JPH0823471B2 - Heating method for veneer veneer in intermittent transfer type hot plate dryer - Google Patents

Description

The present invention relates to a method for heating a veneer veneer in an intermittent transfer type hot plate dryer.

2. Description of the Related Art Conventionally, a veneer veneer (hereinafter simply referred to as a veneer) has been used as a drying device, for example, a "continuous press drying device for a material such as a thick veneer" (Japanese Utility Model Publication No. 59-34872), a "plate material drying device".
(Japanese Patent Publication No. 60-12547), a pair of endless belts are stretched on an appropriate number of rolls so that they can run intermittently.
A single plate transport path is formed in the facing interval of both endless zones, and a suitable number of pairs of heating plates are provided on both sides of the transport path so that at least one of them can approach and separate from the other. , In the process of intermittently transporting the veneer in the endless belt, the veneer is heated and dried through the endless band by the heating plate, which is known as an intermittent transport type hot plate dryer, which is known in this type. The device has no restriction on the conveying direction of the veneer and has relatively good thermal efficiency, and as is apparent from the name of the publication, it is said that the device is suitable for drying an extremely thick veneer. .

By the way, it is suitable for drying a very thick veneer,
Conversely, it implies that it is not suitable for drying relatively thin veneers,
It has been found in the course of development of the present invention that the cause is the heating mode in the above-mentioned type of apparatus, although it is practically not practically used in a general plywood factory.

That is, all the heating plates in the known apparatus of this type have a flat heating surface and uniformly heat the veneer over the entire surface, whereas the heating plate evaporates with heating. Since the water content of the veneer is more likely to be removed to the outside than the central part in the fiber direction of the veneer, both ends dry faster than the central part in the fiber direction of the veneer. There is a tendency to shrink, differences in drying and shrinkage are likely to occur, and the difference in shrinkage is a factor that causes cracks on both end sides in the fiber direction of the veneer. Since the strength in the direction orthogonal to the fiber is weak, the occurrence of cracks due to the difference in shrinkage becomes noticeable, and cracks due to insufficient discharge of steam due to explosive evaporation in the early stage of heating are more likely to occur. As a result, it was found that it was unsuitable for drying relatively thin veneers.

The present invention has been developed to solve the problems in this type of device, including known devices and new models described later, and to improve its versatility and practicality. Specifically, when heating the veneer in the process of intermittently transferring the veneer using the intermittent transfer type hot plate drying device having the above-mentioned configuration, the veneer transfer direction is specified as a direction orthogonal to the fiber, and at the arbitrary position. At least the pair of heating plates should be close to each other,
Regulating the thickness of the veneer and the endless strip to exceed the desired amount, and forcibly bending at least one of the heating plates whose spacing is regulated in the direction orthogonal to the running direction of the endless strip by an arbitrary amount. Thus, at the position of the curved heating plate, the heating is gradually reduced from the central portion in the fiber direction of the veneer toward both ends.

According to such a heating method, as the heating gradually decreases from the central portion in the fiber direction of the veneer at the position of the curved heating plate toward both ends, the heating plate position becomes Since the phenomenon that the difference in drying and shrinkage between the center and both ends in the fiber direction of the plate is suppressed is suppressed, the occurrence of cracks due to the difference in shrinkage is prevented or mitigated, and the gap caused by the curvature of the heating plate is further reduced. The presence of the cracks also prevents the occurrence of cracks due to insufficient discharge of steam, making it possible to satisfactorily dry even relatively thin veneers, making the above-mentioned type of drying device more versatile and practical than before. It is effective because it significantly improves.

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

FIG. 1 is a side view of a drying device applied to the implementation of the heating method according to the present invention, and FIG. 2 is a partial sectional view taken along the line AA in FIG.

In the figure, 1 and 2 are a pair of endless belts stretched respectively on the rolls 1a and 1b and 2a and 2b in order to form a conveying path for the veneer 9 within the facing interval, and with a speed reducer. A drive source 6 composed of an electric motor or the like drives the rollers 1a and 2a to intermittently drive in the direction of the arrow in the drawing.

