Note: Descriptions are shown in the official language in which they were submitted.
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Aircraft Landing Gear With Vibration Damper
FIELD OF THE INVENTION:
The invention relates to an aircraft landing gear having a
landing gear housing and a connecting rod accommodated therein,
with a first and a second steering arm, the first steering arm
of which being indirectly or directly connected with the landing
gear housing and the second steering arm being connected
indirectly or directly with the connecting rod, and with a
vibration damper which has a housing and a damping element, the
damping element being movably arranged in a fluid-filled area,
preferably an oil-filled area, of the vibration damper, in such a
way that the movement of the damping element is damped by the
fluid and wherein the first or the second steering arm is
directly or indirectly connected with the housing and the other
steering arm is indirectly or directly connected with the
damping element, and with a fluid reservoir, preferably an oil
reservoir, which is connected with the fluid-filled area.
BACKGROUND OF THE INVENTION:
An aircraft landing gear of this type is known, for example,
from US 5,224,668. The object of the vibration damper is to
dampen vibrations or oscillations occurring in the landing gear
during rolling, starting and landing, in particular during the
braking process.
In the aircraft landing gear known from US 5,224,668, the
housing of the damper is securely connected (screwed) with a
steering arm of the aircraft landing gear, whereas the shaft
having a damping element is connected with the other steering arm
via a bearing. Since one steering arm is connected with the
landing gear housing and one steering arm with the connecting
rod/wheel axle, a vibrating motion of the connecting rod/wheel
unit about the connecting rod axis on the damper produces a
linear movement between shaft or damping element and the damper
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housing. In the previously known solution, the piston serving as
damping element divides an oil chamber in the damper housing into
two chambers which are interconnected via one or more choke bores.
Oil between these chambers is displaced via the choke(s) by a
linear movement of the piston. This oil movement thereby absorbs
the vibrating motion of the connecting rod assembly. To prevent
cavitation and equalize temperature fluctuations or leakages, an
oil reservoir supplies the respective low-pressure chamber of the
oil reservoir with oil via check valves. In the solution disclosed
in US 5,224,668, the oil reservoir sits, in the form of a separate
container, on top of the vibration damper and is attached there
in such a way that it is in fluid connection with the
chambers of the oil reservoir.
A disadvantage of this previously known solution is that the oil
reservoir is exposed to damage or even separation of the damper
due to impacting parts, for example, by broken stones, birds or
rubber parts of burst tires. A further disadvantage is found in that
hydraulic and/or electric lines must be led over additional steering
arms, so-called slave links, instead of over steering arms due to
the complex design of the vibration damper.
SUMMARY OF THE INVENTION:
The object of the present invention is to further develop an
aircraft landing gear of the aforementioned type in such a way
that the probability of damage or even separation of the oil
reservoir is reduced and thus the reliability of the vibration
damper increased.
According to an aspect of the present invention, there is provided
an aircraft landing gear with a landing gear housing and a
connecting rod accommodated therein, having a first and a
second steering arm, the first steering arm of which being
directly or indirectly connected with the landing gear housing
and the second steering arm directly or indirectly with the
connecting rod, and with a vibration damper which has a
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housing and a damping element, the damping element being
movable in a fluid-filled area of the vibration damper in such
a way that movement of the damping element is damped by the
fluid, and the first or the second steering arm being
indirectly or directly connected with the housing and the
other steering arm directly or indirectly connected with the
damping element, and with a fluid reservoir which is connected
with the fluid-filled area, wherein the fluid reservoir is
integrated in the housing of the vibration damper, and wherein
the fluid reservoir and the damping element are arranged in a
linear arrangement. Proceeding from an aircraft landing gear
having the features of the preamble of claim 1, this object is solved
in that the fluid reservoir is integrated in the housing of the
vibration damper.
According to another aspect of the present invention, there is
provided an aircraft landing gear with a landing gear housing
and a connecting rod accommodated therein, having a first and
a second steering arm, the first steering arm of which being
directly or indirectly connected with the landing gear housing
and the second steering arm directly or indirectly with the
connecting rod, and with a vibration damper which has a
housing and a damping element, the damping element being
movable in a fluid-filled area of the vibration damper in such
a way that movement of the damping element is damped by the
fluid, and the first or the second steering arm being
indirectly or directly connected with the housing and the
other steering arm directly or indirectly connected with the
damping element, and with a fluid reservoir which is connected
with the fluid-filled area, wherein the fluid reservoir is
integrated in the housing of the vibration damper, and wherein
the fluid reservoir and the damping element are arranged in a
linear arrangement, wherein a shaft is provided with which one
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of the steering arms is connected, the shaft comprising a
hollow connected to the fluid reservoir.
