Improvements in Dry Kilns, and in the Method of Operating the same.
Year: 1896

page_text: Date of Application, 4th Feb., 1896-Accepted, 25th July, 1898
COMPLETE SPECIFICATION.
[Communicated from abroad by AARON SAWYER NICHOLS, of Chicago, in the
County of Cook, in the State of Illinois, United States of America,
Manufacturer.]
Improvements in Dry Kilns, and in the Method of Operating
the same.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, 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 relates to the construction of dry kilos and the method of operating
them, and has been devised specially for use with that class of driers consisting of
a series of platens each provided with a coil of heating pipe and placed one above
another in a pile with a thickness of lumber between each adjacent pair of platens.
Driers of this character are most advantageously placed in a suitable sized com-
partment adapted to be entirely closed so as to confine the moisture given off by the
lumber or supplied from the steam pipes, and thereby keep the lumber in a moist
atmosphere during a portion at least of the operation.
The first feature of my invention has for its object the provision of improved
means for ventilating the dry house or compartment containing a drier composed of
individually heated platens to the end that the work done may be facilitated and
improved in character. The second feature relates to a new method of operating
such a kiln, whereby I avoid all checking in the lumber operated upon, and secure
its perfect and thorough drying.
The nature of my invention is fully stated in subsequent parts of this specification,
and such features thereof as relate to construction are shown in the accompanying
drawing, wherein is given a vertical section of the drier compartment, the drier being
shown in elevation.
In said drawing A, A represent the series of platens forming the drier proper,
and B B are a portion of the pipes by which steam is fed to the coils in the interior
of the platens. CC are the usual hydraulic jacks used with the platens.
D is the dry house surrounding the drier made with walls which are non-
conducting of heat, to the end that the temperature within the dry house may
be easily retained at a point above that of the external air, and condensation of
the moisture upon their inner surfaces to be avoided. They may be made of
wood, or brick, or any other non-conducting material or of combinations of such
materials. It is provided with air inlet pipes E which are preferably of metal and
located wholly within the room. The usual method of adimitting cold air through
openings located at the top of the room, I find to be a failure, as the hot air will go
out of such openings instead of allowing cold air to come in, thereby creating a
waste of heat as well as a loss of moisture. My inlet pipes E draw the outside air
from a level near that of the floor I and deliver it inside the room near the top
thereof, which prevents the escape of either heat or moisture through these
pipes. Being thus located the warmth in the room raises the temperature of

page_text: the pipes above that of the air drawn in by them and thus stimulates the draft
through them.
The dry room is also provided with a suitable number of air exhaust pipes F,
preferably of metal. These take the air from the bottom or near the floor of
the drying room and discharge it above the roof, where they are supplied with
suitable cowls or hoods G adapted to prevent down currents and the entrance of
snow and rain and also adapted to increase the upward movement of the air.
No radiators or steam pipes are needed in the drying room if it is suitably con-
structed for the drier, all the heat necessary being obtained from the platens
themselves. I make ro provision in the dry room or house for the condensation of
the moisture, but retain all the moisture driven out of the stock in the surrounding
atmosphere during the first stage of the operation.
Suitable valves H are employed in all the air pipes E and F, and such valves are
preferably provided with operating devices extending to the outside, so that all can
be closed or opened at different stages in the operation without opening the kiln
room.
With this apparatus and house the mode of operation is as follows: The lumber.
having been placed between the platens in the usual manner and the latter lowered.
so as to bear upon both sides of it, the steam is then turnel into the plateus, which
becoming heated soon act upon the wood. This immediate contact of the heated"
platens with both sides of every board converts the moisture therein into vapor
and rises, as is natural with heated air, to the top of the room. I also close all the
air valves H and thus prevent both the entrance of the fresh cold air as well as
the escape of such moisture as may be in the room, and thus produce a condition
of hot moist air in the room, which condition is maintained until it is certain
that the central or inner portions of the stock have become thoroughly heated
through.
I find that it is very essential that the outside of the lumber be kept moist and
thus prevented from drying until the inner portions have become thoroughly heated,
because when the outside is allowed to dry prematurely it seems to crust over the
outside of the lumber and to seal up within it what moisture may then remain
therein, and the more dry heat is applied, the more difficult it becomes to extract
this remaining moisture as the outside continues to dry and shell over, finally
becoming case hardened. This is the cause of honeycombing or interior checking.
The length of time the stock is thus maintained in the wet atmosphere depends
upon the size of stock and kind of wood, thicker stock requiring more than thin and
some wood needing more than others.
When the stock has become thoroughly heated through with hot moist air, the
valves in the pipes E and F are gradually opened to suit whatever stock is being
dried until finally the air is given free circulation.
The heat of the platens, being continued throughout the operation, acts to draw
the moisture from the centre of the stock both ways to the surfaces, and thence
it rises to the top of the room. Upon opening the valves H, the fresh air is also
admitted to the upper part of the room through the pipes E, and there mingles
with the heated and moist air arising from the stock, and being the cooler it chills
the latter so that both fall to the floor where the upward suction in pipes F draws
them out of the room.
As long as there is moisture in the wood there must be moisture in the room,"
hence the first stage of the operation is carried on in a moist atmosphere. The
circulation referred to is continued until all the moisture in the stock has been
drawn out and the surface of the lumber dried off. It is wholly a natural circula-
tion and needs no attention from attendants beyond the opening and closing of
the valves. The heat is also continued in the platens until the lumber is
thoroughly dry.
It will be noticed that by my improved process and apparatus, the heat is
applied directly to the lumber by the platens of the drier, and that the chamber

