JP7575010B2 - Finger joint cutter, wood processed product and its manufacturing method - Google Patents

Description

The present invention relates to a finger joint cutter, a wood processed product and a method for manufacturing the same.

Laminated timber is manufactured by stacking lamina formed by joining finger joints formed by cutting zigzags into the ends of multiple plate materials together vertically (Non-Patent Document 1). It is desirable to have as short a finger joint length (finger length) as possible from the standpoint of reducing processing costs and energy, and reducing cutting waste, but shortening the finger length reduces the relative joint strength. For example, fingers that are shorter than those used in structural laminated timber are used in structural laminated timber.

Here, the finger joints are generally formed by cutting using a blade called a finger joint cutter (e.g., Non-Patent Document 2).

Japanese Agricultural Standards for Laminated Timber (Ministry of Agriculture, Forestry and Fisheries Notification No. 683, March 29, 2018) Kanefusa Co., Ltd., Product information on chip saws, bits, drills, etc., Wood (wood material) processing: Replaceable blade finger cutter, http://www.kanefusa.co.jp/products/001980.html

The present invention was completed in consideration of the above-mentioned circumstances, and the problem to be solved is to provide a finger joint cutter that can form finger joints with a shape that can achieve high strength even if the finger length is shortened. Another problem to be solved is to provide a wood product with a finger joint with a shape that can achieve higher strength than before, and a manufacturing method for the same.

In order to solve the above problems, the inventors conducted various studies on the shape of finger joints. As a result, they discovered that by making the finger joints into a specific shape, high joint strength can be achieved even if the finger length is shortened, and completed the following invention.

The wood product of the present invention, which solves the above problems, has a finger joint with a finger length L of less than 12.0 mm, a scarf slope ratio tan θ of 1/8.8 or less, and a bonding area s per unit cross-sectional area (1 ^mm2 ) in the butt direction of 4.67 ^mm2 or more.

The wood product of the present invention is any one of lamina for structural laminated timber, lamina for cross-laminated timber (CLT), and vertical joint material for wood-frame construction. All of these are expected to be used in areas where large external forces may be applied, and therefore require high strength.

The finger joint cutter of the present invention, which solves the above problems, is a finger joint cutter that cuts the workpiece by rotating around a rotation axis.

The finger joint cutter of the present invention has a cross-sectional shape on a plane including the rotation axis of a solid formed by rotating the blade part once around the rotation axis, the outer shape of the cross-sectional shape on a plane including the pitch direction and length direction of the finger of the finger joint in the wood product of the present invention. A typical example of the configuration has a cylindrical main body with multiple blade parts formed on the outer peripheral surface of the cylinder, and is used as a finger joint cutter by rotating it around the central axis of the cylinder constituting the main body as the rotation axis.

The manufacturing method of the present invention for solving the above problems includes a finger forming step of cutting the workpiece using the finger joint cutter of the present invention to form the fingers. In this case, the feed amount per blade is 0.5 mm or more and 1.75 mm or less.

The wood product of the present invention has high strength despite the presence of vertical joints made by finger joints because of the above-mentioned configuration. The finger joint cutter of the present invention and the manufacturing method of the wood product of the present invention have the above-mentioned configuration, and therefore it is possible to efficiently manufacture the wood product of the present invention.

1 is a schematic diagram of a wood product according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a finger joint cutter according to the present embodiment. FIG. 2 is a schematic diagram of a finger joint cutter according to the present embodiment. FIG. 2 is a schematic diagram of a finger joint cutter according to the present embodiment. 1 is a graph showing the relationship between adhesive area s per unit area and tensile strength in a test sample in this example. 1 is a graph showing the relationship between adhesive area s per unit area and bending strength in a test sample in this embodiment.

