Note: Descriptions are shown in the official language in which they were submitted.
CA 02464071 2004-04-07
- 1 -
A METHOD AND SYSTEM FOR THE TREATMENT
OF BETULA WOOD
TECHNICAL FIELD
s The present invention relates to a method and a
system for the treatment of betula wood to change the
coloration thereof whereby it resembles that of Cherry wood
or heartwood of birch.
1o BACKGROUND ART
It is known to treat timber whereby to transform
its appearance such that it resembles another type of wood.
For example, U.S. Patent Application Publication
2002/0178608 Al, published on December 5, 2002, describes a
i5 method and an apparatus for treating wood whereby it
resembles Bog oak. The method is a chemical method which
involves a sequence of steps under controlled conditions of
time, temperature and pressure and in particular, a steam-
air-ammonia composition is added to the timber. It can
zo treat a wide variety of wood types to resemble Bog oak and
depending on the specific type of wood used, the process is
modified. The wood is treated under pressure within an
appropriate vessel which is constructed for this treatment
and the wood can be introduced therein in a dry or green
2s state but is always treated with the ammonia composition.
The aim of that process and apparatus is to change the
quality of the treated timber to resemble Bog oak timber
which is a higher quality timber. However, that system is
quite expensive and is potentially not friendly to the
3o environment . The timber is also treated in a reactor under
pressure and ammonia is blown therein, which process could
be hazardous to work personnel. Accordingly, many
precautions need to be taken when this timber is manipulated
in and out of the reactor. By using high and low pressures,
35 there are risks of explosion and by using toxic products at
high pressures the reactor must be constructed of expensive
CA 02464071 2004-04-07
- 2 -
material, such as stainless steel. The process as described
in this patent transforms in a radical fashion the
properties of the treated timber, such as increasing the
hardness of the timber whereby the planing and sawing
s thereof causes more wear-and-tear on machinery. The timber
also is subjected to a change of its hygroscopic properties
thereby requiring a different drying process. Accordingly,
not only is the process more costly, but the processing of
the treated timber provides an additional cost.
to When drying wood at high temperature, such as
betula, the object is to extract water from the wood as
quickly as possible. Accordingly, the wood is dried under
conditions that favour evaporation to reduce the humidity
within the wood down to about 6% to 12% (percent). When
15 betula is dried at high temperature, its coloration changes
to the brownish tones, sort of a caramel color. This
coloration change is not adding value to Birch wood and is
mostly considered as a defect of drying. It is known that
this drying process will cause great stress in the wood
2o causing many drying defects such as checks, splits and loose
knots.
SUMMARY OF INVENTION
The present invention concerns the treatment of
z5 betula wood to change its coloration thereof entirely
through the thickness of the wood pieces that are treated.
It is a feature of the present invention to
provide a method and system for the treatment of betula wood
to change the coloration throughout the thickness of the
3o wood to resemble that of Cherry wood or heartwood of birch,
which is a reddish colored wood and wherein various tones of
reddish coloration can be produced.
Another feature of the present invention is to
provide a method and a system for the treatment of betula
35 wood to change the coloration thereof and wherein such
CA 02464071 2004-04-07
- 3 -
system is economic to construct and is not highly toxic and
wherein the system operates under atmospheric pressure.
Another feature of the present invention is to
provide a method and a system for the treatment of betula
s wood to change the coloration thereof and wherein no
chemicals are used in the process and wherein other
properties of the wood are not altered or significantly
altered.
Another feature of the present invention is to
io provide a method and a system for treating betula wood to
change the coloration throughout to resemble that of Cherry
wood or heartwood of birch, which is a reddish-type wood and
wherein the tone of such coloration can be controlled by
modifying the temperature and treatment time.
15 Another feature of the present invention is to
provide a method and a system for the treatment of betula
wood to change the coloration throughout to resemble that of
Cherry wood or heartwood of birch, and wherein during the
method of treatment, the wood is not subjected to a drying
zo stage but on the contrary to a humidifying hot treatment
process and this allows for further peeling or slicing of
the treated wood.
