Patent Description:
Vehicles, such as aircrafts, may use a wheel brake system that includes a multi-disc brake system. For example, the multi-disc brake system may include a disc stack comprising plurality of rotor discs engaged with a wheel and a plurality of stator discs interleaved with the rotor discs. The rotor discs and wheel are configured to rotate around an axle, while the stator discs remain stationary. To decelerate rotational motion of a rotating wheel, the brake system may displace pistons against a pressure plate to compress the rotating rotor discs engaged with the wheel against the stationary stator discs, therefore producing torque that decelerates the rotational motion of the wheel. In some examples, the rotor discs may be engaged with the wheel via rotor drive keys positioned on an interior surface of the wheel. In some examples, stator discs may be engaged with a stationary torque tube surrounding the axle via splines positioned on the torque tube. In some such examples, the brake system may be configured to compress the rotor discs and the stator discs between the piston and a backing plate supported by the torque tube.

<CIT> discloses an aircraft wheel and brake assembly having a wheel member journaled for rotation on a fixed member, which fixed member supports a torque tube member. A plurality of primary friction disks are carried by splines on the wheel member while a plurality of secondary friction disks are carried by splines on the torque tube member with such secondary disks interleaved with the primary friction disks for axial movement towards one end of the torque tube. An actuator, such as a plurality of pistons, is mounted on the fixed member to urge all the friction disks into frictional engagement with each other and against a stationary disk on the one end of the torque tube. A rigid disk is positioned between the actuator and the pluralities of friction disks, and acts as a pressure plate.

<CIT> discloses an aircraft wheel braking arrangement comprising a landing gear structure, a torque tube extending in an outboard direction from the landing gear structure, and an actuator housing disposed outboard from the torque tube. An actuator piston may extend in an inboard direction from the actuator housing for applying a force to a brake stack surrounding the torque tube.

The present invention describes wheel assemblies configured to help limit a maximum displacement achievable between a piston housing and a brake disc stack when a brake system is utilized to reduce and/or substantially prevent a rotation of a wheel. The brake system is configured to compress a brake disc stack to reduce and/or limit rotational motion of the wheel about the wheel axis. For example, an actuator may be configured to compress the disc stack against a portion of a torque tube engaged with the disc stack. Under some circumstances, the compression force of the actuator may cause a linear deformation of the torque tube. The linear deformation may require additional piston travel to assure the compression force on the disc stack is maintained during certain operating conditions, such as a Rejected Take-Off (RTO) stop. The assembly disclosed here uses a mechanical stop configured to unload some portion of the compression force from the torque tube when the torque tube linearly deforms. The mechanical stop is configured to limit the maximum distance between the actuator housing and the disc stack at end of life, even during compression of the brake disc stack.

The disclosure describes articles, systems, and techniques relating to an assembly comprising a wheel and a brake system, and, in particular, an assembly including one or more structures configured to limit the axial displacement of the brake discs under certain conditions. The wheel is configured to rotate around a wheel axis. The brake system includes a disc stack which includes one or more rotor discs and one or more stator discs. For example, the disc stack may include a plurality of rotor discs interleaved with a plurality of stator discs. The rotor discs are rotationally coupled with the wheel, such that a rotation of the wheel around the wheel axis causes rotation of the rotor discs around the wheel axis. The stator discs are configured to remain substantially stationary relative to the wheel and the rotor discs. The brake system is configured to compress the disc stack to cause engagement of friction surfaces on the rotating rotor discs and the stationary stator discs, reducing a rotational speed of the rotor discs around the wheel axis. The rotor discs are configured to engage the wheel, such that the reduction in the rotational speed of the rotor discs causes a reduction in the speed of the wheel.

The brake system includes an actuator defining an actuator housing and configured to compress the disc stack to cause the slowing of the rotor discs and wheel. For example, the actuator may be configured to compress the disc stack against a backing plate supported by a torque tube, wherein the backing plate and the torque tube are configured to remain substantially rotationally stationary with respect to the stator discs. The braking system may be configured such that, when the actuator exerts a compression force to compress the disc stack against the backing plate (e.g., to slow the wheel), the backing plate transmits some portion of the compression force to the supporting torque tube. The portion of the compression force transmitted may cause a linear deformation of the torque tube (e.g., in a direction substantially parallel to the axis of the wheel), increasing a displacement between the actuator housing and the disc stack.

The assemblies disclosed herein are configured to help limit the displacement between the actuator housing and the brake disc stack when the actuator exerts the compression force. In examples, the assembly is configured to help limit the displacement when the compression force causes an excessive linear deformation of the torque tube. Hence, the assembly described herein may be configured to reduce and/or minimize additional piston travel that may be required to assure the compression force on the disc stack is maintained during certain operating conditions, such as a Rejected Take-Off (RTO) stop. The assembly may be configured to limit the maximum distance between the piston housing and the disc stack at end of life, even during compression of the brake disc stack.

The assemblies described herein include a mechanical stop configured to transfer load from the torque tube when the compression force of the actuator causes linear deformation of the torque tube. The mechanical stop may be configured to unload the torque tube in order to limit a displacement (e.g., a maximum distance) between the actuator housing and the brake disc stack. In some examples, the assembly is configured such that the actuator compresses the disc stack against the mechanical stop when the mechanical stop unloads the torque tube. For example, in some examples, the assembly is configured such that the brake system compresses the disc stack against a backing plate until the torque tube experiences a certain amount of linear deformation, at which point the mechanical stop encounters the disc stack to at least partially unload the backing plate and torque tube. In examples, the assembly is configured to reduce and/or substantially cease the linear deformation of the torque tube when the mechanical stop transfers load from the torque tube. In other examples, the mechanical stop is configured to limit or even prevent movement of the backing plate of the brake system in an axial direction (resulting from linear deformation of the torque tube), and the actuator continues to be configured to compress the disc stack against the backing plate even after the torque tube experiences a certain amount of linear deformation.

The assembly may allow a reduction in the amount of reserve actuator capacity (e.g., piston travel) typically provided for situations when the torque tube experiences larger linear deformations (e.g., in high heat environments following, for example, emergency braking events or other relatively high energy vehicle stopping conditions). The assembly may be configured to reduce a required stroke length of the actuator necessary to effectively engage the brake system (e.g., during a static hold of the vehicle by the brake system when the vehicle is parked) when the torque tube experiences the higher linear deformations. By reducing and/or substantially ceasing the linear deformation, the assembly may allow reducing the required stroke length of the actuator. This may result in some measure of space saving when the brake system is positioned within a wheel well of the wheel. Further, by reducing the required stroke, additional brake disc thickness may be added to unused spaces, increasing the amount of wearable brake disc thickness and potentially increasing the life of the brake assembly.

In some examples, the wheel supports the mechanical stop. In examples, the wheel supports the mechanical stop such that, when the actuator compresses the disc stack against the mechanical stop, the mechanical stop transmits a portion (e.g., substantially all) of the compression force to the wheel. Transmission of the compression force to the wheel reduces (or substantially eliminates) the amount of the compression force acting on the torque tube, reducing (or substantially eliminating) any further linear deformation of the torque tube and associated brake disc stack translation. In examples, the mechanical stop is configured to limit a maximum displacement which may occur between an actuator housing and the brake disc stack when the mechanical stop encounters the disc stack.

The assembly may be configured such that a linear deformation of the torque tube (e.g., by exertion of the compression force by the actuator) greater than or equal to a threshold linear deformation causes the mechanical stop to encounter the disc stack. The assembly may be configured such a first linear deformation of the torque tube maintains a displacement between the mechanical stop and the disc stack, and a second linear deformation of the torque tube greater than the first linear deformation causes the mechanical stop to contact the disc stack. The first linear deformation and the second linear deformation may each be a deformation in a direction substantially parallel to the axis of the wheel. In examples, the torque tube is configured such that the actuator causes the first linear deformation under a first heat load and causes the second linear deformation under a second heat load greater than the first heat load. The heat load may be defined by, for example, a temperature at one or more points of the torque tube, a temperature of another component in the wheel and brake system, a temperature within the wheel well of the wheel, or some other suitable parameter. In examples, the torque tube may have a configuration (e.g., may comprise a material and/or a geometry) causing the torque tube to experience a greater degree of linear deformation under a given heat load than other components of the brake system and/or wheel. For example, the torque tube may be relatively thin compared to a rotor drive key or other component of the brake system, which may result in relatively higher temperatures of the torque tube for a given thermal environment (e.g., the thermal environment following an emergency stop.