The wood product and its manufacturing method and finger joint cutter of the present invention will be described in detail below based on the embodiment. The wood product of this embodiment is any one of lamina for structural laminated timber, lamina for cross-laminated timber (CLT), and vertical joint material for frame wall construction. All of these are made by joining boards such as sawn boards by vertical joints (jointing in the direction of the wood fibers). The vertical joints are made by butting finger joints formed on the joint surfaces. The structural laminated timber lamina and the cross-laminated timber lamina are stacked in the thickness direction to form the laminated timber and CLT. The drawings used for the explanation in this embodiment are schematic diagrams, and the individual dimensions, relative positions, number of individual elements, etc. can be changed as appropriate. In this specification, unless otherwise specified, mm is used as the unit of length and ^mm2 is used as the unit of area.

(Wood products)
The woodworked product of this embodiment will be described with reference to FIG. 1. As shown in FIG. 1, the woodworked product of this embodiment is joined between a first member 10 and a second member 20 by a finger joint. The width direction of the figure (the direction of the arrow corresponding to P in the figure: hereinafter referred to as "P direction") at both ends is omitted. In addition, in FIG. 1, there are fingers that are not engaged by butting (fingers 13, 14), but this is for convenience, and such unengaged fingers may or may not exist. From the viewpoint of improving strength, it is preferable to have fewer fingers that are not involved in the joint. For example, it is preferable that the number of fingers formed on each of the first member 10 and the second member 20 is the same, or the number of fingers on one side is the number of fingers on the other side + 1.

The vertical direction of the first member 10 and the second member 20 in the figure (the direction of the arrow corresponding to L in the figure: hereafter referred to as the "L direction") is approximately the direction of the wood fibers. There are no particular limitations on the type of wood constituting the first member 10 and the second member 20. The type is selected appropriately depending on the strength, appearance, etc. required for the application in which the wood product is to be used.

The first member 10 is manufactured by cutting a sawn board and has fingers 11 to 14. The fingers 11 to 14 have a constant cross-sectional shape in the vertical direction of the plane of the drawing, and the cross-sectional shape is preferably a trapezoid whose width narrows toward the top of the drawing, and is preferably an approximately isosceles trapezoid.

Here, the shape of the sawn board is specified in three directions: the grain direction of the wood (longitudinal direction), the width direction, which is the longer direction among the directions perpendicular to the grain direction of the wood, and the thickness direction, which is a direction perpendicular to the grain direction and the width direction of the wood and is shorter than the width direction. The direction in which fingers 11-14 are formed on the sawn board may be such that the width direction coincides with the P direction, or that the thickness direction coincides with the P direction. Also, it may be such that the direction does not coincide with both the width direction and the thickness direction, but coincides with an oblique direction.

The tip thickness of the trapezoid (finger tip thickness) is t1 (mm). Fingers 11 to 14 are arranged with a gap (finger bottom width) t2 (mm) between adjacent fingers. In other words, fingers 11 to 14 are arranged at a finger pitch P (mm) calculated by (the lower thickness of fingers 11 to 14 in the L direction) + (finger bottom width t2).

Fingers 11 to 14 have scarves b, which are parts b that correspond to the legs of the isosceles trapezoid formed by fingers 11 to 14. The shape of scarf b is determined by the "scarf inclination ratio: tan θ", which is expressed as the angle θ with the L direction. It is preferable that the surface of scarf b is smooth.

The finger joint in the processed wood product of this embodiment has the following configuration: finger length L is less than 12 mm, scarf inclination ratio tan θ is 1/8.8 or less, and adhesive area s per unit cross-sectional area (1 ^mm2 ) in the butt direction is 4.67 ^mm2 or more. Preferred upper limits for L include 11 mm, 10.5 mm, 10 mm, 9 mm, 8 mm, 7 mm, 6.5 mm, 6.0 mm, 5.5 mm, and 5.0 mm. Preferred lower limit is 4 mm.

As for tan θ, preferred upper limits include 1/9, 1/10, 1/11, and 1/12. As for the adhesive area s per unit cross-sectional area (1 mm ² ) in the butt direction, preferred lower limits include 5.0 mm ² , 5.5 ^mm 2 , 6.0 mm ² , 6.5 mm ² , 7.0 mm ² , and 7.5 mm ² .

