Patent Description:
Aircraft typically utilize brake systems on wheels to slow or stop the aircraft during landings, taxiing and rejected takeoffs. The brake systems generally employ a brake stack comprising a series of friction disks that may be forced into sliding contact with one another during brake actuation to slow or stop the aircraft. Under various conditions, brake actuation may generate high temperatures in the vicinity of the brake stack that can adversely impact or damage wheels or tires mounted thereon. Dissipation of this heat energy is desired to reduce or eliminate the deteriorative effects on the wheel and tire structure which, in certain instances such as an aborted or rejected take-off, can result in high temperatures that may result in tire ruptures or fires. A heat shield positioned between the brake stack and the wheel can mitigate thermal damage.

A known wheel assembly with a heat shield is disclosed in <CIT>.

According to a first aspect of the invention, a wheel assembly is disclosed, comprising a wheel having a rim and configured to rotate about an axis, a torque bar disposed radially inward of the rim, a heat shield disposed between the wheel and the torque bar, and a heat shield retainer comprising a retainer material, wherein the heat shield comprises a cylindrical structure extending circumferentially about an axis of the wheel and around an inner diameter of the rim, and the heat shield comprises a heat shield material, and a thermal conductivity of the heat shield material is greater than <NUM> W/mK.

In various embodiments, the thermal conductivity of the heat shield material is greater than greater than <NUM> W/mK.

In various embodiments, a thermal conductivity of the retainer material is greater than <NUM> W/mK.

In various embodiments, the wheel assembly further comprises a chin ring comprising a chin ring material, wherein a thermal conductivity of the chin ring material is greater than <NUM> W/mK.

In various embodiments, the heat shield material is evenly distributed throughout the heat shield.

According to the first aspect, the heat shield comprises a first end and a second end spaced apart from the first end,.

wherein the first end of the heat shield includes a first hook member and the second end of the heat shield includes a second hook member.

According to the first aspect, the heat shield retainer includes a first clip member configured to engage the first hook member and a second clip member configured to engage the second hook member.

In various embodiments, the cylindrical structure comprises a metal layer comprising a steel core and an aluminum coating covering the steel core.

In various embodiments, the wheel assembly further comprises a brake stack disposed within the heat shield.

According to a second aspect of the invention, a heat shield for an aircraft wheel assembly is disclosed, comprising an outer layer, and an inner layer spaced apart from the outer layer, wherein at least one of the outer layer and the inner layer comprises a heat shield material evenly distributed across the heat shield, wherein a thermal conductivity of the heat shield material is greater than <NUM> W/mK. According to the second aspect, the heat shield comprises a heat shield retainer comprising a retainer material, and the heat shield further comprises a first end and a second end spaced apart from the first end, the first end of the heat shield including a first hook member and the second end of the heat shield including a second hook member, the heat shield retainer including a first clip member configured to engage the first hook member and a second clip member configured to engage the second hook member.

In various embodiments, the heat shield further comprises a middle layer disposed between the outer layer and the inner layer, wherein the middle layer is made from at least one of an aluminum or an aluminum alloy.

In various embodiments, the heat shield further comprises a dimpled foil layer disposed between the middle layer and the inner layer.

In various embodiments, the heat shield further comprises an insulating core material disposed between the inner layer and the outer layer.

According to a third aspect of the invention, a heat shield for an aircraft wheel assembly is disclosed, comprising a metal layer comprising a steel core and an aluminum coating covering the steel core. According to the third aspect, the heat shield comprises a heat shield retainer comprising a retainer material, and the heat shield further comprises a first end and a second end spaced apart from the first end, the first end of the heat shield including a first hook member and the second end of the heat shield including a second hook member, the heat shield retainer including a first clip member configured to engage the first hook member and a second clip member configured to engage the second hook member.

In various embodiments, the heat shield comprises a thermal conductivity greater than <NUM> W/mK.

In various embodiments, the heat shield comprises a cylindrical geometry.

The accompanying drawings illustrate various embodiments of the invention employing the principles described herein. The illustrated embodiments are meant for description and not to limit the scope of the claims.

