Multi-component sprockets and methods of making

Abstract

A sprocket for a belt system formed from at least two materials, the first being a harder material forming a core and softer material forming a body over-molded on the core. The core may include physical features to mechanically lock the interface between the core and the over-molded body along both the circumferential direction and the axial (lateral) direction. A reinforcing structure may be present at the outermost periphery of the sprocket to improve wear resistance.

Description

MULTI-COMPONENT SPROCKETS AND METHODS OF MAKINGCROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims priority to U.S. Provisional Patent Application No.63 / 777.945, filed March 26, 2025, and entitled “MULTI-COMPONENT SPROCKETS AND METHODS OF MAKING”, the entirety of which is hereby incorporated by reference.BACKGROUND

[0002] Toothed belts that engage sprockets in industrial applications, regular or manual mobility applications (such as pedal powered bicycles), or powered transmission mobility applications (such as electric bicycles or E-bikes, powered wheelchairs, scooters, etc.) usually require some type of belt-tracking to inhibit belt-sprocket misalignment and / or derailment, which can detrimentally affect system performance. Some sprockets include side-flanges as a belt-tracking mechanism, the flanges oriented orthogonal to the teeth of the belt and to the grooves of the sprocket that engage the teeth. Such side flanges constrain the belt laterally.

[0003] Sprockets can be manufactured using various known methods and technologies. In one example, sprockets are formed using a die cast method. In such methods, a mold is used to form the specific shape and dimensions of the sprocket, including the tooth profile for the sprocket and the flange(s). Die cast processes are economical and capable of forming very precise tooth-engaging profiles. However, sprockets having side flanges are difficult to remove from the mold.

[0004] Other methods of forming flanged sprockets are available, including insert molding; however, these techniques can be expensive, time consuming, and may lead to less precise formations.SUMMARY

[0005] The present disclosure is directed to sprockets formed from at least two materials, the first being a harder material forming a core and softer material forming a body over-molded on the core. The core may include physical features to mechanically lock the interface between the core and the over-molded body along both the circumferential direction and the axial (lateral) direction.1 Attorney docket P 23-034WO01 / 869046PCTA reinforcing structure may be present at the outermost periphery of the sprocket to improve wear resistance.

[0006] Described herein, in one particular embodiment, is a sprocket having a core with a hardness, the core configured to be engaged with a shaft; and a body secured to the core, the body having a hardness less than the core hardness, the body over-molded onto the core. In some embodiments, the core is a metal and the body is a softer metal. In some other embodiments, the core is a metal and the body is polymeric. The core may include an anchoring structure to increase the mechanical engagement of the body thereon.

[0007] Another particular embodiment described herein is a sprocket having a core having a hardness, the core having an inner surface configured to be engaged with a shaft and an outer surface having an anchoring structure thereon, the anchoring structure comprising at least one laterally extending rib and a circumferential vein, the core having a body over-molded onto the core, the body having a hardness less than the core hardness, a first side flange integral with the body a and second side flange. The body may include a plurality of teeth integral with and around a circumference of the body.

[0008] Another particular embodiment described herein is a method of making a sprocket. The method includes providing a core having a hardness, and over-molding a body over the core, the body having a hardness less than the core hardness. The body may include a plurality of teeth around the circumference of the body. In some embodiments, a side flange is molded in the same step as the body.

[0009] These and other sprockets may be part of a belt drive system, which includes a belt and a sprocket. Some belt drive systems have a first sprocket accompanying a crank and a second sprocket accompanying a driven shaft, where one or both the sprockets have the features described herein. Thus, an embodiment described herein is a belt drive system having a belt having a plurality of longitudinally spaced belt teeth, and at least one sprocket as described herein. Another embodiment described herein is a belt drive system having a belt having a plurality of longitudinally spaced belt teeth, a first sprocket as described herein accompanying a crank, and a second sprocket accompanying a driven shaft.2 Attorney docket P 23-034WO01 / 869046PCT

[0010] These and other aspects of the technology described herein will be apparent after consideration of the Detailed Description and figures herein.

