WO2017074478A1

WO2017074478A1 - Circular wave drive

Info

Publication number: WO2017074478A1
Application number: PCT/US2015/062728
Authority: WO
Inventors: Jacob P. MARTIN; Nathan D. Ames; Yuan F. Zheng
Original assignee: Martin Jacob P; Ames Nathan D; Zheng Yuan F
Priority date: 2015-10-30
Filing date: 2015-11-25
Publication date: 2017-05-04

Abstract

A circular wave drive system, and a method for use of a circular wave drive, are provided. In one embodiment, a circular wave drive is provided, the circular wave drive comprising: an input ring gear including internal input ring gear teeth; an input cycloidal disc including external input cycloidal disc gear teeth; an output cycloidal disc including external output cycloidal disc gear teeth; an input drive shaft including an eccentric portion and a non-eccentric portion and wherein the eccentric portion and the non-eccentric portion are axially offset from one another, and wherein the non-eccentric portion is oriented in an input ring gear input drive shaft aperture, wherein the eccentric portion is oriented in an input cycloidal disc input drive shaft aperture, and wherein the eccentric portion is oriented in an output cycloidal disc input drive shaft aperture; and primary drive gear including internal primary drive gear teeth.

Description

CIRCULAR WAVE DRIVE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 62/249,147, filed October 30, 2015, which is incorporated by reference herein in its entirety.

BACKGROUND

[0002] A number of devices for transmitting power and reducing motor output speed are currently known. Two such devices are the harmonic drive and the cycloidal drive.

[0003] The more well-known of these devices is the harmonic drive, having been introduced in the 1950's and currently being in wide-spread use. However, the harmonic drive requires the use of a flexspine, which is deliberately deformed repeatedly during operation of the harmonic drive. This deformation of the flexspine fatigues the material from which the flexspine is constructed, which fatigue limits the speed reduction and torque transfer that may be achieved with a harmonic drive.

[0004] Typical versions of the cycloidal drive are of relatively complex construction and operation. The cycloidal drive requires many moving parts, each of which may be a point of failure. The eccentric rotation of the cycloidal disc also produces an undesirable vibration that may be transmitted through the input and output shafts if not compensated for. Finally, contact between the output rollers and the receiving holes in the cycloidal disc may also lead to the wear of both components.

[0005] What is needed is a power transmission/speed reduction device that does not suffer from the described drawbacks of known harmonic and cycloidal drives. Such a device may also offer a more simplistic construction, as well as a long life. SUMMARY

[0006] In one embodiment, a circular wave drive is provided, the circular wave drive comprising: an input ring gear having an inner surface and an input ring gear input drive shaft aperture, wherein the input ring gear includes internal input ring gear teeth oriented on the inner surface; an input cycloidal disc having an outer surface and an input cycloidal disc input drive shaft aperture, wherein the input cycloidal disc includes external input cycloidal disc gear teeth oriented on the outer surface, and wherein the external input cycloidal disc gear teeth at least partially engage the internal input ring gear teeth; an output cycloidal disc having an outer surface and an output cycloidal disc input drive shaft aperture, wherein the output cycloidal disc includes external output cycloidal disc gear teeth oriented on the outer surface; an input drive shaft having a longitudinal length, wherein the input drive shaft includes an eccentric portion and a non-eccentric portion and wherein the eccentric portion and the non-eccentric portion are axially offset from one another along the longitudinal length of the input drive shaft, and wherein the non-eccentric portion is oriented in the input ring gear input drive shaft aperture, wherein the eccentric portion is oriented in the input cycloidal disc input drive shaft aperture, and wherein the eccentric portion is oriented in the output cycloidal disc input drive shaft aperture; and a primary drive gear having an inner surface, wherein the primary drive gear includes internal primary drive gear teeth oriented on the inner surface, and wherein the internal primary drive gear teeth at least partially engage the external output cycloidal disc gear teeth.

[0007] In another embodiment, a circular wave drive is provided, the circular wave drive comprising: an input ring gear having an inner surface and an input ring gear input drive shaft aperture, wherein the input ring gear includes internal input ring gear teeth oriented on the inner surface; an input cycloidal disc having an outer surface and an input cycloidal disc input drive shaft aperture, wherein the input cycloidal disc includes external input cycloidal disc gear teeth oriented on the outer surface, and wherein the external input cycloidal disc gear teeth at least partially engage the internal input ring gear teeth; an output cycloidal disc having an outer surface and an output cycloidal disc input drive shaft aperture, wherein the output cycloidal disc includes external output cycloidal disc gear teeth oriented on the outer surface; an input drive shaft having a longitudinal length, wherein the input drive shaft includes an eccentric portion and a non-eccentric portion and wherein the eccentric portion and the non-eccentric portion are axially offset from one another along the longitudinal length of the input drive shaft, and wherein the non-eccentric portion is oriented in the input ring gear input drive shaft aperture, wherein the eccentric portion is oriented in the input cycloidal disc input drive shaft aperture, and wherein the eccentric portion is oriented in the output cycloidal disc input drive shaft aperture; a primary drive gear having an inner surface, wherein the primary drive gear includes internal primary drive gear teeth oriented on the inner surface, and wherein the internal primary drive gear teeth at least partially engage the external output cycloidal disc gear teeth; an output drive element coupled to the primary drive gear.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The accompanying figures, which are incorporated in and constitute a part of the specification, illustrate various example systems, apparatuses, and methods, and are used merely to illustrate various example embodiments. In the figures, like elements bear like reference numerals.

