WO2011061759A1 - High reduction ratio and easily adaptable planetary gear train with orbiting gears - Google Patents

Abstract

A planetary gear train (10) comprises a stationary member (40), a moveable member (44), and planet gears (18,19), wherein additional orbiting gears (118,119) are added along with the planet gears (18,19). The additional orbiting gears are connected to the moveable member(44) as well as the stationary member (40) of the planetary gear train (10). The stationary member (40) and the movable member (44) have unequal number of teeth. By choosing the minimum difference between the numbers of teeth of the stationary member (40) and the moveable member (44), maximum gear reduction ratio is achievable. Also the number of planetary gears (18,19) can be chosen irrespective of any choice of the difference between the numbers of teeth of the stationary member (40) and the moveable member (44). Additionally the planet gears (18,19) can be interlinked for higher torque carrying capacity. This leads to a high reduction ratio with higher efficiency, higher torsional rigidity and standard teeth profile parameters for the gears.

Description

High Reduction Ratio and Easily adaptable Planetar Gear Train with orbiting gears Field and Background of the Invention:

The present invention relates generally to an improved gear reducer and more particularly to a high ratio, high torsional rigidity and high efficiency planetary gear reducer.

Conventional gear reducers include an input, a stationary ring gear, a moveable ring gear, and at least one planetary gear, wherein the planetary gear teeth mesh with stationary and moveable ring gear teeth. Since the stationary ring gear and the moveable ring gear have different numbers of teeth to allow for relative movement between the two gears, typically two sets of planetary gear teeth are required, one set of planetary gear teeth to mesh with each of, the stationary ring gear and the moveable ring gear. The speed of rotation of ring gear is substantially less than the speed of rotation of planet carrier. This reduced output, in turn, may be used as input to a second stage for further gear reduction. A higher gear reduction requires several stages increasing the cost, weight and complexity; and resulting in reducing mechanical efficiency of the overall system.

Also, devices have been developed whereby a single set of planetary gear mesh with both the stationary ring gear and the moveable ring gear. In one such arrangement, in which the stationary ring gear and the moveable ring gear have different number of teeth; the standard gear teeth parameters of one of the ring gears are modified in order to mesh with single set of planet gear teeth. Generally the above gear reducers have limited number of planets due to assembly constraints, so they lack on torsional rigidity and power transmission characteristics; and this type of designs have limits on the difference in number of teeth between stationary and movable ring gear. The present invention relates to a Planetary Gear speed reduction arrangement wherein the ring gears having different number of teeth are meshed to planet gears through additional orbiting gears in each stage of planetary gear. The additional orbiting gears are arranged such that high torque carrying capacity is achieved along with high gear train reduction ratio; without need of any teeth profile modification.

Uses of Invention:

The invention is usable widely in all reduction gear boxes; the main application areas are Wind turbines, Power industry, Sugar industry, Automotive industry, Material handling equipment, Medical equipment, Robotics machinery, Aviation equipment, Packaging equipment etc.

Also, the new invention is usable as an alternative to worm gear box, based on comparable or more speed ratio achievable and equivalent or better torque carrying capacity and higher efficiency.

Also, the new invention can be used for gearing down or gearing up the speed.

Prior art in the said field of invention and its drawbacks:

Following prior patents/ patent publications can be taken as reference:

Design as per US patent publication number: US 2009/0221396A1 dated Sep 3, 2009

US Patent number 6123640 dated Sep26, 2000

US Patent number 4237750 dated Dec 9, 1980

US Patent number 4194414 dated Mar 25,1980

US Patent number 4864893 dated Sep 12, 1989. Planetary gear boxes of this type are generally known. The planet wheels each have two sets of teeth for continuous meshing with two ring gears (or two sun gears), having different number of teeth. Out of the two ring gears (or two sun gears), one is rotatable and other one is fixed with respect to the gear box housing.

The speed ratio of the planet carrier to the ring gear (or sun gear) provided for output is designated as the Wolfram Ratio. Wolfram ratio increases with increasing number of teeth of planet gear(s) (means bigger gears). Also the wolfram ratio increases; if the difference in number of teeth between both ring gears (or both sun gears) is reduced. Also in some other art already known, the central sun gear meshes with planet wheels and forms a Preliminary ratio with the planet wheels and the stationary ring gear. For increasing the preliminary ratio, there has to be large difference between the number of teeth of sun gear and stationary ring gear. The Wolfram ratio multiplied by the Preliminary ratio results in the Total Overall Ratio.

However, devices have been developed whereby a single set of planetary gears mesh with both the stationary ring gear and the moveable ring gear; for example, the design as per US patent publication number: US 2009/0221396A1. In this gearing system, the stationary ring gear and the moveable ring gear have different number of teeth, and they mesh simultaneously with single set of planetary gear teeth.

It leads to higher reduction ratio; however engaging the single set planetary gear(s) simultaneously to two different gears (of different number of teeth); imposes a requirement for teeth parameters of at least one ring gear to be deviated from standard (for example modifying addendum diameter or pitch diameter), which leads to loss of efficiency. Also this type of arrangement puts a constraint on number of planet gears in relation to the difference in number of teeth of the two ring gears. For example in the reference design as per US patent publication number: US 2009/ 0221396A1, if the difference in number of teeth of two ring gears is one (which is the case for maximum reduction ratio), then this arrangement will not accommodate more than one planet gear. This puts a constraint on torque carrying capacity of the overall system. So it results in contradictory condition, where reduction ratio is enhanced, but torque carrying capacity is limited.

However, design as per the US Patent number 4864893; provide an alternative; where multiple planets can be employed to enhance the balancing and torsional rigidity. But this design also requires gear teeth profile to be deviated from standard which results in loss of efficiency.

Also, in case of both the above referenced designs, the difference in number of teeth of two ring gears cannot be chosen freely. So designing a gear box with specific reduction ratio is not always feasible.