[0011] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary, and the foregoing Background, are not intended to identify key aspects or essential aspects of the claimed subject matter. Moreover, this Summary is not intended for use as an aid in determining the scope of the claimed subject matter. It is to be understood that the scope of the claimed subject matter shall be determined by the claims as issued and not by whether given subject matter addresses any or all issues noted in the Background or includes any features or aspects recited in this Summary.BRIEF DESCRIPTION OF THE DRAWING

[0012] FIG. l is a perspective view of a sprocket configured in accordance with various embodiments described herein.

[0013] FIG. 2 is a perspective cross-section view of a sprocket configured in accordance with various embodiments described herein.

[0014] FIG. 3 is a perspective cross-section view of a core for a sprocket configured in accordance with various embodiments described herein

[0015] FIG. 4 is a perspective view of a flange configured in accordance with various embodiments described herein.

[0016] FIG. 5 is a perspective view of a sprocket configured in accordance with various embodiments described herein.

[0017] FIG.6 is a cross-sectional view of the sprocket of FIG. 5 taken along line 6-6.

[0018] FIG. 7 is a perspective view of a sprocket configured in accordance with various embodiments described herein.

[0019] FIG. 8 is a perspective view of a sprocket configured in accordance with various embodiments described herein.

[0020] FIG. 9 is flow chart illustrating a method of making a sprocket configured in accordance with various embodiments described herein.3 Attorney docket P 23-034WO01 / 869046PCTDETAILED DESCRIPTION

[0021] As indicated above, the present disclosure is directed to sprockets, such as for toothed belt systems, such as mobility applications (such as bicycles, electric bicycles or E-bikes, powered wheelchairs, scooters, etc.) or industrial applications. In some embodiments, the sprockets include at least one lateral alignment element, also referred to as a flange; in some embodiments, the sprockets include two flanges.

[0022] The sprockets described herein are formed from at least two materials, the first being a harder material (e.g., metal) forming an inner core, and the second being a softer material (e.g., polymeric, or a soft metal like aluminum) over-molded body on the core. In some embodiments, the first, harder material is a stiffer material than the second, softer material. The core may include physical features to mechanically lock the interface between the core and the over-molded body along the circumferential direction and / or the axial (lateral) direction. In some embodiments, the sprocket may have an integral flange. In some embodiments, the sprocket has two side flanges, one integral with the over-molded body and one independent therefrom. In other embodiments, one or both flanges may be independent from the over-molded body, being attached to either the overmolded body and / or the core.

[0023] In the following description, reference is made to the accompanying drawing that forms a part hereof and in which is shown by way of illustration at least one specific implementation. The following description provides additional specific implementations. It is to be understood that other implementations are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense. While the present disclosure is not so limited, an appreciation of various aspects of the disclosure will be gained through a discussion of the examples, including the figures, provided below. In some instances, a reference numeral may have an associated sub-label consisting of a lower-case letter to denote one of multiple similar components. When reference is made to a reference numeral without specification of a sub-label, the reference is intended to refer to all such multiple similar components.

[0024] FIG. 1 shows a sprocket 100, such as for use in a mobility or industrial power system with a toothed belt, usually an “endless” belt. The sprocket 100 has a generally disc-like or wheeltype structure having a first side edge 102 and a second side edge 104 with a plurality of parallel -4 Attorney docket P 23-034WO01 / 869046PCTaligned teeth 110 around the outer periphery or circumference of the structure, each tooth 110 having a first end 112 at the first side 102 and a second end 114 at the second side 104, so that the teeth 110 extend from the first side edge 102 to the second side edge 104. The first side 102 to the second side 104 defines the lateral width of the sprocket 100, which is configured for the toothed belt and the belt system in which it is to be installed. The teeth 110 define the outer circumferential and radial edge of the sprocket 100.

