Patent Description:
Aircraft carbon and CMC brake systems typically employ a series of friction disks forced into contact with each other to stop the aircraft. Friction disks splined to a non-rotating wheel axle are interspersed with friction disks splined to the rotating wheel. The friction disks withstand and dissipate the heat generated from contact between one another during braking. During taxi out, carbon friction disks in particular are colder and quicker to wear than when the friction disks are hotter. <CIT> relates to a disc brake unit comprising a multiple discs brake assembly.

A carbon and CMC brake stack is disclosed herein. In various embodiments, the brake stack comprises a first stator having a first stator radially inner end; a first rotor disposed axially adjacent to the first stator, the first rotor having a first rotor radially inner end; a second stator disposed axially adjacent to the first rotor; and a first spring disposed axially between the first stator and the second stator and radially between the first stator radially inner end and the first rotor radially inner end.

In various embodiments, the first spring may be a wave spring. The brake stack further comprises a pressure plate disposed at a proximal end of the brake stack, wherein the first spring is configured to partially compress when a force is applied to the pressure plate that is less than a threshold force. A first stator axial face of the first stator is separated from a first rotor axial face of the first rotor when the first spring is partially compressed. The threshold force may correspond to a threshold pressure between <NUM> psi (<NUM> MPa) and <NUM> psi (<NUM> MPa). The brake stack further comprises a pressure plate disposed at a proximal end of the brake stack, wherein the first spring is configured to fully compress when a force is applied to the pressure plate that is greater than a threshold force. A first stator axial face of the first stator may contact a first rotor axial face of the first rotor when the first spring is fully compressed. The brake stack may further comprisee: a second rotor disposed axially adjacent to the second stator, the second rotor having a second rotor radially inner end; a third stator disposed axially adjacent to the second rotor; and a second spring disposed axially between the second stator and the third stator and radially between a second stator radially inner end of the second stator and the second rotor radially inner end. The second spring may be a second wave spring.

A multi-disk carbon and ceramic matrix composite (CMC) brake system according to the invention is defined in claim <NUM>. According to the invention, the CMC brake system comprises: a brake stack comprising pressure plate; an end plate disposed distal to the pressure plate; a plurality of rotors disposed between the pressure plate and the end plate; a plurality of stators disposed between the pressure plate and the end plate, the plurality of stators interleaved between the plurality of rotors; a first portion of disks having no spring, a second portion of disks having at least a first spring disposed axially between a first stator in the plurality of stators and an adjacent stator in the plurality of stators, the first spring disposed radially inward of a first rotor in the plurality of rotors, wherein the first spring is configured to partially compress when a force is applied to the pressure plate that is less than a threshold force; wherein a first stator axial face of the first stator is separated from a first rotor axial face of the first rotor when the first spring is partially compressed.

In various examples, the first spring comprises a wave spring. The threshold force may correspond to a threshold pressure between <NUM> psi (<NUM> MPa) and <NUM> psi (<NUM> MPa). The first spring may be configured to fully compress when a force is applied to the pressure plate that is greater than a threshold force. A first stator axial face of the first stator may contact a first rotor axial face of the first rotor when the first spring is fully compressed. The multi-disk brake system may further comprise a plurality of the first spring. The plurality of the first spring may be disposed circumferentially about the first stator.

A method of using a multi-disk carbon and ceramic matrix composite (CMC) brake system according to the invention is defined in claim <NUM>. According to the invention, the method comprises: applying a force to a pressure plate of the multi-disk carbon and CMC brake system comprising a brake stack; compressing a spring between a first stator and a second stator; and using a portion of disks in the brake stack if the force is less than a threshold force; and using all disks in the brake stack if the force is greater than the threshold force.

The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present invention, however, may best be obtained by referring to the detailed description and claims when considered in connection with the drawing figures, wherein like numerals denote like elements.

