Abstract:
A bicycle chain ring, including an inner edge fully circumscribing both an opening and an axis of rotation; an inner surface extending between the inner edge and an outer edge where a plurality of chain ring teeth emanate; and a plurality of ramps disposed about the inner surface, wherein at least one of the plurality of ramps has a lifting surface configured to concurrently engage at least one link of a bicycle chain at two or more distinct pivot points along the length of the chain link to initiate stable lift of the bicycle chain without assistance from any of the plurality of chain ring teeth; wherein the lifting surface has a first end proximate the inner edge and a second end proximate the outer edge.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/144,329 filed Dec. 30, 2013, which is a continuation-in-part of U.S. patent application Ser. No. 11/397,234, which issued as U.S. Pat. No. 8,617,015 on Dec. 31, 2013, and which in turn claims priority to U.S. Provisional Patent Application No. 60/721,414, filed Sep. 27, 2005. The present application hereby expressly incorporates by reference the complete disclosure of each of these applications in their entities. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates generally to bicycle cranksets and chain rings. More particularly, this invention relates to bicycle chain rings with selectively placed ramps and chamfering for improved shifting performance. 
         [0003]    Conventional bicycle gear systems typically include a crankset including two or three chain rings affixed to a crank arm spider and a separate simple crank arm. The crank arms of a crankset are configured to receive pedals on one end and to be affixed at the other end to a bottom bracket spindle with bearings for rotation. Conventional bicycle gear systems also typically include a rear cog set, occasionally referred to as a cassette or cluster having one or more gears with teeth configured to rotate a rear wheel through a hub with bearing mechanism. Conventional bicycle gear systems further include a bicycle chain which is driven by the chain rings of the crankset which, in turn, drive the cogs of the rear cog set. The gears of the bicycle may be selectively changed using shifters with control wires attached to front and rear derailleurs. 
         [0004]    Conventional front derailleurs used with cranksets having two or three chain rings push the chain from one ring to the next using lateral motion. During an up-shift, for example, the chain guide of a front derailleur pushes laterally against the side of a chain until the links of the chain finally catch on a tooth of the larger adjacent chain ring and all subsequent links of the chain follow until the chain is aligned with the teeth of the larger adjacent chain ring. A down-shift is achieved by pushing laterally against the chain resting on the larger chain ring until the chain can fall down to the smaller chain ring. 
         [0005]    This conventional method of pushing laterally against the chain with a chain guide provides adequate shifting for most purposes. However, under extreme loading, such as sprinting in the context of racing or out of the saddle climbing, there is a need for quicker shifting, especially up-shifting. A number of solutions have been proposed to improve shifting performance of a front derailleur. 
         [0006]    The inventor of the present application has disclosed an improved front derailleur, see e.g., U.S. Pat. Nos. 6,454,671 and 7,025,698, both to Wickliffe, that solves part of the shifting problem by using a chain guide that physically lifts up the bicycle chain during up-shifts and pulls down the bicycle chain during down-shifts, unlike conventional front derailleurs with their predominantly lateral movement of the bicycle chain, during both up- and down-shifts. 
         [0007]    Other approaches to improving front derailleur shifting performance have focused on redesigning bicycle chains by shaping outer chain links to more readily grab conventional teeth found on conventional chain rings. By shaping outer chain links of a bicycle chain to bow out laterally or to have chamfered or tapered inner surfaces, such chains may be able to grab chain ring teeth quicker. 
         [0008]    Still other approaches to improving front derailleur shifting performance have focused on redesigning the chain rings themselves. For example, U.S. Pat. No. 5,078,653 to Nagano discloses a larger chain ring with selected teeth having reduced height relative to adjacent teeth, i.e., the crests of the selected teeth having been uniformly cut off to reduce height. Additionally, a short pin has been inserted into the inside of the larger chain ring just below the trimmed teeth and opposed to the smaller chain ring. The arrangement disclosed in the &#39;653 patent, facilitates quicker down-shifts by allowing the chain to disengage at the trimmed teeth and be lowered onto the teeth of a smaller chain ring via the short pin. However, there is no indication that the invention disclosed in the &#39;653 patent improves up-shifting, especially during high loads as mentioned above. 
         [0009]    U.S. Pat. No. 6,666,786 to Yahata discloses another improvement to down-shifting performance through the use of chamfered chain ring teeth. However, neither the &#39;653 patent nor the &#39;786 patent appear to address, let alone solve, the problem of achieving improved up-shifting. 
         [0010]    An approach directed toward improving up-shifting by redesigning a conventional chain ring is disclosed in U.S. Pat. No. 5,413,534 to Nagano. Another approach to improving up-shifting by redesigning the chain rings is disclosed in U.S. Pat. No. 6,572,500 to Tetsuka. The &#39;534 and the &#39;500 patents disclose the use of pins or a pin in combination with a tooth and/or tooth chamfering to aid in up-shifting. However, in both patents the pin or teeth engage a given chain link at the point directly between chain link rollers. The load points of a bicycle chain are at each of the chain link rollers (bushings surrounding pins). Thus, the use of pins as disclosed in the &#39;534 and &#39;500 patents to Nagano and Tetsuka, respectively, may increase stress on the chain especially during high loads and, thus, could lead to increased wear and reduce longevity of the chain. 
         [0011]    U.S. Pat. No. 5,876,296 to Hsu et al. discloses the use of an axially oriented recess in combination with a support protrusion to aid in up-shifting. U.S. Pat. No. 5,738,603 to Schmidt et al. discloses a chain ring with pins, chamfered teeth and missing teeth to aid in shifting. Neither of these patents appears to address the added stress to the chain from the allegedly improved up-shifting performance of their respective inventions. 
