U.S. patent application number 14/154653 was filed with the patent office on 2015-07-16 for bicycle sprocket.
This patent application is currently assigned to Shimano Inc.. The applicant listed for this patent is Shimano Inc.. Invention is credited to Atsuhiro EMURA.
Application Number | 20150198231 14/154653 |
Document ID | / |
Family ID | 53485073 |
Filed Date | 2015-07-16 |
United States Patent
Application |
20150198231 |
Kind Code |
A1 |
EMURA; Atsuhiro |
July 16, 2015 |
BICYCLE SPROCKET
Abstract
A bicycle sprocket basically includes a sprocket main body, a
plurality of teeth and at least one projecting member. The teeth
are disposed along a circumferential direction on a radially outer
side of the sprocket main body. The teeth include at least one
first tooth and at least one second tooth. The at least one
projecting member protrudes from an axial surface of the at least
one first tooth. The at least one projecting member is a different
material from the teeth. The at least one projecting member and the
at least one first tooth define a first chain engaging tooth width
for engaging with an outer link of a bicycle chain. The at least
one second tooth defines a second chain engaging tooth width for
engaging with an inner link of the bicycle chain. The first chain
engaging tooth width is greater than the second chain engaging
tooth width.
Inventors: |
EMURA; Atsuhiro; (Osaka,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shimano Inc. |
Osaka |
|
JP |
|
|
Assignee: |
Shimano Inc.
Osaka
JP
|
Family ID: |
53485073 |
Appl. No.: |
14/154653 |
Filed: |
January 14, 2014 |
Current U.S.
Class: |
474/156 |
Current CPC
Class: |
F16H 7/06 20130101; F16H
55/30 20130101; B62M 9/105 20130101 |
International
Class: |
F16H 55/30 20060101
F16H055/30; F16H 7/06 20060101 F16H007/06 |
Claims
1. A bicycle sprocket comprising: a sprocket main body having a
rotational axis; a plurality of teeth disposed along a
circumferential direction on a radially outer side of the sprocket
main body, the plurality of teeth including at least one first
tooth and at least one second tooth; and at least one projecting
member attached to an axial surface of the at least one first tooth
such that the at least one projecting member overlaps the at least
one first tooth in an axial direction as viewed parallel to the
rotational axis, the at least one projecting member being a
different material from the plurality of teeth, the at least one
projecting member and the at least one first tooth defining a first
chain engaging tooth width for engaging with an outer link of a
chain and the at least one second tooth defining a second chain
engaging tooth width for engaging with an inner link of the chain,
the first chain engaging tooth width being greater than the second
chain engaging tooth width, the at least one second tooth being
free of the at least one projecting member.
2. The bicycle sprocket according to claim 1, wherein the at least
one first tooth includes a plurality of the first teeth with each
of the first teeth including the at least one projecting
member.
3. The bicycle sprocket according to claim 1, wherein the at least
one second tooth includes a plurality of the second teeth.
4. The bicycle sprocket according to claim 1, wherein the at least
one first tooth includes a plurality of the first teeth with each
of the first teeth including the at least one projecting member,
and the at least one second tooth includes a plurality of the
second teeth.
5. The bicycle sprocket according to claim 4, wherein the first
teeth and the second teeth are alternately disposed in a
circumferential direction.
6. The bicycle sprocket according to claim 5, wherein a total
number of the plurality of teeth is even.
7. The bicycle sprocket according to claim 4, wherein the at least
one projecting member does not extend below a root tooth radius of
the first teeth such that the at least one projecting member
includes a plurality of separate individual sections.
8. The bicycle sprocket according to claim 4, wherein the at least
one projecting member extends below a root tooth radius of the
first teeth such that the at least one projecting member extends
continuously between at least two of the first teeth and along a
portion of the sprocket main body.
9. The bicycle sprocket according to claim 1, wherein the at least
one projecting member is made of a resin material, and the
plurality of teeth are made of a metallic material.
10. The bicycle sprocket according to claim 1, wherein the at least
one first tooth has a first axial surface and a second axial
surface that is opposite to the first axial surface, and the at
least one projecting member includes a first projecting member that
is attached to the first axial surface of the at least one first
tooth, and a second projecting member that is attached to the
second axial surface of the at least one first tooth.
11. The bicycle sprocket according to claim 10, wherein the at
least one first tooth includes a plurality of the first teeth with
each of the first teeth including the first and second projecting
members, and the at least one second tooth includes a plurality of
the second teeth.
12. The bicycle sprocket according to claim 11, wherein the first
teeth and the second teeth are alternately disposed in a
circumferential direction.
13. The bicycle sprocket according to claim 12, wherein a total
number of the plurality of teeth is even.
14. The bicycle sprocket according to claim 11, wherein the first
and second projecting members do not extend below a root tooth
radius of the first teeth such that each of the first and second
projecting members includes a plurality of separate individual
sections.
