Patent Description:
Bearings are widely used in machinery to support rotatable components about corresponding rotation axes, for example in powerplants to support a shaft thereof. The performance and durability of a bearing is largely driven by its structural and dimensional characteristics, but also by the loading conditions in play, whether they pertain to components supporting the bearing or to components supported by the bearing. Whereas some deformation of the bearing and of its adjoining components may be expected under typical loading conditions, controlling such deformation may be beneficial to bearing durability.

<CIT> discloses a prior art seal and bearing assembly with a bearing outer portion comprising a seal static portion.

According to a first aspect of the present invention, there is provided a bearing housing as set forth in claim <NUM>.

According to a further aspect of the present invention, there is provided a bearing assembly as set forth in claim <NUM>.

According to a further aspect of the present invention, there is provided a turbine engine as set forth in claim <NUM>.

<FIG> illustrates a gas turbine engine <NUM> of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication a fan <NUM> through which ambient air is propelled, a centrifugal compressor <NUM> for pressurizing the air, a combustor <NUM> in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and turbines <NUM> for extracting energy from the combustion gases. A low-pressure turbine shaft <NUM> along a longitudinal axis A1 interconnects a low pressure turbine of the turbines <NUM> and the fan <NUM>, whereas a high-pressure turbine shaft <NUM> also along the longitudinal axis A1 interconnects a high pressure turbine of the turbines <NUM> and the compressor <NUM>. A tower shaft <NUM> along a radial axis A2 interconnects the high-pressure turbine shaft <NUM> and an accessory gearbox <NUM> of the engine <NUM>. In use, pressurized air provided by the compressor <NUM> through a diffuser <NUM> enters the combustor <NUM> for combustion so as to drive the shafts <NUM>, <NUM>, <NUM> via the turbines <NUM>. The shafts <NUM>, <NUM>, <NUM> are supported about their respective axes A1, A2 via bearings. While the Figures and this description discuss the gas turbine engine <NUM> and more particularly a turbofan gas turbine engine, it shall be understood that the present disclosure is applicable to other types of machinery comprising bearing-supported rotatable components.

Referring to <FIG> and <FIG>, there is shown a casting <NUM> of the engine <NUM> with a bearing assembly <NUM> (<FIG>) fitted thereto. The casting <NUM> defines a casting cavity Cc that may be described as a wet cavity as it is exposed to oil provided from an oil system of the engine <NUM>. The bearing assembly <NUM> generally includes a housing <NUM> defining a bearing cavity Cb and a bearing <NUM> fitted to the housing <NUM> inside the bearing cavity Cb. The bearing cavity Cb is in fluid communication with the casting cavity Cc, such that the bearing <NUM> is exposed to oil having flowed from the casting cavity Cc and into the bearing cavity Cb. In <FIG>, only the housing <NUM> is shown, the shaft <NUM>, the gear <NUM> and the bearing <NUM> having been removed in order to show the bearing cavity Cb in detail.