Hence, the assembly may be configured such that the mechanical stop encounters the disc stack depending on a state of the torque tube. For example, the assembly may be configured such that, at relatively low heat loads, the compression force of the actuator is insufficient to generate a linear deformation of the torque tube necessary to cause the mechanical stop to encounter the disc stack (i.e., the linear deformation is less than the second linear deformation described above). Thus, the assembly may be configured to effectively operate under certain conditions wherein braking of the wheel is accomplished without transferring compression load from the torque tube to the mechanical stop. The assembly may be configured such that, at sufficiently high heat loads (e.g., following an emergency stop), the compression force of the actuator may generate a linear deformation of the torque tube sufficient to cause the mechanical stop to encounter the disc stack (i.e., the second linear deformation).

In examples, the actuator defines a first length between a portion of the actuator and the mechanical stop in the absence of the compression force. The actuator may define a second length between the portion of the actuator and a backing plate in the absence of the compression force. The first length may be greater than the second length. The first and second lengths may be measured in parallel directions, e.g., along a wheel axis of the wheel to which the brake assembly is attached. The portion of the actuator may be, for example, a contact area through which the actuator is configured to exert the compression force on the disc stack.

In some examples, the mechanical stop is rotationally coupled to the wheel. The mechanical stop may be configured to rotate with the wheel and configured to encounter a portion of the brake system which also rotates with the wheel (e.g., a rotor disc) in order to limit and/or avoid contact between rotating and relatively stationary portions of the system. For example, the mechanical stop may be configured to rotate substantially synchronously around the wheel axis when the wheel rotates around the wheel axis. In some examples, a pin engaged with the wheel defines the mechanical stop. In some examples, an interior surface of the wheel includes a ledge defining the mechanical stop. In yet other examples, a rotor drive key attached to the wheel and configured to engage a rotor disc defines the mechanical stop. The mechanical stop may be configured to encounter some portion of the disc stack rotationally coupled with the wheel. The mechanical stop may be configured to encounter a rotor disc or a rotor disc component (e.g., a drive insert) configured to rotate synchronously with the rotor disc. In examples, when the actuator is configured to compress the disc stack against the backing plate, the mechanical stop is configured to encounter a rotor disc adjacent to or nearest the backing plate.

<FIG> is a perspective view illustrating an example wheel <NUM>. In some examples, wheel <NUM> is a part of an aircraft vehicle. In other examples, wheel <NUM> may be a part of any other vehicle, such as, for example, any land vehicle or other vehicle. In the example shown in <FIG>, wheel <NUM> includes a wheel rim <NUM> defining an exterior surface <NUM> and interior surface <NUM>. Wheel rim <NUM> includes tubewell <NUM> and wheel hub <NUM>. In some examples, interior surface <NUM> may include an inner diameter of tubewell <NUM> of wheel <NUM>. For example, in some cases, interior surface <NUM> may be referred to as an inner diameter surface of wheel <NUM>. Interior surface <NUM> and wheel hub <NUM> may define a wheel well <NUM> (e.g., a volume) between interior surface <NUM> and wheel hub <NUM>. In some examples, a tire (not shown) may be mounted on exterior surface <NUM> of rim <NUM>. Wheel <NUM> may include an inboard bead seat <NUM> and an outboard bead seat <NUM> configured to retain a tire on exterior surface <NUM> of rim <NUM>. In examples, wheel <NUM> may comprise an inboard section <NUM> (e.g., including inboard bead seat <NUM>) and an outboard section <NUM> (e.g., including outboard bead seat <NUM>). Wheel <NUM> is configured to rotate around the axis of rotation A.

Wheel <NUM> includes a plurality of rotor drive keys <NUM> on interior surface <NUM> of wheel <NUM>, such as rotor drive key <NUM> and rotor drive key <NUM>. In some examples, each rotor drive key of the plurality of rotor drive keys <NUM> extends in a substantially axial direction of wheel <NUM> (e.g., in a direction parallel to the axis of rotation A). The plurality of rotor drive keys <NUM> ("rotor drive keys <NUM>") and interior surface <NUM> are configured to be substantially stationary with respect to each other, such that when wheel <NUM> (and interior surface <NUM>) rotates around axis of rotation A, each of the rotor drive keys (e.g., rotor drive keys <NUM>, <NUM>) translates over a closed path around axis A. Consequently, when wheel <NUM>, interior surface <NUM>, and rotor drive keys <NUM> are rotating around axis of rotation A, a force on one or more of rotor drive keys <NUM> opposing the direction of rotation acts to slow or cease the rotation. As will be discussed, rotor drive keys <NUM> may be configured to receive a torque from a braking system (not shown) configured to reduce and/or cease a rotation of wheel <NUM>. Rotor drive keys <NUM> may be integrally formed with interior surface <NUM>, or may be separate from and mechanically affixed to interior surface <NUM>.

<FIG> is a schematic cross-sectional view illustrating wheel <NUM> and an example brake system <NUM>. Wheel <NUM> includes wheel rim <NUM>, exterior surface <NUM>, interior surface <NUM>, wheel well <NUM>, wheel hub <NUM>, inboard beat seat <NUM>, outboard bead seat <NUM>, inboard section <NUM>, outboard section <NUM>, and rotor drive key <NUM>. <FIG> illustrates wheel rim <NUM> as a split rim wheel with lug bolt <NUM> and lug nut <NUM> connecting inboard section <NUM> and outboard section <NUM>, however wheel rim <NUM> may utilize other configurations (e.g., a unified wheel rim) in other examples.

Wheel <NUM> is configured to rotate about axis A extending through axial assembly <NUM>. Axial assembly <NUM> is figured to support wheel <NUM> while allowing wheel <NUM> to rotate around axis A using bearing <NUM> and bearing <NUM>. For example, bearings <NUM>, <NUM> may define a substantially circular track around axial assembly <NUM>. A torque tube <NUM> is coupled to axial assembly <NUM> (e.g., via bolts <NUM>, <NUM>), such that torque tube <NUM> remains substantially stationary when wheel <NUM> rotates around axial assembly <NUM> and axis A. Torque tube <NUM> may at least partially surround an exterior of axial assembly <NUM>. Axial assembly <NUM> may be mechanically coupled to a strut attached to a vehicle (e.g., a landing gear strut (not shown)).

Brake system <NUM> may be positioned within wheel <NUM> and configured to engage main torque tube <NUM> and rotor drive key <NUM>. Brake system <NUM> is configured to generate a torque to oppose a rotation of wheel <NUM> around axis A and transfer the torque to rotor drive key <NUM>, reducing and/or eliminating the rotation of wheel <NUM> around axis A. Brake system <NUM> includes a disc stack <NUM> which includes one or more rotor discs (e.g., rotor discs <NUM>, <NUM>, <NUM>) and one or more stator discs (e.g., stator discs <NUM>, <NUM>). Rotor discs <NUM>, <NUM>, <NUM> and/or stator discs <NUM>, <NUM> may have any suitable configuration. For example, rotor discs <NUM>, <NUM>, <NUM> and/or stator discs <NUM>, <NUM> can each be substantially annular discs surrounding axial assembly <NUM>. Stator discs <NUM>, <NUM> are coupled to torque tube <NUM> via spline <NUM> and remain rotationally stationary with torque tube <NUM> (and axial assembly <NUM>) as wheel <NUM> rotates. Rotor discs <NUM>, <NUM>, <NUM> are rotationally coupled to rotor drive key <NUM> and interior surface <NUM> and rotate substantially synchronously with wheel <NUM> around axis A.

An actuator <NUM> is configured to compress disc stack <NUM> to bring friction surfaces of rotor discs <NUM>, <NUM>, <NUM> into contact with friction surfaces of stator discs <NUM>, <NUM> generating shearing forces between the discs. A friction surface of a rotor disc and/or stator disc may also be brought into contact with a friction surface of pressure plate <NUM> or a friction surface of backing plate <NUM>. The shearing forces cause rotor discs <NUM>, <NUM>, <NUM> to exert a torque on rotor drive key <NUM> opposing a rotation of wheel <NUM>. In some examples, actuator <NUM> is configured to compress disc stack <NUM> using a pressure plate <NUM>. In these examples, actuator <NUM> may be configured to cause pressure plate <NUM> to translate toward disc stack <NUM> when actuator <NUM> compresses disc stack <NUM>. In examples, actuator <NUM> is configured to cause a piston <NUM> to translate relative to a body <NUM> of actuator <NUM> ("actuator body <NUM>") to exert to compress disc stack <NUM>. Actuator <NUM> may cause piston <NUM> to translate using any suitable method. In some examples, actuator <NUM> is configured to cause translation of piston <NUM> by supplying and/or venting a pressurized hydraulic fluid to or from a piston chamber. In addition or instead, in some examples, actuator <NUM> is configured to cause piston <NUM> to translate through a motion (e.g., a rotary motion) generated by an electric motor.

