A bamboo strip flattening device and a flattening and shaping method

Abstract

The present invention discloses a bamboo sheet flattening device and a flattening and shaping method, which includes a long strip elastic steel belt with an arc-shaped cross-section and a hot press for heating and pressing a long strip arc-shaped bamboo sheet and the long strip elastic steel belt. The initial chord length of the cross-section of the arc-shaped bamboo sheet is less than the chord length of the elastic steel belt; the arc height of the elastic steel belt is less than the initial arc height of the arc-shaped bamboo sheet; both sides of the concave surface of the arc-shaped bamboo sheet, i.e., the bamboo yellow surface, are in contact with the convex surface of the elastic steel belt. After the arc-shaped bamboo sheet and the long strip elastic steel belt are superimposed, they are jointly placed between the upper platen and the lower platen of the hot press; when the distance between the upper platen and the lower platen of the hot press is reduced, both sides of the concave surface of the arc-shaped bamboo sheet slide along the convex arc surface of the elastic steel belt to both sides of the convex arc surface of the elastic steel belt, and the concave surface of the arc-shaped bamboo sheet is in contact with the convex arc surface of the elastic steel belt. The distance between the upper platen and the lower platen continues to be reduced to jointly flatten the long strip arc-shaped bamboo sheet and the long strip elastic steel belt. The present invention realizes drying and shaping of the unfolded long strip bamboo sheet through the heating of the hot press while unfolding, improves the flattening quality of the bamboo sheet, and reduces the problems of bamboo sheet rebound and cracking.

Description

Technical Field

[0001] The present invention relates to the technical field of bamboo flattening, and in particular to a flattening device for long strip-shaped arc-shaped bamboo slices and a flattening and shaping method. Background Art

[0002] In the existing bamboo slice flattening technologies, there are the rolling method and the flat pressing method. In both methods, more than 15% of the bamboo slices crack during flattening, seriously affecting the quality and utilization rate of the bamboo slices. After flattening, the bamboo slices have a large elastic recovery deformation, and the arch height of the arc is still more than 10 mm. It is necessary to re-press and shape the bamboo slices during drying. Pressing heavy objects during the drying process causes the bamboo slices to crack again. Finally, only about 70% of the flattened bamboo slices can be actually utilized. The first reason is that bamboo basically has no transverse tissue and has a low transverse tensile strength. When the flattening speed is fast, the transverse tissue is unevenly stretched and will crack. The second reason is that round bamboo does not have a circular cross-section, mainly an elliptical cross-section, and the ellipticity is also different. Therefore, the arcs of the bamboo slices sawn from the same round bamboo are of different sizes, and the arch heights (arc heights) are also different. In the rolling method equipment, the arc of each roller is fixed. The degree of coincidence between the arc of the bamboo slice and the arc of the roller is different, and the force on each bamboo slice when passing through the roller is different. Some bamboo slices have uneven stress on the transverse tissue and crack. The flat pressing method is to place the bamboo slice between the upper and lower pressing plates and flatten the bamboo slice by applying pressure. During the flat pressing and unfolding process, the pressure on the arc top of the bamboo slice is equal to the force on both ends of the chord as the action force and the reaction force. The reaction force at both ends of the chord can be decomposed into a vertically upward force and a horizontally outward force (outside the arc). The greater the horizontal force, the easier it is for both ends of the chord of the arc-shaped bamboo slice to move outward, and the bamboo slice is easy to fork and flatten. Otherwise, it is not easy to flatten and is prone to arc top cracking problems. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a bamboo slice flattening device and a flattening and shaping method in view of the above-mentioned prior art. The flattening device and the flattening and shaping method realize a certain degree of drying and shaping of the unfolded bamboo slices by heating with a hot press while unfolding the softened arc-shaped long strip bamboo slices under the concave surface (bamboo yellow surface) of the arc-shaped long strip bamboo slice, improve the flattening quality of the bamboo slices, and reduce the problems of bamboo slice rebound and cracking.

[0004] To achieve the above technical purpose, the technical solution adopted by the present invention is as follows:

[0005] A bamboo sheet flattening device includes a long strip of elastic steel belt with an arc-shaped cross-section and a hot press for heating and pressing the arc-shaped long bamboo sheet and the elastic steel belt. The initial chord length of the arc-shaped bamboo sheet is less than the chord length of the elastic steel belt, and the arc height of the elastic steel belt is less than the initial arc height of the arc-shaped bamboo sheet; both sides of the concave (bamboo yellow) surface of the arc-shaped bamboo sheet are in contact with the convex surface of the elastic steel belt, and the arc-shaped bamboo sheet and the elastic steel belt are superimposed together, with the concave surface facing down and placed between the upper platen and the lower platen of the hot press; when the distance between the upper platen and the lower platen of the hot press is reduced, and the hot press is kept in contact with the arc top of the convex surface of the arc-shaped bamboo sheet, the two side edges of the concave (bamboo yellow) surface of the arc-shaped bamboo sheet slide along the convex surface of the elastic steel belt to the two side edges of the convex surface of the elastic steel belt, so that the bamboo yellow surface of the arc-shaped bamboo sheet is in contact with or as much in contact as possible with the convex surface of the elastic steel belt. Then, the distance between the upper hot platen and the lower hot platen is further reduced, and the arc-shaped bamboo sheet and the elastic steel belt are flattened and shaped together.

