Abstract:
An apparatus for facilitating trailer towing is provided comprising a steer axle fixed to a rigid frame by means of a suspension, a selectably adjustable hitch, for receiving a trailer tongue, mounted on the frame and positioned above and forward of the steer axle, a vertically displacing articulated and spring centered tongue support fixed to the front of the frame, the vertically displacing articulated tongue support capable of absorbing vertical displacement between the apparatus and a towing vehicle while maintaining the a forward disposed tongue mount in a horizontal position. The apparatus forms a towing apparatus providing improved stability, traction, control, and maneuverability facilitating wheel traction at speed, through turns and over irregular or undulating terrain. The apparatus is particularly suitable for use in combination with light weight prime mover vehicles.

Description:
FIELD OF INVENTION 
     The present invention generally relates to the field of towing dollies; and, more particularly, to a convertor dolly with a self steering mechanism for adapting trailers for towing behind a prime mover. 
     BACKGROUND OF THE INVENTION 
     Vehicles used for hauling trailers must be capable of sustaining the axle load of the trailer and capable of accommodating the type of hitch provided by the trailer. Further, the towing a trailer can restrict the maneuvering of the combined vehicle and trailer particularly while backing up. The vehicle and trailer combination typically also presents tracking and traction issues. The prior art provides a number of attempts to overcome these difficulties. A common method is to incorporate a convertor dolly which provides at least one axle, a specific type of hitch suitable for accommodating the trailer to be towed, and a tongue for attachment to the prime mover vehicle. The convertor dolly reduces the axle load of the prime mover vehicle and facilitates the prime mover vehicle to provide principally a pulling force. Convertor dollies are arranged such that the dolly functions as an extension of the rear of the prime mover vehicle such that the convertor dolly typically does not rotate or pivot around the prime mover tow point thereby keeping the frame of the dolly and hence the alignment of wheels of the dolly fixed in the direction of the rear of the prime mover vehicle. Prior art convertor dollies have several distinct disadvantages in that the combined trailer, dolly, and prime mover vehicle is difficult to reverse and that the dolly wheels are fixed in the forward position matching the rear wheels of the prime mover vehicle. Because the wheels of a typical convertor dolly do not turn in a steering motion, the combined prime mover vehicle rear wheels and the dolly wheels necessarily bind against the pavement during turning maneuvers thereby reducing control, traction, and stability during turning. Similarly, reversing maneuvers are particularly difficult with prior art convertor dollies because the dolly wheels are not steerable thereby making turning maneuvers while backing up almost impossible. 
     Further, prior art convertor dollies have fixed hitch types for accommodating a specific type of trailer hitch. The fixed hitch types are typically fixed in position relative to the dolly axle thereby limited the adjustability the load on the prime mover vehicle rear axle. 
     Traction is essential for full maneuvering control. The combination prime mover and dolly are rigidly fixed together, in part, so that when in combination with a trailer there is no double articulation of the assembly. A disadvantage of this arrangement is that the prime mover and dolly assembly can be long. The length becomes important when considering the effect on the assembly when traveling over non-level undulating surfaces. As the combination has a least three axles and the frames are fixed relative to each other, traction can be lost on an axle as it is lifted away from a road surface by the other axles. 
     What is needed is an improved convertor dolly capable of providing steering tracking of the dolly wheels in response to the prime mover vehicle turning maneuvers thereby providing improved handling, traction, and maneuverability and being of particular importance to permit backup maneuverability while also providing the ability to adapt a variety of trailer hitch types for hauling. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a new type of trailer dolly, and, more specifically, to a trailer dolly incorporating a steering axle and an articulating and selectably adjustable tongue support providing improved stability, control, and maneuverability, thereby substantially obviating one or more of the problems due to the limitations and disadvantages of the related art. 
