Patent Description:
The disclosure relates to brake systems of a vehicle.

Vehicles, such as aircrafts, may use a wheel brake system that includes a brake assembly. For example, the brake assembly may include a disc stack, which may alternatively be called a heat sink. The disc stack, or heat sink, includes a 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 during a braking operation, the brake assembly may displace pistons 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. The pistons may then be displaced away from the heat sink to allow the wheel to rotate when the braking operation of the vehicle is ceased.

<CIT> discloses a brake cooling system with a plurality of cooling channels, the brake system being configured to be positioned within a wheel cavity.

In some examples, the disclosure is directed to a brake assembly which includes a heat sink, a piston, and a retraction plate. The piston is mechanically separated from (i.e., not mechanically attached to) the retraction plate, and the piston is configured to extend through the retraction plate to contact the heat sink during a braking operation prior to the retraction plate contacting the heat sink.

In some examples, the disclosure is directed to a technique for making a brake assembly. The technique includes positioning a retraction plate adjacent to a heat sink, wherein the retraction plate defines a lumen. The technique also includes positioning a piston adjacent to the retraction plate. The piston is mechanically separated from the retraction plate. The piston is configured to extend through the lumen defined by the retraction plate to contact the heat sink during a braking operation prior to the retraction plate contacting the heat sink.

Vehicle braking assemblies, for example aircraft brake assemblies, may drive one or more pistons to compress a disc stack, or heat sink, during a braking operation. A braking operation, as used herein, is an operation of a vehicle to decelerate or stop rotational motion of a rotating wheel of the vehicle. The compression of the heat sink may generate friction between rotating discs of the disc stack and non-rotating discs of the disc stack, yielding deceleration of the vehicle.

The one or more pistons of the brake assembly may be driven by any suitable mechanism, including, for example, a hydraulic system which drives the one or more pistons using a pressurized liquid, a pneumatic system which drives the one or more pistons using a compressed gas, an electrical system, a mechanical system, or a combination of these or other systems. Regardless of how the one or more pistons are driven to compress the heat sink, the one or more pistons are configured to drive against a retraction plate, which may be configured to be disposed between the one or more pistons during a braking operation. The retraction plate may be configured to apply pressure to the heat sink to compress the heat sink during a braking operation, and displace from the heat sink during non-braking operations to create a clearance between the retraction plate and the heat sink. The clearance allows the wheel to spin under reduced friction during non-braking operations, relative to braking operations. The retraction plate also serves the dual-purpose of serving as a heat shield separating the heat sink, which may generate extreme temperatures during braking operations, from other components of the brake assembly (e.g., a hydraulic system) or other components of the vehicle (e.g., landing gear of an aircraft). Accordingly, the retraction plate may also be called a heat shield.

In some examples, an adjuster system may be used to displace the retraction plate from the heat sink (e.g., in a direction opposite the direction in which the piston is driven during a braking operation) when a braking operation is ceased. The adjuster system may include an adjuster device, and the adjuster device may include a spring configured to apply a spring force in a direction opposite the direction in which the piston is driven during a braking operation. Thus, a clearance may be created between the heat sink and the retraction plate which allows the vehicle to accelerate or cruise without compression of the heat sink. In some examples, the adjuster system may be an internal adjuster system in which a spring is housed internal to a piston of the one or more pistons of the brake assembly. Alternatively, the adjuster system may be an external adjuster system which is located remotely from the piston. For example, an external adjuster system may include an adjuster pin coupled to the retraction plate configured to displace the retraction plate from the heat sink to the default position in which the retraction plate is separated from the heat sink by a clearance. Thus, the retraction plate must be configured to be rigid and stiff enough to withstand the heat and be able to retract the pistons as part of the adjuster system in order to create clearance in non-braking operations.

Although friction surfaces of the heat sink are generally designed to be flat, smooth, and planar, the heat sink may include imperfections on one or more friction surfaces. These imperfections may be areas of the friction surface which are not flat, smooth, and/or planar, and may be caused by uneven wear, machining tolerances, distortion of materials of construction (e.g., carbon or steel), or the like. The imperfections in the friction surfaces may be formed due to the high temperatures and extreme environments involved in such applications. These imperfections may cause vibration during braking operations when the heat sink is compressed.

