Suspension system with pivotally connected A-frame parallelogram

A suspension system has a lower torque rod with a forward end pivotally connected to a hanger and a rearward end pivotally connected to an axle seat assembly. An upper torque rod has a forward end pivotally connected to the chassis intermediate the sides thereof and a rearward end pivotally connected to the axle. Forward and rearward air springs are mounted between the axle seat assembly and the chassis fore and aft of the axle. The upper torque rod functions as the upper arm of a parallelogram and as a lateral stabilizer bar. The upper torque rod and a like torque rod on the opposite side of the vehicle cooperate with the axle to define an A-frame, but the connection of the upper torque rod to the chassis is independent of said opposite torque rod.

BACKGROUND OF THE INVENTION: 
This invention relates to a suspension system incorporating torque rods 
that define a parallelogram; one of the torque rods and a like torque rod 
on the opposite side of the vehicle defines an A-frame configuration; 
these torque rods are independently supported from the frame to provide 
stabilization of pitch as well as lateral stabilization while retaining 
independence of the suspension systems. 
Various parallelogram suspension systems are known. U.S. Pat. Nos. 
4,132,432 and 4,529,224 to Raidel, represent examples of such 
parallelograms. Raidel U.S. Pat. No. 4,500,112 also indicates that 
parallelograms having longitudinally offset pivot points are known and 
Raidel U.S. Pat. No. 4,181,323 indicates that a parallelogram having a 
lower torque beam that is bowed is known. 
A suspension system having a parallelogram wherein the upper component is a 
torque rod and an A-frame configuration is disclosed in U.S. Pat. No. 
4,773,670, filed Feb. 6, 1987 by John E. Raidel II. In that suspension 
system, the A-frame is a unitized member having torque rods joined at 
their inner ends and extending outwardly to the opposite sides of the 
vehicle. In this arrangement, the operation of the suspension system on 
one side of the vehicle affects the suspension system on the opposite side 
of the vehicle 
The present invention is particularly suitable for a steer axle for a 
trailer. The invention incorporates the advantages of the foregoing prior 
art patents, but provides a suspension system with a parallelogram and 
A-frame configuration that is independent of the suspension system on the 
opposite side of the vehicle. 
SUMMARY OF THE INVENTION: 
In this suspension system, a hanger depends from the vehicle chassis and an 
axle seat is connected to the axle. Dual air springs are mounted between 
the axle seat and the chassis at locations immediately forward and 
rearward of the axle. A lower torque beam has pivotal connections between 
the hanger and the axle seat with the forward pivotal connection 
comprising an eccentric bolt assembly. The torque beam is bowed downwardly 
to avoid interference with and provide access to other vehicle components. 
The upper torque rod comprises one half of an A-frame, the other half 
being provided by a like upper torque rod on the opposite side of the 
vehicle. The A-frame upper torque rod has a pivotal connection at one end 
to a bracket that is fixed to the axle and a pivotal connection to a 
bracket that is located at the center of the vehicle. The upper torque rod 
therefore provides lateral stabilization for the suspension system. The 
upper and lower torque rods define a longitudinal parallelogram. The upper 
torque rods of the A-frame are independently mounted and are operatable. 
Therefore the suspension systems for each side of the vehicle are mutually 
independent.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT: 
This suspension system is designed for installation on a trailer having a 
chassis side rail 12 and a steer axle 14. A cross member 16 extends 
transversely between the sides of the vehicle and is integral with the 
side rail 12 and a similar side rail on the opposite side of the vehicle. 
A hanger 20 depends downwardly from the chassis side rail 12 immediately 
below the cross member 16. The hanger has a top plate 22 that may be 
bolted or welded to the chassis and has downwardly dependending laterally 
spaced side plates 24 and 26 for supporting an eccentric bolt and bushing 
assembly 28 of the kind described and illustrated in Raidel U.S. Pat. No. 
3,510,149. 
