U.S. patent application number 14/645467 was filed with the patent office on 2016-08-18 for combination spherical and laminated bearing.
The applicant listed for this patent is Aktiebolaget SKF. Invention is credited to Anthony Carl Bohm.
Application Number | 20160238068 14/645467 |
Document ID | / |
Family ID | 55450980 |
Filed Date | 2016-08-18 |
United States Patent
Application |
20160238068 |
Kind Code |
A1 |
Bohm; Anthony Carl |
August 18, 2016 |
COMBINATION SPHERICAL AND LAMINATED BEARING
Abstract
A bearing includes a laminated bearing portion and a spherical
bearing portion, and the spherical bearing portion is disposed
within the laminated bearing portion or the laminated bearing
portion is disposed within the spherical bearing portion. The
spherical bearing portion includes a ball disposed on a spherical
race, and the ball and the outer race are configured such that a
given break-out force is required to move the ball relative to the
outer race.
Inventors: |
Bohm; Anthony Carl;
(Chicago, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Aktiebolaget SKF |
Goteborg |
|
SE |
|
|
Family ID: |
55450980 |
Appl. No.: |
14/645467 |
Filed: |
March 12, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62115437 |
Feb 12, 2015 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16F 1/40 20130101; F16C
23/045 20130101; F16C 2326/43 20130101; F16C 27/063 20130101; F16C
11/0614 20130101 |
International
Class: |
F16C 21/00 20060101
F16C021/00; F16C 27/06 20060101 F16C027/06; F16C 23/08 20060101
F16C023/08; F16C 23/04 20060101 F16C023/04 |
Claims
1. A bearing comprising: a laminated bearing portion; and a
spherical bearing portion, wherein the spherical bearing portion is
disposed within the laminated bearing portion or the laminated
bearing portion is disposed within the spherical bearing
portion.
2. The bearing as recited in claim 1 wherein the spherical bearing
portion comprises a generally annular outer race having a concave
inner circumferential surface, the inner surface being partially
spherical; and a ball disposed on the outer race and having a
convex, partially spherical, outer surface in contact with the
inner circumferential surface of the outer race, wherein the ball
and the outer race are configured such that a given break-out force
is required to move the ball relative to the outer race.
3. The bearing as recited in claim 2 wherein either: the laminated
bearing portion has a central bore and the spherical bearing
portion is disposed within the central bore of the laminated
bearing portion; or the spherical bearing portion has a central
bore and the laminated bearing portion is disposed within the
central bore of the spherical bearing portion.
4. The bearing as recited in claim 3 wherein the spherical bearing
portion is disposed in the central bore of the laminated bearing
portion and wherein the ball has a generally axially extending
central bore configured to receive a shaft portion.
5. The bearing as recited in claim 3, wherein the laminated bearing
portion is disposed in the central bore of the spherical bearing
portion and wherein the laminated bearing portion has a generally
axially extending central bore configured to receive a shaft
portion.
6. The bearing as recited in claim 3 wherein the laminated bearing
portion includes a plurality of alternating, generally tubular
elastomeric laminae and metallic laminae nested coaxially about a
central axis.
7. The bearing as recited in claim 6 wherein each of the plurality
of elastomeric and metallic laminae have opposing axial ends and an
axial length between the opposing ends, the plurality of
elastomeric and metallic laminae being arranged such that the axial
length of each one of the elastomeric and metallic laminae is
greater than the axial length of all elastomeric and metallic
laminae disposed radially within the each one of the laminae.
8. The bearing as recited in claim 7 wherein each one of the
elastomeric and metallic laminae is partially spherical.
9. The bearing as recited in claim 2 further comprising an outer
housing having a central opening, the laminated and spherical
bearing portions being disposed within the central opening of the
outer housing.
10. The bearing as recited in claim 2, wherein the laminated
bearing is configured to absorb forces ranging from a first,
non-zero level to a second level and wherein the given break-out
force is between the first level and the second level.
