Patent Description:
One casing in a gas turbine engine may be connected to another casing of the gas turbine engine at a joint composed of mating flanges from each casing. The casings are secured to one another by bolting their flanges together. The casings experience loads during operation of the gas turbine engine. These loads may stress the bolts and/or the mating flanges, which may cause deformation of the flanges.

<CIT> discloses a prior art high temperature flange joint, exhaust diffuser and method for coupling two components in a gas turbine engine.

<CIT> discloses a prior art exhaust manifold flange connection.

<CIT> discloses a prior art joint assembly for an annular structure.

<CIT> discloses a prior art casing flange coupling assembly and a corresponding method of redistributing a flange load.

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

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

Further embodiments are provided as set forth in claims <NUM> to <NUM> and <NUM> to <NUM>.

In a further embodiment of the above, the support plate defines a first support plate plane parallel to the flange, the anti-rotation rib extending from the support plate toward the outer flange wall in a direction perpendicular to the first support plate plane.

In a further embodiment of the above, the anti-rotation rib has a radially-innermost surface mated with a radially-outermost surface of the outer flange wall.

In a further embodiment of the above, the support plate defines a first support plate plane parallel to the flange and extending through the support plate, the anti-rotation rib including a first anti-rotation rib extending from the support plate toward the outer flange wall in a direction perpendicular to the first support plate plane, the anti-rotation rib including a second anti-rotation rib extending from the support plate away from the outer flange wall in the direction perpendicular to the first support plate plane.

In a further embodiment of the above, the first and second anti-rotation ribs are symmetric about the first support plate plane.

In a further embodiment of the above, the support plate defines a first support plate plane parallel to the flange and extending through the support plate, the misalignment tab of the support plate disposed at an outer end of the support plate and the support plate having an inner end with a first chamfer and a second chamfer, the first and second chamfers being symmetric about the first support plate plane.

In a further embodiment of the above, the support plate defines a first support plate plane perpendicular to a hole center axis of the support plate hole, and a second support plate plane extending radially through the hole center axis and perpendicular to the first support plate plane, the misalignment tab being symmetric about the second support plate plane.

In a further embodiment of the above, the misalignment tab includes at least one protruding portion and at least one recessed portion, the at least one protruding portion positioned radially outwardly of the at least one recessed portion.

In a further embodiment of the above, the support plate defines a second support plate plane extending radially through a hole center axis of the support plate hole and perpendicular to the flange, the at least one protruding portion being symmetric about the second support plate plane.

There is disclosed a support plate for an engine casing, the support plate comprising: a body having a first side and a second side opposite the first side, the body extending between an outer end and an inner end and defining a center axis; a support plate hole extending through the body between the first and second sides and about the center axis; an anti-rotation rib on one or both of the first and second sides and disposed radially outwardly of the support plate hole; and a misalignment tab extending radially outwardly from the anti-rotation rib at the outer end.

In a further embodiment of the above, the inner end is chamfered.

In a further embodiment of any of the above, the body defines a first support plate plane perpendicular to the center axis and extending through the body between the first and second sides, the anti-rotation rib extending away from the one or both of the first and second sides in a direction perpendicular to the first support plate plane.

In a further embodiment of any of the above, the body defines a first support plate plane perpendicular to the center axis and extending through the body between the first and second sides, the anti-rotation rib including a first anti-rotation rib extending away from the first side in a direction perpendicular to the first support plate plane, the anti-rotation rib including a second anti-rotation rib extending away from the second side and away from the first anti-rotation rib in the direction perpendicular to the first support plate plane.

In a further embodiment of any of the above, the first and second anti-rotation ribs are symmetric about the first support plate plane.

In a further embodiment of any of the above, the body defines a first support plate plane perpendicular to the center axis and extending through the body between the first and second sides, the inner end having a first chamfer and a second chamfer, the first and second chamfers being symmetric about the first support plate plane.

In a further embodiment of any of the above, the body defines a first support plate plane perpendicular to the center axis and extending through the body between the first and second sides, and a second support plate plane extending radially through the center axis and perpendicular to the first support plate plane, the misalignment tab being symmetric about the second support plate plane.

<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 compressor section <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 a turbine section <NUM> for extracting energy from the combustion gases. Some of the components of the gas turbine engine <NUM> are rotatable about a longitudinal center axis <NUM>.

The gas turbine engine <NUM> includes a casing assembly <NUM>. The casing assembly <NUM> is an annular body housing within its interior one or more components of the gas turbine engine <NUM>, such as the fan <NUM>. The casing assembly <NUM> is formed by attaching two components together - a first casing <NUM> and a second casing <NUM>. One or both of the first and second casings <NUM>,<NUM> may be made up of interconnected casing sections or segments. Referring to <FIG>, the casing assembly <NUM> surrounds the fan <NUM> of the gas turbine engine <NUM>, and may thus be referred to as a "fan casing" or a "fan casing assembly". The casing assembly <NUM> in alternate embodiments may enclose or surround other components of the gas turbine engine <NUM>. The specific size, shape, and configuration of the casing assembly <NUM>, as described and/or illustrated herein, is exemplary only. Accordingly, the specific size, shape, and/or configuration of the casing assembly <NUM> generally, as well as portions thereof, may be selected to accommodate other components than the first and second casings <NUM>,<NUM>.

