JPH0798179A - Lumber drying device - Google Patents

Abstract

PURPOSE:To prevent lumber from being warped by a method wherein an abut ting position of an electrode plate against the lumber is detected in order to abut the electrode plate against the lumber and a driving of the electrode plate is controlled based on the results of sensing operation. CONSTITUTION:A high frequency is applied between electrode plates 7 while the electrode plates 7 are being installed on both surfaces of a piece of lumber 4 and the lumber 4 is dried with an induction heating with a high frequency electric field produced between the electrode plates 7. As the drying is carried out, the lumber 4 is shrinked and as the abutting position of the electrode plates 7 is varied, one electrode plate 7 is driven until it abuts against the lumber 4 and then a clearance is prevented from being generated between the electrode plate 7 and the lumber 4. As the drying operation is promoted, strain and stress are produced within the wooden member 4. When the strain and stress are applied to the electrode plates 7, transmission of the strain and stress to the driving motor 14 is prevented by driving force transmitting means (screw jacks) 8 and 9 and the abutted state of the electrode plates 7 against the lumber 4 is kept. With such an arrangement as above, it is possible to prevent warp of the lumber 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wood drying apparatus for drying wood by utilizing the heat generation effect of dielectric heating, and more particularly to a structure for preventing warping of wood due to drying.

[0002]

2. Description of the Related Art Conventionally, in the above wood drying apparatus, wood is held at a predetermined high pressure by a pair of electrode plates to which a high frequency is applied and dielectric heating is performed in this state to cause warp, cracks and wrinkles of wood accompanying drying. There is known a wood drying device that prevents distortion and bending of the wood.

For example, Japanese Utility Model Publication No. 2-18477 discloses that
Laminated wood is placed on a trolley provided with a lower electrode plate on the placement surface, and the upper electrode of the laminated wood is dielectrically heated in a state of being pressed against the upper electrode with a hydraulic cylinder at a pressure of 1 to 6 ton / m ^2. A dryer is shown.

[0004]

The above-mentioned conventional wood drying device requires a hydraulic cylinder for generating the above high pressure and a control device therefor, and the size of the device is large.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a wood drying apparatus capable of preventing the warp of wood with a simple structure.

[0006]

According to the present invention, a pair of electrode plates are provided in a drying chamber so as to be movable in parallel in a direction in which at least one of them comes in contact with and away from the other, and a state in which wood is held by the electrode plates. Is a wood drying apparatus for drying the wood by dielectric heating by applying a high frequency to the electrode plate, wherein the movable electrode plate is provided with a driving force transmitting means for transmitting a driving force only from the driving source side to the electrode plate side. Can be driven by the drive source,
Position detection means for detecting the contact position of the movable electrode plate with the wood, and drive control for controlling the drive of the electrode plate based on the detection result of the position detection means so as to bring the electrode plate into contact with the wood. And means (claim 1).

Further, according to the present invention, in the above-mentioned wood drying apparatus, the drive source is composed of a motor, and the drive force transmitting means is a screw jack fixed on the upper surface of the drying chamber by penetrating the elevating shaft into the drying chamber. The one electrode plate is attached to the lower end of the elevating shaft, and the other electrode plate is provided on the surface of a mounting table provided below the one electrode plate (claim 2). .

The position detecting means may detect the abutting position when the driving force of the driving source exceeds a predetermined value set in advance (claim 3). Further, the position detecting means may detect the distance between the electrode plate and the wood, and detect the contact position when the detected distance reaches a predetermined value set in advance (claim) 4).

Further, the present invention provides a wood drying apparatus for holding wood with a pair of electrode plates provided in a drying chamber, and applying a high frequency to the electrode plates to dry the wood by dielectric heating. One is attached to the upper surface of the drying chamber and is attached to the lower end of a support shaft which is penetrated into the drying chamber and is movably supported only in the downward direction, and the other of the electrode plates is located below the one electrode plate. It is provided on the surface of the wood mounting table provided so that the one electrode plate descends to the top surface of the wood by its own weight (claim 5).

The support shaft may be movable only downward by a ratchet mechanism (claim 6).

[0011]

According to the first aspect of the present invention, at least one of the pair of electrode plates is driven by the driving force transmitted from the driving source through the driving force transmitting means, and is brought into contact with the wood. When it reaches, the drive is stopped and the wood is mounted on both sides.

Next, in this state, a high frequency is applied between the electrode plates, and the high frequency electric field formed between the electrode plates dries the wood by dielectric heating. When the wood contracts due to drying and the contact position of the electrode plates changes, one electrode plate is driven according to this change until it contacts the wood, and a gap is prevented from occurring between the electrode plate and the wood. .

