Compound offset epicyclic drive (COED)

Abstract

A compound offset epicyclic drive (COED) (100) is disclosed. The COED comprises an input shaft (5). A carrier (3) is coupled to one end of the input shaft. The carrier (3) has a first end and a second end. At least one planetary gear (4) is attached at each of the first end and the second end of the carrier (3). A stator (1) comprising a plurality of stator teeth is configured to engage with the planetary gears. A rotor (2) comprising a plurality of rotor teeth is configured to engage with the planetary gears (4). A number the stator teeth is less than a number of the rotor teeth. A rotation of the carrier rotates the rotor with reduced speed.

Description

COMPOUND OFFSET EPICYCLIC DRIVE (COED)FIELD OF THE INVENTION

[0001] The invention relates to an epicyclic drive system.BACKGROUND

[0002] Advanced Robotic, automation and manufacturing applications require advanced actuation systems with large gear reduction. The cheapest way to achieve this is by using multi-stage gear trains. This results in heavy gear boxes, with large mechanical loss as well as inertia, making the actuator unit sluggish. In addition, having multistage gear reduction could cause significant cumulative backlash, even if backlash at individual stages can be negligible.

[0003] Harmonic (strain wave) gear boxes were introduced to address applications where mechanical inertia as well as backlash is to be minimized such as in the case of robotic manipulators. These systems use a flexible spline with external teeth, which is deformed by a rotating elliptical plug to engage with the internal gear teeth of an outer spline. The design and manufacturing of these systems is complicated primarily due to the design constraints for the flex spline.OBJECTS OF THE INVENTION:

[0001] An object of the present invention is to provide a Compound Offset Epicyclic Drive (COED) that is specifically designed to cater to applications requiring significant gear reduction while occupying minimal space and being lightweight.

[0002] Another object of the present invention is to develop a COED that offers the distinct advantage of minimal backlash and non-back drivability, surpassing the limitations of conventional gear reduction or drive systems.

[0003] Another object of the present invention is to develop a COED that eliminates the need for a flex spline, simplifying the overall design and manufacturing process, while still achieving the above-mentioned requirements of high gear reduction, minimal backlash and non-back drivability.

[0004] Yet another object of the present invention is to design a COED with a reduced number of components, ensuring ease of assembly, maintenance, and costeffectiveness.

[0005] Another object of the COED is to provide large variability in reduction from a small to large by changing the number of aligning contact points between the stator and the rotor.SUMMARY OF THE INVENTION:

[0006] A compound offset epicyclic drive (COED) is disclosed. The COED comprises: a) an input shaft, b) a carrier coupled to one end of the input shaft, the carrier having a first end and a second end, c) at least one planetary gear attached at each of the first end and the second end of the carrier , d) a stator comprising a plurality of stator teeth engageable with the at least two planetary gears; ande) a rotor comprising a plurality of rotor teeth engageable with the at least two planetary gears, wherein a number the stator teeth is less than a number of the rotor teeth.

[0007] The stator is a stationary component, connected to an actuator's body, such as a DC motor. The rotor serves as the output of the COED, receiving motion after gear reduction. In an example, the COED may have multiple configurations. In one example, the COED may have the stator and rotor as internal ring gears and in another example, the stator and rotor may be external gears. In an example, it is also possible to have configuration where one of them, stator, or rotor, is internal while the other is external.

[0008] The rotor and the stator are placed in a compound arrangement that allows relative motion between the two. The carrier serves as the input motion to the COED and can be attached to a drive shaft of an actuator like a DC motor. The carrier connects the centres of the compound planetary gears, which mesh with both the stator and the rotor simultaneously. The stator and the planetary gears have the same module to ensure proper gear tooth meshing.

[0009] According to an example implementation of the present subject matter, the rotor has at least one less gear tooth than the stator. This arrangement results in the stator and rotor gear teeth aligning only at one or more over the entire circumference, depending on the difference in number of teeth. One or more compound planetary gears can be attached to the carrier in a manner that meshes with both the stator and rotor at these alignment points.

