Patent Description:
Shock struts with mixed air/oil chambers may typically have a dynamic liquid damping chamber separated from a mixed air/oil chamber by a metering orifice. A shock strut may have gas in the main damping chamber when retracted. It is beneficial in operation if substantially no gas is in the dynamic liquid damping chamber below the metering orifice.

The invention is defined by the shock strut of claim <NUM> and the method of claim <NUM>.

The operation of the disclosed embodiments will become more apparent in light of the following description and accompanying drawings.

The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical changes and adaptations in design and construction may be made in accordance with this disclosure without departing from the scope of the claims.

Shock struts with mixed air/oil chambers may typically have a dynamic liquid damping chamber (e.g., lower chamber) separated from a mixed air/oil chamber (e.g., upper chamber) by a metering orifice. Gas is known to leak into the lower chamber when the shock strut is in the retracted position. As the shock strut is moved to an extended position, such as in preparation for a landing event for example, gas may begin to move back into the upper chamber. The shock strut may be configured to work most efficiently with the lower chamber devoid of any gas. Thus, if there is still gas in the lower chamber during the landing event, the shock strut may not perform at the highest efficiency.

A shock strut, as disclosed herein, may include a percolation tube extending between a first lower chamber and a second upper chamber of the shock strut. The first chamber may be most efficient when filled with a liquid. When retracted, the shock strut may be in a horizontal position, allowing gas to enter the first chamber. When deployed, or extended, liquid may again enter the first chamber from the second chamber and the gas may escape from the first chamber into the second chamber. Movement of the fluid from the second chamber to the first chamber, as well as gas from the first chamber to the second chamber, may be referred to herein as percolation. Addition of a percolation tube in the proximity of the shock strut main metering orifice (metering orifice may be created by use of grooves along the side of a metering pin) may create a flow pattern to speed up the percolation process. This extra passage may be in the form of a tube having its entrance at the same axial location as the main metering orifice, but its exit is at a higher axial location than the orifice with its orientation being at a higher elevation than the main orifice when the strut is retracted. A shock strut, as disclosed herein, may ensure that gas flows up the percolation tube, allowing oil to more quickly flow down through the main metering orifice(s).

With reference to <FIG>, an aircraft <NUM> in accordance with various embodiments may include landing gear such as landing gear <NUM>, landing gear <NUM> and landing gear <NUM>. Landing gear <NUM>, landing gear <NUM> and landing gear <NUM> may generally support aircraft <NUM> when aircraft <NUM> is not flying, allowing aircraft <NUM> to taxi, take off and land without damage. Landing gear <NUM> may include shock strut <NUM> and wheel assembly <NUM>. Landing gear <NUM> may include shock strut <NUM> and wheel assembly <NUM>. Landing gear <NUM> may include shock strut <NUM> and nose wheel assembly <NUM>.

With reference to <FIG>, a landing gear arrangement <NUM> is illustrated, in accordance with various embodiments. Landing gear <NUM> and landing gear <NUM> of <FIG> may be similar to landing gear arrangement <NUM>. Landing gear arrangement <NUM> may comprise a shock strut <NUM>. Shock strut <NUM> may comprise a strut cylinder <NUM> and a strut piston <NUM>. Strut piston <NUM> may be operatively coupled to strut cylinder <NUM>. Strut piston <NUM> may comprise a first end <NUM> disposed within strut cylinder <NUM> and a second end <NUM> extending from strut cylinder <NUM>. Strut cylinder <NUM> may be configured to receive strut piston <NUM> in a manner that allows the two components to telescope together and absorb and dampen forces transmitted thereto. <FIG> illustrates shock strut <NUM> in an extended position <NUM>. <FIG> illustrates shock strut <NUM> in a compressed position <NUM>.