The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration. While these exemplary 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 logical changes and adaptations in design and construction may be made in accordance with this invention and the teachings herein without departing from the scope of the invention, which is limited only within the scope of the appended claims.

In the case of components that rotate about a common axis, a first component that is "radially outward" of a second component means that the first component is positioned at a greater distance away from the 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.

Disclosed herein, according to various examples, is a multi-disk carbon and CMC brake system. The multi-disk carbon and CMC brake system includes a plurality of rotors interleaved between a plurality of stators, a pressure plate at a proximal end, an end plate at a distal end, and at least one spring. As described in greater detail below, the spring is disposed between a first stator and a second stator and radially inward of a rotor. The spring is configured to allow a portion of the rotors and stators to supply the braking when a force applied to the pressure plate is below a threshold force. Additionally, the spring is configured to allow all the rotors and stators to supply the braking when a force applied to the pressure plate is above the threshold force. Carbon composite disks may wear quicker when they are cold. By only using a first portion of disks when a lower brake force is used, the disks being used may heat up more quickly increasing the life of the disks being used and/or reducing the number of cold taxis experienced. Additionally, by not using a second portion of disks when a lower brake force is used, the second portion of disks may have significantly increased life. As such, at overhaul, the first portion of disks may be replaced, and the second portion of disks may remain, reducing cost and time at overhaul.

Referring to <FIG>, a multi-disk carbon and CMC brake system <NUM> is illustrated according to various examples. The system may include a wheel <NUM> supported for rotation around axle <NUM> by bearings <NUM>. Axle <NUM> defines an axis of multi-disk carbon and CMC brake system <NUM> and the various components thereof described herein, and any reference to the terms axis and axial may include an axis of rotation defined by axle <NUM> or a dimension parallel to such axis. Wheel <NUM> includes rims <NUM> for supporting a tire, and a series of axially extending rotor splines <NUM> (one shown). Rotation of wheel <NUM> is modulated by multi-disk carbon and CMC brake system <NUM>. Multi-disk carbon and CMC brake system <NUM> includes torque flange <NUM>, torque tube <NUM>, a plurality of pistons/actuators <NUM> (one shown), pressure plate <NUM>, and end plate <NUM>. Torque tube <NUM> may be an elongated annular structure that includes reaction plate <NUM> and a series of axially extending stator splines <NUM> (one shown). Reaction plate <NUM> and stator splines <NUM> may be integral with torque tube <NUM>, as shown in <FIG>, or attached as separate components.

Multi-disk carbon and CMC brake system <NUM> also includes a plurality of friction disks <NUM>. Each friction disk <NUM> may comprise a solid disk, split disk or friction wear liners and core. The plurality of friction disks <NUM> includes at least one friction wear liners with a non-rotatable core, also known as a stator <NUM>, and at least one friction disk wear liners with a rotatable core, also known as a rotor <NUM>. Stators <NUM> and rotors <NUM> are located adjacent to one another in multi-disk brake system <NUM>, forming a plurality of adjacent stator-rotor pairs. Stators <NUM> may comprise a stator core <NUM> and wear liners <NUM>. Rotors <NUM> may comprise a rotor core <NUM> and wear liners <NUM>. Each friction disk <NUM> includes an attachment structure. In the embodiment of <FIG>, each of the four stators <NUM> includes a plurality of stator lugs <NUM> at circumferentially spaced positions around stator <NUM> as an attachment structure. Similarly, each of the five rotors <NUM> includes a plurality of rotor lugs <NUM> at circumferentially spaced positions around rotor <NUM> as an attachment structure. In the embodiment of <FIG>, pressure plate <NUM>, end plate <NUM>, and friction disks <NUM> are all annular structures made at least partially from a carbon or CMC composite material.

