Workpiece with a finger wedge assembly and method for producing such workpieces

Abstract

The workpieces have a finger joint arrangement (3) at one end, comprising adjacent finger joints (5) separated from each other by grooves (7). The grooves (7) have a groove base (7a) and are bounded by side walls that converge towards the groove base (7a). The finger joints (5) are provided at their free ends with at least one transverse groove (8) extending from the free end over at least a portion of the height of the finger joints (5) and passing through them transversely to their longitudinal direction. In one machining operation, finger joints (5) are inserted into the end face of the workpiece (1). In another machining operation, at least one transverse groove (8) is cut into the finger joints (5) transversely to their main direction, extending from the free end of the finger joints (5).

Description

[0001] The invention relates to a workpiece with a finger joint arrangement according to the preamble of claim 1 and to a method for manufacturing such workpieces according to the preamble of claim 9.

[0002] It is known to join elongated wooden boards firmly together using finger joints. The finger joint forms a self-centering or self-locking end connection, created by milling a series of identical, symmetrical, tapered finger joints into the ends of the boards using a finger joint cutter, which are then glued together.

[0003] Fig. 8 Figure 1 shows such a finger joint with the interlocking finger joints 50 of the connected workpieces 1. The finger joints 50 have a finger length Ij. Also shown are the finger spacing p, the flank inclination α, the finger clearance It and the width bt of the finger tip.

[0004] Finger joints are used for a wide variety of woods. Spruce, in particular, is of great economic importance in timber construction for load-bearing applications. Finger jointing for load-bearing applications is standardized for softwoods (EN 15497 / EN 14080). These standardized finger joints are sufficient for softwood products. Finger joints are characterized by a very large bonding surface, high strength, high dimensional accuracy, and straightforward manufacturing. Even with high-quality softwood, the strength of a finger joint is nearly equivalent to that of unfingered wood.

[0005] Hardwoods can generally achieve significantly higher strengths than softwoods, which places higher demands on finger joints. In hardwood construction products, high-performance materials, or brittle materials, finger joints are often a weak point. The strength of these materials cannot be adequately transferred via finger joints. A frequent cause of failure, either under mechanical stress or even during manufacturing, is stress concentration in the finger joint root 51. This finger joint clearance It leads to a reduction in cross-section and also to a lack of contact between the joining parts. The lack of finger joint clearance It can lead to splitting of the wood in the finger joint root 51 or prevent the clamping pressure from acting on the finger joint flanks to form a high-quality bond between the finger joints.

[0006] The invention is therefore based on the objective of designing the generic workpiece and the generic method in such a way that the strength, economy, manufacturability and precision as well as the aesthetics of the finger joint are optimized and improved.

[0007] This problem is solved according to the invention for the generic workpiece with the characterizing features of claim 1 and for the generic method with the characterizing features of claim 9.

[0008] The finger joint arrangement with its finger joints and transverse groove is easy and precise to manufacture. Despite the transverse groove, good self-locking is achieved when the finger joints of the workpieces to be joined interlock. After pressing the finger joint, a sufficiently high initial strength is achieved. The finger play can be kept to a minimum and is generally less than with a conventional finger joint profile at the same pressing pressure. Only isolated cracks are to be expected in the finger joint, and the tendency to crack is lower than with current finger joint designs. The transverse grooves can be used to completely fill the finger joint with adhesive during pressing. The adhesive can optionally be used as a reinforcing material within the finger joint.

[0009] The workpieces with the finger joints and transverse grooves can be made of hardwood, whereby the design according to the invention ensures that the strength of the finger joint connection is higher than with the current finger joint connection and thus the mechanical properties of the hardwoods can be optimally utilized for the finger-jointed workpiece.

[0010] Finger joints with transverse grooves generally have higher strengths, such as tensile and bending strengths, than conventional finger joint profiles without transverse grooves.