Reference numeral 3 denotes a plurality of upper heating plates which are arranged so as to be capable of moving up and down so as to face a lower heating platen 3 which will be described later on the upper side of the conveying path formed by the endless belts 1 and 2, and heating steam, heating oil, It is heated to the desired temperature by a heat source such as an electric heater,
With the operation of the elevating mechanism 5 to be described later, the endless belts 1 and 2 are intermittently moved up and down in synchronization with the intermittent running.

Reference numeral 4 denotes a plurality of lower heating plates which are arranged below the transport path formed by the endless belts 1 and 2 so as to be able to move up and down so as to face the upper heating plate 4, and include heating steam, heating oil,
It is heated to a desired temperature by a heat source such as an electric heater, and is intermittently moved up and down in synchronization with the intermittent running of the endless belts 1 and 2 in accordance with the operation of the lifting mechanism 5 described later.

Reference numeral 5 denotes an elevating mechanism having an elevating member 5a composed of, for example, a cam or a fluid cylinder, and a controller 5b.
Based on the control of 5b, the elevating member 5a is operated in synchronization with the intermittent operation (stop operation) of the drive source 6 for intermittently running the endless belts 1 and 2, and the upper heating plate 3 and the lower heating plate 4 are intermittently operated. It also has a pressing function for forcibly bending the endless belts 1 and 2 in a direction orthogonal to the running direction of the endless belts 1 and 2 by an arbitrary amount.

Numeral 7 is a stopper provided on the machine frame 8 so as to be located between the upper heating platen 3 and the lower heating platen 4 at four positions on both sides in the direction orthogonal to the traveling direction of the endless belts 1 and 2. And the thickness P is the thickness S of the single plate 9 and the thickness T1 of the endless belts 1.2.
It is set so as to exceed the total thickness of T2 and the desired amount, and is brought into contact with the upper heating platen 3 and the lower heating platen 4 which move up and down,
The closest distance is regulated.

Reference numeral 10 is a tension member composed of a spring, a fluid cylinder, etc., and is an endless belt 1 or 2 constantly or in synchronization with the operation of the drive source 6.
When running, the endless belts 1 and 2 are tensioned by applying appropriate tension to the endless belts 1 and 2 via the rolls 1b and 2b.

The heating method according to the present invention is carried out, for example, in the drying device having the above-mentioned structure. When the single plate 9 is carried in such a device in the direction orthogonal to the fibers, the endless belts 1 and 2 are intermittently operated. In the process in which the veneer 9 is intermittently transported along the transport path as the vehicle travels, as shown in FIG. 3, the lifting mechanism 5 moves the upper heating plate 3 in synchronization with the stoppage of the endless belts 1 and 2. With lowering
Since the lower heating platen 4 is raised, heating is performed by the upper heating platen 3 and the lower heating platen 4 via the endless belts 1 and 2, and then, after a predetermined time has elapsed, as shown in FIG. When the endless belts 1 and 2 run for a while while the upper heating platen 3 is raised and the lower heating platen 4 is lowered, the lifting mechanism 5 causes the upper heating platen 5 to move as shown in FIG. Since 3 is lowered and lower heating platen 4 is raised, heating is performed by upper heating platen 3 and lower heating platen 4 again.

