JPS6237314B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drying device for veneer veneer.

Conventionally, by utilizing the property of veneer veneer (hereinafter referred to as veneer) having flexibility in the direction perpendicular to the fibers, the veneer was placed along the circumferential surface of a heating roll heated to a desired temperature in the direction perpendicular to the fibers. There is a type of drying device that heats and dries the product while transporting the product.

As disclosed in Japanese Patent Publication No. 44-29027, this type of drying device transfers and receives heat directly, so compared to hot air circulation type roll dryers and net dryers, this type of drying device has better thermal efficiency and a shorter drying time. Although it is said to have many advantages, such as being short, if the veneer is not brought into sufficient contact with the surface of the heating roll, a heat insulating layer of air intervenes, which significantly impairs the above advantages.

Therefore, a so-called suction drum method has been proposed, as in the technique disclosed in Japanese Utility Model Publication No. 44-23510, in which the interior of the heating roll is made to have negative pressure and the veneer is adsorbed to the circumferential surface. There are problems such as uncertainty in the transfer of the veneer between the heating rolls, uncertainty in the suction of veneers with missing parts such as rot or chipping, and clogging of the suction holes.

Furthermore, none of the conventional devices has a configuration that actively allows shrinkage of the veneer as it dries, so there is a problem that shrinkage cracks occur in the dried veneer, and the above advantages are not recognized. However, the actual situation was that it could not be put into practical use.

The present invention was developed to eliminate the drawbacks of the conventional drying equipment of this type, and its outline is to meander a plurality of linear bodies arranged on both the front and back sides of a veneer to a plurality of heating rolls. At the same time, on the peripheral surface of each heating roll, a linear body located on the heating roll side of the veneer is positioned in the groove formed on each heating roll, and an appropriate number of linear bodies are placed at arbitrary positions. By adopting a configuration in which each heating roll is driven in a state in which the circumferential speed of the book heating roll is reduced by an arbitrary amount from the circumferential speed of the heating roll immediately preceding each heating roll,
Ensuring contact of the veneer to the circumferential surface of the heating roll,
The present invention provides a highly practical drying device that stabilizes the transfer of the veneer between the heating rolls and facilitates the shrinkage of the veneer as it dries.

Hereinafter, the present invention will be described in more detail with reference to an example of implementation illustrated in the drawings.

The basic structure of the drying device according to the present invention is, as illustrated in FIGS. 1, 2, and 3, for example, as shown in FIG. 1, FIG. 2, and FIG. The heating rolls 2 are arranged in a staggered manner as shown in the figure, and a plurality of linear bodies 3 located on both the front and back surfaces of the veneer 1 are meandered to the plurality of heating rolls 2 via the turning roll 5. At the same time, on the circumferential surface of each heating roll 2, the linear body 3 located on the heating roll side of the veneer 1 is positioned in the groove 7 formed in each heating roll 2, and each heating A meandering veneer transport path is formed along the circumferential surface of the roll 2.

For example, when the veneer 1 is carried into the drying apparatus configured as described above via the carry-in conveyor 4 in a direction perpendicular to the fibers, the veneer 1 is conveyed through the meandering veneer conveyance path by each heating roll. 2, it is alternately heated from both the front and back sides, and is eventually dried and transported onto the transport conveyor 6.

At this time, on the circumferential surface of each heating roll 2, the linear body 3 located on the heating roll side of the veneer 1 is sunk into the groove 7 of each heating roll 2, and Since the linear body 3 located there presses the veneer 1 against the heating roll 2 and ensures contact between the two, not only extremely efficient heat exchange is performed, but also each heating roll 2 Even when the veneer 1 is transferred between the veneers, the plurality of linear bodies 3 hold and guide both the front and back sides of the veneer 1, thereby stabilizing the transfer, so that extremely smooth conveyance can be achieved.

By the way, it is well known that veneer has remarkable anisotropy with respect to shrinkage, and experiments have shown that even with ordinary untreated veneer, the water content is significantly reduced, as shown in Figure 4. It has the characteristic of shrinking significantly in the direction perpendicular to the fibers as the fibers deteriorate, and the shrinkage rate of veneers that have been pre-stretched in the direction perpendicular to the fibers by tender treatment increases further. These veneers with special characteristics are dried using conventional drying equipment.
If a configuration is adopted in which the veneer is conveyed at a uniform conveyance speed while being restrained as much as possible, shrinkage of the veneer due to drying will be inhibited, and shrinkage cracks will inevitably occur in the dried veneer.

Therefore, in the drying apparatus according to the present invention, in addition to the above-mentioned basic configuration, the circumferential speed of an appropriate number of heating rolls located at arbitrary positions can be adjusted to By adding a configuration that drives each heating roll in a state where the speed is reduced by an arbitrary amount compared to It is a diagram.

That is, if the above configuration is added to the apparatus shown in FIGS. 1 to 3, shrinkage due to drying of the veneer 1 can be absorbed when the veneer 1 is transferred between the heating rolls 2 having a deceleration relationship. Therefore, it is possible to suppress the occurrence of cracks due to shrinkage.

In addition, when decelerating the heating roll as described above, the heating roll is gradually decelerated from the upper side in the conveyance direction to the lower side in the conveyance direction at a deceleration rate that approximately corresponds to the shrinkage rate of the veneer as shown in FIG. However, as is known, even untreated veneer has a certain elasticity range (stretchability without cracking), and if necessary, the elasticity range can be adjusted by using a tender. It is also possible to significantly increase the speed reduction rate, so there is no problem even if the deceleration rate does not completely match the shrinkage rate of the veneer.The point is that the circumferential speed of at least one of the heating rolls is equal to If the circumferential speed is reduced by an arbitrary amount compared to the circumferential speed of the veneer, a relationship is established between the two to absorb shrinkage due to drying of the veneer, and the occurrence of cracks due to shrinkage can be suppressed.