         [0012]    Accordingly, there still exists a need in the art for a bicycle chain ring that achieves improved shifting performance without increasing the stress on the bicycle chain, thereby addressing at least some of the shortcomings of the prior art. 
       SUMMARY OF THE INVENTION 
       [0013]    An embodiment of a bicycle chain ring is disclosed. The bicycle chain ring may include a plurality of ramps disposed about an inner surface of the bicycle chain ring, wherein each of the plurality of ramps is configured with a lifting surface to engage a plurality of outer chain links of a bicycle chain during an up-shift. Additional features of other embodiments of a bicycle chain ring include, inside tapers adjacent lifting surfaces of the ramps, inside and outside bevels along tips of teeth to form angled knife edges, outside tapers or notches to selected teeth, partially cutoff teeth and channels between ramps. 
         [0014]    An embodiment of a method for up-shifting a bicycle chain from a smaller bicycle chain ring to a larger bicycle chain ring is also disclosed. The method may include providing a larger bicycle chain ring having the features described herein. The method may further include rotating a crankset including the smaller and larger bicycle chain rings in a forward motion direction. The method may further include urging the bicycle chain toward the inner surface of the larger bicycle chain ring. The method may further include multiple outer chain links of the bicycle chain engaging a lifting surface on a ramp and lifting the bicycle chain off of the smaller bicycle chain ring and onto the larger bicycle chain ring. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0015]    The following drawings illustrate exemplary embodiments for carrying out the invention. Like reference numerals refer to like parts in different views or embodiments of the present invention in the drawings. 
           [0016]      FIG. 1  is a plan view of an inner surface of a bicycle chain ring according to an embodiment of the present invention. 
           [0017]      FIG. 2  is an edge view of a portion of a conventional bicycle chain ring viewed from above the teeth. 
           [0018]      FIG. 3  is an edge view of a portion of an embodiment of a bicycle chain ring according to the present invention. 
           [0019]      FIG. 4  is a plan view of the inside of another embodiment of a bicycle chain ring having 44 teeth configured for a standard 104 mm 4-bolt crankset according to the present invention. 
           [0020]      FIG. 5  is a plan view of the outside of the embodiment of the bicycle chain ring shown in  FIG. 4 . 
           [0021]      FIG. 6  is an enlarged perspective view of a portion of the inside of the bicycle chain ring shown in  FIG. 4 . 
           [0022]      FIG. 7  is a plan view of the inside of yet another embodiment of a bicycle chain ring having 32 contoured teeth configured for a standard 104 mm 4-bolt crankset according to the present invention. 
           [0023]      FIG. 8  is a plan view of the outside of the embodiment of the bicycle chain ring shown in  FIG. 7 . 
           [0024]      FIG. 9  is an enlarged perspective view of a portion of the inside of the bicycle chain ring shown in  FIG. 7 . 
           [0025]      FIG. 10  is a flow chart of an embodiment of a method for up-shifting a bicycle chain from a smaller bicycle chain ring to a larger bicycle chain ring. 
           [0026]      FIG. 11  is a plan view of the inside of a 32 tooth bicycle chain ring on 94 mm mounting bolt centers having five mounting bolt holes according to an embodiment of the present invention. 
           [0027]      FIG. 12  is an enlarged perspective view of a portion of the inside of the bicycle chain ring shown in  FIG. 11 . 
           [0028]      FIG. 13  is a super-enlarged perspective view of a portion of the inside of the bicycle chain ring shown in  FIG. 11-12 . 
           [0029]      FIGS. 14-15  are enlarged perspective views of the outside of the bicycle chain ring shown in  FIG. 11-13 . 
           [0030]      FIG. 16  is a plan view of an embodiment of a 34 tooth bicycle chain ring on 104 mm mounting bolt centers having four mounting holes according to an embodiment of the present invention. 
           [0031]      FIG. 17  is a plan view of an embodiment of a 32 tooth bicycle chain ring compatible with a four mounting hole Shimano™ XTR™ crankset according to an embodiment of the present invention. 
           [0032]      FIG. 18  is a plan view of an embodiment of a 34 tooth bicycle chain ring on 94 mm mounting bolt centers having five mounting holes according to an embodiment of the present invention. 
           [0033]      FIG. 19  is a plan view of an embodiment of a 34 tooth bicycle chain ring on 104 mm mounting bolt centers having four mounting holes according to an embodiment of the present invention. 
           [0034]      FIG. 20  is a plan view of an embodiment of a 34 tooth bicycle chain ring on 110 mm mounting bolt centers having five mounting holes according to an embodiment of the present invention. 
           [0035]      FIG. 21  is a plan view of an embodiment of a 34 tooth bicycle chain ring compatible with a four mounting hole Shimano™ XTR™ crankset according to an embodiment of the present invention. 
           [0036]      FIG. 22  is a plan view of an embodiment of a 44 tooth bicycle chain ring on 94 mm mounting bolt centers having five mounting holes according to an embodiment of the present invention. 
           [0037]      FIG. 23  is a plan view of an embodiment of a 44 tooth bicycle chain ring on 104 mm mounting bolt centers having four mounting holes according to an embodiment of the present invention. 
           [0038]      FIG. 24  is a plan view of an embodiment of a 44 tooth bicycle chain ring on 110 mm mounting bolt centers having five mounting holes according to an embodiment of the present invention. 
           [0039]      FIG. 25  is a plan view of an embodiment of a 44 tooth bicycle chain ring compatible with a four mounting hole Shimano™ XTR™ crankset according to an embodiment of the present invention. 
           [0040]      FIG. 26  is a plan view of an embodiment of a 46 tooth bicycle chain ring on 94 mm mounting bolt centers having five mounting holes according to an embodiment of the present invention. 
