Retractable and extendable wheel assembly

A retractable and extendable wheel assembly for mounting to a vehicle at wheel positions of the vehicle. The assembly comprises an axle shaft on which a wheel having a central axis can rotate, and a strut having a first end pivotally mounted at a first strut mount site to the axle shaft and a second end pivotally mountable at a second strut mount site to the vehicle. Additionally, the assembly includes an inflatable and deflatable air ram having a first end pivotally mounted to the first end of the strut and a second end pivotally mountable to the vehicle at an upper ram mount site substantially directly above the axle shaft. The second strut mount site is situated forward or rearward from the upper ram mount site. Release of air from an inflated air ram results in a retraction of the ram and the vehicle descends. Simultaneously, the strut pivots to thereby allow the vehicle to descend preferably a distance sufficient to bring the base of the vehicle at a level substantially equal to the center axis of the wheel. Inflation of the air rams restores the vehicle to its original height for road travel. Thus, cargo can be safely loaded and unloaded since ramps or other devices for vertically raising or lowering such cargo can be eliminated.

FIELD OF THE INVENTION 
This invention relates in general to vehicle wheel assemblies, and in 
particular to a retractable and extendable wheel assembly wherein an air 
ram and a strut are cooperatively mounted to an axle shaft such that 
deflation of the air ram brings the vehicle closer to the ground for 
convenient loading of cargo such as live animals for example, and such 
that inflation of the air ram raises the vehicle a sufficient vertical 
distance from the ground to permit the vehicle to travel in a conventional 
manner. 
BACKGROUND OF THE INVENTION 
Over-the-road vehicles such as tractor-trailer combination vehicles are 
used in moving significant amounts of freight from site to site, whether 
over long distances or short distances. This freight includes manufactured 
goods, food items, live animals, etc., with most freight collectively 
being of heavy weight and therefore requiring tedious work in its loading 
and unloading to and from a transporting trailer. 
One particular area where loading and unloading presents vulnerability to 
cargo involves the transporting of livestock, and particularly horses. 
Specifically, and as opposed to being freight that can be hand carried, 
live animals must propel themselves into and out of the shipment trailer. 
Consequently, specialized attendants must be present to guide the animals 
along temporary ramps leading from the ground to the trailer. If an animal 
should lose its footing and fall from such a ramp, fractured bones and 
possible animal loss is possible. 
In view of the inconvenience and potential accidents associated with the 
required use of ramps in the loading of shipment trailers, it is apparent 
that a need is present for safer, more direct access to the trailers. 
Accordingly, a primary object of the present invention is to provide a 
retractable and extendable wheel assembly for mounting to a vehicle such 
that the vehicle can be lowered for loading and unloading. 
Another object of the present invention is to provide such a retractable 
and extendable wheel assembly wherein expandability and retractability is 
accomplished through inflation and deflation of an air ram integral with 
the wheel assembly. 
Yet another object of the present invention is to provide such a 
retractable and extendable wheel assembly wherein a pivotally mounted 
support strut operates in cooperation with the air ram to support the 
wheel in place and guide its vertical movement during inflation and 
deflation of the air ram. 
These and other objects of the present invention will become apparent 
throughout the description thereof which now follows. 
SUMMARY OF THE INVENTION 
The present invention is a retractable and extendable wheel assembly for 
mounting to a vehicle at wheel positions of the vehicle. The assembly 
comprises an axle shaft on which a wheel having a central axis can rotate, 
and a strut having a first end pivotally mounted at a first strut mount 
site to the axle shaft and a second end pivotally mountable at a second 
strut mount site to the vehicle. Additionally, the assembly includes an 
inflatable and deflatable air ram having a first end pivotally mounted to 
the first end of the strut and a second end pivotally mountable to the 
vehicle at an upper ram mount site substantially directly above the axle 
shaft. The second strut mount site is situated forward or rearward from 
the upper ram mount site. The air ram is sufficiently inflatable to 
position a vehicle to which the assembly is mounted at an adequate 
vertical distance above a support surface to permit wheel travel of the 
vehicle thereon, and sufficiently deflatable to position the vehicle at a 
vertical distance above said support surface which is less than the 
vertical distance for travel and which is convenient for loading and 
unloading cargo. 
