Patent Description:
This description relates to rotary-to-linear motion conversion devices for use with aircraft cascade reverser actuators.

Conventional linear actuators have output rams that may be driven by a motor or with pneumatic or hydraulic pressure. The actuator may have a lock mechanism to retain the output in a fixed position. Known lock mechanisms, such as taught by <CIT>, engage an actuator synchronization system, and therefore provide only indirect locking to the output ram. Direct locking mechanisms that employ a linear actuator have been developed and typically include a multi-piece housing with increased size and mass. Such actuators include tine locks, an example of which is disclosed by <CIT>. While some tine lock arrangements may allow for a single-piece housing actuator, they have the disadvantage of using a flexing lock element with consequential fatigue considerations. Locking actuators can be operated by a rotary source rather than hydraulically or pneumatically. Present rotary source operated actuators, such as disclosed by<CIT>, have the disadvantage of requiring an electrically operated solenoid mechanism (or other mechanical input separate from the rotary source) to unlock the actuator lock before motion of the ram can commence. Ball lock mechanisms such as taught by <CIT>, <CIT> and <CIT> have the disadvantage of a low external load carrying capability of the ram, because of the point contact stresses imposed on the lock balls. Linear motion lock sleeve and key arrangements, such as disclosed by Kopecek (the inventor of the present disclosure) in <CIT>, include a rotary-to-linear motion conversion mechanism for the lock sleeve and complexity associated therewith. Rotary lock sleeve and key arrangements have also been disclosed by <CIT>. Accordingly, it would be desirable to provide a linear actuator arrangement that overcomes at least some of the problems identified above. <CIT> describes a planetary gear mechanism, in particular for wind power plants, that includes at least one planetary gear stage that has two power-split planetary stages connected in parallel. At least one of the two planetary stages includes a ring gear which is operatively connected to a housing. At least three planetary gearwheels are arranged on an inner circumferential face of the ring gear. The ring gear is flexible in the radial direction and is configured to be adjustable in order to compensate load between the at least three planetary gear wheels and the ring gear.

In general, this document describes rotary-to-linear motion conversion devices. More particularly, this document describes rotary-to-linear motion conversion devices for use with aircraft cascade reverser actuators.

A rotary lock assembly according to the present invention is set out in claim <NUM>. Further advantageous developments of the present invention are set out in the dependent claims.

According to the present invention, a rotary lock assembly includes a first epicyclic gear assembly having a first sun gear assembly, a first ring gear assembly, and a first planet gear assembly mechanically engaged to the first sun gear assembly and the first ring gear assembly, and a second epicyclic gear assembly having a second sun gear assembly configured to be rotated by the first ring gear assembly, a second ring gear assembly, and a second planet gear assembly mechanically engaged to the second sun gear assembly and the second ring gear assembly. The second ring gear assembly is configured to remain fixed relative to motion of the second sun gear assembly.

Various embodiments can include some, all, or none of the following features. The rotary lock assembly can also include a lock key configured for radial displacement between a first lock key configuration and a second lock key configuration, and a lock rotor configured to be rotated by the second planet gear assembly between a first rotor configuration in which radial displacement of the lock key from the first lock key configuration to the second lock key configuration is prevented, and a second rotor configuration in which radial displacement of the lock key from the first lock key configuration to the second lock key configuration is permitted. The rotary lock assembly can also include a first lock rotor stop configured to prevent rotation of the lock rotor in a first direction at the first rotor configuration, and a second lock stop configured to prevent rotation of the lock rotor in a second direction at the second rotor configuration. The rotary lock assembly can also include a lock key retainer configured to be moved linearly between a first lock key retainer configuration in which radial displacement of the lock key from the second lock key configuration to the first lock key configuration is prevented, and a second lock key retainer configuration in which radial displacement of the lock key from the second lock key configuration to the first lock key configuration is permitted. The rotary lock assembly can also include a linear output assembly configured for axial movement relative to radial movement of the lock key, and having an outer surface defining a groove between a first axial groove face and a second axial groove face, and configured to receive the lock key in the first lock key configuration and be prevented from moving linearly based on mechanical interference between the lock key and at least one of the first axial groove face and the second axial groove face. The rotary lock assembly can also include a screw lead engaged to the first planet gear assembly and responsive to revolution of the first planet gear assembly, and a nut engaged with the screw lead and axially movable along the screw lead in response to rotation of the screw lead. The rotary lock assembly can also include a housing engaged to the second ring gear assembly, and an input shaft coupled to the first sun gear assembly and rotatable relative to the housing.

