Improvements in Dry Kilns.
Year: 1894

page_text: Date of Application, 18th Dec., 1894-Accepted, 26th Jan., 1895
COMPLETE SPECIFICATION.
Improvements in Dry Kilns.
I, VICTOR LEE EMERSON, of No. 18 Vansant Building, in the City of
Baltimore, State of Maryland, United States of America, Mechanical Engineer,
do hereby declare the nature of this invention and in what manner the same is
to be performed, to be particularly described and ascertained in and by the
following statement :—
This invention is an improved dry kiln designed particularly for drying lumber,
but useful for drying any other material by heated air, and the object of the
invention is to construct a simple, durable and inexpensive kiln which will be
effective in operation, economical of heat and wherein sufficient moisture (derived
from the substance or material being dried) will be automatically retained during
the initial stages to keep the exposed surfaces of such substance or material from
becoming too dry and to maintain such surfaces in the best condition until the
internal moisture therein has been extracted.
In this improved kiln the operation is such that the heated air is first retained
and caused to circulate in a natural way through the material being dried until the
latter reaches a desired high temperature, density and humidity, its higher
temperature increasing its capacity to absorb moisture, its greater density ensuring
its more equal and thorough dissemination throughout the lumber or other material
that is to be dried, and its humidity preventing the hardening of the exterior surfaces
of the lumber before the interior parts thereof become dry.
The invention is illustrated in the accompanying drawing, in which,
Figure 1 is a part vertical transverse section and part end view of the preferred
form of kiln.
Figure 2 is a central transverse section of a similar but less expensive kiln.
The dry kiln herein shown is constructed as follows: The kiln comprises a
rectangular building closed on both sides and top, but having large doors, A, at
each end which are raised and lowered by cords, A¹, pulleys, A³, and weights, A³,
to allow the entrance and removal of the trucks, Z, carrying the piled lumber, Y.
These trucks run upon railway tracks, ', two of which are preferably laid side by
side through the building, and are elevated sufficiently to enable the heating
pipes, P, or other means of heating, to be placed thereunder. The green hamber
or other material on the trucks is entered at one end of the building and when dried
is removed from the opposite end. During the drying operation the doors, A, are
closed. The lumber, Y, is preferably so piled on the trucks, Z, that the boards
will lie extended lengthwise of the kihn and horizontal, and where there are two
parallel tracks, as in the present instance, there will be a vertical central air-
passage, 1, in the kiln between the two adjoining piles of lumber, and also at each
side of the kiln there will be vertical air-passages, 2, between the exterior sides of
the said lumber piles, Y, and the side walls, b, of the kiln.
Below each vertical side passeige, 2, is a lower chamber, B, formed by vertical
partitions, D, which extend from near the sub-floor, E, of the kiln (which may be wood,
cement, metal or only earth), up to about the level of the lowest layer of boards, Y,
on the trucks. At the top of each partition, D, and over the lower chamber, B, is a
horizontal slatted walk-way, c, through which the heavy air passes from the side
passage, 2, down into chamber, B. Parallel with each lower chamber, B, and along

page_text: the partition, D, thereof is a longitudinal air-supply passage, C, formed by a vertical
partition, d, and a top borizontal partition; it also has a bottom horizontal
partition; d', and an outlet, d; this passage, C, has its inlets for out-door atmosphere
at each end of the kiln, and at intermediate points also, if desired'; doors, C¹, at the
end are for closing the inlets of said passage, C.
Beneath the railway tracks is a system of heating pipes, P, or other means of
heating, which extend lengthwise of the kiln and are connected to suitable header-
pipes (not shown) at each end thereof. When steam is employed for heating, as
in the present instance, the water of condensation may be permitted to escape
from the pipes through self-regulated valved outlets, S, or this water may be
delivered into a drain-tank, p, and then by means of the punip, F, returned back
into the boiler.
Below the pipes is, preferably, a horizontal false bottom or flooring, a, having
a longitudinal central opening, a', extending lengthwise of the kiln. The chamber, B,
at both sides of the kiln cominunicates with the chamber, 4, below said false floor, a,
and sub-floor, E, through passages, e, below the fresh air-passages, C; the outlet, d³,
from the fresh air-passage, C, also communicates with said chamber, 4, as shown
in Figure 1.
The space between the false floor, a, and the heating pipes, P, and between the two
fresh-air passages, C, forms an air chamber, 5, into which air is admitted from the
lower chamber, 4, through the central opening, a'.
