Note: Descriptions are shown in the official language in which they were submitted.
1;Z1~7~ 5
~ HORIZONTAL RIBBON EXTRUSION FROM A
HOPPER AND THREE COMPRESSION ROLLERS
This application is a division of Canadian Serial No.
426,878, filed April 27, 1983, which is a division of
Canadian Serial No. 3441563, filed January 29, 1980, now
Canadian Patent No. 1,150,483, issued July 26, 1983.
I! ~
BACKGRO~ND OF THE INVENTION
1. Field of the Invention
This invention relates to the production of cellular
vitreous slabs or shapes having a substantial part of the volume
composed of gases enclosed in the cells, and is particularly
concerned with the process and apparatus to produce cellular
vitreous refractory material in prescribed shapes and products
therefrom of lighter densities than conventional brick or tile,
and more impermeable.
2. Description of the Prior Art
There is one commercial producer of cellular glass
blocks who uses a process in which powdered or pulverized glass is
the main raw material. The fine particle size glass powder is
mixed with two chemical agents which react to form gas at a
temperature above the point where the glass sinters to seal in the
~qas. The same corporation owns V.S. Patent No. 2,890,127 which
discloses usinq powdered quartzite as the charge and discrete
carbon particles or silicon carbide, the carbon reacting with
Sio2 to produce the foaming qas. It also owns ~.S. Patent No.
2,890,126 which discloses supporting the charge by graphite slabs
and the addition of compounds, such as feldspar, to the mixture of
Patent No. 2,890,127 to decrease viscosity and improve sintering
and cellulation. Commercial production was maintained
30 ~~ intermittently for several years and then abandoned. These two
patents pointed out the radically improved properties obtained
when the glass blocks are of almost pure silica glass. I
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The kiln for the above described commercial process was
made of graphite slabs which acted as resistance heaters. The
charqe was carried in graphite pans in a train throuqh the kiln.
The process was not successful, as I understand the matter,
because it was too expensive and the graphite slabs and pans would
not last. My process avoids expensive grinding to fine particle
size and the use of expensive high quality graphite for kiln parts
and charge pans.
Various patents describe the foaming of various minerals
to avoid the expense of first making powdered glass. None have
resulted in a sustained commercial production of a slab or shape;
however, Dow Chemical did produce ~market development" quantities
of foamed vitreous clay blocks for several years, using clay as a
raw material~ The prior art of bloating clay into lumps of
cellulated material gave Dow the hot lumps which they pressed and
thus welded into blocks. (U.S. Patent 3,056,184).
For centuries, prescribed shapes of roof tile, wall
tile, floor tile, brick, and various ceramic bodies, such as
flower pots, china and the like, have been produced by pressing a
mixture of clay and water then drying and sintering the same.
Such products as bricks have been produced by extruding the clay
mixtures so as to compact the charge into quite dense masses.
"Dry" pressing of the clay mixture at high pressure has also been
employed, extensively.
Such dense clay mixtures produced by dry pressinq or
damp pressing have usually contained from about 5~ to 8% moisture
and have been subiected to from about 100~ psi to (about) 5000
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psi. In the prior art extrusion of clay mixtures, the moisture
content of the clay mixture is usually higher, namely in the
neighborhood of from 15% to 20%, however, very substantial
pressure is still necessary.
Each of the resulting dense mixtures must be dried quite
slowly over an extended period of time so as to permit the gradual
migration of the moisture through the clay. If such a procedure
is not followed, the clay may crack or explode during drying. The
resulting sintered clay is quite dense and holds its original
shape without cracking or crazing. The sintering is at a
temperature below the fusion temperature of the clay which is
employed. I use a mix which is 1QW in moisture and is pressed at
10~J pressures. This enabales the rapid heating of the charge
which may crack on sinterin~ but such cracks are later healed.
In the past, the cellulation of clay materials have been
carried out. For example, Ford, in U.S. Patent No. 2,485~724
taught that by usinq flux~ low temperature foaming of a special
Albany slip clay could be carried out using an oxygen containing
agent and carbon in the form of carbon black. Ford also taught
that urea, sugar, dextrose or molasses could be substituted for
the carbon black to produce bodies havin~ densities of from 10 to
20 lbs. per cuhic foot. The firing temperature was in the
neighborhood of 1500F to 1800F.
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In my U.S. Patent No. 3,967,970 I produced a bloated
clay by firing at about 2100F to 2300F of a mixture of clay,
suqar, sodium or potassium hydroxide and water. In example 4 of
that patent, I substituted trisodium phosphate for the sodium
hydroxide.
The process of the present invention eliminates the
expense, trouble and hazards of using a flux and has thus produced
a foamed product having a higher melting point and more resistant
to water and chemical agents.
U.S. Patent No. 2,337,672 discloses the manufacturers of
multicellular qlass by heating a charge from qlass, oxide of
arsenic, zinc or cadmium and carbon powder to produce a reaction
between the oxide and the carbon.
Other less pertinent U.S. patents relating to bloatin~
of ceramic material include the following:
3,174,870 3,15~,988
3,666,506 2r880,099
3,536,5~3 2,564,978
3,307,~57 2,670,299
~0 None of the prior art patents discussed above disclose
any practical means for producing a foamed mineral block or plate
~uickly and economically.
Accordinqly, the present invention seeks to
provide an apparatus for and method of producing a foamed mineral
article quickly, efficiently and at a low cost.
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The present invention also seeks to provide a foamed
mineral article which is highly insulative and light weight and
yet is resistant to aging, corrosion and water absorption.
Further the present invention seeks to provide a process
and apparatus for producing a foamed mineral material and the
material, itself, which has a high structural strength capable
of forming load bearing walls and roof decks with wide spaced
supports and can be produced in large sheetsO
Other aspects, features and advantages of the present
invention will become apparent from the following detailed
description.
SUMMARY OF THE INVENTION
~ ~ . .....
Briefly described, the invention in one aspect pertains
to an apparatus for feeding raw material as a ribbon in a
horizontal direction, preferably into a kiln for firing
refractory raw material, including a hopper for the raw material,
the hopper having an opening in its bottom portion with a pair
of spaced transversely opposed compression rollers, the inner
peripheries of which are disposed on opposite sides of the
opening for engaging on opposite sides and compressing there-
between and progressively feeding the raw material as a stream
downwardly. A third compression roller is below the one of
the opposed compression rollers, and guide means is provided
for guiding a surface of ~e stream from the other of the opposed
compression rollers to the upper periphery of the third compres-
sion roller. The opposed compression rollers compact and feed
the raw material from the hopper into a stream fed in a down-
ward direction, and the third compression roller and the one of
the opposed compression rollers cooperate to compact and feed
the stream as a ribbon of indeterminate length in a horizontal
direction.
More particularly, the process of the invention as dis-
closed employs low pressure for the compacting of a clay, carbon-
aceous material and moisture, mixture charge followed by rapid
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heating to dry the clay charge and the progressive firing of the
shaped charge, above the fusion temperature, on rollers without
the necessity of carrier plates to produce a preshaped cellular
vitreous impervious lightweight refractory. The movement o~ the
charge through the firing zone is slow; however, no appreciable
sagging of the ribbons of charge take place, due to the high
viscosity of the molten clay involved. Any cracks occuring
during drying or preheating are healed by the bloating of the clay.
~ssentially the same procedure is followed for producing
a preshaped foamed fused silica product employing as a charge,
finely divided silica and a carbonaceous foaming agent.
When a clay or silica ribbon is prepared to be passed
over the rollers of the apparatus, a parting or releasing agent
is in some cases applied to the bottom and perhaps sides of the
ribbon.
The preferred apparatus of the invention includes a
plurality of juxtaposed sets of damp pressing rolls, each of
which is supplied from a hopper with a mixture of clay and/or
shale whose carbonaceous material content and moisture content
has been adjusted. Each set of rolls also co-extrudes a releasing
or parting agent around the sides and bottom of the ribbon o~
clay raw material which is extruded. Nozzles introduce glaze or
engobe to the top of the ribbon.
The force of the rolls feed the ribbons along parallel
horizontal vertically spaced paths to the first warming or pre-
heating chamber of the kiln and, thence, into the firing chamber
along the upper surfaces of rollers. The ends of the rollers
protrude outwardly of the walls of the kiln, the end portions
being supported on circumferentially spaced idler wheels and
can be rotated simultaneously by a common belt.
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Fuel and air are supplied, via headers, to the burners
disposed in staggered relationship in opposed parallel rows
along the sides of the kiln in the firing chamber. Exhaust
ports are disposed opposite to the nozzles, the ports leading
to manifolds which feed to the exit portion of the preheating
chamber of the kiln. Exhaust blowers discharge the flue gases
from the entrance portion of the preheating chamberO In the
preheating chamber, sintering of the ribbons usually takes
place.
Foaming of the sintered clay ribbons takes place at
above about 2000F in the firing chamber as the ribbons are
progressively moved along the rollers in the firing chamber.
The ribbons, emerging from the exit of the firing
chamber, are in the form of impervious cellulated refractory
streams and are passed into an annealing lehr where the temp-
erature thereof is rapidly reduced to annealing temperature
and then annealed. Thence, these products are fed to conveyors
where they are cut into rectangular blocks.
In another aspect of the invention as disclosed a
charge of silica, carbonaceous material and water is produced
in a heated low pressure press. A plate, formed from aluminum
foil or other release agent and a lAyer of pitch and coke or
c~al is produced on the lower surface of the charge, at the same
time the charge is being pressed.
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This compacted silica charge, on its plate, is fed
through the kiln end-to-end and is preheated and foamed in
the manner previously described for clay. Cellular fused silica
blocks are formed.