The housing <NUM> will now be generally described with reference to <FIG>. The housing <NUM> generally comprises an annular wall W extending circumferentially about the axis A2 and axially between opposite first and second housing ends <NUM>, <NUM>. The annular wall W surrounds the bearing cavity Cb. The first housing end <NUM> is spaced from the casting <NUM>, and defines an open side of the bearing cavity Cb via which the bearing <NUM> is received into the bearing cavity Cb. In this case, the first housing end <NUM> is free of any contact except with the bearing <NUM>. The second housing end <NUM> is fitted to a complementary portion of the casting <NUM> so as to be constrained thereby. Thus, the housing <NUM> is held by the casting <NUM> at the second housing end <NUM>. Stated otherwise, the housing <NUM> and the casting <NUM> are arranged relative to one another such that the casting <NUM> opposes axial and radial displacements of the second housing end <NUM> which may otherwise occur under certain loading conditions of the housing <NUM>, for example loads exerted onto the housing <NUM> via the bearing <NUM>. The second housing end <NUM> is affixed to the casting <NUM> via welding, friction or other suitable means, whether directly or indirectly by way of an intermediate structure. In other embodiments, the housing <NUM> and the casting <NUM> form an integral piece, such that the annular wall W may be described as a projection of the casting <NUM>. The housing <NUM> also has an interior housing surface <NUM> extending circumferentially about the axis A2 and axially between the first and second housing ends <NUM>, <NUM>. Proximate to the first housing end <NUM>, the interior housing surface <NUM> has a cylindrical portion 56a that defines a seat 56b. The seat 56b defines a first housing radius Rh1 of the housing <NUM> and circumscribes the bearing cavity Cb. The seat 56b is configured to radially engage the bearing <NUM>, as will be described in greater detail below. The cylindrical portion 56a of the interior housing surface <NUM> extends axially from a first housing location Lh1 proximate to the first housing end <NUM> to at least a second housing location Lh2. Depending on the embodiment, first housing location Lh1 and the second housing location Lh2 may be said to axially delimit the seat 56b. Proximate to the second housing end <NUM>, the interior housing surface <NUM> defines a housing cavity in fluid communication between a casting cavity Cc of the casting <NUM> and the bearing cavity Cb. The bearing cavity Cb may be said to be a portion of the housing cavity sized for receiving the bearing <NUM>. The housing <NUM> also has an exterior housing surface <NUM> extending circumferentially about the axis A2 and axially between the first and second housing ends <NUM>, <NUM>. Proximate to the first housing end <NUM>, the exterior housing surface <NUM> is cylindrical in shape, defines a second housing radius Rh2 of the housing <NUM>, and is disposed radially outward of the interior housing surface <NUM>. Hence, the second housing radius Rh2 is greater than the first housing radius Rh1. A difference between the second and first housing radii Rh2, Rh1 corresponds to a radial thickness Tr of the housing <NUM>. Proximate to the first housing end <NUM>, the annular wall W may thus be said to be cylindrical in shape and to have the radial thickness Tr.

Proximate to the second housing end <NUM>, the exterior housing surface <NUM> is also cylindrical in shape, and yet defines a third housing radius Rh3 of the housing <NUM> that is greater than the second housing radius Rh2. Indeed, as the exterior housing surface <NUM> extends away from the first housing end <NUM> and toward the second housing end <NUM>, the exterior housing surface <NUM> transitions from the second housing radius Rh2 to the third housing radius Rh3 by way of a shoulder 58a. It is contemplated that in other embodiments, a shape of the housing <NUM> may be different. For example, the exterior housing surface <NUM> could transition from the second housing radius Rh2 to the third housing radius Rh3 by way of a conical shape. In other embodiments, the annular wall W could be cylindrical in shape from the first housing end <NUM> to the second housing end <NUM>.

In other embodiments, the housing <NUM> can include additional structures located adjacent to the annular wall W at either one or both of the first housing end <NUM> and the second housing end <NUM>. For instance, the housing <NUM> may extend away from the casting <NUM> to a location past the first housing end <NUM>. In this embodiment, at the first housing end <NUM>, the housing <NUM> has a first housing axial surface 52a extending circumferentially about the axis A2. A plurality of keyways 52b are defined in the first housing axial surface 52a. The keyways 52b are circumferentially spaced from one another and extend radially through the housing <NUM> from the exterior housing surface <NUM> to the interior housing surface <NUM>. The first housing axial surface 52a may thus be said to be formed of sectors that are circumferentially spaced from one another by one of the keyways 52b.

The annular wall W of the housing <NUM> also defines a plurality of holes H that are spaced circumferentially from one another relative to the axis A2 and that extend through the annular wall W toward the axis A2, from the exterior housing surface <NUM> to the interior housing surface <NUM>. The holes H are thus in fluid communication with inside the bearing cavity Cb, and with inside the casting cavity Cc via the bearing cavity Cb. The holes H are spaced axially relative to the first housing end <NUM> so as to be proximate to a side of the bearing <NUM> that faces toward the second housing end <NUM> upon the bearing <NUM> being received by the bearing cavity Cb. In some embodiments, the holes H serve as drain ports, as they allow drainage of oil which would otherwise accumulate onto the bearing <NUM>. The holes H are structured and arranged relative to the seat 56b so as to relieve stress exerted by the housing <NUM> onto the bearing <NUM>. Further characteristics of the holes H and their relationship with the bearing <NUM> will be discussed hereinbelow.

The bearing <NUM> will now be generally described with reference to <FIG>. The bearing <NUM> generally includes an inner race <NUM> extending circumferentially about the axis A2 and mounted to the shaft <NUM>, a series of rolling elements <NUM> disposed circumferentially about the axis A2 and around the inner race <NUM>, an annular cage <NUM> shaped for maintaining each rolling element of the series of rolling elements <NUM> in a suitable spatial relationship relative to one another, and an outer race <NUM> extending circumferentially about the axis A2 and around the series of rolling elements <NUM>.