In the example shown in <FIG>, actuator <NUM> is configured to compress disc stack <NUM> against a backing plate <NUM>. Backing plate <NUM> may be supported by torque tube <NUM>. For example, backing plate <NUM> may be configured to be substantially stationary with respect to torque tube <NUM>. Wheel <NUM> may rotate around backing plate <NUM> when wheel <NUM> rotates around torque tube <NUM>. Brake system <NUM> may be configured such that the compression force exerted on disc stack <NUM> by actuator <NUM> causes disc stack <NUM> to translate toward backing plate <NUM>. For example, the compression force may cause rotor discs <NUM>, <NUM>, <NUM> to translate over rotor drive key <NUM> toward backing plate <NUM> and cause stator discs <NUM>, <NUM> to translate over spline <NUM> toward backing plate <NUM>.

Backing plate <NUM> is configured to resist the translation of disc stack <NUM> and exert a reaction force on disc stack <NUM> opposite the compression force exerted by actuator <NUM>, such that disc stack <NUM> is compressed by actuator <NUM> between pressure plate <NUM> and backing plate <NUM>. When torque tube <NUM> supports backing plate <NUM>, backing plate <NUM> further exerts a force on torque tube <NUM> in response to the compression force. In examples, actuator <NUM> is configured to exert the compression force on disc stack <NUM> toward backing plate <NUM> and substantially parallel to axis A.

Thus, brake system <NUM> may be utilized to reduce and/or eliminate the rotation of wheel <NUM> using a compression force by actuator <NUM> exerted on disc stack <NUM>. Backing plate <NUM> may be configured to react against the compression force, causing a compression of disc stack <NUM>. Torque tube <NUM> may be configured to support backing plate <NUM>, such that torque tube <NUM> experiences a force (e.g., substantially parallel to axis A) when actuator <NUM> exerts the compression force on disc stack <NUM>.

Wheel <NUM> may be used with any variety of private, commercial, or military aircraft or other type of vehicle. Wheel <NUM> may be mounted to a vehicle via, for example, axial assembly <NUM>. Axial assembly <NUM> may be mounted on a strut of a landing gear (not shown) or other suitable component of a vehicle to connect wheel <NUM> to the vehicle. Wheel <NUM> may rotate around axis A and axial assembly <NUM> to impart motion to the vehicle. Wheel <NUM> is shown and described to provide context to the brake system described herein, however the brake system described herein may be used with any suitable wheel assembly in other examples.

<FIG> illustrates an example assembly <NUM> including an example portion of wheel <NUM> and an example portion of brake system <NUM> within wheel well <NUM> defined by wheel <NUM>. <FIG> depicts a cross-section of wheel <NUM> and selected portions of brake system <NUM>, with the cross-section taken parallel to axial direction A in <FIG>. As shown in <FIG>, in examples, rotor drive key <NUM> is supported by wheel <NUM> via one or more fasteners <NUM> (e.g., bolts) attaching rotor drive key <NUM> to wheel <NUM>, and a torque tube <NUM> is engaged with a portion of an axial assembly <NUM> by, e.g., bolt <NUM>.

Wheel <NUM> and rotor discs <NUM>, <NUM>, <NUM> are configured to rotate around torque tube <NUM> and axis A. Stator discs <NUM>, <NUM>, actuator <NUM>, spline <NUM>, and axial assembly <NUM> are configured to remain substantially rotationally stationary with respect to torque tube <NUM>. When torque tube <NUM> is engaged with axial assembly <NUM> and disc stack <NUM> is in an uncompressed condition (e.g., actuator <NUM> is not compressing disc stack <NUM> in a direction towards backing plate <NUM>), torque tube <NUM> is configured to maintain a displacement D between torque tube <NUM> and wheel <NUM>. The displacement D may serve to prevent contact between the rotationally stationary torque tube <NUM> and the rotating wheel <NUM> when wheel <NUM> rotates around axis A. As described above, such contact may cause premature maintenance or replacement of wheel <NUM> and/or brake system <NUM>.

Actuator <NUM> is configured to compress disc stack <NUM> to cause a reduction in the rotational speed of wheel <NUM>, and/or substantially prevent a rotational movement of wheel <NUM> (e.g., when wheel <NUM> is in a parked condition). Actuator <NUM> may be configured to exert a compression force on disc stack <NUM>, causing engagement of the friction surfaces on rotor discs <NUM>, <NUM>, <NUM> and stator discs <NUM>, <NUM>. Actuator <NUM> may be configured to exert the compression force to cause engagement of a friction surface of a rotor disc and/or stator disc with a friction surface of pressure plate <NUM> or a friction surface of backing plate <NUM>. In examples, actuator <NUM> is configured to exert a compression force (e.g., the force F) substantially parallel to axis A on disc stack <NUM>. In examples, actuator <NUM> includes a body <NUM> ("actuator body <NUM>") and a piston <NUM>. Actuator <NUM> may be configured to cause piston <NUM> to translate relative to actuator body <NUM> to exert the compression force on disc stack <NUM>. In examples, actuator <NUM> is configured to cause a piston face <NUM> to exert the compression force on disc stack <NUM> (e.g., via pressure plate <NUM>). Some portion of actuator <NUM> (e.g., actuator body <NUM>) is configured to remain substantially stationary with respect to a portion of torque tube <NUM> and/or axial assembly <NUM> when actuator <NUM> exerts the compression force. In some examples, torque tube <NUM> and/or axial assembly <NUM> are configured to limit movement of actuator body <NUM> when actuator <NUM> exerts the compression force on disc stack <NUM>. In examples, actuator <NUM> is mechanically connected to torque tube <NUM> and/or axial assembly <NUM>.

For example, <FIG> illustrates actuator <NUM> with piston <NUM> in a first position and in a second position relative to actuator body <NUM>. <FIG> illustrates the first position of piston <NUM> in dashed line, and the second position of piston <NUM> in solid line. Actuator <NUM> may be configured to translate piston <NUM> from the first position to the second position to cause piston face <NUM> to exert the compression force on disc stack <NUM>. The first position and the second position may be displaced from each other by an amount of piston travel T. That is, actuator <NUM> may be configured to define a first displacement between piston face <NUM> and a point P on actuator body <NUM> in the first position, and define a second displacement between piston face <NUM> and the point P in the second position, wherein the first displacement and the second displacement define the piston travel T. Actuator <NUM> may be configured to cause piston <NUM> to translate over the piston travel T to exert the compression force on disc stack <NUM>.

Disc stack <NUM> is configured to cause a reduction in the rotational speed of wheel <NUM> and/or substantially prevent rotational movement of wheel <NUM> (e.g., in a parked condition) when actuator <NUM> compresses disc stack <NUM>. A compression force exerted by actuator <NUM> causes friction surfaces on the rotating rotor discs <NUM>, <NUM>, <NUM> to engage friction surfaces on the relatively stationary stator discs <NUM>, <NUM>. Engagement with stator discs <NUM>, <NUM> and/or friction surfaces of pressure plate <NUM> and/or backing plate <NUM> causes rotor discs <NUM>, <NUM>, <NUM> to exert a torque on wheel <NUM> (e.g., via rotor drive key <NUM>), reducing the speed of wheel <NUM>. When wheel <NUM> is substantially stationary with respect to torque tube <NUM> (e.g., when the vehicle is in a parked condition) and actuator <NUM> is compressing disc stack <NUM>, rotor discs <NUM>, <NUM>, <NUM> may resist rotational motion of wheel <NUM>.

