IMPROVEMENTS IN KILNS FOR BAKING PLASTER, IN APPLIANCES FOR PREVENTING THE CHOKING, AND IN MEANS FOR DISTRIBUTING THE HEAT THEREIN
Year: 1873

page_text: LETTERS PATENT to Thomas James Smith, of the Firm of Robertson,
Brooman, and Company, of 166, Fleet Street, in the City of London,
Patent Agents, for the Invention of "IMPROVEMENTS IN KILNS FOR
BAKING PLASTER, IN APPLIANCES FOR PREVENTING THE CHOKING, AND IN
MEANS FOR DISTRIBUTING THE HEAT THEREIN."-A communication from
abroad by Paul François Mabille, of 28, Boulevard de Strasbourg,
Paris, France, Manufacturer.
Sealed the 11th July 1878, and dated the 5th March 1878.
PROVISIONAL SPECIFICATION left by the said Thomas James Smith
at the Office of the Commissioners of Patents, with his Petition,
on the 5th March 1878.
I, THOMAS JAMES SMITH, of the Firm of Robertson, Brooman, and
3 Company, of 166, Fleet Street, in the City of London, Patent Agents,
do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN KILNS FOR BAKING PLASTER, IN APPLIANCES FOR PREVENTING THE CHOKING,
AND IN MEANS FOR DISTRIBUTING THE HEAT THEREIN," to be as follows:-
--

page_text: This Invention comprises several important conditions which hitherto
have been but very imperfectly fulfilled in the baking of plaster.
1st. The complete separation of the dust ordinarily mingled with the
crude or raw material at the moment of charging.
2ndly. The equal spreading of the heat from the furnace within the 5
of burning.
I will describe two arrangements of this kiln, the first intended more
particularly for the burning of ordinary plaster, while the second is:
suited for the production of fine or moulding plaster.
The first arrangement of kiln is composed of a fire-place or furnace
placed at the lower part of a central chamber, the roof or crown of
which is vaulted ovally and constructed of refractory bricks; this
arrangement has the effect of forcing the products of combustion
reflected from the vault to redescend towards the furnace in order to
become completely burnt. At the interior of this chamber above the
furnace are arranged channels or outlets, these being superposed in
alternate order and leading into pipes for conducting the heat into an
annular chamber which surrounds the casing or wall of the inner one.
These pipes which traverse the annular chamber are arranged radially,
and so that the pipes of the one series are in the spaces left between the
pipes in the other series so as to more equally spread the heat, and they
debouch at their other ends into openings made for the purpose in the
exterior wall, which are temporarily stopped with clay to cause the
escaping heated gases to pass through a series of holes into the annular
chamber, and thus into the midst of the mass. The outer wall made of
ordinary bricks has also an ovally vaulted roof terminating in an inverted
funnel-shaped opening, serving for the charging of the crude material

page_text: into the kiln. The material is raised to the upper part of the kiln by an
endless chain of buckets or cups, which one after another discharge their
contents direct into the furnace or into vehicles which are movable
upon rails supported on a platform, and the vehicle when required
5 can be emptied in the funnel-shaped opening to feed the kiln. It is
evident that in this manner several kilns can be supplied at the same
time. When the material has been thus brought to the kiln it is
always largely mingled with dust which more or less became impregnated
with moisture, and causes a caking of the material, or on accumulating
the large particles become imbedded therein, and since dust is not a
conductor of heat it would follow that the larger particles would not
burn sufficiently; and thus a diminution would be caused in the pro-
duction. To obviate these disastrous results the dome of the chamber is
covered with a grating through which the dust will fall and become
separated from the larger particles at the upper part of the chamber.
Thus the dust on arriving at the grating passes through it and enters the
space existing between the grate, and the dome slides down the latter
and follows the conduit formed by the partition. Arrived at the level of
the second series of pipes the dust slides down the exterior partition of
the chamber until it reaches a slope, when it mingles without injury
with the burned material, the action of the heat upon which it has not
hindered. The burned material is taken out through, say, seven
openings closed when required by vertical doors sliding upwards and
downwards, and which are fastened by a chain or other manner. An
eight door is provided for the fire-place. Inclined planes are formed
at intervals around the kiln chamber to direct the burned material in its
descent towards the openings from which it can be removed by hand.
The arrangement of this kiln is such that the descent of the material is
gradual and very regular, that is to say, that as fast as the workman
takes out a shovelful of baked plaster from the opening, the weight of
the mass above causes a gradual and regular descent.
In this second arrangement which, as was stated before, is intended for
the burning of moulding or fine plaster, the two chambers are arranged
in the same manner as in the preceeding as well as the oval grating
which is placed above the of the inner chamber, and the pipes are
also arranged radially and quincunxially. The baking of fine plaster
requires much more care than that from which ordinary plaster or

