Torque transfer coupling and tool for assembly thereof

A tool for installing segments of a coupling having male and female couplers drivingly engaged to one another by the segments, the tool has: a coupler-engaging section engageable to the a female coupler of the couplers for radially supporting the tool relative to the female coupler about a rotation axis of the coupling; and a peripheral wall secured to the coupler-engaging section and extending circumferentially around the rotation axis, a diameter (D2) of the peripheral wall selected to allow insertion of the segments between the female coupler and the peripheral wall, the peripheral wall defining an abutting surface against which radially inner ends of the segments abut during insertion of the segments between the female coupler and the peripheral wall.

TECHNICAL FIELD

The application relates generally to aircraft engines, such as gas turbine engines, and, more particularly, to systems and methods used to transfer torque between two components of said engines.

BACKGROUND OF THE ART

Couplings are used in a wide variety of applications to transfer torque from one rotary component (such as a shaft) of one piece of equipment to a rotary component of another. Common considerations in coupling design include achieving satisfactory dynamic stress resistance and low friction in operating conditions varying across the operation envelope, as well as limiting costs. In aeronautic applications, minimizing weight is also typically a significant design consideration. The individual pieces of equipment can be manufactured separately. Many couplings require to align the axes of the two rotary components within a certain degree of tolerance, to a point which can be difficult or challenging to achieve in practice, and increasing the degree of tolerance to misalignment has represented significant trade-offs or sacrifices on at least some of the design considerations. There always remains room for improvement, such as addressing misalignment tolerance considerations.

SUMMARY

A tool for installing segments of a coupling having couplers drivingly engaged to one another by the segments, the tool comprising: a coupler-engaging section engageable to a female coupler of the couplers for radially supporting the tool relative to the female coupler about a rotation axis of the coupling; and a peripheral wall secured to the coupler-engaging section and extending circumferentially around the rotation axis, a diameter (D2) of the peripheral wall selected to allow insertion of the segments between the female coupler and the peripheral wall, the peripheral wall defining an abutting surface against which radially inner ends of the segments abut during insertion of the segments between the female coupler and the peripheral wall.

In some embodiments, the diameter (D2) of the peripheral wall is greater than a diameter (D1) of a peripheral wall of the female coupler minus two times a length of the segments defined between opposed radial ends of the segments such that the radially inner ends of the segments are circumferentially offset from radially outer ends of the segments.

In some embodiments, the coupler-engaging section defines a cylindrical member receivable within a central bore of the female coupler.

In some embodiments, the peripheral wall defines a plurality of sockets distributed circumferentially around the rotation axis, the plurality of sockets sized to accept the radially inner ends of the segments.

In some embodiments, a handle protrudes from the peripheral wall and away from the coupler-engaging section.

In some embodiments, the tool is made of a material having a hardness being less than that of a material of the female coupler.

In some embodiments, the coupler-engaging section is sized to be engaged to the female coupler via an intermediary component.

In some embodiments, the intermediary component is an anti-rotation nut secured to the female coupler, the coupler-engaging section is sized to be received within a bore defined through the anti-rotation nut.

In another aspect, there is provided a kit comprising the tool as described above; and the segments.

In yet another aspect, there is provided a method of assembling a coupling having a female coupler, a male coupler, and segments for engaging the female coupler to the male coupler, comprising: engaging a tool inside the female coupler to radially support the tool relative to the female coupler; inserting the segments between a peripheral wall of the female coupler and the tool, the tool radially supporting inner ends of the segments; and removing the tool and engaging the male coupler to the segments.

In some embodiments, the engaging of the tool includes inserting a coupler-engaging section of the tool inside a bore of the female coupler.

In some embodiments, the inserting of the segments between the peripheral wall of the female coupler and the tool includes inserting the segments between the peripheral wall and the tool having a diameter (D2) greater than a diameter (D1) of the peripheral wall of the female coupler minus two times a length of the segments defined between opposed radial ends of the segments.

In some embodiments, the inserting of the segments includes angling the segments such that the segments are non-parallel relative to a radial direction relative to a rotation axis of the coupling.

In some embodiments, the inserting of the segments includes sliding the inner ends of the segments into correspondingly shaped sockets defined by the tool.