15. The bicycle sprocket according to claim 11, wherein the first
and second projecting members extend below a root tooth radius of
the first teeth such that the first and second projecting members
extend continuously between at least two of the first teeth and
along a portion of the sprocket main body.
16. The bicycle sprocket according to claim 1, wherein the at least
one projecting member is attached to the at least one first tooth
by an integral molding process.
17. The bicycle sprocket according to claim 10, wherein the first
and second projecting members are attached to the at least one
first tooth by an integral molding process.
18. A bicycle crank assembly including the bicycle sprocket
according to claim 1, the bicycle crank assembly further
comprising: a crank arm including only the single sprocket attached
to the crank arm.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] This invention generally relates to a bicycle sprocket that
drives a bicycle chain.
[0003] 2. Background Information
[0004] Most bicycles have a drive unit or drive train that uses a
chain to transmit the pedaling action from the rider to the rear
wheel. A bicycle drive train typically has one or more front
sprockets provided on a bicycle crank assembly of the bicycle and
one or more rear sprockets provided on a rear hub of the bicycle.
The chain wraps around the front and rear sprockets. Thus, rotation
of the bicycle crank assembly by the rider is transmitted to the
rear wheel by the chain, which meshes with the front and rear
sprockets. A bicycle chain has a plurality of inner links and a
plurality of outer links that are interconnected in an alternating
manner by a plurality of pins. Typically, each of the inner links
includes a pair of parallel inner link plates connected by the pins
that are surrounded by cylindrical rollers. Each of the outer links
includes a pair of parallel outer link plates connected by the pins
of the adjacent inner links. In this way, the inner links and the
outer links are linked alternately. Therefore, when the teeth of a
sprocket all have the same thickness, gaps occur between the outer
link plates and the teeth of the sprocket that are larger than the
gaps between the inner link, plates and the teeth of the sprocket.
In view of this situation, sprockets have been proposed in which
the axial widths of the teeth meshing with the outer links are
greater than the axial widths of the teeth meshing with the inner
links (see, for example U.S. Pat. No, 4,174,642).
SUMMARY
[0005] Generally, the present disclosure is directed to various
features of a bicycle sprocket that has teeth of different axial
widths relative to a rotational center axis direction of the
sprocket for preventing the chain from easily separating from the
teeth of the sprocket.
[0006] In view of the state of the known technology and in
accordance with a first aspect of the present disclosure, a bicycle
sprocket is provided that basically comprises a sprocket main body,
a plurality of teeth and at least projecting member. The sprocket
main body has a rotational axis. The plurality of teeth are
disposed along a circumferential direction on a radially outer side
of the sprocket main body. The plurality of teeth include at least
one first tooth and at least one second tooth. The at least one
projecting member protrudes from an axial surface of the at least
one first tooth. The at least one projecting member is a different
material from the teeth. The at least one projecting member and the
at least one first tooth define a first chain engaging tooth width
for engaging with an outer link of a bicycle chain. The at least
one second tooth defines a second chain engaging tooth width for
engaging with an inner link of the bicycle chain. The first chain
engaging tooth width is greater than the second chain engaging
tooth width.
[0007] In this bicycle crank assembly, the chain is mounted to the
sprocket so that the first tooth of greater axial width engages
with an outer link, and the second tooth of less axial width than
the first tooth engages with an inner link.
[0008] In accordance with a second aspect of the present invention,
the bicycle sprocket according to the first aspect is configured so
that the at least one first tooth includes a plurality of the first
teeth with each of the first teeth including the at least one
projecting member.
[0009] In accordance with a third aspect of the present invention,
the bicycle sprocket according to the first aspect is configured so
that the at least one second tooth includes a plurality of the
second teeth.
[0010] In accordance with a fourth aspect of the present invention,
the bicycle sprocket according to the first aspect is configured so
that the at least one first tooth includes a plurality of the first
teeth with each of the first teeth including the at least one
projecting member, and the at least one second tooth includes a
plurality of the second teeth.
[0011] In accordance with a fifth aspect of the present invention,
the bicycle sprocket according to the fourth aspect is configured
so that the first teeth and the second teeth are alternately
disposed in a circumferential direction.
[0012] In accordance with a sixth aspect of the present invention,
the bicycle sprocket according to the fifth aspect is configured so
that a total number of the plurality of teeth is even.
[0013] In accordance with a seventh aspect of the present
invention, the bicycle sprocket according to the fourth aspect is
configured so that the at least one projecting member does not
extend below a root tooth radius of the first teeth such that the
at least one projecting member includes a plurality of separate
individual sections.
