BEARING WITH SPHERICAL ROTATIONAL DAMPING
FIELD OF THE INVENTION
This invention relates generally to bearings, and more specifically to a bearing
used in the leg of a supported object that damps lateral oscillations of the object.
BACKGROUND OF THE INVENTION
Damping is an expression of the ability of a structure to dissipate kinetic energy
when subjected to loading. Most structures have some inherent ability to damp. A level
of damping is associated with a particular form, material, construction method, or level
of stress of a structure. If a structure dissipates more kinetic energy than would
normally be attributed to that type of structure, then there may be a reduction in loading
for certain types of exciting forces. This, in turn, allows a reduction in strength
requirements of the structure, and thus a cost saving.
An electric power line reactor is an electrical component having one or more
inductor elements connected between a power source and an electrical load. The
reactor opposes rapid changes in current. Thus it attenuates spikes of current and
limits peak currents among other specialized applications. Reactors can generate
forces internally resulting in loads that must be accommodated by their support
structure. As well, reactors are subject to external loading from wind, seismic,
transportation and industrial vibration. They also need separation from the ground by
electrical insulators and distance, which may result in support legs which inherently
have some lateral flexibility that allows oscillations. Linear dampers are known.
Torsional and other rotational dampers are also known. Current damping devices for
such support structures are expensive and large, requiring extra real estate below the
reactor.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained in the following description in view of the drawings that
show:
FIG. 1 is a side sectional view of a damping bearing apparatus showing aspects
of an embodiment of the invention.
FIG 2 shows the apparatus of FIG. 2 with a deflected position of the upper
subassembly relative to the lower subassembly.
FIG 3 shows another embodiment of the invention with a corrugated fluid
deformation element.
FIG 4 shows another embodiment of the invention with spherical fluid
containment surfaces.
FIG 5 shows a partial enlargement of an embodiment of the invention without
fluid.
FIG 6 illustrates a plurality of damping bearing assemblies supporting a structure
such as an electrical smoothing reactor.
DETAILED DESCRIPTION OF THE INVENTION
FIG 1 is a side sectional view of a damping bearing assembly 20 according to
aspects of an embodiment of the invention. A support shaft 22 may be attached to a
bottom mounting plate 24 that is mountable to a foundation or leg. The shaft 22 is
considered to have a centerline or axis 23. A fluid containment vessel 26 is defined by
inner and outer walls 28, 30 on the bottom mounting plate. The inner wall need not be
supplied. The containment walls 28, 30 may be cylindrical as illustrated in FIG 1, or
they may have other shapes as later shown. A fluid 32 providing a design viscosity is
disposed in the containment vessel 26. A flexible boot or other cover (not shown
herein) may seal the top opening 27 of the containment vessel. A pressure seal for the
fluid 32 is not needed in this embodiment, since it may be retained by gravity. A
spherical bearing is provided by a ball portion 34 on a top end of the support shaft 22
and a socket portion 36 mounted in a bearing housing 38. Thus the housing 38 is
supported on the shaft 22 for rotation about a point 40. A plunger 42 is attached to the
housing 38, either directly or via an attachment element 44 such as a plate. The
plunger may take the shape of a solid of rotation about an axis 43, which axis may
include the center of rotation 40. For example, the plunger may be cylindrical. A lower
portion of the plunger is immersed in the fluid 32 and may have one or more fluid
deformation elements 46 such as a laterally extending flange or "potato masher"
element as shown. A top mounting plate 48 may be attached to the bearing housing 38
to support a structure or apparatus such as an electrical reactor coil or other apparatus
that experiences lateral oscillations.
FIG 2 shows the device of FIG 1 with the upper subassembly deflected 3
degrees, exemplifying a deflection by an oscillating reactor or other structure or
apparatus supported thereon. Experiments were performed on this embodiment using
a 20-foot weighted pendulum as an oscillating mass for test purposes. This
embodiment achieved up to about a 10% damping ratio in the rotational plane of
movement using a polyimethylsiloxane damping fluid with a viscosity of 100,000
centistrokes at a frequency of approximately 2 Hz.
"Spherical damping" herein means damping of rotations about a point in multiple
non-parallel planes, especially damping in planes of a given line that includes the
rotation center point. The given line for this specification may be the axis 23 of the
support shaft or a vertical line through the center of rotation 40. Alternately, the given
line may be the axis 43 of a solid of rotation that forms the plunger 42. Planes that
include the latter axis 43 and the rotation center 40 are the most effective damping
planes of this device in the embodiments shown. These are also the most useful
planes for damping lateral oscillations of a reactor or other apparatus via damped legs.