[0011] The workpieces according to the invention can be used, for example, in hardwood construction products (e.g., glulam, cross-laminated timber, structural timber) made of softwood and / or hardwood. High-performance materials, such as veneer materials, hybrid materials, or modified materials, for example, thermally modified wood and chemically modified wood, are also suitable as materials for the workpieces. The workpieces according to the invention can also be used for wood products in outdoor applications.

[0012] Advantageously, the width of the transverse groove decreases towards the groove base, preferably continuously. This design contributes advantageously to high strength and low cracking during machining as well as in the use of the finger joint.

[0013] Depending on the requirements and / or type of workpiece, the width of the transverse groove can remain the same along its length.

[0014] The transverse groove is advantageously bounded by two side walls that converge towards the bottom of the groove.

[0015] The side walls of the transverse groove are advantageously flat, resulting in simple manufacturing.

[0016] Depending on the application of the workpieces, the side walls may not be flat, for example they may have a wave shape.

[0017] If the transverse groove is advantageously designed to be mirror-symmetrical to its longitudinal direction, a uniformly advantageous effect of the transverse groove results with regard to the strength of the finger joint.

[0018] It is entirely possible, if the application and / or the workpiece require it, to design the transverse groove not to be mirror-symmetrical to its longitudinal direction.

[0019] In principle, the side walls can have any design with regard to the function of the transverse groove.

[0020] In an advantageous design, the transverse grooves of adjacent finger joints are aligned with each other. This creates a continuous groove across the width of the workpiece face in the finger joint.

[0021] Depending on the material used for the workpiece and / or the later application of the workpiece, the transverse grooves of all finger joints can have the same length and / or the same width.

[0022] Furthermore, it is possible that the transverse grooves of a finger joint may have different lengths and / or different shapes and / or different widths.

[0023] It is also possible to vary the design of the transverse grooves from finger joint to finger joint and / or the design of the transverse grooves themselves within the finger joint arrangement. In this way, the finger joint arrangement can be optimally adapted to the intended application as well as the workpiece material.

[0024] If the transverse grooves within the finger joint arrangement are advantageously at least partially, preferably completely, filled with adhesive, the adhesive can be used as a reinforcing material for the finger joint.

[0025] In the inventive method, the finger joint arrangements are produced on both end faces of the workpieces in two machining operations performed transversely to each other. In one machining operation, the finger joints are produced. In the other machining operation, the transverse grooves are produced. These crosswise machining operations allow the finger joint arrangement to be produced on the end faces of the workpiece in a simple manner and with minimal machine effort. The sequence of the two machining operations is arbitrary.

[0026] Advantageously, the two processing operations are carried out in directions that are perpendicular to each other.

[0027] The machining operations can also be carried out in directions other than 90°. The machining directions do not have to be linear, but can, for example, be curved.

[0028] A simple, reliable and cost-effective manufacturing process is achieved when the finger joints and / or the transverse grooves are produced by a milling operation.

[0029] Other possibilities include laser cutting, sawing, embossing, scoring, and the like.

[0030] In one possible process, the workpiece is rotated around its longitudinal axis before the second machining operation. This results in the transverse groove penetrating the contour previously produced in the first machining operation during the second operation.

[0031] In an advantageous embodiment, after the second machining operation, the workpiece is rotated back to its initial position about its longitudinal axis. Furthermore, the workpiece is pivoted about its transverse axis so that the other, previously unmachined end face of the workpiece can also be provided with the finger joints and transverse grooves by the two machining operations.

[0032] In another advantageous method, both end faces of the workpiece are machined simultaneously. In this case, two passes of the workpieces through the machine are not necessary.

[0033] To ensure precise production of the finger joint arrangement, it is advantageous to machine the end faces of the workpieces before processing. This allows the end faces to be produced flat and at right angles, enabling the subsequent precise machining of the finger joints and cross grooves.

[0034] In an advantageous method, the end faces of the workpieces, which are provided with the finger joint arrangements, are coated with adhesive on one or both sides. This allows the workpieces to be immediately and firmly joined together via the finger joint arrangements.

