Note: Descriptions are shown in the official language in which they were submitted.
ONE-PIECE DUAL DENSITY ACOUSTICAL PANEL
BACKGROUND OF THE INVENTION
The present invention relates to a rigid acous-
tical core panel member for panel assemblies, partition
assemblies and the like and more particularly to a core
member of the type described being a one-piece rigid struc-
ture of dual density.
Numerous acoustical core materials are presently
available for providing acoustical absorption in furniture
systems, partitions, free standing acoustical screens, wall
panels, ceiling systems and the like. Many of the existing
products suffer deficiencies due to the fact that they
require laminations of secondary members or require secon-
dary manufacturing processes such as sanding or framing in
order to achieve the required panel rigidity, flatness,
impact resistance, tackability, thickness control and
acoustical performance. The equipment and labor necessary
to produce such laminations or secondary production proces-
ses are expensive and, due to the addition of bonding
materials, the product may suffer a deficiency in acoustical
performance and may constitute a possible reduction in fire
and smoke performance.
It has further been well-known in the acoustical
industry that introduction of dead air space behind an
acoustical absorber which is contingent with a wall or
partition assembly significantly increases absorption values
of the absorber due to the fact that the air space behind the ~`
absorber lengthens the path of impinging sound waves passing
through the absorber to the wall or partition so as to
attenuate and thereby reduce the intensity of reflections.
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It is also a known fact that at certain
frequencies, a partition will become acoustically trans~
parent to the resonant panel or "natural frequency" response
characteristics. Up to the present time, techniques for in-
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troducing dead air space within a given panel thickness
have been obtainable only at considerable cost and through
the use of special materials and structures. Further,
there have been no means available, until the present ~;
invention, to include an air space in an acoustical panel
which, when filled with proper acoustical fill ma~erial,
eliminates the reduction in performance at the "natural
frequency" of the partition or panel.
A BRIEF DE:SCRIPTION OF THE PRESENT INVENTION
The present invention solves all of the above- ~
mentioned deficiencies by the provision of a rigid core ~-
material of one-piece construction which economically meets ~`
all of the necessary requirements of its acoustical design
uses and applications.
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A one-piece core is comprised of fibrous mater-
ials bound together with thermosetting resins in such a
~anner as to produce a panel having a first flat surface
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wherein the density adjacent said flat surface is uniform
and of a substantially high density per cubic foot while
the opposing surface which is textured has a lower density
per cubic foot.
This structure overcomes the deficiencies of all
conventional single density core panels and blankets, as
well as the deficiencies of multiple layer composite core
panels and further provides for an exact quantitative speci-
fication of the dual densities to be produced thereby t
allowing for maximization of each required design function.
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The panel molding techniques employed allow for
exact construction of the panel properties to obtain the
desired absorption values, tackability, smoothness of sur-
face, flatness of surface, impact resistance, flame safety
requirements, bonding characteristics, panel rigidity, panel
deflection and
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strength values, thickness tolerances and panel resiliency,
all of said characteristics being obtained at equivalent
cost to standard insulations that provide for sound
absorption only.
The novel core panel of the present invention, in
one preferred embodiment thereof, is formed by providing
a layer or layers of uncured raw fibrous material of sub-
stantially uniform thickness and uniform density. The -~
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uncured material is pressed between a pair of molding
members, one of which is designed to provide a substantially
smooth, flat surface while the other of which is designed
to provide a "waffle-like" configuration, the aforesaid
pressing operation being performed at a predetermined ele-
vated temperature. The uncured layers may preferably be
formed of glass fibers bound in a thermosetting binder.
The operation yields a one-piece core panel having a sub-
stantially smooth, flat surface which is ideal for use in
mounting a decorative treatment thereto and which provides
requisite rigidity without any safrifice in either sound
absorption, thermal conductance or flame safety charaater-
istics.
