Improvements in the Drying of Wood and other Materials and in Apparatus for Use therein.
Year: 1898

page_text: Date of Application, 20th Aug., 1898
Complete Specification Left, 20th May, 1899-Accepted, 8th July, 1899
:
:
PROVISIONAL SPECIFICATION.
Improvements in the Drying of Wood and other Materials and in
Apparatus for Use therein.
We, THE BRITISH NON-FLAMMABLE WOOD COMPANY LIMITED, of 2, Army and
Navy Mansions, Victoria Street, Westminster, and CILARLES HOWARD, of Town-
mead Road. Works, Wandsworth Bridge, Fulham, in the County of London,
Works Manager to the said Company, do hereby declare the nature of this inven-
tion to be as follows:-
This invention relates to improvements in the drying of wood and other materials
and to apparatus for use therein, and its object is to quickly and thoroughly
dry the wood or other material at an equable temperature and thus avoid liability
to checking and warping or other deteriorating results.
According to the most successful means hitherto employed to dry
wood, kilns have been employed in which the air after being heated
is circulated by means of fans around the timber which is stacked. in the kilns.
This air after having taken up a certain amount of moisture from the timber
is allowed either to escape into the atmosphere and make way for a fresh quantity
of heated air from the fans or by suitable devices is led round again to the fan,
and so complete a cycle until it is thoroughly saturated and no longer capable of
taking up any more moisture. In the case of timber that has only a moderate
percentage of moisture the above methods have been found fairly successful,
but the great drawback met with is the changes of temperature which are
experienced in the kilns, and if it is to be led round again through the fans
it has no opportunity of getting rid of any of the moisture which it may have
taken up. Now this change of temperature is liable to have a deteriorating effect
on timber, especially when it has a large percentage of moisture in it.
Now according to our invention we first raise the temperature in the
kiln to a certain heat before submitting the wood to the action of
a. current of warm air, and maintain this heat, until the wood has
become thoroughly warm and we then circulate a current of heated air through
the kiln and around the wood therein continuously, the air being periodically
deprived of its absorbed moisture and maintained at the desired temperature as
hereinafter described. It is preferable to submit the wood to a preliminary
heating as above referred to, for should a current of hot air be at once projected
against the wood before it is thoroughly warm throughout the wood- is apt to
become case hardened, and warping and other ill effects are thus caused.
For the purpose of our invention we employ a kiln of any suitable
air-tight construction, and at the bottom, thereof we preferably provide
a series of steam pipes for the purpose of raising the temperature in the kiln.
Hot air pipes. or conduits with orifices for distributing the air are also provided,
and arranged so as to cause a distribution of air over all the timber. These
pipes serve for introducing the hot air, which is led through them into the kiln
from a suitable heater. Pipes or conduits also are provided in the kiln for

page_text: exhaust by which the air is led to the condenser. The supply and exit air pipes
are so arranged that the circulation of the air passes all round the timber. From
the kiln a suitable pipe or conduit leads to a condenser, an expansion chamber
being preferably interposed between the kiln and condenser. The condenser
is in communication preferably through a similar expansion chamber with the
heater. The circulation of air through the apparatus is maintained by a fan
situated at any suitable part of the cycle.
The operation of the apparatus is as follows:-The wood having been placed
in the kiln steam is first admitted to the steam pipes therein and the temperature
in the kiln gradually raised to the desired degree, say 100° to 120° F. When
the wood has become thoroughly warm the fan is set in operation and the air is
drawn from or propelled through the heater to the kiln. The temperature of this
air should be regulated to that of the kiln. The air is thus distributed within
the kiln and plays around the wood passing away by the exit pipe to the con-
denser where it parts with its moisture absorbed from the wood, and its temperature
is lowered. From the condenser the dried cooled air is led to the heater where
it is again raised to the necessary temperature and is then again delivered to
the kiln, the operation being continuous. This air being now dried and at the
same temperature as the wood in the kiln has a great advantage, the drying being
effected without the result of change of temperature.
Our invention is particularly adapted to wood that has been impregnated
or saturated throughout its thickness for fireproofing or preservative. purposes;
since the objection of casehardening, which prevents the extraction of the moisture
from the centre of the wood is done away with.
We may dispense with the employment of expansion chambers for the air-enter-
ing the heater and condenser, but we prefer to empoy them, since they serve to
prevent the air passing too rapidly through the heater and condenser, which is
liable to lessen the best effects.
Although we have hereinbefore described our invention as applied to the
drying of wood for which it is particularly adapted yet it will be readily under-
stood that it is applicable also to the drying of other materials of a like nature.
Dated this 20th day of August 1898.
J. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London. Chartered Patent Agents.
Improvements in the Drying of Wood and other Materials and in
Apparatus for Use therein.
We, THE BRITISH NON-FLAMMABLE WOOD COMPANY LIMITED, of 2, Army and
Navy Mansions, Victoria Street, Westminster, and CHARLES HOWARD, of Town-
mead Road Works, Wandsworth Bridge, Fulham, in the County of London,
Works Manager to the said Company, do hereby declare the nature of this inven-
tion 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 improvements in the drying of wood and other materials
and to apparatus for use therein, and its object is to quickly and thoroughly
dry the wood or other material at an equable temperature and thus avoid liability
to checking and warping or other deteriorating results.
According to the most successful means hitherto employed to dry wood, kilns
or drying chambers have been employed in which the air after being heated"
is circulated by means of fans around the timber which is stacked in the kilns.

