Toothed belt with asymmetrically contoured teeth

Abstract

A toothed belt with an asymmetric tooth profile, in which the teeth have vertical segments on the front flanks of the teeth that allow the teeth to withstand increased loads, which in turn prevents tooth skipping. A sprocket shaped to smoothly engage and disengage the toothed belt is also described, in which the toothed belt and sprocket form part of a belt drive system.

Description

[Technical Field]

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 396,599, filed August 10, 2022, and entitled "Toothed Belt with Asymmetrically Profiled Teeth," the entire disclosure of which is incorporated herein by reference for all purposes. [Background technology]

[0002] When a shock load acts on a toothed belt and sprocket drive system, the belt teeth may skip over the sprocket teeth and move into the adjacent groove in the direction of belt rotation. This phenomenon is often referred to as "tooth skipping." Tooth skipping, like belt delamination, can cause problems in the operation of the drive system, including tooth wear, material fatigue, and eventual belt failure.

[0003] Another problem that can occur in toothed belt and sprocket drive systems is insufficient meshing between the belt and sprocket, which can cause noise. Because noise reduction is one of the main advantages of belt drives over chain drives, noise caused by insufficient meshing in belt drive systems is highly undesirable.

[0004] Many design strategies for toothed belts and pulley or sprocket profile shapes have been proposed. Representative of this technology is U.S. Patent Application Publication No. 2009 / 0156341, which discloses a belt and sprocket system in which the belt has a tensile cord embedded within the belt body and teeth protruding from the belt body. The teeth have at least two unequal radii connected in series between the tooth tips and tooth bases, and the sprocket has grooves for receiving the teeth, the groove profile having at least one substantially linear portion formed between the at least two unequal radii, and the tooth tips engage a predetermined portion of the sprocket groove to support the tensile cord so that it has a substantially arcuate shape between the tooth bases. However, like other designs, this design focuses on engagement of the tooth tips with the sprocket, rather than engagement of the front flanks of the belt teeth, where force is applied.

[0005] Therefore, there is a need for improvements in belt drive systems that focus on solving problems related to tooth skipping and noise reduction. Summary of the Invention

[0006] 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 features or essential features of the claimed subject matter. Moreover, this Summary is not intended to be used as an aid in determining the scope of the claimed subject matter.

[0007] In some embodiments, a toothed belt is described, the toothed belt generally comprising a main belt body and a plurality of teeth spaced along the entire inner circumference of the belt and extending radially inward from the main belt body. Each tooth of the toothed belt generally has a height extending from a land to a tooth tip, and each tooth has a cross-sectional profile having a vertical segment at a forward side of the tooth, the vertical segment being substantially perpendicular to the main belt body when the toothed belt is in a racked state. The length of the vertical segment of each tooth is less than the height of the tooth.

[0008] In some embodiments, a belt drive system is described that generally includes the toothed belt described in the previous paragraph and a sprocket configured to engage and rotate the toothed belt, the sprocket having a plurality of teeth, and the profile of each tooth of the sprocket and the spaces between adjacent teeth of the sprocket are shaped to smoothly mesh with the teeth of the toothed belt.

[0009] These and other features of the technology described herein will become apparent after review of the Detailed Description and drawings herein. However, it should be understood that the scope of the claimed subject matter is determined by the claims as written, and not by whether they address a problem described in the Background or include a feature or aspect described in the Summary. [Brief explanation of the drawings]

[0010] Non-limiting and non-exhaustive embodiments of the disclosed technology, including preferred embodiments, are described below with reference to the drawings, in which like reference numerals refer to like parts throughout unless otherwise specified.

[0011] FIG. 1 is a perspective view of a toothed belt.

[0012] FIG. 2A is a toothed view showing the tooth profile configured in accordance with various embodiments described herein. FIG. 2 is a side view of a cross section of the belt.

[0013] [FIG. 2B] A tooth profile constructed in accordance with various embodiments described herein. 1 is a cross-sectional view of a tooth of the present invention.

