Patent Description:
A strut is a primary structural member and may be utilized to connect a movable component to a stationary component. For example, a strut may be utilized to connect the turbine-generator units of the RAT to the aircraft. The strut may be configured to pivot relative to the aircraft for deployment of the RAT and stowing the RAT.

Document <CIT> discloses a ram-air turbine (RAT) assembly including a preferentially located mass that modifies the resonance frequency of the assembly.

Disclosed is a strut system for coupling a ram-air turbine (RAT) to an aircraft, including: a strut that includes a strut body, the strut having a strut first end that is configured to connect to the aircraft and rotate about a first axis, the strut having a strut second end that is spaced apart from the strut first end by the strut body and is configured to connect to the RAT, wherein the strut has a strut conduit extending from the strut first end toward the strut second end; and a damper rod that includes a rod body and disposed within the strut conduit, the damper rod having a rod first end that is fixed within the strut conduit at the strut first end, and a rod second end that is spaced apart from the rod first end by the rod body and is located intermediate the strut first end and the strut second end, wherein the rod second end is configured to move along a second axis that is parallel to the first axis.

In addition to one or more of the above aspects of the system, or as an alternate, the rod second end is configured such that is forms a bushing, and the system further includes: a guide shaft that extends through the strut, along the second axis, and through the bushing.

In addition to one or more of the above aspects of the system, or as an alternate, the guide shaft is a shank of a bolt; and the bolt includes a bolt head disposed against an outer surface of the strut, and the bolt has a threaded end spaced apart from the bolt head by the guide shaft and extends through the outer surface of the strut; and the system further includes a nut that is configured to engage the threaded end and secure the bolt to the strut.

In addition to one or more of the above aspects of the system, or as an alternate, the strut first end has a strut inner base that defines an opened end of the strut conduit; and the system further includes: a ring flange that is fixed to the strut inner base, the ring flange having a flange aperture that opens to the strut conduit, wherein the rod first end has a shoulder portion that is larger than the flange aperture and a threaded shaft that extends from the shoulder portion and though the flange aperture; and another nut that is secured to the threaded shaft, to secure the damper rod within the strut conduit.

In addition to one or more of the above aspects of the system, or as an alternate, the rod body is sized so that when the damper rod is secured to the strut inner base, the damper rod is under tension loading against the guide shaft to maintain a slip or sliding contact between the bushing and the guide shaft.

In addition to one or more of the above aspects of the system, or as an alternate, the strut first end has a shaft bore that is defined along the first axis; and the shaft bore is adjacent to the strut inner base and the strut conduit.

In addition to one or more of the above aspects of the system, or as an alternate, the rod body has a rectangular cross section defining a rod width that is wider along the second axis; the strut conduit defines a diameter, wherein the rod width is between sixty percent and ninety percent of the diameter of the strut conduit; the strut conduit defines a first length; and the damper rod defines a second length that is less than the first length. The rod cross section dimensions would be sized such as to allow relative motion at guide shaft to bushing interface due to lateral vibration loads.

In addition to one or more of the above aspects of the system, or as an alternate, the damper rod is formed of high strength steel and the guide shaft is case-hardened metal.

Further disclosed is an aircraft including a ram-air turbine (RAT); a strut system that couples the RAT to the aircraft, the strut system including: a strut that includes a strut body, the strut having a strut first end that is connected to the aircraft and configured to rotate about a first axis, the strut having a strut second end that is spaced apart from the strut first end by the strut body and is connected to the RAT, wherein the strut has a strut conduit extending from the strut first end toward the strut second end; and a damper rod that includes a rod body and disposed within the strut conduit, the damper rod having a rod first end that is fixed within the strut conduit at the strut first end, and a rod second end that is spaced apart from the rod first end by the rod body and is located intermediate the strut first end and the strut second end, wherein the rod second end is configured to move along a second axis that is parallel to the first axis.

In addition to one or more of the above aspects of the aircraft, or as an alternate, the rod second end includes a bushing, and the strut system further includes a guide shaft that extends through the strut, along the second axis, and through the bushing.

In addition to one or more of the above aspects of the aircraft, or as an alternate, the guide shaft is a shank of a bolt; and the bolt includes a bolt head disposed against an outer surface of the strut, and the bolt has a threaded end spaced apart from the bolt head by the guide shaft and extends through the outer surface of the strut; and the system further includes a nut that is configured to engage the threaded end and secure the bolt to the strut.

