Patent Description:
The present subject matter relates generally to a system and method for reducing edge contact stress concentrations in a press-fit, in particular for aeronautic applications, to which the following description refers, but without any loss of generality.

Epicyclic gearing is a widely used in the field of aeronautic engines for transmitting drive and converting power between a turbine engine and a propulsive element, such as a fan. The use of a gearbox with an epicyclic gearing arrangement allows the fan to be rotated at fewer revolutions per unit of time than the rotational speed of the low-pressure shaft of the engine, for greater efficiency. The gearbox rotatably supports a sun gear that is disposed centrally with respect to a ring gear and a plurality of planet gears mounted on a planet-carrier, which are disposed around the sun gear and engage between the sun gear and the ring gear. The low-pressure shaft provides the input to the epicyclic gearing arrangement, being coupled to the sun gear, while the fan is coupled to rotate in unison with the planet-carrier. Each planet gear meshes with the sun gear and with the ring gear, which is held stationary. The shaft of the fan is rotatable on its own bearing that is housed in a sun gear box, which is also called the fan gearbox, that is fixed to the rotationally central region of a carrier. Each planet gear is rotatable on a bearing mounted on a planet pin, which is fixed to the peripheral region of the carrier. <CIT> discloses an epicyclic gearing comprising: a plurality of planet gears circumferentially disposed about a transmission axis and operably coupled to a plurality of planet pins; a planet-carrier, the planet-carrier comprising: a side plate comprising a coupling portion for connecting the side plate to a rotating member or to a static structure, and a central ring coaxial to the side plate along the transmission axis, each planet pin of the plurality of planet pins being coupled to the central ring via a collar, the collar defining a collar axis and comprising an annular body having: a first radial contact face defining a collar outer diameter, the first radial contact face being configured to interface with a pin opening defined by the central ring, a second radial contact face disposed radially inward of the first radial contact face and defining a collar inner diameter centered about a collar axis, the second radial contact face being configured to accept one of the plurality of planet pins, and an axial face extending between the first radial contact face and the second radial contact face, the axial face facing the plurality of planet gears, the axial face defining frustoconical gap. If a predetermined load is reached then the pin will bend and frustoconical abutment surfaces will come into contact, limiting the extent to which the planet pin bends.

<CIT> relates to a journal pin for an epicyclic gear system. The journal pin has a hollow bore and a recessed wall that forms a plenum for delivering oil. <CIT> relates to a planetary gear system, comprising: a carrier body configured to receive planet gears; at least one pin received by said carrier body; and an insert positioned between said carrier body and said at least one pin.

For aviation applications, there is a continuing need to reduce the size and weight of gearboxes and gearbox components while also improving lifespan. Thus, the art is continuously seeking new and improved systems and methods that address the desire to reduce the size and weight of gearboxes. As such, an apparatus and method for reducing edge contact stress concentrations in a press-fit, would be beneficial.

Preferred embodiments are laid down in the dependent claims.

The present invention is directed to a epicyclic gearing for a gas turbine aviation engine according to claim <NUM>.

In an embodiment, the axial face may also include a first axial portion extending along the axial face between the second radial contact face and a first slope face of the channel. The first axial portion may have a first portion thickness. The axial face may also include a second axial portion extending along the axial face between the first radial contact face and a second slope face of the channel. The second axial portion may have a second portion thickness. The second portion thickness may be greater than the first portion thickness. In an additional embodiment, the channel may include a base portion disposed between the first slope face and the second slope face. The base portion may define a first angle relative to the second radial contact face which is less than <NUM>°. The first slope face may define a second angle relative to the second radial contact face which is less than the first angle.

In an additional embodiment, the axial face may be a first axial face at a first axial position. The press-for collar may also include a second axial face extending between the first radial contact face and the second radial contact face at a second radial actual position. The second axial face may define a recess circumscribing the collar axis.

In yet another embodiment, the central ring may include a groove circumscribing the collar axis.

In an additional embodiment, the plurality of planet pins may include at least five planet pins.

The invention is also directed to a method for reducing edge stress concentrations in a press-fit collar for an epicyclic gearing for a gas turbine aviation engine according to claim <NUM>.

