Road-railer suspension system having a spring lift and a stabilizer bar

A vehicle suspension system having a pair of hanger brackets, with one control arm and one torque arm pivotally mounted on one end to each hanger bracket. Each control arm and each torque arm is pivotally attached to one of a pair of axle seats at another end. One end of a stabilizer bar is mounted to a control arm to increase the suspensions roll stability, and resistance to lateral deflection. The pivotal connections on either end of the control arm include a flexible bushing formed with a hole, and a pivot pin extending through the hole. A lift mechanism includes a compression spring acting against a force plate to move a pair of tire-wheel assemblies between ground engaging and non-ground engaging positions through an interconnected lift bar. The lift mechanism will raise the tire-wheel assembly between a non-ground engaging position, a first ground engaging position, and a second ground engaging position for use in roadrailer applications.

BACKGROUND OF THE INVENTION 
1. Technical Field 
The invention relates generally to an improved vehicle suspension system. 
More particularly, the invention relates to air spring suspension systems 
for land vehicles which include a parallelogram kinematic movement. 
Specifically, the invention relates to a parallelogram suspension system 
which is roll stable and resistant to lateral deflection. 
2. Background Information 
Suspensions are available in the prior art which utilize air springs to 
provide a comfortable ride, even for large over-the-road trucks and other 
heavy vehicles. The air springs are typically used in industrial vehicle 
single axle units, or tandem arrangements of two or more axles which are 
either driven or non-driven. 
One drawback of air spring suspensions is that an air spring is essentially 
an air inflated bag and requires auxiliary stabilization. An air suspended 
axle must have separate independent mechanical location and attitude 
controls and stabilized components or it will not function effectively. 
Absent stabilization, the air spring will extend to its maximum length or 
width in the direction of least resistance. Also, lateral loading from 
cornering or negotiating uneven terrain will cause a vehicle supported on 
unstable air springs to lean and possibly roll-over. 
A significant number of air spring suspensions have been developed which to 
a greater or lessor extent, control axle location and attitude. A number 
of suspensions that have been developed are roll rigid, while others are 
roll flexible, each generally being designed for a specific application. 
The most common roll rigid configuration is the trailing beam type 
suspension, most of which use the axle as a torsion rod to provide roll 
rigidity. 
Another type of suspension which has been developed is the parallelogram 
suspension which is not inherently roll rigid, and does not inherently 
provide lateral stiffness. Again, ancillary devices such an anti-roll 
bars, track bars or guide mechanisms have been utilized to stabilize 
typical parallelogram designs. As such, parallelogram type suspensions, 
even with the ancillary devices attached, were often only suitable for low 
center of gravity loads, or on specialized vehicles stabilized by other 
vehicle suspension mechanisms. 
Trailing arm suspensions are brake reactive. That is, when the vehicle 
brakes are applied, the suspension will tend to compress thereby altering 
axle loading and potentially reducing the suspension and brake 
effectiveness. Similarly, when the brakes are applied as the vehicle moves 
in reverse, the suspension will tend to raise up, and pivot about the 
single trailing arm pivot, again altering axle loading and reducing the 
suspension and brake effectiveness. Further, most trailing arm suspensions 
suffer from dock walk such that they move toward or away from the loading 
dock as the suspension moves up or down with the brakes locked. This 
movement is caused from air draining off the air springs, or as a result 
of loads added to or removed from the vehicle, or the temperature changes 
that occur as the trailer remains parked by the dock. Dock walk occurs, in 
part, because between the fully compressed to the fully expanded position 
of the air spring, the free end of the trailing arm travels a significant 
linear distance as a result of movement about a single pivot point. As 
such, with the brakes locked, as they would be while parked at a dock, the 
tires also rotate with the trailing arm and cause forward and rearward 
vehicle motion. Similarly, trailing arm suspensions do not utilize the air 
springs full capacity as the air spring plates are not parallel in extreme 
operating positions, again as a result of the trailing arm pivoting about 
a single pivot point. The rear of the air spring is thus fully extended 
long before the forward part of the air spring. 
