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Having described my invention, I claim:
1. An apparatus for damping vibrations and wave motions of an elongated
structure member having an extended surface, said damping occurring
between said structure member and an elongated extensionally stiff
constraining member having an extended surface offset laterally from and
substantially parallel to said structure member extended surface, said
damping apparatus comprising:
a triangle comprising first and second extensionally stiff legs joined at a
first hinge flexure, at least one of which first and second legs has a
body portion adjacent the first hinge flexure;
distal ends of said first and second legs being connected by means of
second and third hinge flexures respectively to a given length of one of
said extended surfaces, whereby said given length constitutes a third leg
of said triangle;
the triangle extending between and interconnecting the structure member and
the constraining member and serving to transmit motion due to vibrations
in said structure member relative to said constraining member;
at least one standoff having one end fastened to the extended surface of
that member to which said second and third hinge flexures are connected
and the opposite end of said standoff having a body portion remote from
said one end, said standoff being generally aligned with and located
remote from said triangle along the extended surface to which the triangle
is attached;
that member other than the member to which the standoff is fastened
spanning and interconnecting the triangle body portion with said standoff
body portion; and,
at least one oscillatory energy-dissipating mechanism connecting at least
one of said body portions to the member spanning said portions.
2. A damping apparatus according to claim 1 wherein said energy-dissipating
mechanism is a VEM layer.
3. A damping apparatus according to claim 2 wherein said standoff comprises
a second triangle.
4. A damping apparatus according to claim 3 wherein body portions of both
triangles are connected by means of VEM to that one of said members
spanning said portions.
5. A damping apparatus according to claim 2 wherein that member other than
the member to which the standoff is attached comprises a flexurally-stiff
lever which is firmly affixed to one leg of said triangle and wherein said
VEM connects the distal end of said lever to said standoff body portion.
6. A damping apparatus according to claim 5 wherein said first and second
legs are of unequal lengths and wherein said lever is affixed to the
shorter one of said legs, whereby oscillatory motion of said lever is
amplified between said triangle body portion and the distal end of said
lever.
7. A damping apparatus according to claim 6 wherein a plurality of damping
apparatus are provided in closely adjacent relationship and are
interconnected by means of VEM, and wherein at least one of each plurality
of triangles includes a lever, adjacent levers of different apparatus
extending in opposite directions from their respective triangles.
8. A damping apparatus for a structure member having an extended surface
subject to wave motions or flexural vibrations, comprising:
at least two essentially aligned, linearly-extending spaced apart V-shaped
spacer elements each having two substantially rigid legs and a body
portion adjacent to the vertex on the V, each leg having two ends, one end
of each leg being flexurally attached to one end of the other leg at the
vertex to form the V-shape, the V being oriented substantially normal to
the surface of the structure member;
an elongated substantially rigid constraining member spanning said at least
two spacer elements, said constraining member being positioned in a
laterally-offset relation substantially parallel to the surface of the
structure member;
an energy-dissipating mechanism connecting the body portions of the spacer
elements to one of the structure or constraining members, and;
the ends of the legs opposite the vertex being flexurally affixed to the
other of said structure or constraining members.
9. The damping apparatus according to claim 8 wherein said
energy-dissipating mechanism comprises a layer of VEM.
10. The damping apparatus according to claim 9 wherein the member to which
the ends of the legs opposite the vertex are affixed is the damped
structure member and the VEM layer connects the body portions to the
constraining member.
11. The damping apparatus according to claim 10, wherein each said spacer
element is fabricated from a beam member having an interrupted upper
flange, an uninterrupted lower flange offset from the upper flange, and an
interrupted web interconnecting the flanges and substantially
perpendicular to the flanges, the beam member having at least one
longitudinally located slot cutout laterally extending completely through
the upper flange and web to form discrete spacer elements joined by the
lower flange, each V-shaped spacer elements having two ends, a
longitudinal line between the ends and three cutouts through the web, two
of the cutouts disposed on opposite sides of the longitudinal line of each
spacer element adjacent the upper flange to comprise a first hinge flexure
in the web, and the third cutout disposed about the longitudinal
centerline of each spacer element adjacent the lower flange and extending
longitudinally toward both spacer element ends to points adjacent the ends
so as to comprise second and third hinge flexures in the web, the web
between the first and second flexures and the first and third flexures
comprising the two legs of each V-shaped spacer element, respectively, the
upper flange sections of each spacer element comprising its body portion
and the second and third flexures forming the divergent ends of the legs.