In an additional embodiment, the method may also include calculating a first edge stress concentration along the first radial contact face. The method may include calculating a second edge stress concentration along the second radial contact face. Further, the method may include forming a base portion of the channel. The base portion may define a first angle relative to the second radial contact face which is less than <NUM>-degrees. The first angle may be set so as to transmit a portion of the second edge stress concentration radially outward from the radial contact face. The method may include forming a first slope face of the channel. The first slope face may define a second angle relative to the second radial contact face which is less than the first angle, the second angle being set so as to transmit a portion of the second edge stress concentration radially outward from the second radial contact face. The method may further include forming a second slope face of the channel. The second slope face may be disposed radially outward of the first slope face. The base portion may be disposed between the first slope face and a second slope face.

In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention, as defined by the appended claims.

An apparatus and method are generally provided for reducing edge contact stress concentrations in a press-fit. The press-fit collar and method of the present disclosure specifically provide for a press-fit collar for coupling a first component to a second component. The press-fit collar may define a collar axis and include an annular body (e. g, a cylindrical body). The annular body may have a first radial contact face which interfaces with the first component. This radial contact face may also define the outer diameter of the press-fit collar. The annular body may also have a second radial contact face which is radially inward of the first radial contact face. The second radial contact face may define an opening in the center of the annular body and the collar inner diameter. The body may be centered about a collar axis. The second radial contact face may interface with the second component. The contact faces may be joined by an axial face extending between them. The axial face may define a channel which circumscribes the collar axis. The channel may have an asymmetrical cross-sectional profile. The asymmetrical cross-sectional profile may reduce an edge contact pressure in a press-fit joint by directing the stress loads away from the contact faces.

For any given gas turbine engine application, the planet gears are designed to provide a set reduction ratio between the rotational speed of the low-pressure shaft and the rotational speed of the fan shaft. Because each epicyclic gearbox that houses the planet gears is disposed within the flow path of the gas turbine engine, the challenge is to design, on the one hand, a reliable and robust epicyclic gearbox that meets all flight conditions of the engine while, on the other hand, designing a epicyclic gearbox that is compact sufficiently to fit inside the flow path in a way that does not require the entire engine size to be larger and heavier than otherwise would be required in order to accommodate the epicyclic gearbox.

In certain applications, it may be desirable to have a high number of planet gears in the epicyclic gearbox. However, due to the gearbox size limitations described above, these planet gears may be relatively small and may provide a limited space for the planet pins. As a result, the planet pins may be relatively small and may develop high levels of edge contact pressure in the press-fit coupling with the planet carrier.

Reducing edge contact pressures in a press-fit may permit the use of smaller pins. This, in turn, may reduce the requirement to oversize other components. As a result, it may be possible to increase the number of press-fits which may be fitted into a given space or reduce the volume of space while retaining the ability to handle a certain load.

Referring now to the drawings, <FIG> illustrates a cross-sectional view of one embodiment of a gas turbine engine <NUM> that may be utilized with an aircraft for which the present invention can be applied, with the engine <NUM> being shown having a longitudinal or axial centerline axis <NUM> extending therethrough for reference purposes. The engine <NUM> will be discussed in detail below. Although shown as a turbofan jet engine, any suitable turbomachine can be utilized with the systems described herein. For example, suitable turbomachines include, but are not limited to, high-bypass turbofan engines, low-bypass turbofan engines, turbojet engines, turboprop engines, turboshaft engines, propfan engines, and so forth.

<FIG> illustrates a simplified view of an exemplary epicyclic gearing <NUM> and <FIG> depicts a cross-section view of a portion of the epicyclic gearing <NUM>. The exemplary epicyclic gearing <NUM> may be employed in applications wherein a relatively high torque capability is required from a gear train having a reduced volume. For example, the epicyclic gearing <NUM> may be employed in the gas turbine engine <NUM> to transfer a torque load from a low-pressure drive shaft <NUM> to a fan rotor <NUM>.

