Improved Process and Apparatus for Vulcanizing Wood.
Year: 1892

page_text: COMPLETE SPECIFICATION.
Improved Process and Apparatus for Vulcanizing Wood.
I, SAMUEL EDWARD HASKIN, of Avoca, State of New York, United States of
America, Manufacturer, 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 has reference to the preservation of wood, and particularly to that
method of treatment which is known as "wood vulcanizing." Such a process is
described in English Patent Specification No. 3875, dated March 5th 1889,
communicated by me to Reginald Haddan, and the present invention comprises
certain improvements on the method and apparatus described and shown in said
Specification.
The process of wood vulcanization consists in subjecting the timber to a very
high temperature while in a medium of such pressure as prevents evaporization of
the sap, reisn, or other liquid or liquifiable constituents of the wood. The principle
effects of high temperature applied under these conditions are (1) to destroy all
animal or vegetable germs of fermentation, or decomposition, (2) to liquify and
distribute the resinous gummy and similar constituents uniformly throughout the
wood, and to produce therein such chemical change as renders them permanent in
their nature.
It is well known that various antiseptic and preservative substances are of
vegetable origin, and that it is common to attempt the preservation of wood by
impregnating it with substances of an antiseptic character. Whatever antiseptic
or preservative substances are contained in the wood are by the process of
vulcanization rendered active and permanently fixed in the pores and interstices
thereof.
The effect of high pressure is to prevent the evaporation and escape of the
volatizable fluids, although the timber be subjected to as high a temperature as is
employed in distillation to obtain pyroligneous acid and other products. Moreover
the presence of these liquids in the wood is all that preserves the fiber from ignition
or charring by reason of the high temperature of the vulcanizing chamber.
From this explanation of the theory of the general method, the importance of the
improvements hereinafter described will be readily appreciated. In my former
Patent, referred to above, means are described for maintaining a circulation of the
heated air, and this circulation is of great importance, since good results cannot be
obtained by simply keeping the timber in a heated stagnant medium. I have found,
however, that it is very desirable to maintain this circulation in a regular and even
manner, without producing disturbance at any part of the vulcanizing chamber.
Heretofore the air has been admitted into the chamber by a single pipe at one end
thereof, which pipe discharged a large volume of hot air upon the wood adjacent to
that end, producing violent agitation at that point and concentrating there the effect
of the hot air blast. The result is that charring and even ignition are apt to take
place. Moreover the effect is to drive away the sap and juices from the point of
impact of the air blast resulting in a lack of uniformity in the product. A similar
action takes place at the single exit orifice, where the result of air in effecting its
escape produces considerable commotion in the vicinity and causes friction of the
hot air currents over the surface of the timber.
One object of the present invention is to avoid these objections and to produce
substantial equilibrium of compression and temperature throughout all parts of the
vulcanizing chamber, thus securing uniformity of treatment. From what has
already been stated it will be understood that if at any point the pressure fluctuates

page_text: and becomes even momentarily relaxed, the timber at that point is exposed to injury
by the great heat of the chamber.
According to the present invention these difficulties are overcome.by admitting
air simultaneously to all parts of the vulcanizing chamber through a series of
relatively small orifices and by providing also a large number of exit orifices
distributed in like manner throughout the length of said chamber.
A further object of the invention is to effect a gradual cooling down of the timber
without relaxing the pressure and without setting up currents or causing fluctuation
in the vulcanizing chamber. It will be understood that if an ordinary blow-off cock
or valve be used to discharge the hot air at the close of the operation, the consequent
reduction of pressure would permit the highly heated vegetable juices of the timber
to expand into vapor, and thus defeat the object of the treatment.
In carrying out this part of the invention, I provide for introducing at the proper
time into the circulation successive volumes of cold air, displacing equal quantities
of the hot air, but without lowering the pressure: and this operation is repeated
until the hot air is practically all drawn off and the timber cooled down below the
boiling point of its liquid elements at ordinary temperature.
The preferred mode of effecting this operation is by arranging a series (two or
more) of storage reservoirs of ample capacity, and connecting these with the main
circulating pipe and with the air compresser, in such manner that, any one or more
of them can be cut out of the circulating system without affecting the latter, and by
connecting the reservoir thus cut out of the circulating system with the compresser
to be charged with atmospheric air, displacing the heated air therein. When this
is done, the reservoir or reservoirs containing cold air are again connected in the
circulating system, and another or others cut out and charged with cold air by the
compresser. These auxiliary storage chambers or reservoirs may be utilized during
the operation of vulcanizing to contain charges of air above the normal pressure of
operating, so that, at any time the pressure may be increased or maintained by
connecting one of them with the circulating system.
These storage reservoirs are so constructed as to act as condensers to eliminate
the moisture from the compressed air, as described in my Patent above mentioned.
In order that the invention may be fully understood, I will now describe the same
in connection with the accompanying drawing, which forms part of this Specification,
premising however, that the invention is not limited to the construction and
arrangement of parts therein shown.
Fig. I is a diagram illustrating the connections of the several elements of the
system. and
Fig. 11 is a section of the vulcanizing chamber, showing also one of the storage
reservoirs in elevation.
The vulcanizing chamber A may be constructed as described in my Patent
referred to above, and provided with proper pressure and heat indicators, safety
valves and other appurtenances, as therein set forth, but which it is not thought
necessary to illustrate in the accompanying drawings.
The cylinder A is charged with timber as-before-by means of a car B, running
__on_rails ; but it will be obvious that other means whereby the air may admitted
and withdrawn through numerous small apertures would be within the invention.
In the drawings are shown four storage reservoirs C C C³ C, but their number
may be greater or less. The eduction pipe 6 has a separate branch c leading to
each reservoir, and each branch pipe is provided with a cock d. Each reservoir
has a discharge pipe e provided with a stop cock f, and pipes e all connect with. the
main pipe in which is located the circulating pump P. Pipe 7 leads to the heating
chamber H, in which the air is heated by superheated steam conveyed to a coil 8.
Any other suitable means for heating the air to the temperature required may be
employed. A pipe 9 provided with a cock 10 leads from pipe 7 around the heater,
and by using this pipe the heater may be cut out. . M represents.the air compressor.
It is provided with pipes 11, 12, 13, 14, leading respectively to the several reservoirs,

