WO2024076938A1

WO2024076938A1 - Belt drive system

Info

Publication number: WO2024076938A1
Application number: PCT/US2023/075760
Authority: WO
Inventors: Sean Colin HACKING
Original assignee: Hacking Sean Colin
Priority date: 2022-10-02
Filing date: 2023-10-02
Publication date: 2024-04-11

Abstract

A sprocket and belt drive system comprising a belt and one or more rotatable sprockets, where both the sprocket and belt have teeth that mesh with each other. The teeth feature multiple cross- sectional profiles across the transverse width. The belt tooth cross section is narrower in the central region compared to the edge regions, while the sprocket teeth cross sections are broader in the central region. This arrangement allows for cooperative engagement between the belt teeth and sprocket teeth, facilitating motion transfer and self-aligning the belt and sprockets along the axis of rotation.

Description

BELT DRIVE SYSTEM

Inventor(s):

Sean Colin Hacking of Novato, California September 29, 2023

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] The present application claims the benefit of United States Provisional Patent Application Serial Number 63412478, filed 10/2/2022 (October 2^nd 2022), which application is incorporated in its entirety by reference herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

T HE NAMES OR PARTIES TO A JOINT RESEARCH AGREEMENT

[0003] Not applicable.

INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

[0004] Not applicable.

SEQUENCE LISTING

[0005] Not applicable SPECIFICATION

FIELD OF THE INVENTION

[0006] This invention pertains to the realm of power transmission systems, particularly a selfaligning belt drive system with teeth having a variable cross-sectional profile across the transverse width, suitable for applications in motor vehicles, bicycles, and a range of other small vehicles, although its utility is not confined to these applications.

BACKGROUND DISCUSSION

[0007] Traditionally, chain drives have been extensively utilized in bicycles, motor vehicles, and other analogous applications owing to their capability to effectively transmit power between rotating components. Chains are known for their positive engagement, robustness, and ability to transmit high torques. However, they exhibit several notable shortcomings that could impede their utility and operational effectiveness. Some of these limitations include the requirement for regular lubrication, maintenance, cleaning, accompanied by inherent noise generation, poor damping characteristics, substantial mass, and limited drive speed capabilities.

[0008] An acknowledged alternative to chain drives is belt drive systems. Belt drives are celebrated for overcoming many of the aforementioned issues associated with chain drives. They generally require less maintenance, offer quieter operation, are lighter in weight, and are capable of operating at higher speeds. They are also known for their cleaner operation as they do not necessitate lubrication, thereby reducing the maintenance efforts considerably.

[0009] Nonetheless, belt drives come with their own set of challenges. A prominent issue is the difficulty associated with aligning the belt with the sprockets, which is crucial for efficient power transmission and prolonged operational life. Furthermore, conventional belt drives often struggle to maintain a compact profile while transmitting substantial amounts of power, which becomes a significant concern in space-constrained applications such as bicycles and small motor vehicles. [0010] Current designs aimed at ensuring belt and sprocket alignment often employ flanges on the sides of the sprockets. However, this configuration is known to induce problems such as noise generation due to air venting, trapping of debris between the sprocket and belt, increased manufacturing costs, broader sprocket and drive system width, and an augmented system mass.

[0011] Some belt drive systems have resorted to utilizing chevron shaped teeth or teeth otherwise offset from each other to maintain belt tracking. While these configurations may smoothen the drive operation to an extent, they significantly compromise belt flexibility and complicate the manufacturing process.

[0012] Other known systems have adopted a central alignment mechanism, such as employing a central continuous flange that runs in a longitudinal groove in the belt teeth, extending through and bisecting the belt teeth, utilized for many years in applications like snowmobiles, snowblowers, and tractor tread belts. This design, however, is known to compromise tooth strength and integrity, adversely affect wear life, and add to the weight of the sprocket when compared to belts without a longitudinal groove and sprocket guide flange, disadvantages that are particularly significant in drive systems for vehicles and bicycles where weight and durability are paramount. It is also disadvantageous when used in conjunction with a detachable belt utilizing transverse connecting pins placed into transverse cavities within the belt teeth. The connecting pins must generally bridge the longitudinal groove bisecting the teeth, interfering with the alignment flange on the sprocket and weakening the detachable belt connection overall.