11. The bearing as recited in claim 10, wherein the second level is
about 75% of the elastic limit of the laminated bearing.
12. The bearing as recited in claim 10, wherein the second level is
about 50% of the elastic limit of the laminated bearing.
13. The bearing as recited in claim 10, wherein the second level is
about 25% of the elastic limit of the laminated bearing.
14. The bearing as recited in claim 10, wherein the second level is
from about 5% to 50% of the elastic limit of the laminated
bearing.
15. The bearing as recited in claim 2, wherein the laminated
bearing has a lifespan inversely related to the level of force
applied to the laminated bearing, and wherein the breakout force is
selected based on a desired lifespan of the laminated bearing.
16. The bearing as recited in claim 2, wherein the bearing has a
central bore formed in the laminated bearing portion or in the
spherical bearing portion and wherein the bearing has an outer
surface formed on the laminated bearing portion or on the spherical
bearing portion and wherein the laminated bearing is configured to
repeatedly elastically accommodate relative movement between the
bearing central bore and the bearing outer surface of up to a first
magnitude and repeatedly slidably accommodate relative movement
between the bearing central bore and the bearing outer housing of a
second magnitude greater than the first magnitude.
17. A method of operating a bearing comprising a laminated bearing
portion and a spherical bearing portion, the spherical bearing
portion being disposed within the laminated bearing portion or the
laminated bearing portion being disposed within the spherical
bearing portion, the spherical bearing portion comprising a
generally annular outer race having a concave inner circumferential
surface, the inner surface being partially spherical and defining a
central opening, and a ball disposed within the outer race central
opening and having a convex, partially spherical, outer surface in
contact with the inner surface of the outer race portion, the ball
and outer race being configured such that the ball is locked in the
outer race and such that a given break-out force is required to
move the ball relative to the outer race, the method comprising:
repeatedly applying first forces to the bearing to deform the
laminated bearing portion without exceeding the given break-out
force of the spherical bearing.
18. The method as recited in claim 17, including repeatedly
applying second forces to the bearing, the second forces exceeding
the given break-out force and causing the ball to move relative to
the outer race.
19. A bearing comprising: an inner bore, an outer housing, and
means between the inner bore and outer housing for repeatedly
elastically accommodating relative movement between the inner bore
and the outer housing of up to a first magnitude and for repeatedly
slidably accommodating relative movement between the inner bore and
the outer housing of a second magnitude greater than the first
magnitude.
20. The bearing as recited in claim 19, wherein the means comprise
a laminated bearing portion and a spherical bearing portion, and
wherein either the spherical bearing portion is disposed within the
laminated bearing and the inner bore is located in the spherical
bearing portion; or the laminated bearing portion is disposed
within the spherical bearing portion and the inner bore is located
in the laminated bearing portion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of U.S.
Provisional Patent Application No. 62/115,437 filed Feb. 12, 2015,
the entire contents of which are hereby incorporated by
reference.
TECHNOLOGICAL FIELD
[0002] The present disclosure is directed to a bearing having a
first portion configured to respond to frequent but small relative
movements between inner and outer portions of the bearing and a
second portion configured to respond to large, infrequent, relative
movements between the inner and outer portions, and, more
specifically, to a bearing having an laminated bearing portion
configured to respond to frequent but small relative movements
between inner and outer portions of the bearing and a spherical
bearing portion configured to respond to larger, infrequent,
relative movements between the inner and outer portions.
BACKGROUND
[0003] Laminated bearings may be used to accommodate relative
movement between inner and outer components, which movement may
occur along and/or about any one of three mutually perpendicular
axes. Such bearings generally comprise a plurality of alternating,
generally tubular elastomeric laminae and metallic laminae nested
coaxially about a central axis. One common application of such
bearings is at the ends of the pitch arms of rotary wing aircraft,
which pitch arms connected between a rotary swash plate and a pitch
horn of a blade grip that secures one of the blades. However, such
bearings are used in other environments as well.