Parallelogram suspensions were developed to solve a number of the problems 
associated with trailing arm type suspensions. However, parallelogram 
suspensions create problems not present in trailing arm type suspensions. 
Specifically, parallelogram suspensions are not inherently roll rigid nor 
do they inherently provide lateral stiffness. Parallelogram suspensions 
have been found to be a significant advancement over the prior art as they 
provide a relatively stable, safe, and comfortable ride for all types of 
loads. Some of these parallelogram suspensions are included in U.S. Pat. 
Nos. 4,114,923, 4,132,432 and 4,309,045. 
Advantages of the parallelogram stabilized air spring suspensions include 
that the air suspended axle in a parallelogram suspension moves thru a 
very short linear distance and has no rotational motion between the loaded 
and unloaded positions which reduces the problem of dock walk inherent in 
trailing arm type suspensions. 
Further, the parallelogram stabilized suspension permits the air spring's 
full capacity to be utilized as the top and bottom air spring plates 
remain substantially parallel throughout the axle lift operation. 
Specifically, when the air spring is mounted on a moving link of the 
parallelogram it allows the utilization of the air springs full lift 
capability when compared to the typical trailing arm design where the air 
spring travels in an arc and "fans" open stretching the rearmost internal 
reinforcing fibers of the spring while not utilizing even the full travel 
of the forward part of the air spring. 
A further advantage of the parallelogram suspension is its inherent ability 
to maintain a constant caster angle for steerable or caster steering axles 
which are often utilized in auxiliary axle suspensions for tractors and 
trailers. 
The parallelogram suspension inherently provides the above advantages, and 
also locates the axle relative to the longitudinal axis of the vehicle by 
controlling the forward and rearward motions of the axle relative to the 
frame. Moreover, a parallelogram suspension also controls the path which 
the air spring follows as it operates to take up irregularities in the 
road surface. However, the parallelogram suspension alone does not 
stabilize the air spring. Specifically, the parallelogram itself does not 
provide lateral stability to the suspension system. 
Lateral forces act on a suspension system in a variety of ways with the 
most common being that lateral forces act on a suspension as the vehicle 
negotiates a turn. As the vehicle turns, shear stresses act between the 
tire and the road surface causing a lateral stress to be transferred 
through the tire-wheel assembly to the axle. The axle, being rigidly 
attached to the suspension, transfers the lateral forces into the 
parallelogram causing it to laterally deflect. This lateral deflection can 
be extreme and substantially limits the usage of parallelogram 
suspensions. Lateral force may be strong enough under certain loading 
conditions that the tires contact the vehicle frame rails. 
It is thus necessary to provide mechanical means for controlling lateral 
forces on the suspension and its various members. One typical suspension 
where lateral forces are mechanically controlled is shown in U.S. Pat. No. 
3,140,880 in which air springs are disposed between two vertically 
swinging control arms to which the axle is also attached. One feature of 
this suspension is that much of the lateral force is controlled by a 
strong, relatively rigid attachment between the axle and the control arms. 
As such, the lateral force is taken up by the attachment between the 
control arm and the axle. While this prior art suspension system 
presumably functioned for the purpose for which it was intended, it 
suffered from dock walk, brake reactivity, and it did not utilize the full 
lift potential of the air spring. Moreover, it is desirable to provide for 
greater flexibility between the axle and the control arms, while still 
maintaining sufficient lateral stability and thus increase the suspensions 
roll stability. Thus, the second problem inherent in parallelogram air 
spring suspensions is that they are not roll stable. 
Roll instability refers to the lack of sufficient counteracting forces 
operating on the ends of an axle allowing one end of the axle to raise 
relative to the frame a distance greater than the other end of the axle. 
Roll instability is encountered when the vehicle frame tilts or rolls 
relative to the axle; for example, when the vehicle negotiates a turn such 
that the centrifugal and acceleration forces reduce the downward forces 
acting on the inside wheel of the turn, and increase the downward force 
acting on the outside wheel of the turn. Roll instability can also be 
realized when the axle moves relative to the frame; for example, during 
diagonal axle walk. 