Referring to <FIG>, the first casing <NUM> includes and is defined by an annular first casing wall 15W, and the second casing <NUM> includes and is defined by an annular second casing wall 17W. The first casing <NUM> includes a first flange 15F and the second casing <NUM> includes a second flange 17F. The first and second flanges 15F,17F extend substantially radially outwardly with respect to the center axis <NUM> from their respective casing walls 15W,17W. Alternatively, depending on the application of the casing assembly <NUM>, each of the first and second flanges 15F,17F may be oriented at any angle relative to each respective casing wall 15W,17W, or may extend from any other component, that enables the casing assembly <NUM> to function. In an embodiment, one or both of the first and second flanges 15F,17F is a continuous body extending circumferentially relative to the center axis <NUM> around their respective casing walls 15W,17W. In another embodiment, one or both of the first and second flanges 15F,17F includes, or is made up of, discrete flange segments having a circumferential extent relative to the center axis <NUM>.

Referring to <FIG>, the first and second casings <NUM>,<NUM> are secured together by being coupled along the interface of the first and second flanges 15F,17F. The first and second flanges 15F, 17F are abutted together to mate along surfaces of the flanges 15F, 17F, bolts <NUM> are inserted through aligned holes in the first and second flanges 15F,17F, and the bolts are subsequently tightened to secure the mating first and second flanges 15F,17F together, as explained in greater detail below with reference to <FIG>.

Referring to <FIG>, the first flange 15F includes a first flange hole 15FH and the second flange 17F includes a second flange hole 17FH. The first and second flange holes 15FH,17FH are configured to receive a flange bolt, or simply one of the bolts <NUM>. The bolt <NUM> is inserted through each flange hole 15FH,17FH. Some or all of the first and second flange holes 15FH,17FH are aligned along a hole center axis <NUM> of the flange holes 15FH,17FH. The bolt <NUM> is securely fastened with a nut <NUM>. An optional washer or spacer may be inserted over the bolt <NUM> and paired with the nut <NUM>. The first flange 15F defines a first flange mating surface 15FM and an oppositely disposed first flange opposite surface 15FO. The second flange 17F defines a second flange mating surface 17FM and an oppositely disposed second flange opposite surface 17FO. The first flange mating surface 15FM abuts against the second flange mating surface 17FM when the first and second flanges 15F,17F are coupled together. Referring to <FIG>, at least a portion of first and second flange mating surfaces 15FM,17FM is substantially parallel to at least a portion of each respective opposite flange surface 15FO,17FO. Each flange hole 15FH,17FH, respectively, extends between each respective mating surface 15FM,17FM and each opposite surface 15FO,17FO.

Referring to <FIG>, the first flange 15F has a generally rectangular cross-sectional profile and is formed such that the first flange mating surface 15FM extends from an outer flange wall 15FW of the first flange 15F to the first casing wall 15W. The outer flange wall 15FW in <FIG> is the radially-outermost portion of the first flange 15F relative to the center axes <NUM>,<NUM>. The outer flange wall 15FW in <FIG> defines the radially-outermost surface of the first flange 15F relative the center axes <NUM>,<NUM>. Referring to <FIG>, the first flange mating surface 15FM is substantially parallel to the first flange opposite surface 15FO, and the center axis <NUM> of the first flange hole 15FH is oriented substantially perpendicularly to the surfaces 15FM,15FO. The first flange hole 15FH is positioned radially inwardly of the outer flange wall 15FW, with respect to the hole center axis <NUM>. Similarly, the second flange mating surface 17FM extends from a radially-outer wall of the second flange 17F to the second casing wall 17W, and is substantially perpendicular to the second casing wall 17W.

Referring to <FIG>, the first casing wall 15W and the first flange 15F meet at a joint 15J. The joint 15J has, or is composed of, a fillet 15R. The fillet 15R is a rounding of the corner of the joint 15J and is defined by a radius and curvature. The fillet 15R forms the transition between the first casing wall 15W and the first flange 15F. The fillet 15R is along, and forms part of, the first flange opposite surface 15FO and is positioned opposite to the first flange mating surface 15FM.

During operation of the gas turbine engines <NUM>, loads are generated and may act on the casing assembly <NUM>. For example, in the configuration where the casing assembly <NUM> encloses the fan <NUM> of the gas turbine engine <NUM>, a high event load such as fan blade off, in which a fan blade separates from the fan <NUM> and impacts the casing assembly <NUM>, may cause stress to the casings <NUM>,<NUM> and/or to their flanges 15F,17F. It has been observed that such high event loads, in addition to more routine loads imparting stresses over multiple operating cycles of the gas turbine engine <NUM>, may place the flanges 15F,17F under tensile loads and cause one or both of them to "peel" apart (i.e. to separate from each other), or may cause their flange holes 15FH, 17FH to distort in shape.

