The present invention relates to a method and apparatus for manufacturing laminated wood, the method being of the type set forth in the preamble of Claim 1 and the apparatus bein of the type set forth in the preamble of Claim 7.

The laminated wood currently in general use is manufactured by scarfing the approximately 3-nun-thick, rotary-cut plies of wood in the center by means of butt joints. The approximately 1.5-mm- hick outer plies for their part are scarfed by means of lap joints.

Another laminated wood structure is one in which the plies, all of uniform thickness, are scarfed by means of lap joints. This product is sold under the trademark "Micro-Lam" .

Plywood has long been made by scarfing the veneer sheets in a separate scarfing press, whereafter they are glued one on top of the other in a separate work stage. The scarfing is carried out by beveling the ends of the venee sheets at an inclination of 1:20 - 1:10, by spreading glue on the inclined joint surface, and by running the thus secured joint through a press, which presses the joint area over its entire width and somewhat beyond the joint area in the longitudinal direction. The glue used is hot-setting plywood glue, the pressure of the press being very high and the temperature also high. Such scarfing corresponds to the normal plywood manufacturing process.

The object of the present invention is to simplify the process of manufacturing laminated wood in such a way that the gluing of the veneer sheets end to end is carried out

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during the actual laminated-wood manufacturing process. A bevel-sawn joint surface is used for the joining.

As a consequence of the simple manufacturing method, the product is better than a product made by prior manufacturing methods. A product made using butt joints always has at least a few holes which go all tne way through owing to the butt joint failing for one reason or another. Therefore the structure is poor in terms of thermal economy, since thermal energy escapes through the holes produced.

Another advantage gained is a clearly improved appearance owing to the- bevel joint. A lap joint is very unattractive, especially in structures which are left visible in the place of installation. A product scarfed using bevel join-cs is also superior as regards dimensional precision, especially as compared with a product scarfed using lap joints. A product according to the invention can be manufactured from veneer sheets of ^' various lengths, altnoug at each manufacturing stage of one and the same product the veneer sheets are of the same length. For example, "Micro-Lam" must be manufactured, furthermore, from sheets at least 2.5 m long, because otherwise the process cannot be controlled. As regards its loading strength, laminated wood scarfed using bevel joints is clearly better than the above-mentioned products, since the bevel joint is structurally stronger. The tolerance to stacking of a bevel jointed product is also greater than that of the former products, and for this reason the product is especially suitable for highly automated manufacture.

The above advantages are gained by means of the method and apparatus, the characteristics of which are given in the accompanying claims.

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The invention is described below in greater detail with reference to the accompanying drawings, in which

Figure 1 is a schematic and greatly simplified side view of the manufacturing method and apparatus according to the invention, and

Figure 2 shows a side view of the product according to the invention, during the manufacturing stage.

In Figure 1, numeral 1 indicates the veneer storage. From this storage a veneer sheet is transferred via a conveyor and a guide system to a bevel-sawing table 2 having a bevel-saw blade 3 , which saws in a direction transverse to the grain of the veneer. From this point the sawn veneer sheet continues its journey to a length calibration table 4, where so-called scribing blades 15 calibrate the length to a certain dimension and at the same time remove the very thin and usually uneven extreme end of the bevel produced during the bevel sawing at each end of the veneer sheet. Thereafter the veneer sheet travels further to a gluing table 5, where glue spreader 6 spreads the glue on the upper surface of the veneer and also on the upward bevel surface. Even though in the figure the glue spreader is depicted as a nozzle through which the glue is sprayed onto the surface, the spreading can be, for example, by means of a roller or any other known method. After the spreading of the glue the veneer sheet continues its journey to a series of three conveyors 7, 8, 9, the conveyors being in succession and -overlappingly movable one below the other, but in such a way that the first conveyor 7 is fixed. Reference numeral 10 indicates an assembling table, on which the laminated wood is assembled before it passes to the hot press.

The assembling is carried out as follows. A veneer sheet

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which comes from glue spreading, arrives on the conveyor 7, from where it continues its journey to the conveyor 8 and further to the conveyor 9. The assembling of laminated wood begins at the extreme right-hand side edge of the product. Two lengths of veneer are assembled for the lowes ply, whereafter the second ply is started with one length of veneer, and thereafter the third length of veneer for the first ply, the second length of veneer for the second ply and the first length of veneer for the third ply are assembled. This procedure is continued until the total thickness of the laminated wood is reached. Thus the extre left-hand side edge of the laminated-wood product is reached, where the last length of veneer is assembled in place. It is evident that the upper surface of the topmost ply must be without glue, and for this reason the glue spreader 6 spreads glue to only the joint surface of the topmost ply, or glue is spread to the joint surface in a separate device.

The basic principle of the invention is the ^* idea how a bevel joint can be caused to settle in the correct place with precision. Thus there was the idea that the arriving veneer sheets are ru ,_against an assembling stop 12, the stop moving automatically to the correct place, which is straight above that half of the lap joint which is face up. At this stage the veneer sheet is gripped by gripping members 11, which press the ply in place over the other half of the joint, guiding the veneer sheet to the point determined by the assembling stop 12. Thereafter the product is pressed by a preliminary press 13, which is subsequent to the assembling stop and at a distance from it, and thereby the cohesion of the product immediately after each ply is positioned is ensured.

It should be noted that the veneer sheets can be positioned

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by many different methods. One of them was described above by way of example. However, current technology has introduced, for example, optical and electrical devices for use in the art, and by means of these devices it is very practical to arrange the stopping of the veneer sheet at its assembling point in accordance with the invention. On the other hand, it should also be pointed out that instead of gripping the veneer sheet by means of some gripping device, the veneer sheet can be positioned without gripping it, for example by using a suitable pressing member or several members. ^' In practice, optical or electrical operation is more practicable than purely mechanical operation. Of course, various combinations of the above-menutioned operations are possible.

V7hen the last veneer sheet has been brought in place, the product is transferred to the hot press which sets the glue and thereby completes the product. The cutting of the product to a predetermined size is carried out only after the product is finished.

The joints in the plies can be located in accordance with the invention at intervals of about 10 cm from each other. The method and apparatus according to the invention are automated in such a manner that the stop moves automaticall in the desired direction to wait for the next arriving veneer sheet at the intended point of placement.

Also, the whole process works automatically in such a way that it needs to be interfered with only when some disturbance appears in it. By using veneer sheets of uniform length and calibrated precisely to their length, the laminated wood obtained is such that the joints in adjacent plies are not very close to each other. Thus the laminated wood will be strong.

Even though the basic idea of the invention is described above in a highly simplified form, omitting all those parts which are not of primary importance for the understanding of the invention, the invention is, however, to be understood in the extent of the protective scope of the claims. Thus, for example, none of the conveyor units are shown in Figure 1, and the various process stages are indicated only by lines, but the essential characteristics are, however, shown schematically in the figures. In particular, the schematic representation of the assembling stop 12 and the gripping member 11 must be observed. These members can be designed in a manner obvious to an expert in the art, and this manner is not dealt with in any way in greater detail in this description.

The inclination of the bevel joint is determined by many factors, such as the type of wood used, the thickness of the ply, the beveling technique, and other practical conditions. Therefore it is very difficult to give any absolute values for the inclination. However, about 1:1 in the maximum inclination and about 1 30 in the minimum inclination can perhaps be regarded as the extreme values. However, the inclination used in the most common cases is about 1:10 - 1:20, i.e. approximately the same inclina¬ tion as is used when manufacturing plywood, in which the plies are secured to each other in a separate work stage.

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