Bicycle rear derailleur

Details Bicycle rear derailleur Bicycle rear derailleur

1993-11-10

1995-01-10

Buiz, Michael Powell

Endless belt power transmission systems or components

Control for variable input to output speed-ratio

Including belt shiftable axially from one to another surface...

F16H 900

Patent

active

053802535

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a bicycle rear derailleur for shifting a chain onto a desired sprocket of a bicycle free wheel (rear gear) assembled as a multiple sprocket comprising a plurality of diametrically different sprockets, and more specifically, relates to one wherein a distance between a guide pulley of the chain guide and each sprocket of the multiple sprocket assembly can be set at an appropriate distance for improved speed change performance.


BACKGROUND ART

FIG. 6 shows a typical conventional bicycle rear derailleur.
This bicycle rear derailleur 1 is arranged so that by using a control mechanism such as a pantograph link mechanism 2, a chain guide 5 having a guide pulley 3 and a tension pulley 4 can be moved axially of a shaft of a multiple sprocket F.
The pantograph link mechanism 2 has a link base 7 to attach to an end plate 6, for example, of a bicycle frame, a forwardly extending pair of inner and outer link members 8, 9, each pivoted at a base end thereof to the link base 7 so as to move laterally of the bicycle, and a movable member 10 pivoted to respective free ends of the inner and outer link members 8, 9. Each of the constituent members 7, 8, 9, 10 of this pantograph link mechanism 2 are arranged and pivoted in a shape of deformable parallelogram, so that when the pantograph link mechanism 2 is deformed, the movable member 10 is translated laterally of the bicycle.
Since the chain guide 5 is mounted to the movable member 10, it is also translated laterally of the bicycle with the movable member 10 as the pantograph link mechanism 2 deforms.
While the bicycle is running, a chain C runs on a rear side of the tension pulley 4, a front side of the guide pulley 3, and then, a rear side of a sprocket of the multiple sprocket F. Therefore, when the guide pulley 3, which supports a portion of the chain immediately before engaging the multiple sprocket F, is moved axially of the multiple sprocket F as described earlier, the chain C is shifted onto another sprocket which positionally corresponds to the moved guide pulley 3.
As described hereinabove, in the bicycle derailleur, the guide pulley 3 is directly responsible for shifting the chain C, and in order to improve shifting response of the chain C, it is necessary for this guide pulley 3 to be positioned at an appropriate distance, not too close to or too far away, from the multiple sprocket F.
Each of the sprockets constituting the multiple sprocket F is arranged so that a diametrically smallest sprocket is placed at a laterally outermost position, and a diametrically larger one is placed more inward laterally of the bicycle. In an attempt to position the guide pulley 3 at an appropriate distance from each of these diametrically different sprockets, a number of proposals have been made conventionally.
One of these is disclosed in the Japanese Patent Publication Sho 42-23486, wherein pivot pins which link the constituent members of the pantograph link mechanism are slanted inward laterally of the bicycle. This is commonly known as the slant pantograph link mechanism. With this arrangement, when the pantograph link mechanism is deformed to move the chain guide inward laterally of the bicycle, the chain guide moves with inclination, or downwardly as well as inwardly. Since this inclination corresponds to an inclination of a line provided by connecting the outer edges of respective sprockets of the multiple sprocket, it is possible to reduce variation in the distance between the guide pulley and respective corresponding sprockets.
There is a problem however: Since the moving direction of the movable member of pantograph link mechanism is fixed, there is no adaptability to different sprocket configurations, for example, when the multiple sprocket is replaced from what is known as a close-ratio type to a wide-ratio type, or in other words, from a sprocket configuration wherein a gear teeth ratio between sprockets is small to another configuration wherein the same is large.
In an attempt to solve this problem, the Japan

REFERENCES:
patent: 4599079 (1986-07-01), Chappell
patent: 5152720 (1992-10-01), Browning et al.

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