According to the present disclosure, a method of locking a linear actuator includes receiving torque at a first sun gear of a first epicyclic gear assembly, transmitting torque from the first sun gear to a first ring gear of the first epicyclic gear assembly through a first planet gear assembly of the first epicyclic gear assembly, transmitting torque from the first planet gear assembly to a screw, urging movement of a linear output member through a nut configured for linear motion based on rotation of the screw, transmitting torque from the first ring gear to a second sun gear of a second epicyclic gear assembly, and transmitting torque from the second sun gear to a second planet gear engaged between the second sun gear and a second ring gear.

Various examples of the present disclosure can include some, all, or none of the following features. The method can also include urging radial displacement of a lock key from a first lock key configuration to a second lock key configuration based on linear movement of the linear output member. The method can also include contacting, based on movement of the linear actuator, the lock key with an axial groove face of a groove defined in the linear output member and configured to receive the lock key in the first lock key configuration, preventing linear movement of the linear output member based on interference between the lock key and the axial groove face, preventing rotation the screw based on the prevented linear movement of the linear output member, preventing rotation of the first planet gear assembly based on the prevented rotation of the screw, and transmitting substantially all torque received at the first sun gear to the first ring gear. The method can also include transmitting torque from the second planet gear to a lock rotor, and rotating the lock rotor from a first lock rotor configuration to a second lock rotor configuration. The first lock rotor configuration can be a first rotational position defined by a first lock rotor end stop configured to interfere with rotation of the lock rotor in a first direction, and the second lock rotor configuration is a second rotational position defined by a second lock rotor end stop configured to interfere with rotation of the lock rotor in a second direction opposite the first direction. The lock rotor can be configured to prevent radial displacement of a lock key from a first key configuration to a second key configuration in the first lock rotor configuration, and is configured to permit radial displacement of the lock key from the first key configuration to the second key configuration in the second lock rotor configuration.

According to the present invention, a linear actuator includes a housing, a rotary input member rotatably moveable relative to the housing, a linear output member axially movable between a first output position relative the housing, and a second output position relative to the housing, and a rotary lock assembly disposed within the housing and constrained from axial motion, the rotary lock assembly having a first epicyclic gear assembly that includes a first sun gear assembly, a first ring gear assembly, and a first planet gear assembly mechanically engaged to the first sun gear assembly and the first ring gear assembly, and a second epicyclic gear assembly that includes a second sun gear assembly configured to be rotated by the first ring gear assembly, a second ring gear assembly, and a second planet gear assembly mechanically engaged to the second sun gear assembly and the second ring gear assembly. The second ring gear assembly is configured to remain fixed relative to motion of the second sun gear assembly.

The systems and techniques described here may provide one or more of the following advantages. First, a system can lock linear actuators against unintended extension. Second they system can provide more reliable unlocking operations, especially under conditions of high mechanical loads on the linear actuators. Third, the system can automatically provide the additional torque needed to perform the unlocking. Fourth, the system can provide the additional torque without additional control or power inputs.

This document describes systems and techniques for providing rotary-to-linear motion with an actuator device that can be locked to prevent unintentional movement. Some prior locking designs are limited in the amount of tension load that may be applied to the actuator ram while still allowing lock keys to unlock. The designs described in this document provide a capability to unlock the actuator under the high-tension loads that can be generated by the latest technology thrust reversers. As will be discussed in more detail below, the actuator includes features that automatically redirect input torque when needed, in order to overcome binding or lock components under high input forces. In general, the rotary-to-linear conversion function of the actuator is achieved with a multi-stage planetary gearbox, in which one stage drives the rotary-to-linear conversion, and resistance to that conversion drives a second stage that performs unlocking actions. The second stage is gear-reduced to provide increased torque to perform the unlocking, which can be helpful in situations when high linear forces can cause the locking components to bind or otherwise become difficult to unlock.