Between the two parallel lines of railway is a central slatted walk-way, †, up
through which air passes from the lower chambers, 4 and 5. In the side-wall-, b,
of the kiln and at suitable intervals apart are formed vertical passages, 3, the upper
ends of which at the highest point to which lumber will be piled, are open into the
kiln chamber; these passages, 3, have an inclined deflector, g, and an exit, g², to
the atmosphere; on the exterior of the wall this exit is covered by a hood, g².
These passages may also be provided at their lower ends with automatic valves, G,
of any suitable construction which open outwardly to discharge the moist air. The
humidity, density and circulation of the air currents is determined by the higher or
lower location of the aforesaid exits, gl, for the moist air; these exits should always
be located so as to discharge the moist air before it becomes saturated to the dew
point.
The upper portion of the sides of the kiln above the said vertical passage, 3, are
preferably offset or projected exteriorly as shown at, b', forming an inside enlarge-
ment, 7, of the chamber at the top of said passage, 3, to facilitate the settling of the
moistened air into the upper ends thereof.
As shown in Figures 1 and 2, the upper part of the central passage, 1, is closed by
a longitudinal box, H, and side deflector plates, I, which latter over-reach or project
above the tops of adjoining lumber-piles, Y; these deflector plates, I, cause the
heated air which rises vertically assage, 1, to pass laterally in opposite directions
through the spaces, in the lumber-piles, Y.
The operation of the kiln is as follows:
The pipes, P, may be heated by steam, or may be heated by hot air, supplied
from a boiler or furnace, as the case may be, and the air in the kiln-chamber heated
by contact with the pipes, naturally rises and as it cannot pass into passage, 2,
being prevented by the partition, D, and the adjoining bottoms of lumber piles, Y,
the greater volume of the heated air will enter the central passage, 1, and being
prevented from rising to the top of kiln by the deflector, H, I, it is forced to
travel horizontally and laterally over and through the spaces between the boards
or lumber toward the two side passages, 2, and in thus passing thereover it absorbs
moisture from said boards and becomes heavier and denser and partly cooled. The
currents of air thus moving horizontally through the lumber piles will meet the
smaller currents of air rising through the vertical paces between the boards, and
commingle therewith, so that each board is entirely enveloped with currents of hot
air, and the edges of the boards are not dried faster than the broad surfaces. The
heaviest moist air from the lumber will enter the side passages, 2, and descend

page_text: therein by reason of its specific gravity and pass through the slats, c, into the
lower chambers, B, and thence through the passage, e, into chamber, 4, where part
of its moisture will be condensed by contact with the cold floors or the cold currents
of air at outlets, d², coming from passage, C. The descending moist and warm
currents commingling with the said cold air, partially warm the latter and impart
a degree of humidity thereto, and thus instead of currents of hot dry air being
continually discharged against the lumber, hot moist currents are produced by
means of which the exterior surfaces of the boards are kept from becoming dry
while the boards are being heated, and while the moisture is exuding from the
interior of the boards, so that the boards are heated throughout and at the same
time their pores are kept open until all the moisture is extracted. It will be seen,
therefore, that the drying of the boards is uniform throughout, and splitting,
checking, warping or case-hardening of the boards is prevented. It should be noted
that at the beginning of the drying process in this kiln, there is a rapid natural
circulation of air established within the kiln, but no air escapes therefrom at this
period, and the moisture absorbed by the air is retained by the kiln, except that
which is condensed on the sub-floor, E. This may be called the initial or first step
in the process of drying employed in the operation of the kiln.
Very little cold air will be drawn into the chamber, 4, from the fresh air-
passages, C, until the entire mass of air in the kiln-room becomes thoroughly
heated and moist air begins to discharge from the exits, g', in the down-
passages, 3.
This initial circuit of the air continues until the lumber, or other substance, has
been so heated that the heated air passing therethrough, or around, will become
sufficiently rarefied as to ascend, and carry with it in suspension the moisture it has
absorbed. This is the second step. Then the larger currents of heated and
moisture-laden air will flow upward through the side passages, 2, into the upper
part of the kiln-chamber where it meets the numerous currents issuing from the
vertical spaces between the boards, and together these currents pass laterally into
the enlargement, 7, at each side of the kiln where the currents eddy, and the
heaviest moisture-laden atoms will settle and pass down the passages, 3, and escape
through the exits, g', to the atmosphere, while the lighter portions of rarefied air
will not follow downward but will remain in the kiln-chamber, and, as the humid
air passes out of the kiln at exits, g', fresh air will be drawn in at passages, C, to
supply its place; the amount of air entering the kiln from the atmosphere is thus
automatically regulated by, and dependent upon, the amount of saturated air
discharged therefrom at the exits, g¹.