In addition to one or more of the above aspects of the aircraft, or as an alternate, the strut first end has a strut inner base that defines an opened end of the strut conduit; the system further includes: a ring flange that is fixed to the strut inner base, the ring flange having a flange aperture that opens to the strut conduit, wherein the rod first end has a shoulder portion that is larger than the flange aperture and a threaded shaft that extends from the shoulder portion and though the flange aperture; and another nut that is secured to the threaded shaft, to secure the damper rod within the strut conduit.

In addition to one or more of the above aspects of the aircraft, or as an alternate, the rod body is sized so that when the damper rod is secured to the strut inner base, the damper rod is under tension loading against the guide shaft to maintain a contact between the bushing and the guide shaft.

In addition to one or more of the above aspects of the aircraft, or as an alternate, the strut first end has a shaft bore that is defined along the first axis; and the shaft bore is adjacent to the strut inner base and the strut conduit; and the strut system further includes a shaft that is connected to the aircraft and extends through the shaft bore.

In addition to one or more of the above aspects of the aircraft, or as an alternate, the rod body has a rectangular cross section defining a rod width that is wider along the second axis; the strut conduit defines a diameter, wherein the rod width is between sixty percent and ninety percent of the diameter of the strut conduit; the strut conduit defines a first length; and the damper rod defines a second length that is less than the first length.

In addition to one or more of the above aspects of the aircraft, or as an alternate, the damper rod is formed of high strength steel and the guide shaft is case-hardened metal.

Further disclosed is a method of configuring a strut that couples a ram-air turbine (RAT) to an aircraft, including: obtaining the strut that has a strut body, the strut having a strut first end that is configured to connect to the aircraft and rotate about a first axis, the strut having a strut second end that is spaced apart from the strut first end by the strut body and is configured to connect to the RAT, and the strut has a strut conduit extending from the strut first end toward the strut second end; obtaining a damper rod that has a rod body, a rod first end and a rod second end that is spaced apart from the rod first end by the rod body; and securing the damper rod within the strut conduit so that the rod first end is fixed within the strut conduit at the strut first end and the rod second end is located intermediate the strut first end and the strut second end and is configured to move along a second axis that is parallel to the first axis.

In addition to one or more of the above aspects of the method, or as an alternate, the method includes coupling the rod second end to a guide shaft that extends through the strut, along the second axis, via a bushing.

<FIG> shows a ram-air turbine (RAT) <NUM> with a turbine generator unit 110A and a strut <NUM> that connects the RAT <NUM> to an aircraft <NUM> (schematically illustrated). At one end the strut <NUM>, an electrical outlet box <NUM> is located, which includes an outlet <NUM> and cover plate <NUM>. Turning to <FIG>, additional features of the RAT <NUM> are shown, which may be concealed within the aircraft <NUM> by a RAT door <NUM> when stowed. The RAT <NUM>, as indicated, is connected to the aircraft <NUM> via its strut system <NUM> that pivots about a first axis <NUM> (or pivot axis) when deploying or stowing the RAT <NUM>.

The strut system <NUM> includes a strut <NUM>. The strut <NUM> includes a strut body <NUM>. The strut <NUM> has a strut first end <NUM> (or top end) that is connected to the aircraft <NUM> and configured to rotate about a first axis <NUM> (or strut rotation axis). The strut <NUM> has a strut second end <NUM> (or bottom end), separated from the strut first end <NUM> by the strut body <NUM>, and which is connected to the turbine generator unit 110A. The strut <NUM> has a strut inner conduit <NUM> extending from the strut first end <NUM> toward the strut second end <NUM>. The strut first end <NUM> has a strut inner base <NUM> that defines an opened end <NUM> of the strut conduit <NUM>. The strut first end <NUM> has a shaft bore <NUM> that is defined along the first axis <NUM>. The shaft bore <NUM> is adjacent to the strut inner base <NUM> and the strut conduit <NUM>. A shaft <NUM> is connected to the aircraft <NUM>, via aircraft mounts or lugs <NUM>, and extends through the shaft bore <NUM> to provide a pivot for rotational motion of the strut <NUM>. Conductive wires <NUM> extend through the strut conduit and are configured to electrically couple the turbine generator unit 110A to the aircraft <NUM> via the outlet <NUM> (<FIG>). The strut first end <NUM> has an aperture <NUM> (<FIG>) that is adjacent to the strut inner base <NUM> and spaced apart from the strut conduit <NUM>. The aperture <NUM> is utilized to connect the outlet box <NUM> (<FIG>) to the strut.