     The present invention is a trailer dolly comprising a steer axle and an articulating frame construction. The frame is comprising a rectangular frame constructed of I-beams positioned vertically such that the I-beam top and bottom flanges are parallel to the ground. A pair of leaf type suspension springs are mounted to the left and right forward and left and right rear portions of the I-beam frame each being rotatably mounted to a forward mount and rotatably mounted to a first end of a suspension link being, in turn, rotatably mounted to the I-beam frame near the rear of the frame. A steer axle is centrally mounted to the leaf type spring suspension centrally to the bottom of the left and right leaf springs. A pair of shock absorbers are mounted respectively on the left and right sides of the I-beam frame at the proximate end and the distal end is mounted to the steer axle so as to provide dampening of the leaf type spring suspension. The steer axle is a commercially available assembly having an forged axle frame and two wheel assemblies rotatable from left to right around a pin and mounted to each end of the forged axle frame, a configuration well known in the prior art. A steering tie rod is pivotably mounted to tie rods extending from each wheel assembly thereby forcing the wheel assemblies to turn or steer relative to frame in unison. A steering shock absorber is rotatably fixed at one end to the axle frame and the other end is rotatably fixed to the steering tie rod thereby damping side to side motion of the steering tie rod. Finally, a stabilizer bar is provided mounted at one end near one mounting point of the forged axle frame and the leaf type spring suspension and the I-beam frame for purposes of stabilizing side to side thrust of the steer axle since the steer axle is mounted to the I-beam frame by means of the leaf type spring suspension which would allow side to side movement relative to the I-beam frame if otherwise not stabilized. 
     The left and right sides of the I-beam frame extend beyond the front element of the I-beam frame to support two downwardly fixed square tubular elements being welded at an angle to form the rear portion of a rhombic shaped tongue support frame having rear, front, top and bottom structural portions, wherein all four corners of the tongue support frame are pivotably attached so as to allow the tongue frames to articulate upwardly and downwardly. The forward portions of the tongue support frames are welded to a tongue mount plate thereby allowing the tongue plate to move upwardly and downwardly. The tongue support frames each further comprise an upper and lower leaf spring wherein each leaf spring is attached respectively to the top and bottom frame members to centralize the tongue support frame while permitting upward and downward movement of the tongue being attached to a tongue support which in turn is centrally and rotatably bolted to the tongue mount bracket. 
     In combination, the articulating tongue support frame and the rotatable tongue support facilitating even load distribution between the dolly wheels while the steer axle permits the wheels to turn from side to side in response to the maneuvering of the prime mover vehicle thereby eliminating the wheels from binding on the pavement hence enhancing maneuverability and stability. The articulating tongue support permits both the prime mover vehicle axles and the dolly axle to maintain road contact over undulating surfaces. Further the self steering wheels allow improved steering particularly during reversing maneuvers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification illustrate embodiments of the invention and, together with the description, serve to explain the features, advantages, and principles of the invention. 
       In the drawings: 
         FIG. 1  is a front elevation view of the trailer dolly with steering axle according to the present invention showing the dolly supported by the dolly stand. 
         FIG. 2  is a rear elevation view of the present invention illustrated in  FIG. 1 , wherein the steering axle is clearly seen mounted to the bottom of the leaf type spring suspension. 
         FIG. 3  is a right side elevation view of the present invention of  FIG. 1  resting on the dolly stand and illustrating the fifth wheel and goose-neck hitch options. 
         FIG. 4  is a top plan view the trailer dolly according to the present invention. 
         FIG. 5  is top view of the hitch portion according to the present invention showing the removable fifth wheel hitch in position. 
         FIG. 6  is a cross section view of an attachment point of the repositionable hitch mount brackets mounted to the top of the I-beam frame. 
         FIG. 7  is a cross section view of an attachment point of an optional removable hitch to a repositionable hitch mount bracket showing a hitch securing pin in position through the hitch mount bracket and through a mounting hole in the removable hitch. 
         FIG. 8  is a cross section view, similar to  FIG. 7 , showing details of the hitch securing pin in the mounting hole of the removable hitch. 
         FIG. 9 , similar to  FIG. 5 , is top view of the hitch portion according to the present invention showing the removable alternate goose-neck hitch in position. 
         FIG. 10 , similar to  FIG. 6 , is a cross section view of an attachment point of the repositionable hitch mount brackets mounted to the top of the I-beam frame illustrating how the removable hitches are attached in an identical fashion. 
         FIG. 11 , similar to  FIG. 7 , is a cross section view of an attachment point of the optional removable goose-neck hitch, of  FIG. 9 , to a repositionable hitch mount bracket showing a hitch securing pin in position through the hitch mount bracket and through a mounting hole in the removable hitch illustrating the consistent fastener system. 
         FIG. 12  is a top plan view of the steering axle assembly according to the present invention. 
         FIG. 13  is a left side elevation view of the articulating tongue support illustrating the limits of upward and downward motion of the support and the articulating tongue support being driven to a neutral position by leaf type springs. 
         FIG. 14  is a cross section view of the tongue mount with the tongue shown pinned to the tongue mount illustrating the selectable positioning of the tongue. 
         FIG. 15  is a side elevation view of a prime mover vehicle utilizing the convertor dolly according to the present invention with a fifth wheeler type hitch and trailer attached. 