[0009] FIG. 1A is a perspective view of an input end of one example embodiment of a circular wave drive 100.

[0010] FIG. IB is a perspective view of an output end of one example embodiment of circular wave drive 100. [0011] FIG. 1C is an elevational view of an input end of one example embodiment of circular wave drive 100.

[0012] FIG. ID is an elevational view of an output end of one example embodiment of circular wave drive 100.

[0013] FIG. IE is a sectional view of one example embodiment of circular wave drive

100.

[0014] FIG. 2A is a rear elevational view of one example embodiment of an input ring gear 202.

[0015] FIG. 2B is a front elevational view of one example embodiment of input ring gear

202.

[0016] FIG. 2C is a sectional view of one example embodiment of input ring gear 202.

[0017] FIG. 2D is a partial sectional view of one example embodiment of input ring gear

202.

[0018] FIG. 3A is a side elevational view of one example embodiment of an input drive shaft 306.

[0019] FIG. 3B is a front elevational view of one example embodiment of input drive shaft 306.

[0020] FIG. 3C is a sectional view of one example embodiment of input drive shaft 306.

[0021] FIG. 4 is a perspective view of one example embodiment of a bushing 422.

[0022] FIG. 5A is a side elevational view of one example embodiment of an input cycloidal disc 518.

[0023] FIG. 5B is a sectional view of one example embodiment of input cycloidal disc

518.

[0024] FIG. 6A is a side elevational view of one example embodiment of an output cycloidal disc 620. [0025] FIG. 6B is a sectional view of one example embodiment of output cycloidal disc 620.

[0026] FIG. 7 A is a side elevational view of one example embodiment of a primary drive gear 724.

[0027] FIG. 7B is a side elevational view of one example embodiment of primary drive gear 724.

[0028] FIG. 8A is a rear elevational view of one example embodiment of an output drive element 804.

[0029] FIG. 8B is a front elevational view of one example embodiment of output drive element 804.

[0030] FIG. 8C is a sectional view of one example embodiment of output drive element 804.

[0031] FIG. 9 A is a perspective view of an output end of one example embodiment of a circular wave drive 900.

[0032] FIG. 9B is a perspective view of an input end of one example embodiment of circular wave drive 900.

[0033] FIG. 10 is a flowchart illustrating an example method for determining a reduction radio of a circular wave drive.

DETAILED DESCRIPTION

[0034] Example circular wave drive embodiments disclosed herein may be of simpler construction than known harmonic and cycloidal drives. Example circular wave drive embodiments disclosed herein may also be compact in size, offer a large range of speed reduction ratios, are not reverse-drivable, and operate with little to no backlash. Example circular wave drive embodiments disclosed herein are devoid of rollers commonly found in cycloidal drives. [0035] Generally speaking, example circular wave drive embodiments disclosed herein may include a housing having a circular chamber therein. The housing may include a cover that closes a cavity in the housing so as to form the enclosed circular chamber. The housing may be formed of more than one element, selectively fitted together. Teeth may be disposed along an inside circular wall of the chamber (input ring gear). A ring-shaped wheel (input cycloidal disc) may reside within the chamber. The ring-shaped wheel may be integral to, or removably attached to, the housing. The wheel may include external teeth that mesh with the teeth located along the circular inner wall of the housing. The wheel diameter may be smaller than the chamber diameter, such that only a portion of the wheel teeth are meshed with the internal housing teeth at any given time. The wheel may be laminated to a second wheel (output cycloidal disc), which may also include external teeth. The second wheel external teeth may mesh with internal teeth disposed along a portion of an inner wall of an output gear element (primary drive gear).

[0036] Example circular wave drive embodiments disclosed herein may also include a wave generator (input drive shaft). The wave generator may include an input drive shaft having an eccentric portion configured to cause translation of one or more elements (e.g., input cycloidal disc and output cycloidal disc) during rotation of the input drive shaft. The input drive shaft, including the eccentric portion, may have a cross-section that is circular in shape. The eccentric portion may be offset from the central axis of the remainder of the input drive shaft so as to impart an eccentric motion to elements in contact with the input draft shaft when the input drive shaft is rotated. The input shaft portion of the wave generator may extend through an opening in the housing, which may include an input ring gear, either removably or integrally attached to the housing.

[0037] Example circular wave drive embodiments may also employ an output drive element. The output drive element may include a circular-shaped disc having internal peripheral teeth (primary drive gear). The primary drive gear portion of the output drive element may reside within the housing chamber and may be located about an output cycloidal disc. The housing chamber may include an input ring gear, either integral to the housing, or removably attached to the housing. The inner diameter of the primary drive gear of the output element may be greater than the outer diameter of the output cycloidal disc, such that the toothed peripheral surface of the output cycloidal disc is aligned with and is in partial contact with a toothed section of the primary drive gear. The output element portion of the output drive element may form a portion of the housing, and may rotate relative to the input ring gear, which may also form a portion of the housing. The output element portion of the output drive element may be coaxial with the input drive shaft. The output element portion may be oriented on an opposite side of the circular wave drive from the input drive shaft, or alternatively, the output element portion may be oriented on the same side of the circular wave drive as the input drive shaft. Both the input drive shaft and the output element portion of the output drive element may pass through bearings.

[0038] In operation, the input drive shaft of the wave generator may be connected to a rotation-imparting actuator, such as an electric drive motor. The actuator may impart rotational motion to the wave generator, which may cause the eccentric portion thereof to rotate within the input cycloidal disc and the output cycloidal disc. Rotation of the eccentric portion may cause a rotation of the input cycloidal disc along the inner wall of the input ring gear. Rotation of the eccentric portion and the input cycloidal disc may cause rotation of the output cycloidal disc, which may cause rotation of the primary drive gear, which may cause rotation of the output drive element at a reduced speed relative to the rotational velocity of the input drive shaft (reduced by the reduction ratio).

