BICYCLE CHAINRING

Abstract

Bicycle chainring (14; 16; 114; 116; 214) comprising: a chainring main body (40; 60; 140; 160; 240) with an axis of rotation; and a plurality of teeth (42; 62; 142; 162; 242) arranged along a circumferential direction on a radially outer side of the chainring main body (40; 60; 140; 160; 240), wherein the plurality of teeth (42; 62; 142; 162; 242) comprises at least one first tooth (51) and at least one second tooth (52); and at least one projecting element (44; 46; 144; 146; 244) which is attached to an axial surface (54; 56) of the at least one first tooth (51) by means of an integral forming process or bonding such that the at least one projecting element (44; 46; 144; 146; 244) overlaps the at least one first tooth (51) in an axial direction when viewed parallel to the axis of rotation, wherein the at least one projecting element (44; 46; 144; 146; 244) is made of a different material from the plurality of teeth (42; 62; 142;162; 242) is manufactured, and wherein the at least one projecting element (44; 46; 144; 146; 244) and the at least one first tooth (51) define a first chain engagement tooth width (W1) for engagement with an outer link (24) of the chain (20) and the at least one second tooth (52) defines a second chain engagement tooth width (W2) for engagement with an inner link (22) of the chain (20), wherein the first chain engagement tooth width (W1) is larger than the second chain engagement tooth width (W2) and wherein the at least one second tooth (52) is free of the at least one projecting element (44; 46; 144; 146; 244).;

Description

BACKGROUND OF THE INVENTION AREA OF INVENTION This application claims priority over U.S. application no. US 14 / 154,653, which was filed on January 14, 2014. Reference is hereby made to the entire disclosure of U.S. application no. US 14 / 154,653. The present invention relates generally to a bicycle chainring which drives a bicycle chain. BACKGROUND INFORMATION Most bicycles have a drivetrain, or drive unit, which uses a chain to transmit the rider's pedaling motion to the rear wheel. A bicycle drivetrain typically has one or more front chainrings or sprockets, located on the bicycle's crankset, and one or more rear sprockets or chainrings, located on the bicycle's rear hub. The chain engages with the front and rear chainrings or sprockets. Consequently, the rider's rotation of the crankset is transmitted to the rear wheel via the chain, which meshes with the front and rear sprockets or chainrings. A bicycle chain has numerous inner links and numerous outer links, which are alternately connected to one another by numerous pins.Typically, each of the inner links has a pair of parallel inner link plates connected by pins surrounded by cylindrical rollers. Each of the outer links has a pair of parallel outer link plates connected by the pins of the adjacent inner link plates. In this way, the inner and outer links are connected alternately. Consequently, if the teeth of all sprockets have the same thickness, gaps occur between the outer link plates and the teeth of the sprockets or chainrings that are larger than the gaps between the inner link plates and the teeth of the sprockets or chainrings. Given this situation, sprockets or chainrings were...Chainrings have been proposed in which the axial widths of the teeth engaging with the outer links are larger than the axial widths of the teeth engaging with the inner links (see, for example, US 4,174,642 A). DE 10 2006 039 333 A1 describes a sintered sprocket that is rotatable about an axis of rotation and has two opposing sides and teeth formed on the outer circumference, the teeth having tooth heads and two adjacent teeth being separated from each other by a tooth gap, and the tooth gaps having a bottom that is tangent to a circle whose center is the axis of rotation of the sprocket, wherein the sprocket has projections formed on both sides and arranged at the intersections of the circle with radial lines extending from the axis of rotation to the centers of the tooth heads, and a chain drive that uses at least one such sprocket. DE 10 2012 023 819 A1 describes a bicycle front crank assembly for engaging a drive chain, comprising a plurality of teeth formed around the circumference of the chainring, wherein the plurality of teeth has an even number of teeth. The plurality of teeth comprises a first group of teeth and a second group of teeth arranged alternately between the first group of teeth. The first and second groups of teeth are equal in number. Each first and second group of teeth comprises an outer side and an inner side opposite the outer side, and each tooth of the first group of teeth comprises at least one projection on the outer side, and each tooth of the second group of teeth is formed without a first projection on either the outer or inner side. US 4,174,642 A describes a chain drive comprising a sprocket rotatable in a plane and having an even number of wide and narrow tapered teeth, and a flexible chain having successive links with alternating wide and narrow link openings engaging the tooth, wherein the width of the teeth and the width of the link openings are measured in a direction transverse to the plane of sprocket rotation. OVERVIEW OF THE INVENTION In general, the present disclosure relates to various features of a bicycle chainring or sprocket which has teeth of different axial widths or widths with respect to a rotation center axis direction of the chainring in order to prevent the chain from simply coming off the teeth of the chainring or sprocket. In light of the prior art and in accordance with a first aspect of the present disclosure, a bicycle chainring is provided, comprising essentially a chainring body, a plurality of teeth, and at least one projecting element. The chainring body has an axis of rotation. The plurality of teeth is arranged along a