According to another aspect of the present invention, there is
provided an aircraft landing gear with a landing gear housing
and a connecting rod accommodated therein, having a first and
a second steering arm, the first steering arm of which being
directly or indirectly connected with the landing gear housing
and the second steering arm directly or indirectly with the
connecting rod, and with a vibration damper which has a
housing and a damping element, the damping element being
movable in a fluid-filled area of the vibration damper in such
a way that movement of the damping element is damped by the
fluid, and the first or the second steering arm being
indirectly or directly connected with the housing and the
other steering arm directly or indirectly connected with the
damping element, and with a fluid reservoir which is connected
with the fluid-filled area, wherein the fluid reservoir is
integrated in the housing of the vibration damper, and wherein
the fluid reservoir and the damping element are arranged in a
linear arrangement, wherein a shaft is provided with which one
of the steering arms is connected, the shaft comprising a
hollow connected with the fluid-filled area.
Preferably, the fluid reservoir is integrated in the housing
cover. As a result, a very compact construction of the damper is
produced and the reservoir is protected against damage or
separation due to broken stones, birds, tire parts which have
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split off or other parts flying about.
Furthermore, this
compact construction enables hydraulic and/or electric lines,
for example, the brake supply, to be led over the vibration
damper so that, in a preferred embodiment of the invention,
slave links can be omitted.
Accordingly, in a preferred
embodiment of the invention, it is provided that hydraulic
and/or electric lines are led via the vibration damper. For
this purpose, corresponding guides or carriers can be provided.
In a further embodiment of the invention, a shaft is provided
with which one of the steering arms is connected. Preferably,
the shaft serves as a steering arm bolt on which the steering
arm is pivotally mounted.
The damping element can be configured as a piston which is
movable in the fluid-filled reservoir.
In a further embodiment of the invention, it is provided that
the damping element or piston is connected with the shaft or is
a component of the shaft. It is especially advantageous if the
shaft is designed as a hollow shaft and if the hollow of the
shaft is connected with the fluid reservoir.
Thus, the
reservoir can be filled via the hollow of the shaft which can
have a fill-up valve in its end region.
Furthermore, it is especially advantageous if the hollow of the
shaft is connected with the fluid-filled area.
In a preferred embodiment of the invention, the hollow of the
shaft can be connected both with the fluid-filled area in which
the damping element is situated and with the fluid reservoir.
Thus, in this embodiment of the invention, the hydraulic
connection between the fluid-filled area and the fluid reservoir
is led via the shaft or its hollow.
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Furthermore, it can be provided that the piston or shaft divides
the fluid-filled area into two or more chambers which are
connected to one another by one or more choke bores. The choke
bores cause the fluid, in particular the oil, to undergo a
resistance when passing through the bores, as a result of which
the movement of the damping element or the piston is damped
relative to the housing of the vibration damper.
It can thereby be provided that the hollow of the shaft is
fluid-connected with at least one of the chambers, preferably
with both chambers. It is especially advantageous if check
valves are placed in the connecting lines between the hollow of
the shaft and the chambers. With a check valve (anticavitation
valve) each of this type per damping chamber, it is attained
that short and symmetrically equally arranged connecting paths
are present between fluid reservoir and the two damping
chambers. The affect of line losses on the cavitation behaviour
is thereby reduced.
Furthermore, it can be provided that a wall of the fluid
reservoir is formed by a movable, spring-loaded piston which
exerts pressure on the fluid present in the reservoir. The
piston is pushed by one or more springs against the reservoir
and thereby produces a prestress pressure in the fluid.
Furthermore, it can be provided that a viewing window is
situated in the housing of the vibration damper, the piston
being arranged relative to the viewing window in such a manner
that the position of the piston can be seen through the viewing
window. As a result, the fill levels of the reservoir can be
read from the outside with reference to the position of the
piston. In a preferred embodiment of the invention, a glass
ring clamped between two sealing rings protects the reservoir
piston, sealing rings and springs against contamination. In a
further embodiment of the invention, it is provided that an
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overflow bore is provided in a wall of the fluid reservoir, said
overflow bore being separated, in a first piston position, from the
reservoir by a piston seal and, in a second piston position, is
connected with the fluid reservoir when there is excess fluid.
This bore allows e.g. oil to flow out of the reservoir when
there is too much oil in the damper and, as a result, the piston
seal "passes over" the overflow bore, i.e. releases it, so that
oil can flow out of the reservoir.
