Machine element or mechanism – Elements – Cranks and pedals
Reexamination Certificate
1999-12-27
2001-06-12
Green, Mary Ann (Department: 3682)
Machine element or mechanism
Elements
Cranks and pedals
C074S594100
Reexamination Certificate
active
06244135
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved bicycle drive mechanism, whereby energy transmitted through a pedal crank arm to the mechanism is utilized in a more efficient manner, thereby relieving stress upon the bicycle rider.
2. Description of the Related Art
The bicycle has been a tried and proven method of human powered transportation prior to and throughout the present century. Aside from this fact, in terms of efficiency it is renowned as an engineering feat, elegantly demonstrating the true ingenuity of mankind as a species. With this in mind one must consider it no mere coincidence that experts in this field, Wilbur and Orville Wright, were also the progenitors of manned flight.
An early embodiment of the bicycle employed as a drive mechanism a crank operated first sprocket driving a second sprocket by way of a continues loop roller chain, the second sprocket being affixed to the rear wheel of the bicycle. This basic but common design still enjoys widespread use in our present day. An early improvement to this concept of energy transfer was to employ a multiple gear ratio mechanism within the hub of the smaller driven sprocket thereby allowing the rider a choice of up to three different gear ratios. A relatively recent improvement involves employing a first plurality of drive sprockets of various sizes connected by the roller chain to a second plurality of driven sprockets of various sizes. The chain connecting the two separate sets of sprockets is made to move between any combination of the sprockets by a mechanism known as a derailer. In this manner a larger variety of gear ratios are available, ranging from a very low ratio to a relatively high ratio. Other improvements have served to facilitate the ease of operating the above mentioned mechanisms, or producing the bicycle of lighter stronger alloys and comfort enhancing schemes. All of these types of improvements address efficiency somewhat, but to a lesser degree. However, with all of the prior art improvements in the field of bicycle drive mechanisms, which incidentally are in the public domain, none have yet solved the most basic problem, which is utilizing energy transmitted by human muscle tissue in a most advantageous yet simple manner. The improved bicycle drive mechanism disclosed henceforth will overcome this disadvantage and thereby provide a simple solution long sought in the art.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a novel bicycle drive mechanism, whereby energy transmitted to the mechanism will be converted to motion in a simple and efficient manner.
It is another object of the invention to provide a bicycle drive mechanism wherein complexity is substantially minimized, thereby producing an economic benefit in construction.
The object of the present invention is fulfilled by providing an apparatus and method for directing the energy transmitted via a pedal crank to a drive sprocket which possesses the ability to store energy. The stored energy is gradually released as momentum increases, thereby reducing muscle strain during the peak load conditions. The apparatus comprises a pedal crankshaft component, a first toothed sprocket, a bearing disposed upon one face of the sprocket, which the crankshaft extends through, and a flat spiral wound torsion spring, otherwise known as a power spring. By affixing the first sprocket to the outer race of the bearing which has its inner race affixed upon the crankshaft, the sprocket and crankshaft are therefore capable of rotating independently of one another. The power spring, of a predetermined torque rating, is secured at a central point to the crankshaft and at an outer point to the first sprocket. The first sprocket is connected by a chain to a second or driven sprocket which is affixed to the rear wheel of the bicycle in the conventional manner. When force is applied upon the crankshaft, energy is first stored in the power spring proportional to the load, then gradually released as inertia is overcome and momentum increases. Any load can be stored in the power spring at any given moment with little strain upon the rider, therefore it is not required for the rear driven sprocket to be smaller than the drive sprocket as is customary in the art. In fact it is entirely possible for the driven sprocket to be of equal size.
Accordingly, the above summarized bicycle drive mechanism is intended to be a simple and cost effective alternative to the complex, high maintenance, and expensive multiple sprocket bicycle drives of contemporary times. Furthermore, it will allow the effect of multiple gear ratios with the use of only one drive sprocket and one driven sprocket, thereby eliminating the disadvantages of the prior art.
REFERENCES:
patent: 769594 (1904-09-01), Dould
patent: 4753127 (1988-06-01), Baumann
patent: 5426997 (1995-06-01), Brion
patent: 176493 (1905-04-01), None
patent: 326493 (1903-05-01), None
patent: 333787 (1903-12-01), None
patent: 1444 (1904-01-01), None
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