Sprocket with laterally adjustable alignment element

Abstract

A sprocket for a toothed belt system having an alignment element laterally movable within a circumferential groove internally positioned through the teeth of the sprocket. In one particular embodiment, the sprocket has a body having a plurality of teeth longitudinally around a circumference of the body, with a groove extending through the plurality of teeth, the groove having a width. An alignment element is positioned in the groove, the alignment element having a width less than the groove width. The alignment element may move laterally, e.g., at least 3 mm within the groove.

Description

SPROCKET WITH LATERALLY ADJUSTABLE ALIGNMENT ELEMENTCROSS-REFERENCE

[0001] This application claims priority to U.S. provisional application 63 / 599,297 filed November 15, 2023, the entire disclosure of which is incorporated herein by reference for all purposes.BACKGROUND

[0002] Toothed belts that engage sprockets in either 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 rungs of the sprocket that engage the teeth. Such side flanges constrain the belt laterally. Another belt-tracking mechanism is a center flange on the sprocket and a lengthwise cut along the centerline of the belt; in some belt designs, the center cut is not continuous. A center flange also constrains 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 toothengaging profiles. However, sprockets having side flanges are difficult to remove from the mold.

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

[0005] The present disclosure is directed to a sprocket having an internal alignment element, to constrain the belt laterally, the alignment element being adjustable in the lateral direction. Suchlateral adjustment allows for a better alignment of the sprocket in the system and / or better alignment of the belt on the sprocket. The alignment element may be floating, being able to laterally move and reposition itself as needed during use of the sprocket. Alternately, the alignment element may be fixed in place, after having a desired location for the alignment element determined.

[0006] Described herein is an internally aligned sprocket, with the alignment element laterally movable within a circumferential groove. In one particular embodiment, the sprocket has a body having a plurality of teeth longitudinally around a circumference of the body, with a groove extending through the plurality of teeth, the groove having a width. An alignment element is positioned in the groove, the alignment element having a width less than the groove width.

[0007] Another particular embodiment described herein is an internally aligned sprocket having a body having a plurality of teeth longitudinally around a circumference of the body, with a groove extending through the plurality of teeth, the groove having a width, the sprocket also having an alignment element positioned in the groove, the alignment element having a width that is no more than half of the groove width.

[0008] Another particular embodiment described herein is an internally aligned sprocket having a body having a plurality of teeth longitudinally around a circumference of the body, with a groove extending through the plurality of teeth, the groove having a width, the sprocket also having an alignment element positioned in the groove, the alignment element having a width and laterally moveable within the groove at least 1 mm, in some embodiments at least 3 mm.

[0009] Another particular embodiment described herein is a method of making an internally aligned sprocket. The method includes forming a sprocket body and forming a longitudinal groove through the teeth. A ring is provided and placed in the groove, optionally by expanding the ring and then releasing the ring into the groove. The groove may have a width at least twice as much as a width of the ring.

[0010] These and other sprockets may be part of a belt drive system, which includes a belt (e g., an endless belt having a groove) 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 a groove extendingthrough the teeth, and a sprocket as described herein. Another embodiment described herein is a belt drive system having a belt having a plurality of longitudinally spaced belt teeth and a groove extending through the teeth, a first sprocket as described herein accompanying a crank, and a second sprocket accompanying a driven shaft.

[0011] These and other aspects of the technology described herein will be apparent after consideration of the Detailed Description and figures herein.

[0012] 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

[0013] FIG. l is a perspective view of a sprocket.

[0014] FIG. 2 is a side plan view of the sprocket of FIG. 1.

[0015] FIG. 3 A is an end view of the sprocket of FIG. 1, with the alignment element in a first terminal position; FIG. 3B is an end view of the sprocket with the alignment element in an intermediate position; and FIG. 3C is an end view of the sprocket with the alignment element in a second terminal position.

[0016] FIGS. 4A, 4B, 4C and 4D are cross-sectional enlarged views of example arrangements of a sprocket tooth and adjustable alignment element.

[0017] FIG. 5 is an example step-wise method of making a sprocket having a laterally adjustable internal alignment element.

[0018] FIG. 6 is an example step-wise method of using a sprocket.DETAILED DESCRIPTION

[0019] As indicated above, the present disclosure is directed to internally alignable sprockets for toothed belt systems, such as mobility applications (such as bicycles, electric bicycles or E- bikes, powered wheelchairs, scooters, etc.). The alignment element is laterally moveable or adjustable.