[0010] According to an example implementation of the present subject matter, when input motion is applied to the carrier, the planetary gears are rotated, causing the meshing points between the rotor and stator to move along the pitch circle of thegears. Since the stator is fixed, the rotor is forced to rotate relative to the motion of the carrier. A complete rotation of the input shaft (attached to the carrier) results in the output shaft (attached to the rotor) moving by an arc equivalent to the difference in the number of teeth between the rotor and stator. This behaviour remains consistent for both clockwise and counterclockwise rotations of the input shaft.[Oil] In an example, the carrier m may be rigid or complainant. Making the carrier compliant, either through the use of flexure mechanism or by including compliant elements such as springs in the carrier design, prevent backlash in the COED.BRIEF DESCRIPTION OF FIGURES:

[0012] Figure 1 shows an exploded view of the components of the compound offset epicyclic device (COED) for an internal gear configuration in an example embodiment of the present subject matter.

[0013] Figure 2 shows a top view of the COED in an example embodiment of the present subject matter.

[0014] Figure 3 shows an exploded view of the components of the compound offset epicyclic device (COED) in an example embodiment of the present subject matter.

[0015] Figure 4 shows a top view of the components of the COED in an example embodiment of the present subject matter.

[0016] Figure 5 shows a carrier another example embodiment of the present subject matter.

[0017] Figure 6 shows a carrier in another example embodiment of the present subject matter.DETAILED DESCRIPTION:

[0018] The embodiments of the present subject matter are described in detail with reference to the accompanying drawings. However, the present subject matter is not limited to these embodiments which are only provided to explain more clearly the present subject matter to the ordinarily skilled in the art of the present disclosure. In the accompanying drawings, like reference numerals are used to indicate like components.

[0019] This invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

[0020] Various aspects of the proposed drive are described fully hereinafter with reference to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. The teachings disclosed may, however, be embodied in many different models with variations and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. It should be understood that any aspect disclosed herein may be embodied by one or more elements of a claim, and also that the following detailed description does not limit the claims.

[0021] Figure 1 shown an exploded view of a compound offset epicyclic drive (COED) 100 in an example implementation of the present subject matter. The COED 100 comprises an input shaft 5. A carrier 3 is coupled to the input shaft 5. The carrier comprises a first end 3-1 and a second end 3-2. At least one planetary gear 4 is coupled to each of the first end 3-1 and the second end 3-2. In an example, a single planetary gear 4 is shown to be coupled to each of the first end 3-1 and the second end 3-2 of the carrier 3, however, it should be understood that any number of planetary gears may be used in an example implementation. The planetary gear 4 may comprises protrusions or teeth that may be couplable to a recession of teeth of another component.

[0022] The COED 100 comprises a stator 1 and a rotor 2. The stator 1 and the rotor 2 are couplable to the planetary gear 3. According to the present subject matter, the stator 1 and the rotor 2 comprises plurality of teeth that are engageable or couplable to the teeth of the planetary gear 4. According to the present subject matter, the number of teeth of the stator is less that the number of teeth of the rotor.

[0023] While the design presented in this application uses spur tooth design for the stator, rotor and planetary gears, the proposed functionality could be achieved using other types of gears or gear tooth profiles, including but not limited to bevel, helical, and herringbone gears.

[0024] In operation, when input shaft 5 is rotated, the carrier 3 coupled to the input shaft 5 is also rotated. The rotation of the carrier 3 rotates the planetary gear 4. As the planetary gear 4 is engaged with the stator 1 and the rotor 2, the rotation of the planetary gear 4 causes meshing points (teeth) of the rotor and stator to move along the pitch circle of the stator 1. According to the present subject matter the stator 1 is fixed and is not allowed to rotate. Thus, the rotor 2 is forced to rotate relative to themotion of the carrier 3. As the planetary gears 4 rotate due to the rotation of the shaft 5, meshing points between the stator 1 and rotor 2 moves along the gear profile, resulting in the rotation of the rotor at a reduced speed. A complete rotation of the input shaft (attached to the carrier) results in the output shaft (attached to the rotor) moving by an arc equivalent to the difference in the number of teeth between the rotor 2 and stator 1. This behaviour remains consistent for both clockwise and counterclockwise rotations of the input shaft 5.