         FIG. 16  is a top plan view of the vehicle, dolly and trailer combination of  FIG. 15 , wherein the wheel positioning is illustrated when traveling straight forward. 
         FIG. 17  is a top plan view, similar to  FIG. 16 , wherein the wheel position is illustrated when the combination rig is maneuvering a turn. 
         FIG. 18  is a side elevation view of a prime mover vehicle utilizing the convertor dolly according to the present invention with a goose-neck type hitch and trailer attached. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims. Referring now in greater detail to the various figures of the drawings wherein like reference characters refer to like parts, there is shown in a perspective view at  10  in  FIG. 1 , a new type of convertor dolly having a steering axle, adjustable hitch mount, selectable hitch receiver types, adjustable tongue height and articulating tongue support facilitating high maneuverability and stability particularly suitable for use in combination with light weight prime mover vehicles to haul various types of trailers having various types of hitches. 
     The front elevation view of the present invention shown at  10  in  FIG. 1 , showing details of the tongue mount plate  30 , tongue support  56 , tongue  32 , and the upper  34  and lower  36  members of the articulating tongue support frame assembly with the tongue  32  being fastened by bolts  38  to the tongue support  56  which, in turn is centrally bolted to the tongue mount plate  30 . The articulating tongue support assembly is comprising two tongue support frames each being formed from a vertically mounted square tubular steel rear member  42  welded at angle to forward extensions of the steel I-Beam dolly frame  40 . The rear members have an opening to accommodate the pivotably attached top members  34 . Similarly the rear members  42  have an opening to accommodate the similarly pivotably attached bottom frame members  36 . The forward opposing ends of the top  34  and bottom  36  members of the tongue support frame are similarly pivotably attached to similar vertically mounted square tubular front members  48 , see  FIG. 3 , forming the front portion of each tongue support frame and each welded at angle so as to converge to the centrally located tongue mount plate  30  which forms the front of the articulating tongue support assembly thereby providing an upwardly and downwardly articulation of the tongue mount plate  30  relative to the I-Beam dolly frame  40 . The tongue support  56 , bettered viewed in  FIG. 14 , being centrally bolted to the tongue mount plate  30 , may rotate thereby permitting accommodating rotation around the central axis of the dolly relative to the prime mover vehicle while maneuvering over irregular surfaces. 
     Still referring to  FIG. 1 , the tongue support assembly being articulated is centralized to a neutral vertical position by upper  44  and lower  46  centering leaf springs being respectively mounted on each top  34  and bottom  36  member of each tongue support frame. As the tongue mount plate  30  moves relative to the I-Beam dolly frame  40  that the upper centering leaf springs  44  are designed to compress as the tongue support moves downward while the lower center leaf springs  46  compress as the tongue support  30  moves upward relative to the frame  40 . Consequently, the each leaf spring is contained by the frame spring mounts  50  mounted on the top  34  and lower  36  frame members, having an opening and a bottom in which the leaf spring rests without being securely fastened in place thereby restraining the leaf spring end only when the spring compresses. The action of the articulating tongue support assembly is shown in  FIG. 13 . 
     Safety chains  52  are provided, as required by regulation, being attached to the tongue support  30  as shown in  FIG. 1 . Also provided is support stand  54 , welded to the i-beam frame  40 , for convenience of storage, hitching and positioning during the assembly of the dolly  10 , according to the present invention, with a trailer and prime mover vehicle. 
     Referring now to  FIG. 2 , a rear elevation view according to the present invention, where the tongue support frame front members  48  can be seen welded at a converging angle to the tongue mount plate  30  with the rear of the tongue mounting bolt  58  which secures the tongue support to the front of the tongue mount plate  30 . Also visible is the steer axle assembly  60  mounted to the dolly i-beam frame  40  by means of the leaf spring suspension  62  on the left and right sides of the frame. The steer axle assembly is commonly available from manufacturers such as Dana. The steer axle assembly further includes a stabilizing bar  64  for containing side to side motion of the steer axle assembly relative to the i-beam dolly frame  40 . The steer axle assembly provides wheel hubs that are capable of turning from side to side. As detailed in  FIG. 12 , the wheel hubs  66  are linked to each other with a steering connector rod  88  such that the turning angle of one wheel tracks the turning angle of the other. A steering stabilizer shock absorber  90  is provided between the steering connector rod  88  and the steering axle frame. The appropriate tires  68  are selected for a required load application. 