The inner race <NUM> includes a first inner-race end <NUM> and a second inner-race end <NUM> axially opposite to the first inner-race end <NUM>. In this case, the first inner-race end <NUM> faces toward a recess 28a of a gear <NUM> mounted to the shaft <NUM>, and the second inner-race end faces toward a shoulder 24a of the shaft <NUM>. The inner race <NUM> also includes an interior inner-race surface <NUM> extending circumferentially about the axis A2 and axially between the first and second inner-race ends <NUM>, <NUM>. The inner race <NUM> is mounted to the shaft <NUM> via the interior inner-race surface <NUM>. The inner race <NUM> also includes an exterior inner-race surface <NUM> shaped for interfacing with the series of rolling elements <NUM>. In this embodiment, the exterior inner-race surface <NUM> defines a recess sized for receiving the series of rolling elements <NUM>.

The outer race <NUM> includes a first outer-race end <NUM> and a second outer-race end <NUM> opposite the first outer-race end <NUM>. In this case, the first outer-race end <NUM> faces toward the gear <NUM>, and the second outer-race end <NUM> faces toward the casting <NUM>. The outer race <NUM> also includes an interior outer-race surface <NUM> that extends circumferentially about the axis A2 and axially between the first and second outer-race ends <NUM>, <NUM>. The interior outer-race surface <NUM> defines a first outer-race radius Ro1 of the outer race <NUM> that is suitable for interfacing with the series of rolling elements <NUM>. The outer race <NUM> also includes an exterior outer-race surface <NUM> that extends circumferentially about the axis A2 and axially between the first and second outer-race ends <NUM>, <NUM>. The exterior outer-race surface <NUM> extends axially from a first edge 108a to a second edge 108b. The exterior outer-race surface <NUM> defines a second outer-race radius Ro2 of the outer race <NUM> that is greater than the first outer-race radius Ro1, and is suitable for interfacing with the housing <NUM>. Indeed, the exterior outer-race surface <NUM> radially engages the seat 56b of the interior housing surface <NUM>.

In this embodiment, the first outer-race end <NUM> is structured and arranged so as to engage the first housing end <NUM> upon the outer race <NUM> being mounted to the housing <NUM> inside the bearing cavity Cb. At the first outer-race end <NUM>, the outer race <NUM> includes a first outer-race axial surface 102a defining a flange 102b that extends radially to outward of the exterior outer-race surface <NUM>. In this case, the flange 102b is circumferentially sectored, i.e., is formed of a plurality of radial projections, or keys, that are spaced circumferentially from one another. Each one of the keys is sized and arranged to be received by a corresponding one of the keyways 52b. In other embodiments, the keyways 52b are omitted, and the flange 102b engages the first housing axial surface 52a. In other embodiments, the flange 102b is omitted, and the first outer-race end <NUM> does not engage the first housing end <NUM>.

In this embodiment, the second outer-race end <NUM> defines a second outer-race axial surface 104a. The second outer-race end <NUM> transitions from the second outer-race axial surface 104a to the interior outer-race surface <NUM> and to the exterior outer-race surface <NUM> by way of an inner transition surface 104b and an outer transition surface 104c respectively. In this embodiment, both transition surfaces 104b, 104c are tapering, or beveled, surfaces, although other shapes are contemplated. Depending on the embodiment, either one or both of the transition surfaces 104b, 104c may be omitted.