[0035] The subject matter of the application is not only defined by the subject matter of the individual patent claims, but also by all information and features disclosed in the drawings and the description. These are claimed as essential to the invention, even if they are not explicitly stated in the claims, insofar as they are novel, individually or in combination, compared to the prior art.

[0036] Further features of the invention will become apparent from the further claims, the description and the drawings.

[0037] The invention is explained in more detail with reference to an embodiment illustrated in the drawings. The drawings show... Fig. 1 shows a schematic representation of the production of a finger joint arrangement on the end face of a workpiece according to the invention, Fig. 2 shows a perspective view of a finger joint arrangement of the workpiece according to the invention, Fig. 3 shows a representation corresponding to Fig. 2 A further embodiment of a finger joint arrangement of the workpiece according to the invention, Fig. 4 in perspective view two workpieces to be firmly joined together via their finger joint arrangements before joining, Fig. 4 the workpieces according to Fig. 4 After joining with and without adhesive, Fig. 5 in schematic representation a process plan for the production of the workpiece according to the invention, Fig. 5 a in a representation corresponding to Fig. 5 a further flow chart for the manufacture of the workpiece according to the invention, Figs. 6 and 7 in perspective view various embodiments of finger joint arrangements of the workpiece according to the invention, Fig. 8 a finger joint arrangement according to the prior art.

[0038] The workpieces 1 are, for example, boards with a rectangular cross-section. Other cross-sections are, of course, also possible. Each of their end faces 2 is fitted with a finger joint 3. The workpieces 1 are joined together to form a strand via the finger joints 3 on the end faces, in which the workpieces 1 lie one behind the other lengthwise and are joined at their ends. The strand can be cut into individual boards of the desired length using at least one saw.

[0039] A wide variety of materials are suitable for finger joint arrangement 3. Softwood, hardwood, and wood construction products, such as glulam, can be finger jointed using arrangement 3. Other suitable materials include engineered wood products, high-performance materials such as veneer, hybrid materials, and modified materials such as thermally modified wood and chemically modified wood.

[0040] In the strand, the workpieces 1, which are placed one behind the other, are firmly joined together via the finger joint arrangement 3. The finger joint arrangements 3 interlock in such a way that a continuous, gapless strand is formed, in which the interlocking finger joint arrangements 3 of the consecutive wooden workpieces 1 are glued together.

[0041] In Fig. 1 The schematic representation shows the production of the finger joint arrangement 3. The workpiece 1 is first milled on its end face 2 so that adjacent finger joints 5 are formed, which extend, for example, over the height 33 of the workpiece 1 ( Fig. 3 The finger joints 5 taper continuously towards their free end. Between the finger joints 5 are grooves 7 into which the finger joints 5 of the adjacent workpiece 1 can engage when the workpieces 1 are joined together lengthwise, one behind the other, to form a strand.

[0042] Transverse grooves 8 are then milled into the finger joints 5 by crosswise machining operations, creating finger joint sections 4 ( Fig. 1 bis 3 ). In Fig. 1 The two processing directions are designated as "horizontal" and "vertical".

[0043] Based on Fig. 3 The finger joint arrangement 3 is described in more detail. The thickness 27 of the finger joints 5, measured in the width direction 6, decreases continuously towards their free end. The transverse grooves 8 have a width 28, which advantageously increases continuously from the groove base 9 towards the exit end 29 of the transverse grooves 8. Such a tapering of the transverse groove 8 is not strictly necessary; the grooves can have any suitable outline shape, for example, they can also be rectangular.

[0044] The transverse grooves 8 penetrate the finger joints 5 in the width direction 6. Due to the wedge-shaped form of the finger joints 5, the width 30 of the transverse grooves 8 decreases continuously towards the exit end 29.

[0045] Each finger joint 5 has several transverse grooves 8, which are advantageously identical in design and equidistant from one another. The transverse grooves 8 are preferably mirror-symmetrical about their longitudinal center plane. If required, the transverse grooves 8, and thus also the finger joint sections 4 between them, can be asymmetrical.