Another feature of the present invention is to
provide a method and system for the treatment of betula wood
2s whereby to change the coloration thereof and throughout to
resemble that of Cherry wood or heartwood of birch, and
wherein the wood can be treated in the form of timber
pieces, boards or logs disposed in a large treatment chamber
at atmospheric pressures and wherein large quantities of
3o such wood can be treated at the same time without chemical
additives.
According to the above features, from a broad
aspect, the present invention provides a method of treatment
of betula wood to change the coloration thereof. The method
35 comprises the steps of:
CA 02464071 2004-04-07
- 4 -
i) providing a treatment chamber having access
means to introduce and position therein betula wood to be
treated under atmospheric pressure,
ii) closing said access means,
s iii) introducing steam from a steam generating
means into said treatment chamber in a lower section thereof
for subjecting said betula wood to be treated to a hot water
vapor environment,
iv) controlling temperature and humidity levels
to in said treatment chamber over a time span until said betula
wood to be treated has obtained a desired color
transformation which is uniform throughout the thickness
thereof,
v) cooling said treatment chamber for a
15 predetermined period of time, and
vi) removing said treated betula wood after
said predetermined period of time for further processing.
According to the above features, from a broad
aspect, the present invention provides a system for the
2o treatment of betula wood to change the coloration thereof to
resemble that of Cherry wood or heartwood of birch, said
system comprising a treatment chamber having a closable
access means to position and remove betula wood to be
treated therein, a steam generator for supplying steam to
2s said treatment chamber at atmospheric pressure for
subjecting said betula wood to be treated to a hot water
vapor environment, control means for controlling temperature
and humidity levels in said treatment chamber over a time
span until said betula wood has been saturated with water
3o throughout and obtained a desired color transformation which
is uniform throughout the thickness thereof.
BRIEF DESCRIPTION OF DRAWINGS
A preferred embodiment of the present invention
35 will now be described with reference to the accompanying
drawings in which:
CA 02464071 2004-04-07
- 5 -
FIG. 1 is a schematic diagram illustrating the
basic component parts of the treatment system;
FIG. lA is a schematic illustration of a
carriage displaceable on tracks and carrying betula wood
s boards for positioning same in and out of the treatment
chamber over the water basin;
FIG. 2 is a further schematic diagram of the
treatment chamber;
FIG. 2a is a schematic illustration of the valve
to trap as seen in cross-section;
FIG. 3 is a still further schematic diaqram of
the treatment chamber;
FIG. 4A is a graph showing comparative curves of
coloration measurement between treated betula and Cherry
15 wood and heartwood of birch over a simulated time span with
the wood pieces having been varnished and non-varnished;
FIG. 4B is a further graph illustrating the
comparative hardness between the sample board pieces of FIG.
4A; and
2o FIG. 4C is a further graph showing the modulus
of elasticity between the three board samples.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings and more
2s particularly to Figures 1 and 2, there is shown generally at
the basic component parts of the system for treating
betula wood to change the coloration thereof whereby it
resembles that of Cherry wood which is a reddish-tone wood
which is usually utilized for the construction of floors or
3o furniture pieces and kitchen cabinets. The specific types
of birch treated by this process are "betula alleghaniensis"
and "betula papyrifera" which are respectively known in the
industry as Yellow Birch and White Birch. This wood is much
cheaper than that of Cherry wood and is in ample quantities
35 in the Northeast part of North America. By changing the
coloration thereof to a reddish tone, this wood becomes more
CA 02464071 2004-04-07
- 6 -
commercializable and it has properties that resemble closely
that of Cherry wood once its color has been transformed.
Cherry wood is less plentiful and expensive.
The treatment system as herein schematically
illustrated consists of a treatment chamber 11 which is
provided with a large door opening 12 in which there is
displaceably positioned a thick insulated door 13. The
treatment chamber 11 is a reinforced concrete structure
having a water basin 14, also constructed of concrete,
io disposed in the floor 15 thereof. A pair of rail tracks 16
support a carriage 17 above the water basin 14. The
carriage is loaded with betula timber 18 to be treated. As
hereinshown, the track rails 16 extend across the water
basin 14 whereby the carriage and the betula wood are
entirely surrounded by the basin.