[0013] Hence, there is a pressing need for a self-aligning system that does not substantially undermine belt tooth integrity or wear life, is compact, efficiently sheds debris, is easy to manufacture, is compatible with transverse belt connecting pins, and leverages the natural selfaligning behavior exhibited by a belt with multiple cross-sectional profiles across the transverse width. This need is especially acute in applications such as bicycles and motorcycles, which require high power-carrying density and encounter many debris in operation. The present invention addresses this need by introducing a self-aligning belt drive system with variably profiled teeth that mesh with substantially complementary sprocket teeth, thereby offering an effective solution to the long-standing alignment issue in belt drive systems.

[0014] The foregoing patents and commercially available products reflect the current state of the art of which the present inventor is aware. Reference to, and discussion of, these patents is intended to aid in discharging Applicants’ acknowledged duty of candor in disclosing information that may be relevant to the examination of claims to the present invention. However, it is respectfully submitted that none of the above-indicated patents disclose, teach, suggest, show, or otherwise render obvious, either singly or when considered in combination, the invention described and claimed herein.

DISCLOSURE OF INVENTION

[0015] In embodiments the present invention offers a solution to several of the above-described problems by providing self-aligning behavior naturally arising from a belt and sprocket pairing with multiple tooth profile widths.

[0016] The primary aspect of this invention is a belt having teeth with differing cross-sectional profile across the transverse width of the belt, and a sprocket with complementary cross-sectional profiles across the transverse width of the sprocket teeth extending parallel to the rotation axis that can cooperatively engage with the belt tooth profiles when the belt and sprocket are enmeshed in operation.

[0017] Other aspects of the invention will be pointed out or made obvious by the following description of the invention and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG.1 Is a perspective view of the sprocket cooperatively engaging a flat span of the belt;

FIG.2 is a perspective view of a section of belt and the belt teeth;

FIG.3 is a detail perspective view of the belt of FIG.2;

FIG.4 is a perspective view of the bicycle drive belt system;

FIG.5 is a cross section side view of the sprocket cooperatively engaging a flat span of the belt and the sprocket and belt teeth intermeshing;

FIG.6 is a detail cross section view of the sprocket and belt of FIG.5 with teeth intermeshing;

FIG.7 is a side view of the sprocket cooperatively engaging a flat span of the belt;

FIG.8 is a detail side view of the sprocket and belt of FIG.7 with teeth intermeshing;

FIG.9 is a section view of the sprocket taken along the line FIG.9-FIG.9 of the sprocket of FIG.7;

FIG.10 is a detail section view of the sprocket teeth of FIG.7 taken along the line FIG.9-FIG.9 ;

FIG.11 is a perspective view of the sprocket teeth;

FIG.12 is a side view of a bicycle with the belt drive system mounted one the crank and wheel hub;

FIG.13 Is a detail perspective view of the sprocket cooperatively engaging a flat span of the belt;

DETAILED DESCRIPTION OF THE INVENTION

[0018] The belt 1 is comprised of a flat body 3 of flexible material. There are teeth 5, lugs, lobes, or other types of protrusions that extend across the transverse width of the belt 7, on one or more sides of the flat body 3. The flat body 3 may be formed from a flexible and durable body material, such as rubber, plastic or other polymeric material. The belt may be endless, modular, spliced, linear, or otherwise formed into a drive member with a plurality of belt teeth 5. The modular or spliced configurations may utilize a detachable belt utilizing transverse connecting pins placed into transverse cavities within the belt teeth to connect the belt ends formed into an interlocking dado configuration.

[0019] An embodiment uses cords twisted from carbon fibers as a belt reinforcing material, encased the flat body made from a hard rubber and arranged along the longitudinal dimension 9. The reinforcing material may be also formed from strong fibers like steel, glass fiber, polymer, carbon fibers, or a combination of multiple fibers to increase the load carrying capacity of the belt 1.