The detailed description of various embodiments of the invention herein makes reference to the accompanying drawings, which show various embodiments by way of illustration. While these various embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that changes may be made without departing from the scope of the invention. Also, any reference to attached, fixed, connected, or the like may include permanent, removable, temporary, partial, full, and/or any other possible attachment option.

As used herein, a first component that is "radially outward" of a second component means that the first component is positioned at a greater distance away from a common axis than the second component. A first component that is "radially inward" of a second component means that the first component is positioned closer to the common axis than the second component. In the case of components that rotate circumferentially about a common axis, a first component that is radially inward of a second component rotates through a circumferentially shorter path than the second component. As used herein, "distal" refers to the direction outward, or generally, away from a reference component. As used herein, "proximal" and/or "proximate" refer to a direction inward, or generally, towards the reference component. All ranges may include the upper and lower values, and all ranges and ratio limits disclosed herein may be combined. Unless specifically stated otherwise, reference to "a," "an" or "the" may include one or more than one and reference to an item in the singular may also include the item in the plural.

Typically, heat shields for aircraft wheel assemblies comprise thermally insulating materials (i.e., comprising relatively low thermal conductivities) to reduce thermal flux between the brake stack (heat sink) and the wheel assembly. In contrast to the present direction of the field of art, the present invention provides a heat shield made from a high thermal conductivity material, such as aluminized steel, aluminum, or an aluminum alloy, among other materials. After a braking maneuver, a large thermal gradient may be present in a wheel/brake assembly. At rest, the top of the wheel/brake assembly may be hottest due to natural convection, while the bottom of the wheel/brake assembly may be coolest. Furthermore, the inboard side of the wheel/brake assembly may be cooler than an outboard side of the wheel/brake assembly near the webbing of the wheel. By increasing the thermal conductivity of the heat shield, heat flux through the heat shield from hot areas to cooler areas along the circumferential direction may be increased or otherwise enhanced. Furthermore, heat flux through the heat shield from hot areas to cooler areas along the axial direction may be increased or otherwise enhanced. Because the thermal conductivity of air is far less than that of the high thermal conductivity heat shield material, conductive heat transfer through the heat shield may be the dominant mode of heat transfer. As heat is transferred from the upper region to the lower region of the heat shield, the radial thermal gradient (i.e., the thermal gradient along the radial direction) becomes greater resulting in greater heat transfer in the bottom region and faster cooling times. Likewise, as heat is transferred from the outboard region to the inboard region of the heat shield, the radial thermal gradient (i.e., the thermal gradient along the radial direction) becomes greater resulting in greater heat transfer in the inboard region and faster cooling times.

In various embodiments, heat shields comprise one or more segments connected together at their ends by retainers. In this manner, retainers may similarly be made from a high thermal conductivity material. In various embodiments, the heat shield and the heat shield retainer comprises the same high thermal conductivity material.

In various embodiments of braking systems, the heat sink is of greater axial dimension than the wheel rim member into which the heat sink extends. In such a braking system, a chin ring may be attached to an aircraft wheel to prevent an aircraft tire from being heated by radiant energy emitted from the heat sink (tire being in the "line of sight" of the heat sink components). The present invention provides a chin ring comprising a high thermal conductivity material to maximize thermal flux from the heat shield to the chin ring which is generally located at an inboard side of the wheel with better exposure to ambient conditions to aid in shedding heat externally from the wheel.

With combined reference to <FIG>, a schematic view of a wheel assembly <NUM> is illustrated, in accordance with various embodiments. Wheel assembly <NUM> generally comprises a wheel <NUM>, a heat shield <NUM>, and a brake stack <NUM>. A central axis <NUM> extends through the wheel <NUM> and defines an axis of rotation of the wheel <NUM>. The brake stack <NUM> generally comprises a plurality of rotor disks interleaved with a plurality of stator disks positioned intermediate a pressure plate and an end plate. The plurality of rotor disks and the plurality of stator disks are fabricated from various materials, such as ceramic matrix composites, that enable the brake disks to withstand and dissipate the heat generated during and following a braking action.

