ASSEMBLY, BRIDGING TOOL FOR AN ASSEMBLY AND METHOD OF FORMING AN ASSEMBLY

Abstract

A tool for bridging an outer dynamic seal in a shock absorber to enable fluid leakage to be more readily determined. The tool having an insertion portion including one or more bridging channels, and a body portion that is thicker than the insertion portion. The insertion portion being installable within an annulus of a shock absorber to bridge a first shock absorber seal so as to place a portion of the annulus in fluid communication with an exterior of the hydraulic device via the one or more bridging channels.

Claims

1. An assembly comprising: a hydraulic device comprising an outer cylinder slidably coupled to a sliding piston so as to define an annulus between them where the outer cylinder and sliding piston overlap, the hydraulic device further comprising first and second seals provided within the annulus to define an intermediate portion between them, the second seal being arranged to seal the intermediate portion from the interior of the hydraulic device in a substantially fluid tight manner to confine the hydraulic fluid to the device, the first seal being arranged to seal the intermediate portion from an exterior of the device; and a seal bridging tool comprising: an insertion portion including one or more bridging channels, the insertion portion being located within the annulus in parallel with the first seal to bridge the first seal so as to place the intermediate portion in fluid communication with the exterior of the hydraulic device via the one or more bridging channels; and a body portion having a thickness selected to inhibit the body portion from entirely entering the intermediate portion.

2. The assembly according to claim 1, wherein the bridging tool includes a drain hole formed at least partially through the body portion for receiving fluid egressing from the intermediate portion via the one or more channels.

3. The assembly according to claim 2, wherein the bridging tool includes one or more guide channels arranged to direct fluid from the one or more bridging channels to the drain hole when the bridging tool is oriented in a first orientation.

4. The assembly according to claim 1, wherein the insertion portion has generally parallel inner and outer major surfaces and the one or more guide channels are elongate slots formed into the outer major surface.

5. The assembly according to claim 1, wherein the body portion includes an engagement formation comprising one or more of a protrusion, a recess or a hole, the engagement formation being configured to facilitate removal of the seal bridging tool from the hydraulic device.

6. The assembly according to claim 1, wherein the annulus defining region of the sliding piston is cylindrical in shape and the insertion portion has a generally arcuate cross section of corresponding radius to the radius of the sliding piston.

7. The assembly according to claim 6, wherein a side of the body portion facing the sliding piston has an arcuate cross section of corresponding radius to the radius of the sliding piston.

8. The assembly according to claim 1, wherein the assembly comprises an aircraft assembly.

9. The aircraft assembly according to claim 8, wherein the aircraft assembly comprises an aircraft landing gear assembly.

10. A method of forming an assembly, the method comprising the steps of: providing a hydraulic device comprising an outer cylinder slidably coupled to a sliding piston so as to define an annulus between them where the outer cylinder and sliding piston overlap, the hydraulic device further comprising first and second dynamic seals spaced axially from one another within the annulus to define an intermediate portion between them, the second seal being arranged to seal the intermediate portion from the interior of the hydraulic device in a substantially fluid tight manner to confine the hydraulic fluid to the device, the first seal being arranged to seal the intermediate portion from an exterior of the device; providing a seal bridging tool comprising: an insertion portion including one or more bridging channels, the insertion portion for location within the annulus in parallel with the first seal to bridge the first seal so as to place the intermediate portion in fluid communication with the exterior of the hydraulic device via the one or more bridging channels; and a body portion having a thickness selected to inhibit the body portion from entirely entering the intermediate portion; and introducing the insertion portion of the seal bridging tool into the annulus of the hydraulic device.

11. The method according to claim 10, whereby the step of introducing the insertion portion of the seal bridging tool comprises introducing the insertion portion of the seal bridging tool into the annulus simultaneously with inserting an operational part of the hydraulic device.

12. The method according to claim 10, wherein the operational part of the device comprises the first seal.

13. The method according to claim 10, further comprising fitting the assembly to a vehicle.

14. The method according to claim 12, further comprising removing the tool from the annulus prior to operational service of the vehicle.

15. The method according to claim 10, wherein the assembly comprises an aircraft assembly.

16. The method according to claim 15, wherein the aircraft assembly comprises an aircraft landing gear assembly.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0041] FIG. 1 is a schematic cross sectional view of a known aircraft landing gear assembly;

[0042] FIG. 2 is a schematic cross sectional view of the seal assembly of the landing gear assembly of FIG. 1;

[0043] FIG. 3 is a schematic cross sectional view of the seal assembly of a landing gear assembly of FIG. 1 when fitted with a seal bridging tool according to an embodiment of the invention;

[0044] FIG. 4 is schematic perspective view of the seal bridging tool of FIG. 3;

[0045] FIG. 5 is schematic plan view of the seal bridging tool of FIG. 3;

[0046] FIG. 6 is schematic side view of a seal bridging tool according to a further embodiment;

[0047] FIG. 7 is a schematic perspective view of the seal bridging tool of FIG. 6; and

[0048] FIG. 8 is a schematic plan view of the seal bridging tool of FIG. 6.