Comparison between prior art and present invention:

The objective, on which the present invention is based, is to obtain high gear ratios along with high torque carrying capacity. In addition; no deviation from standard gear teeth profile parameters should be required. The main differentiating design feature of the present invention is that the planet gear teeth, are connected to the rotatable and stationary members of the planetary gear train (it may be both ring gears or both sun gears) simultaneously, by using additional orbiting gears. Due to this feature, it is possible to have minimum difference (say 'M') between number of teeth of stationary and movable members of the gear train resulting in high wolfram ratio. Also in the present invention, 'M' can be chosen more freely compared to prior art, so design of particular gear ratio is easier. And, at the same time, multiple interlinked planets can be employed irrespective of value of ' ', which provide enhanced torsional rigidity.

In conventional gear boxes and in prior art, there is limited choice of 'M', resulting in limited choice of overall gear ratio. And number of planets depend on the value of 'M' . In some of the prior art, they require the gear teeth profile parameters of the gears to be deviated from the standard profile resulting in loss of efficiency. Additionally, this type of arrangement has its own inherent drawbacks as explained earlier.

The new invention enables higher reduction ratio, while the drawbacks in the prior art as mentioned above have been eliminated or reduced clearly to a significant extent.

Object (aim) of present invention:

Main objective of the present invention is that it should provide a simple and innovative solution for speed reduction system in which reduction ratio is significantly higher compared to conventional arrangements, while at the same time the torque carrying capacity should be either at par or improved.

Other objectives include that it should be able to be employed to single stage or multi stage planetary gear speed reduction system so that speed reduction advantage can be multiplied, if required. Another objective is that for building multi stage gear box, same gear sets may be utilized multiple times. It may not need all new and different gear sets. In this sense, the solution should be cost effective. Another objective is that the new system should not require deviation from standard gear teeth profile parameters, and should be manufacturable by standard and universally available techniques. Another objective is that it should be as compact as conventional planetary gear arrangements, while providing the higher speed reduction advantage. Another objective is that it should be as efficient as conventional planetary gear arrangements, while providing the higher speed reduction advantage. Another objective of the present invention is that a whole number reduction ratio should be achievable in the new planetary gear arrangement, and a new design arrangement based on the requirement of specific speed ratio can be conceived easily.

Summary of present invention:

In one embodiment, a gear reducer is provided including a rotatable planet carrier supporting at least one planetary gear and at least one orbiting gear for axial rotation thereon. Planetary gear(s) engage with the orbiting gear(s). A stationary ring gear extends around and is engageable with the at least one orbiting gear or one planetary gear, and a moveable ring gear extends around and is also engageable with the at least one orbiting gear or one planetary gear. (In this full text including the 'claims', the terms 'Planetary Gear' and 'Planet Gear' are used interchangeably; both the terms bear the same meaning.)

In another embodiment, a gear reducer is provided including a rotatable planet carrier supporting at least one planetary gear and at least one orbiting gear for axial rotation thereon. Planetary gear(s) engage with the orbiting gear(s). A stationary sun gear is engageable with the at least one orbiting gear or one planetary gear; and a moveable sun gear is also engageable with the at least one orbiting gear or one planetary gear. The gear train sequence, say gear train type '(1)', may start from planet carrier to orbiting gear to planet gear to orbiting gear to moveable ring gear (or sun gear). This type of gear train is shown in FIGS. 3(A) and 7(A). The difference in number of teeth between stationary and movable ring gears (or sun gears), say 'M', can be chosen as low as one, for desired gear reduction. Planetary gear ratio is higher for lower 'M' .

The phase difference between orbiting gears and stationary ring gears (or sun gears); and the phase difference between orbiting gears and movable ring gears (or sun gears), can be minimized to any extent because the radial position of planets can be varied infinitely. The phases of orbiting gears are matched to respective stationary and movable ring gears (or sun gears) at different angular positions, by choosing the appropriate radial position for the planets. So this type of arrangement allows employing multiple planets (and multiple orbiting gears) irrespective of value of ' '. So the overall torsional rigidity of the gear system is enhanced. The figures 15(A) and 15(B) show how the phase difference (between orbiting gear and ring gear) changes with the radial position of planet gear for a specific case. Specific designs involving ring gears and specific designs involving sun gears are also described.

In another type of the gear train sequence, say gear train type '(2)'; may start from planet carrier to orbiting gear to planet gear to moveable ring gear (or movable sun gear). This type of gear train is shown in FIGS. 4(A), 5(A), 8(A) and 9(A).

For minimizing the phase difference, say 'Q', between the orbiting gears/ planet gears and stationary/ movable ring gears (or sun gears); the pairs, of orbiting gear of specific number of teeth and planet gear of specific number of teeth, need to be placed at specific angular positions on planet carrier. Planet and orbiting gears may have different number of teeth. This type of gear train has an advantage of utilizing lesser number of gears. The unique feature of the disclosed design is that, in both types of gear train types '(1)' and '(2)', it is possible to interlink all the orbiting gears and planetary gears in a power train for higher torsional rigidity. For interlinking the power train over full circle, it may be required to employ one or more than one 'Planet Gear type 2' and/or one or more than one idler gears. 'Planet gears type 2' is defined such that the teeth in different sets have specific phase difference with reference to each other; in order to match the phase with other mating gears (mating gears may be orbiting gears or sun gears or ring gears). The relationship between number of teeth of different sets of 'Planet gears type 2', remain same as that for other planetary gears 18/19 as per the enclosed figures. Gears 130 represent 'Planet gears type 2' in the enclosed figures.

Idler gears may also be used to carry power between two orbiting gears or between two planetary gears.

In another embodiment, a gear reducer is provided including a rotatable planet carrier supporting at least one planetary gear and at least one orbiting gear for axial rotation thereon. Planetary gear(s) engage with the orbiting gear(s). A movable sun gear is engageable with the at least one orbiting gear or one planetary gear, and a moveable ring gear as well as a stationary ring gear are also engageable with the at least one orbiting gear or one planetary gear.