[0014] In accordance with an eighth aspect of the present
invention, the bicycle sprocket according to the first aspect is
configured so that the at least one projecting member extends below
a root tooth radius of the first teeth such that the at least one
projecting member extends continuously between at least two of the
first teeth and along a portion of the sprocket main body.
[0015] In accordance with a ninth aspect of the present invention,
the bicycle sprocket according to the first aspect is configured so
that the at least one projecting member is made of a resin
material, and the plurality of teeth are made of a metallic
material.
[0016] In accordance with a tenth aspect of the present invention,
the bicycle sprocket according to the first aspect is configured so
that the at least one first tooth has a first axial surface and a
second axial surface that is opposite to the first axial surface,
and the at least one projecting member includes a first projecting
member that is attached to the first axial surface of the at least
one first tooth, and a second projecting member that is attached to
the second axial surface of the at least one first tooth.
[0017] In accordance with an eleventh aspect of the present
invention, the bicycle sprocket according to the tenth aspect is
configured an that the at least one first tooth includes a
plurality of the first teeth with each of the first teeth including
the first and second projecting members, and the at least one
second tooth includes a plurality of the second teeth.
[0018] In accordance with a twelfth aspect of the present
invention, the bicycle sprocket according to the eleventh aspect is
configured so that the first teeth and the second teeth are
alternately disposed in a circumferential direction.
[0019] In accordance with a thirteenth aspect of the present
invention, the bicycle sprocket according to the twelfth aspect is
configured so that a total number of the plurality of teeth is
even.
[0020] In accordance with a fourteenth aspect of the present
invention, the bicycle sprocket according to the eleventh aspect is
configured so that the first and second projecting members do not
extend below a root tooth radius of the first teeth such that each
of the first and second projecting members includes a plurality of
separate individual sections.
[0021] In accordance with a fifteenth aspect of the present
invention, the bicycle sprocket according to the eleventh aspect is
configured so that the first and second projecting members extend
below a root tooth radius of the first teeth such that the first
and second projecting members extend continuously between at least
two of the first teeth and along a portion of the sprocket main
body.
[0022] In accordance with a sixteenth aspect of the present
invention, the bicycle sprocket according to the first aspect is
configured so that the at least one projecting member is attached
to the at least one first tooth by an integral molding process.
[0023] In accordance with a seventeenth aspect of the present
invention, the bicycle sprocket according to the ten aspect is
configured so that the first and second projecting members are
attached to the at least one first tooth by an integral molding
process.
[0024] In accordance with an eighteenth aspect of the present
invention, the bicycle sprocket according to the first aspect
consists of only a single sprocket, and a single sprocket only.
[0025] Also other objects, features, aspects and advantages of the
disclosed bicycle sprocket will become apparent to those skilled in
the art from the following detailed description, which, taken in
conjunction with the annexed drawings, discloses selected
embodiments of the bicycle sprocket.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Referring now to the attached drawings which form a part of
this original disclosure:
[0027] FIG. 1 is an outside elevational view of a bicycle crank
assembly having first and second sprockets configured in accordance
with a first embodiment;
[0028] FIG. 2 is a partial inside perspective view of the first and
second sprockets of the bicycle crank assembly illustrated in FIG.
1 with a bicycle chain engaged with the teeth of the first (larger)
sprocket;
[0029] FIG. 3 is a partial inside perspective view, similar to FIG.
2, of the first and second sprockets of the bicycle crank assembly
illustrated in FIG. 1, but without the bicycle chain;
[0030] FIG. 4 is an outside perspective view of the first sprocket
of the bicycle crank assembly illustrated in FIGS. 1 to 3;
[0031] FIG. 5 is a partial edge view of the first sprocket
illustrated in FIG. 4 showing one of the first teeth and two of the
second teeth of the first sprocket;
[0032] FIG. 6 is a cross sectional view of the first sprocket as
seen along section line 6-6 of FIG. 4;
[0033] FIG. 7 is a cross sectional view of the first sprocket as
seen along section line 7-7 of FIG. 4;
[0034] FIG. 8 is an outside perspective view of the second sprocket
of the bicycle crank assembly illustrated in FIGS. 1 to 3;
[0035] FIG. 9 is a partial edge view of the second sprocket
illustrated in FIG. 8 showing one of the first teeth and two of the
second teeth of the second sprocket;
[0036] FIG. 10 is an outside elevational view of a bicycle crank
assembly having first and second sprockets configured in accordance
with a second embodiment;
[0037] FIG. 11 is an outside elevational view of a portion of the
first sprocket illustrated in FIG. 10;
[0038] FIG. 12 is a partial edge view of the first sprocket
illustrated in FIGS. 10 and 11 showing one of the first teeth and
two of the second teeth of the first sprocket;
[0039] FIG. 13 is an outside elevational view of a portion of the
second sprocket illustrated in FIG. 10;
[0040] FIG. 14 is a partial edge view of the second sprocket
illustrated in FIGS. 10 and 13 showing one of the first teeth and
two of the second teeth of the second sprocket; and
[0041] FIG. 15 is an outside elevational view of a bicycle crank
assembly having a crank arm with only a single sprocket attach to
the crank arm in accordance with a third embodiment.