Spherical damping is distinguished from rotary or torsional damping, which only damp
rotations around an axis in a plane or planes normal to the axis. It is also distinguished
from linear damping, which only damps linear motions along or parallel to an axis.
FIG 3 shows an embodiment 20B of the invention with an alternate fluid
deformation element 46B having a corrugated or "washboard" geometry with alternating
ridges and furrows in a generally cylindrical solid of rotation. One will appreciate that
other shapes of fluid deformation elements may be envisioned, including plates having
holes for the passage of the fluid, flexible structures that deform under load to provide a
passive limit on damping for high velocity oscillations, or any other apparatus
submerged or in contact with the viscous fluid. As well, elements which may take the
form of a ring may be placed on either side of element 46B and provide damping by the
interaction of the elements and the fluid between the parts.
FIG 4 shows an embodiment 20C of the invention with a containment vessel 26C
with curved containment surfaces 50, 52 of the inner and outer fluid containment walls
28, 30. The shapes of these surfaces maintain constant clearance gaps 54, 56
between the containment walls 28, 30 and the fluid deformation element 46 throughout
the designed limits of travel. Such curved surfaces allow the gaps 54, 56 to be as small
as desired, since the fluid deformation element 46 cannot interfere with the walls. This
in turn allows the damping effect to be as strong as desired, depending inversely on the
gap widths.
FIG 5 shows an embodiment 20D of the invention with a containment vessel 26D
having a curved (spherical) lateral containment surface 50 on the inner wall 28, and a
non-spherical containment surface 52D on the outer wall 30. The first surface 50
provides a constant gap 54 between the inner containment wall 28 and the fluid
deformation element 46 over any amount of deflection. The second surface 52D
provides a gap 56D that varies with deflection. In this example, the gap 56D is greatest
at the neutral or zero deflection position, defined here by radius R. The gap may
decrease symmetrically about R in both directions of rotation in each plane of the
plunger axis 43 or the shaft axis 23. Thus, damping increases with deflection for a
given velocity of the deformation element 46. However, this velocity is normally
maximal as it crosses the neutral position R, so the illustrated profile of the surface 52D
makes the damping force more uniform for large deflection oscillations because the
velocity slows at the extremes of the oscillations. This is just one example of variations
in the shape and spacing of the lateral surfaces of the chamber walls 28, 30 that can
provide any desired spherical damping profile. Moreover, damping performance may
be designed to be different for different directions of oscillation.
FIG 6 illustrates an application of the present invention installed on legs 62
formed with insulators supporting an electrical reactor 60. The supported structure may
be anything that experiences lateral loads, such as electrical coils, capacitors, engines,
and motors. Alternately, it may be a raised structure that experiences horizontal lateral
accelerations from external forces, especially those that are harmonic in nature. In the
illustration of FIG. 6, there is no damping in the translational vertical axis. The spherical
damping provided by the present device is more effective and efficient for damping such
oscillations in minimum space at minimum expense compared to rotary and/or linear
dampers. Since the fluid 32 need not be pressurized, there is no pressure loss or
leakage. Damping does not rely on pressure, so the fluid can be retained in the
containment vessel by gravity alone. The fluid may be selected from available fluids,
semi-fluids, tars, gels, and greases in conjunction with designing the containment
chamber and deformation element shape and clearance profiles to achieve a desired
result in consideration of the fluid properties. A silicone fluid may be selected in one
embodiment because it may provide relatively constant viscosity properties over a
range of ambient temperatures. Damping does not rely on frictional contact between
solid parts (other than incidental damping caused by friction of the supported weight on
the bearing), so there may be no frictional contact between any solid parts of the
assembly during normal operation except in the ball-joint bearing 34, 36. A stop may be
provided if needed to limit excessive deflection.
While various embodiments of the present invention have been shown and
described herein, it will be obvious that such embodiments are provided by way of
example only. Numerous variations, changes and substitutions may be made without
departing from the invention herein. Accordingly, it is intended that the invention be
limited only by the spirit and scope of the appended claims.

CLAIMS
The invention claimed is:
1. A damping bearing that provides relative rotations between first and
second subassemblies about a point, and damps said rotations in multiple non-parallel
planes of a given line through the point, wherein the first subassembly comprises a fluid
containment vessel with a fluid therein, and the second subassembly comprises a
plunger with a fluid deformation element immersed in the fluid, wherein a viscosity of
the fluid resists and damps motions of the fluid deformation element in the non-parallel
planes resulting from said relative rotations about the point.
2. The damping bearing of claim 1, wherein the bearing damps the relative
rotations in all planes of the given line.