[0039] Because the external peripheral surface of the eccentric portion of the input drive shaft and the mating surface of the inner wall of the input cycloidal disc may be separated by a bearing, the coefficient of friction between the eccentric portion of the input drive shaft and the mating surface of the inner wall of the input cycloidal disc may be extremely low.

Consequently, the input cycloidal disc may not rotate in turn with the input drive shaft eccentric portion but, rather, may slide along the peripheral surface of the input drive shaft eccentric portion. This may result in an input cycloidal disc rotational speed that is less than the rotational speed of the input drive shaft and associated actuator. The overall speed reduction between the input and output side of the circular wave drive may depend upon at least one of: the diameter of the wave generator, the number of gear teeth of the input cycloidal disc, the number of gear teeth of the input ring gear, the number of gear teeth of the output cycloidal disc, and the number of gear teeth of the primary drive gear. The overall speed reduction may additionally depend upon the diameters of the various elements noted immediately above. A large diameter may not necessarily have more teeth than a small diameter when two surfaces meet. With various combinations of the diameters and the numbers of teeth, the magnitude of the speed reduction may cover a large range, for example from 8: 1 to 10,000: 1, which may not be possible through the use of existing devices.

[0040] FIG. 1A is a perspective view of an input end of one example embodiment of a circular wave drive 100. Circular wave drive 100 may include an input ring gear 102 and an output drive element 104. Circular wave drive 100 may include an input drive shaft 106.

[0041] Circular wave drive 100 may be configured to receive a rotational input and, via interactions between various elements, output a rotational output reduced by a reduction ratio as described further herein. Circular wave drive 100 may be made of any of a variety of materials, including for example: metals such as steel, alloys, or the like; polymers; organic materials; and the like. Circular wave drive 100 may be made of any material having sufficient strength, hardness, durability, and the like, to perform a rotational reduction for a desired duration of intended use. Any of the various elements of circular wave drive 100 may be formed through any of a variety of methods, including for example: machining, 3D printing/additive manufacturing, forging, and the like.

[0042] Input ring gear 102 and output drive element 104 may together form a housing. Input ring gear 102 and output drive element 104 may be rotatably connected to one another, such that one may rotate relative to the other. Input ring gear 102 and output drive element 104 may be rotatably connected to one another, with an input ring gear/output drive element bearing (not shown) oriented therebetween.

[0043] Input drive shaft 106 may be a shaft having a substantially circular cross-section. Input drive shaft 106 may include eccentric portions (not shown), as described more fully below. Input drive shaft 106 may include a hollow bore 108. Alternatively, input drive shaft 106 may be solid, and devoid of hollow bore 108. Input drive shaft 106 may be operatively connected to a rotation-inducing element, including for example, a rotational actuator configured to impart rotation to input drive shaft 106.

[0044] Input ring gear 102 may include at least one input ring gear mounting element 110. Input ring gear mounting element 110 may include an aperture, perforation, boss, threaded blind hole, non-threaded blind hole, tab, and the like. Input ring gear mounting element 110 may include any of a variety of elements permitting the mounting or otherwise arresting of input ring gear 102 relative to another object, such as a structural element of a mechanical component, the ground, a machine, and the like.

[0045] FIG. IB is a perspective view of an output end of one example embodiment of circular wave drive 100.

[0046] Output drive element 104 may include a hollow center in communication with hollow bore 108. Output drive element 104 may include a solid center, devoid of a hollow center. [0047] Output drive element 104 may include at least one output drive element mounting element 112. Output drive element mounting element 112 may include an aperture, perforation, boss, threaded blind hole, non-threaded blind hole, tab, and the like. Output drive element mounting element 112 may include any of a variety of elements permitting the mounting or otherwise arresting of output drive element 104 relative to another object, such as a structural element of a mechanical component, the ground, a machine, and the like.

[0048] FIG. 1C is an elevational view of an input end of one example embodiment of circular wave drive 100. As illustrated, at least a portion of input drive shaft 106 may be coaxial with input ring gear 102. At least a portion of input drive shaft 106 may be concentric with input ring gear 102.

[0049] FIG. ID is an elevational view of an output end of one example embodiment of circular wave drive 100.

[0050] FIG. IE is a sectional view of one example embodiment of circular wave drive 100.

[0051] Circular wave drive 100 may include input ring gear 102 and output drive element 104, which together may form a portion, or all of, a housing. Output drive element 104 may rotate relative to input ring gear 102, and may engage input ring gear 102 via input ring gear/output drive element bearing 128.

[0052] Input ring gear 102 may include at least one input ring gear mounting element

110, which may include a blind hole. Input ring gear 102 may include input ring gear teeth

132, extending about the inner wall of at least a portion of input ring gear 102.

[0053] Input drive shaft 106 may extend through an aperture in input ring gear 102. An input drive shaft bearing 116 may be oriented between input drive shaft 106 and input ring gear 102, so as to permit rotational motion of input drive shaft 106 relative to input ring gear

102. Input drive shaft bearing 116 may be configured to limit motion of input drive shaft 106 relative to input ring gear 102, to rotational motion, and thus preventing other relative motions between input drive shaft 106 and input ring gear 102.