The present invention also includes a vehicle, and especially a trailer 
vehicle, having such a retractable and extendable wheel assembly at each 
wheel position. The second strut mount site is preferably situated forward 
from the upper ram mount site a sufficient distance to form an angle of 
from about 45 and about 75 degrees between the air ram and the strut when 
the air ram is fully inflated. Release of air from an inflated air ram 
results in a retraction of the ram caused by the weight of the vehicle as 
it forces the air out of the ram and the vehicle descends. Simultaneously, 
the strut and air ram pivot to thereby allow the vehicle to descend 
preferably a distance sufficient to bring the base of the vehicle at a 
level substantially equal to the center axis of the wheel. By so doing, 
the floor of the vehicle is significantly lower than its original height, 
and entry therein is substantially only a step above ground level. As a 
result, loading and unloading the vehicle is easily accomplished. The 
vehicle can be equipped with one or more on-board air pumps to inflate the 
air rams. Once the air rams are inflated, the wheel assembly returns to 
its original configuration with the vehicle at its original height for 
road travel. In this manner, cargo can be safely loaded and unloaded since 
ramps or other devices for vertically raising or lowering such cargo can 
be eliminated. Instead, loading is usually accomplished by taking a single 
vertical step from or to the interior of the vehicle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1 and 2, a horse trailer 10 is shown with a retractable 
and extendable wheel assembly 12 at each wheel position, with each 
assembly 12 having attached thereto a wheel-and-tire unit 16. Each wheel 
assembly 12 in FIG. 1 is in an expanded configuration, resulting in the 
trailer 10 being in a travel configuration for movement over a highway or 
other route. Conversely, each wheel assembly 12 in FIG. 2 is in a 
retracted configuration, resulting in the trailer 10 being near the ground 
to thereby provide loading and unloading thereof via a single step from 
the ground to the trailer interior. 
FIGS. 3-5 show a wheel assembly 12 in an expanded configuration, while FIG. 
6 shows the same assembly 12 in a retracted configuration. In particular, 
the wheel assembly 12 includes an axle shaft 18 to which a wheel-and-tire 
unit 16 is mountable. A strut 20 extends from the trailer 10 to the axle 
shaft 18, and is pivotally mounted at each end. Specifically, the first 
end 22 of the strut 20 is pivotally mounted to the axle shaft 18, while 
the second end 24 thereof is pivotally mounted to a pin 26 within a 
bracket 28 attached to the trailer 10. An inflatable and deflatable air 
ram 30 extends from the trailer 10 to the first end 22 of the strut 20, 
and is pivotally mounted at each end. In particular, the first end 32 of 
the air ram 30 is pivotally mounted to a pin 34 within a bracket 36 
attached to the first end 22 of the strut 20, while the second end 38 of 
the air ram 30 is mounted to a pin 40 within a bracket 42 at an upper ram 
mount site 44 situated substantially directly above the axle shaft 18. As 
is apparent, the pin 34 is forward of the upper ram mount site 44 such 
that an angle of from about 45 to about 75 degrees is formed between the 
strut 20 and the air ram 30 when the air ram 30 is in an extended 
configuration. 
In operation, each wheel assembly 12 is in the extended configuration as 
illustrated in FIGS. 1, 3, 4 and 5 to thereby permit conventional travel 
of the trailer as over a highway or other road surface. Conversely, when 
the trailer is to be loaded or unloaded, air is released from the inflated 
air ram of each assembly 12 to thereby cause retraction of the ram aided 
by the weight of the trailer 10. Simultaneously, both the strut 20 and air 
ram 30 pivot at each respective end thereof and the trailer 10 descends as 
illustrated in FIGS. 2 and 6, thereby permitting single upward and 
downward steps in loading and unloading without use of a loading ramp. 
After loading and/or unloading is completed, the air rams 30 are inflated 
as with a conventional air pump (not shown) that can be provided as 
permanent equipment for the trailer 10, and conventional travel can occur. 
While an illustrative and presently preferred embodiment of the invention 
has been described in detail herein, it is to be understood that the 
inventive concepts may be otherwise variously embodied and employed and 
that the appended claims are intended to be construed to include such 
variations except insofar as limited by the prior art.