Diagonal axle walk occurs when the axle moves relative to the vehicle frame 
which occurs when the wheels at the opposite ends of the axle encounter 
unlike irregularities in a road or off-the-road surface, such as when one 
wheel rides over a curb. As the wheel rides over the curb, an upward force 
acts on that wheel, and a counteracting downward force acts on the wheel 
not riding over the curb. If the suspension is unable to provide 
flexibility between the axle and the frame as the tire-wheel assembly 
travels over the curb or ground irregularity, or alternatively to provide 
the same resilience or flexibility between the axle and the frame as the 
vehicle negotiates a turn, the suspension will be too roll rigid, and may 
cause axle breakage and over-stress vehicle components. Roll rigid 
suspensions are used to stabilize high center of gravity vehicles like 
highway trailers, and are most critical in applications such as tank or 
dump trailers and vans having high volume boxes. In these applications, 
only enough roll compliance is permitted to allow the axle suspension 
combination to negotiate uneven terrain without unduly stressing the 
vehicle frame or axle. Typically, the roll angles of axle to frame are 2 
to 3 degrees in roll rigid environments. That is, if all the load were 
transferred to the tire or tires on one side of the vehicle and the tire 
or tires on the other side of the vehicle are completely off the ground, 
the angle of the axle relative to the frame reaches only about 2 to 3 
degrees for a typical roll rigid suspension. 
Conversely, roll flexible suspensions are used on low height vehicles and 
multi-axle vehicles which are stabilized by only some of the suspensions 
and the added axles merely increase the load carrying capacity of the 
vehicle. In applications where tractive effort is paramount, the 
suspension must be flexible to allow the tires to remain in contact with 
the ground. Specifically, if a given suspension is roll flexible, so that 
the vehicle may have a larger total vehicle weight, the tire must remain 
in ground contact to assure that weight is transmitted to the ground 
through the tire. 
Regardless of whether a roll rigid or roll flexible suspension is required, 
the suspension itself must be roll stable for the safety reasons set forth 
hereinabove. 
Attempts have been made to provide additional resistance to lateral forces 
while simultaneously allowing the frame to "roll" in a controlled manner 
relative to the axle without interfering with the vertical forces 
controlled by the air springs. Prior attempts to provide additional roll 
resistance include the addition of stabilizer bars, roll bars or torsion 
bars secured between the suspension and the frame, or by stiffening the 
connection between the axle and the control arm as described above. One 
such suspension is shown in U.S. Pat. No. 5,083,812. 
Such improvements, however, may nevertheless affect the handling and ride 
of the vehicle, and transfer the load caused by the lateral forces to the 
frame thereby over-stressing vehicle components. Such systems are 
frequently more complex, having many moving components, and may also have 
limited application, especially where the vehicle center of gravity is 
over a predetermined height. 
A roll stable parallelogram suspension which is resistent to lateral forces 
would have a variety of uses. The parallelogram suspension has not been 
used in a roadrailer application as the vertical distances the suspension 
travels magnifies the affect of lateral forces acting on the suspension. 
In the roadrailer application, the axle must be moved between three 
separate positions: a first ground engaging position when the roadrailer 
suspension is operating in highway mode, a second ground engaging position 
when the trailer is raised to engage a rail bogie in coupling mode, and a 
rail mode wherein the tires are lifted above the railing. The size of the 
air spring necessary to move the suspension between these three positions 
made the use of other parallelogram suspensions unrealistic as the affects 
of lateral forces and roll instability could not be overcome while 
trailing beam designs require more airspring travel decreasing ground 
clearance and increasing cost and weight. 
Roadrailer suspensions utilize a lifting mechanism which may either be an 
air spring, or a mechanical spring of the leaf or coil variety. The 
conventional axle lifting mechanism comprises one or more stressed 
mechanical springs such as coil springs or leaf springs acting directly 
between the vehicle frame and axle. When air is relieved from the air 
springs, the mechanical springs raise the axle. The mechanical springs, in 
their condition of diminished stress when the axle is fully raised, must 
still exert sufficient force to support the weight of the axle and 
tire-wheel assemblies such that the wheels remain in the raised position. 
When the air springs are pressurized, the wheels are forced downwardly 
into ground engagement overcoming the mechanical spring force. 
