Vehicle suspension for rough terrain

A suspension assembly for a truck type vehicle comprises a trunnion shaft rotatably mounted to the axle with a pair of spring supports mounted to the trunnion shaft, a pair of coil springs extending between the spring supports and the chassis, a pair of torque rods rotatably mounted and extending between a chassis member and the axle seat, and a torsion roll bar pivotally connected to and extending between the suspension on each side of the vehicle and the chassis frame. In an alternate embodiment, a single piece axle seat and spring support assembly is bolted to the axle for mounting of the springs.

There are many vehicles designed for rough terrain use. One example is the 
military truck-type vehicle which carries payloads comparable to 
over-the-road type vehicles but which must be capable of withstanding the 
greater variations encountered in off-the-road terrain. A critical part of 
the vehicle is the suspension system which must support the vehicle 
chassis above the vehicle axle as it traverses this rough terrain. Some of 
the special problems which must be dealt with are the increased axle 
travel which must be accommodated and which also contributes to a much 
greater axle stabilization problem. As the springs compress and extend in 
response to the terrain, they are subject to greater deformation which 
must be compensated for to maintain control of the vehicle and prevent 
breakage of the springs and wild gyrations of the chassis. Axle 
stabilization is an even greater problem with drive axles, as the pitch of 
the axle must be controlled over a much greater travel. As can be 
appreciated, in a drive train the pitch of the axle must remain fairly 
constant to maintain alignment of the drive line to prevent binding and 
breakage of the transmission. In the typical off-the-road vehicle, more 
than one axle is driven. Furthermore, the forward or steer axle is usually 
one of the driven axles and the suspension for it must provide clearance 
for the turning of the wheels, and the steering components. Thus, the 
suspension must be compact and yet provide open access around the axle 
with clearance as necessary for the relatively large axle travel without 
interfering with the steering components. 
To solve these and other problems, applicant has succeeded in developing a 
suspension design in several embodiments which are uniquely adapted to 
rough terrain vehicles, and which can accommodate substantial loads and 
yet permit a relatively large axle travel with respect to the chassis. A 
first embodiment of this suspension includes an axle seat assembly clamped 
to the axle, the axle seat having provision for clamping the ends of a 
pair of coil type springs thereto. A pair of coil type springs are mounted 
to and extend between the axle seat and the chassis, with one of the coil 
type springs being mounted outboard of the main chassis frame member which 
improves the lateral stability of the axle as well as reducing the 
required height of the suspension as the upper mount for the spring is 
above the main chassis frame member. A forward hanger is rigidly secured 
and depends downwardly from the main chassis frame member and a pair of 
torque rods are pivotally connected and extend between the hanger and the 
axle seat. The torque rods are laterally offset which improves the lateral 
stability of the suspension and are also formed in a curvilinear shape to 
accommodate the inward extension of the wheel as it is steered. An 
overload bumper is secured to the chassis immediately above the axle seat 
and limits the upward vertical movement of the axle with respect to the 
chassis to prevent damage to the suspension. A torsion roll bar is mounted 
to each suspension on both sides of the axle, and is pivotally suspended 
from the chassis by short hanger bars which permits the torsion roll bar 
to follow the movement of the suspension as the axle deflects and yet 
achieve its function of stabilizing the axle should one end of the axle 
deflect differently than the other end of the axle. 
By using coil springs, a greater amount of axle travel can be permitted and 
the unique parallelogram stabilization of the axle provided by the double 
torque rods achieves the necessary axle stabilization to accommodate this 
increased axle travel. The unique clamping assembly for each end of the 
coil springs ensures that they are held in place during vehicle operation 
but yet provide for rapid disassembly for repair or replacement purposes. 
In a second embodiment of this suspension, a trunnion shaft is clamped to 
the axle seat with a spring mount welded to each end of the trunnion 
shaft, the trunnion shaft being rotatable with respect to the axle. The 
coil springs are positioned as in the first embodiment which balances them 
on either side of the trunnion shaft and on either side of the axle which 
helps to center the load directly on the trunnion shaft and axle as the 
trunnion shaft lies transversely to and directly above the axle. With this 
trunnion shaft and spring mount arrangement, as one end of the axle 
deflects more or less than the other end, a movement which would otherwise 
tend to deform the spring generally in the shape of a banana, the spring 
mounts and trunnion shaft are free to rotate about the axle which helps to 
maintain the vertical linearity of the spring and eliminate the "banana" 
shape. In either embodiment, a skid plate may be integrally formed with 
the hanger and provide a nose to deflect obstructions and prevent their 
entry into the suspension area which might cause damage or interfere with 
the vehicle's operation. Because of the unique compact design of 
applicant's suspension, this skid plate and hanger assembly may be placed 
very close to the axle itself so as not to interfere with the ability of 
the vehicle to attack sharp inclines of as much as 45.degree.. 