; The present invention also further comprises
method and apparatus for creating a molded integrated frame
member about the perimeter of a dual density panel of the
type described, said frame being of greater height than the
maximum thickness of the panel so that the resulting panel
assembly, when mounted within furniture, partitions, wall
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panels, and other interior design components, serves
to incorporate an air space into the structure and behind
the acoustical panel to significantly increase acoustical
absorption characteristics, the resulting air space being
provided in a simple and yet inexpensive manner by forming
a rigid, plastic frame about the panel with a frame thick-
ness sufficient to create a dead air space of the desired
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volume. The completed product may then be wrapped in suitable
decorative treatment, placed upon a substrate and then covered
with decorative treatment or the like whereby the interior air
space cooperates with a dual density board to further signifi-
cantly increase the sound attenuation characteristic. If de-
sired, the dead air space may be filled with low density
acoustical blanket fill, for example, so as to prevent the
occurrence of a resonant panel response characteristic of
partitions which might lead to a reduction in performance of
the panel under certain conditions.
The frame provides a rigid assembly not provided
by the core panel per se; provides a precise assembly
thickness capable of lying within a very tight tolerance
range; and provides the highly desirable dead air space.
It is therefore one object of the present invention
to provide a novel one-piece dual density core panel for
use in applications requiring a combination of characteristics
not heretofore being capable of being obtained in one-piece
panel structures, the present invention providing an apparatus
having a dual density construction and exhibiting the salient
characteristics of rigidity, tackability, excellent sound
absorption, thermal insulation properties and high flame
safety levels wherein the core panel so obtain~d is easy to
use, mount and decorate.
Another object of the present invention is to
provide a novel method for producing a one-piece, dual
density panel of the type described above.
Still another object of the present invention
is to provide a novel core panel construction and method
for producing same, the construction including an integrated
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dead air space therewith by providing a rigid frame about
the dual density core panel to yield a simplified inexpensive
structure providing increased sound attenuation at a
considerable savings in both cost and materials.
These objects are attained by the invention which con-
templates a one-piece dual density panel which has specified
thermal and acoustical insulat~on properties comprising a fib-
rous material dispersed in a thermosetting resin binder. The
panel has a first surface and a second surface, with the first
surface of the panel being a substantially smooth planar surface
and the second surface of the panel including a substantially
regular pattern of relatively uniform indentations. The panel
has a first density substantially uniformly along the entire
first surface of the panel and substantially throughout the
entire thickness of the panel at the locations of the indenta-
tions and it has a second density along the second surface of
the panel between the indentations, with the first density
being substantially greater than the second density~ The panel
also includes a rigid molded frame fused to the panel along
the perimeter thereof and it has a frame width substantially
greater than the maximum thickness of the panel so as to create
- a shallow recess defined by the frame and the second surface of
the panel. That shallow recess is adapted to form a hollow
air space when mounted upon a surface.
The invention also contemplates a method for forming
one-piece dual density panels having a desired maximum thickness
and specified thermal and acoustic ratings comprising providing
at least one panel having a first surface and a second surface.
The panel formed comprises a fibrous material dispersed in an
uncured thermosetting resin binder, and the panel further has
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~-~ substantiall~ uniform thicknes~ a~ least as great as the desired
maximum thi~ckness and has a substant~ally uniform density. The
first surface of the panel ~s eng~ged with a plate having a sub-
stantially smootll planar surface, the second surface of the panel
is engaged w~th a tool having a contoured surface including a
substantially regular pattern of rclatively uniform projcctiolls
thereon. The tool is urged towards the plate with the panel
therebetween while maintaining the panel at a temperature
sufficient to cure the thermosetting resin binder, whereby a
substantially regular pattern of relatively uniform indentations
is formed in the second surface of the panel, and whereby the
density of the panel substantially uniformly increases along the
entire first surface of the panel and substantially throughout
the entire thickness of the panel at the locations of the pro-
jections. The density of the panel remains substantially less
than the increased density along the second surface of the panel
between the projections.