In order to compensate for any such anticipated loading, or to reinforce a flange 15F,17F that may have already experienced the effects of such loading, the casing assembly <NUM> is provided with one or more support plates <NUM>. The support plates <NUM> may be added to an existing flange 15F,17F that requires additional structural support or reinforcement against loads which may cause distortion of the flange holes 15FH,17FH or separation of the flanges 15F,17F under high event loads. The support plates <NUM> allow for strengthening a flange 15F,17F of the gas turbine engine <NUM> around the flange hole 15FH,17FH without having to remove the casing <NUM>,<NUM> containing the flange 15F,17F for repair or replacement. By reinforcing or strengthening a flange 15F,17F, the support plates <NUM> may allow for running the gas turbine engine <NUM> at loads higher than those for which the flange 15F,17F was designed, and thereby possibly allow for continued use of the flange 15F,17F without having to re-engineer it or the casing <NUM>,<NUM>.

Referring to <FIG>, the support plate <NUM> has a body <NUM>. The body <NUM> is a planar rectangular prism which has a thickness defined between a first side <NUM> and a second side 32O that is opposite to the first side <NUM>. The body <NUM> also has a height defined between an outer end 32U and an inner end 32I. The body <NUM> has a support plate hole <NUM> that extends through the body between the first and second sides <NUM>,32O. The support plate hole <NUM> is centered about a plate center axis 32A of the body <NUM>. The first and second sides <NUM>,32O are spaced apart from each other in an axial direction relative to the plate center axis 32A. The outer and inner ends 32O,32I are spaced apart from each other in a radial direction relative to the plate center axis 32A, to define the height of the body <NUM>.

In the configuration of the support plate <NUM> in <FIG>, the support plate <NUM> is a "single-hole" support plate <NUM> because it has only one support plate hole <NUM>. The single-hole support plate <NUM> increases the versatility of the support plate <NUM>, because it allows the support plate <NUM> to be used to reinforce any single flange hole 15FH,17FH, which may be desirable for flanges 15F,17F that do not have repeating hole patterns. The versatility provided by the single-hole support plate <NUM> may also allow it to be used to reinforce the flange 15F,17F at "empty" flange holes 15FH,17FH that are not already occupied by harness brackets or the like. However, other configurations of the support plate <NUM> are possible and within the scope of the present disclosure. For example, in another possible configuration of the support plate <NUM>, the support plate <NUM> has multiple support plate holes <NUM> and is used to reinforce a flange 15F,17F which has a repeating hole pattern. This configuration of the support plate <NUM> may include an annular or ring body <NUM>, or a circumferentially-elongated body <NUM>, each of which has multiple support plate holes <NUM> which are circumferentially spaced apart.

<FIG> show the support plate <NUM> mounted and secured against the first flange 15F of the first casing <NUM>. When mounted to the first flange 15F, the first side <NUM> of the body <NUM> abuts against, and mates with, the first flange opposite surface 15FO and is parallel with the first flange mating surface 15FM. When mounted to the first flange 15F, the outer end 32U is the radially-outer end of the body <NUM> relative to the hole center axes <NUM>, and the inner end 32I is the radially-inner end of the body <NUM> and is positioned closer to the first casing wall 15W than the outer end 32U. When mounted to the first flange 15F, the support plate hole <NUM> is aligned with the first and second flange holes 15FH,17FH such that the plate center axis 32A is collinear with the hole center axes <NUM> of the first and second flange holes 15FH,17FH. The bolt <NUM> is inserted through the support plate hole <NUM>, through the first flange hole 15FH, and through the second flange hole 17FH. The support plate <NUM> is secured to the first flange 15F by being fastened to the first flange 15F with the bolt <NUM>, and by tightening the bolt <NUM>. A bolt head <NUM> abuts against the second side 32O of the body <NUM>.

Although <FIG> show one support plate <NUM> secured to the first and second flanges 15F,17F around one pair of their flange holes <NUM>,<NUM>, the casing assembly <NUM> may have multiple support plates <NUM> each secured to a corresponding pair of first and second flange holes 15FH,17FH. One possible example of such a configuration is shown in <FIG> is an example of casing assembly <NUM> in which the flanges 15F,17F do not have repeating hole patterns. Furthermore, although <FIG> show a single-hole support plate <NUM>, the support plate <NUM> may have multiple support plate holes <NUM>, each of which is aligned with one pair of aligned flange holes 15FH,17FH of the flanges 15F,17F. In the configuration of the flanges 15F,17F in <FIG>, the first flange 15F is thinner than the second flange 17F (when measured along an axial direction relative to the aligned center axes <NUM>), such that only one support plate <NUM> may be needed to reinforce the casing assembly <NUM> at the first flange 15F, the second flange 17F being potentially thick enough to adequately resist bending or peeling. However, the casing assembly <NUM> in another embodiment has a second support plate <NUM> secured to the second flange 17F, either in addition to the first support plate <NUM> secured to the first flange 15F or not. Therefore, the description herein related to the support plate <NUM> and its features secured to the first flange 15F applies mutatis mutandis to a second support plate <NUM> secured to the second flange 17F.

