Continuously variable drivetrain

Abstract

Drivetrains and frames for vehicles, equipment, machines, etc. Some embodiments of the drivetrains and frames are particularly suited for human powered machines, such as bicycles and exercise equipment. In some embodiments, a drivetrain includes a reciprocating crank coupled to a crank pivot. A lever couples to the crank via a lever pivot positioned on the crank. A lever stop cooperates with a lever guide surface to guide a motion of the lever as the lever pivots about the lever pivot. The lever and / or the crank are operably coupled to a drive pulley, idler pulley, and / or compound pulley. In some embodiments, a drive cable operably couples the lever and / or the crank to the drive pulley, idler pulley, and / or the compound pulley. In one embodiment, one or more pulleys couple to the lever's distal ends. In some embodiments, the drivetrain includes a wheel hub adapted to receive torque from the crank via a drive pulley.

Description

RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Patent Application 60 / 799,601, filed on May 11, 2006.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates generally to mechanical power transmission systems and more specifically to continuously variable drivetrains. [0004] 2. Related Art [0005] Pulley and belt systems used to transmit mechanical energy are very common and have been used extensively in industry for decades. Their benefits of low cost, reliability, modularity, and high efficiency have created thousands of applications. Typically, two pulleys are used, although three, four, five, or more pulleys may be employed. Generally one belt or cable is used, although systems with multiple belts are not uncommon, such as those used in automobiles. With these systems, two or more pulleys have two or more annular grooves that are designed to accommodate two or more belts. Pulleys can be made from steel, alu...

AI Technical Summary

Benefits of technology

[0018] In some systems the idler pulley is eliminated and the drive cable terminates at and is attached to the crank. This has the effect of reducing the speed at which the drive pulley rotates. In other systems two or more idler pulleys are attached to each crank, which increases the speed at which the drive pulley rotates.

Problems solved by technology

All of these drivetrains suffer from a loss of kinetic energy at the end of each stroke.

Linear drive systems in human powered vehicles have been attempted many times. However, they are not as efficient as commonly used drivetrains, such as sprocket and chain systems used on bicycles, due to the loss of kinetic energy at the end of each stroke.

Many of the human powered linear drive systems are also complex, and each gear, bearing, pulley, cable, chain, or sprocket used in the drivetrain reduces efficiency.

The complex systems are also heavy, and weight is a significant factor in human powered vehicles because it increases inertia and power requirements.

Complex systems are also more expensive and more prone to breaking.

However, power is only efficiently created through about 60 degrees of the stroke, and only becomes very efficient for about 30 degrees of the 360 degree rotary stroke.

This stroke also creates two large torque spikes per revolution.

However, the majority of people are not comfortable pedaling at a high speed and consequently do not maintain a cadence which maximizes the efficiency inherent in a bicycle's rotary stroke.

Further, the most common complaint from individuals riding bicycles is discomfort created by the bike seat.

Recent studies showing that bicycle riding contributes to impotence and other health problems aggravate the discomfort problem caused from bike seats.

However, maximizing the efficiency inherent in the bicycle drivetrain requires that the user stay seated while pedaling.

The second most common complaint among bicycle users is difficulty when shifting.

While this is rarely a problem with avid cyclists, infrequent users routinely shift in the wrong direction, shifting to a higher gear when starting up a hill, or vice versa.

This problem can lead to the chain coming off of a sprocket, binding of the chain, a broken chain, and in rare cases the user getting injured in a fall.

The problem frustrates enough people that it reduces the percentage of the population that ride a bicycle.

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