WO2025171859A1

WO2025171859A1 - Landing gear kinematic-based oil pump system for bogie pivot joint

Info

Publication number: WO2025171859A1
Application number: PCT/EP2024/053548
Authority: WO
Inventors: Nicolas ANTONI; Randy Lee
Original assignee: Safran Landing Systems Canada Inc; Safran Landing Systems SAS
Current assignee: Safran Landing Systems Canada Inc; Safran Landing Systems SAS
Priority date: 2024-02-13
Filing date: 2024-02-13
Publication date: 2025-08-21
Anticipated expiration: 2026-08-13

Abstract

A landing gear for an aircraft having an automated kinematic-based oil pump system is provided. The landing gear includes an oleo strut having an upper strut housing, a piston slidingly received in the upper strut housing, a lower housing, a bogie truck beam pivotably coupled to the lower housing at a bogie pivot joint, and an automated lubrication system. This system can include a lubrication piston, and a lubrication outer cylinder operably coupled to the lower housing by a shaft and having an internal chamber for retaining lubricant therein and being fluidly coupled to a grease fitting of the bogie pivot joint by an oil passageway. Relative movement of the upper strut housing toward the lower housing causes the lubrication piston to travel axially within the lubrication outer cylinder and thereby pump lubricant from the internal chamber to the grease fitting of the bogie pivot joint through the oil passageway.

Description

LANDING GEAR KINEMATIC-BASED OIL PUMP SYSTEM

FOR BOGIE PIVOT JOINT

FIELD OF DISCLOSURE

The present disclosure relates to lubrication of landing gear pivot joints for aircraft. More particularly, the present disclosure relates to kinematic-based oil pump systems to lubricate a bogie pivot joint of a main landing gear during use.

BACKGROUND

Aircraft are typically equipped with landing gear systems that enables the aircraft to taxi, takeoff, and safely land on the ground. Some aircraft utilize landing gear that is retractable, i.e., the landing gear reciprocates between a deployed (extended) position and a stowed (retracted) position. While the vehicle is on the ground, the landing gear is deployed and supports the vehicle. The landing gear typically incorporates main fittings that permit vertical motion to cushion landing impacts or bump perturbations, dampen repeat oscillations, and minimize the tendency for an aircraft to rebound or “bounce.” In this regard, main fittings commonly include oleo -pneumatic shock- absorbing struts (“oleo struts”) that convert kinetic energy into heat by the use of a gas, providing elastic spring characteristics, and oil, providing dampening. In flight, the landing gear retracts, which reduces drag to lower fuel consumption and permit higher cruise speeds. Examples of a known deployable and retractable main fittings are described in U.S. Patent No. 10,549,848, issued to Klim et al., and currently assigned to Safran Landing Systems Canada, Inc., the disclosure of which is incorporated herein in its entirety.

The oleo strut typically includes a piston (inner cylinder) movable with respect to an upper strut housing (outer cylinder) to permit relative motion of the wheel and the aircraft. The configuration utilizes torque links that connect the two telescoping cylinders and prevent the relative rotation of the piston and the upper strut housing to maintain the wheel alignment, such as during taxiing on ground. In some landing gear configurations, an upper torque link is pivotably coupled to the upper strut housing and a lower torque link is pivotably coupled to a lower sliding component of the landing gear that carries the piston (e.g., the yoke of a nose landing gear (NLG), or the bogie truck beam of the main landing gear (MLG)), with an apex pin pivotably coupling the upper and lower torque links together. In this configuration, the angle between the upper and lower torque links decreases as the main fitting compresses to absorb landing impacts or bumps. During use, the relatively high pitch velocities at the lower pivot joint of the lower torque link can cause frictive heat damage to the pivot pin and surrounding components. Current technology landing gear systems require frequent lubrication of the lower pivot joint to prevent heat damage from high pitch velocities, with this lubrication frequency leading to increased service cost and downtime of the aircraft.

SUMMARY

The present disclosure provides examples of automated kinematic-based oil pump systems to lubricate a bogie pivot joint of a main landing gear of an aircraft. In accordance with an aspect of the present disclosure, a landing gear for an aircraft having an automated kinematic-based oil pump system is provided. In an embodiment, the landing gear includes a main fitting configured to be operably coupled to the aircraft, the main fitting having an upper strut housing; a piston slidingly received in the upper strut housing in a telescoping arrangement for relative axial movement between the piston and the upper strut housing; a lower housing operably coupled to the piston; a bogie truck assembly having a bogie truck beam pivotably coupled to the lower housing at a bogie pivot joint; a lubrication piston rod having a first end operably coupled to the upper housing and a second end having a lubrication piston; and a lubrication outer cylinder having an internal chamber for sealingly receiving the lubrication piston, the lubrication outer cylinder operably coupled to the lower housing by a shaft, and the internal chamber configured to retain lubricant therein and being fluidly coupled to a grease fitting of the bogie pivot joint by an oil passageway, wherein relative movement of the upper strut housing toward the lower housing based on a force acting on the landing gear can cause the lubrication piston to travel axially within the lubrication outer cylinder and thereby pump lubricant from the internal chamber to the grease fitting of the bogie pivot joint through the oil passageway.