With reference to <FIG> and <FIG>, loading characteristics of the bearing assembly <NUM> will now be described. The outer race <NUM> is mounted to the housing <NUM> via the exterior outer-race surface <NUM>, namely by a radial engagement between the exterior outer-race surface <NUM> and the seat 56b of the interior housing surface <NUM>. The second outer-race radius Ro2 is greater than the first housing radius Rh1, such that the second outer-race radius Ro2 and the first housing radius Rh1 may be said to define an interference fit. Upon the outer race <NUM> being mounted to the housing <NUM>, the exterior outer-race surface <NUM> overlaps the seat 56b of the interior housing surface <NUM> as it extends away from the first housing end <NUM> toward the second housing end <NUM>. In order to mount the outer race <NUM> to the housing <NUM>, the outer race <NUM> must be axially forced into the bearing cavity Cb, in this case via the first housing end <NUM>. The outer transition surface 104c may act as a wedge that assists in radially-inwardly compressing the outer race <NUM> as it is axially forced in the bearing cavity Cb. As the housing <NUM> receives the outer race <NUM>, the housing <NUM> exerts loads onto the outer race <NUM> via the interior housing surface <NUM>, namely radially-inward compression (schematically shown at Fc) as well as axially-outward friction (schematically shown at Ff), i.e., friction that is directed opposite a direction of insertion of the outer race <NUM>. Also, external support of the bearing assembly <NUM> is provided axisymmetrically and unilaterally (schematically shown at Fs) via the engagement of the second housing end <NUM> with the casting <NUM>. In use, the above-mentioned loading conditions, coupled to loads exerted onto the bearing <NUM> via the inner race <NUM>, lead to radial deformation of the outer race <NUM>. Such deformation may be described as "coning", as the portion of the outer race <NUM> loaded by the housing <NUM> collapses radially inwardly, and increasingly so as it extends into the housing <NUM> toward the second housing end <NUM>. Such deformation may be of a magnitude that is greater near the second outer-race end <NUM> for example at the second edge 108b of the exterior outer-race surface <NUM>, than near the first outer-race end <NUM>, for example at the first edge 108a. The housing <NUM> is provided with features, such as the plurality of holes H, that are sized and arranged for attenuating such deformation. The plurality of holes H locally reduce a stiffness of the housing <NUM> at an axial location of the housing <NUM> that is proximate to the second outer-race end <NUM> upon the outer race <NUM> being mounted to the housing <NUM> so as to mitigate coning, i.e., to render the magnitude of any radial deformation of the outer race <NUM> similar from the first end <NUM> to the second end <NUM>.

A first cross-sectional dimension D1 (<FIG>) of the holes H is defined circumferentially with respect to the axis A2, whereas a second cross-sectional dimension D2 (<FIG>) of the holes H is defined perpendicularly to the first cross-sectional dimension D1. In this embodiment, the holes H are cylindrical, such that the first and second cross-sectional dimensions D1, D2 correspond to diameters of the hole H having a same length. The holes H extend toward the axis A2 at a skew angle Φ relative to the axis A2. Depending on the embodiment, the skew angle may be between <NUM> and <NUM> degrees. In some such embodiments, the skew angle Φ is between <NUM> and <NUM> degrees. In some such embodiments, the skew angle Φ is between <NUM> and <NUM> degrees. In this embodiment, the skew angle Φ is of about <NUM> degrees, and is acute toward the first housing end <NUM> such that the holes H extend axially away from the first housing end <NUM> as they extend radially toward the axis A2. The exterior housing surface <NUM> and the interior housing surface <NUM> respectively define exterior openings H1 and interior openings H2 of the holes H. In embodiments in which the skew angle Φ is acute toward the first housing end <NUM>, each one of the holes H may be said to extend axially away from the second housing end <NUM> as it extends from their corresponding one of the interior openings H2 to their corresponding one of the exterior openings H1. This arrangement of the holes H may assist drainage of oil from the bearing cavity Cb via the holes H, and in some cases deflect oil and possible contaminants away from the bearing <NUM>. The exterior openings H1 extend axially away from the first housing end <NUM> from a first exterior axial location Le1 to a second exterior axial location Le2. The interior openings H2 extend axially from a first interior axial location Li1 to a second interior axial location Li2. The second housing location Lh2 is located between the first housing location Lh1 and the interior openings H2. According to the invention, the second housing location Lh2 is axially spaced from the first interior location Li1 (<FIG>), and hence the seat 56b of the interior housing surface <NUM> stops short of the interior openings H2. In this embodiment, the interior openings H2 are defined in a groove 56c of the housing <NUM> located axially between the cylindrical portion 56a and the second housing end <NUM>. The second housing location Lh2 may (in other embodiments not part of the invention) otherwise correspond to the first interior location Li1 (<FIG>, <FIG>), in which case the cylindrical portion 56a may be said to define at least a portion of the interior openings H2. In this embodiment, due to the acute aspect of the skew angle Φ, the first exterior axial location Le1 is closer to the first housing end <NUM> than the first interior axial location Li1. It should also be noted that the first exterior axial location Le1 is located axially between the first and the second edges 108a, 108b of the exterior outer-race surface <NUM>. By this arrangement, the exterior openings H1 of the holes H overhang a portion of the seat 56b, and thus a portion of the exterior outer-race surface <NUM> via which the seat 56b of the housing <NUM> radially engages the outer race <NUM>, thereby locally reducing the ability of the housing <NUM> to deform the underlying portion of the outer race <NUM>. In this embodiment, the interior housing surface <NUM> defines a radius that is greater than the first housing radius Rh1 at both the first and the second interior axial locations Li1, Li2. In this embodiment, the exterior openings H1 overlap the shoulder 58a, such that the exterior housing surface <NUM> defines the second housing radius Rh2 at the first exterior axial location Le1, and defines a radius that is greater than the second housing radius Rh2 at the second exterior axial location Le2. It should also be noted that at the first exterior location Le1, the interior housing surface <NUM> defines the first housing radius Rh1, such that the housing <NUM> has the radial thickness Tr at the first exterior location Le1.

