Abstract:
A method and a system for treating  betula  wood to change the coloration thereof to resemble that of Cherry wood or heartwood of birch is described. The  betula  wood is introduced in treatment chamber which is under atmospheric pressure. Hot steam from a steam generator is introduced in the treatment chamber in a lower section thereof for subjecting the  betula  wood to be treated to a hot water vapor environment. The temperature and humidity levels in the treatment chamber are controlled over a time span until the  betula  wood is completely saturated with water and has obtained a desired color transformation. This color transformation is uniform throughout the thickness of the wood and thereby hi-lights the grain in the  betula  wood while at the same time changes its color whereby it resembles Cherry wood or heartwood of birch. The treated wood is then cooled in the treatment chamber and removed therefrom for further processing.

Description:
TECHNICAL FIELD  
       [0001]     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.  
       BACKGROUND ART  
       [0002]     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 A1, published on Dec. 5, 2002, describes a 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 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 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 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, there are risks of explosion and by using toxic products at high pressures the reactor must be constructed of expensive 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 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.  
         [0003]     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  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 causing many drying defects such as checks, splits and loose knots.  
       SUMMARY OF INVENTION  
       [0004]     The present invention concerns the treatment of  betula  wood to change its coloration thereof entirely through the thickness of the wood pieces that are treated.  
         [0005]     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 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.  
         [0006]     Another feature of the present invention is to provide a method and a system for the treatment of  betula  wood to change the coloration thereof and wherein such system is economic to construct and is not highly toxic and wherein the system operates under atmospheric pressure.  
         [0007]     Another feature of the present invention is to provide a method and a system for the treatment of  betula  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.  
         [0008]     Another feature of the present invention is to 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.  
         [0009]     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 stage but on the contrary to a humidifying hot treatment process and this allows for further peeling or slicing of the treated wood.  
         [0010]     Another feature of the present invention is to provide a method and system for the treatment of  betula  wood 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 such wood can be treated at the same time without chemical additives.  
         [0011]     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 comprises the steps of: 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, 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 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 predetermined period of time, and vi) removing said treated  betula  wood after said predetermined period of time for further processing.  
         [0012]     According to the above features, from a broad aspect, the present invention provides a system for the 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 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 throughout and obtained a desired color transformation which is uniform throughout the thickness thereof. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0013]     A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which:  
         [0014]      FIG. 1  is a schematic diagram illustrating the basic component parts of the treatment system;  
         [0015]      FIG. 1A  is a schematic illustration of a carriage displaceable on tracks and carrying  betula  wood boards for positioning same in and out of the treatment chamber over the water basin;  
         [0016]      FIG. 2  is a further schematic diagram of the treatment chamber;  
         [0017]      FIG. 2   a  is a schematic illustration of the valve trap as seen in cross-section;  
         [0018]      FIG. 3  is a still further schematic diagram of the treatment chamber;  
         [0019]      FIG. 4A  is a graph showing comparative curves of coloration measurement between treated  betula  and Cherry wood and heartwood of birch over a simulated time span with the wood pieces having been varnished and non-varnished;  
         [0020]      FIG. 4B  is a further graph illustrating the comparative hardness between the sample board pieces of  FIG. 4A ; and  
         [0021]      FIG. 4C  is a further graph showing the modulus of elasticity between the three board samples. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]     Referring now to the drawings and more particularly to  FIGS. 1 and 2 , there is shown generally at  10  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 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 in the Northeast part of North America. By changing the coloration thereof to a reddish tone, this wood becomes more 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.  
         [0023]     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, 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.  
         [0024]     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 perforated distribution conduits  21  adjacent the bottom wall  22  of the water basin  14 , as illustrated in  FIG. 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 thickness.  
         [0025]     As shown in  FIG. 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 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 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.  
         [0026]     The controller device  26  is a computerized 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  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 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.  
         [0027]     A displaceable valve element  30  is provided either in the insulated door  13  or in a wall of the treatment chamber  11 , as shown in  FIG. 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 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 process, when water vapors are diminishing and or cooling, it will permit the influx of air into the chamber to avoid implosion.  
         [0028]     Although in  FIG. 1  there is shown a pair of track rails entering the chamber through a single door, it 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 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 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 the treatment to separate the boards in sheet form with slats, as the wood becomes completely saturated with the hot water vapor during treatment.  
         [0029]     Referring now to the graph illustration in  FIG. 4A , there is illustrated  betula  treated in accordance 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 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 samples. In fact, the varnish Red Cherry wood sample is the wood essence that undergoes a more radical color transformation with time.  
         [0030]     The  betula  sample treated in accordance with the present invention was also measured as to its hardness with these samples and the results of this measurement are illustrated in  FIG. 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 is substantially the same regardless if the wood is varnished or not.  
         [0031]      FIG. 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 compared timbers is substantially equivalent.  
         [0032]     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 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 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  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.  
         [0033]     It is pointed out that with this treatment, the  betula  coloration can be controlled from a light pinkish tint down to a dark reddish brown color whereby to produce wooden boards resembling various tones of Cherry wood. This control of the coloration is achieved by sampling lumber pieces being treated during the treatment process and analyzing the coloration change thereof.  
         [0034]     The water level in the water basin is 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.  
         [0035]     Depending on the nature of the  betula  wood placed in the treatment chamber, that is to say in the form 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  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 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 220° F.  
         [0036]     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 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 within the treatment chamber. The pressure within the treatment chamber is at substantially atmospheric pressure and in the range of about 90 to 110 kPa.  
         [0037]     As previously described, a gate valve  30  is automatically operated to release steam from the chamber 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 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 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 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.  
         [0038]     It is within the ambit of the present invention to cover any obvious modifications of the preferred embodiment described herein, provided such modifications fall within the scope of the appended claims.