     In  FIG. 3 , a left side elevation view, the i-beam dolly frame  40  is constructed from for i-beams forming the front, rear, left and right sides of the frame  40 . The chassis leaf springs  62  are mounted along each bottom of the left and right sides of the frame  40  using conventional pin and link rotational mountings commonly used in leaf spring suspensions. Upward and downward motion of the steer axle relative to the frame is dampened with shock absorbers  74  mounted to each side of the frame and to the steer axle. The tops of the left and right sides of the frame  40  have mounting holes to accommodate hitch mount brackets  76  which are mounted at one end on the left and the opposing end on the right sides of the frame  40  with bolt fasteners  78 . Various hitch types such as a goose-neck hitch  72  or a fifth wheeler hitch  70  are accommodated by the hitch mount brackets  76 . It will be appreciated that the hitch may be positioned forward or backward along the frame  40  so as to optimize the load transferred to the tongue. 
     Details of the articulating tongue support assembly are visible in  FIG. 3  showing the rear  42 , top  34 , bottom  36 , front  48  members of the tongue support frame, wherein the front members  48  are welded to the tongue mount plate  30 . Tongue support  56  is bolted to the tongue mount plate  30  and has a receiver portion for attaching the tongue  32  by means of bolts  38 . Depending upon the tire  68  size, the dolly support  54  is adjustable to position the dolly  10  level for loading and attachment. Note that lateral cinches  80  are provided to cinch the rear members of the tongue support assembly to the prime mover vehicle so as to prevent the dolly  10  from swaying side to side relative to the prime mover vehicle. The cinching allows the dolly  10  to be a relatively rigid extension of the rear of the prime mover vehicle. 
       FIG. 4 , a top plan view, illustrates the attachment of the hitch mount brackets  76  to the frame  40  by means of bolts  78 . A clear view of the tongue support frame shows the support rear frame member  42  rotatably attached to the top member  34  and front members  48  and tongue mount plate  30 . Tongue mount bolt  58  through the tongue support  56  is also visible. An optional tongue support frame stiffener  82  is welded between the top members  34 . The lateral cinches  80  are positioned on each side of the frame. The dolly stand  54  is attached to the front of the dolly i-beam frame  40 . The electric over hydraulic brake system  84 , as required by regulation for this type of apparatus, is mounted at the rear of the frame  40 . 
     A fifth wheeler hitch assembly  70  is illustrated in  FIGS. 5 ,  6 ,  7  and  8  being attached to the top of the dolly frame  40 . In the illustrated configuration the hitch mounting brackets  76  are mounted to the frame  40  with bolts  78  to accommodate the spacing requirement of the hitch  70  so as to position the hitch relative to the axle such that a selected load is maintained on the tongue. The hitch  70  is attached to the hitch mounting brackets  76  by means of removable pins  86  inserted at all four corners of the hitch  70 . The hitch as tabs directed downwardly to fit openings in the hitch mounting brackets  76  and with a hole to receive pins  86 . The hitch mounting bracket  76  further has holes to receive pins  86  such that when the hitch tabs are positioned into the bracket  76 , the pins  86  slide through the hitch mounting bracket on one side, the hole in the hitch tab and then through the hitch mounting bracket on the other side thereby removably securing the hitch to the dolly. 
     Referring to  FIGS. 9 ,  10 , and  11 , showing a goose-neck type hitch  72  similarly and removably attached to the frame  40  wherein the fittings and attachments illustrated in the Figures are the same as those used with the fifth wheeler hitch excepting the hitch  72 . The goose-neck type hitch does not require the width of the fifth wheel hitch to mount and as such holes for the hitch tabs and pins are provided in the appropriate locations. 
       FIG. 15  illustrates the assembled combination of the prime mover vehicle  12 , dolly  10  with a fifth wheeler type hitch  70 , and a fifth wheeler trailer  14 . Note in  FIG. 16 , a top plan view, that the dolly wheels are aligned with the rear and front wheels of the prime mover vehicle. While in  FIG. 17 , the dolly wheels turn to the left in response to a right turn maneuver of the prime mover vehicle  12  as illustrated by the turning angle of the vehicle steer wheels  18 . The left turning of the dolly wheels is in response to the side force induced because the dolly does not pivot with the rear of the vehicle consequently allowing the dolly to maintain stability without the tires binding on the pavement. This turning also permits the combination to be maneuvered backward. If the wheels did not turn, then the trailer is forced to remain in line with the vehicle thereby complicating reverse maneuvers. 
       FIG. 18  illustrates the assembled combination of the prime mover vehicle  12  and dolly  10  with a goose-neck type trailer  16 . Of particular notice is the configurability of the dolly components to provide adjustability of the goose-neck hitch position relative to the dolly axle position.