DETAILED DESCRIPTION OF EMBODIMENTS
[0042] Selected embodiments will now be explained with reference to
the drawings. It will be apparent to those skilled in the bicycle
field from this disclosure that the following descriptions of the
embodiments are provided for illustration only and not for the
purpose of limiting the invention as defined by the appended claims
and their equivalents.
[0043] Referring initially to FIG. 1, a bicycle crank assembly 10
according to a first embodiment is illustrated. In the first
embodiment, the bicycle crank assembly 10 comprises a crank arm 12,
a first sprocket 14 and a second sprocket 16. More broadly
speaking, the bicycle crank assembly 10 basically comprises a crank
arm and at least one sprocket. The first and second sprockets 14
and 16 are bicycle sprockets according to an embodiment. The second
sprocket 16 has fewer teeth than the first sprocket 14. The first
and second sprockets 14 and 16 are front sprockets that can engage
with a bicycle chain 20.
[0044] As seen in FIG. 2, the bicycle chain 20 has a plurality of
inner links 22 and a plurality of outer links 24 that are
interconnected in an alternating manner by a plurality of pins 26.
Typically, each of the inner links 22 includes a pair of parallel
inner link plates 22a. Each of the outer links 24 includes a pair
of parallel outer link plates 24a. Preferably, each of the pins 26
has a roller 26a that is rotatably disposed thereon. Thus, the
bicycle chain 20 is a conventional bicycle chain.
[0045] The crank arm 12 is integrally and non-rotatably fixed to
one end a crankshaft 28. Typically, a second crank arm (not shown)
is non-rotatably attached to the other end of the crankshaft 28.
The crankshaft 28 defines a rotational center axis X of the first
and second sprockets 14 and 16. The at least one sprocket (e.g. the
first and second sprockets 14 and 16) has a rotational center axis
X. The crank arm 12 has a sprocket attachment part 30 and an arm
part 32 provided with a pedal attachment part 32a. The crank arm 12
has a longitudinal center line L that extends between the sprocket
attachment part 30 and the pedal attachment part 32a. The at least
one sprocket (e.g. the first and second sprockets 14 and 16) is
attached to the sprocket attachment part 30 of the crank arm
12.
[0046] The sprocket attachment part 30 can be either integrally to
or separate from the arm part 32. The sprocket attachment part 30
has a plurality (e.g. four) of sprocket attachment arms 34 disposed
at intervals in the circumferential direction. The circumferential
intervals of the sprocket attachment arms 34 may be equal intervals
but may also be unequal intervals. In the first embodiment, the
sprocket attachment arms 34 are disposed at equal intervals. Each
of the sprocket attachment arms 34 has a first attachment part 34a
for attaching the first sprocket 114. The first attachment parts
34a are formed at the distal ends of the sprocket attachment arms
34. Each of the sprocket attachment arms 34 has a second attachment
part 34b for attaching the second sprocket 16. The second
attachment parts 34b are formed farther inward in the radial
direction than the first attachment parts 34a. The first attachment
parts 34a and the second attachment parts 34b include through-holes
or blind bores that are either threaded or not threaded. In the
first embodiment, the first attachment parts 34a are configured
with non-threaded through-holes, and the second attachment parts
34b are configured with blind screw holes. The first sprocket 14 is
fixed to the first attachment parts 34a by first fixing bolts 36.
The second sprocket 16 is fixed to the second attachment parts 34b
by second fixing bolts (not shown).
[0047] The arm part 32 is formed either integrally with or separate
from the sprocket attachment part 30. In the first embodiment, the
arm part 32 is configured integrally with the sprocket attachment
part 30. The pedal attachment part 32a defines a threaded hole in
which a pedal (not shown) can be mounted in the distal end. The arm
part 32 also includes a fixing hole 32b to which the crankshaft 28
is fixed.
[0048] The first sprocket main body 40 has a plurality (e.g. four)
of first fixed parts 40a for fixing to the first attachment parts
34a of the sprocket attachment arms 34. In the first embodiment,
the first fixing parts 40a include through-holes 40b. The first
sprocket 14 is fixed to the sprocket attachment arms 34 by the
first fixing bolts 36 and a nut member (not shown) threaded with
the first fixing bolts 36 in a conventional manner.