circumferential direction on a radial outer side of the chainring body. The plurality of teeth includes at least one first tooth and at least one second tooth. The at least one projecting element is attached to an axial surface of the at least one first tooth by a forming process or bonding, such that the at least one projecting element overlaps the first tooth in an axial direction when viewed parallel to the axis of rotation. The at least one projecting element is made of a different material than that of the teeth.The at least one protruding element and the at least one first tooth define a first chain engagement tooth width for engagement with an outer link of a bicycle chain. The at least one second tooth defines a second chain engagement tooth width for engagement with an inner link of the bicycle chain. The first chain engagement tooth width is larger than the second chain engagement tooth width. The at least one second tooth is free of the at least one protruding element. In this bicycle chainring, the chain is mounted to the chainring or sprocket such that the first tooth, with its larger axial width, engages with an outer link, and the second tooth, with its smaller axial width than the first tooth, engages with an inner link. Preferred embodiments are defined in the dependent claims. Preferably, a bicycle chainring is configured according to the first aspect such that the at least one first tooth has a plurality of first teeth, each of the first teeth having the at least one protruding element. Preferably, the bicycle chainring is configured so that at least one second tooth has a multitude of second teeth. Preferably, the bicycle chainring is configured such that the at least one first tooth has a plurality of first teeth, each of the first teeth having the at least one protruding element, and the at least one second tooth has a plurality of second teeth. Preferably, the bicycle chainring is configured so that the first teeth and the second teeth are arranged alternately in a circumferential direction. Preferably, the bicycle chainring is configured so that the total number of teeth is equal to the number of teeth on each chainring. In accordance with a first aspect of the present disclosure, a bicycle chainring is provided, comprising essentially a chainring body, a plurality of teeth, and at least one projecting element. The chainring body has an axis of rotation. The plurality of teeth is arranged along a circumferential direction on a radial outer side of the chainring body. The plurality of teeth includes at least one first tooth and at least one second tooth. The at least one projecting element is attached to an axial surface of the at least one first tooth by a forming process or bonding, such that the at least one projecting element overlaps the first tooth in an axial direction when viewed parallel to the axis of rotation. The at least one projecting element is made of a different material than that of the teeth.The at least one projecting element and the at least one first tooth define a first chain engagement tooth width for engagement with an outer link of a bicycle chain. The at least one second tooth defines a second chain engagement tooth width for engagement with an inner link of the bicycle chain. The first chain engagement tooth width is larger than the second chain engagement tooth width. The at least one second tooth is free of the at least one projecting element. The at least one projecting element does not extend below a root circle radius of the first teeth, so that the at least one projecting element has a plurality of separate individual sections. Preferably, the bicycle chainring is configured such that the at least one projecting element extends below a foot circle radius of the first teeth such that the at least one projecting element extends continuously between at least two of the first teeth along a section of the chainring main body. Preferably, the bicycle chainring is configured such that at least one protruding element is made of a resin material and the plurality of teeth are made of a metallic material. Preferably, the bicycle chainring is configured such that the at least one first tooth has a first axial surface and a second axial surface opposite the first axial surface, and the at least one projecting element has a first projecting element attached to the first axial surface of the at least one first tooth and a second projecting element attached to the second axial surface of the at least one first tooth. Preferably, the bicycle chainring is configured such that the at least one first tooth has a plurality of first teeth, each of the first teeth having the first and second projecting elements, and the at least one second tooth has a plurality of second teeth. Preferably, the bicycle chainring is configured so that the first teeth and the second teeth are arranged alternately in a circumferential direction. Preferably, the bicycle chainring is configured so that a total number of the many teeth are even. Preferably, the bicycle chainring is configured such that the first and second projecting elements do not extend below a foot circle radius of the first teeth, so that each of the first and second projecting elements has a plurality of separate individual sections. Preferably, the bicycle chainring is configured such that the first and second projecting elements extend below a foot circle radius of the first teeth such that the first and second projecting elements extend continuously at least between two of the first teeth and along a section of the chainring main body. Preferably, the bicycle chainring is configured such that the at least one protruding element is attached to the at least one tooth by means of an integral forming process. Preferably, the bicycle chainring is configured such that the first and second projecting elements are attached to at least