In accordance with another aspect of the present disclosure, a kinematic-based oil pump system for a pivot joint is provided. In an embodiment, the system includes a lubrication piston rod having a first end operably coupled to an upper housing and a second end having a lubrication piston; and a lubrication outer cylinder having an internal chamber for sealingly receiving the lubrication piston, the lubrication outer cylinder operably coupled to a lower housing by a shaft, and the internal chamber configured to retain lubricant therein and being fluidly coupled to a grease fitting of the pivot joint by an oil passageway, wherein relative movement of the upper housing toward the lower housing can cause the lubrication piston to travel axially within the lubrication outer cylinder and thereby pump lubricant from the internal chamber to the grease fitting of the pivot joint through the oil passageway.

In accordance with another aspect of the present disclosure, a landing gear for an aircraft having automated lubrication of a bogie pivot joint is provided. In an embodiment, the landing gear includes a main fitting configured to be operably coupled to the aircraft, the main fitting having an upper strut housing; a piston slidingly received in the upper strut housing in a telescoping arrangement for relative axial movement between the piston and the upper strut housing; a lower housing operably coupled to the piston; a bogie truck assembly having a bogie truck beam pivotably coupled to the lower housing at a bogie pivot joint; and a lubrication system operably coupled between the upper housing and the lower housing, the lubrication system being fluidly coupled to a grease fitting of the bogie pivot joint by an oil passageway, wherein relative movement of the upper strut housing toward the lower housing based on a force acting on the landing gear can cause the lubrication system to pump lubricant to the grease fitting of the bogie pivot joint through the oil passageway. In any of the embodiments of the present disclosure, the oil passageway can be disposed within the shaft such that the shaft delivers lubricant from the internal chamber to the grease fitting of the bogie pivot joint.

In any of the embodiments of the present disclosure, the oil passageway can be contained in an oil line separated from the shaft.

In any of the embodiments of the present disclosure, the landing gear can further include an oil reservoir fluidly coupled to the internal chamber of the lubrication outer cylinder, wherein the oil reservoir can be configured to replenish lubricant after the lubricant is pumped out of the internal chamber by the lubrication piston.

In any of the embodiments of the present disclosure, the landing gear can further include an oil return passageway fluidly coupled between the bogie pivot joint and the oil reservoir, wherein the oil return passageway can be configured to deliver lubricant from the bogie pivot joint to the oil reservoir.

In any of the embodiments of the present disclosure, the oil return passageway further includes a pressure check valve configured to retain a specified pressure of lubricant in the bogie pivot joint before permitting delivery of lubricant from the bogie pivot joint to the oil reservoir.

In any of the embodiments of the present disclosure, the landing gear can further include a spring configured to urge the lubrication piston and the lubrication outer cylinder axially apart.

In any of the embodiments of the present disclosure, the lubrication piston rod can be pivotably coupled to the upper housing, and wherein the shaft is pivotably coupled to the lower housing.

In any of the embodiments of the present disclosure, the landing gear can further include a second lubrication piston rod having a first end operably coupled to the upper housing and a second end having a second lubrication piston; and a second lubrication outer cylinder having a second internal chamber for sealingly receiving the second lubrication piston, the second lubrication outer cylinder operably coupled to the lower housing by a second shaft, and the second internal chamber configured to retain lubricant therein and being fluidly coupled to a grease fitting of the bogie pivot joint by a second oil passageway, wherein relative movement of the upper strut housing toward the lower housing based on a force acting on the landing gear can cause the second lubrication piston to travel axially within the second lubrication outer cylinder and thereby pump lubricant from the second internal chamber to a second grease fitting of the bogie pivot joint through the second oil passageway.

In any of the embodiments of the present disclosure, the landing gear can further include a torque link assembly to prevent relative rotation of the piston and the upper strut housing, the torque link assembly including an upper torque link pivotably coupled to the upper housing at an upper pivot joint; and a lower torque link pivotably coupled to the upper torque link and pivotably coupled to the lower housing at a lower pivot joint, wherein the lubrication piston rod can be pivotably coupled to the upper pivot joint.

In any of the embodiments of the present disclosure, the shaft can be operably coupled to the bogie pivot joint.