[0025] The COED 100 as disclosed in the present subject matter can be used in applications including but not limited to robot actuators, drive / actuators in industries including pharma, textile, and automotive, drive / actuator in machines such as CNC, lathe.

[0026] Figure 2a-2b illustrates a top view of the compound offset epicyclic drive (COED) 100 in an example implementation of the present subject matter. As discussed, the COED 100 comprises the carrier 3. In figure 2, the planetary gear 4 is shown to be engaged with the rotor 2 and the stator 1. According to the present subject matter, a module of the planetary gears 4 is same as of the module of the module of the stator 1 which ensures that the planetary gears 4 has perfect alignment with the stator 1 when meshed.

[0027] As shown in an example embodiment shown in figure 1, the rotor 2 and the stator 1 are shown to be encompassing the planetary gears 4 such that the planetary gears 4 lie inside of the rotor 2 and the stator 1. In such configuration, the rotor 2 and the stator 1 may have an annular shape. Also, in such configuration when the planetary gears 4 lie inside the rotor 2 and the stator 1, a first side 4-1 of the planetary gear 4 is contact with the rotor 2 and the stator 1. The rotor 2 and the stator 1 has teeth arrange on an inner periphery as to couple with the planetary gears 4. Thus, as the planetary gears 4 lie inside the rotor 2 and the stator 1, the configuration of the COED 100 as shown in figure 1 is referred to as internal configuration.

[0028] In an example, the rotor 2 and the stator 1 are shown to be coupled to the first side 4-1 of the planetary gears 4, however, in an example, the rotor 2 may be couplable to a second side 4-2 of the planetary gear 4 and the stator 1 may be couplable to the first side 4- 1 of the planetary gear 4. In another example, the stator 1 may be couplable to the second side 4-2 of the planetary gear 4 and the rotor 2 may be couplable to the first side 4- 1 of the planetary gear 4.

[0029] Figure 2b illustrates meshing points 202 and 204 where the planetary gears 4 are completely aligned and engaged with the rotor 2 and the stator 1. As the planetary gears 4 rotate due to the rotation of the shaft 5, the meshing points 202 and 204 between the stator 1 and rotor 2 moves along the gear profile, resulting in the rotation of the rotor 2 at a reduced speed. A complete rotation of the input shaft (attached to the carrier) results in the output shaft (attached to the rotor) moving by an arc equivalent to the difference in the total number of teeth between the rotor 2 and stator 1. This behaviour remains consistent for both clockwise and counterclockwise rotations of the input shaft 5. In an example, the difference between the total number of teeth between the rotor 2 and stator 1 may be any integer, such as one, two, three etc. as required in use case scenarios.

[0030] Considering an example, the reduction offered by the COED 100 of present subject mater, can be calculated as follows:In an example, consider a pitch circle diameter of the stator 1 is D,A module of the planetary gears 4 and the stator 1 is Z,A number of teeth on the stator Ts = D / Z,The number of teeth on the rotor, denoted as Tr, can be calculated as Tr = Ts -R, where R is the factor that determines the gear reduction N,The Gear Reduction is given by N = ( Ts - R ) / R.

[0031] In an example embodiment, instead of applying the input motion directly to the input shaft 5, it is possible to have a configuration of COED 100 where the input motion is applied to a planetary gears 4, resulting in motion of the carrier 3. In this configuration, the carrier remains common between the planetary gears 4 and the COED 100. This configuration will allow for improved gear reduction, consisting of both gear reduction offered by the planetary gear set along with the gear reduction offered by the COED 100.

