BI-DIRECTIONAL TO UNIDIRECTIONAL GEAR TRAIN

Abstract

BIDIRECTIONAL TO UNI-DIRECTIONAL GEAR TRAIN An apparatus includes a gear train (100) having an input gear (102) configured to be rotated by an input shaft (104), first and second one-way clutches (116, 118), first and second output gears (106, 108) configured to drive rotation of an output shaft (110) via the first and second one-way clutches (116, 118), respectively, and an intermediate gear (112). The second output gear (108) has a smaller outer diameter than the first output gear (106). The input gear (102) is configured to (i) rotate the first output gear (106) in a first direction and (ii) rotate the intermediate gear (112) in the first direction. The intermediate gear (112) is configured to rotate the second output gear (108) in a second direction opposite to the first direction.The first and second one-way clutches (116, 118) are configured to allow the first and second output gears (106, 108) to drive rotation of the output shaft (110) in a single predetermined direction of rotation, regardless of the direction of rotation of the input shaft (104). [FIG.1].

Description

Title of the invention: BIDIRECTIONAL TO UNIDIRECTIONAL GEAR TRAIN Technical field

[0001] This invention relates generally to gearboxes and associated systems and processes. More specifically, this invention relates to a bidirectional to unidirectional gear train. STATE OF THE ART

[0002] Turbomachines and other mechanical devices often have rotating input shafts that are used to drive rotating output shafts. The conversion of the input rotation of an input shaft to the output rotation of an output shaft is generally accomplished using a gear train, called a gear train. SUMMARY

[0003] This invention relates to a bidirectional to unidirectional gear train.

[0004] In a first embodiment, a system includes a rotating shaft having a first end and an opposing second end, a first mechanical device configured to receive a first rotational input from the first end of the rotating shaft, and a second mechanical device configured to receive a second rotational input from the second end of the rotating shaft. The second rotational input is opposite the first rotational input. Each of the first and second mechanical devices includes a gear train that includes an input gear configured to be rotated by the rotating shaft, first and second one-way clutches, first and second output gears configured to drive rotation of an output shaft via the first and second one-way clutches, respectively, and an intermediate gear.The input gear of the first gear train is configured to (i) rotate the first output gear of the first gear train in a first direction and (ii) rotate the intermediate gear of the first gear train in the first direction, and the intermediate gear of the first gear train is configured to rotate the second output gear of the first gear train in a second direction opposite to the first direction. The input gear of the second gear train is configured to (i) rotate the first output gear of the second gear train in the second direction and (ii) rotate the intermediate gear of the second gear train in the second direction, and the intermediate gear of the second gear train is configured to rotate the first . output gear of the second gear train in the first direction. The first and second one-way clutches of each gear train are configured to enable the first and second output gears of the gear train to drive rotation of the associated output shaft in a single predetermined direction of rotation, regardless of the direction of rotation of the rotating shaft relative to the gear train.

[0005] In a second embodiment, an apparatus includes an input gear configured to be rotated by the input shaft, first and second one-way clutches, first and second output gears configured to drive rotation of an output shaft via the first and second one-way clutches, respectively, and an intermediate gear. The second output gear has a smaller outer diameter than the first output gear. The input gear is configured to (i) rotate the first output gear in a first direction and (ii) rotate the intermediate gear in the first direction. The intermediate gear is configured to rotate the second output gear in a second direction opposite the first direction.The first and second one-way clutches are configured to allow the first and second output gears to drive rotation of the output shaft in a single predetermined direction of rotation, regardless of the direction of rotation of the input shaft.

[0006] In a third embodiment, a method comprises applying a rotary input to an input gear of a gear train using an input shaft. The method also comprises rotating an output shaft using first and second output gears of the gear train respectively via first and second one-way clutches and an intermediate gear of the gear train. The input gear (i) rotates the first output gear in a first direction and (ii) rotates the intermediate gear in the first direction. The intermediate gear rotates the second output gear in a second direction opposite to the first direction. The first and second one-way clutches are configured to allow the first and second output gears to drive rotation of the output shaft in a single predetermined direction of rotation, regardless of the direction of rotation of the input shaft.The second output gear has a smaller outside diameter than the first output gear.