Here, the cross-sectional area in the butt direction is the cross-sectional area in the P direction of the first member 10 in Figure 1. Usually, the first member 10 and the second member 20 are members having the same cross-sectional shape in the butt direction. However, when joining the first member 10 and the second member 20 to manufacture a wood product, it is not necessarily necessary that the cross-sectional shapes in the butt direction of the two members are the same. Even if the two members do not have the same cross-sectional shape, the cross-sectional shape can be changed (for example, made the same cross-sectional shape) by processing them with a planer or the like after joining.

The adhesive area s is the area of the part that contacts the finger of the second member 20 that is to be butted. In other words, it is the sum of the areas of the parts that are adhered in the direction in which the first member 10 is butted against the second member 20. For example, it is the area excluding the area of part A that is not involved in the adhesion on the surface of the scarf of fingers 11 to 14. Note that if butt portions are formed on both ends where fingers 11 to 14 are arranged, the butt portions are not included in the adhesive area.

To increase the adhesive area s, increase L, decrease P, and decrease the finger tip thickness t1 and finger bottom width t2. To increase the number of fingers, decrease the scarf slope ratio tan θ. When P is the same, in order to increase the adhesive area, the scarf slope ratio tan θ should be as large as possible within one pitch (the scarf slope ratio tan θ can be increased even if P is the same by decreasing t1 and t2). Increasing the adhesive area s can improve the strength of the joint.

The relationship between the finger length L and the finger pitch P is not particularly limited, but it is preferable that L/P is greater than 2.19, more preferably 3.0 or greater, and even more preferably 3.2 or greater. The relationship between the finger tip thickness t1 and the finger pitch P is also not particularly limited, but it is preferable that t1/P is 0.28 or less, and even more preferably 0.18 or less.

The second member 20 also has fingers formed similar to those of the first member 10. In particular, since it is desirable that the finger joints of the first member 10 and the second member 20 have complementary shapes, the preferred shape of the second member 20 is the same as that described for the first member 10.

(Finger joint cutter)
The finger joint cutter of this embodiment can form a finger joint by cutting the workpiece by rotation. For example, as shown in Fig. 2, it can be composed of a cylindrical main body 30 (the central axis of the cylinder is the rotation axis) and a blade part 40 arranged on the outer circumferential surface of the main body 30.

The figure shows a perspective view of an example of a finger joint cutter in which multiple blade sections 40 are arranged in a single row on the outer peripheral surface of the main body section 30 in the axial direction of the main body section 30, while Figures 3A and 3B show perspective views of an example of a finger joint cutter in which multiple blade sections 40 are arranged in double rows in the axial direction of the main body section 30. Note that the finger joint cutters shown in Figures 2 and 3 have different configurations, but are given the same reference numerals as the main body section 30 and the blade sections 40.

There are no particular limitations on the rotational diameter (cutting arc diameter) of the path of the tip of the blade portion 40 when the finger joint cutter is used (rotated). For example, when considering the reuse of conventional equipment (equipment using conventional finger joint cutters), it is preferable to set it to the same as that of conventional finger joint cutters (for example, about φ150 mm to φ280 mm). In addition, it is preferable to subtract from the radius of the cutting arc diameter the radial length of the blade portion 40, which is about 8 mm to 15 mm, for the diameter of the main body portion 30.

In addition, the main body 30 is made up of multiple parts, which improves maintainability. For example, it can be divided in the axial direction of the cylinder, in the circumferential direction, in the radial direction, or in a combination of these division directions. In the finger joint cutter shown in Figures 2 and 3, the blade 40 is fastened by a blade fastening bolt 41 so that it can be removed freely.

The blade portion 40 has a cross-sectional shape in a plane including the axis of rotation of the path formed by rotating the finger joint cutter of this embodiment once as in use, which is approximately complementary to the cross-sectional shape in a plane including the length direction L and pitch direction P of the finger in the woodwork product of this embodiment described above.

