U.S. patent application number 15/463871 was filed with the patent office on 2017-07-06 for motion transmission system of a bicycle.
This patent application is currently assigned to Campagnolo S.r.l.. The applicant listed for this patent is Campagnolo S.r.l.. Invention is credited to Maurizio Valle.
Application Number | 20170190382 15/463871 |
Document ID | / |
Family ID | 40076613 |
Filed Date | 2017-07-06 |
United States Patent
Application |
20170190382 |
Kind Code |
A1 |
Valle; Maurizio |
July 6, 2017 |
MOTION TRANSMISSION SYSTEM OF A BICYCLE
Abstract
A bicycle freewheel body and sprocket assembly is provided. The
freewheel body has a predetermined axial width. The sprocket
assembly has at least eleven sprockets of various diameters that
are arranged on the freewheel body with a largest diameter sprocket
and a smallest diameter sprocket forming end sprockets of the
sprocket assembly. Each of the end sprockets has an outer face and
the respective outer face of each end sprocket faces in an opposite
directions and the outer faces are spaced from each other along the
freewheel body predetermined axial width. An assembly of at least
eleven sprockets has an overall axial width measured between
respective outer faces of end sprockets in the assembly that is no
greater than 40.5 mm. A chain is comprised of an alternating
succession of inner and outer links, connected to each other at
respective connection ends.
Inventors: |
Valle; Maurizio; (Vicenza,
IT) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Campagnolo S.r.l. |
Vicenza |
|
IT |
|
|
Assignee: |
Campagnolo S.r.l.
Vicenza
IT
|
Family ID: |
40076613 |
Appl. No.: |
15/463871 |
Filed: |
March 20, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13279834 |
Oct 24, 2011 |
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15463871 |
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12187560 |
Aug 7, 2008 |
8454461 |
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13279834 |
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13740636 |
Jan 14, 2013 |
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12187560 |
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12187560 |
Aug 7, 2008 |
8454461 |
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13740636 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B62M 9/10 20130101; F16D
41/24 20130101; B62M 9/12 20130101; F16H 9/24 20130101; F16H 9/06
20130101; F16G 13/06 20130101 |
International
Class: |
B62M 9/10 20060101
B62M009/10; B62M 9/12 20060101 B62M009/12; F16H 9/24 20060101
F16H009/24; F16G 13/06 20060101 F16G013/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 9, 2007 |
IT |
MI2007A001660 |
Claims
1. A bicycle freewheel body and sprocket assembly wherein: the
freewheel body has a predetermined axial width, an outer surface
that is configured to mate with one or more sprockets of the
sprocket assembly, and an internal surface selected to mate with a
hub associated with a bicycle rear wheel; and, the sprocket
assembly has at least eleven sprockets of various diameters that
are arranged on the freewheel body with a largest diameter sprocket
and a smallest diameter sprocket forming end sprockets of the
sprocket assembly, each of the end sprockets has an outer face and
the respective outer face of each end sprocket faces in an opposite
directions and the outer faces are spaced from each other along the
freewheel body predetermined axial width; an assembly of at least
eleven sprockets, that has an overall axial width, measured between
respective outer faces of end sprockets in the assembly, that is no
greater than 40.5 mm; and, a chain comprised of an alternating
succession of inner and outer links, connected to each other at
respective connection ends, each of the links comprising inner and
outer plates that are arranged parallel to each other, the two
plates of both the outer links and the inner links being spaced
apart from each other to define between the two plates a void space
that receives at least one tooth of at least one of the
sprockets.
2. The bicycle freewheel body and sprocket assembly according to
claim 1, wherein at least one tooth of at least one sprocket has a
maximum thickness that is no greater than 1.7 mm.
3. The bicycle freewheel body and sprocket assembly according to
claim 2, wherein the maximum thickness is no greater than 1.6
mm.
4. The bicycle freewheel body and sprocket assembly according to
claim 1, wherein the sprockets vary in size and a distance between
teeth of least two consecutive sprockets of the assembly is at
least equal to an average thickness of the sprockets.
5. The bicycle freewheel body and sprocket assembly according to
claim 4, wherein the distance between the teeth sprockets of the
assembly is at least equal to a thickness of any single
sprocket.
6. The bicycle freewheel body and sprocket assembly according to
claim 4, wherein the distance between the teeth is no greater than
2.2 mm.
7. The bicycle freewheel body and sprocket assembly according to
claim 4, wherein sprockets with the smallest diameter are arranged
at greater distances apart than sprockets with the largest
diameter.
8. The bicycle freewheel body and sprocket assembly according to
claim 7, wherein the sprockets with the smallest diameter are at a
distance apart lower than or equal to 2.5 mm.
9. The bicycle freewheel body and sprocket assembly according to
claim 1, wherein at least six consecutive sprockets have a number
of teeth that differs by one from that of at least one adjacent
sprocket.
10. The bicycle freewheel body and sprocket assembly according to
claim 9, wherein the consecutive sprockets are at least seven in
number.
