Endless belt power transmission systems or components – Positive drive pulley or guide roll – And additional coaxial surface for engaging same belt in...
Reexamination Certificate
1999-03-03
2001-01-23
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Positive drive pulley or guide roll
And additional coaxial surface for engaging same belt in...
C474S902000
Reexamination Certificate
active
06176798
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to bicycle drive mechanisms and, more particularly, to a multiple sprocket assembly for a bicycle which includes a large number of freewheel sprockets.
FIG. 1
is a diagram illustrating a typical bicycle chain drive mechanism. As shown in
FIG. 1
, crank arms
1
having pedals
3
are rotatably coupled to a bicycle frame
2
. A chainwheel assembly C comprising a plurality of sprockets, for example, C
1
and C
2
, are connected to crank arms
1
so that rotating pedals
3
in a circular manner causes sprockets C
1
and C
2
to rotate together with crank arms
1
. A freewheel assembly F comprising a plurality of sprockets F
1
, F
2
, etc. are mounted to the rear wheel of the bicycle (not shown), and a chain
4
selectively engages one of the chainwheel sprockets and one of the freewheel sprockets. A front derailleur
5
having a chain guide
6
is provided to switch the chain among the plurality of chainwheel sprockets, and a rear derailleur
7
having a guide pulley
8
and a tension pulley
9
is provided to switch the chain among the plurality of freewheel sprockets.
It is desirable to increase the number of sprockets, particularly in the rear freewheel, to provide the bicyclist with a greater choice of gears. However, the amount of lateral space in which to mount the chainwheel and/or freewheel is limited by the design of the bicycle and accepted design standards. Thus, in order to fit more sprockets into the available space, it is usually necessary to decrease the spacing between the adjacent sprockets. On the other hand, the minimum spacing between adjacent sprockets is limited by the width of the chain.
FIG. 2
is a top view of a segment of the conventional chain
4
. A typical chain has pairs of outer links
10
A and
10
B which alternate with pairs of inner links
11
A and
11
B, wherein each pair of outer links
10
A and
10
B is connected to a corresponding pair of inner links
11
A and
11
B using a press-fit connecting pin
12
. More specifically, the ends of each outer link
10
A and
10
B and the ends of each inner link
11
A and
11
B have openings for receiving connecting pin
12
therethrough. The corresponding ends of one pair of outer links
10
A and
10
B are aligned with the ends of an associated pair of inner links
11
A and
11
B, with the inner links
11
A and
11
B disposed laterally inwardly of the outer links
10
A and
10
B, so that the openings in the ends are aligned with each other. The ends of inner links
11
A and
11
B include flange sections
11
C and
11
D which abut each other and define the openings of inner links
11
A and
11
B. A roller
13
is disposed between the pair of inner links
11
A and
11
B and is rotatably supported by flange sections
11
C and
11
D. The connecting pin
12
passes through the opening in each link end
10
A,
10
B,
11
A, and
11
B such that the connecting pin
12
is press fit in the outer link ends
10
A and
10
B.
The lateral width of a typical chain
4
thus equals the top width of two outer links
10
A and
10
B plus the top width of two inner links
11
A and
11
B plus the width of the roller
13
(which is approximately equal to the width of the flange sections
11
C and
11
D). As a result, the number of sprockets in the multiple freewheel assembly is limited accordingly. More specifically, the minimum spacing between adjacent sprockets is equal to the thickness of one inner chain plate plus the thickness of one outer chain plate plus the thickness of the laterally projecting portion of the connecting pin plus a small free area to avoid binding of the chain, the sum of which is approximately equal to 2.8 millimeters.
SUMMARY OF THE INVENTION
The present invention is directed to a bicycle drive mechanism which includes a large number of freewheel sprockets, for example, ten or more and preferably fourteen freewheel sprockets. A very narrow chain may be used with the freewheel sprocket cluster to maximize the number of sprockets which can be mounted together.
In one embodiment of the present invention, a plurality of sprockets are coaxially mounted together, wherein a spacing between each pair of adjacent sprockets is less than a thickness of at least one of the plurality of sprockets. In another embodiment of the invention, a plurality of sprockets are coaxially mounted together, wherein a spacing between each pair of adjacent sprockets is less than or equal to approximately 2.0 millimeters. In yet a further embodiment of the present invention, at least ten sprockets are coaxially mounted together to form a first free side sprocket surface facing laterally outwardly and a second free side sprocket surface facing laterally inwardly. A spacing between the first free side sprocket surface and the second free side sprocket surface is less than or equal to approximately 50 millimeters.
In all such embodiments, the sprocket cluster may include a mounting member having a plurality of arms radially extending from a centrally located boss. A first sprocket may be formed as one piece with the mounting member and disposed at the radially outward ends of the plurality of radially extending arms, and a plurality of second sprockets may be mounted to the plurality of radially extending arms coaxially with the first sprocket. If desired, the mounting member may include a plurality of ledges, wherein each second sprocket is mounted on one of the plurality of ledges. A plurality of third sprockets may be mounted to the mounting member so that the third sprockets extend laterally outwardly relative to an outer lateral side surface of the boss. The boss also may include an inner lateral side surface disposed laterally outwardly relative to the first sprocket so that the sprocket cluster may be mounted to a hub such that at least the first sprocket is positioned laterally inwardly of an outer side surface of one of the hub flanges.
The sprocket cluster may be used together with a very narrow chain which accommodates the narrow spacing of the sprockets. Such a chain may include a plurality of intermediate links, a plurality of pairs of outer links, and a plurality of fasteners. Each fastener connects an end of one of the plurality of intermediate links between a corresponding pair of outer links so that the plurality of intermediate links alternate with the plurality of pairs of outer links. Each intermediate link defines a recess between each end thereof for receiving a sprocket tooth therein so that each intermediate link performs the function normally performed by the roller and corresponding pair of inner links in a conventional chain.
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Bucci David A.
Deland James A.
Kaness Matthew A.
Shimano Inc
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