As depicted in <FIG>, the epicyclic gearing <NUM> includes a plurality of planet gears <NUM> which are arranged about a transmission axis (<FIG>, TA). The planet gears <NUM> are circumferentially disposed about the transmission axis (TA). Each of the planet gears <NUM> is operably coupled to a planet pin <NUM> and rotates about respective planet axis (PA). The planet pins <NUM> are coupled to a planet-carrier (carrier) <NUM>. The carrier <NUM> includes a side plate <NUM> (<FIG>) having a coupling portion for connecting the side plate to a rotating member or a static structure. The carrier <NUM> includes a central ring <NUM> (<FIG>). The central ring <NUM> is coaxial with the side plate to <NUM> along the transmission axis(TA). The planet pins <NUM> are coupled to the central ring <NUM> via a press-fit collar <NUM> (<FIG>).

In an embodiment, the planet gears <NUM> may mesh outwardly with the inner toothings <NUM> of a ring gear <NUM>. The planet gears <NUM> may also mesh inwardly with at least one sun gear(s) <NUM>. The sun gear <NUM> may be coaxial and fixed with respect to a shaft <NUM>. In at least one embodiment, the shaft <NUM> may correspond to the low-pressure drive shaft <NUM> of a gas turbine engine.

As shown in <FIG> for example, the planet pin(s) <NUM> may be hollow and generally cylindrical. A first end <NUM> of the planet pin(s) <NUM> may be coupled to the carrier <NUM> via a press/interference fit coupling <NUM>. A second end <NUM> of the planet pin(s) <NUM> may be engaged by a retainer <NUM>, which may be a threaded lock nut. The retainer <NUM> may facilitate securing the planet pin(s) <NUM> in position relative to the carrier <NUM>.

The planet pin(s) <NUM> may include a plurality of feed holes formed therein and extending radially therethrough, as the number and placement of these feed holes is conventional as far as the present invention is concerned, none of them is shown in the drawings herein. In operation, oil may be fed through the planet pin(s) <NUM> and through such feed holes to facilitate the rotation of the planet gears <NUM>.

In an embodiment, an outer surface <NUM> of the planet pin(s) <NUM> may be formed so as to define a plurality of bearing races <NUM>. However, it should be appreciated that the bearing races <NUM> may be a separate component which may be press-fitted to the outer surface <NUM> of the planet pin(s) <NUM>. The bearing races <NUM> may be defined by a pair of guide rails <NUM> which are spaced apart from each other, for example in an axial direction, and extend circumferentially around the planet axis (PA). The respective pairs of guide rails <NUM> may provide guiding surfaces for a respective roller cage <NUM>. Each bearing race <NUM> and the respective roller cage <NUM> may be configured to receive, and rotatably guide therein, a respective plurality of cylindrical rollers <NUM>. The cylindrical rollers <NUM> may facilitate the rotation of the planet gears <NUM> about the planet pins <NUM>. It should be appreciated that while described herein as a plurality of bearing races <NUM>, in some embodiments, a single bearing race <NUM> may be employed.

<FIG> illustrate embodiments of a press-fit coupling <NUM> including a press-fit collar <NUM>, as used for the epicyclic gearing of the present invention. As disclosed herein, the press-fit collar <NUM> may be utilized to couple a first component <NUM> to a second component <NUM>. According to the invention, the first component is the carrier <NUM> and the second component <NUM> is the planet pin <NUM> discussed herein.

According to the invention, the press-fit collar <NUM> defines a collar axis (CA) and an annular body <NUM>. The annular body <NUM> may be formed from a metallic alloy or other material having sufficient load carrying capability. For example the annular body <NUM> may be formed from a material have sufficient load bearing capacity to accept the loads which may be encountered in an epicyclic gearing <NUM> of a gas turbine engine <NUM>.

According to the invention, the annular body <NUM> includes a first radial contact face <NUM>. The first radial contact face <NUM> defines a collar outer diameter (D<NUM>). The first radial contact face <NUM> interfaces with the first component <NUM>. The first radial contact face <NUM> intefaces with a pin opening <NUM> defined by the central ring <NUM>. The radial contact face <NUM> interfaces with the first component <NUM> along substantially the entirety of an axial length (L) of the annular body <NUM>. It should be appreciated that the interface between the first component <NUM> and the first radial contact face <NUM> may be a frictional contact.