Brief description of drawings: FIG. 1 is a partially exploded three dimensional view of an exemplary schematic of a gear reducer of the present invention; FIGS. 2, 6, 6, 10 are the cross-sectional views of exemplary embodiments of the gear reducers located within housings; FIGS. 3(A), 3(B), 4(A), 4(B), 5(A), 5(B), 7(A), 7(B), 8(A), 8(B), 9(A), 9(B), 16(A), 16(B) are the detail views showing the gear train of exemplary gear reducers. Specific gear box designs involving ring gears and specific gear box designs involving sun gears are described in figures 1 1 to 14. The figures 15(A), 15(B) show how the phase difference between orbiting gear and ring gear varies with the radial position of planet gear for a specific case of gear train type '(1)'. The figure 15(C) shows how the phase difference between the orbiting gear and sun gear varies for a specific case of gear train type '(2)'. FIGS. 16(A) and 16(B) show the gear trains, which utilize the advantages of both the gear train type '(1)' and gear train type '(2)' as explained above.

Statement of Invention:

The invention is about a way to engage the planets with stationary and movable members of the gearing system, such that maximum gear ratio is achieved; additionally an innovative way is devised to interlink all the planets in the planetary gear train for higher torsional rigidity. By choosing the minimum difference, say 'M', between the number of teeth of stationary member and the number of teeth of moveable member; maximum gear reduction ratio is achievable. Also maximum number of planets can be employed based on spatial constraints; irrespective of value of 'M' . This leads to a high reduction ratio with higher efficiency and higher torsional rigidity compared to prior art. Also the new invention has more flexibility in the choice of 'M', compared to prior art. In another variation of the same concept, it is possible to have unequal number of teeth in both sets of planetary gear, which are connected to movable as well as stationary members (of equal number of teeth) of the planetary gear train through additional orbiting gears. Even higher gear ratio i s achieved, if there are unequal number of teeth in both sets of planetary gear as well as there are unequal number of teeth between stationary member and movable member.

This invention can be easily employed to the present planetary gear box designs universally, without increasing the gear box sizes significantly, still achieving significant advantage in reduction ratio as well as torsional rigidity. The invented design uses the standard teeth profile parameters for the gears. And the invention can be employed for single as well as multi stage gear box.

Working example for best method of invention:

Although the invention can be used in enormous ways, however different configurations will have their specific advantages in specific situations.

For example, if it is considered to achieve maximum reduction ratio as the prime criteria, then the schematic shown in FIGS.6 and 10 with gear train described in FIG. 7(B) provides the best results in terms of reduction ratio and torsional rigidity along with perfect phase matching.

However, if torsional rigidity is prime criteria, then the schematic shown in FIG. 2, with gear train described in FIG. 3(B) provides the best results in terms of torsional rigidity and reduction ratio along with perfect phase matching. In case of gear train as per FIG. 3(B), more number of planets can be employed compared to gear train as per FIG. 7(B); this is also evident from FIGS. 13 and FIG. 14.

Gear trains in FIGS. 4(B), 5(B), 8(B), 9(B) describe the option, where high reduction ratio/ torsional rigidity is possible with lesser number of gears employed as well as they provide more symmetric planet carrier option. Gear trains as per FIGS. 16(A) and 16(B) describe the option, where high reduction ratio/ high torsional rigidity/ balancing/ symmetric arrangement are feasible along with perfect phase matching.

Detailed Description of Invention with respect to Drawings:

With reference to FIGS. 1 and 2, the gear reducer 10 includes a housing 12 containing the gears of the gear reducer, the housing remaining stationary relative to a rotating input 16 and a rotating output 14. The housing 12 may be made of a metallic material, such as aluminum or steel, or any other material suitably rigid to provide stability for the gear reducer 10 against the forces created by rotation of the input/ output. The housing 12 includes an end cap 13 sealing a first open end of the housing and a second end cap 17 sealing a second open end of the housing. As will be understood by one of ordinary skill in the art, the first and second end caps 13, 17 may have appropriately sized openings to accommodate the input 16 and output 14. The input 16 may be driven by an exterior driving component, such as a motor or drive shaft located outside the housing 12. Additionally, the output 14 may be integral with a moveable sun gear 44 (FIG. 1), or may be connected to the moveable sun gear by a pin 119 (FIG. 2), such that rotation of the moveable sun gear 44 results in rotation of the output 14. In the exemplary embodiment, as shown in FIG. 2, the input 16 may be attached to the planetary gear carrier 20 by, for example, a pin 224, or the input shaft may be integral with the planetary gear carrier such that the number of revolutions of the input 16 equals the number of orbits of the planetary gears 18, 19 around a central longitudinal axis 28.

The planetary gear carrier 20 is rotatably mounted within the housing 12 about the central longitudinal axis 28. The planetary gear carrier 20 includes a base 30 having a front surface 34 facing toward an exit point of the output 14 and a rear surface 36 facing toward an entry point of the input 16. At least one planetary gear support 32 is mounted on and extends perpendicularly from the front surface 34 or the rear surface 36 (FIG. 2) of the base 30. Each planetary gear support 32 is adapted to carry planetary gears 18, 19 and, in one exemplary embodiment (for example in FIG. 1), comprises an elongate cylinder having a portion embedded within the base 30 and a portion protruding from the base on which the planetary gear support 32 is rotatably mounted. The planet gears 18, 19 may be integral with planetary gear support 32 as in Fig 1 or the planet gears 18, 19 may be connected to planetary gear support 32 by pins 101, 102 as in Fig 2. Where a multiple-planetary gear configuration is employed, the multiple planetary gear supports 32 are mounted on the base 30.

At least one orbiting gear support 132 is mounted on and extends perpendicularly from base 30 (FIG. 1). Each orbiting gear support 132 is adapted to carry orbiting gears 118, 119 and, in one exemplary embodiment (for example FIG. 1), comprises an elongate cylinder having a portion embedded within the base 30 and a portion protruding from the base on which the orbiting gear support 132 is rotatably mounted. As will be understood by one of ordinary skill in the art, in general, the bearings for the planetary gear support and orbiting gear support may be placed in single plane or more than one plane as per the spatial constraints suitably within the planetary gear carrier 20.