In some examples, the retraction plate may be mechanically attached to other components within the brake assembly, the brake assembly may be mechanically attached to the wheel, and the wheel may be mechanically attached to the landing gear or other parts of the vehicle. It follows that in examples where the one or more pistons are driven to force the retraction plate against the heat sink during a braking operation, the vibrations caused during braking operations may propagate through some or all of these mechanically attached systems and components. Vibrations that are allowed to propagate into the brake assembly, wheel, or landing gear may have deleterious effects on the affected parts. For example, vibrations may cause material fatigue which negatively impacts the useful life of the component.

In some examples according to the present disclosure, the retraction plate defines a lumen. Rather than pushing the retraction plate into the heat sink to compress the heat sink, the piston may be configured to extend through the lumen and protrude from the retraction plate proximate to the heat sink, such that the piston contacts the heat sink prior to the retraction plate contacting the heat sink during a braking operation. The brake assembly may be configured such that the retraction plate contacts the heat sink after the piston contacts the heat sink during braking, or the retraction plate may not contact the heat sink at all during braking operations. In some examples, the piston may not be mechanically attached to the retraction plate. Thus, the piston is configured to compress the heat sink rather than the retraction plate compressing the heat sink. Advantageously, since the piston is mechanically separated from the retraction plate, vibrations caused by the friction surface(s) of the heat sink may not propagate, or only propagate at a reduced rate, through individual pistons, which are more compliant to vibration and can dampen the effects, to the wheel and/or landing gear. Since the retraction plate may not contact the heat sink, the retraction plate may, in some examples, be isolated from these vibrations. Thus, problems created by unwanted vibrations may be mitigated.

In some examples where the retraction plate defines a lumen, the piston may be covered at a first end proximate the heat sink by a piston cap. In examples described herein, the piston cap may be considered to be part of the piston, because the piston cap is mechanically attached to the piston and not mechanically attached to the retraction plate. As used herein, mechanically attached means physically joined or connected, either directly or indirectly through intervening elements. Components that contact each other without being physically joined or connected are not mechanically attached. Components that are mechanically separated from each other are components that are not mechanically attached to each other.

The piston cap may be a durable member configured to directly contact the heat sink, protecting the piston. In some examples, the piston cap may include a shoulder which extends radially from the piston and seats within a recess in the retraction plate without mechanically attaching to the retraction plate. The retraction plate may thus be displaced toward the heat sink with the piston during a braking operation, forming an interactive mounting feature that allows the piston to retract when brake pressure is removed, but also pulls the retraction plate forward during braking applications. In some cases the piston cap could be neither mechanically attached to the piston or the retraction plate. The piston cap could be trapped in assembly between the piston and the retraction plate. The piston cap could pilot onto the OD or ID of the piston and pass through the lumen on the retraction plate with the shoulder of the piston cap fitting into a recess of the retraction plate. For the purposes of this disclosure in such case the piston cap will be considered part of the piston even though it is mechanically separate from the piston.

In some examples, the one or more pistons may include a plurality of pistons, such as, for example, four, five, six, or more pistons. The pistons may be distributed radially about a central axis of the brake assembly. In examples where the pistons are mechanically separated from the retraction plate and configured to extend through the retraction plate, individual pistons of the plurality of pistons are free to pulse and momentarily separate from the retraction plate as relatively high and low spots on the heat sink present themselves during braking. Example brake assemblies where the piston is mechanically separated from the retraction plate and extends through the lumen defined by the retraction plate may be advantageous in brake assemblies which include a high-pressure hydraulic system, such as, for example, greater than or equal to about <NUM>,<NUM> pounds per square inch (psi), or greater than or equal to about <NUM>,<NUM> psi. The trend in brake systems is to include higher pressure hydraulic systems, <NUM>,<NUM> psi or greater, that require smaller piston sizes to actuate the amount of force required for the system, leading to more designs with external adjusters. These systems may particularly benefit from brake assemblies according to the present disclosure.

<FIG> is a schematic side view illustrating example brake assembly <NUM>. Brake assembly <NUM> is included as part of a brake system of vehicle <NUM>. Although primarily described herein as an aircraft, vehicle <NUM> may be another type of vehicle, such as a land vehicle or a marine vehicle. Brake assembly <NUM> includes central axis L extending into the page along the Y-direction. In some examples, central axis L may be collinear with an axis of a wheel (not pictured) of vehicle <NUM>.

