Glue-free engineering wood beam matched with dowels and dovetail joints and manufacturing process of glue-free engineering wood beam

Abstract

The invention discloses a glue-free engineering wood beam with pins and dovetail joints matched and a manufacturing process of the glue-free engineering wood beam, and relates to the technical field of engineering wood beam manufacturing, the glue-free engineering wood beam comprises a plurality of laminates, a plurality of dovetail joints and a plurality of pins, the laminates are stacked in sequence, the dovetail joints are installed between every two adjacent laminates, and the pins are arranged on the dovetail joints. Each layer of dovetail joint is in one-to-one correspondence in the thickness direction of the laminates, a plurality of pins are arranged on each dovetail joint in a penetrating mode, and the pins sequentially penetrate through the dovetail joints aligned in the thickness direction of the laminates. The shear stress between the laminates can be transmitted, and the overall bending resistance is improved.

Description

Technical Field

[0001] The invention relates to the technical field of engineering wood beam manufacturing, in particular to a glue-free engineering wood beam matched with a pin and a dovetail joint and a manufacturing process thereof. Background Art

[0002] Glueless engineered wood beams are a type of glueless engineered wood, and they belong to the category of engineered wood. The same side of engineered wood includes cross-laminated timber (CLT), glulam (GLT), laminated veneer lumber (LVL), etc. Compared with solid wood sawn timber, they have the following advantages: high mechanical properties, larger size and dimensional stability.

[0003] However, the production of engineered wood requires adhesives, which is not conducive to reducing carbon emissions (adhesive production requires fossil products and consumes energy) and its use as a building material (some adhesives, such as urea-formaldehyde adhesives, emit formaldehyde, which is not good for human health, while adhesives that do not emit formaldehyde have poor gluing effects or are too expensive).

[0004] For traditional adhesive-free engineering wood beams, pins are usually used instead of adhesives to connect the various layers of the engineering wood beams, that is, the pins are used to form a plug-in connection between the various layers to connect the various layers. However, when it bears loads and resists bending, the wooden pins are prone to plastic deformation and rotation, which leads to a weak ability to transfer shear stress between the layers. According to Timoshenko's thick beam theory, for thicker beams, whether the internal shear stress is effectively transferred is an important factor affecting the bending performance of the beam. Therefore, this is the main factor leading to the poor mechanical properties of existing adhesive-free engineering wood beams. Summary of the invention

[0005] The purpose of the present invention is to provide a glue-free engineering wood beam with pin dovetail joints and a manufacturing process thereof, so as to solve the problems existing in the above-mentioned prior art, be able to transfer the shear stress between the layers, and improve the overall bending resistance.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a glue-free engineering wood beam matched with pins and dovetail joints, comprising a plurality of layers of plywood, a plurality of dovetail joints and a plurality of pins, wherein the plurality of layers of plywood are stacked in sequence, and a plurality of dovetail joints are installed between each two adjacent plywood layers, and the dovetail joints of each layer correspond one to one in the thickness direction of the plywood, and a plurality of pins are pierced through each of the dovetail joints aligned in the thickness direction of the plywood. The pins pass through the dovetail joints aligned in the thickness direction of the plywood in sequence.

[0008] In one embodiment, the layer board has three layers, and the three layers of the layer boards are respectively an upper layer board, a middle layer board and a lower layer board.

[0009] In one embodiment, the upper plate and the middle plate are both provided with a plurality of first pin holes for the pins to pass through in the thickness direction, and the first pin holes on the upper plate and the first pin holes on the middle plate correspond one to one in the thickness direction of the plates.

[0010] In one embodiment, the lower end surface of the upper plate, the upper and lower end surfaces of the middle plate, and the upper end surface of the lower plate are all provided with a plurality of trapezoidal grooves, the trapezoidal grooves correspond to the positions of the first pin holes, and the trapezoidal grooves are used to place the dovetail tenons, and the two trapezoidal grooves arranged opposite to each other can buckle and clamp the corresponding dovetail tenons.

