JP2831593B2 - Induction dryer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency drying apparatus, and more particularly to a high-frequency drying apparatus utilizing dielectric heating by high frequency, which is capable of uniformly drying an object to be dried such as plate-like wood. It relates to a drying device.

[0002]

2. Description of the Related Art Conventionally, a high frequency drying apparatus for drying an object to be dried such as a plate-like wood is generally configured as shown in FIG. That is, in a grounded metal drying chamber 31, a first electrode plate 32 located at an upper portion and a second electrode plate 33 located at a lower portion which is opposed to a predetermined interval are provided. ing. The second electrode plate 33 is electrically connected to the drying chamber 31 and has the same ground potential as the drying chamber 31. The reason why the second electrode plate 33 is set to the ground potential is to increase the supply efficiency of high-frequency energy when a high-frequency voltage described later is applied.

A high-frequency power supply 34 is provided outside the drying chamber 31.
, And a high-frequency voltage is applied between the first electrode plate 32 and the second electrode plate 33 from the high-frequency power supply device 34. Further, a vacuum pump 35 is provided outside the drying chamber 31 so that the inside of the drying chamber 31 is depressurized to a predetermined degree of vacuum.

A pair of elevating shafts 36 and 37 having a first electrode plate 32 attached to the lower end thereof are disposed in the upper part of the drying chamber 31 so as to pass through the inside and outside of the drying chamber. One electrode plate 32 is moved up and down.

[0005] In the high-frequency drying apparatus configured as described above, the plate-like object to be dried 38 stacked in a plurality of stages is provided.
Is disposed between the first electrode plate 32 and the second electrode plate 33, and the first electrode plate 32 is pressed against the uppermost drying object 38 by its own weight or at a constant pressure greater than that. As a result, it is pressed between the two electrode plates 32 and 33. The inside of the drying chamber 31 is depressurized to a predetermined degree of vacuum by a vacuum pump 35, and in this state, a high-frequency voltage is applied between the two electrode plates 32 and 33 from a high-frequency power supply 34. This allows
The object to be dried 38 is dielectrically heated, and predetermined drying is performed.

[0006]

However, in the above-mentioned conventional high frequency drying apparatus, the drying state is biased depending on the vertical position between the electrode plates of the object to be dried, and most of the object to be dried is not sufficiently dried. However, since some of the objects to be dried are insufficiently dried, it takes more time to uniformly dry all the objects to be dried.

FIG. 6 shows the results of an experiment conducted to confirm the unevenness of the drying state of the object to be dried in the conventional high-frequency drying apparatus. That is, a plate-like wood (hereinafter, referred to as a “plate”) having a length of 1850 mm, a width of 350 mm, and a thickness of 13 mm is vertically stacked between the two electrode plates 32 and 33 of the above-mentioned high-frequency drying device, and dried under predetermined conditions. It shows the water content of the plate material for each stage when the above is performed. In this figure, the vertical axis indicates the water content, and the horizontal axis indicates the vertical position of the stacked plate members. As for the plate material, the number 1 was in contact with the first electrode plate 32, and the number 13
Are in contact with the second electrode plate 33 and are arranged from the first electrode plate 32 toward the second electrode plate 33 in ascending order.

As is apparent from this figure, the closer to the second electrode plate 33, the greater the value of the water content. That is, predetermined drying is performed for the plate materials of Nos. 1 to 10, but the plate materials of Nos. 11 to 13 are in an insufficiently dried state. Therefore, it takes more time to sufficiently dry all the plate materials.

Therefore, according to the present invention, the unevenness of the drying state in the vertical direction between the electrode plates of the objects to be dried stacked in a plurality of stages, such as plate-like wood, is reduced, and the objects to be dried in each stage are uniformly dried. It is an object of the present invention to provide a high-frequency drying device that can perform the drying.

[0010]

In order to achieve the above object, a high frequency drying apparatus according to a first aspect of the present invention includes a first electrode plate and a first electrode plate in a metal drying chamber. In a configuration in which a second electrode plate which is disposed opposite to the electrode plate and is set to the ground potential is arranged, and a high-frequency voltage is applied between the first electrode plate and the second electrode plate. ,
A heating means is provided only on the second electrode plate at the ground potential.