In a preferred embodiment, the invention additionally
contemplates a method for forming one-piece dual density panels
having a desired maximum thickness and specified thermal and
acoustic ratings, the method comprisiny providing at least one
panel having a first surface and a second surface. The panel
formed comprises a fibrous material dispersed in an uncured
thermosetting resin binder, and the panel further has a sub-
stantially uniform thickness at least as great as the desired
maximum thickness and has a substantially uniform density and at
the same time being substantially free from prior compression or
heating. The first surface of the substantially uncompressed
and unheated panel containing the uncured thermosetting resin
binder is engaged with a plate having a substantially smooth
planar surface, the second surface of the panel is engaged with
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a tool having a contoured surface including a substalltially
regular pattern oE relatively uniform projections forming a
waffle-like pattern. The tool is urged towards the plate with
the panel therebetween in order to compress the panel and form
a substantially regular pattern of relatively uniform indentations
in the second surface of the panel while maintaining the panel at
a temperature sufficient to cure the thermosetting resin binder `
in a single step, and whereby the density of the panel su~-
stantially uniformly increases along the entire first surface
of the panel and substantially throughout the entire thickness
of the panel at the locations of the projections. The density
of the panel remains substantially less than the increased density
along the second surface of the panel between the projections.
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A BRIEF DESCRIPTION OF THE FIGURES
The above as well as other objects of the present
invention will become apparent when reading the accompanying
description and drawings in which:
Figure la is a top perspective view of a one-piece
dual density panel designed in accordance with the principles
of the present invention;
Figure lb shows a bottom perspective view of thc
panel of Figure la;
Figure 2 is an elevational view showing a preferred
manner in which the core panel of Figures la and lb is formed;
Figure 3 shows an elevational view similar to
that shown in Figure 2 and is useful in describing the manner
in which the densities of the dual density board may be
readily adjusted,and Fig. 3a is an alternate embodiment thereof
showing a reversal in the pattern of the projections.
Figures 4 - 10 show perspective views of various
applications and embodiments of the dual density panel of
the present invention.
Figure 11 shows a perspective view of a one-
piece molded acoustical frame assembly for providing a
sound attenuating structure incorporating a dead air space
therein.
Figure 12 shows a sectional view of the structure
of Figure 11 further incorporating acoustical fill in the
dead air cavity.
Figure 13 shows a simplified perspective view
of apparatus used for forming the assembly of Fi~ures 11 and 12.
DETAILED DESCRIPTION OF THE INVENTION
AND ITS PREFERRED EMBODIMENTS
Figures la and lb show a one-piece dual density
core panel 10 which is formed of a fibrous material such as,
for example, fibre glass and which is provided with one
surface 10a which is substantially smooth and flat while the
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opposite surface 10b is provided with a regular pattern
of depressions or indentations 10c wherein the raised portions
of surface 10b surrounding each of the indentations 10c sub-
stantially define a "waffle-like" pattern. The panel may
be formed of fibre glass of a substantially uniform density
and bound together with a thermosetting binder. Suitable
binders are phenolic, silicone, melamine and urea resins.
The fibrous material may be fibre gla~s, or mineral wool,
for example.
The preferred manner in which the one-piece dual
density core panel is formed is to provide a substantially
flat sheet of uncured material of reasonably uniform (and
known) thickness and density. The sheet is placed between
a first metallic plate 12 (see Fig. 2) having a substantially
smooth, flat surface 12a. A metallic forming tool 13 having
a regular pattern of truncated round, shaped or pointed
substantially conical projections 13a, which may or may not
be flattened at their tops 13c, is pressed upwardly into the
aforementioned uncured sheet 10. The pictured tool member
is truncated to show one preferred shape of the indentation
tool. Other shapes such as triangular or round could be
just as successfully employed, and are part of this inven-
- tion.