11. The bicycle freewheel body and sprocket assembly according to
claim 10, wherein the consecutive sprockets are at least eight in
number.
12. The bicycle freewheel body and sprocket assembly according to
claim 11, wherein the consecutive sprockets are at least nine in
number.
13. The bicycle freewheel body and sprocket assembly according to
claim 9, wherein the at least six consecutive sprockets comprise a
sprocket with eighteen teeth.
14. Bicycle comprising a bicycle freewheel body and sprocket
assembly according to claim 1.
15. A motion transmission system including a sprocket assembly of
at least eleven sprockets defining a sprocket assembly width
between respective outer faces of end sprockets of the sprocket
assembly, wherein the sprocket assembly mounts to a hub that
rotates about a rotation axis and a predetermined axial distance
being defined on the hub between a first plane, substantially
perpendicular to the rotation axis, comprising at least one point
of attachment seats for spokes closest to a freewheel body of the
hub, and a second plane, substantially perpendicular to the
rotation axis and defined at a frame attachment portion, wherein
the sprocket assembly width is less than, or equal to, the
predetermined axial distance, wherein a chain that engages the
sprockets has a maximum thickness in a direction of the rotation
axis between and including 4.6 mm and 5.8 mm, and wherein the chain
comprises an alternating succession of outer and inner links,
connected to each other at respective connection ends, each of the
links comprising two respective plates arranged parallel to each
other, the two plates of both the outer links and the inner links
being spaced apart from each other to define between the two plates
a void space that receives a tooth of a sprocket, wherein the
sprocket assembly width, measured between respective outer faces of
end sprockets in the assembly, is no greater than 40.5 mm.
16. A motion transmission system including a sprocket assembly of
at least eleven sprockets defining a sprocket assembly width
defined between respective outer faces of end sprockets of the
sprocket assembly, wherein the sprocket assembly mounts to a hub
that has a predetermined axial distance defined on the hub between
a first plane, perpendicular to a rotation axis, comprising at
least one point of attachment seats for spokes closest to a
freewheel body of the hub, and a second plane, perpendicular to the
rotation axis and defined at a frame attachment portion, wherein
the sprocket assembly width is less than, or equal to, the
predetermined axial distance, wherein a chain that engages the
sprockets has a maximum thickness in a direction of the rotation
axis between and including 4.6 mm and 5.8 mm, wherein the chain
comprises an alternating succession of outer and inner links,
connected to each other at respective connection ends, each of the
links comprising two respective plates arranged parallel to each
other, the two plates of both the outer links and the inner links
being spaced apart from each other to define between the two plates
a void space that receives a tooth of a sprocket, wherein the
sprocket assembly width, measured between respective outer faces of
end sprockets in the assembly, is no greater than 40.5 mm.
17. A bicycle freewheel body and sprocket assembly wherein: the
freewheel body has a predetermined axial width, an outer surface
that is configured to mate with one or more sprockets of the
sprocket assembly, and an internal surface selected to mate with a
hub associated with a bicycle rear wheel; and, the sprocket
assembly has at least eleven sprockets of various diameter that are
arranged on the freewheel body with a largest diameter sprocket and
a smallest diameter sprocket forming end sprockets of the sprocket
assembly, each of the end sprockets has an outer face and the
respective outer face of each end sprocket faces in an opposite
directions and the outer faces are spaced from each other along the
freewheel body predetermined axial width by a distance that is no
greater than 42.5 mm; an assembly of at least eleven sprockets,
that has an overall axial width, measured between respective outer
faces of end sprockets in the assembly, that is no greater than
40.5 mm; and, a chain comprised of an alternating succession of
inner and outer links, connected to each other at respective
connection ends, each of the links comprising inner and outer
plates that are arranged parallel to each other, the two plates of
both the outer links and the inner links being spaced apart from
each other to define between the two plates a void space that
receives at least one tooth of at least one of the sprockets.
18. A motion transmission system comprising: at least eleven
toothed sprockets in a sprocket assembly that is mounted on a
freewheel body having a frame attachment portion and a spoke
attachment portion that are spaced apart by a predetermined axial
distance; the at least eleven sprockets assembly is mounted on the
freewheel body with a largest diameter sprocket and a smallest
diameter sprocket being a respective end sprocket of the at least
eleven sprockets assembly, wherein the largest diameter sprocket is
immediately adjacent to the spoke attachment portion and the
smallest diameter sprocket is immediately adjacent to the frame
attachment portion; and, a chain comprised of alternating inner and
outer links that are connected to each other, wherein, each inner
link and each outer link is comprising of two spaced apart plates
that define a void that receives one tooth of at least one of the
at least eleven toothed sprockets, and the chain remains within the
predetermined axial distance when it moves from the smallest
sprocket to the largest sprocket.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to: Italian patent application
MI2007A001660, filed Aug. 9, 2007; U.S. application Ser. No.