[0020] The transverse belt teeth 5 are formed from the body material extending away from the flat body 3, and are spaced in the longitudinal direction 9 along said belt on at least one side of the flat body, and have a transverse profile or cross-section 11 that is generally normal to the load applied to the belt. This configuration allows said belt to be flexible along a neutral axis between the teeth 5 that allows for bending around a sprocket 13. Most commonly, the teeth 5 are disposed on the inner circumference 15 of the belt 1, but may also be disposed on the outer circumference 17. The belt can be produced by molding, extrusion, machining, grinding, or other manufacturing processes.

[0021] The belt teeth 5 are formed with more than one cross-section 11, which varies across the transverse width 7 of each tooth. In this configuration, the belt is comprised of multiple cross- sectional profiles 11 that are transversely aligned in order to leave as much flexible area between the belt teeth as possible. The multiple cross-sectional profiles 11 of each belt tooth generally extend the same distance from the flat body 3 of the belt 1, forming a tooth peak 19 that is uninterrupted across the transverse width, although many configurations are possible which confer self-aligning advantages.

[0022] The transverse belt teeth 5 are formed into a shape that can cooperatively engage with sprocket teeth 21 to transmit force or power to or from the sprocket 13. The transverse belt teeth 5 fit into transverse grooves 23 in between sprocket teeth 21.

[0023] The sprocket is comprised of a rotatable circular body 25 or frame that supports circumferential teeth 21, protrusions, or lugs, which have a sprocket tooth cross-sectional profile 27 transverse the body and parallel to a rotation axis 29. The rotatable body 25 and teeth 21 rotate about the rotation axis 29.

[0024] The sprocket body 25 and sprocket teeth 21 can be made from steel, aluminum, plastic, or other durable materials. The sprocket body 25 and sprocket teeth 21 can be made of the same or different materials, formed by stamping, laser cutting, molding, extrusion, forging, waterjet cutting, machining, hobbing, grinding, or other process. In an embodiment, the sprocket 13 is formed from steel plates which have the profiles of the sprocket teeth and other features, each stacked and welded together to form the full-width sprocket 13.

[0025] The sprocket teeth 21 are formed into a shape that can cooperatively engage the belt teeth 5 to transmit force or power to or from the belt when the sprocket comes into proximity to the belt. The sprocket teeth fit into the valleys between the belt teeth 31.

[0026] The sprocket teeth 21 are formed from more than one cross-sectional profile 27, which varies across the transverse width of the sprocket teeth 21. There are multiple tooth crosssections, shapes, or profiles, which are transversely aligned in a configuration that is substantially complementary to the belt tooth cross-sections 11. There may be a central region which is a broader cross-section 35 or narrower cross-section 37. An embodiment has a small, centralized region 35 which is broader in cross section than the rest of the sprocket tooth. [0027] One or more of the sprocket teeth 21 may have a constant cross-section, a cross-section that varies between teeth, or a cross-section that is not completely complementary to the belt tooth 5 shapes, as long as it doesn't interfere with the smooth operation of the system. This can serve different goals in manufacturing, aesthetics, sound, and debris shedding, depending on the application. The different cross-sectional profiles may have a distinct stepwise transition between them, or a curved, chamfered, or otherwise smoothed transition between them.

[0028] An embodiment utilizes a centralized region which has a broader cross section 35 than the rest of the sprocket tooth, having a transverse width that is less than the transverse width of the complementary narrower portion of the belt tooth 39, providing some clearance between the features on the sprocket and belt, and allowing some small amount of float and misalignment of the sprocket and belt to account for entrapped debris and manufacturing and operational tolerances. The edges of the centralized region 35 have alignment chamfers 41 which aid in the smooth self-alignment of the belt and sprocket.