In a still further embodiment of the invention disclosed
there may be two stage extruders, each having three feed rollers
to feed a charge as a ribbon from hopper horizontally to the
kiln. The parting agent is sprayed from below onto the ribbon
and the glaze or engobe from above. The kiln of the embodiment
has muffle plates to produce vertically spaced chamb~rs above
and below the ribbons, the chambers exhausting into the drying
or preheating zone of the kiln.
In yet another disclosed embodiment the kiln is depicted
as ram fed with preassembled pans containing charges of green
or raw silica. The sections of the pan are either preassembled
to receive a hand rammed charge or respectively provided with
pressed charges which upon melting form a monolithic or unitary
fused product.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. lA is a schematic vertical sectional view of one
embodiment of an apparatus for producing cellulated refractory
material according to the present invention, the apparatus being
shown as processing clay charges;
Fig. lB is a continuation of the view of the apparatus
shown in Fig. lA;
Fig. lC is a continuation of the view of Fig7 lB;
Fig. 2 is a vertical sectional view taken substantially
along line 2-2 in Fig. lA;
Fig. 3 is a vertical sectional view taken substantially
along line 3 - 3 in Fig. lA;
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Fig. 4 is a vertical sectional view taken substantially
along line 4-4 in Fig. lB;
Fig. 5 is a vertical sectional view taken substantially
along line 5-5 in Fig lB;
Fig. 5 is a vertical sectional view taken substantially
along line 6 6 in Fig. lC;
Fig. 7 i5 a vertical sectional view taken substantially
along line 7-7 in Fig. lC;
Fig. 8 is a vertical sectional view similar to Fig. 4
of a modified form of the kiln of the present invention;
Fig. 9 is a vertical sectional view similar to Fig. 5
of a modified form of the present invention;
Fig. 10 is a vertical sectional view of the front
portion of a second embodiment of the present invention showing
a press assembly for forming successive rectangular charges to be
fed to the kiln;
Fig. 11 is an enlarged fragmentary side elevational
view showing the drive for the horizontal feed rollers of the
kiln of Figs. lA; lB and lC;
Fig. 12 is a view similar to Fig. 11 but showing the
drive for those feed rollers which are spaced apart more than
the rollers of Fig. 11;
Fig. 13A is a vertlcal sectional view similar to
Fig. lA but showing a thlrd embodiment of apparatus for
producing cellulated refractory material;
Fig. 13~ is a continuation of the view shown in
Fig. 13A;
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Fig. 13C is a continuation of the view shown in Fig.
13B and showing the glaze applicators and the annealing lehr;
Fig. 14 is a vertical sectional view taken substantially
along line 14 14 in Fig. 13A;
Fig. 15 is a vertical sectional view taken substantially
along line 15-15 in Fig. lA;
Fig. 16 is a vertical sectional view taken substantially
along line 16-16 ln Fig. 13A,
Fig. 17 is a vextical view taken substantially along
line 17-17 in Fig. 13B;
Fig. 18A is a vertical sectional view similar to
Fig. lA and Fig. 13A showing a fourth embodiment of ~y invention;
~ig. 18B is a con~inuation of Fig. 18A; and
Fig. 19 is an exploded perspective view of abutting
sections forming a first pan for receiving an unpressed charge
of sand or brickettes;
Fig. 20 is an exploded perspective view of several
abutting sections forming a pan, the sections being shown after
being pressed with their respective portions of the total charge;
2Q Fig. 21 is a perspective view of the assembled pan of
Fig. 20, without the charge; and
Fig. 22 is a fragmentary plan view of a portion of the
pan of Fig. 20 and 21 with its charge within the kiln of Fig.
13A, 13B and 13C, the sides and vertical alignment rollers of
the kiln being shown in cross-section.
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DESCRIPTION OE' THE PREFERRED EMBODIMENTS
Referring now in detail to the embodiments chosen
for the purpose of illustrating the apparatus of the present
invention, numeral 10 in Fig. 1 denotes a vertically disposed
hopper having parallel triangular end walls 11 joined hy
downwardly converging s~de walls 12 which terminate in a
rectangular opening at the bottom portion of the hopper. A set
of damp pressing rollers is carried at the opening of the
hopper 10. This set includes a pair of opposed compression
rollers 13 carried by brackets 14 for rotation about spaced,
parallel, horizontally disposèd, axes or axles 15 rotated in
opposite direc~.ions for compacting and feeding the material or
charge contained in the hopper 10 into a curved conduit 16
having a rectangular cross sectional area. End rollers 19
disposed along axes or axles perpendicular to axles 15 cooperate
with rollers 13 for compacting and driving the material into
conduit 16.
The rollers 13 and 19 thus extrude a rectangular
ribbon 20 of the raw material or charge in a vertical downward
path into the upper end portio~ of the conduit 16. The curved
contour of the conduit 16 progressively alters the course of
the ribbon 20 from a vertical path to a horizontal path, the
lower end portion 17 of the conduit 16 protruding in a horizontal
direction outwardly from the conduit 16 to provide a slide plate
along which the ribbon 20 p~ogressively moves. The upper surface
of the slide plate 17 is aligned with the upper periphery of
a plurality of parallel disposed, infeed, conveyor rollers 18
which are formed either of steel or ceramic material. The
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infeed rollers 18 are rotated in synchronization so as to form a
live deck for the conveyance of the ribbon 20 into the entrance
port 9 in the front or entrance end 26 of a kiln, denoted
generally by the numeral 25. Thust the ribbon 20 forms a
continuous charge of rectangular cross section which is moved
through the kiln 25 from the entrance end 26 to the exit end 27 of
the kiln 25.
As seen in Fig. 1A the hopper 10 is compartmented to
provide a main charge receiving compartment 21 and a releasing or
parting agent compartment 22. A U-shaped partition 23 separates
the two compartments 21 and 22. In more detail, partition 23
includes opposed truncated, triangular shaped, downwardly
converging, parallel, side walls 24, joined by their forward edges
to the side walls 11. The rear edges of the side walls 24 are
respectively joined to the edges of a transverse rectangular
partition plate 26a. Thus, a U-shaped secondary or parting agent
compartment 22 is devined by a portion of hopper 10 and the
partition 23 which also surrounds three sides of the main charge
receiving chamber 21a
A mixture consisting of clayey material, water and
carbonaceous material (adjusted as to carbonaceous material and
moisture) after being granulated and thoroughly mixed, is fed into
the main compartment 21. A parting or releasing agent is fed in~o
the compartment 22. This parting or releasing agent can be any of
a variety of agents which are employed for preventing sticking of
surfaces in a mold. I prefer, in order to keep the rollers 35 and
36 clean, to use a damp mixture of fire clay and fire clay grog
which has the double function of separating the extruded ribbon 20
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~Z~;)7S~S
of clayey material from the rollers in the kiln 25 and also
confine the width of expansion of the ribbon 20, transversely.
Furthermore, the parting or releasing agent around the sides and
bottom of the ribbon 20 may be made strong enough to resist
breaking off in case of a sticky spot on the rollers 35 and 36
caused by an inadvertent contamination.
An alternative partin~ agent mixture of silica sand
bonded with moist clay to about 8 to 20% clay may be used, to giv
adequate bond to substantially hold the parting layer through the
green and dry stages. This would give a stronger bond upon
firing, except that the sudden expansion of the sand grain at
about 1073F largely breaks the bond. Then in case of a sticky
spot of molten material on the rollers, the sand grains are given
up to the spot until the stickiness i~ covered.
In case the charge is silica or clay with a fusion
temperature above about 2900F, the parting agent should be pitch
bonded carbonaceous material such as coke or coal.
When a pitch or tar bonded coke or coal is to be used a
the parting agent, it is preferahle to employ a low pressure
rectan~ular press 202 of Fig. 10 in which the platen 203 of the
press 202 receives the parting as a first layer and the clay or
silica charge is loaded, thereover.
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In more detail, the press 202 includes a vertically
disposed double acting hydraulic or air cylinder 204, the piston
rod of which reciprocates in a vertical path a rectangular flat
metal press plate 20S.
The heated rectangular platen 203 is disposed in a
fixed position in registry below the plate 205. Below the
plate 203 is a vertically moveable border supporting plate 206
which carries an upstanding border member 207 surrounding the
edge portions of the platen 203. Legs 208, projecting through
holes in the support plate 206, support the platen 203.
A ram 209 reciprocates the plate 206 and hence border
member 207 in a vertical path from the position shown in broken
lines to the position shown in full lines in Fig. 10.
Mounted for horizontal movement across platen 203 is
a ram plat2 211 carried by the piston rod Qf a horizontally
disposed ram 213. A slide plate 213 on the side of platen 203
provides a deck over which ~uccessive charges 220 are fed from
press 202 into the oven or kiln 225 for processing.
In operation the plate 205 is retracted and the border
member 207 raised around the platen 206. The charge, which
may consist of an aluminum sheet, a carbonaceous material and a
binder on the sheet as a thin layer, and the silica charge
thereover, is placed in the border member 207 on the platen 203.
The material is then pressed by plate 205 through actuation of
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l ~ ()75~S
of the press cylinder 204 and then the plate 205 is retracted
Thereafter, the border member 207 is stripped downwardly and the
ram 213 actuated to move ram plate 211 over the platen 203 and
urge charge 220 into kiln 225. Successive charges 220 form a
ribbon entering kiln 225 where it is then treated in the same
manner as ribbon 20 in kiln 25.