12/187,560, filed Aug. 7, 2008, now issued U.S. Pat. No. 8,454,461;
U.S. application Ser. No. 13/279,834, filed October 24, 2011; U.S.
application Ser. No. 13/279,843, filed Oct. 24, 2011 (abandoned);
and U.S. application Ser. No. 13/740,636, filed Jan. 14, 2013, all
of which are incorporated by reference as if fully set forth.
FIELD OF INVENTION
[0002] The field of the invention relates to a motion transmission
system of a bicycle.
BACKGROUND
[0003] In a bicycle transmission system, the combination of a guide
toothed wheel with a small diameter with a sprocket with a large
diameter allows demanding climbs to be easily handled. However,
this same combination, over flat land or going downhill, is
disadvantageous since the cyclist's energy is dissipated, due to
the fact that the cyclist is obliged to pedal quickly while the
bicycle moves forwards slowly.
[0004] In order to make the aforementioned combination more
suitable for the route to be made, it is known to equip the bicycle
with a plurality of guide toothed wheels and with a plurality of
sprockets, which can be combined with each other based upon
requirements, through appropriate gearshifting devices.
[0005] Because bicycle components have reached a high degree of
standardization, the characteristic size of components such as
frame, gearshifting devices, freewheel body or chain do not greatly
vary, so that most bicycles use three guide toothed wheels and up
to ten sprockets.
[0006] However, certain bicycle transmission systems show a
sprocket assembly comprising more sprockets, the largest of which
are arranged partially over the spokes of the wheel of the bicycle.
The sprockets have a minimum thickness, in the area of engagement
with the chain, equal to 1.76 mm, whereas the distance between
adjacent sprockets is lower than the minimum thickness of the
sprockets themselves, and in particular is equal to 1.66 mm. In
order to be made to rotate, the sprocket assembly illustrated
requires the use of a special-shaped chain. The aforementioned
chain comprises, in alternating succession, a first link,
consisting of two plates that are parallel and spaced apart to
define the area of engagement with a tooth of a sprocket, and a
second link, consisting of a single plate shaped like a "bridge" so
as to define in a central portion thereof a seat for coupling with
the next tooth of the sprocket.
[0007] The aforementioned chain, thanks to the second link made
with a single plate, has a maximum thickness much smaller than a
conventional chain and for this reason it can also be used when
there is a space between the sprockets that is smaller than the
thickness of the sprockets themselves.
[0008] The aforementioned chain wears down quickly because of the
continuous friction between the teeth of the sprockets and the
second links consisting of a single shaped plate. This makes it
subject to premature structural yielding.
[0009] Further, in such an arrangement, the sprockets that are
arranged over the spokes of the wheel have a large diameter, i.e.
they have a very high number of teeth. Since the number of teeth of
the smallest sprocket of known sprocket assemblies is now
standardized and goes up to about 11-12 teeth, it follows that
passing from the smallest sprockets to the largest ones there is a
non-linear increase in diameters, and therefore in the number of
teeth. In other words, the cyclist notices a great difference in
effort necessary to pedaling from one sprocket to an adjacent
sprocket that has a great difference in teeth compared to the
previous one. Therefore, it is possible that the cyclist is not
able to find the optimum combination of sprockets and guide toothed
wheels even with such a large number of sprockets.
[0010] In addition to the above, the total bulk of the sprocket
assembly is very high at the bicycle wheel, for which reason the
chain, when engaging the end sprockets, is inclined with respect to
the guide toothed wheels and therefore more subject to friction,
wear and tension peaks.
SUMMARY
[0011] Throughout the present description and in the subsequent
claims, the expression "motion transmission system" in a bicycle is
used to indicate the assembly of at least some of the components
active in the transmission of motion, imparted by the cyclist
through pedaling, from the crank arms to the rear wheel of the
bicycle.