The annular body <NUM> includes a second radial contact face <NUM>. The second radial contact face <NUM> is disposed radially inward of the first radial contact face <NUM>. The second radial contact face <NUM> defines a collar inner diameter (D<NUM>). The collar inner diameter (D<NUM>) is centered about the collar axis (CA). The second radial contact face <NUM> interfaces with the second component <NUM>. The second radial contact face <NUM> accepts and secures the planet pin <NUM>. In an embodiment, the second radial contact face <NUM> may interface with the second component <NUM> along substantially the entirety of the axial length (L) of the annular body <NUM>. It should be appreciated that the interface between the second component <NUM> and the second radial contact face <NUM> may be a frictional contact.

As is depicted in <FIG>, the annular body <NUM> includes an axial face <NUM> extending between the first radial contact face <NUM> and the second radial contact face <NUM>. In an embodiment, the axial face <NUM> may be oriented toward a load acting on the second component <NUM>. The axial face <NUM> defines a channel <NUM> having an asymmetrical cross-sectional profile. As is particularly illustrated in <FIG> and <FIG>. The channel <NUM> circumscribes the collar axis (CA). The asymmetrical cross-sectional profile of the channel <NUM> is configured to reduce an edge contact pressure within the press-fit coupling <NUM>. In an embodiment, the geometry of the asymmetrical cross-sectional profile may permit at least a <NUM>% reduction in contact pressure relative to a press-fit collar lacking the channel <NUM>. For example, the geometry of the channel <NUM> may alleviate the contact pressure developed at the second radial contact face <NUM> by permitting the distribution of the loading developed therein to a greater portion of the press-fit collar <NUM>. This distribution may be attributable to an increase in the flexibility of the press-fit collar <NUM> resulting from the asymmetrical cross-sectional geometry of the channel <NUM> circumscribing the collar axis (CA). It should be appreciated that the cross-sectional profile of the channel <NUM> may lack a radial symmetry and/or an axial symmetry.

Referring particularly to <FIG> and <FIG>, in an embodiment, the press-fit collar <NUM> may include a first axial portion <NUM> extending along the axial face <NUM> between the second radial contact face <NUM> and a first slope face <NUM> of the channel <NUM>. The first axial portion <NUM> may define a first portion thickness <NUM>. Additionally, in an embodiment, the press-fit collar <NUM> may include a second axial portion <NUM> extending along the axial face <NUM> between the first radial contact face <NUM> and a second slope face <NUM> of the channel <NUM>. The second axial portion <NUM> may define a second portion thickness <NUM>. In an embodiment, the second portion thickness <NUM> may be greater than the first portion thickness <NUM>. It should be appreciated that the first axial portion <NUM>, being thinner than the second axial portion <NUM>, may result in a portion of the second radial contact face <NUM> having a flexibility which is greater than a maximal flexibility of the first radial contact face <NUM>. It should further be appreciated that the first axial portion <NUM> and the second axial portion <NUM> may be positioned at the same axial location.

In an embodiment, the channel <NUM> may also include a base portion <NUM> disposed between the first slope face <NUM> and the second slope face <NUM>. The base portion may define a first angle <NUM> relative to the second radial contact face <NUM>. The first angle <NUM> may be less than <NUM>-degrees. For example, in an embodiment, the first angle <NUM> may be greater than <NUM>-degrees and less than or equal to <NUM>-degrees. In an additional embodiment, the first angle <NUM> may be greater than <NUM>-degrees and less than <NUM>-degrees. In a further embodiment, the first angle <NUM> may be greater than or equal to <NUM>-degrees and less than or equal to <NUM>-degrees. Additionally, the first slope face <NUM> may define a second angle <NUM> relative to the second radial contact face <NUM> which is less than the first angle <NUM>. For example, in an embodiment, the second angle <NUM> may be less than <NUM>-degrees. In an additional embodiment, the second angle <NUM> may be greater than or equal to <NUM>-degrees and less than or equal to <NUM>-degrees. In a further embodiment, the second angle <NUM> may be greater than or equal to <NUM>-degrees and less than or equal to <NUM>-degrees.