In some embodiments, the tool is rotated until a first segment of the segments is receivable within first connections of the female coupler and within a first socket of the sockets of the tools.

In some embodiments, the rotating of the tool includes rotating the tool after the tool is engaged inside the female coupler.

In some embodiments, the inserting of the segments includes inserting retaining tabs of the segments within gaps defined between the peripheral wall of the female coupler and a retaining ring.

In some embodiments, the removing of the tool includes pulling on the tool in an axial direction relative to a rotation axis of the coupling.

In some embodiments, the segments is radially locked relative to the female coupler before the removing of the tool.

In some embodiments, the radially locking of the segments includes radially locking the segments with a retaining ring abutting retaining tabs of the segments.

DETAILED DESCRIPTION

FIG.1illustrates an aircraft engine depicted as a gas turbine engine10of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication a fan12through which ambient air is propelled, a compressor section14for pressurizing the air, a combustor16in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section18for extracting energy from the combustion gases. The fan12, the compressor section14, and the turbine section18are rotatable about a central axis11of the gas turbine engine10. In the embodiment shown, the gas turbine engine10comprises a high-pressure spool having a high-pressure shaft20drivingly engaging a high-pressure turbine18A of the turbine section18to a high-pressure compressor14A of the compressor section14, and a low-pressure spool having a low-pressure shaft21drivingly engaging a low-pressure turbine18B of the turbine section to a low-pressure compressor14B of the compressor section14and drivingly engaged to the fan12. It will be understood that the contents of the present disclosure may be applicable to any suitable engines, such as turboprops and turboshafts, and reciprocating engines, such as piston and rotary engines without departing from the scope of the present disclosure.

In the embodiment shown, the low-pressure shaft21is drivingly engaged to an accessory22. The accessory may be, for instance, a generator, a gearbox, a pump, and so on. In the present case, a coupling30is used to transmit a rotational input from the low-pressure shaft21to the accessory22. The coupling30may allow the removal of the accessory22, either for maintenance or for substitution for another accessory. The coupling30is further described in U.S. patent application Ser. No. 17/022,203 filed on Sep. 16, 2020, the entire contents of which are incorporated herein by reference in their entirety.

Referring toFIGS.2-3, the coupling30is described in more details. In the embodiment shown, the coupling30has two rotary members32,34, presented here in the form of shafts, and is used generally for the function of transferring torque from one of the rotary members32to the other34. Each of the two rotary members32,34is connected to a respective one of a female coupler31and a male coupler33. There can be some degree of misalignment (e.g. angle α) which may need to be accommodated between the axes of these rotary members32,34. The rotary member32may be drivingly engaged to the low-pressure shaft21via a spline coupling. Other couplings are contemplated. In some embodiments, the rotary member32may be made monolithic with the low-pressure shaft21.

In the embodiment shown, the female coupler31defines a recess36that is circumscribed by a peripheral wall35extending around a rotation axis of the coupling30, which, in the present case, corresponds to the central axis11. The rotation axis may be different than the central axis11in some embodiments. The peripheral wall35forms a radially inner-facing surface that will be referred to herein as more concisely as the inner face38. The male coupler33has a peripheral wall37extending around the rotation axis11. The peripheral wall37forms a radially outer-facing surface, or outer face40, that is received into the recess36. The outer face40has a smaller diameter than the inner face38, and a spacing42is present between the inner face38and the outer face40. The peripheral wall35of the female coupler31defines a plurality of connections35A. The peripheral wall37of the male coupler33defines a plurality of connections37A. In the present embodiment, these connections35A,37A are sockets having a substantially cylindrical shape and are interspaced with ridges or crests35B,37B. Other shapes are contemplated.

