IMPROVEMENTS IN THE METHOD OF AND APPARATUS FOR IMPREGNATING WOOD
Year: 1882

page_text: LETTERS PATENT to William Phillips Thompson of the Agency for Foreign
Patent Solicitors, 6 Lord Street Liverpool in the county of Lancaster, and
of 323 High Holborn in the county of Middlesex Civil Engineer for an
Invention of "IMPROVEMENTS IN THE METHOD OF AND APPARATUS FOR
IMPREGNATING WOOD." A communication to him from abroad by L. Libert
de Paradis, retired Colonel of the Austrian Army of Vienna in the empire
of Austria.
PROVISIONAL SPECIFICATION left by the said William Phillips Thompson
at the Office of the Commissioners of Patents on the 27th July 1882.
WILLIAM PHILLIPS THOMPSON of the Agency for Foreign Patent Solicitors,
6 Lord Street, Liverpool in the County of Lancaster, and of 323 High Holborn in
the County of Middlesex, Civil Engineer "IMPROVEMENTS IN THE METHOD OF
AND APPARATUS FOR IMPREGNATING WOOD [A communication to him from abroad
by L. Libert de Paradis, retired Colonel of the Austrian Army, of Vienna in the
empire of Austria.]
""
This invention relates to improvements in the methods of and means for
impregnating or "pickling
"wood so as to remove from the same those substances
that are liable to cause decomposition therein, to extract all moisture, and moreover
to saturate the cellular tissues with a powerful antiseptic leaving ultimately a
resinous covering or coating on said tissues, so that the wood treated according to
this invention will become durable and capable of bearing greater strains.
Wood of inferior qualities, sap wood and the like, when so treated, will become
capable of use for purposes for which heretofore high class wood could alone be
utilized.
The apparatus required for carrying the said improvements into practice is as
follows:
1) A steam generator which may be an ordinary portable tubular boiler which
will have to work at a pressure of from 2 to 3 atmospheres.
2) A steam superheater for drying and superheating steam, this may have
an independent furnace and an independent system of tubes, a pressure gauge, and
a thermometer.

page_text: 3) A tar vaporizing boiler heated by means of a coil with superheated steam,
which however may, in addition to, or instead of the steam coil have an independent
furnace. This boiler is also fitted with a pressure gauge, two thermometers, test
cocks and a level indicator.
4) An impregnating chamber preferably of sheet iron. This chamber is fitted
inside with a coil for heating the same by steam; a perforated steam distributing
pipe extending through the length of the chamber and capable of being connected
at will with the steam generator, the superheated, or the tar-vaporizer, or, when
required, with an exhausting apparatus; an air distributing pipe similar in
construction to the foregoing.
Externally the impregnating apparatus has the following fittings: A steam
jet ejector which when connected with the steam distributing pipe serves to
exhaust the impregnating chamber, a similar device for the air distributing tube,
thermometers, pressure and vacuum gauges.
The said chamber may also be fitted with "dogs" or carriers for the timber to
be placed therein.
This set of apparatus may either be stationary and on a masonry foundation
or mounted on framings with wheels so as to be portable and suitable for roads
or railways &c. In the latter case it may have a casing which when let down
or otherwise suitably adjusted may serve as a platforın to increase the working
space. On the same frame or frames a suitable engine may also be provided to
facilitate working.
In constructing such movable apparatus it will be found convenient to mount
the steam generator, the super heater and the tar vaporizer on one common frame
and the impregnating chamber on a separate one.
Suitable pipes and stop cocks are provided for connecting the various parts
of the set of apparatus as required.
The wood to be impregnated is placed in the impregnating chamber which is
then filled with wet steam whereby the wood is heated and lixiviated. Superheated
steam is then admitted to dry the same. When this is done the lighter vapours
from the tar vaporizer are admitted to the impregnating chamber and penetrate
the wood; these serve as an antiseptic. When this part of the process is completed,
the temperature in the tar vaporizer is rapidly raised and the vapours of the
heavier oils carried into the impregnating chamber and become deposited on the
cellular tissues. When cooled these heavy oils resinify and form protecting covering
or coating for the fibre of the wood.
The wood is then gradually cooled by exhausting the chamber containing it.
This part of the process will require special care, as a too sudden cooling is
undesirable.
It is obvious that the temperatures and pressures that are to obtain for each
of the said processes must necessarily vary to such an extent with circumstances,
such as the quality of the wood or the purpose for which it is to be used and
so forth, that it is not practicable to lay down any fixed rule in that respect. It is
preferred to use in this process what are known as the heavy oils of wood tar and
coal tar, such as Creosote Phenol, Napthaline, and Anthracene.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Phillips Thompson in the Great Seal Patent Office on
the 27th January 1883.
WILLIAM PHILLIPS THOMPSON of the Agency for Foreign Patent Solicitors
6 Lord Street Liverpool in the County of Lancaster and of 323 High Holborn
in the County of Middlesex Civil Engineer "IMPROVEMENTS IN THE METHOD
OF AND APPARATUS FOR IMPREGNATING WOOD." A communication to me from
abroad by L. Libert de Paradis retired Colonel of the Austrian Army, of Vienna
in the empire of Austria
The object of this invention is a process (new as a whole) for impregnating
wood and apparatus suitable for the same.
By this process the following effects are produced.
1-The substances present in the wood and imperilling the same by the danger
of rapid decomposition are removed.
2 All moisture is eliminated from the wood by a sharp drying process.
3 The cellular structure which remains almost pure is saturated with a powerful
antiseptic.
4 Mechanical protection is afforded to the cellular structure by a varnish like
covering independent from the influence of weather and non-soluble in dampness.
To actually attain all this it is requisite that the agencies used herein should
penetrate the wood not only superficially but to its very inmost fibres which can
take place only when these agents are used in the finest state of division namely as
vapours.
This is true both with relation to the first operation the lixivation for which
wet steam is employed but also for the second operation, the drying which is most
dangerously effected by superheated steam, and for the third and fourth operations,
the impregnation properly so called, in which what are known as heavy oils of
wood tar and coal tar such as creosote, Phenol, Napthaline, Anthracine, are allowed
to act, in the form of vapour upon the wood. These oils in a short time become
resinous and then form a mechanical protection also, especially against moisture
which forms the chief reason for the warping shrinking and tearing of the wood;
moreover these resinified oils form a substitute for the inter cellular substances
that have been partly destroyed and the firmness of the wood is thereby so
increased, that common cheap classes will become suitable for purposes for which
till now only fine costly kinds could be used The same may be said of the
utilization of sapwood. A fifth and final operation, which, though it cannot be
properly included in the impregnating process, deserves special attention as the
resisting power of the wood will depend on its being carried out carefully, is the
cooling of the impregnated pieces, which, to avoid fissures or cracks must be
carried out the more slowly the larger the shortest diametrical dimension of a
piece may be; slow cooling has also the considerable advantage that the oils retain
their fluidity a longer time and more easily penetrate into the interior of the
wood, the tendency for this being always present by reason of difference in
temperature and density.
The apparatus for carrying out the five operations are.
1. A steam generator namely a tubular portable engine-boiler which has to
work at a pressure of 2-3 atmospheres.
2-A steam superhealer in which steam is dried and heated as required. It has
a separate furnace an appropriate system of tubes, a pressure gauge, and a
thermometer,