The orbiting gears 1 18, 1 19 may be integral with orbiting gear support 132 as in Fig 1 or the orbiting gears 1 18, 1 19 may be connected to orbiting gear support 132 by pins. The orbiting gearsl 18, 1 19 engage constantly with the planet gears 18, 19 (Fig. 1). (Orbiting gears are not shown in FIG. 2 for the sake of clarity.) When a multiple- planetary gear configuration is employed, the multiple orbiting gear supports 132 are mounted.

A stationary sun gear 40 and the moveable sun gear 44 are mounted within the housing 12 in a configuration to constantly engage the orbiting gear(s) 118, 119 and/ or planetary gears 18/ 19, as the case may be as described below. The stationary sun gear 40 is fixedly secured to the housing 12 and.contains a plurality of external teeth 38. The moveable sun gear 44 is rotatably mounted within the housing 12 and has plurality of external teeth 42. FIGS. 3(A), 3(B), 4(A) and 4(B) describe the different gear train schematics for the gear box as described in FIG. 2. Each of the planetary gears 18, 19 contain a plurality of external teeth 24, 25. The planetary gears 18, 19 may have equal number of teeth or may have unequal number of teeth.

In FIGS. 3(A) and 3(B), each of the orbiting gears 118, 1 19 contain a plurality of external teeth 124, 125 respectively. The orbiting gears 118, 119 may or may not have equal number of teeth. Each of the planetary gear teeth 24, 25 are adapted to engage with the orbiting gear teeth 124, 125 respectively. The orbiting gear teeth 124 are adapted to engage the stationary sun gear teeth 38 and the orbiting gear teeth 125 are adapted to engage the moveable sun gear teeth 42. The sun gears 40, 44 may have equal number of teeth or may have unequal number of teeth. In case, multiple planet gears/ orbiting gears sets are employed, then the angular positions of all the sets may not be symmetric. Also, the planets may need to be located at different radial locations. For orbiting gears teeth 124, 125 to engage with sun gear teeth 38, 42; the orbiting gears teeth 124, 125 have to be in phase with sun gear teeth 38, 42 at respective locations. The phase of orbiting gears teeth 124, 125 can be varied infinitely by changing the radial position of planet gear 18, 19. So the proper radial position of planet gear is selected for orbiting gears to come in phase with sun gears 40, 44.

FIG. 3(B) describes one of the several ways to interlink all the planets and orbiting gears in this type of gear train. The interlinked gear train is capable to carry higher torque compared to gear train in FIG. 3(A), but the gear reduction ratio remains unchanged. In this type of gear train, it may be required to employ one or more than one 'Planet gears type 2' and/or one or more than one idler gears as, defined earlier. Gears 130 represent 'Planet gears type 2'. Interlinked gear train can be formed without gears 130 also, in which case, it may not be continuous over the full circle around the sun gears.

In FIG. 4(A), the orbiting gear 118 contains plurality of external teeth 124. The planetary gear 18/ 19 has two sets of teeth 24 and 25. The planetary gear teeth 24 are adapted to engage with the orbiting gear teeth 124. The orbiting gear teeth 124 are adapted to engage the moveable sun gear teeth 42 and the planetary gear teeth 25 are adapted to engage the stationary suri gear teeth 38. FIG. 4(B) describes one of the many ways to interlink all the planets and orbiting gears in this type of gear train. The interlinked gear train is capable to carry higher torque compared to gear train in FIG. 4(A), but the gear reduction ratio remains unchanged. In general, it is possible to form an interlinked gear train; by using one or more than one 'Planet gears type 2'. Gears 130 represent 'Planet gears type 2' in FIG. 4(B).

For orbiting gear/ planet gear teeth to engage with sun gears teeth; the orbiting gears/ planet gear teeth have to be in phase with sun gear teeth 38, 42 at respective locations. The phases can match in following two ways:

by selecting the appropriate number of teeth on planet gear and orbiting gear, for a given set of stationary/ movable sun gear teeth. If the planetary gears 18, 19 have equal number of teeth and the moveable sun gear44/ the stationary sun gear40 have unequal number of teeth, then all the planets in the same gear train may have different number of teeth as well as all the orbiting gears in the same gear train may have different number of teeth. The gear ratio is decided only by the number of teeth on stationary/ movable sun gears.

In general, it is possible to match phase by using one or more than one 'Planet gears type 2', and specific number. of teeth in orbiting gears.

In a specific example with reference to FIGS. 3(A), 3(B), 4(A) and 4(B), the number of teeth 38 in the stationary sun gear is (SSI) 60, the number of teeth 42 in the moveable sun gear is (SS2) 61. The number of teeth in both sets of planet gear is equal. The difference in number of teeth (SS2-SS1 ) is maintained minimum for maximum reduction ratio. The planetary ratio (PR1) = 1 : [1-(SS1/SS2)]. So PR1 = 1 :61.

There can be 3 possible cases for the gear trains shown in FIGS. 3(A), 3(B), 4(A) and 4(B):

The planetary gears 18, 19 have equal number of teeth and the moveable sun gear44/ the stationary sun gear40 have unequal number of teeth. In this case, the gear ratio is decided by sun gears 40, 44. All the orbiting/ planet gears may be different in the gear train containing multiple planets/ orbiting gears.

The planetary gears 18, 19 have unequal number of teeth and the moveable sun gear44/ the stationary sun gear40 may have unequal number of teeth. In this case, maximum gear ratio is achievable. In this case, the sun gears 40/ 44 and planet gears 18/ 19; both contribute to the total gear ratio.

In a specific example with reference to FIGS. 3(A), 3(B), 4(A) and 4(B), the number of teeth 38 in the stationary sun gear is (say 'SSI ') 80, the number of teeth 42 in the moveable sun gear is (say 'SS2') 81. The number of teeth (say 'PGT1 ') in planet gear teeth set 18 is 60, and number of teeth (say 'PGT2') in planet gear teeth set 19 is 61. The planetary ratio (PR1) = 1 : [1-(SS1/SS2*PGT2/PGT1)]. So PR1 = 1 :243.

