Oil pipe cover and mechanical reduction gear for an aircraft turbomachine comprising such a cover

An oil pipe cover for a mechanical reduction gear of a turbomachine, for example of an aircraft, is configured to be fixed to a planet carrier of the reduction gear and to be mounted on an axial end of a hydrodynamic bearing tubular support of a planet gear of the reduction gear. The oil pipe cover has an annular body extending around an axis (Y) and having a mounting central orifice on the axial end. The body has two diametrically opposed circumferential deflectors: a first deflector having a circumferential oil guiding surface located radially outwards with respect to the axis (Y), and a second deflectors having a circumferential oil guiding surface located radially inwards with respect to the axis (Y).

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119 to French Patent Application No. 1907574, filed Jul. 8, 2019, which is herein incorporated by reference in its entirety.

FIELD

Embodiments of the present disclosure relate to the field of mechanical reduction gear for turbomachines, e.g., for aircraft.

BACKGROUND

The prior art comprises WO-A1-2010/092263, FR-A1-2 987 416, FR-A1-3 041 054, EP-A1-2 317 181 and US-A1-2005/215389, which is herein incorporated by reference in their entirety.

The role of a mechanical reduction gear is to change the speed and torque ratio between the input and output shafts of a rotary drive mechanism.

The new generations of dual-flow turbomachines, in particular those with a high dilution ratio, comprise a mechanical reduction gear to drive the shaft of a fan. Usually, the purpose of the reduction gear is to transform the so-called fast rotation speed of the shaft of a power turbine into a slower rotation speed for the shaft driving the fan.

Such a reduction gear comprises a central pinion, called the sun gear, a ring gear and pinions called the planet gears, which are meshed between the sun gear and the ring gear. The planet gears are held by a frame called a planet carrier. The sun gear, the ring gear and the planet carrier are planetary gears because their axes of revolution coincide with the longitudinal axis X of the turbomachine. The planet gears each have a different axis of revolution Y, they are equally distributed on the same operating diameter around the axis of the planetary gears. These axes Y are parallel to the longitudinal axis X.

There are several reduction gear architectures. In the prior art of dual-flow turbomachines, the reduction gears are of the planetary or epicyclic type. There are also so-called differential or “compound” architectures.

On a planetary reduction gear, the planet carrier is fixed and the ring gear constitutes the output shaft of the device which rotates in the opposite direction to that of the sun gear.

On an epicyclic reduction gear, the ring gear is fixed and the planet carrier constitutes the output shaft of the device which rotates in the same direction as the sun gear.

On a differential reduction gear, no element is fixed in rotation. The ring gear rotates in the opposite direction to that of the sun gear and that of the planet carrier.

The reduction gears can comprise one or more meshing stages. This meshing is achieved in different ways such as by contact, by friction or even by magnetic fields. There are several types of contact meshing, such as straight or herringbone toothings.

A reduction gear must be lubricated and the supply of lubricating oil to the rotating components of a reduction gear can be problematic. The oil is usually supplied to the reduction gear via a lubricating oil distributor.

The planet gears are guided in rotation by bearings which are lubricated. The bearings may consist of rolling elements (ball bearings, roller bearings, tapered roller bearings, etc.) or may be hydrodynamic bearings. In the latter case, each planet gear is rotatably mounted on and around a tubular support of the planet carrier, which is supplied with oil and which is configured to form an oil film between the outer periphery of the support and the inner periphery of the planet gear. For this purpose, in the current technique, each planet gear comprises an internal cylindrical surface which extends around an external cylindrical surface of the support and which delimits with the latter an annular space for the formation of the oil film. This space is supplied with oil by oil conveying pipes which are formed in the support and extend from the outer cylindrical surface to an internal cavity of the support which is supplied with oil by the aforementioned distributor.

This disclosure relates to a reduction gear, the planet gears of which are guided by hydrodynamic bearings.

However, there are problems with the current technology:

In a hydrodynamic or plain bearing, the oil heats up due to the oil shear in a non-negligible way. The warmer oil is located in an oil wedge close to the axis of the engine. This hot oil is thrown out of the bearing axially and is then redirected to the outer radius of the reduction gear due to the centrifugal effect. This oil touches the solid components (the tubular supports, the planet gears, and the ring gear) of the reduction gear and heats by convection heat transfer these solid components;

this heating is penalizing because the hotter tubular supports will heat up the oil in the enclosure of the bearing;

the hotter supports will heat the oil in the internal cavities of these supports, which are supplied with oil, which will reduce the viscosity of the oil, increase the eccentricity of the bearing, and result in oil friction losses of the bearing;

the heating of the solid components of the reduction gear generates higher friction losses in the bearings and increases the possibility of the seizure between the ring gear and the planet gears.