           [0041]      FIG. 27  is a plan view of an embodiment of a 46 tooth bicycle chain ring on 104 mm mounting bolt centers having four mounting holes according to an embodiment of the present invention. 
           [0042]      FIG. 28  is a plan view of an embodiment of a 46 tooth bicycle chain ring on 110 mm mounting bolt centers having five mounting holes according to an embodiment of the present invention. 
           [0043]      FIG. 29  is a plan view of an embodiment of a 46 tooth bicycle chain ring compatible with a four mounting hole Shimano™ XTR™ crankset according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0044]    Embodiments of the present invention include chain rings for bicycles having specially shaped ramps, tapers and profiled teeth for improved shifting. The embodiments of the chain rings of the present invention may be retrofitted to existing bicycle cranksets and can be configured for any standard bolt on configuration and number of teeth. For example and not by way of limitation, the embodiments of chain rings of the present invention may include middle chain rings in 32 tooth “compact” or 34 tooth “standard” configurations with either four or five bolt mounting structures. Additionally, the embodiments of chain rings of the present invention may include outer (large or big) chain rings in 44 tooth “compact” or 46 tooth “standard” configurations with either four or five bolt mounting structures. In road bike configurations (dual chain ring or “double crankset”), the embodiments of chain rings of the present invention may include outer (big) chain rings in 53 tooth “standard” configurations with five bolt mounting structures. Of course, any number of teeth or bolt patterns may be used with the chain rings of the present invention and all such variations are considered to be within the scope of the present invention. 
         [0045]    An embodiment of a bicycle chain ring is disclosed. The bicycle chain ring may include a plurality of ramps disposed about an inner surface of the bicycle chain ring, wherein each of the plurality of ramps is configured with a lifting surface to engage a plurality of outer chain links of a bicycle chain during an up-shift. Lifting surfaces on each of the ramps may include linear, bilinear, multilinear, or curved profiles according to various embodiments of the bicycle chain ring. The ramps end at a trough or recess between two adjacent teeth according to another embodiment of the present invention. Furthermore, one of the two adjacent teeth may be partially cutoff, according to yet another embodiment of the present invention. 
         [0046]    Another embodiment of a bicycle chain ring may include an inside taper in the bicycle chain ring. The inside taper may be located adjacent to each of the plurality of ramps. The inside taper may provide decreasing bicycle chain ring thickness in a direction opposite normal rotation (forward motion) of the bicycle chain ring during an up-shift. According to another embodiment, the bicycle chain ring may further include partially cutoff teeth located radially outward from an outer end of each of the plurality of ramps. According to another embodiment, the bicycle chain ring may further include a plurality of non-partially cutoff teeth in between each of the partially cutoff teeth. According to a further embodiment, each non-partially cutoff tooth may have an inside bevel located proximate its tip. According to a still further embodiment, the bicycle chain ring may further include outside bevels located in tips of all teeth except for the partially cutoff teeth. 
         [0047]    Another embodiment of a bicycle chain ring may further include an outside taper in each tooth immediately adjacent to and in a clockwise direction from a partially cutoff tooth when viewing an inside surface of the bicycle chain ring, see  FIGS. 5 and 8  and related discussion, below. Still another embodiment of a bicycle chain ring may further include angled knife edges in each non-partially cutoff tooth when viewed from an edge of the bicycle chain ring looking down onto tips of the non-partially cutoff teeth, wherein the angled knife edges are not parallel to a plane running through the bicycle chain ring, see  FIG. 3  and related discussion below. In yet another embodiment of a bicycle chain ring, a channel may be formed in the inside surface of the bicycle chain ring between adjacent ramps. 
         [0048]    Embodiments of bicycle chain rings according to the present invention may have any suitable number of teeth, but more particularly in the range from 30 to 54 teeth. Embodiments of bicycle chain rings according to the present invention may have four or five support structures each having a mounting hole configured for attachment to a crank arm spider. 
         [0049]    Embodiments of bicycle chain rings according to the present invention may include ramp structural width ranging from about 2 mm to about 30 mm. Ramp structural width may be measured in parallel to an inside surface of the bicycle chain ring and perpendicular to a lifting surface of the ramp. Embodiments of bicycle chain rings according to the present invention may include ramp structural thickness ranging from about 2 mm to about 5 mm. Ramp structural thickness may be measured perpendicular from the inside surface of the bicycle chain ring to the top surface of a ramp. 
         [0050]      FIG. 1  is a plan view of an inner surface of a bicycle chain ring  100  according to an embodiment of the present invention. The bicycle chain ring  100  may include a circular structural member  102  having a plurality of contoured teeth  150 A-D replicated serially in a clockwise manner about a circumference of the circular structural member  102 . The bicycle chain ring  100  may further include a plurality of ramps  108  that are raised up from, and regularly disposed about, the inner surface of circular structural member  102 . 
         [0051]    Each of the plurality of ramps  108  may be configured with a lifting surface  110  to engage a plurality of outer chain links of a bicycle chain (not shown) to aid in lifting the bicycle chain from a smaller chain ring (also not shown) that is concentric but displaced away from the inner surface of bicycle chain ring  100 . Each lifting surface  110  of each ramp  108  may run generally from a periphery  112  of an inner opening  120  to an outer end  122  near the base of a partially cutoff tooth  150 D as shown in the illustrated embodiment of bicycle chain ring  100 . However, lifting surfaces  110  need not extend all the way to the periphery  112  of inner opening  120 , for example, see ramp starts  128 . 
         [0052]    According to an embodiment of the present invention, lifting surfaces  110  may be linear in profile as shown in  FIG. 1 . Alternatively, according to another embodiment of bicycle chain ring  400  of the present invention, at least one of the lifting surfaces may be multi-linear in profile (e.g., see  410  in  FIG. 4 ). According to still another embodiment of bicycle chain ring  100  of the present invention, at least one of the lifting surfaces  110  may be arcuate or curved in profile, not shown in FIGS. 