The planetary gears 18, 19 have Unequal number of teeth and the moveable sun gear 44/ the stationary sun gear 40 have equal number of teeth. In this case, the gear ratio is decided by planetary gears 18, 19 only. This type of gear train is described in FIGS. 5(A) and 5(B). The planetary gear teeth 24 are adapted to engage with the orbiting gear teeth 124. The orbiting gear teeth 124 are adapted to engage the stationary sun gear teeth 38 and the planetary gear teeth 25 are adapted to engage the moveable sun gear teeth 42. FIG. 5(B) represents the arrangement, where the orbiting and planetary gears are interlinked for higher torsional rigidity.

The phase of orbiting gears teeth/ planet gear teeth can be varied by selecting the right combination of number of teeth on planet gears/ orbiting gear/ sun gears. FIG. 15 (C) shows, how the phase difference changes with changing number of teeth on Sun gears for specific number of teeth on planet gear and orbiting gear. In case, multiple planet gears/ orbiting gears sets are employed, then the angular positions of all the sets may be symmetric. All the planets may be same, as well as all orbiting gears may be same. This arrangement provides a symmetric and balanced alternative.

In a specific example with reference to FIGS. 5(A) and 5(B), the number of teeth 38 and 42 in the stationary/ moveable sun gear is (SSI) 91 , the number of teeth 24 in the planetary gear is (PP1) 27, the number of teeth 25 in the planetary gear is (PP2) 28. (If, the number of teeth 124 in orbiting gear is taken 27, then it matches phase with 91 teeth sun gear.) The planetary ratio (PRl ) = 1 : [1-(PP1/PP2)]. So PRl = 1 :27.

For a specific reduction ratio, the set of planet gear/ orbiting gear can be chosen freely as per the above calculation. And the sun gear teeth can be chosen such that it can match phase with the chosen planet gear/ orbiting gear set and based on how many interlinked planet/ orbiting gears are required for specific torque capacity requirement.

FIG. 6 describes the gear box similar to one described in FIG. 2 above; except that ring gears are utilized in place of sun gears. A stationary ring gear 40 and the moveable ring gear 44 are mounted within the housing 12 in a configuration to constantly engage the orbiting gear(s) 1 18, 119. The stationary ring gear 40 is fixedly secured to the housing 12 and contains a plurality of internal gear teeth 38. The moveable ring gear 44 is rotatably mounted within the housing 12 and contains a plurality of internal teeth 42.

FIGS. 7(A), 7(B), 8(A), 8(B), 9(A), 9(B) describe the gear train schematics for the gear box as described in FIG. 6. The description of FIGS. 7(A), 7(B), 8(A), 8(B), 9(A), 9(B) remain same as description of FIGS. 3(A), 3(B), 4(A), 4(B), 5(A), 5(B) respectively, except that ring gears 40/44 having internal teeth 38/42 are utilized in place of sun gears 40/44 having external teeth 38/42.

With reference now to FIG. 10, planetary gear 18 is shown meshing directly with the movable sun gear 44. Also, planetary gear 18 is connected to the stationary ring gear 140, and planetary gear 19 is connected to the moveable ring gear 144 via additional orbiting gears (conceptually, the arrangement of orbiting gears may be similar to the gear train shown in FIGS. 7(A), 7(B), 8(A), 8(B), 9(A), 9(B)); such that the planetary gear teeth 18/19 are connected with stationary ring gear teeth 138 and movable ring gear teeth 142; through orbiting gears. As noted above, the input 16 is connected to sun gear 44. Rotation of the input 16 results in rotation of the planetary gear(s) 18; rotation of the planetary gear(s) 18 results in rotation of the moveable ring gear 144 with respect to the stationary ring gear 140. Rotation of the moveable ring gear 144 results in simultaneous rotation of the output 14.

In a specific example with reference to FIG. 10, the number of teeth in the input sun gear 44 is (SSI) 54, the number of teeth in the moveable ring gear 144 is (RR2) 109, and the number of teeth in the stationary ring gear 140 is (RRl) 108; both sets of planet gears have equal number of teeth; then the preliminary planetary ratio (PRl) is (RR1/SS1) +1. The preliminary planetary ratio (PRl) in this example is 3. Wolfram ratio is 109. The total overall gear ratio OR = 3*109 = 327.

FIGS. 11 to 15 describe specific example of design of a gear train. All the gears in these examples are considered with module 2.

FIG. 11 shows two sun gears; the gear teeth are represented by the radial lines. Gear 40 shows 61 teeth sun gear and gear 44 shows 60 teeth sun gear. With reference now to FIG. 12, this is a specific design example based on the gear train described in FIG. 3(A). In the centre, the gears 40 and 41 (as per FIG. 12) are shown superimposed, such that one of them represents stationary sun gear and other one represents movable sun gear. The gear teeth are shown by radial lines, so that the phase difference between different gear teeth can be ascertained with ease. Gears 18 represent planet gears. In this example, both sets of planet gear have equal number of teeth. In this specific design example, planets 18 are 8 in number. Gears 118 represent orbiting gears which mesh with stationary sun gear 40. In this specific design example, orbiting gears 118 are 7 in number. Gears 119 represent orbiting gears which mesh with movable sun gear 44; orbiting gears 1 19 are 8 in number. In this example, all the Planet gears and orbiting gears are taken each of 18 teeth. In order to match the phases of orbiting gears 1 18,1 19 teeth with the phases of sungears 40, 44 teeth, the planets 18 are positioned at different radial/ angular positions. The arrangement shows one of the various possible arrangements of planets and orbiting gears. It is evident that even if the difference in number of teeth between two sun gears is one, still multiple planetary/ orbiting gears can be employed for carrying more torque carrying capacity.