12. The damping apparatus according to claim 9 wherein the member to which
the ends of the legs opposite the vertex are affixed is the constraining
member and the VEM layer connects the body portions to the damped
structure member.
13. The damping apparatus according to claim 8, wherein the body portion of
each spacer element has a horizontally-extending lever portion which is
substantially parallel to the surface of said structure member.
14. The damping apparatus according to claim 8, wherein the V-shaped spacer
elements are formed from a rectangular plate, each spacer element having
an upper edge, a lower edge, a first side edge and a second side edge, an
upper opening and a lower opening, said openings being positioned adjacent
the lower edge and first side edge, the lower opening extending through
the lower edge, the upper opening being connected to the second side edge
by a slot, the space between the openings comprising a first flexural
hinge joint, the area below the slot comprising one of said legs and the
remaining area of the plate comprising the other of said legs, and said
body portion extending above said slot and generally parallel to the
surface of the structure member.
15. The damping apparatus according to claim 14, wherein one of said spacer
elements is tilted slightly off normal to the surface of the damped
structure with the horizontally-extending body portion of said spacer
element being firmly affixed to the member attached to the spacer elements
by VEM, said second spacer element being immediately adjacent the tilted
spacer element, said second spacer element having a horizontal lever
extending from and overlapping the spacer element with said tilted leg,
said lever being attached by VEM to the member to which the other V-shaped
spacer element body portions are attached by VEM. |
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Claims |
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Description |
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This invention relates to an energy-dissipating apparatus for damping
vibrational oscillations which produce extensional strains in a beam,
plate, shell or skin structure.
BACKGROUND OF THE INVENTION
Numerous apparatuses have been designed for attachment to structural
members subjected to vibration for minimizing its effects, such as noise
and metal fatigue. For example, U.S. Pat. No. 4,425,980 issued Jan. 17,
1984 to Miles illustrates how an aircraft skin dissipates vibration
induced therein by fastening a second skin or structure thereto by means
of a viscoelastic material, commonly called and referred to hereinafter as
VEM. Examples of vibration dampers for use with beams and metal plates,
hereinafter referred to as the damped member, are illustrated in U.S. Pat.
Nos. 3,078,969 to Campbell, and 3,262,521 to Warnaka. Various applications
of the latter have been proposed to deaden vibrations in bulkheads of both
above and below-surface marine vessels and structural members such as
beams and girders used in bridges and buildings.
In some previous damping art, the damped member has been metal and the
damping apparatus typically includes at least two linearly-extending
substantially rigid members generally in the form of thin plates. The
plates typically each have at least one surface oriented substantially
normal to the surface of the damped member and an entire edge either
firmly affixed to the damped surface (e.g., by welding) or resiliently
attached by a VEM layer to the damped surface. The generic term "standoff"
may be used hereinafter to describe the orientation of the plate
protruding outwardly from the surface, both in relation to the prior art
and to my invention. In either case, the plates are positioned regularly
or randomly in a row or series relationship to one another and are usually
resiliently connected together by the VEM layer at the edges of the plates
remote from the damped surface. The VEM typically completely encapsulates
the plate edges.
When the wave motion of the structure whose vibration is to be damped
causes oscillation about a plane through its neutral axis, the motion is
directed outwardly by the plates due to their offset relationship from the
neutral axis. The vibrations exhibit themselves as compound movements at
the remote ends or edges of the plates, both parallel and perpendicular to
the damped surface. As the damped member vibrates, the VEM layer between
the adjoining plates' faces and edges is subjected to shearing and
extensional forces, or a combination thereof. The energy-absorbing nature
of the VEM dissipates some of the vibration and wave energy, resulting in
the damping effect. The more the wave motion is amplified and the more the
VEM layer is restricted from moving relative to the structure member, the
greater the damping effect.