[0049] As seen in FIGS. 3 to 5, the first sprocket 14 includes a
first sprocket main body 40, a plurality of teeth 42 and at least
one projecting member 44 or 46. The at least one projecting member
44 or 46 is a different material from the teeth 42. Preferably, the
at least one projecting member 44 or 46 is made of a resin material
such as preferably a fiber-reinforced resin material. Preferably,
the plurality of teeth 42 are made of a metallic material such as
preferably aluminum, titanium, stainless steel, magnesium,
beryllium or other suitable metallic materials. The first sprocket
main body 40 and the teeth 42 can be both made of a metallic
material, and can be formed integrally as a one-piece, unitary
member. If weight saving is needed and/or desired, the first
sprocket main body 40 can include a non-metallic material such as
preferably a fiber-reinforced resin material while the teeth 42 can
include a metallic material. When the projecting members 44 and 46
are made of resin material, as illustrated, the projecting members
44 and 46 can be attached to the first sprocket main body 40 and
the teeth 42 by the integral molding process or adhesive. In
particular, the integral molding process can be performed such that
the resin of the projecting members 44 and 46 can extend into
dimples preferably formed on the first sprocket main body 40 and
the teeth 42 during formation of the projecting members 44 and
46.
[0050] The first sprocket main body 40 has a rotational axis that
corresponds to the rotational center axis X of the first sprocket
14. The plurality of teeth 42 are disposed along a circumferential
direction on a radially outer side of the sprocket main body 40.
Here, in the first embodiment, for example, the first sprocket 14
has thirty-six of the plurality of teeth 42. Thus, a total number
of the plurality of teeth 42 is even for the first sprocket 14. The
plurality of teeth 42 includes at least one first tooth 51 and at
least one second tooth 52. The at least one first tooth 51 has a
first axial surface 54 and a second axial surface 56 that is
opposite to the first axial surface 54. The at least one projecting
member 44 or 46 axially protrudes from one of the axial surfaces 54
or 56 of the at least one first tooth 51. Here in the first
embodiment, the at least one projecting member 44 or 46 is attached
to the at least one first tooth 51 by an integral molding process
or adhesive. Preferably, the at least one projecting member 44 or
46 includes a first projecting member 44 that is attached to the
first axial surface 54 of the at least one first tooth 51, and a
second projecting member 46 that is attached to the second axial
surface 56 of the at least one first tooth 51. Preferably, the
first and second axial surfaces 54 and 56 include textured surface
having dimples or the like such that the resin of the projecting
members 44 and 46 can extend into dimples of the first sprocket
main body 40 and the teeth 42 during formation of the projecting
members 44 and 46. Preferably, as in the first embodiment, the
first and second projecting members 44 and 46 are attached to the
at least one first tooth 51 by an integral molding process.
[0051] As seen in FIG. 5, the at least one projecting member 44 or
46 and the at least one first tooth 51 define a first chain
engaging tooth width W1 for engaging with the outer link 24 of the
bicycle chain 20. The at least one second tooth 52 defines a second
chain engaging tooth width W2 for engaging with the inner link 22
of the bicycle chain 20. The first chain engaging tooth width W1 is
greater than the second chain engaging tooth width W2. The first
chain engaging tooth widths W1 of the first teeth 51 are preferably
in a range from 2.5 ram to 5.4 ram, and more preferably in a range
from 3.0 mm to 4.5 ram. When the first chain engaging widths W1 of
the first teeth 51 are in such a range, the first teeth 51 can
readily engage the outer link plates 24a without engaging with the
inner link plates 22a. The second chain engaging tooth widths W2 of
the second teeth 52 are preferably in a range from 1.5 ram to 2.3
ram. When the second chain engaging widths W2 of the second teeth
52 are in such a range, the second teeth 52 have the necessary
rigidity and readily engage with the inner link plates 22a. The
first teeth 51 are preferably formed into a "+" (plus) shape as
seen from the radially outer side, as shown in FIG. 5. The second
teeth 52 are preferably formed into a "-" (minus) shape as seen
from the radially outer side. The first teeth 51 and the second
teeth 52 taper so as to gradually decrease in axial width toward
the radially outer side. The first teeth 51 and the second teeth 52
thereby engage more readily with the outer link plate 24a and the
inner link plates 22a. In the first embodiment, the first teeth 51
are identical to the second teeth 52 in terms of height in the
radial direction.
[0052] Preferably, the at least one first tooth 51 includes a
plurality of the first teeth 51 with each of the first teeth 51
including the at least one projecting member 44 or 46. Preferably,
the at least one second tooth 52 includes a plurality of the second
teeth 52, which are free of the projecting members 44 and 46. The
first teeth 51 and the second teeth 52 are alternately disposed in
a circumferential direction. While the first and second teeth 51
and 52 are illustrated as straight symmetrical teeth, it will be
apparent from this disclosure that the first and second teeth 51
and 52 can be asymmetrical teeth, twisted teeth, shifting teeth
with shifting features, and/or the like.