[0004] The degree of movement allowed by a laminated bearing is
determined in part by the number of elastomeric lamellae used as
well as their properties. For example, each of the elastomeric
lamellae is formed from an elastomeric material having an elastic
limit. Each lamina can therefor be subjected to forces of up to a
predetermined amount and still return elastically to its original
shape and size. Forces greater than the elastic limit of the lamina
will permanently deform the lamina. The plurality of the lamella in
the laminated bearing thus allow the bearing to withstand a given
level of strain without being permanently deformed. The entire
bearing may therefore be described as having its own elastic limit,
that is, a maximum force or strain to which the bearing can be
subjected without permanently damaging the bearing.
[0005] While a laminated bearing can be subjected to forces or
strains that approach its elastic limit without causing permanent
damage, the amount of strain applied to the bearing will affect its
usable life. It is therefore generally desirable to limit the
forces to which a laminated bearing is subjected to some fraction
of the elastic limit of that bearing. In general, the lower the
maximum strain levels to which a bearing is subjected, the longer
the operating life of the bearing will be. On the other hand using
a bearing such that it is never subjected to more than, for
example, 1 percent of its elastic limit generally results in
bearing that is much larger and more expensive than necessary. A
balance must therefore be struck between the size of the bearing
and the length of its operating life.
[0006] The maximum strain level to which a bearing can be subjected
without unnecessarily shortening its operating life will depend on
many factors, including the materials used for the elastomeric and
metallic lamellae, the number of lamellae provided, the
configuration of the bearing, and the types of forces to which the
bearing is subjected, e.g., rotational, radial, axial, tilting,
etc. However, it may generally be assumed that subjecting a bearing
to strains less than 50% of the elastic limit of the bearing is
desirable.
[0007] It would therefore be desirable to provide an improved
laminated bearing that provides the benefits of conventional
laminated bearings and that limits the maximum strains to which the
laminated bearing is subjected in order to increase the service
life of the bearing while at the same time accommodating a large
range of forces in a non-destructive manner.
SUMMARY
[0008] These problems and others are addressed by embodiments of
the present disclosure, a first aspect of which comprises a bearing
that includes a laminated bearing portion and a spherical bearing
portion, and in which the spherical bearing portion is disposed
within the laminated bearing portion or the laminated bearing
portion is disposed within the spherical bearing portion.
[0009] Another aspect of the disclosure comprises a method of
operating a bearing which bearing includes a laminated bearing
portion and a spherical bearing portion, the spherical bearing
portion being disposed within the laminated bearing portion or the
laminated bearing portion being disposed within the spherical
bearing portion. The spherical bearing portion comprises a
generally annular outer race having a concave inner circumferential
surface, the inner surface being partially spherical and defining a
central opening, and a ball disposed within the outer race central
opening and having a convex, partially spherical, outer surface in
contact with the inner surface of the outer race portion. The ball
and the outer race are configured such that the ball is locked in
the outer race and such that a given break-out force is required to
move the ball relative to the outer race. The method includes
repeatedly applying first forces to the bearing to deform the
laminated bearing portion without exceeding the given break-out
force of the spherical bearing.
[0010] A further aspect of the disclosure comprises a bearing
having an inner bore, an outer housing, and means between the inner
bore and outer housing for repeatedly elastically accommodating
relative movement between the inner bore and the outer housing of
up to a first magnitude and for repeatedly slidably accommodating
relative movement between the inner bore and the outer housing of a
second magnitude greater than the first magnitude.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] These and other aspects and features of the disclosure will
be better understood upon a reading of the following detailed
description together with the attached drawings, wherein
[0012] FIG. 1 is a sectional elevational view of a bearing
according to an embodiment of the present disclosure.
[0013] FIG. 2 is a perspective view of the bearing section of FIG.
1.
