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Патент USA US3021257

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Feb. 13, 1962
J. F. STEPHENS
3,021,247
METHOD OF FORMING WALL PANEL TILES
Original Filed March 30, 1956
4 Sheets-Sheet 1
INVENTOR.
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Feb. 13, 1962
J. F. STEPHENS
3,021,247
METHOD OF FORMING WALL PANEL TILES
Original Filed March 30, 1956
4 Sheets-Sheet 2
INVENTOR.
Josef/2 F ?ézf/rexzs
Feb. 13, 1962
J. F. STEPHENS
3,021,247
METHOD OF FORMING WALL PANEL TILES
Original Filed March 30, 1956
4 Sheets~$heet 5
25
22
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Feb. 13, 1962
'
J. F. STEPHENS
METHOD OF‘ FORMING WALL PANEL TILES
Original Filed March 50, 1956
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3,021,247
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4 Sheets-Sheet 4
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INVENTOR.
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United States Patent '0
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1
2
tiles, the mat would be completely contained within the
mold, the major faces being between plates or mold
3,021,247 ,
METHOD OF FORMING WALL PANEL TILES
platens with the edges formed by framing portions of the
Joseph F. Stephens, Kansas City, Mo., assignor to Gustin
‘ Bacon Manufacturing Company, I a corporation of
Missouri
.
'
Original application Mar. 30, 1956, Ser. No. 575,130.
Divided and this application July 5, 1957, Ser. No.
670,330
3,021,247
Patented Feb." 13, .1962
.
2 Claims. (Cl. 156-422)
mold on all four edges. In such case a single piece of
mat or preform was used as the charge into the mold.
Thus, it became desirable to provide a method of mold
ing the tiles which would easily produce the grooved
edges without wrinkling the major faces of the tiles so
that a system of the tileswould make a smooth, unbroken
This invention relates to the suspension of acoustical
‘paneled face. Furthermore, when it became clear that
it was desirable to provide deeper grooves in the edges
insulation panels and refers more particularly to a sus
of the mat than the semicyclindrical ones shown in my
pended acoustical panel system employing deformable,
original application and, especially, when it was desired
to form thejgrooves of different thicknesses at varying
yet semirigid acoustical. tiles therein.
‘
This application is a continuation-in-part of my copend 15 depths in the mat it was obvious that the old molding
ing application, Serial No. 544,183, entitled “Acoustical
technique was inadequate to, perform the desired task.
Insulation Paneling System,” ?led November 1, 1955, and
Therefore, it became necessary to provide a method of
a division of my application, Serial No. 575,130, ?led
molding acoustical panels wherein relatively deep grooves
March 30, 1956, entitled “Acoustical Insulation Paneling
could be formed in the edges of the tile without wrinkling
20 or distortion of the major faces of the tile and also grooves
System.”
~ ‘
Conventional acoustical insulation panel boards or tiles
of varying thickness at varying depths therein.
are generally rigid, nonresilient and noncompressible
Therefore, an object of the present invention is to pro—
pieces. Even in the instances when a ?brous mat, such
‘vide an acoustical paneling system employing a plurality
as a glass ?ber'mat bonded wtih a plastic resin, has been
of resilient, yet semirigid insulating tiles therein and 00
employed, such mats have been of similar character, em 25 operating suspending means for the tiles with which the
ploying stiff, heavy glass ?bers and comprising relatively
tiles are engaged by deformation of the physical structure
high density compositions with a brittle, punky structure. ,
of the tiles themselves.
»
,
.
Conventional wall boards or insulating panels must be
Another object. of the present invention is to provide
mounted essentially like any rigid construction element
an acoustical paneling system employing a plurality of
relative the wall surface‘which is desired to be insulated. 30 resilient ?ber mat acoustical panels and suspending means
Thus, if they are to be applied directly to a wall surface,
for spacing the panels relative a wall surface, the suspend
adhesive or securing means applied individually to each
ing means engaging the edges of the acoustical mats by
panel must be employed. If it is desired to space such
virtue of the deformability and resilience of the mats
conventional acoustical panels relative or away from the
themselves and not requiring any additional mechanical
wall surface (“drop ceiling” suspension systems), elab
orate frameworks are necessitated, said frames requiring
individual ?xation of, the separate tiles thereto by conven
attachment therebetween.
.