[0025] The teeth 110 are placed, sized, and shaped to engage with grooves of a toothed belt. Present between adjacent teeth 110 is a groove 115, which is the trough between the sidewalls of adjacent teeth 110.

[0026] The sprocket 100 is formed by a body 120 that is over-molded onto a core 130. In some embodiments, the teeth 110 may be part of the body 120, e.g., integrally formed with the body 120.

[0027] The core 130 is configured to be seated on and / or engaged with a hub, shaft or other such member that passes centrally through the core 130 to support the sprocket 100. The core 130 has sufficient stiffness and strength to inhibit slippage on the engaged hub or shaft.

[0028] The core 130 may include physical features to mechanically lock the interface between the core 130 and the over-molded body 120, details of which are provided below.

[0029] Relatively, the core 130 is formed from a harder material than the body 120. In some embodiments, the core 130 is formed from a metal, such as iron, steel, or nickel and is cast (e.g., sand cast) or machined. The material for the core 130 may be selected to provide the necessary radial stiffness to transfer torque and power from the belt engaged with the sprocket 100 to the shaft on which the sprocket 100 is mounted, and vice versa. In some embodiments, the hardness of the core 130 is at least 90 HB (Brinell hardness), while in some embodiments the hardness of the core 12 is at least 130 HB or at least 200 HB. Cast iron may have a hardness of 150-250 HB, depending on the particular type (e.g., ductile cast iron, gray cast iron, malleable cast iron, etc.). Hardened tool steel may have a hardness of 600-900 HB. Stainless steel is about 200 HB.

[0030] In some embodiments, the hardness of the core 130 is greater than that of the body 120 by at least 10 HB, such as by at least 25 HB.5 Attorney docket P 23-034WO01 / 869046PCT

[0031] Tn some embodiments, the body 120 may be made from a polymeric or elastomeric material, such as rubber, polyurethane, polycarbonate, polyamide, polyethylene, polyphthalamide, or isocyanate, or other material that can be molded onto the core 130. In some designs, a soft metal, such as aluminum, is used for the body 120. Aluminum has a Brinell hardness of about 95 HB. Mild steel has a hardness of about 120 HB.

[0032] In some embodiments, the sprocket 100 may also include an outer reinforcing structure 140 forming the circumferential or radial-most portion of the sprocket 100. In some embodiments, the reinforcing structure 140 may be a metal toothed ring. The reinforcing structure 140 may be constructed to form the outer surface of the teeth 110 and the grooves 115 between adjacent teeth 110. Tn a variant, the reinforcing structure 140 may form the entire structure of the teeth 110.

[0033] In some embodiments, the reinforcing structure 140 is made from a high hardness and / or high wear-resistant material that increases the use life of the sprocket 100 by providing a more durable belt-engaging surface than the material (e.g., polymeric material) of the body 120. The reinforcing structure 140 may form the entire circumferential surface and may be present on the surface of the body 120 or may be partially embedded within the body 120. Examples of suitable materials for the outer reinforcing structure 140 include, but are not limited to, metals (e.g., nickel, steel, iron), ceramics, carbide and nitride materials, and polymers (e.g., aramids), any or all of which may be provided as a continuous material (e.g., fdm or coating) or as wires, strands, fibers, felts, woven materials, and nonwoven materials. An example of a reinforcing structure 140 that can be embedded at least partially into the body 120 is a flocked, aramid woven fabric.

[0034] The reinforcing structure 140 may be provided on the sprocket 100 prior to or subsequent to over-molding the body 120 onto the core 130. Depending on the material and type of reinforcing structure 140, the material of the structure 140 could be applied as a coating on the body 120, e.g., a silicon carbide flame sprayed coating.