[0014] FIG. 3 is a graph showing a relationship between a moment
and an amount of bearing rotation.
[0015] FIG. 4 is a sectional perspective view of a bearing
according to another embodiment of the disclosure.
DETAILED DESCRIPTION
[0016] Referring now to the drawings, wherein the showings are for
purposes of illustrating presently preferred embodiments of the
disclosure only and not for the purpose of limiting same, FIGS. 1
and 2 show a bearing 10 according to an embodiment of the present
disclosure. The bearing 10 of this embodiment is symmetric about a
central axis of rotation 12 and has a circular cross section
perpendicular to the axis of rotation 12. The terms "radial" and
"axial" may therefore be used hereinafter to describe the relative
locations of elements of the bearing. However, these terms are not
intended to limit the present disclosure to bearings that have
circular cross sections, and terms such as "radial" are also
intended to describe a direction away from a central axis even if
the cross section of the bearing perpendicular to the axis of
rotation is not circular.
[0017] The bearing 10 includes an outer member 14 having a radially
outer surface 16 and a radially inner surface 18 and having a first
thickness in the axial direction. The outer surface 16 is convex
and the inner surface 18 is concave, and, preferably, the inner
surface 18 (or at least part of the inner surface 18) is a
spherical surface, that is, a surface all points of which are a
constant distance from a center point. The bearing also includes an
inner member 20 having a radially outer surface 22 and a radially
inner surface 24 and having a second thickness in the axial
direction. The radially outer surface 22 is convex and preferably
spherical, and the second axial thickness of the inner member 20 is
less than the first axial thickness of the outer member 14. The
outer member 14 and the inner member 20 are coaxial, and the inner
member 20 is axially centered with respect to the outer member
14.
[0018] A first sheet or lamina of elastomeric material 26a is
bonded to the inner surface 18 of the outer member 14, and a
thirteenth sheet or lamina of elastomeric material 26m is bonded to
the outer surface 22 of the inner member 20. Eleven central
lamellae 26b-26l are disposed between the first lamina 26a and the
thirteenth lamina 26m in this embodiment, and one metallic shim or
metallic lamina 28 is disposed between each adjacent pair of
elastomeric laminae 26a-26m. A total of twelve metallic shims
28a-28l are present in this embodiment, with a first metallic shim
28a disposed between the first elastomeric lamina 26a and the
second elastomeric lamina 26b. Different numbers of elastomeric
laminae and metallic shims can be used without exceeding the scope
of this disclosure, and this number will be based on the forces
that must be accommodated by the laminated bearing.
[0019] The axial lengths of the elastomeric lamellae 26a-26m
decrease in the direction from the first elastomeric lamella 26a to
the thirteenth elastomeric lamella 26m, and the axial lengths of
the metallic lamellae 28a-28l decrease from the first metallic
lamella 28a to the twelfth metallic lamella 28l as well so that the
axial length of the bearing, defined by edges of the nested
elastomeric lamellae 26 and the metallic lamellae 28 decreases from
the outer member 14 to the inner member 20.
[0020] The bearing 10 further comprises a shell 30 mounted inside
the inner member 20, the shell 30 having an outer side 32 connected
to the radially inner surface 24 of the inner member 20 and an
inner surface 34 that is concave and preferably spherical. The
inner surface 34 of the shell 30 forms a race for a spherical
bearing ball 36, and the bearing ball 36 has a spherical outer
surface 38 in contact with the inner surface 34 of the shell 30 and
a central bore 40 coaxial with the shell 30.
[0021] The outer member 14, the inner member 20 and the plurality
of nested elastomeric lamellae 26a-26m and metallic lamellae
28a-28l together form a laminated bearing 42. The laminated bearing
is configured to allow small amounts of relative axial, radial,
rotational and tilting movement between the outer member 14 and the
inner member 20, and, in particular, is configured to accommodate
small changes that are frequent and/or rapid. The shell 30 and the
spherical ball 36 together form a spherical bearing 44. The bearing
10 may therefore be described as a spherical bearing 44 mounted
inside a laminated bearing 42.