A plurality of circumferentially arranged links or segments44occupy the spacing42. Each segments44has an radially inner end46connected to the inner face38, and an radially outer end48connected to the outer face40. The inner end46is engaged to a respective one of the connections37A of the peripheral wall37of the male coupler33. The outer end48is engaged to a respective one of the connections35A of the peripheral wall35of the female coupler31. A shape of the radially inner end46and of the radially outer end48are selected to matingly engage the connections35A,37A. The connections35A,37A are used to prevent the radially inner end46and the radially outer end48from circumferentially sliding along the inner face38and the outer face40they are connected to, and thereby fix the relative circumferential position between the inner end46and the outer end48. The connection can be pivotal, rigid, or pivotal with a partial rigidity. Different types of connections can be used in different embodiments. Depending of the exact choice of connection type, the segment-receiving connections formed in the inner face and the outer face can involve a corresponding form of irregularity in the surface geometry. The irregularity can be in the form of a seat such as a protrusion, recess, or other shape complementary to the shape of the corresponding end, or in the form of a slot or hole to receive a pivot pin, to name some possible examples. The segments extend obliquely, in the sense that the general orientation L of their length between the inner end46and the outer end48is inclined, or slanted, e.g. by angle β, from the radial orientation R. In other words, the outer end of each segment is circumferentially offset from the segment's inner end by an arc A. In other the radially inner end46is circumferentially offset from the radially outer end48relative to the rotation axis A1.

In the embodiment shown, the segments44are pivotally engaged within their connections35A,37A. The pivotal connections may be provided via engagement between rounded ends of the segments44and the matching connections35A,37A in the form of rounded sockets in the inner face38and the outer face40. In an alternate embodiment, for instance, the pivotal connection can be achieved via an axially protruding pin in each one of the ends, and a corresponding slot to receive the pin tips on both axial sides of the segment, for instance. In still another embodiment, the connections can be provided in the form of rounded protrusions formed in the corresponding one, or both, of the inner face and the outer face, and a rounded recess of a matching shape can be formed in the corresponding end or ends of the segment, thereby inversing the male/female roles, to name another possible example.

In some embodiments, connections which allow for pivoting of the segments around one or both ends can be preferred, whereas in other embodiments, non-pivotal, or partially pivoting connections which cause bending deformation in the segment in addition to compressive stress may be preferred. The connections which are part of the male member may be referred to as the male member connections and the connections which are part of the female member can be referred to as the female member connections for simplicity.

The segments44are configured to work in compression during torque-transfer operation, and transfer torque by a combination of their compression stress (there can also be some degree of bending stress if the connection is not purely pivotal) and of their inclination/obliqueness β. In an embodiment where the female coupler31is the driving member, the inner end46of each segments44will be circumferentially offset from the outer end48in the direction of the torque T, which results in compressing the segments44. In an alternate embodiment where the male coupler33is the driving member, the outer ends48of the segments44would instead be circumferentially offset from the inner ends46in the direction of application of the torque T, which would also result in compressing the segments during torque transfer. Accordingly, the direction in which the inner ends46are circumferentially offset from the outer ends48may be selected as a function of the orientation of the torque T, and of whether the female coupler31or the male coupler33is the driving member, with the goal of subjecting the segments to compression during torque transfer.

The segments44may be configured in a manner to operate collectively, but as independent bodies from the point of view of stress gradients. The segments44may be separate individual components, mechanically connected to one another only indirectly, via the male coupler33and the female coupler31. By operating partially or fully in compression, and by being shaped and sized appropriately, they may each independently transfer a portion of the torque, without individually imparting shear or tensile stress into an adjacent segment. They may be relatively slender (i.e. thin in the orientation normal to their length in a transverse plane), which can allow them to elastically deform to a greater extend than, thicker components, or than a component forming a full annulus. This may contribute in accommodating a satisfactory degree of axial misalignment a between the male coupler33and the female coupler31. Moreover, the segments44can have an axial dimension, referred to herein as width W, which is significant relative to their length, such as in the same order of magnitude, similar or greater dimensions, to spread the compressive force along the width W. Spreading a given amount of compressive force (stemming from a given amount of torque T) along a greater width W, can limit the compressive force density, and allow a greater amount of torsion between the two axially opposite sides. In some embodiments, the torsion deformation capability of the segments can be harnessed to accommodate misalignment. In yet some other embodiments, it can be preferred to segment the segments into two or more components along their axial length, allowing the individual components to work independently from another, without transmitting torsion stress from one component of the segment to the adjacent other one. The width W can be significantly greater than the thickness, for instance. The coupling30can be designed in a manner for the full width to remain in contact with both of the female coupler31and the male coupler33due to deformation. The segments44can accommodate misalignment by deformation rather than by displacement relative to the members, which can be favorable from the point of view of wear resistance. In other embodiments it can be preferred to reduce the width W as much as possible in a manner to reduce weight, for instance.