[0014] Embodiments are described in more detail below with reference to the accompanying drawings, which form a part hereof and which show, by way of example, specific embodiments. These embodiments are disclosed in sufficient detail to enable those skilled in the art to practice the invention. However, embodiments may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Accordingly, the following detailed description is not to be taken in a limiting sense.

[0015] FIG. 1 illustrates a typical belt 100 having a main belt body 102 made of a flexible material having a back surface 104 and a front surface 106 and provided with a plurality of load-bearing cords 108. Certain cords 108 are triple-clad, although in other embodiments, the cords 108 may be single or clad. The cords 108 may be, for example, carbon cords, polymer cords (e.g., polyester, aramid), fiberglass cords, etc. A plurality of teeth 110 are formed on the front surface 106, and while trapezoidal teeth are shown schematically in FIG. 1 for illustrative purposes only, it is understood that the belt 100 may have an asymmetric tooth profile in accordance with various embodiments described herein. Lands 121 are present between adjacent teeth 110.

[0016] Each tooth 110 extends perpendicular to the longitudinal direction of the belt 100, with multiple teeth 110 aligned along the longitudinal direction of the belt 100. In use, the teeth 110 on the front surface 106 contact a drive mechanism, such as a toothed gear or sprocket. In FIG. 1 , the toothed belt 100 is shown lying flat in a racked state rather than with any degree of curvature. In this racked state, the belt 100 has a longitudinal axis 131.

[0017] With reference to FIG. 2A, a toothed belt 200 configured in accordance with various embodiments is shown. The toothed belt 200 generally includes a main belt body portion 202 and a plurality of teeth 210 extending radially inward from the body portion 202, for example, when the belt is circular, such as an endless belt. The main belt body portion may have a thickness t, which is not limited and will vary based on the particular application of the belt 200. In FIG. 2A, the toothed belt 200 is shown in a racked state, with the belt 200 having a longitudinal axis 231.

[0018] 2A shows a single tooth 210, it should be understood that a large number of teeth 210 are disposed around the entire inner circumference of the main body portion 202 and are equally spaced apart from one another by lands 221 between adjacent teeth 210, as shown in FIG. 1. It should further be understood that each tooth 210 included in the belt 200 is generally of the same shape and size (specific details of which are described in more detail below).

[0019] As further shown in FIG. 2A , each tooth 210 has a height h extending from a land 221 adjacent the tooth 210 to a tip 222 of the tooth, although the maximum height h may not be at the center of the tooth 210. Each tooth 210 further has a leading side 223 and a trailing side 224 based on the direction of travel of the belt 200, and FIG. 2A includes an arrow 230 indicating the direction of travel of the belt 200. The leading side 223 is the side of the tooth 210 on which force acts, typically via a sprocket tooth pressing against the leading side 223, to move the toothed belt 200 in the direction indicated by the arrow 230, and the trailing side 224 is the side of the tooth 210 opposite the leading side 223. As described in more detail below, the trailing side 224 of each tooth 210 is generally shaped to provide smooth meshing between the sprocket and the toothed belt 200, i.e., to provide smooth engagement and disengagement of the sprocket tooth into the spaces between the teeth 210 of the toothed belt 200.

[0020] 2B, the cross-sectional profile of tooth 210 is shown. The cross-sectional profile of tooth 210 has a vertical segment 225 at the leading side 223 of tooth 210 between land 221 and tip 222 of tooth 210. Vertical segment 225 is perpendicular (i.e., orthogonal) to the direction of force exerted by the sprocket tooth on tooth 210. This vertical segment 225 increases the load that can be exerted by tooth 210, thereby allowing a greater force to be exerted on the belt without the belt jumping relative to the sprocket tooth.

[0021] 2B, where point P2 represents the radially outer end of vertical segment 225 and point P3 represents the radially inner end of vertical segment 225 based on the loop-shaped curved belt. When belt 200 is in a rack (i.e., flat) state and extends across longitudinal axis 231 of main body portion 202, vertical segment 225 forms angle 226 with longitudinal axis 231. To achieve a desired vertical position for vertical segment 225, angle 226 is approximately 90°. In other words, vertical segment 225 is positioned approximately perpendicular to longitudinal axis 231 and main belt body portion 202. In some embodiments, angle 226 need not be exactly 90°, for example; in some embodiments, angle 226 is within a range of 86° to 110°, in which case vertical segment 225 provides a desired improvement in the magnitude of force acting on tooth 210 without causing tooth skipping.

