Land vehicles – Wheeled – Occupant propelled type
Reexamination Certificate
2002-10-28
2003-07-22
Morris, Lesley D. (Department: 3611)
Land vehicles
Wheeled
Occupant propelled type
Reexamination Certificate
active
06595538
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is directed to a shock absorbing wheel suspension apparatus and related method. Although the preferred embodiment is described with respect to the rear suspension on a mountain bike, persons of ordinary skill in the art will understand that the invention may be readily utilized in other configurations and devices, especially those using chain drive power on a suspended wheel, including (by way of example and not by way of limitation) suspensions for motorcycles, tricycles, four-wheeled vehicles, and other vehicles.
The following table sets forth U.S. patents which may be material to the patentability of the invention:
U.S. Pat. No.
Inventor
Issued
4,789,174
Lawwill
12/88
5,121,937
Lawwill
6/92
5,217,241
Girvin
6/93
5,244,224
Busby
9/93
5,306,036
Busby
4/94
5,409,249
Busby
4/95
5,441,292
Busby
8/95
5,474,318
Castellano
12/95
5,509,679
Leitner
4/96
5,628,524
Klassen et al.
5/97
5,671,936
Turner
9/97
5,678,837
Leitner
10/97
Also, a number of Internet websites currently display bicycles having wheel suspensions. Examples can be seen at the websites for the following companies: Cyber Cyclery, Intense Cycles, Inc., GT Bicycles, Mountain Cycle, Schwinn, and Ventana Mountain Bikes.
Although current bicycle suspension designs typically include shock absorption capabilities that are intended, among other things, to provide comfort and safety and, ideally, to allow the tires to maintain contact with the ground (even on uneven surfaces) and have traction on rough, steep climbs and descents, current designs have a number of inherit faults or shortcomings.
Among other things, suspensions typically permit riders to descend with greater speed, control and comfort. Moreover, although the suspension provides some benefits for climbing (and, as indicated, definitely provides important benefits to descending), many (if not most) current designs are actually generally considered a hindrance to climbing. During climbing, most prior art suspensions “suck” power (as described below); the less kinetically efficient designs typically “suck” the most power during climbing. In addition, many prior art suspension designs are so bulky or contorted that they add undesirable weight to the bicycle, which also “sucks” power from the rider, especially during climbing.
While some of the benefits provided by the invention might be achievable by using idler pulleys and other components, such approaches presumably would add weight (for the extra components) and the additional drag of pulleys would of course require additional energy to propel (from the rider, the engine, etc.)
In addition, it would presumably be difficult (or even impossible) to utilize such a pulley system on a bicycle with otherwise conventional industry standard components (gears, derailleurs, etc.). In other words, such pulley approaches might not be able to use an “off-the-shelf” set of gears.
Several examples of these shortcomings are further discussed below.
1. Pedaling power Loss Due to Drive Torque Induced Suspension Movement (“Torque Reactive” Suspensions).
All current bicycle rear suspensions of which the inventors are aware have a tendency to either compress or extend the rear suspension when subjected to drive chain and wheel drive loads. Designs that compress the rear suspension cause the rider's power to be used for compressing the shock absorber. The potential energy transferred to the shock absorber is dissipated as heat by the damping medium in the shock absorber. Designs that extend the suspension under load waste power by lifting the mass of the bike and rider with each stroke. Designs that attempt to exploit the chain loads to create torque against the suspension create a binding action of the suspension under pedal torque loads, which reduces ride quality and limits compliance-induced traction under hard pedaling.
Because an average human being can generate a maximum of about three quarters (¾) horsepower and can do so for only a very short time, and can generate only about {fraction (1/10)} of a horsepower for extended periods, even small power losses can have a significant effect on the rider and the riding experience. In the designs described in the preceding paragraph, potential energy is typically returned out of phase to the pedals' and cranks' power stroke and is thus wasted as heat dissipated in the damper instead of power used to propel the bicycle forward.
In addition, suspension designs that are torque reactive feel mushy, sluggish and unresponsive to pedaling input.
Also, with a typical rear suspension design, the wheel follows an arc-like path when encountering a bump, forcing the wheel to be displaced in a forward as well as an upward direction (in contrast, and as shown by a comparison of
FIGS. 3 and 6
of the preferred embodiment of the invention, as discussed below, the present invention provides much more nearly vertical wheel motion in response to bumps). Thus, when absorbing shocks, the prior art wheels must travel forward, frequently in an uphill direction. This increases the bump shock force transmitted to the sprung portion of the bicycle because the wheel is not moving perpendicularly away from the bump. It also requires more forward drive energy from the rider to overcome the resulting “rearward” component of such bump forces. Additionally, the suspensions will kickback that motion to the pedals, causing additional wasted energy and muscle irritation and premature fatigue from the uneven loading while pedaling.
This and other of the problems discussed herein are especially acute in human-powered devices such as bicycles, because the human power plant typically provides such low RPM that the jacking or torque reaction happens (and is felt) with each revolution, rather then just “once” as might be experienced under acceleration from an internal combustion engine, for example.
2. Lock Up of the Rear Suspension Caused by Brake Induced Torque.
Almost all current art bicycle rear suspension designs place the anchor for their rear brakes (be it either a disc brake caliper or traditional rim surface caliper type brakes) in a position where the application of brake force causes an extending force or “jacking” to be exerted on the rear suspension. This “jacking” force causes the rear suspension to lose its effectiveness under heavy braking loads, as the jacking may lock out the suspension, and/or cause the rear of the bike to raise, forcing the rider forward and shifting the center of mass over the front wheel, thereby causing instability of the bike and rider. This jacking can manifest itself as “wheel hop” and instability under heavy braking on rough surfaces.
Current suspension designs (as opposed to rigid rear linkages) create this unsafe (or at least difficult-to-control) jacking. Some designs utilizing a disc brake will counter these jacking forces by anchoring the brake forces with a separate member attached to the frame away from the wheel suspension. Although this approach works to eliminate the brake “jacking” problem, it introduces additional weight and components (thus not lending itself to simple design), and may limit the bicycle frame's kinetic responsiveness (which is one of the main points of having a suspension in the first place). Other brake arrangements actually stiffen or even lock out the suspension while braking, even though arguably the most important time for suspension functions are likely demanded while braking for obstacles or rough and technical terrain.
3. Proper Shock Absorber Motion Ratio.
The motion ratio of the bike's shock absorber is critical to proper suspension operation. The motion ratio of the suspension bikes currently on the market runs the range from rapidly rising to rapidly falling. There are major drawbacks as you move toward either end of the spectrum.
A very rapid rising rate causes the suspension to be too soft and active in the initial part of the wheel travel, causing bobbing and wasting pedaling energy while quickly blowing through the initial travel on big bumps and
Ellsworth Anthony S.
Kojima Mike
Ellsworth Anthony S.
Hollrigal Greg S.
Luby Matthew
Morris Lesley D.
Stout, Uxa Buyan & Mullins, LLP
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