one of the first teeth by means of an integral forming process. Preferably, the bicycle chainring consists of a single chainring or sprocket alone. Further tasks, features, aspects and advantages of the disclosed bicycle chainring or sprocket will become apparent to the person skilled in the art from the detailed description given below, which, in conjunction with the accompanying drawings, discloses selected embodiments of the bicycle chainring. BRIEF DESCRIPTION OF THE DRAWINGS Reference is now made to the accompanying drawings, which form part of this original disclosure: Fig. 1 is a side view from the outside of a bicycle crank assembly having first and second chainrings, configured in accordance with a first embodiment; Fig. 2 is a partial perspective view from the inside of the first and second chainrings of the bicycle crank assembly shown in Fig. 1, with a bicycle chain engaging the teeth of the first (larger) chainring; Fig. 3 is a partial perspective view from the inside, similar to Fig. 2, of the first and second chainrings of the bicycle crank assembly shown in Fig. 1, but without the bicycle chain; Fig. 4 is a perspective view from the outside of the first chainring of the bicycle crank assembly shown in Fig. 1, Fig. 2 to Fig. 3; Fig. 5 is a partial edge view of the chainring shown in Fig. 1.Fig. 4 shows the first chainring, showing one of the first teeth and two of the second teeth of the first chainring; Fig. 6 is a sectional view of the first chainring as seen along section line 6-6 of Fig. 4; Fig. 7 is a sectional view of the first chainring as seen along section line 7-7 of Fig. 4; Fig. 8 is a perspective view from the outside of the second chainring of the bicycle crank assembly shown in Fig. 1, Fig. 2 to Fig. 3; Fig. 9 is a partial edge view of the second chainring shown in Fig. 8, showing one of the first teeth and two of the second teeth of the second chainring; Fig. 10 is a side view from the outside of a bicycle crank assembly having first and second chainrings, configured in accordance with a second embodiment; Fig. 11 is a side view from the outside of a section of the first chainring shown in Fig. 10; Fig. 12 is a partial edge view of the one shown in Fig.Fig. 10 and Fig. 11 show the first chainring, showing one of the first teeth and at least two of the second teeth of the first chainring; Fig. 13 is an external side view of a section of the second chainring shown in Fig. 10; Fig. 14 is a partial edge view of the second chainring shown in Fig. 10 and Fig. 13, showing one of the first teeth and two of the second teeth of the second chainring; and Fig. 15 is an external side view of a crank assembly with only a single chainring attached to the crank arm, in accordance with a third embodiment. DETAILED DESCRIPTION OF THE EXECUTION FORMS Selected embodiments are explained below with reference to the drawings. It will be apparent to those skilled in the art in bicycle technology from this disclosure that the following descriptions of the embodiments are given for illustrative purposes only and not for the purpose of limiting the invention as defined by the attached claims and their equivalents. With initial reference to Fig. 1, a bicycle crank assembly 10 is shown in accordance with a first embodiment. In the first embodiment, the bicycle crank assembly 10 comprises a crank arm 12, a first chainring 14, and a second chainring 16. More generally, the bicycle crank assembly 10 essentially comprises a crank arm and at least one chainring or sprocket. The first and second chainrings 14 and 16 are bicycle chainrings according to one embodiment. The second chainring 16 has fewer teeth than the first chainring 14. The first and second chainrings 14 and 16 are front chainrings that can be engaged with a bicycle chain 20. As can be seen in Fig. 2, the bicycle chain 20 has a plurality of inner links 22 and a plurality of outer links 24, which are interconnected in an alternating manner by means of a plurality of pins 26. Typically, each of the inner links 22 has a pair of parallel inner link plates 22a. Each of the outer links 24 has a pair of parallel outer link plates 24a. Preferably, each of the pins 26 has a roller 26a which is rotatably mounted thereon. Consequently, the bicycle chain 20 is a conventional bicycle chain. The crank arm 12 is integrally and non-rotatably attached to one end of a crankshaft 28. Typically, a second (not shown) crank arm is non-rotatably attached to the other end of the crankshaft 28. The crankshaft 28 defines a center-of-rotation axis X for the first and second chainrings 14 and 16. The at least one chainring (e.g., the first and second chainrings 14 and 16) has a center-of-rotation axis X. The crank arm 12 has a chainring mounting part 30 and an arm part 32, provided with a pedal mounting part 32a. The crank arm 12 has a longitudinal centerline L located between the chainring mounting part 30 and the pedal mounting part 32a. The at least one chainring (e.g., the first and second chainrings 14 and 16) is attached to the chainring mounting part 30 of the crank arm 12. The chainring mounting part 30 can be either integral to or separate from the arm part 32. The chainring mounting part 30 has a plurality (e.g., four) of chainring mounting arms 34, arranged at intervals in the circumferential direction. The circumferential intervals of the chainring mounting arms 34 can be equal or unequal. In the first embodiment, the chainring mounting arms 34 are arranged at equal intervals. Each of the chainring mounting arms 34 has a first mounting part 34a for attaching the first chainring 14. The first mounting parts 34a are formed at the distal ends of the chainring mounting arms 34. Each of the chainring mounting arms 34 has a second mounting part 34b for attaching the second sprocket 16.The second mounting parts 34b are formed further inwards in the radial direction than