[0054] Circular wave drive 100 may include an input cycloidal disc 118. Input cycloidal disc 118 may be oriented within at least a portion of input ring gear 102. Input cycloidal disc 118 may include input cycloidal external gear teeth 134. Input cycloidal external gear teeth 134 may at least partially engage input ring gear teeth 132.

[0055] Input drive shaft 106 may be operative ly connected to input cycloidal disc 118. Input drive shaft 106 may include an eccentric portion, which may engage a hollow central portion of input cycloidal disc 118. An input drive shaft/input cycloidal disc bearing 126 may be oriented between input drive shaft 106 and input cycloidal disc 118, so as to permit rotation of one relative to the other.

[0056] Circular wave drive 100 may include an output cycloidal disc 120. Output cycloidal disc 120 may be oriented within at least a portion of input ring gear 102. Input cycloidal disc 118 may be operatively connected to an output cycloidal disc 120. Output cycloidal disc 120 may be fixed to input cycloidal disc 118 via any of a variety of fasteners, including for example: a bolt, a rivet, a screw, an adhesive, a weld, an interference fit, and the like. Alternatively, output cycloidal disc 120 may be integrally formed with input cycloidal disc 118, such that the two are machined, forged, printed, or otherwise created as a single part. Output cycloidal disc 120 may include external output cycloidal disc gear teeth 136 oriented about its periphery.

[0057] Circular wave drive 100 may include a bushing 122 oriented between output cycloidal disc 120 and input drive shaft 106. Bushing 122 may act to simply maintain output cycloidal disc 120 as centered on an eccentric portion of input drive shaft 106. Bushing 122 may act as a bearing to permit a reduced friction interface between input drive shaft 106 and output cycloidal disc 120. [0058] Circular wave drive 100 may include a primary drive gear 124. Output drive element 104 may be operatively connected to primary drive gear 124. Output drive element 104 may be fixed to primary drive gear 124 via any of a variety of fasteners, including for example: a bolt, a rivet, a screw, an adhesive, a weld, an interference fit, and the like. Alternatively, output drive element 104 may be integrally formed with primary drive gear 124, such that the two are machined, forged, printed, or otherwise created as a single part.

[0059] Primary drive gear 124 may be at least partially contained within a portion of input ring gear 102. Primary drive gear 124 may include internal primary drive gear teeth 138 oriented about an inner wall of primary drive gear 124.

[0060] Primary drive gear 124 may be oriented about the periphery of output cycloidal disc 120. Output cycloidal disc gear teeth 136 may at least partially engage primary drive gear teeth 138. Output cycloidal disc gear teeth 136 may at least partially mesh with primary drive gear teeth 138.

[0061] Input drive shaft 106 may be operatively connected to output drive element 104 via an input drive shaft/output drive element bearing 130, which may allow rotational motion between input drive shaft 106 and output drive element 104.

[0062] It is understood that all bearings referenced herein may be any of a variety of bearings as appropriate to allow rotational motion between the elements described. For example, the bearings may include any of: ball bearings, roller bearings, plain bearings, thrust bearings, and the like. In some embodiments, combinations of various bearings may be used in place of any of the bearings noted herein.

[0063] In practice, a rotational force may be input to input drive shaft 106, which may cause rotation of input drive shaft 106. Input drive shaft 106 may be permitted to rotate within input ring gear 102 via input drive shaft bearing 116. An eccentric portion of input drive shaft 106 may engage input cycloidal disc 118 via input drive shaft/input cycloidal disc bearing 126, which eccentric rotation may cause input cycloidal disc 118 to engage and rotate along input ring gear teeth 132. Rotation of input cycloidal disc 118 may cause a like eccentric rotation of output cycloidal disc 120. Eccentric rotation of output cycloidal disc 120 may cause output cycloidal disc 120 to engage and rotate along primary drive gear 124. Rotation of primary drive gear 124 may cause rotation of output drive element 104, which may be configured to rotate relative to input ring gear 102 via input ring gear/output drive element bearing 128. The speed of rotation of output drive element 104 may be reduced relative to the speed of rotation of input drive shaft 106 via a reduction ratio.

[0064] It is contemplated that circular wave drives 100 and 900 of FIGS. 1A-1E and 9A and 9B, respectively, may be used in any of a variety of actuation and/or gear reduction applications, including for example: robotic actuation, mechanical actuation, aerospace actuation, vehicle transmissions, and the like.

[0065] The circular wave drives described herein, including for example, circular wave drives 100 and 900, may include two or more stages of cycloidal gears. In one embodiment, a circular wave drive may include two stages of cycloidal gears. In another embodiment, a circular wave drive may include three stages of cycloidal gears. In another embodiment, a circular wave drive may include more than two stages of cycloidal gears. In one embodiment, a circular wave drive may include two or more stages of cycloidal gears, wherein the two or more stages of cycloidal gears are subtractive. The circular wave drive may include two stages of cycloidal gears, and the two stages may be subtractive. In one embodiment, the inclusion of multiple stages of cycloidal gears may permit a circular wave drive to have high reduction ratios. In one embodiment, the inclusion of multiple stages of cycloidal gears, wherein the stages are subtractive, may permit a circular wave drive to have high reduction ratios. [0066] The reduction ratio of input drive shaft 106 rotational velocity to output drive element rotational velocity may be calculated through the following formula:

-1

where a = the number of gear teeth of input ring gear 102;

where b = the number of gear teeth of input cycloidal disc 118;

where c = the number of gear teeth of primary drive gear 124; and

where d = the number of gear teeth of output cycloidal disc 120.