[0012] The present invention relates, in a first aspect thereof, to
a motion transmission system of a bicycle, comprising a sprocket
assembly adapted to be mounted on a freewheel body of a hub of a
bicycle rear wheel and a bicycle chain adapted to engage the
sprockets of the sprocket assembly, the sprocket assembly
comprising at least eleven sprockets, the hub being able to rotate
about a rotation axis and comprising a plurality of attachment
seats of the spokes of the rear wheel of the bicycle and a
fastening portion to a frame of the bicycle, a predetermined axial
distance being defined on the hub between a plane, substantially
perpendicular to the rotation axis, comprising the points of the
spoke attachment seats closest to the freewheel body and a plane,
substantially perpendicular to the rotation axis and defined in the
fastening portion to the frame, comprising the attachment points to
the frame closest to the freewheel body, wherein all of the
sprockets of the sprocket assembly, when they are associated with
the freewheel body, have an overall axial width or bulk smaller
than, or equal to, the predetermined axial distance, and in that
the chain has a maximum thickness in the direction of the rotation
axis comprised between 4.6 mm and 5.8 mm, the extreme values being
included.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Certain characteristics and advantages shall become clearer
from the following detailed description of a preferred embodiment
thereof, made with reference to the attached drawings and given for
indicating and not limiting purposes. In such drawings:
[0014] FIG. 1 schematically shows a side view of a bicycle
comprising a motion transmission system;
[0015] FIG. 2 schematically shows a longitudinal section view of a
portion of the motion transmission system of FIG. 1, i.e. of a
sprocket assembly mounted on a freewheel body of a hub of a bicycle
rear wheel, such a sprocket assembly being engaged with a bicycle
chain;
[0016] FIG. 3 schematically shows a plan view from above of the
sprocket assembly of FIG. 2 mounted in a bicycle frame;
[0017] FIG. 4 schematically shows a plan view from above of a
complete transmission system according to the present invention
mounted on a bicycle frame, FIG. 3 being an enlarged detail of this
FIG. 4;
[0018] FIGS. 5 and 6 schematically show a plan view from above and,
respectively, a top side view of the chain of FIG. 2;
[0019] FIG. 7 schematically shows a longitudinal section view of a
portion of the chain of FIGS. 5 and 6, taken according to the plane
traced with the line VII-VII of FIG. 6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Introduction
[0020] The present invention relates, in a first aspect thereof, to
a motion transmission system of a bicycle, comprising a sprocket
assembly adapted to be mounted on a freewheel body of a hub of a
bicycle rear wheel and a bicycle chain adapted to engage the
sprockets of the sprocket assembly, the sprocket assembly
comprising at least eleven sprockets, the hub being able to rotate
about a rotation axis and comprising a plurality of attachment
seats of the spokes of the rear wheel of the bicycle and a
fastening portion to a frame of the bicycle, a predetermined axial
distance being defined on the hub between a plane, substantially
perpendicular to the rotation axis, comprising the points of the
spoke attachment seats closest to the freewheel body and a plane,
substantially perpendicular to the rotation axis and defined in the
fastening portion to the frame, comprising the attachment points to
the frame closest to the freewheel body, wherein all of the
sprockets of the sprocket assembly, when they are associated with
the freewheel body, have an overall axial bulk smaller than, or
equal to, the predetermined axial distance, and in that the chain
has a maximum thickness in the direction of the rotation axis
comprised between 4.6 mm and 5.8 mm, the extreme values being
included.
[0021] The use of a sprocket assembly having the aforementioned
axial bulk and of a chain having the aforementioned thickness
allows, on the one hand, a high strength of the transmission system
with at least eleven sprockets to be ensured, at the same time
allowing conventionally-shaped chain and sprockets to be used, to
the advantage of the simplicity of construction and reliability of
the transmission system. In particular, the chain is smaller in
size than the chains currently used for sprocket assemblies with
ten sprockets, so as to allow narrower sprockets and/or smaller
distances between conventional sprockets to be used, which results
in a lightweight assembly.
[0022] More specifically, although the maximum thickness of the
chain is less than that currently used for a chain of a sprocket
assembly with ten sprockets, the aforementioned thickness of the
chain ensures a surprisingly high strength, and in particular it is
possible to use a conventionally-shaped chain, which is
sufficiently strong, contrary to certain prior art that suggests
using a specially-shaped chain. In addition thereto, conventional
chains, thanks to the presence of a bush able to rotate freely in
the link engaged by a tooth, ensure that the friction between the
tooth and the chain does not limit the smooth running of the
transmission system.
[0023] Moreover, the transmission system described herein provided
for the use of a sprocket assembly in which no sprocket is intended
to be arranged over the spokes of the wheel of the bicycle, for
which reason the sprockets added after the tenth one can
advantageously be intermediate sprockets, and not end sprockets
with a large diameter as required in the prior art. This enormously
increases the linearity of the increase in diameter of the
sprockets, since it is possible for example to have a greater
number of adjacent sprockets with a difference in teeth equal to
just one tooth.
[0024] Moreover, the use of a sprocket assembly having an axial
bulk such as to be able to be entirely housed on the freewheel body
of the hub without being arranged over the spokes of the wheel
allows such a sprocket assembly to be suitably positioned, for
which reason it can be ensured that the chain, when engaging the
end sprockets, is not excessively inclined, thus limiting its wear
and the generation of tension peaks.
[0025] The chain may comprise an alternating succession of outer
links and inner links, connected each other at respective
connection ends, each link, outer and inner, comprising two
respective plates, outer and inner, being arranged parallel and
spaced apart to define a space for receiving a tooth of a sprocket.
The shape of the chain of the transmission system may be
conventional, which contributes to the simplicity and
cost-effectiveness of manufacturing the transmission system.
[0026] The maximum thickness may be between 4.8 mm and 5.6 mm, the
extreme values being included. Preferably, the maximum thickness is
comprised between 5 mm and 5.5 mm, the extreme values being
included. These aforementioned maximum thicknesses of the chain
ensure a sufficiently high reliability.
[0027] Preferably, the axial width or bulk is lower than or equal
to 46 mm, and more preferably lower than or equal to 43.5 mm.
[0028] In this way, the aforementioned sprocket assembly can be
housed in a conventional bicycle having wheels and frame of
standardized size.