In any of the embodiments of the present disclosure, the lubrication system can comprise an axial piston type pump or a screw ball type pump.

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 of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of the claimed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: FIGURE 1 depicts one example of an aircraft, such as a passenger or cargo aircraft, shown in bottom view, in which technologies and/or methodologies of the present disclosure may be employed;

FIGURE 2A is a perspective view of a portion of a main landing gear system of an aircraft in accordance with aspects of the present disclosure, showing a bogie truck assembly coupled to a main fitting;

FIGURE 2B is a side view of a portion of the main landing gear system of FIGURE 2A, showing the main landing gear system in an extended position; and

FIGURE 2C is a side view of a portion of the main landing gear system of FIGURE 2A, showing the main landing gear system in a compressed position.

DETAILED DESCRIPTION

The detailed description set forth above in connection with the appended drawings, where like numerals reference like elements, are intended as a description of various embodiments of the present disclosure and are not intended to represent the only embodiments. Each embodiment described in this disclosure is provided merely as an example or illustration and should not be construed as preferred or advantageous over other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed.

As will be described in more detail below, the present disclosure provides examples of systems for lubrication of landing gear pivot joints for aircraft. Embodiments of the present disclosure include kinematic -based oil pump systems to lubricate a bogie pivot joint of a main landing gear during use, such as during taxiing, landing, and takeoff. Pivot joints include bearing surfaces between components of the main landing gear that require lubrication to reduce friction and damage during use. Current technology landing gear typically includes pivot joints having manual lubrication fittings, e.g., grease fittings, grease nipples, Zerk fittings, grease Zerks, Alemite fittings, or the like, and require manual maintenance to ensure that the pivot joint has sufficient lubrication. In aircraft main landing gear systems, the bogie pivot joint between a bogie housing and a lower torque link experiences relatively high pitch velocities due to the high-frequency, large displacement oscillations in the bogie truck beam, coupled with relatively high contact pressures due to the low-frequency, high bogie pivot joint loading (carrying the dynamic weight of the aircraft). Based on this loading, extreme fricative heat damage at the bogie pivot joint is typically only partially mitigated by manual lubrication service, even at low-intervals, and can experience premature wear and failure. Kinematic-based lubrication of the bogie pivot joint provides reduced friction during relative movement of the components of the joint, which will extend the time duration between failures and/or replacement of the components. Reducing manual lubrication of the pivot joints of the landing gear would lower the cost of maintenance of the aircraft and reduce downtime during servicing.

In embodiments described herein, the kinematic-based oil pump systems include automated lubrication of the bogie pivot joint to reduce friction effects on the components. The automated lubrication is performed using the relative movement of the components of the main fitting, e.g., the telescoping movement between the upper strut housing and the piston, which causes the system to lubricate the bogie pivot joint. In some embodiments, a lubrication piston rod can be coupled to a portion of the upper strut housing, e.g., an upper torque link pin, such that movement of the upper strut housing is transferred to the lubrication piston rod. The lubrication piston rod can include a lubrication piston that is sealingly received within a lubrication outer cylinder containing lubricant (e.g., oil, grease, etc.). The lubrication outer cylinder can be operably coupled to the bogie pivot joint such that movement of the bogie truck beam is transferred to the lubrication outer cylinder. The coupling of the lubrication outer cylinder to the bogie pivot joint can include an oil passageway fluidly coupled to a grease fitting on the bogie pivot joint, which is configured to route lubricant to the internal surfaces of the bogie pivot joint. During use, relative movement of the components of the main fitting cause movement of the lubrication piston within the lubrication outer cylinder, directing the lubricant through the oil passageway and the grease fitting, and to the internal surfaces of the bogie pivot joint. In some embodiments, a lubricant return passageway is operably coupled between the bogie pivot joint and an oil reservoir configured to replenish the lubrication outer cylinder with lubricant. Configurations of the kinematic-based oil pump systems for aircraft can reduce manual maintenance intervals and prolong the duration of time between component replacement, among other advantages.

Although embodiments of the present disclosure may be described with reference to kinematic-based oil pump systems for aircraft, one skilled in the relevant art will appreciate that the disclosed embodiments are illustrative in nature and therefore should not be construed as limited to such an application. It should therefore be apparent that the disclosed technologies and methodologies have wide application, and therefore may be suitable for use with many types of suspension and pivot joint architectures, including automobiles, buses, trains, heavy equipment, and the like. Accordingly, the following descriptions and illustrations herein should not limit the scope of the claimed subject matter.