[0029] An embodiment features sprocket teeth 21 that extend away from the central sprocket body 25 in a direction parallel to the axis of rotation, serving to lighten the sprocket body 25 and provide an easy path for debris to escape entrapment at the sprocket-belt interface 43.

[0030] The variable sprocket tooth cross-section 27 may be formed from a single part, or created by an elongate member which is formed in the shape of the tooth profile and wrapped around and connected to the sprocket teeth 21. In one embodiment, the broader tooth profile 35 is formed from a wire bent into a sprocket profile shape, and inserted into a complementary groove formed in the sprocket teeth 21 so that it is retained while the drive is operating and serves the same function as a sprocket produced from a single piece of material. The variable sprocket tooth cross-section may also be formed with plates of material stacked and welded together, as mentioned previously.

[0031] A groove 45 that slopes away from the sprocket centerline and toward the axis of rotation may be formed in between the sprocket teeth 21 to encourage the shedding of debris trapped between the belt teeth 5 and sprocket teeth 21. This groove may have various shapes and configurations that create an open path towards the axis of rotation 29 for debris to be shed away from the belt-sprocket interface 43.

[0032] The sprocket 13 and the belt 1 cooperatively engage in a way the belt 1 wraps around the sprocket 13, or the sprocket 13 rolls against a flat span of belt 1, and force or power can be transmitted between the belt 1 and one or more sprockets 13. The sprocket 13 is either rotated by the belt 1 in the driven configuration or rotates to drive the belt in the driving configuration. In an embodiment, there is a drive sprocket 47 and a driven sprocket 49, with the belt 1 transmitting rotational power between them.

[0033] In embodiments, belt drive system is implemented as a bicycle 50 drive system 51 for transmitting motive force from the rider or motor to the drive wheel 55. A drive sprocket 47 is rotatably mounted to the central pedal crank 53, and a driven sprocket 49 is mounted to rear wheel hub 57, with the belt 1 spanning between them. It may be incorporated in pedal assist bicycles, in electric bicycles and scooters, in electric motorcycles, and in numerous other wheeled vehicles. Moreover, the inventive drive system may be embodied in any system comprising drive and driven sprockets in which reliably transmitting power between a drive sprockets 47 and driven sprocket 49 confers one or more mechanical advantage on the system.

[0034] In an embodiment, the tooth cross-section 11 near the center of the belt is narrower than the edges of the belt, and this engages cooperatively with a broader cross section near the center of the sprocket tooth 35 to provide self-aligning of the belt 1 on the sprocket 13. The belt drive system is self-aligning because the broader tooth region of the sprocket 35 cannot engage with the broader tooth region of the belt 59, as they are not complementary profiles. The broad cross sections 35 of the sprocket teeth may only fit with the narrow cross section 39 of the belt teeth, and the narrow cross sections of the sprocket teeth 37 may only fit with the broad cross sections 59 of the belt teeth.

[0035] This self-aligning is advantageous for the construction of more compact belt drive systems but does not compromise tooth integrity or power rating to a high degree since the belt teeth 5 are substantially intact across the belt transverse width 7. [0036] The muti-profile configuration described herein is compact, easy to manufacture with traditional techniques, reduces noise from engagement and air venting, reduces system vibration, and operates smoothly in low- wrap -angle applications due to the different tooth profiles engaging at slightly different times during operation.

[0037] The belt drive system disclosed herein can have application to a wide variety of apparatus utilizing belt drives, including, but not limited to, cycles such as motorcycles and bicycles. Any embodiment is intended to be non-limiting unless expressly limited by the scope of the attached claims.

[0038] Unless otherwise indicated, all numbers expressing dimensions and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about”.

[0039] In this application and the claims, the use of the singular includes the plural unless specifically stated otherwise. In addition, use of “or” means “and/or” unless stated otherwise. Moreover, the use of the term “including”, as well as other forms, such as “includes” and “included”, is not limiting.

