U.S. patent application number 16/423961 was filed with the patent office on 2019-09-12 for bicycle crank arm and chainring carrier assembly.
This patent application is currently assigned to SRAM, LLC. The applicant listed for this patent is SRAM, LLC. Invention is credited to TREVOR COLE KRUGMAN, JAMES ISAAC MEYER.
Application Number | 20190276114 16/423961 |
Document ID | / |
Family ID | 51662984 |
Filed Date | 2019-09-12 |
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United States Patent
Application |
20190276114 |
Kind Code |
A1 |
MEYER; JAMES ISAAC ; et
al. |
September 12, 2019 |
BICYCLE CRANK ARM AND CHAINRING CARRIER ASSEMBLY
Abstract
A bicycle chainring structure is provided. The chainring
structure includes a plurality of teeth disposed about the radially
outer circumference of the chainring structure and a pairing
feature including a wall forming a radially interior profile formed
on the chainring structure, the radially interior profile defined
by lobes extending radially inward. The chainring structure also
includes a torque-transmitting coupling formed in the chainring
structure, the torque-transmitting coupling including a plurality
of chainring holes disposed in the radially inward extending lobes
and configured to receive input torque from a crank arm and
transmit the input torque to the plurality of teeth.
Inventors: |
MEYER; JAMES ISAAC;
(SPEARFISH, SD) ; KRUGMAN; TREVOR COLE;
(SPEARFISH, SD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SRAM, LLC |
Chicago |
IL |
US |
|
|
Assignee: |
SRAM, LLC
Chicago
IL
|
Family ID: |
51662984 |
Appl. No.: |
16/423961 |
Filed: |
May 28, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14038364 |
Sep 26, 2013 |
10343745 |
|
|
16423961 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B62M 9/105 20130101;
B62M 3/00 20130101; Y10T 74/2165 20150115 |
International
Class: |
B62M 3/00 20060101
B62M003/00; B62M 9/10 20060101 B62M009/10 |
Claims
1. A chainring structure, comprising: a plurality of teeth disposed
about the radially outer circumference of the chainring structure;
a pairing feature including a wall forming a radially interior
profile formed on the chainring structure, the radially interior
profile defined by lobes extending radially inward; and a
torque-transmitting coupling formed in the chainring structure, the
torque-transmitting coupling including a plurality of chainring
holes disposed in the radially inward extending lobes and
configured to receive input torque from a crank arm and transmit
the input torque to the plurality of teeth.
2. The chainring structure of claim 1, wherein the
torque-transmitting coupling is configured to transmit
substantially all of the torque applied to the chainring structure
from the crank arm.
3. The chainring structure of claim 1, wherein the pairing feature
is configured to position the chainring structure on the crank
arm;
4. The chainring structure of claim 1, wherein the chainring
structure comprises a chainring carrier and a separate
chainring.
5. The chainring structure of claim 1, wherein the chainring
structure includes power meter elements.
6. The chainring structure of claim 1, wherein the
torque-transmitting coupling provides a substantially uniform load
transfer between the chainring structure and the crank arm.
7. The chainring structure of claim 1, wherein the pairing feature
is defined by eight ("8") lobes extending radially inward.
8. The chainring structure of claim 1, wherein each lobe includes a
single chainring hole of the plurality of chainring holes.
9. The chainring structure of claim 1, wherein at least two of the
chainring holes include an angled section; and the chainring
structure further comprising: a plurality of fasteners, at least
two of the plurality of fasteners having an fastener alignment
feature formed thereon to cooperate with the corresponding angled
section of the chainring carrier holes to align and connect the
chainring structure on the crank arm.
10. The chainring structure of claim 9, wherein the angled section
is formed midway along two or more of the plurality of chainring
holes.
11. The chainring structure of claim 10, wherein at least two of
the fasteners include a head portion and a threaded portion that
are formed on opposite sides of the fastener alignment feature.
12. The chainring structure of claim 11, wherein at least two of
the carrier holes includes a straight-sided first section and a
straight-sided second section flanking the angled section, the
first section being wider than the second section.
13. The chainring structure of claim 9, wherein the alignment
features and the angled sections are both tapered and wherein each
forms an angle of 90 degrees.
14. The chainring structure of claim 1, wherein the radially
interior profile of the chainring structure is sized and shaped to
be arranged in a predetermined rotational position relative to an
exterior profile of a post portion of the crank arm.
15. The chainring structure of claim 14, wherein the exterior
profile of the post includes a key that positions the chainring
carrier on the crank arm in the predetermined rotational
position.
16. The chainring structure of claim 15, wherein the plurality of
chainring holes is disposed on a bore circle diameter.