It should be appreciated that the geometry of the asymmetrical cross-sectional profile of the channel <NUM> may be formed so that the second angle <NUM> is less than the first angle <NUM> and the first angle <NUM> is less than <NUM>-degrees. Such an asymmetrical cross-sectional profile may facilitate the transfer of contact stress concentrations from the second radial contact face <NUM> radially outward from the collar axis (CA). For example, the contact stress concentrations may be transferred from the first angle <NUM> toward a third angle <NUM> defined between the base portion <NUM> and the first radial contact face <NUM>. In an embodiment, the third angle <NUM> may be greater than <NUM>-degrees. Accordingly, in an embodiment, the angle formed between the base portion <NUM> and the first slope face <NUM> may be greater than the angle formed between the base portion <NUM> and the second slope face <NUM>. As such, the stress concentrations may be transferred from the first slope face <NUM>/base portion <NUM> angle toward the second slope face <NUM>/base portion <NUM> angle. Therefore, it should be appreciated that decreasing the magnitude of the second angle <NUM> may reduce contact stress concentrations along the second radial contact face <NUM>. Additionally, it should be appreciated that the second portion thickness <NUM> may be determined by establishing a fourth angle <NUM> between the second slope face <NUM> and the first radial contact face <NUM>.

Referring now to <FIG> and <FIG>, in an embodiment, the axial face <NUM> may be a first axial face located at a first axial position. In such an embodiment, the press-fit collar <NUM> may also include a second axial face <NUM> extending between the first radial contact face <NUM> and the second radial contact face <NUM>. The second axial face <NUM> may be located at a second axial position. The second axial face <NUM> may define a recess <NUM>. The recess <NUM> may circumscribe the collar axis (CA). In an embodiment, the recess <NUM> may be centered between the first radial contact face <NUM> and the second radial contact face <NUM>. The recess <NUM> may be configured to increase the flexibility of the press-fit collar <NUM> thereby reducing an edge contact stress concentration.

Referring now to <FIG>, in an embodiment, first component <NUM> may include a groove circumscribing the collar axis (CA). In such an embodiment, the groove <NUM> may be positioned radially outward of the press-fit collar <NUM>. The groove <NUM> may be oriented in the same axial direction has the channel <NUM>. In an embodiment, the groove <NUM> may have a maximal depth which is less than a maximal depth of the channel <NUM>. It should be appreciated that the groove <NUM> may facilitate a reduction in an edge contact stress concentration of the press-fit collar <NUM>.

Referring now to <FIG>, a flow diagram of a method <NUM> for reducing edge contact stress concentrations in the press-fit coupling <NUM> is presented. In general, the method <NUM> will be described herein with reference to the press-fit collar <NUM> shown in <FIG>. Although <FIG> depicts steps performed in a particular order for purposes of illustration and discussion, the methods discussed herein are not limited to any particular order or arrangement.

As shown in <FIG>, the method <NUM> includes at <NUM>, forming the channel having an asymmetrical cross-sectional profile circumscribing the collar axis in the axial face of the press-fit collar. The press-fit collar defines the collar axis and includes the annular body having the first radial contact face and the second radial contact face. The axial face extends between the first radial contact face and the second radial contact face. As shown at <NUM>, the method <NUM> includes pressing the press-fit collar into the opening defined by the first component so that the first radial contact face interfaces with the first component. As shown at <NUM>, the method <NUM> includes pressing the second component into the opening defined by the second radial contact face of the press-fit collar so that the second radial contact face interfaces with the second component thereby coupling the second component to the first component.

In an embodiment, forming the channel having the asymmetrical cross-sectional profile may include calculating a first edge stress concentration along the first radial contact face and a second edge stress concentration along the second radial contact face. The method may also include forming the base portion of the channel. The base portion may define the first angle relative to the second radial contact face which is less than <NUM>°. The first angle may be set so as to transmit a portion of the second edge stress concentration radially outward from the second radial contact face. The method may also include forming the first slope face of the channel. The first slope face may define the second angle relative to the second radial contact face which is less than the first angle. The second angle may be set so as to transmit a portion of the second edge stress concentration radially outward from the second radial contact face. The method may also include forming the second slope face of the channel. The second slope face may be disposed radially outward of the first slope face. The base portion may be disposed between the first slope face and the second slope face.

