Patent Document

This application is a continuation of U.S. patent application Ser. No. 13/311,735, filed Dec. 6, 2011. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to chainrings, and more particularly, to a solitary chainring for use with a conventional chain in a bicycle drivetrain system including a bicycle crank. 
     Bicycles and other chain-driven vehicles typically employ one or more chainrings and a set of rear hub mounted sprockets connected by a chain. Various mechanisms are used to maintain the chain on the chainring and sprockets. These mechanisms include chain guards, chain tensioners, chain catchers, derailleur configurations and so on. 
     While riding a vehicle with a chain driven drivetrain, management of the chain and chainring engagement is particularly important to safe and effective propulsion of the bicycle. Keeping the chain engaged with the chainring can be difficult, which is especially true of geared bicycles which can experience severe changes in chain tension, and energetic motion of the chain, especially from riding over rough terrain. 
     Moreover, the chainring in any bicycle can potentially touch the chain stay of the bicycle frame when the crank is in a position where high loads are applied by the rider, causing an elastic deformation of the bicycle frame and the crankset. This can lead to damage to the frame and chainring and cause other problems. 
     The invention provides an enhanced drive chain management, especially for a bicycle that can successfully and reliably be ridden over rough and challenging terrain. 
     SUMMARY OF THE INVENTION 
     The invention provides, in one aspect, a bicycle chainring for engagement with a drive chain. The bicycle chainring includes a plurality of teeth extending from a periphery of the chainring wherein roots of the plurality of teeth are disposed adjacent the periphery of the chainring. The plurality of teeth include a first group of teeth and a second group of teeth, each of the first group of teeth wider than each of the second group of teeth. At least some of the second group of teeth arranged alternatingly and adjacently between the first group of teeth, and at least some of the first and second group of teeth being asymmetric about a radial tooth centerline along the direction of the chainring circumference. 
     The invention provides, in another aspect, a bicycle chainring for engagement with a drive chain. The bicycle chainring includes a plurality of teeth extending from a periphery of the chainring wherein roots of the plurality of teeth are disposed adjacent the periphery of the chainring. The plurality of teeth including a first group of teeth and a second group of teeth, each of the first group of teeth wider than each of the second group of teeth. At least some of the second group of teeth arranged alternatingly and adjacently between the first group of teeth. Each of the first and second group of teeth include a front flank and a rear flank; and the front and rear flanks are asymmetric with respect to each other along the direction of the chainring circumference. 
     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 
       In the drawings: 
         FIG. 1  is a top view of a conventional drive chain; 
         FIG. 2  is a side view of the conventional drive chain of  FIG. 1 ; 
         FIG. 3  is an isometric view of a combined drive chain and chainring according to the invention engaged by a drivetrain; 
         FIG. 4  is a side view of the chainring according to the invention; 
         FIG. 5  is a close up of the chainring of  FIG. 4 ; 
         FIG. 6  is a side view of a combined drive chain and chainring according to the invention engaged by a drive chain with the outer link plates removed; 
         FIG. 7  is a front isometric view of the chainring according to the invention; 
         FIG. 8  is a front isometric view of the chainring according to  FIG. 7 , engaged by a drive chain; 
         FIG. 9  is a rear isometric view of the chainring according to  FIG. 7 , engaged by a drive chain; 
         FIG. 10  is a front view of the chainring according to the invention; 
         FIG. 11  is a front view of the chainring according to the invention engaged by a drive chain; 
         FIG. 12  is a cross sectional view through line B-B of  FIG. 5  of one type of gear tooth according to one group of teeth; 
         FIGS. 13-15  are cross sectional views through line A-A of  FIG. 5  of alternative types of gear teeth that are different than the tooth of  FIG. 12  and according to another group of teeth; and 
         FIG. 16  is a partial side view of the chainring according to the invention with rollers of a chain engaged with the teeth of the chainring. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the invention will herein be described with reference to the drawings. It will be understood that the drawings and descriptions set out herein are provided for illustration only and do not limit the invention as defined by the claims appended hereto and any and all their equivalents. For example, the terms “first” and “second” or “left” and “right” are used for the sake of clarity and not as terms of limitation. 
     Referring to  FIGS. 1 and 2  of the drawings, numeral  10  generally indicates a conventional roller drive chain for a bicycle or any similar chain-driven device. The drive chain  10  generally includes outer chain links  12  and inner chain links  14  which are pivotally mounted on and connected to the outer chain links by pins  16 ,  18 . The outer chain links  12  are alternatingly interleaved with the inner chain links  14 . 