[0006] As a further improved technical solution of the present invention, the long strip of elastic steel belt is an elastic steel belt after heat treatment, and the arc-shaped long bamboo sheet is a softened arc-shaped bamboo sheet; the initial chord length of the arc-shaped bamboo sheet is less than the chord length of the elastic steel belt; the length of the long strip of elastic steel belt (the length in the direction perpendicular to its cross-section) is not less than the length of the arc-shaped long bamboo sheet.

[0007] As a further improved technical solution of the present invention, both side edges of the convex surface of the long strip of elastic steel belt are provided with flanges bent outward in the convex direction. The flanges form a 90° angle with the convex arc surface of the elastic steel belt, and the height of the flanges is less than the wall thickness of the arc-shaped bamboo sheet; the arc length of the convex surface of the elastic steel belt is not greater than the width (belt) of the arc-shaped bamboo sheet after being flattened and extended or the arc length of the bamboo yellow surface.

[0008] As a further improved technical solution of the present invention, the thickness of the elastic steel belt is 0.5 - 1.5 mm; the height of the flange is 6 - 8 mm.

[0009] As a further improved technical solution of the present invention, from one end to the other end of the long strip of elastic steel belt, the arc length of its cross-section gradually increases or decreases. The widths at both ends of the long strip of elastic steel belt in the length direction perpendicular to its cross-section are different, or the arc lengths at both ends of the elastic steel belt are different. Because the long round bamboo has a large end and a small end (the diameter near the root is larger, and the diameter near the tip is smaller), the long bamboo sheets obtained by splitting the round bamboo have different arc lengths at different cross-sections. Correspondingly, the arc change of the long strip of elastic steel belt in the length direction is consistent with the arc change of the long bamboo sheet in the length direction.

[0010] To achieve the above technical purpose, another technical solution adopted by the present invention is:

[0011] A method for flattening and shaping bamboo sheets includes the following steps:

[0012] Step 1: Obtain a long strip of arc-shaped bamboo slice;

[0013] Step 2: Perform pretreatment on the arc-shaped bamboo slice;

[0014] Step 3: Obtain a long strip of elastic steel belt with an arc-shaped cross-section. The chord length of the elastic steel belt is greater than the initial chord length of the softened arc-shaped bamboo slice, and the arc height of the elastic steel belt is less than the arc height of the softened arc-shaped bamboo slice;

[0015] Step 4: Stack and place the arc-shaped long bamboo slices processed in Step 2 on the long strip of elastic steel belt. The radian directions of the arc-shaped bamboo slice and the elastic steel belt are the same and downward;

[0016] Step 5: Flatten the arc-shaped bamboo slice and the elastic steel belt together by applying pressure and heat;

[0017] Step 6: Keep the elastic steel belt and the arc-shaped bamboo slice flattened for a preset time so that the flattened bamboo slice undergoes dry shrinkage under the action of heat. Then stop applying pressure and heat, and the flattening and shaping of the bamboo slice are completed.

[0018] As a further improved technical solution of the present invention, it specifically includes the following steps:

[0019] Step 1: Obtain a long strip of arc-shaped bamboo slice;

[0020] Step 2: Soften the arc-shaped bamboo slice and remove the bamboo green and bamboo yellow on the arc-shaped bamboo slice;

[0021] Step 3: Obtain a long strip of elastic steel belt with an arc-shaped cross-section. The chord length of the elastic steel belt is greater than the initial chord length of the arc-shaped bamboo slice, and the arc height of the elastic steel belt is less than the arc height of the softened arc-shaped bamboo slice;

[0022] Step 4: Stack and place the arc-shaped bamboo slice processed in Step 2 on the elastic steel belt. The radian directions of the arc-shaped bamboo slice and the elastic steel belt are the same, and they are placed together between the upper pressing plate and the lower pressing plate of the hot press. The arcs of the arc-shaped bamboo slice and the elastic steel belt are downward;

[0023] Step 5: Flatten the arc-shaped bamboo slice by applying pressure and heat through the upper pressing plate and the lower pressing plate of the hot press;

[0024] Step 51: When applying pressure, apply pressure slowly. First, keep the upper pressing plate in contact with the arc top of the arc-shaped bamboo slice and then stay;