the first mounting parts 34a. Both the first mounting parts 34a and the second mounting parts 34b have through holes or blind holes, which may or may not be threaded. In the first embodiment, the first mounting parts 34a are configured with unthreaded through holes, and the second mounting parts 34b are configured with blind screw holes. The first chainring 14 is attached to the first mounting parts 34a using first mounting screws 36. The second chainring 16 is attached to the second mounting parts 34b using second mounting screws (not shown). The arm part 32 is formed either integrally or separately from the chainring mounting part 30. In the first embodiment, the arm part 32 is configured integrally with the chainring mounting part 30. The pedal mounting part 32a defines a threaded bore into which a pedal (not shown) can be mounted at a distal end. The arm part 32 also has a mounting hole 32b to which the crankshaft 28 is fixed. A first chainring main body 40 has a plurality (e.g., four) of first fixing parts 40a for fixing the first mounting parts 34a of the chainring mounting arms 34. In the first embodiment, the first fixing parts 40a have through holes 40b. The first chainring 14 is screwed to the chainring mounting arms 34 by means of the first mounting screws 36 and a nut element (not shown) with the first mounting screws 36 in a conventional manner. As shown in Figures 3, 4 to 5, the first chainring 14 comprises a first chainring body 40, a plurality of teeth 42, and at least one projecting element 44 or 46. The at least one projecting element 44 or 46 is made of a different material than that of the teeth 42. Preferably, the at least one projecting element 44 or 46 is made of a resin material, such as, for example, preferably a fiber-reinforced resin material. Preferably, the plurality of teeth is made of a metallic material, such as, for example, preferably aluminum, titanium, stainless steel, magnesium, beryllium, or another suitable metallic material. The first chainring body 40 and the teeth 42 can both be made of a metallic material and can be integrally formed as a single unitary element.If weight reduction is required and / or desired, the first chainring main body 40 can be made of a non-metallic material, preferably a fiber-reinforced resin material, while the teeth 42 can be made of a metallic material. If the protruding elements 44 and 46 are made of resin material, they can be attached to the first chainring main body 40 and the teeth 42 by means of an integral molding process or bonding, as shown. In particular, the integral molding process can be carried out such that the resin of the protruding elements 44 and 46 can extend into recesses, which are preferably formed on the first chainring main body 40 and the teeth 42, during the molding of the protruding elements 44 and 46. The first chainring main body 40 has an axis of rotation that corresponds to the center-of-rotation axis X of the first chainring 14. The plurality of teeth 42 are arranged along a circumferential direction on a radially outer side of the chainring main body 40. In the first embodiment, the first chainring 14 has thirty-six of the plurality of teeth 42. Consequently, the total number of the plurality of teeth 42 for the first chainring 14 is even. The plurality of teeth 42 comprises at least one first tooth 51 and at least one second tooth 52. The at least one first tooth 51 has a first axial surface 54 and a second axial surface 56, which is opposite the first axial surface 54. The at least one projecting element 44 or 46 projects axially from at least one of the axial surfaces 54 or 56 of the at least one first tooth 51.In the first embodiment, the at least one projecting element 44 or 46 is attached to the at least one first tooth 51 by means of an integral forming process or adhesive. Preferably, the at least one projecting element 44 or 46 has a first projecting element 44 which is attached to the first axial surface 54 of the at least one first tooth 51 and a second projecting element 46 which is attached to the second axial surface 56 of the at least one first tooth 51. Preferably, the first and second axial surfaces 54 and 56 have a textured surface which has depressions or the like, so that the resin of the projecting elements 44 and 46 can extend into these depressions of the first chainring main body 40 and the teeth 42 during the forming of the projecting elements 44 and 46.Preferably, as in the first embodiment, the first and second projecting elements 44 and 46 are attached to the at least one first tooth 51 by means of an integral forming process. As shown in Fig. 5, the at least one projecting element 44 or 46 and the at least one first tooth 51 define a first chain engagement tooth width W1 for engagement with the outer link 24 of the bicycle chain 20. The at least one second tooth 52 defines a second chain engagement tooth width W2 for engagement with the inner link 22 of the bicycle chain 20. The first chain engagement tooth width W1 is larger than the second chain engagement tooth width W2. The first chain engagement tooth width W1 of the first teeth 51 is preferably in the range of 2.5 mm to 5.4 mm and particularly preferably in the range of 3.0 mm to 4.5 mm. If the first chain engagement tooth widths W1 of the first teeth 51 are in such a range, the first teeth 51 can simply engage with the outer link plates 24a without engaging with the inner link plates 22a. The second chain engagement tooth widths W2 of the second teeth 52 are preferably in a range of 1.5 mm to 2.3 mm.If the second chain engagement tooth widths W2 of the second teeth 52 lie within such a range, the second teeth 52 have the necessary stiffness and engage easily with the inner link plates 22a. The first teeth 51 are preferably in a "+" (plus) shape, as seen from the radially outer side, as shown in Fig. 5. The second teeth