<FIG> illustrates a front perspective view of an example linear actuator <NUM> incorporating aspects of the disclosed embodiments. The actuator <NUM> has an outer housing <NUM> and an output ram <NUM> (e.g., a linear output assembly). The output ram <NUM>, which is capable of axial movement or motion (depicted by direction arrow <NUM>) into and out of the housing <NUM>, such as from a retracted output position as shown in <FIG>. In some embodiments, the linear actuator <NUM> can be part of a thrust reverser actuation system (TRAS). As a non-limiting example, the ram <NUM> may be attached to a door, panel, or engine thrust reverser, while the housing <NUM> is attached to a frame of a larger object, such as, but not limited to, an airplane. Movement of the ram <NUM> thereby determines the position of the door, panel, or thrust reverser, or other attaching surface.

Within the housing <NUM>, an actuator (not shown) drives the extension and retraction of the output ram <NUM> based on rotational energy received from a synchronization shaft (not shown) connected to the actuator through an aperture 122a and/or 122b. This actuator will be described in more detail in the descriptions of <FIG>. In some embodiments, the linear actuator <NUM> can also include a sensor configured to provide positional signals or information that is representative of the linear output position (e.g., extension or retraction) of the output ram <NUM>.

When the output ram <NUM> is retracted into the housing <NUM>, a locking rotary actuator mechanism <NUM> may be locked to prevent inadvertent or unintended extension of the ram <NUM> from the housing <NUM>. The locking rotary actuator mechanism <NUM> for the linear actuator <NUM> is discussed in more detail below.

<FIG> and <FIG> show cross section views of an example locking rotary actuator mechanism <NUM> in a locked configuration. In some embodiments, the locking rotary actuator mechanism <NUM> can be the example locking rotary actuator mechanism <NUM> of <FIG>.

The locking rotary actuator mechanism <NUM> includes a housing <NUM>, rotary input shaft member <NUM>, and a linear output assembly <NUM>. Rotation of the rotary input shaft member <NUM> (e.g., by a synchronization shaft, by a direct-drive motor) urges linear motion of the linear output member <NUM> through an epicyclic gear assembly <NUM>, a rotary lock assembly <NUM>, and a rotary-to-linear motion conversion assembly <NUM>. The rotary-to-linear motion conversion assembly <NUM> includes a screw lead <NUM> that is rotated by the epicyclic gear assembly <NUM>, and a nut <NUM> that is affixed to the linear output assembly <NUM> and is driven linearly as the screw lead <NUM> rotates.

The rotary lock assembly <NUM> includes a collection of lock keys <NUM> that are configured for radial displacement and to engage with a groove <NUM> defined in a radially outer surface of the linear output assembly <NUM>. The groove <NUM> includes an axial groove face 266a and an axial groove face 266b. The axial groove face 266b is configured with a bevel that is complimentary to a bevel <NUM> of the lock key <NUM>. In some embodiments, the bevel <NUM> is angled typically about <NUM> degrees from the radially outward direction. When locked, the lock keys <NUM> prevent the linear output assembly <NUM> from extending by contacting the axial groove face 266b. The lock keys <NUM> are prevented from moving radially out of the locked position by a lock rotor <NUM>. The lock rotor <NUM> can be partly rotated to selectively prevent and permit radial movement of the lock keys <NUM>. The lock rotor <NUM> is discussed in more detail in the description of <FIG>.

The epicyclic gear assembly <NUM> includes an epicyclic gear subassembly 212a and an epicyclic gear subassembly 212b. The screw lead <NUM> is rotated by the rotary input shaft member <NUM> thought the epicyclic gear subassembly 212a. The lock rotor <NUM> is rotated by the rotary input shaft member <NUM> through the epicyclic gear subassembly 212b.

The epicyclic gear subassembly 212a includes a sun gear assembly <NUM>, a ring gear assembly <NUM>, and a planet gear assembly <NUM>. The epicyclic gear subassembly includes a sun gear assembly <NUM>, a ring gear assembly <NUM>, and a planet gear assembly <NUM>. The ring gear assembly <NUM> is affixed (e.g., grounded) to the housing <NUM> or otherwise prevented from rotating relative to the rotary input shaft member <NUM>, the screw lead <NUM>, and the other components of the epicyclic gear assembly <NUM>. The sun gear assembly <NUM> is affixed to or otherwise configured to be driven by rotation of the ring gear assembly <NUM>. A planet carrier <NUM> connects the planet gear assembly <NUM> to the screw lead <NUM> such that rotation of the planet gear assembly <NUM> can urge rotation of the screw lead <NUM>. A planet carrier <NUM> connects the planet gear assembly <NUM> to the lock rotor <NUM> such that rotation of the planet gear assembly <NUM> can urge rotation of the lock rotor <NUM>.

