Patent Application
20240295251
Embodiments of the disclosure relate to aircraft landing gear, and in particular to a system and method to restrict gas backflow in an aircraft strut during rebound damping.
Aircraft landing gear include shock absorbers which use a combination of gas and hydraulic fluid to reduce compression forces during landing. For example, U.S. Pat. No. 9,650,128 to Fenny et al. describes an aircraft landing gear that incorporates an oleo strut for shock absorption during landing. U.S. Pat. No. 10,689,098 to Waltner et al. describes an adaptive aircraft landing gear that may incorporate an oleo strut and may use a controller and various means to add or remove fluids from the strut to control the dampening of the landing gear. U.S. Patent Publication No. 2018/0079494 to Cottet et al. describes an aircraft landing gear that may incorporate an oleo strut and may use a metering pin positioned to meter the flow of fluids through the orifice plate to control fluid flow.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Other aspects and advantages of the invention will be apparent from the following detailed description of the embodiments and the accompanying drawing figures.
In embodiments, the present disclosure includes a gas backflow restrictor system as part of an aircraft strut. The strut defines an inner volume having a first chamber and a second chamber. An orifice plate is positioned within the inner volume and separates the first chamber and the second chamber. A standpipe is attached to the orifice plate and extends longitudinally within the inner volume, the standpipe has a plurality of openings extending through a thickness of a wall forming the standpipe and the standpipe further defines an inner channel. A restrictor is mounted within the inner channel, the restrictor has a shelf extending into the inner channel and forms a central opening. The shelf is configured to reduce gaseous flow through one or more of the plurality of openings of the standpipe and toward the orifice plate.
In other embodiments, the present disclosure includes a combination of an orifice plate and a gas back flow restrictor as part of an aircraft strut. The orifice plate is positioned within a cylinder of the aircraft strut and separates a first chamber from a second chamber. The gas backflow restrictor is coupled to the orifice plate and is positioned above the orifice plate within the cylinder, the gas backflow restrictor having a shelf extending inwardly to create a central opening. The shelf is configured to reduce gaseous flow toward the orifice plate during a compression phase of the aircraft strut to thereby reduce gaseous flow through the orifice plate during an extension phase.
In yet another embodiment, the present disclosure includes a method of restricting gas backflow in an aircraft strut during rebound damping. The method includes separating a first chamber of an inner volume from a second chamber of the inner volume within the aircraft strut with an orifice plate; and mounting a restrictor within the inner volume at a position above the orifice plate, the restrictor having a shelf extending inwardly and creating a central opening. When the aircraft strut is in a compression phase, the restrictor reduces gaseous flow toward the orifice plate to thereby reduce gaseous flow through the orifice plate in an expansion phase.
Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:
The drawing figures do not limit the invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention.
The following detailed description references the accompanying drawings that illustrate specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense. The scope of the invention is defined only by the appended claims, along with the full scope of the equivalents to which such claims are entitled.
In this description, references to “one embodiment,” “an embodiment,” or “embodiments” mean that the feature or features being referred to are included in at least one embodiment of the technology. Separate references to “one embodiment,” “an embodiment,” or “embodiments” in this description do not necessarily refer to the same embodiment and are also not mutually exclusive unless so stated and/or except as will be readily apparent to those skilled in the art from the description. For example, a feature, structure, act, etc. described in one embodiment may also be included in other embodiments, but is not necessarily included. Thus, the technology can include a variety of combinations and/or integrations of the embodiments described herein.
Landing gear in aircraft generally employ an oleo strut or shock absorber, in which a fluid is forced to flow between chambers by flowing through an orifice plate with openings. The resistance created by the fluid being incompressible provides a damping force during landing, thereby making the landing smoother. Prior to landing of the aircraft, the oleo strut is unweighted and in a fully extended position. When the wheels of the landing gear touchdown, the strut undergoes compression, wherein fluid is forced from one chamber to another as the aircraft's weight and downward momentum are absorbed. After landing, the strut undergoes partial extension as the downward momentum is reduced and/or removed. After the aircraft takes off again, the wheels are unweighted, and the strut can return to full extension.
During the compression stage, hydraulic fluid is forced through openings of the orifice plate with a high velocity, which in turn creates one or more areas of low pressure around a stream of the hydraulic fluid. In some landing gear, the hydraulic fluid and gas are not separated, and gas, such as nitrogen, may flow through the low-pressure region faster than hydraulic fluid, wherein the gas will flow toward an orifice plate during a compression phase. When the landing gear changes direction from compression to extension during landing, the flow direction is reversed and any nitrogen near the orifice plate will then flow through the plate instead of hydraulic fluid which reduces the rebound damping force of the landing gear. Accordingly, it is desirable to provide a solution to restrict gas flow to the orifice plate to improve rebound damping of landing gear.
