Apparatus and method for improving the lateral stability of vehicles

An apparatus includes a vehicle having at least one tire mounted on a support member. The tire has a centerline that substantially defines a first tipline of the vehicle. A device, which has a diameter that is smaller than the diameter of the tire, is attached to the support member. The device includes a contact surface having a centerline that substantially defines a second tipline of the vehicle. When the tire is loaded and deflects such that the device interacts with a support surface, the tipline of the vehicle is moved from the first tipline to the second tipline to improve the stability of the vehicle.

BACKGROUND OF THE INVENTION 
The present invention relates generally to vehicles and machines that 
experience shifting centers of mass during use and, more particularly, to 
an apparatus and method for improving the stability of such vehicles. 
To provide favorable ride, handling and traction, most automobiles and 
similar vehicles have their lateral centers of mass located at some point 
substantially along the longitudinal axes thereof. (See FIGS. 1A and 1B.) 
However, other vehicles, such as excavators, boom lifts and other 
machines, have centers of mass that move significantly during use. (See 
FIGS. 2A-2C.) 
For example, as the boom of a boom lift is extended and a load is applied 
to the platform or bucket thereof, the lift's center of mass moves 
outwardly toward the supporting wheels or tracks. (See FIG. 3.) If a 
sufficient load is applied to the boom, the center of mass will move 
beyond the wheels and the lift will tip over. The imaginary line along a 
support surface (e.g., the ground) about which a vehicle tips has been 
denominated the "tipline." 
By defining the tipline of a vehicle as near to the perimeter of the 
vehicle's chassis as possible, the stability of the vehicle is increased. 
This increase in stability permits the vehicle to perform its intended 
function with the minimum amount of necessary counterbalance weight, which 
results in lower costs, improved flotation on soft surfaces, easier 
transport, etc. 
A standard vehicle has two lateral tiplines separated by a distance 
substantially equal to the track width thereof. Vehicles incorporating 
conventional tires tend to tip about a line defined substantially at the 
lateral centerline of the tires (i.e., where the tires contact the support 
surface). (See FIGS. 4A and 4B.) 
To achieve maximum vehicle stability, narrow and stiff solid rubber tires 
are preferred on excavators and other similar machines. However, wide and 
soft pneumatic tires have typically been used instead to decrease the 
ground bearing pressure of narrow tires (i.e., to prevent damage to 
fragile surfaces or to improve vehicle flotation on soft surfaces), to 
allow the use of small diameter tires to provide clearance for rotating 
machine components while still providing adequate tire capacity, and to 
improve ride, comfort and traction. 
In an attempt to balance the conflicting needs of vehicle stability on one 
hand and ride, comfort, flotation, load capacity and traction on the other 
hand, foam-filled and dual tires have been utilized. 
Particularly in Europe, foam-filled tires are popular and widely used. 
These tires are typically formed by filling a standard pneumatic tire with 
a urethane foam. In the event of tire puncture, the urethane foam prevents 
the tire from deflating. Although foam-filled tires are not as costly as 
solid rubber tires, they possess all of the other disadvantages of solid 
rubber tires. Moreover, because the width and shape of foam-filled tires 
are the same as the original, pre-filled pneumatic tires, foam-filled 
tires do not provide as much vehicle stability as solid rubber tires. 
As stated above, dual tires have also been used to improve vehicle 
stability. By employing dual tires, the tipline of a vehicle or machine is 
moved to the center of the outboard tire. (See FIG. 5.) 
However, there is an inherent risk factor in using dual tires. If one tire 
of the pair is damaged during vehicle use, the other tire may be 
unintentionally overloaded. For example, if the outboard tire of a dual 
pair is deflated, the tipline of the vehicle is then defined at 
substantially the centerline of the inboard tire, which results in a less 
stable condition then if the vehicle were initially designed for only a 
single tire. Further, the use of dual tires results in the increased cost 
of installing and maintaining twice as many tires per vehicle. 
It is worthwhile noting that two other devices, which have not been used to 
improve vehicle stability, have been developed for allowing vehicles to be 
operated on flat tires. 
An external disk, which has a slightly smaller diameter than the respective 
tire of a vehicle, is mounted adjacent to and either inboard or outboard 
of the tire. If the tire is deflated, the disk supports the vehicle above 
the ground and allows it to be operated for a limited time (e.g., for 
emergencies) at restricted speeds. Such an external disk is disclosed in 
South African Patent No. 90/2717 and has been manufactured and sold in the 
Republic of South Africa by "Express Trailer Repairs" under the name 
"TRUCKSAVER." 