The outer surface <NUM> of the strut <NUM> has an actuator eyelet <NUM>, located adjacent to the strut first end <NUM>. An actuator <NUM> is mounted between the aircraft <NUM> and the strut <NUM>. This configuration controls a rotational position of strut <NUM> relative to the aircraft <NUM> by extending an actuator piston <NUM>. The outer surface <NUM> of the strut <NUM> has a door link eyelet <NUM>, located adjacent toward the strut second end <NUM>. A door link <NUM> is connected between the RAT door <NUM> and the strut <NUM>, which controls motion of the RAT door <NUM> when the strut <NUM> is moved via the actuator <NUM>.

As disclosed in greater detail herein, the strut system <NUM> may be configured to dampen resonance induced loads that could occur along the first axis <NUM> (e.g., a lateral direction for the strut system <NUM>) when the RAT <NUM> is in the deployed state.

Turning to <FIG> and <FIG>, the strut system <NUM> includes a damper rod <NUM>, which is located in the strut conduit <NUM>. The damper rod <NUM> includes a rod body <NUM>. The damper rod <NUM> has a rod first end <NUM> that is fixed within the strut conduit <NUM> at the strut first end <NUM>. The damper rod <NUM> has a rod second end <NUM> that is spaced apart from the rod first end <NUM> by the rod body <NUM> and is located intermediate the strut first end <NUM> and the strut second end <NUM>. The rod second end <NUM> is configured to move along a second axis <NUM> (<FIG>) that is parallel to the first axis <NUM>. The damper rod <NUM> may be high strength steel, as compared with the guide shaft <NUM> which may be a case-hardened metal component.

The rod second end <NUM> houses a bushing <NUM>. The strut system <NUM> further includes a guide shaft <NUM> that extends through the strut <NUM>, along the second axis <NUM>, and through the bushing <NUM>.

As shown in <FIG> the strut system <NUM> includes a bolt <NUM> and the guide shaft <NUM> is a shank of the bolt <NUM>. The bolt <NUM> has a bolt head <NUM> disposed against an outer surface <NUM> (or outer wall) of the strut <NUM>. The bolt <NUM> has a threaded end <NUM> spaced apart from the bolt head <NUM> by the guide shaft <NUM> and extends through the outer surface <NUM> of the strut <NUM>. The strut system <NUM> includes a nut <NUM> (or first nut) engages the threaded end <NUM> to secure the bolt <NUM> to the strut <NUM>. In one embodiment the guide shaft <NUM> is a pin.

The rod body <NUM> has a rectangular cross section defining a rod width W, which is configured to be wider along the second axis, i.e., its vibration axis. The strut conduit <NUM> defines an (inner) diameter D. The rod width W is between fifty percent and ninety percent of the diameter D of the strut conduit <NUM>. This configuration enables the bushing <NUM> to slide against the guide shaft <NUM> sufficiently to generate friction and cause friction (Coulomb) damping. The rod cross section dimensions would be sized such as to allow relative motion at guide shaft to bushing interface due to lateral vibration loads. That is, the rod cross section would be sized to allow relative motion and would be based on the magnitude and the frequency range of the vibration loads.

The strut conduit <NUM> defines a first length L1 and the damper rod defines a second length L2 that is less than the first length L1. For example, the second length L2 is <NUM> to <NUM> percent of the first length L1. In some embodiments, the second length L2 is <NUM> to <NUM> percent of the first length L1. The longer configuration of the damper rod <NUM> will have more movement at rod second end <NUM>, which will change the damping characteristics of the strut system <NUM>. The rod body <NUM> is sized so that when the damper rod <NUM> is secured to the strut inner base <NUM>, the damper rod <NUM> is under tension loading against the guide shaft <NUM>. This configuration maintains a slip or sliding contact between the bushing <NUM> and the guide shaft <NUM> to provide the friction for the generation of damping when the damper rod <NUM> moves relative to the strut body <NUM>.

As shown in <FIG> and <FIG>, the strut system <NUM> further includes a ring flange <NUM> that is fixed to the strut inner base <NUM>. The ring flange <NUM> has a flange aperture <NUM> (<FIG>) that opens to the strut conduit <NUM>. The rod first end <NUM> has a shoulder portion <NUM> that is larger than the flange aperture <NUM>. The rod first end <NUM> has a threaded shaft <NUM> that extends from the shoulder portion <NUM> and though the flange aperture <NUM>. The strut system <NUM> includes another nut <NUM> (or second nut) that is secured to the threaded shaft <NUM>, to secure the damper rod <NUM> within the strut conduit <NUM>.

