Improvements in Impregnating Wood and other Cellulose.
Year: 1898

page_text: Improvements in Impregnating Wood and other Cellulose.
We, MAX BACHERT, Manufacturer, of the Borough of Manhattan, in the City,
County, and State of New York, and DAVID WEBSTER O'NEIL, Manufacturer, of
the City of Newark, in the County of Essex and State of New Jersey, United
States of America, 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:
Our invention relates to cellulose preservation by saturation or impregnation.
The invention consists in preserving cellulose such as wood, by completely satu-
rating it uniformly through and through by an atmosphere surcharged with
aqueous vapour. Every fibre or pore of the cellulose is thus fully opened or
expanded. The water of condensation is then withdrawn from the cellulose.
While its cells are opened this water is replaced by a liquid preserving compound
which penetrates every fibre of the cellulose. The material is then slowly dried.
The solid particles of the preservative are uniformly deposited throughout every
fibre of the cellulose.
Commercial lumber or wood is that form of cellulose to which we have found
our invention admirably adapted, and fireproofing the kind of preserving to
which at present we have given special attention. Our invention is however
applicable to all forms of cellulose and all kinds of preservatives.
The invention, for illustrative purposes, will be described in connection with the
fireproofing of commercial wood but its application, as stated above, is of wider
scope.
The first step of enveloping the wood in an atmosphere surcharged with aqueous
vapour preferably at a low pressure, say from 110° to 200° Fahrenheit, in a
closed chamber within which the wood is placed, is of great importance. A higher
temperature can be used with some kinds of woods.
This process of saturation makes a sponge of the wood by opening its cells and
pores throughout.
The preliminary saturation may be a continuous or an intermittent process.
If live or dry steam be used and maintained at a high temperature, a discoloura-
tion of the wood results, injuring and destroying its natural beauty and colour.

page_text: The elasticity of the wood is impaired and its tensile strength is weakened. More-
over such heat will not open the cells of the wood. The outer surface becomes
sealed by this character of heat, forming an impenetrable outer shell which
effectually resists the passage of the preservative fluid. In addition, the effect
of such heat tends to distort the wood and concave its edges or sides.
In the use of such aqueous vapour at low temperature the pores or cells of the
wood are opened. The wood retains its colour and its elasticity and tensile
strength are unimpaired.
After the enveloping of the wood in such surcharged atmosphere, the saturated
wood is then evaporated preferably by a vacuum caused in a closed chamber, which
leaves the pores or cells fully opened and receptive of the preservative compound.
The vacuum may be continuous, or may be broken and re-established as desired,
to effect the required evaporation.
The wood is then submerged and saturated in a preservative fluid admitted to
the closed chamber where the liquid is maintained under pressure and the pre-
servative forced into the heart of the wood and into every pore and fibre thereof.
The wood is then dried at a low temperature, say from 85° to 125° slowly.
After this last step of the process the product is complete for any use to which it
may be put or fashioned. Under the process it has neither warped or shrunk.
It retains its original colour, its tensile strength, and its elasticity.
If the preservative liquid employed in the process has been a fireproofing com-
pound (such for instance as sulphate of ammonia and phosphate of ammonia) the
shavings of this product taken from the very heart or sap absolutely will not burn.
The blow-pipe flame applied to the wood will not burn the wood. After a long
time under this fierce heat the surface will char slightly but there is no blaze or
fire remaining when the blow-pipe is removed.
The product thus treated has great and increased non-conducting properties. A
blow-pipe flame directed against a piece of half-inch wood for a considerable time
does not warm the wood upon the opposite side. Live electric wires with no
insulation may be safely laid against wood-work, fixtures, or the like, made from
this wood as no flame arises.
Wood staining is generally a preservative and may be used with or without the
fireproofing compound. By the word "preservative" is meant to include all filler
and staining compounds also.
In the accompanying drawings we have shewn an apparatus for carrying out
our invention, but it will be understood that this apparatus is capable of great
variation, depending upon the material to be operated upon and the conditions
of operation. In this drawing Figure 1 is a broken-away side elevation of a
cylinder suitable for enclosing the wood to be treated. Figure 2 is a plan view
thereof, and Figure 3 is an enlarged sectional elevation of the cylinder and the
liquid containing tank and the piping appertaining to the same.
In the drawing A is a cylinder in which the wood to be treated is enclosed.
This cylinder is preferably of metal about three-quarters of an inch thick in order
to withstand the internal pressure to which the cylinder is subjected in use. This
cylinder is shewn as provided with rails a upon which cars containing the lumber
to be treated are run. It is likewise shewn as closed at one end and is open
at the other end c in order to admit the cars, which end c is adapted to be closed
by a head c which is put in place and bolted securely to the cylinder after the
lumber to be treated has been placed in the cylinder so as to entirely close the
cylinder, except at the points where the pipe or pipes for conveying steam or liquid
thereto enter. At the bottom or other convenient place inside the cylinder is a
steam coil comprising a series of steam pipes d which run the length of the cylinder.
These pipes receive steam to heat the contents of the cylinder. Located adjacent
to these pipes within the cylinder and running the length thereof is a pipe e
which is apertured and the apertures of which increase gradually in size through-
out its length from the point of entrance of the steam so as to deliver the same
quantity of fluid at all points. These pipes may be covered with a body of water.