Therefore, a need exists for a road-railer suspension which is 
parallelogram stabilized and is roll stable, but which is also resistent 
to lateral forces. 
SUMMARY OF THE INVENTION 
Objectives of the invention include providing a road-railer suspension 
system which includes kinematic parallelogram movement. 
Another objective is to provide a parallelogram road-railer suspension 
which is resistent to lateral forces. 
A further objective is to provide a parallelogram type road-railer 
suspension which is roll stable. 
Yet another objective is to provide a parallelogram air spring suspension 
which will operate equally well on most vehicles. 
A still further objective is to provide such a vehicle suspension system 
which is of simple construction, which achieves the stated objectives in a 
simple, effective and inexpensive manner, and which solves problems and 
satisfies needs existing in the art. 
These and other objectives and advantages of the invention are obtained by 
the improved road-railer suspension system, the general nature of which 
may be stated as including a pair of parallel and spaced apart 
parallelogram means for at least partially stabilizing an axle relative to 
a frame and adapted to extend between an axle and a frame; spring means 
for resiliently controlling the vertical movement of an axle relative to a 
frame adapted to extend between a frame and an axle; a stabilizer bar 
having a first end and a second end extending between said pair of 
parallelogram means; mounting means for mounting one of said first and 
second ends to each parallelogram means; and a pair of axle lift means for 
moving the axle between a ground engaging and a non-ground engaging 
position.

Similar numerals refer to similar parts throughout the drawings. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
The improved vehicle suspension system of the present invention is 
indicated generally at 1, and is particularly shown in FIGS. 1, 2 and 3, 
and is particularly adapted to be mounted on a vehicle 2, such as a truck 
or trailer. Vehicle 2 includes a cargo box 3 supported by a pair of frame 
rails 4 extending longitudinally along the length of vehicle 2. Suspension 
system 1 includes a pair of hanger brackets 5 welded to a pair of parallel 
and spaced-apart slide channels 6. Slide channels 6 are spaced apart a 
distance equal to the distance between frame rails 4 and are mounted to 
frame rails 4 with a plurality of mounting bolts 7. Suspension system 1 
further includes a forward suspension 10 and a rearward suspension 11 for 
supporting a forward axle 12 and a rearward axle 13, respectively. Each 
axle 12 and 13 supports a tire-wheel assembly 9 at each end thereof. 
Inasmuch as both the forward and rearward suspensions 10 and 11 are 
similar, with the forward suspension 10 being merely reversed from the 
rearward suspension 11 with respect to hanger bracket 5, only forward 
suspension 10 will be described in detail. Forward suspension 10 includes 
a pair of parallel and spaced apart control arms 14, and a pair of 
parallel and spaced apart torque arms 15 pivotally mounted to respective 
hanger brackets 5 at corresponding pivots 16 and 17. The length of each 
torque arm 15 may be adjusted via threaded adjustment nuts 18 in a manner 
well known in the art. The ends of each control arm 14 (FIG. 4) include a 
mounting boss 35 integrally formed with a hole 36. 
Forward suspension 10 further includes a pair of spaced-apart axle seats 20 
from which axle 12 depends. Each torque arm 15 connects to a corresponding 
axle seat 20 at a pivot 21. An axle seat weldment 22 depends from each 
axle seat 20 and one control arm 14 attaches to each axle seat weldment 22 
at a pivot 23. One hanger bracket 5, control arm 14, torque arm 15 and 
axle seat weldment 22, thus form a kinematic parallelogram indicated 
generally at 24 in FIG. 1. 
An air spring 25 is mounted between each axle seat 20 and a spring mounting 
plate 19 adjacent a slide channel 6 by any convenient attachment means 
such as bolts 26, shown in FIGS. 1 and 3. Moreover, an air nozzle 27 is 
provided in each air spring 25 to inflate the air spring in a manner well 
known in the art. 