In other words, when there is one blade, the shape of that blade is generally complementary to the shape of the finger joint. When there are multiple blades, the combined shape of the multiple blades can be generally complementary to the shape of the finger joint. Even if the shapes of all of the blades of the finger joint cutter are not generally complementary to the shape of the finger joint, it is sufficient that the partial shape of the part that comes into contact with the workpiece for cutting is generally complementary.

In the case where multiple blades are provided, they can be distributed in the circumferential direction on the outer circumferential surface of the main body 30 or in the direction of the rotation axis. The blades 40 are fixed to the main body 30, and the fixing method can be either an easily removable method or a method that cannot be easily removed, such as welding.

The material constituting the blade can be a material used for general woodworking blades. For example, the blade can be made of a matrix high-speed steel or a base material made of a cemented carbide containing 0.5% to 0.8% C, 4% to 6% Cr, 0% to 2% W, 2% to 6% Mo, 1% to 2% V, and Fe as the main component, based on the total mass. Furthermore, a hard film can be formed on the surface of the base material. The hard film can be formed by PVD, containing at least Cr and N. The surface roughness of the cutting edge is preferably Ra 0.30 μm or less, and more preferably Ra 0.10 μm or less.

(Manufacturing method of wood processed products)
The method for manufacturing a processed wood product of this embodiment includes a finger forming step of cutting a workpiece with the finger joint cutter of this embodiment to form a finger joint consisting of fingers in the processed wood product of this embodiment. The processed wood product of this embodiment can be manufactured without using the method for manufacturing a processed wood product of this embodiment, but it is preferable to use the method for manufacturing a processed wood product of this embodiment. Here, the feed amount per blade is 0.5 mm or more and 1.75 mm or less.

The two components are bonded and joined by butting and interlocking the finger joints formed in the finger forming process. An appropriate adhesive is used for bonding. Examples of adhesives include aqueous polymer-isocyanate adhesives, resorcinol resin adhesives, resorcinol-phenol co-condensation resin adhesives, melamine resin adhesives, melamine-urea co-condensation resin adhesives, one-liquid polyurethane adhesives, and vinyl acetate resin emulsion adhesives. It is desirable to apply an appropriate pressure during bonding, an example of which is 4 MPa or more, and preferably 8 MPa or more.

Test 1
The wood product of the present invention and the manufacturing method thereof will be described based on examples using two cedar materials, grades L50 and L80.

- Manufacturing of test samples For each of the cedars (grades L50 and L80), a pair of test pieces (each 125 mm wide, 33 mm thick, and 435 mm long) with finger joints with the finger length L, finger pitch P, finger tip thickness t1, finger bottom width t2, and bonding area s per unit cross-sectional area (1 ^mm2 ) values shown in Table 1 were prepared, and the finger joints were butted together and bonded. Resorcinol resin was used as the adhesive, and the pieces were pressed for 10 seconds while applying an external force of 5 to 10 MPa in the butting direction, and then held for one month in an atmosphere of 20°C and relative humidity of 55 to 60%. Then, the four sides were machined with a planer to produce test samples with a width of 120 mm, a thickness of 29 mm, and a length of approximately 840 mm. In manufacturing the test samples, a finger joint cutter having a shape complementary to the shape of the formed fingers was manufactured and cut (finger formation process). The tensile strength and bending strength of each of the obtained test samples were measured. The results are also shown in Table 1. Note that the strength of the wood itself is shown as test sample 0.

As is clear from Table 1, it was confirmed that the tensile strength tends to increase as L/P and the adhesive area per unit cross-sectional area s increase. It was found that even higher tensile strength can be achieved when L/P is more than 2.19. Even higher tensile strength can be achieved when the adhesive area per unit cross-sectional area s is 4.4 ^mm2 or more, and a high strength that meets both the L80 and L50 standards was shown when it was 7.09 mm2 or ^more .

The smaller the t1/P, the higher the tensile strength. It was found that even higher tensile strength could be achieved by making t1/P less than 0.28, or even less than 0.20 or 0.18. High tensile strength could be obtained with tan θ of 1/8.8 or less.