In practice the first effect of the cool wet lumber is to produce down currents of
air in the passage, 2, by reducing its volume and increasing its gravity consequent
upon its absorption of moisture; this action continues until the lumber or material
is heated to near the temperature of the heated air which is passing through it into
passage, 2; when the lumber is so heated the air will have become sufficiently
rarefied to ascend to the top of kiln-chamber and carry with it a due proportion of
moisture. This moist air collects in the enlargement, 7, out of the line of the
upward current until its volume and humidity causes it to gravitate down the
passage, 3, and discharge at the exits, g', to the atmosphere. Of course as soon as
any moist air is discharged from the kiln the drying proper commences and the
humidity of the air within the kiln begins to decrease, until eventually only clear
dry air will remain therein after all the moisture in the material undergoing
treatment has been extracted.
The construction and operation of the kiln shown in cross section in Figure 2 is
substantially identical with that of Figure 1, and the same reference letters refer
to like parts. This kiln differs from that shown in Figure 1 in that the air-supply
passage, C, and sub-floor, E, are dispensed with, and the air is admitted directly
under the sides of kiln from the atmosphere. In the construction shown in Figure 2
the fresh external air is introduced at the sides and bottom, at, J, and is the
equivalent of the supply-outlets for fresh air designated, d², in Figure 1.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is,―
1. A drying kiln having a drying chamber; supports for sustaining the material
to be dried; descending air-passages in the side walls having their upper parts
open to receive the moist air from said drying chamber and provided with exits to
the external atmosphere, said exits located above said supports.
2. A drying kiln having a drying chamber resting on a suitable base; and
descending air-passages having their upper parts open to receive the moist air from
said drying chamber and provided with exits to the external atmosphere, said exits
located between said upper openings and the said base.
3. A drying kiln having in combination a drying chamber; means for supplying
heat; a false door or bottom below the heater and having an opening communi-
cating with the drying-chamber; a fresh-air supply passage, C, having an outlet, d²,
below said false floor; and a lower down-passage or chamber, B, having a lateral
passage, e, below said fresh-air outlet.
4. A drying kiln having in combination a drying chamber; means for supplying
neat; a false floor or bottom below the heater and having an opening communi-
cating with the drying-chamber; and a lower down-passage or chamber, B, having
a lateral passage, e, for delivering moist air below said false floor or bottom.
5. A drying kiln having in coinbination a drying chamber; means for supplying
heat; descending air-outlet passages in the side walls and open at their top; and
an exterior projection, b', in the upper portion of the side walls to facilitate the
settling of the moist air into the top opening of said descending passages.
6. A drying kiln having in combination a drying chamber; means for supplying
heat; a false flour or bottom below the heater and having an opening communi-
cating with the drying chamber; a sub-floor, E, below the said false floor; and a
down-passage or chamber, B, communicating from the drying-room to the chamber
formed between the false floor and sub-floor.
7. A drying kiln having in combination a drying chamber; descending air-
passages having their upper ends open to receive moist air from said chamber and
provided with exits to the external atmosphere; and a lower down-passage or
chamber communicating from the said drying-chamber to the base below said
chamber.
8. A drying kiln having in combination a drying chamber; means for supplying
the chamber with heat; descending passages, 3, for discharging moist air to the
external atmosphere; a passage or chamber, B, for moist air communicating from
the said drying chamber downward to the base below the chamber; and a fresh
air supply passage or inlet intersecting the said down-passage.
9. A drying kiln having in combination a drying chamber; air-circulating
vertical passages in the drying chamber; means in the chamber for supplyin
heat; communications, B, from the drying chamber extending down and below the
means for supplying heat and thence opening again into the drying-chamber; and
descending air-passages having their upper part open to receive moist air from th
drying-chamber and provided with exits to the external atmosphere.
10. A drying kiln having in combination a drying-chamber; means for supplyin
heat; two vertical side passages; a central vertical passage; and a deflector,
above the said central passage to cause the heat to pass laterally in opposit
directions.
Dated this 24th day of November 1894.