U.S. patent application number 15/275811 was filed with the patent office on 2017-12-14 for assembly, bridging tool for an assembly and method of forming an assembly.
The applicant listed for this patent is Safran Landing Systems UK Limited. Invention is credited to Daniel Charles Kendrick, Andraz Vatovec.
Application Number | 20170356519 15/275811 |
Document ID | / |
Family ID | 54249329 |
Filed Date | 2017-12-14 |
United States Patent
Application |
20170356519 |
Kind Code |
A9 |
Kendrick; Daniel Charles ;
et al. |
December 14, 2017 |
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.
Inventors: |
Kendrick; Daniel Charles;
(Gloucester, GB) ; Vatovec; Andraz; (Gloucester,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Safran Landing Systems UK Limited |
Gloucester |
|
GB |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20170089418 A1 |
March 30, 2017 |
|
|
Family ID: |
54249329 |
Appl. No.: |
15/275811 |
Filed: |
September 26, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16F 9/3620130101; B64F
5/50 20170101; B64F 5/60 20170101; B64C 25/60 20130101; F16F
2230/24 20130101; F16F 9/3264 20130101; F16F 9/185 20130101; F16F
9/062 20130101 |
International
Class: |
F16F 9/32 20060101
F16F009/32; B64C 25/60 20060101 B64C025/60; F16F 9/18 20060101
F16F009/18; F16F 9/36 20060101 F16F009/36 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2015 |
EP |
15187104.3 |
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
[0001] This application claims the benefit of and priority to
European Application 15187104.3, filed Sep. 28, 2015, the contents
of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] It is common for an assembly such as aircraft landing gear
or car suspension system to include a piston and cylinder type
hydraulic device such as a shock absorber or actuator.
[0003] A piston and cylinder hydraulic device can be provided with
an internal seal arranged to confine hydraulic fluid to the device.
However, hydraulic fluid can leak beyond the seal if the seal is
not capable of withstanding the pressure of the hydraulic fluid;
for example, if the seal is damaged during assembly of the
hydraulic device.
[0004] Such leakage can remain undetected until after the shock
absorber has been fitted to the assembly and in some cases until
the assembly has been fitted to a larger assembly such as an
aircraft or other vehicle. This can result in significant cost and
delay, particularly in the case of an aircraft landing gear
assembly.
SUMMARY OF THE INVENTION
[0005] According to a first aspect of the present invention, there
is provided an assembly comprising: [0006] 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, and first and second 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 the exterior of the device; and
[0007] a seal bridging tool comprising: [0008] 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 [0009] a body portion which
is relatively thick in comparison to the thickness of the insertion
portion to inhibit the body portion entering the intermediate
portion.
[0010] Thus, a bridging tool is applied to the hydraulic device for
bridging an outer seal to enable any fluid which leaks past an
inner seal within the hydraulic device to pass beyond the outer
seal such that the leakage be more readily determined from the
exterior of the hydraulic device. The bridging tool is not an
operational part of the hydraulic device or assembly to which the
hydraulic device is applied. Rather, the tool is intended to be
removed before the assembly enters into operational service. The
tool can assist an engineer in determining that an inner seal, such
as a static or dynamic seal, within the hydraulic device has failed
to withstand internal fluid pressure. The tool can therefore reduce
the likelihood of a hydraulic device with a damaged or otherwise
unsuitable inner seal being fitted to an assembly such as an
aircraft or aircraft landing gear assembly.
[0011] The first seal can comprise an environmental seal; for
example, a scraper seal. An environmental seal is generally not
intended to provide a substantially fluid tight seal to inhibit the
passage of shock absorber fluid; however, this can occur.
[0012] The first and/or second seal can each comprise one or more
dynamic or a static seals.
[0013] The tool can be of unitary construction.
[0014] The one or more guide channels can be elongate slots formed
between generally parallel inner and outer major faces of the
insertion portion, the inner face being arranged in use to face the
sliding piston. The channels are formed into the outer face, in
some cases extending through the thickness of the insertion portion
to the inner face.
[0015] Thus, the seal can press against the outer face of the
insertion portion to encourage leaked fluid to pass the seal via
the guide channels.
[0016] The bridging tool can include a drain hole formed at least
partially through the body portion for receiving fluid regressing
from the intermediate portion via the one or more channels. The
hole can be blind, so as to define a reservoir for collecting
leaked fluid.
[0017] This can aid an engineer in locating leaked fluid.
[0018] The bridging tool can include 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 orientated in a first
orientation.
[0019] This can increase the likelihood of leaked fluid being
directed to the hole.
[0020] The body portion can includes an engagement formation such
as a protrusion, recess or hole which is arranged to facilitate
removal of the engagement tool from the hydraulic device.
[0021] The annulus-defining region of the sliding piston can be
cylindrical in shape and the insertion portion can have a generally
arcuate cross section of corresponding radius to the radius of the
sliding piston. The side of the body which faces the sliding piston
can have an arcuate cross section of corresponding radius to the
radius of the sliding piston.
[0022] This can reduce the likelihood of leaked fluid escaping
between the sliding piston and/or first seal on the one hand, and
the tool on the other hand, which can increase the likelihood of
leaked fluid passing the first seal via the guide channels of the
tool.
[0023] The assembly can comprises an aircraft assembly, such as an
aircraft landing gear assembly.
[0024] The invention is particularly useful when applied to an
aircraft assembly because later stage intervention can be
particularly costly and time consuming, especially in the case of
an aircraft landing gear, which might require the aircraft being
jacked up to permit disassembly, inspection and potentially
replacement.
[0025] According to a second aspect of the present invention, there
is provided a seal bridging tool arranged to be inserted into an
annulus of a hydraulic device to form an assembly, the 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 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 the
exterior of the device, [0026] the bridging tool comprising: [0027]
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
[0028] a body portion which is relatively thick in comparison to
the insertion portion to inhibit the body portion entering the
intermediate portion.
[0029] Optional features of the first aspect can be applied to the
tool of the second aspect in an analogous manner.
[0030] According to a third aspect of the present invention, there
is provided a method of forming an assembly, the method comprising
the steps of: [0031] 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; [0032] introducing the insertion portion of a seal
bridging tool according to the second aspect into the annulus of
the hydraulic device.
[0033] The step of introducing a seal bridging tool can comprise
introducing a seal bridging tool into the annulus in conjunction
with the an operational part of the hydraulic device comprising the
first dynamic seal; for example, a gland nut.
[0034] This can reduce the likelihood of introduction of the tool
causing damage to the first seal.
[0035] The method can further comprise a step of fitting the
assembly to a vehicle, such as an aircraft.
[0036] The method can further comprise a step of removing the tool
from the annuals prior to operational service of the vehicle.
[0037] The assembly can comprise an aircraft assembly such as an
aircraft landing gear assembly and the vehicle is an aircraft.
[0038] Optional features of the first aspect can be applied to the
hydraulic device and/or tool of the third aspect in an analogous
manner.
[0039] These and other aspects of the present invention will become
apparent from, and clarified with reference to, the embodiments
described herein.
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.
* * * * *