Hereinafter, by repeating the same operation, heating to the veneer 9 is sequentially repeated, and the veneer 9 will be dried and carried out before long. In the method of the present invention, the upper heating is performed at the time of heating. The board 3 and the lower heating board 4 contact the stopper 7, and the closest distance between them is the thickness S of the single plate 9 and the thickness T1 of the endless belts 1 and 2.
・ The total thickness of T2 and T2 is regulated so that it exceeds the desired amount.
Since it is forcibly curved in the direction orthogonal to the running direction of the vehicle by an arbitrary amount, for example, by the amount corresponding to the desired amount, the relative positional relationship between each heating platen 3 and 4 and the endless belts 1 and 2 Shows the state as shown in FIG.
Phenomenon in which the difference in drying and shrinkage between the central part and the both ends of the veneer 9 in the fiber direction occurs as a result of the heating at the position of V being gradually reduced from the central part in the fiber direction of the veneer 9 toward both ends. Is suppressed, the occurrence of cracks due to the difference in contraction is prevented or reduced, and the presence of the gaps associated with the curvature of the heating plates 3 and 4 also prevents the occurrence of cracks due to insufficient discharge of steam. Thus, it becomes possible to satisfactorily dry even a relatively thin veneer.

It should be noted that which pair of heating plates should be forcibly bent while controlling the closest distance, the initial water content of the veneer, the desired dryness, the degree of bending of the heating plate, etc. It is effective to set in accordance with various conditions of the above, and it is not necessarily uniformly set. Although it may be possible to perform the forced bending and the forced bending, in reality, in a general usage of drying normal raw veneer to a water content within a range that can be used for plywood, The occurrence of at least the difference in drying at the end is relatively slight, so mainly at the time corresponding to the early and / or middle stages of drying,
Restricting the closest distance and forcing a pair of heating plates at the positions corresponding to the initial and / or middle stages of drying so that the heating gradually decreases from the center of the veneer toward both ends. There was no problem even if bending was performed.

Further, from the viewpoint of uniform drying, it is preferable to forcibly bend both of the pair of heating plates with the closest spacing regulated, as in the above-mentioned embodiment, but it is not necessarily limited to this, and only one of them, for example, may be used. However, due to the interposition of the endless belt, air, which is a poor heat conductor, gradually intervenes gradually from the central part in the fiber direction of the veneer toward both ends, and heating is inversely proportional to it. It is effective because it gradually decreases. In short, if one or more heating plates are in a curved state, the corresponding effect can be obtained.

And the closest spacing and the degree of curvature are the thickness of the veneer
It can be set appropriately according to various conditions such as initial moisture content and desired degree of drying, but as a general tendency, relatively thin veneers are easy to dry, and the effect of suppressing the difference in drying and shrinkage due to the gradual reduction of heating. Since it is difficult to manifest, it is preferable to make the closest approach distance relatively wide and to bend relatively large, on the contrary, it is difficult to dry a relatively thick veneer, and the occurrence of cracks due to difference in shrinkage becomes visible. Since it is difficult, it is preferable to make the closest spacing relatively narrow and to make it relatively small.

Further, as illustrated in the above-mentioned examples, if the closest spacing and the degree of curvature are set to such an extent that no gap is formed in the central portion in the fiber direction of the veneer, the thermal efficiency is most effective, but it is not always the case. There is no need to limit the setting, and even if there is a slight gap in the central portion of the veneer in the fiber direction, the decrease in thermal efficiency due to the presence of the gap does not hinder practical use. Even if the board was curved to some extent in the same direction as the running direction of the endless belt, the decrease in thermal efficiency, the difference in drying, etc., were practically acceptable.

Further, in the above-described embodiment, the machine frame is provided with the stopper so as to regulate the closest distance. However, as illustrated in FIG. 5, either one of the heating plates (the lower heating plate 4 in the embodiment is used). ) Can be provided with a stopper 7 to regulate the closest distance, and the point is that if the closest distance can be regulated to exceed the total thickness of the veneer and the endless belt by a desired amount, any regulation Means may be used.

In addition, from the general tendency described above, it is possible to process veneers with different thicknesses by using the same stopper by changing the degree of curvature. Correspondingly, it does not matter if you change the thickness of the stopper,
Alternatively, if necessary, as shown in FIG. 6, an adjusting member 7a such as a screw may be utilized to arbitrarily adjust the closest distance.