[0007] Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Brief Description of the Drawings

[0008] For a more complete understanding of this invention, reference is now made to the following description taken in conjunction with the following accompanying drawings, in which:

[0009] [Fig.l] and [Fig.2] illustrate an example of a bidirectional to unidirectional gear train according to the present invention;

[0010] [Fig.3] and [Fig.4] illustrate example operations of a gear train bidirectional to unidirectional according to the present invention; and

[0011] [Fig.5], [Fig.6] and [Fig.7] illustrate an example of a system which integrates multiple bidirectional to unidirectional gear trains according to the present invention. DETAILED DESCRIPTION

[0012] FIGURES 1 through 7, described below, and the various embodiments used to describe the principles of the present invention are provided for illustrative purposes only and should not be construed in any way as limiting the scope of this invention. Those skilled in the art will understand that the principles of the present invention can be implemented in any type of suitably arranged device or system.

[0013] As described above, turbomachinery and other mechanical devices often include rotating input shafts that are used to drive rotating output shafts. The conversion of input rotation of an input shaft to output rotation of an output shaft is typically accomplished using a gear train, referred to as a gear train. Unfortunately, turbomachinery and other mechanical devices are typically designed to receive input rotation in a specific direction, which is typically expressed as either clockwise (CW) or counterclockwise (CCW) rotation. In some situations, due to space or other constraints, it is not possible to provide a desired direction of rotation to a turbomachinery or other mechanical device.In other situations, it may be desired to use multiple turbomachines or other mechanical devices, but the direction of rotation may be reversed at the locations of the turbomachines or other mechanical devices. One approach to solving the latter problem might be to design different versions of the turbomachines or other mechanical devices that accept input rotations in different directions, but this may lead to inefficiencies in design and preparation, lead to installation errors, and require personnel to keep different devices in stock for use.

[0014] This invention relates to bidirectional to unidirectional gear trains that have the capability of converting bidirectional input rotation into unidirectional output rotation. In other words, a bidirectional to unidirectional gear train generates output rotation in the same direction (clockwise or counterclockwise) regardless of whether the input rotation is clockwise or counterclockwise. As described in more detail below, the gear train includes an input gear, first and second output gears, and an intermediate gear. The input gear may be coupled to an input shaft, and both the first and second output gears may be coupled to an output shaft.The input gear is configured to simultaneously drive the first output gear and the intermediate gear, and the intermediate gear is configured to drive the second output gear. The one-way clutches are positioned between the first and second output gears and the output shaft, and the one-way clutches enable the first or second output gears to drive the output shaft to rotate in the same direction. During operation, the first output gear can be used to drive the output shaft when the input shaft rotates in one direction, and the second output gear can be used to drive the output shaft when the input shaft rotates in the opposite direction. In this way, the output shaft rotates in the same direction regardless of the direction of rotation of the input shaft.

[0015] This invention also relates to systems that may use multiple instances of such a bidirectional to unidirectional gear train. For example, a system may include multiple mechanical devices, such as multiple turbomachines like electric generators with integrated or coupled oil pumps. The multiple mechanical devices may be coupled to opposite ends of a rotating input shaft. Accordingly, the mechanical devices may receive input rotation in different directions, such as when one mechanical device at one end of the rotating input shaft receives clockwise input rotation and another mechanical device at the opposite end of the rotating input shaft receives counterclockwise input rotation.Each mechanical device may have an instance of the bidirectional to unidirectional gear train, which allows each mechanical device to convert its respective input rotation into an output rotation suitable for use by the mechanical device or another device. In this way, a common design may be used for the mechanical devices, rather than separate designs for mechanical devices used in different locations.