A steam generator 19, which is herein a gas-
fired boiler, located exteriorly of the structure 11,
supplies hot steam into the water 20 contained within the
water basin 14. This is done by disposing a plurality of
2o perforated distribution conduits 21 adjacent the bottom wall
22 of the water basin 14, as illustrated in Figure 2, and
feeding hot steam in the basin through the conduits 21 which
are connected to a supply conduit 23 which connects to the
boiler. . This hot steam released within the water 20 causes
the water to boil and releases hot water vapors 24 within
the chamber 11 whereby to completely saturate the chamber
and the betula with hot water vapors. Accordingly, the
stacks of betula timber 18 disposed over the water basin
become saturated with hot water vapors throughout its
3o thickness.
As shown in Figure 3, thermal sensors 25 and
25', only two shown herein but a plurality of these could be
disposed within the treatment chamber, provide temperature
information signals to a controller device 26 whereby to
monitor the temperature within the chamber. Because the
temperature within the chamber is produced by the hot water
CA 02464071 2004-04-07
vapors released from the water basin, it is possible to
control the temperature by controlling the amount of hot
steam supplied to the distribution conduits 21 by the
boiler. Accordingly, by controlling the boiler, we can
s control the heat within the chamber, which chamber always
remains completely saturated with hot water vapors.
Therefore, by monitoring temperature we also monitor the
humidity level within the chamber.
The controller device 26 is a computerized
io device and it is provided with an interface comprised of
switches and dials 27 whereby an operator can interface with
the computer to set the parameters thereof depending on the
condition of the betula wood that is placed within the
chamber and the computer controls the boiler. The betula
15 wood is treated during a predetermined time span until a
desired color transformation has been obtained. To verify
the color transformation during the processing time, there
is provided a trap door 28 in a wall of the treatment
chamber 11 to provide access into the chamber to extract
2o sample wood pieces which can then be cut and planed to
verify the extent of the color transformation on the surface
and throughout the thickness of the treated betula wood.
A displaceable valve element 30 is provided
either in the insulated door 13 or in a wall of the
2s treatment chamber 11, as shown in Figure 2, to communicate
the inside atmosphere within the treatment chamber with
outside atmosphere. This valve element is in the form of a
hinge door 31 suspended on a top hinge 32 and capable of
swinging out of the chamber or into the chamber as indicated
3o by arrows 33 and 34, respectively. Accordingly, if
excessive steam pressure builds up within the chamber, the
door 31 will swing outwardly in the direction of arrow 33
and release steam from the chamber when the chamber is at
full vapor capacity. During the cooling cycle of the
35 process, when water vapors are diminishing and or cooling,
CA 02464071 2004-04-07
it will permit the influx of air into the chamber to avoid
implosion.
Although in Figure 1 there is shown a pair of
track rails entering the chamber through a single door, it
s is to be understood that a door could be provided at both
ends of a treatment chamber and that two or more carriages
17 may be supported on the tracks. When a carriage is
positioned in the chamber to treat the betula, another one
is being loaded with stacks of betula timber in a stand-by
to position outside one of the doors. The treated betula then
exits the other door for further processing while the stand-
by carriage is then disposed within the chamber. This type
of arrangement permits the treatment process to be more
efficient as there is very little time loss between the
15 removal of a treated betula wood from the treatment chamber
and the repositioning of a further load of betula timber to
be treated. It is also pointed out that the stacks of
betula timber may consist of boards which are disposed in
facial contact with one another. It is not necessary for
2o the treatment to separate the boards in sheet form with
slats, as the wood becomes completely saturated with the hot
water vapor during treatment.
Referring now to the graph illustration in
Figure 4A, there is illustrated betula treated in accordance
2s with the present invention (herein identified as "Cherry
Birch"), both in a varnish and a non-varnish form, and
compared to heartwood of birch (also called Red Birch) and
to Red Cherry wood, also varnished and non-varnished. It
can be seen that the coloration along the x-axis of these
3o samples is substantially different. The transformation of
the coloration of these samples during an aging test shows
that during aging of these wood products, represented by the
y-axis, that there is a significant difference in the
coloration change between the varnish and non-varnish
35 samples. In fact, the varnish Red Cherry wood sample is the
CA 02464071 2004-04-07
- 9 -
wood essence that undergoes a more radical color
transformation with time.