On the other hand, as a means for forcibly bending the heating platen in the direction orthogonal to the traveling direction of the endless belt by an arbitrary amount, one heating platen is moved closer to or away from the other heating platen as exemplified in the above embodiment. Therefore, it is convenient to use an elevating mechanism, and if it is an elevating mechanism having an elevating member (for example, a fluid cylinder) whose pressing force is variable, the degree of bending can be arbitrarily changed, which is convenient. However, the present invention is not limited to this. For example, a pressing member dedicated to bending is provided on the side opposite to the heating surface of a heating plate that is fixedly provided above or below the conveyance path, and only forcible bending is performed. However, it does not matter what kind of forcible bending means is required as long as the desired heating plate can be forcibly bent in an orthogonal direction to the running direction of the endless belt.

Further, from the viewpoint of heat transfer property, strength, etc., it is desirable that each of the endless belts is made of metal, and also metals having corrosion resistance such as stainless steel or metals having corrosion resistant coating such as plating. Although it is not particularly limited and is not necessarily limited to a non-perforated strip, a non-perforated strip can be used to remove deposits such as wood powder and resin adhering to the peripheral surface. It is convenient to use a leaf spring-shaped scraping member in contact with the outer periphery thereof.

Furthermore, the intermittent transfer type hot platen drying apparatus applicable to the implementation of the method of the present invention is not limited to the intermittent transfer type hot platen drying apparatus having a one-step flat transfer path as exemplified in the above embodiment. For example, the applicant of the present invention has previously described "a veneer veneer drying device" (Japanese Patent Laid-Open No. 63-91477) and "a method for correcting the trajectory of an endless belt in a veneer veneer drying device" (Japanese Patent Laid-Open No. 63-63119).
-226588 gazette) and the like, a device having a configuration for forming a series of meandering single-plate conveying paths consisting of a combination of flat roads, curved roads, flat roads, curved roads, and flat roads. However, the point is that the heating method according to the present invention can be applied as long as it is an intermittent transfer type hot plate drying device that substantially combines an endless band and a heating plate to dry a single plate.

[Brief description of drawings]

The drawings are for explaining the present invention. FIG. 1 is a side view of a drying apparatus applied to the implementation of the heating method according to the present invention, and FIG. 2 is a line AA in FIG. Partial cross-section,
FIG. 3 is an explanatory view of the operation of the apparatus illustrated in FIGS. 1 and 2, FIG. 4 is a partial sectional view taken along line BB in FIG. 3, and FIGS. It is a fragmentary sectional view of other drying equipment applied to implementation of the heating method which concerns. 1,2 ... Endless band, 3 ... Upper heating plate, 4 ... Lower heating plate, 5 ... Lift mechanism, 6 ... Drive source, 7 ... Stopper, 8 ... Machine frame, 9 ... Single plate , 10 …… tension member, P ……
Stopper thickness, S ... Single plate thickness, T1, T2 ... Endless belt thickness

Continuation of front page (56) References JP-A-63-233288 (JP, A)

Claims (1)

[Claims] 1. A pair of endless belts are stretched on an appropriate number of rolls so as to be able to intermittently run to form a veneer veneer conveyance path within the facing interval of both endless belts, and to both sides of the conveyance path. At least one of the veneer veneer is heated in the process of intermittently carrying the veneer veneer by using the intermittent carrying type hot plate drying device provided with a suitable number of pairs of heating plates that can approach and separate from the other.
The transport direction of the veneer veneer is specified as the direction orthogonal to the fiber, and the closest distance between at least a pair of heating plates at arbitrary positions is regulated to a distance that exceeds the total thickness of the veneer veneer and the endless belt by a desired amount. In addition, by forcibly bending at least one of the heating plates whose spacing is regulated in the direction orthogonal to the running direction of the endless belt by an arbitrary amount, the veneer unit is placed at the position of the curved heating plate. A method for heating a veneer veneer in an intermittent transfer type hot plate dryer, characterized in that heating is gradually reduced from the central part to both ends of the plate in the fiber direction.