Wood joining structure and method thereof

Abstract: The present invention aims, in a large sized wood made building or other wood made member using field, to provide an adhereing and joining technique of the wood member which is excellent in strenght, beautiful outlook and workability. In joining one side wood (1) and another side wood (2), a plurality of slits (S₁,S₂) are respectively formed to the end portions of the wood desired to be joined such that each corresponding slits of both sides make same surface upon abutting said both end portions, and each other of the wood end portions formed with said slits are fixed by the temporary fixing means to a desired joining state and then an adhesive agent is applied into the interior surfaces of the slits, and the connecting plate (CP) made of reinforced plastic material applied with the adhesive agent on the surfaces thereof is inserted into a gap formed to same flat surfaces by slits of one side wood end portion and slites of another side wood end portion corresponding to this so as to cover over said both slits end then the adhesive agent is hardened whereby each other of the wood end portions are joined and fixed.

Description: FIELD OF THE INVENTION The present invention relates to a joining technique by adhering of wood, and more particularly to a joining technique by adhering method especially exerting an effect in joining toward lengthwise direction or multiple directions of long size material or else in joining toward perpendicular direction. BACKGROUND OF THE INVENTION The wood has been widely used from old days as an optimum material for a building material and furniture from many advantages such as beauty of quality sense, easiness of working, or easiness of obtaining, and capableness of recycling as resources. And, in case of intending to utilize the wood as described above, a matter which has been always a problem from old days to nowadays is a problem of handling how to handle a joining portion between members, in other word, a handling capable of bearing against a stress operating to the joining portions. For instance of building material, nails or metal fittings have been used for the joining of column or girder in a small size house, and bolts, lug screws, drift pins have been used for the joining of trass of a large size building. GB-A-2 245 676 describes also a method for joining a pair of mitred members by forcing a metal connector into preformed slots adjacent the mitred ends. However, in order to join the members without decreasing of strength by these methods, a number of joining materials or large sized metal fittings are required. As a result, problems are occurred that its cost is increased and beautiful appearance is decreased. On the other hand, in accordance with an adhering method, the joining portion can be processed in small and beautiful, but this method is limited to a material that the member size is small as a furniture and a stress for transferring is not so big. In a utilization of an adhering joining in a large wooden building, a great expectation has been had until now, but for a realization of this, an inducement of higher and newer adhesive agent in an adhering strength and a fireproof characteristic and a development of simple and reliable processing technique are indispensable. SUMMARY OF THE INVENTION The present invention aims to solve above-described conventional problems and to this end it is proposed a joining method according to appending claims 1 and 11. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 is a perspective view showing a slit formation in a first preferred embodiment of the present invention, FIG.2 is a perspective view showing a state that two members are temporarily fixed by facing the slit portions each other, FIG.3 is a perspective view showing a process for inserting the connecting plate into the slit portion of joining portion, FIG.4 is a perspective view showing a load test of the lumber joined to a straight direction, FIG.5 is a perspective view showing a slit formation in a second preferred embodiment of the present invention, FIG.6 is a perspective view showing a state that two members are temporarily fixed by facing the slit portions each other, FIG.7 is a perspective view of a case that the slits of different sizes are alternately faced in FIG.5, FIG.8 is a perspective view showing a process for inserting the connecting plate into the slit portions of joining portion in FIG.5, FIG.9 is a perspective view of a case that a size of the connecting plate is made to a half of the slit in FIG.5, FIG.10 is a diagram showing a third embodiment of the present invention, and is a perspective view showing a temporary fixing state in a joining toward rectangular two directions of the lumber, FIG.11 is a perspective view showing a process for inserting the connecting plate into the slit portion in FIG.10, FIG.12 is a perspective view showing a process for winding a sticker tape for a leak prevention of adhexive agent and a holding after inserting the connecting plate in FIG.10, FIG.13 is a perspective view showing a load test of the lumber joined toward rectangular two directions, FIG.14 is a diagram showing a fourth embodiment of the present invention, and is a view of a case for joining a width member(beam member) to a lumber opening