     The outer chain links  12  have paired outer link plates  20  and the inner chain links have paired inner link plates  22 . Typically, rollers  24  are arranged around the pins  16 ,  18 . The plates  20 ,  22  are provided with holes  30  at their ends  32 . The pins  16 ,  18  typically extend through and project out of the holes  30 , although no projection at all is considered to be optimal. The pins  16 ,  18  are externally riveted at their ends  34 ,  36  during the assembly of the roller chain  10 . While the pin  16  may be made of round stock, pin  18  may be made of tube stock, as in the roller chain  10  in  FIG. 2 . A narrow middle part  38 , which helps to determine the positioning of the roller chain  10  extends between the two circular ends  32  of each of the outer link plates  20  and the inner link plates  22 . 
     As seen best in  FIG. 1 , and as viewed from above (or below) the chain, the interleaving of the outer links  12  and inner links  14  creates corresponding alternating outer link spaces  40  and inner links spaces  42 . Generally, the outer link spaces  40  are openings defined by the outer link plates  20  and rollers  24 . Generally, the inner link spaces  42  are openings defined by the inner link plates  22  and rollers  24 . 
     The inner link spaces  42  are generally rectangular with the long axis of the rectangle aligned with the long axis (A) of the chain  10  (as viewed as in  FIG. 1 ). The axial length of the inner link spaces  42  is determined by the distance between the rollers  24 , while the distance between the inner link plates  22  determines the transverse spacing of the inner link spaces. 
     As seen in  FIG. 1 , the outer link spaces  40  are generally in the shape of a “cross” or in other words, a “plus.” The axial length of the outer link spaces  40  is determined by the distance between the rollers  24 , while the distance between the outer link plates  20  determines the transverse spacing of the outer link spaces. 
     It can be seen that the transverse spacing between the outer link plates  20  is greater than the spacing between the inner link plates  22 . Thus, because the transverse width of the rollers  24  determines the spacing of the inner link plates  22 , the rollers dictate the transverse spacing D 1  of the inner link spaces  42 . Similarly, since the outer link plates  20  are positioned on the pins  16  (or  18 ) on the outboard sides of the inner link plates  22 , the transverse spacing D 2  of the outer link spaces  40  is dictated by the sum of the transverse width of the rollers  24  and the thickness of two inner link plates. 
     Referring to  FIG. 3 , a chainring  50  according to the invention is used with a conventional chain  10 . Chainrings typically have a large plurality of teeth compared to cassettes, for example, having about 20 or more teeth. A crank or crank arm  48  is in a typical position and attached to the chain ring  50  in a well-known manner. The crank side of the chainring  50  is shown in  FIG. 3 , which is the outboard side  54  of the chainring. The outboard side also faces away from the vehicle to which it is attached. The opposite of the outboard side  54  of the chainring  50  is the inboard side  56 . The inboard side  56  faces toward the vehicle. 
     Generally, force applied to the crank arm  48  (typically in a downward direction, for example) causes rotation of the chainring  50  in a like direction (clockwise). Rotation of the chainring  50  causes the chain  10  to be drawn over and advanced about the chainring. 
     The chainring  50  has a plurality of teeth  52  formed about the periphery  51  of the chainring, with the total number of the plurality of teeth consisting of an even number. The plurality of teeth  52  include a first group of teeth  58  and a second group of teeth  60  arranged in an alternating fashion and wherein the first group of teeth is equal in number to the second group of teeth. In a most general form, the invention provides the first group of teeth  58 , that is configured to be received by and fitted into the outer link spaces  40 , and a second group of teeth  60  that is configured to be received by and fitted into the inner link spaces  42 . 
     The overall shape of the chainring periphery  51  may be generally circular or non-circular, that is elliptical, oval, polygon, or parabolic, for example. All of the examples of chainrings provided herein are shown with a circular periphery  51 . 
     Each of the first group of teeth  58  is configured to engage with the chain  10  via an outer link space  40 . Each of the second group of teeth  60  is configured to engage with the chain  10  via an inner link space  42 . 
     Turning to  FIG. 12 , each of the second group of teeth  60  has a shape which in a cross sectional view is generally rectangular, particularly at or near the base or root of the tooth. The cross sectional view is taken through a plane parallel to the top land  80  of the tooth and passing through the base circle position of the tooth, i.e., about halfway between the root circle and the outside circle. 
