Patent Description:
EMAs are braking assemblies that forcefully move a translating member (such as a "ball nut") against a brake disk stack to generate an actuation force. This actuation force drives the ball nut into forceful engagement with the brake disk stack to generate a braking force. <CIT> describes an electromechanical bridle operating method.

An electromechanical actuator (EMA) is disclosed and defined in claim <NUM>. The EMA comprises an EMA housing, a ball nut extending axially within the EMA housing, a ball screw extending axially within the ball nut, and/or an actuator drive unit (ADU) housing extending axially within the ball screw, the ADU housing having a proximal stop that extends radially outward of the ADU housing. The ball nut is configured to translate axially in a proximal direction in response to a rotation by the ball screw, and the ball nut is configured to be halted in the axially proximal translation in response to contact with the proximal stop. The proximal stop is coupled to the ADU housing. The proximal stop comprises a continuous annular structure. The ball nut contacts with the proximal stop as the ball nut translates axially to halt the axially proximal translation of the ball nut. The proximal stop includes a compliant surface. The ball nut is configured to advance axially in a distal direction away from the proximal stop and/or to retract axially in the proximal direction towards the proximal stop. A position of the ball nut may be determined based upon a gear ratio.

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

The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration and their best mode. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the inventions, it should be understood that other embodiments may be realized and that logical, chemical and mechanical changes may be made without departing from the scope of the present invention as defined by the appended claims. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option.

As used herein, an "inner surface" may comprise any surface that is situated radially inward of any other surface with respect to the axis, as defined herein, labeled A-A'. Thus, an inner surface may be situated radially inward of an "outer surface" with respect to the axis A-A'.

In addition, the EMA may extend along the axis defined by the line marked A-A'. The portion near A may be referred to as proximal and the portion near A' may be referred to as distal. In that regard, A is proximal to A' and A' is distal to A. Translation in an axial direction towards A is considered movement in a proximal direction and translation in an axial direction towards A' is considered movement in a distal direction.

With reference to <FIG>, a cross-sectional schematic view of a conventional EMA <NUM> is shown. The EMA <NUM> may comprise an EMA housing <NUM>, an actuator drive unit ("ADD") housing <NUM>, a ball nut <NUM>, a ball screw <NUM>, and a disc or "puck" <NUM>. The EMA housing <NUM> may comprise a generally annular structure configured to house the ball nut <NUM> and extending along the axis A-A'. The ball nut <NUM> may comprise a generally annular housing that extends axially along the axis A-A' within the EMA housing <NUM>. The ball screw <NUM> may comprise a generally annular housing that extends axially along the axis A'A' within the ball nut <NUM>. The ADU housing <NUM> may comprise a generally annular housing that extends axially along the axis A-A' at least partially radially inward of the ball screw <NUM>. A variety of drive components may be housed within the ADU housing <NUM>, such as, for example, an electromechanical drive motor, drive shaft, gearing system, and the like. The ADU housing <NUM> may comprise a stationary (non-rotating, non-translating) component. The puck <NUM> may comprise a generally disc shaped element, and the puck <NUM> may be coupled to a distal portion of the ball nut <NUM>.

An inner surface of the ball nut <NUM> may be helically threaded. Likewise, an outer surface of the ball screw <NUM> may be helically threaded. As described above, the ball screw <NUM> may be housed within the ball nut <NUM>, and the threading on the outer surface of the ball screw <NUM> may interface with or mate with the threading on the inner surface of the ball nut <NUM>.

During operation, the ball screw <NUM> may rotate about an axis A-A'. As the ball screw <NUM> rotates, the threading on the ball screw <NUM> may cooperate with the threading in the ball nut <NUM> to drive the ball nut <NUM> in a distal direction. As the ball nut <NUM> translates distally, the puck <NUM> coupled to the ball nut <NUM> may also translate distally. The puck <NUM> may contact a brake stack (e.g., a brake stack associated with an aircraft wheel) to apply force to the brake stack, thereby slowing and/or halting the rotation of the aircraft wheel.

With reference to <FIG>, a longitudinal perspective view of a conventional ball nut <NUM> (looking from A to A' toward a distal portion of the ball nut <NUM> along the longitudinal axis A-A') is shown. This ball nut <NUM> includes a concentrically situated projection <NUM> or "tooth," located at a distal portion of the ball nut <NUM>.

With reference to <FIG>, a longitudinal perspective view of a distal portion of a conventional ball screw <NUM> is shown. The ball screw <NUM> includes a concentrically situated projection <NUM> or tooth as well. This projection <NUM>, like the projection <NUM>, is situated at a distal portion of the ball screw <NUM>.

In operation, as described above, as the ball screw <NUM> rotates, the ball nut <NUM> may translate proximally (and/or distally) along the axis A-A' until the projection <NUM> in the ball screw <NUM> rotates into contact with the projection <NUM> in the ball nut <NUM>. As the projection <NUM> makes contact with the projection <NUM>, the ball nut <NUM> may be halted in its proximal progress, even as the ball screw <NUM> may attempt to rotate in an effort to force the ball nut <NUM> proximally into a home stop or stowed position.

A variety of disadvantages are associated with the conventional system depicted at <FIG>. For example, the projection <NUM> may rotate with substantial angular momentum into the projection <NUM>. As this occurs, the projection <NUM> and/or the projection <NUM> may chip or break. Failure of either projection <NUM> and/or <NUM> may result in expulsion of the entire ball nut <NUM> from its housing within the EMA housing <NUM>, leaving the ball nut <NUM> (and/or other components) behind as litter and/or other dangerous debris. Such an event may, in addition, result in brake failure. Thus, a variety of disadvantages are associated with existing conventional systems.