_ Another object of the invention ‘is to provide an acous
tical paneling system employing a plurality of ‘resilient
tional securing means. Drop ceiling suspension systems
?brous mats and suspending means for spacing said mats
are desirable in that they require no ?nished ceiling under
relative ‘a wall surface which engages only the edges of
them between the tiles and ceiling service elements as 40 said mats, the suspension means being entirely hidden
ducts, conduits, wires, etc., may be installed and, ?nally,
acoustical tile with air space behind it absorbs sound
more e?iciently than tile ?xed to a hard surface.
In my application, Serial No. 544,183, mentioned
above, of which this application is a continuation-in-part,
resilient insulating panels with cooperating mounting
from view by the mats‘they ‘support.
'
,
Another object of the invention is to provide an acous
tical paneling system comprising insulating tiles and sus
pending means therefor of a character which perm-it the
selection of tiles of any desired size by varying the spac
ing of the suspension means relatively themselves and
means engaging semi-cylindrical grooves in the edges of ' wherein miscellaneously shaped and sized tiles maybe
the panels are shown. This construction is operative but
employed to ?t wall areas of the same character.
has certain‘drawbacks. Thus, the relatively shallow semi
. Another object of the invention is to provide an acous
50
cylindrical grooves in the edge of the mat engageable,
tical paneling system comprising a plurality of resilient,
by cylindrical crow’s feet on spacing arms in some in
stances do not offer as positive support as may be desired.
deformable, yet semirigid insulating tiles and suspension
means therefor, wherein the character of- the engagement
Particularly this is the case where individual panels
. between the insulating panels and the suspension means
of relatively large area are used and more weight must
permits the employment of suspension means of a mini
be carried by the crow’s feet. Thus it becomes desirable 55 mum size and wherein’a plurality of the acoustical tiles
to provide a better construction for the paneling grooves
are engaged by andsuspended relative a single suspension
and engaging crow’s feet to support such larger area
panels while still permitting the snap-on panel mounting
Another object of the invention is to provide ‘an acous
tical paneling system suitable for employment as a drop'
feature. Also, where a greater distortion of the panels
60 ceiling suspension system which employs essentially ?re
is required to mount them on the spacing arm crow,
feet, it is possible to obtain a positive compression on,
resistant tile thereby permitting compliance with recent
all panels, thus resulting in a more uniform and smooth ~ changes in ?re codes requiring such materials.
face to the whole paneling system while also permitting
Anolher object of the invention is to provide an acous
element.
I
_
'
"
more frictional support of the panels by themselves.
tical paneling system employing a plurality of resilient,
shown in my original application was that while the semi
cylindrical grooves as shown therein could ‘be produced
vfor spacing said mats relative a wall surface wherein’
grooves are formed in the edges of‘the mats to be engaged
by squeezing in portions of the mold against the edges of
by the suspending means, the grooves having portions
1 Another problem that arose relative the constructions 65 yet shape-retaining ?brous mats and suspending means
a single piece of mat to be molded to form the grooves,
therein of greater thickness and portions therein of ‘lesser
it was relatively di?icult to avoid wrinkling near the edges 70 depth to'engage correspondingly shaped portions of the
of the major faces, that is, the top and bottom faces of
suspension means whereby to provide ‘very sure and
the tile or panel piece. In such a method of form-ing the
' stable mounting of the tiles relative the suspension means.
3,021,247
3
4
Another object of the invention is to provide grooved
tiles engageable by suspension means, the grooves having
parts of varying thicknes to engage portions of varying
thickness on the suspension means, the suspension means
be employed in the inventive paneling system must be
resilient and deformable, yet essentially semirigid 1n
character. Functionally, this description means that the
edges‘ or faces thereof which permits the provision of a
paneling system of smooth, undistorted face.
?bers of the character described may be bonded together
with'a plastic, preferably thermoselting, resin to form this
tile must be deformable relative itself to decrease its
dimension in any direction and yet be of su?icient rigidity
and resilience to snap back to its original shape after the
with‘a wall surface or a unitary grid construction mount
deforming force is removed and, when returned to that
able on the wall surface as a unit.