[0011] In one embodiment, each of the trapezoidal grooves penetrates the layer plate in the width direction of the layer plate.

[0012] In one embodiment, the layer plate has a length of 1400 mm, a width of 75 mm, and a thickness of 25 mm; and the spacing between adjacent dovetail joints in the length direction of the layer plate is 80 mm.

[0013] In one embodiment, the dovetail tenon is a double dovetail structure, and each of the two long side walls of the dovetail tenon is provided with a dovetail groove, and a plurality of second pin holes are provided in the thickness direction of the dovetail tenon, and the second pin holes are used to connect the pins; the dovetail tenon is 75 mm long, 10 mm thick, and 20 mm wide, and the angle of the opening of the dovetail tenon is 152°.

[0014] In one embodiment, the second pin holes on each of the dovetail tenons are two arranged along the length direction of the dovetail tenon, and the hole distance between the two second pin holes is 29 mm, the distance between the pin hole and the nearest wide side on the dovetail tenon is 23 mm, and the hole diameter of the second pin hole is 10 mm.

[0015] The present invention also provides a manufacturing process for manufacturing a glue-free engineering wood beam with a dovetail joint according to any one of the above technical solutions, comprising the following steps:

[0016] S1. Planing of logs: using a planer to plane two adjacent sides of the logs flat;

[0017] S2. Log planing: Use a planing machine to plan the log obtained in S1 to a thickness of 25 mm;

[0018] S3. sawing of logs, using a sliding table saw to flatten the sides of the logs obtained in S2, and processing the logs to a width of 75 mm to obtain laminates;

[0019] S4. Use ArtCAM software to draw the CNC milling machine tool path diagram and output the nc file;

[0020] S5. Milling of trapezoidal grooves on the layers, using a CNC machine tool to mill trapezoidal grooves on the layers in S3, and punching the first pin hole on the layers;

[0021] S6. Processing of dovetail joints: take several logs and saw them into the required size, use a vertical milling machine to mill out the bevels on both sides of the dovetail joint, then process the length of the dovetail joint to be consistent with the width of the layer board, and then punch a second pin hole on the dovetail joint;

[0022] S7. Assemble the layer boards and dovetail tenons. First align the layer boards and then install the dovetail tenons into the reserved trapezoidal grooves.

[0023] S8. Drive the pins into the corresponding first pin holes and second pin holes.

[0024] In one embodiment, in S7, when assembling the dovetail joints, the dovetail joints located in the middle of the layer board are installed first, and then the dovetail joints located at the ends of the layer board are installed.

[0025] Compared with the prior art, the present invention has achieved the following technical effects:

[0026] The glue-free engineering wood beam with pin dovetail joints provided by the present invention and its manufacturing process include several layers of plywood, several dovetail joints and several pins. The several layers of plywood are stacked in sequence to form the engineering wood beam. Several dovetail joints are installed between each two adjacent plywood layers. The dovetail joints have excellent shear resistance and can transfer the shear stress between the plywood layers. The dovetail joints of each layer correspond to each other one by one in the thickness direction of the plywood. Several pins are pierced on each dovetail joint. The cooperation of the dovetail joints and the pins can compositely resist rotation, reduce the attenuation of the shear resistance caused by the rotation of the dovetail joints due to shear, and make the overall bending resistance higher. The pins pass through the dovetail joints aligned in the thickness direction of the plywood in sequence, thereby realizing a stable connection between the layers of plywood without adding any adhesive, reducing carbon emissions and benefiting human health. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 It is a front view of the glue-free engineering wood beam matched with the pin dovetail tenon in Example 1;

[0029] Figure 2A top view of the glue-free engineered wood beam matched with the pin dovetail tenon in Example 1;

[0030] Figure 3 It is a side view of the glue-free engineered wood beam matched with the pin dovetail tenon in Example 1;

[0031] Figure 4 It is a front view of the dovetail tenon in the first embodiment;