[0040] The above disclosure is sufficient to enable one of ordinary skill in the art to practice the invention, and provides the best mode of practicing the invention presently contemplated by the inventor. While there is provided herein a full and complete disclosure of the preferred embodiments of this invention, it is not desired to limit the invention to the exact construction, dimensional relationships, and operation shown and described. Various modifications, alternative constructions, changes and equivalents will readily occur to those skilled in the art and may be employed, as suitable, without departing from the true spirit and scope of the invention. Such changes might involve alternative materials, components, structural arrangements, sizes, shapes, forms, functions, operational features or the like.

[0041] Therefore, the above description and illustrations should not be construed as limiting the scope of the invention, which is defined by the appended claims.

Claims

CLAIMS What is claimed as invention is:

1. A sprocket and belt system comprising: a belt, the belt comprising a plurality of longitudinally spaced belt teeth, said belt teeth having a cross-section that varies across the transverse width of said belt so that there are one or more regions of said belt teeth that have a relatively narrower cross-section; and at least one sprocket configured to engage said belt, said sprocket comprising a plurality of sprocket teeth arrayed on the outer circumference, said sprocket rotatable about a rotation axis; wherein each of said sprocket teeth have a transverse width parallel to said rotation axis, each of said sprocket teeth configured to be received between adjacent belt teeth, each of said sprocket teeth having a cross-section that varies across said transverse width of said sprocket so there are relatively broader cross-section regions; and wherein said sprocket teeth and said belt teeth being configured so that said broader cross-section regions of said sprocket are brought into proximity of said narrower cross-section regions of said belt teeth when said sprocket and said belt are in cooperative engagement to provide self-aligning operation. The sprocket and belt drive system of claim 1, wherein the relatively broader sprocket tooth cross-section region from claim 1 is formed from a separate elongate member that is fixed to the sprocket outer circumference. The sprocket and belt drive system of claim 1, wherein said system is used in a bicycle to drive the rear wheel. The sprocket and belt drive system of claim 1 , wherein said sprocket is formed from plates of material which have the variable profiles of the said sprocket teeth and other features, each stacked and fastened together to form the full-width sprocket. The sprocket and belt drive system of claim 1, wherein the belt is formed from one or more flexible modules connected by transverse connecting pins inserted into transverse cavities in said belt teeth which detachably link the ends of said modules utilizing a dado configuration. The sprocket and belt drive system of claim 1, wherein said belt teeth have a tooth peak which is uninterrupted across the entire transverse width of each said tooth. The sprocket and belt drive system of claim 1, wherein said belt teeth and said sprocket teeth are formed with clearances between them when they intermesh of no more than l/5^th of the belt tooth pitch dimension. The sprocket and belt drive system of claim 1, wherein said sprocket is formed by stamping, laser cutting, molding, extrusion, forging, waterjet cutting, machining, hobbing, grinding, then welding multiple pieces of formed sheet metal into the final shape. The sprocket and belt drive system of claim 1, wherein said belt teeth and said sprocket teeth are not uniformly formed or arrayed, in manner to introduce irregularity which disrupts debris entrapment and resonant vibration. The sprocket and belt drive system of claim 1, wherein said sprocket has a pitch line diameter which is less than the pitch line diameter of said belt when wrapped around said sprocket, so that said belt teeth are subjected to non-uniform force by intermeshing of said sprocket teeth, depending on the location each of said belt teeth is arrayed around the circumference of said sprocket. The sprocket and belt drive system of claim 1, wherein said belt teeth and said sprocket teeth are formed with thin caps of a wear-resistant material fastened to the wear surfaces of each tooth. The sprocket and belt drive system of claim 1, wherein said sprocket teeth have centering chamfers on the surfaces which first engage said belt teeth when entering cooperative engagement with said belt during operation. The sprocket and belt drive system of claim 1, wherein said belt tooth cross sectional profile is narrower in the transverse central region of said belt. The sprocket and belt drive system of claim 1, wherein said belt tooth cross sectional profile is narrower in the transverse offset region of said belt. The sprocket and belt drive system of claim 1, wherein said belt tooth cross sectional profile has up to 20 relatively narrower regions across the transverse width of said belt tooth.