Torque flange <NUM> may be mounted to axle <NUM>. Torque tube <NUM> is bolted to torque flange <NUM> such that reaction plate <NUM> is near an axial center of wheel <NUM>. End plate <NUM> is connected to a surface of reaction plate <NUM> facing axially inward. Thus, end plate <NUM> is non-rotatable by virtue of its connection to torque tube <NUM>. Stator splines <NUM> support pressure plate <NUM> so that pressure plate <NUM> is also non-rotatable. Stator splines <NUM> also support stators <NUM> via stator cores <NUM>. Stator cores <NUM> engage stator splines <NUM> with gaps formed between stator lugs <NUM>. Similarly, rotors <NUM> engage rotor splines <NUM> via rotor core <NUM> with gaps formed between rotor lugs <NUM>. Thus, rotor cores <NUM> of rotors <NUM> are rotatable by virtue of their engagement with rotor splines <NUM> of wheel <NUM>.

As shown in <FIG>, rotors <NUM> with rotor cores <NUM> are arranged with end plate <NUM> on one end, pressure plate <NUM> on the other end, and stators <NUM> with stator cores <NUM> interleaved so that rotors <NUM> with rotor cores <NUM> are directly or indirectly adjacent to non-rotatable friction components. Pistons/actuators <NUM> are connected to torque flange <NUM> at circumferentially spaced positions around torque flange <NUM>. Pistons/actuators <NUM> face axially toward wheel <NUM> and contact a side of pressure plate <NUM> opposite friction disks <NUM>. Pistons/actuators <NUM> may be powered electrically, hydraulically, or pneumatically.

In various examples, in response to actuation of pistons <NUM>, a force, towards reaction plate <NUM>, is exerted on the rotatable friction disks <NUM> and the non-rotatable friction disks <NUM>. The rotatable friction disks <NUM> and the non-rotatable friction disks <NUM> are thus pressed together between pressure plate <NUM> and end plate <NUM>.

<FIG> illustrates a portion of a multi-disk carbon and CMC brake system <NUM> from <FIG> prior to actuation of the multi-disk carbon and CMC brake system <NUM>, in accordance with various embodiments, is depicted. In various embodiments, the multi-disk carbon and CMC brake system <NUM> from <FIG> comprises a brake stack <NUM>. The brake stack <NUM> comprises a pressure plate <NUM> at a proximal end of the brake stack <NUM> and an end plate <NUM> at a distal end of the brake stack <NUM>. The brake stack <NUM> comprises a plurality of rotors <NUM> disposed between the pressure plate <NUM> and the end plate <NUM>. The brake stack <NUM> further comprises a plurality of stators <NUM> interleaved between the plurality of rotors <NUM>. The brake stack further comprises a centerline <NUM> about which the plurality of rotors <NUM> rotate. When the brake stack <NUM> is in a non-actuated state (e.g., not in use / operation), each rotor in the plurality of rotors <NUM> is separated from each stator in the plurality of stators by a gap. In various embodiments, the gap is between <NUM> inches and <NUM> inches (<NUM> - <NUM>), or between <NUM> inches and <NUM> inches (<NUM> - <NUM>), or between <NUM> inches and <NUM> inches (<NUM> - <NUM>).

In various embodiments, the plurality of rotors <NUM> comprises a first rotor <NUM> disposed proximate the pressure plate <NUM>. The first rotor <NUM> is axially adjacent to the pressure plate <NUM>. In various embodiments, the plurality of stators <NUM> comprises a first stator <NUM> disposed proximate the first rotor <NUM>. The first stator <NUM> is axially adjacent to the first rotor <NUM>. In various embodiments, the plurality of rotors <NUM> further comprises a second rotor <NUM>, a third rotor <NUM>, a fourth rotor <NUM>, and a fifth rotor <NUM>. In various embodiments, the plurality of stators <NUM> further comprises a second stator <NUM>, a third stator <NUM>, and a fourth stator <NUM>. Although depicted as a brake stack comprising five rotors and four stators, any number of rotors and stators is within the scope of this disclosure. The second rotor <NUM> is disposed axially adjacent to the first stator <NUM> and the second stator <NUM>. The third rotor <NUM> is disposed axially adjacent to the second stator <NUM> and the third stator <NUM>. The fourth rotor <NUM> is disposed axially adjacent to the third stator <NUM> and the fourth stator <NUM>. The fifth rotor <NUM> is disposed axially adjacent to the fourth stator <NUM> and the end plate <NUM>.