In various embodiments, shock strut <NUM> may comprise an orifice plate <NUM>. In various embodiments, a liquid, such as a hydraulic fluid and/or oil may be located within strut cylinder <NUM>. Further, a gas, such as nitrogen or air, may be located within strut cylinder <NUM>. Strut cylinder <NUM> and strut piston <NUM> may, for example, be configured to seal such that fluid contained within strut cylinder <NUM> is prevented from leaking as strut piston <NUM> translates relative to strut cylinder <NUM>. Orifice plate <NUM> may separate a first chamber (also referred to herein as a dynamic liquid chamber <NUM> from a second chamber (also referred to herein as a mixed fluid chamber) <NUM>. In this regard, during operation, a liquid, such as a hydraulic fluid and/or oil may be located within dynamic liquid chamber <NUM> and a mixture of a gas, such as nitrogen or air, and the liquid may be located within mixed fluid chamber <NUM>.

In various embodiments, shock strut <NUM> may comprise a metering pin <NUM>. Metering pin <NUM> may be coupled to strut piston <NUM>. Metering pin <NUM> may translate with strut piston <NUM>. Metering pin <NUM> may be received by orifice plate <NUM>. In this regard, orifice plate <NUM> may comprise a metering pin aperture <NUM>. Metering pin <NUM> may be received by metering pin aperture <NUM>. Metering pin <NUM> may extend through orifice plate <NUM>. Metering pin <NUM> may comprise one or more metering grooves <NUM> disposed along the length (along the Z-direction) of metering pin <NUM>. As described herein, metering groove <NUM> and orifice plate <NUM> may define a flow channel through which liquid may travel from dynamic liquid chamber <NUM> to mixed fluid chamber <NUM> in response to shock strut <NUM> moving to a compressed position, such as compressed position <NUM> for example.

In various embodiments, a percolation aperture <NUM> may be disposed in orifice plate <NUM>. Percolation aperture <NUM> may be in fluid communication with dynamic liquid chamber <NUM>. Percolation aperture <NUM> may be in fluid communication with mixed fluid chamber <NUM>. In various embodiments, shock strut <NUM> may further include a percolation tube <NUM>. Percolation tube <NUM> may extend from percolation aperture <NUM>. Stated differently, Percolation tube <NUM> may extend from orifice plate <NUM>. Percolation tube <NUM> may be configured to allow gas to escape from dynamic liquid chamber <NUM> into mixed fluid chamber <NUM> in response to shock strut <NUM> moving from a retracted position to a deployed position.

In various embodiments, strut piston <NUM> and strut cylinder <NUM> may extend along centerline axis <NUM>. In various embodiments, metering pin <NUM> may be concentric with strut piston <NUM>. In various embodiments, orifice plate <NUM> may be concentric with strut cylinder <NUM>.

With reference to <FIG>, a portion of shock strut <NUM> moving from a retracted position to a deployed position is illustrated, in accordance with various embodiments. In the retracted position, shock strut <NUM> may be oriented substantially horizontal. In this regard, gravity may cause gas to travel from mixed fluid chamber <NUM> into dynamic liquid chamber <NUM> when shock strut <NUM> is in the retracted position. As shock strut <NUM> moves (see arrow <NUM>) from the retracted position to the deployed position, gravity may cause liquid in mixed fluid chamber <NUM> to move into dynamic liquid chamber <NUM>. In various embodiments, shock strut <NUM> may rotate (e.g., about the Y-axis) as shock strut <NUM> moves from the retracted position to the deployed position. In the illustrated embodiment, liquid is illustrated below fluid level line <NUM>, with gas being located above fluid level line <NUM> in mixed fluid chamber <NUM>. Similarly, liquid is illustrated below fluid level line <NUM>, with gas being located above fluid level line <NUM> in dynamic liquid chamber <NUM>.

