JPH01186494A - Landing gear mechanism - Google Patents

Abstract

PURPOSE: To reduce or negate a large damping load generated when a landing gear mechanism passes through corrugations during taxying by providing a bypass valve assembly having a sliding member on a restrictor assembly. CONSTITUTION: The pressure in an upper piston chamber 19 is increased to the pressure of an air chamber 30 filled in advance at one point while a main piston 5 is moved to the inside after a landing energy stroke is completed, and a second piston 28 is moved along the main piston 5 to provide a soft spring during taxying. As the pressure in the upper piston chamber 19 is increased, the piston 28 is separated from a restrictor assembly 6 to release the coupling with a probe 23, and a slide section 22 is moved to a release position where a fluid can flow by bypassing a main orifice 15, thereby a large damping load generated when a landing gear mechanism 1 passes through corrugations during taxying is largely reduced or negated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a landing gear system having a bypass valve assembly that substantially reduces or negates large damping loads as the landing gear mechanism passes over undulations during taxiing. It concerns the device mechanism. It should be noted that such landing gear mechanisms are specifically designed to meet the requirements of high performance aircraft and allow such aircraft to operate on relatively uneven runways.

(Background Art) The landing gears of high-performance aircraft, such as those used by the military, are not designed to be operated on uneven runways that have been temporarily repaired, for example, in areas damaged by bombing. It is customary.

U.S. Patent No. 455,232 dated November 12, 1985
As disclosed in No. 4, by giving the landing gear various low bounce load areas, the landing gear can be made effective even when the takeoff weight is large, and it can also be used on uneven runways. The shock strut stroke necessary to absorb the desired landing energy can be obtained during landing so that the landing gear is not damaged during landing.

Furthermore, according to the landing gear disclosed in that patent, the landing gear extends by distinguishing between the extension of the buffer strut during normal driving and the extension of the shock strut when a tire accidentally gets stuck in a pothole during forward motion. This prevents cavitation in the lower piston chamber of the landing gear during full extension, and provides rebound damping to the piston as it approaches the end of its stroke during full extension.

In addition, the landing gear of that patent may be provided with a device that substantially reduces or eliminates the large damping loads when the landing gear passes over undulations. Simply put, this means that once the landing energy stroke is completed and the working fluid is allowed to flow more freely from the lower piston chamber, bypassing the main flow orifice, and into the upper piston chamber, the taxi-in stroke bypass is immediately activated. This can be done by opening the valve.

DISCLOSURE OF THE INVENTION The landing gear mechanism of the present invention can have one or more of the many features disclosed in that patent. However, the present landing gear mechanism is capable of reducing or virtually eliminating the large damping loads that would otherwise be generated when the landing gear passes over undulations during taxiing, and is more effective than the corresponding mechanisms of the previously mentioned patents. A novel bypass valve assembly is provided that is more suitable for placement in small spaces.

According to the invention, a landing gear mechanism of the type previously described is provided with a simple bypass valve assembly which substantially reduces or eliminates the large damping loads when the landing gear passes over undulations during taxiing. Landing gear mechanism can be obtained.

According to the invention, the bypass valve assembly also includes:
It can be easily accommodated within a relatively narrow space within the envelope of a standard landing gear, such as the nose wheel of a high performance military aircraft.

Further in accordance with the present invention, the bypass valve assembly may be incorporated into a restrictor assembly that also controls the rate of inward stroke of the landing gear mechanism during landing of the aircraft.

Additionally, in accordance with the present invention, a pressure-driven second air stage of the landing gear mechanism may be used to control the opening and closing of the bypass valve assembly.

The landing gear mechanism restrictor assembly of the present invention comprises:
a bypass valve assembly having a sliding member axially movable relative to the restrictor assembly to open and close one or more bypass orifices of the restrictor assembly; can do. The sliding member is held in a closed position as long as the landing gear mechanism is within a specified stroke range, as opposed to a fully extended position by the second piston. Note that the second piston is subject to the pressure of a pre-filled second chamber which urges the second piston into engagement with a probe connected to the sliding member. However, at some point during the inward movement of the main piston after the landing energy stroke is completed, the pressure in the upper piston chamber within the landing gear mechanism is
As the pressure in the chamber increases, the second piston will move along the main piston to provide a flexible spring during taxiing. As the pressure in the upper piston chamber increases, the second piston moves away from the restrictor assembly and disengages the probe, allowing the sliding member to allow fluid to bypass the primary orifice. It will be moved to an open position where possible. therefore,
The large damping loads that would otherwise be generated when the landing gear mechanism passes over undulations during taxiing can be significantly reduced or eliminated.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

1 and 2 are diagrams showing one embodiment of a landing gear mechanism 1 according to the present invention, which normally comprises a main shock strut 2 including an outer main cylinder 3. FIG. The main cylinder is provided with a trunnion 4 at its upper end, i.e., at its fuselage side end, for connection to the fuselage of the aircraft in a conventional manner. Although not shown, suitable support struts and drag supports may be provided to support the landing gear mechanism in the lowered position to support the airplane while on the ground, during takeoff and landing, and to retract the landing gear mechanism during flight. be able to do so.

