JPH07111302B2 - 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.

Conventionally, as a dryer for veneer veneer (hereinafter simply referred to as veneer), for example, "continuous press dryer for materials such as thick veneer" (Japanese Utility Model Publication No. 59-34872), "plate material dryer"
As disclosed in (Japanese Patent Publication No. 60-12547), a pair of endless belts are stretched over an appropriate number of rolls so that intermittent traveling is possible, and a single-plate conveying path is provided within the facing interval of both endless belts. As it forms
An appropriate number of pairs of heating plates, at least one of which can be brought into contact with and separated from the endless belt, are arranged on both sides of the conveying path. There is known an intermittent transfer type hot plate dryer for heating and drying a veneer through a band, and this known type device has no restriction on the transfer direction of the veneer and has a relatively high thermal efficiency. It was good, and as is apparent from the title of the above publication, it was said to be suitable for drying an extremely thick veneer.

By the way, the fact that it is suitable for drying extremely thick veneer implies that it is unsuitable for drying relatively thin veneer, and it is hardly used in general plywood factories. In the actual situation, it was revealed during the development process of the present invention that the cause was the heating mode in the above-mentioned type of apparatus.

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. The water content of the veneer that evaporates is more easily removed to the outside at both ends than in the central part in the fiber direction of the veneer, so both ends dry faster than in the central part in the fiber direction of the veneer. Tend to contract,
Differences in drying and shrinkage tend to occur, and the difference in shrinkage is
This will cause cracks on both ends of the veneer in the fiber direction, but the thinner the veneer is, the weaker the strength in the direction orthogonal to the fiber, so the occurrence of cracks due to the difference in shrinkage becomes more noticeable. As a result, it was found that it was considered unsuitable for drying relatively thin veneer.

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, in the intermittent transfer type hot plate drying apparatus having the above-mentioned configuration, at least one heating plate at an arbitrary position is preliminarily provided with a convex surface whose heating surface has a convex shape in a direction orthogonal to the running direction of the endless belt. By forming on the heating platen and transporting the veneer in the direction orthogonal to the fiber, at the position of the convex heating platen, the heating is gradually reduced from the central part in the fiber direction of the veneer to both ends. It is a heating method characterized by urging.

According to such a heating method, with the gradual decrease in heating from the central portion in the fiber direction of the veneer at the position of the convex heating plate toward both ends, at the position of the convex heating plate, Since the phenomenon in which the difference in drying and shrinkage between the central portion and both ends in the fiber direction of the veneer is suppressed is suppressed, the occurrence of cracks due to the difference in shrinkage tends to be prevented or reduced, and a relatively thin single plate is used. This is effective because the plate can be dried well, and the versatility and practicality of the drying device of the above type is significantly improved as compared with the conventional one.

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 1a are a pair of endless belts stretched respectively on rolls 2a, 2b and 2c, 2d so as to form a conveying path for the veneer 10 within a facing space between them, and with a speed reducer. A drive source 7 composed of an electric motor or the like drives the rollers 2a and 2c to intermittently drive and drive in the direction of the arrow shown.

Numeral 3 is an upper convex heating plate which is arranged so as to be able to move up and down to the upper half of the first half of the conveyance path formed by the endless belts 1 and 1a, and is provided by a heating source such as heating steam, heating oil, and electric heater. The heating surface 3a heated to a desired temperature has a convex shape in a direction orthogonal to the traveling direction of the endless belts 1 and 1a, and the endless belts 1 and 1a are paired with a lower convex heating plate 4 described later. Heat the veneer 10 through it slightly non-uniformly.

Reference numeral 4 denotes a lower convex heating plate which is arranged so as to be able to move up and down to the lower side of the front half of the conveyance path formed by the endless belts 1 and 1a and is heated to a desired temperature by a heat source such as heating steam. The heating surface 4a has a convex shape in a direction orthogonal to the traveling direction of the endless belts 1 and 1a, and in a pair with the upper convex heating platen 3,
The veneer 10 is heated non-uniformly via the endless belts 1 and 1a.