         [0053]    According to an embodiment of a bicycle chain ring  100  shown in  FIG. 1 , each of the plurality of ramps  108  may begin near a support structure  104  or at a periphery of an inner opening  112  of the circular structural member  102 . Each of the plurality of ramps  108  ends at a trough or recess  114  between teeth  150 A and  150 D. The thickness and width of the structure used to form the plurality of ramps  108  may be of any suitable dimension. Furthermore, any suitable material may be used to form the chain rings  100  according to embodiments of the present invention, for example and not by way of limitation, aluminum, titanium, steel and carbon fiber. 
         [0054]    According to another embodiment of the present invention, bicycle chain ring  100  may further include an inside taper  116  in the circular structural member  102  located above each of the plurality of ramps  108 . The inside taper  116  may be achieved by any suitable means including, but not limited to machining, stamping or investment casting. The inside taper  116  may be linear in nature and reduce the thickness of the circular structural member  102  above each ramp  108  in any amount ranging from 0 mm to approximately 2 mm. The inside taper  116  may begin, for example along the curved lines  117  and extend through teeth  150 C and  150 D to an outer end  122  where the taper is greatest. The inside taper  116  provides decreasing circular structural member  102  thickness in a direction opposite normal rotation, R, of the bicycle chain ring  100  during an up-shift. See  FIG. 3  and related discussion below for further illustration of inside taper  116 . 
         [0055]    According to still another embodiment of the present invention, bicycle chain ring  100  may further include partially cutoff teeth  150 D located radially above an outer end  122  of each of the plurality of ramps  108 . Nonpartially cutoff teeth  150 A-C may be found between the partially cutoff teeth  150 D. Generally speaking, all teeth  150 A-D shown in  FIG. 1  are contoured or profiled to improve shifting characteristics as described herein. 
         [0056]      FIG. 2  is an edge view of a portion of a conventional bicycle chain ring, shown generally at  200 , viewed from above the teeth  250 . The relative dimensions of  FIG. 2  are not drawn to scale, but, are exaggerated for ease of explanation. A conventional bicycle chain ring  200  may have an inside surface  240  and an outside surface  242 . A conventional bicycle chain ring  200  may have generally uniform shaped teeth  250  having knife edge points  234  separated by generally uniformly rounded troughs  236  that support round bushings (not shown) of a bicycle chain (not shown). Conventional bicycle chain rings  200  may also have an outer ridge  238  and/or an inner ridge (not shown) for structural support.  FIG. 2  also illustrates a center plane  270  (see dotted line) that is coplanar with knife edge points  234 . 
         [0057]    In contrast,  FIG. 3  is an edge view of a portion of an embodiment of a bicycle chain ring  300  according to the present invention (as indicated on  FIG. 1  by bent arrows  3 ). As with  FIG. 2 , the relative dimensions of  FIG. 3  are not drawn to scale, but are exaggerated for ease of explanation. The view of a portion of bicycle chain ring  300  shown in  FIG. 3  illustrates a top view of four adjacent contoured teeth  350 A-D. Bicycle chain ring  300  may also have an outer ridge  338 , according to the embodiment shown in  FIG. 3 . Bicycle chain ring  300  may further include rounded troughs  336  for supporting cylindrical bushings (not shown) of a bicycle chain (not shown) in between each of the contoured teeth  350 A-D, However, the surfaces of rounded troughs  336  are not uniform like the rounded troughs  236  of the conventional bicycle chain ring  200  ( FIG. 2 ) because of the additional novel features of the contoured teeth  350 A-D. 
         [0058]    The portion of an embodiment of a bicycle chain ring  300  illustrates a ramp  308  having a lifting surface  310  for engaging a bicycle chain (not shown) during up-shifts. The ramp  308  with lifting surface  310  is a unique feature that is completely missing from conventional bicycle chain ring  200 . While some conventional bicycle chain rings have pins, they still do not have ramps  308  with extended lifting surfaces for engaging multiple links of a bicycle chain. The pins associated with some conventional bicycle chain rings only engage a single bicycle chain link. However, the inside lifting surfaces  110  and  310  of ramps  108  and  308  of the embodiments of bicycle chain rings  100  and  300  of the present invention are capable of supporting a plurality of bicycle chain links. This feature of embodiments of the present invention provides better support to lift a bicycle chain during up-shifts. This feature is especially important during hard up-shifts, for example when sprinting or when the rider is out of the saddle during climbing, thereby putting substantial tensile force on the chain. 
         [0059]    The lifting surface  310  on ramp  308  is expanded (below the dashed line in  FIG. 3 ) along inside taper  316  (shown generally below bracket in  FIG. 3 ). The inside taper  316  is formed in the inside of bicycle chain ring  300 . The inside taper  316  narrows the overall thickness of the teeth  350 A-D and troughs (saddles)  336  by a distance, d, defined by a distance measured from inside surface  340  (shown in part by dashed line in  FIG. 3 ) to the deepest chamfer cut point  352 . That inside taper distance, d, may be any amount up to about 2 mm according to various embodiments of bicycle chain ring  300 . 