[0016] FIGURES 1 and 2 illustrate an exemplary bidirectional to unidirectional gear train 100 according to the present invention. As illustrated in FIGURES 1 and 2, the gear train 100 includes an input gear 102, which may be coupled to and rotate with an input shaft 104. The input shaft 104 represents a structure that may provide input rotation to the gear train 100. As illustrated herein, the input shaft 104 may rotate clockwise and / or counterclockwise. The exact direction of rotation of the input shaft 104 may vary depending on the application. In some embodiments, for example, the input shaft 104 may rotate in only one direction (either clockwise or counterclockwise), such as when the input shaft 104 is configured or is coupled to another component that is configured to rotate in only one direction.In other embodiments, the direction of rotation of the input shaft 104 may vary over time.

[0017] The gear train 100 also includes a first output gear 106 and a second output gear 108, each of which can be coupled to and rotated about an output shaft 110. The output shaft 110 represents a structure that can provide output rotation from the gear train 100, for example, to an external component designed to receive rotation in a specific direction. As illustrated herein, the output shaft 110 can only rotate in one direction, either clockwise or counterclockwise. Again, the exact direction of rotation of the output shaft 110 can vary depending on the application. The gear train 100 further includes an intermediate gear 112, which can be connected to and rotated with an intermediate shaft 114.The intermediate shaft 114 represents a structure which can allow the intermediate gear 112 to rotate freely in both directions.

[0018] The output gears 106 and 108 are respectively connected to the output shaft 110 using one-way clutches 116 and 118. Each one-way clutch 116 and 118 represents a structure that allows the associated output gear 106 and 108 to drive the rotation of the output shaft 110 in one direction and prevent the rotation of the output shaft 110 in the opposite direction. In other words, the one-way clutches 116 and 118 are configured to engage the output shaft 110 and allow it to be respectively driven by the output gears 106 and 108 in one direction and to disengage and prevent the output shaft 110 from being respectively driven by the output gears 106 and 108 in the opposite direction.For example, the one-way clutch 116 may engage and allow the first output gear 106 to drive the output shaft 110 in one direction (e.g., counterclockwise), in which case the one-way clutch 118 may disengage and allow the second . output gear 108 to rotate freely without driving the output shaft 110. Further, the one-way clutch 118 may engage the second output gear 108 and allow the output shaft 110 to be driven in the same direction (e.g., counterclockwise), in which case the one-way clutch 116 may disengage and allow the first output gear 106 to rotate freely without driving the output shaft 110. As described below, this configuration allows the conversion of the input rotation of the input shaft 104 (in either direction) into a known one-way output rotation of the output shaft 110.Each one-way clutch 116 and 118 may be any suitable structure configured to allow selective driving of the output shaft 110 depending on the direction of rotation, such as an overrunning clutch, a roller clutch, a ratchet clutch, or another type of one-way clutch.

[0019] Each gear 102, 106, 108, 112 includes any suitable structure having teeth or other features that can interact with and rotate or be rotated by another gear. Each gear 102, 106, 108, 112 may be formed using any suitable material, such as one or more metals. Each gear 102, 106, 108, 112 may also be formed using any suitable technique, such as an additive or subtractive preparation process. In addition, each gear 102, 106, 108, 112 may have any suitable size, shape, and dimensions.

[0020] In some embodiments, such as that illustrated in FIGURES 1 and 2, the input gear 102 may have a substantially uniform outer diameter, at least at the portions of the input gear 102 that contact the first output gear 106 and the intermediate gear 112. Additionally, in some embodiments, the first and second output gears 106 and 108 may have different outer diameters, such as where the first output gear 106 has a larger outer diameter than the second output gear 108. Among other things, this may allow the intermediate gear 112 to be positioned partially over the first output gear 106 in the view illustrated in [Fig.l], which may help reduce the overall size of the gear train 100.That is, when the gear train 100 is viewed from a direction parallel to the axes of the input and output shafts 104 and 110, a portion of the intermediate gear 112 may overlap a portion of the first output gear 106. However, the actual sizes of the gears 102, 106, 108, 112 may vary depending on a number of factors.