BRIEF DESCRIPTION OF THE DRAWINGS:
Further details and advantages of the invention are described in
greater detail with reference to an example of an embodiment
illustrated in the drawings, showing:
Figure 1: a side view of an aircraft landing gear according to
the prior art,
Figure 2: a perspective representation of the vibration damper
according to the invention with steering arms arranged
thereon,
Figure 3: a side view of an aircraft landing gear according to
the invention,
Figure 4: a perspective view of the vibration damper according
to the invention,
Figure 5: a view according to Figure 4 in an enlarged
representation, and
Figure 6: a longitudinal section through the vibration damper
according to the invention.
DETAILED DESCRIPTION OF THE DRAWINGS:
Figure 1 shows an aircraft landing gear according to the prior art
in a schematic side view. The landing gear consists of the
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landing gear housing 10 in which the connecting rod 20 is
accommodated. The steering arm 30 is in a swivel connection
with the landing gear housing 10 and steering arm 40 is in a
swivel connection with the connecting rod 20. Both steering
arms 30, 40 are connected with the vibration damper 13 on whose
upper side the oil reservoir 11 is located. The housing of the
damper 13 is securely connected (screwed) with the upper
steering arm 30, while the shaft of the damper 13 is connected
with the lower steering arm 40 via a bearing. A vibrating
motion of the connecting rod/wheel unit about the connecting rod
axis produces a linear movement between shaft and damper housing
on the damper 13. In the manner known from US 5,224,668, the
shaft divides the oil reservoir of the damper 13 into two
chambers in the damper housing, said chambers being connected
with one another via the choke bores. The aforementioned linear
movement between shaft and housing of the damper 13 causes the
oil to be displaced between the chambers via the choke. This
oil movement dampens the vibrating motion of the connecting rod
assembly. The oil reservoir 13 supplies the respective low-
pressure chamber via check valves, in particular to prevent
leakages and cavitation and to equalize fluctuations in
temperature.
As can be seen in Figure 1, the oil reservoir 11 is situated in
an exposed position and is therefore exposed to damages which
could lead to a destruction of the oil damper 11 and result
therein that the damping properties of the damper 13 are lost.
It can also be seen in Figure 1 that so-called slave links 12
are connected with the landing gear housing 10 and the
connecting rod 20, said slave links 12 being swivel-mounted on
the landing gear housing 10 and on the connecting rod 20 and
also pivotally interconnected. The slave links 12 serve to
guide lines, for example, of electric or hydraulic lines, as
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required e.g. for the brake supply of the wheel shown in Figure
1.
Figure 2 shows a perspective view of the vibration damper 50
according to the invention with the steering arms 30, 40
arranged thereon. The vibration damper 50 has a housing 51 with
which the upper steering arm 30 is screwed together.
Furthermore, the damper 50 has a shaft 60 (see Figs. 5, 6) on
which the lower steering arm 40 is swivel-mounted by means of a
bearing. The shaft 60 has a piston which is housed so as to be
axially movable in an oil reservoir formed in the housing 51 and
the movement of which results in the displacement of the oil, as
a result of which a damping effect is obtained.
Contrary to the arrangement according to Figure 1, the oil
reservoir is not configured as a container placed on the
vibration damper 50, but is integrated in the housing cover 51',
as will be described in greater detail below. The air vents 59
are located on the upper side of the vibration damper 50. By
integrating the oil reservoir in the housing 51 of the vibration
damper 50, a very compact construction is produced which makes
it possible to lead hydraulic and/or electric lines, in
particular the brake supply, via the vibration damper, for which
purpose the conducting line 58, shown in Figure 2, is provided.
In a preferred embodiment of the invention, the slave links 12
shown in Figure 1 can thus be omitted.
The upper steering arm 30 according to Figure 2 is swivel-
mounted on the landing gear housing 10 and the lower steering
arm 40 is swivel-mounted on the connecting rod 20.
The upper steering arm 30 does not have to be situated directly
on the landing gear housing 10 and the lower steering arm 40 not
directly on the connecting rod 20. Rather, the invention also
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provides for an indirect arrangement, such that, for example,
the upper steering arm 30 is swivel-mounted on a component
arranged on the landing gear housing 10 and, for example, the
lower steering arm 40 is connected with the wheel axle.
Figure 3 shows a side view of the aircraft landing gear with the
main landing gear strut with landing gear housing 10 and
connecting rod 20 which is housed in the landing gear housing 10
so as to be axially movable. The upper steering arm 30 is
swivel-mounted on the landing gear housing 10 and the lower
steering arm 40 is swivel-mounted on the connecting rod 20. In
their respectively other end region, both steering arms 30, 40
are connected with the vibration damper 50. A perspective view
of the vibration damper 50 according to Figure 3 is shown in
Figure 4.