An elongated constraining element or member is typically attached to the
VEM layer and bridges the remote ends of at least two plates. This
arrangement increases the shear forces in the VEM layer and enhances the
damping effect. The VEM layer generally isolates the constraining member
from the damped surface such that there is no substantially rigid
connection between the constraining member and the damped member.
There is a product produced by Swedish Acoustic Products Innovations of
Goteburg, Sweden which has only a point of each standoff or plate welded
to the damped member. When such damping apparatus is utilized, however,
although the stiffness of the damped member can remain essentially uniform
along the length of the damping apparatus, the point contact of each
standoff can cause loss of perpendicularity of each standoff to the damped
surface during oscillatory strains. This has the potential of producing
less shear in the VEM layer and thus reduced damping effect, since the
energy-dissipating arrangement is stiff in both flexure and shear.
SUMMARY OF THE INVENTION
In a preferred form of the invention, a plurality of upstanding standoffs
in the form of V-shaped spacer elements with substantially extensionally
stiff or rigid legs are spaced a regular or random distance apart and are
generally linearly-aligned in a row or series with each spacer element
having the divergent ends of the legs affixed to the damped surface by a
hinge flexure. At least one of the legs of the V adjacent the vertex of
the V includes a body portion of the spacer element to provide an
attaching area or surface. The vertex comprises a first hinge flexure
which allows rotation or pivoting of the legs relative to one another. The
attachment points of the divergent ends of the V to the damped surface
comprise second and third hinge flexures to allow rotation or pivoting of
the legs relative to the damped surface. The length of the legs of the V
amplify vibratory motion parallel as well as perpendicular to the damped
surface while adding very little flexural stiffness to the damped member
due to the substantially point contact of the hinge flexures of the legs
with the damped surface. The first hinge flexure at the vertex of the V
remains essentially perpendicular to the damped surface to a line drawn
through the vertex between the second and third hinge flexures. In
essence, an imaginary line drawn perpendicular to the surface through the
first hinge flexure remains essentially perpendicular throughout and after
flexible motion, except in an arrangement where the legs are of unequal
lengths. In the latter case, some motion parallel to the surface of the
damped member may occur, but the spacer element remains stiff in shear. A
constraining member bridging or spanning at least two spacer elements or
standoffs is disposed generally parallel to the damped surface at the
remote ends of the spacer elements adjacent their respective body portions
and is attached by the VEM layer to the body portions. The constraining
member can be somewhat flexible but must be extensionally stiff to resist
elongation parallel to the row orientation of the spacer elements. The
spacer elements maximize the damping energy transmitted to the VEM layer
by enabling enlargement of the movement of the damped surface and
minimizing the resistance to bending.
It is the principal objective of the invention to provide an improved
energy-dissipating apparatus for damping vibrational oscillations in a
damped member susceptible to receiving induced vibration.
A more specific object is to provide a unique spacer element for use in
such an apparatus wherein the spacer element structure transmits greater
shear force to a VEM layer both parallel and perpendicular to the damped
surface than heretofore.
A further object is to provide an improved spacer element in which the
geometry of the spacer element can be made to correspond to the particular
frequency range of the structure to be damped.
A further object is to provide a cantilevered arm affixed to one leg of a
first spacer element or standoff and serving as both a motion-amplifying
lever and a constraining member, with the distal end of the cantilevered
arm being connected by a VEM layer to at least one other standoff.
A further object is to provide for multiple rows of cantilevered arm
damping structures to be closely positioned adjacent one another and the
cantilevered arms connected together by a VEM layer so as to effectively
dampen vibrations of differing wave lengths and frequencies.
A further object is to provide an apparatus for damping vibrational
oscillations where such damping structure or structure to be damped is
partly or wholly made from structural materials other than metal.