[0020] By use of the term “internal alignment element” or variation thereof, what is intended is an alignment element positioned axially or laterally between a first outer wall, side or surface of the sprocket and the opposite outer wall, side or surface. An internal alignment element may be centered between the walls, sides, or surfaces, or may be offset closer to one side or the other.

[0021] 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.

[0022] FIGS. 1, 2 and 3A, 3B, 3C show various features of a sprocket 100, such as for use in a mobility power system with a toothed belt, usually an “endless” belt. The figures show the sprocket 100 with a body 102 having a generally disc-like or wheel-type structure, the body 102 having a first side 104 (see, FIG. 3B) and a second side 106 (see, FIG. 3B) with a plurality of parallel teeth 110 around the outer periphery or circumference of the body 102, each tooth 110 having a first end 114 at the first side 104 and a second end 116 at the second side 106, so that the teeth 110 extend from the first side 104 to the second side 106. The first side 104 to the second side 106 defines the 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.

[0023] The teeth 110 are placed, sized, and shaped to engage with teeth, particularly between adjacent teeth, of a toothed belt. Present between adjacent teeth 110 is a land 115, which is the trough between the sidewalls of adjacent teeth 110.

[0024] The distance between adjacent teeth 110, which is generally the length of the lands 115 in the longitudinal or circumferential direction (the width of the lands 115 being measured from side 104 to side 106), is equal to or essentially equal to (e.g., a little less, e.g., a little more) than the pitch length of the belt (the approximate length of a tooth) with which the sprocket will engage. The teeth 110 are evenly spaced around the circumference of the sprocket 100. The number of teeth 110 and the distance between adjacent teeth 110 may be adjusted based on the sprocket diameter and the dimensions of the teeth 1 10 (e g., width, as measured orthogonal to the direction between the first end 114 and the second end 116).

[0025] The sprocket 100 includes an internal alignment element 120 extending circumferentially around the sprocket 100 and positioned between the first side 104 and the second side 106. The internal alignment element 120 engages with a groove, slice or cut present in the belt with which the sprocket 100 engages. The groove, slide or cut may be continuous along the length of the belt or may be discontinuous, e.g., present between the belt teeth. The alignment element 120 facilitates tracking of the belt on the sprocket 100 when in operation and inhibits lateral movement of the belt in relation to the sprocket 100.

[0026] The alignment element 120 is positioned in a groove 122 present in the teeth 110 between the first side 104 and the second side 106. The groove 122 is typically centered between the first side 104 and the second side 106, but it some embodiments it may be desired to have the groove 122 offset closer to one side 104, 106 than the other. The groove 122, measured in the axial direction from side 104 to side 106, is wider than the alignment element 120. In some embodiments, the groove has a width that is at least twice that of the alignment element 120 (in other words, the width of the alignment element is no more than half of the width of the groove 122). Having the groove 122 wider than the alignment element 120 allows lateral movement of the alignment element 120 within the groove 122.

[0027] The groove 122 has a first side wall 124 (FIG. 3B) and a second side wall 126 (FIG. 3B). The width of the groove 122, from the side wall 124 to the side wall 126 may be at least 3 mm to 10 mm, although it may be greater as it will depend greatly on the overall width of the teeth 110and the sprocket 100 and also on the dimensions of the alignment element 120. In some embodiments, e.g., for very narrow sprockets and / or very narrow alignment elements, the width of the groove 122 may be less than 3 mm. The width of the groove 122 is typically no more than 20% of the width of the sprocket 100, in some embodiments no more than 10%. The width of the groove 122 is greater than the width of the alignment element 120, in some embodiments twice (2x) as wide, in other embodiments, 3x or 4x or 5x as wide.

[0028] In some embodiments, the total allowable lateral movement of the alignment element 120 within the groove 122 is at least 1 mm, in other embodiments at least 3 mm and yet in other embodiments at least 5 mm. In other embodiments, the total allowable lateral movement is no more than 1 cm, in other embodiment no more than 8 mm, and in other embodiments no more than 5 mm. For purposes of discussion herein, the lateral movement is measured for the center of the alignment element 120. FIGS. 3A, 3B and 3C show the alignment element 120 in three different locations in the groove 122; in FIG. 3A, the alignment element 120 is located against the first wall 124 of the groove 122, in FIG. 3B the alignment element 120 is intermediate between the two walls 124, 126 (e.g., centered in the groove 122), and in FIG. 3C, the alignment element 120 is located against the second wall 126 of the groove 122.