The present disclosure provides a simple, effective and economical improvement for improving the flow and discharge of the oil in a turbomachine mechanical reduction gear.

SUMMARY

The present disclosure relates to examples of an oil pipe cover for a mechanical reduction gear of a turbomachine, in particular for an aircraft. In an embodiment, the cover is configured to be fixed to a planet carrier of the reduction gear and to be mounted on an axial end of a tubular support for a hydrodynamic bearing of a planet gear of the reduction gear. The cover comprises an annular body extending around an axis and comprising a mounting central orifice on the axial end. In one or more embodiments, the body comprises one or more of the following in any combination:a first circumferential deflector having a first predetermined circumferential extent around the axis, this first deflector comprising a circumferential oil guiding surface located radially outwards with respect to the axis,a second circumferential deflector having a second predetermined circumferential extent around the axis, this second deflector comprising a circumferential oil guiding surface located radially inwards with respect to the axis, the first and second deflectors being substantially diametrically opposed with respect to the axis, andoil discharge pipes which pass substantially axially through the body and which are diametrically opposed with respect to the first deflector, these pipes opening axially on the side of the second deflector, radially inside the latter with respect to the axis.

The solution proposed in the present disclosure is a modification of the two covers of the bearing or of the planet carrier in order to channel the hot oil coming from the bearing to the outside of the reduction gear in order to avoid convective heating of the components of the reduction gear. The modifications comprise at least oil discharge pipes and two deflectors per cover. One of the deflectors is intended to be located facing the oil wedge so as to prevent the hot oil from heating the tubular support. This hot oil is then centrifugally carried to the second deflector, which serves to prevent the hot oil from escaping from the reduction gear and heating the planet gear. The hot oil in the second deflector is then discharged through the pipes. This solution prevents the heating of components of the epicyclic reduction gear due to the hot oil of the bearing, and at the same time allows the cold oil supplying the tubular support to flow out freely at the periphery of the support in view of the formation of the hydrodynamic oil film.

The solutions proposed herein are compatible with an epicyclic reduction gear, the ring gear of which is fixed in the engine's frame. The solutions are compatible with any type of toothing (straight, herringbone), any type of planet carrier, whether monobloc or cage-carrier type.

The cover according to one or more embodiments of the present disclosure may comprise one or more of the following features, taken in isolation from each other, or in combination with each other:each of the first and second circumferential extents is between 160 and 360°, and for example between approximately 160 and 200°,the first deflector comprises circumferential ends close to the circumferential ends of the second deflector so that oil flowing on the guiding surface of the first deflector can then flow onto the guiding surface of the second deflector,the first deflector has a generally flared shape (e.g. conical or biconical but other shapes are possible) on the side opposite the body and/or the second deflector has a generally flared shape (e.g. conical or biconical but other shapes are possible) on the side of the body,the first deflector comprises, at a free end located on the side opposite to the body, a circumferential edge oriented radially outwards with respect to the axis; this edge is optional,the body comprises an oil accumulating circumferential tub, this tub being diametrically opposed with respect to the second deflector and opening on the side of the first deflector, radially outside the latter,the second deflector comprises, at a free end located on the side opposite to the body, a circumferential edge oriented on the side opposite to the body; this edge is optional,the tub has a circumferential extent around the axis of the support which is less than or equal to 360°, e.g. between 90 and 180°,the tub has in axial section a generally triangular or rectangular or circular shape, the base of which located radially outwards and the apex of which is located radially inwards, with respect to the axis of the support,the first and second deflectors and the oil discharge pipes are formed in a single piece.

This present disclosure also relates to examples of a mechanical reduction gear of a turbomachine, in particular for an aircraft. In an embodiment, the reduction gear comprises:a sun gear having an axis of rotation,a ring gear which extends around the sun gear and which is configured to be immobile in rotation around the axis,planet gears which are meshed with the sun gear and the ring gear and which are held by a planet carrier which is configured to be rotatable around the axis, each of the planet gears being guided in rotation by a hydrodynamic bearing comprising (or formed by) a tubular support around which the planet gear is rotatably mounted, each of the tubular supports comprising a first annular groove located at a first axial end of the support, and a second annular groove located at a second opposite end of the support, the first and second grooves being oriented axially in opposite directions,a lubricating oil distributor which is configured to supply oil to internal cavities of the tubular supports, each of the tubular supports having oil conveying pipes from its internal cavity to its outer periphery for forming an oil film between the support and the planet gear.