of length member(column), and is a perspective view of a temporarily fixed state that two members make the slit portions to be faced, FIG.15 is a view of a case for joining a length member(column) to a lumber opening of a width member(beam member) in the fourth embodiment, FIG.16 is a perspective view showing a process for inserting the connecting plate into the slit portion in FIG.14, FIG.17 is a perspective view showing a process for inserting the connecting plate into the slit portion in FIG.15, FIG.18 is a perspective view showing a compression test of the lumber joined in a C-shape by three members of big cross section, FIG.19 is a side view showing a joining state of various kinds in the joining strength test of fourth embodiment, FIG.20 is a view showing a fifth embodiment of the present invention, and is a perspective view showing a pattern of the lumber end portion and a cut out state of the slit, FIG.21 is a front view showing a joining portion in FIG.19. FIG.22 is a view showing a sixth embodiment of the present invention, and is a perspective view showing each lumber end portion and a cut out state of the slit, FIG.23 is a front view showing a joining portion in FIG.22, FIG.24 is a seventh embodiment of the present invention, and is a perspective view showing a joined state of each lumber end portion and a pattern of the connecting plate, FIG.25 is a view showing an eighth embodiment of the present invention, and is a perspective view showing a joined state of each lumber end portion and a relative relation of the connecting plate, FIG.26 is a view showing a ninth embodiment of the present invention, and is a perspective view showing a joined state of each lumber end portion, FIG.27 is a front view showing a pattern of the connecting plate and a joined state of the lumbers 1, 2, 3 seen from arrow A direction in FIG.26, FIG.28 is a front view showing a pattern of the connecting plate and a joined state of the lumbers 4, 5, 6 seen from arrow B direction in FIG.26, and FIG.29 is a view showing a tenth embodiment of the present invention, and is a perspective view showing a pattern of the connecting plate and a joined state of each lumber end portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG.1 to FIG.4 are views showing a first embodiment, and two members are joined in straight direction in this embodiment. First, the slits S1,S2 are respectively formed by a round saw SM in a direction perpendicular to the end surfaces of the lumbers 1,2 to be joined(refer to FIG.1). The lumber used here is a cryptomeria collective material (5 layers, 100x75), and sizes and patterns of each slit are carried out by three kinds of approximately 2.6mm(thickness or gap width) x 25mm width x 75mm length (lumber thickness), 2.6mm(thichness) x 50mm width x 75mm length (lumber thickness), and 2.6mm(thickness) x 75mm width x 75mm (lumber thickness). (Refer to hereinafter described table 1) Further, the slits are formed by five rows with 20mm gaps, but the row numbers of the slits are suitably determined corresponding to the pattern and size of the lumber. Next, as shown in FIG.2, two lumbers(collective material) 1,2 are made to face each other in lengthwise direction so as to make each slit S1(5 rows) and S2(5 rows) to face each other and continue whereby form same surfaces, a transparent sticker tape T (temporary fixing method) is sticked to both side surfaces and bottom surface excluding top surface of abutting portion (joining portion) of the lumbers 1,2 whereby the lumbers 1,2 are held to a joining state. In this state, as shown in FIG.3, an epoxy resin adhesive agent (it may be an acryl or polyurethane group) is applied into an interior of the slit portion SO of five rows constructed by the respectuve five row slits 1,2 and at the same time, the connecting plate CP applied with same adhesive agent to both surfaces is inserted into the slit portion SO and then they are left in air until the adhesive agent would be hardened. Leakage of the adhesive agent can be prevented by using of the sticker tape T (temporary fixing method), and a viewing of the adhered state becomes possible by using the transparent material. Here, the connecting plate CP is formed with a glass fiber reinforced epoxy resin of 2mm thickness, and this size pattern is made to fit to the slit portion SO. Further, in applying the adhesive agent to the connecting plate CP, the surface is cleaned by a methylethylketone resin and the like, and when the adhesive agent is in lack at a time that the connecting plate CP is inserted into the slit portion SO, it is further injected. In this embodiment, the connecting plate CP is formed by a glass fiber reinforced epoxy resin material, but a carbon fiber reinforced epoxy resin material can be used, and a polyester can also be used as a resin material. Moreover, for the glass fiber reinforced epoxy resin material, a matter of material property having a tensile strength of 10 - 20 times of the wood, a thermal conductivity of 1 - 5 times, a linear expansion rate, and a Young's modulus are employed. A test material which has been adhered and joined toward lengthwise direction by the above-described process and elapsed one week is disposed with the joining portion at the central portion of span 1100mm as shown in FIG.4, and as a result of excuting a