JP2003094406A - Method for drying lumber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for drying lumber at a low cost wherein drying for obtaining a required moisture content can be realized in a short time, crack and deformation are not generated in the lumber and a thermal stress is not applied to the lumber. SOLUTION: By applying intensively to both ends or one end of the lumber a heating method, a heating vapour method, a smoke heating method, a dehumidifying method, an infrared radiation heating method, a microwave heating method, a high frequency heating method, a reduced pressure method and a drying treatment of combining them, a gradation of a moisture content and a gradation of a vapour pressure are generated between an inside of the lumber and its end part, and the moisture content is successively decreased from the end part of the lumber. Thereby, the whole of the lumber is introduced to a required moisture content without generating the crack and the deformation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for drying wood which can be adjusted to a predetermined water content at low cost without causing cracking or deformation easily and reliably.

[0002]

2. Description of the Related Art Conventionally, felled wood has shrinkage and deformation during drying due to its high water content, which deteriorates the appearance quality and significantly reduces the processing accuracy. The water content is adjusted in advance by natural drying or artificial drying so that the water content will be the specified value.

In recent years, due to market distribution, artificial drying is generally adopted, which allows drying in a short period of time.
For example, there are hot-air method, steam method, smoke method, dehumidification method, infrared heating method, high-frequency heating method, decompression method, etc. Among them, there are methods that can dry only free water up to the fiber saturation point and those after the fiber saturation point. There is a method that can dry up to the combined water, and it is used properly depending on the target moisture content.

These drying methods include heating the entire wood, reducing the pressure,
It is exposed to a dehumidifying atmosphere.For example, wood is subject to thermal stress due to heat sources such as hot air method, steam method, smoke method, infrared heating method, high frequency heating method, etc. It is easy to occur and consumes a large amount of power.

In addition, these drying methods include a drying furnace for containing the whole wood, a decompression can body, a supply facility for feeding a carrier gas of a conditionally set air quality for promoting drying, and its discharge. For this purpose, an exhaust / suction device, a high-frequency heating method, an electrode installed inside the can body, a high-frequency power supply device for controlling the electric energy supplied thereto, and the like are necessary, and the scale of the equipment becomes large.

[0006] Further, since the water content of the outer peripheral portion of the wood is dried inward, the outer peripheral portion of the wooden material lowers in water content first and contracts, and the difference between the inner and outer contractions caused thereby causes cracking and deformation. Although the drying conditions are controlled so that inconvenience does not occur easily, it is still impossible to prevent cracking and deformation.

[0007]

Therefore, the present invention has been made to solve the above-mentioned problems, in which both or one of the ends of the wood is intensively subjected to some kind of drying treatment so that the inside of the wood is not dried. The water content of the entire wood is reduced to the water content of the end by a natural mechanism that causes a water content gradient or a vapor pressure gradient with the edge and then tries to eliminate this gradient. It is an object of the present invention to provide a method for drying wood that can be adjusted to.

[0008]

In order to achieve the above-mentioned object, the method for drying wood according to the present invention has the requirements described in each claim, and is described in claim 1. In the invention described above, the drying treatment is intensively applied to both ends or one end of the wood, and a moisture content gradient or a vapor pressure gradient is generated only in the one-dimensional direction between the inside and the end of the wood so that the moisture content is sequentially obtained from the end of the wood. The gist of the present invention is to obtain wood which is adjusted to a predetermined water content without cracking or deformation by reducing the water content.

[0009] Further, although the drying method having the function as the drying is targeted in claim 2, the general drying method is taken up here and each of them has its own effect, but each has the best advantage. It is possible to efficiently dry wood of high dry quality in a short period of time by combining the drying methods that are utilized in the above.

According to the third aspect of the present invention, the moisture content gradient and the vapor pressure gradient are propagated to the central portion of the wood because the vascular bundle cross section of the wood is exposed on the end surface subjected to intensive drying treatment. It is easy and has the effect of lowering the water content in a short period of time, and efficient drying can be performed.

Further, due to the nature of the wood that shrinks during the drying process, the water content gradient and the vapor pressure gradient are generated only in the vascular direction, which has higher strength and lower shrinkage than the outer peripheral direction and the half-shaped direction, and the entire wood is dried. It is an effective and reliable method of drying wood that does not cause cracks or deformations, which promotes the formation of water content and vapor pressure gradient in the outer peripheral direction and half-shaped direction.

In the invention described in claim 4, the wood having the skin or the log having the skin removed has a form which brings about the effect of preventing cracking and deformation of the whole of the present invention well, but of course, the square wood and the plate are also large. effective.

The invention according to claim 5 is an atomization treatment for suppressing natural drying from the outer peripheral direction for the purpose of optimally controlling the water content distribution from the outer peripheral portion to the central portion in the cross section of the wood.
Wet treatment such as spray spraying and high-humidification treatment is effective in preventing cracks and deformation.