The tool 13 is moved by drive means D (which may
be piston driven) toward surface 12a of cooperating metallic
member 12 and is pressed into the uncured panel until the
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recesses 13b between projections 13a are uniformly spaced
a distance Tl from surface 12a, distance Tl being the total
thickness of the panel after undergoing the forming treat-
ment shown in Figure 2. The process is maintained at a
temperature level sufficient to cure and set the binder
by heating means H.
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As can clearly be seen, the portions of the
panel being treated between the upper surface 13c of each
projection 13a and surface 12a of cooperating metallic plate
12 undergoes maximum compression whereas the portion of the
panel between recesses 13b and surface 12a undergoes minimal
compression in the region between projections. The effective
compression between a pair of adjacent projections such as,
for example, the projections 13c and 13c' of Figure 2 can
be seen to taper off to either side of the upper surfaces
13c so as to "merge" in the region Rl between projections
thereby providing a substantially constant high density
region immediately at and beneath surface lOa and providing
a substantially constant low density region at and immed-
iately beneath the projections formed in the panel by the
recesses 13b of tool 13, these lowest density regions being
designated R2.
The manner in which the densities in regions Rl
and R2 may be most easily adjusted can best be understood
from a consideration of Figure 3 wherein the height of the
single projection 13a of tool 13 (only one such projection
being shown in Figure 3 for purposes of simplicity) is
adjusted to provide requisite adjustments in core densities
therefore providing a corresponding change in the indentation
formed in the core panel 10. In the example shown in Figure
3, and providing there is no change in the thickness or
density of the uncured sheet, increasing the depth of the
indentation from an indentation formed by a projection having
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a height A to an indentation formed by a projection having
a height B, increases the density of the board in the
region of surface lOa while the overall thickness of the
board is controlled by the final spacing of elements 12 and
13. Thus, the stress density characteristics o the fibrous
core panel are determined by the distance Tl-A ~or Tl-B, as
the case may be).
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Dual density panels of the type described have
been formed with equal success over the range of design para-
meters such as:
Surface densities, 3-30 lbs. per cubic foot;
typical core panel thicknesses 1/8 - 3 inches; typical
tool indentation depth from 1/16 - 2 7/8 inches; typical core
indentation surface area from 0.02-114 sq. inches (per indenta-
tion-chosen to control uniformity of density at the working
surface); typical projection configurations, flat top, round
top, pointed top, curved top, square, rectangle or trapezoidal
top; available forms: flat sheets, sheets having a curved
radius and die-cut parts.
Some examples of one-piece dual density core panels
formed in accordance with the method of the present inventio
are as follows:
1. Two uncured layers each having a substantially
uniform thickness of one inch and a density of 0.85 lbs. per
cubic foot were treated with a tool to form indentations having
a depth of 3/16 inches. The core panel is formed of
fiber glass in a thermosetting binder of phenolic resin. The
two members 12 and 13 were pressed together to form a one-
piece panel having a total thickness of 3/8`' and a
surface density at the non-textured side of 9 lbs. per
cubic foot. The temperature level maintained during the
treatment was in the range from 350 to 450~F and the
members 12 and 13 preferably being maintained in position as
shown, for example, in Figure 2 for a period of 0.5 minutes.
2. Three uncured layers each having a sub-
stantially uniform thickness of one inch and a density of
1.00 lb. per cubic foot were treated with a tool to form
indentations having a depth of 5/8 inches. The core panel
is formed of fibre glass in a thermosetting binder of phenolic
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resin. The two members 12 and 13 were pressed together to
form a one-piece panel having a total thickness of 1" and a
surface density at the non-textured side of 8.0 lbs. per
cubic foot. The temperature level maintained during the
treatment was in the range from 350 to 450F and the
members 12 and 13 preferably being maintained in position
as shown, for example, in Figure 2 for a period of 1.5
minutes.
