Multi-speed transmission

Details Multi-speed transmission Multi-speed transmission

1997-11-28

1999-11-02

Marmor, Charles A

192 clutches and power-stop control

Clutches

Velocipede free wheel

743375, 74354, 280260, F16D 2300, F16H 334

Patent

active

059752661

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a multi-speed transmission for transmitting power between a pair of shafts. In particular, the present invention relates to a multi-speed transmission wherein a uni-directional free wheeling mechanism is provided between a gear and its shaft so that the gear rotates freely about its shaft when the gear rotates in a preselected direction relative to the rotation of its shaft and so that the gear is locked to its shaft at all other times. As a result, only one gear set transmits power from an input shaft to an output shaft when a plurality of gears of the input shaft are interconnected to a plurality of gears of the output shaft.
Transmissions are utilized in a wide variety of vehicles and stationary equipment to transmit power and to change rotational speeds between input and output shafts. Generally, power is supplied to the input shaft either mechanically or non-mechanically. In applications where power is mechanically applied to the input shaft, a clutch mechanism is usually required to interrupt the transmission of power and to shift gear speeds.
Bicycles are examples where the power supply is provided to the input shaft by non-mechanical means. As a result, the rotation of the input shaft may be easily interrupted without a clutch mechanism. Bicycles typically include chain derailleur mechanisms for shifting a drive chain from one sprocket to an adjacent sprocket to change speed ratios. Most multi-speed bicycles have derailleurs and multiple sprockets at both the front pedal hubs and rear wheel hubs to provide a variety of speed ratios. Furthermore, most chain sprocket systems may be shifted under full power.
However, chain and sprocket systems suffer from several key disadvantages. The multiple sprockets at both the front pedal hubs and the rear wheel hubs are interconnected by the drive chain which extends along a substantial length of the bicycle. As a result, chain and sprocket systems are difficult to house or enclose. Consequently, the chain and sprockets are susceptible to damaging impacts and are exposed to road elements such as dirt and water. Damaging impacts may cause the derailleur mechanisms or sprockets to become bent or misaligned which may impair shifting between sprockets. Moreover, road elements may also come in contact with the derailleur, chain or sprocket to hamper shifting or even damage the components. As a result, the performance of chain and sprocket systems becomes impaired unless the chain and sprocket systems are periodically cleaned and adjusted.
In addition, chain and sprocket systems have inherent design limitations which limit the effective number of speed ratios which may be provided. As a result, chain and sprocket systems do not provide as many speed ratios as indicated by their conventional designations. For example, a bicycle having three sprockets at the front pedal hub and seven sprockets at the rear wheel hub is conventionally designated as a "21 speed" bicycle. Although the bicycle has 21 sprocket combinations, the "21 speed" bicycle actually provides only 11 speed ratios as illustrated by Table 1. Table 1 shows twenty-one sprocket combinations and their associated speed ratios for a typical "21-speed" bicycle. Table 1 also shows the percent of change between speed ratios of adjacent sprocket combinations.


TABLE 1 ______________________________________ Speed Ratios and Percent of Change of "21-Sprocket Combination" Chain and Sprocket System Pedal Hub Sprocket Teeth 48 38 28 Rear Percent Rear Percent Rear Percent Hub of Hub of Hub of Teeth Ratio Change Teeth Ratio Change Teeth Ratio Change ______________________________________ 30 3.69 15.4 26 3.20 13.3 23 2.82 30 2.92 17.6 15.4 20 2.40 26 2.53 15.0 13.3 17 2.09 23 2.24 30 2.15 13.0 17.6 15.4 15 1.85 20 1.90 26 1.87 15.4 15.0 13.3 13 1.60 17 1.65 23 1.65 13.0 17.6 15 1.46 20 1.40 15.4 15.0 13 1.27 17 1.22 13.0 15 1.08 15.4 13 0.93 ______________________________________ sprocket

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