Turning to <FIG>, a flowchart shows a method of manufacturing a strut system <NUM> of a RAT <NUM>. As shown in block <NUM>, the method includes obtaining the strut <NUM> having the strut body <NUM> and the strut first end <NUM> that is configured to connect to the aircraft <NUM> and rotate about the first axis <NUM>. The strut <NUM> has a strut second end <NUM> spaced apart from the strut first end <NUM> by the strut body <NUM> and is configured to connect to the RAT turbine generator unit 110A. The strut <NUM> has a strut inner conduit that extends from the strut first end <NUM> toward the strut second end <NUM>. As shown in block <NUM>, the method includes obtaining a damper rod <NUM> that has a rod body <NUM>, a rod first end <NUM> and the rod second end <NUM> that is spaced apart from the rod first end <NUM> by the rod body <NUM>. As shown in block <NUM>, the method includes securing the damper rod <NUM> within the strut conduit <NUM>. With this configuration, the rod first end <NUM> is fixed within the strut conduit <NUM> at the strut first end <NUM> and the rod second end <NUM> is located intermediate the strut first end <NUM> and the strut second end <NUM> and is configured to move along the second axis <NUM> that is parallel to the first axis <NUM>. As shown in block <NUM>, the method includes coupling the rod second end <NUM> to the guide shaft <NUM> that extends through the strut <NUM>, along the second axis <NUM>, via the bushing <NUM>.

The above disclosure provides a strut system <NUM> of a RAT <NUM> for connecting a RAT turbine generator unit110A to an aircraft <NUM>. The strut <NUM> includes an inner damper rod <NUM>, located in a strut conduit <NUM>, which dampens resonant induced forces generated along the pivot axis when the RAT is deployed. A guide shaft <NUM> is disposed on a second axis <NUM> that is parallel to the first axis <NUM> and extends through a bushing <NUM> of the damper rod <NUM> to frictionally dampen sliding motion of the damper rod <NUM>. The effect is dampening the resonance induced forces in the strut via the application of frictional (i.e., Coulomb) damping. The damper rod <NUM> may be high strength steel and the guide shaft <NUM> may be a case-hardened metal component. The rod first end <NUM> of the damper rod <NUM> may be connected to the strut inner base <NUM> inside the strut conduit <NUM>. The bushing <NUM> may be attached to the rod second end <NUM> of the damper rod <NUM>. The guide shaft <NUM> may extend through the outer surface <NUM> of the strut <NUM> and through the bushing <NUM> and may be locked against the strut <NUM> by a nut <NUM>. The rod first end <NUM> of the damper rod <NUM> may include a threaded shaft <NUM> so that it may be secured to the strut inner base <NUM>. The rod body <NUM> may be sized so that when the damper rod <NUM> is secured to the strut inner base <NUM>, the damper rod <NUM> is under tension loading against the guide shaft <NUM> to maintain a contact between the bushing <NUM> and the guide shaft <NUM>. With the disclosed configuration, vibrations in the lateral direction, along the first axis <NUM>, cause the guide shaft <NUM> and bushing <NUM> to slide against each other, resulting in frictional energy dissipation, reducing resonant generated forces.

With the above embodiments, static and dynamic loads are transferred either way between the aircraft and the turbine-generator unit of the RAT through the strut. The inner damper rod mounted within the strut reduces the vibration loads that are transferred from the aircraft to the RAT.

Claim 1:
A strut system (<NUM>) for coupling a ram-air turbine (<NUM>), RAT, to an aircraft (<NUM>), comprising:
a strut (<NUM>) that includes a strut body (<NUM>), the strut having a strut first end (<NUM>) that is configured to connect to the aircraft and rotate about a first axis (<NUM>), the strut having a strut second end (<NUM>) that is spaced apart from the strut first end by the strut body and is configured to connect to a RAT turbine generator unit (110A),
and a damper rod (<NUM>) that includes a rod body (<NUM>);
characterised in that
the strut has a strut conduit (<NUM>) extending from the strut first end toward the strut second end; and
further characterised in that the damper rod (<NUM>) is disposed within the strut conduit, the damper rod having a rod first end (<NUM>) that is fixed within the strut conduit at the strut first end, and a rod second end (<NUM>) that is spaced apart from the rod first end by the rod body and is located intermediate the strut first end and the strut second end, wherein the rod second end is configured to move along a second axis (<NUM>) that is parallel to the first axis.