page_text: 3-A tar vaporizing boiler heated internally by pipes with superheated steam
but to assist or replace the same has an independent furnace also.
On this tar vaporizing boiler there are a safety valve 1 pressure guage,
2 Thermometers, a level indicator and two test cocks, the one opening from the
steam. space the other from the lowest admissible level of the liquid.
4 A horizontal cylindrical impregnating chamber of sheet iron containing in
the interior: a a coil pipe for heating by steam to compensate the heat lost by
radiation. b a steam distributing pipe passing through the entire length of the
chamber at the top is perforated and can be connected at will with the steam
generator the superheater or the tar vaporizing boiler or with an exhauster.
c a similarly constructed, namely also perforated air outlet or distributing tube
passing through the chamber at the bottom thereof and capable of being connected
with or cut off from the outer atmosphere and may if required be connected with
an exhauster,
Externally the chamber has the following fittings & a steam jet ejector which
when in connection with the steam distributing pipe closed to the outside uses the
latter as a section pipe to suck up the upper layers when the chamber is to be
exhausted e a steam boiler ejector which in connection with the air distributing
pipe acts similarly on the layers below f two thermometers at top and bottom on
the front side, g on the rear side a patent pressure and vacuum gauge on which the
degree of steam pressure or of exhaust can be read to within one atmosphere, excess
pressure, and a thermometer.
These 4 apparatus above described can be combined as desired into fixed or
portable impregnating establishments.
In the first case they are erected under cover on masonry foundation and can
work continuously.
In the second case they are mounted on solid wheeled frames for locomotion on
road and railway and the steam generating apparatus are mounted on one frame
the impregnating. chamber on a second and in some cases on a third the cooling
chamber; such portable impregnating establishments are especially adapted for
long railway lines which take their supply of sleepers at various points they will
however.be of special service if very considerable, but only temporary activity in
building is to be shewn in any particular place.
The annexed drawings show an impregnating establishment arranged to be
portable so as to move on a railroad.
Figs 1 and 2 are elevation and plan of the car which carries the portable boiler A
superheater B and tar vaporizing boiler C the sides of the car are supposed to be
partly removed.
Fig 3 is a skeleton of a cross section through the front part of this car showing
the portable boiler A and the steam superheater with the smoke stack common
to both.
:
:
Fig 4 is a side view of the impregnating chamber the left hand side wall being
supposed to be removed, and
Fig 5 shows a transverse section of the same filled with railway sleepers.
: Fig 6 is a longitudinal section, and,
Fig 7 transverse section through the tar vaporizing boiler.
After the impregnating chamber is filled with the timber to be impregnated in
such manner as will best utilize the space for which dogs h h moving on rails S
may be used the timber is first treated with wet steam; for this purpose the cocks
1. 2. 3. are opened, all other cocks remain closed. The wet steam then enters
the impregnating chamber through the perforated steam distributing tube a
Figs 1. 2. 4. 5.
After the steaming with wet has lasted so long that the wood has been pene-
trated by it throughout its thickness, a gradually increasing temperature is produced
by opening the cocks 4 and 5 and correspondingly partly closing-cock. 1. as besides
the wet steam superheated steam is also introduced.