[0029] The depth of the groove 122, measured radially into the tooth 110, is typically at least 2 mm and depends greatly on the dimensions (e g., height or depth) of the tooth 110 and of the alignment element 120. The groove 122 may extend through the depth of the tooth 110.

[0030] When seated in the groove 122, the alignment element 120 may be the same height as the teeth 110 (e.g., the groove 122 is as deep as the alignment element 120 is high) or may be greater, e.g., extending above the top level of the teeth 110, or may be less, e.g., extending below the top level of the teeth. In some embodiments, the alignment element 120 may not sit at the base of the groove 122.

[0031] The alignment element 120 and the groove 122 may have any cross-sectional shape; FIGS. 4A through 4D show various alternate designs. For example, if the alignment element 120 is formed by a wire, the cross-sectional shape may be circular or oval / oblong. Other shapes for the alignment element 120 include rectangular, triangular, trapezoidal. The groove 122 may be essentially any shape that accepts the alignment element 120 therein and allows lateral movement in the groove 122. As an example, when the alignment element 120 is trapezoidal, the correspondinggroove 122 may also be trapezoidal, or dove-tailed; such a design may inhibit radial (outward) displacement of the alignment element from the groove. As another example, the groove 122 may include an undercut, having a greater width at the base of the groove 122 than at the exposed top of the groove 122, thus allowing increased lateral movement of the alignment element.

[0032] Turning to FIGS. 4A through 4D, each of these examples has a tooth 210 with an alignment element 220 positioned in a groove 222, the groove 222 having a first wall 224 and a second wall 226.

[0033] In FIG. 4A, a tooth 210A has a thin, rectangular alignment element 220A positioned in a rectangular groove 222A having a first wall 224A and a second wall 226A. The alignment element 220A seats on the bottom or floor of the groove 222A and extends above the depth of the groove 222A. The width of the groove 222A is approximately three times the width of the alignment element 220A. For a sprocket with such a design, the alignment element 220A will have a continuous longitudinal engagement with a belt running on the sprocket.

[0034] In FIG. 4B, a tooth 210B has a wire alignment element 220B positioned in a rectangular groove 222B having a first wall 224B and a second wall 226B. The alignment element 220B does not extend out from the depth of the groove 222B but rather is recessed into the groove 222B; in this shown design, the alignment element 220B does not rest on the bottom or floor of the groove 222B but is “floating.” The width of the groove 222B is less than twice the width of the wire alignment element 220B. For a sprocket with such a design, the alignment element 220B will have a discontinuous longitudinal engagement with a belt running on the sprocket, engaging with the wire alignment element 220B between the teeth 210B.

[0035] In FIG. 4C, a tooth 210C has a rectangular alignment element 220C positioned in a rectangular groove 222C having a first wall 224C and a second wall 226C. The alignment element 220C, resting on the bottom or floor of the groove 222C, is level with the top of the groove 222C. The width of the groove 222C is approximately five to six times the width of the alignment element 220C. For a sprocket with such a design, the alignment element 220C will have a discontinuous longitudinal engagement with a belt running on the sprocket, engaging with the alignment element 220C between the teeth 210C.

[0036] In FIG. 4D, a tooth 210D has a wire alignment element 220D positioned in trapezoidal or dove-tail groove 222D having a first wall 224D and a second wall 226D. The wire alignment element 220D is fully seated within the groove 222D and has a diameter greater than the top width, inhibiting the wire alignment element 220D from being removed from the groove 222D. The wire alignment element 220D can move laterally between the first wall 224D and the second wall 226D. For a sprocket with such a design, the wire alignment element 220D will have a discontinuous longitudinal engagement with a belt running on the sprocket, engaging with the wire alignment element 220BD between the teeth 210D.