[0032] In another example, the number of planetary gears 4 can vary from one to a maximum number limited by the number of alignment points between the stator and the rotor. Varying the number of alignment points by varying the difference in number of teeth between rotor 2 and stator 1 allows for varying the gear reduction offered by the COED 100.

[0033] According to the present subject matter, a number of locations at which the planetary gears 4 fully aligned depends on the difference between the number of teeth of the rotor 2 and the stator 1. According to an example implementation, when the number of teeth on the rotor 2 are two less than the stator 1 , two meshing points 202 and 204 are created where the teeth of the planetary gears 4 is fully aligned with the rotor 2 and the stator 1.

[0034] Figure 3 shows a compound offset epicyclic drive (COED) 300 in another example embodiment of the present subject matter. The COED 300 comprises an input shaft 5. A carrier 3 is coupled to the input shaft 5. The carrier comprises a first end 3-1 and a second end 3-2. At least one planetary gear 4 is coupled to each of the first end 3-1 and the second end 3-2. In an example, a single planetary gear 4 is shown to be coupled to each of the first end 3-1 and the second end 3-2 of the carrier3, however, it should be understood that any number of planetary gears may be used in an example implementation. The planetary gear 4 may comprises protrusions or teeth that may be couplable to a recession of teeth of another component.

[0035] The COED 300 comprises a stator 1 and a rotor 2. The stator 1 and the rotor 2 are couplable to the planetary gears 4. According to the present subject matter, the stator 1 and the rotor 2 comprises plurality of teeth that are engageable or couplable to the teeth of the planetary gear 4. According to the present subject matter, the number of teeth of the stator is less that the number of teeth of the rotor.

[0036] In external configuration, the rotor 2 and the stator 1 are held between the planetary gears 4 such that planetary gears 4 lie outside the rotor 2 and the stator 1.

[0037] In operation, when input shaft 5 is rotated, the carrier 3 coupled to the input shaft 5 is also rotated. The rotation of the carrier 3 rotates the planetary gear 4. As the planetary gear 4 is engaged with the stator 1 and the rotor 2, the rotation of the planetary gear 4 causes meshing points (teeth) of the rotor and stator to move along the pitch circle of the stator 1. According to the present subject matter the stator 1 is fixed and is not allowed to rotate. Thus, the rotor 2 is forced to rotate relative to the motion of the carrier 3. As the planetary gears 4 rotate due to the rotation of the shaft 5, a meshing point between the stator 1 and rotor 2 moves along the gear profile, resulting in the rotation of the rotor at a reduced speed. A complete rotation of the input shaft (attached to the carrier) results in the output shaft (attached to the rotor) moving by an arc equivalent to the difference in the number of teeth between the rotor 2 and stator 1. This behaviour remains consistent for both clockwise and counter clockwise rotations of the input shaft 5.

[0038] Figure 4a-4b illustrates a top view of compound offset epicyclic drive (COED) 300 in an example implementation of the present subject matter. The figure4a-4b shows the external configuration when the rotor 2 and the stator 1 is held between the planetary gears 4 as shown in figure 4a. As discussed, according to the present subject matter, a number of locations at which the planetary gears 4 fully aligned depends on the difference between the number of teeth of the rotor 2 and the stator 1. According to an example implementation, when the number of teeth on the rotor 2 are two less than the stator 1, two meshing points 404 and 404 are created where the teeth of the planetary gears 4 is fully aligned with the rotor 2 and the stator 1.

[0039] Figure 5 illustrates a carrier 500 in an example embodiment of the present subject matter.

[0040] The carrier 500 comprises a first portion 504 and a second portion 506. The first portion 504 and the second portion 506 comprise planetary gears 508. The first portion 504 and the second portion 506 are held by at least one flexure mechanism 510. The flexure mechanism 510 provides pressure on the planetary gears 508 and keeps the planetary gears 508 forced outwards. This ensures that the planetary gears 508 are tightly engaged with the teeth of the rotor and the stator and backlash is prevented during rotation of the planetary gears 508.