     The rectangular cross section and overall width WO 1  of each of the second group of teeth  60  should closely match the configuration of each of the inner link spaces  42  ( FIG. 1 ). The cross section shown of each of the second group of teeth shows that the outboard side  54  is generally planar and the inboard side  56  is also generally planar. Each of the second group of teeth  60  may fill over about 75% of the axial distance D 1  of a corresponding space in the chain  10 . Preferably, each of the second group of teeth  60  may fill over about 80% of D 1  of a corresponding space in the chain  10 . More preferably, each of the second group of teeth  60  may fill over about 85% of D 1  of a corresponding space in the chain  10 . 
     Turning to  FIG. 13-15 , each of the alternative versions of teeth  58   a ,  58   b ,  58   c  of the first group of teeth  58  (see  FIG. 3 ) has a shape which in a cross sectional view, taken through the tooth as in  FIG. 12 , has the same longitudinal length L T  as that of the second group of teeth  60  ( FIG. 12 ). Each of the first group of teeth  58  may fill over about 75% of the distance D 2  of a corresponding space in the chain  10 . Preferably, each of the first group of teeth  58  may fill over about 80% of D 2  of a corresponding space in the chain  10 . More preferably, each of the first group of teeth  58  may fill over about 85% of D 2  of a corresponding space in the chain  10 . 
     Each of the first group of teeth  58  has the additional feature of an outboard or first protrusion  62  on the outboard side  54  of each alternative teeth  58   a ,  58   b , and  58   c .  FIG. 13  also demonstrates that the inboard side  56  of tooth  58   a  can be the same (i.e., without a protrusion) as the inboard side  56  of each of the second group of teeth  60 . The first protrusion  62  is configured to fit into the corresponding part of outer link spaces  40  of chain  10  ( FIG. 1 ) and has a width W 1 . The protrusion  62  functions to help maintain the chain  10  on the chainring  50  ( FIG. 3 ). The protrusion  62  causes an overall width WO 2  of each of teeth  58   a  to be greater than the overall width WO 1  of each of teeth  60  by the extent of protrusion  62 . 
       FIG. 14  is another embodiment of a tooth  58   b  of the first group of teeth  58 . In particular, tooth  58   b  is similar to those of  FIG. 13 , with the additional feature of an inboard or second protrusion  64  on the inboard side  56  of the tooth. The protrusion  64  has a width W 2  that is less than the width W 1  of the protrusion  62  of tooth  58   a , or alternatively, greater than W 1 . The protrusions  62 ,  64  cause an overall width WO 3  of each of teeth  58   b  to be greater than the overall width WO 1  of each of teeth  60  by the extent of protrusions  62 ,  64 . Furthermore, WO 3  is greater than WO 2 . 
       FIG. 15  is yet another embodiment of a tooth  58   c  of the first group of teeth  58 . In particular, tooth  58   c  is similar to that of  FIG. 14 , with an inboard or second protrusion  66  on the inboard side  56  of the tooth. The protrusion  66  has a width W 1  that is equal to the width W 1  of the protrusion  62  of tooth  58   a . The protrusions  62 ,  66  cause an overall width WO 4  of each of teeth  58   c  to be greater than the overall width WO 1  of each of teeth  60  by the extent of protrusions  62 ,  66 . Furthermore, WO 4  is greater than WO 3 . 
     It will be understood that the various configurations of the teeth  58  include protrusions that are positioned along the side or sides of each tooth in a position where they effectively function to assist in positioning the chain on the chainring  50 , including positions that are adjacent or at the base of each tooth or higher on each tooth  58 . 
       FIG. 4  and  FIG. 6  is an outboard side  54  of chainring  50  and the driving direction DD. The first group of teeth  58  is alternatingly arranged with the second group of teeth  60 . 
     The configuration of the second group of teeth  60  may be defined, with respect to the outboard and inboard sides  54 ,  56  of each of the teeth  60 , by forming an inner link receiving recess  72  in the chainring  50  that represents material removed from the sides of the teeth  60 . The inner link receiving recess  72  also serves to define the cross-sectional shape of each of the group of teeth  58 . The inner link receiving recess  72  defines the outboard and inboard sides  54 ,  56  of each tooth and extends from the front flank  68  of one of the group of teeth  58  to a rear flank  70  of an adjacent one of the group of teeth  58  in the drive direction DD. Each inner link receiving recess  72  is configured to receive the length L p  an inner link plate  22  of the chain ( FIG. 6 ). Each recess  72  has a base surface  72   a  that extends in an axial direction and a wall  72   b  ( FIG. 7 ) that extends radially. The base surface  72   a  may describe a smoothly curving contour, and may be generally in the shape of a “U”. 