Now, with reference to <FIG>, an EMA <NUM> is shown. The EMA <NUM> may, like the EMA <NUM>, comprise an EMA housing <NUM>, a ball nut <NUM>, a ball screw <NUM>, an ADU housing <NUM>, and a disc or puck <NUM>. As above, the EMA housing <NUM> may comprise a generally annular structure configured to house the ball nut <NUM> and extending along the axis A-A'. The ball nut <NUM> may comprise a generally annular housing that extends axially along the axis A-A' within the EMA housing <NUM>. The ball screw <NUM> may comprise a generally annular housing that extends axially along the axis A-A' within the ball nut <NUM>. The ADU housing <NUM> may comprise a generally annular housing that extends axially along the axis A-A' at least partially radially inward of the ball screw <NUM>.

According to the invention an electromechanical drive motor is housed in the ADU housing. A variety of further drive components may be housed within the ADU housing <NUM>, such as, for example, drive shaft, gearing system, and the like. The puck <NUM> may comprise a generally disc shaped element, and the puck <NUM> may be coupled to a distal portion of the ball nut <NUM>.

However, as shown in greater detail at <FIG>, the EMA <NUM> described herein may comprise an ADU housing <NUM> comprising a projection or stop <NUM> extending radially outward of the ADU housing <NUM>. The stop <NUM> may extend radially outward such that it is raised above an outer surface of the ADU housing <NUM>. In addition, the stop <NUM> may be disposed substantially at a proximal portion of the ADU housing <NUM> and may comprise a "T-shaped" or doglegged structure.

The proximal portion of the stop <NUM> incorporates a compliant or shock absorbing material, such as foam or rubber. This material may dissipate energy, as described below, as the ball nut <NUM> comes into contact with the stop <NUM>. The stop <NUM> may be coupled to the ADU housing <NUM> in any suitable manner. For instance, the stop <NUM> may be screwed into the ADU housing <NUM>, heat bonded to the ADU housing <NUM>, forged integral to the ADU housing <NUM>, riveted to the ADU housing <NUM>, bolted into the ADU housing <NUM>, adhesively bonded to the ADU housing <NUM>, and the like.

In operation, as the ball nut <NUM> translates axially in a proximal direction, the ball nut <NUM> comes into contact with the stop <NUM>. As the ball nut <NUM> comes into contact with the stop <NUM>, the proximal translation of the ball nut <NUM> is halted. The stop <NUM> may however, unlike other conventional systems, resist or eliminate EMA <NUM> failure. For example, the stop <NUM>, comprising a continuous annular structure, may not rely upon one or more simple projections (e.g., projections <NUM> and <NUM>) to arrest the angular momentum of the ball nut <NUM>. Rather, the large (continuous) surface area of the stop <NUM> may permit the dissipation of angular and axial momentum over a much larger, surface area.

Dissipation of angular and axial momentum over this larger surface area reduces the overall stress experienced by any particular portion of the ball nut <NUM> and/or ball screw <NUM> (e.g., the projections <NUM> and <NUM> in the conventional system), particularly as the ball nut <NUM> and/or the ADU housing <NUM> and/or stop <NUM> may be manufactured, for durability and strength, from steel or a steel alloy, such as, for example, a hardened steel. The system of the present invention therefore embodies a much more reliable, failure-resistant, ball nut <NUM> stopping system. The cost and weight of the system of the present invention may also be reduced over that associated with more conventional systems, as projections <NUM> and <NUM> may be eliminated in favor of the stop <NUM>.

In various embodiments, from the stop <NUM>, a computer-based system comprising a processor and a tangible, non-transitory, memory coupled to the processor may track or count the number of motor rotations or revolutions as the ball nut <NUM> advances distally from the stop <NUM>. This information, in combination with a gear ratio and/or a distance of a portion of the ball nut <NUM> (e.g., the distal edge of the ball nut <NUM>) from the stop <NUM> may permit the computer-based system to calculate the position of the ball nut <NUM> and/or the ball nut <NUM> actuating mechanism. The location of the ball nut <NUM> and/or actuator may be fed back into the computer-based system to control the advancement and/or retraction of the ball nut <NUM> during operation.

Claim 1:
An electromechanical actuator, EMA, (<NUM>) for use as a braking assembly comprising:
an EMA housing (<NUM>);
a ball nut (<NUM>) extending axially within the EMA housing (<NUM>); an actuator drive unit, ADU, housing (<NUM>) disposed radially inward to the bull nut and extending axially within the ball screw (<NUM>), the ADU housing (<NUM>) having a proximal stop (<NUM>) that is coupled to and protrudes from an outer surface of a proximal portion of the ADU housing (<NUM>); and
a ball screw (<NUM>) extending axially within the ball nut (<NUM>); and
wherein the ball nut (<NUM>) is configured to advance axially in a distal direction away from the proximal stop (<NUM>) and to retract axially in a proximal direction in response to a rotation by the ball screw (<NUM>), and
wherein the ball nut (<NUM>) is configured to be halted in the axially proximal translation in response to contact with the proximal stop (<NUM>);
characterised in that the EMA further comprises:
an electromechanical drive motor housed in the ADU housing (<NUM>),
and in that the proximal stop comprises a continuous annular structure and includes a compliant surface comprising at least one of a foam or rubber.