The locking rotary actuator mechanism <NUM> uses a lost motion mechanism incorporating the epicyclic gear assembly <NUM> that operates as a star gear (e.g., grounded planet gear assembly <NUM> where the sun gear assembly <NUM> drives the ring gear assembly <NUM>) during the unlocking process of the lock keys <NUM>, and then operates as a planetary gear (e.g., grounded ring gear assembly <NUM> where the sun gear assembly <NUM> drives the planet gear assembly <NUM>). In some implementations, this arrangement can provide force for unlocking of the lock as long as tension loads upon the output ram <NUM> are not too great. This is because tension loads on the piston are reacted into a radially outward force on the lock keys <NUM> by the bevel <NUM> and the axial groove face 266b. The tension load on the piston therefore results in an increased frictional force between the lock key <NUM> and an inner face of the lock rotor <NUM>. This friction force opposes the unlocking torque on the ring gear assembly <NUM> when the epicyclic gear subassembly 212a is operating in star (unlocking) mode.

Referring now to <FIG>, the example locking rotary actuator mechanism <NUM> is shown in an initial state of unlocking. In the illustrated example, a high tension exists on the linear output assembly <NUM>. High tension loads imposed on the linear output assembly <NUM> (e.g., by advanced technology thrust reversers) during the unlocking process can create a frictional force between the lock keys <NUM> and the lock rotor <NUM> that is high enough to prevent rotation of the lock rotor <NUM> during the unlocking process. Without the help of additional mechanical force provided by the epicyclic gear subassembly 212b, such frictional forces could prevent unlocking in some circumstances.

With the linear output assembly <NUM> locked, the rotary-to-linear motion conversion assembly <NUM> is substantially prevented from operating and the screw lead <NUM> substantially prevented from rotating. As such, the planet carrier <NUM> and the planet gear assembly <NUM> are also substantially prevented from moving. As such, the carrier <NUM> of planet gear assembly <NUM> is substantially grounded.

The rotary input shaft member <NUM> is rotated, which urges rotation of the sun gear assembly <NUM>. Substantially all of the torque provided by the sun gear assembly <NUM> is transmitted through the planet gear assembly <NUM> (e.g., which is currently grounded) to the ring gear assembly <NUM>. The ring gear assembly <NUM> rotates, urging rotation of the sun gear assembly <NUM>.

Since the ring gear assembly <NUM> is grounded to the housing <NUM>, rotation of the sun gear assembly <NUM> urges rotation of the planet gear assembly <NUM>. Rotation of the planet gear assembly <NUM> is transmitted along the planet carrier <NUM> to urge rotation of the lock rotor <NUM>. In the illustrated example, substantially all of the torque provided at the rotary input shaft member <NUM> is transmitted to the lock rotor <NUM>, and the epicyclic gear subassembly 212b provides a gear reduction that multiplies the force that is available to overcome friction between the lock keys <NUM> and the lock rotor <NUM>.

<FIG> shows a cross section view of the example locking rotary actuator mechanism <NUM> in a partly unlocked configuration. Once the friction between the lock keys <NUM> and the lock rotor <NUM> has been overcome, the lock rotor <NUM> can begin to rotate such that the lock keys <NUM> are permitted to move radially outward. With the lock keys <NUM> being able to move, the linear output assembly <NUM> and the rotary-to-linear motion conversion assembly <NUM> are also able to start moving.

With the screw lead <NUM> able to rotate, the planet carrier <NUM> and the planet gear assembly <NUM> are also able to start to rotate. At this stage, a relatively small portion of the torque at the sun gear assembly <NUM> is available for transfer through the planet gear assembly <NUM> and the planet carrier <NUM> to start initial rotation of the screw lead <NUM> and cause an initial extension movement of the linear output assembly <NUM>. Movement of the linear output assembly <NUM> causes mechanical interference between the axial groove face 266b and the bevel <NUM>, which urges radially outward movement of the lock keys <NUM>.