[0022] Each of the elastomeric lamellae 26 that form the laminated
bearing 42 has various properties. In this embodiment, each of the
elastomeric lamellae 26 is formed from the same material, and the
elastomeric lamellae 26 thus have similar or substantially
identical properties. However, various ones of the elastomeric
lamellae 26 could be formed of different materials and have
different properties if desired. One of the properties of the
elastomeric lamellae is the elastic limit of the material from
which they are formed. That is, each of the elastic lamellae can
withstand a given stress or force per unit area without being
permanently deformed. Greater amounts of stress or force, on the
other hand, will change the structure of the lamellae in such a
manner that the lamella will not return to its original shape or
form when the stress or force is removed.
[0023] Conventional laminated bearings are designed so that the
elastic limit of the elastomeric layers of the bearing will not be
exceeded during use. That is, a conventional bearing must be
designed to withstand the greatest forces to which it is likely to
be subjected in a particular environment. These extreme forces may
rarely occur, but if the bearing is not designed to accommodate
them, the bearing will be permanently damaged any time they are
encountered. Conventional bearings therefore generally operate over
a range of forces that are only a faction of the elastic limit of
the elastomeric materials contained therein in order to provide a
margin of error and to accommodate occasional extreme forces.
[0024] In addition, it has been found that it is generally
desirable to limit the forces to which a laminated bearing is
exposed so that the lamellae of the bearing are prevented from
exceeding a certain fraction of the elastic limit of each
lamella--below 75 percent or 50 percent or 25 percent of the
elastic limit of the material used in the lamellae, for example.
This is because repeated exposure to forces close to the elastic
limit of the lamellae may shorten the life of the bearing. Thus, in
conventional laminated bearings, not only must the bearing be
designed so that the elastic limit of the elastomeric material is
not exceeded under any anticipated use conditions, but it may be
desirable to design the elastomeric bearing so that the forces to
which the bearing is exposed do not exceed, for example, 50% of the
elastic limit of the material from which the lamellae are formed.
This can lead to the use of oversized or overdesigned laminated
bearings in order to ensure a sufficiently long life of the
bearing.
[0025] Laminated bearings are well-suited for use in environments
where small changes occur in the relative positions of the inner
and outer portions of the bearing, especially when these changes
are rapid and/or frequent. However, conventional laminated bearings
are not able to accommodate relatively large changes in the
relative positions of the inner and outer portions. Spherical
bearings, made from metal or other materials, on the other hand,
can withstand significant forces and accommodate larger angular and
rotational changes between an inner member or ball and an outer
member or race. However, the frictional contact between the ball
and the race may lead to rapid wear, especially when such bearings
are used to accommodate frequent small, and in particular, rapid
changes in the relative positions of the elements supported by the
bearing.
[0026] The present inventor has addressed these issues by mounting
a spherical bearing 44 inside a laminated bearing 42 to provide the
laminated bearing 42 with some of the beneficial qualities of
spherical bearings. To this end, the ball 36 of the spherical
bearing 44 is fitted or swaged in the shell 30 so that a certain
minimum level of force is required to cause the ball 36 to move in
the race formed by the inner surface 34. This force may sometimes
be referred to as a "break-out" force and may be applied to the
ball 36 by a shaft (not illustrated) running through the axial bore
40 of the ball 36. Conventional spherical bearings are generally
designed to have a low break-out force to allow a smooth transition
to dynamic motion. In the present embodiment, the break-out force
is significantly greater than normal.