[0067] Accordingly, where one desires a specific reduction ratio, one may design circular wave drive 100 such that the number of gear teeth of each of input ring gear 102, input cycloidal disc 118, primary drive gear 124, and output cycloidal disc 120 effect the desired reduction ratio.

[0068] Circular wave drive 100 may include an input drive backlash (backlash measured from input drive shaft 106) and an output drive backlash (backlash measured from output drive element 104.

[0069] Input drive backlash may be any of a variety of backlashes, including for example, a backlash between about 20 degrees and about 100 degrees. Input drive backlash may be between about 30 degrees and about 80 degrees. Input drive backlash may be between about 68 degrees and about 79 degrees. Input drive backlash may be between about 20 degrees and about 40 degrees. Input drive backlash may be between about 25 degrees and about 35 degrees. Input drive backlash may be between about 28 degrees and about 32 degrees. Input drive backlash may be about 30 degrees. [0070] Output drive backlash may be any of a variety of backlashes, including for example, a backlash between about 1 degree and about 2 degrees. Output drive backlash may be between about 1.2 degrees and about 2.0 degrees. Output drive backlash may be between about 1.4 degrees and about 1.8 degrees. Output drive backlash may be between about 1.2 degrees and about 1.6 degrees. Output drive backlash may be about 1.4 degrees.

[0071] In one embodiment, circular wave drive 100 is not reverse-drivable, and as such can only be operated in one rotational direction. In another embodiment, circular wave drive 100 is reverse-drivable, and as such can be operated in more than one rotational direction.

[0072] Input drive shaft 106 and output drive element 104 may rotate in the same direction. Input draft shaft 106 and output drive element 104 may be oriented on opposite sides of circular wave drive 100. Alternatively, input drive shaft 106 and output drive element 104 may be oriented on the same side of circular wave drive 100.

[0073] FIGS. 2A-2D illustrate one example embodiment of an input ring gear 202. Input ring gear 202 may be substantially similar to input ring gear 102 illustrated in FIGS. 1A-1E. Input ring gear 202 may include internal input ring gear teeth 232 oriented about an inner surface. Input ring gear teeth 232 may have a sinusoidal tooth profile. Input ring gear teeth 232 may have any of a variety of gear tooth profiles.

[0074] Input ring gear 202 may include at least one input ring gear mounting element 210.

[0075] Input ring gear 202 may include an input drive shaft aperture 240, through which input drive shaft 106 may pass (illustrated in FIGS. 1A, 1C, and IE above). A non-eccentric portion of input drive shaft may be oriented within input drive shaft aperture 240.

[0076] Input ring gear 202 may include an input drive shaft bearing engagement surface 242. Input drive shaft bearing 116 may engage input drive shaft bearing engagement surface 242. Input drive shaft bearing 116 may be contained within input drive shaft bearing engagement surface 242 via friction fit, a set screw, an adhesive, and the like.

[0077] Input ring gear 202 may include an input ring gear/output drive element bearing engagement surface 244. Input ring gear/output drive element bearing 128 may be contained within input ring gear/output drive element bearing engagement surface 244 via friction fit, a set screw, an adhesive, and the like.

[0078] FIGS. 3A-3C illustrate one example embodiment of an input drive shaft 306. Input drive shaft 306 may be substantially similar to input drive shaft 106 illustrated in FIGS. 1A, 1C, and IE. Input drive shaft 306 may have a hollow bore 308. Alternatively, input drive shaft 306 may be solid, and may be devoid of hollow bore 308.

[0079] Input drive shaft 306 may include an input drive shaft bearing engagement surface

346. Input drive shaft bearing 116 may be oriented upon input drive shaft bearing engagement surface 346. Input drive shaft bearing 116 may be contained upon input drive shaft bearing engagement surface 346 via friction fit, a set screw, an adhesive, and the like.

[0080] Input drive shaft 306 may include a non-eccentric portion 345 and an eccentric portion 347. Non-eccentric portion 345 and eccentric portion 347 may be axially offset from one another along the longitudinal length of input drive shaft 306. Eccentric portion may have a centerline CL2 that is offset from the centerline CLl of non-eccentric portion 345.

Centerline CLl may be the centerline of the remainder of input drive shaft 306, including input drive shaft bearing engagement surface 346 and an input drive shaft/output drive element bearing engagement surface 352, all of which may be part of non-eccentric portion

345. The offset between centerline CLl and CL2 may be about half the amplitude of either input ring gear teeth 132 or input cycloidal disc gear teeth 134. In one embodiment, the offset between centerline CLl and CL2 may be less than half the amplitude of either input ring gear teeth 132 or input cycloidal disc gear teeth 134. [0081] Eccentric portion 347 may include an input drive shaft/input cycloidal disc bearing engagement surface 348. Input drive shaft/input cycloidal disc bearing 126 may be oriented on input drive shaft/input cycloidal disc bearing engagement surface 348. Input drive shaft/input cycloidal disc bearing 126 may be contained upon input drive shaft/input cycloidal disc bearing engagement surface 348 via friction fit, a set screw, an adhesive, and the like.

[0082] Eccentric portion 347 may include a shoulder 349 against which input drive shaft/input cycloidal disc bearing 126 may be oriented and contained.

[0083] Eccentric portion 347 may include a bushing engagement surface 350, upon which bushing 122 may be contained. Bushing 122 may be contained on bushing engagement surface 350 via friction fit, a set screw, an adhesive, and the like.

[0084] Non-eccentric portion 345 may include input drive shaft/output drive element bearing engagement surface 352. Input drive shaft/output drive element bearing 130 may be contained on input drive shaft/output drive element bearing engagement surface 352 via friction fit, a set screw, an adhesive, and the like.