Further, when drying causes a strain stress in the wood and the strain stress acts on the electrode plate, the transmission of the strain stress to the driving source side is interrupted by the driving force transmitting means, and the electrode plate is cut off. The contact state of the wood with the wood is maintained, which prevents the wood from warping.

According to the second aspect of the present invention, the elevating shaft of the screw jack is lowered by the driving force of the motor, whereby the electrode plate is brought into contact with the upper surface of the wood. When the strain stress generated in the wood due to the drying acts on the electrode plate, the transmission of this strain stress to the drive source side is blocked by the screw jack, and the contact state of the electrode plate with the wood is maintained. This prevents warping of the wood.

According to the third aspect of the invention, when the electrode plate comes into contact with the wood, the load on the drive source increases, and the drive force of the drive source increases. When the driving force exceeds a predetermined value, it is determined that the electrode plate has reached the contact position, and the driving of the electrode plate is stopped.

According to the fourth aspect of the present invention, the distance between the electrode plate and the wood is detected, and when the distance reaches a predetermined value, it is determined that the electrode plate has reached the contact position, and the electrode plate is driven. Is stopped.

According to the fifth aspect of the invention, the one electrode plate is lowered by its own weight and placed on the upper surface of the wooden piece. When the wood shrinks due to drying and the height of the wood becomes low, the one electrode plate also descends due to its own weight, and the contact state between the one electrode and the wood is maintained. In addition, strain stress is generated in the wood due to drying, and when this strain stress acts on the electrode plate, the upward movement of the electrode plate is restricted by the support shaft to maintain the contact state of the electrode plate with the wood. As a result, the occurrence of warping of wood is prevented.

According to the sixth aspect of the invention, the ratchet mechanism restricts the upward movement of the support shaft of the electrode plate.

[0019]

FIG. 1 is a side sectional view showing the structure of a wood drying apparatus according to the present invention. Further, FIG. 2 is a plan view of the wood drying apparatus.

The wood drying apparatus mainly comprises a drying chamber 1, a vacuum pump 2 for setting the inside of the drying chamber 1 to a predetermined vacuum state, and a high frequency generator 3 for generating a high frequency.

The drying chamber 1 is provided with a storage port for the wood 4 at one end, and a lid 101 for sealing is provided at the storage port. In the drying chamber 1, a carriage 5 for placing the wood 4 is movably arranged on a rail 6. A lower electrode plate 71 of the pair of electrode plates 7 to which the high frequency generated by the high frequency generator 3 is applied is attached to the wood mounting surface of the carriage 5. The upper electrode plate 72 of the pair of electrode plates 7 is mounted above the lower electrode plate 71 so as to be able to move up and down through a pair of screw jacks 8 and 9 provided on the upper surface of the drying chamber 1. .

The screw jacks 8 and 9 include drive shafts 81 and 91 provided with a worm gear (not shown), a worm wheel (not shown) meshed with the worm gear, and a lift shaft 82 screwed to the worm wheel. , 92, and the elevating shafts 81, 91 penetrate into the drying chamber 1 and are fixedly installed at appropriate places on the upper surface of the drying chamber 1. The upper electrode plate 72 is fixed to the lower ends of the elevating shafts 82 and 92. In addition, the sprocket 10,
Torque keepers 12 and 13 provided with 11 are attached.

On the upper surface of the drying chamber 1, screw jacks 8 and 9 are attached.
The drive motor 1 is biased toward the one long side in the center of
4 is fixed. The drive motor 14 is provided with a worm gear reduction mechanism (not shown) including a worm gear and a worm wheel at the tip of the rotor shaft, and the chain couplings 15 and 16 are provided at both ends of the support shaft of the worm wheel to provide a tip end portion. Drive shafts 17 and 18 to which sprockets 19 and 20 are respectively fixed are connected. Then, between the sprockets 10 and 19 and between the sprockets 1
Chains 21 and 22 are respectively wound between 1 and 20, and the drive shafts 17 and 18 and the screw jacks 8 and 9 are connected to each other.