The low pressure press 202 is normally used to exert a
pressure of from about S0 psi to about 1000 psi and can be used in
place of the rollers 13 and 19 for forming clay charges with or
without a parting agent alona the bottom surface or bottom and
¦ i ~url-ce- Or the clay ~h~e
1;Z0'~515
Disposed above the slide plate 17 is a drying heater
28 the function of which i8 to dry the upper surface of ribbon
20 as it emerges from the conduit 16 in a horizontal path. The
heater 28 can, if desired, be an electrical resistance heater
or a gas heater or any of a variety of heaters which would
supply sufficient heat fox simply drying the upper surface of the
ribbon 20. Rearwardly of the heater 28, along the path of the rib-
bon 20, is a color coating nozzle assembly 29 which extends trans-
versely across and above the path of travel of the ribbon 20.
The function of this nozzle asse~bly 29 is to feed engobes or
glaze onto the upper surface of the ribbon 20, af~er the surface
has been dried. Of course, the color coating may be omitted when
desired.
Thus, at this stage, the ribbon 20 is travelling in a
horizontal path and has a releasing agent along it~ bottom and
side surfaces and a glaze or engobe along its upper surface.
A second hopper 110 which is identical to the hopper 10 is
disposed adjacent to hopper 10 for providing a second ribbon
120 for entry into the kiln 25. This second hopper 110 includes
rectangular downwardly converging side walls 112 and truncated
triangular walls 111 forming a rectangular downwardly converging
hopper. The hopper 110 also includes opposed feed rollers
112 rotating on axles 115 and supported by brackets 114. Further-
more, the hopper 110 includes side rollers 119 which cooperate
with the feed roller~ 113 in creating a downwardly directed stream
or ribbon 120 which is received within the curved conduit 116.
Conduit 116 gradually alters the path of the ribbon 120 from a
vertical downwardly directed path into a horizontally directed
path. Like the hopper 10 the hopper 110 includes a paxtition
123 so that the ribbon 120 is provided with a releasing
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~LZ~)75~5
agent along its bottom surface and side surfaces. Furthermore,
the upper surface of the ribbon 120 as it emerges in a horizontal
path is supported by a slide plate 117 and is heated by a heater
128 adjacent to its upper surface. A glaze applying nozzle
assembly 129 is provided for spraying glaze onto the heated
and dried, upper surface of the ribbon 120. Thence, the ribbon
120 enters the kiln 25 through a rectangular opening or port 109
spaced vertically above the rectangular entrance port 9 for the
ribbon 20. Thus, the ribbons 20 and 120 are disposed and go
through the kiln 25 from ~he entrance end 26 to the exit end
27 along parallel horizontal vertically spaced paths.
In more detail~ the kiln 25 or at least the lining
of the kiln, is formed of refractory material. It is generally
rectangular in shape throughout its length. In the central
portion of the kiln 25 is a vertical partition 30 which
separates the interior of the kiln 25 into a drying and pre-
heating chamber 31 and a firing chamber 32. In other words,
the chambers 31 and 32 are disposed in tandem along the longitu-
dinal path which is traveled by the ribbons 20 and 120. The
partition 30 has two vertically spaced openings or ports 30a
and 130a through which the ribbons 20 and 120 pass. Ports 9,
30a and 60 are horizontally aligned ports, 1l09, 130a and 160
are in horizontal alignment above ports 9, 30a and 60.
-~ All burners 40 heating the kiln 25 are preferably
in the firing chamber 32, the drying and preheating chamber 31
receiving the exhaust, flue or stack gases from the firing
chamber 32.
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~2~751S
As pointed out above/ the kiln 25 and particularly
the firing zone or chamber 32, is made of or lined with
refractory material which will withstand temperatures in the
neighborhood of 2300F and up to 3300F in some instances.
Chamber 31 is less critical in that it is always at a l~wer
temperature than chamber 32, but refractory material should be
used for lining this chamber 31. The rollers 35 and 135 in the
preheating chamber 31 and the rollers 36 and 136 in the firing
chamber 32 are of suitable refractory material, such as high
alumina or fused silica. The rollers 35 and 36 are disposed
along a horizontal path and extend transversely of the kiln 25,
the ends of each rollers 35 and 36 protruding outwardly through
appropriate holes on opposite inner side walls 37 and 38 and outer
side walls of the kiln 25.
The upper peripheries of the rollers 35 and the upper
peripheries of the rollers 36 are disposed along a common hori-
zontal plane and are adapted to receive and support by its lower
surface, the ribbon 20. In like fashion, the rollers 135 and 136
protrude outwardly through appropriate holes in the side walls 37
and 38 and provide upper peripheries which are in a common plane
and receive the bottom surface of the ribbon 120 for supporting
the same. The plane of rollers 135 and 136 is parallel to and
above the plane of rollers 35 and 36.
` While I have utilized a kiln 25 with two paths of
travel for the raw material or ribbons 20 and 120 through the kiln
25 being fed respectively by rollers 13, 19, 18, 113 and 119, the
number of streams of raw materia] can be multiplied, as desired,
through a duplication of the systems here disclosed. Thus,
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additional lines of hopper 10, llOt rollers 13, 113, 15, 115 etc.
and a corresponding number of rollers 35, 36 and 135, 136, may
be utilized in a single kiln, if desired.
For providing a means for heating the firing chamber
32 I have provided a plurality of spaced lateraIly directed fuel
i.e., oil or gas, combustion nozzles or burners 40 which protrude
through the walls 38 defining the chamber 32. The nozzles 40
on one side of the chamber 32 are staggered with respect to the
nozzles 40 on the other side wall 38 of the chamber 32.
Furthermore, there are horizontal rows of such staggered nozzles
40 below the row of rollers 36, and between the row of rollers 36
and the rollers 136, and between the roof 41 and the row of,
rollers 136. Thus, flames from the noz71es 40 are introduced
laterally in alternate directions both over and under the
ribbons 20 and 1~0.
Respectively, trans~ersely opposite to nozzles 40 are
the gas discharge poxts 42 in the side walls 38. The discharge
ports 42 are, thus, arranged in horizontal rows corresponding
to the rows of nozzles 40 and are also in staggered relationship
with respect to the trans~ersely disposed ports 42. It is now
seen that each side wall 38 has three vertically spaced rows in
which there is alternately a discharge port 42 and a nozzle 40
equally spaced, longitudinally. Each nozzle 40 directs its
flame transversely across the firing chamber 32 so that a sub-
stantial amount o`f combustion gases travel through the oppos~d
port 42 and out of the chamber 32.
~Z07S15
With the nozzles 40 being in staq~ered relationship
transversely in each horizontal row, there are generated rotary
flows of qases alternately clockwise and counterclockwise over and
below the ribbons 20 and 120.
Each nozzle 40 is disposed longitudinally equidistant
between two adjacent rollers 36 and 136 and protrudes through and
are supported by the side wall 38. Combustible gas, such as
natural gas is supplied from a gas header 43 through individual
branch lines 43a to the nozzles 40. An air header 47 supplies air
under pressure through lines 44a so as to present air for mixture
with the gas at the nozzles 40. The headers 43 and 44 are
disposed on opposite sides 48 of the firin~ chamber 32. A similar
arrangement may be made for burning oil or other fuel.
As seen best in Fig. 5, the kiln 25 is provided with
outer walls 44 which are spaced outwardly of and parallel to inner
side walls 38. Upper and lower horizontal walls 45 and 46 join
the upper and lower edges of walls 44 to their respective inner
side walls 38 to form horizontally extending channels or
passageways 47 on opposite sides of the inner side walls 37. End
walls 56 which are parallel to rear end wall 27 closes the
downstream ends of channels 47.
The walls 44, 45, 46 def~ine manifolds which enclose all
of the exhaust port 42 so that they communicate, on their
spective sides, with the horizontally extendinq channels 47.
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Spaced blocks 57 below walls 46 provide support or these
manifolds.
The walls 44, 45, 46 extend in an upstream direction
over the opposite side walls 37 of the upstream~end portion of
the chamber 31 to terminate at end walls 58. Opposed, vertically
spaced flue or stack gas, lnlet ports 59 are provided in the
end portions of side walls 37, as seen in Fig. lB, so as to
communicate with the channels 47, as shown best ïn Fig. 4.
Thus, channels 47 conduct all flue gases from the firing chamber
32 and introduce them laterally through ports 59 on opposite
sides of chamber 31 both above and below the ribbons 20 and 120
in the downstxeam end of chamber 31 and such gases pass in an
upstream direction, as indicated by the arrows being received
by discharge ports 48 disposed in the walls 37 adjacent to
the front 26 or entrance end of chamber 31.
The transversely opposed discharge ports 48 communicate
with opposed, upwardly extending suction ducts 55 communicating
with exhaust manifolds 4g disposed exteriorly of kiln 25 adjacent
the walls 37. These exhaust manifolds 49 lead upwardly into an
intake duct 50 which is connected to the intake ports of an
exhaust blower 51 driven by a motor 52 through belt 53. The
fan or blower 51 discharges through a stack 54 to the atmosphere.
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Individual controls for nozzles 40 including strategi-
cally located pyrometers and valves (not shown) which enable an
operator to control the transverse heating zones of the firing
chamber 32 so that the heat in the firing chamber 32 may
be maintained within quite close tolerances. The transverse flow
of these gases, both above and below the moving ribbons 20 and
120 enable the firing chamber 32 to be maintained at an
appropriate temperature for progressively firing and foaming or
cellula~ing of successive increments of the clay ribbons 20 and
120, as they move along the firing chamber 32. The proportion
of air to fuel is maintained in various zones, as desired, for
oxidizing neutral, or reducing conditions.