Brake assembly <NUM> includes heat sink <NUM>, pistons 106A, 106B, 106C (collectively, "pistons <NUM>"), and retraction plate <NUM>, which are configured to interact to decelerate vehicle <NUM> during a braking operation. Brake assembly <NUM> may also include other elements or systems not pictured. For example, brake assembly <NUM> may include a housing or other mechanical support elements, which may mechanically support brake assembly <NUM> and protect components of brake assembly <NUM> from impact and/or the external environment. Additionally, brake assembly <NUM> may include a system configured to drive pistons <NUM> to compress heat sink <NUM>, such as a hydraulic system, a pneumatic system, an electrical system, a mechanical system, or combinations thereof. The electrical system may be configured to allow for control of brake assembly <NUM> by an operator, such as a pilot, through a controller.

Heat sink <NUM> includes a 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 central axis L, while the stator discs remain stationary. To decelerate rotational motion of a rotating wheel during a braking operation, pistons are driven to compress the rotating rotor discs engaged with the wheel against the stationary stator discs within heat sink <NUM>, therefore producing torque that decelerates the rotational motion of the wheel. In some examples, brake assembly <NUM> may be a carbon brake, and as such heat sink <NUM> may include carbon. Additionally, or alternatively, heat sink <NUM> may include steel. Heat sink <NUM> including carbon may provide benefits including increased temperature resistance and/or reduced weight.

Retraction plate <NUM> is configured to displace toward heat sink <NUM> (into the page in <FIG>) during braking operations, and displace away from heat sink <NUM> (out of the page in <FIG>) during non-braking operations. Retraction plate <NUM> may include a strong and tough material configured to interact with heat sink <NUM>. A strong material, as defined herein, is a material which provides a stiff, rigid interface to transfer forces between the pistons <NUM> and the adjuster system <NUM>. A tough material, as defined herein, does not break down through interaction with heat sink <NUM> or operation withing the extreme environment of brake assembly <NUM>. Retraction plate <NUM> is also configured to act as a heat shield protecting pistons <NUM> and, for example, the hydraulic system configured to drive the pistons from the extreme heat generated by heat sink <NUM>. As such, retraction plate <NUM> may be called a heat shield. Brake assembly <NUM> may include additional heat shields beyond retraction plate <NUM>. In one non-limiting example, retraction plate <NUM> may include steel.

In some examples, retraction plate <NUM> may be disposed between pistons <NUM> and heat sink <NUM> during a braking operation. In such examples, retraction plate <NUM> may be forced toward heat sink <NUM> by pistons <NUM> when pistons <NUM> are driven, such that retraction plate <NUM> compresses heat sink <NUM> to decelerate vehicle <NUM>.

Alternatively, in examples according to the present disclosure as best illustrated in <FIG>, retraction plate <NUM> may define lumens 112A, 112B, 112C (collectively "lumens <NUM>"). Pistons <NUM> may extend through retraction plate <NUM> to contact heat sink <NUM>. In such examples, retraction plate <NUM> may or may not be configured to also contact heat sink <NUM>. If retraction plate <NUM> contacts heat sink <NUM>, it may be configured to do so only after pistons <NUM> contact heat sink <NUM>. Pistons <NUM> may be configured to extend through lumens <NUM> defined by retraction plate <NUM> to contact heat sink <NUM> during a braking operation, and pistons <NUM> may be configured to contact heat sink <NUM> prior to retraction plate <NUM> contacting heat sink <NUM> during the braking operation.

Brake assembly <NUM> includes adjuster system <NUM>. Adjuster system <NUM> may be a mechanical system which includes adjuster devices 110A, 110B, 110C (collectively, "adjuster devices <NUM>) that are configured to displace retraction plate <NUM> away from heat sink <NUM> (out of the page in <FIG>) when vehicle <NUM> is in a non-braking operation, creating clearance C (<FIG>). In the illustrated example of <FIG>, adjuster devices <NUM> are external adjusters, which are located remotely from pistons <NUM> and connected by an adjuster pin to retraction plate <NUM>.