The heat shield <NUM> is secured directly or indirectly (e.g., via one or more torque bars and/or via a chin ring, among other indirect connections) to the wheel <NUM> between a radially inward surface of the wheel <NUM> and the brake stack <NUM>. In various embodiments, the heat shield <NUM> is secured directly or indirectly to the wheel <NUM> between a radially inward surface of the wheel <NUM> and a plurality of torque bars <NUM>. Heat shield <NUM> may be concentric with the wheel <NUM>.

Heat shield <NUM> may be made from a material comprising a high thermal conductivity. Heat shield <NUM> may be comprised of a material, such as a metal or metal alloy, comprising a thermal conductivity that is greater than <NUM> Watts per meter Kelvin (W/mK) (<NUM> BTU/(h ft °F)), in accordance with various embodiments, greater than <NUM> W/mK (<NUM> BTU/(h ft °F)), in accordance with various embodiments, greater than <NUM> W/mK (<NUM> BTU/(h ft °F)), in accordance with various embodiments, and/or greater than <NUM> W/mK (<NUM> BTU/(h ft °F)), in accordance with various embodiments. In this regard, with momentary reference to <FIG>, heat shield <NUM> may comprise a metal <NUM> comprising a high thermal conductivity material <NUM> evenly distributed throughout heat shield <NUM>. Stated differently, the entire heat shield <NUM> comprises the high thermal conductivity material <NUM>. In various embodiments, heat shield <NUM> may be made from aluminized steel. Aluminized steel may comprise a thermal conductivity of between <NUM> and <NUM> W/mK (between <NUM> and <NUM> BTU/(h ft °F)), in accordance with various embodiments. The high thermal conductivity material may comprise an aluminum alloy coating evenly distributed across the entire heat shield <NUM>. In this regard, with momentary reference to <FIG>, heat shield <NUM> may comprise an aluminized steel sheet <NUM> comprising a steel core <NUM> and an aluminum coating <NUM> covering the steel core <NUM>. In various embodiments, aluminum coating <NUM> may be evenly distributed throughout the surface of aluminized steel sheet <NUM>. For example, steel core <NUM> may be hot-dip coated in the aluminum coating <NUM>. Steel core <NUM> may comprise a carbon steel or a stainless steel, among other types of iron alloys, in accordance with various embodiments. Aluminum coating <NUM> may comprise an aluminum, or an aluminum alloy, such as an aluminum-silicon alloy, or an aluminum-zinc alloy, among other types of aluminum alloys. In various embodiments, heat shield <NUM> may be made from aluminum. Aluminum may comprise a thermal conductivity of between <NUM> and <NUM> W/mK (between <NUM> and <NUM> BTU/(h ft °F)), in accordance with various embodiments. In various embodiments, heat shield <NUM> may be made from copper. Copper may comprise a thermal conductivity of between <NUM> and <NUM> W/mK (between <NUM> and <NUM> BTU/(h ft °F)), in accordance with various embodiments. However, heat shield <NUM> may be made from various metals or metal alloys comprising a high thermal conductivity, as described herein. As used herein, the thermal conductivity provided for various materials may be the thermal conductivity of the material at room temperature. In various embodiments, the heat shield material comprises a melting temperature of no less than <NUM> °F (<NUM>) so as to withstand heat generated by the brake stack.

In various embodiments, the heat shield material comprising the high thermal conductivity is evenly distributed throughout the heat shield <NUM>. Stated differently, the entire heat shield <NUM> may comprise the high thermal conductivity heat shield material. In this manner, heat flux from areas of higher temperatures to areas of lower temperatures of the heat shield <NUM> is facilitated and/or maximized in both circumferential and axial directions.

During a braking maneuver heat is generated by brake stack <NUM>. This heat (i.e., radiant heat and/or convection heat) may travel upwards, as illustrated by arrows <NUM> in <FIG>. Heat shield <NUM> may absorb this heat to reduce the temperature of wheel <NUM>. Due to the high thermal conductivity of heat shield <NUM>, heat is more easily conducted through heat shield <NUM> to evenly distribute heat around the entire circumference of heat shield <NUM>. In various embodiments, heat <NUM> that radiates or convectively travels upwards within wheel <NUM> may be conductively transferred downwards through heat shield <NUM>, as represented by arrows <NUM>. In this manner, the high thermal conductivity of heat shield <NUM> drives conductive heat transfer through heat shield <NUM> to be a dominant form of heat transfer to minimize radiant or convective heat transfer from brake stack <NUM> and/or heat shield <NUM> to wheel <NUM>.