page_text: of the kiln is warmed by the heat derived from the same platens. It results"
from this that the lumber is subjected to a high heat and the temperature which
prevails in the chamber outside of the platens, while it may be less than that.
which the lumber receives directly from the platens, is yet sufficiently high to
prevent condensation of the pervading moisture. The atmosphere thus becomes
surcharged with the vapor and the surface of the wood so softened that the escape
of the moisture from its interior is facilitated, and by maintaining the heat in the
platens and this moist and hot condition of the air until the interior parts of the
wood have become thoroughly heated, I effectually drive out all confined moisture
from the wood and prevent casehardening. I am also enabled to greatly quicken
the drying operation.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, as communicated to me by
my foreign correspondent, I declare that what I claim is :-
1st. The improved dry kiln or room consisting of a chamber, the walls whereof
are adapted to prevent condensation of the moisture within it, an air inlet and an
air outlet pipes located within the chamber and each provided with a valve whereby
it may be closed, the inlet pipes drawing in the outside air and discharging it near
the top of the chamber, and the outlet pipes drawing the inside air from the floor
of the chamber and discharging it above the top thereof, and means for stimu-
lating the draft through said outlet pipes, in combination with a series of individually
heated platens adapted to receive the lumber between them and exert heat.
thereon, and also adapted to warm the air within the chamber, substantially as
specified.
2nd. The improved dry kiln or room consisting of a chamber, the walls whereof
are adapted to prevent condensation of the moisture within it, air inlet and air
outlet pipes located within the chamber and each provided with a valve whereby
it may be closed, the inlet pipes drawing in the outside air and discharging it near
the top of the chamber, and the outlet pipes drawing the inside air from the floor
of the chamber and discharging it above the top thereof, in combination with a
series of individually heated plateus adapted to receive the lumber between them
and exert heat thereon, and also adapted to warm the air within the chamber,
substantially as specified.
3rd. The improved dry kiln or room consisting of a chamber, the walls whereof
are adapted to prevent condensation of the moisture within it, air inlet and air
outlet pipes located within the chamber and each provided with a valve whereby it
may be closed, the inlet pipes drawing in the outside air and discharging it near the
top of the chamber, and the outlet pipes drawing the inside air from the floor of the
chamber and discharging it above the top thereof, and means for stimulating
the draft through said outlet pipe in combination with means for heating the
chamber and lumber, substantially as specified.
4th. The improved process of drying lumber without interior checking, consisting
in subjecting the lumber to the action of heat in the presence of a confined and
quiet body of air holding the moisture driven out of the lumber without condensa-
tion, such heat and moisture being continued until the lumber has been both warmed
and softened entirely through, and then gradually establishing an air circulation
through the room, substantially as specified.
5th. The improved process of drying lumber without interior checking, consisting
in subjecting each piece of the lumber to the direct action of a heating device in
the presence of a confined and quiet body of air charged with and holding the
moisture driven out of the lumber without condensation, such heat and moisture
being confined until the lumber has been both warmed and softened entirely through,
and then gradually establishing an air circulation through the room, substantially
as specified.
6th. The improved process of drying lumber, consisting in first subjecting the

page_text: lumber to the action of heat in the presence of a confined quiescent body of air also
heated and adapted to take up and hold without condensation the moisture given
off by the lumber, for a period sufficient to warm and soften the lumber entirely
through, and then gradually replacing the moist confined air with fresh air,
substantially as specified.
Dated this 4th day of February 1896.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.