Also visible in <FIG> is a lock key retainer <NUM> configured to be moved linearly between a first lock key retainer configuration in which radial displacement of the lock keys <NUM> from the unlocked position to the locked position is prevented, and a second lock key retainer configuration in which radial displacement of the lock key <NUM> from the unlocked position to the locked position is permitted. The lock key retainer <NUM> includes a stationary portion <NUM> that is directly or indirectly affixed to the housing <NUM> to remain substantially unmoved relative to movement of the linear output assembly <NUM>. The lock key retainer <NUM> also includes a moveable portion <NUM> that is configured to move linearly relative to the stationary portion <NUM>. The lock key retainer <NUM> also includes a bias member <NUM> (e.g., a spring) that is partly compressed between the stationary portion <NUM> and the moveable portion <NUM>, to urge the moveable portion <NUM> into contact with the linear output assembly <NUM>. In the illustrated example, the lock key retainer <NUM> is compressed and inactive, but the function of the lock key retainer <NUM> will be discussed further in the description of <FIG>.

<FIG> and <FIG> show cross section views of the example locking rotary actuator mechanism <NUM> in an unlocked configuration. The lock rotor <NUM> is configured to rotate through a limited, predetermined range of angles (e.g., about <NUM> degrees) between a hard stop at a position corresponding to the locked configuration (e.g., in which the lock keys <NUM> are able to fully escape the groove <NUM>) and another hard stop at a position corresponding to a fully unlocked configuration (e.g., in which the lock keys <NUM> are prevented from escaping the groove <NUM>). The configuration of the lock rotor <NUM> is discussed in more detail in the description of <FIG>.

In <FIG>, the lock rotor <NUM> is hard stopped at the position that corresponds to the unlocked configuration. The hard stop prevents further rotation of the lock rotor <NUM>, substantially grounding the lock rotor <NUM> and preventing further rotation of the planet carrier <NUM>, the planet gear assembly <NUM>, the sun gear assembly <NUM>, and the ring gear assembly <NUM>. With the ring gear assembly <NUM> effectively grounded, substantially all of the torque provided at the rotary input shaft member <NUM> to be directed through the planet gear assembly <NUM> and the planet carrier <NUM> to the screw lead <NUM> to urge extension of the linear output assembly <NUM>. With the lock keys <NUM> being fully escaped from the groove <NUM>, the linear output assembly <NUM> is able to extend.

As the linear output assembly <NUM> extends its output position, the bias member <NUM> expands between the stationary portion <NUM> and the moveable portion <NUM>, urging the moveable portion <NUM> to follow the linear output assembly <NUM> as it extends. The moveable portion <NUM> provides a radial face that substantially extends the radially outermost surface of the linear output assembly <NUM>. As the linear output assembly <NUM> extends beyond the axial output position location of the lock keys <NUM>, the moveable portion <NUM> moves to provide a physical barrier that keeps the lock keys <NUM> in the radially extended, unlocked position.

In <FIG>, the linear output assembly <NUM> continues to extend while the lock keys <NUM> are maintained in their unlocked positions. Retraction of the linear output assembly <NUM> is performed by reversing the rotation of the rotary input shaft member <NUM>, which brings the linear output assembly <NUM> back into contact with the moveable portion <NUM> to urge compression of the bias member <NUM> and allow the lock keys <NUM> to move radially out of the unlocked position toward the locked configuration within the groove <NUM>. Once the linear output assembly <NUM> is fully retracted, the sun gear assembly <NUM> effectively becomes grounded, and torque is directed toward rotation of the lock rotor <NUM> toward the locked position. The lock rotor <NUM> is configured to urge the lock keys <NUM> to move radially inward into the groove <NUM> and prevent them from being displaced radially (e.g., due to tension on the linear output assembly <NUM>).

<FIG> show a front perspective and a cross section view of an example lock key <NUM>. In some embodiments, the lock key <NUM> can be the example lock key <NUM> of <FIG>. The lock key <NUM> has a front face <NUM> and a rear face <NUM>. The rear face <NUM> includes a bevel <NUM> (e.g., angled about <NUM> degrees relative to the rear face). In some embodiments, the bevel <NUM> can be the bevel <NUM>. In the locked configuration, the bevel <NUM> contacts the axial groove face 266b to prevent extension of the linear output assembly <NUM>.

The lock key <NUM> has bottom surface <NUM> that is configured to rest against the linear output assembly <NUM> in the locked configuration and rest against the moveable portion <NUM> of the lock key retainer <NUM> in the unlocked configuration. The bottom surface <NUM> includes bevels 712a and 712b that can guide radially inward movement of the lock key <NUM> (e.g., moving into locking position within the groove <NUM>).