17. The chainring structure of claim 16, wherein a majority of the
radially inward extending lobes include a vacant space between
particular lobes that extends radially inward of the bore circle
diameter, and at least one alignment vacant space between other
lobes extends to a point radially outward of the bore circle
diameter at the radially innermost extent of the alignment vacant
space.
Description
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/038,364, filed Sep. 26, 2013, the contents
of which are herein included by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] This invention relates to bicycles. In particular the
invention relates to a crank arm and chainring carrier
assembly.
[0003] The crankset is the component of a bicycle drivetrain that
converts the pedaling motion of the rider's legs into rotational
motion used to drive a chain or belt, which in turn drives a rear
wheel of the bicycle. The crankset typically carries one or more
chainrings or chainwheels attached to one of the two crank arms of
the crankset--commonly the right-side crank arm--either directly or
through a chainring carrier. The crankset is connected to the rider
by pedals attached to the crank arms, to the bicycle frame by a
bottom bracket and axle, and to a rear sprocket, cassette or
[0004] The chainring or chainrings are typically attached to the
right-side crank arm of the crankset and supported by a chainring
carrier. In one such example, the chainring carrier may be separate
from the drive-side crank arm. Other chainring carriers are
integral to the drive-side crank arm. Separate, detachable
chainring carriers enable a wide variety of chainring patterns to
be used with the same crank arm.
[0005] A category of power meters are used on bicycles by
integration into a chainring carrier, such as those designed and
manufactured by Quarq.RTM.. The chainring carrier power meter
includes strain gages and electronics to measure the torque applied
thereto and when combined with angular velocity, power can be
calculated. Chainring carrier-based power meters are typically
assembled to a crank arm in the same fashion as non-power meter
chainring carriers, via a press or interference fit. While
connection of these chainring carriers to the crank arm is largely
via the press fit of chainring carrier to crank arm via
interconnected splines or the like, the connection may be
supplemented by screws, although the screws do not function to any
significant extent in transmitting torque from one part to another.
These press fit connections convey most or all of the torque from
the crank arms to the chainring carrier through the splined
connection of crank arm and chainring carrier.
[0006] When attaching a chainring carrier to a crank arm the
connection between the chainring carrier and crank arm should
provide for quick and simple installation and result in a reliable
connection. When the chainring carrier includes power meter
elements, the connection should also take into consideration the
transfer of torque from the crank arms to the chainring carrier
such that accurate torque measurements can be made by the power
meter.
[0007] There is a demand, therefore, to provide a bicycle with an
effective crank arm and chainring carrier assembly. The invention
satisfies the demand.
SUMMARY OF THE INVENTION
[0008] The invention provides, in one aspect, a crank arm and
chainring carrier assembly. The assembly includes a crank arm. A
chainring carrier is sized and shaped to connect to the crank arm.
A first pairing feature is formed on one of the crank arm and the
chainring carrier and a second pairing feature is formed on the
other of the crank arm and the chainring carrier to position the
chainring carrier on the crank arm. A clearance is defined between
the first and second pairing features when the first and second
pairing features are paired. A torque-transmitting coupling is
formed on the crank arm and the chainring carrier configured to
transmit substantially all of the torque applied to the chainring
carrier from the crank arm.
[0009] Other aspects of the invention provide an assembly wherein
the chainring carrier may include power meter elements. The
chainring carrier may be a spider including a plurality of arms and
wherein at least some of the power meter elements are disposed on
the plurality of arms to sense strain. The clearance may
substantially inhibit torque transfer between the first and second
pairing features. The torque-transmitting coupling may provide a
substantially uniform load introduction between the chainring
carrier and the crank arm. The assembly may include a planar seat
on the crank arm. The chainring carrier may be shaped and sized to
abut the seat. The seat may include a plurality of crank arm holes
formed therein. The plurality of crank arm holes may number at
least eight. At least some of the plurality of crank arm holes may
be substantially centered on a bore circle diameter. The plurality
of crank arm holes may be substantially centered on the bore circle
diameter. The plurality of crank arm holes may be distributed
substantially evenly about the bore circle diameter. The chainring
carrier may include a plurality of chainring carrier holes, at
least two of the chainring carrier holes including an angled
section; and a plurality of fasteners, at least two of the
plurality of fasteners having an alignment feature formed thereon
to cooperate with the corresponding angled section of the chainring
carrier holes to align and connect the chainring carrier on the
crank arm to form the torque-transmitting coupling and to maintain
the clearance between the first and second pairing features. The
angled section may be formed about midway along each of the
plurality of carrier holes. The fasteners may include a head
portion and a threaded portion formed on opposite sides of the
alignment feature. A least two of the carrier holes includes a
straight-sided first section and a straight-sided second section
flanking the angled section, the first section being wider than the
second section. The alignment features and the angled sections may
both be tapered and wherein each forms an angle of about 90
degrees. The clearance may substantially avoid a redundant load
transfer between the carrier and the crank arm through the first
and second pairing features. The first pairing feature may be a
portion of the interface. The first pairing feature may include a
post portion formed radially inward of the seat. The interface may
include a socket sized and shaped to receive a spindle. The socket
may at least be in part defined by an interior profile of the post.