With reference now to FIG. 13, this is another specific design example based on the gear train described in FIG. 3(B). In case of design in FIG. 13, the planets and orbiting gears sets are shown interlinked around the sun gears, ' so that higher torsional rigidity is achieved. In this specific design example, planets 18 are 14 in number. Orbiting gears 1 18, 119 are same as in FIG. 12. The arrangement shows one of the various possible interlinking arrangements of planets and orbiting gears. Compared to design example shown in FIG. 12, here more number of planets are employed, so higher torsional rigidity and better power characteristics are achieved.

However in this specific design, the interlinked gear train of orbiting gears and planet gears does not complete a full circle around the sun gears.

With reference now to FIG. 14, this is a specific design example based on the gear train described in FIG. 7(B). This power train is similar to the power train described in FIG. 13; however, in place of sun gears (of 60 teeth and 61 teeth); FIG. 14 design employs ring gears 40, 44 of 100 internal teeth and 101 internal teeth respectively. The design shows the interlinked planets and orbiting gears sets, so that high torsional rigidity is achieved. In this case, although more number of planets can be employed, still the gear box overall size remains unchanged. FIGS. 15(A) and 15(B) describe, for specific case with reference to the gear train in FIGS. 3(A), 3(B), 7(A) and 7(B); how the phase difference (that is angular deviation) between teeth of orbiting gears and teeth of ring gears (or sun gears) changes with the radial position of planet gears. Horizontal axis of the chart represents the different radial positions of the planet and vertical axis represents the phase difference/ deviation in degrees. It is evident from the chart, that multiple radial positions of planets satisfy the condition of zero phase difference. The FIGS. 15(A) and 15(B) show the same chart at different scales, in order to emphasize the fact that the radial positions of planets can be chosen very precisely. FIG. 15(C) describes how the phase difference varies with reference to the gear train in FIGS. 5(A), 5(B), 9(A) and 9(B). Horizontal axis of the chart represents the number of teeth on sun gears/ ring gears and vertical axis represents the phase difference/ deviation in degrees; for a specific chosen planet gear/ orbiting gear set. The planet gear/ orbiting gear may be chosen (based on the reduction ratio required) prior to choosing the sun gear/ ring gear. The choice of sun gear/ ring gear may be made based on spatial constraints and number of planets required for a specific torque requirement. It is clear from the chart that for a specific chosen planet gear/ orbiting gear set, the phase difference comes within acceptable limits for multiple choices of sun gears/ ring gears.

With reference now to FIG. 16(A), this gear train has the advantage of both the gear trains described in FIGS. 3(A) and 5(A) in terms of phase matching, interlinking and maximized gear ratio. The gear train includes planet gears which have 2 sets of unequal number of teeth. The planet gears are connected to movable and stationary sun gears through orbiting gears. The movable and stationary sun gears also have unequal number of teeth. For a specific reduction ratio, both the sets of planet gear teeth are chosen; and according to spatial constraints, torque carrying capacity requirement; the number of teeth on sun gears and orbiting gears can be chosen. The radial position of the planets can be varied infinitely, so by changing the radial position .of planet gears; the phases of orbiting gears can be matched perfectly to respective phases of stationary and movable sun gears. Also, the planet/ orbiting gears are possible to be interlinked for higher torsional rigidity. If the movable and stationary sun gears also have equal number of teeth, then this arrangement provides a symmetric and balanced design alternative.

FIG. 16(B) describes the gear train similar to gear train described in FIG. 16(A), except that movable and stationary ring gears of equal number of teeth; are employed in place of movable and stationary sun gears. This type of gear train may be preferred for specific overall gear box size requirements. This gear train combines the advantages of gear trains described in FIGS. 3(A) and 5(A).

Although exemplary embodiments in accordance with the present invention have been described, one of ordinary skill in the art will appreciate that various modifications may be made to the embodiments without departing from the spirit and scope of the invention as described and claimed as follows:

Claims

I claim:

1. A gearing system comprising; a rotatable planet carrier supporting set(s) of planetary gear(s) and orbiting gear(s) for axial rotation thereon; the set of planetary gear(s) and orbiting gear(s) may be called 'PO set' (There may be 3 types of 'PO set'- say, 'PO set , 'PO set 2' and 'PO set 3'); a stationary ring gear engageable with any gears out of the 'PO set'; and a moveable ring gear engageable with any gears out of the 'PO set'.

'PO set comprises one number of planetary gear (PG1) and one number of orbiting gear (OG1). For example, FIGS. 4(A), 5(A), 8(A) and 9(A) comprise this type 'PO set Γ. Both Planetary gear (PG1) and orbiting gear (OG1) have external teeth. Planetary gear (PG1 ) teeth mesh with orbiting gear (OG1) teeth. Say 'PGT' represents number of teeth on planetary gear (PG1), and 'OGT' represents number of teeth on orbiting gear (OG1). The 'PGT' may or may not be equal to 'OGT'. The planetary gear may comprise only one set of teeth (as in FIGS. 4(A) and 8(A)); or more than one sets of teeth (as also in FIGS. 5(A) and 9(A)). The orbiting gear (OG1) may also comprise only one set of teeth; or more than one sets of teeth. Different sets of teeth (for Planetary Gear or Orbiting Gear) may have equal number of teeth or may have unequal number of teeth and these sets may match in phase with each other or may have specific pre-determined phase difference with respect to each other. 'Planet gears type 2' are defined as Planetary Gears having more than one set of teeth (either equal or unequal number of teeth in different sets) with specific pre-determined phase difference among different sets (of teeth). 'PO set 2' comprises one planetary gear (PG1) and two orbiting gears (OG1 and OG2). For example, FIGS. 1, 3(A), 7(A) and 12 comprise this type 'PO set 2'. Planetary gear (PG1), as well as orbiting gears (OGl and OG2) have external teeth. Planetary gear teeth engage simultaneously with both the orbiting gears teeth (PG1 engages OGl, PG1 engages OG2). The orbiting gears (OGl and OG2) also may comprise only one set of teeth; or more than one sets of teeth. Say 'PGT' represents number of teeth of planetary gear (PG1); 'OGTl ' represents number of teeth of orbiting gear (OGl) and 'OGT2' represents number of teeth of orbiting gear (OG2). 'PGT' may or may not be equal to 'OGTl ' as well as 'PGT' may or may not be equal to 'OGT2'. The planetary gear (PG1) may comprise only one set of teeth (say, number of teeth in one set is 'PGT1 ') or planetary gear (PG1) may comprise more than one sets of teeth (say, number of teeth in sets are 'PGT1 ', 'PGT2'... etc.), Different sets of teeth (for Planetary Gear or Orbiting Gear) may have equal number of teeth or may have unequal number of teeth and these sets may match in phase with each other or may have specific pre-determined phase difference with respect to each other. 'Planet gears type 2' are defined as Planetary Gears having more than one set of teeth with specific pre-determined phase difference among different sets (of teeth).