Figure 5 shows an enlarged representation of this vibration
damper 50. The vibration damper 50 consists essentialy of the
damper housing 51 with housing cover 51' in which the oil
reservoir is accommodated. The shaft 60, in whose end region
the fill-up valve 62 is located, extends from the damper housing
51. The fill-up valve 62 serves to fill the oil reservoir via
the shaft 60 configured as a hollow shaft.
The first (upper) steering arm 30 and the second (lower)
steering arm 40 are placed on the shaft 60. The first steering
arm 30 is screwed together with the housing 51, as can be seen
for example in Fig. 2, whereas the second steering arm 40 is
swivel-mounted on the shaft 60 via a bearing.
As can also be seen in Figure 5, the viewing window 56 through
which the fill level of the oil reservoir can be read is located
in the housing cover 51'.
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The detailed design of the vibration damper 50 according to the
invention can be found in Figure 6. As noted above, the shaft
60 extends out of the housing 51 of the vibration damper 50,
said shaft being configured as a hollow shaft and having the
hollow 61. The shaft 60 is closed in its end region by the
fill-up valve 62. The oil reservoir 54 which is connected with
the hollow 61 of the shaft 60 and can, accordingly, be filled
via the fill-up valve 62 is located in the housing 51 or under
the housing cover 51'. A wall of the oil reservoir 54 is formed
by the piston 55 which is accommodated in the housing 51 or
housing cover 51' so as to be axially movable. The latter is
loaded by two springs which are supported on the housing cover
51' and exert a force on the piston 55 in direction of the oil
reservoir 54, according to Fig. 6, a force which is exerted
toward the right. As can be seen in Figure 6, the hollow 61 of
the shaft 60 is connected with the oil reservoir 54 via two
intersecting bores. The viewing window 56 through which the
position of the piston 55 can be seen is located on the upper
side of the housing cover 51', so that the fill level of the oil
reservoir 54 can be read. The glass ring forming the viewing
window 56, which is situated on the inside and is clamped
between two sealing rings, protects the sealing rings of the
reservoir piston 55, the piston itself and also the springs
against contamination.
As can also be seen in Figure 6, the overflow bore 57 which is
separated from the oil reservoir 54 by the piston seal 55'
during normal operating conditions is situated in the wall of
the housing 51 or the housing cover 51'. If there is too much
oil in the oil-filled area of the vibration damper 50, the
reservoir piston 55 is in a position which is shifted toward the
left vis-à-vis Figure 6, so that a connection between oil
reservoir 54 and overflow bore 57 is opened and oil can flow off
accordingly until the piston seal 55' blocks a connection
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between oil reservoir 54 and overflow bore 57. The piston seal
55' is configured as a seal that extends peripherally and seals
the oil reservoir 54.
As can also be seen in Figure 6, the shaft 60 is widened in the
area of the oil area 53, as a result of which a rotating piston
52 is formed which is moved back and forth in the oil area 53
according to the vibrations that occur. A design with several
pistons is also feasible. The piston-shaped section 52 of the
shaft 60 adjoins the corresponding wall of the housing 51 via
seals. The piston 52 divides the oil area 53 into chambers
which are connected to one another by choke bores provided in
the piston 52. When the piston moves in the oil area 53, oil is
moved through the choke bores located in the piston 52 due to
the enlargement or reduction of the chambers and, as a result,
a damping is produced. As can also be seen in Figure 6, springs
are provided which move the shaft 60 or the piston 52 attached
to it in one piece are moved into the centred neutral position.
Each of the chambers is connected with the hollow 61 of the
shaft 60 and thus also with the oil reservoir 54 via a
connecting line 80, 81.
Check valves are provided in the
connecting lines 80, 81, the respective low-pressure chamber
being supplied with oil from the oil reservoir 54 via said check
valves to prevent cavitation, compensate leakages and prevent
fluctuations in temperature. The connecting line 80 connects
the oil reservoir 54 with the chamber shown on the right in Fig.
6 and the connecting line 81 connects the oil reservoir 54 with
the chamber shown on the left in Fig. 6.
At least one
anticavitation valve (check valve) each per damping chamber is
arranged in the shaft 60. This produces short and symmetrically
similar connecting paths between reservoir 54 and the two
chambers. As a result, the affect of line losses on the
cavitation behaviour is reduced.
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As can be seen in Figure 6, on the whole, a very compact
arrangement is produced which makes it possible to lead
hydraulic or electric lines, e.g. the brake supply, via the
vibration damper 50, as shown for example in Figure 3. The
corresponding line 58 is shown in Figure 2.
Due to the arrangement of the oil reservoir 54 in the housing 51
or in the housing cover 51', one obtains not only a compact
construction but the danger of damages or even the separation of
the oil reservoir from the damper is greatly reduced in
comparison to the solution known from the prior art.
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