A METHOD, OR METHODS OF DRYING, SEASONING, AND HARDENING WOOD AND OTHER ARTICLES, PARTS OF WHICH ARE APPLICABLE TO THE DESICCATION OF VEGETABLE SUBSTANCES GENERALLY
Year: 1844

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, we, ROBERT
DAVISON, of Brick Lanc, in the County of Middlesex, Civil Engineer, and
WILLIAM SYMINGTON, of East Smithfield, in the County of Middlesex, Civil
Engineer, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Twenty-eighth day of March, in the seventh year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto us, the said
Robert Davison and William Symington, our exors, adiñiors, and assigns,
Her especial licence, full power, sole privilege and authority, that we, the said
Robert Davison and William Symington, our exors, adñiors, and assigns, and
such others as we, the said Robert Davison and William Symington, our exors,
adñiors, or assigns, should at any time agree with, and no others, from time to
time and all times thereafter during the term of years therein expressed,
should and lawfully might make, usc, exercise, and vend, within that part of
Her said Majesty's United Kingdom of Great Britain and Ireland called
England, Her Dominion of Wales, and the Town of Berwick-upon-Tweed, our
Invention of "A METHOD, OR METHODS OF DRYING, SEASONING, AND HARDENING
WOOD AND OTHER ARTICLES, PARTS OF WHICH ARE APPLICABLE TO THE DESICCATION
OF VEGETABLE SUBSTANCES GENERALLY;" in which said Letters Patent there is
contained a proviso, that we, the said Robert Davison and William Symington,

page_text: shall cause a particular description of the nature of our said Invention, and in
what manner the same is to be performed, under our hands and seals, or under
the hand and seal of one of us, to be inrolled in Her Majesty's High Court of
Chancery within six calendar months next and immediately after the date of
the said in part recited Letters Patent, as in and by the same, reference being
thereunto had, will more fully and at large appear.
NOW KNOW YE, that, in compliance with the said proviso, we, the said
Robert Davison and William Symington, do hereby declare that the nature
of our said Invention, and in what manner the same is to be performed, are
fully described and ascertained in and by the present Specification thereof,
that is to say-
The nature of the first or principal branch of our said Invention consists in
drying, seasoning, and hardening wood and other articles, among which other
articles we include generally all things made of wood or chiefly of wood, such
as ships, barges, punts, tanks, &c., by means of rapid currents of heated air,
and the manner in which we produce these rapid currents of heated air is as
follows: We make use of an apparatus for the purpose, such as is represented
in Figures 1, 2, and 3, Sheet No. I. of the Drawings hereunto annexed;
Figure 1 being a sectional elevation, Figure 2 a plan, and Figure 3 a trans-
verse section of the same. A is a furnace; a, a, a, are horizontal pipes which
extend along the sides of the furnace; and b, b, b, pipes of a horse-shoe form,
which rise vertically from the horizontal pipes and communicate therewith;
e is a passage for the inlet to the horizontal pipes of atmospheric air from a
fan blower or other impelling apparatus; d, a passage by which the heated
air rushing from the pipes is conveyed to the place where it is to be applied.
The arrows indicate the course of the air from the beginning to the end of
the process. The articles to be subjected to the heated currents may be
of two sorts, either such as can be heated by external application, as logs,
deals, and portable wooden articles of all sorts, or such as must have the
heated currents applied interiorly, as ships, tanks, &c. In the case of the
former class of articles, they must be placed in close chambers, galleries,
vaults, or flues. These chambers and other places may be of any suitable
form or magnitude, but we recommend that they should be built of fire-brick
(at least the inner part) with double walls, that is to say, that a small space
should be left between the two walls for the purpose of preventing loss of heat
by radiation, and also that there should be double doors or shutters for intro-
ducing or removing the wood. Flues or channels for the heated air may be
constructed in parallel lines, either in the floors or in the upright walls of a
building, having narrow openings, through which the heated air may issue in