The present invention aims to solve the above problem by using a restrictor device to restrict gas flow to the orifice plate of the landing gear. The restrictor extends into an inner channel of the standpipe 100 and blocks at least some of the gas backflow. This is demonstrated in simplified form in
Strut 200 further includes an orifice plate 220 which may include an exterior seal 218 between an exterior perimeter of the orifice plate 220 and the inner cylinder 224. The seal 218 may prevent fluid flow but allows for the orifice plate 220 to slidingly engage with the inner cylinder 224. The orifice plate 220 primarily functions to separate the first chamber 226 from the second chamber 206, and the orifice plate 220 may include one or more openings to provide fluid flow therethrough during the compression and extension phases of the strut. A standpipe 204 is attached to the orifice plate 220 and includes openings 210 to again allow fluid flow. In other words, one or more openings in the orifice plate 220 and standpipe 204 enable fluid coupling between the chambers 226, 206. When the strut 200 compresses or extends, hydraulic fluid 230 is forced from one chamber to the other through orifice plate 220, and the resistance to this flow creates the damping force.
In embodiments, as would be understood by those skilled in the art, a metering pin 228 is coupled to a first end (not shown) of the inner cylinder 224 and extends longitudinally along a central axis within the inner cylinder 224 and passes through a central port 222 of the orifice plate 220. As will be understood, the central port 222 and metering pin 228 are sized such that when the metering pin 228 extends through the central port 222, a flow path around the metering pin 228 remains open to allow hydraulic fluid to flow therethrough. In other words, the metering pin 228 does not block hydraulic fluid flowing through the central port 222. Other features of strut 200 that are known to one of skill in the art but are not described herein may be found in U.S. U.S. Pat. No. 11,204,075, filed Apr. 9, 2019, and U.S. patent application Ser. No. 18/170,247, filed Feb. 16, 2023, the disclosures of which are herein incorporated by reference in their entirety.
As previously discussed, during compression, the inner cylinder 224 may slidingly engage with the outer cylinder, 202, wherein hydraulic fluid is forced through the orifice plate 220, thereby providing shock absorption. Hydraulic fluid will flow out of central port 222 with high velocity which can create areas of low pressure around the stream of hydraulic fluid. According, in order to reduce gas flow toward the orifice plate 220, the restrictor 212 may be added to the standpipe 204.
As shown, the restrictor 212 includes a tubal body 215 that fits within an inner channel 209 defined by an inner diameter of the standpipe 204. The body 215 may include one or more openings 205 that correspond to one or more openings 210 of the standpipe 204, providing for a location to secure the restrictor 212 to the standpipe 204. In embodiments, one or more connectors 214a-b extend through the corresponding openings to secure the restrictor 212 in place. It is contemplated that any means of connection understood by those skilled in the art could be used. In the embodiment shown, the connectors 214a-b include hi-lock fasteners 217a-b extending through the aligned openings with spacers 219a-b positioned in openings 210 of the standpipe 204 to ease installation of the hi-lock fasteners 217a-b.
The restrictor 212 includes a shelf 216 that extends inward from the tubal body 215. The shelf 216 extends into the inner channel 209 of the standpipe and at a position below at least some of the openings 210. In embodiments, the shelf 216 extends all around the inner diameter of the body 215, however it is contemplated that not all embodiments may require the shelf 216 to be continuous. The shelf 216 forms a central opening 211 having a diameter greater than a diameter of the central port 222 through the orifice plate. This ensures that the shelf 216 does not cause an obstruction or hinder operation of the strut. The flow area of the central opening 211 is larger than the flow area of the central port 222 so there is negligible damping added during compression while the flow area of opening 211 is small enough to restrict nitrogen backflow.
The shelf 216 is positioned vertically to maximize the volume of the hydraulic fluid below the shelf 216 when the strut 200 is in an extended position and creates a physical block in the area of low pressure created by the high velocity stream of hydraulic fluid, which in turn blocks at least a portion of gas from flowing toward the orifice plate 220. This improves rebound damping associated with the strut 200. As discussed, the restrictor 212 may be adapted or modified for various models of struts, and may be added after manufacturing of the strut 200 or during manufacturing.
In alternative embodiments, the restrictor may be designed into a standpipe and include a shelf attached directly to the standpipe to block gas backflow. In other words, the restrictor may be just a shelf attached to the standpipe, such as during manufacturing of the standpipe.
In
Although the invention has been described with reference to the embodiments illustrated in the attached drawing figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims.
Having thus described various embodiments of the invention, what is claimed as new and desired to be protected by Letters Patent includes the following:
This application claims the benefit of priority of U.S. Provisional Patent Application No. 63/488,230, filed on Mar. 3, 2023, the disclosure of which is herein incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63488230 | Mar 2023 | US |