A main strut piston 5 is disposed axially movably within the outboard main cylinder 3 and extends outwardly beyond the outboard end of the main cylinder with a suitable trunnion mount 7 at its outboard end; Attach the wheel and tire assembly thereto.

The main strut piston 5 has a generally annular retracting portion, and a restrictor inside the main strut piston.
The assembly 6 is imparted with relative sliding motion. This restrictor assembly 6 is connected to the fuselage side end of the outer main cylinder 3 by an orifice support tube 8 extending therebetween.

As shown, the orifice support tube 8 preferably extends a substantial portion of the length of the main cylinder 3 to rigidly support the restrictor assembly 6. Note that this assembly is located coaxially within the main cylinder adjacent to its outer end and extends coaxially within the main piston 5. The restrictor assembly comprises an annular sleeve portion 9 which can be screwed on the outer end of the orifice support tube 8 at its inner portion. The outer diameter portion (0,
A ring seal 10, suitably inserted in D), slidably seals into engagement with the inner diameter of the main piston 5 and prevents fluid flow therebetween.

The restrictor assembly 6 may be provided with one or more main orifices. In the illustrated embodiment,
A single main orifice 15 is connected to the restrictor sleeve 9
extends through the axis of a nut 16 that is threaded into a counterbore 17 in the outer end of the restrictor assembly so that restricted flow passes through the restrictor assembly while the landing gear is in its compression stroke when the aircraft lands. From the lower piston chamber 18 to the seal ring 10
so that it flows into the upper piston chamber 19 on the opposite side. This orifice 15 may be a fixed orifice as shown. However, it is also clear that by replacing this fixed orifice with a variable orifice, it is also possible to control the dynamic load stroke curve of the landing gear within certain limits at each strut-stroke position, as is well known in the art. .

The restrictor assembly 6 incorporates a taxi-in-stroke bypass valve 20 to open one or more bypass orifices 21 in the restrictor sleeve 9 so that fluid flows through the main orifice 15 while the aircraft is taxiing. Bypassing and allowing free flow from the lower chamber 18 to the upper piston chamber 19 greatly reduces or eliminates the large damping loads created when the landing gear passes over undulations. In the illustrated embodiment, four such
restrictor bypass orifices 21 at equal intervals.
It is provided around the sleeve 9.

The bypass orifices 21 are selectively opened and closed in response to the axial position of the brake member 22 within the restrictor sleeve 9. A probe 23, suitably attached to the axially inner end of the sliding member 22 by a pair of angularly mounted pins 24, 25, is provided on the radial flange 27 of the axially inner end of the restrictor sleeve. It penetrates through the central opening 26. When the landing gear is fully extended as shown in FIG. 1, the probe 23 engages the second piston 28 in the orifice support tube 8 and moves the sliding member 22 into the position shown in FIG. An outer land 29 on the moving member overlappingly engages the bypass orifice 21 and forces it into a position blocking flow therefrom. This second
The piston 28 is part of the pressure-actuated second air stage and helps provide a relatively flexible spring to the landing gear during taxiing as described below.

the second piston 28 and the upper end of the orifice support tube 3;
That is, a second air chamber 30 is provided between the fuselage side end portion,
A desired amount of atmospheric air is prefilled through a suitable passage 31 formed in the fuselage end of the main cylinder 3 which communicates with this second air chamber. When the landing gear mechanism 1 is fully extended as shown in FIG. The sliding member 22 seats and engages the inner end of the restrictor sleeve 9 and forces the probe 23 slightly outwardly until it is flush with the inner end of the restrictor sleeve 9. The land 29 located in the bypass orifice 21 is brought into a position to block fluid flow through the bypass orifice 21 as described above. However, fluid still flows from the lower piston chamber 18 into the center of the restrictor sleeve 9 on one side of the ring seal 10 via the main orifice 15 at the outer end of the drift sleeve 9 and into the ring seal 10. It can freely flow into the upper piston chamber 19 through a plurality of radial passages or radial ports 35 provided in the restrictor sleeve opposite the seal. Note that the same applies to the opposite case.