page_text: By the tube b Fig 2 the wet steam is conducted from generator A to the super-
heater by tube, C it leaves the superheater as superheated steam.
This concludes the first operation of steaming.
The second operation, the rapid drying, is effected by treating, the wood with
pure superheated steam whose temperature is gradually raised to 100° C.
To this end the cock I is entirely closed and cocks 2. 3. 4. and 5 remain open.
In this operation also, the steam passes into the interior of the chamber through.
the steam distributing pipe a
Whilst the drying is effected steam is produced in the tar vaporizing boiler either.
by rising the furnace d of same Fig. 6 and 7 or by the use of superheated steam;
in the latter case cock 1 and 5 are closed and cocks 4 and 6 are opened and the.
steam produced in the tar vaporizing boiler is conducted by the short pipes a¹
or a² into the steam distributing pipe a and thereby led into the impregnating
chainber for the purpose of impregnation whilst the steam from the steam heating
pipes e having parted with a portion of its heat to the tar passes through cocks 7.
and 8 (2 and 3 being closed) into the coiled heating pipe f of the impregnating
chamber Figs 4 and 5. and arrives into the open air through the exhaust pipe g the
cock 11 being open.
The tar vaporizing boiler may also be used for alternately or simultaneously
feeding two impregnating chambers
The tar oils formed during the third operation and utilized in the form of
vapours are the lightest of the so called heavy tar oils and specially the Phenols.
from Coal tar and creosotes from wood tar which are also the most active anti-
septics and are absorbed with the greatest avidity by the wood fibres dried to the
utmost limits.
The operation takes place at a temperature of from 180° C. to 230° C.
The next, fourth operation really forms a continuation of the preceding one
carried on a higher temperature. The position of the cocks remains the same till
the operation is finished. The temperature is raised for the purpose of volatilizing
the heavy tar oils also, specially Napthalene and Anthracine by the deposition
whereof upon the fibre and their subsequent resinification mechanical protection of
the wood fibre is obtained.
It is not possible to lay down a rule for the duration of the separate operations
as this depends on too many varying conditions such as the age, quality, texture,
dimensions and degree of dryness of the wood, the place of growth of the timber
et cetera, a measure for this can be found only by experience and even then it will
generally be of local significance only.
As a rule it may be assumed that a beechwood or oaken railway cross sleeper is
perfectly impregnated in eight hours whilst softer wood or pieces of smaller size
require much less time.
After the above described fourth operation is carried out the impregnating
process is finished; as however a too rapid lowering of the temperature is liable
injuriously to affect the timber, it will be well to subject the same to gradual
cooling especially if the pieces are rather large and if great strength is required
therein This can take place either in the impregnating chamber itself, or in a
chamber that can be heated and the ventilation thereof can be regulated.
In the instance illustrated in the drawing the cooling is effected by exhausting
from above the aëriform contents of the chamber by starting the ejector M all other
connection with the apparatus A B C being cut off.
At the same time the cock 12 on the air exhausting pipe o is opened.
A second ejector N on the air distributing pipe o is used only when it is desired
to evacuate the interior of the chamber in the shortest possible time.
By the slow cooling the tar oils are moreover kept in a fluid condition for a
longer time so that time is afforded for their even distribution in the interior of
the wood.
E E Figs 2 and 3 are the sides of the car which as shewn in the Figure can
partly be placed in a horizontal position so as to increase the working space.

page_text: P is the portable engine which is obviously not indispensible but will be applicable
for working the feed pumps for the boilers for raising and lowering the dogs h and
for other operations.
Having now described the invention as communicated to me it being the best
mode known to me of carrying it into effect I wish it to be understood that what I
believe to be new and desire to protect under the hereinbefore in part recited
Letters Patent is
1st In the impregnation of wood the employment of superheated steam for drying
the previously steamed wood.
2nd In the impregnation of wood the use of superheated steam for evaporating
tar oils and for heating the impregnating chamber to more than 150°
3rd In impregnating wood the employment of carbon compounds obtained by
fractional distilling at over 180° C and which are strongly separated from one
another and which are used in a vaporous state and in that natural sequence
which is alone capable of penetrating the tissues of wood and of subsequently
mechanically coating the same.
4th In the impregnation of wood the use of an apparatus consisting of a steam
generator, steam superheater, and tar-vaporizing boiler in combination with a wood
impregnating chamber in which the tar vapours and the superheated steam can be
conducted as set forth.
5th The described systematic slow cooling of the contents of the impregnating
chamber with or without the use of one or several ejectors for the purpose set forth
and either in the impregnating chamber itself or in a heatable chamber the
ventilation whereof is capable of regulation.
In witness whereof I William Phillips Thompson have hereunto set my hand
and seal this twenty sixth day of January in the year of our Lord one
thousand eight hundred and eighty three