page_text: cement is made, which comes into direct contact with the gases of com-
bustion occupying into the mass of plaster through the holes in the
pipes.
The result required to be obtained from the moulding or fine plaster
necessitates a peculiar combination of conduits, permitting the sup- 5
pression of the holes. The pipes are superposed in six rays attached to
conduits established in the interies of the walls of the two chambers,
and which lead up to the upper portion of the kiln opposite to cach. At
the exterior of the kiln are arranged openings plugged with clay.
The products of combustion escape from the fire-place through flues, 1
and from thence passing by the pipes discharge themselves at the upper
part of the kiln. In this passage the heat passing into the interior of
the walls through the conduits communicates its heat during its passage,
and thus gives a uniform baking without the material being soiled by
contact with the gases or smoke which might escape. This arrange-
ment of kilns effects a great economy in the baking of moulding or fino
plaster which hitherto has been costly and imperfect. The crude
material is fed into the kiln in the same manner as in the preceding
instance, and the extraction is effected in a like manner.
SPECIFICATION in pursuance of the conditions of the Letters Patent, 20
filed by the said Thomas' James Smith in the Great Seal Patent
Office on the 5th September 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
JAMES SMITH, of the Firm of Robertson, Brooman, and Company, of 166,
Fleet Street, in the Oity of London, Patent Agents, send greeting.
26
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fifth day of March, in the year of our
Lord One thousand eight hundred and seventy-three, in the thirty-sixth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Thomas James Smith, Her special licence 30
that I, the said Thomas James Smith, my executors, administrators,
and assigns, or such others as I, the said Thomas James Smith, my

page_text: I will describe two arrangements of this kiln; the first intended more
particularly for the baking of ordinary plaster, while the second is suited
for the production of fine or moulding plaster.
The construction of the kiln will be readily understood on reference to
the annexed Drawings.
Figure 1 is a vertical section of the first arrangement of kiln, and
Figure 2 is a horizontal section of the same showing the exterior
action.
Figures 3 and 4 show in vertical and horizontal section the second
arrangement of kiln.
.
The first arrangement of kiln is composed of a fire-place or furnace A
placed at the lower part of a central chamber B, the roof or crown of
which is vaulted ovally, and constructed of refractory bricks. This
arrangement has the effect of forcing the products of combustion reflected
from the vault to redescend towards the furnace, in order to become
completely burnt. At the interior of this chamber B above the furnace
are arranged channels or outlets C, O, O, these being superposed in
alternate order, and leading into pipes D for conducting the heat into
an annular chamber F which surrounds the casing or wall of the inner
chamber B. These pipes D, which traverse the annular chamber, are
arranged radially, and so that the pipes of the one series are in the spaces
left between the pipes in the other series so as to more equally spread
the heat, see Figure 2, and they debouch at their other ends into openings
made for the purpose in the exterior wall G, which openings aro
temporarily stopped with plugs of clay H to cause the escaping heated
gases to pass through a series of holes 6 into the annular chamber F, and
thus into the midst of the baking mass. The chamber F is made of
ordinary bricks, and has also an ovally vaulted roof terminating in an
inverted funnel-shaped opening J serving for the charging of the crude
plaster into the kiln. The plaster is raised to the upper part of the kiln 3
by an endless chain of buckets or cups I, which one after another dis-
charge their contents direct into the furnace, or into vehicles which are
movable upon rails supported on a platform. These vehicles, when
required, can be emptied in the funnel-shaped opening J to feed the
kiln. It is evident that in this manner, several kilns can be supplied at 8
the same time.
1