[0041] In an example, the flexure mechanism 510 is shown as V shaped, however, it should be understood that that the flexure mechanism 510 may have any shape based on the requirement. In an example, the flexure mechanism 510 may be made up of steel, carbon fiber, composite materials, or any alloy. In an example, more than one flexure mechanism may be used to hold the first portion 504 and the second portion 506 of the carrier 500.

[0042] Figure 6 illustrates a carrier 600 in another example implementation of the present subject matter.

[0043] The carrier 600 comprises a first portion 604 and a second portion 606. The first portion 604 and the second portion 606 comprise planetary gears 608. The first portion 604 and the second portion 606 are held by plurality compliant springs 610. The plurality of compliant springs 610 provides pressure on the planetary gears 608 and keeps the planetary gears 608 are forced outwards. This ensures that the planetary gears 608 are tightly engaged with the teeth of the rotor and the stator and backlash is prevented during rotation of the planetary gears 608. In an example, the plurality of compliant spring 610 may be made up of steel, carbon fiber, composite materials, or any alloy.

[0044] Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the invention as herein described.

[0045] In the several embodiments provided in this application, the disclosed drive may be implemented in another manner.

[0046] The term based on is not exclusive and allows for being based on additional factors not described unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of “a”, “an” and “the” include plural references. The meaning of “in” includes “in” and “on”

[0047] As used herein the terms “and” and “or” may be used interchangeably to refer to a set of items in both the conjunctive and disjunctive in order to encompass the full description of combinations and alternatives of the items. In either case, the set is to be interpreted as meaning each of the items singularly as alternatives, as well as any combination of the listed items.

[0048] The description above is merely illustrating the technical scope of the present disclosure, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present disclosure. Therefore, the embodiments of the present disclosure described above may be implemented separately or in combination with each other.

[0049] The embodiments disclosed in the present disclosure are intended to illustrate rather than limit the scope of the present disclosure, and the scope of the technical spirit of the present disclosure is not limited by these embodiments. The scope of the present disclosure should be construed by claims below, and all technical spirits within a range equivalent to claims should be construed as being included in the right scope of the present disclosure.

[0050] While only certain features have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the disclosure.

Claims

I / We claim:

1. A compound offset epicyclic drive (COED) (100) comprising: an input shaft (5); a carrier (3) coupled to one end of the input shaft, the carrier having a first end and a second end; at least one planetary gear (4) attached at each of the first end and the second end of the carrier; a stator (1) comprising a plurality of stator teeth configured to engage with the planetary gears; a rotor (2) comprising a plurality of rotor teeth engageable with the planetary gears (4), wherein a number the stator (1) teeth is less than a number of the rotor (2) teeth.

2. The COED (100) as claimed in claim 1, when stator remains stationary when input shaft is rotated.

3. The COED (100) as claimed in claim 1, wherein the carrier comprises: a first portion having the first end; a second portion having the second end; the first portion and the second portion being held by at least one flexure mechanisms.

4. The COED (100) as claimed in claim 1, wherein the first portion and the second portion are held by a plurality of compliant springs.

5. The COED (100) as claimed in claim 1, wherein each of the at least two planetary gears comprise a first side and a second side.

6. The COED (100) as claimed in claim 5, wherein the rotor and the stator are engageable to the first side of the at least two planetary gears.

7. The COED (100) as claimed in claim 5, wherein the rotor is engageable to the first side of the planetary gear and the stator is engageable to the second side of the planetary gear.

8. The COED (100) as claimed in claim 5, wherein the rotor is an annular shaped rotor, and the plurality of rotor teeth is provided at an inner periphery of the annular shaped rotor and the rotor teeth is engageable by the first side of the planetary gears.

9. The COED (100) as claimed in claim 5, wherein the rotor and the stator are placed between the at least two planetary gears and the rotor and the stator are engaged by the second side of the at least two planetary gears.

10. The COED (100) as claimed in claim 1, wherein the stator teeth and the planetary gears have same module.

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