‘
shape, retain it even when being suspended only by the
"i ‘Another object of the’invention is to provide a method
of molding the paneling tiles having grooves in the edges
edges thereof. I have discovered that a resilient ?brous
thereof‘with'or‘without portions of the'gr'ooves being 10 mat may be fabricated to these speci?calions. Such a
mat is preferably composed of glass ?bers having an aver
of'varying thickness to engage suspension means of vari
age diameter of less than ten microns, and preferably
able thickness, which method of molding will provide
about four microns randomly oriented in the mat. Glass
the grooved tiles as‘ desired without any distortion of the
either- being separate 'members separately engageable
Other‘ and further‘ objects of the invention will appear
in the course of the following description.
mat. A number of plastics are suitable for such a binder
including phenol condensation products, melamine resins,
ureaformaldehyde resins, urea-melamine resins and vinyl
'
In the drawings, which form a part of the instant speci
chloride acetate resins. Such a binder is preferably em:
?cation and are to be read in conjunction therewith, em
bodim'ent's‘ of the invention are shown and, in the various 20 ployed in a ratio of 15 to 35% by weight of the thermal
insulation of 17 to 55% by weight based on the weight
views, like numerals are employed to indicate like parts.
‘FIG. 1 is a perspective view of an acoustical tile hav
of the glass ?bers. The ?bers and binder, when bonded
ing deep grooves of varying thickness for various depths
together to compose the mat, should form a mat having
thereof suitable for use in an acouslical paneling system
a density in the range of two to ?ve pounds per cubic
embodying the invention.
foot.
FIG. 2 is a bottom perspective view of a plurality of
FIG. 1 shows an acoustical insulation tile 10 formed
the inventive mounting elements to be employed with a
from such a mat and having grooves formed in the
grooved tile as in FIG. 1 in the preferred form of the
edge thereof.
invention positioned relaiive ceiling furring strips.
nearest the edge of the mat of relatively lesser thickness
and the internal portions thereof away from the edges of
the mat of relatively greater thickness. These portions
are respectively indicated at 11 and 11a. The grooves
are employed to engage suspending means of a character
to be described. The grooves may be varied in positron
and length on the edges of the mat‘ relative one of the
types of suspending means to be described but the form
shown in FIG. 1 having grooves completely circumferen
tial on the edges of the mat isadaptable to all of the forms
of suspension means‘ disclosed in the speci?cation. Such
grooves 11 and 11a may be formed in the edge of the,
mat by an inventive method of molding the mat which
will be laler described. The deeper portions 11a of the
grooves should be formed according to the shape of the
suspension means employed. Thus the portions 11a of
FIG. 1 are cylindrical but may be molded triangular,
FIG. 3 isa perspective view of a single one of the
inventive suspension means employed in the preferred
form of the acoustical paneling system engaged with a
Single acoustical insulating tile having deep variable thick
ness grooves suitable for use in the inventive panelingv
system.
'
'
'
'
’
FIG. 4 is a bottom perspective view of a modi?cation‘
of the inventive paneling system showing a modi?ed grid
suspension means engaged by an acoustical tile having
deep grooves of varying thicknes suitable for use there
with in the practice of the modi?ed form of the invention.
FIG. 5 is a schematic exploded perspective view of the
apparatus employed in the inventive method of molding
the acoustical tiles employed in the inventive paneling
system.
'
i
'
FIG. 6 is a side sectional view of a stage in the inventive
molding method using apparatus of FIG. 5.
The grooves have the portion thereof
square, etc.
FIG. 7 is a view identical to that of FIG. 3 except the
Since drop ceiling installations are rapidly superseding
ceiling suspension means employed therein has spline
portions in they groove engaging feet thereof of triangular
the old type of acoustical tile adhered to a ?nished ceil
ing, it is important to note that ?re code regulations re
quire all tile used in drop ceilings to be of a ?reproof
form in cross section rather than cylindrical form as in
FIG. 3, the triangular spline portions engaging grooves
nature. Tile that would burn does so much more readily
in the mat having the deeper portions thereof formed also
and violently if there is an air space behind it. The tile
disclosed is ?reproof and meets the ?re code requirements,
in addition to possessing the qualities set forth.
triangular‘ in cross section to receive and engage the
spline portions.
"FIG. 8 ‘is a view identical to that of FIG. 5 except the
' (FIGS. 2, 3 and 7 illustrate the preferred'form of the
acoustical tile suspension means having spacing arms 12
with screw portion 13 at the upper end thereof engage
able with wall surfaces or furring strips 14 to be laid on
wall surfaces and a plurality of acoustical tile groove
the suspension means shown in FIG. 7 as opposed to 60 engaging feet 15. Feet 15 are ?xed radially to the outer
those of FIGS. 3 and 4.
ends of spacing arms 12. The width of feet 15 is pref
FIG. 9 is a partial side sectional view of valstage in the
erably equal to twice the depth of the acoustical tile
framing member (the central piece in the ?gure) em
ployedto give form to the grooves in the ?nished mat has
the groove forming portions thereof limited in extent
and shape to’ form grooves‘only for the modi?cation of
inventivemolding method using the apparatus of FIG. 8.