These and other advantages of applicant's suspensions are more fully 
described and disclosed in the drawings and preferred embodiment which 
follows.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Applicant's first embodiment 20 of his suspension for rough terrain is 
shown in FIGS. 1-7 and generally includes an axle seat 22 bolted or 
clamped to an axle 24 with a trunnion shaft and spring support assembly 26 
rotatably mounted to the axle seat 22. A pair of coil type springs 28 are 
clamped to the trunnion shaft and spring support assembly 26 and extend 
upwardly to the chassis 30 where they are similarly clamped. A pair of 
torque rods 32 are pivotally connected and extend between a hanger 34 
bolted to and extending downwardly from chassis 30, and the trunnion shaft 
and spring support assembly 26. A torsion roll bar 36 is pivotally 
connected to the rear of trunnion shaft and spring assembly 26 on either 
side of the vehicle and is suspended from the chassis by hanger assembly 
38. One or more shock absorbers 40 are bolted to and extend between the 
chassis 30 and trunnion shaft and spring support assembly 26. Thus, 
applicant's first embodiment 20 provides parallelogram control in a coil 
spring type suspension with a trunnion shaft spring mount to maintain the 
vertical linearity of the springs 28 as the axle 24 deflects with respect 
to the chassis 30. The torsion roll bar 36 is similarly pivotally mounted 
to follow the movement of the axle 24 and suspension 20 without loss of 
function. Having generally described the major components and 
sub-assemblies of the first embodiment 20, applicant will now proceed with 
a more detailed description of the various parts thereof. 
As shown more particularly in FIG. 6, axle seat 22 includes a bottom 
bracket 42 having gussets 44 to strengthen it and an upper bracket 46, 
brackets 42, 46 being clamped together by U-bolts 48. Upper bracket 46 has 
shoulders 50 (see FIG. 1) around which U-bolts 48 fit in a partially 
recessed manner. A bearing sleeve 52 surrounds a trunnion shaft 54 
rotatably mounted to upper bracket 46, trunnion shaft 54 being transverse 
to axle 24. Thus, trunnion shaft 54 is free to rotate within bearing 
sleeve 52 and upper bracket 46 in response to changes in loading or 
angular orientation of axle 24 with respect to chassis 30, as explained in 
more detail hereinafter. 
As best shown in FIG. 5, a forward spring support assembly 56 and a 
rearward spring support assembly 58 are secured to the ends of trunnion 
shaft 54 and are free to pivot as trunnion shaft 54 rotates. As shown in 
FIG. 3, the fore spring support assembly 56 includes a generally circular 
clamp plate 60 with an upturned periphery 62 to clamp the fore coil type 
spring 64 thereto with bolt assembly 66. The fore spring support assembly 
56 also includes a generally peripheral upturned side plate 68 which 
partially surrounds the lower end of fore coil spring 64 to form a pocket 
therefor and maintain it in place during operation. A pair of downwardly 
depending bracket members 70 provide a mounting position for the pivotal 
mounting of the lower torque rod 72 with bolt assembly 74. Similarly, an 
outboard bracket member 76 provides a convenient mounting for the aft end 
of upper torque rod 78 by bolt assembly 80. Thus, the aft end of each 
torque rod 72, 78 is pivotally connected to the fore spring support 
assembly 56. 
As shown in FIGS. 1 and 4, a hanger assembly 82 is bolted to the chassis 30 
by bolts 84 and extends downwardly therefrom. Hanger assembly 82 includes 
a center vertical bracket 86 with an outboard angle bracket 88 and an 
inboard bracket 90 welded thereto and providing the mounting means for the 
universal joints 92, 94 at the fore end of torque rods 72, 78, 
respectively. Universal joints 92, 94 may be of a type disclosed and 
described in application Ser. No. 341,474, filed Jan. 21, 1982, also an 
invention of applicant and the disclosure of which is incorporated herein 
by reference. 
The upper end of the forward coil spring 64 is coiled with an ever 
decreasing radius to form a generally flattened surface to facilitate its 
mounting. As best shown in FIG. 3, the upper end of coil spring 64 fits 
within a circular bracket 96 and is secured to chassis 30 with a bolt and 
washer assembly 98. As best shown in FIGS. 1 and 2, the upper end of rear 
coil spring 100 is secured in the same manner by bolt and washer assembly 
102, except that an outboard bracket assembly 104 permits mounting of the 
spring above the main chassis frame member 30 and outboard therefrom. 