In accordance with one of the main features of the present invention, each 
pivot 16 and 23 (FIG. 4) includes a flexible rubber bushing 28 formed with 
a hole 29. Rubber bushing 28 is bonded to an inner sleeve 28A which is 
press-fit within a hole 36 that is formed in each mounting boss 35 of 
control arm 14. Pivots 16 and 23 also include a pivot pin 30 which is 
fitted into inner sleeve 28A in hole 29 of flexible bushing 28 and clamps 
the ends of inner sleeve 28A to prevent rotation of pin 30 within sleeve 
28A. Inasmuch as a pivot pin 30 is fitted into each bushing 28, and each 
bushing 28 is press-fit into control arm 14, any movement between control 
arm 14 and pivot pins 30 occurs as a result of distortion in flexible 
bushings 28. Bushings 28 provide relatively little lateral deflection in 
the range of 0.12 inches to 0.25 inches. Pivots 17 and 21 are also fitted 
with bushings (FIG. 4). 
Alternatively, a bearing 65 (FIG. 4A) may be press-fit into each flexible 
bushing 28, and pivot pin 30 may be slip-fitted into the bearing to 
provide movement between bushing 28 and pivot pin 30 thereby reducing the 
stress on bushing 28. 
In accordance with another of the main features of the invention, a tubular 
stabilizer bar 31 extends between spaced apart control arms 14, and is 
normal to slide channels 6 and is formed with a pair of ends 33 (FIG. 4). 
Each control arm 14 is formed with a through hole 32 which accepts one end 
33 of stabilizer bar 31 and is capped with a cover plate 34. A weld 37 
extends around stabilizer bar 31 adjacent each hole 32. Bushings 28 and 
stabilizer bar 31 combine to provide a roll stable suspension resistent to 
lateral deflection as is described in more detail below. 
Two pairs of spaced apart mounting brackets 40 extend from stabilizer bar 
31 (FIG. 4). Each pair of mounting brackets 40 includes two brackets 40A 
which are formed with through mounting holes 41. Each pair of mounting 
brackets 40 of forward suspension 10 is part of a respective outer lifting 
mechanism, indicated generally at 42A and 42B in FIGS. 1-4, which are 
collectively referred to as 42. Each lifting mechanism 42 also includes a 
lift bar 43 pivotally coupled at one end to a corresponding pair of 
mounting brackets 40 by passing a bolt 44 through mounting holes 41 and 
lift bar 43. An opposing end of each lift bar 43 is received through an 
aperture 45 (FIGS. 9-11) formed in the center of a spring cup 46 and is 
secured to spring cup 46 with an adjustment nut 47, a washer 48 and a 
bushing 49. Each spring cup 46 includes a peripheral flange 50 and an 
integral cup-shaped central portion 51. Each spring cup 45 and each lift 
bar 43 is mounted within a tubular housing 52 (FIGS. 2, 3). 
Each lifting mechanism 42 also includes a compression spring 53 mounted 
within housing 52 (FIGS. 5-6). One end of spring 53 abuts peripheral 
flange 50 of spring cup 46, while the other end of spring 53 bears against 
a force plate 54 of tubular housing 52. Tension forces exerted on spring 
cup 46 may be varied by adjusting the axial location of adjustment nut 47 
along lift bar 43. Tubular housing 52 includes a cover plate 55 extending 
over the spring cup 46, with a hole being formed therein to provide access 
to adjustment nut 47. 
As discussed above, two lift mechanisms 42 are provided to lift forward 
axle 12. Referring specifically to FIG. 4, forward axle 12 is raised and 
lowered via the outer lift mechanisms 42A and 42B. Similarly, the rearward 
axle 13 is raised and lowered via the operation of the inner lift 
mechanisms 42C and 42D. 
As apparent to one of ordinary skill in the art, forward suspension 10 may 
be utilized when only a single axle vehicle suspension system 1 is 
required. However, if tandem axle arrangements are required, for example 
those arrangements utilized on known trailer vehicles, a forward 
suspension 10 is utilized in combination with rearward suspension 11 as 
shown specifically in FIG. 1. Rearward suspension 11 is reversed from 
forward suspension 10 with respect to hanger bracket 5. In this manner, 
the overall length of the tandem unit may be significantly reduced when 
compared to standard tandem trailing arm suspensions which cannot be 
reversed, and existing parallelogram suspensions wherein the rearward 
suspension 11 is not reversed. In the exemplary embodiment, the overall 
tandem arrangement has a length in the range of 60 to 70 inches. 