The betula sample treated in accordance with the
present invention was also measured as to its hardness with
s these samples and the results of this measurement are
illustrated in Figure 4B. The analysis of these samples is
done by a well known test program of SAS Statistics and it
shows that there is not much difference between the hardness
of these wood products. The result shows that the hardness
to is substantially the same regardless if the wood is
varnished or not.
Figure 4C illustrates the modulus of elasticity
of the tested samples. The average value obtained for each
of these samples illustrates that the flexibility of the
i5 compared timbers is substantially equivalent.
The method of treatment of the betula wood is
now summarized. Betula wood is loaded on the carriage 17
and is disposed in the treatment chamber 11 over the water
basin 14 and the entry door 13 is closed. Hot steam is then
2o supplied to the water basin 14 to heat the water. Hot water
vapors are released from the water either by boiling the
water or from the hot steam injected in the water, whereby
to saturate the betula wood with hot water vapor and fills
the entire treatment chamber. The treatment goes on for
2s several hours and the wood is saturated throughout its
thickness. The temperature and humidity levels in the
treatment chamber are controlled by a controller device
which may be entirely computer-controlled or could interface
with an operator. The computer device controls the boiler
30 19 which supplies the hot vapors into the water basin and by
controlling the supply of vapor we can control the
temperature and the humidity in the chamber.
It is pointed out that with this treatment, the
betula coloration can be controlled from a light pinkish
35 tint down to a dark reddish brown color whereby to produce
wooden boards resembling various tones of Cherry wood. This
CA 02464071 2004-04-07
- 10 -
control of the coloration is achieved by sampling lumber
pieces being treated during the treatment process and
analyzing the coloration change thereof.
The water level in the water basin is
s automatically controlled by the use of an overflow pipe 29.
Steam will condense in the treatment chamber into the basin
14 to be evacuated through the overflow drain.
Depending on the nature of the betula wood
placed in the treatment chamber, that is to say in the form
to of stacked boards with the boards having a certain thickness
or in the form of large timber pieces or logs, the treatment
time will vary. Also, the amount of humidity contained
within the betula material when introduced in the chamber
will affect the treatment time. It is pointed out that the
15 betula wood before entering the treatment chamber preferably
has a humidity content of at least 30%. If the betula wood
has undergone natural drying by being exposed to outside
atmosphere in warm climatic conditions, then before its
treatment in the treatment chamber, it undergoes a water
2o spray treatment whereby it absorbs humidity. It is pointed
out that the humidity level in the treatment chamber 11 is
maintained above 80% and preferably above 90%. Also, the
desired temperature maintained within the treatment chamber
should be above 140°F and can attain up to about 200°F to
z5 220°F.
The computer automatically controls the boiler
to maintain a substantially constant temperature within the
treatment chamber. By maintaining such a temperature, the
humidity level is assured as water vapors are continuously
3o released from the hot water in the water basin. However,
the agitation of the water and the amount of humidity
released is a function of the amount of steam and
temperature of the steam released through the distribution
conduits 21 and this controls the temperature and humidity
35 within the treatment chamber. The pressure within the
CA 02464071 2004-04-07
- 11 -
treatment chamber is at substantially atmospheric pressure
and in the range of about 90 to 110 kPa.
As previously described, a gate valve 30 is
automatically operated to release steam from the chamber
s during the treatment process when there is too much pressure
within the chamber and to admit outside air therein during
the cooling cycle. After the wood has been adequately
treated to achieve a desired coloration change, the steam
supply is cut off and the cooling step begins. The
io treatment time takes approximately between 12 hours and 100
hours, and the cooling cycle time is usually a few hours
whereby the betula wood is not exposed to an abrupt
atmospheric change wherein evaporation would take place
extremely quickly and the consequence thereof would produce
15 hyper dehydration in the surfaces of the betula wood pieces
and this would cause secondary problems in the drying stage
when the lumber is disposed in conventional dryers. Usually
the treated betula will sit in the treatment chamber for a
few hours before being brought out and during these few
2o hours the temperature and humidity in the chamber slowly
diminish. Because the betula is fully impregnated with
water vapors, it will take a few more hours to dry the
timber in conventional dryers.
It is within the ambit of the present invention
2s to cover any obvious modifications of the preferred
embodiment described herein, provided such modifications
fall within the scope of the appended claims.