         [0060]    Another feature of bicycle chain ring  300  is the angled knife edges  334  of teeth  350 A-C.  FIG. 3  illustrates a center plane  370  (see dotted line) that clearly shows that the angled knife edges  334  are noncoplanar, i.e., angled knife edges  334  do not fall along the center line  370 , but are angled to it. The angling of the knife edges  334  of teeth  350 A-C provides enhanced bicycle chain meshing during an up-shift because the bicycle chain twists during an up-shift from a smaller to larger chain ring. Note that the angling of the knife edges  334  shown in  FIG. 3  are exaggerated for ease of explanation and may not actually be angled as greatly as illustrated. The angling of the knife edges  334  tracks the twisting of the bicycle chain to more quickly engage the bicycle chain than without the angled knife edges  334 . This feature improves up-shifting performance (faster) relative to knife edges points  234  (see  FIG. 2 .) having no angling. This feature may also improve chain meshing when the bicycle chain is being driven at an angle relative to rear cogs associated with a freewheel or cassette mechanism. Poor chain meshing is characterized by lack of consistent seating of the bicycle chain in troughs  236  and may be caused by the bicycle chain being driven at an angle relative to rear cogs. Poor chain meshing may also be characterized by increased noise resulting from the lack of consistent seating of the bicycle chain and its cylindrical bushings in troughs  236 . 
         [0061]    Still another feature illustrated in  FIG. 3  is outside taper  356  in contoured tooth  350 A. Outside taper  356  works in conjunction with ramp to the right of tooth  350 A (not shown) to narrow the thickness of contoured tooth  350 A and thereby making it easier for tooth  350 A to grab the bicycle chain ring  300  during an up-shift. According to another embodiment, outside taper  356  may be a short bevel or chamfer along the outside edge of tooth  350 A rather than the taper along the entire width of tooth  350 A shown in  FIG. 3 . Note that four contoured teeth  350 A-D are shown associated with the ramp  308 , in  FIG. 3 . However, any number of teeth, three to seven may be associated with each ramp according to other embodiments of the present invention. In those other instances, the tooth having an outside taper would be left of cutoff tooth  350 D in the view of  FIG. 3 . For example, see outside taper  556  in  FIG. 5  and related discussion below. 
         [0062]    Structural thickness, t, of ramps  308  may range from about 2 mm to about 5 mm according to embodiments of the present invention. Structural thickness, t, less than about 2 mm may not provide enough lifting surface along the ramp  308  for efficient up-shifting. Structural thickness, t, greater than about 5 mm may cause the bicycle chain to unnecessarily catch when the chain is tracking in smaller chain rings and angled in toward the larger chain ring because of rear cog alignment. 
         [0063]    Referring to  FIGS. 1 and 3 , partially cutoff teeth  150 D and  350 D do not have a knife edge  334  because the upper portion of teeth  150 D and  350 D have been removed. The purpose for reducing the profile of teeth  150 D and  350 D by partially cutting off the upper portion of teeth  150 D and  350 D is to provide a point of lateral entry of the bicycle chain over the bicycle chain ring  100  and  300  during an up-shift. Thus, the partially cutoff teeth  150 D and  350 D encourage lateral movement of the bicycle chain from a small bicycle chain ring onto bicycle chain rings  100  and  300 . This encouraging of lateral movement improves shifting performance over conventional bicycle chain rings such as the one illustrated in  FIG. 2 , where all of the teeth  250  are of identical height profile. Incidentally, the partially cutoff teeth  150 D and  350 D also improve down-shifting for essentially the same reason: encouraging lateral movement of the bicycle chain. However, during a down-shift, the bicycle chain is urged off of bicycle chain ring  300 . 
         [0064]    Embodiments of bicycle chain rings  100  and  300  illustrated in  FIGS. 1 and 3  may have three contoured teeth  150 B-D and  350 B-D or four contoured teeth  150 A-D and  350 A-D associated with each ramp  108  and  308 . However, other combinations and numbers of contoured teeth  150 A-D and  350 A-D may be associated with ramps  108  and  308  consistent with the present invention. Such other combinations and numbers of contoured teeth are considered to be within the spirit and scope of the present invention. 
         [0065]      FIG. 4  is a plan view of the inside of another embodiment of a bicycle chain ring  400  having  44  contoured teeth  450 A-D configured for a standard 104 mm 4-bolt crankset according to the present invention. Bicycle chain ring  400  may be used as a large chain ring on a mountain bike crankset. The axis of rotation  133  and the direction of rotation R are highlighted in  FIG. 4 . It will be readily apparent to one of ordinary skill in the art that the invention is not limited to any particular mounting bolt pattern, mounting bolt number, number of teeth or bolt pattern radius. 
         [0066]    Contoured teeth  450 A-D may include inside bevels  460  along the tips to achieve the angled knife edges ( 334  in  FIG. 3 ) as a feature of the present invention. Inside bevels  460  form portions of the angled knife edges ( 334  in  FIG. 3 ) that improve bicycle chain meshing as described herein. Inside bevels  460  may be of any shape that improves bicycle chain meshing and therefore, reduce noise and improves shifting performance relative to bicycle chain rings without such features. 
         [0067]    According to the embodiment of bicycle chain ring  400 , ramps  408  may be linear profile ramps  408 A or bilinear profile ramps  408 B. The bilinear profile ramps  408 B may be partially formed on support structures  104 , thus allowing for longer ramps and bilinear configurations. Ramps  408 A-B may include gaps (not shown) according to other embodiments of bicycle chain ring  400 , but each ramp  408 A-B always supports more than a single link as distinguished from pins used in prior art chain rings.  FIG. 4  also illustrates structural members  104  (four shown) and their associated mounting holes  106 . 
         [0068]      FIG. 4  also illustrates the regions of inside taper  416  adjacent the lifting surface  410  of each ramp  408 A-B. Inside taper  416  may take any form or shape that narrows the thickness of the bicycle chain ring  400  above the ramps  408 A-B according to various embodiments of the present invention. See also  FIG. 6  and related discussion below for an enlarged view of inside taper  416 . The structural width, w, of any given ramp  408 A-B may be of any suitable dimension that provides consistent support of a bicycle chain. Any structural width, w, less than about 2 mm, may lack suitable wear characteristics for use on bicycles over extended periods of time. Structural width, w, may vary from among the ramps  408  located on a single bicycle chain ring  400  according to other embodiments of the present invention, e.g., see  FIGS. 7 and 9 , below. Structural width, w, may fall within the range from about 2 mm to about 30 mm according to various embodiments of the present invention. 