<FIG> illustrates a perspective view of an example disc stack <NUM> illustrating stator discs <NUM>, <NUM> interleaved with rotor discs <NUM>, <NUM>, <NUM>. Disc stack <NUM> may be positioned between pressure plate <NUM> and backing plate <NUM>. Axis A is included for reference to <FIG>. Disc stack <NUM> is illustrated in an uncompressed condition with opposing friction surfaces of adjacent stator and rotor discs disengaged. For example, as illustrated at <FIG>, an air gap G exists between rotor disc <NUM> and adjacent stator disc <NUM> such that friction surface <NUM> of rotor disc <NUM> and friction surface <NUM> of stator disc <NUM> are substantially disengaged (e.g., not in contact with each other). The air gap G may have any suitable value (e.g., may be larger or smaller than illustrated, relative to disc stack <NUM>). Each of stator discs <NUM>, <NUM> and rotor discs <NUM>, <NUM>, <NUM> may have a first friction surface (e.g., friction surface <NUM> of rotor disc <NUM>) and a second friction surface (e.g., friction surface <NUM> of rotor disc <NUM>) on an opposite side of the respective disc from the first friction surface. In some examples, each of stator discs <NUM>, <NUM> and rotor discs <NUM>, <NUM>, <NUM> may be substantially annular shaped discs, but may have other shapes in other examples.

Rotor discs <NUM>, <NUM>, <NUM> are configured to rotate substantially synchronously with wheel <NUM> (<FIG>). In some examples, each of rotor discs <NUM>, <NUM>, <NUM> include a plurality of drive slots configured to engage a rotor drive key of wheel <NUM> to cause the rotation. For example, rotor disc <NUM> includes drive slot <NUM> on an outer perimeter <NUM> of rotor disc <NUM>. Drive slot <NUM> is configured to engage a rotor drive key (e.g., rotor drive key <NUM> (<FIG>) to cause rotor disc <NUM> to rotate substantially synchronously with wheel <NUM>. Stator discs <NUM>, <NUM> are configured to substantially remain rotationally stationary with respect to torque tube <NUM> (<FIG>) as rotor discs <NUM>, <NUM>, <NUM> rotate.

Each of stator discs <NUM>, <NUM> may include a plurality of spline slots configured to engage a spline of torque tube <NUM> to substantially maintain stator discs <NUM>, <NUM> rotationally stationary relative to rotor discs <NUM>, <NUM>, <NUM>. That is, stator discs <NUM>, <NUM> are configured to not rotate when rotor discs <NUM>, <NUM>, <NUM> rotate. For example, stator disc <NUM> includes spline slot <NUM> on an inner perimeter <NUM> of stator disc <NUM>. Spline slot <NUM> is configured to engage a spline (e.g., spline <NUM> (<FIG> and <FIG>) to cause stator disc <NUM> to substantially remain rotationally stationary with respect to torque tube <NUM>. In similar manner, pressure plate <NUM> and/or backing plate <NUM> may include a plurality of spline slots (e.g., spline slot <NUM> on inner perimeter <NUM> of pressure plate <NUM>) configured to cause pressure plate <NUM> and/or backing plate <NUM> to substantially remain rotationally stationary with respect to torque tube <NUM>. When actuator <NUM> (<FIG> and <FIG>) exerts the compression force F (e.g., on pressure plate <NUM>), disc stack <NUM> is compressed between pressure plate <NUM> and backing plate <NUM>, eliminating the gap G and causing the friction surfaces (e.g., friction surface <NUM> and friction surface <NUM>) to engage.

Backing plate <NUM> is configured to exert a reaction force F1 on disc stack <NUM> in response to the compression force F against backing plate <NUM>. In some examples, backing plate <NUM> is configured to engage a portion of torque tube <NUM>, such that torque tube <NUM> substantially limits movement of backing plate <NUM> in a direction away from pressure plate <NUM> in a direction parallel to axis A. In some examples, backing plate <NUM> is configured to exert a force F2 (<FIG> and <FIG>) on torque tube <NUM> in response to the compression force F. Thus, torque tube <NUM> (<FIG> and <FIG>) may be configured such that when actuator <NUM> exerts the compression force F on disc stack <NUM>, torque tube <NUM> experiences a force F2 based on the compression force F. In examples, the compression force F and the force F2 are substantially parallel to axis A.

Disc stack <NUM> may include components additional to those depicted in <FIG> and/or described above. For example, disc stack <NUM> can include one or more rotor drive inserts configured to insert at least partially within a drive slot of a rotor disc. For example, disc stack <NUM> may include rotor drive insert <NUM> (<FIG>) configured to insert at least partially within drive slot <NUM> (<FIG>) of rotor disc <NUM>. As another example, disc stack <NUM> may include one or more spline inserts configured to insert at least partially within a spline slot of a stator disc. For example, disc stack <NUM> may include spline insert <NUM> (<FIG>) configured to insert at least partially within spline slot <NUM> (<FIG>) of stator disc <NUM>. As used herein, disc stack <NUM> may include one or more rotor discs such as rotor disc <NUM>, <NUM>, <NUM>, one or more stator discs such as stator disc <NUM>, <NUM>, and other components configured to rotate and/or translate as a substantially rigid body with at least one of the rotor discs (e.g., rotor discs <NUM>, <NUM>, <NUM>) and/or the stator discs (e.g., stator discs <NUM>, <NUM>).

In examples, torque tube <NUM> (<FIG>) may comprise a material having a ductility that results in a linear deformation of torque tube <NUM> under some conditions (e.g., under a high heat load following an emergency stop of a vehicle using brake system <NUM>). For example, when actuator <NUM> exerts the compression force F causing the force F2 on torque tube <NUM>, the ductility of the material may result in the force F2 causing the linear deformation. The linear deformation of torque tube <NUM> may be substantially parallel to axis A. In some examples, the linear deformation may cause torque tube <NUM> to extend towards wheel <NUM>, reducing the displacement D (<FIG>) between torque tube <NUM> and wheel <NUM>. The linear deformation of torque tube <NUM> may increase a displacement between actuator body <NUM> (e.g., point P) and disc stack <NUM>, increasing the piston travel T required by actuator <NUM> in order to assure that the compression force F is maintained. Assembly <NUM> is configured to limit the piston travel T which may be required by actuator <NUM> by limiting a maximum distance between actuator housing <NUM> (e.g., point P) and disc stack <NUM> under certain operating conditions, such as a Rejected Take-Off (RTO) stop. Hence, assembly <NUM> may act to reduce the reserve capacity requirements of actuator <NUM> which might be otherwise required when brake system <NUM> operates under certain conditions.

The reduction in the displacement D between torque tube <NUM> and wheel <NUM> may be more pronounced toward the end of the operating life for a given disc stack <NUM>. For example, as rotor discs <NUM>, <NUM>, <NUM> and stator discs <NUM>, <NUM> wear and the individual disc thickness are reduced (e.g., thickness substantially parallel to axis A), the linear deformation of torque tube <NUM> may cause a greater reduction of the displacement D. For example, at the end of life, the greater reduction in the displacement D may occur as a result of higher temperatures caused by a reduction in heat sink material as disc stack <NUM> and/or other components of brake assembly <NUM> wear over life. Ensuring that at least some portion of the displacement D remains between torque tube <NUM> and wheel <NUM> may limit the dependence of the displacement D on the thickness of disc stack <NUM>, allowing for less frequent replacement of disc stack <NUM>. In addition, as the displacement D reduces, the available travel of piston <NUM> may become a factor as the individual disc thicknesses are reduced. By ensuring that some portion of the displacement D is maintained over the life of brake system <NUM>, the necessary translation of piston <NUM> in a direction parallel to axis A to cause sufficient compressing of disc stack <NUM> in end-of-life scenarios may be reduced, allowing for a measure of space saving within assembly <NUM>.

As shown in <FIG>, assembly <NUM> includes a mechanical stop <NUM> configured to limit a translation of disc stack <NUM> when actuator <NUM> exerts the compression force F on disc stack <NUM> under certain operation conditions. In examples, mechanical stop <NUM> is configured to limit a translation of disc stack <NUM> in a direction substantially parallel to axis A. For example, mechanical stop <NUM> may be configured to limit the translation of disc stack <NUM> when torque tube <NUM> linearly deforms in a manner that leads to a reduction in the displacement D (e.g., when actuator <NUM> causes the linear deformation of torque tube <NUM>). Mechanical stop <NUM> may be configured to limit the translation of disc stack <NUM> when torque tube <NUM> linearly deforms over a displacement less than the displacement D. In some examples, mechanical stop <NUM> is configured to exert a reaction force on disc stack <NUM> when mechanical stop <NUM> encounters disc stack <NUM>. For example, mechanical stop <NUM> may be configured such that, when torque tube <NUM> linearly deforms under the influence of force F2, mechanical stop <NUM> encounters and exerts a reaction force on disc stack <NUM> to reduce the force F2 experienced by torque tube <NUM>. The reduction of the force F2 on torque tube <NUM> may substantially cease the linear deformation and resulting extension of torque tube <NUM> toward wheel <NUM>, preserving at least some portion of the displacement D between torque tube <NUM> and wheel <NUM>, and limiting the linear translation of disc stack <NUM> when actuator <NUM> exerts the compression force F.