Reference numeral 5 denotes an upper heating plate which is arranged so as to be able to move up and down to the upper half of the conveyance path formed by the endless belts 1 and 1a, and which is heated to a desired temperature by a heat source such as heating steam. The surface has a normal flat shape and is paired with a lower heating plate 6 which will be described later to uniformly heat the single plate 10 through the endless belts 1 and 1a.

Reference numeral 6 denotes a lower heating plate which is fixedly provided on the lower side of the latter half of the conveyance path formed by the endless belts 1 and 1a, and which is heated to a desired temperature by a heat source such as heating steam. The surface has a normal flat shape, and the single plate 10 is uniformly heated through the endless belts 1 and 1a in pairs with the upper heating plate 5.

Reference numeral 8 denotes a control mechanism having an elevating member 8a composed of a cylinder or the like and a controller 8b. Under the control of the controller 8b, the elevating member 8a is actuated in response to intermittent running of the endless belts 1 and 1a. The upper convex heating platen 3, the lower convex heating platen 4 and the upper heating platen 5 are intermittently moved up and down.

Reference numeral 9 denotes a scraping member composed of a leaf spring or the like, and each endless belt 1
・ Continuously scrape off resin, wood powder, and other deposits on 1a.

The heating method according to the present invention is carried out, for example, in a drying device having the above-mentioned structure, and a single plate 10 is provided in such a device.
When is loaded in a direction orthogonal to the fibers, the veneer belts 1 and 1a are intermittently run, and the veneer 10 is intermittently transported along the transport path in synchronization with the stop of the endless belts 1 and 1a. Since the control mechanism 8 lowers the upper convex heating platen 3 and the upper heating platen 5, and also raises the lower convex heating platen 4, the upper convex heating platen 3 and the lower convex heating platen 4 are connected via the endless belts 1a. Further, heating is performed by the upper heating plate 5 and the lower heating plate 6, and after a predetermined time has elapsed, the control mechanism 8 raises the upper convex heating plate 3 and the upper heating plate 5 and lowers the lower convex heating plate 4. When the endless belts 1.1a run for a while in synchronism with and stop, the control mechanism 8 lowers the upper convex heating platen 3 and the upper heating platen 5, and also raises the lower convex heating platen 4, so that the upper part is again moved up. Heating is performed by the convex heating platen 3 and the lower convex heating platen 4, and the upper heating plate 5 and the lower heating platen 6. Be played.

Hereinafter, by repeating the same operation, the heating of the veneer 10 is repeated in sequence, and the veneer 10 is eventually dried and carried out. According to the method, the upper convex heating platen 3 and the lower part are heated. The heating surfaces 3a and 4a of the convex heating platen 4 have a convex shape with respect to the direction orthogonal to the running direction of the endless belts 1.1a, and the veneer 10 is also moved in the direction orthogonal to the fibers by the endless belts 1.1a. Since it is transported, it is a biconvex heating platen 3 during operation (heating).
4 and the relative positional relationship between the endless belts 1.1a and the veneer 10 are as shown in FIG. 3, and the heating at the positions of the biconvex heating plates 3 and 4 is in the fiber direction of the veneer 10. As a result of being gradually reduced from the central portion toward both ends, at the positions of the biconvex heating plates 3 and 4, there is a phenomenon that a difference in drying and shrinkage occurs between the central portion and both ends in the fiber direction of the veneer 10. Since it is suppressed, the occurrence of cracks due to the difference in shrinkage tends to be prevented or reduced, and even a relatively thin veneer can be dried well.

Next, in the embodiment illustrated in FIG. 4 and FIG. 5, the present applicant has previously described “a veneer veneer drying device” (Japanese Patent Laid-Open No. 63-91477) / “a veneer veneer drying device” ( (Japanese Patent Laid-Open No. 63-96471) ・ "Process length can be shortened as proposed in" Endless belt trajectory correction method in veneer veneer dryer "(Japanese Patent Laid-Open No. 63-226588). It is an application example of the most basic type of drying equipment among the new type drying equipment.