bending test by a two points loading method interposing this portion, the joining strength is as shown in following tabel 1, in case that a length of the slit is taken to 75mm, its bending strength has become to 342kg/cm 2 - 375kg/cm 2 , and it has exhibited a numercal value of equal with the bending strength 345kg/cm 2 of a cryptomeria structural collective material(first class). And, in a damaging condition, a break down of the wood and an exfoliation of the adhered layer, and a cut down of the connecting plate(reinforced plastic material) have been about simultaneously occurred. From above result, it was proved that when the lumber is adhered and joined by interposing a reinforced plastic material connecting plate of pertinent size between the slits by the above-described process, it can be made to an integral body without decreasing the strength. Length of ERP conneting plat (cm x cm) Number of ERP connecting plate Maximum load (kg) Maximum bending moment (10 2 kgxcm) Bending strength (kg/cm 2 ) 5.0 x 7.5 5 1190 173 184 5.0 x 7.5 5 810 178 189 10.0 x 7.5 5 1148 259 268 10.0 x 7.5 5 1138 249 266 10.0 x 7.5 5 1056 231 246 10.0 x 7.5 5 995 218 232 15.0 x 7.5 5 1551 339 362 15.0 x 7.5 5 1605 351 375 15.0 x 7.5 5 1465 321 342 15.0 x 7.5 5 1585 347 370 * A bending material strength of the cryptomeria is 345 kg/cm 2 in class 1, and 285 kg/cm 2 in class 2. The cryptomeria collective material used for this test has a strength characteristic of this range. The second embodiment will be described with reference to FIG.5 to FIG.9. This embodiment is basically same as aformentioned first embodiment, and two members having big cross sectional area are joined in straight direction. First, slits S1,S2 are respectively formed by a band saw SM in perpendicular direction to the end surfaces of the lumbers 1,2 desired to be joined (refer to FIG.5). The lumbers used in this embodiment is a larch collective material {It is constructed to twelve layers by a drawn plate(lamina) of 150mm x 300mm}. Next, as shown in FIGS.6 and 7, two lumbers(collective material) 1,2 are abutted to lengthwise direction, and each slit S1(7 rows), S2(7 rows) is made to form same surfaces by respectively confronting and continueing, and the adhesive tape T (temporary fixing method) is firmly fixed to both side surfaces and to bottom surface of the abutted portion (joined portion) of the lumbers 1,2 whereby the lumbers 1,2 are fixed to a joined state. In this state, as shown in FIG.8 and FIG.9, an epoxy resin adhesive agent is applied into the slits SO of seven rows made of the slits 1,2 of the seven rows and at the same time, the connecting plates CP applied with same adhesive agent are inserted into the slits SO and then left in air until the adhesive agent is hardened. Other processes are same as aforementioned embodiments shown in FIG.1 to FIG.4. The joined portion of the lumber (test matrials) joined to the lengthwise direction by the process as above is placed at central portion of span of 4000mm as shown in FIG.4, and a bending test is carried out by a two points load system. Following table 2 is a table showing the test result. Slit size (mm) width by length Connecting plate size width by length Number of connecting plate Maximum load (10 3 Kg) Maximum bending moment (10 3kg x cm) Bending strength (Kg/cm 2 ) (lumber thickness) S1:150x300 S2:150x300 300x300 (a) 7 9.29 650 289 S1:150x150 S2:150x150 300x150 (b) 7 10.2 3 716 318 S1:200x300 S2:200x300 400x300 (c) 7 11.2 5 788 350 S1:200x150 S2:200x150 400x150 (d) 7 11.5 4 808 359 S1:200x300 & 250x300 are alternately formed S2:same as S1 400x300 & 500x 300 are alternately placed (e) 7 12.7 806 382 S1:200x150 & 250x150 are alter- 400x150 & 500x 150 are 7 12.0 0 889 395 nately formed S2:same as S1 alternately placed (f) As will be clear from above table, the size and pattern of each slit of both S1,S2 is made to be alternately placed with a matter of about 3mm(thickness) x 150mm(width) x 300mm(length, equal to the thickness of the lumber), a matter of 3mm(thickness) x 200mm(width) x 300mm(length, equal to the thickness of the lumber), and a matter of 3mm(thickness) x 200mm(width) x 300mm(length, equal to the thickness of the lumber) and a matter of 3mm(thickness) x 250mm(width) x 300mm(length, equal to the thickness of the lumber) (refer to FIG.7). And, the slits are formed with seven rows by 20mm intervals. On the other hand, for the connecting plate CP, the test is carried out by using both of a case of same size with the slit { (a),(c),(e) in the table 2 }, and a case that the size of the lengthwise direction(lumber thickness direction) is a half of the lumber thickness { (b),(d),(f) in the table 2 ). In accordance with the result of the test, the joining strength increases in response to the increasing of length of the slit as is clear in the table 2, and in case of (e) and (f), their bending strengths come to 382 - 395 kg/m 2 , and they exhibited numerical values of extremely close to the bending strength 405 kg/m 2 of a larch collective material for structural material(class 1). Further, since a difference of the bending strength is extremely small in case of 300mm and in case of 150mm of the size of length of the connecting plate CP, in case of the bending member, a sufficient bearing strength was exerted by inserting the connecting