The invention comprises an acoustical paneling system
made up’ of .a plurality of resilient, deformable, yet semi
rigid insulating tiles and suspension means for position
grooves 11. Acoustical tiles as are shown in FIG. 1 with
continuous grooves in the outside edges thereof may
be employed with the preferred modi?cation of the sus
pending means. In this case, the groove engaging feet
15 only engage the corner portions of the grooves. Al~~
ternatively, tiles 10 may be formed for this type of sus~
ing the tiles relative wall surfaces, the system in combi
nation'providing a continuous panel of acoustical insula
tion‘; Two modi?cations of the vinvention are shown in
pension means having grooves 11 positioned only adjacent
the ‘?gures. The general nature of the acoustical panels 70 the corners of the tiles and of a length essentially equal
suitable for use in'the inventive system will‘ be ?rst de
to the length of the groove engaging feet 15. The groove
scribed and the speci?c modi?cations of the invention
engaging feet have spline portions 15a and flat pieces
as embodied in the suspension means and the inter
engagernent of the tiles therewilh.
'
The acoustical panels for insulating tiles which may
15b therebetween. The form of the spline pieces is iden
tical with that of the form of the’ inner portions of the
75
grooves 1.1a 5? thatths Portionshq will snugly. ?t.
3,621,224‘?
5
,
6
.
around the spline portions 15a. The depth of the tile
spline sections 17b and ?at sections 17a function the
groove portions 11 is equal to one-half the width of the
same as in the preferred modi?cation of mounting arm
?at portions 15b on the crow foot arms.
to engage the thicker and thinner portions of the grooves
It should be
noted that the spline pieces of the crow feet may be any
11 and 11a, the spline sections 17b being variable in
shape desired in cross section (that is, cylindrical, tri
angular, square, etc.) to offer the maximum frictional
form as splines 15a to engage grooves 11a of like vari
able form. Here a plurality of engaging arms 17 form
engagement. FIG. 7 (the ?gure being numbered with
a grid of preferably rectangular partitions. The arms 17
primes to distinguish from FIG. 3) illustrates the tri
are suspended, preferably at their intersections, by spac
angular form of the spline portions ‘with the thickened
' ing legs 18 having wall engaging plates 19 thereon. The
part or base of the triangle adjacent the edge of the 10 engaging arms 17 shown are positioned centrally of the
grooves. The deeper portions 11a of the grooves 11a
grid, but, as‘ in the previous modi?cation, the side and
in this form are, of course, molded congruent'to the
corner ‘arms of the total grid frame may have only three
or two arms 17 meeting at a junction respectively and
form of the spline pieces. Since the mat is‘ resilient, there
is no problem of inserting the grooves over the spline
portions.
the side and end arms 17 and spacing legs 18 may be in
15 half-section to permit complete enclosure thereof by the
Acoustical tile suspending means of this preferred
modi?cation may be employed having only three or two
shown) it is alsopcontemplated that no outside bounding
radial feet 15 and with half-section feet 15 or half or
‘arm 17 ring the grid, but, instead, wall moldings be em- 7
quarter-section arms 12 to form the end and side pieces
of a panel wall system, as is shown in FIG. 2. Such end
ployed to ‘support the boundary tiles. It should also be
noted that it is not necessary to have spacing legs 18
engaging grooves 11 of tiles 10.
In a variation (not
and side pieces generally employ pointed rather than
at each arm 17 junction as the provision of a few regu
screw tips of arms 12. Depth washers 16 may be em
larly spaced relative the total grid will suffice.