In an additional embodiment, forming the channel having the asymmetrical cross-sectional profile may also include defining the first axial portion extending along the axial face between the second radial contact face and the first slope face. The first axial portion may define a first portion thickness. The method may also include defining the second axial portion extending along the axial face between the first radial contact face and the second slope face. The second axial portion may define a second portion thickness which is greater than the first portion thickness. Additionally, the method may include positioning the channel at a location which results in a first portion thickness configured to reduce the edge contact stress concentration at the second radial contact face. Further, the method may include establishing the second portion thickness to reduce the stress concentration at the first radial contact face by setting the fourth angle between the second slope face and the first radial contact face.

Referring again to <FIG>, in general, the engine <NUM> may include a core gas turbine engine (indicated generally by reference character <NUM>) and a fan section <NUM> positioned upstream thereof. The core engine <NUM> may generally include a substantially tubular outer casing <NUM> that defines an annular inlet <NUM>. In addition, the outer casing <NUM> may further enclose and support a booster compressor <NUM> for increasing the pressure of the air that enters the core engine <NUM> to a first pressure level. A high-pressure, multi-stage, axial-flow compressor <NUM> may then receive the pressurized air from the booster compressor <NUM> and further increase the pressure of such air. The pressurized air exiting the high-pressure compressor <NUM> may then flow to a combustor <NUM> within which fuel is injected by a fuel system <NUM> into the flow of pressurized air, with the resulting mixture being combusted within the combustor <NUM>. The high energy combustion products are directed from the combustor <NUM> along the hot gas path of the engine <NUM> to a first (high-pressure, HP) turbine <NUM> for driving the high-pressure compressor <NUM> via a first (high-pressure, HP) drive shaft <NUM>, and then to a second (low-pressure, LP) turbine <NUM> for driving the booster compressor <NUM> and fan section <NUM> via a second (low-pressure, LP) drive shaft <NUM> that is generally coaxial with first drive shaft <NUM>. After driving each of turbines <NUM> and <NUM>, the combustion products may be expelled from the core engine <NUM> via an exhaust nozzle <NUM> to provide propulsive jet thrust.

It should be appreciated that each turbine <NUM>, <NUM> may generally include one or more turbine stages, with each stage including a turbine nozzle and a downstream turbine rotor. As will be described below, the turbine nozzle may include a plurality of vanes disposed in an annular array about the centerline axis <NUM> of the engine <NUM> for turning or otherwise directing the flow of combustion products through the turbine stage towards a corresponding annular array of rotor blades forming part of the turbine rotor. As is generally understood, the rotor blades may be coupled to a rotor disk of the turbine rotor, which is, in turn, rotationally coupled to the turbine's drive shaft (e.g., drive shaft <NUM> or <NUM>).

Additionally, as shown in <FIG>, the fan section <NUM> of the engine <NUM> may generally include a rotatable, axial-flow fan rotor <NUM> that configured to be surrounded by an annular fan casing <NUM>. In particular embodiments, the (LP) drive shaft <NUM> may be connected directly to the fan rotor <NUM> such as in a direct-drive configuration. In alternative configurations, the (LP) drive shaft <NUM> may be connected to the fan rotor <NUM> via a gearbox <NUM>, which may have an epicyclic gearing <NUM> in an indirect-drive or geared-drive configuration. Such speed reduction devices may be included between any suitable shafts / spools within engine <NUM> as desired or required. It should be appreciated that the gearbox <NUM> may be located at any suitable location within the engine <NUM>, to include the LP turbine <NUM>.

It should be appreciated by those of ordinary skill in the art that the fan casing <NUM> may be configured to be supported relative to the core engine <NUM> by a plurality of substantially radially-extending, circumferentially-spaced outlet guide vanes <NUM>. As such, the fan casing <NUM> may enclose the fan rotor <NUM> band its corresponding fan rotor blades <NUM>. Moreover, a downstream section <NUM> of the fan casing <NUM> may extend over an outer portion of the core engine <NUM> so as to define a secondary, or by-pass, airflow conduit <NUM> that provides additional propulsive jet thrust.