For example, <FIG> illustrates assembly <NUM> with mechanical stop <NUM> encountering disc stack <NUM>. Actuator <NUM> has translated piston <NUM> from a first position (indicated in dashed line) to a second position (indicated in solid line) to cause piston face <NUM> to encounter disc stack <NUM> (e.g., pressure plate <NUM>) to exert the compression force F on disc stack <NUM>. Actuator <NUM> has caused piston <NUM> to translate over the piston travel Tm to exert the compression force F. The compression force F causes a linear translation of disc stack <NUM> toward backing plate <NUM>.

Mechanical stop <NUM> may be configured to encounter one or more rotor discs (e.g., rotor discs <NUM>, <NUM>, <NUM>) and/or one or more stator discs (e.g., stator discs <NUM>, <NUM>) when the compression force F causes torque tube <NUM> to linearly deform under certain conditions. With mechanical stop <NUM> encountering disc stack <NUM> (e.g., drive insert <NUM> and/or rotor disc <NUM>), mechanical stop <NUM> exerts a reaction force F3 opposing compression force F. The exertion of the reaction force F3 reduces and/or substantially eliminates the necessary reaction force imparted by backing plate <NUM>, reducing and/or substantially eliminating the force F4 on torque tube <NUM>. Reducing and/or substantially eliminating the force F4 on torque tube <NUM> may reduce and/or substantially eliminate further linear deformation of torque tube <NUM>. Reducing and/or substantially eliminating the further linear deformation of torque tube <NUM> limits further linear translation of disc stack <NUM> in a direction away from actuator body <NUM> (e.g., point P), limiting the amount of piston travel Tm required to maintain a sufficient compression force F. Hence, with mechanical stop <NUM> having encountered disc stack <NUM>, brake system <NUM> limits a maximum distance between actuator housing <NUM> (e.g., point P) and disc stack <NUM> under certain operating conditions. This may reduce the reserve capacity requirements of actuator <NUM> which might be otherwise required in the absence of mechanical stop <NUM>.

In examples, mechanical stop <NUM> is configured to reduce and/or substantially eliminate the force F4 on torque tube <NUM> (e.g., by exerting the reaction force F3) when actuator <NUM> causes torque tube <NUM> to experience a threshold linear deformation. Mechanical stop <NUM> may be configured to encounter disc stack <NUM> to exert the reaction force F3 when torque tube <NUM> experiences a linear deformation sufficient to reduce the displacement D (<FIG>) to the displacement D2 (<FIG>). Mechanical stop <NUM> may be configured to at least partially unload torque tube <NUM> (e.g., by exerting the reaction force F3) to substantially cease the linear deformation, in order to limit the maximum distance between actuator housing <NUM> (e.g., point P) and disc stack <NUM>. In examples, assembly <NUM> is configured such that actuator <NUM> compresses disc stack <NUM> at least partially against mechanical stop <NUM> when mechanical stop <NUM> encounters disc stack <NUM>. When mechanical stop <NUM> encounters disc stack <NUM>, assembly <NUM> may be configured such that actuator <NUM> compresses disc stack <NUM> against both backing plate <NUM> and mechanical stop <NUM>, such that mechanical stop <NUM> substantially acts to reduce the amount of compression force F transmitted to torque tube <NUM>.

Mechanical stop <NUM> may be configured to possess a greater axial stiffness than torque tube <NUM> in a direction substantially parallel to the direction of the compression force F. For example, mechanical stop <NUM> may comprises a material and/or have a geometry causing the axial stiffness of mechanical stop <NUM> to exceed that of torque tube <NUM>. The greater axial stiffness may act to ensure mechanical stop <NUM> sufficiently unloads torque tube <NUM> without allowing additional linear deformation of mechanical stop <NUM> and/or torque tube <NUM>.

Mechanical stop <NUM> may be configured to encounter any portion of disc stack <NUM>. In some examples, mechanical stop <NUM> is configured to encounter a drive insert (e.g., drive insert <NUM>) of disc stack <NUM> when actuator <NUM> compresses disc stack <NUM>. As another example, mechanical stop may be configured to encounter a spline insert (e.g., spline insert <NUM>) of disc stack <NUM> when actuator <NUM> compresses disc stack <NUM>. In other examples, mechanical stop <NUM> is configured to encounter a disc in disc stack <NUM> having a greater displacement from actuator <NUM> than another disc in disc stack <NUM>, in order that compression force F causes a greater number of friction surfaces within disc stack <NUM> to engage (e.g., to substantially preserve braking power).

Mechanical stop <NUM> may be configured such that, when mechanical stop <NUM> encounters disc stack <NUM>, a plurality of rotors discs and/or stator discs is compressed between actuator <NUM> and mechanical stop <NUM>. In examples, mechanical stop <NUM> is configured to encounter a rotor disc (e.g., rotor disc <NUM>) of disc stack <NUM> adjacent to or nearest backing plate <NUM>. For example, mechanical stop <NUM> may be configured to encounter rotor disc <NUM> when torque tube <NUM> experiences the threshold linear deformation, such that compression of disc stack <NUM> against mechanical stop <NUM> continues to cause engagement of friction surfaces between rotor disc <NUM> and stator disc <NUM>, between stator disc <NUM> and rotor disc <NUM>, between rotor disc <NUM> and stator disc <NUM>, and between stator disc <NUM> and rotor disc <NUM>.

<FIG> illustrates assembly <NUM> with disc stack <NUM> in an uncompressed condition (e.g., without a compression force exerted by actuator <NUM>). Assembly <NUM> is configured such that, absent a compression force from actuator <NUM>, assembly <NUM> substantially maintains a clearance (measured in a direction parallel to axis A) between disc stack <NUM> and mechanical stop <NUM>. Assembly <NUM> may be configured such that, when actuator <NUM> compresses disc stack <NUM>, disc stack <NUM> encounters backing plate <NUM> prior to mechanical stop <NUM>. In examples, in the absence of a compression force from actuator <NUM>, actuator <NUM> defines a first length L1 between actuator <NUM> and mechanical stop <NUM> and a second length L2 between actuator <NUM> and backing plate <NUM>, with the first length L1 greater than the second length L2. The first length L1 and the second length L2 may be defined by a specific point on actuator <NUM>, such as point P on actuator body <NUM>. The first length L1 and the second length L2 may be substantially parallel. In examples, the first length L1 and the second length L2 may be substantially parallel to axis A.

Disc stack <NUM> is configured to translate substantially parallel to axis A when compressed by actuator <NUM>. Assembly <NUM> may be configured such that the first length L1 and the second length L2 are substantially parallel to the direction of translation of disc stack <NUM>. Hence, assembly <NUM> may be configured such that compression of disc stack <NUM> causes disc stack <NUM> (e.g., rotor disc <NUM>) to encounter backing plate <NUM> prior to encountering mechanical stop <NUM>. Further, assembly <NUM> may be configured such that a threshold linear deformation of torque tube <NUM> substantially causes disc stack <NUM> to encounter mechanical stop <NUM> (e.g., a linear deformation over a distance ΔL between the first distance L1 and the second distance L2). Thus, assembly <NUM> may be configured such that, when actuator <NUM> causes torque tube <NUM> to experience a linear deformation below the threshold linear deformation (or substantially no linear deformation), actuator <NUM> causes compression of disc stack <NUM> against backing plate <NUM> while maintaining a displacement between disc stack <NUM> and mechanical stop <NUM>. When actuator <NUM> causes torque tube <NUM> to experience a linear deformation substantially equal to or above the threshold linear deformation, actuator <NUM> causes compression of disc stack <NUM> against backing plate <NUM> and mechanical stop <NUM>.

Although <FIG>, <FIG> and <FIG> discuss a linear deformation of torque tube <NUM> in a direction substantially parallel to axis A reducing a displacement D (<FIG>) substantially parallel to the axis A, the disclosure herein is not so limited. Mechanical stop <NUM> may be configured to reduce and/or elimination a linear deformation of torque tube <NUM> occurring in any direction, and the displacement D may be a displacement in any direction and between any portions of assembly <NUM>. In examples, the displacement D is a displacement between a first portion (e.g., a first component) of assembly <NUM> and a second portion (e.g., a second component) of assembly <NUM>, wherein the first portion is configured to rotate when wheel <NUM> rotates and the second portion is configured to remain substantially stationary relative to the rotation of the first portion.