The claim 6 specifies that a plurality of pieces of wood are dried at the same time. However, in the conventional general drying method, the wood is treated under the same drying condition even if the wood has a different water content. As a result, the drying quality varies, but in the present invention, it is possible to individually finish the drying while easily checking the water content and it is possible to cope with the flexibility and the increase or decrease in the number of drying treatments without lowering the drying efficiency. In addition to having a high degree of expandability, the concentrated drying processing at the end provides a small-scale facility and highly fuel- and power-efficient operation.

An end surface of wood which is tapered, sawtoothed, irregularly shaped or partially processed into those shapes as defined in claim 7 or an end surface of wood having an average surface roughness Ra = 10 micrometer or more. Then the area is increasing,
Therefore, the drying time can be shortened.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of a drying apparatus used in a method for drying wood according to the present invention will be described below with reference to the drawings.

In FIG. 1, the dry air introduced by the air supply duct hose 5a from the dry air generator 4 such as heated air, heated steam, smoked heated air, and dehumidified air passes through the casing 3a and ends 2b of the wood 1. The air that has been intensively blown to the air is accelerated by the temperature rise, and the humidified air is returned to the dry air generator 4 through the exhaust duct hose 5b, and a portion of fresh air is taken in to adjust the water content. However, it is also possible that the exhaust gas from the casing 3 is suddenly released to the outside air.

Further, the spraying device 6 composed of the water pipe 6b and the plurality of sprays 6a around the outer peripheral portion 2c of the wood 1 is used for a wetting method for controlling the water content distribution of the outer peripheral portion 2c of the wood 1 and its periphery. It is an example of a device that is turned on / off while checking the transition of the water content distribution, and can be applied to the example of the embodiment of the drying device described below.

In FIG. 2, in the case of infrared heating, a heater 8 for generating infrared rays is provided in the casing 3b for preventing heat diffusion.
a, electric energy is supplied from the infrared heating power supply device 7 by the wiring 9a, moisture evaporation is promoted by the temperature rise of the end portion 2b of the wood 1, and as a result, high-humidity air is supplied to the outer periphery of the casing 3b. It exchanges with the outside air through the air holes 10a installed.

In FIG. 3, in microwave heating, a casing 3c which also functions as an electromagnetic wave shield also serves as a waveguide 13.
Electric power is supplied from the microwave heating power supply device 11 to the microwave oscillator 12 built in the through the wiring 9b, and the moisture of the end portion 2b of the wood 1 is directly heated,
The air that has been evaporated to have high humidity is replaced with the outside air through the air holes 10b provided on the outer periphery of the casing 3c.

In FIG. 4, there are an electrode 15a and an electrode 15b in the casing 3d which also has a function of shielding electromagnetic waves in high frequency heating, and the power source device 14 for high frequency heating to the wiring 9c.
A high-frequency voltage is applied to increase the temperature of the end portion 2b of the wooden piece 1 to promote moisture evaporation, and the humidified air is replaced with the outside air through the air holes 10c provided on the outer periphery of the casing 3d.

In FIG. 5, in the combination of the decompression method and the infrared heating method, the casing 3e having the end portion 2b of the wood 1 therein is provided.
Is sealed with wood 1 and O-ring 18 and duct hose 17
Although it is connected to the vacuum pump 16 through a vacuum pump 16, the boiling point of the water contained in the end portion 2b is reduced by a decompression method and the latent heat supply for the water evaporation as in the infrared heating described above is terminated. A combination of the depressurization method and microwave heating or high-frequency heating is also effective, as well as accelerating the drying by receiving the portion 2b.

In FIG. 6, in the combination of the infrared heating method and the microwave heating method, there is an infrared generating heater 8b and a microwave oscillator 12 built in a casing 3f in which the end 2b of the wood 1 is contained. Device 7, 11
The electric energy is supplied from the inside of the wood 1 to accelerate the evaporation of water due to the temperature rise of the end 2b of the wood 1. As a result, the humidified air is replaced with the outside air through the air holes 10d provided on the outer periphery of the casing 3f.

On the other hand, in this combination, the water at the end portion 2b of the wood 1 is directly heated by the microwave heating, so that the water comes out from the inside of the wood, and as a result, to the end portion 2b covered with water drops. Infrared heating is effective for water evaporation, and is an effective combination that brings out the advantages of each.

In FIG. 7, in the combination of the infrared heating method and the microwave heating method with the decompression method added, the decompression casing 3g connected to the vacuum pump 16 is provided with an infrared generation heater 8c.
And a microwave oscillator 12 are built-in and are respectively connected to the power supply devices 7 and 11 by the wirings 9a and 9b. In this combination, in addition to the advantages of the combination of the infrared heating method and the microwave heating method described above, It has features such as promoting the leaching of water from the inside of wood by lowering the boiling point of water.

FIG. 10 shows a part of a concrete example of the end 2a or the end 2b of the wood 1 described in claim 7, where A is a tapered shape, B is a saw shape, and C is a partially tapered part. It has a curved shape and can increase the surface area.

The example of the embodiment of the drying apparatus shown in FIGS. 1 to 9 is a form in which only one end portion 2b of the log material is dried. However, if both end portions are simultaneously dried, the moisture content can be reduced in a short period of time. It is possible to lower it, or it is also possible to use a log material with a skin, a square material, or a plate material with the skin removed only from the casing insertion portion.