The lock key <NUM> also has a crown <NUM> that is configured to contact the lock rotor <NUM>. In the locked configuration, a top surface <NUM> of the crown contacts an inner radius of the lock rotor <NUM> to retain the lock key in the radially inward, locked configuration. In the unlocked configuration, the crown <NUM> extends into a corresponding, radially outward recess in the lock rotor that can rotate into and out of radial alignment with the crown <NUM>.

The crown <NUM> includes a radiused face 724a and a radiused face 724b. During locking, the lock rotor <NUM> rotates relative to the lock key <NUM>, and the radiused faces 724a-724b act as ramps against the circumferential ends of the lock rotor recesses to urge the lock key <NUM> to move radially inward into the locked configuration.

<FIG> depict an exemplary embodiment of a lock assembly <NUM>. In some embodiments, the lock assembly <NUM> can be the example rotary lock assembly <NUM> of <FIG>. The lock assembly <NUM> includes an epicyclic gear assembly such as the example epicyclic gear subassembly 212b.

A sun gear <NUM> (e.g., the example sun gear assembly <NUM>) of the epicyclic gear arrangement may provide the mechanical drive input to the gear assembly, and a planet carrier <NUM> couples a screw lead (e.g., the screw lead <NUM>) to a planet gear <NUM> to provide the energy to extend and retract the linear output assembly <NUM>. An outer diameter of the ring gear <NUM> (annulus, shown in <FIG> and <FIG>) of the epicyclic gear arrangement may be nested in a bearing race and directly attached to a lock rotor <NUM> visible in <FIG> (e.g., the lock rotor <NUM>) via a rotor extension <NUM>. In operation, the ball screw serves as the driver, and the linear output member is responsive to the rotation of the ball screw to move axially.

In an exemplary embodiment, rotation of the lock rotor <NUM> to move to the unlocked position may be provided by the epicyclic gear assembly initially operating in what is known as a "star" mode, during a lost motion stroke. With reference to <FIG>, the rotor extension <NUM> (which is coupled to ring gear <NUM>) acts as a key that engages a radial slot <NUM> that defines the rotational end stops of the lock rotor <NUM> from the locked to unlocked position. In some embodiments, a torsion spring may be included that directly biases the lock rotor <NUM> to the locked position.

In use, to extend the linear output assembly <NUM>, energy is input (such as via a motor, for example) to the sun gear assembly <NUM>. Because the linear output assembly <NUM> is constrained from any axial motion or movement or motion by a collection of lock keys <NUM> (e.g., the lock keys <NUM>), the screw lead <NUM> cannot turn and advance the linear output assembly <NUM>. Therefore, the planet carrier <NUM> is locked until the lost motion unlocks the lock keys <NUM>. As such, the only response to the rotation input by the sun gear <NUM> is to rotate the ring gear <NUM>, which is coupled to the lock rotor <NUM>. The unlocking of the lock keys <NUM> in response to rotation of the lock rotor <NUM> mechanically coincides with the rotor extension <NUM> bottoming out in the slot <NUM>. Bottoming out of the rotor extension <NUM> in the slot <NUM>, and unlocking the lock keys <NUM>, thereby results in locking the ring gear <NUM> and freeing the planet carrier <NUM> to allow a planet gear <NUM> to revolve around the sun gear <NUM>. Thus, the epicyclic gear arrangement changes from star mode (fixed planet carrier <NUM>, free sun gear <NUM>, and free annulus <NUM>) to planetary mode (fixed annulus <NUM>, free sun gear <NUM>, and free planet carrier <NUM>). In the planetary mode, the energy input to the sun gear <NUM> is used to cause the planet gear <NUM> to revolve around the sun gear <NUM>, and drive the planet carrier <NUM>, which, in turn drives the screw lead <NUM> and thereby, via nut <NUM>, causes the linear output assembly <NUM> to move axially.

To retract the linear output assembly <NUM> and rotate the lock rotor <NUM> to the locked position, this process is reversed. The motor driving the sun gear <NUM> reverses direction. The ring gear <NUM> reverses the load direction and attempts to rotate the lock rotor <NUM> from the unlocked position to the locked position. However, the lock keys <NUM> are constrained in the withdrawn position within the grooves <NUM> of the lock rotor <NUM> by the lock key retainer <NUM>, and thereby prevent any rotation of the lock rotor <NUM>. This effectively locks the ring gear <NUM> (e.g., via rotor extensions <NUM>), and defines the epicyclic mode. Therefore, the input rotation of the sun gear <NUM> is transferred to the planet carrier <NUM>, which causes the screw lead <NUM> to rotate, and retract the linear output assembly <NUM>.