3. The damping bearing of claim 1, wherein the plunger and the fluid
deformation element thereon are shaped as a solid of rotation about the given line.
4. The damping bearing of claim 1, wherein the plunger is shaped as a
cylinder, the given line is the axis of the cylinder, and the fluid deformation element
comprises a flange on a lower end of the cylinder.
5. The damping bearing of claim 1, wherein the plunger is shaped as a
cylinder, the given line is the axis of the cylinder, and the fluid deformation element
comprises corrugations on a lower end of the cylinder.
6. The damping bearing of claim 1, wherein the fluid deformation element is
disposed between radially inner and outer lateral fluid-bounding surfaces of the
containment vessel, and said surfaces are spherical about the point.
7. The damping bearing of claim 1, wherein a lateral fluid-bounding surface
of the containment vessel is shaped and spaced from the fluid deformation element to
provide a gap there between that varies symmetrically with the relative rotations about a
neutral position of the relative rotations.
8. The damping bearing of claim 1, wherein a lateral fluid-bounding surface
of the containment vessel is shaped and spaced from the fluid deformation element to
provide a gap there between that decreases symmetrically with the relative rotations
about a neutral position of the relative rotations in said non-parallel planes.
9. The damping bearing of claim 1, wherein the first subassembly further
comprises:
a bottom mounting plate attached to the fluid containment vessel;
a support shaft attached to the bottom mounting plate; and
a ball portion on an end of the support shaft; and
the second subassembly further comprises:
a socket portion around the ball portion; and
a housing retaining the socket portion;
wherein the plunger is attached to the housing, and the ball and socket portions
provide a ball joint interface between the first and second assemblies that enables the
relative rotations about the point.
10. The damping bearing of claim 9 and further bearings meeting claim 9
mounted in respective legs supporting an electrical smoothing reactor and damping
oscillations thereof in all lateral directions by a damping ratio of over 6%.
11. A damping bearing comprising:
a first subassembly comprising a fluid containment vessel containing a fluid;
a second subassembly comprising a fluid deformation element immersed in the
fluid; and
a ball-joint bearing that provides relative rotations between the first and second
subassemblies about a given point;
wherein the relative rotations are damped by a viscosity of the fluid resisting
motions of the fluid deformation element.
12. The damping bearing of claim 11, wherein the first subassembly further
comprises a support shaft attached to a bottom mounting plate, the second
subassembly further comprises a bearing housing, and the ball-joint bearing comprises
a ball portion on an upper end of the support shaft and a socket surrounding the ball in
the bearing housing.
13. The damping bearing of claim 12 wherein the shaft comprises an axis that
passes through the given point, and the damping apparatus damps the relative rotations
in multiple non-parallel planes of the shaft axis by a ratio of over 6%.
14. The damping bearing of claim 11, wherein the fluid deformation element is
shaped as a solid of rotation about a given line that passes through the given point, and
the damping apparatus damps the relative rotations in multiple non-parallel planes of
the given line by a ratio of over 6%.
15. The damping bearing of claim 11, wherein the fluid deformation element
comprises a flange on an end of a cylindrical plunger that is immersed in the fluid.
16. The damping bearing of claim 11, wherein the fluid deformation element
comprises washboard corrugations on an end of a cylindrical plunger that is immersed
in the fluid.
17. The damping bearing of claim 11, wherein the fluid deformation element is
disposed between radially inner and outer lateral fluid-bounding surfaces of the
containment vessel, and said surfaces are spherical about the given point.
18. The damping bearing of claim 11, wherein a lateral fluid-bounding surface
of the containment vessel is shaped and spaced from the fluid deformation element to
provide a gap there between that remains constant with displacement magnitude about
a neutral position of the relative rotations.
19. The damping bearing of claim 11, wherein a lateral fluid-bounding surface
of the containment vessel is shaped and spaced from the fluid deformation element to
provide a gap there between that changes with displacement magnitude about a neutral
position of the relative rotations.
20. A damping bearing comprising:
a first subassembly comprising a non-pressurized fluid containment vessel
retaining a fluid by gravity;
a second subassembly comprising a cylindrical plunger comprising a fluid
deformation element on a lower end of the plunger immersed in the fluid; and
a joint that provides relative rotations between the first and second
subassemblies about a point;
wherein the relative rotations are damped by a viscosity of the fluid resisting
motions of the fluid deformation element, providing a damping ratio of over 6% in
multiple planes of a cylinder axis of the plunger without frictional contact between any
solid parts of the plunger, deformation element, or fluid containment vessel.