Land vehicles – Wheeled – Occupant propelled type
Reexamination Certificate
2001-03-21
2003-04-01
DePumpo, Daniel G. (Department: 2611)
Land vehicles
Wheeled
Occupant propelled type
Reexamination Certificate
active
06540244
ABSTRACT:
TECHNICAL FIELD
The present invention primarily relates to a driving mechanism for a human-powered vehicle such as a bicycle, a wheelchair, a boat, or a human-powered airplane, or a human-powered machine comparable to a human-powered vehicle, for example, a muscle training machine.
BACKGROUND ART
The driving mechanism for a bicycle and the driving mechanism for a leisure recreational pedal boat are identical in principle. Both driving mechanisms comprise a rotational axle, two cranks, or the left and right cranks, and a pair of pedals. More specifically, the two cranks are rendered different in rotational phase by 180°, with one end of each crank being fixed to the rotational axle at a right angle. The other end of each crank is provided with a shaft, which is anchored to the crank at a right angle, and around which a pedal is rotationally fitted. Torque is generated as an operator steps on the pedal, and this torque is used to rotate the propelling means, such as a wheel, a propeller, or the like, of a human-powered vehicle to move the vehicle. In recent years, there have appeared a tricycle and a four-wheel-cycle, in addition to a bicycle, and they seem to have been used even for competitive sports, in Europe and the United States. However, the driving mechanism for a human-powered vehicle has not changed at all in principle.
A bicycle is very widely used as means for recreation, means for commuting to and from school or work, and means for competition, and therefore, the bicycle industry is very large. Here, the present invention will be described with reference to a bicycle for the sake of simplicity.
A bicycle has been developed in accordance with its usage, and therefore, there are many kinds of bicycles different in structure and appearance. As far as the present invention is concerned, which relates to a driving mechanism for a human-powered vehicle, there are bicycles equipped with a speed changing mechanism for improving a bicycle in speed and climbing performance. There are various speed changing mechanisms. Basically, they comprise a plurality of sprockets attached to a follower axle, that is, the rear wheel axle (hereinafter, this type of sprocket will be referred to as “follower axle sprocket”), and only a single sprocket attached to the driving axle by a chain, whereas some of them comprise a plurality of sprockets attached to the driving axle (hereinafter, this type of sprocket will be referred to as “chain ring”), and the aforementioned follower axle sprockets, which are connected to each other by a chain. Also widely used in the field of a human-powered vehicle are driving mechanisms equipped with a planetary gear mechanism attached to the follower axle. It should be noted here that in this patent application, the human-powered vehicle driving mechanism means a driving mechanism for transmitting human power to the speed changing mechanism of a human powered vehicle, or the propelling means, for example, a wheel, a propeller, and the like, of a human-powered vehicle.
In principle, a speed changing mechanism does not improve energy conversion efficiency, regardless of its configuration. In other words, it does not increase the total amount of the power transmitted to a propelling means (bicycle rear wheel, boat propeller, and the like), or reduce the total amount of energy consumed by a driver per hour.
If an attempt is made by a bicycle rider to climb a slope using the same speed increasing ratio as that used when the rider is running on flat land, a □larger force is necessary, and whether or not the rider can continue riding the bicycle is determined by the strength of the legs of the rider. To the rider, a speed changing mechanism is an apparatus for trading the speed of applying force for the applied force, or an apparatus for optimizing the balance between speed of applying force and the applied force. In other words, if the muscular force becomes insufficient upon uphill riding, the speed changing mechanism is down-shifted to reduce the speed increasing ratio, allowing the muscles to move at a higher speed with a smaller amount of force, and yet producing the same amount of power. However, reducing the speed increasing ratio below a certain level is meaningless. That is, as the speed increasing ratio is reduced in order to keep the bicycle running, the rider must pedal faster to rotate the driving axle faster in reverse proportion to the decrease in the speed increasing ratio, which in turn causes the rider to reach his or her limit in physical capacity, and also increases the friction and/or vibrations for which the bearings and chain of the driving mechanism are responsible. Eventually, it becomes impossible for the rider to keep the bicycle balanced to continue riding.
The provision of a speed changing mechanism does not guaranty increase in the power input. Thus, it is obvious that there is a limit in the improvement in slope climbing performance. Therefore, a means for increasing the power input by a rider has been desired. Here, the power input by a rider means the amount of the power (amount of work per unit of time) transmitted from the rider of a bicycle, that is, a human-powered vehicle, to the bicycle through the driving mechanism of the bicycle. In a speed changing mechanism, the revolution of its output shaft is in inverse proportion to the amount of the torque output through the output shaft, the product of the two (revolution of the output shaft and the amount of the torque output through the output shaft) remains constant. In other words, a speed changing mechanism allows the speed increasing ratio, that is, the balance point between the muscular speed and force, to be changed in accordance with the physical capacity of a rider and the riding conditions, in the direction to allow the rider to feel more comfortable. In principle, however, a speed changing mechanism does not change the overall amount of the power input by a rider, and therefore, the overall amount of the power output through the output shaft does not change.
Changing the length of a crank results in a trade-off between the speed at which a rider moves his or her muscles, and the amount of muscular force generated by him or her per pedaling stroke. Optimizing the crank length sometimes results in a small amount of increase in output, but this does not mean increase in input.
There are a certain number of inventions regarding the above described driving mechanism for a human-powered vehicle, for which patent applications have been submitted (U.S. Pat. Nos. 4,125,239, 4,706,516, 4,807,491, and the like). According to them, the cranks of a bicycle are configured so that they can be lengthened or shortened, and the rotational phases of the cranks are synchronized with the lengthening or shortening of the cranks with the use of a planetary gear based mechanism or a cam based mechanism so that the cranks become longest when they are horizontally extending forward to increase the amount of the maximum torque input by the rider.
In the case of the above described driving mechanism for a human-powered vehicle, as one of the pedals moves past the position where the crank to which the pedal is attached is horizontal, it enters a part of its rotational range in which the crank to which the pedal is attached begins to shorten. In this rotational range of the pedal, the force which acts in the radial direction of the locus of the pedal shaft, that is, a component of the force input by the rider through the pedal, drastically increases and resists the shortening of the crank, interfering with the rotation of the crank.
Even in the case of the human-powered vehicle driving mechanism described above, as long as the force applied to a pedal is always made to act tangential to the locus of the pedal shaft, this force does not interfere with the rotation of the crank. Actually, however, the ankle joints, knee joints, and hip joints, are limited in their ranges of movement, and therefore, the force applied to the pedal always acts downward in the virtually vertical direction regardless of
DePumpo Daniel G.
Fitzpatrick ,Cella, Harper & Scinto
Luby Matthew
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