plate only to a place which receives a tensile stress. And, for a damage condition, an exfoliation of the adhering layer and a cut down of the lumber and the lumber are substantially simultaneously occurred. From above result, when the lumbers are adhered and joined to a lengthwise direction by interposing the reinforcing plastic material connecting plate of appropriate size by above-described process, it was proved that they can be made to be integral without almost reducing the strength. And next, a third embodiment will be described with reference to FIG.10 to FIG.13. In this embodiment, two members are joined toward rectangular direction. The slits S1,S2 of 2.6mm thickness are cut by a round saw in perpendicular direction to the end surface of cryptomeria collective material(five layers, 100mmx75mm) 1,2 as same as the first embodiment. The length of each slit is 75mm, the width is 75mm as same as the case of the collective material 1,2, the interval is 20mm, and the row numbers are five. Thus, the collective mterial 1,2 formed with the slits S1,S2 are rammed to the rectangular direction as shown in FIG.10, and the slit portion SO is formed by gathering each slit S1,S2 of five rows of the end surface, and the transparent sticker tape T is applied and fixed to both side surfaces and bottom surface of the joining place including also a leakage preventing purpose of the adhesive agent in this state. Successively, both side surfaces of the connecting plate(glass fiver reinforced epoxy resin) of size of 75mm x 150mm with 2mm thickness are are cleaned by a methylethylketon and the like and an epoxy adhesive agent is applied, and then this is inserted into the slit portions SO of five rows (FIG.11). At this time, the adhesive agent is applied also to interior surface of the slit portion. And, as shown in FIG.12, the joined portion is wound by a sticker tape T and fixed and then left in air until the adhesive agent would be hardened. When the test body adhered and joined to a rectangular direction in above-described process is place with the adhered and joined portion at a center as showin in FIG.13 and a tensile load is applied through a bolt at a position distanced 424mm away in a rectangular two directions from there, the joined strength has exhibited the numerical value equal to the bending strength of the cryptomeria collective material as shown in next table 3. And, for the damaged condition, the cut down of the lumber and the exfoliation of the adhesive agent are substantially simultaneously occurred. From above result, when the lumber is adhered and joined to a rectangular direction by interposing the reinforced plastic connecting plate of appropriate size between the slits by the above process, it has become clear that they are possible to make to be integral without reducing the strength. Length of FRP connecting plate (cm x cm) Number of FRP connecting plate Maximum load (kg) Maximum bending moment (10 2 kg x cm) Bending strength (kg/cm 2 ) 15.0x7.5 5 1195 395 382 15.0x7.5 5 920 276 295 15.0x7.5 5 888 266 280 * The bending material strength of the cryptomeria collective material is 345 kg/cm 2 in class 1, and 285 kg/cm 2 in class 2. The cryptomeria collective material used in this test has a strength charactaristic of this range. Further, in above-described two embodiment, it is thought that when the sizes of the connecting plate and slit are increased, the joining strength will be more enhanced. And next, a fourth embodiment will be described with reference to FIG.14 to FIG.19. This embodiment is basically same as the above-described third embodiment, and two members of big cross section are joined to a rectangular direction. The lumber used in this embodiment is a larch collective material(it is made to twelve layers by a single plate of 150mm x 300mm). First, the slits S1,S2 are respectively formed by a round saw at the end surface of the lumbers 1,2 desired to be joined(refer to FIG.5). Successively, as shown in FIG.14 and FIG.15, two lumbers(collective material) 1,2 are abutted to rectangular direction, and each slit S1(seven rows), S2(seven rows) are made to form a same surface with continueing each other. And, the sticker tape T is fixed to both sides and bottom of the joining portion of the lumber 1.2 whereby the lumber 1,2 are fixed to a joined state. In this state, as shown in FIG.16 and FIG.17, an epoxy resin adhesive agent is applied into the slits SO of seven rows made by the slits 1,2, and on the other hand, the connecting plate CP applied with same adhesive agent is inserted into the slits SO and then they are left in air until the adhesive agent would be hardened. Following table 4 is a table showing the result of joined strength test executed by variously changing the sizes of the slit and the connecting plate. This test is a compression test, as shown in FIG.18, executing by placing a test matrial formed by the embodiment such that the load point comes to both end portions of the test material. Further, (a) - (h) shown in the table 4 correspond to FIG.19 (a) -(h). lit size mm)width length lumber hickness) Connecting plate width Number of connecting Maximum load (10 3 kg) Maximum bending moment (10 3 kg x cm) Bending strengt (kg/cm 2 ) 1:300x300 2:150x300 450x300 (a) 7 7 7.77 649 288 S1:300x300 S2:250x300 550x300 (b) 7 7 8.44 