Another object is to provide a standoff in the form of a triangular hinged
flexure, in which the member in which vibrations are induced constitutes
one side of the triangle.
A further object is to provide for fixed attachment of a cantilevered arm
to a leg of the triangle in a manner which amplifies motion at the end of
the arm.
Another object is provide for legs of such triangle to be of unequal
lengths and for attaching such cantilevered arm in a position on the
shorter one of said legs to obtain maximum amplification of motion.
Other objects will become apparent from the following description, in which
reference is made to the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic cross-sectional side view of one embodiment of the
invention showing a row of V-shaped spacer elements with divergent ends of
the legs affixed to the surface of a damped member. Body portions adjacent
the vertices of the V's are attached by a VEM layer to a constraining
member spanning multiple spacer elements.
FIG. 2 is a schematic cross-sectional side view of the embodiment of FIG. 1
illustrating, in an exaggerated fashion, how the vertices of the V's
remain essentially perpendicular to the surface of the damped structure
while the surface stretches during oscillatory vibration of the structure
member.
FIG. 3 is a schematic cross-sectional side view of an alternate embodiment
of the invention showing the divergent ends of the legs of the spacer
elements firmly affixed to the constraining member.
FIG. 4 is a side view of one embodiment of the invention functionally
identical to that of FIG. 1.
FIG. 5 is an isometric view of an embodiment of the invention functionally
similar to that of FIG. 1, wherein the spacer elements have two legs of
differing lengths, the divergent ends of which are affixed to the damped
surface and the horizontal body portions of which are attached by the VEM
to the constraining member. Each spacer element further includes a
motion-amplifying lever.
FIG. 6 is a schematic diagram of two of the spacer elements and through the
levers when connected to the shorter leg of a spacer levers shown in FIG.
5 illustrating how motion can be amplified element.
FIG. 7 is an isometric view of an embodiment of the invention employing
spacer elements similar to those of FIG. 5, but arranged to function
similarly to the schematic view of FIG. 3.
FIG. 8 is a side view of yet another embodiment using an alternate design
of spacer elements essentially
FIG. 9 illustrates a plurality of spacer elements essentially like that of
FIG. 8 in a row.
FIG. 10 is a cross-sectional view taken along lines 10--10 of FIG. 9.
FIG. 11 is an isometric view of an embodiment which functions somewhat
similarly to that of FIG. 1, wherein one leg of a spacer element is firmly
affixed to the constraining member by a body portion or a substantially
rigid arm member to make the constraining member a motion-enlarging
cantilevered arm of that spacer element. At least a second spacer element
body portion is connected by the VEM layer to the cantilevered arm at a
point remote from the first spacer element.
FIG. 12 is an isometric view of multiple assemblies or sets of the damping
apparatus of FIG. 11 functioning as a compound damping apparatus.
FIG. 13 is a simplified view of a damping apparatus in which a pair of
standoffs are interconnected by a lever/constraining member affixed to one
standoff and connected to the other by VEM.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In order to appreciate the phenomenon that is taking place within a spacer
element about to be described, one should imagine a triangle with three
stiff legs surrounding a centrally-open area, and also assume that there
is a pivotal hinge flexure at each of the three vertices of the triangle.
Neither leg is capable of rotating or pivoting with respect to an adjacent
leg about a hinge flexure at one of its ends because it is inhibited from
doing so by being locked against rotation by the other two legs. However,
if one of the legs is capable of repetitive longitudinal stretching and
contraction from extensional strains induced in that one leg from
vibrational or wave motion thereof, the hinge flexure at the vertex of the
other two legs will move toward and away from the one leg during the one
leg's alternate shortening and lengthening. When such extensional strains
are induced in the one leg, those strains cause generally perpendicular
motion in the hinge flexure between the other two legs through lengthwise
movement of the other two legs and pivoting due to flexibility at the
hinge flexure connecting them. The latter hinge flexure can be said to be
soft in flexure and stiff in shear with respect to the one vibrating leg,
which, according to this invention, is a structure member whose
oscillatory motion is to be damped by dissipation of energy. With this in
mind, let us now proceed to a detailed description of certain embodiments
of the invention.