[0085] FIG. 4 is a perspective view of one example embodiment of a bushing 422. Bushing 422 may be substantially similar to bushing 122 illustrated in FIG. IE. Bushing may be substantially annular, with an inner input drive shaft engagement surface 154 and an outer output cycloidal disc engagement surface 156. Bushing 422 may be contained on input drive shaft 106, or output cycloidal disc 120 via friction fit, a set screw, an adhesive, and the like.

[0086] FIGS. 5A and 5B illustrate one example embodiment of an input cycloidal disc 518. Input cycloidal disc 518 may be substantially similar to input cycloidal disc 118 illustrated in FIG. IE. [0087] Input cycloidal disc 518 may include external input cycloidal disc gear teeth 534. Input cycloidal disc gear teeth 534 may have a sinusoidal tooth profile. Input cycloidal disc gear teeth 534 may have any of a variety of gear tooth profiles.

[0088] Input cycloidal disc 518 may include at least one output cycloidal disc mounting element 558. At least one output cycloidal disc mounting element 558 may permit input cycloidal disc 518 to be coupled to, so as to move with, output cycloidal disc 120. Output cycloidal disc mounting element 558 may include an aperture, perforation, boss, threaded blind hole, non-threaded blind hole, tab, and the like. Output cycloidal disc mounting element 558 may include any of a variety of elements permitting the mounting or otherwise arresting of input cycloidal disc 518 relative to output cycloidal disc 120.

[0089] Input cycloidal disc 518 may include an input drive shaft aperture 559. Input drive shaft aperture 559 may permit passage of input drive shaft 106 through input cycloidal disc 518. Eccentric portion 347 (see FIGS. 3A and 3C) of input drive shaft 106 may be oriented within input drive shaft aperture 559, such that rotation of input drive shaft 106 causes input cycloidal disc 518 to rotate in an eccentric pattern.

[0090] Input cycloidal disc 518 may include an input drive shaft/input cycloidal disc bearing engagement surface 560. Input drive shaft/input cycloidal disc bearing 126 may be contained within input drive shaft/input cycloidal disc bearing engagement surface 560 via friction fit, a set screw, an adhesive, and the like.

[0091] FIGS. 6 A and 6B illustrate one example embodiment of an output cycloidal disc 620. Output cycloidal disc 620 may be substantially similar to output cycloidal disc 120 illustrated in FIG. IE.

[0092] Output cycloidal disc 620 may include external output cycloidal disc gear teeth

636. Output cycloidal disc gear teeth 636 may have a sinusoidal tooth profile. Output cycloidal disc gear teeth 636 may have any of a variety of gear tooth profiles. [0093] Output cycloidal disc 620 may include at least one input cycloidal disc mounting element 662. At least one input cycloidal disc mounting element 662 may permit output cycloidal disc 620 to be coupled to, so as to move with, input cycloidal disc 518. Input cycloidal disc mounting element 662 may include an aperture, perforation, boss, threaded blind hole, non-threaded blind hole, tab, and the like. Input cycloidal disc mounting element 662 may include any of a variety of elements permitting the mounting or otherwise arresting of output cycloidal disc 620 relative to input cycloidal disc 518. In one embodiment, output cycloidal disc 620 may be bolted (via input cycloidal disc mounting elements 662) to input cycloidal disc 518 (via output cycloidal disc mounting elements 558). In one embodiment, output cycloidal disc 620 and input cycloidal disc 518 are integrally connected, or integrally formed from a single element, and the combination is devoid of input cycloidal disc mounting elements 662 and output cycloidal disc mounting elements 558.

[0094] Output cycloidal disc 620 may include a bushing engagement surface 664, to which bushing 422 may be contacted.

[0095] Output cycloidal disc 518 may include an input drive shaft aperture 665. Input drive shaft aperture 665 may permit passage of input drive shaft 106 through output cycloidal disc 620. Eccentric portion 347 (see FIGS. 3A and 3C) of input drive shaft 106 may be oriented within input drive shaft aperture 665, such that rotation of input drive shaft 106 causes output cycloidal disc 620 to rotate in an eccentric pattern.

[0096] FIGS. 7A and 7B illustrates one example embodiment of a primary drive gear 724. Primary drive gear 724 may be substantially similar to primary drive gear 124 illustrated in FIG. IE.

[0097] Primary drive gear 724 may include internal primary drive gear teeth 738.

Primary drive gear teeth 738 may have a sinusoidal tooth profile. Primary drive gear teeth

738 may have any of a variety of gear tooth profiles. [0098] Primary drive gear 724 may include at least one output drive mounting element 766. At least one output drive mounting element 766 may permit primary drive gear 724 to be coupled to, so as to move with, output drive element 104. Output drive mounting element 766 may include an aperture, perforation, boss, threaded blind hole, non-threaded blind hole, tab, and the like. Output drive mounting element 766 may include any of a variety of elements permitting the mounting or otherwise arresting of primary drive gear 724 relative to output drive element 104. In one embodiment, primary drive gear 724 may be bolted (via output drive mounting element 766) to output drive element 104. In one embodiment, primary drive gear 724 and output drive element 104 are integrally connected, or integrally formed from a single element, and the combination is devoid of output drive mounting element 766.

[0099] Primary drive gear 724 may include an output cycloidal disc aperture 767, within which output cycloidal disc 620 may be oriented. Output cycloidal disc gear teeth 636 may engage, and at least partially mesh with, primary drive gear teeth 738.