[In operation, the grid arms 17 {are suspended by legs
ployed to regulate the extension of the spacing arms 12
from the wall surface and thereby to provide equal spac
18 from a wall surface or furring strips 14 attached to
ing distances for each suspension means. As may be 25 wall surfaces. It is, of course, not necessary that the
readily seen by looking at FIG. 2, a suspension means of
grid partitions be rectangular in shape but only that the
the preferred type may be engaged by only one acoustical
form of the tiles be congruent with the form of the par
tile (corner suspension), two acoustical tiles (edge sus
titions. After the grid is positioned relative the wall
pending means) or four acoustical tiles (central sup
surface, the partitions between the engagingarms 17
port). As previously noted, the end and side suspension
are ?lled by deforming grooved tiles 10 to engage the
means may be formed in half and quarter-section as
shown in FIG. 1 so, when tiles‘ are ?tted into the‘ groove
engaging ‘feet of the entire set of suspension elements,
all of the groove engaging feet are completely hidden
arms 17 with the grooves 11 thereof. When all the par
titions have been ?lled, an essentially continuous acousti
cal paneling system will have been provided.
In both modi?cations of the inventive acoustical panel
from view by the essentially continuous panel surface. 35 ing system, the panel tiles may be removed from and
Alternatively, wall molding strips may be employed to
replaced into the suspension means at will. This fea~
retain and support the edges of the tiles at the panel
ture permits of vaccess to the space above the tiles where- f
boundaries (not shown).
in heating, ventilating,‘ and air conditioning ducts, elec
I
,
‘
In operation, wood furring strips 14 may or may not
trical conduits for lighting or other purposes are nor
be attached to the ceiling or wall surfaces and are spaced 4.0 mally disposed; thus making such equipment accessible.
properly relative one another. Spacing arms ‘12, pref
erably having depth washers 16 thereon, are then screwed
It further permits of the removal of the tile from the
suspension means for cleaning or resurfacing and restora
tion to place in the suspension system without any dis
or driven into the wall surface or furring strips 14 or
may previously be attached to the latter before mount
turbance of the elements of the latter.
ing on the wall. The groove engaging feet 15 may or 45
FIGS. 5, 6, 8 and 9 illustrate the inventive method of
may not be detachable from the spacing arms 12 for
forming the panels employed in the inventive acoustical
easier mounting thereof. The distance between the spac- ~
insulation paneling system. The showings of FIGS. 5,
ing arms 12 of separate suspension means depends upon
6,8 and 9are essentially schematic. FIGS. 8 and 9
the length and width of the acoustical tiles. It may be
are identical to FIGS. 5 and 6 save in that the form of
readily seen that odd shaped or nonrectangular pieces 50 the inner groove molding portions are triangular in cross
may be employed by varying the attachment of the spac
section and limited in extent to mold grooves adapted
ing arms 12 to the wall surface or the angles of the groove
only for use with suspension elements of the forms of
engaging feet 15 relative one another on the arm 12.
FIG. 3 and FIG. 7. The numbers in FIGS. Sand 9 are
After the suspension‘ means have been vattached to the 7
primed to distinguish from FIGS. 5 and 6.
wall surface, the acoustical tiles are deformed so that 55
The method comprises the steps of (1) laying a half
the grooves 11 thereof may be engaged by the groove
thickness of green uncured mat 20 on the bottom platen ~
engaging feet 15. Note that it is practically; necessary
21 of a mold,’ (2) laying a framing member 22 on the
green mat half-thickness 20, the framing'member having
to deform the tile in at least two directions, therefore re
quiring quite a great deal of resiliency in the tile itself.
a cutout portion therein so shaped as to de?ne the areas
When the tiles have all been engaged on the feet 15, a 60 of the tile edge in which grooves are to be formed (the
smooth, continuous, self-supporting acoustical panel ‘has
been provided completely covering the suspension means.
The great depth of‘ the grooves in‘the panels necessi
tates extreme compression of the panels in the mounting
framing member in FIG. 5 having enlarged inner circum
ferential portion 23 to form the enlarged inner portions
of the grooves in the mat), (3) then placing a second ~
half-thickness of green uncured mat 24 on top of the
process and also permits employment of panels of a size
framing member 22, and (4) closing the upper platen 25
which provide positive compression among the ‘panels
of the mold on the assembly under such conditions of
thereby further sealing the lines of contact of the in
dividual panels and aiding in producing a continuous
heat and pressure as to cure the mat and form a ?nished
face of the total panel system.
grooves of the desired form.
‘
FIG. 4 illustrates an acoustical tile of the form shown 70
panel of the desired density and resilience with edge
~
Stated in other words, the method comprises molding
in FIG. 1 mounted on a second modi?cation of the sus
wall panel tiles with grooved edges wherein a hollow cen- >
pending means.