[0035] In one particular example of the sprocket 100, the body 120 is a urethane material, the core 130 is a cast or machined iron, and the reinforcing structure 140 is steel.6 Attorney docket P 23-034WO01 / 869046PCT

[0036] FIG. 2 shows a perspective cut away interior view of a sprocket 200 having a body 220 over-molded onto a center core 230, the sprocket 200 having one integral flange 252 and one discrete flange 254.

[0037] Similar to the sprocket 100 of FIG. 1, the sprocket 200 has a generally disc-like or wheel-type structure having a first side edge 202 and a second side edge 204 with a plurality of parallel-aligned teeth 210 around the outer periphery or circumference of the structure, each tooth 210 having a first end 212 at the first side 202 and a second end 214 at the second side 204, so that the teeth 210 extend laterally from the first side edge 202 to the second side edge 204. The teeth 210 define the outer circumferential and radial edge of the sprocket 200.

[0038] The sprocket 200 has a body 220 that defines the teeth 210 and is over-molded onto a central core 230. The core 230 may include physical features to mechanically lock the interface between the core 230 and the over-molded body 220. FIG. 3 shows the core 230 without the body 220.

[0039] As shown in FIG. 3, the core 230 includes the first side edge 202 and the second side edge 204 that define the lateral direction of the core 230 and also of the sprocket 200. The core 230 has an inner surface 232 configured to be seated on and / or engaged with a hub, shaft or other such member that passes centrally through the core 230 to support the sprocket 200. Radially opposite the inner surface 232 is an outer peripheral or circumferential surface 234 that has physical features that inhibit lateral and circumferential movement of the body 220 in relation to the core 230 when the body 220 is positioned on the core 230 .

[0040] Present on the outer surface 234 is an anchoring structure that includes laterally extending ribs 236 and a circumferentially extending vein 235. The anchoring vein 235 and ribs 236 extend radially out from the outer surface 234, providing a mechanical scaffold around which the over-molded body 220 can engage. The anchoring structure extends above the core 230 a sufficient amount to provide a mechanical grapnel or foothold for the body 220. In some embodiments, the anchoring structure extends above the outer surface 234 of the core 230 at least about 2 mm and typically no more than about 1 cm. These dimensions may differ based on the overall dimensions of the core 230. In the design shown in FIG. 3, multiple laterally extending ribs 236 are equally spaced around the circumference of the core 230, and the one circumferentially extending vein 235 is laterally centered around the core 230. In other designs, the anchoring structure may extend7 Attorney docket P 23-034WO01 / 869046PCTradially inward from the outer surface 234, providing a ditch or trench into which the over-molded body 220 can seat. Similar to the protruding anchoring structure shown in FIG. 3, the ditch or trench anchoring structure may be comprised of a circumferentially extending vein trench with multiple rib trenches extending laterally. Whether trenches or protrusions are used for the anchoring structure, the specific spacing of the vein and ribs is not limited to what is shown in Fig.3. For example, the vein may be positioned axially off center on the core 230, the ribs may be unevenly spaced about the circumference of the core 230, and / or ribs extending in opposite directions from the vein may be aligned or offset from one another. When the body 220 is overmolded onto the core 230, the ribs 236 inhibit circumferential movement of the body 220 in relation to the core 230 and the vein 235 inhibits lateral movement of the body 220 in relation to the core 230.

[0041] When core 230 includes an anchoring structure as described previously, the radial inner surface of the body 220 placed on the core 230 will include corresponding recesses and / or protrusions to mate with the anchoring structure. For example, when the core 230 includes a protruding vein around the circumference of the core 230 that is centered along the axial length of the core, the body 220 will include a recess that also extends around the circumference of the body and which is sized and shaped to receive the protruding vein.

[0042] Returning to FIG. 2, present at each side edge 202, 204 is a side flange 252, 254, respectively. In this design, the side flange 252 is integral with the body 220 whereas the side flange 254 is not. FIG. 4 shows the side flange 254 removed from the sprocket 200. In this sprocket 200, the flange 254 is retained adjacent to the body 220 and to the core 230 with at least one fastener 255.