Thus, the cellulated or expanded vitreous clay, denoted
by the numerals 20a and 120a, progressively and continuously
emerge through dischaxge ports 60 and 160 in the rear end 27, onto
support rollers 61, 161.
As the cellulated vitreous clay ribbons 20a and 120a
emerge from the kiln 25, the upper sur~aces thereof can, if
desired, be treated with additional surfacing material, such as
a dry granular fritted glaze 62. The glaze or coating material
62 is retained in a hopper 63, adjacent one side of kiln 25.
The bottom portion of hopper 63 is provided with a transversely
extending, hollow, distribution cylinder 65 carrying a horizontally
disposed screw conveyor 64. The distribution cylinder 65 communi-
cates at one end with hopper 63 and is provided, at its lower side
with a plurality of axially spaced holes 66.
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Since the cylinder 65 will be subjected to very
substantial heat, it being disposed transversely across the
upper portion of the path of travel of the expanded or bloated
clay ribbon 20a, a means for cooling both the coating material
62 and the cylinder or trough 65 is provided. This means for
cooling includes a hollow central shaft 67 for conveyor 64,
through which water under pressure is directed. The shaft 67
and the screw conveyor 64, which is attached to shaft 67, are
rotated by a motor 68 and chain drive 69. Water is fed to the
shaft 67 by pump 70 through a pipe 71, shaft 167, pipes 72 and 73,
from a tank 74. A return line 75 delivers the cooling water back
to tank 74.
Shaft 167 is identical to shaft 6? and carries a screw
conveyor 64 in a cylinder or trough 165 of a hopper 163 driven
by motor 168 and chain 169 for feeding fritted glaze 162 through
holes 166 onto the upper surface or ribbons 120a. The cylinder
165 extends transver~e~ over ribbon 120a.
Spouts 76 and 17Ç on the ends of cylinders 66, 166,
feed any excess fritted glaze 62 or 162 to receptacles 77, 177.
~y selective operation of the m~tors 68, 168, fri~ted
glaze 62, 162 is delivered to the hot upper surfaces of
ribbons 20a, 120a. The glaze immediately becomes molten to
provide a glazed surface thereon.
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1~()75~1lS
As pointed out above, the end portions of rollers 35,
36, 135, 136 protrude outwardly through appropriate holes in walls
37, 38, 44, 237, 238, 244 of the kiln 25 and 225. As seen in Fig.
12, the rollers 35, for example, which support the charge prior to
sintering and are in the drying and preheating chamber 31, can be
spaced apart from each other by greater distance than the spacing
of the rollers 3fi. With such greater spacing, each end portion of
the rollers 35, outwardly of the kiln is confined by three
circumferentially spaced idler wheels 70a, 70b, 70c. The idler
wheels 70a, 70b, 70c are supported for rotation by stub shafts 71
which project into the outer walls 44. The axis of each lowermost
wheel 70c is vertically below the roller 35 which it supports.
A con~inuous steel belt 72, passing between each wheel
70c and its associated roller 35, tc the next and then to the next
provides synchronized drive for all rollers 35. The same belt 72
also passes beneath all rollers 36, as seen in Fig. 11, beinq
received between the end portion of each roller 3fi and its
associated wheel 73c which is there beneath.
Since rollers 36 are closer together, they can share an
additional wheel 73b which is between them and rides against the
peripheries of the adjacent rollers 36 above the axial plane of
such rollers 3h. Such wheels 73b aid the belt 72 in synchronizing
rotation of rollers 36. The outboard roller 36 has an outer idler
wheel 73a circumferentially spaced from wheels 73b and 73c for
that roller 36.
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12~7~15
Belt 72 passes round appropriate drive or guide rollers
74 outboard of the rollers 35 and 36. A motor (not shown) may
drive belt 72. Rollers 135, 136 have a similar drive. Lehr
80 is provided with a similar drive for its rollers. The drives
may be on one or both sides of the kiln or lehr to drive one or
both end portions of the rollers.
At locations along the path of travel of the ribbons
20, 120, if there is expansion or contrac~ion of the ribbons, it
may be found desirable to permit une or several of the rollers,
such as rollers 35, 36, 135, 136 to idle. This can easily be
accomplished by shifting the appropriate associated wheel or
wheels 70c and/or 73c laterally inwardly or outwardly so that
they are out of alignment with belt 72.
After the bloating ribbons 20a and 120 emerge from the
kiln 25, and after additional glaze 62 has been supplied to the
upper surface of the material, if desired, the ribbons 20a and
120a pass into an annealing lehr denoted generally by the numeral
80. The annealing lehr 80, like the kiln 25, is separated into
compartments, the first being a cooling chamber 81 and the others
annealing chamb~rs 82a, 82b, 82c. The lehr 80 includes a front
wall 83/ an intermediate partitions 84a, 84b, 84c, 84d and a
rear wall 85. In addition, it has front side walls 86 and rear
side walls 87 as well as a top 88 and a bottom 89.
Rollers 87 and 187 form horizontal conveyors for the
ribbons 20a and 120a in the first chamber 81. Rollers 88 and
188 form horizontal conveyors in the second chamber 82. The
front wall 83 is provided with port~ 90 and 190 through which
-27-
12~)751~i
the respective ribbons 20a and 120a pass into the chamber 81.
The partitions 84a, 84b, 84c, 84d are provided with ports, such
as ports 91 and 191, through which the ribbons 20a and 120a pass
from the chamber 81 into the successive chambers 82a, 82h, 82c,
82d. The rear wall 85 is provided with ports 92 and 192
~hrough which the ribbons 20a and 120a emerge from the lehr 80.
Additional transverse rollers 93 and 193 form horizontal
conveyors for the cooled ribbons 20a and 120a which emerge from
the lehr 80.
1~ For rapidly cooling the ribbons 20a, 120a in the
cooling chamber 81, a forced draft circulating air system 119
is provided. This system ll9e includes three transversely extend-
ing metal baffles 95, 96, 97 and a bottom plate 98 disposed in
the chamber 81. Plate 95 was disposed above ribbon 120a; plate
96 below the ribbon 120a and rollers 187; plate 97 above ribbon
2da and below plate 96, plate 98 below ribbon 20a and rollers
87 and plate 99 below plate 98. Plates 96 and 97 were formed
of transverse valleys and ridges to accommodate the rollers 87
and 187. Plates 95, 96, 97 and 98 are perforated or foraminous.
Thus, the plate 95 and the top of the lehr 80 formed
an upper plenum~ plates 96 and 97 a middle plenum and plates
98 and 99 a lower plenum. These plenums are connected to the
d~scharge side of a blower 100 through a branch duct lOla and
a manifold 101 so that cooling air is forced into the plenums and
directed against the upper and lower surfaces of the ribbons 20a
and 120a as shown by the arrows in Fig. 7.
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~Z~7S~S
Exhaust air is taken out of the chamber 81 via ducts
102 leading from the opposite side of the lehr 80 at the level
of the ribbons 20a, 120a. These ducts 102 lead to an exhaust
manifold 103 which communicates with a header 104. A common
exhaust duct 105 is connected by a branch duct 106 to the
header 104.
A cross-over duct 107, leads from header 104 via tee
108a to the intake of blower 100. The other duct 108b connected
to tee 108a opens to ambient air. By manipulation of the damper
lQ8, in tee 108a, the ratio of ambient air to recirculated air
is manipulated for cooling of the ribbons 20a, 120a in chamber
81.
The annealing oven is made up of a series of chambexs
82a, 82b, 82c, 82d, similar to chamber 81, respectively having
individually controlled circulating air systems 119a, ll9b, ll9c,
119d identical to the system ll9e described. All headers, such
as header 104, discharge, to the common duct 105, the heat there-
from being used for heat as need~d in the plant, or as preheated
air to burners.
After emerging from the annealing lehr 80, the ribbons
20a and 120a are transversely cut during thelr path of travel
so as to produce rectanguIar slabs. These slabs are on the order
of 4 feet to 8 feet wide, cut to length as ordered. Trimming of
edges, planing of surfaces, and cutting into smaller pieces is
done as required. Roof tile may be fabricated with interlocking
joints.
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~2~)~SlS
Periodically throughout the length of travel of the
ribbons 20 and 120 and the continuation of such ribbons, namely
the ribbons 20a and 120a, there are provided vertically disposed
guide rollers 121 which are on opposite sides of the path of
ribbon 20, 120, 20a, 120a so as to guide the ribbons through the
respective ovens 25 and 80.
In Figs. 8 and 9 is illustrated a kiln 225 which is
identical to kiln 25 except that it has vertical guide rollers
280 and drives therefor. In more detail, the kiln 225 includes
inner walls 238, outer side walls 244, horizontal walls 245, 246,
roof 241 and bottom 242 and rollers 235, 236, 335, 336 which
receive and transport the ribbons 220 and 320 through the
preheating chamber 231 and firing chamber 232. Fuel is supplied
in the firing chamber 232 through nozzles 240.
As seen in Figs. 8 and 9, there are a plurality of
longitudinally spaced opposed, pairs of vextically disposed
guide rollers 280 in kiln 225, projection up between the adjacent
horizontal rollers 235, 236, 335, 336. The function of such
rollers 280 is to guide the charges 220 and 320 in their long-
itudinal path through kiln 225. The ends of rollers 280 protrude
through appropriate holes in top 241 and bottom 242 of kiln 225.
The bottom portions of vertical rollers 280 are received and
journalled by thrust bearings 281. The upper end portions of
rollers 280 pass through bearings 282 and protrude outwardly
th~refrom.