FIGURE 1 depicts one example of an aircraft 100, such as a passenger or cargo aircraft, shown in bottom view, in which technologies and/or methodologies of the present disclosure may be employed. The aircraft 100 can include a nose landing gear system 110, and a kinematic-based oil pump system (see FIGURES 2A-2C) integrated at least partially into a right main landing gear system 120a and a left main landing gear system 120b. Although embodiments of the present disclosure are described herein with reference to the main landing gear systems 120a and 120b, the kinematic -based oil pump systems are also suitable for use with the nose landing gear system 110 and other systems where automated lubrication is beneficial, such as the trailing arm to shock strut joint, trailing arm to main fitting joint, etc. As used herein, left and right directions are in reference to the perspective of the pilot seated in the cockpit facing the standard forward direction of travel. The landing gear systems 110, 120a, and 120b can include various components configured to support the body of the aircraft 100 above the ground surface, e.g., wheels, tires, shock absorbers, brackets, hydraulics, sensors, controllers, etc., and such components are not shown for the sake of clarity in the FIGURES. It should be appreciated that the aircraft 100 illustrated in FIGURE 1 should not be considered limiting on the present disclosure, and the landing gear systems can be arranged in various other configurations with fewer or additional components as desired. In addition, the particular location of the landing gear systems, the quantity of wheels and tires, and the other aspects of the aircraft 100 illustrated in FIGURE 1 should not be considered limiting on the present disclosure, as the components may be positioned at various locations.

FIGURE 2A is a perspective view of a portion of a main landing gear system 120a of an aircraft in accordance with aspects of the present disclosure, showing a bogie truck assembly 201 coupled to an oleo-pneumatic shock-absorbing strut 200 (hereinafter “oleo strut 200”). The bogie truck assembly 201 can be movably coupled to the oleo strut 200 to enable these components to move relative to one another for absorbing forces imparted into the landing gear system 120a by the runway, and to protect the aircraft 100 from significant impacts, vibrations, bounces, etc. The oleo strut 200 includes an upper strut housing/main fitting 220 (hereinafter “upper strut housing 220”) that is configured to receive a piston 222 therein in a telescoping arrangement for relative movement between the upper strut housing 220 and the bogie truck assembly 201. In this regard, the piston 222 can be rigidly coupled to a lower housing 224 such that impacts received by the bogie truck assembly 201 result in movement of the piston 222 within the upper strut housing 220, which can include internal components (not shown) configured to absorb the forces and dampen the movements.

Rotation of the piston 222 within the upper strut housing 220 must be controlled to maintain proper wheel alignment of the main landing gear system 120a. To control such rotation, the main landing gear system 120a can include a torque link assembly 202 having an upper torque link 210 and a lower torque link 212. The torque link assembly 202 is configured to permit the telescoping movement between the piston 222 and the upper strut housing 220 while preventing rotation of the piston 222 within the upper strut housing 220. The upper torque link 210 is pivotably coupled to the upper strut housing 220 with an upper pivot pin 214 forming an upper pivot joint 215. The lower torque link 212 is pivotably coupled to the lower housing 224 with a lower pivot pin 218 forming a lower pivot joint 219. The upper and lower torque links 210 and 212 are also pivotably coupled together to form a torque link pivot joint 216.

During use of the main landing gear system 120a, the upper and lower torque links 210 and 212 prevent the rotation of the piston 222 within the upper strut housing 220, but permit the telescoping movement of the piston 222 within the upper strut housing 220 by rotational movements at the upper pivot joint 215, the torque link pivot joint 216, and the lower pivot joint 219. For example, during compression of the oleo strut 200, such as when the aircraft is landing, the lower pivot joint 219 moves closer to the upper pivot joint 215, which begins at a first angle a (FIGURE 2B) and closes the angle between the upper and lower torque links 210 and 212 to a second angle P (FIGURE 2C; see the transition from FIGURE 2B to FIGURE 2C). In the illustrated embodiments, the upper and lower torque links 210 and 212 are generally shown as control arms or A-arms, having split leg members pivotably coupling to either side of a pivot joint. In other embodiments, the upper and lower torque links 210 and 212 can have other suitable configurations to prevent the rotation of the piston 222 within the upper strut housing 220. For example, the torque link pivot joint 216 is shown in a stacked configuration with portions of the upper and lower torque links 210 and 212 adjacent to one another. In other embodiments, one of the upper and lower torque links 210 and 212 can have an H-arm configuration, where the torque link pivot joint 216 can have a split leg member pivotably coupled thereto. Other pivot configurations are also within the scope of the present disclosure.