[0027] An amount of force smaller than the break-out force is
required to keep the ball 36 from re-locking in the shell 30 after
the break-out force has been exceeded The phrase "dynamic friction
force" will be used herein to refer to the level of force at which
the ball 36 relocks in the shell 30. The spherical bearing 44 thus
does not begin to operate until an applied force exceeds the
break-out force, and will continue to operate until the applied
force falls below the dynamic friction force. At that point, the
spherical bearing 44 relocks in the shell 30, and the laminated
bearing 42 again begins to operate. The dynamic friction force may
be, for example, 80% or more of the break-out force.
[0028] The break-out force and dynamic friction forces are selected
such that the bearing 10 will function with the spherical bearing
42 locked under most operating conditions. Under such conditions,
the spherical bearing 44 behaves essentially as part of the inner
member 20 of the laminated bearing and merely transmits forces from
the shaft in the central bore 40 to the elastomeric lamellae
26a-26m. Under these operating conditions, the laminated bearing 42
will absorb substantially all forces applied to the bearing.
However, when forces are applied to the bearing 10 greater than the
spherical bearing break-out force, the ball 36 will shift in the
shell 30. The spherical bearing 42 will thereafter move and
accommodate changes in the orientation of the shaft and the outer
member 14 until the force applied to the bearing falls below the
dynamic friction force and the ball 36 once again locks in the
shell 36. At this time, the laminated bearing 42 will once again
accommodate all forces applied to the bearing 10. In typical use,
it is expected that the relative movement allowed by the ball 36
breaking free of the shell 36 will quickly relieve stress on the
bearing 10 so that the forces experienced by the bearing 10 rapidly
fall below the dynamic friction force and allow the laminated
bearing 42 to once again become the primary mechanism for
accommodating changes in the relative positions of the inner and
outer parts of the bearing 10.
[0029] The break-out force may be exceeded when the rotational or
angular movement between the shaft and the outer member 14 is
greater than can be accommodated by the laminated bearing 42, that
is, at the point that the laminated bearing 42 has been stressed to
a predetermined maximum amount. The break-out force will then be
exceeded, and the ball 36 will move in the shell 30 to prevent any
further increase of force on the laminated bearing 42. Alternately,
sudden, large forces may exceed the break-out force and release the
ball 36 from the shell 30, thereby also protecting the laminated
bearing 42 from potentially damaging levels of stress. However,
because the laminated bearing 42 accommodates most forces, the
spherical bearing 44 operates infrequently and thus wears at an
acceptably slow rate. FIG. 3 graphically illustrates this
transition between the operation of the laminated bearing 42 and
operation of the spherical bearing 44.
[0030] The break-out force is generally set, by appropriate swaging
of the ball 36 and the shell 30, to be a fraction of the elastic
limit of the materials from which the lamellae 26a-26m are formed.
The dynamic friction force is determined largely by the materials
from which the ball 36 and shell 30 are formed and the materials
with which they are coated. The application of suitable
low-friction materials, such as polytetrafluoroethylene (PTFE), to
the friction surfaces of the ball 36 and the shell 30 will keep the
dynamic friction force and break-out force relatively close
together. The break-out force must not exceed the elastic limit of
the elastomeric lamellae 26a-26m in the laminated bearing 42, and
thus may be set to be from about e.g., 5% to about 75% of the
elastic limit of the lamellae, for example, to 10%, 20%, 30%, 40%
or 50% of the elastic limit. In general, the operating life of a
laminated bearing can be determined based on the number and
magnitude of oscillations to which it is subjected. Laminated
bearings will last longer when they are not subjected to forces
that approach the elastic limit of their lamellae. Therefore,
laminated bearings are generally configured to withstand forces of
up to a given amount. If greater forces need to be accommodated, a
larger laminated bearing, that is, one having larger lamellae
and/or a greater number of lamellae should be used.