are preferably shaped in a "-" (minus) shape when viewed from the radially outer side. The first teeth 51 and the second teeth 52 are tapered, so that their axial width gradually decreases towards the radially outer side. This facilitates the engagement of the first teeth 51 and the second teeth 52 with the outer link plates 24a and the inner link plates 22a. In the first embodiment, the first teeth 51 are identical to the second teeth 52 with respect to their height in the radial direction. Preferably, the at least one first tooth 51 comprises a plurality of first teeth 51, each of which has the at least one projecting element 44 or 46. Preferably, the at least one second tooth 52 comprises a plurality of second teeth 52 which are free of the projecting elements 44 and 46. The first teeth 51 and the second teeth 52 are arranged alternately in a circumferential direction. While the first and second teeth 51 and 52 are shown as perfectly symmetrical teeth, it is apparent from this disclosure that the first and second teeth 51 and 52 can be asymmetrical teeth, twisted teeth, switching teeth with switching features, and / or the like. The at least one projecting element 44 or 46 extends below a root radius R of the first teeth 51, such that the at least one projecting element 44 or 46 extends continuously between at least two of the first teeth 51 and along a section of the chainring main body 40. Preferably, each of the first teeth 51 has both of the first and second projecting elements 44 and 46. Equally preferably, in this first embodiment, the first and second projecting elements 44 and 46 extend below a root radius R of the first teeth 51 such that the first and second projecting elements 44 and 46 extend continuously between at least two of the first teeth 51 and along a section of the chainring main body 40. The second chainring 16 will now be explained with reference to Figures 1 to 3, 8, and 9. Essentially, the second chainring 16 has the same configuration as the first chainring 14, except that the second chainring 16 is smaller and has fewer teeth than the first chainring 14. Given the similarity between the first and second chainrings 14 and 16, the second chainring 16 will only be discussed briefly here. The second chainring 16 comprises a second chainring body 60, a plurality of teeth 62, and first and second projecting elements 64 and 66 alternating with the teeth 62. The first and second projecting elements 64 and 66 are made of a different material than the teeth 62. Preferably, the first and second projecting elements 64 and 66 are made of a resin material, such as a fiber-reinforced resin. Preferably, the teeth 62 are made of a metallic material, such as preferably aluminum, titanium, stainless steel, magnesium, beryllium, or another suitable metallic material. The second chainring body 60 and the teeth 62 can both be made of a metallic material and can be integrally formed as a single unitary element.If weight saving is required and / or desired, the second chainring main body 60 may be made of a non-metallic material, such as preferably a fiber-reinforced resin material, while the teeth 62 may be made of a metallic material. The second chainring main body 60 has a plurality (e.g., four) of second fixing parts 60a for fixing the second mounting parts 34b (see Fig. 1) of the chainring mounting arms 34. The second fixing parts 60a are configured with through holes. The second chainring 16 is attached to the chainring mounting arms 34 by means of the second mounting screws (not shown), which are screwed into the blind holes of the second mounting parts 34b. In the first embodiment, for example, the second chainring 16 has twenty-four of the plurality of teeth 62. Therefore, a total number of the plurality of teeth 62 is just for the second chainring 16. The teeth 62 have first and second chainring teeth 71 and 72. The first and second projecting elements 64 and 66 protrude from opposing axial surfaces 74 or 76 of the first teeth 71. The first and second chainring teeth 71 and 72 of the second chainring 16 have the same configurations and the same axial widths as the first and second chainring teeth 51 and 52 of the first chainring 14, as described above. The second chainring main body 60 has a plurality of (e.g., four) of the second fixing parts 60a for fixing the second mounting parts 34b of the chainring mounting arms 34. In the first embodiment, the second fixing parts 60a have through holes 60b.In the first embodiment, the first and second projecting elements 64 and 66 are attached to the first teeth 71 by means of an integral forming process or adhesive. With reference to Figures 10, 11, 12, 13 to 14, a bicycle crank assembly 110 is shown in accordance with a second embodiment. In the second embodiment, the bicycle crank assembly 110 has a crank arm 112, a first chainring 114, and a second chainring 116. Here, the crank arm 112 is identical to the crank arm 12 as described above. With regard to the first and second chainrings 114 and 116, only descriptions of the differences between them and the first and second chainrings 114 and 116 are given. As can be seen in Fig. 10, the crank arm 112 is integrally and non-rotatably attached to one end of a crankshaft 128. The crank arm 112 has a chainring mounting part 130 and an arm part 132 and is equipped with a pedal mounting part 132a. The crank arm 112 has a longitudinal center line L which extends between the chainring mounting part 130 and the pedal mounting part 132a. The first and second chainrings 114 and 116 are fixedly attached to the chainring mounting part 130 of the crank arm 112 by means of four chainring mounting arms 134. Each of the chainring mounting arms 134 has a first mounting part 134a for attaching the first chainring 114 and a second mounting part 134b for attaching the second chainring 116 in the first manner, as in the first