The support plate <NUM> has one or more features which help to orient it correctly with respect to the first flange 15F, and which prevent it from being installed incorrectly on the first flange 15F. Some of these features are now described in greater detail.

Referring to <FIG>, one of these features is an anti-rotation rib <NUM> of the support plate <NUM>. The anti-rotation rib <NUM> helps to prevent the support plate <NUM> from rotating about the plate center axis 32A when it is being applied against the first flange 15F and secured in place by torqueing the bolt <NUM>. The anti-rotation rib <NUM> (sometimes referred to herein simply as the "rib <NUM>") thus helps the support plate <NUM> to have the correct orientation when the support plate <NUM> is being secured to the first flange 15F. The rib <NUM> also helps to prevent the support plate <NUM> from being installed incorrectly on the flange 15F by helping to ensure that the support plate <NUM> has the correct orientation. The rib <NUM> thus contributes to making the support plate <NUM> "mistake-proof", or less prone to being installed incorrectly.

The rib <NUM> may have any suitable shape or form to achieve such functionality. For example, and referring to <FIG>, the rib <NUM> includes a body <NUM> that has a height measured radially relative to the plate center axis 32A. The body <NUM> has a rib wall <NUM> that lies in a single straight plane (or possible a singly slightly curved plane). The rib <NUM> has a circumferential extent relative to the hole center axes <NUM> when the support plate <NUM> is installed on the first flange 15F, and is present on opposite circumferential sides of the hole center axes <NUM>. The rib <NUM> is positioned between the outer and inner ends 32U,32I of the body <NUM> of the support plate <NUM>. The rib <NUM> is located on the first side <NUM> of the body <NUM>, and extends transversely to the first side <NUM> toward the first flange 15F.

In order to achieve its anti-rotation function, the rib <NUM> abuts against the outer flange wall 15FW of the first flange 15F when the support plate <NUM> is positioned against the first flange 15F. Referring to the configuration of the rib <NUM> in <FIG>, the rib wall <NUM> defines or forms a radially-innermost surface of the rib <NUM>, relative to the hole center axes <NUM>. This radially-innermost surface abuts against, and mates with, part of the outer flange wall 15FW overlying the first flange hole 15FH. The outer flange wall 15FW forms an exposed, radially-outermost surface of the first flange 15F relative to the hole center axes <NUM>. The rib <NUM> is thus positioned radially outwardly of the outer flange wall 15FW, relative to the hole center axes <NUM>, when the support plate <NUM> is placed against the first flange 15F. The abutment of the rib wall <NUM> against the outer flange wall 15FW stops the support plate <NUM> from rotating about the plate center axis 32A when the bolt <NUM> is torqued. The anti-rotation functionality provided by the rib <NUM> may be beneficial to the single-hole support plate <NUM> of <FIG>, which may have a greater tendency to rotate about the plate center axis 32A when the bolt <NUM> is torqued. The configuration of the rib <NUM> in <FIG> shows the rib <NUM> extending over and overlaying most of the outer flange wall 15FW in an axial direction relative to the hole center axes <NUM>. In another possible configuration of the rib <NUM>, the rib <NUM> is axially longer than shown in <FIG> such that it extends axially over and overlays both the outer flange wall 15FW of the first flange 15F and some or all of the outer flange wall 17FW of the second flange 17F, such that the rib <NUM> abuts both flanges 15F,17F.

<FIG> show another feature of the support plate <NUM>, a misalignment tab <NUM>, which helps to orient the support plate <NUM> correctly with respect to the first flange 15F, and which prevents it from being installed incorrectly on the first flange 15F. The misalignment tab <NUM> helps to prevent the plate center axis 32A from aligning with the hole center axis <NUM> of the first flange 15F when the support plate <NUM> is incorrectly oriented with respect to the first flange 15F, as explained in greater detail below. Since the center axes 32A,<NUM> are misaligned when the support plate <NUM> is incorrectly oriented, the misalignment tab <NUM> helps to prevent the support plate <NUM> from being installed incorrectly on the first flange 15F because the bolt <NUM> cannot be inserted through the misaligned support plate and first flange holes <NUM>,15FH. The misalignment tab <NUM> (sometimes referred to herein simply as the "tab <NUM>") thus helps the support plate <NUM> to have the correct orientation when the support plate <NUM> is being secured to the first flange 15F. The tab <NUM> also helps to prevent the support plate <NUM> from being installed incorrectly on the flange 15F, thereby helping to make the support plate <NUM> "mistake-proof", or less prone to being installed incorrectly.