The upper ends of rollers 280 receive sprockets 283
around which passes a continuous chain 284 which drives the
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opposed pairs of rollers 280 in opposite directions at approxi-
mately the same peripheral speed of the rollers 235, 236, 335,
336.
The spacing of the rollers 2B0 is a matter of choice;
however, they should be sufficiently close to prevent appreciable
lateral movement of the charge 220 or 320. The lehr 80 and the
kiln 25 can be equipped with such vertical rollers, as rollers
280, if desired.
THIRD EMBODIMENT
The third embodiment depicted in Figs. 13A, 13B, 13C,
14, 15, 16 and 17 has multistage extruders formed of rectangular
vertically disposed hoppers'310 and 410 having downwardly
converging side walls 312 and'412 joined by triangular end walls
311 and 411 and compression rollers 313, 313a, 313b, 319, 413,
413a, 413b and 419.
The power dxive compression rollers 313, 313a are
disposed on opposite sides of the mouth of hopper 310 and, with
end rollers 319, compress and feed the charge as a rectangular
compacted stream, downwardly. Thus, the axles`315 o these
rollers 313, 313A and the axis of rollers'319 are disposed in a
common horizontal plane.
The second stage power driven compression rollers 313b
is disposed below roller 313 with its axis parallel to the axles
315 of rollers 313, 313a. The rollers'313 and 313b cooperate to
squeeze and feed, as a stream, the charge horizontally. A curved
sheet 317, concentric with the periphery of roller 313 defines
-31-
)75~5
an intermediate chamber therebetween. The sheet 317 extends from
adjacent the inner periphery of roller 313a to adjacent the
inner periphery of roller 313b and functions as a guide means
to guide the outer surface of the stream. Thus, rollers 313 and
313a give the clay charge an initial squeeze feeding the stream
downwardly and the rollers 313, 313b a second and subsequent
squeeze, feeding the stream horizontally. Additional opposed
rollers (not shown) can constitute subsequent stages for
cooperating with rollers 313, 313a, 313b in shaping, compressing
and feeding the charge as a rectangular ribbon 320 of indeter-
minate or continuous length fed horizontally onto a receiving
slide plate 317a arranged outwardly adjacent to the upper per-
ipher~ of roller 313b. Thence, live rollers 318 feed the ribbon
320 into the horizontal kiln 325 through opening or entrance
port 309 in front or entrance end 326 to subsequently emerge as
a hot cellulated product from the exit opening or port 360 in
the exit end 327 of the kiln 235.
The hopper 310 receives a premixed raw or green
charge formed of a mixture of clay7 water and carbonaceous
material, as described abo~e.
The hopper 410 has ide~tical end walls 411, side
walls 412, rollers 413, 413a, 413b, 419, curved sheet 417, slide
plate 417a and heater 428 for discharging a compacted horizontal
ribbon 420 of green clay charge, identical to and abo~e ribbon
320.
Ribbon 320 is fed next to a coating zone where glaze
or engobe is sprayed onto the upper surface of the ribbon 320
~2~15
by a nozzle assembly 329 having a horizontal header 329a
carrying a plurality of spaced downwardly directed nozzles 329b.
Below the emerging ribbon 320 is another nozzle assembly 329c
group of nozzles 329d carried by a transversely extending header
329e. The nczzles 329d discharge a parting or releasing agent
onto the bottom perhaps the sides of ribbon 320. The parting
agent is preferably a slip formed of raw, high temperature,
fire clay and water and sufficiently fluid to pass through
the nozzles 329d.
Nozzle assemblies 429 and 429c, similar to noæzle
assemblies 329, 329c, are provided for ribbon 420.
Thence, the power driven xol~ers 318 and 418 feed the
ribbons 329, 420 through ports 309, 409 into kiln 325.
Horizontal power driven or live rollers 335 receive ribbon 320
and horizontal power driven rollers 435 receive the ribbon 420.
The upper peripheries of rollers 335 and 435 form parallel
horizontal conveyors which feed the ribbons 320 and 420 at
uniform rates through the kiln 325, the rollers 335, 435 being
driven as illustrated in Figs. 11 and 12.
According to the present embodiment, the kiln 325 is
provided with a plurality of horizontally disposed muffle plates
330a, 330b, 330c, 330d which partition the kiln 325, throughout
its length into a plurality of alternately spaced combustion
chambers and muffle chambers, the combustion chambers being the --
longitudinal extending chamber 347a, 347b and 347c. Thus, the
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~Z5~7~15
upper chamber 347a i5 above the top ribbon 420; the inter-
mediate chamber 347b is between upper rollers 435 and lower
rollers 335; and the lower chamber 347c is below the rollers
335. ~he purpose of the combustion chambers 347a, 347b and
347c is to separat~ the ribbons 320 and 420 from the combustion
gases so that the ribbons will be in a reducing or neutral
atmosphere, at least during the period in which the temperature
of the ribbons is above about 800F.
The muffle plates 330a and 330b thus define,
therebetween, a tubular upper muffle chamber 431 and the plates
330c and 330d, the lower muffle chamber 331 within which are
the rollers 435 and 335 and the ribbons 420 and 320. Baffles or
muffle plates 330a and 330c are inclined slightly so that the
latter portion of chambers 331, 431 progressively widen gradually
toward the exit ports 360 and 460 and corresponding portions of
chambers 347a and 347b progres~ively narrow toward the end 327.
The muffle plates 330at 330b/ 330c, 330d preferably
formed of sheets of fused silica which will permit temperatures
within the kiln 325 of up to about 2700F. To produce such
muffle plates, the silica charge for the kiln 525 should be
provided with a silica or sand glaze along the upper surface
and then after firing, the glaze thus formed should be sawed off
of the foamed remaining product. A succession of fused silica
sheets disposed transversely side~edge to side edge in the kiln
will make up each of muffle plate 330a, 330bJ 330c, 330d~ When
installed, the sheets should be heated initially to about 2300F.
At that temperature, the sheets will 510wly devitrify to produce
cristobalite crystals which have less tendency to sag at higher
temperatures. Thereafter, the higher temperatures, up to about
2700F, can be used.
-34-
)7S~
The rollers 335 and 435 protrude through the side
walls 344 of the kiln 325, the end portions thereof being
supported by wheels or rolls 370a, 370b, 3~0c and driven by
belts 372, as described above ~or the preceding embodiment.
Staggered fuel nozzles 340a, disposed in about the
last half, direct an ignited air and gas mixture transversely
across the upper chamber 347a for heating it, while similar
staggered nozzles 340b and 340c do the same for the central or
intermediate chambers 347b and 347c, respectively. Air lines 300
supply air through branch lines 301 to the nozzles 340a, 340b,
340c while gas or oil fuel lines 302 and branch lines 303 supply
the fuel, thereto.
At the entrance end of kiln 325, an exhaust assembly
or means, which is identical to the exhaust assembly of Fig. 1,
is provided. It includes a motor 52 driving, through belt 53,
a blower 41 for drawing the products of combustion from the
discharge ends of chambers 347a, 347b, 347c, through ports 348a,
348b, 348c and manifolds 349, and discharging the same through
exhaust stack 354.
As seen in Fig. 13c, the ribbons 320a and 420a, after
being bloated or cellulated, are fed ~eneath the glaze applicators
363 and 463 and thence to annealing oven or lehr 380 having
successive chambers provided with air systems 419a~ 419b, 419c,
419d, the lehr being identical to lehr 80.
It is thus seen that the gases of combustion which are
formed in the rear of the interior of the kiln by the burning of
i~751~
fuel by nozzles 340a, 340b, 340c, are fed forwardly toward the
front of the kiln 325 and exhausted, therefrom as the charges
are moved in counter flow relationship thereto. Thus, the
entering ribbons 320 and 420 of charge are progressively dried,
then preheated, then fused and cellulated as it is moved
through the kiln.
In the fourth embodiment depicted in Figs. 18a and
18br a rectangular kiln 525, having parallel juxtaposed,
freely rotating, rollers 535, and live or driven rollers 536.
Rollers 535 receive, from a ramp or platform 510, a charqe S20
carried in a tray or pan 521. This pan 521 is rammed, by a
reciprocating hydraulic ram 522, through entrance opening 509
in front wall 526, into the firing chamber 531 of the kiln 525.
Pan 521 i5 received on the roller hearth, formed by horizontal
idler rollers 535, and is moved thereon by being pushed by
successive similar pans 521, with their charges 520, as such
pans are successively fed by the ram 522 into the kiln 525.
The kiln 525 is heated by iuel burners !not shown)
as in the preceding embodiments and the products of combustion
exhausted by blower 551 through stack 554, the suction being
drawn through exhaust ports 548. The pan 521 thus eventually
reaches the line rollers 536 at the exit end within the kiln 525
which, when actuated, discharge the pan through momentarily
opened exit port or opening 56Q laligned with opening 509~ when
the vert-cally slideable door 561 on the kiln 525 is raised by a
ram 562 to the position shown in Fig. 18B in broken lines.
-36-
~z~s~s
A motor (not shown) drives, through a unidirectional
drive, all rollers 536, so that some resistance to feed along
rollers 536 is encountered. This applies a back pressure which
keeps the juxtaposed tandem arranged pans 521 on rollers 535 and
536 in abutting relationship.
A pivoted finger or switch arm 563 connected to switch
564 as shown in Fig. 18b acts as an electrical control means
for both the motor (not shown) for rollfrs 536 and ram 562, so
that the door 561 is opened when ~he arm S63 is moved toward
door 560 by the cellulated charge 520a, and the rollers 536,
thereafter, actuated so as to discharge one tray 521 from the
oven or kiln 525. Then the door 561 is closed and another cycle
can commence.