That is, a pair of endless belts 11 and 11a, a plurality of rolls 12a
12b, 12c, 12d and 12e, 12f, 12g, 12h are respectively meandered and stretched so that they can be intermittently driven and driven by a driving source 17 via a roll 12f in the direction of the arrow shown in the figure, and a flat road.・ Bent road ・
A series of veneer conveyor paths consisting of a combination of flat roads, curved roads and flat roads are formed, and upper convex heating platen 13 and lower convex heating are provided on both sides of the upper and middle flat roads. An upper heating plate 15 and a lower heating plate 16 are respectively arranged on both sides of the board 14 and on the lower side flat road, and further, based on the control by the controller 18b of the control mechanism 18, the endless belts 11 and 11a. In synchronism with the gap running, the veneer 10 is loaded into the drying device configured to intermittently move the upper convex heating platen 13 and the upper heating platen 15 up and down via the elevating member 18a in the direction orthogonal to the fibers and heated. And 19 is a scraping member in the figure.

Even when applied to such a type of drying device, as shown in FIG. 6, at the positions of the biconvex heating plates 13 and 14, the endless belts 11 and 11a are located.
Heating surface 13a having a convex shape in the direction orthogonal to the traveling direction of the
Since the heating of 14a is gradually reduced from the central portion of the veneer 10 in the fiber direction toward both ends, the same effect as in the above-mentioned embodiment can be obtained.

Further, the new-type drying device has an advantage that the process length can be shortened as compared with a known type device by adopting a configuration of forming a series of meandering single-plate conveying paths, and further, if necessary. By changing or adding a predetermined member, effective actions and effects can be exerted in addition to the above, but since they are apparent from the publications related to the above-mentioned application, detailed description will be omitted.

As is clear from both of the above-mentioned examples, according to the heating method of the present invention, it is possible to satisfactorily dry a relatively thin veneer. It is effective because the property is significantly improved as compared with the conventional one.

It should be noted that it is effective to set the suitable number of convex heating plates, the arrangement position, etc. according to various conditions such as the initial water content of the veneer, the desired dryness, and the degree of convexity of the convex heating plate. However, it is not necessarily fixed uniformly, and if necessary, all the heating plates may be formed as convex heating plates, or some heating plates and convex heating plates may be exchanged at any time. Although it does not matter, in reality, in a general usage of drying a normal raw veneer to a water content in a range usable for plywood, the difference in drying and shrinkage at the end of drying is Since the generation is relatively slight, as in the above-mentioned Examples, convex heating is mainly performed so that the heating is gradually reduced from the central part in the fiber direction of the veneer toward both ends, mainly in the early stage or middle stage of drying. Even if the board is arranged with emphasis
There was no problem in practical use.

Further, from the viewpoint of uniform drying, it is preferable that the convex heating plates are arranged in pairs on both sides of the single plate as in the above-mentioned Examples, but the present invention is not limited to this, and even if the convex heating plates are Even if only one sheet is fixedly arranged below the veneer conveyance path, the heat loss from the central part of the veneer toward the both ends in the fiber direction due to the interposition of the endless belt. It is effective because the air, which is a conductor, intervenes in a gradually increasing manner and the heating gradually decreases in inverse proportion to it, which is effective. In short, by providing one or more convex heating plates, a corresponding effect can be obtained.

Furthermore, the degree of convexity of the convex heating plate may be appropriately set according to various conditions such as the thickness of the veneer, the initial water content, the desired degree of dryness, etc. The heating surface of the convex heating plate in contact with the heat transfer surface is extremely small due to the rapid transfer of heat, but not only in the direction orthogonal to the running direction of the endless belt, but also in all other directions. Also has a tendency to be deformed into a concave shape, in other words, a concave curved surface.