705 313 S1:150x300 S2:150x300 300x300 (c) 7 2.58 215 96 S1:200x300 S2:200x300 400x300 (d) 7 4.55 380 169 S1:150x300 S2:300x300 400x300 (e) 7 7.15 597 265 S1:200x300 S2: 300x300 500x300 (f) 7 9.60 802 356 S1:150x300 S2:150x300 300x300 (g) 7 2.25 188 84 S1:200x300 S2:200x300 400x300 (h) 7 4.15 347 154 As will be clear from above table 4, the joining strength increases in response to the increasing of length of the slit, and increases in response to the distance from the material end(lumber opening) of the lumber of the connecting plate CP becoming small, and when the connecting plate CP reaches up to the material end(lumber opening), it increases remarkably. And, it has become clear that a case that the lumber opening of the width member(beam) 2 is joined to the side surface of the length member(column) (refer to FIG.15), of which joined strength is stronger than a case that the opening of the length member(column) 1 is joined to the side surface of the width member(beam) 2 (refer to FIG.14). For the break down condition, in case that the connecting plate is not present up to the material end, the lumber is broken down at adjacent of the connecting plate end portion of the material end side, and in case that the connecting plate is reached up to the material end, the adhered layer of the connecting plate has been exfoliated and then the lumber is broken down at adjacent of the connecting plate end portion of interior side. Accordingly, it is thought that when the sizes of the interior side (opposite side to the material end(lumber opening)} of the connecting plate and the slit are increased than 200mm, the joining strength can be increased more a little. From above result, it has become clear that when the lumber is adhered and joined by interposing the reinforced plastic connecting plate of appropriate size between the slits by the above-described process, it is possible to make to be integral without reducing the strength. FIG.20 and FIG.21 are views showing a fifth embodiment, in which the lumbers 1,2 are joined to a straight direction. FIG.20 is a perspective view before the joining, and FIG.21 is a front view after the joining. At here, each end surface of the lumbers 1,2 is not changed from aforementioned embodiment except that it is formed to a slant surface of 45 degrees angle. FIGS.22 and 23 are views showing a sixth embodiment, in which three members are joined rectangularly to three directions. FIG.22 shows a state that the slits S1,S2 and S3 are respectively formed to each end surface of the collective materials 1,2 and 3, and FIG.23 is a plane view showing a state that each end surface of these collective matrials 1,2, and 3 are abutted and the slit portion SO is formed, and aforementioned connecting plate CP is inserted into this whereby the three collective materials are joined. Details of the process is deleted because it is same as aforementioned. FIG.24 is a plane view showing a seventh embodiment, in which four members are joined to four directions. In this embodiment, the abutting end surfaces of the four collective materials 1,2,3 and 4 are formed to protrude in a shape of an isosceles triangle such that they are inserted each other, and the confronting each collective materials become to straight, and the adjoining collective materials are rectangularly crossed. In {(FIG.24(a)}, the slit portion SO is made by the slits formed to each end portions, to which the connecting plate CP of a shape shown in FIG.24(a) is inserted and fixed whereby the four collective materials are joined as shown in FIG.24(a). Details of the process is deleted becuase it is same as aforementioned. FIG.25 is a plane view showing an eight embodiment, in which four members are joined rectangularly to four directions. In this embodiment, the end surfaces of each collective materials 1,2,3 and 4 are rectangularly formed. Others are same as aforementioned. FIG.26 to FIG.28 are views showing a ninth embodiment in accordance with the present invention, in whcih six members are joined rectangularly to six directions. FIG.26 is a perspective view showing a coupling relation in the joining portion of the end portion of each collective material 1,2,3,4,5, and 6, and the connecting plates CP1,CP2 are inserted into the slits formed to the end portions of each collective materials 1,2,3,4,5 and 6 as shown in FIG.27. FIG.28(a) is a perspective view showing the aforementioned connecting plate CP1, and FIG.28(b) is a paerspecive view showing also the connecting plate CP2. The connecting plate CP2 shown in FIG.28(b), of which shape differs from the connecting plate CP2 shown in FIG.27 in order to increase the strength. FIG.29 is a view showing a tenth embodiment, in which six members are joined rectangularly to six directions. FIG.29(a) is a perspective view showing a coupling relation in the joining portion of each end portion of the collective materials 1,2,3,4,5 and 6, and FIG.29(b) is a prespective view showing a connecting plate CP used for this. In this embodiment, the end surfaces of each collective material are right angled, to which each slit is formed whereby abutted as shown in FIG.29(a). The connecting plate of a shape shown in (b) is interposed between each slits whereby each collective matrial is fixed. Details are deleted because it is same as aforementioned.