[0029] The distance between two end sprockets of the sprocket
assembly, measured between respective faces of the end sprockets
facing outwardly from the sprocket assembly, may be lower than or
equal to 42.5 mm, and preferably lower than or equal to 40.5
mm.
[0030] In this way the chain can engage the sprocket with the
smallest diameter with sufficient margin as not to slide in the
frame of the bicycle, and the gearshift can position the chain on
the sprocket with the largest diameter without interfering with the
spokes of the wheel.
[0031] The sprockets may have a predetermined position and are
spaced apart.
[0032] In another embodiment of the transmission system, the
sprocket with the smallest diameter of the sprocket assembly has 11
or 12 teeth and the sprocket with the largest diameter has a number
of teeth comprised between 23 and 27.
[0033] The transmission system has a sprocket assembly comprising a
combination of eleven sprockets selected from the following: [0034]
a first combination with sprockets having 11, 12, 13, 14, 15, 16,
17, 18, 19, 21, 23 teeth respectively; [0035] a second combination
with sprockets having 11, 12, 13, 14, 15, 16, 17, 19, 21, 23, 25
teeth respectively; [0036] a third combination with sprockets
having 11, 12, 13, 14, 15, 17, 19, 21, 23, 25, 27 teeth
respectively; [0037] a fourth combination with sprockets having 12,
13, 14, 15, 16, 17, 18, 19, 21, 23, 25 teeth respectively; [0038] a
fifth combination with sprockets having 12, 13, 14, 15, 16, 17, 19,
21, 23, 25, 27 teeth respectively.
[0039] In another alternative, the transmission system has a
sprocket assembly comprising a combination of twelve sprockets
selected from the following: [0040] a first combination with
sprockets having 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 23
teeth respectively; [0041] a second combination with sprockets
having 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 23, 25 teeth
respectively; [0042] a third combination with sprockets having 11,
12, 13, 14, 15, 17, 18, 19, 21, 23, 25, 27 teeth respectively;
[0043] a fourth combination with sprockets having 12, 13, 14, 15,
16, 17, 18, 19, 20, 21, 23, 25 teeth respectively; [0044] a fifth
combination with sprockets having 12, 13, 14, 15, 16, 17, 18, 19,
21, 23, 25, 27 teeth respectively.
[0045] The sprockets may have a maximum thickness, at an engagement
area with the chain, lower than or equal to 1.7 mm, and more
preferably lower than or equal to 1.6 mm.
[0046] The distance between at least two consecutive sprockets of
the sprocket assembly, measured between the engagement area with
the chain of the sprocket with the smallest diameter and an
adjacent sprocket, is greater than or equal to the thickness of the
sprockets. Moreover, the distance between all of the consecutive
sprockets of the sprocket assembly may be greater than or equal to
the thickness of the sprockets.
[0047] The distance between consecutive sprockets may be lower than
or equal to 2.2 mm.
[0048] This makes it possible to use a chain with plates of the
links having relatively large thicknesses and thus being
sufficiently strong.
[0049] The sprockets with a smaller diameter may be placed at
greater distances apart than the sprockets with a larger diameter.
Further, the sprockets with a smaller diameter may be at a distance
apart lower than or equal to 2.5 mm.
[0050] Such distances between sprockets allow the passage of a
conventionally-shaped chain with particularly strong sections.
[0051] At least six consecutive sprockets may have a number of
teeth that differs by one from that of at least one adjacent
sprocket. Moreover, one of the at least six sprockets has eighteen
teeth.
[0052] Moreover, the consecutive sprockets may be at least seven in
number. Even further, the consecutive sprockets may have at least
eight or at least nine in number.
[0053] In this way, in the movement of the chain from one sprocket
to another the cyclist does not notice a great difference in
effort.
[0054] The transmission system may comprise at least one guide
toothed wheel associated with at least one crank arm and adapted to
be engaged by the chain at the same time as one of the sprockets of
the sprocket assembly. The at least one toothed wheel may be made
from aluminum alloy and has a maximum thickness, in the engagement
area of the chain, lower than or equal to 1.7 mm. Further, the
maximum thickness of the at least one toothed wheel and of the
sprockets, in the respective engagement areas of the chain, is the
same. In particular, the maximum thickness may be lower than or
equal to 1.6 mm in combination with a chain having a thickness
lower than or equal to 5.5 mm.
[0055] Thanks to the dimensions indicated above it is possible to
make toothed wheels that are light and sufficiently strong.
[0056] In a second aspect thereof, the sprocket assembly for a
bicycle rear wheel comprises at least eleven sprockets, wherein all
of the sprockets of the sprocket assembly have an overall axial
width or bulk lower than or equal to 46 mm.
[0057] Such a sprocket assembly may have, individually or in
combination, all of the structural and functional characteristics
discussed above with reference to the sprocket assembly of the
motion transmission system and therefore has all of the
aforementioned advantages.
[0058] In particular, the axial bulk of the sprocket assembly is
preferably lower than or equal to 43.5 mm.