Mechanical stop <NUM> may be supported in any manner sufficient to allow mechanical <NUM> to encounter disc stack <NUM> and exert reaction force F3 on disc stack <NUM>. Mechanical stop <NUM> may be configured such that a movement of mechanical stop <NUM> is substantially limited in response to the exertion of reaction force F3. The movement of mechanical stop <NUM> may be substantially limited by any portion of wheel <NUM>, brake system <NUM>, axial assembly <NUM> (<FIG>), or some other component or system sufficient to limit the movement of mechanical stop <NUM> when mechanical stop <NUM> exerts the reaction force F3. Mechanical stop <NUM> may be configured such that, when mechanical stop <NUM> exerts the reaction force F3 on disc stack <NUM>, some portion of wheel <NUM>, brake system <NUM>, axial assembly <NUM> (<FIG>), or another component or system exerts a substantially equal and opposite force on mechanical stop <NUM> to limit the movement of mechanical stop <NUM>. The portion of wheel <NUM>, brake system <NUM>, axial assembly <NUM> (<FIG>), or other component or system supporting mechanical stop <NUM> may be configured to possess a greater axial stiffness than torque tube <NUM> in a direction substantially parallel to the direction of the compression force F, in order to allow mechanical stop <NUM> to transfer load from torque tube <NUM> in a manner limiting any additional linear deformation of torque tube <NUM>.

In some examples, some portion of wheel <NUM> is configured to substantially limit movement of mechanical stop <NUM> when mechanical stop <NUM> encounters disc stack <NUM>. For example, wheel <NUM> may support mechanical stop <NUM> such that, when actuator <NUM> compresses disc stack <NUM> against mechanical stop <NUM>, mechanical stop <NUM> transmits at least a portion of compression force F to wheel <NUM>. In examples, mechanical stop <NUM> is configured to transmit some portion or substantially all of reaction force F3 to wheel <NUM>. Wheel <NUM> may be configured to exert a substantially equal and opposite force on mechanical stop <NUM> to limit the movement of mechanical stop <NUM>. Hence, mechanical stop <NUM> may be configured to at least partially unload a portion of the compression force F from torque tube <NUM> by transferring a portion of the compression force F from torque tube <NUM> to wheel <NUM> when mechanical stop <NUM> encounters disc stack <NUM>.

In some examples, mechanical stop <NUM> is rotationally coupled to wheel <NUM>, such that a rotation of wheel <NUM> causes a rotation of mechanical stop <NUM>. For example, mechanical stop <NUM> may be configured to rotate synchronously with wheel <NUM>. In some examples, mechanical stop <NUM> is rotationally coupled with wheel <NUM> and configured to encounter a portion of disc stack <NUM> (e.g., rotor disc <NUM> and/or drive insert <NUM>) rotationally coupled to wheel <NUM>, in order to substantially avoid contact between mechanical stop <NUM> and portions of disc stack <NUM> configured to be rotationally mismatched with mechanical stop <NUM>. This may serve to minimize or even prevent contact between components configured to rotate with wheel <NUM> (e.g., mechanical stop <NUM>) and components configured to remain substantially stationary relative to torque tube <NUM>. Such contact may result in a need for unscheduled maintenance or early replacement of one or more components of wheel <NUM> or brake system <NUM>.

Mechanical stop <NUM> can have any suitable configuration. In some examples, mechanical stop <NUM> is an elongated member engaged with wheel <NUM> and defining a shank <NUM>. Shank <NUM> is configured to encounter disc stack <NUM> and exert the reaction force F3 on disc stack <NUM>. Mechanical stop <NUM> may be configured and positioned such that shank <NUM> extends in a direction from interior surface <NUM> of wheel <NUM> toward disc stack <NUM>. Shank <NUM> may be configured to encounter disc stack <NUM> when mechanical stop <NUM> encounters disc stack <NUM>. In some examples, mechanical stop <NUM> includes a pin <NUM> defining shank <NUM> and having a head <NUM> attached to shank <NUM>. Wheel <NUM> may be configured to engage some portion of pin <NUM> to limit movement of at least shank <NUM> relative to wheel <NUM>. For example, wheel <NUM> may be configured to substantially trap a portion of mechanical stop <NUM> (e.g., head <NUM>) between inboard section <NUM> and outboard section <NUM> of wheel <NUM>. Wheel <NUM> may be configured to limit the movement of pin <NUM> in any suitable manner, including through internal or external threads defined by wheel <NUM>, a fastener and/or locking device configured to engage pin <NUM> and wheel <NUM>, an interference and/or engineering fit between pin <NUM> and a recess defined by wheel <NUM>, or a welded, soldered, or other connection between pin <NUM> and wheel <NUM>.

<FIG> illustrates another example mechanical stop <NUM>, which is configured as a step or ledge engaged with wheel <NUM>. Mechanical stop <NUM> is an example of mechanical stop <NUM>. Mechanical stop <NUM> extends from the interior surface <NUM> of wheel <NUM> (e.g., extends radially inward from interior surface <NUM>). Mechanical stop <NUM> may be configured to act as a substantially rigid body relative to wheel <NUM>. In some examples, mechanical stop <NUM> defines a bearing surface <NUM> configured to encounter disc stack <NUM> when torque tube <NUM> experiences a threshold linear deformation (e.g., a linear deformation causing the displacement D2 (<FIG>)). Bearing surface <NUM> may be configured to exert the reaction force F3 (<FIG>) on disc stack <NUM> when bearing surface <NUM> encounters disc stack <NUM>. In examples, bearing surface <NUM> is configured to substantially face some portion of disc stack <NUM>. Bearing surface <NUM> may be configured to substantially abut some portion of disc stack <NUM> when mechanical stop <NUM> encounters disc stack <NUM>.

Bearing surface <NUM> may be a substantially planar surface in some examples and a curvilinear surface in other examples. In some examples, bearing surface <NUM> defines a surface complementary to a surface of disc stack <NUM>. For example, bearing surface <NUM> may be configured to complement a surface of a brake disc (e.g., rotor disc <NUM>) when bearing surface <NUM> encounters the surface of the brake disc. As an example, in some examples, support bearing surface <NUM> comprises a first planar surface and the surface of the brake disc defines a second planar surface, where the first and second planar surfaces are substantially parallel (e.g., parallel or nearly parallel to the extent permitted by manufacturing tolerances) when disc stack <NUM> is positioned within wheel well <NUM>. As another example, one of the first bearing surface or the second bearing surface can be a convex surface, with the other being a concave surface configured to receive and at least partially mate with the convex surface when mechanical stop <NUM> encounters disc stack <NUM>. As another example, one of the first bearing surface or the second bearing surface can define a protrusion, and the other of the first bearing surface or the second bearing surface can define a recess configured to receive and at least partially mate with the protrusion when mechanical stop <NUM> encounters disc stack <NUM>.

Bearing surface <NUM> defines a height measured in a direction perpendicular to axis A, where the height is sufficient to cause bearing surface <NUM> to encounter disc stack <NUM> when actuator <NUM> causes a threshold linear deformation of torque tube <NUM>. Bearing surface <NUM> may define a width measured in a direction perpendicular to the height and axis A. In some examples, the width of bearing surface <NUM> defines an arc around axis A. Bearing surface <NUM> may define a substantially constant height over the width of bearing surface <NUM>. In some examples, bearing surface defines a varying height over the width of bearing surface <NUM>.

<FIG> illustrates another example mechanical stop <NUM>, which is shown as being engaged with a component <NUM> of wheel <NUM> ("wheel component <NUM>"). Mechanical stop <NUM> is an example of mechanical stop <NUM> and/or mechanical stop <NUM>. In the example shown in <FIG>, mechanical stop <NUM> is engaged with wheel component <NUM>. Wheel component <NUM> may be a portion of rotor drive key <NUM>. Wheel component <NUM> may be configured to be substantially stationary with respect to interior surface <NUM> of wheel <NUM>, such that when wheel <NUM> (and interior surface <NUM>) rotates around axis A, wheel component <NUM> rotates around axis A. Thus, rotation wheel of component <NUM> around axis A causes a rotation of mechanical stop <NUM> around axis A. Wheel component <NUM> may be, for example, the portion of rotor drive key <NUM>, or some other component of assembly <NUM> configured to rotate around axis A when wheel <NUM> rotates around axis A.