In some embodiments, an even greater degree of axial misalignment may be accommodated by selecting, for the material of the segments44, a material having a Young's modulus significantly lower than the Young's modulus of the material forming the female coupler31and the male coupler33. For instance, in a scenario where the female coupler31and the male coupler33are made of steel, the segments can be made of a suitable plastic. A plastic material with greater viscoelastic behavior can be preferred to accommodate rapid overload, but may be less performant in terms of recovery factor at slower loading rates. Polyimide plastic materials such as Vespel™ may be an interesting candidate due to features such as heat resistance, and can have a Young's modulus two degrees or magnitude lower (˜100 times lower) than the Young's modulus of steel. Depending on the embodiment, other materials can be selected, such as other plastics, structured materials like metal foams, aerogels, and 3D-printed un-isotropic metal lattices which provide a low apparent Young modulus and even be more suitable at higher temperature environments. Similarly, lower cost materials than Vespel™ may be preferred in lower temperature environments.

Another potential reason for selecting a different material for the segments than for the male and female members is that it may be preferred for the material of the segment to have a greater coefficient of thermal expansion than the coefficient of thermal expansion of the male and female members. Indeed, in cases where the typical operation temperature range of the coupling is significantly above ambient temperature/standard atmospheric conditions, having a greater coefficient of thermal expansion can simplify assembly. Indeed, the length of the segments can be designed to be shorter that the distance between the members which they are designed to occupy during operation conditions. Accordingly, the segments can be inserted easily into the spacing, with some degree of play allowed at, say, 20° C., and be designed to grow and extend as the temperature rises during normal operation, in a manner to stabilize in an equilibrium configuration where the combination of thermal growth and deformation from mechanical stress lead to maintaining a given design slant angle β at a given set of conditions of torque and temperature, and depart from this target slant angle within set tolerances as the torque and temperature vary within the operation envelope. Similarly, and the thermal “shrinking” can be harnessed at disassembly, to avoid the phenomena of worn parts becoming “hooked” on others, especially in blind assemblies.

The slant angle β can also affect the density of the compressive stress. In one embodiment, it can be preferred to optimize the slant angle β in a manner to minimize compressive stress density. In a scenario where it is also preferred to limit backlash to within 2 degrees, it can be preferred to select a slant angle of between 52 and 60 degrees measured from the outer pitch diameter tangent, with the range of between 54 and 58 degrees being more preferred in some embodiments. The ideal slant angle can be of 55 degrees in one embodiment, for instance. In other words, the angle β can be of between 30 and 38 degrees, preferably between 32 and 36, and ideally of about 35 degrees.

Referring more particularly toFIG.3, in the embodiment shown, the segments44extend between a first axial end face41at a first axial end and a second axial end face43at a second axial end and opposite the first axial end face41. Each of the segments44includes each a first tab45axially protruding from the first axial end face41and away form the second axial end face43, and a second tab47axially protruding from the second axial end face43and away from the first axial end face41. The first tab45and the second tab47are engaged by a first retaining ring50and by a second retaining ring51of the female coupler31, respectively. The first tab45and the second tab47may be off-centered relative to a mid-plane intersecting both of inner ends46and outer ends48of the segments44and intersecting the first axial end face41and the second axial end face43. In other words, the segment44may be non-symmetric.

The peripheral wall35of the female coupler31defines notches. Namely, each of the crests35B defines a first notch35C and a second notch35D axially spaced apart form the first notch35C relative to the rotation axis A1. The first notch35C is sized to receive the first retaining ring50. The second notch35D is sized to receive the second retaining ring52. The first tab45is disposed radially between the first retaining ring50and the peripheral wall35of the female coupler31. The second tab47is disposed radially between the second retaining ring51and the peripheral wall35of the female coupler31. The first retaining ring50and the second retaining ring51bias the first tab45and the second tab47radially outwardly against the peripheral wall35and are used to maintain the segments44in engagement within their connections35A.