[0032] Figure 5 is a top view of the dovetail tenon in Example 1;

[0033] Figure 6 is a side view of the dovetail tenon in the first embodiment;

[0034] In the figure: 1-upper plate, 2-middle plate, 3-lower plate, 4-dovetail tenon, 5-pin, 6-second pin hole. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The purpose of the present invention is to provide a glue-free engineering wood beam with dovetail joints and a manufacturing process thereof, so as to solve the problems existing in the prior art, transfer the shear stress between the layers and improve the overall bending resistance.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Embodiment 1

[0039] like Figure 1-Figure 6As shown, the present embodiment provides a glue-free engineering wood beam matched with pins and dovetails, comprising a plurality of plywood layers, a plurality of dovetails 4 and a plurality of pins 5. The plurality of plywood layers are stacked in sequence to form an engineering wood beam, and a plurality of dovetails 4 are installed between each two adjacent plywood layers. The dovetails 4 have excellent shear resistance and can transfer shear stress between the plywood layers. The dovetails 4 of each layer correspond to each other in the thickness direction of the plywood, and a plurality of pins 5 are pierced on each dovetail 4. The cooperation of the dovetails 4 and the pins 5 can compositely resist rotation and reduce the attenuation of shear resistance caused by the rotation of the dovetails 4 due to shear, so that the overall bending resistance is higher. The pins 5 pass through the dovetails 4 aligned in the thickness direction of the plywood in sequence, thereby realizing a stable connection between the plywood layers without adding any adhesive, thereby reducing carbon emissions and being beneficial to human health.

[0040] Specifically, the layer board has three layers, and the three layers are respectively an upper layer board 1, a middle layer board 2 and a lower layer board 3. Those skilled in the art can also adjust the number of the layer boards adaptively according to actual needs. The layer boards are tangentially cut boards made of larch wood. Those skilled in the art can also choose other woods.

[0041] The upper plate 1 and the middle plate 2 are provided with a plurality of first pin holes for the pins 5 to pass through in the thickness direction, and the first pin holes on the upper plate 1 and the first pin holes on the middle plate 2 correspond to each other in the thickness direction of the plates, so that the same pin 5 can pass through the upper plate 1 and the middle plate 2 in sequence and connect to the lower plate 3, thereby ensuring the connection stability among the upper plate 1, the middle plate 2 and the lower plate 3. Because the lower plate 3 mainly bears tensile stress in the glueless engineering wood beam matched with the pin dovetail tenon, the first pin holes are not provided on the lower plate 3, thereby avoiding weakening the tensile strength of the lower plate 3.

[0042] The lower end surface of the upper plate 1, the upper and lower end surfaces of the middle plate 2, and the upper end surface of the lower plate 3 are all provided with a plurality of trapezoidal grooves. The distance between the trapezoidal groove at the end and the corresponding end on the plate is 60 mm. The trapezoidal groove corresponds to the position of the first pin hole, and the trapezoidal groove is used to place the dovetail tenon 4. The two trapezoidal grooves arranged opposite to each other can buckle and clamp the corresponding dovetail tenon 4. Through the cooperation of the dovetail tenon 4 and the trapezoidal groove, compared with the traditional connection only by pins, the contact area with the plate is increased, the dovetail tenon 4 has a stronger ability to transmit shear force between the plates, and the wood grain direction of the dovetail tenon 4 is made parallel to the wood grain direction of the plate, taking advantage of the high axial shear strength of the wood, and thus having greater compressive strength, and stronger ability to resist displacement between the plates. At the same time, the cooperative connection between the dovetail tenon 4 and the plate has a locking feature, which can resist the rotation of the dovetail tenon.

[0043] Each trapezoidal groove runs through the layer board in the width direction of the layer board, which is convenient for processing and saves processing time. The length of the layer board is 1400mm, the width is 75mm, and the thickness is 25mm; the spacing between adjacent dovetail joints 4 in the length direction of the layer board is 80mm, which is verified to be the most suitable parameter through simulation analysis. In actual application, technicians in this field can also select other parameters according to actual needs.