Having now described the improved vehicle suspension system 1, the method 
of operation is as follows. 
When vehicle 2 is moving in a straight line and tire-wheel assemblies 9 at 
opposite sides of vehicle 2, roll over similar irregularities, there is no 
significant differential vertical movement between the respective 
parallelograms 24 supporting axle 12. Forces in suspension system 1 are 
controlled primarily by air springs 25, with minor lateral forces being 
controlled by pivots 16, 17, 21 and between the members of parallelogram 
24. 
However, the forces act differently on suspension system 1 when vehicle 2 
encounters road conditions which cause differential vertical swinging of 
control arms 14 attached to common axle 12. Differential vertical swinging 
of control arm 14 occurs when vehicle 2 negotiates a turn or when one 
tire-wheel assembly 9 traverse a bump or depression while the opposite 
tire-wheel assembly 9 passes over an unlike surface. Absent stabilizer bar 
31, pivotal connections 16, 17, 21 and 23 would not provide sufficient 
roll stability for the vehicle. Stabilizer bar 31 increases roll stability 
by resisting the tendency of parallelogram 24 to roll relative to frame 
rails 4. When vehicle 2 traverses an irregularity in the road, the force 
from the irregularity will cause one tire-wheel assembly 9 to raise toward 
the vehicle. As tire-wheel assembly 9 raises, one parallelogram 24 will 
pivot upwardly and will transmit force to the opposing parallelogram 24, 
causing a downward force to act thereon. The associated movement of 
respective control arms 14 will twist stabilizer bar 31 in torsion which 
will resist the twisting. Consequently, stabilizer bar 31 resists the 
displacement of control arms 14 to increase the roll stability of vehicle 
2. 
Similarly, as vehicle 2 negotiates a turn, cargo box 3 will tend to rotate 
out of the turn applying opposite forces on the suspension which will 
similarly apply torsion to stabilizer bar 31, thereby resisting the 
rotation of the cargo box relative to the ground surface. 
Lateral forces also act on suspension system 1 when vehicle 2 negotiates a 
turn which will tend to deflect the parallelogram in a horizontal 
direction transversely with respect to frame rails 4 which distorts 
control arms 14 and torque arms 15 out of the usual planar configuration. 
Parallelogram 24 offers little resistance to lateral deflection with the 
only resistance being offered by flexible bushings 28 at pivots 16, 17, 21 
and 23. Stabilizer bar 31 primarily resists this movement in the improved 
suspension. Specifically, as the vehicle negotiates a turn, the lateral 
forces will cause each parallelogram 24 positioned on opposite sides of 
the axle to distort, applying a moment to each end of stabilizer bar 31 
which is rigidly attached to control arms 14. The amount of lateral 
deflection permitted by stabilizer bar 31 is directly proportional to its 
modulus and size. As such, when lateral forces act on suspension system 1, 
a portion of stabilizer bar 31 is in tension and a portion is in 
compression, urging stabilizer bar 31 to assume a sinusoidal 
configuration. 
Regarding the operation of lifting mechanism 42, and referring specifically 
to FIGS. 3, 10 and 11, compression spring 53 is sufficiently prestressed 
to move axle 12 and tire-wheel assembly 9 to the lifted position and 
retain the same in the lifted position. More particularly, when air spring 
25 is deflated, compression spring 53 will push against force plate 54 and 
move stabilizer bar 31, interconnected axle 12 and tire-wheel assembly 9 
to the raised position. Compression spring 53 provides the lifting force 
when it expands against force plate 54 to move spring cup 46, which in 
turn moves interconnected lift bar 43. The force translated through lift 
bar 43 is transferred to stabilizer bar 31, to move axle 12 to the 
position shown in FIG. 11. 
When it is desired to transmit load to tire-wheel assemblies 9, air springs 
25 are inflated to exert downward force on stabilizer bar 31. Air springs 
25 inflate to exert force on axle 12, and consequently on lift bar 43. 