'PO set 3' comprises multiple interlinked planetary gears /orbiting gears sets. The characteristics of each of planetary gears/ orbiting gears sets remain same as the characteristics of planetary gear/ orbiting gear for 'PO set or 'PO set 2' above. The planetary gears and orbiting gears are interlinked such that they form a continuous power train as also described in FIGS. 3(B), 4(B), 5(B), 7(B), 8(B), 9(B), 13, 14, 16(A) and 16(B). The power train may also consist of one or more than one 'Planet gears type 2' as defined above and/or one or more than one idler gears. For example, Gears 130 represent 'Planet gears type 2' in the enclosed figures. Idler gears may be used to carry power between two orbiting gears or two planetary gears. This interlinked power train may or may not be continuous over a full round.

2. The gearing system of claim 1 , in which; the stationary ring gear engages with orbiting gear (OG1), orbiting gear (OG1 ) engages with Planetary gear (PGl); and moveable ring gear engages with the orbiting gear (OG2), orbiting gear (OG2) engages with Planetary gear (PGl). One such gear train is described in FIG. 7(A).

3. The gearing system of claim 1 , in which; the stationary ring gear (or movable ring gear) engages with orbiting gear (OG1); orbiting gear (OG1) engages with Planetary gear (PGl); and moveable ring gear (or stationary ring gear) engages with the Planetary gear (PGl). Such gear train is described in FIGS. 8(A) and 9(A).

4. The gearing system of claims 1, 2; in which; the number of teeth (say, MRN) on moveable ring gear and number of teeth (say, SRN) on stationary ring gear is not equal. (The difference between the number of moveable ring gear teeth (MRN) and the number of stationary ring gear teeth (SRN) may be just one.) The planetary gear (PGl) may comprise only one set of teeth (say, number of teeth in one set is 'PGT1 '), and PGl simultaneously engaging with two orbiting gears OG1 and OG2. Or the planetary gear (PGl) may comprise two sets PG11 and PG12 (say, number of teeth in 2 sets PG11 and PG12 are 'PGT1 ' and 'PGT2' respectively); each engaging with the two different orbiting gear OG1 and OG2 (PG11 engages OG1 and PG12 engages OG2); where number of teeth in both sets may or may not be equal ('PGT1 ' = 'PGT2' or 'PGT1 '≠ 'PGT2'). One such gear train is described in FIG. 7(A).

5. The gearing system of claims 1, 2; in which, the number of teeth (say, MRN) on moveable ring gear and number of teeth (say, SRN) on stationary ring gear is equal. The planetary gear (PGl) may comprise two sets PG11 and PGl 2 (say, number of teeth in 2 sets PGl 1 and PG12 are 'PGT1 ' and 'PGT2' respectively); each engaging the two different orbiting gear OG1 and OG2 (PG11 engages OG1 and PGl 2 engages OG2); where number of teeth in both sets is not equal ('PGT1 '≠ 'PGT2'). One such gear train is described in FIG. 16(B).

6. The gearing system of claims 1, 3; in which, the number of teeth (say, MRN) on moveable ring gear and number of teeth (say, SRN) on stationary ring gear is not equal. (The difference between the number of moveable ring gear teeth (MRN) and the number of stationary ring gear teeth (SRN) may be just one.) The planetary gear (PGl) may comprise only one set of teeth (say, number of teeth in one set is 'PGT1 ') and PGl engages simultaneously with orbiting gear OG1 and Ring gear (either movable or stationary). Or the planetary gear (PGl ) may comprise two sets PG11 and PG12; (say, number of teeth in 2 sets PG11 and PGl 2 are 'PGT1 ' and 'PGT2 respectively'; PGl 1 engages orbiting gear OG1 and PG12 engages either movable or stationary ring gear); where number of teeth in both sets may or may not be equal ('PGT1 '= 'PGT2' or 'PGT1 '≠ 'PGT2'). One such gear train is described in FIG. 8(A).

7. The gearing system of claims 1, 3; in which, the number of teeth (say, MRN) on moveable ring gear and number of teeth (say, SRN) on stationary ring gear is equal. The planetary gear (PGl) may comprise two sets PG11 and PG12; (say, number of teeth in 2 sets PG1 1 and PG12 are 'PGT1 ' and 'PGT2 respectively'; PG11 engages orbiting gear OG1 and PG12 engages either movable or stationary ring gear); where number of teeth in both sets is not equal ('PGT1 '≠ 'PGT2'). One such gear train is described in FIG. 9(A).

8. The gearing system of claims 1 to 7 above; in which, the moveable ring gear engages with multiple orbiting gears or multiple planetary gears; and stationary ring gear engages with multiple orbiting gears or multiple planetary gears. The orbiting gears and planetary gears are interlinked as per 'PO set 3' described in claim 1 above. Such gear train is described in FIGS. 7(B), 8(B), 9(B) and 14.

9. The gearing system of claims 1 to 8 above; comprising only one set of planetary gear(s) and orbiting gear(s) denoted by 'PO set' in claim 1 above.

10. The gearing system of claims 1 to 8 above; comprising more than one set of planetary gear(s) and orbiting gear(s) denoted by 'PO set' in claim 1 above.