[0044] The dovetail tenon 4 is a double dovetail structure, and each of the two long side walls of the dovetail tenon 4 is provided with a dovetail groove. A plurality of second pin holes 6 are provided in the thickness direction of the dovetail tenon 4, and the second pin holes 6 are used to connect the pins 5. The number of the first pin holes and the second pin holes 6 is the same, and they correspond one to one in the vertical direction, thereby facilitating the installation of the pins 5. The dovetail tenon 4 is 75 mm long, 10 mm thick, and 20 mm wide. The angle of the opening of the dovetail tenon 4 is 152°, which has been verified to be the most suitable parameter through simulation analysis. In actual application, technical personnel in this field may also select other parameters according to actual needs.

[0045] The second pin holes 6 on each dovetail 4 are two arranged along the length direction of the dovetail 4, and the hole spacing between the two second pin holes 6 is 29 mm, the distance between the pin hole and the wide side closest to the dovetail 4 is 23 mm, and the aperture of the second pin hole 6 is 10 mm, which is verified to be the most suitable parameter by simulation analysis. In actual application, those skilled in the art may also select other parameters according to actual needs. The dovetail 4 is preferably made of larch, and those skilled in the art may also select other wood or other materials.

[0046] The pin 5 is also made of wood, and has a length of 55 mm and a diameter of 10 mm. Those skilled in the art may also select other parameters according to actual needs.

[0047] Embodiment 2

[0048] This embodiment provides a manufacturing process for manufacturing the glue-free engineering wood beam with dovetail joints in the first embodiment, comprising the following steps:

[0049] S1. Planing of logs: using a planer to plane two adjacent sides of the logs flat;

[0050] S2. Log planing: Use a planing machine to plan the log obtained in S1 to a thickness of 25 mm;

[0051] S3. sawing of logs, using a sliding table saw to flatten the sides of the logs obtained in S2, and processing the logs to a width of 75 mm to obtain laminates;

[0052] S4. Use ArtCAM software to draw the CNC milling machine tool path diagram and output the nc file;

[0053] S5. Milling of trapezoidal grooves on the layers, using a CNC machine tool to mill trapezoidal grooves on the layers in S3, and punching the first pin hole on the layers;

[0054] S6. Processing of dovetail tenon 4: take several logs and saw them into the required size, use a vertical milling machine to mill the bevels on both sides of the dovetail tenon 4, and then process the length of the dovetail tenon 4 to be consistent with the width of the laminate, and then punch a second pin hole 6 on the dovetail tenon 4;

[0055] S7. Assemble the layers and dovetail tenon 4, first align the layers, and then insert the dovetail tenon 4 into the reserved trapezoidal groove;

[0056] S8. Nail the pin 5 into the corresponding first pin hole and second pin hole 6.

[0057] Specifically, in S7, when assembling the dovetail tenons 4, the dovetail tenons 4 located in the middle of the layer board are installed first, and then the dovetail tenons 4 located at the ends of the layer board are installed to reduce stress accumulation.

[0058] The mathematical relationship between the flexural properties of the glueless engineering wood beam with dovetail joints and the degree of connection between the plies in Example 1 is derived. When the plies are completely unconnected and there is no slippage in the connection between the plies, the flexural strength and flexural elastic modulus of the two can be obtained by deriving the formula.