In various embodiments, each rotor in the plurality of rotors <NUM> is disposed along a radially outward from centerline <NUM> in relation to each stator in the plurality of stators <NUM>. In various embodiments, the pressure plate <NUM> and the end plate <NUM> are radially aligned with the plurality of stators <NUM>.

In various embodiments, the brake stack <NUM> further comprises a first spring <NUM>. The first spring <NUM> may be disposed between the second stator <NUM> and the third stator <NUM>. The first spring <NUM> may be coupled to a circumferential portion of the second stator <NUM> proximate a radially inner end of the second stator <NUM> and a circumferential portion of the third stator <NUM> proximate a radially inner end of the third stator <NUM> by any method known in the art. In various embodiments, the first spring <NUM> is a free component and installed in a compressed state or an uncompressed state. In various embodiments, the first spring <NUM> is a wave spring, a coiled wave spring, a scrowave spring, or any other spring known in the art. In various embodiments, the first spring <NUM> is made of stainless steel, such as A-<NUM> stainless steel, <NUM>-<NUM> PH stainless steel, <NUM>-<NUM> PH stainless steel, or the like. In various embodiments, the first spring <NUM> is made of any high temperature metal known in the art, such as a nickel alloy, cobalt, or the like.

In various embodiments, the first spring <NUM> is installed in an uncompressed state at its free height. In various embodiments, "free height," as disclosed herein, is a spring distance between two components when the spring is in an uncompressed state. The first spring <NUM> may have a free height measured in the axial direction that is substantially equal to, or less than, a distance D1 between the second stator <NUM> and the third stator <NUM>. In various embodiments, a gap between a stator and an adjacent rotor is a function of the available brake running clearance. The running clearance may be a design choice based on the design intent of a multi-disk brake system.

In various embodiments, the brake stack <NUM> comprises a second spring <NUM>. The second spring <NUM> may be disposed between the third stator <NUM> and the fourth stator <NUM>. The second spring <NUM> may be coupled to a circumferential portion of the third stator <NUM> proximate a radially inner end of the third stator <NUM> and a circumferential portion of the fourth stator <NUM> proximate a radially inner end of the fourth stator <NUM>. The second spring <NUM> may be the same type of spring or a different type of spring as the first spring <NUM>. In various embodiments, the second spring <NUM> is the same type of spring as the first spring <NUM>.

In various embodiments, the brake stack <NUM> comprises a third spring <NUM>. The third spring <NUM> may be disposed between the fourth stator <NUM> and the end plate <NUM>. The third spring <NUM> may be coupled to a circumferential portion of the fourth stator <NUM> proximate a radially inner end of the fourth stator <NUM> and a circumferential portion of the end plate <NUM> proximate a radially inner end of the end plate <NUM>. The third spring <NUM> may be the same type of spring or a different type of spring as the first spring <NUM>. In various embodiments, the second spring <NUM> is the same type of spring as the first spring <NUM>.

Referring now to <FIG>, a cross-sectional view of brake stack <NUM> along section A-A from <FIG> is depicted, in accordance with various embodiments. The third rotor <NUM> comprises a radially inner end <NUM> and a radially outer end <NUM>. The second stator <NUM> comprises a radially inner end <NUM> and a radially outer end <NUM>. Radially outer end <NUM> of second stator <NUM> is illustrated as a hidden line in section A-A as it is hidden from view in section A-A because it is behind third rotor <NUM>. In various embodiments, first spring <NUM> comprises a radially inner end <NUM> and a radially outer end <NUM>. In various embodiments, first spring <NUM> is disposed between radially inner end <NUM> of third rotor <NUM> and radially inner end <NUM> of second stator <NUM>.

