Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 11/323,605, filed Dec. 29, 2005 and entitled Powered Trailer Dolly, the entire disclosure of which is herein incorporated by reference for all purposes. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to towing devices, especially to powered towing dollies used to move trailered or wheeled loads short distances while being steered with a handle. 
       SUMMARY 
       [0003]    Wheeled loads such as mobile homes, camping trailers and trailered boats are designed to be attached to a vehicle and towed from one location to another. They are also designed to be detached from the vehicle allowing the vehicle more ease of movement when towing is not required. Trailered loads typically have a tongue extending forward of the load to attach to the vehicle. The load weight of a trailer should be substantially over the wheels but tongue weight can be considerable, making manual towing difficult. Moving a camping trailer to hook it to the vehicle or to get garage access behind the camping trailer can be very difficult. Pulling the unit by hand to get it moving can be challenging. Once moving, it can be dangerous trying to steer the unit and more dangerous trying to stop it. Trailer movement can be undertaken more safely and less strenuously by using a tow dolly. 
         [0004]    Tow dollies come in many configurations and may be powered or unpowered. Unpowered dollies are often configured with two side by side wheels, a handle and a ball that mates to a trailer hitch. Pulling on the dolly handle leverages against the wheels and lifts the trailer tongue putting the tongue weight on the dolly wheels. This dolly configuration provides a handle for ease of maneuvering and the trailer tongue is supported by pushing down on the handle which is much less difficult than lifting. Substantial physical force may still be required to start moving the trailered load. 
         [0005]    Powered dollies limit the pulling force required by applying motive power to the wheels. Many configurations of powered dollies are used. Powered dollies often have a heavy frame and three or four wheels to support the added weight of motor, drive train or a power source. Some powered dollies have lifting mechanisms as part of the load support. Some are sized to support the user. 
         [0006]    Dollies may be used infrequently and may have to be stored. They may need to be lifted or transported themselves. Powered dollies may be complex and require maintenance. Gas powered units require gas, oil and regular maintenance. 
         [0007]    A light, powered dolly for trailers with low complexity and a small footprint for easy storage would be advantageous for those needing to move trailers and wheeled loads. 
         [0008]    The device described is a powered dolly including a single wheel assembly with double side by side treads closely spaced and separated by a drive gear. The drive gear is fixed to the wheel assembly. Torque may be applied to the wheel assembly by a linked chain between the drive gear and a geared drive motor. A control handle for steering may extend transversely to the direction of travel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0009]      FIG. 1  is a perspective view of a powered dolly showing a handle separated from the main housing, a trailer tongue and trailer tongue jack. 
           [0010]      FIG. 2  is a cutaway perspective view of the powered dolly of  FIG. 1  showing the wheels, motor, drive chain, body and handle. 
           [0011]      FIG. 3  is a perspective view of the bottom of the dolly of  FIG. 1  showing the body, wheel, axle and drive sprocket. 
           [0012]      FIG. 4  is a cross section view of a wheel assembly showing the wheel body, the treads and wheel gear. 
           [0013]      FIG. 5  is a cross section view of a wheel assembly showing the wheel bodies, the treads and wheel gear. 
           [0014]      FIG. 6  is a perspective view of a powered dolly shown pulling a boat to attach to a vehicle with the user steering the dolly and trailer with a handle. 
           [0015]      FIG. 7  is a perspective view of an alternate configuration of a powered dolly showing the body, wheels, motor and a power source. 
       
    
    
     DETAILED DESCRIPTION  
       [0016]    Referring to  FIG. 1 , a tug or powered dolly  10  is shown. Powered dolly  10  may include a body  12 , wheel assembly  14 , drive motor  16 , support receptacle  18 , steering handle  20 , motor controls  22 , handle receptacle  24 , control cables  26  and power cables  28 . Dolly  10  receives a vertical support member such as a trailer jack  30  at support receptacle  18  and retains tongue jack  30  during movement. Tongue jack  30  is connected to tongue  36 . Handle  20  is used for steering and stabilizing dolly  10 . Handle  20  supports motor control  22  and handle  20  is received by handle receptacle  24 . Control cable  26  connects motor control  22  to motor  16 . Power cable  28  runs from motor  16  to a power supply not shown. 
