Land vehicles – Wheeled – Running gear
Reexamination Certificate
2001-12-07
2003-07-01
Dickson, Paul N. (Department: 3616)
Land vehicles
Wheeled
Running gear
C280S124178, C280S681000
Reexamination Certificate
active
06585286
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to a vehicle suspension and particularly to a vehicle suspension adapted for the vocational vehicle market. The invention reduces the manufacturing cost and overall system weight of vehicle suspensions.
FIG. 1
illustrates a known vehicle suspension designated
20
designed to support vehicle frame rails (not shown) positioned on opposite sides of a vehicle center line in spaced relation above vehicle axles (not shown) of a tandem axle configuration for the vehicle. It will be appreciated that vehicle suspension components positioned on one side of the vehicle to support the vehicle frame rail of that side above its adjacent ends of the axles are duplicated on the other side of the vehicle to support the opposite vehicle frame rail above the opposite ends of the vehicle axles.
Vehicle suspension
20
includes an equalizing beam
22
extending longitudinally between the ends of the axles on a particular side of the vehicle. Equalizing beam
22
is connected to a vehicle frame rail bracket
24
by way of, among other things, bolster springs
26
.
In this known vehicle suspension
20
, the bolster springs
26
are positioned coincident with the wind up center of equalizing beam
22
to eliminate axle load transfer during braking and acceleration of the vehicle. In this arrangement, the bolster springs
26
are positioned inboard of the centerline of equalizing beam
22
. This positioning of the bolster springs
26
creates a moment imbalance, which necessitates the use of a cross tube
28
to resist the moment forces.
Cross tube
28
extends laterally between the equalizing beams
22
positioned on opposite sides of the vehicle. The use of this cross tube increases manufacturing cost and overall system weight of the vehicle suspension. Additionally, use of this vehicle suspension requires an equalizing beam
22
that is unduly large and heavy, thereby translating into additional cost of the vehicle suspension, and in the case of commercial vehicles, reducing payload capacity.
FIG. 2
illustrates another prior vehicle suspension generally designated
30
designed to eliminate the shortcomings of the vehicle suspension
20
shown in
FIG. 1
, particularly those shortcomings that result from the moment imbalance due to the position of the bolster springs thereof. For the vehicle suspension
30
, its bolster springs
32
are positioned above the equalizing beam
34
in a manner such that they are symmetrically positioned with respect to the vertical plane extending longitudinally through the center line of the equalizing beam. In other words, the bolster springs
32
are symmetrically inboard and outboard of the beam, thereby eliminating the requirement of a cross tube.
By positioning the bolster springs
32
vertically above the equalizing beam
34
, however, the suspension
30
couples the vertical and articulation motions with the fore-and-aft motion. This coupling creates axle load transfer under braking and acceleration. It also reduces vehicle ride comfort.
One unique feature of the suspension disclosed herein is the repositioning of rubber bolster springs for performance and enhancement. The bolster spring pairs are positioned about a suspension walking beam on opposite sides thereof. This permits the uncoupling of the articulation and vertical motions of a walking beam suspension from the induced fore/aft motion by repositioning the rubber bolster springs coincident with the windup center of the walking beam. It also eliminates the necessity of a cross tube, further reducing cost and weight from the suspension system.
The use of split bolster springs provides the benefit of the bolsters being coincident with the windup center of the beam without the penalty of either a cross tube to absorb the moment imbalance of inboard bolsters, or the penalty of an excessively large beam to span outside of the bolsters. The split bolster spring arrangement uncouples the vertical and articulation motions from induced fore/aft motions, resulting in improved vehicle braking and ride characteristics.
The split bolster arrangement allows the bolsters to be lowered to straddle the beam, thereby situating their line of action coincident with the beam centerline. This eliminates the fore/aft motion induced by vertical or articulation motion. Also, because the bolster pairs are symmetrically inboard and outboard of the beam, there is no moment imbalance and therefore no requirement for a cross tube.
The fundamental principle behind the inherent benefits of the split bolster configuration is the static equilibrium equation, (i.e., &Sgr;M=0). By lowering the bolster line of action to the beam centerline, the moment arm has been reduced to zero, thus eliminating fore/aft motion. By positioning the bolster pair symmetrically straddling the beam, the resultant moment is zero.
The addition of molded-in studs for assembly reduces the width of the part, allowing the outboard bolster springs to be positioned alongside the beam without interference to the tire. This increases the quantity of rubber bolsters required per suspension resulting in improved economies of scale, thereby reducing unit cost. As a result, there is enhanced suspension articulation (increased range of motion) and ride quality.
Referring back to
FIG. 2
, the fabricated equalizing beam
34
of the vehicle suspension
30
illustrated therein includes two symmetric channeled sections
36
,
38
that must be projection-welded together at a center weld
40
. The projection-welding process requires a special set up and often suffers from a blow-through condition in production. The center weld is discontinuous and positioned on the bottom side of fabricated equalizing beam
34
, which can result in stresses that may contribute to tensile load conditions. The center weld also makes it difficult, if not impossible, to attach brackets on beam
34
at a center location thereof. As shown, the bolster springs
32
are connected to the equalizing beam
34
by downwardly extending brackets positioned on longitudinally opposite sides of center weld
40
.
Another unique feature of the disclosed suspension is that a fabricated walking beam is designed in a simplified manner to eliminate weld complexity. In the fabricated beam, fewer components and improved weld conditions are present. The main channel is formed by a U-shaped one piece structure, rather than the two piece design used in conventional fabricated beams. This results in a continuous weld condition on the top surface of beam, eliminating the need for the discontinuous center weld, which is often difficult to produce. Additionally, a simple fabricated bracket has been attached to the walls of the main channel on both the inboard and outboard walls to permit mounting of the split pair bolster spring assembly. Because this simple bracket design is common to both sides of the beam, it eliminates part complexity.
The fabricated beam reduces actual welding time, in addition to the number of setups, and time required for each setup. In addition, the positioning of the weld at the top of the beam permits the weld to work in compression rather than tension, providing greater durability.
The fabricated beam eliminates the need for a center weld, thereby improving the inherent strength of the beam and improving manufacturability. Positioning of the welds at the top of the beam places the welding in a compression load condition, making it an inherently durable structure.
With regard to the fabricated beam, there is a reduced number of components. It is also reduced weight (improved design optimization). Also, the designed “racetrack” feature on the A-shaped side brackets improves welding over prior art beams.
With prior vehicle suspensions, a different saddle must be maintained for use on each particular vehicle frame configuration. This requires a unique saddle to be designed, developed, maintained and stored for each unique vehicle frame configuration. It will be appreciated by those skilled in the art that this enduring problem has i
Adema Daniel R.
Dudding Ashley T.
Gottschalk Michael J.
Jable Roger D.
Wall Christopher B.
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
Dickson Paul N.
Ilan Ruth
The Boler Company
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