The bogie truck assembly 201 can include various components configured to carry sets of aircraft wheels of the main landing gear system 120a. Although the illustrated bogie truck assembly 201 of FIGURES 2A-2C is configured to carry two sets of wheels (four total wheels), embodiments of the present disclosure are suitable for use with any number of wheels sets in a landing gear system, for example, three sets of wheels (see FIGURE 1), greater than three sets of wheels, or a single set of wheels such as the configuration used on the nose landing gear 110. The bogie truck assembly 201 is configured to carry two sets of wheels and can include a fore axle 230 and an aft axle 232, each rotatably coupled to a bogie truck beam 226. The bogie truck beam 226 can be pivotably coupled to the lower housing 224 at a bogie pivot joint 227. In this regard, during maneuvers of the aircraft, such as landing and takeoff when both sets of wheels do not contact the runway simultaneously, the bogie truck beam 226 is permitted to articulate about the bogie pivot joint 227 and accommodate the relative skew of the runway with respect to the aircraft 100. In some embodiments, the lower housing 224 can be pivotably coupled to a fore brake rod 240 and an aft brake rod 242 configured to control the application of the brakes (not shown) during landing, such by articulation of the bogie truck beam 226.

The various pivot joints 215, 216, 219, and 227 require friction reduction between the rotating components (e.g., between the upper pivot pin 214 and internal surfaces of an aperture in the upper strut housing 220) to prevent premature wear, heat damage, and/or malfunction of the system. In some embodiments, friction reduction can be achieved by providing a smooth surface finish on the components and supplying a lubricant therebetween. In other embodiments, one or more bearings (ball, roller, needle, etc.) can be used to reduce the friction between the rotating components. As shown, the upper pivot joint 215 can include a plurality of grease fittings 215a, the torque link pivot joint 216 can include a plurality of grease fittings 216a, and the lower pivot joint 219 can include a plurality of grease fittings 219a, each configured to receive and distribute grease/oil to the friction surfaces of the components of the upper pivot joint 215, the torque link pivot joint 216, and the lower pivot joint 219, respectively. The grease fittings 215a, 216a, and 219a can be used by service personnel during manual lubrication of the pivot joints 215, 216, and 219, respectively.

As noted above, the bogie pivot joint 227 experiences severe loading from relatively high pitch velocities due to the high-frequency, large displacement oscillations in the bogie truck beam 226, coupled with relatively high contact pressures due to the low-frequency, high bogie pivot joint 227 loading (carrying the dynamic weight of the aircraft). Conventional bogie pivot joints are manually lubricated at various service intervals; however, typical service intervals may not be frequent enough to maintain acceptable friction levels within the bogie pivot joint based on the severe loading conditions. As a result, these conventional bogie pivot joints can experience premature wear and failure. Embodiments of the present disclosure include a kinematic-based oil pump system 204 configured to provide automated lubrication of the bogie pivot joints 227 to reduce friction effects on the components, prolonging the life of the joint, lowering the cost of maintenance, and reducing downtime of the aircraft. In the illustrated embodiments, the kinematic-based oil pump system 204 includes an axial piston type pump that utilizes the relative movement between the upper strut housing 220 and the lower housing 224 to actuate an oil pump to deliver lubricant to the bogie pivot joint 227. In these embodiments, compression of the oleo strut 200 causes the kinematic -based oil pump system 204 to deliver lubricant to the bogie pivot joint 227 by actuating the axial piston pump. In some embodiments, the delivery can be controlled by an adjustment device, such as a device that measures pressure in the bogie pivot joint 227 to control the delivery of lubricant. In other embodiments, a rotational pump can be used with the system 204, such as a screw ball type pump.

The following description references a first assembly of the kinematic -based oil pump system 204 having components with the designation 254a, 252a, etc. In the illustrated embodiment, a second assembly having similar components in the 254b, 252b, on a second side of the landing gear 102a is provided (see components in dotted line in FIGURE 2A). Embodiments of the present disclosure can include any number of assemblies to provide lubrication to the bogie pivot joint 227. The kinematic -based oil pump system 204 includes a lubrication piston rod 254a having a first end pivotably coupled to the upper pivot joint 215 and a second end having a lubrication piston 252a. In other embodiments, the first end of the lubrication piston rod 254a can be pivotably coupled to any suitable location on the upper strut housing 220, such as a boss, rib, standoff, etc.

The lubrication piston 252a can be sealingly received within a lubrication outer cylinder 250a, within which the lubrication piston 252a travels axially during relative movement between the upper strut housing 220 and the lower housing 224. In this regard, the lubrication outer cylinder 250a can be filled in a lower portion of its internal chamber with lubricant (oil, grease, etc.) such that axial translation of the lubrication piston 252a within the lubrication outer cylinder 250a causes an increase in pressure in the lubricant, effectively pumping the lubricant to the desired friction control location (e.g., the bogie pivot joint 227). A substantially closed end of the lubrication outer cylinder 250a can be operably coupled to the bogie pivot joint 227 by an oil-delivery shaft 260a having an oil passageway therein. The oil-delivery shaft 260a can be configured to both rigidly couple the lubrication outer cylinder 250a to the lower housing 224, and also have an oil passageway therethrough to deliver lubricant to the bogie pivot joint 227, e.g., through a grease fitting (not shown) and can include an internal passageway 261a (FIGURES 2B and 2C) to deliver the lubricant directly into the bogie pivot joint 227 between the friction surfaces.

