Aircraft shock absorbers

Abstract

Aircraft shock absorber (1) with two tubular components (10, 20), wherein the first component (10) has a liquid-filled chamber (4) inside it, and the second component (20) is arranged to be displaceable along a common longitudinal axis in the first component (10), the shock absorber (1) has two seals (31, 32) arranged in series in the direction of the common longitudinal axis between the outer surface of the second component (20) and the inner surface of the first component (10), and the shock absorber (1) has a bypass line (5, 5a, 5b) which can be closed by a switching valve (60) and which connects the fluid-filled chamber (4) and the space (6) between the seals (31, 32), characterized by the fact that the aircraft shock absorber (1) has a filling line (75) and a filling valve (70) independent of the switching valve (60), wherein the filling line (75) can be used independently of the position of the changeover valve (60), the filling valve (70) can be operated independently of the position of the changeover valve (60), and a first part of the bypass line (5a) simultaneously represents a section of the filling line (75).

Description

[0001] The present invention relates to an aircraft shock absorber. Such shock absorbers are installed, for example, in the nose and main landing gear of aircraft.

[0002] A number of aircraft shock absorbers are known in the prior art. DE 10 2004 031 995 A1 discloses a shock absorber of this type with hydraulic damping in the form of a fluid-filled chamber in which a throttle element is slidably mounted and moved when the shock absorber is in motion, as well as a gas spring. Further relevant examples from the prior art include US 4,924,975 A and US 5,310,139 A.

[0003] Fig. Figure 1 shows a cross-section through another aircraft shock absorber from the prior art. The shock absorber has an upper end 2, which forms the connection point for the aircraft fuselage, and a lower end 3, which is directly or indirectly connected to the wheel axle. The shock absorber 1 comprises an outer tube 10, which encloses an oil chamber 4. An inner tube 20 is arranged concentrically within this outer tube 10 and is displaceable along the longitudinal axis of the shock absorber. Damping occurs when the inner tube 20 or the other components located on the inner tube within the oil chamber changes motion.

[0004] Between the outer tube 10 and the inner tube 20 is a sealing element 30, which seals the oil chamber from the environment. This sealing element, as well as other comparable sealing elements from the prior art, features a replacement sealing system in accordance with the construction recommendations of the SAE (Society of Automotive Engineers) standards for aircraft, SAE ARP 4912.

[0005] The aim of the present invention is to provide an aircraft shock absorber with an improved sealing element and a replacement sealing element.

[0006] This problem is solved according to the invention with an aircraft shock absorber according to claim 1. Advantageous embodiments are described in the dependent claims.

[0007] Accordingly, an aircraft shock absorber is provided with at least two tubular components. A first component defines or encloses a fluid-filled chamber, and a second component is slidably arranged within this first component or within the fluid-filled chamber. The second component is slidable along a common longitudinal axis of the two components. According to the invention, the shock absorber has at least two seals arranged in series along the common longitudinal axis between the outer surface of the second component and the inner surface of the first component, and at least one bypass line for the hydraulic fluid located in the fluid-filled chamber, which can be closed by a switching valve and connects the fluid-filled chamber to an intermediate space located between the seals.

[0008] In one embodiment, the components are designed as concentrically arranged and optionally round or substantially round tubes, wherein the first tube has an inner diameter or circumference that is slightly larger than the outer diameter or circumference of the second tube. In this embodiment, the common longitudinal axis of the two components is defined by the longitudinal axis of the tubes.

[0009] In one embodiment, the bypass line can be reversibly closed by the switching valve.

[0010] The fluid is preferably a hydraulic fluid, for example hydraulic oil.

[0011] In one embodiment, the aircraft shock absorber according to the invention is a shock absorber for a nose landing gear. In another embodiment, it is a shock absorber for the main landing gear.

[0012] In one embodiment, the first or second component of the aircraft shock absorber is suitable and intended to be connected directly or indirectly to the wheel axle of the aircraft, and the other component is suitable and intended to be connected directly or indirectly to the aircraft body.

[0013] In one embodiment, the shock absorber has exactly two seals arranged in series in the direction of the common longitudinal axis and / or exactly one bypass line that can be closed by a switching valve between the outer surface of the second component and the inner surface of the first component.

[0014] In a preferred embodiment, the first and / or the second seal is arranged in the space between the outer surface of the second component and the inner surface of the first component and completely surrounds the second component. Preferably, the first and / or the second seal completely seals the space between the outer surface of the second component and the inner surface of the first component.

[0015] In a further, preferred embodiment, the first and / or the second seal is designed as a sealing ring enclosing the outer surface of the second component or as a sealing ring completely enclosing the inner surface of the first component.