[0022] The length of vertical segment 225 (measured between P2 and P3) is generally less than the height h of tooth 210. There is generally no limit to the length of vertical segment 225, as long as it is less than the height h of tooth 210. In some embodiments, the length of vertical segment 225 is between 10% and 90% of the height h of tooth 210. In some embodiments, the length of vertical segment 225 is between 30% and 60% of the height h of tooth 210.

[0023] The vertical segment 225, having a length less than the height h of the tooth 210, allows the front side 223 of the tooth 210 to have a first curvature 227 between the land 221 and the vertical segment 225, i.e., between the land 221 and the radially outer end P2, and a second curvature 228 between the vertical segment 225 and the tip 222 of the tooth 210, i.e., between the radially inner end P3 and the tip 222 of the tooth 210. The first curvature 227 is between points P1 and P2 shown in FIG. 2B, and the second curvature 228 is at a point midway between points P3 and P4 and P5. These curvatures 227, 228 provide a gradual transition near the connection between the tooth 210 and the main belt body 202 and near the tip 222 of the tooth 210. The first curvature 227 and the second curvature 228 facilitate shaping of the tooth profile and provide good meshing between the toothed belt and the sprocket.

[0024] The rearward flank 224 of the tooth 210 may be provided with a third curved portion 229. The third curved portion 229 extends from the tip 222 of the tooth 210 to the juncture of the rearward flank 223 of the tooth 210 and the main belt body. This third curved portion 229 extends from a point midway between points P4 and P5 to point P8. The third curved portion 229 thus has a convex portion and a concave portion. In some embodiments, the third curved portion 229 is free of, or substantially free of, vertical segments, and the rearward flank 224 of the tooth 210 does not include a vertically disposed segment (i.e., a segment that is substantially perpendicular to the main belt body). By providing the rearward flank of the tooth 210 in this manner, the tooth profile shapes described herein smoothly enter and exit the sprocket, which improves meshing and reduces noise.

[0025] Tables 1 and 2 below provide non-limiting example data for the locations of points P1 through P8 and the radii of curvature R1 through R6 of the segments between adjacent points. This data is illustrative only, and the values of both points P1 through P8 and R1 through R6 can be easily adjusted. The only constant in the given data is that there is no radius of curvature between points P2 and P3 because the segment between points P2 and P3 is a perpendicular segment 225.

[0026] Tables 1 and 2 use the axes shown in Figure 2B, where the X axis is the bottom of tooth 210 (e.g., land 221) and the Y axis is the center of tooth 210, essentially equal to the base of anterior flank 223 and the base of posterior flank 224. The Y axis may or may not be at tip 222, i.e., tip 222 may be offset from the center or Y axis of tooth 210. The data in the tables is normalized and has no associated units.

[0027] The data in Table 2 indicates that the X position between points P2 and P3 does not change, and therefore indicates that vertical segment 225 is vertical. However, in embodiments in which the vertical segment is substantially vertical, e.g., subtending an angle between 86° and 110°, the X position between points P2 and P3 may change slightly. Nevertheless, because vertical segment 225 is a straight segment, there is no radius of curvature for this segment. [Table 1] [Table 2]

[0028] 2A and 2B and Tables 1 and 2, in addition to having a vertical segment 225 on the posterior side 223, tooth 210, and variations thereof according to this disclosure, are asymmetrical about the tooth's Y-axis, with the posterior side 223 having a different profile than the anterior side 224. In some embodiments, the overall profile of the anterior side 224 is arc-shaped (convex, concave, or a combination thereof), while the anterior side 224 may have a linear segment. The tooth tip 222 may be offset relative to the posterior side 223 or the anterior side 224.