In other embodiments, the function of coupling of the lubrication outer cylinder 250a to the lower housing 224 and the function of the oil passageway can be separated into multiple components. For example, the lubrication outer cylinder 250a can be rigidly coupled to the lower housing 224 by a shaft, rod, or bracket at a different suitable location (e.g., a boss, standoff, rib, etc.), such that relative movement between the upper strut housing 220 and the lower housing 224 causes the lubrication piston 252a to move axially within the lubrication outer cylinder 250a and pump lubricant. Similarly, a separate oil passageway (oil line, oil hose, etc.) can be fluidly coupled between the internal chamber of the lubrication outer cylinder 250a and the bogie pivot joint 227 to deliver the lubricant thereto.

The kinematic-based oil pump system 204 can further include an oil reservoir 256a that is fluidly coupled to the internal chamber of the lubrication outer cylinder 250a to replenish lubricant after it is pumped out of the internal chamber by the lubrication piston 252a. The oil reservoir 256a can be configured to transfer lubricant into the internal chamber of the lubrication outer cylinder 250a by way of gravity, vacuum, or pressure. The internal chamber of the lubrication outer cylinder 250a can include a spring 258a that is configured to urge the lubrication piston 252a and the lubrication outer cylinder 250a apart after compression.

Other embodiments of the present disclosure include a lubricant return passageway 257, which is shown in FIGURE 2A in broken line representing an optional component of the kinematic -based oil pump system 204. The lubricant return passageway 257 can be fluidly coupled between the bogie pivot joint 227 and the oil reservoir 256a such that excess lubricant is routed back to the oil reservoir 256a rather than escaping the bogie pivot joint 227. In this regard, the lubricant return passageway can include a pressure check valve (not shown) to ensure that the intended volume and pressure of lubricant is retained in the bogie pivot joint 227 during use of the main landing gear 120a. Although the lubricant return passageway 257 is shown on a first side of the landing gear 102a for clarity purposes, a second lubricant return passageway (not shown) can be configured on the second side of the landing gear 102a, such as a passageway fluidly coupled between the bogie pivot joint 227 and the oil reservoir 256b such that excess lubricant is routed back to the oil reservoir 256b rather than escaping the bogie pivot joint 227. In other embodiments, the lubricant return passageway 257 can be routed through a different location on the bogie truck beam 226, such as a central location along the pivot axis of the bogie pivot joint 227. The central location routing may have a single port within the bogie truck beam 226 and then the lubricant return passageway can be configured to split the returning lubricant to both the oil reservoirs 256a and 256b, or multiple ports may be included within the bogie truck beam 226. In these embodiments, the oil-delivery shafts 260a and 260b may deliver lubricant near the outer ends of the bogie pivot joint 227, and the lubricant return passageway 257 may pick up excess lubricant at a central location along the pivot axis, such that the lubricant travels along the bogie pivot joint 227 before being returned to the oil reservoirs 256a and 256b.

FIGURES 2B and 2C are a side views of a portion of the main landing gear system 120a, showing the main landing gear system 120a in an extended position with the first angle a between the upper and lower torque links 210 and 212 (FIGURE 2B) and a compressed position with the second angle P between the upper and lower torque links 210 and 212 (FIGURE 2C). As described above, the main landing gear system 120a is expected to transition from the extended position in FIGURE 2B toward the compressed position in FIGURE 2C as a result of various upward forces acting on the main landing gear system 120a, such as the forces during landing, taxiing, takeoff, etc. For example, when the aircraft 100 lands, the main landing gear 120a and 120b impacts the runway causing an upward force that compresses the oleo strut 200, imparting a relative movement between the upper strut housing 220 and the lower housing 224. This relative movement translates to a movement of the lubrication piston 252a within the lubrication outer cylinder 250a, thereby pumping lubricant through the oil-delivery shaft 260a and into the bogie pivot joint 227, reducing the friction therein. The timing of such oil delivery is advantageous in that the bogie pivot joint 227 receives lubricant from the kinematic-based oil pump system 204 as the joint is experiencing its most severe loading. In this regard, lubricant delivery by the kinematic-based oil pump system 204 is not only automated, but timed to coincide with the most severe loading conditions of the bogie pivot joint 227, thereby extending the life of the wear components.