[0021] FIGURES 3 and 4 illustrate exemplary operations of the bidirectional to unidirectional gear train 100 according to the present invention. As illustrated in [Fig. 3], the input shaft 104 rotates clockwise, which causes the input gear 102 to rotate clockwise as well. This clockwise rotation of the input gear 102 causes the first output gear 106 to rotate counterclockwise. This clockwise rotation of the input gear 102 also causes the gear 112 to rotate counterclockwise, which causes the second output gear 108 to rotate clockwise. The opposite directions of rotation of the output gears 106 and 108 (which are coupled to the same output shaft 110) are accommodated using the one-way clutches 116 and 118.More specifically, the one-way clutch 116 is engaged and the one-way clutch 118 is disengaged here, allowing the first output gear 106 to rotate the output shaft 110 counterclockwise. The second output gear 108 can continue to rotate clockwise, but the one-way clutch 118 prevents the second output gear 108 from driving the output shaft 110 to rotate.

[0022] As illustrated in [Fig.4], the input shaft 104 rotates counterclockwise, which causes the input gear 102 to rotate counterclockwise as well. This counterclockwise rotation of the input gear 102 causes a clockwise rotation of the first output gear 106. This counterclockwise rotation of the input gear 102 also causes a clockwise rotation of the gear 112, which causes the second output gear 108 to rotate clockwise. Again, the opposite directions of rotation of the output gears 106 and 108 (which are coupled to the same output shaft 110) are accommodated using the one-way clutches 116 and 118.More specifically, the one-way clutch 118 is engaged and the one-way clutch 116 is disengaged here, allowing the second output gear 108 to rotate the output shaft 110 counterclockwise. The first output gear 106 can continue to rotate clockwise, but the one-way clutch 116 prevents the first output gear 106 from driving the output shaft 110 to rotate.

[0023] Accordingly, the output shaft 110 can rotate counterclockwise regardless of the direction of rotation of the input shaft 104. It should be noted, however, that the direction of rotation of the output shaft 110 can be clockwise using appropriate modifications of the design of the gear train 100, for example by reversing the directions in which the one-way clutches 116 and 118 engage and disengage.

[0024] Although FIGURES 1 and 2 illustrate an example of a bidirectional to unidirectional gear train 100 and FIGURES 3 and 4 illustrate examples of operation of the bidirectional to unidirectional gear train 100, various modifications may be made to FIGURES 1-4. For example, the sizes of various gears 102, 106, 108, 112 in the gear train 100 may be set or adjusted to provide the desired gear ratios in the gear train 100. In addition, the one-way clutches 116 and 118 may be configured to engage and disengage in the desired directions to impart the desired rotation to the output shaft 110.

[0025] FIGURES 5-7 illustrate an exemplary system 500 that integrates multiple bidirectional to unidirectional gear trains 100 according to the present invention. As shown in FIGURES 5 and 6, the system 500 includes a pair of generators 502 and 504 and an accessory gearbox 506. The accessory gearbox 506 represents a structure used with an aircraft engine to drive various accessories associated with an aircraft or the aircraft engine. In this example, the accessory gearbox 506 includes a rotating shaft 602, which is used to drive the generators 502 and 504. In some embodiments, the generators 502 and 504 may represent turbomachinery, such as electric generators with integrated or coupled oil pumps. As a particular example, each of the generators 502 and 504 may include an oil pump connected to an electric generator.

[0026] As can be seen here, shaft 602 can be designed to rotate in only one direction, which in this example is counterclockwise in the views illustrated in FIGURES 5 and 6. Accordingly, shaft 602 (which represents an input shaft for each generator 502 and 504) has opposite directions of rotation from the perspective of generators 502 and 504. That is, when viewing generator 502 from one perspective along shaft 602, shaft 602 rotates counterclockwise relative to generator 502. Whereas when viewing generator 504 from the same perspective along shaft 602, shaft 602 rotates clockwise relative to generator 504.