Fuel nozzles Inot shown) but similar to nozzles 40 and
340a, 340b, 340c, heat the kiln 525.
Either tray or pans, such as pan 620, of Fig. 19
can be used as the pans such as pan 520 or the pans such as tray
or pans 720 depicted in Figs. 20, 21 and 22 can be used as the
successlve pans such as pan 520. Indeed pans 620 and 720 may be
intermixed.
Referring specifically to Fig. 19 the sections tray or
pans 620 include a pair of opposed end segments 621 and a
plurality of intermediate segments 622. Segments 622 are each
channel members having flat rectanguIar bottom plates 623 and
upright, opposed, spaced, parallel, rectanguIar side plates 624
projecting from opposite edges of bottom plate 623. ``
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~2~)~751S
The end sections are also channel members having
rectangular base plate 625 and side plates 626. One end is
closed by a rectangular end plate 627.
In use, the sections 624 and 625 are assembled
by simply being placed edge to edge, on platform 510 to
form pan 620, closed on its sides and bottom. The silica
charge of raw sand, water and carbonaceous material is hand
packed or rammed into the pan 620 and the ram 522 is used to
push each pan 620 successively into the oven.
The panels or plates 623, 624t 625, 626, and 627
are formed from sheets of refractory material, i.e. pressed
carbon, such as coke fines or charcoal granules. Pitch or tar
may be employed as a binder for the coke or charcoal and
as an adhesive to join the appropriate edges together.
When the sand fuses in the kiln 525, the charge
holds the segments or sections 622, 623 together until the
charge is cooled after becoming fused and cellulated. The
fu~ed silica can be cooled quite rapidly and needs no annealing
thus, no lehr is requ~red. External rollers 566 in front of
rollers 536, deliver the silica to an area where it cools and
the sections 621 and 622 are remoued for reuse.
Referring to Figs. 20, 21 and 22, a second form of seg-
mented or sectional pan 720 includes a plurality of abutting flat
rectangular intermediate bottom plates 723 and end plates 723a
which are each provided with a pressed or compacted right prism
or rectangular block 724 of silica charge. A conventional press
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~Z'~)75~S
(not shown) can be employed to compact each block 724 onto its
associated bottom plate 723 or 723a, or the blocks may be pressed
separately and then placed on the base. The outer or side ends
725 of the block 724 should terminate inwardly of the end ed~es
726 of the bottom plate 723. The sides 727 of each block 723
should end in ali~nment with the side edges 7290 The outer edges
729a of end block 724a should terminate inwardly of the outer
edges 729a or end plates 726a.
Thus, the plates 723, 723a, when assembled have
perimeter portions which receive thereon longitudinal spaced
parallel side bars 730 and spaced parallel transverse end bars 731
which form elements of a removable rim, resting on but not secured
to the plates 723~ 723a, as shown in Fig. 21. Bars 730 extend the
len~th of the juxtaposed plates 723 and 723a, the bars 731 are
inwardly of ends of bars 730.
When assembled, the pan 720 has the individual blocks
723 and 723a abutting each other. These blocks 723 and 723a fuse
together as the silica charge, formed by blocks 723, 723a, fuses
and cellulates, while passing through the oven or kiln 525.
As seen in Fig. 22, vertical idler rollers 580 disposed
at spaced intervals within the kiln 525, guide the pans, such as
pan 720, through the kiln 525, the rollers 580 preventing
appreciable outward movemant o side bars 730 and the bars 731
preventinq appreciable movement inwardly.
(
~ ~ 7 51 ~
The elements namely plates 723, 723a, and bars 730,
73l are quite readily stripped from the monolithic rectangular
product af~er it has cellulated, fused and then cooled.
Thus, a small press, ~not shown) can be used to
process a very long cellulated fused silica product .
.The trays 620 and720 are inexpensive and
expendable. It is expected therefore that one, two or three
uses is all that they would ~ithstand~ Being of carbonaceous
material or carbon, they may be consumed by oxygen and water
vapor. Hence, they function to assume a reducing condition around
the charge and ~hen the hot trays and charges are dischar~ed to
the atmosphere, they may be consumed by the ambient air.
The fact that the trays and expendable permits the
burning of fuel, such as gas, oil or solid fuels, i.e., wood
or coal, ~ithin the kiln to generate products of combus~ion, such .
as water vapor~. These products of combustion are consumed by
reacting with the carbon of the trays.
In any of the embodiments where either a clay charge
cr~ silica charge is employed and if the kiln 25, 225, 325, or 525
is app~oximately 40 feet long9 the speed of the fee~ through the
kiln should be such as to leave the charge in ~he kiln from about
lO minutes to about 60 minutes, depending on the thickness of the
charge. Thus, a 3/8 inch thick charge should be moved at about
two feet per minute to re~ain in the kiln for 20 minutes hhile a
five inch thick charge should move at about one foot per minute.
- .1
-40- I
. 1
c ~
~v~s~s
The spacing of the rollers in the ~iln should ~e
such as to preclude appreciable sagging, particularly after the
char~e has been fused and is in a relatively vlscous condition.
Thus, in the lat~er part of the ~iln~ care should be taken to
provi~e the rollers at spacings of less than about five inches
on center. Thus too will vary with the thic~ness of ~he charge.
If the charge is thin, i.e., about 3/8 inch, the rollers should
be arranged at about 1 1/2 inches apart, on centers, and if the
charge is thick, for example r five inches thic~, the rollers
should be about four inches apart, on center.
In the kiln prior to the point or zone in which
fusion ta~es place, the ribbons are sufficiently self-supporting
for the rolleTs to be from about six inches to twenty four inchcs
apart, on center.
The charges, supported on plates or in trays, have
no such problem of sagging, since the car~on sheets are
sufficiently rigid to provide support. The rollers should,
however, be suficiently numerous to support a segment of a pan
by two or more rollers at all times.
_. i
.~ . ,
Closer spaced rollers interrupt the continuity of
the ~er-ical wall, ent;rely, or leave ~ery thin columns of
refractory t;all and/or liner between the rollers, wi~h lit~le
clearance around the rollers.
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(- ~2~)751S
~ h conventional refractories> it is difficult to
maintain ~all support above the rollers, due to movement and
shearing due to thermal expansion, particularly in multiple
deck and muffled kilns. For this reason the ~iln is built of
fused silica, as a rule, in any part subjected to not more
than abou~ 2700F, and support wall sections on the cold sides
Solid or cemented layers do not crack off due to differentia.l
expansion.
It is noted that in tne usual operating tem.peratures
in the hot zone, the fused silica will tend to devitrify in time,
converting to cristobalite which has a disruptive thermal
expansion below about 600F. The kilns are normally operated
for months at full temperature, and it is simple in this case
and in many other operations to maintain th~ devitrified parts
above 600F by a smal1 holding fire.
'
.
-4Z-
1;;:075~L5
PXOCESSES
From the foregoinq description, the operation or process
of the apparatus should be apparent. One charge which can be
satisfactorily processed to a foamed or bloated clay product is
made up by wei~ht of 100 parts clay, from about 6 parts to about
15 parts water, and from about 1/20 part to about 2 parts
available carbon in carbonaceous material. This I term a moist
c]ay charge or mix.
The clays which I have found useful as a raw material
L0 include surface clays, ball clays, ~aolin, shale, and bentonite.
Other clay-like materials are useful for my process, the essential
quality being the small ultimate particle size of the material and
the ability to sinter into an impervious mass. Thus r clays and
clay like materials which have a mean particle size of less than 2
microns are particularly useful in my process. Such clays are
found in nature in rock like form. They should be erushed to a
granular form, typically to pass through a 6 mesh screen.
There are innumerable organic or carbon compounds which
are useful as the carbonaceous material in my process. They,
'0 however, must be soluble in water and must char upon being heated~
Therefore, sugar, or sodium lignite (Orzan A) is quite useful as
~he carbonaceous material.
It will be remembered that if organic materials are
present in clay, itself, soluble carbonaceous material is used in
less amount so that the total of the naturally occuring
carbonaceous material and the added available carbon is up to
about 2 parts per 100 parts clay.
~ZU7S:15
~ nother charge which can be processed to a foamed fused
mineral is made up of silica, carbonaceous material and water.
A useful silica raw material is a sedimentary quartzite
occurring naturally in massive form, having an average crystallite
diameter of about 10 microns and less, preferably between 5 and 10
microns, and containing negligible intercrystalline material. A
preferably useable silica raw material contains at least 99
SiO2, on an oxide basis. Such a silica raw material may be
found, for instance, in Arkansas, Ilinois, and California and has
l0 the followinq typical chemical analysis:
TABLE I
Percent
SiO2 99.2
Fe23 0.10
A123 0.14
CaO 0.05
rrio2 O. 01
MgO 0.03
Alkalies 0.27
Ignition loss0.20
In practice, the quartzite material is crushed after
removal from the mine, typically to pass through about a 6 mesh
screen. If a purer form of silica is desirable, a silica flour
obtained by fine grinding quar~zite sand or gravel should be used.
The addition thereto of colloidal silica improves the surface area
of the quartzite, as will be explained/ hereinafter.
The charge is formed by admixing 1000 parts silica and
from about 1/2 part to about 4 parts available carbon in soluble
carbonaceous material and sufficient water to provide for the
~l2~75~L5
thorough distribution of the soluble carbonaceous material and the
colloidal silica, if present. Hence, from about 50 to about 10n
parts water is recommended. The silica charge must be placed on
plates which are fed end to end through the kiln 25 in place or
ribbons 20, 120.
fitill another form of silica raw material is
diatomaceous earth which is a very porous form of silica and foams
quite readily. It is not, however, a pure form of silica and its
lack of resistance to acids detracts from its usefulness.