Here, the average value standards for strength performance of lamina for structural laminated timber in the JAS standard for laminated timber are tensile strength of 16.5 N/ ^mm2 for L50 and 21.5 N/ ^mm2 for L80, and bending strength of 27.0 N/ ^mm2 for L50 and 36.0 N/ ^mm2 for L80. Compared with these average value standards, the underlined strength values are higher, and test samples 1 to 3 and 6 made with L50, and test samples 1 and 2 made with L80 met these average value standards.

When manufacturing another finger joint cutter with reference to Table 1, the finger length L, finger pitch P, finger tip thickness t1, finger bottom width t2, and adhesive area s shown in Table 1 can be increased or decreased. The range of increase or decrease can be about 1%, 2%, 5%, or 10%.

An approximation curve (logarithmic approximation) showing the relationship between the adhesive area s per unit cross-sectional area and strength was derived from the experimental results. The derived results are shown in Figure 4 (tensile strength) and Figure 5 (flexural strength). In the figures, the solid line corresponds to grade L50 for structural laminated timber laminas in the JAS standard for laminated timber, and the dashed line corresponds to L80. Auxiliary lines are drawn so that it is possible to see the adhesive area that corresponds to the average standard strength of the strength performance of structural laminated timber laminas in the above-mentioned JAS standard for laminated timber.

As is clear from Figures 4 and 5, the adhesive areas that satisfy the average value standards for the strength performance of structural laminated timber laminas in the JAS standard for laminated timber are 3.24 ^mm2 for tensile strength L50 and 3.95 ^mm2 for L80, and 3.27 ^mm2 for bending strength L50 and 4.67 ^mm2 for L80. Therefore, it was found that in order for structural laminated timber laminas to satisfy L80 in the JAS standard for laminated timber, the adhesive area per unit area s should preferably be 4.67 ^mm2 or more.

10: First member 11-14: Fingers 20: Second member 21-22: Fingers L: Finger length P: Finger pitch t1: Finger tip thickness t2: Finger bottom width s: Bonding area per unit cross-sectional area b: Finger scarf θ: Scarf inclination angle 30: Main body 40: Blade

Claims (6)

The finger joint is made of wood joined vertically with a finger joint, the finger length L being less than 10.5 mm or more than 4 mm, the scarf slope ratio tanθ being 1/10 or less, the adhesive area s per unit cross-sectional area (1 ^mm2 ) in the butt joint direction being 6.0 mm2 or ^more , and the finger length L (mm)/finger pitch P (mm) being 3.0 or more .
A wood product that is any of the following: lamina for structural laminated timber, lamina for cross-laminated timber (CLT), and vertical joint material for frame construction structures. 2. The wood product according to claim 1, wherein the finger length L is 8 mm or less . 3. The wood product according to claim 1, wherein the finger tip thickness t1 (mm)/finger pitch P (mm) is 0.18 or less. A finger joint cutter that cuts a workpiece by rotating around a rotation axis,
A finger joint cutter, wherein the outer shape of a cross-sectional shape of a solid formed by rotating the blade portion once around the rotation axis, in a plane including the rotation axis, has a shape that is approximately complementary to the cross-sectional shape of the finger joint of any one of claims 1 to 3 , in a plane including the pitch direction and length direction of the fingers. The blade portion is
A base material made of matrix high speed steel or cemented carbide containing, based on the total mass, 0.5% or more and 0.8% or less of C, 4% or more and 6% or less of Cr, 0% or more and 2% or less of W, 2% or more and 6% or less of Mo, 1% or more and 2% or less of V, and Fe as a main component;
A hard coating containing at least Cr and N and formed on the surface by PVD;
The finger joint cutter according to claim 4 , comprising: The method includes a finger forming step of cutting the workpiece to form the fingers using the finger joint cutter according to claim 4 or 5 ,
The feed amount per blade is 0.5 mm or more and 1.75 mm or less.
Manufacturing method for wood products.

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