Therefore, in particular, the heating surface of the convex heating platen, which is located at a portion corresponding to the initial stage of drying, is formed so as to have a somewhat convex shape with respect to the deformation amount with respect to the direction orthogonal to the running direction of the endless belt. Is preferred, and further in all other directions,
It is more preferable to form a slightly convex shape in consideration of the amount of deformation, and as a result, to form a slightly convex curved shape at the beginning. The heating surface of the normal heating plate to be positioned is also formed so as to have a convex shape in every direction in advance, that is, to have a slightly convex curved shape at the beginning, and is flattened as the veneer is heated. It does not matter even if it is configured like this.

Although not shown in the drawings as a specific means for forming the heating surface to have a convex shape, the heating surface of the heating plate is flatly processed in a conventional manner, and then plastically deformed into a desired shape using a press or the like. Or a processing means for flattening the heating surface in a state where the reverse (concave) strain is applied to the heating plate beforehand, and then releasing the strain to restore and deform the convex shape. As illustrated in FIG. 7, the supporting member 20 is fixed side by side on the non-heating surface side opposite to the heating surface 3a of the heating platen 3, and the heating platen 3 is forcibly elasticized by using the pressing member 21 such as a push bolt. In addition to general working means such as assembling means for deforming, when using, for example, high-pressure heating steam as a heat source, the heating plate has different expansion degrees between the heating surface side and the non-heating surface side. Form and expand with the introduction of heating steam so that the heating surface has a convex shape. Permissible instead, short heating surface is sufficient if Teisure the desired convex.

Further, due to the difference in the forming means, etc., when the microscopic heating surface is a curved surface as shown in the examples of FIGS. 1 and 2, the refracting surface as shown in the examples of FIGS. 4 and 5 is used. Although it is not shown in the drawing, or a case where the surface is a composite surface of a bending surface and a refracting surface, which is not shown, in the experiment, since no remarkable difference in heating was observed between them, There is no problem in practical use on either side, but in terms of contact stability,
It is preferable that the center is locally flat or almost flat.

On the other hand, 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. However, it is not necessarily limited to a non-perforated strip, and there are no particular restrictions on the form of members other than the heating plate, including the endless belt drive source and tension mode, or the heating plate control mechanism. However, the heating method according to the present invention can be applied to any intermittent transport type hot plate drying apparatus that dry a single plate by combining a substantially endless belt and a heating plate.

[Brief description of drawings]

The drawings are for explaining the present invention. FIG. 1 is a side view for explaining a drying apparatus applied to the implementation of the heating method according to the present invention, and FIG. 2 is a portion taken along the line AA in FIG. Sectional drawing, FIG. 3 is an operation explanatory view of FIG. 2, FIG. 4 is a side explanatory view of another drying device applied to the implementation of the heating method according to the present invention, and FIG.
The figure is a partial cross-sectional view taken along the line BB in FIG. 4, and FIG.
FIG. 7 is an explanatory view of the operation of the drawing, and FIG. 7 is a front view of the heating plate. 1,1a, 11,11a …… Endless strip, 3,13 …… Upper convex heating plate, 3a, 13
a …… Heating surface of upper convex heating plate, 4,14 …… Lower convex heating plate, 4
a, 14a …… Heating surface of lower convex heating plate, 5,15 …… Upper heating plate, 6,16 …… Lower heating plate, 7,17 …… Drive source, 8,18 …… Control mechanism, 10 …… Veneer

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. In an intermittent transfer type hot plate dryer, at least one of which is provided with a proper number of pairs of heating plates that can be brought into contact with and separated from the endless belt.
At least one heating plate at an arbitrary position is formed in advance as a convex heating plate whose heating surface is convex in the direction orthogonal to the running direction of the endless belt, and the veneer veneer is conveyed in the direction orthogonal to the fiber. By doing so, at the position of the convex heating plate, heating is gradually reduced from the central part in the fiber direction of the veneer veneer toward both ends, and the veneer single plate in the intermittent transfer type hot plate dryer is characterized in that How to heat the plate.