[0037] The alignment element 120, 220 may be a single element extending circumferentially around the sprocket or may be formed of multiple pieces. As an example, the alignment element 120, 220 may be wire that is placed in the groove 122, 222 around the sprocket body 102 and then connected to form a continuous ring; for example, a metal ring can be welded or soldered. Another example for the alignment element 120, 220 is an open or single turn snap ring or a split ring. Yet another example is a circular split ring having more than one turn, such as a “key chain” ring.

[0038] The choice of the ring with single turn or multiple turns mainly depends on the ring size, the groove size, and also the sprocket body size. For a small ring, it is more difficult to expand the size of the ring; hence, double / multiple turns are beneficial. For a larger ring, it is easier to expand radially; therefore, a single turn is more economical. Another consideration when choosing turns is the ring overall width along the axial dimension. A greater width can be better achieved by multiple turns of thin cross section than a single turn of thick cross section.

[0039] The alignment element 120, 220 may be floating in the groove 122, 222, being able to laterally move and reposition itself as needed in the groove 122, 222 during use of the sprocket. Alternately, the alignment element may be fixed in place, after having been calibrated with a desired location for the alignment element determined.

[0040] The alignment element 120, 220 may be glued, welded, soldered, or otherwise adhered in the desired location. Additionally or alternately, the alignment element 120, 220 may be fixed in the desired location via a locking mechanism, such as a spacer or shims or a set screw. The locking mechanism may be permanent or may be removeable and replaceable, for example, to readjust the location or reuse the sprocket in a different system.

[0041] FIG. 5 provides an example method 300 for forming a sprocket as described herein.In a first step 302 of the method 300, a sprocket body is formed. The sprocket body is composed of a wheel-type structure with a plurality of teeth extending around the outer circumference of the wheel. The sprocket may be formed by casting, molding, machining, 3D printing, waterjet cutting, plasma cutting, forging or by another suitable process.

[0042] In step 304, a groove is formed in the teeth, extending around the circumference in the periphery the sprocket body. The groove may extend the depth of the teeth or may be less than the depth of the teeth. The groove may be formed by machining, waterjet cutting, plasma cutting, or by other suitable process. The groove may be centered in the sprocket body or may not be centered.

[0043] In some methods, the groove of step 304 may be made simultaneously with the sprocket itself, in step 302.

[0044] In step 306, a ring is provided and in step 308 the ring is expanded. The ring can be a circular split ring, e.g., a closed loop, open end ring. The ring may have one or more turns, and is expandable from a relaxed, unstressed state to an expanded state. The ring has a width that is less than the width of the groove, in some embodiments, no more than one half of the width of the groove.

[0045] The expanded ring is placed onto the sprocket body and into the groove in step 310 and in step 312 is released to allow the ring to seat in the groove. The ring may be able to laterally move within the groove.

[0046] Another suitable method of making a sprocket includes providing a sprocket body having an outer periphery with a groove in the outer periphery, expanding a circular ring, positioning the ring over the groove, and releasing the ring into the groove. Yet another suitable method of making a sprocket includes forming a sprocket body having an outer periphery, creating a circumferential groove in the outer periphery expanding a circular split ring from a natural state to an opening state, positioning the ring over the groove, and releasing the ring into the groove. In all of the methods, the groove has a lateral width that is greater than the width of the ring.

[0047] FIG. 6 provides an example method 400 for using a sprocket having a laterally adjustable alignment element, such as the sprocket 100 or variations thereof, or a sprocket made bythe method 300. Tn a first step 402 of the method 400, the sprocket is mounted on a shaft; the mounting may be with, e.g., a bushing. The sprocket may be mounted as a driven wheel, a drive wheel, an idler, or a tensioner. A corresponding toothed belt, having a center longitudinal groove or cut therein, is mounted on the sprocket in step 404.

[0048] In step 406, the lateral position of the alignment element in relation to the belt is calibrated to obtain proper tracking and alignment of the belt and the sprocket. In some embodiments, this may entail running the belt over the sprocket to have the system obtain a steady state. After the desired position of the alignment element in the groove is determined, the alignment element is locked in that position, in step 408, by a suitable mechanism, such as by tack welding the alignment element to the sprocket, or by inserting shims or spacers into the groove adjacent the alignment element, or by placing a set screw in a threaded hole.

[0049] In other methods, the alignment element is not locked into position, but left to float laterally within the groove.