A dual pedestal type axle seat assembly 30 is connected to the axle 14 by U 
bolts 32. The axle seat assembly 30 is formed with two transversally 
spaced verticle plates 34 and 36 that are suitably reinforced by cross 
members and gussets as is conventional. The axle seat assembly 30 has 
forward and rearward pedestals 38 and 40 for supporting dual air springs 
42 and 44 that in turn are bolted to the side rail 12. 
A downwardly curved lower torque rod 48 has a forward end 50 journaled on 
the eccentric bolt and bushing assembly 28 and has a rearward end 52 
journaled on a bushing 54 that is mounted between the side plates 34 and 
36 of the axle seat assembly 30. Just inboard of the axle seat assembly 
30, a bracket 58 incorporates a saddle 60 that is welded to the axle 14. 
As shown in FIG. 2, there is a similar bracket 58, associated with a 
suspension system on the opposite side of the vehicle. 
A plate 64 is welded to the cross beam 16 at a position equidistant from 
the sides of the chassis and supports a bracket 66. An upper torque rod 68 
has a forward end 70 with a bearing 72 mounted on bolts 74 and 76 
supported by the bracket 66. The rearward end 78 of the upper torque rod 
68 has a bearing 80 mounted on bolts 82 and 84 supported by the rear 
bracket 58. A similar upper torque rod 68' has a forward end 70' similarly 
supported by the bracket 66 and a rearward end 78' similarly supported by 
a bracket 58'. As can be seen in FIG. 2, the upper torque rod 68 is 
oriented at an angle to the longitudinal axis of the vehicle, and the 
upper torque rods 68 and 68' cooperate with the axle 14 to define an 
A-frame. As illustrated in FIG. 1, the longitudinal distance between the 
forward and rearward ends 70 and 78 of the upper torque rod 68 is 
substantially the same as the distance between the forward and rearward 
ends 50 and 52 of the lower torque rod 48. Also as shown in FIG. 1, the 
upper torque rod 68 is staggered rearward of the lower torque rod 48. 
Nevertheless, longitudinally the upper and lower torque rods 68 and 48 
form a parallelogram that maintains stabilization of the pitch of the axle 
14 during verticle movements of the axle relative to the chassis. 
Spaced inwardly, the axle seat assembly 30 supports a lower shock absorber 
bracket 87. There is a transverse beam 86 between the side rails 12 that 
supports an upper shock absorber bracket 88. A shock absorber 90 is 
mounted between the lower bracket 87 and the upper bracket 88. 
The torque rods 68 and 68' cooperate to provide A-frame stabilization of 
the axle 14 and because the torque rods 68 and 68' are oriented at angles 
to the longitudinal axis of the vehicle, they provide lateral 
stabilization of the axle 14. A separate stabilizer bar is not required. 
Moreover, the torque rods 68 and 68' being independently connected to the 
bracket 66, the suspension 10 functions independently of a similar 
suspension on the opposite side of the vehicle. 
Operation 
The arrangement of the torque rods 48 and 68 of this suspension system 10 
provide both longitudinal and transverse stabilization of the axle 14, and 
the suspension system 10 operates independently of a similar suspension 
system on the other side of the vehicle. For longitudinal stabilization, 
the torque rods 48 and 68 function as a parallelogram even though their 
ends are staggered and even though the upper torque rod 68 is inboard of 
the lower torque rod 48 and is at an angle to a longitudinal plane. 
Lateral stabilization is provided by the transverse component of the upper 
torque rod 68 by virtue of its orientation. 
Since the axle seat assembly 30 is rigidly connected to the axle 14, and 
because the parallelogram maintains stabilization of the pitch of the axle 
14, vertical movements of the axle relative to the chassis are absorbed 
generally equally by the air springs 42 and 44. 
There are various changes and modifications which may be made to the 
invention as would be apparent to those skilled in the art. However, these 
changes or modifications are included in the teaching of the disclosure, 
and it is intended that the invention be limited only by the scope of the 
claims appended hereto.