In various embodiments, as shock strut <NUM> rotates from the retracted position (e.g., substantially horizontal) to the deployed position (e.g., substantially vertical), a flow path (also referred to herein as a gas flow path) <NUM> may form through percolation tube <NUM>, allowing gas to travel from dynamic liquid chamber <NUM> to mixed fluid chamber <NUM>. A flow path (also referred to herein as a liquid flow path) <NUM> may form through metering groove <NUM> (between metering pin <NUM> and orifice plate <NUM>), allowing fluid to travel from mixed fluid chamber <NUM> to dynamic liquid chamber <NUM>. Flow path <NUM> and flow path <NUM> may exist simultaneously, allowing gas to be more quickly evacuated from dynamic liquid chamber <NUM>. Thus, percolation tube <NUM> may allow for dynamic liquid chamber <NUM> to more quickly become ready for a full energy landing (i.e., in response to being filled with liquid) after extending from the retracted position.

With reference to <FIG>, shock strut <NUM> is illustrated in the deployed position, moving from an extended position, to a compressed position, such as during a landing event for example. As strut piston <NUM> compresses into strut cylinder <NUM>, the volume of dynamic liquid chamber <NUM> is reduced, forcing liquid from dynamic liquid chamber <NUM> into mixed fluid chamber <NUM>. A flow path <NUM> may be defined by metering pin <NUM> and orifice plate <NUM>. A flow path <NUM> may be defined by percolation tube <NUM>. Liquid may be forced from dynamic liquid chamber <NUM>, through metering groove <NUM> (between metering pin <NUM> and orifice plate <NUM>), into mixed fluid chamber <NUM>, via flow path <NUM>. Liquid may be forced from dynamic liquid chamber <NUM>, through percolation tube <NUM>, into mixed fluid chamber <NUM>, via flow path <NUM>. Thus, percolation tube <NUM> may be configured to both allow for gas to escape from dynamic liquid chamber <NUM> into mixed fluid chamber <NUM> and to meter the flow of liquid from dynamic liquid chamber <NUM> into mixed fluid chamber <NUM>. Thus, the cross-sectional area (taken in the X-Y plane) of percolation tube <NUM> may be taken into account when designing metering groove <NUM>.

In various embodiments, orifice plate <NUM> may comprise a first axially facing surface <NUM> and a second axially facing surface <NUM>. Second axially facing surface <NUM> may be located opposite orifice plate <NUM> from first axially facing surface <NUM>. In various embodiments, percolation tube <NUM> may be flush with first axially facing surface <NUM>. In various embodiments, percolation tube <NUM> may extend from second axially facing surface <NUM>.

With reference to <FIG>, percolation tube <NUM> may extend upwards (positive Z-direction) from orifice plate <NUM> by a dimension <NUM>. By extending percolation tube <NUM> into mixed fluid chamber <NUM>, liquid may be prevented from entering percolation tube <NUM> from mixed fluid chamber <NUM> while gas travels from dynamic liquid chamber <NUM> into mixed fluid chamber <NUM> through percolation tube <NUM>. In various embodiments, dimension <NUM> may be between one-half inch and twelve inches (<NUM> - <NUM>). In various embodiments, dimension <NUM> may be between one inch and six inches (<NUM> - <NUM>). In various embodiments, dimension <NUM> may be between one inch and four inches (<NUM> - <NUM>).

With reference to <FIG>, a cross-section view of an orifice plate <NUM>, metering pin <NUM>, and percolation tube <NUM> is illustrated, in accordance with various embodiments. In various embodiments, orifice plate <NUM> may comprise an outer diameter surface <NUM> and an inner diameter (ID) surface <NUM>. In this regard, orifice plate <NUM> may comprise an annular geometry. In various embodiments, ID surface <NUM> may define metering pin aperture <NUM>. Metering pin aperture <NUM> may be concentric with centerline axis <NUM>. In various embodiments, metering grooves <NUM> and ID surface <NUM> of orifice plate <NUM> may define corresponding flow paths (e.g., flow path <NUM>) through which liquid may travel in response to shock strut <NUM> being compressed, with momentary reference to <FIG>. In various embodiments, the cross-sectional area of metering grooves <NUM> may vary along the axial direction (Z-direction). For example, the cross-sectional area of metering grooves <NUM> may decrease along the positive Z-direction. In this regard, a metering area may be defined by the cross-sectional area defined by metering grooves <NUM> and ID surface <NUM>.

