Land vehicles – Wheeled – Running gear
Reexamination Certificate
2000-09-06
2002-04-02
Swann, J. J. (Department: 3611)
Land vehicles
Wheeled
Running gear
C267S052000
Reexamination Certificate
active
06364333
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to vehicle suspension systems, and more specifically to a connector installed between a longitudinal leaf spring suspension and the associated axle of the vehicle. The present connector includes a pivot axis normal to the elongate axis of the axle and generally parallel to the elongate axis of the spring, permitting the axle to move angularly and laterally without imposing torsional forces on the leaf spring, thereby eliminating lateral binding of the spring and corresponding reduction in spring rate and travel.
2. Description of the Related Art
While most motor vehicles are adapted for travel over relatively smooth surfaces with only occasional travel over speed bumps, driveway ramps, etc., a relatively large class of vehicles is adapted for travel over relatively rough and unimproved surfaces. Such vehicles are usually constructed as light trucks or sport utility vehicles, and generally have relatively large suspension travel in order to provide for use over rough and unimproved surfaces. While such vehicles have found favor among the general public for recreational purposes, they are also widely used by construction firms, the military, and other users as well.
The two most important considerations in the suspension action of such vehicles are total travel, i. e., the amount of movement from full compression (“bump”) to full extension (“droop”), and articulation, i. e., the difference in travel extremes between diagonally opposite wheels or wheel assemblies at diagonally opposite corners of the vehicle. These characteristics are of critical importance in extreme terrain conditions, as obviously a wheel and tire which is not in contact with the underlying surface, is incapable of providing any tractive force (acceleration, braking, and/or steering) to propel and control the vehicle.
As a result, manufacturers and aftermarket suppliers alike have attempted to develop various solutions for these travel and articulation problems. It will be noted that as suspension travel is increased in any given vehicle, the problem of providing sufficient articulation becomes more critical. Greater suspension travel results in greater angularity in drive lines and axles relative to one another and to the vehicle chassis, creating an even greater problem in avoiding binding somewhere in the system.
This is particularly true in vehicles with solid axle systems, where the suspension elements (springs and shock absorbers) are connected between an axle which extends across the vehicle and the vehicle chassis or frame. While many vehicles adapted for rough terrain usage have independent suspensions with coil springs, a large number of such vehicles (particularly older vehicles) have solid axles (perhaps front and back) suspended by leaf springs, as this system has proven to be extremely durable and reliable.
However, such solid or straight axle drive and suspension systems are difficult to provide with sufficient articulation to correspond with the relatively large wheel travel which may be installed in the system, either by the manufacturer or by means of aftermarket or individually fabricated and installed components. While it is relatively straightforward to provide additional fender clearances, longer and/or taller springs, longer shock absorbers, etc., for increased suspension travel, this increased travel results in interference with the articulation of such solid axle and leaf spring suspension configurations. This is because as the axle articulates angularly and laterally relative to the vehicle chassis, e. g., with the left wheel raised and the right wheel lowered, the resulting angle of the axle produces an angular twist in the leaf spring assembly at each end of the axle.
These leaf spring assemblies are conventionally formed of a series of separate springs of different lengths, laminated together by a corresponding series of shackles or the like. As the distal ends of the spring are secured to the vehicle by lateral pivot bolts or pins, the distal ends maintain the angular orientation of the vehicle about their lateral pivot axes, while the center of the spring, which is bolted to the axle, is twisted to align with the lateral angle of the axle. It will be seen that this results in the twisting of the spring assembly, with resulting binding and resistance to spring travel and movement. It also places severe shear forces at the ends of the spring-to-chassis attachment bolts, leading to their early failure.
Accordingly, a need will be seen for a leaf spring to axle articulating connector which permits a solid axle to articulate angularly and laterally relative to the vehicle chassis, while simultaneously maintaining the linear alignment of the leaves of the leaf spring assembly at each end of the axle and their attachment points to the chassis. The present invention essentially comprises a longitudinally oriented pivot axis positioned between the center of the leaf spring assembly and its attachment to a solid or straight axle in a vehicle. The present invention thus allows full and complete angular movement of the axle relative to the longitudinal axis of the vehicle, while obviating any twisting forces in the leaf spring assembly. The present articulating connector may be used with front and rear wheel drive solid axle systems, with either overslung or underslung axle and spring assemblies.
A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 3,494,609 issued on Feb. 10, 1970 to Henry C. Harbers, Jr., titled “Leaf Spring And Axle Seats,” describes a series of clamps and shims for rigidly securing a leaf spring assembly to a solid axle housing, to preclude misalignment of the axle relative to the spring and vehicle (i. e., “toe-in” and “toe-out”). The Harbers, Jr. attachments teach away from the present invention, as they are expressly configured to prevent any relative movement between the axle and the spring assembly.
U.S. Pat. No. 3,591,163 issued on Jul. 6, 1971 to Richard D. Anderson, titled “Mounting,” describes a plate for attaching a traction bar to a leaf spring suspension for a solid axle housing. The mounting holes for the plate are punched or stamped from the plate, to form a series of noncircular, tapered holes and corresponding scrap components. Each of these scrap components is further modified by removing a portion thereof, which when the components are reassembled with the plate, provide bolt passages therethrough. The stamped scrap components may be oriented in their holes in the plate as desired, thereby positioning the bolt holes as required for different U-bolt and spring dimensions, etc. As in the Harbers, Jr. assembly, the Anderson device teaches away from any movement between suspension components and axle, and is further directed only to longitudinal shifting of the axle, rather than angular movement relative to the vehicle's horizontal axis.
U.S. Pat. No. 3,730,508 issued on May 1, 1973 to Daniel Marian et al., titled “Variable Offset Spring Mounting Block For Load-Bearing Vehicles,” describes an assembly comprising a pair of mating blocks, one of which secures to the axle and the other of which secures to the leaf spring attachment point. The two blocks include mating teeth, holes and pins, or other means for adjusting their mating fit, thereby adjusting the longitudinal position of the axle relative to the spring and vehicle. As in the other devices of the related art discussed above, the Marian et al. device is a rigid assembly when installed, and does not provide for any movement between the axle and spring.
U.S. Pat. No. 3,913,937 issued on Oct. 21, 1975 to William F. Longworth et al., titled “Universal Axle Pad And Clamp Assemblies For Vehicle Suspensions,” describes an assembly for securing a solid axle and leaf spring assembly together. The assembly includes indicia for aligning the axle about its elongate axis, for adjusting the pinion ang
Dunn David R.
Litman Richard C.
Swann J. J.
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