page_text: This air after having taken up a certain amount of moisture from the timber is
allowed either to escape into the atmosphere so as to make way for a fresh quantity
of heated air from the fans or by suitable devices it is led round again to the fan,
so as to complete a cycle until it is thoroughly saturated and no longer capable of
taking up any more moisture. In the case of timber that has only a moderate
percentage of moisture the above methods have been found fairly successful,
but the great drawback met with is the changes of temperature which are
experienced in the kilns, and if the air is to be led round again through the fans.
as is sometimes done it has no opportunity of getting rid of any of the moisture
which it may have taken up. Now this change of temperature is liable to have
a deteriorating effect on timber, especially when it has a large percentage of.
moisture in it.
The method of drawing the circulating air from the atmosphere, and discharging
it thereto after passing through the kiln, has the drawback of inequality of drying.
depending on the hydrometrical state of the atmosphere at the time of the with-
drawal.
Now according to our invention we first raise the temperature in the kiln or
drying chamber to a certain heat gradually before submitting the wood to the
action of a current of warm air, and maintain this heat, until the wood has
become thoroughly warm and we then circulate a current of heated air through.
the kiln and around the wood therein continuously, the air being periodically
deprived of its absorbed moisture and maintained at the desired temperature as.
hereinafter described. It is preferable to submit the wood to a preliminary
heating as above referred to, for, should a current of hot air be at once projected.
against the wood before it is thoroughly warm throughout, the wood is apt to
become case hardened, and warping and other ill effects are thus caused.
For the purpose of our invention we employ a kiln or drying chamber of any
suitable air-tight construction, and at the bottom thereof we preferably provide.
a series of steam pipes for the purpose of raising the temperature in the kiln.
Hot air pipes or conduits with orifices for distributing the air are also provided,
and arranged so as to cause a distribution of air over all the timber.. These
pipes serve for introducing the hot air, which is led through them into: the kiln.
from a suitable heater. Pipes or conduits are also provided in the kiln for
exhaust by which the air is led to the condenser. The supply and exit pipes.
are so arranged that the circulation of the air passes all round the timber. From
the kiln a suitable pipe or conduit leads to a condenser, an expansion chamber
being preferably interposed between the kiln and condenser. The condenser
is in communication, preferably through a similar expansion chamber, with the
heater. The circulation of air through the, apparatus is maintained by a fan
situated at any suitable part of the cycle.
:
The operation of the apparatus is as follows:-The wood having been placed.
in the kiln steam is first admitted to the steam pipes therein and the temperature
in the kiln gradually raised to the desired degree, say 100° to 120° F. This
preliminary heating may be dispensed with, but we find it gives good results
preventing-too sudden changes of temperature: When the wood has
become thoroughly warm the fan is set in operation and the air is
drawn from or propelled through the heater to the kiln. The temperature of this
air should be regulated to that of the kiln. The air is thus distributed within
the kiln and plays around. the wood, passing, away by the exit pipe- to the con-
denser where it parts with its moisture absorbed from the wood, and its temperature
is lowered. From the condenser the dried cooled air is led to the heater where
it. is again raised to the necessary temperature and is then again delivered to
the kiln, the operation being continuous. This air being now dried and at the
same temperature as the wood in the kiln has a great advantage the drying being
effected without the result of change of temperature, which latter is apt to cause
cracking and warping:

page_text: Our invention is particularly adapted to wood that has been impregnated
or saturated throughout its thickness for fireproofing or preservative purposes,
since the objection of case hardening, which prevents the extraction of the moisture
from the centre of the wood is-done away-with.
+
We may dispense with the employment of expansion chambers for the air enter-
ing the heater and. condenser, but we prefer to employ them, since they serve to
prevent the air passing too rapidly through the heater and condenser, which is
liable to lessen the best effects.
Although we have hereinbefore described our invention as applied to the
drying of wood for which it is particularly adapted yet it will be readily under-
stood that it is applicable also to the drying of other materials of a like nature.
Reference is made to the accompanying illustrative drawings in which :-
Figure 1 is a plan, partly in horizontal section of a suitable arrangement of
apparatus for carrying out this invention.
Figure 2 is a vertical section on the line 2-2 of Figure 1..
Figure 3 is a plan, partly in horizontal section of the condenser drawn to a
larger scale.
In these figures, A is the drying chamber constructed in an air-tight manner
of masonry; BB are serpentine coils of steam piping arranged on or slightly
above the floor of the kiln. C C are rails arranged between the steam coils B and
with their upper edges higher than the upper surfaces of the said steam coils.
1) D is a perforated pipe for supplying hot dry air to the drying chamber A. E is
a perforated pipe for exhausting the moisture laden air from the drying chamber.
Fis a condenser for cooling the moisture-laden air and thus depriving it of its
moisture. which is drained away by suitable means. G is a heater of any suitable
kind, preferably of the steam-coil type delivering through a duct
into the
pipe DD; it serves for heating the cooled dry air coming from the condenser F.
His a fan for circulating the air through the apparatus; it is shown situated
between the condenser F and the exhaust pipe E from which it draws the moist
air through a duct h. I is a steam engine for driving the fan H. K is a steam
boiler for supplying steam to the steam coils B through a pipe b, and to the
heater G and steam engine I through pipes not shown.
The condenser F shown in Figure 3 is of the cold water type and is composed
of rows of coil piping f. The casing of the condenser includes the two expansion
chambers L L
The drying chamber A having been charged with the wood or other material
to be dried, steam is passed from the boiler K through the steam coils B exhaust-
ing at B and by this means gradually raising the temperature of the drying
chamber to the required temperature. This constitutes the preliminary heating.
The fan H is then started, withdrawing the moist air from the drying chamber
by the perforated pipe, E, and duct and driving it through the condenser F
and thence into the heater G and through the duct g and perforated pipe DD
into the drying chamber again.
Having now, particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is:
1. The method of drying wood and other materials of like nature which consists in
circulating a current of hot dry air around the wood in a continuous cycle, the air
being periodically deprived of its absorbed moisture, and being maintained at the
desired temperature by periodical heating, substantially as herein before described. 5
2. In connection with the method specified in the preceding claim, thoroughly
warming the wood by gradually heating the same by the action of a current of
warm air prior to treatment with hot dry air, substantially as herein before
described.
3. For carrying out the method or methods of drying wood and other materials 5
of like nature, as specified in the preceding claims, an apparatus comprising an

page_text: air tight kiln or drying chamber with air supply and exhaust ducts, an air heater,
a condenser for drying air, and a fan for circulating air through the kiln, the
heater, and the condenser, the whole arranged and operating substantially as
described and shown.
4. In apparatus of the kind specified in the preceding claim, the interposition
of air expansion chambers between the kiln and the condenser, and between the
condenser and the heater, substantially as described and for the purposes specified.
Dated this 18th day of May 1899.
J. O. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London. Chartered Patent Agents.