Further, Hutchinson and Rodgard Corporation have marketed an internal disk 
that allows deflated pneumatic tires to operate for a limited time at 
restricted speeds and/or distances. The disk is mounted to a tire's rim at 
the centerline thereof, and is sized to contact the inside of the tire 
when the tire deflates to approximately 50% of its normal height. This 
device does not increase the tipping stability of the vehicle because the 
disk, and thus the tipline, is still positioned at substantially the 
centerline of the tire and a large deflection (i.e., greater than 50% of 
the tire's height) is needed for the internal disk to contact the tire and 
thus the ground. 
SUMMARY OF THE INVENTION 
The present invention provides an apparatus and method for improving the 
stability of vehicles having shifting centers of mass while, at the same 
time, retaining the advantageous and desirable characteristics of 
pneumatic tires, including ride comfort, flotation, load capacity and 
traction. 
According to a first aspect of the present invention, an internal device is 
mounted on a pneumatic tire's wheel assembly to improve a vehicle's 
stability. The tire performs like a normal pneumatic tire during normal 
vehicle use conditions. In this manner, the internal device does not 
influence the pneumatic tire's desired ride, traction, flotation, tire 
wear and other characteristics. However, when the tire is highly loaded 
(i.e., when the vehicle is in a near-tipping condition), the tire deflects 
sufficiently to allow the internal device to contact the inner surface 
thereof. Consequently, the tipline is moved from the centerline of the 
tire to the centerline of the internal device's contact surface. Further, 
in this operating mode, the tire functions as a cushion between the 
internal device and a support surface (e.g., the ground, deck, etc.), 
thereby decreasing the ground bearing pressure of the internal device. 
According to a second aspect of the present invention, an external device 
is attached to a pneumatic tire's wheel assembly to improve a vehicle's 
stability. Like the internal device discussed directly above, the external 
device does not detrimentally influence the pneumatic tire's desired 
characteristics. However, when the tire is highly loaded, the tire 
deflects sufficiently to allow the external device to contact the support 
surface (e.g., the ground, deck, etc.). Consequently, the tipline is moved 
from the centerline of the tire to the centerline of the external device's 
contact surface. 
According to a third aspect of the present invention, an apparatus includes 
a vehicle having at least one tire operatively associated with a support 
member. The tire has a centerline that substantially defines a first 
tipline of the vehicle. A device, which has a diameter that is smaller 
than the diameter of the tire, is attached to the support member. The 
device includes a contact surface having a centerline that substantially 
defines a second tipline of the vehicle. When the tire is loaded and 
deflects such that the device interacts with a support surface, the 
tipline of the vehicle is moved from the first tipline to the second 
tipline to improve the stability of the vehicle. 
According to a fourth aspect of the present invention, a method of 
improving the stability of a vehicle includes the following steps: 
providing a vehicle having at least one tire operatively associated with a 
support member, the tire having a centerline that substantially defines a 
first tipline of the vehicle; providing a device, which has a diameter 
that is smaller than the diameter of the tire, including a contact surface 
having a centerline that substantially defines a second tipline of the 
vehicle; attaching the device to the support member; loading the vehicle 
such that the contact surface of the device interacts with a support 
surface to move a tipline of the vehicle from the first tipline to the 
second tipline. 
According to a fifth aspect of the present invention, an apparatus includes 
a vehicle having at least one pneumatic tire mounted on a support member. 
The tire has a first diameter and a centerline that substantially defines 
a first tipline of the vehicle. A ring is operatively associated with the 
support member and is disposed within the tire. The ring has a width and 
an outside diameter that is smaller than the first diameter. Further, the 
ring includes a contact surface that is larger than the width thereof and 
has a centerline that substantially defines a second tipline of the 
vehicle. When the tire is loaded and deflects such that the ring interacts 
with a support surface, the tipline of the vehicle is moved from the first 
tipline to the second tipline to improve the stability of the vehicle. 