Furthermore, with reference to <FIG>, heat generated by brake stack <NUM> may tend to accumulate within wheel <NUM> towards the outboard side <NUM> of wheel <NUM> in the general region circumscribed by dashed line <NUM>. In addition to circumferential distribution of heat, heat shield <NUM> may further evenly distribute heat along the axial direction to draw heat from within wheel <NUM> (i.e., the region generally within dashed line <NUM>) towards an inboard side <NUM> of wheel <NUM>, as illustrated by arrow <NUM>, which may be better exposed to ambient conditions to remove heat from within wheel <NUM>. Furthermore, heat may be transferred conductively to other components such as a chin ring (e.g., see chin ring (e.g., see chin ring <NUM> of <FIG>), or a retainer (e.g., see retainer <NUM> of <FIG>), in accordance with various embodiments. In this regard, chin ring <NUM> and/or retainer <NUM> may similarly be made from a high thermal conductivity material, as provided herein.

Referring now to <FIG>, a wheel <NUM> having a heat shield is provided. In various embodiments, the wheel <NUM> includes an outboard lip <NUM>, coupled to a wheel disk <NUM> by a plurality of wheel tie bolts <NUM>, and an inboard lip <NUM> defining a rim <NUM> about the wheel disk <NUM>. A hub <NUM> is centered through the wheel disk <NUM> and may comprise one or more bearings <NUM>. The rim <NUM> extends axially with respect to the hub <NUM> about a circumference of the wheel disk <NUM>. A heat shield <NUM> is disposed radially inward of the rim <NUM> between the inboard lip <NUM> and the wheel disk <NUM> of the wheel <NUM>. Heat shield <NUM> may be similar to heat shield <NUM> of <FIG>. In various embodiments, the heat shield <NUM> includes a cylindrical structure <NUM> extending circumferentially about an axis of the hub <NUM> and around an inner diameter of the rim <NUM>. In various embodiments, the heat shield <NUM> may be coupled proximate the rim <NUM> by a plurality of fasteners <NUM> and may be held proximate the rim <NUM>, with a chin ring <NUM> proximate the inboard lip <NUM>, by an interference between the heat shield <NUM> and a plurality of torque bars <NUM>, in accordance with various embodiments. In various embodiments, the plurality of torque bars <NUM> may be coupled to the wheel disk <NUM> at an outboard end and may be coupled to the heat shield <NUM> at an inboard end proximate the chin ring <NUM> by the plurality of fasteners <NUM>. The plurality of torque bars <NUM> may extend into torque bar apertures <NUM> disposed in wheel disk <NUM>. As described below, in various embodiments, the heat shield <NUM> may comprise one or more heat shield segments <NUM> that are arranged and assembled circumferentially proximate the inner diameter of the wheel <NUM>.

For clarity purposes, one of the torque bars <NUM> is removed in <FIG>, exposing a heat shield retainer <NUM>. Heat shield retainer <NUM> may secure two ends of heat shield <NUM> relative to one another. In various embodiments, heat shield <NUM> may be secured by the torque bars <NUM> and/or heat shield retainer <NUM> from radial movement, thereby preventing the heat shield <NUM> from radial deflection. In various embodiments, heat shield <NUM> may be secured by the chin ring <NUM> from radial movement, thereby preventing the heat shield <NUM> from radial deflection.