This force is sufficient to overcome the counteracting forces exerted by 
compression spring 53, and as air springs 25 push down on axle 12, 
interconnected stabilizer bar 31 will also move downwardly, pulling 
pivotally attached lift bars 43 to the ground engaging position. As each 
lift bar 43 moves downwardly, it will pull against an associated spring 
cup 46 to compress spring 53 against force plate 54, and suspension system 
1 moves to a first lowered position shown in FIG. 9. When air spring 25 is 
inflated to the first lowered position, or highway mode, only a portion of 
the air spring overall effective length is utilized, and tire-wheel 
assemblies 9 are spaced sufficiently far from frame rails 4 to allow 
vehicle to comfortably ride over the road surface. 
When air springs 25 are fully inflated, they exert a sufficient force on 
axle 12 to overcome the counteracting forces exerted by compression 
springs 53, and stabilizer bar 31 is moved to a second lowered position, 
or coupling mode, shown specifically in FIG. 10. Each lift bar 43 thus 
pivots at mounting brackets 40 to further compress spring 53 by applying a 
force to spring cup 46. Suspension system 1 is placed in the coupling mode 
shown in FIG. 10 when vehicle 2 is being coupled to a rail bogie. After 
coupling, air springs 25 are fully deflated to move vehicle suspension 
system 1 to the position shown in FIG. 11, thereby moving tire-wheel 
assemblies 9 out of ground engaging contact. After vehicle 2 has been 
transported via the railroad bogie, air springs 25 are reinflated to move 
suspension system 1 to the position shown in FIG. 10. Vehicle 2 is then 
pulled away from the rail bogie, with the air springs then being partially 
deflated to the highway mode position shown in FIG. 9, for ground engaging 
contact to be pulled by a known tractor vehicle. 
Vehicle suspension system 1 provides a parallelogram axle 12 with all the 
advantages known in the art, while still providing a suspension that is 
resistent to lateral forces and is roll stable. Parallelogram 24 operates 
such that as tire-wheel assemblies 9 move into and out of a ground 
engaging position, control arm 14 and torque arm 15 pivot in unison to 
maintain a constant caster angle. Similarly, inasmuch as axle 12 moves 
only a short distance axially and rotationally between the lifted and 
non-lifted positions, vehicle suspension system 1 will substantially 
reduce dock walk. Further, inasmuch as the pitch of axle 12 is maintained 
relative to the vehicle, and the axle travels a short axial distance 
relative to the frame rails, substantially the entire lift capacity of air 
spring 25 is utilized. Stabilizer bar 31 enhances the lateral stability 
and roll stability of the parallelogram stabilized suspension. 
Accordingly, the invention described hereinabove, successfully overcome 
problems associated in the art, and create a parallelogram suspension, as 
well as a roll stable suspension. Moreover, the suspension system of the 
present invention also provides an air ride suspension system which is 
resistant to lateral deflection. Still further, the suspension system of 
the present invention provides a parallelogram lift suspension which is 
movable between a non-ground engaging position, a first ground engaging 
position, and a second lowered ground engaging position for utilization on 
a roadrailer vehicle. The parallelogram roadrailer suspension essentially 
utilizes the entire useful length of air springs 25 and the caster angle 
remains almost constant in both the non-ground engaging position, and the 
first and second ground engaging positions. 
Accordingly, the improved vehicle suspension system is simplified, provides 
an effective, safe, inexpensive, and efficient device which achieves all 
the enumerated objectives, provides for eliminating difficulties 
encountered with prior devices, and solves problems and obtains new 
results in the art. 
In the foregoing description, certain terms have been used for brevity, 
clearness and understanding; but no unnecessary limitations are to be 
implied therefrom beyond the requirement of the prior art, because such 
terms are used for descriptive purposes and are intended to be broadly 
construed. 
Moreover, the description and illustration of the invention is by way of 
example, and the scope of the invention is not limited to the exact 
details shown or described. 
Having now described the features, discoveries and principles of the 
invention, the manner in which the improved vehicle suspension system is 
constructed and used, the characteristics of the construction, and the 
advantageous, new and useful results obtained; the new and useful 
structures, devices, elements, arrangements, parts and combinations, are 
set forth in the appended claims.