[0016] In one embodiment, the first and / or the second seal is arranged or fixed to the outer surface of the second component. In another embodiment, the first and / or the second seal is arranged or fixed to the inner surface of the first component.

[0017] In one embodiment, the two seals are equivalent. Preferably, the two seals are of identical construction.

[0018] In one embodiment, the outer seal is pressurized when the bypass line is open. An open bypass line means the diverter valve is in an open position, allowing fluid to flow from the fluid-filled chamber into the space between the seals and back again via the bypass line. In this embodiment, the pressure is applied by the fluid from the fluid-filled chamber and from the space between the seals.

[0019] In one embodiment, the inner seal is pressure-balanced when the bypass line is open. Pressure-balanced in this context means that it is not subjected to pressure exerted by the fluid on one side. This can be achieved by ensuring that the pressure acting directly on the inner seal from the fluid-filled chamber corresponds to the pressure exerted by the space between the seals. In this embodiment, when the bypass line is open, the fluid pressure extends from the fluid-filled chamber into this space.

[0020] The outer seal is the seal that, compared to the inner seal, faces away from the liquid-filled chamber along the common longitudinal axis and is located further away from the head of the second component. The inner seal is the seal that, compared to the outer seal, faces the liquid-filled chamber along the common longitudinal axis and is located closer to the head of the second component. Another definition arises from the position of the two seals in the operating state, i.e., when mounted on the aircraft.

[0021] In the event that the first component is directly or indirectly connected to the aircraft body and the second component is directly or indirectly connected to the wheel axle, the inner seal is the upper seal and the outer seal is the lower seal.

[0022] In one embodiment, the inner seal is pressurized when the bypass line is closed. In this embodiment, when the bypass line is closed, the fluid pressure in the fluid-filled chamber does not extend into the space between the seals. Therefore, the inner seal is pressurized on one side only by the fluid-filled chamber.

[0023] In one embodiment, the outer seal is not pressurized when the bypass line is closed. In this embodiment, the outer seal is in contact with the hydraulic fluid exclusively via the space between the seals and thus via the bypass line. Therefore, closing the bypass line relieves the pressure on the outer seal.

[0024] In one embodiment, the inner seal is a secondary seal or a replacement seal, while the outer seal performs the primary sealing function.

[0025] In one embodiment, during normal operation of the aircraft damper, in which both dampers are intact, the bypass line is open. The inner seal is pressure-balanced and does not perform a sealing function. The outer seal takes over this function completely. Should the outer seal leak, the pressure can be relieved from the outer seal by closing the changeover valve in the bypass line. The intact, previously unused inner seal then assumes the sealing function until the outer seal is serviced or replaced.

[0026] Within the scope of the invention, it is also conceivable that the inner seal serves as the primary seal and the outer seal as a backup seal. In normal operation, the bypass line or the switching valve is then closed, and the entire hydraulic pressure acts on the inner seal. Should this seal leak, the hydraulic line can be opened, thereby equalizing the pressure on the inner seal. The outer backup seal then takes over the sealing function.

[0027] In one embodiment, the bypass line and the changeover valve are arranged in or on the outer component. The changeover valve may be visible or accessible from the outer surface of the aircraft shock absorber. Preferably, the position of the changeover valve is identifiable from the outside. For this purpose, a colored or topographical position marker, for example a notch, may be provided.

[0028] In one embodiment, the switching valve is located on a valve housing which is attached to the outer surface of the first component. Preferably, in this embodiment, at least part of the bypass line also runs within this valve housing.

[0029] The changeover valve preferably comprises a valve sleeve, an actuating pin, and a valve spool. In one embodiment, the changeover valve can be opened and closed with a commercially available tool. Preferably, the changeover valve has a connection, preferably on the actuating pin, for a commercially available hex key, Allen key, or similar tool.

[0030] In a further embodiment, an aircraft shock absorber according to the invention also has a filling line and / or a filling valve, which is preferably independent of the switching valve. The filling valve and / or the filling line serve to empty and fill the fluid-filled chamber, for example for maintenance of the strut by replacing the hydraulic medium or changing the fluid pressure in the chamber.

[0031] In one embodiment, the filling valve is mounted on the same valve housing as the changeover valve. In another embodiment, the filling valve and / or the filling line and the changeover valve and / or the bypass line form a single structural unit.

[0032] In one embodiment, the filling line can be used independently of the position of the changeover valve and / or the filling valve can be actuated independently of the position of the changeover valve. In other words, in this embodiment, the filling line and / or the filling valve can function both in the activated and in the deactivated state of the changeover valve, i.e., in the open and closed state of the bypass line.