page_text: thin streams and spread itself over the surface of the wood. If the openings
are in the floor, the wood will require to be placed in an upright position, with
suitable racks or bars to lean the same against; but if the heated air is
admitted in a horizontal direction, standards and skeleton shelves will be
necessary to lay the wood upon. The great object in all cases should be to
bring the heated air as speedily as possible into contact with the wood to be
dried, seasoned, and hardened, and to allow it, after it has done its office, to
pass away as speedily. Furnaces and apparatus for the production of rapid
currents of heated air may be erected to prepare any quantity of timber or
articles in wood at one time, but care should be taken that whatever the size
of the outlet may be from the series of pipes or vessels by which the heat is
generated, an outlet of at least equal dimensions is left for the free exit of the
air and vapours thrown off. It should also be observed in constructing the open
spaces in the floor or upright walls for the stream of heated air to pass towards
the timber or other wooden articles to be seasoned, that the superficial area of
the whole of them combined does not exceed the outlet of the principal outlet
of the pipes at the extremity of the furnace, so that a free current of heated air
may be allowed to pass uniformnly throughout the chamhers containing the wood
to be prepared. With respect to the second class of articles, namely, those
which must have the heated air applied to them interiorly, as ships, barges, &c.,
they must, before introducing the hot currents of air, be covered in from the
external atmosphere, and made as air-tight as may be conveniently practicable,
except at the inlet provided for the admission of the hot air, and the outlet for
the escape of the hot air and vapours. The temperature proper to be given
to the air, and velocity to the current, in each case will depend on the size,
density, and maturity of the wood to be acted on. We find by our experi-
ments that woods generally may be advantageously subjected to currents of
air raised to a temperature of from four hundred to five hundred degrees
Fahrenheit, when the currents are impelled at the rate of one hundred feet per
second; but when the wood is in a green state, it is better to commence at
a Jower temperature, say, from one hundred and fifty to two hundred degrees,
and gradually to raise it to the high degrees before stated, as the desiccation
proceeds, an object which may be in some cases facilitated by carrying a cold
air drain from the fanner or other propelling apparatus, and attaching a
damper to it, so that any quantity of cold air required to reduce the temperature
of the hot current may from time to to time be admitted. When again the
wood is in the log or unconverted state it should be bored or augered out in
the centre, and the current of hot air caused to traverse it as well interiorly as
exteriorly, whereby much time will be saved in the process of desiccation, and

page_text: a more uniformı result obtained.
Woods treated in this manner, and with the
above modifications when requisite, part rapidly with their natural sap, and any
other aqueous matter which they may contain, and the fibres are brought closer
together, acquiring thus more rigidity and strength. Hence, the peculiar
fitness of wood so prepared for all kinds of house fittings, furniture, carriage
building, musical and other instruments (especially in warm climates). For
woods that are to be exposed to the weather, such as those used for ship
building, harbour work, and other out-of-door purposes, this process is also
extremely advantageous, because not only of the greater strength and durability
thus imparted to them, but of the latent seeds of dry rot being removed by the
high temperature to which they have been exposed. From their great dryness,
too, and the extreme rarification of the air remaining in their pores, they
imbibe, particularly when in a heated state, with peculiar readiness any oily or
other preservative mixture which may be applied to them, in order to prevent
moisture from re-entering. With respect to the time required to season the
wood upon this plan, much must depend upon the original state of dryness it
may be in, as well as the quality and temperature of the heated air forced into
contact with it; and it may suffice to remark that the wood may safely remain
thus exposed till any escape of moisture ceases to be perceptible. This may
be readily known, either by applying a mirror or any other polished surface to
the outlet, or by calculating the quantity of moisture removed from the wood,
which will be found to range between one-fourth and one-fifteenth of its whole
weight. For the purpose of ascertaining more correctly the amount of moisture
removed from time to time where the articles are placed in seasoning chambers,
as before described, an opening should be constructed in the chamber in any
convenient position, through which a specimen of the wood may be withdrawn
and weighed.
The parts of our said Invention applicable to the desiccation of vegetable
substances generally, are all those parts which are necessary to the production
of rapid currents of heated air; and the substances to which we consider this
mode of desiccation more particularly applicable are sugar, coffee, starch,
(as regards especially its conversion into dextrine,) wheat and other grain,
feathers, hair, stuffs, yarns, textile fabrics, paper, leather, hats, and other felted
fabrics, oil cloths, colours, peat, artificial fuel, &c. From the following
description of the methods we follow or propose to follow in the desiccation
of the first four of the above enumerated articles, the modifications (if any)
required for other cases will be readily deduced and understood. By the
present method of drying sugar the heating medium has no further current
given to it than arises from the rarification of the air, which comes into