Wheel component <NUM> is configured to limit movement of mechanical stop <NUM> when mechanical stop <NUM> exerts a reaction force (e.g., reaction force F3 (<FIG>)) on disc stack <NUM>. In some examples, mechanical stop <NUM> is configured such that, when actuator <NUM> compresses disc stack <NUM> against mechanical stop <NUM>, mechanical stop <NUM> transmits a force to wheel component <NUM> caused by the compression force of actuator <NUM> acting on mechanical stop <NUM>. Wheel component <NUM> may be configured to exert a substantially equal and opposite force on mechanical stop <NUM> to limit the movement of mechanical stop <NUM> in a direction parallel to axis A.

Wheel <NUM> is configured to limit movement of wheel component <NUM> relative to wheel <NUM> when wheel component <NUM> exerts a force on mechanical stop <NUM> (e.g., when actuator <NUM> causes mechanical stop <NUM> to transmit force to wheel component <NUM>). For example, wheel <NUM> may be configured to limit motion of wheel component <NUM> in a direction substantially parallel to the direction of a compression force (e.g., compression force F (<FIG>, <FIG>) exerted by actuator <NUM> on disc stack <NUM>. Wheel <NUM> may be configured to exert a substantially equal and opposite force on wheel component <NUM> when mechanical stop <NUM> transmits force to wheel component <NUM>. Hence, mechanical stop <NUM> may be configured to substantially transfer some portion of the compression force F exerted by actuator <NUM> from disc stack <NUM> to wheel <NUM>. Mechanical stop <NUM> may be configured to reduce and/or substantially eliminate the load on torque tube <NUM> caused by actuator <NUM>, such that linear deformation of torque tube <NUM> reduces and/or substantially ceases and a maximum distance between actuator housing <NUM> (e.g., point P) and disc stack <NUM> is limited.

In examples, wheel component <NUM> is attached to or defined by rotor drive key <NUM>. For example, wheel component <NUM> may be portion of rotor drive key <NUM>, e.g., mechanical stop <NUM> may be a unitary (e.g., substantially inseparable) portion of rotor drive key <NUM> or separate from and attached to rotor drive key <NUM>. As discussed above, wheel <NUM> may be configured to limit movement of rotor drive key <NUM> relative to wheel <NUM> using, e.g., one or more fasteners <NUM> (e.g., bolts) attaching rotor drive key <NUM> to wheel <NUM>. In examples, instead of or in addition to fasteners <NUM>, wheel <NUM> may be configured to receive a protrusion <NUM> of rotor drive key <NUM> within a recess <NUM> defined by wheel <NUM>.

Rotor drive key <NUM> may be configured to exert a force on wheel <NUM> (e.g., via fasteners <NUM>, protrusion <NUM>, or another attachment mechanism) when mechanical stop <NUM> transmits a force to rotor drive key <NUM> (e.g., caused by the compression force of actuator <NUM> acting on mechanical stop <NUM>). Wheel <NUM> may be configured to exert a substantially equal and opposite force on rotor drive key <NUM> when mechanical stop <NUM> transmits the force to rotor drive key <NUM>. Hence, rotor drive key <NUM> may be configured to substantially transfer some portion of the compression force F exerted by actuator <NUM> from disc stack <NUM> to wheel <NUM>, when mechanical stop <NUM> encounters disc stack <NUM>.

In some examples, rotor drive key <NUM> is configured to possess a greater axial stiffness than torque tube <NUM> in a direction substantially parallel to the direction of the compression force F. For example, rotor drive key <NUM> may comprise a material and/or have a geometry causing the axial stiffness of rotor drive key <NUM> to exceed that of torque tube <NUM>. The greater axial stiffness may enable rotor drive key <NUM> to sufficiently unload torque tube <NUM> without a linear deformation of rotor drive key <NUM> and/or an additional linear deformation of torque tube <NUM>.

In the example shown in <FIG>, mechanical stop <NUM> defines a bearing surface <NUM> configured to encounter disc stack <NUM> when torque tube <NUM> experiences a threshold linear deformation (e.g., a linear deformation causing the displacement D2 (<FIG>)). Bearing surface <NUM> may be an example of bearing surface <NUM>, and may be configured relative to disc stack <NUM> in the same manner as that discussed for bearing surface <NUM> and disc stack <NUM>.

Example wheel assemblies described herein can include any suitable number of mechanical stops. <FIG> schematically illustrates a portion of assembly <NUM> having a plurality of mechanical stops including mechanical stop <NUM>, mechanical stop <NUM>, and mechanical stop <NUM>. Assembly <NUM> is shown from a direction looking down axis A. That is, <FIG> illustrates wheel <NUM> with axis A perpendicular to the page. Mechanical stops <NUM>, <NUM>, <NUM> are each examples of mechanical stop <NUM>, mechanical stop <NUM>, and/or mechanical stop <NUM>. <FIG> further illustrates interior surface <NUM>, wheel hub <NUM>, inboard bead seat <NUM>, and plurality of rotor drive keys <NUM> engaged with interior surface <NUM>. Brake system <NUM> is omitted from <FIG> for clarity. Mechanical stops <NUM>, <NUM>, <NUM> are positioned around axis A within wheel well <NUM> of wheel <NUM>.

Each of mechanical stops <NUM>, <NUM>, <NUM> may be configured to exert a reaction force (e.g., reaction force F3 (<FIG>)) on disc stack <NUM> when mechanical stops <NUM>, <NUM>, <NUM> encounter disc stack <NUM>. Mechanical stops <NUM>, <NUM>, <NUM> may be configured around axis A to distribute the exertion of the reaction force on disc stack <NUM> (e.g., to reduce stress and/or eliminate concentrations on portions of disc stack <NUM>). For example, mechanical stops <NUM>, <NUM>, <NUM> may be configured to exert the reaction force at one or more locations on rotor disc <NUM>, <NUM>, <NUM> and/or stator disc <NUM>, <NUM>. Mechanical stops <NUM>, <NUM>, <NUM> may be configured to exert the reaction substantially force around a perimeter of rotor disc <NUM>, <NUM>, <NUM> and/or stator disc <NUM>, <NUM>. Assembly <NUM> may include any number of mechanical stops arranged in any manner sufficient to cause one or more of the mechanical stops to encounter disc stack <NUM> (<FIG>, <FIG>, <FIG>) when actuator <NUM> compresses disc stack <NUM> (e.g., when actuator <NUM> causes torque tube <NUM> to experience the threshold linear deformation).

Each of mechanical stops <NUM>, <NUM>, <NUM> may be radially displaced from axis A. For example, <FIG> illustrates mechanical stop <NUM> radially displaced from axis A by the radius R. Each of mechanical stops <NUM>, <NUM>, <NUM> may be radially displaced from axis A by an individual radius from axis A. The individual radii may define a different displacement for each mechanical stop and/or substantially similar displacements for one or more mechanical stops. In examples, mechanical stops <NUM>, <NUM>, <NUM> are positioned with wheel well <NUM> to define a substantially circumferential pattern around axis A. Mechanical stops <NUM>, <NUM>, <NUM> may be evenly or unevenly spaced around axis A. Mechanical stops <NUM>, <NUM>, <NUM> may be spaced such that a spacing distance (e.g., an arc length) between adjacent mechanical stops is substantially equal around axis A. Mechanical stops <NUM>, <NUM>, <NUM> may be spaced such that the spacing distance (e.g., the arc length) between adjacent mechanical stops varies around axis A. The spacing distance and/or arc length may be defined in a place substantially perpendicular to axis A.

In examples, each mechanical stop <NUM>, <NUM>, <NUM> is configured to reside substantially between adjacent rotor drive keys in the plurality of rotor drive keys <NUM>. For example, <FIG> illustrates mechanical stop <NUM> positioned substantially between rotor drive key <NUM> and the adjacent rotor drive key <NUM>. Mechanical stop <NUM> may be configured to reside closer to rotor drive key <NUM> than rotor drive key <NUM>, further away rotor drive key <NUM> than rotor drive key <NUM>, or substantially equidistant from rotor drive key <NUM> and rotor drive key <NUM>. In some examples, mechanical stop <NUM> may extend substantially from rotor drive key <NUM> to rotor drive key <NUM>, such that mechanical stop <NUM> is configured to exert the reaction force on disc stack <NUM> over a larger area (e.g., to reduce stress on disc stack <NUM>).