In some examples, pistons <NUM> may not be mechanically attached to retraction plate <NUM>. Pistons <NUM> may be configured to extend through lumens <NUM> to compress heat sink <NUM>. In this way, the stiffer and more rigid retraction plate <NUM>, which may be mechanically attached to other components of brake assembly <NUM> and/or vehicle <NUM>, may be isolated from contacting heat sink <NUM>, thus eliminating potential vibration modes induced by the stiffer retraction plate during braking operations. Configured in this way the useful life of brake assembly <NUM> may be lengthened, and may provide increased braking control, response, and stability. Other benefits may include improved thermal protection of the piston housing and brake fluid, catalytic oxidation protection to the heat sink.

<FIG> is a schematic cross-sectional view of an example portion of brake assembly <NUM> of <FIG>, illustrating a close-up cross-sectional view of adjuster device <NUM>. As mentioned above, adjuster device <NUM> is an external adjuster arrangement.

Adjuster device <NUM> includes an adjuster pin <NUM> which is countersunk at first end <NUM> into retraction plate <NUM>, such that first end <NUM> of adjuster pin <NUM> is positioned between first surface <NUM> of retraction plate <NUM> and second surface <NUM> of retraction plate <NUM>. First surface <NUM> of retraction plate <NUM> is proximal to heat sink <NUM>, and second opposite surface <NUM> of retraction plate <NUM> is distal to heat sink <NUM>.

Adjuster pin <NUM> extends from first end <NUM> to second end <NUM> opposite first end <NUM>. Spring <NUM> surrounds adjuster pin <NUM> for at least a portion of the length of adjuster pin <NUM>. Spring <NUM> is fixed near second end <NUM> of adjuster pin <NUM>. When pistons <NUM> (<FIG>) are driven toward heat sink <NUM>, spring <NUM> compresses, allowing retraction plate <NUM> to be displaced toward heat sink <NUM>, reducing clearance C, which is the gap between retraction plate <NUM> and heat sink <NUM>. In some examples, as illustrated in <FIG>, at system pressures configured for releasing brake torque (i.e. the vehicle is in a non-braking operation) the adjuster pin <NUM> coupled with expander device <NUM> may be prevented from being displaced by adjuster tube <NUM>. Thus, the spring causes retraction plate <NUM> to displace in the direction away from heat sink <NUM> by pushing adjuster tube <NUM> in the direction away from heat sink <NUM>, such that retraction plate <NUM> returns to the default position where clearance C is maintained between retraction plate <NUM> and heat sink <NUM> throughout the life of the brake. In such a state, rotating components of heat sink <NUM> are allowed to rotate freely.

External adjuster device <NUM> advantageously allows for smaller diameter pistons <NUM> relative to internal adjuster arrangements, because the pistons do not require a spring. An external adjuster arrangement may result in reduced fluid volume, which may reduce the weight of the vehicle. Further advantages may include one or more of balanced static and dynamic torque capability, increased pressure torque response, improved pressure-torque sensitivity control, and/or improved reliability through elimination of extra adjuster pin seals.

<FIG> is a schematic side view of an example portion of a braking assembly according to the present disclosure. <FIG> illustrates a schematic close-up view of piston 106A and the associated bushing assembly <NUM> of <FIG>. Bushing <NUM> is used to contain piston 106A within the larger hydraulic system.

Piston 106A extends from first end <NUM> proximal to heat sink <NUM> to second opposite end <NUM> distal to heat sink <NUM>. Piston 106A includes a pressurized side <NUM> at second end <NUM>. Pressurized side <NUM> connects piston 106A to a hydraulic system for driving piston 106A towards heat sink <NUM>.

Retraction plate <NUM> is configured to act as a heat shield and, as such, is made from a tough, heat resistant material such as steel. Retraction plate <NUM> defines lumen 112A passing through retraction plate <NUM> from first surface <NUM> to second surface <NUM>. Piston 106A is configured to extend through retraction plate <NUM> from second surface <NUM> to first surface <NUM> and protrude a distance P into clearance C between first surface <NUM> of retraction plate <NUM> and heat sink <NUM>. Thus, piston 106A is configured to contact heat sink <NUM> before retraction plate <NUM> contacts heat sink <NUM> during a braking operation.

Piston 106A includes piston cap <NUM>, which is configured to interact with heat sink <NUM> and protect piston 106A. Piston cap <NUM> may be made out of any suitable tough material, such as, for example, steel. Piston cap <NUM> covers first end <NUM> of piston 106A. and may extend along a portion of the length of piston 106A between first end <NUM> and second end <NUM>.

