Land vehicles – Wheeled – Running gear
Reexamination Certificate
2002-03-16
2004-12-14
English, Peter C. (Department: 3616)
Land vehicles
Wheeled
Running gear
C280S124154, C267S194000, C267S225000
Reexamination Certificate
active
06830256
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A “MICROFICHE APPENDIX”
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to and, in particular, to improvements in the methods and apparatus for using a rebound spring carried on a shock absorber that is intended to utilize the unsprung weight of the wheel/axle system during rebound. More particularly, it is to resist rollover, sway, yaw and other chassis motion.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In the past ten years the numbers of sport utility vehicles “SUV” and pickup trucks have increased dramatically to the point where those vehicles are more popular than the millions of passenger cars on the road. The SUV and trucks inherently have a higher center of gravity (CG) than normal passenger cars due to the need for higher ground clearance for bad weather travel (snow and ice), off-road use and/or for pickup truck payloads. Vehicles with a higher CG have a greater propensity to sway or even rollover during abrupt lane changes and evasive steering maneuvers than the lower normal passenger cars.
One important arrangement of all these vehicles is the method of suspension used. Except for the use of hydraulic shock absorber damping resistance to rebound, all vehicle chassis and body loads are supported on the vehicle axles with various types of suspensions that have springs that resist primarily load and jounce of each wheel axle. No existing suspensions using coil springs, load leaf springs, air springs, torsion bars or rubber blocks suspensions have any other provision for rebound control of the forces due to inertia or gravity type negative suspension loads. Particularly, those rebound forces occurring at the inside wheel during hard cornering or if a wheel drops into a pothole.
Typically, changes in suspension loads while driving straight along a road are caused generally by reactions to bumps, potholes, and roughness encountered by the vehicle wheels during their interaction with the road surface. Thus the suspension springs and associated shock absorbers quell the harshness and movements being transmitted to the body/chassis.
The sway or side to side rolling motions that vehicles experience due to cornering forces, also cause vehicle springs to be loaded or unloaded, depending which way the vehicle is rolling during cornering. Many vehicles have an anti-sway/roll bar installed to help the vehicle body resist the rolling actions. These devices help the vehicle partially resist roll but only as it relates to the body lean, because they are fixed to the sprung mass and leaning with the body. Thus, they can actually reduce the load on the unloaded side of the vehicle. They use the body as a structure to support the torsion bar of the anti sway system transferring wheel jounce motion across to the opposite side. The disclosure herein will obviate the need for anti-sway bars, saving the cost of providing and installing them. Shock absorbers only dampen the bouncing movement of the vehicle wheels and suspension caused by the reaction to road surface, cornering and braking. Thus, the rate of sway may be affected only to a minor degree.
A floating aluminum piston is placed between the fluid moving piston and the end of the shock body. The floating piston has nitrogen gas behind it that is at a preset pressure. This piston is used in racing shocks and other lift type shocks to do two things, first to pressurize the fluid at all times and second to raise the vehicle ride height. It is not practical to fill the entire shock body with fluid on both sides of the fluid piston. This ensures that as the fluid moving piston moves away from the end of the cavity as it would during extension or “rebound” travel, it does not permit a vacuum to form behind the fluid piston and sucking against the shock travel. It maintains a pressure front against the fluid to ensure that it is induced to pass the fluid piston during jounce travel. The fluid piston has holes in it to allow the fluid to pass by it and flexible shims on both sides of the fluid piston are adjusted in strength to set the resistance to flow through the piston during normal movement. Stiffer shims result in higher resistance to the fluid being compressed against them.
All this and the use of nitrogen pressure against the piston are typical of existing shock absorber design. The basic tubular shock absorber is well known to skilled artisans, and is a commodity and is disclosed in numerous patents. The typical shock absorber is designed to dampen motion and with coil over springs adjust the ride height and/or spring stiffness.
U.S. Pat. No. 2,160,541 has a paired spring suspension connected in series to only support load and jounce with the added spring coupled in line with the main spring for increasing the effective spring constant at the extremes of suspension travel. The techniques disclosed in the various embodiments of '541 are in the nature of an overload spring that engages and changes the spring constant at the extremes of wheel travel. There is no spring in '541 connected to specifically resist rebound forces due to diverging motion of the sprung weight to unsprung weight. The disclosure of '541 specifically states that the higher spring constant results in less flex (on page 2 column 1 at lines 6 to 8), “ . . . which opposes any tendency of the vehicle to overturn laterally when negotiating a curve.” In each embodiment of '541 the springs act in unison to control primarily load and jounce and there is no teaching of a particular connection to directly apply rebound reaction of unsprung weight to one of the springs. The graph in '541 showing wheel travel verses spring forces verifies these conclusions. U.S. Pat. No. 5,263,695 discloses a refinement of the '541 teaching that includes a shock absorber for damping motion and an elastic block to ameliorate the transition between first and second springs for carrying the load. In addition to many disclosures in '695 of prior paired spring configurations there is a specific explanation in column 5, lines 1 through 5 as follows:
“The suspension according to the invention produces a comfort level which is higher the more the transition from one stiffness to the other takes place progressively (see the patents cited in the state of the art).”
The state of the art referred to includes prior patents of the same inventor and the acknowledgements of those prior patents clearly identifies the teachings as merely two springs of different stiffness in series. Even in FIG. 7 of '695 the springs are concentrically mounted but act in series, see column 4, lines 8 through 12. At best the structures for multiple springs shown in these patents have differing spring rates to give an allegedly more comfortable ride but do not specifically disclose rebound control.
U.S. Pat. No. 3,830,517 is a motorcycle rear wheel spring suspension wherein a top spring is longer and absorbs upward road shock and a bottom spring absorbs the rider's weight. Nothing is disclosed about resisting rebound with either the top or bottom spring and no attachment of the springs is shown or described that would operate to control rebound of the sprung weight.
U.S. Pat. No. 3,049,359 has a pair of coaxial coil springs designed to maintain ride height by automatic screw adjustment of the smaller and lighter inner tension coil spring. No disclosure of rebound control of sprung weight is made and the inner tension coil spring loadings are varied only in so far as the ride height is less or more than required as such the size and strength of the inner tension spring would be insufficient to transfer the unsprung weight to the chassis and resist rebound. Moreover the working travel of both springs appears to be the same; thus, no rebound control is possible.
No existing suspension system suspends the chassis and/or body between opposing springs to counter load and jounce and reaction and rebound
English Peter C.
Passman Aaron
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