In accordance with this invention and as best can be seen in FIG. 1, the
damping of a structure member 1 subject to flexural vibrations and wave
motion having an extended surface 2 to be damped is provided by a
combination of V-shaped spacer elements 3, a substantially rigid
non-extendible constraining member 6, and a VEM layer 5. Each spacer
element 3 has two extensionally stiff or rigid legs 8 and a body portion 4
adjacent the vertex of the V. One end of each leg 8 is firmly but flexibly
affixed to the other leg 8 at the vertex of the V as at a first hinge
flexure 9. The first hinge flexure 9 allows the divergent ends of the legs
8 to rotate or pivot. The spacer elements 3 are arranged in a
linearly-extending row or line and are regularly or randomly located with
the V of each preferably being oriented substantially normal to the damped
surface 2. The constraining member 6 is positioned in an offset relation
and is preferably substantially parallel to the damped surface 2.
The spacer elements 3 can be oriented with the divergent ends of each leg 8
attached to either the damped surface 2 as in FIG. 1 (where the V of each
spacer element is inverted) or to the constraining member 6 as shown in
FIG. 3 (where each V is right-side up), the attachment points comprising a
second hinge flexure 10 and a third hinge flexure 11 which allow pivoting
of each leg 8 relative to the member 1 or 6 with minimal resistance. The
VEM layer 5 resiliently attaches the body portions 4 to the other member
of said members 1 or 6 and serves as an energy absorber for dissipating
energy. The VEM is selected to have a stiffness or modulus of elasticity
that is substantially less than that of the damped member 1 or 6, the
spacer elements 3, and the constraining member 6 and is characterized by
high energy-dissipation capability. Various well-known materials of this
type may be used, such as asphalt, waxes, soft rubber, rubber-like
polymers and many other elastic or plastic materials having the desired
energy-absorbing properties. Where the term energy-dissipating mechanism,
viscoelastic material or VEM is used, it is intended to include all such
energy-dissipating materials or devices mechanical or electronic,
including dashpots or frictionally-contacting members which function to
dissipate energy. The energy-dissipating mechanisms illustrated herein are
all passive, however, such mechanism may be active and fall within the
scope of the appended claims.
When the damped member 1 is subjected to flexural vibrations, bending
occurs about a neutral axis 7 through the damped member 1. This flexing,
exaggerated for better understanding, is shown in one direction only in
FIG. 2, it being understood that member 1 will also flex in the opposite
direction from the static condition of the neutral axis 7. The net effect
of the flexural vibrations is to cause repetitive extensional strains in
the surfaces of member 1, alternately stretching and contracting the
surface of member 1 along its length. As the damped member 1 bends at the
neutral axis 7 in the direction shown in FIG. 2, the second and third
hinge flexures 10 and 11 move slightly further apart as the surface 2
elongates. While this is occurring, the first hinge flexure 9 and body
portion 4 remain both parallel and perpendicular to the damped surface 2
although moving very slightly closer to surface 2. The first hinge flexure
9 stays directly perpendicular to a line 12 drawn tangent to surface 2 as
shown by dotted line 12'. The dotted line 12' is midway between the second
and third hinge flexures 10 and 11 in those instances where legs 8 are of
equal length. It is this movement of the first hinge flexure 9 as
translated through the body portion 4 to the VEM layer 5 which causes the
shear energy to be resisted and dissipated in the VEM layer 5.
The spacer elements 3 can be made in any of a great variety of ways and
configurations. For example, the elements can be constructed from any
standard beam member having at least one flange, such as an I-beam,
Z-beam, or T-beam member. In the case of an I-beam, at least one
longitudinally spaced slot laterally extending completely through the
upper flange and the web, but not through the lower flange, forms discrete
spacer elements joined together by the lower flange. The lower flange must
be relatively thin and flexible compared to the damped member and be
positioned close to damped surface 2 in order to keep the neutral axis of
the combination as close as possible to the original neutral axis 7 of the
damped member 1. This results in minimizing the energy stored in the lower
flange during flexure of the damped member 1 and transmits the maximum
energy to the VEM layer 5. When constructed in any cross-sectional
configuration in beam fashion, each spacer element may have three cutouts
through the web to form the three hinge flexures and the V-shape with two
legs for proper transfer of energy to the VEM layer.