In the processing of either the clay charge or the
silica charge, the charge is compacted using either a low pressure
press or rolls, such as rollers 13 and 1g. The clay charge will
extrude into the ribbons 20, 120. The silica charge, however, may
require carryin~ plates or carriers 200 along its bottom surface.
The carrying plate 200 is expendable and if a carrier
plate is used it is made in the same press where the charge is
compacted. The plate 200 is formed of a binder and carbon
material. It is preferably composed of a binder and carbonaceous
material such as pitch and coXe fines or pitch and coal dust, as
is practiced in the carbon formin~ arts. The plate 200 is
produced on an aluminum foil sheet or other parting agent 201 in
press 202 so that it does not stick to the heated platen 203. The
aluminum will melt in the kiln 25 and burn up. If desired, silica
sand corresponding in purity to the silica of the interior may be
placed on the upper surface of the silica charge (without a
blowing agent) to form a glaze, when fired.
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~ 751~
When the fused vitreous cellulated silica is ~elted and
since the successive silica charges in chamber 32 are abutting as
they are passed through chamber 32, the silica of one plate 200
fuses to the silica of the next so that the ribbon produced by the
silica in kiln 25 progressively becomes integral.
It should be pointed out also that the plates 200 are to
be removed from the ribbon of fused silica, once the cellulated
fused silica has cooled.
When the charge enters the kiln 25, regardless of
whether it is a silica charge or a clay charge, it is subjected to
about a 600F temperature and is progressively subjected to
increasing temperatures so that, as it reaches the end of its
travel in chamber 31, the charge is beinq subjected to
environmental temperatures of from about 50~F to about 200DF less
than the temperature of the gases of the firing zone or chamber
32. The charge then enters the firing chamber 32 where the
temperature should be maintained, for example, as follows:
For surface clay charges and bentonite charges - 2000F
to 2300F. For other clay charges, 2100~F to 3100F. For silica
charges - 3000F to 3300F.
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1~751S
In any event, the temperature and turbulence, which
determine the heat transfer characteristics, should be such that
there is not more than about 150F te~perature differential
between the surface temperature of the charge and the lowest
temperature in the interior of the charge.
While time of firing and temperatures vary for each raw
material and thickness of the final product, I have found in using
California clays mined in the vicinity of Corona, that roof tile
sheet, 1" to 1 1/2" thick and weighing about 5 lbs. per square
foot, can be made by preheating the charge for about 30 minutes
and then firinq for about 30 minutes at a temperature in the
firing zone or chamber 32 of about 2140F.
Sintering of the charqe usually takes place when the
charge is about 100F to about 500F below the melting point of
the clay of the silica in the charge. Thus, sintering may take
place lar~ely in the preheating chamber 31.
In the chamber or firin~ zone 32, the charge
progressively swells or bloats as cellulation takes place and upon
emerging from the chamber 32, the foamed or cellulated raw
material has a density of 8 lbs. per cubic foot to about 100 lbs.
per cubic foot and has a glassy, vitreous, cellular structure of
mostly non-innerconnecting cells~
When good results are obtained 98% of the cells have a
diameter of less than 2mm and in many cases less than 1mm. This
fine cell structure gives uniformly thin cell walls which make for
ease in fabrication.
~ 15
If the raw material is silica so that a foamed fused
silica product is produced, it is not necessary to feed the
product to the annealing lehr or oven 80. Instead it must be
cooled rapidly to about 2000F and then as rapidly as is
convenient.
with all other materials, the product must be fed to the¦
annealing lehr 80 and therein progressively cooled. For best
results, the annealing curve for each product should be
established experimentally. When producing the roof tile from
Corona clay, as described above, a curve similar to that of 1/4"
thick plate glass gives good results.
As pointed out above, when the foamed or cellulated clay
ribbons 20a, 120a which are now fused or vitreous enter the lehr
80 they are initially cooled quite rapidly in oven 81 by the
introduction of ambient air under forced draft conditions against
the ribbon surfaces. This reduces the temperature of the ribbons
20a, 120a to jus~ about annealing temperature. Thereafter, the
products pass through the annealinq chambers 82a, 82b, 82c, 82d
where the ribbons are gradually cooled and are then fed out to
rollers 93, 193, emer~ing at a permissible temperature to finish
cooling on the rollers 93~ 193.
The speed of the ribbons or plates through the kiln 25
and lehr 80 is from about 3" per minute to about 72" per minute
and the spacing of the rollers 36, 136 toward the dischar~e end of
chamber 32 is from about 1" to about 6" on centers.
~2~7S~S
The viscosity of the material ~urinq cellulation is from
about 4.8 x 106 poises to 5.2 x 106 poisesl and the material
does not sag between rollers.
From a theoretical standpoint, it is known (Norton's
Text ~Refractories") that iron bearing clays melt at temperatures
which are as much as 200F lower under reducing conditions than
under oxidizing conditions. Thus, in producing the clay charge
which constitute the ribbons 20 and 120, I incorporate with the
clay, soluble carbonaceous material and water in such proportions
that the solution of carbon containing material coats all the
particles of the clay. Thus when compacted under low pressures of
from 50 psi to 1000 psi, a ribbon of damp clay is produced, the
clay being sufficiently loose that in the initial heating the
moisture will be driven out of the mixture and leave the carbon
containing compound as a very thin coating on all of the ultimate
particles of the clay. The carbon containing compound, such as
sugar i5 uniformly distributed throughout the mass and is
thoroughly admixed with each particle as a coating thereon.
Further heating of the clay charge causes it to sinter, at which
23 time cracks may appear in the surface.
In the chamber 31, however, the atmosphere has an excess
of air or oxygen and is, therefore, an oxidizing atmosphere. One
or more surfaces of the ribbons 20 and 120 are kept in this
oxidizing condition from just before fusion of the ribbon or plate
ntil discharge to the cooler temperatures. The temperature jast
_49_
~07SlS
before sinterin~ and during firin~ is sufficiently hiqh that the
carbon in the surface area of the charge is burned out to a
limited depth from the surface of the clay. Thus, a shell of hiqh
meltiny point material is created partially or completely around
the ribbon 20 or 120 or the plate.
In the interior of the charge, however, reducin~
conditions exist, due to the presence of the organic or
carbonaceous material. Hence, under carefully controlled
temperature conditions within the firing chamber 32, the ribbons
20 and 120 will be maintained so that the shell does not melt or
become to sticky to run over the rollers, while the major portion
of this charge is meltin~. As the clay melts, the iron oxide in
the clay and the carbon on the surface of each particle can
diffuse so as to react with each other to release carbon monoxide
and carbon dioxide to the molten viscous clay, thereby blowing the
clay to form a multitude of closed bubbles.
If a parting agent or releasing agent is employed for
the bottom surface of the ribbon 20 or 120, or the bottom and side
surfaces thereof, this releasing or parting agent, upon heating in
the kiln is more inert than the clay itself and thus does not
stick to the surfaces of the rollers. Furthermore, this releasing
agent or parting agent, if supplied on three sides, creates a
cradle beneath and on the sides of the ribbons 20 and 120 so as to
confine the charge durinq the period in which it is foamed or
cellulated.
I have also found that when cellulation occurs in the
firinq chamber and the temperature is maintained so as to render
~Z{~7S15
the viscosity of the clay at about 5 x 106 poises, the clay is
sufficiently tacky to adhere to the rollers which support the same
unless the oxidized skin or other parting is present, and yet is
sufficiently viscous that the gas generated by the reaction of the
carbonaceous or organic material and the iron oxide or similar
oxides of the clay create small bubbles which do not break out,
but expand the clay and provide closed cells of essentially
uniform consistency.
Through adjustin~ the carbon content of the clay, the
proper amount of gas is formed to give the desired density.
Adjustment of the moisture and degree of pressing gives a clay
ribbon strong enough to pass over the rollers, but not so dense as
to require a long drying time at low temperature.
The carbon reduction of the iron oxides and other
oxygen rich compounds in the clay is possible at lower
temperatures; however, a substantial part of the reaction is
delayed until the meltinq of the charge~ It is an essential part
of my process that the carbon coating is deposited on each minute
ultimate particle in the interiors of the large aqglomerated
~articles of the clay as mined or crushed. Thus, when the clay
melts and molecular diffusion becomes faster, the physical meetinq
of the iron oxide and the carbon is over a very short distance and
the reaction takes place promptly. This phenomenon acts as a
built-in control to produce gas after sintering but promptly upon
melting.
Some porous rocks of compacted ~uartz crystallites are
forme~ with crystallites or particles almost as small as the
~207S~IS
ultimate particles in clay lumps. ~iatomaceous earth also is
silica of fine ~ltimate particle size but less pure than the purer
sands. These silicas, such as quartz crystallites or diatomaceous
earth, have larger specific surface areas than pulverized sand
and, therefore, larger interfaces. This is another way of saying
that a thinner layer of carbon covers a lesser depth of silica and
thus the molecular diffusion is quicker due to a shorter path. In
some instances the carbon reacts with the silica to produce
silicon carbide which subsequently upon further heating reacts
with more silica to produce silicon monoxide and carbon monoxide
which are the gases in a silica body or in a high temperature
aluminum silicate such as ball clay.
In my preferred procedure for producing foamed fused
silica of a purer composition, I add sugar and water to a small
quantity of commercial colloidal silica solution which is then
thorouqhly admixed with commercial silica flour. This qives a
dispersion of carbon over a much larger surface area than could
otherwise be produced even by grinding the silica to minute siæe.