[0027] As noted above, one approach to handling these opposite rotation directions may be to use separate distinct designs for generators 502 and 504. However, this increases development and recurring costs and requires the use of separate hardware. Therefore, this approach could require keeping different components in stock and could lead to a generator being mistakenly installed in an unusable position.

[0028] As illustrated in [Fig. 7], each generator 502 and 504 may comprise or be coupled to an instance of the gear train 100, where the input shaft 104 represents or is coupled to the rotating shaft 602. Each generator 502 and 504 in this example comprises an electrical generator formed using a rotor 702 and a stator 704. The output shaft 110 of the associated gear train 100 may cause the rotor 702 to rotate, causing the stator 704 to generate electrical power 706. The output shaft 110 may also be coupled to and drive an oil pump 708. This arrangement can be replicated in both generators 502 and 504, allowing each generator 502 and 504 to drive its associated oil pump 708 in the same direction of rotation, independently of the generators 502 and 504 of the two input shafts 104 of the gear trains 100.

[0029] By incorporating an instance of the gear train 100 described above into each generator 502 and 504, the generators 502 and 504 can have a common design regardless of the direction of rotation of the shaft 602 relative to the generators 502 and 504. Therefore, the gears 100 in the generators 502 and 504 allow a single design to be used, which can reduce development costs and recurring costs since it allows common hardware to be used. This can also reduce potential installation errors, since it does not matter which device is installed on the left and right sides of the shaft 602. In other words, the generators 502 and 504 are interchangeable.Additionally, when generators 502 and 504 represent electrical generators with integrated or coupled oil pumps 708, it becomes possible to adjust the pump flow rates higher or lower for different rotation directions of shaft 602 if necessary or desired. As a particular example, if one generator 502 or 504 has higher losses or is otherwise less efficient compared to the other generator 504 or 502 due to the difference in input rotation direction, the gear ratios of the less efficient generator 502 or 504 may be adjusted to rotate its oil pump 708 at a higher speed (to compensate for its lower efficiency and provide better cooling).

[0030] Although FIGURES 5-7 illustrate an example of a system 500 that incorporates multiple bidirectional to unidirectional gear trains 100, various modifications may be made to FIGURES 5-7. For example, one or more instances of the bidirectional to unidirectional gear train 100 may be used with any other suitable mechanical device and in any other suitable system.

[0031] It may be advantageous to establish the definitions of certain words and expressions used in this patent document. The terms "include" and "comprise", as well as their derivatives, mean inclusion without limitation. The term "or" is inclusive, meaning and / or. The phrase "associated with," and its derivatives, can mean to comprise, be comprised in, interconnect with, contain, be contained in, connect to or with, couple to or with, be communicable with, cooperate with, intertwine, juxtapose, be close to, be related to or with, have, have a property of, have a relationship to or with, or the like. The phrase "at least one of," when used with a list of items, means that different combinations of one or more of the listed items may be used, and that only one item from the list may be necessary. For example, "at least one of: A, B, and C" involves any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C.

[0032] The description in the present invention should not be construed to imply that any particular element, step, or function is an essential or critical element that must be included within the scope of the claim. The scope of the patented subject matter is defined solely by the allowed claims. Furthermore, none of the claims invoke 35 USC § 112(f) with respect to any of the appended claims or claim elements unless the exact words “means to” or “step to” are explicitly used in the particular claim, followed by a participle phrase identifying a function.The use of terms such as (but not limited to) "mechanism," "module," "device," "unit," "component," "element," "member," "apparatus," "machine," "system," "processor," or "control device" in a claim is understood and intended to refer to structures known to those skilled in the art, as modified or improved by the features of the claims themselves, and is not intended to invoke 35 USC§ 112(f).