In the embodiments of <FIG> and <FIG>, of <FIG>, of <FIG> and of <FIG>, the housing <NUM> and the outer race <NUM> are arranged relative to one another such that the interior openings H2 of the holes H do not overlap the exterior outer-race surface <NUM>. By this arrangement, the second edge 108b of the exterior outer-race surface <NUM> is fully circumscribed by the seat 56b of the interior housing surface <NUM>. This allows to minimize circumferential variation in the radial deformation of the outer race <NUM> proximate to the second outer race end <NUM>. In the embodiment of <FIG> and <FIG>, the first interior axial location Li1 is spaced axially away from the first housing end <NUM> such that the second edge 108b of the exterior outer-race surface <NUM> is located axially between the first edge 108a and the first interior axial location Li1. Stated otherwise, the exterior outer-race surface <NUM> extends axially toward the plurality of holes H from the first edge 108a located proximate to the first housing end <NUM> to the second edge 108b located proximate to the first interior axial location Li1. The exterior outer-race surface <NUM> also stops short of the interior openings H2, i.e., the second edge 108b of the exterior outer-race surface <NUM> is spaced axially from the first interior axial location Li1. The interior openings H2 of the holes H overlap a portion of the second outer-race end <NUM>. Indeed, the outer transition surface 104c extends across the first interior axial location Li1 as it extends from the second edge 108b to the second outer-race axial surface 104a. It should be noted however that the portion of the second outer-race end <NUM> overlapped by the interior openings H2 is spaced radially inwardly from the interior housing surface <NUM> and thus from the interior openings H2.

<FIG> shows an example not part of the present invention of the bearing assembly <NUM>. In this embodiment, the cylindrical portion 56a of the interior housing surface <NUM> extends axially from the first housing location Lh1 to across the interior openings H2 toward the second housing end <NUM>, and thus defines the interior openings H2. The seat 56b is adjacent to the interior openings H2 of the holes H at the first interior axial location Li1. The skew angle Φ of the holes H is acute toward the first housing end <NUM>. The exterior housing surface <NUM> defines the second housing radius Rh2 at the first exterior axial location Le1 and at the second exterior axial location Le2. The interior housing surface <NUM> defines the first housing radius Rh1 at the first interior axial location Li1 and at the second interior axial location Li2. The interior openings H2 of the holes H do not overlap the exterior outer-race surface <NUM> nor any other portion of the outer race <NUM>. For instance, the second edge 108b of the exterior outer-race surface <NUM> and the second outer-race end <NUM> (in this case consisting of the second outer-race axial surface 104a) are at the first interior axial location Li1.

<FIG> shows another example not part of the present invention of the bearing assembly <NUM>. In this embodiment, the cylindrical portion 56a of the interior housing surface <NUM> extends axially from the first housing location Lh1 to across the interior openings H2 toward the second housing end <NUM>, and thus defines the interior openings H2. The seat 56b is adjacent to the interior openings H2 of the holes H at the first interior axial location Li1. The skew angle Φ of the holes H is acute toward the first housing end <NUM>. The exterior housing surface <NUM> defines the second housing radius Rh2 at the first exterior axial location Le1 and at the second exterior axial location Le2. The interior housing surface <NUM> defines the first housing radius Rh1 at the first interior axial location Li1 and at the second interior axial location Li2. The interior openings H2 of the holes H do not overlap the exterior outer-race surface <NUM>. For instance, the second edge 108b of the exterior outer-race surface <NUM> is at the first interior axial location Li1. However, the interior openings H2 of the holes H do overlap the second outer-race end <NUM>, as the outer transition surface 104c extends past the first interior axial location Li1 toward the second interior axial location Li2 as it extends from the second edge 108b to the second axial outer-race surface 104a. Also, the outer transition surface 104c tapers as it extends from the second edge 108b, such that it remains spaced radially inwardly from the interior housing surface <NUM> and thus of the interior openings H2.