The post portion may extend axially from the crank arm. The second
pairing feature may include interior profile formed on the
chainring carrier. The post portion may include an exterior
profile. The interior profile of the chainring carrier may be sized
and shaped to be arranged in a predetermined rotational position on
the exterior profile of the post portion and the clearance may be
defined therebetween when the chainring carrier is paired to the
crank arm. The exterior profile may be substantially parallel to
the interior chainring carrier profile. The exterior profile may
include lobes. A majority of the lobes may extend radially to or
past a bore circle diameter. The exterior profile of the post may
include a key that positions the chainring carrier on the crank arm
in the predetermined rotational position. The key may be a
protrusion of the post that extends radially short of the bore
circle diameter. The chainring carrier may be configured to attach
to two or more chainrings.
[0010] Another aspect of the invention provides a crank arm and
chainring carrier assembly, including a crank arm having a
plurality of crank arm holes formed therein. A chainring carrier
has a plurality of carrier holes formed therein. At least two of
the plurality of carrier holes is formed with an angled section. A
first pairing feature is formed on one of the crank arm and the
chainring carrier and a second pairing feature is formed on the
other of the crank arm and the chainring carrier to position the
chainring carrier on the crank arm. A clearance is defined between
the first and second pairing features when the first and second
pairing features are paired. A plurality of fasteners is provided
and at least two of the plurality of fasteners has an alignment
feature formed thereon to cooperate with the corresponding angled
section of the chainring carrier holes to align and connect the
chainring carrier on the crank arm to form a torque-transmitting
coupling of the crank arm and the chainring carrier and to maintain
the clearance between the first and second pairing features.
[0011] In another aspect, a bicycle chainring structure is
provided. The chainring structure includes a plurality of teeth
disposed about the radially outer circumference of the chainring
structure and a pairing feature including a wall forming a radially
interior profile formed on the chainring structure, the radially
interior profile defined by lobes extending radially inward. The
chainring structure also includes a torque-transmitting coupling
formed in the chainring structure, the torque-transmitting coupling
including a plurality of chainring holes disposed in the radially
inward extending lobes and configured to receive input torque from
a crank arm and transmit the input torque to the plurality of
teeth
[0012] These and other features and advantages of the present
invention will be more fully understood from the following
description of one or more embodiments of the invention, taken
together with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] In the drawings:
[0014] FIG. 1A is a top view of a chainring carrier and crank arm
assembly according to a first embodiment of the invention attached
to a spindle and having a chainring mounted on the chainring
carrier;
[0015] FIG. 1B is a perspective view of the chainring carrier and
crank arm assembly of FIG. 1A with the spindle omitted;
[0016] FIG. 1C is an exploded view of the assembly of FIG. 1B with
fasteners;
[0017] FIG. 1D is a cross sectional view of the assembly of FIG. 1C
with fasteners;
[0018] FIG. 2 is a side view of a crank arm, specifically the side
that faces the bicycle;
[0019] FIG. 3 is a cross sectional view of line 3-3 of FIG. 2;
[0020] FIG. 4 is an enlarged cross sectional view of FIG. 3;
[0021] FIG. 5 is an enlarged side view of FIG. 2;
[0022] FIG. 6A is a top view of a chainring carrier and crank arm
assembly connected to a spindle and chainring according to a second
embodiment of the invention;
[0023] FIG. 6B is a perspective view of the chainring carrier and
crank arm assembly of FIG. 6A with the spindle omitted;
[0024] FIG. 6C is an exploded view of the assembly of FIG. 6B with
fasteners;
[0025] FIG. 7 is a side view of the crank arm of FIG. 6A;
[0026] FIG. 8 is a cross sectional view of line 8-8 of FIG. 7;
[0027] FIG. 9 is an enlarged cross sectional view of FIG. 8;
[0028] FIG. 10 is an enlarged side view of FIG. 7;
[0029] FIG. 11 is a first side view of a chainring carrier
according to the invention;
[0030] FIG. 12 is a second side view of the chainring carrier of
FIG. 11;
[0031] FIG. 13 is an enlarged cross sectional view of the chainring
carrier according to the invention through line 13-13 of FIG. 11;
and
[0032] FIG. 14 is a side view of a fastener to connect and align
the chainring carrier on the crank arm according to the invention;
and
[0033] FIG. 15 is a cross sectional view of the fastener of FIG. 14
through lines 15-15 of FIG. 14.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] Referring to FIGS. 1-15, a crank arm and chainring carrier
assembly 20 includes an elongated crank arm 22 and chainring
carrier 24 according to one embodiment of the invention. The
chainring carrier 24 and crank arm 22 are separately formed. The
chainring carrier 24 is sized and shaped to be fixed to the crank
arm 22 by a plurality of fasteners 56 (FIGS. 14, 15) as will be
discussed in detail below. It will be understood that the chainring
carrier 24 may be configured to carry a separate chainring 27, or
two or more chainrings, by way of tabs 26, flanges, openings or
other known structures that are positioned at or near the outer
periphery of the chainring carrier. One embodiment of the chainring
carrier 24 is referred to as a spider.