In some embodiments, each of the tubular supports is fixed to the planet carrier via two covers which are each defined according to any one of the particularity of the present disclosure and which are respectively and coaxially mounted on the axial ends of the tubular support, the cover mounted on the first axial end of the support having its deflectors which are axially engaged in the first groove, and the cover mounted on the second axial end of the support having its deflectors which are axially engaged in the second groove.

The reduction gear according to one or more embodiments of the present disclosure may comprise one or more of the following features, taken in isolation from each other, or in combination with each other:the conveying pipes are substantially located in the same plane passing through the axis of the support,the plane passes substantially at the level of the discharge pipes,the conveying pipes open into the same groove formed in an external cylindrical surface of the support,the discharge pipes open axially on the side of the second deflector at the first or second groove of the support,the pipes have a cylindrical, rectangular, porthole shaped, etc.

The present disclosure furthermore relates to a turbomachine, in particular for aircraft, comprising a mechanical reduction gear as described above.

DETAILED DESCRIPTION

FIG. 1describes a representative and non-limiting turbomachine1which comprises a fan S, a low-pressure compressor1a, a high-pressure compressor1b, an annular combustion chamber1c, a high-pressure turbine1d, a low-pressure turbine1eand an exhaust nozzle1h. The high-pressure compressor1band the high-pressure turbine1dare connected by a high-pressure shaft2and form a high-pressure (HP) body with it. The low-pressure compressor1aand the low-pressure turbine1eare connected by a low-pressure shaft3and form a low-pressure body (LP) with it.

The fan S is driven by a fan shaft4which is driven by the LP shaft3by a reduction gear6. This reduction gear6is usually of the planetary or epicyclic type.

The following description refers to a reduction gear of the epicyclic type, in which the planet carrier and the sun gear are movable in rotation, the ring gear of the reduction gear being fixed in the frame of the engine.

The reduction gear6is positioned in the upstream part of the turbomachine. In this patent application, the terms upstream and downstream refer to the general direction of gas flow in the turbomachine, along its axis of extension or rotation of its rotors. A fixed structure comprising schematically, here, an upstream part5aand a downstream part5bwhich makes up the engine casing or stator5is arranged so as to form an enclosure E surrounding the reduction gear6. This enclosure E is herein closed upstream by seals at the level of a bearing allowing the passage of the fan shaft4, and downstream by seals at the level of the LP shaft3.

FIG. 2shows an epicyclic reduction gear6. On the input side, the reduction gear6is connected to the LP shaft3, e.g. via internal splines7a. In this way, the LP shaft3drives a planetary pinion called the sun gear7. Classically, the sun gear7, whose axis of rotation is combined with that of the turbomachine X, drives a series of pinions called planet gears8, which are equally distributed on the same diameter around the axis of rotation X. This diameter is equal to twice the operating center distance between the sun gear7and the planet gears8. The number of planet gears8is generally defined between three and seven for this type of application.

All planet gears8are held by a frame called planet carrier10. Each planet gear8rotates around its own axis Y and meshes with the ring gear9.

On the output side there is:In this epicyclic configuration, all planet gears8drives the planet carrier10around the axis X of the turbomachine. The ring gear is fixed to the engine casing or stator5via a ring gear carrier12and the planet carrier10is fixed to the fan shaft4.In another planetary configuration, all planet gears8are held by a planet carrier10which is attached to the engine casing or stator5. Each planet gear drives the ring gear which is attached to the fan shaft4via a ring gear carrier12.

Each planet gear8is mounted freely in rotation by a bearing11, e.g., of the rolling bearing or hydrodynamic bearing type. Each bearing11is provided on one of the tubular supports10bof the planet carrier10and all the supports are positioned relative to each other by one or more structural frames10aof the planet carrier10. There is a number of tubular supports10band bearings11equal to the number of planet gears. For operational, mounting, manufacturing, control, repair or replacement reasons, the supports10band the frame10acan be separated into several parts.