In various embodiments, percolation aperture <NUM> may be disposed in the upper half of orifice plate <NUM> (e.g., above line <NUM>, in the negative X-direction) when shock strut <NUM> is in the retracted position. In various embodiments, percolation aperture <NUM> may be disposed in the upper fourth of orifice plate <NUM> (in the negative X-direction) when shock strut <NUM> is in the retracted position (i.e., located above the halfway point <NUM> between the centerline axis <NUM> and outer diameter surface <NUM>. In this regard, percolation aperture <NUM> may be radially offset from metering pin aperture <NUM>. Percolation tube <NUM> may engage orifice plate <NUM> at percolation aperture <NUM>. Percolation tube <NUM> may be coupled to orifice plate <NUM> at percolation aperture <NUM>. In various embodiments, percolation tube <NUM> is threadingly attached to percolation aperture <NUM>.

In various embodiments, a cross-sectional area of percolation aperture <NUM> may be less than the aggregate cross-sectional area of metering grooves <NUM> when shock strut <NUM> is in a fully extended position, with momentary reference to <FIG>. In various embodiments, a cross-sectional area of percolation aperture <NUM> is between five percent and fifty percent of the aggregate cross-sectional area of metering grooves <NUM> when shock strut <NUM> is in a fully extended position, with momentary reference to <FIG>.

With reference to <FIG>, a method <NUM> for manufacturing an orifice plate is provided, in accordance with various embodiments. Method <NUM> includes forming a metering pin aperture into the orifice plate (step <NUM>). Method <NUM> includes forming a percolation aperture into the orifice plate (step <NUM>). Method <NUM> may include coupling a percolation tube to the orifice plate (step <NUM>).

With combined reference to <FIG>, step <NUM> may include forming metering pin aperture <NUM> into orifice plate <NUM>. Step <NUM> may include forming percolation aperture <NUM> into orifice plate <NUM>. Step <NUM> and step <NUM> may include drilling, casting, milling, or any other suitable method. Step <NUM> may include coupling percolation tube <NUM> to orifice plate <NUM>. Step <NUM> may include rotating percolation tube <NUM> into percolation aperture <NUM> to threadingly attach percolation tube <NUM> to orifice plate <NUM>. Step <NUM> may include pressing percolation tube <NUM> into percolation aperture <NUM>. Step <NUM> may include soldering, welding, and/or brazing percolation tube <NUM> to orifice plate <NUM>.

Claim 1:
A shock strut (<NUM>), comprising:
a first chamber (<NUM>);
a second chamber (<NUM>);
a metering pin (<NUM>); and
an orifice plate (<NUM>), the orifice plate (<NUM>) comprising:
a metering pin aperture (<NUM>) extending through the orifice plate (<NUM>); and
a percolation aperture (<NUM>) extending through the orifice plate (<NUM>),
wherein the orifice plate (<NUM>) comprises an annular geometry defined by a first axially facing surface, a second axially facing surface disposed opposite the orifice plate (<NUM>) from the first axially facing surface, an inner diameter surface, and an outer diameter surface,
wherein the metering pin aperture (<NUM>) is defined by the inner diameter surface, and the metering pin aperture (<NUM>) is configured to receive a metering pin (<NUM>),
wherein a cross-sectional area of the percolation aperture (<NUM>) is less than that of a metering area defined between the inner diameter surface and the metering pin (<NUM>),
wherein the percolation aperture (<NUM>) extends from the first axially facing surface to the second axially facing surface; and
wherein the first chamber is located opposite the orifice plate from the second chamber;
characterized in that the percolation aperture (<NUM>) is configured to allow a gas to move from the first chamber to the second chamber in response to the shock strut moving from a retracted position to a deployed position and further comprising a percolation tube (<NUM>) extending from the percolation aperture (<NUM>).