1. Field of the Invention
The present invention relates to a method of producing a veneer for laminated veneer lumber which is widely used for furniture frameworks, structural members for frameworks, steps, windows, doors, flooring and surfaces.
2. Related Art
Laminated veneer lumber (hereinafter abbreviated to as "LVL") having a thickness of about 9 to 70 mm is made of veneers each having a thickness of about 2 to 4 mm which are cut from logs of broad-leaved trees or needle-leaved conifers by means of a rotary lathe or slicer and are laminated and bonded to each other so that the directions of the fibers are in parallel with each other.
For example, a veneer 20a which constitutes such an LVL is produced by a method as follows: a stock material 20 having a thickness of about 1200 to 3000 mm is rotatably chucked by a spindle 21 at the center of opposite end faces thereof as shown in FIG. 2. A rotary lathe blade 22 having a nose angle of about 20.degree. to 23.degree. is provided to enable the stock material 20 to be cut at a thickness of about 2 to 4 mm. The nose bar 23 is arranged so that the front and of the nose bar 23 is positioned above the cutting edge of the rotary lathe blade 22. The stock material 20 is continuously rotated in a given direction represented by an arrow by energizing a spindle driving mechanism 24 which is associated with the spindle 21. The veneer is thus continuously produced by cutting the stock material 20 at a given thickness by the rotary lathe blade 22.
However, since the spindle 21 which rotatably supports the stock material 20 has a diameter which is very much smaller than that of the stock material 22, the spindle 21 is unable to smoothly rotate the stock material 20 unless an output torque from the spindle driving mechanism 24 is large.
The veneer which is cut out from the base material is wavy and is not smooth over the entire surface.
Accordingly, a rotary saw-like drive roll 26 which is provided with a multiplicity of engaging teeth 25 along the outer periphery thereof as shown in FIG. 3 is set in a position equal to or above the nose bar 23. The drive roll 26 is operated simultaneously with the driving of the spindle 21 to start the cutting of the stock material 20. The stock material 20 is caused to be rotated by penetrating the teeth 25 of the drive roll 26 into the stock material 20. When the diameter of the stock material 20 is decreased by the cutting, either of the spindle 21 or the drive roll 26 is turned off. The veneer 20a is produced by cutting the stock material 20 with either one of the spindle 21 or the drive roll 26.
Cutting of the stock material 20 using the spindle 21 together with the rotary saw-like drive roll 26 having a multiplicity of teeth 25 along the outer periphery thereof decreases the necessary output torque of the spindle drive mechanism 24.
Since the cut veneer 20a is punched on the right side thereof by the teeth 25 of the drive roll 26, a tenderizing effect occurs resulting in that a veneer which is relatively smooth over the entire surface thereof can be produced.
However, a multiplicity of punched holes are formed over the entire surface of the cut veneer 20a. In other words, cracks are inevitably formed on the right side of the veneer. The veneer is cut from the base material as if a screen were dispersed from a roll. These cracks will be referred to as "right side cracks". The radial length between the center of the stock material 20 and the cutting edge of the rotary lathe blade 5 differs from the radial length between the center of the stock material 20 and the front end of the nose bar 4.
As a result of this, part of the stock material 20a is deformed in front of the cutting edge of the rotary lathe blade due to lateral compression. Formation of cracks at predetermined intervals on the reverse side of the cut veneer is inevitable as shown in FIGS. 2 and 3. These cracks will be referred to as "reverse side cracks".
In an LVL 10 in which the veneers which are thus produced by the known method are laminated and bonded to each other with a bonding agent, the veneers 10a, 10b, 10c, 10d and 10e which constitutes the LVL 10 per se have the reverse side cracks as well as a multiplicity of punched holes on the right side thereof as shown in FIG. 4.
Accordingly, if the LVL 10 comprising laminated such veneers each having cracks on the opposite sides thereof is subjected to cutting or surface curving working by means of a molder, part of the fibers or fiber bundle remains on the cut or worked surface, resulting in wool or fuzzy grains on the surface thereof.
In an extreme case, fiber bundles are cut away from the surface, resulting in shallow depressions.
Accordingly, in order to coat the LVL for surface finishing, it is necessary to pretreat the cut or worked surface of the LVL by sanding the surface to provide smoothness or filling depressions with putty. Therefore, the LVL is not necessarily advantageous as a lumber product.