[0046] The transverse grooves 8 of each finger joint 5 have the same length. It is conceivable that the transverse grooves 8 of a single finger joint 5 have different lengths and / or shapes. It is also possible that the transverse grooves 8 of adjacent finger joints 5 have different lengths and / or shapes.

[0047] Preferably, the finger joints 5 with their transverse grooves 8 are of the same design, which allows for simple manufacturing of the finger joint arrangement 3.

[0048] The finger joint sections 4 and the transverse grooves 8 of the finger joint arrangement 3 are arranged in horizontal and vertical rows next to each other or one above the other.

[0049] The transverse grooves 8 are bounded by side walls 10, 11, which can converge towards the groove base 9 and connect at an angle to the outer sides 31, 32 of the finger-joint sections 4. Depending on the shape of the transverse grooves 8, the side walls 10, 11 can also run parallel to each other. The side walls 10, 11 do not have to be flat, but can have any suitable shape.

[0050] The embodiment according to Fig. 2 is basically designed in the same way as the described embodiment according to Fig. 3 The only difference is that the transverse grooves are 8 shorter.

[0051] Based on Fig. 5 The process for manufacturing the finger joint arrangement 3 on the end face of the workpieces 1 is explained in more detail using an example. Manufacturing the workpieces 1 with the finger joint arrangements 3 is possible in a variety of ways. Therefore, the procedure described below should not be understood as a limiting approach.

[0052] The workpieces 1 are, for example, elongated wooden boards that are fed transversely to their longitudinal direction in feed direction 12. First, one end face 2 of the workpiece 1 is machined with a tool 13, which can be, for example, a cutting tool, so that a flat end face is formed.

[0053] If the workpiece 1 already has an end face 2 sufficient for producing the finger joint arrangement 3, machining with the tool 13 is not necessary.

[0054] In the feed direction 12 behind the tool 13 is a milling cutter 14, with which the finger joints 5 are milled into the end face 2 of the workpiece 1 in a vertical milling operation. The finger joints 5 extend over the height 33 of the workpiece 1 ( Fig. 3 ).

[0055] After milling the finger joints 5, the workpiece 1 is rotated about its longitudinal axis 15. The workpiece 1 is now positioned such that its broad sides 16, 17 are parallel to the drawing plane. Next, using a further tool 18, preferably a milling cutter, the end face 2 of the workpiece 1, which is provided with the finger joints 5, is machined so that the transverse grooves 8 are formed in the finger joints 5. The milling cutter 18 has a number of milling discs corresponding to the number of transverse grooves 8.

[0056] After machining by the tool 18, the end face 2 of the workpiece 1 is provided with the finger joint arrangement 3. In a subsequent work step, the finger joint arrangement 3 or the corresponding end face 2 of the workpiece 1 is glued, for which a suitable gluing device 19 is provided.

[0057] After the gluing process, the workpiece 1 is rotated again by 90° about its longitudinal axis 15 and turned about a transverse axis 20, so that the already milled end face 2 is shown in the illustration according to. Fig. 5 The workpiece 1 points downwards. It is transported back to the tool 13 in the transport direction 21, 22. The other, unmachined end face 2 of the workpiece 1 is then machined, if necessary, to create a flat end surface. This end face is then subsequently machined in the same manner as previously described.

[0058] After the second end face 2 has been glued with the gluing device 19, the workpiece 1 is fed in its longitudinal direction in the transport direction 23 to the further processing stage. In this further processing stage, the workpieces 1 are joined together in a known manner by means of their finger joint arrangements 3 on both end faces 2 and pressed together. A workpiece strand is formed, which is sawn into individual parts.

[0059] In the described procedure, the finger joints 5 are first produced in a vertical milling process and then the transverse grooves 8 are introduced into the finger joints 5 in a horizontal milling process.

[0060] How Fig. 5a As shown, it is also possible to first mill the transverse grooves 8 into the end face 2 of the workpiece 1 in a horizontal milling operation and then to produce the finger joints 5 in a vertical milling operation. The workpiece 1 is initially guided so that its broad sides 16, 17 lie in the plane of the drawing.