[0059] The distance between two end sprockets of the sprocket
assembly, may be measured between respective faces of the end
sprockets facing outwardly from the sprocket assembly, is lower
than or equal to 42.5 mm, and more preferably lower than or equal
to 40.5 mm.
[0060] The sprockets may have a predetermined position and are
spaced apart.
[0061] In another embodiment of the sprocket assembly, the sprocket
with the smallest diameter has 11 or 12 teeth and the sprocket with
the largest diameter has a number of teeth comprised between 23 and
27.
[0062] The aforementioned sprocket assembly may comprise a
combination of eleven sprockets selected from the following: [0063]
a first combination with sprockets having 11, 12, 13, 14, 15, 16,
17, 18, 19, 21, 23 teeth respectively; [0064] a second combination
with sprockets having 11, 12, 13, 14, 15, 16, 17, 19, 21, 23, 25
teeth respectively; [0065] a third combination with sprockets
having 11, 12, 13, 14, 15, 17, 19, 21, 23, 25, 27 teeth
respectively; [0066] a fourth combination with sprockets having 12,
13, 14, 15, 16, 17, 18, 19, 21, 23, 25 teeth respectively; [0067] a
fifth combination with sprockets having 12, 13, 14, 15, 16, 17, 19,
21, 23, 25, 27 teeth respectively.
[0068] In another alternative, the sprocket assembly may comprise a
combination of twelve sprockets selected from the following: [0069]
a first combination with sprockets having 11, 12, 13, 14, 15, 16,
17, 18, 19, 20, 21, 23 teeth respectively; [0070] a second
combination with sprockets having 11, 12, 13, 14, 15, 16, 17, 18,
19, 21, 23, 25 teeth respectively; [0071] a third combination with
sprockets having 11, 12, 13, 14, 15, 17, 18, 19, 21, 23, 25, 27
teeth respectively; [0072] a fourth combination with sprockets
having 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 23, 25 teeth
respectively; [0073] a fifth combination with sprockets having 12,
13, 14, 15, 16, 17, 18, 19, 21, 23, 25, 27 teeth respectively.
[0074] The sprockets may have a maximum thickness, at an engagement
area with a bicycle chain, lower than or equal to 1.7 mm, and more
preferably lower than or equal to 1.6 mm.
[0075] The distance between at least two consecutive sprockets of
the sprocket assembly, measured between the engagement area with a
bicycle chain of the sprocket with the smallest diameter and an
adjacent sprocket, may be greater than or equal to the thickness of
the sprockets.
[0076] Moreover, the distance between all of the consecutive
sprockets of the sprocket assembly may be greater than or equal to
the thickness of the sprockets.
[0077] Preferably, the distance between consecutive sprockets is
lower than or equal to 2.2 mm.
[0078] In another embodiment of the sprocket assembly, the
sprockets with a smaller diameter may be placed at greater
distances apart than the sprockets with a larger diameter. The
sprockets with a smaller diameter may be at a distance apart lower
than or equal to 2.5 mm.
[0079] At least six consecutive sprockets may have a number of
teeth that differs by one from that of at least one adjacent
sprocket. Moreover, one of the at least six sprockets preferably
has eighteen teeth.
[0080] Further, the consecutive sprockets may be at least seven in
number. Even further, the consecutive sprockets may be at least
eight or at least nine in number.
[0081] In a third aspect thereof, the bicycle chain comprises an
alternating succession of outer links and inner links, connected
each other at respective connection ends, each link, outer and
inner, comprising two respective plates, outer and inner, arranged
parallel and spaced apart to define a space for receiving a tooth
of a sprocket of a sprocket assembly of a bicycle rear wheel,
wherein it has a maximum thickness comprised between 4.6 mm and 5.8
mm, the extreme values being included.
[0082] Such a bicycle chain has, individually or in combination,
all of the structural and functional characteristics discussed
above with reference to the chain of the motion transmission system
and therefore has all of the aforementioned advantages.
[0083] In particular, the maximum thickness is between 4.8 mm and
5.6 mm, the extreme values being included, and more preferably
between 5 mm and 5.5 mm, the extreme values being included.
[0084] In a fourth aspect thereof, a bicycle comprises a
transmission system, and/or a sprocket assembly and/or a chain of
the type described above.
[0085] Such a bicycle may have, individually or in combination, all
of the structural and functional characteristics discussed above
with reference to the aforementioned transmission system and/or
sprocket assembly and/or chain.
[0086] In a fifth aspect thereof, a bicycle comprises a sprocket
assembly having at least eleven sprockets, wherein the sprocket
assembly is positioned so that the difference between the distance
of the sprocket with the smallest diameter from a chain line of the
bicycle and the distance of the sprocket with the largest diameter
from the chain line is lower than or equal, in absolute value, to 4
mm.
[0087] In such a bicycle, when the chain is in the engagement
positions of the end sprockets, it is not excessively inclined and
it is not subject to wear and tension peaks.