In response to the linear output assembly <NUM> coming to the fully retracted position, the lock key retainer <NUM> is pushed out of the way (axially) by the linear output assembly <NUM> and the lock keys <NUM> are aligned with the groove <NUM> in the linear output assembly <NUM>. In response to the linear output assembly <NUM> being fully retracted, and thus no longer capable of any further axial motion, the screw lead <NUM> (and thus planet carrier <NUM>) is locked, and the epicyclic gear arrangement transitions from planetary mode to star mode. This now allows the lock rotor <NUM> to rotate from the unlocked to the locked position, pushing the lock keys <NUM> radially inward into the groove <NUM>, thus re-locking the linear output assembly <NUM>.

It will be appreciated that the output rotation direction of the ring gear <NUM> and lock rotor <NUM> during the lost motion stroke (e.g., star mode) is opposite of that of the planet carrier <NUM> and the screw lead <NUM> during extension of the linear output assembly <NUM> (e.g., planetary mode). This is a fundamental characteristic of epicyclic gears operated in both star and planetary modes. This lost motion feature results in a design that is self-locking and self-unlocking without any additional commands or signals required in addition to the drive torque.

To increase clarity, additional cross sectional figures of the lock assembly <NUM> as described herein and shown in <FIG> are provided. <FIG> depicts a cross section view of the epicyclic arrangement shown in <FIG> including the sun gear <NUM>, planet gear <NUM>, ring gear <NUM>, and planet carrier <NUM>. <FIG> depicts a cross section view of the epicyclic arrangement shown in <FIG> including the ring gear <NUM>, planet carrier <NUM>, and rotor extension <NUM>. <FIG> depicts a cross section view of the lock rotor <NUM> with lock keys <NUM> in the locked position.

As shown in <FIG>, the lock rotor <NUM> is disposed coaxially with the linear output assembly <NUM>, and includes a bore <NUM> having an inner surface <NUM> that interfaces with a crown <NUM> of the lock key <NUM>. A lock ring <NUM> is grounded (e.g., fixed relative to the housing) and includes grooves <NUM> that guide the lock keys <NUM> and restrict their displacement to radial motion. In an exemplary embodiment, an inside radius of the bore <NUM> will be approximately equal to an outside radius of the crown <NUM> when the lock key <NUM> is engaged with the radial groove <NUM>. In use, in response to the lock rotor <NUM> being disposed in the locked position of <FIG> and <FIG>, the bore <NUM> interfaces with the crown <NUM> of the lock key <NUM> and the lock key <NUM> is restrained from any outward radial motion (such as the lock key motion illustrated in <FIG>, for example). Therefore, the lock key <NUM> engages and is retained or held within, the groove <NUM> of the linear output assembly <NUM> by the rotation of the rotary input shaft member <NUM>.

<FIG> shows a flow diagram of an example process <NUM> for operating a linear actuator. In some implementations, the process <NUM> can be performed by all or part of the example linear actuator <NUM> of <FIG> and/or the example locking rotary actuator mechanism <NUM> of <FIG>.

At <NUM>, torque is received at a first sun gear of a first epicyclic gear assembly. For example torque from the rotary input shaft member <NUM> can be received at the sun gear assembly <NUM>.

At <NUM>, torque is transmitted from the first sun gear to a first ring gear of the first epicyclic gear assembly through a first planet gear assembly of the first epicyclic gear assembly. For example, torque can be transmitted from the sun gear assembly <NUM> to the ring gear assembly <NUM> through the planet gear assembly <NUM>.

At <NUM>, torque is transmitted from the first planet gear assembly to a screw. For example, rotation of the planet gear assembly <NUM> can urge rotation of the screw lead <NUM> through the planet carrier <NUM>.

At <NUM>, movement of a linear output member is urged through a nut configured for linear motion based on rotation of the screw. For example, rotation of the screw lead <NUM> relative to the nut <NUM> can urge linear movement of the linear output assembly <NUM>.

<NUM>, torque is transmitted from the first ring gear to a second sun gear of a second epicyclic gear assembly. For example, rotation of the ring gear assembly <NUM> can urge rotation of the sun gear assembly <NUM>.