[0035] The elongated crank arm 22 has a distal end portion 28 with
a threaded hole 29 that is shaped and sized for receiving a pedal
(not shown) as is well known in the art. The crank arm 22 has a
proximal end portion 30 that connects to the chainring carrier 24.
The proximal end portion 30 may include an insert 32, which is used
in composite crank arms. The proximal end portion 30 may also be a
portion of the crank arm 22 formed as a one-piece or multiple piece
crank arm made of metal, for example.
[0036] The crank arm 22 has a planar seat or shoulder 33 formed on
the crank arm or fixedly connected to the proximal portion 30 of
the crank arm against which the chainring carrier 24 abuts and is
kept flush against when the chainring carrier is mounted to the
crank arm in a location fit, i.e., wherein mechanical sizes of
mating parts are such that, when assembled, the parts are
positioned, as desired, in relation to each other.
[0037] The crank arm 22 may have a socket 34 that is configured to
receive a bottom bracket spindle or axle 25 in a well-known manner,
for example, via an interference fit. The crank arm 22 includes a
first pairing feature 100A. The first pairing feature 100A may be
included on a post portion 35 of the crank arm 22, the post portion
extending axially A from the seat 33.
[0038] In one example, the socket 34 is configured to receive a
tapered eight-lobe spline as provided on a commercially available
BB30-type bottom bracket spindle 25 (FIG. 1). The spindle 25 fits
within the socket 34 in a press or interference fit. In another
example, the spindle 25 may include rectangular section splines, as
provided on a commercially available GXP.RTM. bottom bracket
spindle (FIG. 6). It will be understood that the socket 34 may be
shaped and sized to receive any of a number of spindle or axle
configurations. The crank arm 22 may include a crank arm bolt 36 to
fasten the crank arm to a spindle 25 as is well known. The socket
34 may be considered to be defined, at least in part, by the
interior profile 38 of the post portion 35 and the crank arm bolt
36, if present. The interior profile 38 and socket 34 are shaped
and sized to be connected to a spindle/axle part 25.
[0039] The seat 33 includes a plurality of threaded crank arm holes
40, formed therein, for receiving fasteners. Some of all of the
crank arm holes 40 may be formed about and/or spaced evenly along a
predetermined bolt or bore circle diameter "BCD" about the post
portion 35 or not along the BDC.
[0040] The radially exterior wall of the post portion 35 defines an
exterior profile 42. The exterior profile 42 of the post portion 35
may be configured to roughly parallel the interior profile 38 or it
may be configured as a different profile. The exterior profile 42
is one embodiment of the first pairing feature 100A.
[0041] In one example, the exterior profile 42 includes a plurality
of lobes 44 that extend radially and between the crank arm holes
40. At least some of the lobes 44 extend outwardly to a radial
distance near or past the bore circle diameter BCD. Some of the
lobes 44 may extend radially a distance less than the bore circle
diameter BCD. The lobes may be rounded or tooth shaped or other
suitable shapes. One or more of the lobes 44 may have a different
shape and/or size than the other lobes to function as a key 64 with
a corresponding negative feature on the chainring carrier 24 such
that the chainring carrier is oriented in a desired predetermined
manner on the crank arm 22.
[0042] Referring to FIGS. 11-13, the chainring carrier 24 includes
a plurality of carrier holes 46, some or all of which are formed in
the same bore circle diameter BCD as the interface 32 and in
position to align with the crank arm holes 40 of the interface. The
carrier holes 46 may be non-threaded. In one example, there are
eight carrier holes 46 and eight crank arm holes 40, but other
numbers of holes are contemplated. Some or all of the carrier holes
46 may have an angled section 48, formed in the chainring carrier,
at or about a midsection of each hole, the purpose of which will be
described below.