In the above structure, the wood 4 is dried by the following procedure. First, the dolly 5 is carried out from the storage opening of the drying chamber 1, the wood 4 is stacked and placed on the dolly 5, and then loaded into the drying chamber 1 and fixed at a predetermined position in the drying chamber 1. Subsequently, after closing the lid 101 and sealing the inside of the drying chamber 1, the drive motor 14 is driven to lower the upper electrode plate 72. The driving force of the driving motor 14 is the driving shafts 17, 18,
It is transmitted to the drive shafts 81 and 91 of the screw jacks 8 and 9 via the chains 21 and 22 and the torque keepers 12 and 13, and the drive shafts 81 and 91 are rotationally driven to move the lifting shafts 82 and 92 downward. The upper electrode plate 72 descends.

Then, when the upper electrode plate 72 comes into contact with the upper surface of the wood 4, the lowering of the upper electrode plate 72 is restricted, whereby the load torque increases. The driving force of the drive motor 14 increases in accordance with the increase of the load torque, and when the torque exceeds a predetermined torque, the torque keepers 12 and 13 operate to transmit the driving force of the drive motor 14 to the screw jacks 8 and 9. Be cut off. As a result, the upper electrode plate 72 is pressed against the upper surface of the wooden piece 4 with its own weight or a low pressure larger than that.

Subsequently, the vacuum pump 2 is operated to set the inside of the drying chamber 1 to a predetermined vacuum pressure, and then the high frequency generator 3 is activated to apply a high frequency of a predetermined frequency to the electrode plate 7. When a high frequency is applied to the electrode plate 7, a high frequency electric field is formed between the upper electrode plate 72 and the lower electrode plate 71, and the wood 4 is dielectrically heated by the high frequency electric field to promote drying.

At this time, when the wood 4 contracts due to drying and the height h of the wood 4 gradually decreases, the load torque decreases due to the decrease of the height h of the wood 4, and the drive motor 14 accordingly. Driving force is reduced. When the driving force of the drive motor 14 drops below a predetermined torque, the torque transmission blocking function of the torque keepers 12, 13 is released, and the driving force of the drive motor 14 is transmitted to the screw jacks 8, 9.
The upper electrode plate 72 is lowered. Then, when the upper electrode plate 72 comes into contact with the upper surface of the wood 4, the torque keeper 12, 1 is again provided.
3, the transmission of the driving force of the drive motor 14 to the screw jacks 8 and 9 is interrupted, and the upper electrode plate 72 is pressed against the upper surface of the wood 4 with a predetermined pressure. That is, the upper electrode plate 72 descends according to the decrease in the height h due to the contraction of the wooden piece 4, and the contact state of the upper electrode plate 72 with the wooden piece 4 is maintained.

As the drying of the wood 4 progresses, the wood 4
A strain stress that distorts the plate surface in the up-down direction is generated in the inside of the, and an upward pushing force due to the strain stress acts on the upper electrode plate 72.
However, since the upper electrode plate 72 is supported by the screw jacks 8 and 9 and the transmission of the pushing force to the drive motor 14 side is blocked by the screw jacks 8 and 9, the upper electrode plate 72 is transferred to the upper surface of the wood 4. The contact state is maintained, whereby the pushing force reacts from the upper electrode plate 72 to the upper surface of the wood 4, and the warp of the wood 4 due to the strain stress is prevented.

Then, the drying process is performed for a preset time, and when the process is completed, the driving of the vacuum pump 2 and the high frequency generator 3 is stopped, and the drive motor 14 is driven in the reverse direction to drive the upper electrode plate 72. Then, the cart 5 is carried out of the drying chamber 1 and the wood 4 is taken out.

In the above embodiment, the torque keeper 1 controls the transmission of the driving force of the drive motor 14 to the screw jacks 8 and 9.
2 and 13 to control the contact and holding of the upper electrode plate 72 with respect to the wood 4, but the torque keeper 12, 13
Instead of the above, a torque detection sensor that detects the load torque of the drive motor 14 and a control device that controls the drive of the drive motor 14 based on the detection signal of the torque detection sensor are provided, and the detection value of the torque detection sensor is a predetermined torque. Is exceeded,
When it is determined that the upper electrode plate 72 has come into contact with the wood 4, the driving of the drive motor 14 is stopped, and when the detected value becomes equal to or less than the predetermined torque, the contact state of the upper electrode plate 72 with the wood 4 is released. The drive motor 14 may be driven upon determining that the drive has been performed.

Further, as shown in FIG. 3, a distance sensor 2 including a light emitting element and a light receiving element is provided at a proper place on the lower surface of the upper electrode plate 72.
3, the distance sensor 23 may detect the distance d between the lower surface of the upper electrode plate 72 and the upper surface of the wood 4 to control the drive of the drive motor. In this method, since the lowered position of the upper electrode plate 72 can be detected with high accuracy, the upper electrode plate 72 can be held in contact with the wood 4 without being pressed, and at the same time, the upper electrode plate 72 can be held.
It is also possible to hold the upper electrode plate 72 in a state in which the upper electrode plate 72 is pressed against the wood 4 with a predetermined pressure by stopping the driving of the drive motor 14 after a lapse of a predetermined time after detecting the contact position of the wood 4 with the wood 4.