         [0069]      FIG. 5  is a plan view of the outside of the embodiment of the bicycle chain ring  400  shown in  FIG. 4 . In the view of  FIG. 5  outer ridge  538  appears as a circle underneath contoured teeth  450 A-D,  FIG. 5  also illustrates structural members  104  (four shown) and their associated mounting holes  106 .  FIG. 5  further illustrates the outside bevel  554  of contoured teeth  450 , particularly contoured teeth  450 A-C and not including partially cutoff teeth  450 D (i.e., all teeth other than cutoff teeth  450 D). Outside bevel  554  provides enhanced bicycle chain meshing as described above. Another feature of bicycle chain ring  400  illustrated in  FIG. 5  is outside taper  556 . Outside taper  556  is associated with contoured teeth  450 A or  450 B, depending on the number of contoured teeth (three or four) associated with a given ramp  408 . Outside taper  556  narrows contoured teeth  450 A or  450 B at a position adjacent to cutoff teeth  450 D. The outside taper  556  is configured to grab the inside of a bicycle chain link between cylindrical bushings. Thus, outside taper  556  can more quickly grab the bicycle chain (not shown) during an up-shift because the profile of contoured teeth  450 A or  450 B is narrower. Outside taper  556  may also improve chain meshing as described above, Embodiments of outside taper  556  may encompass most of the body of contoured teeth  450 A or  450 B as shown in bicycle chain ring  400  of  FIG. 5 . Alternatively, outside taper  556  may be a smaller chamfer, bevel or notch (not shown in  FIG. 5 , but see  FIG. 8  and outside notch  856 ) on the body of contoured teeth  450 A or  450 B nearest contoured teeth  450 D according to other embodiments of the present invention. 
         [0070]      FIG. 6  is a perspective view of a portion of the inside of the bicycle chain ring  400  shown in  FIG. 4 , enlarged to show detail. The portion of the bicycle chain ring  400  shown in  FIG. 6  includes two ramps  408 , more specifically a linear profile ramp  408 A and a bilinear profiled ramp  408 B.  FIG. 6  also highlights the  FIG. 6  also illustrates a support structure  104 , a mounting hole  106 , a lifting surface  410  on each ramp  408 A-B, contoured teeth  450 A-D, inside bevels  460  associated with contoured teeth  450 A-C and inside taper  416  adjacent ramps  408 A-B.  FIG. 6  further illustrates a channel  670  that is formed between adjacent ramps  408 A-B on the inside surface of bicycle chain ring  400  according to the present invention. Channel  670  provides a space for the bicycle chain during up-shifts. The lifting surface  410  shown in  FIG. 6  has a first width at a first point  471  located adjacent to the inner edge  472  or inner periphery. At a second point  473 , the lifting surface has a second width that is greater than the first width. The first point  471  and second point  473  are located distant from each other and configured to simultaneously striking two distinct portions of a bicycle chain when the lifting surface first acts upon the chain. The ramps  408  also include disengagement surfaces  474  that are located near the teeth  460 . The planar disengagement surfaces  474  are adjacent to and perpendicular to the inner surface of the chain ring as well as being adjacent to the lifting surfaces  410 . 
         [0071]      FIG. 7  is a plan view of the inside of yet another embodiment of a bicycle chain ring  700  having 32 contoured teeth  750 A-D configured for a standard 104 mm 4-bolt crankset according to the present invention. Bicycle chain ring  700  may be configured as a middle chain ring on a mountain bike crankset Bicycle chain rings  400  and  700  together may form a compact set of chain rings for a mountain bike crankset Bicycle chain ring  700  may include a circular structural member  702 , a plurality of support structures  704  (four shown), each with mounting holes  106  (four shown). Bicycle chain ring  700  may further include ramps  708 A-B (eight total: four ramps  708 A and four ramps  708 B) of various widths, w, depending on the location of the ramp  708 A-B. For example and not by way of limitation, ramp  708 A may include relatively narrow width, w 1 . Whereas ramp  708 B may have a relatively wide width, w 2 , that encompasses mounting hole  106 , as shown in  FIG. 7 . As noted above, ramp structural width, w, w 1  or w 2 , may be anywhere in the range from about 2 mm to about 30 mm. Structural thickness (not shown in  FIG. 7 ) of ramps  708 A-B may be as described above for the embodiment of bicycle chain ring  300  in  FIG. 3 . 
         [0072]    Referring again to  FIG. 7 , each ramp  708 A-B is configured with a lifting surface  710 . Each ramp  708 A-B may be associated with three or five contoured teeth  750 A-E depending on the size and location of the associated ramp  708 A-B. Partially cutoff teeth  750 E are separated by nonpartially cutoff, contoured teeth  750 A-D. Of course, contoured teeth  750 A-E shown in the embodiment of  FIG. 7 , may have similar features and characteristics to contoured teeth  150 A-D,  350 A-D and  450 A-D, as other embodiments described above. Bicycle chain ring  700  may further have inside tapers  716  adjacent the lifting surfaces  710  of each ramp  708 A-B. Inside tapers  716  may have similar features and characteristics to inside tapers  116  ( FIGS. 1 ) and  316  ( FIG. 3 ) described above.  FIG. 7  also illustrates support structures  704  and associated mounting holes  106 . 