[0033] Although this disclosure has described certain embodiments and generally associated methods, modifications and permutations of these embodiments and methods will be apparent to those skilled in the art. Accordingly, the above description of exemplary embodiments does not define or restrict this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of the present disclosure, as defined by the following claims.

Claims

Claims

1. An apparatus comprising: a gear train (100) comprising: - an input gear (102) configured to be rotated by an input shaft (104); - first and second one-way clutches (116, 108); - first and second output gears (106, 108) configured to drive rotation of an output shaft (110) via the first and second one-way clutches (116, 118), respectively, the second output gear (108) having a smaller outer diameter than the first output gear (106); and - an intermediate gear (112); wherein the input gear (102) is configured to (i) rotate the first output gear (106) in a first direction and (ii) rotate the intermediate gear (112) in the first direction; wherein the intermediate gear (112) is configured to rotate the second output gear (108) in a second direction opposite to the first direction;and wherein the first and second one-way clutches (116, 118) are configured to allow the first and second output gears (106, 108) to drive rotation of the output shaft (110) in a single predetermined direction of rotation, regardless of the direction of rotation of the input shaft (104).;

2. The apparatus of claim 1, wherein: the input shaft (104) is configured to rotate clockwise or counterclockwise; and the gear train (100) is configured to cause the output shaft (110) to rotate in the predetermined single rotational direction when the input shaft (104) rotates clockwise and when the input shaft (104) rotates counterclockwise.

3. The apparatus of claim 1 or 2, wherein a portion of the intermediate gear (112) overlaps a portion of the first output gear (106) when the gear train (100) is viewed from a direction parallel to an axis of the output shaft (110).

4. The apparatus of one of claims 1 to 3, wherein: the first one-way clutch is configured to engage when the first output gear (106) rotates in one of the first and second directions and to disengage when the first output gear (106) rotates in the other of the first and second directions; and the second one-way clutch is configured to engage when the second output gear (108) rotates in one of the first and second directions and to disengage when the second output gear (108) rotates in the other of the first and second directions.

5. The apparatus of one of claims 1 to 4, wherein: the gear train (100) is part of or coupled to a generator (502, 504); and the generator (502, 504) is coupled to a rotating shaft (602) forming part of an aircraft accessory gearbox (506).

6. The apparatus of claim 5, wherein the gear train (100) is configured to cause the output gear to rotate in the predetermined single rotational direction, regardless of whether the generator (502, 504) receives a first rotational input from a first end of the rotating shaft (602) or a second rotational input from a second end of the rotating shaft (602).

7. The apparatus of one of claims 1 to 6, wherein: the gear train (100) is part of or coupled to a generator (502, 504); the generator (502, 504) comprises: an electric generator; and an oil pump (708) coupled to or integral with the electric generator; and the output shaft (110) is configured to drive the electric generator and the oil pump (708).

8. A system (500) comprising: a rotating shaft (602) having a first end and an opposite second end; a first apparatus according to one of claims 1 to 7, configured to receive a first rotary input from the first end of the rotating shaft (602); and a second apparatus according to one of claims 1 to 7, configured to receive a second rotary input from the second end of the rotary shaft (602), the second rotary input being opposite the first rotary input; wherein the first and second apparatuses respectively comprise first and second gear trains (100), the input gear (102) of each of the first and second gear trains (100) being configured to be rotated by an input shaft (104) formed by the rotary shaft (602);wherein wherein the input gear (102) of the first gear train (100) is configured to (i) rotate the first output gear (106) of the first gear train (100) in a first direction and (ii) rotate the intermediate gear (112) of the first gear train (100) in the first direction, and wherein the intermediate gear (112) of the first gear train (100) is configured to rotate the second output gear (108) of the first gear train (100) in a second direction opposite to the first direction;wherein the input gear (102) of the second gear train (100) is configured to (i) rotate the first output gear (106) of the second gear train (100) in the second direction and (ii) rotate the intermediate gear (112) of the second gear train (100) in the second direction, and wherein the intermediate gear (112) of the second gear train (100) is configured to rotate the first output gear (106) of the second gear train (100) in the first direction.;

9. The system of Claim 8, wherein: the first and second apparatuses comprise first and second generators (502, 504); and the rotating shaft (602) is part of an aircraft accessory gearbox (506).