[0050] The sprocket 100 or variations thereof may include a debris shedding element, such as a chamfered region in the land 115, which facilitates removal of dirt, dust, fluid, and other debris from the volume between adjacent teeth 110. In some embodiments, a debris shedding hole or passage may be present through the alignment element 120 to provide lateral fluid communication from one side of the alignment element 120 to the other side.

[0051] Examples of suitable materials for the alignment element 120 include metal (e.g., steel, stainless steel, nickel, iron, aluminum, alloys), composite materials, polymeric fibers such as Kevlar® aramid fiber and other polymeric fibers, and thermoplastic and / or thermoset polymer(s) (e.g., polycarbonate, polyamide, polyethylene, polyphthalamide) including fiber-reinforced polymers.

[0052] Examples of suitable materials for the sprocket 100 and variations thereof include thermoplastic and / or thermoset polymer(s) (e.g., polycarbonate, polyamide, polyethylene, polyphthalamide), including fiber-reinforced polymers, metal (e g., steel, stainless steel, nickel, iron, aluminum, alloys), and composite materials.

[0053] The sprocket 100 and variations thereof described herein can generally be manufactured using any known and suitable technique. For example, the sprockets may bemachined, molded (e g., injection molded), die cast, forged, 3D printed, hobbed, plasma cut, water jet cut, or made by a combination of procedures.

[0054] The sprocket 100 and variations thereof described herein can be centrally mounted on a shaft, e.g., a rotatable shaft. The sprocket may have a central hub for mounting the sprocket on a shaft. In other embodiments, the center of the sprocket may be configured to receive a bushing therein, the bushing used to secure the sprocket to a shaft. Any type of hub or bushing can be used, with the shape and dimensions of the center of the sprocket adjusted to accommodate any suitable type of hub or bushing, and any hub or bushing shaped and sized to accommodate any suitable shaft.

[0055] Thus, described herein is at least one specific example of a sprocket having a laterally adjustable internal, circumferential alignment element. 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.

[0056] 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.

[0057] 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.

[0058] 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 ofdescription 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.

Claims

CLAIMS1. A sprocket compri sing : a body having a plurality of teeth longitudinally around a circumference of the body, with a groove extending through the plurality of teeth, the groove having a width; and an alignment element positioned in the groove, the alignment element having a width that is no more than half of the groove width or that is laterally moveable within the groove at least 1 mm or at least 3 mm.

2. The sprocket of claim 1, wherein the alignment element is laterally moveable within the groove at least 1 mm.

3. The sprocket of claim 2, wherein the alignment element is moveable within the groove at least 3 mm.

4. The sprocket of claim 2, wherein the alignment element has a circular cross-section.

5. The sprocket of claim 2, wherein the alignment element has a rectangular cross-section.

6. The sprocket of claim 2, wherein the groove extends into each of the plurality of teeth at least 2 mm.

7. The sprocket of claim 6, wherein the groove extends an entire depth of the teeth.

8. The sprocket of claim 2, wherein the alignment element extends above the plurality of teeth.

9. The sprocket of claim 2, wherein the alignment element does not extend above the plurality of teeth.

10. The sprocket of claim 1, wherein the alignment element width is no more than half of the groove width.11 . The sprocket of claim 10, wherein the groove width is at least 3x the alignment element width.

12. The sprocket of claim 11, wherein the groove width is at least 4x the alignment element width.

13. The sprocket of claim 10, wherein the alignment element is fixed to the groove to inhibit lateral movement of the alignment element in the groove.

14. The sprocket of claim 10, wherein the alignment element has a circular cross-section.

15. The sprocket of claim 10, wherein the alignment element has a rectangular cross-section.

16. The sprocket of claim 10, wherein the groove extends into each of the plurality of teeth at least 2 mm.

17. The sprocket of claim 16, wherein the groove extends an entire depth of the teeth.

18. The sprocket of claim 10, wherein the alignment element extends above the plurality of teeth.

19. The sprocket of claim 10, wherein the alignment element does not extend above the plurality of teeth.

20. A belt drive system comprising: a belt having a plurality of longitudinally spaced belt teeth and a groove extending through the teeth; and a sprocket according to any of the previous claims.21 . A belt drive system comprising: a belt having a plurality of longitudinally spaced belt teeth and a groove extending through the teeth; a first sprocket according to any of claims 1-19 accompanying a crank; and a second sprocket accompanying a driven shaft.

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