page_text: The pipe e serves to bring steam to the cylinder and connects with a pipe f which
leads outside of the cylinder to a T-coupling g to which a pipe h is connected on
one side. This pipe h leads from the pressure pump (not shewn) and serves to
bring liquid to the cylinder from the pressure pump at a suitable time, as will
be explained. A pipe i connects to the opposite side of the T and serves to admit
steam to the cylinder through pipes f and e at the appropriate time and to
exhaust the same therefrom. This pipe is provided with a plurality of branch
pipes kl, the source of steam supply being connected to the pipe and the pipe k
being an exhaust pipe, to which an exhaust pump may be applied to exhaust the
steam from the cylinder when the pressure in the cylinder is below atmospheric
pressure.
B is the mud-drum of the cylinder which is connected to a cross-coupling C by
one arm m of the said coupling, the opposite arm n of the said coupling preferably
serving as a vent to clear out the mud-drum. Connected to the arm m' is a pipe D
which may be provided with a valve and leads to the bottom of a tank E con-
taining the fireproofing solution. A valve e¹ serves to govern and control the exit
of liquid from the tank into the pipe D, the valve d serving to control the passage
of liquid through the pipe to the cylinder. Connected to the other arm n¹ of the
coupling C is a pipe F provided with a valve fl and leading to the tank E. This
pipe serves to return the unexpended liquid from the cylinder to the tank E.
Located along the top of the cylinder is a series of pressers G each of which consists
of a follower o carried upon a screw shaft p working in a bracket q and passing
through a stuffing box r. These pressers when screwed down upon the lumber.in
the cylinder serve to hold the said lumber firmly in place during the operation..
The cylinder may likewise be provided with one or more thermometers H for
indicating the temperature of the interior of the cylinder. The cylinder may
likewise be provided with a pipe I which is provided with the usual stop-cock
and may be connected to an air-pump or to a condenser.
The mode of operating the apparatus shewn to fireproof wood is as follows:-
The lumber placed upon cars is run into the cylinder, the cars running on the rails a.
The head of the cylinder is put in place and the pressers screwed down upon the
lumber to hold it firmly. After the lumber has been placed in the cylinder, water
may be introduced to the depth of from three to six inches, all the valves, of the
apparatus, with the exception of the steam-pipe valve, are closed and a vacuum
having been formed in the cylinder steam at low pressure and temperature is intro-
duced, passing through the pipes igf and e and into the open part of the
cylinder through the body of water for a period of from one to eight hours.
This steaming is continued and the temperature in the cylinder being maintained,
say between 110° to 200° Fahrenheit, depending upon the kind of wood to be
treated and the moisture thoroughly penetrates the wood. This step of the process
is quite important as the effect of such steaming is to open the pores of the wood
and fill the same with moisture. At the proper time, determined by practice, the
steam is shut off and the valve leading to the vacuum pump opened. Thereupon
the vacuum or air pump is started, which has the effect of exhausting air and
steam from the cylinder and causing the moisture to rapidly evaporate out of the
wood, leaving the pores of the wood open. The vacuum is maintained until the
wood has been robbed of a great amount of its moisture and practically reduced to
its original weight, but the vacuum should be broken about every three hours so
that the accumulated water of condensation in the cylinder may be drawn off.
When the lumber has been dried and the water of condensation drawn off, the
openings of the cylinder should again be closed and another vacuum formed,
say from twenty to twenty-eight inches. The preserving solution is then let
in by opening the valves and e¹ and allowing the liquid to flow from the tank E
through the pipe D into the cylinder. This solution is allowed to fill the cylinder
and then the liquid should be shut off by closing the valves e¹ and d. The valve
of the air-pump pipe I is then closed and the pressure pump set in operation to pump
liquid into the cylinder through the pipe h whose cock has been opened for that