[0088] The distance of the sprocket with the smallest diameter from
the chain line is equal to the distance of the sprocket with the
largest diameter from the chain line.
Description
[0089] With initial reference to FIG. 1, a bicycle 51 is shown to
which a motion transmission system in accordance with the present
invention is applied, wholly indicated with 59.
[0090] The bicycle 51 of FIG. 1 comprises a frame 53 to which a
front wheel 55 and a rear driving wheel 57 are connected.
[0091] What makes the front wheel 55 different from the rear
driving wheel 57 is that the second receives the motion from the
transmission system 59 of the bicycle 51. This system comprises a
pair of crank arms 50 directly coupled with one or more guide
toothed wheels 12. The crank arms 50 are supported in rotation in
the frame 53 through a bottom bracket assembly 14 comprising a
shaft and some bearings. The guide toothed wheels 12 engage a chain
15 to transmit the torque applied by the cyclist on the crank arms
50 to a sprocket assembly 16 coupled with the rear driving wheel
57.
[0092] In particular, the rear driving wheel 57 comprises a rim 58,
some spokes 18 and a hub 20. The hub 20 is per se known and for
this reason is only schematically illustrated: it comprises a first
body 56 (FIG. 3) coupled with the rim 58 through the spokes 18 and
a second body that rotates as a unit with the sprocket assembly 16.
The second body is indicated with reference numeral 22 in FIG. 2
and is known as freewheel body since it is free to rotate with
respect to the first body 56 in a direction of rotation, and move
it into rotation in the opposite direction. The rotation axis is
indicated with X in FIG. 2.
[0093] On the first body 56 of the hub 20 there are seats 54 (FIG.
3) for the attachment of the spokes 18 to the hub 20. On the
axially opposite side to the seats 54, the hub 20 comprises a
portion 540 for attachment to the frame 53 of the bicycle 51.
[0094] The sprocket assembly 16 comprises a plurality of driven
toothed wheels, known as sprockets, having a different outer
diameter to one another: in the example illustrated in FIGS. 2-4,
there are eleven sprockets and they are indicated with reference
numerals 1 to 11, from the sprocket 1 having the largest outer
diameter to the sprocket 11 having the smallest outer diameter.
[0095] A gearshifting device 24, illustrated in FIG. 1, allows the
chain 15 to be moved from an engagement condition with a sprocket
to an engagement condition with another sprocket. A similar device
can also be provided in the area of the crank arms 50 in the case
in which there is more than one guide toothed wheel 12. In this way
the sprockets and the toothed wheels can be associated with each
other through the chain 15 in a plurality of combinations.
[0096] With reference to FIGS. 2 and 3, the sprocket assembly 16
has a size such as to be able to be entirely housed in the space of
the hub 20 between the portion 540 for attachment to the frame 53
of the bicycle 51 and the portion of body 56 where the seats 54 are
made. In particular, the sprocket assembly 16 is of a size such as
to be able to be housed in the space E between the planes Z and Y,
where Z is the plane, perpendicular to the axis X of the hub 20,
passing through the points of the seats 54 closest to the freewheel
body 22, and Y is the plane, perpendicular to the axis X and
defined in the portion for attachment to the frame 53 of the hub,
passing through the points of the hub 20 where the attachment to
the frame 53 takes place and that are closest to the freewheel body
22.
[0097] In particular, the portion of the frame 53 to which the
wheel is fastened in general is shaped like a fork with a face
facing towards the sprocket assembly 16, indicated with reference
numeral 159 in FIGS. 2 and 3 and the points of the hub 20 where the
attachment to the frame 53 takes place and that are closest to the
freewheel body 22 are defined at a plane defined on the face
159.
[0098] The space E has a predetermined axial distance greater than
or equal to 46 mm and the sprocket assembly 16 has an axial bulk
lower than or equal to 46 mm, preferably lower than or equal to
43.50 mm. Further, the sprocket with the smallest diameter 11 has a
distance F from the face 159 of the frame 53 at least equal to 2 mm
or such that when the chain 15 engages it the distance G of the
chain 15 from the frame 53 is at least equal to 0.5 mm.
[0099] Moreover, the distance M between the faces 1a and 11a of the
sprockets 1 and 11 facing towards the outside of the sprocket
assembly 16 is lower than or equal to 42.5 mm, and preferably lower
than or equal to 40.5 mm, compared with an engagement area of the
sprockets made on the freewheel body 22 with a length N lower than
or equal to 39 mm.
[0100] With reference to FIG. 3 it can be seen that thanks to the
size of the sprocket assembly 16 it can be positioned substantially
symmetrically with respect to the chain line LC of the bicycle 51,
conventionally defined by the standardization rules at a
predetermined distance W from the middle plane MD of the bicycle 51
(in the case of use of a pair of guide toothed wheels associated
with the crank arms, the chain line is arranged substantially at
half the distance between the two guide toothed wheels). This means
that the face 1a of the sprocket 1 with the largest diameter and
the face 11a of the sprocket 11 with the smallest diameter have
respective distances DS' and DS'' from the chain line LC that are
substantially equal or with a difference lower than 4 mm.