1 1. The gearing system of claims 1 to 10 above; comprising a movable sun gear in addition. One such arrangement is described in FIG. 10. The movable sun gear may be engaged to one or more than one planet gears or the movable sun gear may be engaged to one or more than one orbiting gears. The planet gears or orbiting gears that are engaged to movable sun gear; may have 'additional set' of teeth for engagement with movable sun gear. The number of teeth On the said 'additional set' may or may not be equal to the number of teeth on other sets of teeth on planet gears or orbiting gears.

12. A gearing system comprising: a rotatable planet carrier supporting set(s) of planetary gear(s) and orbiting gear(s) for axial rotation thereon; the set of planetary gear(s) and orbiting gear(s) may be called 'PO set' (There may be 3 types of 'PO set'- say, 'PO set , 'PO set 2' and 'PO set 3'), a stationary sun gear engageable with any gears out of the 'PO set'; and a moveable sun gear engageable with any gears out of the 'PO set'. The definitions of 'PO set , 'PO set 2' and 'PO set 3' are same as given in claim 1 above.

13. The gearing system of claim 12, in which; the stationary sun gear engages with orbiting gear (OGl), orbiting gear (OGl) engages with Planetary gear (PGl); and moveable sun gear engages with the orbiting gear (OG2), orbiting gear (OG2) engages with Planetary gear (PGl). One such gear train is described in FIG. 3(A).

14. The gearing system of claim 12, in which; the stationary sun gear (or movable sun gear) engages with orbiting gear (OGl); orbiting gear (OGl) engages with Planetary gear (PGl); and moveable sun gear (or stationary sun gear) engages with the Planetary gear (PGl). Such gear train is described in FIGS. 4(A) and 5(A).

15. The gearing system of claims 12, 13; in which, the number of teeth (say, MRN) on moveable sun gear and number of teeth (say, SRN) on stationary sun gear is not equal. (The difference between the number of moveable sun gear teeth (MRN) and the number of stationary sun gear teeth (SRN) may be just one.) The planetary gear (PGl) may comprise only one set of teeth (say, number of teeth in one set is 'PGTl '), and PGl simultaneously engaging with two orbiting gears OGl and OG2. Or the planetary gear (PGl) may comprise two sets PGl l and PG12 (say, number of teeth in 2 sets PGl l and PG12 are 'PGTl ' and 'PGT2' respectively); each engaging with the two different orbiting gear OGl and OG2 (PGl l engages OGl and PGl 2 engages OG2); where number of teeth in both sets may or may not be equal ('PGTl ' = 'PGT2' or 'PGTl '≠ 'PGT2'). One such gear train is described in FIG. 3(A) and 16(A).

16. The gearing system of claims 12, 13; in which, the number of teeth (say, MRN) on moveable sun gear and number of teeth (say, SRN) on stationary sun gear is equal. The planetary gear (PGl) may comprise two sets PGl l and PG12 (say, number of teeth in 2 sets PGl l and PG12 are 'PGTl ' and 'PGT2' respectively); each engaging the two different orbiting gear OGl and OG2 (PGl l engages OGl and PGl 2 engages OG2); where number of teeth in both sets is not equal ('PGTl '≠ 'PGT2').

17. The gearing system of claims 12, 14; in which, the number of teeth (say, MRN) on moveable sun gear and number of teeth (say, SRN) on stationary sun gear is not equal. (The difference between the number of moveable sun gear teeth (MRN) and the number of stationary sun gear teeth (SRN) may be just one.) The planetary gear (PGl) may comprise only one set of teeth (say, number of teeth in one set is 'PGT1 ') and PGl engages simultaneously with orbiting gear OG1 and Ring gear (either movable or stationary). Or the planetary gear (PGl) may comprise two sets PGl 1 and PGl 2; (say, number of teeth in 2 sets PGl 1 and PGl 2 are 'PGT1 ' and 'PGT2 respectively'; PG11 engages orbiting gear OG1 and PG12 engages either movable or stationary sun gear); where number of teeth in both sets may or may not be equal ('PGT1 ' = 'PGT2' or 'PGT1 '≠ 'PGT2'). One such gear train is described in FIG. 4(A).

18. The gearing system of claims 12, 14; in which, the number of teeth (say, MRN) on moveable sun gear and number of teeth (say, SRN) on stationary sun gear is equal. The planetary gear (PGl ) may comprise two sets PG1T and PG12; (say, number of teeth in 2 sets PG11 and PG12 are 'PGT1 ' and 'PGT2 respectively'; PGl l engages orbiting gear OG1 and PG12 engages either movable or stationary sun gear); where number of teeth in both sets is not equal ('PGT1 '≠ 'PGT2'). One such gear train is described in FIG. 5(A).

19. The gearing system of claims 12 to 18 above; in which, the moveable sun gear engages with multiple orbiting gears or multiple planetary gears; and stationary sun gear engages with multiple orbiting gears or multiple planetary gears. The orbiting gears and planetary gears are interlinked as per 'PO set 3' described in claim 1 above. Such gear train is described in FIGS. 3(B), 4(B), 5(B), 13.

20. The gearing system of claims 12 to 19 above; comprising only one set of planetary gear(s) and orbiting gear(s) denoted by 'PO set' in claim 1 above.

21. The gearing system of claims 12 to 19 above; comprising more than one set of planetary gear(s) and orbiting gear(s) denoted by 'PO set' in claim 1 above.

22. The gearing system of claims 1 to 21 above utilizing spur gear form or helical gear form or any other suitable form for its member gears.

23. The gearing system of claims 1 to 22 above comprising the planet carriers, which have been dynamically or statically balanced for vibration free operation.

24. The gearing system comprising one stage or more than one stage of the gearing systems described in claims 1 to 23 above.

25. The gearing system of claims 1 to 24 described above utilized for speed reduction or utilized for speed increasing / speed multiplication.

26. A gearing system utilizing anyone or more than one gearing arrangements as described in claims 1 to 24 above along with any additional gears.