According to a sixth aspect of the present invention, an apparatus includes 
a vehicle having a tire mounted on a support member. The tire has a first 
diameter and a centerline that substantially defines a first tipline of 
the vehicle. A disk is operatively associated with the support member and 
is disposed outside of the tire. The disk has a first width and an outside 
diameter that is smaller than the first diameter. Furthermore, the disk 
includes a contact surface having a second width that is larger than the 
first width thereof and a centerline that substantially defines a second 
tipline of the vehicle. When the tire is loaded and deflects to such an 
extent that the disk interacts with a support surface, the tipline of the 
vehicle is moved from the first tipline to the second tipline to improve 
the stability of the vehicle. 
The present invention provides a vehicle that offers the advantages of 
pneumatic tires (i.e., improved ride, flotation and traction) as well as 
the advantage of improved vehicle stability that results from having 
devices that interact with a support surface and are associated with the 
tires near the perimeter of the vehicle's chassis. 
The present invention, together with other aspects and attendant advantages 
thereof, will best be understood upon consideration of the following 
detailed description taken in conjunction with the appended drawings.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
It should be understood that the term "vehicle," as used herein, is 
intended to include any suitable stationary or mobile vehicles, machines 
or equipment, such as automobiles, excavators, back hoes, boom lifts, and 
the like. 
The present invention is described below in terms of a single tire on a 
vehicle. However, it should be understood that the present invention may 
be utilized on some or all of the tires on a vehicle. 
Turning now to the drawings, FIGS. 1A-5 were discussed above in the 
Background section of the application and may be referred to herein 
regarding the various embodiments of the present invention. 
FIGS. 6-9F illustrate the first preferred embodiment of the present 
invention. As best shown in FIG. 6, a conventional pneumatic tire 100 is 
mounted to a wheel assembly 102. 
In the preferred embodiment, a device or ring 106 is mounted to the wheel 
assembly 102 within the tire 100 in any suitable manner. Preferably, as 
shown in FIGS. 8A-9F, the ring 106 is donut-shaped and is formed in three 
arcuate portions or segments that are equally spaced along a 360 degree 
circle and that may be interconnected and mounted to the wheel assembly 
102. The arcuate portions may be interconnected with one another via bolts 
or mechanically locked fasteners 107. The number of arcuate segments is a 
function of tire and wheel assembly size and ease of mounting. For 
example, the ring 106 could be formed of 1, 2, 4, 5 or more segments. 
Furthermore, the ring 106 may be formed and mounted to the wheel assembly 
102 in any suitable manner. 
As shown in FIGS. 6 and 7, the ring 106 includes an inner or mounting 
portion 108 that transitions to an enlarged contact surface 110 along the 
outer periphery thereof. Preferably, the contact surface 110 may be 
approximately twice as wide as the width of the inner portion 108. 
However, the inner portion 108 and the contact surface 110 may have any 
suitable width dimensions. 
The ring 106 is preferably mounted on the wheel assembly 102 at a position 
offset from the centerline thereof to improve vehicle stability. As 
discussed above, the centerline of the tire 100 substantially defines a 
first tipline of the vehicle. Likewise, as best shown in FIG. 7, the 
centerline of the contact surface 110 substantially defines a second, 
improved tipline. 
The ring 106 may be positioned at any location between the centerline and 
the outer edge of the wheel assembly 102. As discussed in more detail 
below, the stability of the vehicle improves in relation to the distance 
between the centerline of the tire 100 and the location of the contact 
surface 110. 
In a preferred embodiment, the contact surface 110 of the ring 106 is 
located as far outboard of the wheel assembly 102 as possible while still 
remaining within the tire 100. Furthermore, while the inner portion 108 of 
the ring 106 may be mounted at any suitable location on the wheel assembly 
102, the contact surface 110 may be located as far outboard as possible, 
resulting in a ring 106 that may be curved or non-linear. 
As shown in FIGS. 6 and 7, the diameter of the ring 106 is smaller than the 
normal operating diameter of the tire 100. The performance characteristics 
of the tire 100 during normal vehicle use (i.e., when lightly-loaded or 
during normal travel) may be analyzed to determine the normal deflection 
range of the tire 100. By correspondingly sizing the diameter of the ring 
106 to prevent the ring 106 from contacting the inner surface 112 of the 
tire 100 during normal vehicle use, the desirable ride, comfort, traction 
and other characteristics of the tire 100 will not be compromised by the 
ring 106. 