During landing, the bypass orifice 21 remains closed, so that the entire working fluid flows from the lower piston chamber 18 through the main orifice 15 to the upper piston chamber 19, providing maximum orifice access to the landing gear mechanism during landing. Landing dynamics will be given. However, at some point during the retraction of the main piston 5, the outer end of the second piston 28 is also The pressure in the active upper piston chamber 19 will rise to the pressure in the prefilled second air chamber 30, which will cause the second piston to move along the main piston. Therefore, a relatively soft spring is applied to the landing gear mechanism during taxiing.

As shown in FIG. 1, when the second piston is fully seated in the restrictor sleeve 9, the upper piston chamber 1
In order to increase the surface area of the second piston 28 subjected to the initial pressure in the restrictor sleeve 27, the inner surface of the restrictor sleeve 27 is preferably conically tapered, with a conical recess formed by a portion of the taper passing through its flange. An axial passage 36 is provided which communicates with 38.

As the second piston 28 moves inwardly (i.e. to the left in FIGS. 1 and 2), the spring 40 acting on the outer end of the slide member 22 forces the slide member axially inwardly. is engaged with the internal locking shoulder 41 of the restrictor sleeve 9 to provide a full radial passage between the bypass orifice 21 and a plurality of radially extending passageways 42 spaced around the slide member. Outer circumferential groove 4 of the sliding member communicating with the passage
3. With the bypass orifice 21 open, as shown in FIG. to reduce constraints on inward movement while taxiing on uneven runways, and to allow the landing gear mechanisms to move inward more quickly if necessary.

As can be seen from the foregoing, the runway irregularity bypass valve assembly of the present invention is extremely simple and effective in substantially reducing or eliminating large damping loads when the landing gear mechanism passes over undulations during taxiing. provide a means to do so. As mentioned above, such a bypass valve assembly can be effectively incorporated into a restrictor assembly to simplify the structure of the bypass valve assembly, and to combine the restrictor assembly and the bypass valve assembly with superior performance. This facilitates integration into relatively narrow spaces within the envelope of common landing gear, such as the nose wheel of a military aircraft. It also provides a simple mechanism for opening and closing the bypass valve during inward or outward movement of the landing gear mechanism, respectively.

[Brief explanation of the drawing]

FIG. 1 is a partial longitudinal cross-sectional view of one example of the landing gear mechanism of the present invention in a fully extended position with the bypass valve assembly in the closed position; FIG. FIG. 3 is a partial vertical cross-sectional view of the landing gear mechanism shown in the figure. 1...Landing gear mechanism 2...Main buffer strut 3...
- Outer main cylinder 4... Trunnion 5... Main strut piston 6... Restrictor assembly 7... Trunnion mount 8... Orifice support tube 9... Sleeve portion 10
...Ring seal 15...Main orifice 16
...Natsuto 17...Counterbore 18...
・Lower piston chamber 19...Upper piston chamber 20・
... Taxi in-stroke binoculars valve 21 ... Bypass orifice 22 ... Sliding part 23 ... Probe 24
, 25... Pin 26... Opening 27...
Flange 28... Piston 29... Land 30... Air chamber 31, 35.36.4
2... Passage 38... Conical recess 40... Spring
41...Locking shoulder portion 43...Peripheral groove Patent applicant Pneumo Apex Corporation

Claims (1)