A core panel produced in accordance with the methods
set forth hereinabove may be utilized to replace any standard
absorber product in any acoustical application where standard
materials do not supply the needed properties. In field uses,
the core panels may be exposed to continuous operating
temperatures of the order of 450F without experiencin~ any
degradation in either appearance or operating charac-tcristics.
For example, as shown in Figure 4, the finished one-piece
dual density panel 10 may be positioned with its textured
side against a metallic or other barrier septum 14. Although
not shown in Figure 4, the core panel may be coextensive
with the septum 14.
In other applications, a pair of one-piece dual
density core panels 10 and 10' may be arranged back-to-back
with the textured surfaces in engagement wherein the smooth
surfaces are provided on both sides of the resultant core.
As shown in Figure 6, the one-piece core panels 10 and 10'
may be arranged substantially in the same manner as shown in
Figure 5, but with a metallic or other dense acoustical barrier
15 positioned therebetween to add additional significant
transmission loss acoustical qualities to the resultant com-
posite structure so as to absorb sound and even totally blocksound transmission through the composite assembly.
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The smoother surface lOa of the one-piece core
panel assembly lends itself readily to the application of
a decorative material or finish enabling "tiles" of the
core panel to be mounted upon a suspended ceiling framework
16 as shown in Figure 7 with the decoratively finished side
facing downward to provide an aesthetically appealing
acoustical ceiling tile having the requisite thermal, acous-
tical, strength and flame withstanding characteristics.
Figure 8 shows the manner in which two panels
10 and 10' may be mounted with their smooth faces in engage-
ment for utilization in acoustical furniture to increase
available dead air space area under fabrics or blanket
insulations.
Figure 9 shows the manner in which one suitable
decorative sheet or coating is affixed to the flat surface
lOa of panel 10 to provide a tile or panel lending itself
readily for use as an acoustical wall or ceiling treatment.
Figure 10 shows an arrangement in which a pair of
one-piece dual density panels 10 and 10' are arranged with
the textured surfaces in engagement and wherein the smoother
exterior surfaces are covered with a decorative fabric or
sheet 17 (also as shown in Figure 9). The need for an
adhesive to affix the back-to-back core panels is eliminated
through the employment of the channels 18-21 each having
channel arms which are arranged to embrace the marginal por-
tions of the flat surfaces lOa and lOa' to provide an
aesthetically appealing edge finish around all four edges of
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the assembly as well as to securing the assembly components
together. One of the decorative channels 18 may be
provided with suitable openings 18a for receiving threaded
fasteners 22 having eyelets for suspending the decorative
panels, for example, from a ceiling. The channels 18-21
may be secured to the panels by a force-fitting arrangement,
by adhesive means, by providing "corner
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keys" at the engaging corner of each decorative channel or
any other suitable mounting assembly may be provided.
The pattern of projections provided on the tool
may be the reverse of that shown in Figures 2 and 3. For
example, as shown in Figure 3a, the truncated conical shaped
projections 13 may be replaced by truncated conical shaped
recesses 13' surrounded by and defined by the projections
14'. The resulting dual densities substantially conform
to those obtained with the tool of Figures 2 and 3.
Figures 11 and 12 show another preferred
embodiment 30 of the present invention which is comprised
of a dual density one-piece core panel member 10 of the
type described hereinabove and shown, for example, in
Figures 1-3a. Member 10 has molded thereto a rigid fr,ame
comprised of the four joined sides 31a-31d, adjacent ends
of said sides being joined to one another forming corners
Cl-C4 and further being joined to the sides of the core panel
11 so as to form a unitary one-piece structure. The sides
31a-31d defining the frame are formed of a suitable plastic
material such as, for example, epoxy or a suitable thermosetting
plastic and is produced by forming the frame in a molding
process and then fusing the frame to the panel. Alternatively,
the frame may be both molded and fused to the panel at the
same time.