[0053] The at least one projecting member 44 or 46 extends below a
root tooth radius R of the first teeth 51 such that the at least
one projecting member 44 or 46 extends continuously between at
least two of the first teeth 51 and along a portion of the sprocket
main body 40. Preferably, each of the first teeth 51 includes both
of the first and second projecting members 44 and 46. Also
preferably, in this first embodiment, the first and second
projecting members 44 and 46 extend below a root tooth radius R of
the first teeth 51 such that the first and second projecting
members 44 and 46 extend continuously between at least two of the
first teeth 51 and along a portion of the sprocket main body
40.
[0054] Now, the second sprocket 16 will be discussed with reference
to FIGS. 1 to 3, 8 and 9. Basically, the second sprocket 16 has the
same configuration as the first sprocket 14, except that the second
sprocket 16 is smaller than the first sprocket 14 and has fewer
teeth than the first sprocket 14. In view of the similarity of the
first and second sprockets 14 and 16, the second sprocket 16 will
only be briefly discussed herein.
[0055] The second sprocket 16 includes a second sprocket main body
60, a plurality of teeth 62, and first and second projecting
members 64 and 66 on alternating ones of the teeth 62. The first
and second projecting members 64 and 66 are a different material
from the teeth 62. Preferably, the first and second projecting
members 64 and 66 are made of a resin material such as preferably a
fiber-reinforced resin material. Preferably, the teeth 62 are made
of a metallic material such as preferably aluminum, titanium,
stainless steel, magnesium, beryllium or other suitable metallic
materials. The first sprocket main body 60 and the teeth 62 can be
both made of a metallic material, and can be formed integrally as a
one-piece, unitary member. If weight saving is needed and/or
desired, the first sprocket main body 60 can include a non-metallic
material such as preferably a fiber-reinforced resin material while
the teeth 62 can include a metallic material.
[0056] The second sprocket main body 60 has a plurality (e.g. four)
of second fixed parts 60a for fixing to the second attachment parts
34b (see FIG. 1) of the sprocket attachment arms 34. The second
fixed parts 60a are configured from through-holes. The second
sprocket 16 is fixed to the sprocket attachment arms 34 by the
second fixing bolts (not shown) that are threaded into blind bores
of the second attachment parts 34b.
[0057] Here in the first embodiment, for example, the second
sprocket 16 has twenty-four of the plurality of teeth 62. Thus, a
total number of the plurality of teeth 62 is even for the second
sprocket 16. The teeth 62 include first and second sprocket teeth
71 and 72. The first and second projecting members 64 and 66
protrude from opposite axial surfaces 74 or 76 of the first teeth
71. The first and second sprocket teeth 71 and 72 of the second
sprocket 16 have the same configurations and the same axial widths
as the first and second sprocket teeth 51 and 52 of the first
sprocket 14, respectively, as discussed above. The second sprocket
main body 60 has a plurality (e.g. four) of second fixed parts 60a
for fixing to the second attachment parts 34b of the sprocket
attachment arms 34. In the first embodiment, the second fixing
parts 60a include through-holes 60b. In the first embodiment, the
first and second projecting members 64 and 66 are attached to the
first teeth 71 by an integral molding process or adhesive.
[0058] Referring now to FIGS. 10 to 14, a bicycle crank assembly
110 according to a second embodiment is illustrated, in the second
embodiment, the bicycle crank assembly 110 comprises a crank arm
112, a first sprocket 114 and second sprocket 116. Here, the crank
arm 112 is identical to the crank arm 12 as discussed above.
Regarding the first and second sprockets 114 and 116, only
descriptions of the differences of the first and second sprockets
114 and 116 from the first and second sprockets 14 and 16 will be
provided.
[0059] As seen in FIG. 10, the crank arm 112 is integrally and
non-rotatably fixed to one end a crankshaft 128. The crank arm 112
has a sprocket attachment part 130 and an arm part 132 provided
with a pedal attachment part 132a. The crank arm 112 has a
longitudinal center line L that extends between the sprocket
attachment part 130 and the pedal attachment part 132a. The first
and second sprockets 114 and 116 are fixedly attached to the
sprocket attachment part 130 of the crank arm 112 by four sprocket
attachment arms 134. Each of the sprocket attachment arms 134 has a
first attachment part 134a for attaching the first sprocket 114 and
a second attachment part 134b for attaching the second sprocket 116
in the same manner as the first embodiment.