According to a second aspect of the present invention, in the high-frequency drying apparatus according to the first aspect, the first electrode plate is disposed so as to be located between a pair of second electrode plates at a ground potential. It is characterized by having.

According to a third aspect of the present invention, in the high frequency drying apparatus according to the first or second aspect, the heating means provided on the second electrode plate which is set to the ground potential is based on steam. Features.

[0013]

In the high-frequency drying apparatus according to the first aspect, the second electrode plate is heated by providing the heating means on the second electrode plate which is set to the ground potential. The dried body is supplementarily heated.

In the high-frequency drying apparatus according to the second aspect, the first electrode plate is disposed so as to be located between the pair of second electrode plates at the ground potential, so that the dielectric heating efficiency is not reduced. The arrangement volume of the object to be dried between the electrode plates is increased.

In the high frequency drying apparatus according to the third aspect, since the heating means provided on the second electrode plate is based on steam, an efficient heating means with a simple configuration is realized.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view schematically showing a high-frequency drying apparatus according to the present invention. In this figure, the high-frequency dryer has a metal drying chamber 1 grounded. The drying chamber 1 has a door (not shown), and the object to be dried is taken in and out by opening and closing the door. This drying room 1
Inside, there is provided a first electrode plate 2 located at an upper portion, and a second electrode plate 3 located at a lower portion which is opposed to the first electrode plate 2 at a predetermined interval. Have been. The size of the first electrode plate 2 and the second electrode plate 3 is equal to or larger than the area of the object to be dried disposed between the electrode plates 2 and 3. Further, the second electrode plate 3 is configured such that a plurality of through holes 4 (only one is shown in the figure) serving as vapor passages are provided in parallel along the plate surface within the thickness. The drying chamber 1 is fixed at a predetermined height from the bottom of the drying chamber 1 and is electrically connected to the drying chamber 1.
And the same ground potential. One end of the through-hole 4 of the second electrode plate 3 is connected to a steam supply pipe 5, and the other end thereof is connected to a steam discharge pipe 6. The inlet pipe 5 and the outlet pipe 6 are made of, for example, metal.

A high frequency power supply 7 is provided outside the drying chamber 1 so that a high frequency voltage is applied between the first electrode plate 2 and the second electrode plate 3 from the high frequency power supply 7. It has become. A vacuum pump 8 is provided outside the drying chamber 1.
Is provided, and the pressure in the chamber is reduced to a predetermined vacuum pressure.

At the upper part of the drying chamber 1, a pair of elevating shafts 9, 10 with the first electrode plate 2 attached to the lower end are arranged, and the elevating shafts 9, 10 are installed outside the drying chamber 1. The first electrode plate 2 is moved up and down by an elevating mechanism (not shown) including a screw jack, a worm gear, and the like.

The high-frequency drying apparatus of the present invention having the above-described configuration has the same configuration as the conventional one except for the configuration of the second electrode plate 3, and has a plate-like shape stacked in a plurality of stages. The object to be dried 11 includes a first electrode plate 2 and a second electrode plate 3.
The first electrode plate 2 is pressed against the uppermost plate material 11 by the lowering operation of the elevating shafts 9, 10 to be pressed between the two electrode plates 2, 3. The second electrode plate 3 is fed with high-temperature steam into the through hole 4 via the inlet pipe 5 and the outlet pipe 6 and is heated to a predetermined temperature. The inside of the drying chamber 1 is depressurized to a predetermined degree of vacuum by a vacuum pump 8, and in this state, a high-frequency power supply
, A high-frequency voltage is applied.

As a result, the object to be dried 11 is dielectrically heated, and the object to be dried 11 in the vicinity thereof is supplementarily heated by the heated second electrode plate 3 to perform drying. When the object to be dried 11 is a plate-like wood (hereinafter, referred to as a plate), the plate contracts as the drying proceeds,
Since the thickness is slightly reduced, a gap is formed between the electrode plates 2 and 3. If the generation of this gap is left unchecked, the plate material will be warped. Therefore, an elevating mechanism that controls the elevating shafts 9 and 10 detects the generation of the gap and lowers the first electrode plate 2, and the gap between the electrode plates is reduced. It operates so that it does not occur. This allows
The plate material is dried without warping.