[0043] The chainring carrier 24 includes a second pairing feature
100B. The second pairing feature 100B is defined by an interior
chainring carrier profile 50 that may be generally parallel to the
exterior profile 42 of the post 35 to provide a location fit with
the first pairing feature 100B. The interior chainring carrier
profile 50 may be sized and shaped to provide a clearance 104
between the interior chainring carrier profile and the exterior
profile 42. The clearance 104 may be about 0.3 millimeters. Under
normal riding conditions, the clearance 104 is maintained by the
assembly 20. In other words, torque is not transferred through the
first and second pairing features 100A, B, i.e., directly from the
exterior profile 42 to the carrier profile 50, when typical forces
of the magnitude generated by pedaling and riding are applied to
the crank arm 22, because the clearance is maintained therebetween.
For purposes of the present invention, the cooperative combination
of the interior chainring carrier profile 50 and the exterior
profile 42 of the post 35 may be considered first and second
pairing features 100A, B.
[0044] The chainring carrier 24 may be constructed to provide for
power meter elements. For example, the chainring carrier 24 may be
provided with a plurality of arms 52 and strain gages 54 may be
arranged on the arms or like features, as known in the art. It will
be understood that the strain gages 54 are connected to circuitry
(not shown) to generate power information, which may be transmitted
to a suitable head unit/readout (not shown), as is known in the
art.
[0045] As shown in FIG. 13, at least some of the carrier holes 46
have a wide section 70, which transitions at the angled section 48
through the chainring carrier 24 to a narrower section 72. The
carrier holes 46 are shaped and sized to receive fasteners 56 and
cooperate therewith to mount the chainring carrier 24 to the crank
arm 22.
[0046] Turning to FIGS. 14 and 15, the assembly 20 is assembled
with the fasteners 56, which may be, for example, bolts, centering
bolts or centering screws. The fasteners 56 may have a head 58 with
a tool-engaging socket or tool-engaging feature at one end and a
threaded end 60 opposite the head. The head 58 generally fits into
the wide section 70. The threaded end 60 fits within the narrower
section 72 (FIG. 13). Between the head 58 and threaded end 60 is a
centering or alignment feature 62 that has an angled, cone or
conical shape or section to fit to and/or cooperate with the angled
midsection 48 of the crank arm holes 40. The angled midsection is
tapered and may be configured to be about 90 degrees as shown by CF
(FIG. 14). Insertion and tightening of the fasteners 56 in the
carrier holes 46 of the chainring carrier 24 and into the crank arm
holes 40 of the seat 33 causes the carrier holes to become aligned
with the crank arm holes and causes the chainring carrier to be
aligned and fastened in place on the interface 32. The action of
the alignment feature 62 of the fasteners 56 on the angled section
48 of the crank arm holes 40 cause proper alignment of the
chainring carrier on the crank arm. It also has an objective of
maintaining the clearance 104, at least to produce an initial
alignment state of the chainring carrier 24 on the crank arm 22. In
other words, the chainring carrier 24 is aligned by the fasteners
56 on the crank arm 22 without "clocking," i.e., an "out of phase"
position of the chainring carrier on the interface 32.
[0047] It is believed that if the chainring carrier 24 shifts on
the crank arm 22 resulting in contact between the exterior profile
42 of the interface 32 and the interior chainring carrier profile
50, a condition known as "clocking", that an offset shift in power
meter response can result. It is believed that clocking can result
in less accurate power measurement in the chainring carrier. If the
carrier 24 is not a power meter, the avoidance of clocking may not
be as important. Thus, it is believed that it is advantageous that
all of the torque from the crank arm 22 to the chainring carrier 24
is transmitted solely through a torque-transmitting coupling 102,
i.e., the mounting of the chainring carrier 24 on the crank arm 22
by the fasteners 56, and no torque is transmitted from the first
and second pairing features 100A, B, e.g., the exterior profile 42
to the interior chainring carrier profile 50. A further advantage
of the crank arm assembly 20 according to the invention is that
dimensional tolerances between the chainring carrier 24 and crank
arm 22 need not be as tight as an assembly that is designed for an
interference fit or a slip fit.
[0048] While this invention has been described by reference to a
particular embodiment, it should be understood that numerous
changes could be made within the spirit and scope of the inventive
concepts described. Accordingly, it is intended that the invention
not be limited to the disclosed embodiment, but that it have the
full scope permitted by the language of the following claims.
* * * * *