page_text: purpose. The pressure pump forcing liquid into the cylinder subjects the liquid
in the cylinder to a considerable pressure, thereby forcing the said liquid into the
pores of the wood. These pores being very thoroughly opened by the steaming
and the subsequent drying in the vacuum, readily receive the liquid so that the
lumber is very thoroughly permeated and saturated with the liquid. The liquid may
be warmed in the cylinder by passing steam through the steam coils d. When the
lumber has been very thoroughly saturated, the liquid is drawn off from the cylinder
and pumped back into the tank through the pipe F. The lumber being saturated
with the liquid, is now slowly evaporated in order to leave the solid ingredients of
the solution uniformly distributed in the pores of the wood. The wood is now
slowly dried at a low heat.
Hard wood, such as mahogany, and large ship timbers and other hard woods,
can be as thoroughly impregnated with the preserving compound as can thin
quarter-inch soft wood.
Especial stress is laid upon the wood retaining its natural colour under our
process in order to take the usual light oil and varnish decorations and the like
under the methods in vogue for treating wood which has not been fireproofed.
In the hot or dry heat processes in use, many light woods are darkened or dis-
coloured from dark shades to that approaching the colour of mahogany and
rendered useless for the originally designed purpose.
The difference which exists between this particular product and the mode of
obtaining the same, and those which are and have been in common practice, are,
although important, not apparent at first glance. It is all the difference between
success and failure and heretofore it has been supposed that either live steam or
any heat of equivalent temperature was necessary to fit the wood for proper pre-
servation. This is apparent from the modes followed in vulcanizing wood wherein
the albuminous constituents, etc., are sought to be retained in the hardened con-
dition. A like hardened and repellent surface was always' produced where such
high temperatures were used, either to season or to unseason the wood preliminary
to impregnation. The elasticity of the timber, to the full extent of its treatment
with high temperature, was permanently impaired and the colour changed so as
to render it useless where light effects were desired. The product of such previous
process was brittle, discoloured and unfit for a great many purposes to which this
product can be readily applied. The uniform impregnation and the retaining of
its original elasticity, leaves it capable of uniform bending or other manipulation
and, when dressed down, its surfaces, no matter to what degree planed, are equally
fireproofed or preserved.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed we declare that what we
claim is:
1. The herein described method of saturating wood and other cellulose with
preservatives, which consists in enclosing the same within a receptacle, enveloping
the wood in an atmosphere surcharged with aqueous vapour at the temperature
substantially as specified to soften and open the same, removing the vapour or
water from the chamber and contents, and then impregnating the wood uniformly
throughout with wood-saturating material under pressure, and, finally, drying the
same slowly at a low drying temperature as set forth.
2. The process of preserving and fireproofing wood and other cellulose, which
consists in saturating or opening its very fibre and cell throughout with aqueous
vapour at low pressure and temperature as specified, then removing the vapour or
water from the wood, then impregnating the open fibre uniformly through and
through with a fireproofing solution under pressure, and, finally, drying the wood
slowly at a low drying temperature substantially as set forth.
3. The process of preserving and fireproofing wood and other cellulose, which
consists in enveloping the same within a closed receptacle with an atmosphere
saturated with aqueous vapour maintained at about 110° to 200° Fahrenheit, to

page_text: soften and open the wood, then producing a vacuum and removing the vapour and
water from the wood, impregnating the wood uniformly throughout with fire-
proofing solution under pressure, and, finally, drying the wood at a temperature
ranging from 85° to 125° Fahrenheit, substantially as set forth.
4. The hereinbefore described product, being fireproofed wood impregnated
uniformly throughout and retaining its natural colour, elasticity, and tensile
strength, substantially as set forth.
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.