         [0017]      FIG. 2  is a cutaway view of powered dolly  10  of  FIG. 1 . Similar numbering to the previous figure is used here and in subsequent figures for clarity. Shown again are body  12 , wheel assembly  14 , drive motor  16 , steering handle  20 , motor controls  22  and power cables  28 . Also shown are drive chain  34 , drive sprocket  36 , wheel gear  38  (included in wheel assembly  14 ), and axle  40 . Drive chain  34  transfers power from motor  16  and drive sprocket  36  to wheel gear  38 . Wheel gear  38  is positioned between two wheels or tread faces and recessed from the largest circumference of the wheel in such a way as to not contact the pavement while in use. 
         [0018]    Direction of travel of dolly  10  is perpendicular to axle  40  and support receptacle  18 . Dolly  10  may move forward or backward. 
         [0019]    Wheel assembly  14  is supported in body  12  by axle  40  attached to body  12 . Support receptacle  18  is sized to receive tongue jack  30  or other vertical member connected to a tow load. Support receptacle  18  may be attached to body  12  above and perpendicular to wheel axle  40  so the vertical load is transferred to wheel axle  40  and the wheels with a minimum of twisting forces that would tend to make body  12  roll forward or back. The narrow width of wheel assembly  14  permits for a compact design and minimizes the forces required to steer dolly  10 . The double wheels also increase the lateral stability, preventing dolly  10  from falling sideways. 
         [0020]    Body  12  may substantially enclose wheel assembly  14 . Body  12  may be an open frame. 
         [0021]    Wheel assembly  14  may include a pair of wheels connected by axle  40  and separated by wheel gear  38 . Axle  40  when assembled to wheel assembly  14  is located at the wheel axis. In an alternate configuration, wheel assembly  14  may be one wheel with two tread faces separated by wheel gear  38 . Wheel assembly configurations are discussed further below. 
         [0022]    Motor  16  may be any appropriately sized motor with speed adequate to the gear reduction. Motor  16  may be 12 volt, 120 volt or 240 volt. Motor  16  may be a gasoline or diesel motor, hydraulic, pneumatic or other drive source. Motor  16  may include geared speed reduction. 
         [0023]    In a preferred mode, motor  16  is a 12 volt motor compatible with a vehicle battery with a power of 1.5 horsepower and a gear reduction of 153:1. The drive sprocket/gear wheel configuration may provide a further 6:1 gear reduction. In the preferred mode, wheel diameter is 10 inches, gear diameter is 7 inches and sprocket gear diameter is 1.25 inches. 
         [0024]    As dolly  10  starts pulling to move the load, the wheels apply a horizontal force at axle  40  to body  12  while the load is still at rest. This results in a rotational or torque force between body  12  and support receptacle  18 . Support receptacle  18  and body  12  may be sized to absorb the torque forces which are maximized at startup and diminish as the load begins moving. Preferably, the vertical distance between the tongue  32  and body  12  are minimized to reduce the torque forces. 
         [0025]    Motor controls  22  located on handle  20  may include controls for forward motion, reverse motion, and stopping. Motor controls  22  may also include speed control. Motor controls  22  are operably connected to motor  16 . Control  22  on handle  20  makes access to the controls more convenient during towing and maneuvering, but controls can be located anywhere including body  12  or on a separable remote control unit. 
         [0026]    Handle  20  may be configured for steering of dolly  10 . Handle  20  may be removable from body  12  for storage. Handle receptacle  24  may extend from body  12  in the plane perpendicular to the direction of travel. This orientation allows the user to stand as far as possible from the path of dolly  10  and the load, minimizing the risk of being run over by the dolly or load. 
         [0027]      FIG. 3  is a bottom view of dolly  10  with drive chain  34  removed. Shown again are body  12 , wheel assembly  14 , drive motor  16 , power cables  28 , drive sprocket  36 , wheel gear  38  and axle  40 . Wheel assembly  14  is attached to body  12  with appropriate spacers, washers and thrust bearings (not shown) to allow unrestricted rotational movement of the wheels with minimal transverse movement along axle  40 . Motor  16  may also be mounted to body  12 . The motor mount may provide a range of positions for motor  16  to adjust tension to drive chain  34 . 