embodiment. As can be seen in Figs. 10, 11, and 12, the first chainring 114 has a first chainring body 140 and a plurality of teeth 142 and at least one projecting element 144 or 146 arranged on alternating teeth 142. Preferably, the teeth 142 have a plurality of first teeth 151 and a plurality of second teeth 152. Each of the first teeth 151 has one or both of the projecting elements 144 and 146. Preferably, the second teeth 152 are free of the projecting elements 144 and 146. The first and second projecting elements 144 and 146 are made of a different material than that of the teeth 142, as in the first embodiment. Preferably, the first and second projecting elements 144 and 146 are made of a resin material, such as, for example, preferably a fiber-reinforced resin material.Preferably, the teeth 142 are made of a metallic material, such as preferably aluminum, titanium, stainless steel, magnesium, beryllium, or any other suitable metallic material. The first chainring main body 140 and the teeth 142 can both be made of a metallic material and can be integrally formed as a single unitary element. If weight savings are required and / or desired, the first chainring main body 140 can be made of a non-metallic material, such as preferably a fiber-reinforced resin material, while the teeth 142 can be made of a metallic material. The first chainring main body 140 and the teeth 142 are identical to the first chainring main body 40 and the teeth 42 of the first embodiment. However, the first and second projecting elements 144 and 146 differ from the first and second projecting elements 44 and 46 of the first embodiment. In the second embodiment, the at least one projecting element 144 or 146 does not extend below a root circle radius R of the first teeth 142, so that the at least one projecting element 144 or 146 has a plurality of separate individual sections 144a and 146a. Preferably, each of the first teeth 151 has both of the projecting elements 144 and 146, which do not extend below the root circle radius R of the first teeth 151, so that each of the first and second projecting elements 144 and 146 has a plurality of separate individual sections 144a and 146a.Here, in the second embodiment, the foreground elements 144 and 146 are attached to the first teeth 151 by means of an integral forming process or adhesive, similar to the first embodiment. As can be seen in Figs. 10, 13 and 14, the second chainring 116 has a second chainring main body 160, a plurality of teeth 162, and first and second elements 164 and 166 on alternating teeth 162. Preferably, the teeth 162 have a plurality of first teeth 171 and a plurality of second teeth 172. Each of the first teeth 171 has one or both of the aforementioned elements 164 and 166. Preferably, the second teeth 172 are free of the aforementioned elements 164 and 166. The first and second projecting elements 164 and 166 are made of a different material than that of the teeth 162, as in the first embodiment. Preferably, the first and second projecting elements 164 and 166 are made of a resin material, such as, for example, preferably a fiber-reinforced resin material. In the second embodiment, the first and second projecting elements 164 and 166 are attached to the first teeth 171 by means of an integral forming process or adhesive. Preferably, the teeth 162 are made of a metallic material, such as, for example, preferably aluminum, titanium, stainless steel, magnesium, beryllium, or any other suitable metallic material. The first chainring main body 160 and the teeth 162 can both be formed from a metallic material and can be integrally formed as a single unitary element.If weight reduction is required and / or desired, the second chainring main body 160 may be made of a non-metallic material, such as preferably a fiber-reinforced resin material, whereas the teeth 162 may be made of a metallic material. The second chainring main body 160 and the teeth 162 are identical to the second chainring main body 60 and the teeth 62 of the first embodiment. However, the first and second projecting elements 164 and 166 differ from the first and second projecting elements 64 and 66 of the first embodiment. In the second embodiment, the projecting elements 164 and 166 do not extend below a root circle radius R of the second teeth 171, so that the at least one projecting element 164 or 166 has a plurality of separate individual sections 164a and 166a. Preferably, each of the first teeth 171 has both of the projecting elements 164 and 166, which do not extend below the root circle radius R of the first teeth 171, so that each of the first and second projecting elements 164 and 166 has a plurality of separate individual sections 164a and 166a.In the second embodiment, the foreground elements 164 and 166 are attached to the first teeth 171 by means of an integral forming process or adhesive, similar to the first embodiment. With reference to Fig. 15, a bicycle crank assembly 210 is shown in accordance with a third embodiment. Here, the bicycle crank assembly 210 has a crank arm 212 with only one single chainring 214, which is attached to the crank arm 212. With the crank assembly 210, the chain 20 does not simply disengage from the chainring 214, for example, when riding on a rough surface. Here, the crank arm 212 is identical to the crank arm 12 as described above, except that the second mounting part has been removed from the crank arm 212, so that only the chainring 214 can be attached to the crank arm 212. The chainring 214 is identical to either the first chainring 14 or the first chainring 114. In Fig. 15, the chainring 214 is shown as being identical to the first chainring 14. Consequently, the chainring 214 has a chainring body 240 and a plurality of teeth 242. In view of the similarity of the crank arm 212 and the chainring 214 to the corresponding parts of the previously described