In the above embodiment, the screw jacks 8,
The lifting shafts 82 and 92 of 9 are used as support shafts for the upper electrode plate 72, and a mechanism for transmitting the driving force of the drive motor 14 to the support shafts through the screw jacks 8 and 9 is adopted. The structure is not limited to the above.
Of the upper electrode plate 72 due to the strain stress generated in the wood 4,
Any other transmission mechanism may be used as long as it is a mechanism that holds the upper electrode plate 72 in a state of contacting or press-contacting the upper surface of the wood 4.

For example, as shown in FIG. 4, a drive motor 24
The driving force may be transmitted via the spur gear 25 to the worm wheel 26 that is screwed onto the lifting shaft 82.

Further, it may be constituted by a drive mechanism which converts the rotational force of the drive motor into a vertical movement of the support shaft of the upper electrode plate and transmits it directly.

FIG. 5 shows an example of such a drive mechanism. The rotor shaft 271 of the drive motor 27 is a hollow shaft, and the female screw portion 272 is formed on the inner peripheral surface of the rotor shaft 271. A male screw portion 281 is formed on the outer peripheral surface of the, and the support shaft 28 is screwed to the rotor shaft 271.

The main body of the drive motor 27 is formed integrally with the support portion 102 of the drying chamber 1, and the rotor shaft 27
1 is rotatably supported within the support shaft 102.
Therefore, when the rotor shaft 271 of the drive motor 27 rotates, the rotational force is directly transmitted to the support shaft 28, and the support shaft 28 moves up and down while rotating.

Further, in the above embodiment, the upper electrode plate is lowered by the driving force of the drive motor, but the upper electrode plate is made relatively heavy and is lowered by its own weight to be placed on the upper surface of the wood. May be. With this configuration, the upper electrode plate descends by its own weight according to the contraction of the wood, so that it is not necessary to detect the descending position of the upper electrode plate or control the descending drive of the upper electrode plate according to the contraction of the wood.

FIG. 6 shows an example of a mechanism for lowering the upper electrode plate by its own weight. A ratchet mechanism is provided in the supporting mechanism of the supporting shaft 29 of the upper electrode plate 72 so that the supporting shaft 29 can be moved only in the downward direction. The upper electrode plate 72 is prevented from moving upward due to the strain stress generated in the wood 4.

A tooth portion 103 that flows downward is formed on the inner peripheral surface of the support portion 102 that supports the support shaft 29 of the upper electrode plate 72, and a claw that engages with the tooth portion 103 is formed at an appropriate position of the support shaft 29. The protrusion 291 is provided so as to be biased outward. Further, the claw 291 is provided so as to be able to change its position between a projecting position projecting from the support shaft 29 and a storage position housed in the support shaft 29, and the lever portion 292 provided at the upper end of the support shaft 29 allows the pawl 291 to move. The protruding position of the claw 291 and the storage position can be changed. Therefore, the lowered electrode plate 72 causes the lever 292 to move the claw 291 to the support shaft 2
It can be lifted by setting it to the storage position of 9 and releasing the engagement of the claw 291 with the tooth portion 103.

[0040]

As described above, according to the present invention,
A pair of electrode plates are provided in the drying chamber so that at least one of them can move in parallel to the other in a direction in which they move toward and away from each other. A wood drying device for drying wood,
The movable electrode plate can be driven by the drive source via the drive force transmission means that transmits the drive force only from the drive source side to the electrode plate side, and at the same time, the dielectric heating can be performed in the state of being closely attached to the wood. Therefore, even when strain stress is generated in the wood due to the drying, the movement of the electrode plate is restricted by the driving force transmitting means, and the warp of the wood due to the drying can be prevented with a simple structure.

Further, according to the present invention, the rotational force of the motor is transmitted to the elevating shaft of the electrode plate via the screw jack, and the elevating shaft is lowered to bring the electrode plate into contact with the upper surface of the wood. Even when a pushing force acts on the electrode plate due to the strain generated in the wood, the screw jack interrupts the transmission of the pushing force to the motor side, and the upward movement of the electrode plate is reliably prevented.

Further, according to the present invention, the driving force of the driving source is detected to detect the contact position of the electrode plate with the wood, so that the descending control of the electrode plate can be easily performed.