During operation of the engine <NUM>, it should be appreciated that an initial air flow (indicated by arrow <NUM>) may enter the engine <NUM> through an associated inlet <NUM> of the fan casing <NUM>. The air flow <NUM> then passes through the fan blades <NUM> and splits into a first compressed air flow (indicated by arrow <NUM>) that moves through conduit <NUM> and a second compressed air flow (indicated by arrow <NUM>) which enters the booster compressor <NUM>. The pressure of the second compressed air flow <NUM> is then increased and enters the high-pressure compressor <NUM> (as indicated by arrow <NUM>). After mixing with fuel and being combusted within the combustor <NUM>, the combustion products <NUM> exit the combustor <NUM> and flow through the first turbine <NUM>. Thereafter, the combustion products <NUM> flow through the second turbine <NUM> and exit the exhaust nozzle <NUM> to provide thrust for the engine <NUM>.

<FIG> provides a block diagram of an example computing system <NUM> that is representative of a computing device for implementing the method <NUM> as defined by the present invention. As shown, the computing system <NUM> may include one or more computing device(s) <NUM>. The one or more computing device(s) <NUM> may include one or more processor(s) <NUM> and one or more memory device(s) <NUM>. The one or more processor(s) <NUM> may include any suitable processing device, such as a microprocessor, microcontroller, integrated circuit, logic device, or other suitable processing device. The one or more memory device(s) <NUM> may include one or more computer-readable media, including, but not limited to, non-transitory computer-readable media, RAM, ROM, hard drives, flash drives, or other memory devices.

The one or more memory device(s) <NUM> may store information accessible by the one or more processor(s) <NUM>, including computer-readable instructions <NUM> that may be executed by the one or more processor(s) <NUM>. The instructions <NUM> may be any set of instructions that when executed by the one or more processor(s) <NUM>, cause the one or more processor(s) <NUM> to perform operations. The instructions <NUM> may be software written in any suitable programming language or may be implemented in hardware. In some embodiments, the instructions <NUM> may be executed by the one or more processor(s) <NUM> to cause the one or more processor(s) <NUM> to perform the processes for reducing edge contact stress concentration in a press-fit, or for implementing any of the other processes described herein.

The memory device(s) <NUM> may further store data <NUM> that may be accessed by the processor(s) <NUM>. For example, the data <NUM> may include the number of gears pairs to be supported, dissipated loads, volume limitations, manufacturing processes, or material properties as described herein. The data <NUM> may include one or more table(s), function(s), algorithm(s), model(s), equation(s), etc. according to example embodiments of the present subject matter.

The one or more computing device(s) <NUM> may also include a communication interface <NUM> used to communicate, for example, with the other components of system. The communication interface <NUM> may include any suitable components for interfacing with one or more network(s), including for example, transmitters, receivers, ports, controllers, antennas, or other suitable components.

For instance, processes discussed herein may be implemented using a single computing device or multiple computing devices working in combination. Databases, memory, instructions, and applications may be implemented on a single system or distributed across multiple systems. Distributed components may operate sequentially or in parallel.

Claim 1:
An epicyclic gearing (<NUM>) for a gas turbine aviation engine (<NUM>), the epicyclic gearing (<NUM>) comprising:
a plurality of planet gears (<NUM>) circumferentially disposed about a transmission axis (TA) and operably coupled to a plurality of planet pins (<NUM>);
a planet-carrier (<NUM>), the planet-carrier comprising:
a side plate (<NUM>) comprising a coupling portion for connecting the side plate to a rotating member or to a static structure, and
a central ring (<NUM>) coaxial to the side plate along the transmission axis (TA), each planet pin (<NUM>) of the plurality of planet pins (<NUM>) being coupled to the central ring (<NUM>) via a press-fit collar (<NUM>); and
the press-fit collar (<NUM>) defining a collar axis (CA) and comprising an annular body having:
a first radial contact face (<NUM>) defining a collar outer diameter, the first radial contact face (<NUM>) interfacing with a pin opening defined by the central ring (<NUM>),
a second radial contact face (<NUM>) disposed radially inward of the first radial contact face and defining a collar inner diameter centered about a collar axis (CA), the second radial contact face (<NUM>) accepting one of the plurality of planet pins (<NUM>), and
an axial face (<NUM>) extending between the first radial contact face (<NUM>) and the second radial contact face (<NUM>), the axial face (<NUM>) facing the plurality of planet gears, the axial face (<NUM>) defining a channel (<NUM>) having an asymmetrical cross-sectional profile, the channel (<NUM>) circumscribing the collar axis (CA), wherein the asymmetrical cross-sectional profile reduces an edge contact pressure.