The tab <NUM> may have any suitable shape or form to achieve such functionality. For example, and referring to <FIG>, the tab <NUM> extends radially outwardly from the rib <NUM>, relative to the plate center axis 32A. The tab <NUM> is positioned radially outwardly of the support plate hole <NUM>, relative to the plate center axis 32A. The tab <NUM> thus forms a radially-outward extension of the support plate <NUM>, such that part of the support plate <NUM> (i.e. the tab <NUM>) protrudes radially outwardly from the outer flange wall 15W when the support plate <NUM> is secured to the first flange 15F. The height of the tab <NUM> (measured along a direction radial to the plate center axis 32A) contributes to misaligning the holes <NUM>,15FH when the support plate <NUM> is incorrectly oriented with respect to the first flange 15F. In the configuration of the tab <NUM> shown in <FIG>, the tab <NUM> has a circumferential extent relative to the hole center axes <NUM> when the support plate <NUM> is installed on the first flange 15F, and is present directly radially outwardly of the holes <NUM>,15FH and radially aligned therewith when the support plate <NUM> is secured to the first flange 15F. The tab <NUM> is centered on the support plate <NUM>. The tab <NUM> is positioned at the outer end 32U of the body <NUM> of the support plate <NUM>, and defines the radially-outermost surface of the support plate <NUM>, relative to the hole center axes <NUM>, when the support plate <NUM> is secured to the first flange 15F.

Referring to the configuration of the tab <NUM> in <FIG>, the tab <NUM> includes one or more protruding portions <NUM> and one or more recessed portions <NUM>. The protruding portion <NUM> is positioned radially outwardly of the recessed portions <NUM> relative to the plate center axis 32A. The protruding portion <NUM> is thus a bump forming the outer end 32U of the support plate <NUM> which helps to prevent the holes <NUM>,15FH from aligning when the support plate <NUM> is incorrectly oriented with respect to the first flange 15F, as explained in greater detail below. Referring to the configuration of the tab <NUM> in <FIG>, the tab <NUM> defines a outer tab wall <NUM> which defines the radially-outermost surface of the support plate <NUM>, relative to the aligned axes 32A,<NUM> when the support plate <NUM> is secured to the first flange 15F. The outer tab wall <NUM> along the recessed portions <NUM> is positioned radially closer to the plate center axis 32A than the outer tab wall <NUM> along the protruding portion <NUM>. The outer tab wall <NUM> along the protruding portion <NUM> lies in a single straight plane that is perpendicular to a line being radial to the plate center axis 32A. The outer tab wall <NUM> along the recessed portions <NUM> lies in a curved plane that slopes toward the plate center axis 32A from the outer tab wall <NUM> along the protruding portion <NUM>. In one possible configuration, the protruding portion <NUM> has a height measured along a radial line from the plate center axis 32A that is greater than a distance between the first casing wall 15W and the radially-innermost surface of the first flange hole <NUM>. In another possible configuration, the protruding portion <NUM> has a height measured along a radial line from the plate center axis 32A that is less than half the distance between the first casing wall 15W and the radially-innermost surface of the first flange hole <NUM>. It will thus be appreciated that the height of the tab <NUM> may be any value which causes misalignment of the holes <NUM>,15FH when the support plate <NUM> is incorrectly oriented with respect to the first flange 15F. Determining the height of the tab <NUM> may involve identifying the scenarios where the bolt <NUM> may still be inserted through the misaligned holes <NUM>,15FH, and selecting the height to avoid these scenarios.

Other configurations for the tab <NUM> are possible. For example, the tab <NUM> in another possible configuration has only a single protruding portion <NUM> and no recessed portions <NUM>. For example, in another possible configuration of the support plate <NUM> and referring to <FIG>, the tab <NUM> has two protruding portions <NUM> on opposite circumferential ends of the body <NUM>, where the protruding portions <NUM> are spaced apart by a single recessed portion <NUM>. In the configuration of <FIG>, the tab <NUM> is on either end of the support plate <NUM>, such that the recessed portion <NUM> provides a clearance which allows for a bracket <NUM> to be attached to the support plate <NUM>. The bracket <NUM> may be used to attach objects such as a wiring harness to the support plate <NUM>, and thus to the first flange 15F.

The ability of the misalignment tab <NUM> to orient the support plate <NUM> correctly with respect to the first flange 15F, and to prevent the support plate <NUM> from being installed incorrectly on the first flange 15F, may be better appreciated with reference to <FIG>. The support plate <NUM> is shown in <FIG> in an incorrect orientation with respect to the first flange 15F, in which the tab <NUM> is positioned "upside down" (i.e. abutting the first casing wall 15W). When the support plate <NUM> is positioned incorrectly with respect to the first flange 15F, <FIG> show that the protruding portion <NUM> of the tab <NUM> prevents the plate center axis 32A from aligning with the hole center axis <NUM>. Thus, the tab <NUM> stops the support plate and first flange holes <NUM>,15FH from being aligned when the support plate <NUM> is positioned incorrectly with respect to the first flange 15F, such that the bolt <NUM> is prevented from being inserted into the holes <NUM>,15FH and thus the support plate <NUM> cannot be secured to the first flange 15F. The installer will only be able to secure the support plate <NUM> to the first flange 15F by flipping the support plate <NUM> so that the misalignment tab <NUM> is radially outward. In this way, the misalignment tab <NUM> contributes to making the support plate <NUM> "mistake proof", because it allows the support plate <NUM> to be secured to the first flange 15F only when the support plate <NUM> has the correct orientation.