[0029] As mentioned above, the toothed belt embodiments described herein are used in conjunction with a sprocket to engage and rotate the toothed belt. The combination of a toothed belt and a sprocket may comprise a belt drive system. The sprocket typically has teeth and grooves sized and shaped to provide a dynamic fit between the toothed belt and the sprocket, allowing the sprocket teeth to smoothly engage and disengage from the toothed belt. More specifically, the shape of the sprocket teeth, the shape of the grooves between the sprocket teeth, and the spacing between the sprocket teeth are all designed to accommodate at least a vertical segment of the leading flank of the toothed belt teeth. This vertical segment necessitates that the sprocket design have a "hollowed-out" profile that accounts for the vertical segment of the toothed belt teeth. By obtaining a sprocket design that is specifically configured to engage the specific profile of the toothed belt (i.e., the vertical segment of the leading flank of the toothed belt teeth), the sprocket provides a smooth mesh with the toothed belt teeth, which contributes to both the performance and noise reduction of the belt drive system.

[0030] Any method can be used to manufacture the toothed belts described herein. In some embodiments, the toothed belts are manufactured using a molding process, including a slab molding process. When a molding process is used, a mold is fabricated to mold the teeth having the asymmetric profile shape with vertical segments described herein.

[0031] The materials of the toothed belts 100, 200 described herein are generally not limited, and any materials can be used for the different elements of the toothed belt. Typically, the primary materials used for the main belt body 102, 202 and the teeth 110, 210 are polymeric materials such as natural or synthetic rubber materials, although other suitable materials (e.g., polyurethane) can also be used. Various fiber materials can also be included in the main belt body and / or teeth to add structural stability to the belt; in other embodiments, the belts can be fiber-free or substantially fiber-free. The toothed belts 100, 200 shown in FIGS. 1 and 2A can also have additional features not shown in the figures. For example, a protective layer can be provided on the outer surface of the teeth 110, 210, a backing layer can be provided on the radially outer surface of the main belt body 102, 202, and / or a plurality of reinforcing fibers can be embedded within the main belt body 102, 202.

[0032] Various advantages are obtained with the toothed belts described herein. Some of these advantages have already been described, such as the ability to withstand heavy loads and provide noise reduction. Additionally, the toothed belts described herein tolerate larger hub loads compared to existing profiles. The improved performance allows for a reduction in belt width for comparable specifications or an increase in the breadth of applications compared to published tooth profiles. Additionally, users benefit from the designs described herein due to improved performance in terms of reduced noise and less tooth skipping. High performance drive system performance is provided at a low price for mid-market applications.

[0033] From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.

[0034] Although the present technology has been described in language specific to structure and materials, it is to be understood that the invention defined in the appended claims is not limited to the particular structure and materials described. Rather, specific features are described as forms of implementing the claimed invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the appended claims.

[0035] Unless otherwise indicated, all numerical values or expressions used in this specification (except in the claims), such as those indicating sizes, physical properties, and the like, are understood to be modified in all instances by the term "about." At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the claims, each numerical parameter described in the specification or claims that is modified by the term "about" should be construed, at the very least, in light of the number of significant digits recited and by applying rounding techniques. Furthermore, all ranges described herein should be understood to encompass and support claims that recite all subranges or individual numerical values subsumed therein. For example, a range recited as 1 to 10 should be considered to encompass and support claims that recite all subranges or individual numerical values between and / or including the minimum value of 1 and the maximum value of 10. That is, all subranges beginning at or above 1 and ending at or below 10 (e.g., 5.5 to 10, 2.34 to 3.56, etc.) or 1 to 10 (e.g., 3, 5.8, 9.9994, etc.).

Claims

1. a main belt body portion; a plurality of teeth evenly spaced along an inner circumference of the belt, each tooth extending radially inward from said main belt body, each tooth having a height extending from a land to a tooth tip, and a cross-sectional profile of each tooth A vertical segment is provided on the front side of the tooth, the vertical segment being substantially perpendicular to the longitudinal axis of the main belt body when the toothed belt is in a rack state, the vertical segment having a length shorter than the height of the tooth. Toothed belt.