In various embodiments, the heat shield retainer <NUM> assumes the form of a C-clip in cross section (see <FIG>) having a length in an axial direction A. However, heat shield retainer <NUM> may assume the form of any suitable geometry in cross section. In various embodiments, the heat shield segment <NUM> comprises a cylindrically shaped structure <NUM> comprising an inner surface <NUM> (or first surface) and an outer surface <NUM> (or second surface) with respect to a radial direction R. In various embodiments, the heat shield segment <NUM> extends a circumferential distance <NUM> and an axial distance <NUM>, respectively, in both a circumferential direction C and the axial direction A. In various embodiments, the axial distance <NUM> of the heat shield segment <NUM> may equal the distance between a first axial location (or inboard end) proximate an inboard lip and a second axial location (or outboard end) proximate a wheel disk of a wheel, such as, for example, the inboard lip <NUM> and the wheel disk <NUM> of the wheel <NUM>.

In various embodiments, the circumferential distance <NUM> may span the entire circumference of an inner surface of a wheel, to form a single-segment heat shield, or may span a fraction of the entire circumference, to form a multiple-segment heat shield (e.g., a heat shield assembly including a first heat shield segment and a second heat shield segment and a first heat shield retainer and a second heat shield retainer). In various embodiments, for example, the circumferential distance <NUM> may equal the distance between adjacent pairs of a plurality of torque bars, thereby forming a multiple-segment heat shield, where the number of heat shield segments equals the number of torque bars. In various embodiments, the number of heat shield segments forming a multiple-segment heat shield may be an integral number, regardless of the number of torque bars.

With reference to <FIG>, the heat shield segment <NUM> may include a first end <NUM> (or first circumferential end) and a second end <NUM> (or second circumferential end). Heat shield retainer <NUM> may comprise a high conductivity material, as described herein. In this manner, heat shield retainer <NUM> may comprise a conduction path between first end <NUM> and second end <NUM> to provide circumferential transfer of heat between adjacent ends of a heat shield and/or adjacent heat shield segments. In various embodiments, the first end <NUM> includes a first hook member <NUM> and the second end <NUM> includes a second hook member <NUM>. The first hook member <NUM> may be configured to engage a first clip member <NUM> of the heat shield retainer <NUM> and the second hook member <NUM> may be configured to engage a second clip member <NUM> of the heat shield retainer <NUM>. While the first hook member <NUM> and the second hook member <NUM>, and the first clip member <NUM> and the second clip member <NUM>, respectively, are each illustrated as having a curved U-shape profile in cross section (e.g., corresponding to the C-clip shape of the heat shield retainer <NUM> illustrated in <FIG>), the disclosure contemplates other shapes or profiles, such as, for example, square- or V-shaped cross sectional shapes or profiles. Additionally, in various embodiments, the heat shield segment <NUM> includes a mount aperture (or several such apertures) that is configured to secure the heat shield to the wheel and/or chin ring using, for example, a screw or bolt or the like extending through the mount aperture and into the wheel.

In various embodiments, the heat shield assembly <NUM> is assembled by positioning the first end <NUM> and the second end <NUM> of the heat shield segment <NUM> adjacent one another, as illustrated in <FIG>, and then sliding the heat shield retainer <NUM> in a direction parallel to the axial direction A, such that the first clip member <NUM> and the second clip member <NUM> engage, respectively, the first hook member <NUM> and the second hook member <NUM> of the heat shield retainer <NUM>. While the heat shield retainer <NUM>, the first clip member <NUM> and the second clip member <NUM>, and the first hook member <NUM> and the second hook member <NUM>, are each illustrated as extending in a direction substantially parallel with the axial direction A, the disclosure contemplates each of the foregoing components may be configured to extend along directions other than parallel to the axial direction A. In various embodiments, for example, each of the foregoing components may be configured to extend at an angle with respect to the axial direction A without loss of generality. In addition, the first clip member <NUM> and the second clip member <NUM>, and the first hook member <NUM> and the second hook member <NUM>, may each extend substantially along the entire length of the heat shield segment <NUM> and the heat shield retainer <NUM>, or the various components may extend along only a portion or a plurality of portions of the respective lengths. Furthermore, in accordance with various embodiments, the first end <NUM> and the second end <NUM> of the heat shield segment <NUM> may be coupled together without the use of a separate retainer. In this manner, the first end <NUM> and the second end <NUM> may interlock directly around each other to secure the first end <NUM> and the second end <NUM> together.