[00100] FIGS. 8A-8C illustrate one example embodiment of an output drive element 804. Output drive element 804 may be substantially similar to output drive element 104 illustrated in FIGS. 1A, IB, ID, and IE.

[00101] Output drive element 804 may include at least one output drive mounting element

812. Output drive element mounting element 812 may include an aperture, perforation, boss, threaded blind hole, non-threaded blind hole, tab, and the like. Output drive element mounting element 812 may include any of a variety of elements permitting the mounting or otherwise arresting of output drive element 804 relative to another object, such as a structural element of a mechanical component, the ground, a machine, and the like.

[00102] Output drive element 804 may include at least one primary drive gear mounting element 870. At least one primary drive gear mounting element 870 may permit output drive element 804 to be coupled to, so as to move with, primary drive gear 724. Primary drive gear mounting element 870 may include an aperture, perforation, boss, threaded blind hole, non- threaded blind hole, tab, and the like. Primary drive gear mounting element 870 may include any of a variety of elements permitting the mounting or otherwise arresting of output drive element 804 relative to primary drive gear 724. In one embodiment, primary drive gear 724 may be bolted (via output drive mounting element 766) to output drive element 804 (via primary drive gear mounting element 870). In one embodiment, primary drive gear 724 and output drive element 804 are integrally connected, or integrally formed from a single element, and the combination is devoid of output drive mounting element 766 and primary drive gear mounting element 870.

[00103] Output drive element 804 may include an input ring gear/output drive bearing engagement surface 872. Input ring gear/output drive bearing 128 may be contained upon input ring gear/output drive bearing engagement surface 872 via friction fit, a set screw, an adhesive, and the like.

[00104] Output drive element 804 may include an input drive shaft aperture 873. Input drive shaft aperture 873 may permit passage of input drive shaft 106 through at least a portion of output drive element 804.

[00105] Output drive element 804 may include an input drive shaft/output drive bearing engagement surface 874. Input drive shaft/output drive bearing 130 may be contained within input draft shaft/output drive bearing engagement surface 874 via a friction fit, a set screw, an adhesive, and the like.

[00106] FIGS. 9 A and 9B illustrate one example embodiment of a circular wave drive

900. Circular wave drive 900, as shown, illustrates the various gears and the interaction thereof within circular wave drive 900. Circular wave drive 900 is shown for illustrative purposes only and does not contain various additional elements illustrated in circular wave drive 100. Circular wave drive may operate substantially similarly to circular wave drive 100.

[00107] Circular wave drive 900 may include an input ring gear 902, having internal gear teeth. Circular wave drive 900 may include an input drive shaft 906 having an eccentric section (as can be seen in FIG. 9B). Circular wave drive 900 may include an input cycloidal disc 918 having external gear teeth, which at least partially engage, and at least partially mesh with, the internal gear teeth of input ring gear 902. Circular wave drive 900 may include an output cycloidal disc 920 having external gear teeth, and which is fixed to input cycloidal disc 918. Circular wave drive 900 may include a primary drive gear 924 having internal gear teeth, which at least partially engage, and at least partially mesh with, the external gear teeth of output cycloidal disc 920. Primary drive gear 924 may be connected to an output drive element (not shown).

[00108] FIG. 10 is a flowchart illustrating an example method 1000 for determining a reduction radio of a circular wave drive. Method 1000 includes selecting a desired reduction ratio for the circular wave drive (step 1010). Method 1000 further includes providing a circular wave drive including: an input ring gear having internal gear teeth (a); an input cycloidal disc having external gear teeth (b), the input cycloidal disc gear teeth at least partially engaging the input ring gear teeth; an output cycloidal disc having external gear teeth (d), the output cycloidal disc fixed to the input cycloidal disc; a primary drive gear having internal gear teeth (c), and the primary drive gear teeth at least partially engaging the output cycloidal disc gear teeth (step 1020). Method 1000 further includes calculating a reduction ratio using the equation: Reduction Ratio = -1

where a = the number of gear teeth of input ring gear 102; 202;

where b = the number of gear teeth of input cycloidal disc 118; 518;

where c = the number of gear teeth of primary drive gear 124; 724; and

where d = the number of gear teeth of output cycloidal disc 120; 620 (step 1030).

[00109] To the extent that the term "includes" or "including" is used in the specification or the claims, it is intended to be inclusive in a manner similar to the term "comprising" as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term "or" is employed (e.g., A or B) it is intended to mean "A or B or both." When the applicants intend to indicate "only A or B but not both" then the term "only A or B but not both" will be employed. Thus, use of the term "or" herein is the inclusive, and not the exclusive use. See Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995). Also, to the extent that the terms "in" or "into" are used in the specification or the claims, it is intended to additionally mean "on" or "onto." To the extent that the term "substantially" is used in the specification or the claims, it is intended to take into consideration the degree of precision available or prudent in manufacturing. To the extent that the term "selectively" is used in the specification or the claims, it is intended to refer to a condition of a component wherein a user of the apparatus may activate or deactivate the feature or function of the component as is necessary or desired in use of the apparatus. To the extent that the term "operatively connected" is used in the specification or the claims, it is intended to mean that the identified components are connected in a way to perform a designated function. As used in the specification and the claims, the singular forms "a," "an," and "the" include the plural. Finally, where the term "about" is used in conjunction with a number, it is intended to include ± 10% of the number. In other words, "about 10" may mean from 9 to 11.

[00110] As stated above, while the present application has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art, having the benefit of the present application. Therefore, the application, in its broader aspects, is not limited to the specific details, illustrative examples shown, or any apparatus referred to. Departures may be made from such details, examples, and apparatuses without departing from the spirit or scope of the general inventive concept.