Referring now to <FIG>, a cross-sectional view of a brake stack <NUM> along section A-A from <FIG> is depicted, in accordance with various embodiments. In various embodiments, the brake stack <NUM> comprises a plurality of springs <NUM> disposed circumferentially around second stator <NUM>. In various embodiments, each spring in the plurality of springs <NUM> is disposed between radially inner end <NUM> of the third rotor <NUM> and radially inner end <NUM> of the second stator <NUM>. In various embodiments, each spring in the plurality of springs <NUM> is a coil spring, or any other spring known in the art.

Referring now to <FIG>, a portion of a multi-disk carbon and CMC brake system <NUM> from <FIG> during actuation of the multi-disk carbon and CMC brake system <NUM> in a first type of braking event, in accordance with various embodiments, is depicted. A "first type of braking event," as described herein, is braking to slow an aircraft during taxi, a non-emergency landing, or the like. In various embodiments, a first type of braking event occurs at a braking pressure applied to the brake stack <NUM> that is less than a threshold brake pressure. A threshold brake pressure may be a design choice and vary based on design intent. For example, a threshold brake pressure may be between <NUM> psi and <NUM> psi (<NUM> kPa - <NUM> kPa), or <NUM> psi and <NUM> psi (<NUM> kPa - <NUM> kPa), or between <NUM> psi and <NUM> psi (<NUM> kPa - <NUM> kPa).

During a first type braking event, the first spring <NUM> is partially compressed to a height of D2. In various embodiments, D2 is less than D1. In various embodiments, D2 is between <NUM> inches and <NUM> inches less than D1. In a first braking event, pressure plate <NUM> is actuated axially toward end plate <NUM>. An axial face of pressure plate <NUM> contacts a first axial face of first rotor <NUM>, a second axial face of first rotor <NUM> contacts a first axial face of first stator <NUM>, a second axial face of first stator <NUM> contacts a first axial face of second rotor <NUM>, and a first axial face of second stator <NUM>. In various embodiments, due to the partial compression of first spring <NUM>, a second axial face of second stator <NUM> is separated from a first axial face of third rotor <NUM> by a gap. Similarly, due to the partial compression of first spring <NUM>, a second axial face of third rotor <NUM> is separated from a first axial face of third stator <NUM> by a gap. By limiting the brake stack to only utilizing two rotors and two stators during a first braking event, the number of landing cycles experienced by the unutilized disks is effectively reduced. For carbon disks in particular, the rotors and stators in use may heat up quicker resulting in greater wear life compared to a typical brake stack utilizing all rotors and stators.

In various embodiments, second spring <NUM> and third spring <NUM> may be partially compressed as well during a first braking event. Due to the partial compression of second spring <NUM>, a second axial face of third stator <NUM> is separated from a first axial face of fourth rotor <NUM> by a gap, and a second axial face of fourth rotor <NUM> is separated from a first axial face of fourth stator <NUM> by a gap. Similarly, due to the partial compression of third spring <NUM>, a second axial face of fourth stator <NUM> is separated from a first axial face of fifth rotor <NUM> by a gap, and a second axial face of fifth rotor <NUM> is separated from a first axial face of end plate <NUM> by a gap.

Referring now to <FIG>, a portion of a multi-disk carbon and CMC brake system <NUM> from <FIG> during actuation of the multi-disk carbon and CMC brake system <NUM> in a second type of braking event, in accordance with various embodiments, is depicted. A second type of braking event, as described herein, is braking during performance and emergency landings, service stops, or the like. In various embodiments, a second type of braking event occurs at a braking pressure applied to the brake stack <NUM> that is greater than a threshold brake pressure. In various embodiments, the threshold brake pressure may be between <NUM> psi and <NUM> psi (<NUM> kPa - <NUM> kPa).