[0043] As shown in FIG. 2, integral flange 252 does not radially overlap with core 230. In contrast, discrete flange 254 may be sized and dimensioned such that flange 254 at least partially radially overlaps both core 230 and body 220. By radially overlapping core 230, this allows discrete flange 254 to be secured with core 230 via fasteners that extend through flange 254 and into core 230.

[0044] In one particular example of the sprocket 200, the body 220 and the flange 252 are aluminum (e.g., B390 aluminum), the core 230 is a cast ductile iron (e.g., 65-45-12 iron), and the flange 254 is steel (e.g., a mix of 1008 / 1010 steel).8 Attorney docket P 23-034WO01 / 869046PCT

[0045] Another sprocket 500 is shown in FIGS. 5 and 6, and is similar in some respects to the sprocket 200 of FIG. 2. The sprocket 500 has a generally disc-like or wheel -type structure having a first side edge 502 and a second side edge 504 with a plurality of parallel-aligned laterally extending teeth 510 around the outer periphery of the sprocket 500.

[0046] The sprocket 500 has a body 520 that is over-molded onto a central core 530, the core 530 including physical features to mechanically lock the interface between the core 530 and the over-molded body 520.

[0047] Seen in FIG. 6, the core 530 has an inner surface 532 configured to be seated on and / or engaged with a hub, shaft or other such member that passes centrally through the core 530 to support the sprocket 500. Radially opposite the inner surface 532 is an outer peripheral or circumferential surface 534 that has an anchoring structure that inhibits lateral and circumferential movement of the body 520 in relation to the core 530. Seen in FIG. 6 is a circumferentially extending vein 535, which inhibits lateral movement of the body 520 in relation to the core 530.

[0048] Present at each side edge 502, 504 is a side flange 552, 554, respectively. In this design, the side flange 554 is integral with the body 520 whereas the side flange 552 is not. FIG. 7 shows the body 520 on the core 530 with only the one, integral, flange 554 (i.e., with side flange 552 removed). FIG. 7 also illustrates how reinforcing structure 540 can be positioned over the teeth of body 520. Reinforcing structure 540 may be similar or identical to reinforcing structure 140 shown in FIG. 1 and described previously, and generally provides a wear resistant surface to the teeth of body 520.

[0049] In the design shown in FIGs. 5 and 6, neither flange 552 nor flange 554 radially overlap core 530. With respect to discrete flange 552, the inner diameter of flange 552 may be approximately equal to an outer diameter of core 530, which permits flange 554 to be moved axially along the length of the core 530 where the axial length of core 530 is longer than the axial length of body 520. In this design where flange 552 does not radially overlap core 530, flange 552 may be secured to body 520 via fasteners that extend through flange 552 and into body 520.

[0050] In one particular example of the sprocket 500, the body 520 and the flange 554 are B390 aluminum, the core 530 is ductile iron 65-45-12 and the flange 552 is steel 1008 / 1010.9 Attorney docket P 23-034WO01 / 869046PCT

[0051] Another sprocket is shown in FIG. 8 as sprocket 800. The sprocket 800 has the same general features as the previous sprockets 200, 500, including a body 820 with a plurality of teeth 810 over-molded onto a core 830, and two flanges 852, 854, at least one of which (e.g., flange 852) is independent and attached to the body 820. In the design shown in FIG. 8, an outer reinforcing structure 840 is present over the teeth 810. Reinforcing structure 840 may be similar or identical to reinforcing structure 140 shown in FIG. 1 and described previously, and generally provides a wear resistant surface to the teeth 810.

[0052] In one particular example of the sprocket 800, the body 820 is a reinforced polymer and the core 830 is a taper lock hub made of iron. The independent flange 852 may be the same reinforced polymer used for the body 820. In another particular example of the sprocket 800, the body 820 (and optionally the independent flange 852) is an injection over-molded polyurethane.