Referring now toFIG.4, in the embodiment shown, the female coupler31may be splined to the low-pressure shaft21and retained engaged to the low-pressure shaft21via a bolt60. A threading engagement may be defined between the female coupler31and the bolt60. To prevent the bolt60from unthreading, an anti-rotation nut61is engaged to both of the bolt60and the female coupler31. The anti-rotation nut61has a first section61A received radially between the female coupler31and the bolt60and a second section61B that axially abuts against the bolt60. The second section61B defines one or more locking tab(s)61C that is axially received within a correspondingly shaped slot31S defined by the female coupler31. Hence, the anti-rotation nut61is non-rotatable relative to the female coupler31. The female coupler31defines an annular groove31G sized to accept a snap ring (not shown) to axially lock the anti-rotation nut61to the female coupler31. The anti-rotation nut61defines a bore61D.

In some cases, for instance when the central axis11of the gas turbine engine10is substantially parallel to a ground, it may be difficult to insert the segments44without them falling down by gravity. A tool70is being described herein and may be used to assemble the segments44during an assembly process. The tool70described below may at least partially alleviate these drawbacks.

Referring now toFIGS.5-6, the tool70has a fore section71, also referred to as a coupler-engaging section, that is used for securing the tool70to the female coupler31. In the embodiment shown, the fore section71is cylindrically shaped and is sized to be received within the bore61D of the anti-rotation nut61. Peripheral walls of the fore section71and of the bore61D may contact each other such that the tool70may remain substantially immobile relative to the female coupler31by itself thanks to the cooperation of the fore section71and the bore61D. A tight fit may be provided therebetween. It will be appreciated that the tool70may include any suitable means for supporting the tool relative to the female coupler31about a rotation axis of the coupling30without departing from the scope of the present disclosure. For instance, the tool may define one or more prongs receivable within the slots31S of the female coupler31, a shaft section receivable within an aperture of the female coupler31or within a hollow passage of a shaft to which the female coupler31is engaged. In some cases, the tool may engage an outer face of the female coupler31.

In the embodiment shown, the tool70includes a handle72via which a user can manipulate the tool to insert the fore section71inside the female coupler31. The fore section71and the handle72are located at opposite side of a central section73of the tool70. In the depicted embodiment, the central section73is sized to axially overlap the peripheral wall35of the female coupler31. The central section73has a peripheral wall73A that defines connections73B, shown as sockets, that have shapes that substantially correspond to the shape of the connections37A defined by the peripheral wall37of the male coupler33. Hence, the tool70is used to simulate the presence of the male coupler33to ease assembly of the segments44.

The peripheral wall73A of the tool70is therefore used as an abutting surface against which the radially inner ends46rest after their outer ends48they have been inserted into the connections35A of the peripheral wall35of the female coupler31. In one variant, the central section73of the tool70may be a cylinder against which the inner ends46of the segments44rest. In other words, the central section73of the tool70need not define sockets or connections.

As shown inFIG.5, in the embodiment shown, to properly angle the segments44for subsequent insertion of the male coupler33, a diameter D2 of the peripheral wall73A of the central section73of the tool70is greater than a diameter D1 of the peripheral wall35of the female coupler31minus two times a length of the segments44. This may ensure that the segments44are non-parallel to a radial direction relative to the central axis11and that the outer ends48of the segments are circumferentially offset form the inner ends46of the segments44when they are inserted in to the connections35A of the female coupler31. In other words, this diameter D2 of the peripheral wall73A of the tool70may be selected such that the segments44have the desired angle that they will have when the male coupler33is engaged to the segments44. The length of the segments44extends from their inner ends46to their outer ends48. It will be appreciated that the diameters D1 and D2 are taken from deepest most locations of the connections or sockets. In other words, the diameters D1, D2 do not extend from the crests that bound the sockets, but extends from locations between the crests.

The tool70may be made of a material having a hardness being less than that of a material of the female coupler31. For instance, the female coupler31may be made of a metallic material whereas the tool70, or at least the peripheral wall73A of the tool70, may be made of plastic or any other suitable material sufficiently soft to avoid damaging the female coupler31. Different parts of the tool70(e.g., fore section71, handle72, and central section73) may be made of different material.

Referring now toFIGS.6-8, the steps used to assemble the couplings30are illustrated. As shown inFIG.6, the tool70is engaged to the female coupler31to radially support the tool relative to the female coupler31. As explained above, this may be done by moving the tool70along a first axial direction A1 relative to the central axis11and relative to the female coupler31. In the embodiment shown, the tool70is supported by the fore section71being received into the bore61D defined by the anti-rotation nut61. But, other means of radially supporting the tool70relative to the female coupler31are contemplated as explained above. Moreover, the tool70need not be directly engaged to the female coupler31and may be engaged to the female coupler31via an intermediary component, such as the anti-rotation nut61in the present embodiment.