In the foregoing description, specific details are set forth to provide a thorough understanding of exemplary embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that the embodiments disclosed herein may be practiced without embodying all of the specific details. In some instances, well-known process steps have not been described in detail in order not to unnecessarily obscure various aspects of the present disclosure. Further, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein.

The present application may reference quantities and numbers. Unless specifically stated, such quantities and numbers are not to be considered restrictive, but exemplary of the possible quantities or numbers associated with the present application. Also in this regard, the present application may use the term “plurality” to reference a quantity or number. In this regard, the term “plurality” is meant to be any number that is more than one, for example, two, three, four, five, etc. The terms “about,” “approximately,” “near,” etc., mean plus or minus 10% of the stated value. For the purposes of the present disclosure, the phrase “at least one of A and B” is equivalent to “A and/or B” or vice versa, namely “A” alone, “B” alone or “A and B.”. Similarly, the phrase “at least one of A, B, and C,” for example, means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C), including all further possible permutations when greater than three elements are listed.

It should be noted that for purposes of this disclosure, terminology such as “upper,” “lower,” “vertical,” “horizontal,” “fore,” “aft,” “inner,” “outer,” “front,” “rear,” etc., should be construed as descriptive and not limiting the scope of the claimed subject matter. Further, the use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings.

Throughout this specification, terms of art may be used. These terms are to take on their ordinary meaning in the art from which they come, unless specifically defined herein or the context of their use would clearly suggest otherwise.

The principles, representative embodiments, and modes of operation of the present disclosure have been described in the foregoing description. However, aspects of the present disclosure, which are intended to be protected, are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present disclosure. Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present disclosure as claimed.

Claims

CLAIMS The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A landing gear for an aircraft having an automated kinematic -based oil pump system, the landing gear comprising: an oleo strut configured to be operably coupled to the aircraft, the oleo strut having an upper strut housing; a piston slidingly received in the upper strut housing in a telescoping arrangement for relative axial movement between the piston and the upper strut housing; a lower housing operably coupled to the piston; a bogie truck assembly having a bogie truck beam pivotably coupled to the lower housing at a bogie pivot joint; a lubrication piston rod having a first end operably coupled to the upper housing and a second end having a lubrication piston; and a lubrication outer cylinder having an internal chamber for sealingly receiving the lubrication piston, the lubrication outer cylinder operably coupled to the lower housing by a shaft, and the internal chamber configured to retain lubricant therein and being fluidly coupled to a grease fitting of the bogie pivot joint by an oil passageway, wherein relative movement of the upper strut housing toward the lower housing based on a force acting on the landing gear causes the lubrication piston to travel axially within the lubrication outer cylinder and thereby pump lubricant from the internal chamber to the grease fitting of the bogie pivot joint through the oil passageway.

2. The landing gear of Claim 1, wherein the oil passageway is disposed within the shaft such that the shaft delivers lubricant from the internal chamber to the grease fitting of the bogie pivot joint.

3. The landing gear of Claim 1, wherein the oil passageway is contained in an oil line separated from the shaft.

4. The landing gear of any of Claims 1-3, further comprising an oil reservoir fluidly coupled to the internal chamber of the lubrication outer cylinder, wherein the oil reservoir is configured to replenish lubricant after the lubricant is pumped out of the internal chamber by the lubrication piston.

5. The landing gear of Claim 4, further comprising an oil return passageway fluidly coupled between the bogie pivot joint and the oil reservoir, wherein the oil return passageway is configured to deliver lubricant from the bogie pivot joint to the oil reservoir.

6. The landing gear of Claim 5, wherein the oil return passageway further comprises a pressure check valve configured to retain a specified pressure of lubricant in the bogie pivot joint before permitting delivery of lubricant from the bogie pivot joint to the oil reservoir.

7. The landing gear of any of Claims 1-6, further comprising a spring configured to urge the lubrication piston and the lubrication outer cylinder axially apart.

8. The landing gear of any of Claims 1-7, wherein the lubrication piston rod is pivotably coupled to the upper housing, and wherein the shaft is pivotably coupled to the lower housing.

9. The landing gear of any of Claims 1-8, further comprising: a second lubrication piston rod having a first end operably coupled to the upper housing and a second end having a second lubrication piston; and a second lubrication outer cylinder having a second internal chamber for sealingly receiving the second lubrication piston, the second lubrication outer cylinder operably coupled to the lower housing by a second shaft, and the second internal chamber configured to retain lubricant therein and being fluidly coupled to a grease fitting of the bogie pivot joint by a second oil passageway, wherein relative movement of the upper strut housing toward the lower housing based on a force acting on the landing gear causes the second lubrication piston to travel axially within the second lubrication outer cylinder and thereby pump lubricant from the second internal chamber to a second grease fitting of the bogie pivot joint through the second oil passageway.