During a second type braking event, an axial face of each rotor in the plurality of rotors <NUM> contacts an axial face of an adjacent stator in the plurality of stators <NUM>. Additionally, an axial face of pressure plate <NUM> contacts an axial face of first rotor <NUM>, and an axial face of fifth rotor <NUM> contacts an axial face of end plate <NUM>. During the second type braking event the first spring <NUM> is fully compress to a height of D3. In various embodiments, the height D3 is less than the height D2 from <FIG> during a first type braking event. In various embodiments, D3 is substantially equal to a width of a rotor in the plurality of rotors <NUM>.

Referring now to <FIG>, a method <NUM> of using a multi-disk carbon and CMC brake system, in accordance with various embodiments, is depicted. The method comprises applying a force to a pressure plate of a multi-disk carbon and CMC brake system (step <NUM>). The force is applied in the axial direction. The multi-disk carbon and CMC brake system may comprise a brake stack in accordance with <FIG>. The method further comprises compressing a spring disposed between a first stator in a plurality of stators and a second stator in a plurality of stators (step <NUM>). A plurality of rotors are interleaved between the plurality of stators, as depicted in <FIG>. The method further comprises using a portion of disks in the brake stack if the force is less than a threshold force (step <NUM>). For example, a portion of disks may comprise at least one rotor and at least one stator. In various embodiments, the threshold force corresponds to a threshold pressure. In various embodiments, the threshold pressure is between <NUM> psi and <NUM> psi (<NUM> kPa - <NUM> kPa), or <NUM> psi and <NUM> psi (<NUM> kPa - <NUM> kPa), or between <NUM> psi and <NUM> psi (<NUM> kPa - <NUM> kPa). The method further comprises using all disks in the brake stack if the force is greater than the threshold force (step <NUM>). For example, each rotor in a plurality of rotors contacts an adjacent stator in a plurality of stators when the force is greater than the threshold force.

Referring now to <FIG>, a first spring <NUM>, in accordance with various embodiments, is illustrated. In various embodiments, first spring <NUM> comprises a wave spring <NUM>. Wave spring <NUM> comprises a plurality of annular sheets <NUM>. Each annular sheet in the plurality of annular sheets <NUM> has a sinusoidal shape along the circumference of the annular sheet. Each annular sheet in the plurality of annular sheets <NUM> is coupled to an adjacent annular sheet in the plurality of annular sheets <NUM> at a crest of the annular sheet and the adjacent annular sheet.

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.

Moreover, where a phrase similar to "at least one of A, B, and C" is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, Band C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C.

For example, steps that may be performed concurrently or in different order are illustrated in the figures to help to improve understanding of embodiments of the present invention.

Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it may be within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. 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 multi-disk carbon and ceramic matrix composite (CMC) brake system comprising:
a brake stack (<NUM>) comprising:
a pressure plate (<NUM>) disposed at a proximal end of the brake stack;
an end plate (<NUM>) disposed distal to the pressure plate (<NUM>);
a plurality of rotors (<NUM>) disposed between the pressure plate (<NUM>) and the end plate (<NUM>);
a plurality of stators (<NUM>) disposed between the pressure plate (<NUM>) and the end plate (<NUM>), the plurality of stators (<NUM>) interleaved between the plurality of rotors (<NUM>);
a first portion of disks having no spring, a second portion of disks having at least a first spring (<NUM>) disposed axially between a first stator in the plurality of stators (<NUM>) and an adjacent stator in the plurality of stators (<NUM>), the first spring (<NUM>) disposed radially inward of a first rotor in the plurality of rotors (<NUM>), wherein the first spring (<NUM>) is configured to partially compress when a force is applied to the pressure plate (<NUM>) that is less than a threshold force; characterized in that
a first stator axial face of the first stator is separated from a first rotor axial face of the first rotor when the first spring (<NUM>) is partially compressed.