Land vehicles – Wheeled – Running gear
Reexamination Certificate
1998-12-18
2001-03-27
Johnson, Brian L. (Department: 3618)
Land vehicles
Wheeled
Running gear
C280S124174
Reexamination Certificate
active
06206407
ABSTRACT:
BACKGROUND
The present invention relates to vehicle suspension systems and, more specifically, to suspension systems for tandem axles which are particularly useful in rugged environments, such as at off-road construction sites.
Numerous suspension systems exist for supporting the weight of trucks together with the payload being carried by the truck.
A number of known designs utilize so-called walking beams, one on each side of a vehicle and positioned below the axles in combination with a cross-tube extending between the walking beams at a low point of the suspension. These designs suffer from a number of disadvantages, such as increased weight and low ground clearance.
Other designs utilize mechanically complex constructions which add to the expense of the designs.
In certain designs, to provide adequate clearance for the suspension system, the frame rails are supported at a relatively high elevation resulting in a vehicle with an increased ride height. This tends to adversely affect the stability of the vehicle.
In some known designs, it is difficult to replace components of the designs. In other designs, entire subassemblies must be replaced even though only a few components of the subassembly have worn out. This makes repairs more difficult and/or more expensive.
It is also often desirable in vehicles operated in rugged environments to provide reduced resistence to cross articulation and vertical articulation of the axles. Cross articulation is a condition where one axle is angled at one angle relative to horizontal, and the other axle is angled at an opposite angle relative to horizontal. Vertical articulation is where one axle is at a higher elevation than the other axle of the tandem pair.
The present invention relates to a vehicle suspension system and method which is directed toward overcoming these and other disadvantages of the prior art. The invention is not limited to a vehicle suspension system which overcomes all of the above disadvantages of known systems, as the present invention is directed toward overcoming one or more of the disadvantages of known systems.
SUMMARY
A vehicle suspension system is provided for coupling elongated frame rails to first and second axles, the axles extending in a direction transverse to the frame rails. Each axle has opposed outer end portions projecting outwardly beyond the frame rails. At each side of the vehicle, in proximity to the frame rail at the respective side of the vehicle, a vehicle suspension is provided which includes a leaf spring assembly comprised of one or more leaf springs and, most preferably, a plurality of leaf springs. The leaf spring assembly has first and second end portions and a central portion between the end portions. The leaf spring assembly extends from the outer end portion of the first axle to the outer end portion of the second axle. A bushing is coupled to the frame rail. The bushing includes at least three arcuate reinforcing plates with elastomeric material disposed between the plates. The leaf spring assembly is coupled to the bushing, most preferably by a clamp, to thereby couple a central portion of the leaf spring to the frame rail through the bushing. A first leaf spring mount couples the first end portion of the leaf spring assembly to the outer end portion of the first axle, and a second leaf spring mount couples the second end portion of the leaf spring assembly to the outer end portion of the second axle. In one specific form, these mounts are each designed to move in shear relative to the received leaf spring and portion as the axles articulate. More specifically, in an illustrated embodiment, the first and second leaf spring mounts may include shear pads receiving the leaf spring end portions therebetween. The shear pads move in shear during cross and vertical articulation of the axles.
The bushing is preferably at the elevation of the frame rail. In addition, the first end portion of the leaf spring assembly is preferably positioned above and overlays the outer end portion of the first axle, and the second end portion of the leaf spring assembly is preferably positioned above and overlays the outer end portion of the second axle. This provides a vehicle suspension system which permits a vehicle to be constructed with a low ride height while still providing significant clearance between the underside of the suspension system and the ground.
The bushing preferably has arcuate reinforcing plates each having an arc about a center which intersects a central portion of the leaf spring assembly. As a result, an efficient load transfer path is provided from the leaf springs through the bushings to the frame rails, while resistence to articulation of the axles by the suspension is reduced.
Upper and lower clamping elements may be positioned to apply a clamping force to an elongated section of the central portion of the leaf spring assembly, with the leaf spring assembly positioned between these clamping elements. In a specifically illustrated embodiment, U-bolts are used to interconnect the clamping elements to clamp the leaf spring assembly therebetween. These U-bolts each have a cross-piece or base which, in the illustrated embodiment, is positioned in a respective recess provided in the upper clamping element, with the legs of each U-bolt extending downwardly along the opposite side of the leaf spring assembly and through respective leg receiving apertures in the lower clamping element. In this embodiment, the lowermost arcuate plate of the bushing is mounted to the upper clamp element and captures the bases of the U-bolts in the recesses.
A specialized bushing mounting bracket may be used to couple the bushing to the frame rail. In an illustrated form, the bushing mounting bracket includes a rod supporting portion extending downwardly below the bushing and outwardly at a location below the leaf spring assembly. A first tie rod extends from the rod supporting portion of the bushing mounting bracket to the first leaf spring mount at the outer end portion of the first axle. A second tie rod extends from the rod supporting portion of the mounting bracket to the second leaf spring mount at the outer end portion of the second axle. In addition, the bushing mounting bracket has a body with an upper wall portion having an inner surface positioned adjacent to an outer surface of an upright web of the frame rail for coupling thereto to mount the bushing mounting bracket to the frame rail. An arcuate bushing engaging portion projects outwardly from the wall portion and away from the frame rail. This bushing engaging portion is positioned for coupling to an upper one of the arcuate reinforcing plates of the bushing. The bushing mounting bracket also includes a shelf positioned to lie beneath a lower flange portion of the frame rail. The shelf has an upwardly projecting lip spaced from the inner surface of the wall portion of the bushing mounting bracket. The lower flange portion of the rail, when the bushing mounting bracket is in place, is positioned adjacent to the shelf portion and between lip and inner surface of the wall portion. As a further aspect of the bushing mounting bracket, the rod supporting portion may include first and second downwardly projecting legs separated from one another by a void positioned therebetween. The first and second tie rods may each be mounted to the first and second legs, with the void providing clearance for the rods.
A stop may be mounted to the rod supporting portion of the bushing mounting brackets so as to project upwardly toward the underside of the leaf spring assembly. During normal loading of the vehicle suspension system, the stop is spaced from the underside of the leaf spring assembly. In contrast, if, for example, the rear end of the vehicle is raised for repair purposes, the stop limits the extent to which the suspension may drop downwardly, thereby protecting the bushing. In addition, respective stops may be provided on the frame rail for limiting the extent to which the outer end portions of the first and second axles may be raised relative to one
Crow Frank S.
Fuchs Daniel G.
Hynes Paul R.
Fischmann Bryan
Freightliner LLC
Johnson Brian L.
Klarquist Sparkman Campbell & Leigh & Whinston, LLP
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