[Claims] 1. A landing gear mechanism for a high-performance aircraft, comprising a main cylinder (3), a main strut piston (5) movable in the axial direction within the main cylinder (3), and a main strut piston (5) movable in the axial direction within the main cylinder (3). Built into the cylinder, upper and lower piston chambers (19, 1) are formed by the main cylinder (3) and strut piston (5).
8), said restrictor member (6) defining a flow path of working fluid from said lower piston chamber (18) to said upper piston chamber (18) during landing.
9), further comprising orifice means (15) for controlling the flow of said working fluid into said lower piston chamber (18) whenever the landing gear engages in undulation during taxiing.
increasing the flow rate from to the upper piston chamber (19);
comprising bypass valve means (20) for reducing damping loads that would occur if the entirety of said working fluid were required to flow through said orifice means (15), said bypass valve means (20) comprising: The orifice means (15
) and the restrictor member (6) between open and closed positions for opening and closing the bypass passage means (21), respectively.
A sliding member (2
2), and means (23, 28) for holding the sliding member (22) in the closed position until the pressure in the upper piston chamber (19) reaches a predetermined level after landing; said means (23) for retaining the movable member (22) in a closed position;
, 28) is a second piston (2) having a first surface area.
8), in its surface area a second piston (2
8) A landing gear mechanism characterized in that a predetermined pressure is continuously applied by a second pressure source that presses the sliding member (22) toward the sliding member (22). 2. The mechanism according to claim 1, wherein the second piston (28) is arranged in the upper piston chamber (19) that presses the second piston (28) away from the sliding member (22). said second piston (28) has a second surface area on which a fluid pressure of
The force applied to the second piston (28) is caused by the pressure in the upper piston chamber (19) which holds the sliding member (22) in the closed position when the main strut piston (5) is fully extended. ) A landing gear mechanism characterized in that the force is greater than the force applied to the landing gear mechanism. 3. The arrangement according to claim 2, wherein the pressure in the upper piston chamber (19) increases to the pressure of the second pressure source while the landing gear mechanism is being compressed after landing; the second piston (28) is moved away from the sliding member (22), and the landing gear mechanism moves the second piston (28) away from the sliding member (22), and the landing gear mechanism moves the second piston (28) away from the sliding member (22). Landing gear mechanism characterized in that it comprises spring means (40) for moving (22) into an open position. 4. A device according to claim 3, wherein said restrictor member (6) comprises a restrictor sleeve (9) held within said main cylinder (3) and relatively fixed thereto, said restrictor sleeve ( 9) extends within said main strut piston (5), said main strut piston (5) being axially disposed relative to said restrictor sleeve (9) between a fully extended position and a compressed position. sealing means (10) movable between said restrictor sleeve (9) and the main strut piston (5) forming a sliding seal therebetween;
said restrictor sleeve (9) having said orifice means (15) and bypass passage means (21) therein, said sliding member (22) said said restrictor sleeve (9) having said said orifice means (15) and bypass passage means (21) therein; Bypass passage means (21)
said restrictor sleeve (
9) A landing gear mechanism characterized in that the inside is slidable in the axial direction. 5. The mechanism according to claim 4, wherein the sliding member (22
) has an outer land (29) on its surface which prevents the flow of fluid through the bypass passage means (21) when the slide member (22) is in the closed position, and has an outer land (29) on its surface which prevents the flow of fluid through the bypass passage means (21) when the slide member (22) is in the closed position; communicating with the bypass passage means (21) of the restrictor sleeve (9) when the moving member (22) is present;
a plurality of radial passages (
42) A landing gear mechanism comprising: 6. The mechanism according to claim 4, wherein the sliding member (22
), the pressure of the second pressure source is in the upper piston chamber (
19) projecting beyond the inner end of the restrictor sleeve (9) to move the sliding member (22) into a closed position when the pressure in the second A landing gear mechanism characterized in that it has a probe (23) that engages a piston (28). 7. A mechanism according to claim 6, wherein the inner end of the restrictor sleeve (9) is provided with a flange (27) having a central aperture (26) from which the probe (23) projects, and the orifice means ( 15) on one side of said sealing means (10) said restrictor sleeve (
9) and said lower piston chamber (18), said sealing means (10) being provided by a plurality of additional radial passages (35) provided in said restrictor sleeve (9). On the other side said restrictor sleeve (9
) and the upper piston chamber (19),
Furthermore, an axial passage (36) passing through the end flange (27) of the restrictor sleeve (9) is provided in the second surface area of the second piston (28) in the upper piston chamber ( Landing gear mechanism, characterized in that the fluid pressure in (19) is applied via said axial and radial passages (35, 36) of said restrictor sleeve (9). 8. The mechanism according to claim 7, wherein a side of the end flange (27) facing the second piston (28) is formed into a conically tapered shape to form a conical recess (38), and the second piston (28) increases said second surface area of said second piston (28) which is subject to pressure in said upper piston chamber (19) when fully seated on said end flange (27); Features a landing gear mechanism. 9. A landing gear mechanism according to claim 4, wherein the main strut piston (5) extends into the main cylinder (3) and projects at the inner end of the main strut piston (5). an orifice support tube (8) is attached to the orifice support tube (8), said restrictor sleeve (9) is attached to the outer end of said orifice support tube (8), and said second piston (28) is mounted within said orifice support tube (8). The orifice support tube ( 28 8) is provided with a second air chamber (30);
The second piston (28) is provided with means (31) for pre-filling the second air chamber (30) with a predetermined amount of atmospheric air.
act on said first surface area of said second piston (
28) toward the inner end of the restrictor sleeve (9). 10. The mechanism according to claim 9, wherein the sliding member (2
2) beyond the inner end of the restrictor sleeve (9), the second piston (28) is pressed by the pressure in the second air chamber (30) and the restrictor sleeve (9) A landing gear characterized in that it comprises a probe (23) that engages the second piston (28) when the sliding member (22) is moved to the closed position by engaging the inner end of the landing gear. mechanism.