When the first electrode plate 2 is heavy, a gap between the electrode plates can be prevented by natural descent due to its own weight without using the above-described elevating mechanism.

FIG. 2 shows the results of an experiment conducted to confirm the unevenness of the drying state of the object to be dried in the high-frequency drying apparatus of the present invention. That is, both electrode plates 2, 3
In the meantime, the same plate material as in the above-described conventional experimental example is vertically
Except for stacking and heating the second electrode plate 3, the moisture content of the plate material for each stage when dried under the same conditions as in the above-mentioned conventional experimental example is shown in the same manner as the conventional method. is there.

As is clear from this figure, in the high-frequency drying apparatus of the present invention, the plate materials at each stage are all in substantially the same dry state, and the ground potential which was insufficiently dried in the conventional high-frequency drying apparatus. Second electrode plate 3
Significant improvements have been made to nearby plates. Therefore, in the high-frequency drying apparatus of the present invention, since the unevenness of the drying state in the vertical direction between the electrode plates of the object to be dried such as the plate material can be reduced, uniform drying can be performed.

In the above embodiment, the object 1 to be dried is placed between one first electrode plate 2 and one second electrode plate 3.
1, the arrangement of the electrode plates is such that a pair of second electrode plates 3, in which the first electrode plate 2 is set to the ground potential, as shown in FIG. 3, between the first electrode plate 2 and one of the second electrode plates 3, and between the first electrode plate 2 and the other second electrode plate 3. It is good also as a structure which arrange | positions the to-be-dried body 11 to both. In this case, a pair of second electrode plates 3 and 3 provided with a heating means similar to the second electrode plate 3 shown in FIG. 1 is used.
Heat 3 If the distance between the first electrode plate 2 and the second electrode plate 3 is simply widened, the dispersion in the dry state is increased. However, such a disadvantage can be solved by the above configuration. Body 1 to be dried without causing
The number of stacking stages can be doubled, and the objects to be dried in the doubled stages can be placed in substantially the same uniform drying state.

In the embodiment shown in FIG. 1, the first electrode plate 2 is composed of a thin electrode plate 2a and a thick press plate 2b made of an insulating material such as synthetic resin, as shown in FIG. May be configured in combination. By doing so, the first electrode plate 2 to which a high voltage is applied and the drying chamber 1
Can be realized with a simple configuration. In the case of the embodiment shown in FIG. 3, since the first electrode plate 2 only needs to generate an electric field, it can be constituted only by a thin electrode plate.

In any of the embodiments, the thickness of the second electrode plate 3 is inevitably increased due to the use of steam as the heating means. In the case where a sheet-like heater configured by, for example, printing is used, and the heater is attached to the electrode plate, the thickness of the electrode plate can be reduced. When the thickness of the electrode plate is reduced, if necessary, the electrode plate may be combined with a press plate similar to that shown in FIG.

Further, the vacuum pump 8 in the above embodiment is not always required. If the drying chamber is depressurized, drying can be promoted at a low temperature, so that the drying efficiency is high.
Even in this case, uniform drying can be performed as in the above-described embodiment.

Further, the high-frequency drying apparatus according to the present invention enables a truck to be carried into the drying chamber 1 through a door (not shown), and the second electrode plate 3 and the plate material to be dried are placed on the truck. The body 11 may be placed. In this case, since the heat capacity is large depending on the material of the bogie, the heat of the object to be dried 11 is deprived by the dielectric heating. However, the heating temperature of the second electrode plate 3 is increased only by increasing the heating temperature. Uniform drying of the steps can be maintained.

The high-frequency drying apparatus according to the present invention is characterized in that the heating means is provided only on the second electrode plate which is set to the ground potential as described above. It does not employ a known technique of heating the electrode plate in order to prevent the heat of the object to be dried from being absorbed by the electrode plate and radiated to the outside.