[0053] Any flange that is not integral with the body (e g., flange 254, 552, 852, etc.) may be mechanically fastened (e.g., bolted) or otherwise attached to the desired location, such as by welding. The flange may be permanently affixed or may be removeable and replaceable, for example, to facilitate placement of an endless belt on the sprocket.

[0054] FIG. 9 provides an example method 900 for forming a sprocket as described herein. In a first step 902 of the method 900, a sprocket core is formed, such as by machining, molding, or casting. The core may be formed from, e.g., metal, and may include an anchoring structure (e.g., rib(s) and / or vein(s)) on its exterior surface to increase physical engagement with the sprocket body. The core formed in step 902 may be similar or identical to any of cores 130, 230, 530, or 830 previously described herein.

[0055] After the core is formed in step 902, the sprocket body, optionally with teeth, is molded over the core in step 904. The body material is less hard than the material of the core and may be, e.g., polymeric. The body formed in step 904 may be similar or identical to any of bodies 120, 220, 520, or 820 previously described herein.

[0056] If desired, a reinforcing structure that provides a wear resistant surface to the teeth can be provided in step 906 over the body. This may be subsequent to or simultaneous to forming the body in step 904. The wear resistant surface provided in step 906 may be similar or identical to reinforcement structure 140, 540 or 840 previously described herein.10 Attorney docket P 23-034WO01 / 869046PCT

[0057] After the body has been molded over the core (and after the wear resistant surface has been provided over the teeth of the body, if desired), a side flange is attached in step 908. The side flange attached in step 908 may be similar or identical to side flange 254, 552, or 852 previously described herein. As mentioned previously, any manner of attaching the side flange to the sprocket can be used, including via fasteners or via welding. The side flange may be attached specifically to the core or body of the sprocket, depending on the specific sprocket design used.

[0058] The sprocket 100, 200, 500, 800 or variations thereof may include a debris shedding element, such as a chamfered region in the groove, which facilitates removal of dirt, dust, fluid, and other debris from the volume between adjacent teeth. In some embodiments, a debris shedding hole or passage may be present through the flange(s) to provide debris ejection ports in an axial direction.

[0059] The core of the sprocket 100, 200, 500, 800 and variations thereof described herein can generally be manufactured using any known and suitable technique. For example, the core may be machined, molded (e.g., injection molded), die cast, forged, 3D printed, hobbed, plasma cut, waterjet cut, or made by a combination of procedures. Any anchoring structure on the core may be formed together with the core or subsequent to forming the core.

[0060] The sprocket 100, 200, 500, 800 and variations thereof described herein have a core that can be centrally mounted on a shaft, e.g., a rotatable shaft, in some embodiments with the addition of a hub. In other embodiments, the core of the sprocket may be configured to receive a bushing therein, the bushing used to secure the sprocket to a shaft. Any type of bushing can be used, with the shape and dimensions of the center of the sprocket core adjusted to accommodate any suitable type of hub or bushing, and any hub or bushing shaped and sized to accommodate any suitable shaft.

[0061] The sprockets 100, 200, 500, 800 and variations thereof having a body over-molded onto the core provide several advantages over their counterparts made from a single material.Because the over-molded body is softer than the core, the body inherently has a lower density than the core, providing a lower mass and thus lower inertia at the outer circumference of the sprocket. The tooth profile may be more accurate and precise due at least to the ability to use a material for the body different from the material of the core, the material of the body being more amenable to precise and accurate tooth formation. An integrally molded flange eliminates the need to attach the11 Attorney docket P 23-034WO01 / 869046PCTflange to body or core. Over-molding allows fast cycle time, which is suitable for large scale production. Appropriate selection of the core material and the body material improves technical viability and sprocket performance.