         [0028]    The functionality of wheel gear  38 , drive chain  34  and sprocket  36  may be implemented by different components and still be within the scope of this disclosure. Wheel gear  38  may be driven by a shaft and worm gear from motor  16  rather, than a drive chain. The components may be pulleys and a belt. 
         [0029]    Wheel gear  38  is fixed in common rotation with at least one of the pair of wheels to transfer torque and motion to the wheel. The second wheel may rotate independently to allow ease of turning and maneuvering of dolly  10  while in motion or idling. Alternatively, both wheels may be fixed in common rotation to wheel gear  38  providing torque to both wheels. 
         [0030]    The circumference of wheel gear  38  may be smaller than the outside circumference of wheel assembly  14 . This configuration limits contamination by ground debris and wear that would occur with ground contact. Wheel assembly  14  with a wheel gear size approaching the wheel size also provides the largest gear reduction practicable. 
         [0031]      FIG. 4  is a cross section through the center of wheel assembly  14  showing one possible configuration of wheel assembly  14  and wheel gear  38 . Wheel assembly  14  has a single wheel body  50  which mounts treads  52  and  52 ′ on the outer circumferences. Wheel gear  38  is attached to wheel body  50  on an inner circumference between treads  52  and  52 ′. 
         [0032]      FIG. 5  is a cross section through the center of an alternative configuration of wheel assembly  14 . Wheel assembly  14  includes a first wheel body  60  and a second wheel body  60 ′. Wheel body  60  mounts tread  62  on its circumference. Wheel body  60 ′ mounts tread  62 ′ along its circumference. Wheel gear  38  is disposed between wheel body  60  and wheel body  60 ′. Wheel bodies  60  and  60 ′ and wheel gear  38  are commonly mounted on axle shaft  40 . Axle  40  is located at the wheel axis. 
         [0033]    Wheel bodies  60  and  60 ′ and wheel gear  38  may also be joined by one or more connectors  64  to maintain common rotation of the parts. Alternatively, connectors  64  may only be common to wheel gear  38  and one wheel body  60 . This may allow free rotation of one wheel while the other wheel is driven. One free wheel in this configuration may provide ease of steering dolly  10  since only one wheel must pivot on the pavement during dolly rotation rather than two wheels. One free wheel also reduces torque stresses on wheel assembly  14  during maneuvering. 
         [0034]    Alternately, axle  40  may be a keyed shaft. A gear or wheel key mounted to a keyed shaft will rotate only with the shaft. Gear  38  and at least one wheel body may be attached to the keyed shaft in order to maintain common rotation orientation and to transfer torque to the wheel. When the wheel and gear maintain a common rotation orientation they are fixed in rotation. 
         [0035]    Traction faces may be any material that prevents slipping of the wheel assembly against the road surface. Traction faces on the wheel bodies can be pneumatic, hydraulic or solid tires. 
         [0036]      FIG. 6  is a perspective view  100  of dolly  10  in use. A trailered load  110  is being moved to a position proximate a vehicle  120  using dolly  10 . Trailer  110  includes tongue  32  and tongue jack  30 . Trailer tongue  32  is configured to connect to a ball  150  on vehicle  120 . Dolly  10  is steered by the operator using handle  20 . Steering with handle  20  rotates dolly  10  about the axis of tongue jack  30 , redirects the pulling force and direction of travel of dolly  10 , causing trailer  110  to turn. 
         [0037]    Referring to  FIG. 7 , an alternate configuration of dolly  10  is shown including a power supply  200 . Power supply  200  may be a generator, a lead acid battery, another battery using a different chemistry or any source which provides an appropriate motive force to motor  16 . Source  200  and motor  16  could be a hydraulic pump and hydraulic drive or a compressor and air drive. This configuration, with power source  200  proximate to dolly  10 , removes the need for cables connected to a separate, fixed power source allowing dolly  10  to be used in remote locations. Additional pivoting wheels or castors may be provided for support, mobility and stability. 
         [0038]    While specific examples have been presented, these are examples only. The configuration can be varied and components can be rearranged and still fall within the scope of this disclosure. 
         [0039]    Although the present invention has been shown and described with reference to the foregoing operational principles and preferred embodiments, it will be apparent to those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope of the invention. The present invention is intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims.

Technology Category: 7