At <NUM>, torque is transmitted from the second sun gear to a second planet gear engaged between the second sun gear and a second ring gear. For example, torque applied to the sun gear assembly <NUM> can be transmitted to the planet gear assembly <NUM>, which is engaged between the sun gear assembly <NUM> and the ring gear assembly <NUM>.

In some implementations, the process <NUM> can also include urging radial displacement of a lock key from a first lock key configuration to a second lock key configuration based on linear movement of the linear output member. For example, the lock rotor <NUM> can be moved from a locked rotational position to an unlocked rotational position, which can allow the lock keys <NUM> to move radially outward from a locked configuration to an unlocked configuration.

In some implementations, the process <NUM> can also include contacting, based on movement of the linear actuator, the lock key with an axial groove face of a groove defined in the linear output member and configured to receive the lock key in the first lock key configuration. In the first configuration, the lock key can prevent linear movement of the linear output member based on mechanical interference between the lock key and the axial groove face, and can prevent rotation the screw based on the prevented linear movement of the linear output member. With rotation of the screw prevented, rotation of the first planet gear assembly is also prevented based on the prevented rotation of the screw, which can cause substantially all torque received at the first sun gear to be transmitted to the first ring gear. For example, the linear output assembly <NUM> can contact the lock keys <NUM> in the groove <NUM> to prevent further axial movement of the linear output assembly <NUM>. With movement of the linear output assembly <NUM> stopped, rotation of the screw lead <NUM>, the sun gear assembly <NUM>, and the planet carrier <NUM> is stopped. With the planet carrier <NUM> prevented from moving, substantially all torque from the sun gear assembly <NUM> is transmitted to the ring gear assembly <NUM>.

In some implementations, the process <NUM> can also include transmitting torque from the second planet gear to a lock rotor, and rotating the lock rotor from a first lock rotor configuration to a second lock rotor configuration. For example, movement of the planet gear assembly <NUM> can be transmitted to the lock rotor <NUM> through the planet carrier <NUM>.

In some implementations, the first lock rotor configuration can be a first rotational position defined by a first lock rotor end stop configured to mechanically interfere with rotation of the lock rotor in a first direction, and the second lock rotor configuration is a second rotational position defined by a second lock rotor end stop configured to mechanically interfere with rotation of the lock rotor in a second direction opposite the first direction. For example, the example radial slot <NUM> can defines the rotational end stops of the lock rotor <NUM> from the locked to unlocked position.

In some implementations, the lock rotor can be configured to prevent radial displacement of a lock key from a first key configuration to a second key configuration in the first lock rotor configuration, and is configured to permit radial displacement of the lock key from the first key configuration to the second key configuration in the second lock rotor configuration. For example, <FIG> shows that the lock rotor <NUM> includes grooves <NUM> that guide the lock keys <NUM> and restrict their displacement to radial motion. In response to the lock rotor <NUM> being disposed in the locked position of <FIG> and <FIG>, the bore <NUM> can interface with the crown <NUM> of the lock key <NUM> and the lock key <NUM> can be restrained from any outward radial motion (such as the lock key motion illustrated in <FIG>, for example). Therefore, the lock key <NUM> engages and is retained or held within, the groove <NUM> of the linear output assembly <NUM> by the rotation of the rotary input shaft member <NUM>. When the lock rotor <NUM> is rotated to bring the grooves <NUM> into radial alignment with the crowns <NUM>, the lock keys <NUM> have sufficient space to move radially outward, out of contact with (and thus unlocking) the linear output assembly <NUM>.

Claim 1:
A rotary lock assembly comprising:
a first epicyclic gear assembly (212a) comprising
a first sun gear assembly (<NUM>),
a first ring gear assembly (<NUM>), and
a first planet gear assembly (<NUM>) mechanically engaged to the first sun gear assembly and the first ring gear assembly; and
a second epicyclic gear assembly (212b) comprising
a second sun gear assembly (<NUM>) configured to be rotated by the first ring gear assembly,
a second ring gear assembly (<NUM>) characterised in that the second ring gear assembly (<NUM>) is configured to remain fixed relative to motion of the second sun gear assembly, and the second epicyclic gear assembly (212b) further comprises
a second planet gear assembly (<NUM>) mechanically engaged to the second sun gear assembly and the second ring gear assembly.