Patent Application
20070151776
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.
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.
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.
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.
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.
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.
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
Referring to
Direction of travel of dolly 10 is perpendicular to axle 40 and support receptacle 18. Dolly 10 may move forward or backward.
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.
Body 12 may substantially enclose wheel assembly 14. Body 12 may be an open frame.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Referring to
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.
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.