Assembly <NUM> may include any suitable number of mechanical stops between adjacent rotor drive keys (e.g., rotor drive key <NUM> and rotor drive key <NUM>) and the mechanical stops may be arranged in any pattern relative to the adjacent rotor drive keys. For example, a first mechanical stop and a second mechanical stop can be between rotor drive key <NUM> and rotor drive key <NUM>, with the first mechanical stop closer to rotor drive key <NUM> than rotor drive key <NUM> and the second mechanical stop closer to rotor drive key <NUM> than rotor drive key <NUM>.

Mechanical stops described herein, including mechanical stops <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, as well as wheel <NUM> and brake system <NUM>, and the components thereof, may be made from any suitable material. For example, the material may be any material of suitable strength for the intended use of mechanical stops <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, wheel <NUM>, brake system <NUM>, and the components thereof. In some examples, the material includes a metal or a metal alloy. For example, the material may include a nickel alloy or steel alloy. As one example, the material may include stainless steel.

Mechanical stops <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, wheel <NUM>, brake system <NUM>, and the components thereof can be formed using any suitable technique. Mechanical stops <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, wheel <NUM>, brake system <NUM>, and the components thereof may be forged, casted, made from bar stock, additive manufactured (e.g., three-dimensionally (3D) printed), extruded, drawn, or be produced using other suitable methods. In some examples, mechanical stops <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, wheel <NUM>, brake system <NUM>, and the components thereof may be machined to define the configurations described herein. In other examples, Mechanical stops <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, wheel <NUM>, brake system <NUM>, and the components thereof may be formed without having to be substantially machined.

In some examples, wheel <NUM> may be finish machined from a near-net-shaped aluminum forging and contain an axial assembly and/or wheel rim for assembly of brake system <NUM> and/or mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> onto wheel <NUM>. In other examples, wheel <NUM> may be manufactured in a different manner. In yet other examples, wheel <NUM> may be obtained rather than manufactured. Wheel <NUM> may be made of any suitable material. In some examples, wheel <NUM> includes a metal or a metal alloy. For example, wheel <NUM> may include aluminum, a nickel alloy, a steel alloy (e.g., stainless steel), titanium, a carbon-composite material, or magnesium.

Brake discs described herein, including rotor discs <NUM>, <NUM>, <NUM> and stator discs <NUM>, <NUM>, may be manufactured from any suitable material. In some examples, the brake discs described herein may be manufactured from a metal or a metal alloy, such as a steel alloy. In some examples, the brake discs may be manufactured using a ceramic material, such as a ceramic composite. In some examples, the brake discs may be manufactured from a carbon-carbon composite material. In some examples, the brake discs may be manufactured using a carbon-carbon composite material having a high thermal stability, a high wear resistance, and/or stable friction properties. The brake discs may include a carbon material with a plurality of carbon fibers and densifying material. The carbon fibers may be arranged in a woven or non-woven as either a single layer or multilayer structure.

<FIG> is a flow diagram illustrating an example method for compressing a disc stack using an actuator. While the technique is described with reference to specific example wheel <NUM>, brake system <NUM>, and mechanical stops <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> described herein, the technique may be used with other components in other examples.

The method includes compressing a disc stack <NUM> using an actuator <NUM> (<NUM>). Brake system <NUM> may be configured such that compression of disc stack <NUM> by actuator <NUM> causes engagement of the friction surfaces of rotor discs <NUM>, <NUM>, <NUM> and stator discs <NUM>, <NUM>, reducing and/or substantially preventing the rotation of wheel <NUM>. Rotor discs <NUM>, <NUM>, <NUM> and stator discs <NUM>, <NUM> may be configured to translate in a direction substantially parallel to an axis A of wheel <NUM> when actuator <NUM> compresses disc stack <NUM>. Actuator <NUM> is configured to exert a compression force F against disc stack <NUM> to compress disc stack <NUM>. In examples, actuator <NUM> includes an actuator body <NUM> and a piston <NUM> configured to translate relative to actuator body <NUM> to cause the compression of disc stack <NUM>. Actuator <NUM> may be configured to cause a translation of piston <NUM> relative to actuator body <NUM> using a supply of a pressurized hydraulic fluid, one or more electric motors, or some other appropriate methodology.

Actuator <NUM> may be configured to compress disc stack <NUM> against backing plate <NUM> using the compression force F. Backing plate <NUM> may be configured to transmit at least some portion of the compression force F to torque tube <NUM>. Torque tube <NUM> may be configured to exert a reaction force on backing plate <NUM> in response to the compression force F. Torque tube <NUM> may be configured such that, under certain conditions (e.g., a high heat load), torque tube <NUM> linearly deforms as torque tube <NUM> exerts the reaction force on backing plate <NUM>.

Linear displacement of disc stack <NUM> is limited using a mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> (<NUM>). For example, disc stack <NUM> may encounter mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> when actuator <NUM> compresses disc stack <NUM>, due at least in part to the stretching of torque tube <NUM> in a direction parallel to axis A. Mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be configured to exert a reaction force F3 (<FIG>) against disc stack <NUM> when mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> encounters disc stack <NUM>. Mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be configured to reduce the reaction force exerted by torque tube <NUM> on backing plate <NUM> when mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> exerts the reaction force F3. Thus, mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> is configured to limit the linear displacement of disc stack <NUM> when mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> encounters disc stack <NUM>. Mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be configured to limit and/or substantially cease the linear deformation of torque tube <NUM> when mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> encounters disc stack <NUM>.

Assembly <NUM> may be configured such that, when actuator <NUM> compresses disc stack <NUM>, disc stack <NUM> encounters backing plate <NUM> prior to mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. In some examples, assembly <NUM> defines a first length L1 between actuator <NUM> and mechanical stop <NUM> and a second length L2 between actuator <NUM> and backing plate <NUM>, with the first length L1 greater than the second length L2. In examples, the first length L1 and the second length L2 may be substantially parallel to axis A. Assembly <NUM> may be configured such that a threshold linear deformation of torque tube <NUM> caused by the compression F from actuator <NUM> substantially causes disc stack <NUM> to encounter mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

Some portion of the reaction force F3 exerted by mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> is transferred to wheel <NUM>. Wheel <NUM> may be configured to substantially limit movement of mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> when mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> exerts the reaction force F3. Wheel <NUM> may be configured to exert a force on mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> in response to the reaction force F3 exerted by mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> on disc stack <NUM>. In some examples, mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> is an elongate pin supported and/or defined by wheel <NUM>. In some examples, mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> is a step or ledge supported and/or defined by wheel <NUM>. In some examples, mechanical stop <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> is supported by a wheel component <NUM> of wheel <NUM>. Wheel component <NUM> may be a rotor drive key <NUM>, <NUM> in a plurality of rotor drive keys <NUM> coupled to an interior surface <NUM> of wheel <NUM>.

Claim 1:
An assembly (<NUM>) comprising:
a wheel (<NUM>) configured to rotate around a wheel axis (A);
a brake system (<NUM>) comprising:
a disc stack (<NUM>) comprising a rotor disc (<NUM>, <NUM>, <NUM>, <NUM>) and a stator disc (<NUM>, <NUM>), wherein the rotor disc (<NUM>, <NUM>, <NUM>, <NUM>) is rotationally coupled to the wheel (<NUM>), and wherein the wheel (<NUM>) is configured to rotate relative to the stator disc (<NUM>, <NUM>); and
an actuator (<NUM>) defining an actuator housing and configured to compress the disc stack (<NUM>),
wherein the brake system (<NUM>) is configured to compress the disc stack (<NUM>) by limiting the linear movement of the disc stack (<NUM>) by exerting a reaction force on the disc stack (<NUM>) when the actuator (<NUM>) compresses the disc stack (<NUM>), and
wherein a portion of the brake system (<NUM>) is configured to linearly deform when the brake system (<NUM>) exerts the reaction force; and
a mechanical stop (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) configured to reduce the reaction force exerted by the brake system (<NUM>) when the linear deformation of the portion of the brake system (<NUM>) causes the mechanical stop (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) to encounter the brake system (<NUM>), such that the mechanical stop (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) limits a linear displacement of the disc stack (<NUM>) relative to the actuator housing,
characterized in that the mechanical stop (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) is rotationally coupled to the wheel (<NUM>).