For the same reasons as mentioned above, the toothing of a reduction gear can be separated into several helixes, each having a median plane P. In our example, we detail the operation of a reduction gear with several helixes with one ring gear separated into two half-ring gears:An upstream half-ring gear9aconsisting of a rim9aaand a fastening half-flange9ab. On the rim9aais located the upstream helix of the toothing of the reduction gear. This upstream helix meshes with that of the planet gear8which meshes with that of the sun gear7.A downstream half-ring gear9bconsists of an edge9baand a mounting half-flange9bb. On the edge9bais located the downstream helix of the toothing of the reduction gear. This downstream helix meshes with that of the planet gear8which meshes with that of the sun gear7.

If the widths of helixes vary between the sun gear7, the planet gears8and the ring gear9because of toothing overlaps, they are all centered on a median plane P for the upstream helixes and on another median plane P for the downstream helixes. In the case of a double row roller bearing, each row of rolling elements is also preferably, but not necessarily, centered on two median planes.

The fastening half-flange9abof the upstream ring gear9aand the fastening half-flange9bbof the downstream ring gear9bform the fastening flange9cof the ring gear. The ring gear9is fixed to a ring gear carrier by assembling the fastening flange9cof the ring gear and the fastening flange12aof the ring gear carrier using a bolted assembly for example.

The arrows inFIG. 2describe the oil flow in the reduction gear6. The oil enters the reduction gear6from the stator part5into a distributor13by different means which will not be specified in this view as they are specific to one or more types of architecture. The distributor13comprises injectors13aand arms13b. The function of the injectors13ais to lubricate the toothings and the function of the arms13bis to lubricate the bearings. The oil is fed to the injector13ato exit through the end13cto lubricate the toothings. The oil is also fed to arm13band flows through the supply port13dof the bearing11. The oil then flows through the support10binto one or more cavities10cto exit through pipes10dto lubricate the bearings of the planet gears.

FIGS. 3 to 7illustrate a representative and non-limiting embodiment of the mechanical reduction gear6according to the present disclosure.

The above description applies to this reduction gear6insofar as it is technically compatible with the following.

The tubular support10bof each planet gear8comprises a one-piece body in the example shown which comprises two coaxial annular walls20a,20bwhich extend one around the other and which are connected to each other by an annular web20c.

The inner annular wall20bis closed at one end by a bulkhead20dand has an axial end open on the opposite side to receive oil supplied by the oil distributor (not shown). The inner wall20bthus defines the cavity10cfor receiving lubricating oil.

The outer annular wall20ahas an axial length or dimension measured along the axis Y which is close to (e.g., within 10%) that of the wall20b. The wall20acomprises an outer cylindrical surface20aawhich is configured to delimit with an inner cylindrical surface (not visible) of the bearing an annular oil-receiving and oil-film-forming space for the formation of a hydrodynamic bearing.

The web20chas a shorter length measured in the same way, so that the axial ends of the walls20a,20bdelimit between them annular grooves21a,21b. This configuration provides a certain flexibility to the support10bat the level of each of its axial ends.

The support10bthus comprises a first annular groove21alocated on one side and the opening of which opens in the axial direction, and a second annular groove21blocated on the opposite side and the opening of which opens axially on the side opposite to the groove21a. These grooves21a,21bare generally U-shaped in cross-section.

The support10bcomprises lubricating oil conveying pipes10dfor conveying lubricating oil from the cavity10cto the outer periphery of the support10b. In the example shown, there are three such pipes10d, although this number is not restrictive. They each have a generally elongated and cylindrical shape. They are aligned and evenly spaced in a plane M passing through the axis Y of the support10b, which is the plane of the drawing inFIG. 3.

The radially outer ends of the pipes10dopen in the same groove23formed on the outer surface20aaof the support10b. This groove23has a generally elongated shape and extends substantially in the plane M. The radially inner ends of the pipes10dopen into the cavity10c.

At each of its axial ends, the support10bcomprises a cylindrical edge10efor mounting a cover30. The edges10eextend around the axis Y. They are located on the inner wall20band extend axially in opposite directions.

Each edge10ecomprises an outer cylindrical surface10e1for mounting the corresponding cover30and which is connected to a radial annular surface20b1of the inner wall20b. The edge10ewhich is located at the level of the bulkhead20dextends protruding therefrom.

In the example shown, the covers30have the dual function of fixing the tubular support10bto the planet carrier10(shown inFIG. 7) and oil supply pipe of the hydrodynamic bearing comprising (formed by) the support10b.

The covers30located at the ends of each support10bof the planet carrier are identical and are best seen inFIGS. 4 to 6.