embodiments, the crank arm 212 and the chainring 214 are not discussed and / or illustrated in further detail here. Projecting elements of the chainring 214 can be attached to the first chainring body 240 and the teeth 242 as shown, or only to the teeth 242. The projecting elements (only one shown) are formed from a different material than that of the teeth 242. In Fig. 15, alternating teeth 242 have the projecting elements (only the projecting element 244 is shown, as only one axial face of the sprocket 214 is depicted). For example, the teeth 242 have a plurality of first teeth 51 and a plurality of second teeth 52, in which the opposing axial faces of the first teeth 51 have the projecting elements. In other words, the other axial face of the chainring 214 also has a projecting element, in the same manner as shown in Figs. 2, 3, 4, 5, 6 to 7. Alternatively, the foreground elements of the chainring 214 can be configured as shown in Fig. 11 and Fig. 12.As in the embodiments described above, the leading elements of the chainring 214 are made of a resin material, preferably a fiber-reinforced resin material. Preferably, the teeth 242 are made of a metallic material, preferably aluminum, titanium, stainless steel, magnesium, beryllium, or any other suitable metallic material. The first chainring main body 240 and the teeth 242 can both be made of a metallic material and can be integrally formed as a single unitary element. If weight savings are required and / or desired, the first chainring main body 240 can be made of a non-metallic material, preferably a fiber-reinforced resin material, whereas the teeth 242 can be made of a metallic material.If the protruding elements of the chainring 214 are made of resin material as shown, the protruding elements of the chainring 214 can be attached to the first chainring main body 240 and the teeth 242 by means of the integral molding process or adhesive. In particular, the integral molding process can be carried out such that the resin of the protruding elements of the chainring 214 extends into recesses, which are preferably arranged on the first chainring main body 240 and the teeth 242, during the molding of the protruding elements of the chainring 214. While only selected embodiments have been chosen to represent the present invention, it is apparent to those skilled in the art from this disclosure that a multitude of changes and modifications can be made to it without departing from the focus of the invention as defined by the appended claims. For example, the size, shape, location, or orientation of the various components can be changed as needed and / or desired, provided that the changes do not substantially affect their intended function. Similarly, in the bicycle crank assemblies of the first and second embodiments, the first and second teeth are provided with different axial widths on both chainrings; however, the present invention is not limited to this. Rather, it is evident from this disclosure that the bicycle crank assemblies 10 and 110 can have a third chainring, while crank assemblies 10 and 110 have only two chainrings. In the first to third embodiments, the first teeth were shaped in a “+” (plus) shape, as can be seen from the radially outer side; however, the present invention is not limited to this. These teeth can also be shaped in other forms, such as diamond-shaped, trapezoidal, triangular, and hexagonal. In the first to third embodiments there are four chainring mounting arms, however the number of chainring mounting arms is not limited to four. In the first to third embodiments, the chainring main body and the plurality of teeth are integrally formed; however, the present invention is not limited thereto. The chainring main body and the plurality of teeth can be formed separately. For example, the plurality of teeth can be formed from metal, and the chainring main body can be formed from a synthetic resin, such as carbon fiber reinforced resin, or from a different metal than the teeth (a lightweight metal, such as aluminum, for example) to reduce weight. According to the present invention, the protruding elements can be made of an elastomeric material. Preferably, the protruding elements can be made of an elastomeric material with high abrasion resistance. The terms "left" and "right" are used to designate the right side when viewing the bicycle from behind, and the left side when viewed from behind. Likewise, it should be clear from this revelation that the terms "first" and "second," as used here, are employed to describe different components, but these components are not limited by these terms. These terms are merely used to distinguish the components from one another. Consequently, for example, a first component described above could be called a second component, and vice versa, without deviating from the teaching of this revelation.The term "attached" and its derivatives encompasses configurations in which the element is directly secured to another element; configurations in which the element is indirectly secured to the other element by securing the element to one or more intermediate elements, which are then in turn secured to the other element; and configurations in which one element is integral with another element, with one element essentially being part of the other. This definition also applies to terms and their derivatives with similar meanings, such as "mounted," "connected," "glued," "fixed," "secured," "coupled," "linked," or "fastened." Finally, the degree terms, such as "essentially," "by," and "approximately," as used herein, signify a reasonable amount of deviation from the modified term such that the final result is not significantly altered. Accordingly, the above descriptions of the embodiments are given for illustrative purposes only and not for the purpose of limiting the invention as defined by the attached claims.