<FIG> shows yet another example not part of the present invention of the bearing assembly <NUM>. In this embodiment, the holes H extend radially relative to the axis A2, i.e., the skew angle Φ is a right angle. The holes H in this case have an elliptical cross-section, wherein the first cross-sectional dimension D1 is a length of a short axis thereof and the second cross-sectional dimension D2 is a length of a long axis thereof.

In embodiments such as those described hereinabove, the holes H are sized as a function of one or more dimensions of the housing <NUM> proximate to the second outer-race end <NUM> so as to achieve adequate radial deformation of the outer race <NUM>. For example, the first cross-sectional dimension D1 (<FIG>, <FIG>) may be sized as a function of the radial thickness Tr of the housing <NUM> at a rated axial location of the housing <NUM>. The rated axial location may be contiguous to the holes H on a side thereof that is proximate to the first housing end <NUM> and thus, in the depicted embodiments, corresponds to the first exterior location Le1. The rated location may be between the first housing location Lh1 and the first exterior location Le1. In embodiments, the first-cross-sectional dimension D1 is greater than the radial thickness Tr. In some such embodiments, the first cross-sectional dimension D1 is greater than <NUM> times the radial thickness Tr. In some such embodiments, the first cross-sectional dimension D1 is less than <NUM> times the radial thickness Tr. In some such embodiments, the first cross-sectional dimension D1 is between <NUM> and <NUM> times the radial thickness Tr. Moreover, the first cross-sectional dimension D1 may be sized as a function of a circumferential thickness Tc (<FIG> and <FIG>) of the housing <NUM> defined between the holes H at the exterior housing surface <NUM>, i.e., a minimum distance between two consecutive exterior openings H1. In embodiments, the first-cross-sectional dimension D1 is greater than the circumferential thickness Tc. In some such embodiments, the first cross-sectional dimension D1 is greater than <NUM> times the circumferential thickness Tc. In some such embodiments, the first cross-sectional dimension D1 is less than <NUM> times the circumferential thickness Tc. In some such embodiments, the first cross-sectional dimension D1 is between <NUM> and <NUM> times the circumferential thickness Tc. Hence, depending on the embodiment, the first cross-sectional dimension D1 may be at least equal to at least one of the radial thickness Tr of the annular wall W and the minimum distance between exterior openings H1 of consecutive holes of the plurality of holes H.

Claim 1:
A bearing housing (<NUM>) for a bearing (<NUM>) having an outer race (<NUM>), the bearing housing (<NUM>) comprising:
an annular wall (W) extending about an axis (A2) and axially between a first end (<NUM>) and a second end (<NUM>), the annular wall (W) including:
a plurality of holes (H) spaced circumferentially from one another and spaced axially from the first end (<NUM>), the plurality of holes (H) extending through the annular wall (W) toward the axis (A2);
an exterior housing surface (<NUM>) extending about the axis (A2) and defining exterior openings (H1) of the plurality of holes (H); and
an interior housing surface (<NUM>) extending about the axis (A2) and defining interior openings (H2) of the plurality of holes (H), the interior housing surface (<NUM>) having a cylindrical portion (56a) defining a seat (56b) for radial engagement with the outer race (<NUM>), the cylindrical portion (56a) extending axially from a first location (Lh1) proximate to the first end (<NUM>) to at least a second location (Lh2) between the first location (Lh1) and the interior openings (H2),
wherein each hole of the plurality of holes (H) extends toward the axis (A2) at a skew angle (Φ) relative to the axis (A2), the skew angle (Φ) being acute toward the first end (<NUM>); and
wherein the seat (56b) axially stops short of the interior openings (H2) and the exterior openings (H1) of the holes (H) overhang a portion of the seat (56b).