10. The system of Claim 8 or 9, wherein each of the first and second apparatuses comprises: an electric generator (502, 504); and an oil pump (708) coupled to or integral with the electric generator (502, 504).

11. A system according to any one of claims 8 to 10, wherein: the rotating shaft (602) is configured to rotate clockwise relative to the first mechanical device and counterclockwise relative to the second mechanical device; and the first and second gear trains (100) of the first and second apparatuses are configured to cause the two output shafts (110) to rotate in the single predetermined rotation direction when the rotating shaft (602) rotates clockwise and when the rotating shaft (602) rotates counterclockwise.

12. The system of any one of claims 8 to 11, wherein in each of the first and second gear trains (100), the second output gear (108) of the gear train (100) has a smaller outer diameter than the first output gear (106) of the gear train (100).

13. The system of claim 12, wherein in each of the first and second gear trains (100), a portion of the intermediate gear (112) of the gear train (100) overlaps a portion of the first output gear (106) of the gear train (100) when the gear train (100) is viewed from a direction parallel to an axis of the associated output shaft (110).

14. The system of any one of claims 8 to 13, wherein: the first one-way clutch of each gear train (100) is configured to engage when the first output gear (106) of the gear train (100) rotates in one of the first and second directions and to disengage when the first output gear (106) of the gear train (100) rotates in the other of the first and second directions; and the second one-way clutch of each gear train (100) is configured to engage when the second output gear (108) of the gear train (100) rotates in one of the first and second directions and to disengage when the second output gear (108) of the gear train rotates in the other of the first and second directions.

15. The system of any one of claims 8 to 14, wherein the first and second mechanical devices are interchangeable.

16. A method comprising: transmitting a rotational input to an input gear (102) of a gear train (100) using an input shaft (104); and rotating an output shaft (110) using first and second output gears (106, 108) of the gear train (100) respectively via first and second one-way clutches (116, 118) and an intermediate gear (112) of the gear train (100); wherein the input gear (102) (i) rotates the first output gear (106) in a first direction and (ii) rotates the intermediate gear (112) in the first direction; wherein the intermediate gear (112) rotates the second output gear in a second direction opposite to the first direction;wherein the first and second one-way clutches (116, 118) are configured to allow the first and second output gears (106, 108) to drive rotation of the output shaft (110) in a single predetermined direction of rotation, regardless of the direction of rotation of the input shaft (104); and wherein the second output gear (108) has a smaller outer diameter than the first output gear (106).;

17. The method of Claim 16, wherein: the gear train (100) represents a first gear train (100); and the method also comprises: transmitting a rotary input to an input gear (102) of a second gear train (100), the rotary input to the input gear (102) of the second gear train (100) being opposite to the rotary input to the input gear (102) of the first gear train (100); and rotating another output shaft (110) using first and second output gears (106, 108) of the second gear train (100) respectively via first and second one-way clutches (116, 118) and an intermediate gear (112) of the second gear train (100).

18. A method according to Claim 16 or 17, wherein: the gear train (100) is part of or coupled to a generator; and transmitting the rotary input to the input gear (102) comprises transmitting the rotary input to the input gear (102) based on rotation of a rotary shaft (602) forming part of an aircraft accessory gearbox (506).

19. The method of Claim 18, wherein: the generator comprises an electric generator and an oil pump coupled to or integral with the electric generator; and the output shaft (100) drives the electric generator and the oil pump.

20. A method according to any one of Claims 16 to 19, wherein: the input shaft (104) is configured to rotate clockwise or counterclockwise; and the gear train (100) causes the output shaft (110) to rotate in the predetermined single rotational direction when the input shaft (104) rotates clockwise and when the input shaft (104) rotates counterclockwise.

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