[0060] As seen in FIGS. 10, 11 and 12, the first sprocket 114
includes a first sprocket main body 140 a plurality of teeth 142,
and at least projecting member 144 or 146 disposed on alternating
ones of the teeth 142. Preferably, the teeth 142 include a
plurality of the first teeth 151 and a plurality of the second
teeth 152. Each of the first teeth 151 includes one or both of the
projecting members 144 and 146. Preferably, the second teeth 152
are free of the projecting members 144 and 146. The first and
second projecting members 144 and 146 are a different material from
the teeth 142 as in the first embodiment. Preferably, the first and
second projecting members 144 and 146 are made of a resin material
such as preferably a fiber-reinforced resin material. Preferably,
the teeth 142 are made of a metallic material such as preferably
aluminum, titanium, stainless steel, magnesium, beryllium or other
suitable metallic materials. The first sprocket main body 140 and
the teeth 142 can be both made of a metallic material, and can be
formed integrally as a one-piece, unitary member. If weight saving
is needed and/or desired, the first sprocket main body 140 can
include a non-metallic material such as preferably a
fiber-reinforced resin material while the teeth 142 can include a
metallic material.
[0061] The first sprocket main body 140 and the teeth 142 are
identical to the first sprocket main body 40 and the teeth 42 of
the first embodiment. However, the first and second projecting
members 144 and 146 are different from the first and second
projecting members 44 and 46 of the first embodiment. Here in the
second embodiment, the at least one projecting member 144 or 146
does not extend below a root tooth radius R of the first teeth 151
such that the at least one projecting member 144 or 146 includes a
plurality of separate individual sections 144a and 146a.
Preferably, each of the first teeth 151 includes both of the
projecting members 144 and 146, which do not extend below the root
tooth radius R of the first teeth 151 such that each of the first
and second projecting members 144 and 146 includes a plurality of
separate individual sections 144a and 146a. Here in the second
embodiment, the projecting members 144 and 146 are attached to the
first teeth 151 by an integral molding process or adhesive, similar
to the first embodiment.
[0062] As seen in FIGS. 10, 13 and 14, the second sprocket 116
includes a second sprocket main body 160, a plurality of teeth 162
and first and second members 164 and 166 on alternating ones of the
teeth 162. Preferably, the teeth 162 include a plurality of the
first teeth 171 and a plurality of the second teeth 172. Each of
the first teeth 171 includes one or both of the projecting members
164 and 166. Preferably, the second teeth 172 are free of the
projecting members 164 and 166.
[0063] The first and second projecting members 164 and 166 are a
different material from the teeth 162 as in the first embodiment.
Preferably, the first and second projecting members 164 and 166 are
made of a resin material such as preferably a fiber-reinforced
resin material. In the first embodiment, the first and second
projecting members 164 and 166 are attached to the first teeth 171
by an integral molding process or adhesive. Preferably, the teeth
162 are made of a metallic material such as preferably aluminum,
titanium, stainless steel, magnesium, beryllium or other suitable
metallic materials. The first sprocket main body 160 and the teeth
162 can be both made of a metallic material, and can be formed
integrally as a one-piece, unitary member. If weight saving is
needed and/or desired, the first sprocket main body 160 can include
a non-metallic material such as preferably a fiber-reinforced resin
material while the teeth 162 can include a metallic material.
[0064] The second sprocket main body 160 and the teeth 162 are
identical to the second sprocket main body 60 and the teeth 62 of
the first embodiment. However, the first and second projecting
members 164 and 166 are different from the first and second
projecting members 64 and 66 of the first embodiment. Here in the
second embodiment, the projecting member 164 or 166 do not extend
below a root tooth radius R of the second teeth 171 such that the
at least one projecting member 164 or 166 includes a plurality of
separate individual sections 164a and 166a. Preferably, each of the
first teeth 171 includes both of the projecting members 164 and
166, which do not extend below the root tooth radius R of the first
teeth 171 such that each of the first and second projecting members
164 and 146 includes a plurality of separate individual sections
164a and 166a. Here in the second embodiment, the projecting
members 164 and 166 are attached to the first teeth 171 by an
integral molding process or adhesive, similar to the first
embodiment.
[0065] Referring now to FIG. 115, a bicycle crank assembly 210
according to a third embodiment is illustrated. Here, the bicycle
crank assembly 210 has a crank arm 212 with only a single sprocket
214 attached to the crank arm 212. With the bicycle crank assembly
210, the bicycle chain 20 does not easily disengage from the
sprocket 214 when, for example, riding on a rough terrain.
[0066] Here, the crank arm 212 is identical to the crank arm 12, as
discussed above, except that the second attachment part has been
eliminated from the crank arm 212 such that only the sprocket 214
can be attach to the crank arm 212. The sprocket 214 is identical
to either the first sprocket 14 or the first sprocket 114. In FIG.
15, the sprocket 214 is illustrated as being identical to the first
sprocket 14. Thus, the sprocket 214 includes a sprocket main body
240 and a plurality of teeth 242. In view of the similarity of the
crank arm 212 and the sprocket 214 to the corresponding parts of
the prior embodiments, as discussed above, the crank arm 212 and
the sprocket 214 will not be discussed and/or illustrated in
further detail.