[0059] For a beam made of a material with a linear behavior phase, when it is subjected to four-point bending, the flexural modulus of elasticity is given by

[0060]

[0061] Where E is the bending elastic modulus, L is the outer span, L1 is the distance between the upper and lower supports on the same side, ΔP is the initial load increment differential, Δy is the initial deflection increment differential, ΔP / Δy is the slope of the initial linear part, I is the area moment of inertia of the neutral axis, and for a rectangular section, I is

[0062]

[0063] Where b is the width of the rectangular section, h is the height of the rectangular section, and substituting formula (2) into formula (1) yields

[0064]

[0065] Assume that the thickness of n groups is h1, h2, h3, ... n The total thickness of the laminated components without bonding or any other interaction between them is h The beam is uniformly transmitted to each layer of the plate. For the initial linear stage, the load borne by the i-th beam is obtained from formula (3):

[0066]

[0067] The load on the overall beam is the sum of the loads on each layer, and the bending elastic modulus of the overall beam is

[0068]

[0069] When the thickness of each layer is the same (h1 = h2 = h3 = h i =h / n)

[0070]

[0071] The calculation formula for flexural strength is:

[0072]

[0073] Among them, f bi is the bending strength, M is the maximum bending moment, and for a member subjected to four-point bending,

[0074]

[0075] When the cross section of the beam is a rectangular beam, substitute formula (2) and formula (8) into formula (7) to obtain

[0076]

[0077] For a particular material, the flexural strength f bi is a constant value. Assume that there are n groups of thicknesses h1, h2, h3, ... n The total thickness of the stacked beams without bonding is h The maximum load that the i-th beam can bear is

[0078]

[0079] Because there is no bonding or friction between the layers, and the thickness is the same, the maximum load that the overall beam with a thickness of h can withstand is actually the sum of the maximum loads that each layer can withstand. The bending strength of the overall beam is

[0080]

[0081] Because the thickness of each layer of beam is the same (h1 = h2 = h3 = h i =H / n), so formula (11) can be simplified to

[0082]

[0083] When there is no slippage at all between the layers, the beam can actually be regarded as a beam without interlayer division. Therefore, for a beam composed of n layers of equal thickness and a beam with no slippage at all between the layers, the bending elastic modulus of the former is 1 / n of the latter. 2 , the flexural strength of the former is 1 / n of the latter. At the same time, it can also be seen that for multi-layer beams, whether the interlayer shear stress is effectively transferred is the main factor affecting the flexural mechanical properties of the beam.

[0084] In practice, no matter how the layers are connected, the strength of the connection can only be between the two situations where the layers are completely unconnected and where there is no slippage at all. Therefore, the bending strength and bending elastic modulus should be between the two ideal connection methods. For glueless engineering wood beams composed of three layers of laminates, in existing studies, relying on the friction between traditional plates and the semi-rigid connection provided by traditional pins, the bending elastic modulus can only reach 29.7%, and the bending strength can reach 41.2%. The relative slip between the layers and the failure to effectively transmit the shear stress are still the main factors affecting the bending mechanical properties of glueless engineering wood beams. Therefore, there is great potential for improving the bending mechanical properties of traditional glueless engineering wood beams.

[0085] In the first embodiment, the glue-free engineering wood beam matched with the pin dovetail tenon forms a composite structure with the pin 5 and the dovetail tenon 4. The contact area between the dovetail tenon 4 and the layer board is larger than the contact area between the pin 5 and the layer board, and the grain direction of the dovetail tenon 4 is parallel to the grain direction of the layer board. Such a grain direction effectively utilizes the advantage of the axial shear strength of the wood and has a stronger ability to resist displacement between the layer boards. The composite structure formed by the pin 5 and the dovetail tenon 4 helps the dovetail tenon 4 to resist rotation and provides it with additional bending moment to resist rotation. The shape of the dovetail tenon 4 helps to combine the layer boards, and because the dovetail tenon 4 connection structure usually has greater rigidity, it can resist rotation.

[0086] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core idea of ​​the present invention, that is, for engineered wood manufactured by stacking layers, connectors are added between the layers to resist the slippage of the layers, and the shear stress between the layers when subjected to bending loads is transferred, thereby improving the bending resistance of the engineered wood. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scopes, and it is not limited to wooden beams, but can also be applied to engineered wood (such as CLT boards and GLT boards, etc.). In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A glue-free engineering wood beam with dovetail joints, characterized in that: It includes a plurality of layers of layer boards, a plurality of dovetail tenons and a plurality of pins. The plurality of layers of layer boards are stacked in sequence, and a plurality of dovetail tenons are installed between each two adjacent layer boards. The dovetail tenons of each layer correspond to each other in the thickness direction of the layer boards, and a plurality of pins are pierced through each dovetail tenon aligned in the thickness direction of the layer boards in sequence.