         [0073]      FIG. 8  is a plan view of the outside of the embodiment of the bicycle chain ring  700  shown in  FIG. 7 . In the view of  FIG. 8 , outer ridge  838  appears as a circle underneath contoured teeth  750 A-E.  FIG. 8  also illustrates the outside bevel  854  of contoured teeth  750 , particularly contoured teeth  750 A-D and not including partially cutoff teeth  750 E (i.e., all teeth other than cutoff teeth  750 E). Outside bevel  854  provides enhanced bicycle chain meshing as described above.  FIG. 8  also illustrates outside notch  856 . Outside notch  856  is associated with contoured teeth  750 A or  750 C depending on the number of contoured teeth (three or five) associated with a given ramp  708  (not shown in  FIG. 8 ), Outside notch  856  narrows contoured teeth  750 A or  750 C at a position adjacent to cutoff teeth  750 E. The outside notch  856  is configured to grab the inside of a bicycle chain link between cylindrical bushings (not shown) in the chain (also not shown). Thus, outside notch  856  can more quickly engage the bicycle chain (not shown) during an up-shift, because the profile of contoured teeth  750 A or  750 C is narrower. Outside notch  856  may also improve chain meshing as described above. Other embodiments of outside notch  856  may encompass most of the body of contoured teeth  750 A or  750 C as shown in outside taper  556  of bicycle chain ring  400  of  FIG. 5 .  FIG. 8  also illustrates support structures  704  and associated mounting holes  106 . 
         [0074]    Referring now to  FIG. 9 , a perspective view of a portion of the inside of the bicycle chain ring  700  of  FIG. 7  is enlarged to show detail. The portion of the bicycle chain ring  700  shown in  FIG. 9  includes two linear ramps  708 A-B, more specifically a narrow width (w 1 ) linear profile ramp  708 A and a wide width (w 2 ) linear profiled ramp  708 B (see also  FIG. 7 ).  FIG. 9  also illustrates a support structure  704 , a mounting hole  106 , a lifting surface  710  on each ramp  708 A-B, contoured teeth  750 A-E and inside taper  716  adjacent ramps  708 A- 13 .  FIG. 9  further illustrates a channel  970  that is formed between adjacent ramps  708 A-B on the inside surface of bicycle chain ring  700  according to the present invention. Channel  970  provides a space for the bicycle chain during up-shifts. 
         [0075]    Referring generally to  FIGS. 1 and 3-7 , embodiments of bicycle chain rings,  100 ,  300 ,  400  and  700  include between two and five nonpartially cutoff, contoured teeth  150 A-C,  350 A-C,  450 A-C and  750 A-D (see  FIG. 11 , below for an example of five nonpartially cutoff teeth) separating any two nearest cutoff teeth  150 D,  350 D,  450 D and  750 E. The centers of mounting holes  106  may be on the circumference of a circle 104 mm in diameter according to a particular embodiment of the bicycle chain rings of the present invention. According to alternative embodiments, centers of mounting holes  106  may be on the circumference of a circle 94 mm or 110 mm in diameter. The bicycle chain rings  100 ,  300 ,  400  and  700  disclosed herein may be configured for compatibility with any commercially available crankset, for example and not by way of limitation, cranksets manufactured by Shimano™, Campagnolo™, Race Face™, Truvativer™, Richey™, Nashbar ™, FSA™, and any other manufacturer or model of crankset. 
         [0076]    Yet another feature of the partially cutoff teeth  150 D,  350 D,  450 D and  750 E disclosed herein is the angle, θ, at which such teeth are cutoff. Referring specifically to  FIG. 7 , note that angle, θ, is shown as measured from tangential line, l 1 , to angled line, l 2 , traced through the top of partially cutoff teeth  750 E. By partially cutting off teeth  750 E at angle, θ, the bicycle chain is given clearance it needs during a down-shift to be able to move laterally past the partially cutoff tooth  750 E and drop off chain ring  700  to engage the next smaller chain ring (not shown). During a down-shift, the partially cutoff tooth  750 E allows an entire chain link to move laterally towards the inside of bicycle chain ring  700  and past the partially cutoff tooth  750 E without making contact with tooth  750 E, This feature promotes faster down-shifts. The angled (θ) cutoff teeth  750 E are preferred to tangentially cutoff teeth of the prior art (see e.g., U.S. Pat. No. 5,078,653 to Nagano as discussed above in the background) because the bicycle chain comes off of chain ring  700  at an angle approximated by angle, θ, not tangentially, during a down-shift. 
         [0077]      FIG. 10  is a flow chart of an embodiment of a method  1000  for up-shifting a bicycle chain from a smaller bicycle chain ring to a larger bicycle chain ring. Method  1000  may include providing  1002  a larger bicycle chain ring as described herein. Method  1000  may further include rotating  1004  a crankset including the smaller and larger bicycle chain rings in a forward motion direction. Method  1000  may further include urging  1006  the bicycle chain toward the inner surface or side of the larger bicycle chain ring. This urging  1006  may be achieved by activating a front derailleur having a chain guide that pushes laterally against the sides of a bicycle chain. Alternatively, urging  1006  may be achieved by activating a front derailleur such as those described in U.S. Pat. No. 6,454,671 and U.S. Published Patent Application No. US20020177498, both to the present inventor, Christopher A. Wickliffe, thereby lifting a lower outside corner of a bicycle chain toward the larger bicycle chain ring. Method  1000  may further include multiple outer chain links of the bicycle chain engaging  1008  a lifting surface on a ramp and lifting  1010  the bicycle chain off of the smaller bicycle chain ring and onto the larger bicycle chain ring. 