[0031] Those of ordinary skill in the art of laminated bearing
design may identify an optimal operating range for a laminated
bearing. That is, the bearing may have an intended operating life
of a certain number of cycles or oscillations as long as the
oscillations are below a certain size. The size may be expressed as
an amount of force applied against the bearing or, alternately, as
an amount of movement, for example, rotational or other angular
movement in degrees, or radial or axial displacements in
millimeters. Bearing manufacturers thus may identify, for a given
laminated bearing, a level of force or an angular or other amount
of movement which should not be exceeded if a user wishes to
maximize the life of the laminated bearing. The present inventor
contemplates setting the break-out force of the spherical bearing
to be approximately equal to the high end of this design range of
the laminated portion of the bearing so that the laminated bearing
substantially always operates within its design range and such that
the spherical bearing does not operate until larger forces and/or
larger movements need to be accommodated.
[0032] FIG. 4, illustrates a bearing 50 according to a second
embodiment. Bearing 50, in general terms, comprises a laminated
bearing 52 mounted inside a spherical bearing 54; that is, the
locations of the laminated bearing and the spherical bearing of the
first embodiment are reversed. Specifically, the bearing 50
includes a shell 56 having a radial outer surface 58 and a convex,
preferably spherical, inner surface 60 which inner surface 60 forms
a race for a spherical ball 62. The ball 62 has a central bore 64,
and the shell 56 is swaged to the ball 62 such that a certain
break-out force is required to move the ball 62 relative to the
shell 56. An outer member 66 of the laminated bearing 52 has a
radially outer surface 68 mounted in the central bore 64, and the
outer member 66 has an spherical inner surface 70. A laminated
bearing inner member 72 has a spherical outer surface 74 radially
spaced from the inner surface 70 of the outer member 66. A first
elastomeric lamella 76a is mounted to the inner surface 70 of the
outer member 66, a tenth elastomeric lamella 76j is mounted to the
outer surface 74 of the inner member and second through ninth
elastomeric lamellae 76b-76i are mounted between the first
elastomeric lamella 76a and the tenth elastomeric lamella 76j.
Metallic shims or metallic lamellae 78a-78i are mounted between
each adjacent pair of elastomeric lamellae, with a first metallic
lamella 78a mounted between first elastomeric lamella 76a and the
second elastomeric lamella 76b. The inner member 72 has a central
bore 80 which can be mounted to a shaft (not illustrated).
[0033] In operation, the bearing 50 performs in substantially the
same manner and the bearing 10 discussed above. That is, the
relative motion between a shaft mounted in the central bore 80 of
the inner member and the shell 56 is accommodated by the laminated
bearing as long as the level of force and/or amount of movement
that must be accommodated is below a given level. When that level
is exceeded, the break-out force that holds the ball 62 in the
shell 56 is also exceeded, and further relative motion between the
central bore 80 of the inner member and the shell 56 is
accommodated by the movement of the ball 62 in the shell 56.
[0034] Bearings such as the bearings 10 and 50 described above may
be used in various environments. One common use of such bearings is
at the ends of the pitch arms of rotary wing aircraft, which pitch
arms are connected between a rotary swash plate and a pitch horn of
a blade grip that secures one of the blades. In this environment,
small and/or frequent and/or rapid changes occur between the ends
of the pitch arm and the structures to which they are mounted, and
most of these motions are accommodated by the laminated bearing 42
of the bearing 10 or the laminated bearing 52 of the bearing 50.
However, when the pitch arm moves to a greater extend relative to
the structure to which it is mounted, the spherical bearing 44 of
the bearing 10 or the spherical bearing 54 of the bearing 50 breaks
free and accommodates the motion. In this manner, the laminated
bearing need only be sized to accommodate the most common degree of
relative movement likely to be encountered in a given environment,
and the spherical bearing can accommodate the less common motions
without requiring the use of an oversized laminated bearing.
[0035] The present invention has been described herein in terms of
several presently preferred embodiments. Modifications and
additions to these embodiments may become apparent to persons of
ordinary skill in the art upon reading the foregoing description.
It is intended that all such modifications and additions comprise a
part of the present invention to the extent they fall within the
scope of the several claims appended hereto.
* * * * *