Another misalignment or mistake-proof feature of the tab <NUM> is also shown in <FIG>. The edges of the protrusion portion <NUM> of the tap <NUM> are straight and free of bevels or chamfers. These straight edges prevent the first side <NUM> of the support plate <NUM> from being placed flush against the first flange mating surface 15FM of the first flange 15F, because the straight edges of the protrusion portion <NUM> do not conform to the shape of the fillet 15R at the joint 15J between the first casing wall 15W and the first flange 15F. If the installer mistakenly moves the support plate <NUM> radially outward to place the first side <NUM> of the support plate <NUM> flush against the first flange mating surface 15FM, then the center axes 32A,<NUM> will be misaligned such that the bolt <NUM> will not be able to be inserted through the support plate and first flange holes <NUM>,15FH.

Referring to <FIG>, the support plate <NUM> and its mistake-proof features disclosed herein help reduce the possibility, and may even completely prevent, the incorrect installation of the support plate <NUM> against the first flange 15F. This allows for a substantially or completely "mistake-proof" assembly of the support plate <NUM> with the first flange 15F, such that the installer may perform such installation "blind" (i.e. without actually seeing the first flange 15F). Such a blind installation may be performed in an aircraft engine <NUM> which is still mounted to a wing of the aircraft, and in which it is difficult to see or access the first flange 15F. The inability to see the support plate <NUM> during its attachment to the first flange 15F, which might otherwise have prevented the installation of the support plate <NUM> or required dismounting the engine <NUM>, may no longer be an impediment to the installer from completing the work, because the mistake-proof features of the support plate <NUM> may allow the installer to still correctly attach the support plate <NUM> to the first flange 15F and thereby reinforce the first flange 15F.

Referring to <FIG>, when properly installed against the first flange 15F, the support plate <NUM> helps to structurally reinforce or strengthen the first flange 15F. The inner end 32I of the body <NUM> of the support plate <NUM> is chamfered, or has a chamfer <NUM>. One or both sides <NUM>,32O of the body <NUM> at the inner end 32I has a transitional wall 34T of the chamfer <NUM>. The transitional wall 34T extends between a side wall 32W of the body <NUM> on the first or second sides <NUM>,32O and a bottom wall 32B of the body <NUM> defining the radially-innermost surface of the body <NUM> relative to the aligned axes 32A,<NUM>. The transitional wall 34T may be a bevel, radius or any other surface that is shaped to be complementary to a shape of the fillet 15R, so that the chamfer <NUM> can be abutted against, and mate with, the fillet 15R at the joint 15J between the first casing wall 15W and the first flange 15F. For example, in the configuration of the support plate <NUM> in <FIG>, the transitional wall 34T is curved over its length, such that chamfer <NUM> is defined by a radius of curvature that matches or is similar to a radius of curvature of the fillet 15R. The curvature of the chamfer <NUM> is complementary to the curvature of the fillet 15R (e.g. the chamfer <NUM> has a convex curvature matching the concave curvature of the fillet 15R), so that they can be mated together.

The complementary shapes between the chamfer <NUM> and the fillet 15R may allow for tension loads acting on the casing walls 15W,17W to be transferred to the support plate <NUM> at the chamfer <NUM>. The chamfer <NUM> allows the inner end 32I of the support plate <NUM> to bear a portion of the load along the fillet 15R and parts of the casing wall 15W proximate the fillet 15R. The chamfer <NUM> may thus provide additional load bearing capacity to the support plate <NUM>. By reinforcing the joint 15J between the first casing wall 15W and the first flange 15F, the chamfer <NUM> of the support plate <NUM> helps to reinforce the fillet 15R during flange loading, and may reduce the tension loads causing the flanges 15F,17F to "peel" apart (i.e. to separate from each other). By abutting against the joint 15J at the fillet 15R, the chamfer <NUM> may help to lower bending at the flange 15F,17F. The complementary shapes between the chamfer <NUM> and the fillet 15R may allow for clearances or gaps between the support plate <NUM> and the fillet 15R to be minimized or eliminated, helping to ensure that the support plate <NUM> can be installed flush with the first flange 15F and thus will not interfere with the fillet 15R which might impact the bolt clamp stack.

Referring to <FIG>, the body <NUM> of the support plate <NUM> is symmetrical. As explained in greater detail below, the symmetry of the support plate <NUM> contributes to its mistake-proof attributes. The support plate <NUM> defines a first support plate plane P1. The first support plate plane P1 is parallel to the first flange 15F when the support plate <NUM> is secured to the first flange 15F. The first support plate plane P1 is parallel to the first flange mating and opposite surfaces 15FM,15FO of the first flange 15F when the support plate <NUM> is secured to the first flange 15F. The first support plate plane P1 (sometimes referred to herein simply as "the first plane P1") extends through the body <NUM> of the support plate <NUM>. The first plane P1 extends through the body <NUM> of the support plate <NUM> between the first side <NUM> and the second side 32O. The first plane P1 extends through the body <NUM> of the support plate <NUM> between the first side <NUM> and the second side 32O, and is spaced equidistantly from the first and second dies <NUM>,32O. The first plane P1 is parallel to the first side <NUM> and the second side 32O. The first plane P1 is perpendicular to the plate center axis 32A. The first plane P1 is perpendicular to the aligned center axes 32A,<NUM> when the support plate <NUM> is secured to the first flange 15F.