~ he silica flour has a particle size of about 15 microns
equivalent diameter while colloidal silica is approximately 1000
times smaller. This means that the surface area of a given mass
of colloidal silica has 1000 times the surface area of the same
mass of silica flour. Thus, I use approximately two parts by
weight colloidal silica to 100 parts by weight silica flour and
thereby increase the effective surface area of the silica flour by
about 20 times. This proportionally increases the area of
interface for reaction between the carbon and the silica. Thus,
en the charge of silica, colloidal silica and carbon is heated
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1~ ~2075~S
in the kiln 25, the carbon is quite uniformly distributed
throughout the silica and, upon heating, the moisture is driven
off and the carbon ultimately reacts with the silicon to produce
silicon carbide and then the silicon carbide reacts with silica to
produce silicon monoxide and carbon monoxide.
Cellulated vitreous fused silica product can also be
made from crushed silica rocks, such as quartzite rock or
diatomaceous earth, to provide agglomerates of less than 1/2 inch
diameter. These crushed rocks are admixed with colloidal silica
sol and a soluble carbon compound, which will char upon heating,
disolved in water. The solution will penetrate the agglomerates
and coat its small particles therein. The subsequent heating will
drive off the moisture, leaving the colloidal silica and carbon
uniformly distributed on the particles. Continued heating will
cause a reaction between the carbon and the available silica and
between the carbon and available oxygen to cause cellulation as
the silica fuses.
Suitable foamed materials can be produced according to
my invention from surface clays, shales, bentonites, diatomaceous
earth, and silica. Surface clays and shales obtained from brick,
roof tile and flower pot plants in California, Georgia and Germany
have ~een found suitable for my processes~ Such clays and shales
should be crushed to pass typically through about a 6 mesh per
inch screen.
Swellinq bentonite from Wyoming and South Dakota and
non-swelling bentonite from Mississippi and California are also
useful for producing foamed material accordinq to the ~resent
~zo~s~s
invention. All of these clays (shale and bentonite being referred
to as a clay) have been successfully processed in the ollowing
manner:
In successive batches, sugar and sodium lignite (ORZAN
A) were respectively dissolved in water and then the water was
mixed with the clay so as to produce a damp pressing consistency
for the clay. In some instances where the clay had a high
moisture content, the clay was admixed with drier clay so as to
provide an ultimate moisture content of 6% to 15% by weight. Even
when only 3% or 4~ of the total water was added to the clay, the
sugar or sodium lignite was added to this water, prior to the time
it was admixed with the clay
The various samples of the resulting mixtures were each
pressed into cakes in flat dies or were hand packed onto carrying
plates. The pressed cakes were dried before firing. Cakes or
looser packs on carrying plates were individually pushed into a
laboratory kiln at approximate temperatures determined by
observinq the swelling behavior. The temperatures used were from
2050F to 2250~F No clays failed to cellulate.
I have found that some clays have naturally occurring
therein, orqanic materials containing carbon. These organic
materials are well distributed in the clay and present no
particular problem except that they must be considered. Thus, in
some instances, it is not necessary to add carbonaceous material
to the clay. In some instances, where extremely hiqh organic
material content is contained in the clays, they should be admixed
with other clays so that the resulting charge has about 2% by
weight organic material in the mixture. If more than about 2%
organic material is contained in the mixture, overblowing and
-54-
~Z(~7SlS
irregularities in the cellular structure will occur. When less
blowing or foaming is desired, the organic material in the charge
is reduced accordingly. This can be done by admixing with other
clays of low organic content. The resulting foamed or cellulated
clay will be more uniform and less densely celulated. When
charges were produced with all of the clays, shales, bentonites,
mentioned above impermeable cellulated pieces of good uniformity
were obtained in all cases, except where an excess of or~anic
material was contained in the char~es.
A better understanding of my invention will be had by
reference to the followin~ specific examples.
EXAMPLE I
A clay from Fremont, Calirofnia, (Interlockinq Tile Co.
passed throu~h 6 mesh scree, was mixed as follows:
1000 parts clay
10 parge sucrose
110 parts tap water
a 12' square tile was formed by pressinq at 100 psi, to
about 1~' thickness.
m e tile was introduced into a 700F atmosphere for 15
minutes, thence into a controlled atmosphere whereby the tile was
substantially sintered without burnin~ out the carhon derived from
the su~ar, as the temperature was raised to about 20nOF in a
reducin~ atmosphere.
~ _5s_
~ 7515
The tile was passed over rollers at about 12" per minute
for 20 minutes in an oven at about 2100F in an oxidizing
atmosphere. The rollers were clean and new before this run and
the tile passed over without being stopped b~ sticking to the
rollers. There was no evidence of sa~gin~ between rollers. The
tile had expanded to about 16" to 16" and had a reddish brown skin
due to the skin oxidation. The interior was greensh dark gray and
cellulated to about 30 lbs. per cubic foot.
A number of runs were repeated, and some sticky spots of
molten clay or glaze from various experiments were on the rollers
and began to pull of patches of oxidi~ed skin as the conti~uous
interior material softened and cellulated.
EXAMPLE II
Green tiles from Example I were painted on the bottom
and sides with an engobe of raw and calcined high temperature
fireclay, after preliminary drying.
These tiles were fired as in Example I and showed less
tendency to cause sticky spots on the rollers, but where a sticky
spot existed there was still a tendency to pull off the engobe and
oxidized sXin~ which could build until the conveyor would be~ome
inoperable. The tile expanded laterally to about 16" x 16".
EXAMPLE III
A mixture of 60 parts calcined fi~eclay to 40 parts raw
fireclay and 10 parts water was spread over the bottom of a die
cavity and patted up on the sides. The die was then filled with
the clay charge from Exampe I and tiles pressed otherwise as in
Example I.
~V7SlS
These tiles were filed as in Example I and cellulate~ to
about the same density. It was noted that while the tile had
expanded laterally to about 16" x 1~" in Example I and II, the
tile of this example expanded in thickness rather than laterally.
EXAMPLE IV
A parting agent was made by mixing 12 parts raw fireclay
to 88 parts silica sand and 10 parts water. This mixture was used
to make the bottom coating of the tile of Example I and processed
as in Example II. When tile with this bottom coating was passed
over the rollers in firinq, the sand, exposed to a sticky spot,
was pulled of only as it was exposed, until eventually the sticky
spots on the rollers were well covered. In subsequent runs these
rollers were then able aqain to receive the clay char~e without
the charge sticking.
E XAMPLE V
~ ile similar to Example I were made with Wyoming
bentonite instead of clay and the sugar addition was reduced to
about 2 parts per 1000 parts of bentonite. At a firing
temperature of about 2300F similar reults were obtained as in
Exampies I, II and III.
EXAMPLE VI
In the bottom of the die I spread a sheet of aluminum
foil and spread a dry mixture of 2 parts pulverized petroleum coke
and 1 part puliverized pitch from a foundry supply house. The die
was then heated by a qas flame to melt the pitch, then it was
pressed to make a carbon plate. This procedure was repreated to
make additional carbon plates from less than 1/16" thick to more
than 1/~" thick.
~L~()7~5
The carbon plates were then cooled and loaded with a
charge about 8" x 8" x 1" by placing a form on the plate and
fillin~ the form and hand ramminq.
Eor this Example VI the charge was Mississippi M & D
ball clay, mixed with sucrose and water as in Example I. The
sample was fired on one of the carbon plates, going directly from
room temperature into the kiln at about 2800F, where it was fired
for about 20 minutes. Temperature was adjusted by trial and error
to achieve good cellulation.
In all the above examples, the cellulated specimens
which were brought into cold air, from the kiln, fragmented from
thermal shock. At the end of a run some specimens were placed in
an annealing box and the cooling rate adjusted to qive unbroken
samples.
EXAMPLE VII
This was a repeat of Example VI, except that crushed
diatomaceous earth was substituted for the clay. The temperature
was adjusted by observation of the melting and cellulation, and
was ~udged to be about 3100F. m e sucrose addition was about 2
parts per 1000. ~ood cellulation was obtained at about 20 pounds
per cubic footl and the product did not break when brought from
the kiln temperature into cold air.
EXAMPLE VI I I
The procedure of Example VII was repeated except that
porous quartzite rock (see TAble I) was crushed and used in lieu
of the diatomaceous earth.
ll
~58- ,
l ~Z~7515
The firing temperature was about 3200F. ~uick coolinq ¦
was successful and cellulation was good after about 30 minutes
firinqO
EXAMPLE IX
The procedure of Example VII and VIII was followed
except that the charqe was a purer quartzite silica, principally a
purchased 325 mesh silica flour, 99.8% pure silica.
To this charge per 1000 parts was added 4 parts sucrose
in 49 parts water and 80 parts silica sol that contained 30% of
the silica sol as colloidal silica of 15 millimicrons diameterO
Firing was on the carbon plate at about 3200F for about
30 minutes. The sample was cooled quickly upon dischar~e from the
kiln and the carbon from the plate trimmed off. Cellulation was
qood at a density of 18 to 24 pounds per cubic foot.
EXAMPLE X
_
Samples of about 20 surface clays were collected from
California, Geoergia and Germany. All of these were tried alonq
the lines of Example I, adding more or less to no su~ar. All the
spe~imens could be cellulated successfu~ly.
Six commercial ball clays and a Geor~ia Kaolin were also
formed on carbon plates and cellulated using the above procedure.
It will be obvious to those skilled in the art that m~ny
variations may be made in the embodiments here chosen for the
~ 7515
purpose of illustratinq the present invention and that full resort
may be had to the doctrine of equivalents without departing from
~c~ b~ i n ~
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