Claims

1. A circular wave drive, comprising:

an input ring gear having an inner surface and an input ring gear input drive shaft aperture,

wherein the input ring gear includes internal input ring gear teeth oriented on the inner surface;

an input cycloidal disc having an outer surface and an input cycloidal disc input drive shaft aperture,

wherein the input cycloidal disc includes external input cycloidal disc gear teeth oriented on the outer surface, and

wherein the external input cycloidal disc gear teeth at least partially engage the internal input ring gear teeth;

an output cycloidal disc having an outer surface and an output cycloidal disc input drive shaft aperture,

wherein the output cycloidal disc includes external output cycloidal disc gear teeth oriented on the outer surface;

an input drive shaft having a longitudinal length,

wherein the input drive shaft includes an eccentric portion and a non- eccentric portion and wherein the eccentric portion and the non-eccentric portion are axially offset from one another along the longitudinal length of the input drive shaft, and

wherein the non-eccentric portion is oriented in the input ring gear input drive shaft aperture,

wherein the eccentric portion is oriented in the input cycloidal disc input drive shaft aperture, and wherein the eccentric portion is oriented in the output cycloidal disc input drive shaft aperture; and

a primary drive gear having an inner surface,

wherein the primary drive gear includes internal primary drive gear teeth oriented on the inner surface, and

wherein the internal primary drive gear teeth at least partially engage the external output cycloidal disc gear teeth.

2. The circular wave drive of claim 1, further comprising an output drive element coupled to the primary drive gear.

3. The circular wave drive of claim 1, wherein the input cycloidal disc is couple to the output cycloidal disc.

4. The circular wave drive of claim 1, wherein the input drive shaft includes an input drive shaft bearing engagement surface in the non-eccentric portion of the input drive shaft, wherein the input ring gear includes an input drive shaft bearing engagement surface, wherein an input drive shaft bearing is oriented about the input drive shaft bearing engagement surface of the input drive shaft, and within the input drive shaft bearing engagement surface of the input ring gear.

5. The circular wave drive of claim 1, wherein the internal input ring gear teeth and the external input cycloidal disc gear teeth each have a sinusoidal tooth profile.

6. The circular wave drive of claim 1, wherein the external output cycloidal disc gear teeth and the internal primary drive gear teeth each have a sinusoidal tooth profile.

7. The circular wave drive of claim 1, wherein:

the internal input ring gear teeth, the external input cycloidal disc gear teeth, the external output cycloidal disc gear teeth, and the internal primary drive gear teeth have an amplitude, the input drive shaft non-eccentric portion has a centerline,

the input drive shaft eccentric portion has a centerline, and

the non-eccentric portion centerline and the eccentric portion centerline are offset from one another by a distance of about half the amplitude.

8. The circular wave drive of claim 1, further comprising an output drive element coupled to the primary drive gear, wherein the output drive element is rotatably connected to the input ring gear via an input ring gear/output drive element bearing.

9. The circular wave drive of claim 1, wherein the input drive shaft is rotatably connected to the input cycloidal disc via an input drive shaft/input cycloidal disc bearing.

10. The circular wave drive of claim 1, further comprising a bushing oriented between the eccentric portion of the input drive shaft and the output cycloidal disc.

11. A circular wave drive, comprising:

an output cycloidal disc having an outer surface and an output cycloidal disc input drive shaft aperture, wherein the output cycloidal disc includes external output cycloidal disc gear teeth oriented on the outer surface;

an input drive shaft having a longitudinal length,

wherein the eccentric portion is oriented in the input cycloidal disc input drive shaft aperture, and

wherein the eccentric portion is oriented in the output cycloidal disc input drive shaft aperture;

a primary drive gear having an inner surface,

wherein the internal primary drive gear teeth at least partially engage the external output cycloidal disc gear teeth;

an output drive element coupled to the primary drive gear.

12. The circular wave drive of claim 11, wherein the input cycloidal disc is couple to the output cycloidal disc.

13. The circular wave drive of claim 11, wherein the input drive shaft includes an input drive shaft bearing engagement surface in the non-eccentric portion of the input drive shaft, wherein the input ring gear includes an input drive shaft bearing engagement surface, wherein an input drive shaft bearing is oriented about the input drive shaft bearing engagement surface of the input drive shaft, and within the input drive shaft bearing engagement surface of the input ring gear.

14. The circular wave drive of claim 11 , wherein the internal input ring gear teeth and the external input cycloidal disc gear teeth each have a sinusoidal tooth profile.

15. The circular wave drive of claim 11, wherein the external output cycloidal disc gear teeth and the internal primary drive gear teeth each have a sinusoidal tooth profile.

16. The circular wave drive of claim 1 1, wherein:

the internal input ring gear teeth, the external input cycloidal disc gear teeth, the external output cycloidal disc gear teeth, and the internal primary drive gear teeth have an amplitude,

the input drive shaft non-eccentric portion has a centerline,

the input drive shaft eccentric portion has a centerline, and

17. The circular wave drive of claim 11, wherein the output drive element is rotatably connected to the input ring gear via an input ring gear/output drive element bearing.

18. The circular wave drive of claim 11 , wherein the input drive shaft is rotatably connected to the input cycloidal disc via an input drive shaft/input cycloidal disc bearing.

19. The circular wave drive of claim 11, further comprising a bushing oriented between the eccentric portion of the input drive shaft and the output cycloidal disc.

20. The circular wave drive of claim 11, wherein the input ring gear includes at least one input ring gear mounting element.