FIG. 4 shows an I-beam 27 having slots 13 extending through an interrupted
upper flange 20 and a web 19 so as to configure the I-beam 27 into
discrete interconnected spacer elements 3a. Such construction can be
produced by machining, chemically milling, stamping or other known
technique. The upper flange 20 of the spacer elements 3a became body
portions 4a which are resiliently attached by the VEM layer 5 to the
constraining member 6. A lower flange 18 is attached to the damped surface
2 as by small welds 16 or other fastening, such as by bonding or
mechanical means. Each spacer element 3a has two upper slots 14 disposed
on opposite sides of a longitudinal dot-dash line 21 of each spacer
element 3a directly below body portion 4a, the minimal material between
the upper slots 14 comprising the first hinge flexure 9. A third slot 15
is disposed about and, in this embodiment, perpendicular to the
longitudinal line 21 of each spacer element 3a adjacent the lower flange
18. Slot 15 extends to points adjacent the sides of each spacer element 3a
to form the second and third hinge flexures 10 and 11. Together, flexures
9, 10 and 11 define a triangular hinged flexure with slot 15 comprising a
central opening and the portion of the web 19 between flexures 9 and 10
and flexures 9 and 11 comprising the first and second legs 8. The third
leg of the triangle in this embodiment is both the flange 18 and the
member 1.
FIG. 5 shows an embodiment which functions similarly to that of FIG. 1
wherein each spacer element 3d is fabricated from a plate and has cutouts
14d and 15d which correspond to slots 14 and 15 of FIG. 4 to define the
spacer element 3d. There are short and long legs 8d which are attached at
a first hinge flexure 9 defined by a notch 26 adjacent cutout 14d. The
legs form a V-shape with the divergent ends of the legs 8d being affixed
to the damped member 1 at hinge flexures 10 and 11. Body portion 22
attached to one leg 8d adjacent the vertex of the V extends vertically
from the legs 8d away from the damped surface 2 and integral therewith is
a horizontal lever body portion 17 extending substantially parallel to the
damped member 1. The constraining member 6 is positioned in a horizontally
offset relation substantially parallel to the damped surface 2 and is
resiliently attached by the VEM layer 5 to the horizontal lever body
portions 17. It will be noted that the horizontal lever body portion 17 is
connected to the shorter of the two legs 8d through the body portion 22.
As the spacer element 3d flexes, its shorter leg pivots or rotates through
a greater angle than the longer leg, amplifying the motion from the
shorter leg toward the cantilevered distal end of body portion 17. This
amplification results in greater energy dissipation in the VEM 5 than
occurs when the legs are of equal length. Where the entire cantilevered
body portion 17 is connected to the constraining member 6, energy
dissipation progressively increases from that end of body portion 17 where
it is connected to body portion 22 toward the distal end of body portion
17.
FIG. 6 depicts in exaggerated fashion what occurs in the FIG. 5 structure
as the elements move back and forth between their static full-line
positions in opposite directions from the full-line positions. Dotted-line
positions are shown in one direction only for clarity. The horizontal body
portions 17 comprise a pair of cantilevered arms with their distal ends
near-abutting. As the arms move toward their dotted-line positions, there
is a vertical motion component consisting of the dimension X and a
horizontal motion component consisting of dimension Y. The longer the
arms, the larger will be the dimensions of X and Y at the distal ends. As
the perpendicular and parallel shear are imparted to the VEM, the damping
structure more effectively dissipates energy than one which compensates
for single component forces only. The ratios of the arms can be adjusted
to adapt the spacer elements 3d for a particular damping application.