[0062] The above specification and examples provide a complete description of the structure and use of exemplary implementations of the invention. The above detailed description, therefore, is not to be taken in a limiting sense. It is to be understood that other implementations are contemplated and may be made without departing from the scope or spirit of the present disclosure. Additionally, elements or features of one example, design, embodiment or implementation may be applied to any other example, design, embodiment or implementation described herein to the extent such contents do not conflict. The above detailed description, therefore, is not to be taken in a limiting sense.

[0063] Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties are to be understood as being modified by the term “about,” whether or not the term “about” is immediately present. Accordingly, unless indicated to the contrary, the numerical parameters set forth are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein.

[0064] As used herein, the singular forms “a”, “an”, and “the” encompass implementations having plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and / or” unless the content clearly dictates otherwise.

[0065] Spatially related terms, including but not limited to, “bottom,” “lower”, “top”, “upper”, “beneath”, “below”, “above”, “on top”, “on,” etc., if used herein, are utilized for ease of description to describe spatial relationships of an element(s) to another. Such spatially related terms encompass different orientations of the device in addition to the particular orientations depicted in the figures and described herein. For example, if a structure depicted in the figures is turned over or flipped over, portions previously described as below or beneath other elements would then be above or over those other elements.12 Attorney docket P 23-034WO01 / 869046PCT

Claims

CLAIMS1. A sprocket compri sin :a core having a hardness, the core configured to be engaged with a shaft; anda body secured to the core, the body having a hardness less than the core hardness, the body over-molded onto the core.

2. The sprocket of claim 1, wherein the core hardness is at least 90 HB.

3. The sprocket of claim 1 , wherein the core hardness is at least 10 HB more than the body hardness.

4. The sprocket of claim 2, wherein the body has a plurality of teeth around a circumference of the body, the teeth integral with the body.

5. The sprocket of claim 4, further comprising a reinforcing structure on the plurality of teeth.

6. The sprocket of claim 1, further comprising a side flange integral with the body.

7. The sprocket of claim 6, further comprising a second side flange opposite the integral side flange, the second side flange being discrete from the core and the body.

8. The sprocket of claim 1, wherein the core comprises an anchoring structure on an outer surface of the core, the anchoring structure comprising at least one laterally extending rib and a circumferential vein.

9. The sprocket of claim 1, wherein the core comprises iron and the body comprises aluminum.

10. The sprocket of claim 1 , wherein the core comprises a metal and the body comprises a polymeric or elastomeric material.13 Attorney docket P 23-034WO01 / 869046PCT11. A sprocket comprising:a core having a hardness, the core having an inner surface configured to be engaged with a shaft and an outer surface having an anchoring structure thereon, the anchoring structure comprising at least one laterally extending rib and a circumferential vein;a body secured to the core, the body having a hardness less than the core hardness, the body over-molded onto the core and comprising a plurality of teeth integral with and around a circumference of the body;a first side flange integral with the body; anda second side flange opposite the first side flange, the second side flange being discrete from the core and the body.

12. The sprocket of claim 11, wherein the core comprises iron and the body comprises aluminum.

13. The sprocket of claim 11, wherein the core comprises a metal and the body comprises a polymeric or elastomeric material.

14. A method of making a sprocket, the method comprising:providing a core having a hardness; andover-molding a toothed body over the core, the body having a hardness less than the core hardness.

15. A belt drive system comprising:a belt; anda sprocket comprising:a core having a hardness, the core having an inner surface configured to be engaged with a shaft and an outer surface having an anchoring structure thereon, the anchoring structure comprising at least one laterally extending rib and a circumferential vein;a body secured to the core, the body having a hardness less than the core hardness, the body over-molded onto the core and comprising a plurality of teeth integral with and around a circumference of the body;14 Attorney docket P 23-034WO01 / 869046PCTa first side flange integral with the body; anda second side flange opposite the first side flange, the second side flange being discrete from the core and the body.15 Attorney docket P 23-034WO01 / 869046PCT

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