However, as best shown in FIG. 7, when the tire 100 is highly-loaded due to 
the vehicle's center of mass approaching the tipline, the tire 100 
deflects to such an extent that the contact surface 110 of the ring 106 
contacts the inner surface 112 of the tire 100, and thus interacts with 
the ground or other support surface. When the contact surface 110 of the 
ring 106 interacts with the ground, the tipline of the vehicle is 
transferred from substantially the centerline of the tire 100 to 
substantially the centerline of the contact surface 110, thereby improving 
the stability of the vehicle in this condition. 
After the load is removed from the tires and the vehicle is in its normal 
operating mode, the tire 100 will substantially regain its normal 
operating diameter and the contact surface 110 of the ring 106 will 
disengage the inner surface 112 of the tire 100. Consequently, the tipline 
of the vehicle will return to substantially the centerline of the tire 
100. 
The second preferred embodiment of the present invention is illustrated in 
FIG. 10. As shown therein, a conventional pneumatic tire 200 is mounted to 
a wheel assembly 202. Alternately, a solid rubber or other suitable tire 
may be utilized. 
An external device or disk 206 is attached to the wheel assembly 202 by any 
suitable means. For example, the disk 206 may be attached to the wheel 
assembly 202 by means of the same fasteners that attach the wheel assembly 
202 to the vehicle (i.e., by means of an adapter that occupies the space 
between the disk 206 and the wheel mounting flange 216). 
If, however, an obstruction in the wheel assembly 202 prevents such a 
mounting, the disk 206 may be mounted to the wheel rim. For example, as 
shown in FIG. 10, a separate ring 212 is welded to the rim near the bead. 
An adapter 214 is bolted to the ring and is removable for access to the 
wheel assembly mounting bolts and other components. The disk 206 is, in 
turn, bolted to the adapter 214. 
Preferably, the external disk 206 is a substantially solid disk. However, 
any suitable donut-shaped disk or other device may be attached to the 
wheel assembly 202. 
As shown in FIG. 10, the external disk 206 has a substantially constant 
width and includes an edge 208 that defines a contact surface 210. In an 
alternate embodiment, similar to the disk 106 shown in FIGS. 6-9, the edge 
208 may define an enlarged contact surface 210. 
The disk 206 is preferably attached to the wheel assembly 202 at a position 
outboard of the tire 200 to improve vehicle stability. As discussed above, 
the centerline of the tire 200 substantially defines a first tipline of 
the vehicle. Likewise, as shown in FIG. 10, the centerline of the contact 
surface 210 substantially defines a second, improved tipline. 
The diameter of the external disk 206 is smaller than the normal operating 
diameter of the tire 200. As discussed above with respect to the first 
preferred embodiment, the diameter of the external disk 206 is sized to 
prevent the disk 206 from contacting the ground or other support surface 
during normal vehicle use. 
When the tire is highly-loaded due to the vehicle's center of mass 
approaching the tipline, the tire 200 deflects to such an extent that the 
contact surface 210 of the disk 206 contacts the ground or other support 
surface. When the contact surface 210 of the disk 206 contacts the ground, 
the tipline of the vehicle is transferred from substantially the 
centerline of the tire 200 to substantially the centerline of the contact 
surface 210, thereby improving the stability of the vehicle in this 
condition. 
After the load is removed from the tires and the vehicle is in its normal 
operating mode, the contact surface 210 of the disk 206 disengages the 
ground or other support surface. Consequently, the tipline of the vehicle 
will return to substantially the centerline of the tire 200. 
In an alternate embodiment, the external disk 206 may be attached to the 
wheel assembly 202 by means of an adjustable telescoping member (not 
shown). In this embodiment, the disk 206 may be positioned in a variety of 
positions outboard of the tire 200 to improve the vehicle's stability. 
As described above, the present invention provides an apparatus and method 
for improving the stability of vehicles, including automobiles, 
excavators, boom lifts and the like. By attaching a disk-like device to 
the wheel assembly of a tire, the tipline of the vehicle may be moved 
closer to, or even beyond, the perimeter of the vehicle's chassis. 
It should be understood that the tires 100 and 200 disclosed herein could 
alternatively be embodied by something other than a pneumatic tire such 
as, for example, a semi-pneumatic tire. 
It should be appreciated that the present invention may be modified or 
configured as appropriate for the application. The embodiments described 
above are to be considered in all respects only as illustrative of the 
present invention, and not restrictive. The scope of the invention is 
indicated by the following claims rather than by the foregoing 
description. All changes which come within the meaning and range of 
equivalency of the claims are to be embraced within their scope.