10. The landing gear of any of Claims 1-9, further comprising a torque link assembly to prevent relative rotation of the piston and the upper strut housing, the torque link assembly comprising: an upper torque link pivotably coupled to the upper housing at an upper pivot joint; and a lower torque link pivotably coupled to the upper torque link and pivotably coupled to the lower housing at a lower pivot joint, wherein the lubrication piston rod is pivotably coupled to the upper pivot joint.

11. The landing gear of any of Claims 1-10, wherein the shaft is operably coupled to the bogie pivot joint.

12. A kinematic-based oil pump system for a pivot joint, the system comprising: a lubrication piston rod having a first end operably coupled to an upper housing and a second end having a lubrication piston; and a lubrication outer cylinder having an internal chamber for sealingly receiving the lubrication piston, the lubrication outer cylinder operably coupled to a lower housing by a shaft, and the internal chamber configured to retain lubricant therein and being fluidly coupled to a grease fitting of the pivot joint by an oil passageway, wherein relative movement of the upper housing toward the lower housing causes the lubrication piston to travel axially within the lubrication outer cylinder and thereby pump lubricant from the internal chamber to the grease fitting of the pivot joint through the oil passageway.

13. The system of Claim 12, wherein the upper housing is an upper strut housing of an oleo strut of an aircraft landing gear, wherein the lower housing is coupled to a piston slidingly received in the upper strut housing in a telescoping arrangement for relative axial movement between the piston and the upper strut housing.

14. The system of Claim 13, further comprising a torque link assembly to prevent relative rotation of the piston and the upper strut housing, the torque link assembly comprising: an upper torque link pivotably coupled to the upper housing; and a lower torque link pivotably coupled to the upper torque link and pivotably coupled to the lower housing.

15. The system of Claim 14, further comprising a bogie truck assembly having a bogie truck beam pivotably coupled to the lower housing at the pivot joint.

16. The system of any of Claims 12-15, wherein the oil passageway is disposed within the shaft such that the shaft delivers lubricant from the internal chamber to the grease fitting of the pivot joint.

17. The system of any of Claims 12-16, further comprising an oil reservoir fluidly coupled to the internal chamber of the lubrication outer cylinder, wherein the oil reservoir is configured to replenish lubricant after the lubricant is pumped out of the internal chamber by the lubrication piston.

18. A landing gear for an aircraft having automated lubrication of a bogie pivot joint, the landing gear comprising: an oleo strut configured to be operably coupled to the aircraft, the oleo strut having an upper strut housing; a piston slidingly received in the upper strut housing in a telescoping arrangement for relative axial movement between the piston and the upper strut housing; a lower housing operably coupled to the piston; a bogie truck assembly having a bogie truck beam pivotably coupled to the lower housing at a bogie pivot joint; and a lubrication system operably coupled between the upper housing and the lower housing, the lubrication system being fluidly coupled to a grease fitting of the bogie pivot joint by an oil passageway, wherein relative movement of the upper strut housing toward the lower housing based on a force acting on the landing gear causes the lubrication system to pump lubricant to the grease fitting of the bogie pivot joint through the oil passageway.

19. The landing gear of Claim 18, wherein the lubrication system comprises an axial piston type pump or a screw ball type pump.

20. The landing gear of Claim 18, wherein the lubrication system comprises: a lubrication piston rod having a first end operably coupled to the upper housing and a second end having a lubrication piston; and a lubrication outer cylinder having an internal chamber for sealingly receiving the lubrication piston, the lubrication outer cylinder operably coupled to the lower housing by a shaft, and the internal chamber configured to retain lubricant therein and being fluidly coupled to a grease fitting of the bogie pivot joint by an oil passageway, wherein the relative movement of the upper strut housing toward the lower housing causes the lubrication piston to travel axially within the lubrication outer cylinder and thereby pump the lubricant.

21. The landing gear of Claim 20, wherein the oil passageway is disposed within the shaft such that the shaft delivers lubricant from the internal chamber to the grease fitting of the bogie pivot joint.

22. The landing gear of Claim 21, wherein the oil passageway is contained in an oil line separated from the shaft.

23. The landing gear of Claim 20, further comprising an oil return passageway fluidly coupled between the bogie pivot joint and the internal chamber, wherein the oil return passageway is configured to deliver lubricant from the bogie pivot joint to the internal chamber.

24. The landing gear of Claim 23, wherein the oil return passageway further comprises a pressure check valve configured to retain a specified pressure of lubricant in the bogie pivot joint before permitting delivery of lubricant from the bogie pivot joint to the internal chamber.