SPECIFICATION DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0049] Referring first to FIG. 1, a known aircraft landing gear assembly comprising an oleo-pneumatic shock absorber is shown generally at 10. The shock absorber 10 forms the main strut of the aircraft landing gear.

[0050] The shock absorber comprises an inner housing portion 12, slidably coupled in an outer housing portion 14 via bearings 26. The inner housing portion is known in the art as a slider, sliding tube, inner cylinder, or piston, and the outer housing portion is known as a main fitting, or outer cylinder.

[0051] The sliding piston 12 and main fitting 14 together define an internal cavity or chamber 16 which contains shock absorber fluid. In the illustrated embodiment the chamber 16 contains oil 20 in a lower portion thereof and gas 22 in an upper portion thereof. The oil 20 and gas 22 together make up the shock absorber fluid.

[0052] The region where the sliding piston 12 and main fitting 14 overlap defines an annulus A between adjacent surfaces of the sliding piston 12 and main fitting 14. The annulus A varies in size in accordance with the extension state of the shock absorber 10. The term annulus can mean a ring-like space which has a cylindrical or non-cylindrical cross sectional profile.

[0053] Referring additionally to FIG. 2, an annular ring 18 is housed within the annulus A, adjacent to the open end of the main fitting 14. The annular ring 18 carries seals to confine the shock absorber fluid to the chamber 16.

[0054] A pair of dynamic seals 24 are mounted on the inner cylindrical face 18a of the annular ring 18 and arranged such that one or both of them press against the sliding piston 12 as the shock absorber extends and retracts, inhibiting the passage of shock absorber fluid from the chamber 16 to the outside environment.

[0055] A pair of static seals 28 are mounted on the outer cylindrical face 18b of the annular ring 18 to bear against the corresponding inner face 14b of the main fitting 14.

[0056] The annular ring 18 is locked in place within the annuls A between a shoulder portion 14c of the main fitting 14 and a gland nut 32 which is screwed into engagement with threaded end portion 14d of the main fitting 14.

[0057] In order to prevent dirt and other contaminants from entering the annulus A, an outer environmental seal 34 known in the art as a scraper seal or an extruder seal is provided. The scraper seal 34 is mounted in groove formed in the inner surface of the gland nut 32 between an outer flange 32a and an inner flange 32b so that its position is fixed relative to the cylinder 14.

[0058] The outer flange 32a also prevents larger objects from entering the annulus A through the gap between the outer surface of the sliding piston 12 and the inner surface of the main fitting 14. The outer flange 32a extends so that it is proximal to the outer surface of the piston 12, leaving a very small gap G between the inner edge of the flange 32a and the outer circumference of the sliding piston 12. This gap G may be engineered to accommodate for deflections in the sliding piston 12 during normal use such that during maximum lateral deflection of the sliding piston 12, it does not come into contact with the outer flange 32a.

[0059] The present inventors have identified that if the dynamic seals 24 or the static seals 28 fail then hydraulic fluid can leak and gather within the portion of the annulus A between the seals 24, 28 and scraper seal 34. This portion of the annulus A will be referred to herein as the intermediate portion IA of the annulus A. The leaked fluid can remain within the intermediate portion IA until such time that there is sufficient pressure for the leaked fluid to pass the scraper seal 34 or sealant within the threaded union between the gland nut 32 and main fitting 14. The process of the intermediate portion IA filling can take several months, meaning that detection might not occur until the shock absorber has been assembled into, say, a landing gear assembly, which in turn might have already been fitted to an aircraft assembly, thereby requiring time consuming and costly last minute interventions.

[0060] Referring now to FIGS. 3 to 5, a seal bridging tool according to an embodiment of the invention is shown generally at 40. The tool 40 is arranged to be applied to the landing gear assembly shock absorber of FIGS. 1 and 2 as a non-operational part which is arranged to enable the leakage of hydraulic fluid into the intermediate portion IA to be detected at a relatively early stage.

[0061] The tool 40 has a generally planar insertion portion 42 and a relatively bulbous body portion 44.

[0062] The insertion portion 42 is arranged to be installed within the gap G between the scraper seal 34 and the sliding piston 12. The insertion portion 42 is preferably shaped to conform or match the shape of the gap G, taking into account deflection of the scraper seal 34.

[0063] Guide channels in the form of slots 46 in the insertion portion enable leaked fluid to bypass the scraper seal 34. The slots 46 are long enough to span the seal 34 so that one end of each slot 46 communicates with the exterior of the shock absorber and the other end of each slot 46 communicates with the intermediate portion IA. This arrangement is particularly advantageous when applied to a tool 40 in which the insertion portion 42 is shaped to conform to or match the shape of the gap G, taking into account deflection of the scraper seal 34, because the seal 34 can press against the outer face of the insertion portion to encourage leaked fluid to pass the seal 34 via the guide channels. Likewise, the conforming inner face of the tool 40 can inhibit passage of fluid between the inner face of the tool 40 and the sliding piston 12.