That is, in the conventional high-frequency drying apparatus shown in FIG. 5, various confirmations were made as to the cause of the unevenness in the drying state. As a result, the second electrode plate 33 was at the ground potential together with the drying chamber 31. The electric flux density is higher on the first electrode plate 32 side than on the second electrode plate 33 side, and the electric flux density is higher on the second electrode plate 33 side than on the first electrode plate 32 side. This is based on the fact that it was found that the electric flux density was small. That is, initially, it was supposed that the influence was due to the temperature distribution in the drying chamber or the effect of heat radiation from the electrode plates. However, the upper electrode plate in the drying chamber 31 was set to the ground potential, and the lower electrode plate was set to the high voltage potential. It has been clarified that even when the above condition is satisfied, the dried object on the ground potential side on the upper side is insufficiently dried.

In view of the above, as a result of further confirmation experiments, since the second electrode plate 33 is at the ground potential together with the drying chamber 31, the first electrode plate 32 and the second electrode plate 33 Between the first electrode plate 32 and the drying chamber 31 and between the first electrode plate 32 and the second electrode plate 3.
As a result, the electric flux density is higher on the first electrode plate 32 side and lower on the second electrode plate 33 side. The object to be dried on the side of the first electrode plate 32 having a high density is sufficiently dried since the dielectric heating efficiency is high, but the object to be dried on the side of the second electrode plate 33 having a low electric flux density is high. It was clarified that the drying was insufficient due to the low water content.

Therefore, according to the present invention, the heating means is provided only on the second electrode plate which is set to the ground potential, which is the lower side of the dielectric heating efficiency, and the object to be dried in the vicinity of the second electrode plate is supplementarily heated. In this way, the objects to be dried in each stage are heated substantially uniformly, whereby the dried state of the objects to be dried in each stage is made substantially uniform. Therefore, since it is not necessary to provide a heating means for all the electrode plates, the structure is simplified and the cost can be reduced.

Since the heating means is provided only on the second electrode plate which is set to the ground potential, the inlet pipe 5 and the discharge pipe 6 when steam is used as the heating means as in the above embodiment. It is not necessary to consider the insulation between the metal drying chamber 1 and. For this reason, it is not necessary to use a heat-resistant expensive insulating material for the inlet pipe 5 and the outlet pipe 6, and a metal pipe is sufficient. Therefore, when a metal member is used, the cost can be reduced accordingly.

[0035]

As described above, according to the first to third aspects of the present invention, the heating means is provided only on the second electrode plate which is set to the ground potential to positively heat the second electrode plate. Therefore, the object to be dried on the side of the second electrode plate having a low dielectric heating efficiency can be supplementarily heated to uniformly dry the object to be dried in each stage.

According to the second aspect of the present invention, since the first electrode plate is located between the pair of second electrode plates at the ground potential, the dielectric heating efficiency is reduced. Therefore, the volume of the object to be dried between the electrode plates can be increased.

According to the third aspect of the present invention, since the heating means provided on the second electrode plate is based on steam, an efficient heating means can be achieved with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a high-frequency drying apparatus according to an embodiment of the present invention.

FIG. 2 is a view showing a water content of a plate material of each stage of the high frequency drying apparatus of FIG. 1;

FIG. 3 is a cross-sectional view of a main part showing a modification of the arrangement of electrode plates of the high-frequency drying device of the present invention.

FIG. 4 is a cross-sectional view showing a modification of the first electrode plate of the high frequency drying device of the present invention.

FIG. 5 is a sectional view of a main part of a conventional high-frequency drying apparatus.

6 is a diagram showing the water content of the plate material of each stage of the high-frequency drying device of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drying chamber 2 1st electrode plate 3 2nd electrode plate 4 Through-hole 5 Inlet pipe 6 Discharge pipe 7 High frequency power supply 8 Vacuum pump 9 Elevating shaft 10 Elevating shaft 11 Body to be dried 2a Thin electrode plate 2b Press Board

Claims (3)

(57) [Claims] A first electrode plate in a metal drying chamber;
The first electrode plate is disposed so as to face the second electrode plate, and a second electrode plate that is set to the ground potential is provided, and a high-frequency voltage is applied between the first electrode plate and the second electrode plate. The high-frequency drying apparatus according to claim 1, wherein a heating unit is provided only on the second electrode plate which is set to the ground potential. 2. The high-frequency drying apparatus according to claim 1, wherein the first electrode plate is disposed so as to be located between a pair of second electrode plates at a ground potential. 3. The high-frequency drying apparatus according to claim 1, wherein the heating means provided on the second electrode plate which is set to the ground potential is based on steam.