       FIG. 5  is the profile of each tooth of the teeth  58 ,  60  in more detail. The inner link receiving recess  72  is formed in the chainring  50  and can be seen extending along the side of each of the second group tooth  60  and extending from the load side, front or leading flank  68  of one of the group of teeth  58  to a rear flank  70  of an adjacent one of the group of teeth  58  in the drive direction DD. The recess  72  is configured to receive the length L p  ( FIG. 6 ) of an inner link plate  22 . Each tooth may have a top land  80 . The base surface  72   a  may extend to the top land  80  of each of the teeth  58 . The front flank  68  of each tooth includes a contact zone  74 , where a roller  24  ( FIG. 1 ) contacts the tooth. 
     Above the contact zone  74  is an optional tip portion  76 . The roller  24  does not contact the tip portion  76  under normal driving conditions. The tip portion  76  may protrude forwardly from a line drawn along the contact zone  74  a distance T. The protruding tip portion  76  functions to engage a chain link earlier than a chain lacking the tip portion and provides better guiding of the chain. 
     An optional hook feature  78  is a feature that may be formed on the rear flank  70  of each of teeth  58 ,  60 . The hook feature  78  is positioned along the rear flank  70  and may cooperate with the tip portion  76  to provide better guiding of the chain. The hook feature  78  may include a portion of the rear flank  70  being aligned in the radial direction R. 
     Turning to  FIG. 7  the first group of teeth  58  and the second group of teeth  60  of the chainring  50  are arranged in an alternating fashion. An optional feature of each of the first group of teeth  58  and second group of teeth  60  is a respective outer chamfer  82   a ,  82   b . Each of the first group of teeth  58  has an outer chamfer  82   a , which may be an arcuate face formed on the outboard side  54  or shoulder of each tooth. Each of the second group of teeth  60  has an outer chamfer  82   b , which may be an arcuate face formed on the outboard side  54  or shoulder of each tooth. The outer chamfer of  82   b  of each tooth  60  may have an extent C 1  that is greater relative to the extent C 2  of the outer chamfer  82   a  of each tooth  58 . 
     Turning to  FIGS. 8 and 9  the chainring  50  includes chain  10  positioned and engaged thereon. Outer chain links  12  are positioned on the first group of teeth  58 . Inner chain links  14  are positioned on the second group of teeth  60 . 
       FIGS. 10 and 11  respectively is a front view of the chainring  50  without a chain  10  and with a chain. An optional feature of all of the teeth  58 ,  60  of the chainring  50  is an offset OS of the center of the tooth tip or top land  80  from the center line CL in a direction toward the inboard side  56  of the chainring. This offset feature provides better guiding of the chain to one side of the chainring. 
     Turning to  FIG. 16 , a chainring  50  includes a number of teeth  58 ,  60 . Link  1  of a chain engaged on the chainring  50  is represented by line L 1 , and link  2  and link  3  are represented by lines L 2 , L 3  respectively. The line of each of L 1-3  is drawn between the centers of the axis of each of the chain rollers  24 . 
     The hook feature  78  is shown on the rear flank  70  of each of teeth  58 ,  60 . The hook feature  78  is positioned along the rear flank  70  and may cooperate with the tip portion  76  of the front flank  68  to provide better guiding of the chain. The hook feature  78  may include a portion of the rear flank  70  being aligned in the radial direction R. The hook feature  78  has a radially outermost extent  78   a  where the hook feature and the link centerlines L 1-3  intersect. Alternately, the outermost extent  78   a  may be higher than the centerlines L 1-3  providing more room for the roller to engage the teeth in the driving direction. The curved line  90  is the path of the roller  24  when it disengages the tooth. 
     In use, the chain  10  is installed with each of the outer chain links  12  on one of the first group of teeth  58  and each of the inner chain links  14  on one of the second group of teeth  60 . As the chainring  50  is rotated by the crank  48 , the chain  10  is drawn about the chainring, and the outer chain links  12  and the inner chain links  14  are sequentially engaged with respective first and second ones of the groups of teeth  58 ,  60 . As detailed above, the various features of the chainring  50  function to guide and maintain the chain  10  thereon. 
     While this invention has been described by reference to particular embodiments, 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 embodiments, but that it have the full scope permitted by the language of the following claims.

Technology Category: b