FIG. 7 is an embodiment similar to FIG. 5 except that the flexured ends of
legs 8e of spacer elements 3e are attached to the constraining member 6
rather than to the damped member 1e and the horizontal body portion 17e is
resiliently attached by the VEM layer 5 to the damped surface 2e. The
damped member 1e is shown as square tubing in this embodiment, in order to
provide surface 2e with sufficient area for bonding of VEM 5 thereto.
FIG. 8 shows a preferred spacer element 3f which is more easily
manufactured and has less waste material than spacer elements of other
embodiments. FIG. 8 is functionally identical to FIG. 5 but has lower
manufacturing cost and higher weight. Lower edge 23 may be relieved from
contact with the surface of the damped member 1 as shown, but it is not
essential to provide such relief. Spacer element 3f is rectangular in
overall shape with a lower notch or opening 15f extending upwardly from
lower edge 23 adjacent an edge 30 of spacer element 3f. A slot 28 extends
inwardly from an edge 31 of spacer element 3f and preferably terminates at
an enlarged punched or drilled opening 29 adjacent lower opening 15f. Use
of the opening 29 allows for lower cost manufacturing. The slot 28, lower
opening 15f and opening 29 of the slot 28 define short and long legs 8f
which are connected at the first hinge flexure 9. They also define body
portion 4f which comprises vertical body portion 22f and horizontal lever
body portion 17f. The spacer element 3f is connected to the damped surface
2 at second hinge flexure 10 and third hinge flexure 11. The horizontal
body portion 17f is resiliently connected by VEM layer 5 to the
constraining member 6. The function of spacer elements 3f is similar to
that described in connection with FIGS. 5 and 6.
As shown in FIG. 9, a substantially rigid extension 22g' of a short leg 8g
of an abbreviated spacer element 3g' is affixed firmly to the constraining
member 6, forming a pair of levers 17g' and 17g" extending outwardly from
the extension 22g'. The lever body portions 17g of at least a second
spacer element 3g remote from the first spacer element 3g' is connected to
the lever 17g' and/or the lever 17g" through VEM 5. Upon deflection of the
damped member 1, motion is transmitted toward the VEM 5 through both the
spacer elements 3g and the levers which comprise the constraining member
6. This bi-directional motion transmission better focuses the shear forces
toward the VEM while utilizing the advantageous amplification derived from
the levers.
FIG. 10 illustrates one manner of mounting spacer element 3g' angularly and
slotting that element differently as at slot 28'.
FIG. 11 shows another embodiment of the invention which functions somewhat
similarly to that of FIG. 9 but utilizes legs of equal length.
FIG. 12 is the embodiment of FIG. 11 of multiple side-by-side assemblies or
gangs of damping apparatus and having VEM layers 5 laterally connecting
adjacent constraining members 6. The arms 24 can be staggered in relation
to the assemblies to change the damping effect. A central constraining
member 6' may be sandwiched between separate VEM layers on the inside
surface of each constraining member 6. This embodiment illustrates the use
of longitudinally-staggered fastening points for the cantilevered arms,
thus enabling a single damping structure to effectively damp both long and
short wave vibrations, either or both of which may have both vertical and
horizontal motion components.
FIG. 13 is an extremely simplified construction of damping apparatus in
which the advantage of motion amplification can be achieved between a
first standoff 50 and a second standoff 52 both firmly affixed to
structure member 1. A portion 54 of standoff 50 serves as both a
constraining member and a cantilevered motion amplifying arm. The distal
end of portion 54 is attached by VEM 5 to the distal end of standoff 52.
The generic term standoff has been used in connection with FIG. 13 to
illustrate that the motion amplifying leverage of a cantilevered arm is
beneficial with or without the particular type of spacer element described
in the previous embodiments.
It should be understood that while prior art damping apparatuses and the
damped structure are typically made of metal, structural materials other
than metal (e.g. composites or plastics) may be used both as the damping
apparatus and structure to be damped.
Various other changes may be made without departing from the spirit and
scope of the claims.
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