[0061] As previously described, the cross grooves 8 are created using the milling cutter 18 in the horizontal milling process. If necessary, the end face 2 of the workpiece 2 can be machined beforehand with the tool 13.

[0062] As in the previous procedure, the workpiece 1 is then rotated 90° about its longitudinal axis 15 so that its broad sides 16, 17 are perpendicular to the drawing plane. The finger joints 5 are produced in a vertical milling operation using the milling cutter 14.

[0063] The adhesive is applied to the end face 2 with the finger joint arrangement 3 using the gluing device 19. Following the previous procedure, the workpiece 1 is rotated again by 90° about its longitudinal axis 15 and then turned 180° about its transverse axis 20. The workpiece 1 is then transported through the machine again to produce the finger joint arrangement 3 on the other end face.

[0064] In the procedure according to Fig. 5a The transverse grooves 8 are advantageously visible only inconspicuously on the narrow side of the workpiece 1.

[0065] In both methods, it is advantageous if the gluing of both end faces 2 of the workpiece 1 only takes place after the second pass of the workpiece.

[0066] Basically, it is sufficient to glue only one end face 2 with the finger joint arrangement 3, since the workpieces 1 are connected to each other via the finger joint arrangement 3 with their end faces 2.

[0067] In another possible procedure, the workpieces 1 are not turned by 180°. Then the milling cutters 14, 18 are positioned on the machine in such a way that they can produce the finger joints 5 and the transverse grooves 8 on both end faces 2 without a further machine pass.

[0068] Tools other than milling cutters can also be used to produce the finger joints 5 and the transverse grooves 8. For example, lasers, saws, embossing devices, scoring tools and the like can also be used for production.

[0069] Furthermore, it is possible to produce the finger joint arrangements 3 simultaneously on both end faces 2 during the pass through the machine. The transverse grooves 8 can be produced with the same or different lengths. A second pass of the workpiece 1 through the machine is not required.

[0070] Fig. 6 Figure 1 shows an exemplary finger joint arrangement 3 in which the transverse grooves 8 of one finger joint 5 have the same length, but the transverse grooves of adjacent finger joints 5 have different lengths. In the exemplary embodiment, the length of the transverse grooves 8 decreases from the outer finger joints 5 towards the center of the end faces 2, so that the transverse grooves 8 have their shallowest depth at half the width of the finger joint arrangement 3.

[0071] This design is only an example. The length of the transverse grooves 8 can also vary in other ways.

[0072] Generally speaking, the following applies: Fig. 5 and 5a The described procedure should not be regarded as a restrictive training.

[0073] The described finger joint arrangement 3 is achieved by machining the end faces 2 crosswise to produce the finger joints 5 and the transverse grooves 8. The two machining operations are carried out at an angle to each other, advantageously at a right angle. The purpose of producing the transverse grooves 8 is to achieve a more uniform stress distribution in the finger joint between adjacent workpieces 1.

[0074] Fig. 7 Figure 1 shows as a further example that the transverse grooves 8 lie at an angle α deviating from 90°, here at 30°, to the milling direction of the finger joints 5.

[0075] The described finger joint arrangement 3 with the transverse grooves 8 has the advantage that milling can be carried out almost without tear-out. After pressing the workpieces 1 connected to each other via the finger joint arrangements 3, a high initial strength is achieved. The finger play is generally less than the finger play in conventional finger joint arrangements without transverse grooves at the same pressing pressure. In addition, the tendency to crack is low despite a closed finger joint. After pressing, the transverse grooves 8 can be completely filled with adhesive. The transverse grooves 8 are open towards the broad side 16, 17 of the workpieces 1.

[0076] In contrast, the interlocking finger joints 5 can be seen on the narrow sides 25, 26.

[0077] Fig 4a The image on the right shows, by way of example, the adhesive 24 embedded in the transverse grooves 8 of the finger joints 5. It can completely fill the transverse grooves 8.