[0101] This means that when the chain 15 is engaged respectively
with the sprocket 1 with the largest diameter and with the sprocket
11 with the smallest diameter it is inclined with respect to the
chain line LC by substantially equal acute angles a' and a'', as
shown in FIG. 4. Preferably, the angles a' and a'' are between
2.25.degree. and 3.75.degree..
[0102] The sprocket assembly 16 meets the measurements indicated
above since the sprockets from 1 to 11 have a thickness O
substantially constant along a radial direction, and lower than or
equal to 1.7 mm and, moreover, the distance P between most of the
adjacent sprockets is greater than the thickness of the sprockets
but lower than or equal to 2.3 mm.
[0103] Actually, the thickness of the sprockets could also be
variable along a radial direction, but what's more is that in the
engagement area with the chain 15 sprockets from 1 to 11 have a
maximum thickness lower than or equal to 1.7 mm and preferably
lower than or equal to 1.6 mm.
[0104] Preferably, moreover, all of the sprockets are placed at a
distance P apart lower than or equal to 2.2 mm.
[0105] Alternatively, some sprockets are at a distance apart
greater than 2.2 mm. According to the preferred embodiment shown in
FIG. 2, the sprockets 9, 10 and 11 are at distances apart P' and
P'' equal to 2.4 and 2.5 mm.
[0106] The chain 15 is illustrated in detail in FIGS. 5 to 7 and
has a conventional shape. It comprises an alternating succession of
outer links 60 and inner links 61, connected each other at
respective connection ends 60a and 61a.
[0107] Each outer link comprises two outer plates 15a and each
inner link 61 comprises two inner plates 15b. The plates of each
link are arranged parallel and spaced apart to define a space for
receiving a tooth of a sprocket. The outer plates 15a are farther
apart than the inner plates 15b and they partially overlap them at
the respective connection end 60a and 61a. A rivet 15c rotatably
joins the inner plates 15b to the outer plates 15a at the
respective connection ends 60a and 61a.
[0108] In particular, the ends 60a of the outer plates 60 have
respective holes 60b and the ends 61a of the inner plates 61 have
respective holes 61b, the holes 60b and 61b having substantially
the same diameter and being aligned to house the rivets 15c. Around
the rivet 15c, between the two inner plates 15b, there is a bush
15d capable of rotating freely about the axis of the rivet (FIG.
7). Between the rivet 15c and the bush 15d flanged portions 61c of
the inner plates 15b are arranged, located around the holes 61b and
extending towards the inside of the link 61.
[0109] The maximum thickness R of the chain 15 is lower than or
equal to 5.8 mm and preferably lower than or equal to 5.5 mm.
[0110] In any case, the chain has a minimum thickness greater than
or equal to 4.6 mm, preferably greater than or equal to 4.8 mm and
even more preferably greater than or equal to 5 mm. These values
ensure sufficient structural strength to satisfy the current
technical standards. In the case in which the guide toothed wheels
12 associated with the crank arms 50 are made from aluminum alloy,
at least in the part intended to engage the chain 15, the latter
preferably has a thickness comprised between 5 and 5.7 mm.
[0111] With the sizes indicated above, some combinations of eleven
sprockets that can be housed substantially in the space in which
the combinations of ten sprockets of the prior art are housed, are
the following: [0112] first combination with sprockets having 11,
12, 13, 14, 15, 16, 17, 18, 19, 21, 23 teeth respectively; [0113]
second combination with sprockets having 11, 12, 13, 14, 15, 16,
17, 19, 21, 23, 25 teeth respectively; [0114] third combination
with sprockets having 11, 12, 13, 14, 15, 17, 19, 21, 23, 25, 27
teeth respectively; [0115] fourth combination with sprockets having
12, 13, 14, 15, 16, 17, 18, 19, 21, 23, 25 teeth respectively;
[0116] fifth combination with sprockets having 12, 13, 14, 15, 16,
17, 19, 21, 23, 25, 27 teeth respectively.
[0117] Some combinations with twelve sprockets are the following:
[0118] first combination with sprockets having 11, 12, 13, 14, 15,
16, 17, 18, 19, 20, 21, 23 teeth respectively; [0119] second
combination with sprockets having 11, 12, 13, 14, 15, 16, 17, 18,
19, 21, 23, 25 teeth respectively; [0120] third combination with
sprockets having 11, 12, 13, 14, 15, 17, 18, 19, 21, 23, 25, 27
teeth respectively; [0121] fourth combination with sprockets having
12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 23, 25 teeth respectively;
[0122] fifth combination with sprockets having 12, 13, 14, 15, 16,
17, 18, 19, 21, 23, 25, 27 teeth respectively.
[0123] Of course, a person of ordinary skill in the art can bring
numerous modifications and variants to the motion transmission
system of a bicycle described above, in order to satisfy contingent
and specific requirements, all of which are anyway covered by the
scope of protection as defined by the following claims.
* * * * *