The rear spring support assembly 58, as best shown in FIGS. 1, 2 and 5, 
includes an inboard bracket extension 106 which provides the pivotal 
mounting point for torsion roll bar 36 by bolt assembly 108. The torsion 
roll bar 36 is further stabilized by one or more hanger assemblies 38 
which are bolted by bolts 112 to the main frame members 30. Each hanger 
assembly 38 includes a pair of downwardly extending bracket members 114 
between which is mounted the upper end of hanger arm 116 by bolt assembly 
118. The lower end of hanger arm 116 includes a clamp and bushing assembly 
120 secured by bolts 122 to a medial portion of torsion roll bar 36. Thus, 
hanger assemblies 38 permit limited deflection of torsion roll bar 36 to 
follow the movement of axle 24 and yet retain its desired function of 
resisting torsion and roll between the axle 24 and chassis 30. 
As best shown in FIG. 7, a skid plate 124 may be formed at the fore of 
hanger 34. With this feature, the upper and lower torque rods 130, 132 
have an upward bend and the universal joints 134, 136 are inverted which 
add to the compactness of the second embodiment 124 to permit a greater 
angle "a" of attack and hence angle of skid plate 124. 
As best shown in FIGS. 8-11, virtually the same suspension as is shown in 
applicant's first embodiment 20 may be provided with a fixed angle seat 
and spring support assembly 128. An upper bracket assembly 138 is bolted 
to axle 24 by U-bolts 140, with lower bracket 142 "seating" the axle 24 
therebetween. The upper bracket assembly 138 includes a main spring 
support bracket 144 extending the length of the assembly to provide 
mounting for both fore and aft coil springs 146, 148 as in the first 
embodiment 20. A center overload platform 150 matches and lines up with an 
overload bumper 152 affixed to chassis member 30 to restrict the upward 
movement of axle 24 with respect thereto to prevent damage to the 
suspension. Of course, one or more shock absorbers 154 may be mounted to 
and extend between the chassis 30 and the axle seat and spring support 
assembly 128. 
OPERATION 
Applicant's suspension systems are designed to provide a safe reliable ride 
over particularly rough terrain, such as that encountered in off-the-road 
travel by a military vehicle. The parallelogram stabilization provided by 
the torque rods extending between a chassis member and the axle seat 
stabilize the axle to maintain its pitch as it moves with respect to the 
chassis. The coil springs are generally balanced across the axle and, in 
the embodiment utilizing a trunnion shaft, are balanced across the 
trunnion shaft to center the load on the axle as the axle moves 
vertically. For those vehicles expected to encounter particularly rough 
terrain, the trunnion shaft embodiment permits the spring support brackets 
to pivot or rotate with respect to the axle to maintain the vertical 
linearity of the springs as one wheel or the other, but not both, moves 
vertically with respect to the chassis and therefore moves in a somewhat 
arcuate manner and not directly vertically. This could be caused by one 
wheel or the other going over a pothole or log. This motion would 
otherwise tend to deform the spring into a "banana" shape which causes 
instability and increased stress leading to early failure or damage to the 
suspension. However, with applicant's second embodiment not having the 
trunnion shaft, the suspension is perfectly adequate for most rough 
terrain. The trunnion shaft merely provides increased ability to handle 
extreme terrain. 
The torsion roll bar is pivotally connected to each suspension on opposite 
sides of the vehicle and is suspended by one or more hanger arm assemblies 
from the main frame of the chassis. This permits limited deflection of the 
torsion roll bar as the axle moves through the pivoting movement of the 
hanger arm assembly and the pivotal connection at each suspension. The 
torsion roll bar remains fully operative as the axle moves without 
limiting axle movement or interfering with suspension operation. Another 
feature of applicant's suspensions is the skid plate which can be formed 
at the nose or forward end of the hanger assembly and which blocks the 
entry of obstructions into the suspension area of the vehicle and yet 
permits a desirable 45.degree. angle of attack for the vehicle wheel 
against the terrain. The compactness of applicant's suspensions permits 
this angle of attack and yet includes the parallelogram axle control 
through the pair of torque rods pivotally attached to and extending 
between the hanger assembly and the axle seat. An overload bumper may be 
secured to the frame and a bumper platform secured to the top of the axle 
seat for contact with the overload bumper to limit vertical axle movement 
to prevent excessive compaction of the coil springs and possible damage 
thereto. To further enhance the compactness of the suspension, the rear 
coil spring mount is achieved by an outboard bracket member extending 
above the level of the main chassis frame. Of course, one or more shock 
absorbers may be conveniently mounted and extend between the chassis and 
the axle seat or spring support assembly, as appropriate. 
Various changes and modifications to the invention would be apparent to one 
of ordinary skill in the art upon a reading of applicant's disclosure. 
These changes and modifications are included within the teaching of 
applicant's invention which is limited only by the scope of the claims 
appended hereto.