Each cover30comprises a body of generally annular shape around an axis which is the axis Y of the tubular support10bwhen assembled one onto the other.

Each cover30comprises a radial annular flange on the outer periphery of the body or radial tabs32for fixing to the planet carrier10. This flange or radial tabs32have screw passage orifices32aor similar configured to be screwed into threaded holes of the planet carrier10or for passing through orifices in the planet carrier and receiving nuts.

Each cover30furthermore comprises at the inner periphery of the body a mounting orifice34for mounting on one end of a support10band in particular on an edge10e. The orifice34comprises an internal cylindrical surface34aintended to cooperate with the surface10e1of the support10bfor centering the cover30on the support10b. The cover30further comprises a radial annular surface36at its inner periphery which is intended to be applied axially against the radial surface20b1of the support10b.

The surface34ahas a diameter D1slightly larger than the diameter of the surface10e1. The surface36extends substantially between the diameter D1and a diameter D2greater than D1.

On a first circumference of diameter D3, greater than D2, the ring gear31comprises a first circumferential deflector38.

On a second circumference of diameter D4, greater than D3, the ring gear31comprises a second circumferential deflector40.

The first deflector38has a predetermined circumferential extent al around the axis Y, which is, for example, between approximately 160 and 200° (FIG. 5).

This deflector38has a generally flared shape on the opposite side of the body and comprises a circumferential oil guiding surface38a, which is located radially outwards with respect to the axis Y (FIGS. 3, 4 and 6).

The deflector38comprises, at a free end located on the side opposite the body, a circumferential edge38boriented radially outwards with respect to the axis Y. Measured along the axis Y, the deflector38has a length L1and its edge has a thickness E (FIG. 3). The edge38bincreases the oil holding capacity of the deflector38.

The second deflector40has a predetermined circumferential extent α2around the axis Y, which is, for example, approx. 160 to 200°.

This deflector40has a generally flared shape on the side of the body and comprises a circumferential oil guiding surface40a, which is located radially inwards with respect to the axis Y.

The deflector40comprises, at a free end located on the opposite side of the body, a circumferential edge40binclined with respect to the rest of the deflector. Measured along the axis Y, the deflector40has a length L2similar to L1and its edge40bhas a length L3which is 30 to 80% of the length L2.

With reference toFIG. 2which shows an axial section of the support10band the covers30, it can be seen that the first deflector38has a generally frustoconical shape or is inclined with respect to the axis Y at an angle of approximatively 20 to 50°. The second deflector40has a generally biconical shape and comprises a first part on the side of the body, which is inclined with respect to the axis Y at an angle in the range of approximatively 30 to 60°, and a second part on the opposite side, which is inclined with respect to the axis Y at an angle in the range of approximatively 10 to 40°. The radius of the first deflector decreases towards the median plan of the bearing, while the radius of the second deflector increases towards the median plan of the bearing. Changing the taper of the second deflector increases its oil holding capacity.

As can be seen in the drawings, the deflectors38,40are approximately diametrically opposed with respect to the axis Y. Due to their circumferential extents being close to or even greater than 180°, the circumferential ends of the deflector38are close to (e.g., adjacent or overlapping when viewed along axis Y) those of the deflector40, which facilitates the oil flow, as will be described in more detail in the following. In a particular example of embodiment of the present disclosure, the circumferential ends of the deflectors are separated from each other by an angle of approximatively 5 to 10° so as to facilitate the manufacture of the cover, in particular by machining.

The cover30furthermore comprises oil discharge pipes42which pass substantially axially through the body and which are diametrically opposed with respect to the deflector38. These pipes42may be slightly inclined with respect to the above-mentioned axis. These pipes42open axially on the side of the deflector40, radially inside the latter with respect to the axis Y.

In the example shown, the cover30comprises a series of five pipes42which are distributed over an angular sector with a circumference of diameter D6, this diameter D6being between D3and D4in the example shown (FIG. 3).

The pipes42have a generally cylindrical shape and extend parallel to the axis Y.

In addition, the cover30in the example shown comprises a circumferential oil accumulation tub44, also known as an oil wedge. This tub44is diametrically opposite to the deflector40and opens on the side of the deflector38, radially outside the latter.

The tub44has a circumferential extent around the axis Y of between 100 and 150°. It extends in the radial direction between a circumference of diameter D7and a circumference of diameter D8, these diameters being greater than D1, D2, D3and D6.

As can be seen inFIG. 3, in axial section, this tub44has a generally triangular shape with the base located radially outside and the apex located radially inside.