The support plate <NUM> defines a second support plate plane P2. The second support plate plane P2 is perpendicular to the first flange 15F when the support plate <NUM> is secured to the first flange 15F. The second support plate plane P2 is perpendicular to the first flange mating and opposite surfaces 15FM,15FO of the first flange 15F when the support plate <NUM> is secured to the first flange 15F. The second support plate plane P2 (sometimes referred to herein simply as "the second plane P2") extends through the body <NUM> of the support plate <NUM>. The second plane P2 contains the plate center axis 32A of the body <NUM>, extends radially from the plate center axis 32A, and has an upright or vertical orientation when the support plate <NUM> is secured to the first flange 15F. The second plane P2 is perpendicular to the first plane P1. The second plane P2 is perpendicular to the first and second sides <NUM>,32O of the body <NUM>. The second plane P2 may be considered to be a center plane because it contains the plate center axis 32A.

Some of the mistake-proof features of the support plate <NUM> are symmetrical about one or both of the first and second planes P1,P2. For example, and referring to <FIG>, the rib <NUM> includes a first rib 40A and a second rib 40B. The first and second ribs 40A,40B extend from the body <NUM> in a direction that is perpendicular to the first plane P1. The first rib 40A extends from the first side <NUM> of the body <NUM> in a direction that is perpendicular to the first plane P1 and also extends toward the outer flange wall 15FW. The first rib 40A is thus able to jut out over, and abut against, the outer flange wall 15FW. The second rib 40B extends from the second side 32O of the body <NUM> in a direction that is perpendicular to the first plane P1 and also extends away from the outer flange wall 15FW. Referring to <FIG>, the first and second anti-rotation ribs 40A,40B are symmetric about the first plane P1. The first and second ribs 40A,40B have reflectional symmetry (i.e. line or mirror symmetry), in that the first support plate plane P1 bisects the body <NUM> of the support plate <NUM>, dividing it into two pieces in which the ribs 40A,40B are mirror images of each other. The symmetry of the ribs 40A,40B about the first plane P1 and their presence on both sides <NUM>,32O of the support plate <NUM> helps to ensure that the support plate <NUM> will be correctly positioned against the first flange 15F, because the installer can abut either side <NUM>,32O of the support plate <NUM> against the first flange 15F. This contributes to the mistake-proof attributes of the support plate <NUM>, and further assists with a blind installation of the support plate <NUM>.

Another of the mistake-proof features of the support plate <NUM> that is symmetrical about one or both of the first and second planes P1,P2 is the misalignment tab <NUM>. For example, and referring to <FIG>, the tab <NUM> is symmetric about the second plane P2. Referring to <FIG>, the protruding and recessed portions <NUM>,<NUM> of the tab <NUM> are symmetric about the second plane P2. The tab <NUM> has reflectional symmetry (i.e. line or mirror symmetry), in that the second support plate plane P2 bisects the body <NUM> of the support plate <NUM>, dividing it into two pieces in which the protruding and recessed portions <NUM>,<NUM> are mirror images of each other. The symmetry of the tab <NUM> about the second plane P2 helps to ensure that the support plate <NUM> will be correctly positioned against the first flange 15F, because the installer can abut either side <NUM>,32O of the support plate <NUM> against the first flange 15F. This contributes to the mistake-proof attributes of the support plate <NUM>, and further assists with a blind installation of the support plate <NUM>.

Another of the mistake-proof features of the support plate <NUM> that is symmetrical about one or both of the first and second planes P1,P2 is the chamfer <NUM>. For example, and referring to <FIG>, the chamfer <NUM> includes a first chamfer 34A and a second chamfer 34B. The first and second chamfers 34A,34B are at the inner end 32I. The first and second chamfers 34A,34B are shaped such that their transitional walls 34T slow toward the first plane P1 from the side walls 32W of the body, and also slope toward each other. The first chamfer 34A is present on the first side <NUM> of the body <NUM>, and the second chamfer 34B is present on the second side 32O of the body <NUM>. The first and second chamfers 34A,34B are symmetric about the first plane P1. Referring to <FIG>, the first and second chamfers 34A,34B have reflectional symmetry (i.e. line or mirror symmetry), in that the first support plate plane P1 bisects the body <NUM> of the support plate <NUM>, dividing it into two pieces in which the chamfers 34A,34B are mirror images of each other. The symmetry of the chamfers 34A,34B about the first plane P1 and their presence on both sides <NUM>,32O of the support plate <NUM> (i. e a "double chamfer" at the inner end 32I) helps to ensure that the support plate <NUM> will be correctly positioned against the first flange 15F, because the installer can abut either side <NUM>,32O of the support plate <NUM> against the first flange 15F. This contributes to the mistake-proof attributes of the support plate <NUM>, and further assists with a blind installation of the support plate <NUM>.