Here a plurality of engaging arms 17
ter framing member 22 is placed between two half thick-p
form a grid of preferably rectangular partitions. The en
gaging arms 17 in cross section have spline section 17a
21 and 25, then compressing the two mat thicknesses
and ?at section 17b joining the spline sections.
nesses of green, uncured mat 20 and 24 and mold halves
The 75 around the framing member under such conditions of
3,021,247
7
8
pressure and temperature as to cure the mat and‘ fuse
the thicknesses thereof to the desired density with grooves
in the edges thereof.
Since the showings of FIGS. 5, 6, 8 and 9 are schematic,
invention without departing from the scope thereof, it
is to be understood that allv matter hereinabove set forth
or shown in the accompanying drawings is to be inter
preted as illustrative and not in a limiting sense.
the means for moving the mold halves toward and away
Having thus described my invention, I claim:
1. A method of forming resilient, deformable wall
from one another are not shown nor are the heating con
nections to the mold halves shown. Such heating con
panel tiles with grooved edges to receive the groove,
nections may be electrical lines to resistance elements in
engaging feet of mounting arms comprising the steps of
laying a half thickness of green uncured mat on the bot
the mold platens or ?uid flow lines (steam, hot air, etc.)
of conventional type.
10 tom platen of a mold, laying a framing member on the
It is evident that the framing member may be of any
green mat having a cutout portion. therein so shaped as
desired form relative the mat sections. Thus the fram
to de?ne with the noncutout portions thereof the areas
ing member may be without the enlarged inner rim 23,
of the tile edge in which grooves are‘ to be formed, plac
thereby to form only regular grooves in the edges of the
ing a second half thickness of green uncured mat on
mat. Also, the enlarged portions 23 may be merely of 15 top of said framing member, and applying the upper
a length equal to the length of the crow’s feet in the
platen of the mold on top of the assembly under such
paneling suspension system (see FIG. 8). The only
structural requirement of the framing member is that it
conditions of heat and pressure as to cure the mat and
form an integral ?nished panel of the desired density and
be formed with a central cutout portion of lesser area
resilience with edge grooves of the desired form and re
than the area of the green mat section so that the fram 20 moving said frarning member from the edge grooves of
ing member will overlie the edges of the mat to some
said panel after curing of the mat and formation of said
extent in the molding process to form the grooves there
integral ?nished panel.
in. The preferred form of framing member is shown
in FIG. 5.
2. A method of molding resilient, deformable wall
panel tiles with grooved edges comprising placing a hol
The effect of the use of such a frame mem
ber is to establish a parting line within the green stock 25 low center framing member between two half thicknesses
half-way through the thickness of the mat, so‘ that the'
of green uncured mat and a pair of mold halves, then
crowding. of the stock during the molding operation is in
compressing the two mat thicknesses on the framing mem
av direction normal to the major faces of the mat rather '
her under such pressure and temperature as to cure the
than normal to the edges. This technique becames of
mat and fuse the thicknesses thereof centrally of said.
greater importance as the suspending means crow’s feet 30 framing member into an integral member of the desired
are enlarged for greater positive. support. With this
molding method wrinkles may be completely avoided
in the formation of the mat. It is obvious, of course,
that the two pieces of mat knit together in the curing
operation to form a unitary panel.
density with grooves in the edges thereof de?ned by the
framing member and removing said framing member
from theedge grooves of said integral member.
35
From the foregoing it will, be seen. that this invention
is one well. adapted to attain all of the. ends and objects
hereinabove set forth together with other advantages
which are obvious and which are inherent to the invention.
It will be understood that. certain features and. sub 40
combinations are of utilityv and may be employed with
out reference to other features and subcombinations.
This is contemplated by and isv within the scope of the
claims.
As many. possible embodiments may be made of the 45
References Cited in the ?le of this patent
UNITED STATES PATENTS
1,641,648
'Speer ______________ __ Sept. 6, 1927
1,911,374
Loetscher __________ __ May 30, 1933'
2,157,622
Neesen et a1. ________ __ May 9, 1939
27,582,922
Crowley et al. _____V_V____ Jan. 15, 1,952,‘
2,647,072
Smith ______________ __ J‘ulyv 28,v 1953
2,659,687
2,748,048
Moore ___V____V _______ __ Nov. 17,1953
Russell ______ _.. ______ __ May 29, 1956’
2,770,386
Mitchell et a1. _______ __ Nov. 13, 1956
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