[0033] In a further embodiment, at least one section of the bypass line corresponds to at least one section of the filling line. A further section of the bypass line and / or a further section of the filling line, preferably a further section of each line, run separately from one another. The opening of the bypass line and the filling line into the common section is preferably T-shaped. The common section preferably comprises the section of the bypass line facing the liquid-filled chamber from the switching valve, or in other words, the section between the switching valve and the liquid-filled chamber.

[0034] In one embodiment, at least a portion of the filling line runs within the changeover valve, optionally within the actuating pin of the changeover valve. In another embodiment, the bypass line and the filling line merge at the seat of the changeover valve. In this context, the valve seat is understood to be the point where the bypass line can be closed by the changeover valve.

[0035] Further details and advantages of the invention are explained in more detail with reference to an exemplary embodiment shown in the figures. These show: Fig. 1: a longitudinal section through a prior art aircraft shock absorber, Fig. 2: a longitudinal section through an area relevant to the invention of an aircraft shock absorber according to the invention with the switching valve in the open position, Fig. 3: a longitudinal section through an area relevant to the invention of an aircraft shock absorber according to the invention with the switching valve in the closed position, Fig. 4: An external view of an area relevant to the invention of an aircraft shock absorber according to the invention.

[0036] Fig. Figure 2 schematically shows a longitudinal section through an area relevant to the invention of an aircraft shock absorber according to the invention with the switching valve in the open position. The area shown includes, among other things, a section of the first component 10, a section of the second component 20, two seals 31 and 32, a bypass line 5, a space between the seals 6 and a switching valve 60.

[0037] The second component 20 is designed as a tube with a round cross-section and is arranged concentrically within the first component 10, which is also designed as a tube with a round cross-section. Components 10 and 20 share a common longitudinal axis running vertically (not shown in the drawing). The first component 10 defines or surrounds a liquid-filled chamber 4. The bypass line 5 opens into this liquid-filled chamber 4 at a location not shown in the drawing.

[0038] To seal the contact area between the inner tube 20 and the outer tube 10, the aircraft shock absorber has two sealing rings 31 and 32. The inner sealing ring 32 provides a secondary seal, while the outer sealing ring 31 is the primary seal. A gap 6 extending around the inner circumference of the tube 10 is located between the sealing rings 31 and 32. This gap is in direct contact with the fluid-filled chamber 4 via the bypass line 5.

[0039] The arrangement further comprises a valve housing 50 with a changeover valve 60. The valve includes a valve sleeve 55, a valve spool 63, an anti-rotation device 64, and an actuating pin 61. The valve spool 63 is slidably mounted within the sleeve 55. Part of the bypass line 5 runs within the valve housing 50.

[0040] In Fig. Figure 2 shows the valve in the open position. With the changeover valve open, fluid can flow unhindered from a first section 5b of the bypass line 5 into a second section 5a of the bypass line, and thus unhindered from the fluid-filled chamber 4 into the space 6 between the seals 31 and 32. This position corresponds to the normal operation of the aircraft shock absorber shown.

[0041] Under normal operating conditions, the pressure in the space 6 is the same as in the fluid-filled chamber 4. This results in the same fluid pressure on both sides of the inner seal 32. This seal is pressure-balanced and does not provide a seal between the fluid-filled chamber 4 and the outer surface of the aircraft shock absorber. This sealing function is entirely performed by the outer seal 31, which is pressurized on one side from the space 6.

[0042] The in Fig. The arrangement shown in Figure 2 further includes a filling valve 70, which is also arranged on the valve housing 50. A filling line 75, which can be reversibly closed by this filling valve 70, runs through the valve housing 50, the valve sleeve 55, and the valve spool 63, and opens into the bypass line 5 at the valve seat 65. Starting from the valve seat 65, the first part 5b of the bypass line simultaneously forms a section of the filling line 75.

[0043] The drawing shows the filling valve 70 in its closed position. When the filling valve 70 is opened, liquid can be drawn from chamber 4 or liquid can be poured into chamber 4 via line 75.

[0044] Fig. Figure 3 shows a schematic longitudinal section through the same area of ​​an aircraft shock absorber according to the invention as Fig. 2, however, with the changeover valve in the closed position 60.