Further, according to the present invention, since the distance between the electrode plate and the wood is detected to detect the contact position of the electrode plate with the wood, the descending control of the electrode plate can be performed with high accuracy. You can

Further, according to the present invention, in a wood drying apparatus for holding wood between a pair of electrode plates provided in a drying chamber and applying a high frequency to the electrode plates to dry the wood by dielectric heating, The plates are arranged in parallel in the vertical direction, the upper surface of the drying chamber is penetrated into the drying chamber, and the upper electrode plate is attached to the lower end of the support shaft that is supported so as to be movable only in the downward direction by, for example, a ratchet mechanism. Since the upper electrode plate is lowered to the upper surface of the wood by its own weight, the driving means of the electrode plate and the detecting means of the lowered position can be omitted, and the lowering control of the electrode plate and the warp of the wood can be prevented with a simple structure. You can

[Brief description of drawings]

FIG. 1 is a side sectional view showing a structure of a wood drying apparatus according to the present invention.

FIG. 2 is a plan view of a wood drying apparatus according to the present invention.

FIG. 3 is a cross-sectional view of essential parts showing another detection method for detecting the contact position of the upper electrode plate with the upper surface of wood.

FIG. 4 is a perspective view of essential parts showing a second embodiment of the driving mechanism for the upper electrode plate.

FIG. 5 is a cross-sectional view of essential parts showing a third embodiment of the drive mechanism for the upper electrode plate.

FIG. 6 is a sectional view of an essential part showing a mechanism for lowering an upper electrode plate by its own weight.

[Explanation of symbols]

 1 Drying Room 101 Lid 102 Supporting Part 103 Teeth 2 Vacuum Pump 3 High Frequency Generator 4 Wood 5 Truck 6 Rail 7 Electrode Plate 71 Lower Electrode Plate 72 Upper Electrode Plate 8,9 Screw Jack 10, 11, 19, 20 Sprocket 12 , 13, torque keeper 14, 24, 27 drive motor 15, 16 chain coupling 17, 18 drive shaft 21, 22 chain 23 distance sensor 25 spur gear 26 worm wheel 28, 29 support shaft 291 pawl

Claims (6)

[Claims] 1. A pair of electrode plates are provided in a drying chamber so that at least one of them can move in parallel to and away from the other, and a high frequency is applied to the electrode plates while holding wood between them. In the wood drying device for drying the wood by dielectric heating, the movable electrode plate is made drivable by the drive source via the drive force transmission means for transmitting the drive force only from the drive source side to the electrode plate side. Position detecting means for detecting the contact position of the movable electrode plate with the wood, and drive for controlling the drive of the electrode plate based on the detection result of the position detecting means so as to bring the electrode plate into contact with the wood. A wood drying apparatus comprising a control means. 2. The wood drying apparatus according to claim 1,
The drive source is composed of a motor, and the driving force transmission means is a screw jack fixed on the upper surface of the drying chamber by penetrating the lifting shaft into the drying chamber, and the one electrode plate is attached to the lower end of the lifting shaft. The wood drying apparatus is characterized in that the other electrode plate is provided on a surface of a mounting table provided below the one electrode plate. 3. The wood drying apparatus according to claim 1 or 2, wherein the position detecting means has a detecting means for detecting a driving force generated by the driving source, and a detection result of the detecting means is set in advance. A wood drying apparatus, comprising: a determining unit that determines whether or not a predetermined value has been reached, and the contact position is detected when the driving force reaches a predetermined value. 4. The wood drying apparatus according to claim 1 or 2, wherein the position detecting means is a distance detecting means for detecting a distance between the movable electrode plate and the wood, and a detection result of the distance detecting means is set in advance. And a discriminating means for discriminating whether or not the predetermined value has been reached, and detecting the contact position when the distance reaches the predetermined value. 5. A wood drying apparatus for holding wood between a pair of electrode plates provided in a drying chamber, and applying high frequency to the electrode plates to dry the wood by dielectric heating, wherein one of the electrode plates is dried. On the upper surface of the chamber, penetrate into the drying chamber, and
Attached to the lower end of a support shaft movably supported only in the downward direction, the other of the electrode plates is provided on the surface of a wood mounting table provided below the one electrode plate, and A wood drying apparatus, wherein the electrode plate is adapted to descend to the upper surface of the wood by its own weight. 6. The wood drying apparatus according to claim 5,
A wood drying apparatus, wherein the support shaft is movable only downward by a ratchet mechanism.