In FIG. 8, in one embodiment of drying a plurality of pieces of wood by an infrared heating method, one power source device 7 branches by a wiring 9a to supply power to an infrared ray generating heater 8a, but another drying method is used. In the same way, it is possible to easily dry more than one simultaneously by branching from one dry air source device or one power supply device with a duct hose or wiring. It is possible to individually turn off the dry air or electric energy when the predetermined water content in the range of 30% to 30% is reached.

FIG. 9 shows an embodiment for drying a plurality of pieces of wood. The drying is carried out by the air supply duct hose 5a from the dry air generator 4 such as heated air, heated steam, smoked heated air, dehumidified air or the like. The wind blows multiple pieces of wood 1 through the casing 3h.
The air that has been intensively blown to the end portion 2b of the air-conditioner and the moisture evaporation is promoted by the temperature increase here and becomes high humidity is returned to the dry air generator 4 through the exhaust duct hose 5b, and a part of fresh outside air is removed. Although the intake water is adjusted and circulated, the exhaust from the casing 3h may be suddenly released to the outside air.

Regarding the transition of the water content of these woods, since the portion used as a processing material is exposed to the outside, the water content of the wood is constantly measured by a portable water content meter set on the outer periphery of the wood. You can easily follow this.

[0031]

EFFECTS OF THE INVENTION In the present invention, since the wood end face is intensively subjected to the drying treatment which maximizes the characteristics of wood having anisotropy in strength and shrinkage, the wood is not cracked or deformed. It is a reliable method of drying to a predetermined water content.

In the present invention, wood can be brought to a desired moisture content within a short period of time without undergoing a thermal history, and since the transition of the moisture content can be easily checked, it fails. As a result, it is possible to obtain a stable wood drying quality.

On the other hand, as compared with the general artificial drying method, the drying apparatus according to the present invention is a simple and low-cost apparatus, and because of the local drying process, the desired water content in operation with less fuel and electric power consumption. It is a resource-saving and environmentally friendly drying method.

[Brief description of drawings]

FIG. 1 is an example of a form diagram of a drying method in which heated air, heated steam, dehumidified air, and smoked heated air are used as drying air and a spraying device is provided.

FIG. 2 is an example of a form diagram of an infrared heating and drying method.

FIG. 3 is an example of a configuration diagram of a microwave heating and drying method.

FIG. 4 is an example of a form diagram of a high-frequency heating and drying method.

FIG. 5 is an example of a form diagram of a combination of a decompression method and an infrared heating and drying method.

FIG. 6 is an example of a configuration diagram of a combination of an infrared heating drying method and a microwave heating drying method.

FIG. 7 is an example of a form diagram of a combination of an infrared heating drying method and a microwave heating drying method in which a depressurization method is added.

FIG. 8 is an example of a form diagram of drying a plurality of pieces by one power source of an infrared heating drying method.

FIG. 9 is an example of a form diagram in which a plurality of pieces of wood are simultaneously dried.

FIG. 10 shows some examples of end face shapes of wood.

[Explanation of symbols]

1 Wood 2a, 2b Wood end, 2c Wood outer circumference 3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h Casing 4 Dry air generator 5a Air supply duct hose 5b Exhaust duct hose 6 Spraying device 6a Water Piping 6b Spray 7 Infrared heating power supply device 8a, 8b, 8c Infrared ray generation heater 9a, 9b, 9c Wiring 10a, 10b, 10c, 10d Electromagnetic wave leakage prevention air hole 11 provided in the casing 11 Microwave heating power supply device 12 Microwave oscillator 13 Waveguide 14 High frequency heating power supply device 15a, 15b Electrode 16 Vacuum pump 17 Vacuum piping 18 O-ring

Claims (7)

[Claims] 1. A method for drying wood, characterized in that both ends or one end of the wood is intensively subjected to a drying treatment so that the whole wood is adjusted to have a predetermined water content. 2. The drying treatment intensively applied to both ends or one end of the wood is heated air, heated steam, smoked heated air, dehumidified air, infrared heating, microwave heating, high frequency heating and a combination of two or more of these. The method for drying wood according to claim 1, which is a drying treatment using reduced pressure and a combination thereof and reduced pressure and a combination of two or more kinds thereof. 3. The method for drying wood according to claim 1 or 2, wherein the end of the wood is a main opening or an end opening. 4. The method for drying wood according to claim 1, wherein the wood is a wood having a skin, a log having a skin removed, a square or a plate. 5. The method of drying wood according to any one of claims 1 to 4, wherein the outer peripheral surface of the wood other than the end is subjected to a wet treatment. 6. The method for drying wood according to claim 1, wherein the wood is a plurality of wood, and the drying processing is performed at the same time. 7. The wood has an end surface having an average surface roughness Ra = surface roughness of 10 μm or more or an end surface having a tapered shape, a sawtooth shape, an uneven shape or a combination thereof. The method for drying wood according to any one of claims 1 to 6.