As can best be appreciated from Figure 12, the
width D2 of the frame members measured in the direction
shown in Figure 12 is substantially greater than the
maximum thickness Dl of the core panel 10 so as to create a
recess defined by the frame and textured or dimpled surface lOa
to create a dead air space 32.
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The structure 30 may be employed in contract
furniture, partitions, wall panels and other interior
applications. For example, the structure of Figure 11 may
- be completely wrapped in a fabric and mounted as a panel
upon an interior wall, the textured or dimpled surface lOa
being positioned to confront such an interior wall. For
example, the panels may be formed in the conventional 4 ft.
x 8 ft. size and mounted as finishing panels for a room or
other enclosed areas. As another alternative, the assembly
may be employed as an integral part of a free standing
acoustical screen. For example, considering a section of
S ft. x 5 ft. screen supported by two legs of six inch
height for a space or work area divider, the central portion
of the acoustical screen may, for example, be a 5 ft. x
5 ft. masonite center spacer board having frames of the
same dimension mounted on opposite surfaces of the spacer
board with the smooth surfaces lOb (Figs. 6 and 12) consti-
tuting the exterior surfaces of the screen assemblies and
thereby defining a pair of dead air spaces. The exterior
surfaces may then be covered with a suitable fabric treatment~
As another application, the free standing acoustical
screens described hereinabove may be provided with further
sound attenuating qualities by filling each dead air space
32 (see Fig. 12) with a suitable acoustical blanket fill 33
such as, for example, a low density fiber glass or mineral
wool blanket having a density less than 4 lbs. per cubic foot,
to eliminate any resonant panel effect. Alternatively, a
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uniform density board (rigid or semi-rigid) may be inserted
in the dead air space; or sprayed sound absorptive fill may
be used therein.
As another application somewhat similar to that
shown in Figure 5 or Figure 10, assemblies of the type shown
13a.
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in Figure 11 may be mounted in back-to-back fashion so
as to define an interior dead air space of double volume
(i.e. twice D2 minus Dl) and the resulting back-to-back
assembly may be utilized as acoustical ceiling baffles.
Applications of the frame assembly are about as broad as
those for the individual core panel described hereinabove.
The acoustical characteristics are greater than those
obtained through the use of panels not incorporating such
frames and is further an extremely advantageous cost
efficient method for achieving panel rigidity, maximum
acoustical absorption and required thickness tolerances at
extremely low cost as compared with products and processes
presently available.
Maximum absorption is attained by use of the
dual density rigid acoustical absorber panel 10 which has
its lower density per cubic foot surface, i.e. the dimple
surface lOa, facing the dead air space while the smooth
surface facilitates the application of fabrics treatment,
spraying or other treatment or finish of the panel for
decorative appeal purposes. The molding process utilized
to form the frame members makes it possible to control
panel thickness to a very high degree of precision which is
not capable of being achieved by the core panel per se.
In addition, the materials of the frame member and core
panel are highly compatible with one another so as to assure
simple and yet intimate fusion and joining between the
elements forming the assembly.
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Figure 13 shows one technique for forming
the frame about a dual density core panel 10 in which a
heated (metallic) substrate 40 is provided with an elongated
recess or channel 41 filled with an epoxy or other suitable
thermosetting material. One edge of the core panel 10 is
~ positioned immediately above and adjacent to one side of
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recess 41 filled with the epoxy 42. The recess has a width
D which conforms to the desired width of the final frame
to be formed as was described hereinabove (Fig. 12). Heat
is applied to the substrate 40 sufficient to set the epoxy
and fuse the adjacent edge of the core panel thereto. Channel
41 is coated with a suitable release agent so as to facilitate
removal of the epoxy or other thermosetting material once it
has become set. Each of the remaining three sides of the
panel are created in a similar fashion to form the completed
frame.
Although there has been described a preferred
embodiment of this invention, many variations and modifica-
tions will now be apparent to those skilled in the art.
Therefore, this invention is to be limited, not by the ~ !
specific disclosure herein, but only by the appended claims.
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