[0067] Projecting members of the sprocket 214 can be attached to
the first sprocket main body 240 and the teeth 242 as shown or just
to the teeth 242. The projecting members (only one shown) are
formed of a different material from the teeth 242. In FIG. 15,
alternating ones of the teeth 242 include the projecting members
(only the projecting member 244 is shown since only one axial side
of the sprocket 214 is illustrated). For example, the teeth 242
include a plurality of first teeth 51 and a plurality of second
teeth 52 in which opposite axial surfaces of the first teeth 51
include the projecting members In other words, preferably, the
other axial side of the sprocket 214 also preferably includes a
projecting member in the same manner as shown in FIGS. 2 to 7.
Alternatively, the projecting members of the sprocket 214 can be
configured as seen in FIGS. 11 and 12.
[0068] As in the prior embodiments, the projecting members of the
sprocket 214 are made of a resin material such as preferably a
fiber-reinforced resin material. Preferably, the teeth 242 are made
of a metallic material such as preferably aluminum, titanium,
stainless steel, magnesium, beryllium or other suitable metallic
materials. The first sprocket main body 240 and the teeth 242 can
be both made of a metallic material, and can be formed integrally
as a one-piece, unitary member. If weight saving is needed and/or
desired, the first sprocket main body 40 can include a non-metallic
material such as preferably a fiber-reinforced resin material while
the teeth 242 can include a metallic material. When the projecting
members of the sprocket 214 are made of resin material, as
illustrated, the projecting members of the sprocket 214 can be
attached to the first sprocket main body 240 and the teeth 242 by
the integral molding process or adhesive. In particular, the
integral molding process can be performed such that the resin of
the projecting members of the sprocket 214 can extend into dimples
preferably formed on the first sprocket main body 240 and the teeth
242 during formation of the projecting members of the sprocket
214.
[0069] While only selected embodiments have been chosen to
illustrate the present invention, it will be apparent to those
skilled in the art from this disclosure that various changes and
modifications can be made herein without departing from the scope
of the invention as defined in the appended claims. For example,
the size, shape, location or orientation of the various components
can be changed as needed and/or desired so long as the changes do
not substantially affect their intended function.
[0070] Also in the bicycle crank assembly of the first and second
embodiments, the first and second teeth having different axial
widths are provided to both of the sprockets, but the present
invention is not limited as such. Furthermore, while each of the
bicycle crank assemblies 10 and 110 has only two sprockets, it will
be apparent from this disclosure that the bicycle crank assemblies
10 and 110 can include a third sprocket.
[0071] In the first to third embodiments, the first teeth were
formed into + shapes as seen from the radially outer side, but the
present invention is not limited as such. These teeth may also be
formed into other shapes such as diamonds, trapezoids, triangles,
and hexagons.
[0072] In the first to third embodiments, there are four sprocket
attachment arms, but the number of sprocket attachment arms is not
limited to four.
[0073] In the first to third embodiments, the sprocket main bodies
and the pluralities of teeth are formed integrally, but the present
invention is not limited as such. The sprocket main bodies and the
pluralities of teeth may be formed separately. The pluralities of
teeth may be made of metal, for example, and the sprocket main
bodies may be made of a synthetic resin such as a carbon fiber
reinforced resin or a different metal than the teeth, for example
(a light metal such as aluminum, for example), to reduce
weight.
[0074] According to the present invention, the projecting members
can be made of an elastomeric material. Preferably, the projecting
members can be made of an elastomeric material having high abrasion
resistance.
[0075] As used herein, the following directional terms "left" and
"right" are used to indicate the "right" when referencing from the
right side as viewed from the rear of the bicycle, and the "left"
when referencing from the left side as viewed from the rear of the
bicycle. Also it will be understood that although the terms "first"
and "second" may be used herein to describe various components
these components should not be limited by these terms. These terms
are only used to distinguish one component from another. Thus, for
example, a first component discussed above could be termed a second
component and vice-a-versa without departing from the teachings of
the present invention. The term "attached" or "attaching", as used
herein, encompasses configurations in which an element is directly
secured to another element by affixing the element directly to the
other element; configurations in which the element is indirectly
secured to the other element by affixing the element to the
intermediate member(s) which in turn are affixed to the other
element; and configurations in which one element is integral with
another element, i.e. one element is essentially part of the other
element. This definition also applies to words of similar meaning,
for example, "joined", "connected", "coupled", "mounted", "bonded",
"fixed" and their derivatives. Finally, terms of degree such as
"substantially", "about" and "approximately" as used herein mean an
amount of deviation of the modified term such that the end result
is not significantly changed.
[0076] Thus, the foregoing descriptions of the embodiments
according to the present invention are provided for illustration
only, and not for the purpose of limiting the invention as defined
by the appended claims and their equivalents.
* * * * *