page_text: contact with the outer surface of the cockle or steam pipes. Now, instead
of this we cause the air, heated to any degree found beneficial, to be impelled
in the manner before explained through pipes or vessels, and thence to circu-
late in the drying chambers at any rate of speed that may be most approved
of, and, consequently, the evaporation is carried on in a compound ratio
of the temperature and velocity of the current. We allow the chambers
(or stoves, as they are termed,) where the sugar is placed to dry, to remain
as they are at present, but make an inlet in the bottom of the chambers
for the admission of the heated air, and make the orifice of the exit pipe
at top considerably larger than the one by which the heated air is admitted,
as otherwise the current would be retarded in consequence of the air
expanding by the absorption of moisture. Next, with respect to coffee;
according to the present mode of drying and preparing coffee, the cylinders
in which the berries are placed are of necessity made air-tight or nearly
so, in order to prevent the sulphur or other injurious products of the fuel
from finding their way into the cylinders. The coffee is not only thus
deprived of its natural moisture, but all the vapours as they are evolved,
from want of a sufficient current to carry them off, are again absorbed
or dried up in the body of the coffee. Instead of these close cylinders
we propose to use a perforated or pierced cylinder, by which means the
heated media (rapid currents of hot air) are driven immediately into con-
tact with the coffee, and as it becomes heated, all the vapours or acrid
matters which it contains are at once expelled, without the least chance of
their being again absorbed by the coffee. The vapours and spent heat pass
off through hollow axles, with which the pierced cylinder is supplied, and in
this way the coffee is rendered of a much purer and milder quality than usual.
We have found in practice that air propelled at a velocity of one hundred feet
per second, and heated to five hundred and fifty degrees Fahrenheit, is the best
speed and temperature for the desiccation of coffee. Figure 7, 8, and 9,
Sheet II., represent an apparatus well adapted to this purpose; Figure 7 being
a sectional plan; 8 a transverse end elevation; and 9 a longitudinal sectional
elevation. The arrows represent the course of heated air from the heating
pipes. C is the inlet from the hot-air chamber in a perforated or pierced
cylinder with hollow axles, the cylinder having a door or slide for the
admission of the coffee. n is a double cover, which may be made of sheet iron
or other metal, and the space between the two thicknesses being charged with
charcoal dust or other approved non-conductor; o, hook, for the purpose of
raising the cover; p, p, hinges; 7, weigh bar, for the purpose of guiding the
perforated cylinder to bearings 1, 1, over the trough (1) after the drying of the

page_text: coffee is completed; s, handle; t, clutch; u, handle and lever, for throwing
the clutch in and out of gear; v, v, bearings; w, rigger, for giving motion to
cylinder; x, tube, for carrying off vapours and spent heated air; y, y, brick-
work; z,, bearers to carry the same; 1, trough or tray, for receiving coffee
from the cylinders; 2, slide or damper, for shutting off the hot air.
With
respect to starch, and its conversion into dextrine, (the British gum so exten-
sively used by calico manufacturers,) the mode at present adopted is to place
it in oblong iron trays, and heat it in ovens raised to a temperature of from
two hundred and eighty to three hundred and twenty degrees Fahrenheit; but
on this plan there is always great risk of the process of torrefication being
carried too far, to the injury of the colour and quality of the product;
and it almost always happens that before the temperature which is requi-
site for the conversion of the starch into gum has been reached, the
water originally combined with the starch, and which would facilitate the
formation of the gum, has become wholly dissipated.
The more quickly
the heat can be applied, the less the degree of heat which is required, and the
better the dextrine produced; that is to say, the conversion of the starch into
a soluble gum is effected at a lower temperature when the heat acts upon it
while combined with water, than it does when the starch is exhausted of
water. We propose therefore to substitute for the present heating ovens,
chambers provided with inlet and outlet passages, bearing the proportional
relations to one another before stated, and to drive currents of air through the
same, heated to about two hundred and fifty degrees Fahrenheit, which we
believe will be found sufficient for the purpose, or to as much higher a degree
as may be found necessary; whereby the heat will be applied so quickly, or, as
it were, suddenly, that the conversion must take place while there is yet abun-
dance of moisture embodied in the starch. Feathers, hair, stuffs, and other
articles of that class, require to be treated in a manner somewhat different
from any of the others. It is well known that the quill or body part of
feathers, when new, contains much moisture and animal matters, which if not
removed become putrid and offensive. Feathers also which have been long in
use lose their elasticity, and become knotted and hard. For the purpose of
removing the moisture and animal matters, as well as restoring old feathers
to their original soft and elastic state, we cause rapid currents of heated air,
propelled as before described, to pass through or between the feathers, s
and while the desiccating process is going on the feathers are subjected to
beaters driven with a considerable velocity, for the purpose of separating
them from dust or other adhering matter. Figures 5 and 6, Sheet I.,
represent an apparatus adapted to this modification of our Invention. B is

page_text: an inlet for hot air; e, double cylinder, perforated below and at top for the
admission and exit of heated air. A felt or other non-conductor is placed
between the two thicknesses of metal, for the purpose of preventing loss of heat
by radiation. f, f, standards for supporting the double cylinders; g, hinged
door for the admission of feathers; h, shaft with arms or beaters composed of
cane, wood, or other material; i, pulley rigger or handle for driving the shaft
and beaters; j, outlet for moisture, dust, or spent heat; k, valve for closing
the outlet; 1, slide and outlet for feathers after seasoning.
And having now described the nature of our said Invention, and in what
manner the same is to be performed, we declare that what we claim is, the
employment, as herein-before described, of rapid currents of heated air to
effect the drying, seasoning, and hardening of wood and other articles, and the
application, as herein-before exemplified, to the desiccation of vegetable
substances generally, of so much of our Invention as is applicable thereto.
In witness whereof, I, the said Robert Davison, on behalf of myself and
the said William Symington, have hereunto set my hand and seal,
this Twenty-eighth day of September, One thousand eight hundred and
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