  and  88  and  90  and  92  allow for clearance of the back ends of the connecting links  64  and  66  to partially clear the shank  52  resulting in further turning capability, as shown in  FIG. 13 . The articulation of the linkage is reversed as the tow vehicle and trailer return to a straight orientation. 
     Initial setup of the trailer/tow vehicle combination is accomplished as shown in  FIG. 10 . The H-shaped and V-shaped pivot members  54  and  68  are held in a centered position by temporarily installing the tips  148  and  150  of locating pin  152  into setup holes  154  and  156  of pins  120  and  86 . The trailer is then coupled at the hitch ball  20 , and the tow vehicle is moved forward enough to let the trailer track straight behind it. The length of the adjustable link  10  is adjusted, as previously described, until it can be placed over the mounting balls  24  and  22 . The adjustable link is then locked in position by tightening clamps  48  and  50  and retained on the mounting balls  22  and  24  by installing clips  44  and  46 . The locating pin  152  is then removed and the installation is complete. The next time the trailer is hitched, it is first connected to the hitch ball  20 . The connecting links can then be rotated using a wrench until the distance between the front and back sway control balls  22  and  24  allows placement of the adjustable link over them. The hitching process is completed by installing clips  44  and  46 . 
     Normally, when hitching with a conventional hitch, the position of the trailer tongue must be directly over the hitch ball. An additional benefit of the invention is that when positioning the tow vehicle relative to the trailer for hitching, the side to side alignment can be off by a couple of inches. The final alignment can be done by rotating the connecting links  64  and  66  thereby moving the hitch ball  20  directly under the trailer tongue  16 . The trailer is then hitched and the adjustable link  10  is installed as previously described. 
     In a first alternate form of the anti-sway hitch bar assembly, shown in  FIG. 14 , the bolting flanges  166  and  168  are extended with a plurality of bolt holes to allow for adjustment of the height of the ball mount  18  to the height of the shank  52 .  FIG. 15  shows the anti-sway hitch bar inverted, allowing for further height adjustment in the opposite direction. 
     A second alternate form of the anti-sway hitch bar is shown in  FIGS. 16 through 20 . In this embodiment, the second pivot member and the ball mount (shown as  68  and  18  of  FIG. 6 ) are made as one piece (shown as  212  of  FIGS. 16 and 17 ), thereby eliminating the flanges  94 ,  96  and bolts  102 ,  104  (shown in  FIGS. 3 ,  4 ,  5  and  6 ). As shown in  FIG. 19 , the hitch ball  20  is attached by inserting the threaded portion  208  through a hole  210  in the upper portion of the second pivot member  212  and held in place by a nut  214 . The second pivot member  212  also has sockets  216  and  218  for attaching the spring bars  26  and  28 .  FIGS. 18A and 18B  show the upper sockets  216  and lower sockets  218  which engage with the upper pin  220  and lower pin  222  of the trunnion  206  portion of the spring bars  26  and  28 . When assembling the spring bars into the second pivot member  212 , the spring bar is tilted as shown in  FIG. 18B . The lower pin  222  is inserted into the lower socket  218 , and then rotated thereby sliding the upper pin  220  into the open ended upper socket  216 . The opposite end of the spring bar is then attached, and the tension in the spring bar maintains the position shown in  FIG. 18A . 
     In this form of the anti-sway hitch bar, the height adjustment of the hitch ball, as shown in  FIGS. 14 and 15  can be alternately accomplished in two different ways. 
     The first way is shown in  FIGS. 21 through 24 . In this embodiment, the shank section is split into a forward shank section  224  and a rearward shank section  226 . The forward section  224  is rigidly attached to a forward flange  228 . The rearward section  226  is rigidly attached to a rearward flange  230 , and rigidly attached to the first pivot member is  54  (see  FIG. 24 ). Both flanges  228  and  230  have a plurality of aligned holes  232  to accommodate fastening with bolts  234  and nuts  236 . Height is adjusted by removing the bolts  234  and nuts  236 , moving the flanges  228  and  230  relative to each other and re-assembling in the desired position (See  FIG. 23 ). 
     The second form of height adjustment is shown in  FIGS. 25 through 27 . In this embodiment, the shank  238  is composed of a forward section  240  and an offset rearward section  242 , and is detachable from the first pivot member  54 . In this form of the invention, the first pivot member has a hollow square portion  244 , where the shank  238  can be inserted and held in place by a bolt  246  and nut  248 . Height adjustment is accomplished by selecting a shank bar with the desired offset between a forward centerline  250  and rearward centerline  252 . The shank bar  238  can also be rotated about the longitudinal centerline  250  to shift the height in the opposite direction. 
     An alternate embodiment of the adjustable link assembly  11  is shown in  FIGS. 28 through 33 . In this embodiment, the adjustable link assembly  10  is replaced by a multiple pin bracket  172 , and engaging clip  174  attached to one or both of the spring bars  26 ,  28 . In addition, there is an engaging tool  13 . When installed, the bracket  172  and clip  174  rigidly connect the tip  176  of the spring bar  26  to the frame of the trailer  184 , thereby eliminating the rotation between the ball mount  18  and the trailer tongue  16 . 
     The multiple pin bracket  172  consists of a flat section  180  with integral pins  178  arranged in a generally vertical alignment, and a stud  196 . The bracket  172  is secured by bolts  182 , or otherwise securely mounted to the frame  184  of the trailer. The engaging clip  174  consists of a slotted section  186 , and a flanged section  188 , a hitch pin  190 , and bolts  192 , which attach it to the spring bar  26 . The engaging tool  13  consists of a handle  194 , a pivot pin  196 , a hollow base  198 , a hook portion  200 , and a chain section  204 . 
     In use, the trailer is attached at the ball  20 . The spring bar  26  is pivotally attached at its trunniun  206 , and the front end of the trailer is raised via a tongue jack until the engaging clip is close enough to the pin bracket to facilitate engagement of the clip  174  to the bracket  172 . The base  198  of the engaging tool  13  is placed over the stud  196  of the bracket  172 , and the hook portion  200  is placed under the lower side of the spring bar  26 . The handle portion  194  is then manually raised until the slotted portion  186  of the clip  174  can be moved over and lowered onto one of the pins  178  of the bracket  172 . The hitch pin  190  is then inserted through a pin hole in the clip, thereby securing the clip  174  to the bracket  172 . 
     The initial setup of the alternate bracket and clip embodiment is done by first hitching the trailer to the ball mount  18  and anti-sway shank  12 , with the alignment tool  152  inserted. The trailer and tow vehicle are then driven straight forward until the trailer is tracking straight behind the tow vehicle. The spring bar is then pivotally attached at the trunniun  206 . The multiple pin bracket  172  is temporarily clamped in position, and the clip is engaged over one of the pins  178  utilizing the engaging tool  13  as previously described. The weight distribution of the hitch can be then checked and adjusted as required by moving the clip to one of the other pins  178 . Once the desired alignment of the trailer and weight distribution are achieved, the frame of the trailer can be drilled to facilitate bolting  182  the bracket  172  to the frame  184  of the trailer. The alignment tool  152  is then removed and the setup is complete. 
     CONCLUSION, RAMIFICATIONS AND SCOPE 
     This invention provides an effective method of controlling sway in a towed trailer. In addition, this invention is adaptable to standard equalizing hitch components. While the description above contains many details, these should not be construed as limiting the scope of the invention, but as a preferred embodiment of the invention. Accordingly, the scope of the invention should be determined by the claims, not the specifics of the preferred embodiment.