page_text: each pipe being provided with a stop cock m so that the compresser may be
connected with any one or more of the reservoirs, or cut off altogether.
It is evident that if cocks d and fare all open the four reservoirs will be connected
in the circulating systems; but during the operation of vulcanizing, it will not be
necessary to connect more than one of these reservoirs with the circulating system,
as it has only to perform the function of condensing the moisture. During this time
the other reservoirs may remain charged with air under high pressure to be utilized
as occasion may require.
When the timber has been subjected to the action of the compressed heated air a
sufficient period of time (which time as well as the degree of heat employed will
vary with the character of the timber) the reservoir or reservoirs at the time being
in the circulating system is or are cut off' therefrom by closing cocks d and f, leaving
however a free passage through at least one of the reservoirs. Assuming that
C and C are cut out of the circulating system, being filled with hot compressed
air, their blow off cocks will be opened, as well as cocks m in the pipes leading
from the compresser, and the heated air will be displaced by air at ordinary
temperature. In the mean time the main circulation continues unchecked through
reservoirs C C and the escape of air from reservoirs C¹ C² does not disturb the
steadiness of the circulation. Cocks m and g of the reservoirs C¹ C³ are now closed
and cocks d and opened, so that the cold air in these reservoirs gradually mingles
with the heated air, and, while this continues the reservoirs C3 C4 may be cut out,
and filled with cold air as before described. By alternating in this way, the
temperature of the vulcanizing chamber is gradually lowered, while a uniform
circulation is maintained, and the pressure also kept up. It will, however, be
understood that, as the temperature falls, it will not be necessary to maintain so
high a pressure as is required during the vulcanizing operation; but the pressure
may also be gradually reduced, always keeping it high enough, to prevent
volitilization of the liquid constituents of the wood.
By the manner herein described of admitting the air to the vulcanizing chamber
and withdrawing it from the same through a number of relatively small orifices,
I not only avoid the difficulties mentioned in the first part of this Specification but
am able to employ, when it is desirable, a higher degree of heat than could safely
be used heretofore. This is possible because of the provision for preventing
fluctuations of pressure and friction of hot air over the surface of the timber.
It is to be understood that whenever "air" is referred to herein, it is intended
to include equivalent aeriform fluids.
Having now particularly described and ascertained the nature of this inven-
tion and the manner in which the same is to be performed, I declare that what I
claim is :-
1. In apparatus for vulcanizing wood, the combination with the chamber in which
the wood is treated, of an air compresser, an air heater, an induction conduit
communicating with said chamber through numerous relatively small orifices at
different points in said chamber, and a suitable eduction conduit whereby heated
compressed air may circulate uniformly through said chamber, substantially as
described.
2. In apparatus of the character described the combination with the chamber in
which the wood is treated, of an air compresser an air heater, an induction conduit
communicating with said chamber through numerous relatively small orifices, and
an eduction conduit likewise communicating with said chamber through numerous
small orifices, substantially as and for the purpose set forth.
3. In the art of wood vulcanization, the improvement consisting in circulating
through the vulcanizing chamber heated compressed air, and then without interrupting
the circulation or relaxing the pressure introducing into the circulating system
successive volumes of cold air, until the wood is cooled down below the boiling
point of its liquid or liquifiable constituents, substantially as described.

page_text: 4. The process described of vulcanizing wood consisting in maintaining through
the vulcanizing chamber a steady circulation of heated and compressed air, and then
cutting out successive volumes of heated air, and introducing in place thereof cold
compressed air, constantly maintaining the circulation and pressure, substantially as
set forth.
D
1
1
T
1000
JOHN WAUGH,
Agent.