page_text: When the plaster has been thus brought to the kiln it is always largely
mingled with dust, which, if allowed to fall into the furnace, would moro
or less become impregnated with moisture, and cause a caking of the
plaster, or accumulating the large particles would become embedded
3 therein, and since dust is not a conductor of heat it would follow that
they would not burn sufficiently, and thus a diminution would be caused
in the production. To obviate these disastrous results the dome of the
chamber B is covered with a grating X of the same form, which is
supported by the upper series of pipes D. To the base of this grating X
an iron partition M is attached, intended to conduct the dust and keep it
separated from the larger particles while they are baking. Thus the
dust on arriving at the grating passes through it and enters the space
existing between the grate, and the dome B slides down the latter and
follows the conduit formed by the partition. Arrived at the level of the
second series of pipes the dust slides down the exterior partition of the
chamber B until it reaches the inclined plane or slope K, when it
mingles without injury with the baked plaster, the action of the heat
upon which it has not hindered. The baked plaster is taken out through,
say, seven openings L, closed when required by vertical doors sliding
upwards and downwards, and fastened by a chain or in other manner.
An eighth door I is provided for the fire-place. Inclined planes K are
formed at intervals around the kiln chamber to direct the baked plaster
in its descent towards the openings L, from which it can be removed by
hand or other convenient means. The arrangement of this kiln is such
that the descent of the material is gradual and very regular, that is to
say, that as fast as the workman takes out a shovelfull of baked plaster
from the opening the weight of the mass above causes a gradual and
regular descent of the whole baking mass.
In the second arrangement of kiln, which, as was stated before, is
intended for the burning of moulding or fine plaster, the two chambers
B, F, aro arranged in the same manner as the preceding, as well as the
oval grating which is placed above the dome of the inner chamber B,
and the pipo D are also arranged radially and quincunxially. The baking
of fine or moulding plaster requires much more care than ordinary plaster
which comes into direct contact with the gases of combustion escaping
into the mass of plaster through the holes 6 in the pipes D.
The result required to be obtained from the moulding or fine plaster

page_text: necessitates a peculiar combination of conduits, permitting the suppression
of the holes b, as clearly shown in Figures 3 and 4. The pipes D are
superposed in six rays attached to conduits N established in the interior
of the walls of the two chambers B and F which lead to the upper portion
of the kiln. Opposite to each at the exterior of the kiln are arranged
openings plugged with clay.
The products of combustion escape from the fire-place A through the
channels or flues C, O, and from thence, passing by the pipes D, dis-
charge themselves at the upper part of the kiln. In this progress the
products of combustion passing into the interior of the walls through the
conduits N communicate their heat during its passage, and thus give an
uniform baking without the material being deteriorated by contact with
the gases or smoke which may have escaped. This arrangement of kiln
effects a great economy in the baking of moulding or fine plaster which
hitherto has been costly and imperfect. The crude plaster is fed into :
the kiln in the same manner as in the preceding instance, and the
extraction is effected in a like manner.
It will of course be understood that the number of discharge openings
at the base of these kilns is variable so long as more than one are
employed. All kinds of combustible can be burned in these kilns.
And having now described the nature of the said Invention, and in
what manner the same is to be performed, I declare that I claim,―
First. The arrangement of kiln for baking ordinary plaster, as herein-
beforo described and shewn with reference to the accompanying Drawings
Figures 1 and 2.
Secondly. The arrangement of kiln for baking fine or moulding plaster,
as herein-before described and shown with reference to the accompanying
Drawings, Figures 3 and 4.
Thirdly. The grating X placed over the dome B in order to separate the
dust from the larger particles of the plaster to be baked, as herein-before
described and shewn with reference to the accompanying Drawings.
Fourthly. The peculiar arrangement of the conduits N in the second
arrangement of kiln for baking fine or moulding plaster in order to
avoid the contact of the plaster with the products of combustion, and
to establish the distribution of the heat throughout the kiln, as herein-

page_text: efore described and shown with reference to Figures 3 and 4 of the
ccompanying Drawings.
And, Fifthly. The arrangement of the inclined plane or slope K at the
ase of the kiln, in order to facilitate its discharge, as herein-before
escribed and shown in the accompanying Drawings.
In witness whereof, I, the said Thomas James Smith, have hereunto
set my hand and seal, this First day of September One thousand
eight hundred and seventy-three.
T. J. SMITH. (L.s.)