Claims: A method for joining two wooden members (1, 2) each including a respective end portion, comprising the steps of forming a plurality of slits (S1, S2) in each end portion ; abutting said end portions such that the slits (S1) of one of said end portions are aligned with the slits (S2) of the other of said end portions ; fixing said end portions together with temporary fixing means (T) ; applying an adhesive agent to interior surfaces of said slits; inserting connectif plates (CP) into said aligned slits (S1, S2) for connecting the abutted end portions of said wooden members (1, 2), said connecting plates (CP) being affixed within said aligned slits upon hardening of said adhesive agent. The method of claim 1, wherein said temporary fixing means (T) includes a transparent tape having a sticky backing. The method of claim 1, wherein said connecting plates (CP) are formed of a reinforced plastic material. The method of claim 3, wherein said reinforced plastic material is an epoxy resin reinforced by a glass fiber. The method of claim 3, wherein said reinforced plastic material is an epoxy resin reinforced by a carbon fiber. The method of claim 2, wherein said connecting plates (CP) are formed of a reinforced plastic material. The method of claim 6, wherein said reinforced plastic material is an epoxy resin reinforced by a glass fiber. The method of claim 6, wherein said reinforced plastic material is an epoxy resin reinforced by a carbon fiber. The method of claim 1, wherein said adhesive agent is an epoxy resin. The method of claim 9, wherein said epoxy resin is an acryl or polyurethane group epoxy resin. A method for joining two wooden members (1, 2) each including a respective end portion, comprising the steps of : forming a plurality of slits (S1, S2) in each end portion ; abutting said end portions such that the slits (S1) of one of said end portions are aligned with the slits (S2) of the other of said end portions ; fixing said end portions together with temporary fixing means (T) ; providing connecting plates (CP) ; applying an adhesive agent on the exterior surfaces of said connecting plates (CP) ; inserting said connecting plates (CP) into said aligned slits (S1, S2) for connecting and affixing the abutted end portions of said wooden members (1, 2). The method of claim 11, wherein said temporary fixing means (T) includes a transparent sticker tape. The method of claim 11, wherein said connecting plates (CP) are formed of a reinforced plastic material. The method of claim 13, wherein said reinforced plastic material is an epoxy resin reinforced by a glass fiber. The method of claim 13, wherein said reinforced plastic material is an epoxy resin reinforced by a carbon fiber. The method of claim 12, wherein said connecting plates (CP) are formed of a reinforced plastic material. The method of claim 16, wherein said reinforced plastic material is an epoxy resin reinforced by a glass fiber. The method of claim 16, wherein said reinforced plastic material is an epoxy resin reinforced by a carbon fiber. The method of claim 1, wherein said adhesive agent is an epoxy resin. The method of claim 9, wherein said epoxy resin is an acryl or polyurethane group epoxy resin.

Inventors: FUJII TSUYOSHI, MIYATAKE ATSUSHI, FUJII, TSUYOSHI, MIYATAKE, ATSUSHI
Applicants: FORESTRY AND FOREST PRODUCTS R, FORESTRY AND FOREST PRODUCTS RESEARCH INSTITUTE
Application year: 1993
Main classification: F16B12
IPC codes: F16B12