The support plate <NUM> thus has features that are symmetrical in perpendicular planes P1,P2 of the support plate <NUM>. This symmetry contributes to making the support plate <NUM> mistake proof, because it allows for either side <NUM>,32O of the support plate <NUM> to be installed against the first flange 15F. This symmetry of the support plate <NUM>, in combination with the anti-rotation rib <NUM> and the misalignment tab <NUM>, helps to prevent installation of the bolt <NUM> until the support plate <NUM> is positioned in the correct configuration to reinforce the structural integrity of the first flange 15F.

Referring to another possible configuration of the support plate <NUM> in <FIG>, the first and second ribs 140A,140B extend perpendicularly outwardly from their respective sides <NUM>,132O of the body <NUM> of the support plate <NUM>. The two protruding portions <NUM> of the tab <NUM> are spaced inwardly toward the middle of the body <NUM> from the first and second ribs 140A,140B. The features of the support plate <NUM> shown in <FIG> have the same symmetry about the first and second planes P1,P2 described above. The description provided above of the features of the support plate <NUM> and their attributes applies mutatis mutandis to the features of the support plate <NUM> in <FIG>.

In operation, and referring to <FIG>, the support plate <NUM>,<NUM> may be attached to the first flange 15F as follows. The installer first abuts either side <NUM>,32O of the body <NUM> against the first flange mating surface 15FM. If the installer feels or observes that the body <NUM> is not flush against the first flange mating surface 15FM, they installer may move the body <NUM> until <NUM>) one of the ribs 40A,40B is abutting against the outer flange wall 15FW, <NUM>) the protruding portion <NUM> of the misalignment tab <NUM> extends radially outwardly of the outer flange wall 15FW, and <NUM>) one of the chamfers 34A,34B is flush against the fillet 15R of the joint 15J between the first casing wall 15W and the first flange 15F. The holes <NUM>,15FH will only be aligned if all three of these events occur, such that the support plate <NUM>,<NUM> can only be secured to the first flange 15F with the bolt <NUM> in the correct position when all three of these events have occurred.

Referring to <FIG>, there is disclosed a method of reinforcing or strengthening the flange 15F of the casing <NUM>. The method includes abutting the support plate <NUM>,<NUM> against a portion of the flange 15F. The method includes aligning the support plate hole <NUM> with the flange hole 15FH by abutting an outer end of the support plate <NUM>,<NUM> against the outer flange wall 15FW, and by having part of the support plate <NUM>,<NUM> protrude radially outwardly from the outer flange wall 15W. The method includes securing the support plate <NUM>,<NUM> to the portion of the flange 15F. There is also disclosed a method of retrofitting a flange 15F of an engine casing <NUM> with the support plate <NUM>,<NUM>, based on the disclosure herein. There is also disclosed a method of repairing a flange 15F of an engine casing <NUM> with the support plate <NUM>,<NUM>, based on the disclosure herein. These methods may include inspecting the flange 15F for damage, and validating the installation of the support plate <NUM>,<NUM>, such as with a stress engineer. There is also disclosed a method of blindly installing a support plate <NUM>,<NUM> on a flange 15F of an engine casing <NUM>, based on the disclosure herein. There is also disclosed a method of replacing an existing support plate on a flange 15F of an engine casing <NUM> using the support plate <NUM>,<NUM> disclosed herein, based on the disclosure herein. These methods may include preventing the support plate <NUM>,<NUM> from being secured in every or any orientation except a single orientation in which the support plate hole <NUM> is aligned with the flange hole 15FH.

Claim 1:
A support plate system for a gas turbine engine comprising:
a gas turbine engine casing (<NUM>) having an annular casing wall (15W) defining a center axis (<NUM>), a flange (15F) extending from the annular casing wall (15W) radially outwardly to an outer flange wall (15FW), the flange (15F) having a plurality of flange holes (15FH) radially inward of the outer flange wall (15FW), each of the plurality of flange holes (15FH) having a hole center axis (<NUM>); and
a support plate (<NUM>) comprising:
a body (<NUM>) having a first side (<NUM>) and a second side (<NUM>) opposite the first side (<NUM>), the body (<NUM>) extending between an outer end (<NUM>) and an inner end (32I) and defining a center axis (32A) of the support plate (<NUM>);
a support plate hole (<NUM>) extending through the body (<NUM>) between the first and second sides (<NUM>, <NUM>) and about the center axis (32A);
an anti-rotation rib (<NUM>) on one or both of the first and second sides (<NUM>, the anti-rotation rib (<NUM>) abutting the outer flange wall (15FW);
characterised in that
the anti-rotation rib is disposed radially outwardly of the support plate hole (<NUM>); and the support plate (<NUM>) is further comprising
a misalignment tab (<NUM>) extending radially outwardly from the anti-rotation rib (<NUM>) at the outer end (32U), the misalignment tab (<NUM>) configured to prevent the center axis (32A) of the support plate (<NUM>) from aligning with the hole center axis (<NUM>) of an associated one of the plurality of flange holes (15FH) when the support plate (<NUM>) is incorrectly oriented with respect to the flange (15F).