[0064] The body portion 44 aides in handling of the tool and ensures that the tool 40 is not ingested into the shock absorber. The body portion 44 is preferably shaped to conform or match the space between the gland nut 32 and the sliding piston 12. The body portion 44 can protrude axially from the space.

[0065] The body portion 44 preferably incorporates a cross-hole 49, or other coupling formation to simplify disassembly, which can be used to pull the tool 40 out from underneath the scraper 34 and remove it when fluid leakage monitoring is complete and before the landing gear enters service.

[0066] The slots 46 are preferably in communication with guide vanes (not shown) shaped to direct leaked fluid into a drainage hole 48, which can be blind for collection and measurement, or can be open to permit leaking fluid to be identified through egress of the fluid from the tool 40.

[0067] The tool 40 can be red in colour so that it is distinguishable from operational parts of the shock absorber. A tag can also be fitted to the body portion 44 which highlights that the tool 40 should be removed before operational service of the aircraft.

[0068] As will be appreciated, the tool 40 dimensions will depend on specific application, accounting for factors such as the sliding tube 12 outer diameter, scraper squeeze and the size of the gap G between the gland nut 32 and sliding tube 12.

[0069] In the illustrated embodiment the insertion portion 42 can have a thickness TI of 0.75 mm, and length LI which is sufficient to enable each channel 46 to extend either side of the scraper seal 34 when the tool is fitted. The major surfaces of the insertion portion 42 are arcuate with a radius R which corresponds to the radius of the sliding piston 12. The surface of the body portion 44 arranged to face the siding piston 12 is preferably also arcuate of radius R.

[0070] The width WB of the body portion 44 can be such that the body portion 44 can extend into and be housed within a castellation of the gland nut 32. The width WB can match the internal width dimension of a castellation. This can ensure that the tool 40 maintains its intended location during torqueing of the gland nut 32, exploiting the fact that a torqueing tool uses only six of the twelve available castellations. Alternatively, as illustrated in FIGS. 6 to 8, a castellation engagement portion 50 of the body 44 of width WB can be arranged to protrude with a maximum thickness Tmax that enters the castellation while the remainder of the body has a relatively thin profile of thickness Tmin that fits within the radial space, shown as RS in FIG. 2, between the gland nut 32 and the slider 12. The relatively thin portion of the body 44 includes the guide vanes 45 that direct leaked fluid from the channels 46 in the insertion portion 42 to the drainage hole 48. The relatively thick portion 50 includes the cross hole 49.

[0071] In other embodiments, the tool can have any suitable shape and configuration which includes an insertion portion including one or more bridging channels, the insertion portion being located within the annulus in parallel with an outer seal to bridge the outer seal so as to place the intermediate portion in fluid communication with the exterior of the hydraulic device via the one or more bridging channels and a body portion which is a relatively thick in comparison to the insertion portion to inhibit the body portion entering the intermediate portion.

[0072] The tool 40 can be manufactured from a material which will not cause damage to the mating surfaces of the hydraulic device and which will be of sufficient strength so that it maintains its structure when being fitted and removed; for example, a hard plastics material.

[0073] In use, the tool 40, 40 is preferably installed within the gap G between the scraper seal 34 and the sliding piston 12 at the production assembly stage, where the gland nut 32 and scraper seal 34 are screwed onto the main fitting 14. This can reduce the likelihood of damage to the scraper seal 34. It can then be maintained in position until such time that the landing gear would enter flight testing.

[0074] Alternatively, the tool 40, 40 can be inserted into the gap G once the gland nut 32 has been screwed into the main fitting 14. The tip 43 of the tool 42 can have smooth, rounded edges to reduce the likelihood of the tool 42 damaging the scraper seal 34 during installation.

[0075] Thereafter, leaked hydraulic fluid which passes the scraper seal 32 via the channels 46 is guided into the drainage hole 48, allowing for collection and facilitating monitoring by volume of fluid lost.

[0076] The tool 40, 40 is removed from gap G when fluid leakage monitoring is complete and before the landing gear enters service.

[0077] While the foregoing description has focussed on an aircraft landing gear assembly, it will be appreciated that the tool according to embodiments of the invention can usefully be applied to various assemblies, such as vehicle assemblies which require a hydraulic shock absorber or actuator.

[0078] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be capable of designing many alternative embodiments without departing from the scope of the invention as defined by the appended claims. In the claims, any reference signs placed in parenthesis shall not be construed as limiting the claims. The word comprising does not exclude the presence of elements or steps other than those listed in any claim or the specification as a whole. The singular reference of an element does not exclude the plural reference of such elements and vice-versa. Parts of the invention may be implemented by means of hardware comprising several distinct elements. In a device claim enumerating several parts, several of these parts may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.