[0045] Closing the bypass line 5 in the area of ​​the valve seat 65 interrupts the connection between the fluid-filled chamber 4 and the space 6 between the seals 31 and 32. The chamber 6 and the outer sealing ring 31 are therefore no longer pressurized. The inner sealing ring 32 is thus directly pressurized on one side by the fluid from chamber 4 and is no longer pressure-balanced, as there is no longer any pressure in the space 6. The sealing function is completely taken over by the inner seal 31. This position corresponds to the backup operation of the aircraft shock absorber shown.

[0046] In normal operation ( Fig. 2) The entire pressure acts on the outer sealing ring 31, while the inner sealing ring 32 is pressure-balanced and experiences no wear. Should the outer sealing ring 31 now leak, the valve 60 can be closed ( Fig. 3), whereby the inner replacement seal 32 completely takes over the sealing function until the primary seal 31 can be replaced.

[0047] The related to Fig. The function described in section 2, namely filling and emptying chamber 4 using the filling valve 70 and the filling line 75, is retained even in backup operation. Whether the valve 60 is closed or open, the liquid channel 75 opens into the first part of the bypass line 5b at the valve seat 65 and, when the filling valve is open, provides a passage to the liquid-filled chamber 4.

[0048] Fig. 4 shows an exterior view of the building. Fig. 2 and Fig. Figure 3 shows a longitudinal section of an aircraft shock absorber according to the invention. The valve housing 50 is screwed to the first component 10. The valve sleeve 55 and the valve 60 with actuating pin 61 are embedded in the valve housing 50. The filling valve 70 is also attached to the valve housing 50.

[0049] The changeover valve 60 has a hexagonal head on the actuating pin 61, which can be screwed into the valve sleeve by turning it clockwise. This screwing action allows the valve spool to be moved into a closed position ( Fig. 3) be transferred.

[0050] The actuating pin 61 has a marking 62 in the inlet area into the valve sleeve 55, through which the valve position is visible from the outside.

[0051] The changeover valve 60 also has a head with an external hexagon.

Claims

[1] Aircraft shock absorber (1) with two tubular components (10,20), whereby the first component (10) has a liquid-filled chamber (4) in its interior, and the second component (20) is arranged displaceably along a common longitudinal axis in the first component (10), the shock absorber (1) has two seals (31, 32) arranged in series in the direction of the common longitudinal axis between the outer surface of the second component (20) and the inner surface of the first component (10), and the shock absorber (1) has a bypass line (5, 5a, 5b) which can be closed by a changeover valve (60) and which connects the liquid-filled chamber (4) and the space (6) between the seals (31, 32), characterized by , that the aircraft shock absorber (1) has a filling line (75) and a filling valve (70) independent of the switching valve (60), wherein the filling line (75) can be used regardless of the position of the changeover valve (60), the filling valve (70) can be operated independently of the position of the changeover valve (60), and a first part of the bypass line (5a) simultaneously represents a section of the filling line (75). [2] Aircraft shock absorber (1) according to claim 1, wherein both seals (31, 32) are arranged in the space between the outer surface of the second component (20) and the inner surface of the first component (10) and completely enclose the second component (20). [3] Aircraft shock absorber (1) according to claim 1 or 2, wherein the seals (31, 32) are equivalent and preferably structurally identical seals (31, 32). [4] Aircraft shock absorber (1) according to one of the preceding claims, wherein one of the seals (31, 32) represents an inner seal (32) and one of the seals (31, 32) represents an outer seal (31), and wherein when the bypass line (5, 5a, 5b) is open, the outer seal (31) is pressurized and the inner seal (32) is pressure-equalized. [5] Aircraft shock absorber (1) according to one of claims 1 to 3, wherein one of the seals (31, 32) represents an inner seal (32) and one of the seals (31, 32) represents an outer seal (31), and wherein when the bypass line (5, 5a, 5b) is closed, the inner seal (32) is pressurized and the outer seal (31) is not pressurized. [6] Aircraft shock absorber (1) according to one of the preceding claims, wherein one of the seals (31, 32) represents an inner seal (32) and one of the seals (31, 32) represents an outer seal (31), and wherein the outer seal (31) serves as the primary seal and the inner seal (32) as the backup seal during normal operation of the aircraft shock absorber (1). [7] Aircraft shock absorber (1) according to one of the preceding claims, wherein the bypass line (5, 5a, 5b) and the changeover valve (60) are arranged in or on the first component (10). [8] Aircraft shock absorber (1) according to one of the preceding claims, wherein the filling line (75) and the changeover valve (60) are designed as a structural unit. [9] Aircraft shock absorber (1) according to one of the preceding claims, wherein at least a first section of the bypass line (5a) and at least a first section of the filling line (75) correspond to one another and wherein a second section of the bypass line (5b) and a second section of the filling line (75) run separately from one another.

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