2. 2. The toothed belt of claim 1, wherein said vertical segment forms an angle with respect to the longitudinal axis of said main belt body when said belt is in a racked condition, said angle being between 86° and 110°.

3. 3. The toothed belt of claim 2, wherein the angle of said perpendicular segment relative to the longitudinal axis of said main belt body is 90 degrees when said belt is in a racked state.

4. 2. The toothed belt according to claim 1, wherein the length of said vertical segment is 10 to 90% of the height of said tooth.

5. 2. The toothed belt according to claim 1, wherein the length of said vertical segment is 30 to 60% of the height of said tooth.

6. The cross-sectional contour shape of each tooth is a first curved portion extending from the land to a radially outer end of the vertical segment on a forward side of the tooth; a second curved portion at a front side of the tooth, the second curved portion extending from a radially inner end of the vertical segment to a tip of the tooth; 2. The toothed belt according to claim 1.

7. The cross-sectional contour of each tooth is further 2. The toothed belt of claim 1, further comprising a third curved portion at a rear flank of said tooth, said third curved portion extending from said tooth tip to said land, said third curved portion being substantially free of vertical segments.

8. 8. The toothed belt of claim 7, wherein the third curved portion is formed for smooth meshing between the toothed belt and a corresponding sprocket.

9. 8. The toothed belt according to claim 7, wherein the third curved portion is formed to reduce noise during meshing of the toothed belt with a corresponding sprocket.

10. a main belt body portion; a plurality of teeth evenly spaced along an inner circumference of the belt, each tooth extending radially inward from the main belt body, each tooth having a height extending from a land to a tooth tip, and a cross-sectional profile of each tooth A vertical segment is provided on the front side of the tooth, the vertical segment being substantially perpendicular to the longitudinal axis of the main belt body when the toothed belt is in a rack state, the vertical segment having a length shorter than the height of the tooth. A toothed belt; a sprocket configured to engage and rotate the toothed belt, the sprocket having a plurality of teeth; The contour shape of each tooth of the sprocket and the spaces between adjacent teeth of the sprocket are shaped so as to smoothly mesh with the teeth of the toothed belt. Belt drive system.

11. 11. The belt drive system of claim 10, wherein the profile of each tooth of the sprocket and the spacing between adjacent teeth of the sprocket are specifically adapted for the sprocket to accommodate the vertical segment of the toothed belt.

12. 12. The belt drive system of claim 11, wherein the vertical segment forms an angle with respect to a longitudinal axis of the main belt body when the belt is in a racked condition, the angle being within the range of 86 degrees to 110 degrees.

13. 13. The belt drive system of claim 12, wherein the angle of the vertical segment relative to the longitudinal axis of the main belt body is 90 degrees when the belt is in a racked condition.

14. 12. The belt drive system of claim 11, wherein the length of the vertical segment is 10 to 90% of the tooth height.

15. 12. The belt drive system of claim 11, wherein the length of the vertical segment is 30 to 60% of the tooth height.

16. a main belt body having a longitudinal axis; a plurality of teeth evenly spaced along an inner circumference of the belt, each tooth having a leading side, a trailing side, and a height extending from a land to a tip of the tooth; The cross-sectional profile of each tooth is asymmetrical with respect to a Y axis evenly located between the front side land and the rear side land; At the front side of the tooth, when the toothed belt is in a rack state, the cross-sectional shape has a vertical segment that is substantially disposed on the main belt body portion, and the vertical segment has a length that is shorter than the height of the tooth. Toothed belt.

17. 17. The toothed belt of claim 16, wherein the vertical segments have a length of 10 to 90% of the height of the teeth.

18. 18. The method of claim 17, wherein the length of the vertical segment is 30 to 60% of the height of the tooth. Toothed belt.

19. 17. The toothed belt of claim 16, wherein said vertical segment forms an angle with said main belt body when said belt is in a racked condition, said angle being between 86° and 110°.

20. 20. The toothed belt of claim 19, wherein the angle of the perpendicular segment relative to the longitudinal axis of the main belt body is 90 degrees when the belt is in the racked condition.

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