As shown inFIG.7, once the tool70is in place, the segments44may be inserted into the connections35A of the female coupler31. The segments44may be moved in the first axial direction A1 relative to the female coupler31to insert the outer ends48into the connections35A. In the present case, the inner ends46are inserted into the connections73B that are defined by the central section73of the tool70. Because the length of the segments44between their inner ends46and outer ends48is greater than a distance along a radial direction relative to the central axis11between the tool70and the peripheral wall35of the female coupler31, the segments44may be angled to be non-parallel to the radial direction before being slid into the connections35A of the female coupler31and into the connections73B of the tool70. As explained above, the tool70need not define the connections73B and may define a cylindrical surface against which the inner ends46of the segments44may abut.

The first retaining ring50may be inserted into the corresponding notches defined by the peripheral wall35of the female coupler31before the tool70is engaged to the female coupler31. Hence, when the segments44are inserted into the connections35A, they may be inserted until the first tabs45of the segments44are received radially between the peripheral wall35of the female coupler31and the first retaining ring50.

As shown inFIG.8, once all of the segments44are in place within the connections35A of the female coupler31, the tool70may be disengaged. This may be done by moving the tool70along a second axial direction A2 being opposed to the first axial direction A1. In the present case, the second retaining ring51is inserted into the corresponding notches defined by the peripheral wall35of the female coupler31before the tool70is removed. However, in some cases, once all of the segments44have been inserted into the connections35A, they may cooperate with one another to radially maintain themselves radially relative to the female coupler31. Hence, in some cases, it may be possible to install the second retaining ring51after the tool30has been removed. In some cases, it may be possible to install a given number (e.g. half) of the segments and then remove the tool30. The segments installed may cooperate with one another to radially support one another.

Referring now toFIG.9, a process of assembling the coupling30is shown at900. The tool70is engaged inside the female coupler31to radially support the tool70relative to the female coupler31at904. The segments44are inserted between the peripheral wall35of the female coupler31and the tool70at904. As shown, the tool radially supports the inner ends46of the segments44. The tool70is removed and the male coupler33is engaged to the segments44at906.

In the embodiment shown, the engaging of the tool at902includes inserting the fore section71of the tool70inside the bore of the female coupler31. In the present case, this bore is defined by the anti-rotation nut61of the female coupler31. As illustrated inFIG.5, the inserting of the segments44between the peripheral wall35of the female coupler31and the tool70at904includes inserting the segments44between the peripheral wall35and the tool70having the diameter D2 greater than the diameter D1 of the peripheral wall35of the female coupler31minus two times a length of the segments44defined between the inner ends46and the outer ends48of the segments44. In some cases, the inserting of the segments at904may include angling the segments44such that the segments44are non-parallel relative to a radial direction relative to a rotation axis of the coupling30, which corresponds here to the central axis11of the gas turbine engine10. The inserting of the segments44at904may include sliding the inner ends46of the segments44into the sockets or connections73B defined by the tool70. Alternatively, the inner ends46of the segments44may be abutted against a cylindrical face of the tool. However, inserting the inner ends46of the segments44in the sockets that have shapes substantially matching a shape of the connections of the male coupler33may facilitate the assembly of the male coupler33at906.

The tool70may be rotated about the rotation axis until a first segment of the segments44is receivable within the connections35A of the female coupler31and within a first socket or connection73B of the connections73B of the tools70. The tool70may be rotated after the tool70is engaged inside the female coupler31.

As depicted inFIGS.3and7, the inserting of the segments44includes inserting the first tabs45of the segments44within gaps defined between the peripheral wall35of the female coupler31and the first retaining ring50.

As shown inFIG.8, the removing of the tool at906may include pulling on the tool in the second axial direction A2. The segments44may be radially locked relative to the female coupler31either before or after the removing of the tool70. In the present case, the segments44are radially locked before the tool is removed. Radially locking the segments44may include locking the segments44with the second retaining ring51abutting the second tabs47of the segments44.