As is clear from the above, according to the drying apparatus according to the present invention, veneers can be quickly and stably dried with good thermal efficiency, and the occurrence of shrinkage cracks can be prevented or significantly reduced. Therefore, it is effective, and the effect of implementing the present invention in a plywood factory is extremely large.

The heating rolls may be arranged in a staggered manner with an interval equal to or greater than the thickness T of the veneer between the heating rolls as in the above-described embodiment; You can change the heating rolls as you like, such as arranging them close to each other with the same spacing as the heating rolls, or arranging the heating rolls at variable intervals, and the number of heating rolls arranged also depends on the drying conditions. It can be set arbitrarily to correspond.

Furthermore, as a heating means for the heating roll, it is appropriate to introduce a heat medium such as heated steam into the inner hole 9 of the heating roll to heat it, but the heating temperature does not necessarily have to be uniform. For example, it is acceptable to adopt a heating method in which the temperature is reduced by an arbitrary amount in stages from the upper side in the conveying direction where it comes into contact with a veneer with a relatively high moisture content to the lower side in the conveying direction where it comes into contact with a veneer with a relatively low moisture content. If necessary, for example, room temperature water or cooling water may be introduced into the inner hole 9 of the heating roll located at the end in the conveying direction to heat the roll to room temperature or minus temperature (cooling). In addition to attaching a large number of fins to the veneer, heating rolls designed to circulate room-temperature water or cooling water are placed at arbitrary positions to solidify steam near the surface of the veneer during the drying process and promote vaporization. It is also possible to achieve heat recovery.

On the other hand, although it is possible to use various narrow belts, strings, etc. as the linear body, it is possible to use a stretchable linear body made of a coil spring, heat-resistant synthetic resin, etc. Therefore, it is effective to apply appropriate elongation in advance before tensioning.In any case, if the deceleration rate of the heating roll does not match the shrinkage rate of the veneer and the veneer is extremely long, Since there is a risk that conveyance errors may accumulate at the relay part between each heating roll and cause buckling of the veneer, the length S of the relay part between each heating roll should be set to approximately the thickness T of the veneer. It has been found through experiments that it is preferable to set the magnification to 200 times or less.

Therefore, for example, as shown in the embodiment shown in Fig. 5, in which a suitable number of heating rolls are combined into a set and multiple sets are connected in series to suit the drying conditions, some of the heating rolls are relayed. If the length of the section exceeds the above-mentioned preferred value, an appropriate number of turning rolls are arranged in the relay section so that the linear traveling distance L of the linear body is approximately 200 times the thickness T of the veneer. It is preferable to set it so that it is less than twice that.

Furthermore, the arrangement pitch P of the linear bodies required to maintain proper contact between the veneer and the heating roll cannot be determined unconditionally, as it varies depending on the width of the linear bodies, etc. However, generally good results were obtained by setting the thickness to less than approximately 150 times the thickness of the veneer.

The drying device according to the present invention can be applied to so-called pre-drying, which sets the finished moisture content of a veneer higher than a normal value, or quickly dries only the surface of a veneer. It is also possible to heat only one side of a veneer intensively by setting a difference in the heating temperature of the heating roll, and it is also possible to apply adhesive applied to the surface of the veneer. The range of application is extremely wide, as it can be applied to applications in which materials other than veneers are heated and dried, such as applications in which a cured film is formed by heating.

[Brief explanation of the drawing]

The drawings are for explaining the present invention, and FIG. 1 is an explanatory side view of the drying device according to the present invention, and FIG.
The figure is a partial sectional view taken along the line X-Y in Figure 1, Figure 3 is a partial front view of Figure 1, Figure 4 is an explanatory diagram showing the correlation between moisture content and shrinkage rate of veneer, FIG. 5 is an explanatory side view of another embodiment of the drying device according to the present invention. 1... Single plate, 2... Heating roll, 3... Linear body, 4... Loading conveyor, 5... Turning roll, 6
... Carrying out conveyor, 7... Groove provided in heating roll, T... Thickness of veneer, S... Length of relay section, L
... Straight line traveling distance of the linear body, P... Arrangement pitch of the linear body.

Claims (1)

[Claims] 1. A plurality of linear bodies arranged on both the front and back surfaces of a veneer veneer are wound in a meandering manner around a plurality of heating rolls, and a veneer single plate is wound on the circumferential surface of each heating roll. The linear body located on the heating roll side of the plate is positioned in the groove formed in each heating roll, and the circumferential speed of an appropriate number of heating rolls at arbitrary positions is adjusted to the heating roll located just before each heating roll. A veneer veneer drying apparatus characterized in that each heating roll is driven in a state where the peripheral speed of the roll is reduced by an arbitrary amount. 2. The veneer veneer drying device according to claim 1, which uses a stretchable linear body made of a coil spring or the like. 3 Drive each heating roll in such a state that the circumferential speed of an appropriate number of heating rolls is gradually decelerated from the upper side in the conveyance direction to the lower side in the conveyance direction at a deceleration rate that approximately corresponds to the shrinkage rate of the veneer veneer. A drying device for a veneer veneer according to claim 1 or 2. 4. A veneer veneer according to claim 1, 2, or 3, comprising a plurality of linear bodies arranged at intervals of about 150 times or less the thickness of the veneer veneer. drying equipment.