Claims

Bicycle chainring (14; 16; 114; 116; 214) comprising: a chainring main body (40; 60; 140; 160; 240) with an axis of rotation; and a plurality of teeth (42; 62; 142; 162; 242) arranged along a circumferential direction on a radially outer side of the chainring main body (40; 60; 140; 160; 240), wherein the plurality of teeth (42; 62; 142; 162; 242) comprises at least one first tooth (51) and at least one second tooth (52); and at least one projecting element (44; 46; 144; 146; 244) which is attached to an axial surface (54; 56) of the at least one first tooth (51) by means of an integral forming process or bonding such that the at least one projecting element (44; 46; 144; 146; 244) overlaps the at least one first tooth (51) in an axial direction when viewed parallel to the axis of rotation, wherein the at least one projecting element (44; 46; 144; 146; 244) is made of a different material from the plurality of teeth (42; 62; 142;162; 242) is manufactured, and wherein the at least one projecting element (44; 46; 144; 146; 244) and the at least one first tooth (51) define a first chain engagement tooth width (W1) for engagement with an outer link (24) of the chain (20) and the at least one second tooth (52) defines a second chain engagement tooth width (W2) for engagement with an inner link (22) of the chain (20), wherein the first chain engagement tooth width (W1) is larger than the second chain engagement tooth width (W2) and wherein the at least one second tooth (52) is free of the at least one projecting element (44; 46; 144; 146; 244).; Bicycle chainring (14; 16; 114; 116; 214) comprising: a chainring main body (40; 60; 140; 160; 240) with an axis of rotation; and a plurality of teeth (42; 62; 142; 162; 242) arranged along a circumferential direction on a radially outer side of the chainring main body (40; 60; 140; 160; 240), wherein the plurality of teeth (42; 62; 142; 162; 242) comprises at least one first tooth (51) and at least one second tooth (52); and at least one projecting element (44; 46; 144; 146; 244) which is attached to an axial surface (54; 56) of the at least one first tooth (51) by means of an integral forming process or bonding such that the at least one projecting element (44; 46; 144; 146; 244) overlaps the at least one first tooth (51) in an axial direction when viewed parallel to the axis of rotation, wherein the at least one projecting element (44; 46; 144; 146; 244) is made of a different material from the plurality of teeth (42; 62; 142;162; 242), and wherein the at least one projecting element (44; 46; 144; 146; 244) and the at least one first tooth (51) define a first chain engagement tooth width (W1) for engagement with an outer link (24) of the chain (20), and the at least one second tooth (52) defines a second chain engagement tooth width (W2) for engagement with an inner link (22) of the chain (20), wherein the first chain engagement tooth width (W1) is larger than the second chain engagement tooth width (W2), and wherein the at least one second tooth (52) is free from the at least one projecting element (44; 46; 144; 146; 244), wherein at least one projecting element (44; 46; 144; 146; 244) does not extend below a root circle radius (R) of the first teeth (51), such that the at least one of the preceding elements (44; 46; 144; 146; 244) has a plurality of separate individual sections (144a; 146a; 164a; 166a).; Bicycle chainring (14; 16; 114; 116; 214) according to claim 1 or 2, wherein the at least one first tooth (51) has a plurality of first teeth (51), each of the first teeth (51) having the at least one projecting element (44; 46; 144; 146; 244). Bicycle chainring (14; 16; 114; 116; 214) according to claim 3 insofar as referred back to claim 1, wherein the at least one projecting element (44; 46; 144; 146; 244) extends below a root circle radius (R) of the first teeth (51) such that the at least one projecting element (44; 46; 144; 146; 244) extends continuously between at least two of the first teeth and along a section of the chainring main body (40; 60; 140; 160; 240). Bicycle chainring (14; 16; 114; 116; 214) according to one of claims 1 to 4, wherein the at least one second tooth (52) has a plurality of the second teeth (52). Bicycle chainring (14; 16; 114; 116; 214) according to one of claims 1 to 5, wherein the at least one projecting element (44; 46; 144; 146; 244) is made of a resin material and the plurality of teeth (42; 62; 142; 162; 242) are made of a metallic material. Bicycle chainring (14; 16; 114; 116; 214) according to one of claims 1 to 6, in which at least a first tooth (51) has a first axial surface (54) and a second axial surface (56) which is opposite the first axial surface (54), and at least one projecting element (44; 46; 144; 146; 244) has a first projecting element (44; 46; 144; 146; 244) which is attached to the first axial surface (54) of the at least one first tooth (51), and a second projecting element (44; 46; 144; 146; 244) which is attached to the second axial surface (56) of the at least one first tooth (51). Bicycle chainring (14; 16; 114; 116; 214) according to claim 7, wherein each of the first teeth (51) comprises first and second projecting elements (44; 46; 144; 146; 244). Bicycle chainring (14; 16; 114; 116; 214) according to one of claims 1 to 8, wherein first and second teeth (52) are arranged alternately in a circumferential direction, in particular a total number of teeth (42; 62; 142; 162; 242) is straight. Bicycle chainring (14; 16; 114; 116; 214) according to one of claims 1 to 9, wherein at least one projecting element (44; 46; 144; 146; 244), in particular all projecting elements (44; 46; 144; 146; 244), is / are attached to the at least one first tooth (51) by means of an integral forming process.

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