[0078] Fig. 4a Figure 1 shows two workpieces 1 firmly connected to each other via their end-face finger joint arrangements 3, wherein the finger joint arrangements 3 of the two workpieces 1 are pressed together in a known manner. In the left figure, the workpieces 1 are firmly connected to each other without adhesive by pressing the finger joint arrangements 3 together. In the right figure, the adhesive 24 is additionally applied between the two finger joint arrangements 3.

[0079] Fig. 4 shows the two workpieces 1 before they are joined together.

[0080] As exemplified from the Fig. 2 and 3 As can be seen, the finger joint arrangement 3 can be adapted to the properties of the material of the respective workpiece 1 by means of different depths of transverse grooves 8.

[0081] Stress concentrations in the area of ​​the finger joint base 51 are reduced. The described design of the finger joint arrangement 3 further inhibits the notch effect of the finger joints 5. A particular advantage is that the adhesive 24 can also be used as a reinforcing material.

[0082] The finger joint arrangement 3 makes it possible to increase the strength of the finger joint connection, and the finger joint arrangement 3 can be manufactured economically, precisely and easily.

[0083] After pressing the finger joint, sufficient initial strength is achieved. Furthermore, it has been shown that finger joint arrangement 3 allows for less finger play than conventional finger joint profiles.

[0084] The transverse grooves 8 act as relief grooves and can be completely filled with the adhesive 24 after the finger joint has been pressed.

[0085] The transverse grooves 8 ensure a uniform stress distribution in the finger joint and can lead to a reduction of the hydraulic pressure in the glue during pressing, both of which result in reduced cracking in the finger base 51.

Claims

1. Workpiece with a finger joint arrangement (3) at one end, comprising adjacent finger joints (5) separated from each other by grooves (7) having a groove base (7a) and bounded by side walls that converge towards the groove base (7a), characterized by the fact that the finger joints (5) are provided at their free ends with at least one transverse groove (8) which extends from the free end over at least a part of the height of the finger joints (5) and penetrates them transversely to their longitudinal direction.

2. Workpiece according to claim 1, characterized by the fact that the width (28) of the transverse groove (8) decreases in the direction towards its groove base (9), preferably continuously, or remains constant.

3. Workpiece according to claim 1 or 2, characterized by the fact that the transverse groove (8) is bounded by two side walls (10, 11) converging towards the base of the groove (9).

4. Workpiece according to one of claims 1 to 3, characterized by the fact thatthe side walls (10, 11) of the transverse groove (8) are flat.

5. Workpiece according to one of claims 1 to 4, characterized by the fact that the transverse groove (8) is formed in a mirror-symmetrical manner to its longitudinal direction.

6. Workpiece according to one of claims 1 to 5, characterized by the fact that the transverse grooves (8) of adjacent finger joints (5) lie aligned one behind the other.

7. Workpiece according to one of claims 1 to 6, characterized by the fact that the transverse grooves (8) of all finger joints (5) have the same length and / or the same width.

8. Workpiece according to one of claims 1 to 7, characterized by the fact that the transverse grooves (8) are at least partially, preferably completely, filled with adhesive (24).

9. Method for producing a workpiece (1) according to one of claims 1 to 8, in which finger joints (5) are introduced into the end face (2) to form a finger joint arrangement (3) in a machining operation, characterized by the fact thatIn another machining operation, at least one transverse groove (8) is introduced into the finger joints (5) transverse to the main direction of the finger joints (5), which extends from the free end of the finger joints (5).

10. Method according to claim 9, characterized by the fact that The two processing operations are carried out in directions that are perpendicular to each other.

11. Method according to claim 9 or 10, characterized by the fact that the finger joints (5) are produced by a milling process.

12. Method according to any one of claims 9 to 11, characterized by the fact that The transverse groove (8) is created by a milling process.

13. Method according to any one of claims 9 to 12, characterized by the fact that the end faces (2) of the workpieces (1) are subjected to a machining process prior to the machining operations.

14. Method according to any one of claims 8 to 13, characterized by the fact that The end faces (2) of the workpieces (1) provided with the finger joint arrangements (3) are glued with adhesive (24).

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