In some examples, as illustrated, piston cap <NUM> includes shoulder <NUM>. shoulder <NUM> may be a lip or ridge which extends radially from piston 106A (up and down on the page in <FIG>). In some examples, shoulder <NUM> may be configured to seat in recess <NUM> of retraction plate <NUM>. During a braking operation of vehicle <NUM>, piston 106A may be driven towards heat sink <NUM>, and may displace retraction plate <NUM> towards heat sink <NUM>. Piston cap <NUM> is configured to contact and compress heat sink <NUM>, decelerating vehicle <NUM>. When the braking operation is ceased, retraction plate <NUM>, and piston 106A, may be forced back to the default position at clearance C by adjuster system <NUM>.

Piston 106A is mechanically separated from (i.e., not mechanically attached to) retraction plate <NUM>. Bushing assembly <NUM> is mechanically attached to retraction plate <NUM> either directly or indirectly and supports and constrains piston 106A while piston 106A is allowed to translate within bushing assembly <NUM>. Therefore, vibrations induced by imperfections in friction surfaces of heat sink <NUM> may not propagate, or only propagate at a reduced rate through the individual pistons <NUM> to other components of the brake assembly.

<FIG> illustrate a portion of example braking assembly <NUM> during different stages of a braking operation. The conceptual illustration are side views, with hidden elements in broken lines. Braking assembly <NUM> of <FIG> may be an example of braking assembly <NUM> of <FIG>, and may be described similarly, with similar reference numbers indicating similar elements. <FIG> illustrate braking assembly <NUM> in a non-braking operation, with piston <NUM> seated within lumen <NUM> of retraction plate <NUM> and clearance C separating retraction plate <NUM> and heat sink <NUM>. In some examples, retraction plate <NUM> is configured to serve an additional safety function, as such, is made from a strong, stiff material such as steel. Retraction plate <NUM> defines lumen <NUM> passing through retraction plate <NUM> from first surface <NUM> to second surface <NUM>. Piston <NUM> is configured to extend through retraction plate <NUM> from second surface <NUM> to first surface <NUM> into clearance C between to contact heat sink <NUM> to provide braking during a braking operation, as illustrated in <FIG>. Thus, piston <NUM> is configured to contact heat sink <NUM> before retraction plate <NUM> contacts heat sink <NUM> during a braking operation. However, as illustrated in <FIG>, if the heat sink <NUM> oxidizes and allows for piston <NUM> to begin to punch through heat sink <NUM> (e.g., a first stationary stage of heat sink <NUM>), retraction plate <NUM> may contact heat sink <NUM> may contact heat sink <NUM>, increasing the surface area in contact with heat sink <NUM>, preventing further protrusion of piston <NUM> through heat sink <NUM>.

<FIG> is a flowchart illustrating an example technique for forming a braking assembly according to some examples of the present disclosure. While described with respect to example brake assembly <NUM> of <FIG>, it will be understood that the technique of <FIG> may be used to form other brake assemblies, and brake assembly <NUM> may be formed by other techniques.

The technique of <FIG> includes positioning retraction plate <NUM> adjacent to heat sink <NUM> (<NUM>). Retraction plate <NUM> defines lumen 112A.

The technique of <FIG> also includes positioning piston 106A adjacent to retraction plate <NUM> (<NUM>). Piston 106A is mechanically separated from retraction plate <NUM>. Piston 106A is configured to extend through lumen 112A to contact heat sink <NUM> during a braking operation of vehicle <NUM> prior to retraction plate <NUM> contacting heat sink <NUM>.

Claim 1:
A brake assembly (<NUM>, <NUM>) comprising:
a heat sink (<NUM>, <NUM>);
a piston (<NUM>, <NUM>); and
a retraction plate (<NUM>, <NUM>) defining a lumen (<NUM>, <NUM>);
wherein the piston (<NUM>, <NUM>) is mechanically separated from the retraction plate (<NUM>, <NUM>),
wherein the piston (<NUM>, <NUM>) is configured to extend through the lumen (<NUM>, <NUM>) defined by the retraction plate (<NUM>, <NUM>) to contact the heat sink (<NUM>, <NUM>) during a braking operation, and
wherein the piston (<NUM>, <NUM>) is configured to contact the heat sink (<NUM>, <NUM>) prior to the retraction plate (<NUM>, <NUM>) contacting the heat sink (<NUM>, <NUM>) during the braking operation.