         [0078]    Additional embodiments of bicycle chain rings according to the present invention are shown in  FIGS. 11-29 .  FIG. 11  is a plan view of the inside of a 32 tooth bicycle chain ring  1100  on 94 mm mounting bolt centers having five mounting bolt holes according to an embodiment of the present invention.  FIG. 12  is an enlarged perspective view of a portion of the inside of the bicycle chain ring  1100  shown in  FIG. 11 .  FIG. 12  provides an enlarged illustration of mounting hole  106 , ramps  1108 A and  1108 B, and inside taper  1116  associated with this embodiment of a bicycle chain ring  1100 . The ramp  1108 A includes a lifting surface with a concave portion  1117  adjacent to the inner edge  FIG. 13  is a super-enlarged perspective view of a portion of the inside of the bicycle chain ring  1100  shown in  FIG. 11-12 .  FIG. 13  illustrates inside taper  1116 , mounting hole  106  and ramp  1108 A.  FIG. 13  also illustrates a seamless transition  1123  between the inner side of the ring and the inwardly extending surface. The inwardly extending surface includes a portion that is flush with the edge. The concave portion highlighted in  FIG. 12  includes a portion that is flush with the inner edge (see also  FIG. 11 ). 
         [0079]      FIGS. 14-15  are enlarged perspective views of the outside of the bicycle chain ring  1100  shown in  FIG. 11-13 .  FIGS. 14-15  shows an enlarged perspective view of outer ridge  1138 , outside bevels  1154  and outside notch  1156 .  FIG. 15  also shows mounting hole  106  and an obstructed view of inside taper  1116 . 
         [0080]    It is important to note that the ramps  108 ,  308 ,  408 A-B,  708 A-B and  1108 A-B, on the inside surface of the bicycle chain rings  100 ,  300 ,  400 ,  700  and  1100  disclosed herein, contact and lift the bicycle chain directly underneath the load points, i.e., chain link rollers (bushings and pins), of multiple chain links during an up-shift. Each ramp engages the bicycle chain directly below the chain link rollers and lifts at multiple load points (below each chain link roller). This is in distinct contrast to conventional bicycle chain rings with pins that attempt to accomplish the same task. Such conventional pin lifting is necessarily at a single load point (between two chain link rollers) to accomplish the bicycle chain lifting. Thus, the ramps  108 ,  308 ,  408 A-B,  708 A-B and  1108 A-B, of the present invention spread the load over multiple load points. 
         [0081]      FIG. 16  is a plan view of an embodiment of a 34-tooth bicycle chain ring on 104 mm mounting bolt centers  1600  having four mounting holes  1602  according to an embodiment of the present invention.  FIG. 17  is a plan view of an embodiment of a 32-tooth bicycle chain ring  1700  compatible with a four mounting hole-Shimano™ XTR™ crankset (not shown) according to an embodiment of the present invention. Chain ring  1700  includes 4 mounting holes  1702 .  FIG. 18  is a plan view of an embodiment of a 34-tooth bicycle chain ring on 94 mm mounting bolt centers  1800  having five mounting holes  1802  according to an embodiment of the present invention.  FIG. 19  is a plan view of an embodiment of a 34-tooth bicycle chain ring on 104 mm mounting bolt centers  1900  having four mounting holes  1902  according to an embodiment of the present invention.  FIG. 20  is a plan view of an embodiment of a 34-tooth bicycle chain ring on 110 mm mounting bolt centers  2000  having five mounting holes  2002  according to an embodiment of the present invention.  FIG. 21  is a plan view of an embodiment of a 34-tooth bicycle chain ring  2100  compatible with a four mounting hole Shimano™ XTR™ crankset (not shown) according to an embodiment of the present invention. Chain ring  2100  includes four mounting holes  2102 .  FIG. 22  is a plan view of an embodiment of a 44-tooth bicycle chain ring on 94 mm mounting bolt centers  2200  having five mounting holes  2202  according to an embodiment of the present invention.  FIG. 23  is a plan view of an embodiment of a 44-tooth bicycle chain ring on 104 mm mounting bolt centers  2300  having four mounting holes  2302  according to an embodiment of the present invention.  FIG. 24  is a plan view of an embodiment of a 44-tooth bicycle chain ring on 110 mm mounting bolt centers  2400  having five mounting holes  2402  according to an embodiment of the present invention.  FIG. 25  is a plan view of an embodiment of a 44-tooth bicycle chain ring  2500  compatible with a four mounting hole Shimano™ XTR™ crankset (not shown) according to an embodiment of the present invention. Chain ring  2500  includes four mounting holes  2502 .  FIG. 26  is a plan view of an embodiment of a 46-tooth bicycle chain ring on 94 mm mounting bolt centers  2600  having five mounting holes  2602  according to an embodiment of the present invention.  FIG. 27  is a plan view of an embodiment of a 46-tooth bicycle chain ring on 104 mm mounting bolt centers  2700  having four mounting holes  2702  according to an embodiment of the present invention.  FIG. 28  is a plan view of an embodiment of a 46-tooth bicycle chain ring on 110 mm mounting bolt centers  2800  having five mounting holes  2802  according to an embodiment of the present invention.  FIG. 29  is a plan view of an embodiment of a 46-tooth bicycle chain ring  2900  compatible with a four mounting hole Shimano ™ XTR™ crankset (not shown) according to an embodiment of the present invention. Chain ring  2900  includes four mounting holes  2902 . Chain ring  2900  further includes twelve ramps  2908  having a leading edge  2930  that is curved in profile. Thus, ramps  2908  have both a linear profile and a curved profile on the leading edge  2930 . 
         [0082]    While the foregoing advantages of the present invention are manifested in the illustrated embodiments of the invention, a variety of changes can be made to the configuration, design and construction of the invention to achieve those advantages. Hence, reference herein to specific details of the structure and function of the present invention is by way of example only and not by way of limitation.