In various embodiments, heat shield segment <NUM> may be a single layer heat shield or a multi-layer heat shield. An example dual-layer heat shield <NUM> is illustrated in <FIG>. With momentary reference to <FIG>, a dual-layer heat shield <NUM> may comprise a first layer <NUM> comprising a high thermal conductivity material, and a second layer <NUM> comprising the high thermal conductivity material spaced apart from the first layer <NUM>. First layer <NUM> may be crimped at its edges to second layer <NUM>. In various embodiments, an air pocket may be disposed between the first layer <NUM> and the second layer <NUM>. In various embodiments, the air pocket may be filled with a core material, such as core material <NUM> with momentary reference to <FIG>. Core material <NUM> may comprise a ceramic fiber insulation, or the like. First layer <NUM> may comprise an exposed surface facing radially outwards. Second layer <NUM> may comprise an exposed surface facing radially inwards. Core material <NUM> may be sandwiched between the first layer <NUM> and the second layer <NUM>.

With reference to <FIG>, a section view of a heat shield <NUM> is illustrated, in accordance with various embodiments. Heat shield <NUM> may comprise an outer layer <NUM> (also referred to herein as a first layer), an inner layer <NUM> (also referred to herein as a second layer), and a middle layer <NUM> (also referred to herein as a third layer). In various embodiments, the middle layer <NUM> may be made from aluminum or an aluminum alloy. In various embodiments, the inner layer <NUM> and/or the outer layer <NUM> may be made from a high thermal conductivity material, such as aluminized steel for example. However, in various embodiments, the inner layer <NUM> and/or the outer layer <NUM> may be made from stainless steel. In this manner, middle layer <NUM> may comprise a high thermal conductivity such that the middle layer <NUM> evenly distributes heat along heat shield <NUM> in all directions (e.g., circumferential and axial directions). In various embodiments, a thin foil layer <NUM> (also referred to herein as a dimpled foil layer) may be disposed between the inner layer <NUM> and the middle layer <NUM>. Foil layer <NUM> may be provided as a radiant heat barrier between the inner layer <NUM> and the middle layer <NUM>. The foil layer <NUM> may be dimpled to maintain its position between the inner layer <NUM> and the middle layer <NUM>. Dimpled foil layer <NUM> may be configured to mitigate radiative heat from a brake stack from heating middle layer <NUM> above the melting temperature of the aluminum or aluminum alloy. Dimpled foil layer <NUM> may be made from a metal material such as stainless steel or aluminized steel, or the like. Dimpled foil layer <NUM> may comprise a sheet of metal with a plurality of dimples <NUM> configured to contact inner layer <NUM> and/or middle layer <NUM> to maintain proper spacing between inner layer <NUM>, dimpled foil layer <NUM>, and middle layer <NUM>. In various embodiments, outer layer <NUM>, inner layer <NUM>, and middle layer <NUM> may be crimped together at their edges. In various embodiments, outer layer <NUM> and middle layer <NUM> are spaced apart via an air gap (see <FIG>) and/or via an insulating core material (see <FIG>).

However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the invention. The scope of the invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more.

After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the invention in alternative embodiments.

Claim 1:
A wheel assembly, comprising:
a wheel having a rim (<NUM>) and configured to rotate about an axis;
a torque bar (<NUM>) disposed radially inward of the rim;
a heat shield (<NUM>, <NUM>) disposed between the wheel and the torque bar, wherein the heat shield comprises a cylindrical structure extending circumferentially about an axis of the wheel and around an inner diameter of the rim;
wherein the heat shield (<NUM>, <NUM>) comprises a heat shield material, and a thermal conductivity of the heat shield material is greater than <NUM> W/mK; characterised in that the heat shield further comprises a heat shield retainer (<NUM>) comprising a retainer material;
wherein the heat shield comprises a first end (<NUM>) and a second end (<NUM>) spaced apart from the first end,
wherein the first end of the heat shield (<NUM>, <NUM>) includes a first hook member (<NUM>) and the second end of the heat shield includes a second hook member (<NUM>), wherein the heat shield retainer includes a first clip member (<NUM>) configured to engage the first hook member and a second clip member (<NUM>) configured to engage the second hook member