In the mounting position shown inFIG. 3, the covers30are arranged symmetrically with respect to a median plane O perpendicular to Y and passing through the center of the support10b. The covers30are engaged on the edges10eof the support10bin such a way that the deflectors38,40engage axially in the grooves21a,21b.

When all the supports10band their covers30are fixed to the planet carrier10, the configuration shown inFIG. 7is obtained. In the example shown, the covers are all identical and arranged identically around their axis Y and the axis X of the reduction gear. Alternatively, the covers of one reduction gear could be different, or they could be identical but arranged differently on the reduction gear. This depends, among other things, on the center of gravity of each cover and the positions of the above-mentioned oil wedges.

The directions of rotation of the planet gears8are indicated by the arrows F1inFIGS. 4 and 7. The arrow F2represents the direction of rotation of the sun gear7and the arrow F3represents the direction of rotation of the planet carrier10.

During operation, oil is injected through the distributor13(FIG. 2) into the cavities10cof the supports10band flows to the grooves23through the pipes10d, so that oil films are formed between the supports10band their planet gears8. This oil tends to flow on the sides of the supports10binto the grooves21a,21b. The deflectors38are located on the side of the axis X of rotation of the planet carrier10and the oil in the groove21atends in the deflector location area to accumulate in the tubs44and then to flow onto the surfaces38aof the deflectors under the effect of centrifugal forces. This oil flows circumferentially from the tub44to the circumferential ends of the deflectors38where it then flows to the deflectors40and is guided by the surfaces40aof these deflectors40to the pipes42. The oil then flows through these pipes42to be drained to the outside and preferably recycled.

The alternative embodiments inFIGS. 8 and 9show on the one hand that the deflectors38′,40′ of the cover30′ are not necessarily frustoconical. The deflector38′ has a generally curved cross-section with the concavity oriented radially outwards with respect to the axis Y. The deflector40′ has a generally curved cross-section with the concavity oriented radially inward with respect to the axis Y. On the other hand, the tub44has a generally circular or rounded cross-sectional shape inFIG. 8and a generally rectangular shape inFIG. 9. In each of the alternative embodiments ofFIGS. 8 and 9, the tub44has a circumferential extent of 360° around the axis Y.

FIG. 10shows an alternative embodiment of a cover30in which the pipes42′ have a generally elongated shape in the circumferential direction around the axis Y, the so-called “porthole.”

The gains brought by this present disclosure include, for example:global cooling of the components of the reduction gear,increase in the seizure margin between the ring gear and planet gears and between the planet gears and sun gear,approximately 10% less friction loss of the bearing (lower oil temperature),possible reduction of the length of the toothing of the ring gear and the planet gear,lower oil flow rate,better evacuation of calories,possible reduction of the length of the tubular supports of the bearings and planet gears,possible reduction of the risk of contact between the planet gears and these supports.

The detailed description set forth above in connection with the appended drawings, where like numerals reference like elements, are intended as a description of various embodiments of the present disclosure and are not intended to represent the only embodiments. Each embodiment described in this disclosure is provided as an example or illustration and should not be construed as preferred or advantageous over other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Similarly, any steps described herein may be interchangeable with other steps, or combinations of steps, in order to achieve the same or substantially similar result.

Generally, the embodiments disclosed herein are non-limiting, and the inventors contemplate that other embodiments within the scope of this disclosure may include structures and functionalities from more than one specific embodiment shown in the FIGURES and described in the specification. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present disclosure. Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present disclosure as claimed. For example, the present disclosure includes additional embodiments having combinations of any one or more features described above with respect to the representative embodiments.

The present application may include references to directions, such as “first,” “second,” “vertical,” “horizontal,” “front,” “rear,” “left,” “right,” “top,” and “bottom,” etc. These references, and other similar references in the present application, are intended to assist in helping describe and understand the particular embodiment (such as when the embodiment is positioned for use) and are not intended to limit the present disclosure to these directions or locations.

The present application may also reference quantities and numbers. Unless specifically stated, such quantities and numbers are not to be considered restrictive, but exemplary of the possible quantities or numbers associated with the present application. Also in this regard, the present application may use the term “plurality” to reference a quantity or number. In this regard, the term “plurality” is meant to be any number that is more than one, for example, two, three, four, five, etc. The term “about,” “approximately,” etc., means plus or minus 5% of the stated value. The term “based upon” means “based at least partially upon.”