2. The glue-free engineering wood beam with dovetail joint according to claim 1 is characterized in that: The layer plates have three layers, and the three layers are respectively an upper layer plate, a middle layer plate and a lower layer plate.

3. The glue-free engineering wood beam with dovetail joint according to claim 2 is characterized in that: The upper plate and the middle plate are both provided with a plurality of first pin holes for the pins to pass through in the thickness direction, and the first pin holes on the upper plate and the first pin holes on the middle plate correspond one to one in the thickness direction of the plate.

4. The glue-free engineered wood beam with dovetail joint according to claim 3 is characterized in that: The lower end surface of the upper plate, the upper and lower end surfaces of the middle plate, and the upper end surface of the lower plate are all provided with a plurality of trapezoidal grooves, the trapezoidal grooves correspond to the positions of the first pin holes, and the trapezoidal grooves are used to place the dovetail tenons, and the two trapezoidal grooves arranged opposite to each other can buckle and clamp the corresponding dovetail tenons.

5. The glue-free engineered wood beam with dovetail joint according to claim 4 is characterized in that: Each of the trapezoidal grooves penetrates the layer plate in the width direction of the layer plate.

6. The glue-free engineered wood beam with dovetail joint according to claim 3, characterized in that: The length of the layer board is 1400 mm, the width is 75 mm, and the thickness is 25 mm; the spacing between the adjacent dovetail joints in the length direction of the layer board is 80 mm.

7. The glue-free engineered wood beam with dovetail joint according to claim 1, characterized in that: The dovetail tenon is a double dovetail structure, and each of the two long side walls of the dovetail tenon is provided with a dovetail groove, and a plurality of second pin holes are provided in the thickness direction of the dovetail tenon, and the second pin holes are used to connect the pins; the dovetail tenon is 75 mm long, 10 mm thick, and 20 mm wide, and the angle of the opening of the dovetail tenon is 152°.

8. The glue-free engineered wood beam with dovetail joint according to claim 7, characterized in that: There are two second pin holes on each dovetail tenon arranged along the length direction of the dovetail tenon, and the hole distance between the two second pin holes is 29 mm, the distance between the pin hole and the nearest wide side on the dovetail tenon is 23 mm, and the hole diameter of the second pin hole is 10 mm.

9. A manufacturing process for producing glue-free engineering wood beams with dovetail joints according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Planing of logs: using a planer to plane two adjacent sides of the logs flat; S2. Log planing: Use a planing machine to plan the log obtained in S1 to a thickness of 25 mm; S3. sawing of logs, using a sliding table saw to flatten the sides of the logs obtained in S2, and processing the logs to a width of 75 mm to obtain laminates; S4. Use ArtCAM software to draw the CNC milling machine tool path diagram and output the nc file; S5. Milling of trapezoidal grooves on the layers, using a CNC machine tool to mill trapezoidal grooves on the layers in S3, and punching the first pin hole on the layers; S6. Processing of dovetail joints: take several logs and saw them into the required size, use a vertical milling machine to mill out the bevels on both sides of the dovetail joint, then process the length of the dovetail joint to be consistent with the width of the layer board, and then punch a second pin hole on the dovetail joint; S7. Assemble the layer boards and dovetail tenons. First align the layer boards and then install the dovetail tenons into the reserved trapezoidal grooves. S8. Drive the pins into the corresponding first pin holes and second pin holes.

10. The manufacturing process of the glue-free engineering wood beam with dovetail joint according to claim 9 is characterized in that: In S7, when assembling the dovetail tenons, the dovetail tenons located in the middle of the layer board are installed first, and then the dovetail tenons located at the ends of the layer board are installed.

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