[0025] Step 52: Then apply pressure slowly and stay again;

[0026] Step 53: Repeat Step 52 according to the preset number of times;

[0027] Step 54: When the lower surface (bamboo yellow) of the arc-shaped bamboo slice fits with the upper surface (outward convex surface) of the elastic steel belt, increase the pressure of the hot press until the arc-shaped bamboo slice and the elastic steel belt are completely flattened;

[0028] Step 6: After the elastic steel strip and the arc-shaped bamboo strip are flattened, they stay between the upper pressing plate and the lower pressing plate for a preset time, so that the flattened bamboo strip is dried to a certain extent under the thermal action of the upper pressing plate, completing flattening and shaping. Then, the pressure is released, and the flattening of the bamboo strip is completed.

[0029] As a further improved technical solution of the present invention, step 1 is specifically as follows: First, the long round bamboo is longitudinally cut into arc-shaped long bamboo strips with equal central angles and at most 4 equal parts; the arc-shaped bamboo strips are sawed and processed into bamboo strips with equal chord widths, so that the two sides of the finally flattened arc-shaped bamboo strip are in a parallel state.

[0030] As a further improved technical solution of the present invention, step 3 is specifically as follows: Take a long elastic steel strip. The chord length of the elastic steel strip is greater than the initial chord length of the softened arc-shaped bamboo strip, and the arc height of the elastic steel strip is less than the arc height of the softened arc-shaped long bamboo strip; the thickness of the elastic steel strip is 0.5-1.5 mm. The elastic steel strip is a heat-treated arc-shaped elastic steel strip, and the elastic steel strip is an alloy steel such as a manganese steel strip or a stainless steel strip;

[0031] The pressure-resistant deformation force of the arc surface of the heat-treated long elastic steel strip is slightly greater than the pressure-resistant deformation force of the arc surface of the softened arc-shaped long bamboo strip, and the hardness of the heat-treated elastic steel strip is greater than the hardness of the softened arc-shaped bamboo strip. That is, under the same pressure, the arc surface of the bamboo strip deforms first, and the arc surface of the steel strip deforms only after the pressure is slightly increased. After the external force is withdrawn, the elastic steel strip can return to its initial state for reuse.

[0032] As a further improved technical solution of the present invention, hemming is provided on both side edges of the elastic steel strip, and the hemming is used to limit the width extension of the arc-shaped bamboo strip (especially the inner bamboo yellow surface). Without the restriction of the steel strip hemming, the width of the flattened bamboo strip is about the arc length of the bamboo green surface, resulting in the bamboo yellow surface being subjected to a tensile force during the flattening process of the bamboo strip. The uneven extension of the bamboo yellow surface is restricted, and the width of the bamboo strip is greater than the arc length of the bamboo yellow surface. Since bamboo lacks transverse tensile tissue, the bamboo strip is prone to cracking. The steel strip hemming can limit the extension of the bamboo in the width direction, making the flattened width approximate to the arc length of the bamboo yellow surface, and reducing the cracking of the bamboo strip.

[0033] As a further improved technical solution of the present invention, the temperature of the upper pressing plate and the lower pressing plate in the hot press in step 5 is 80-120 °C, and the temperature of the upper pressing plate is higher than that of the lower pressing plate;

[0034] In steps 51 and 52, the loading speed of the hot press is 2-3 cm / min.

[0035] The beneficial effects of the present invention are:

[0036] The present invention realizes the unfolding of the softened bamboo strips by adding an elastic steel strip with a curvature under the bamboo-yellow surface of the arc-shaped bamboo strips. The chord length of the elastic steel strip is larger than the initial chord length A of the softened arc-shaped bamboo strips, the arc length is similar to that of the arc-shaped bamboo strips, and the arch height is slightly smaller than the arch height B of the softened arc-shaped bamboo strips. While unfolding the bamboo strips, the upper and lower pressing plates are heated to dry and shape the unfolded bamboo strips, improve the flattening quality of the bamboo strips, and reduce the springback of the bamboo strips.

[0037] Before flattening the arc-shaped bamboo strips of the present invention, the long round bamboo is longitudinally sawn into long arc-shaped bamboo strips with equal central angles and at most 4 equal parts. The chord length of the arc-shaped bamboo strips is processed and sawn into equal-width bamboo strips between 8-9 cm, so that the two sides of the finally flattened arc-shaped bamboo strips can be in a parallel state. At the same time, flanges can be provided on both sides of the long elastic steel strip, or flanges can not be provided. When flanges are provided, the extension of the concave surface of the side of the arc-shaped bamboo strip will be restricted when pressed by the steel strip flange 1, preventing the bamboo strip from cracking.

[0038] The cross-section of the long elastic steel strip is arc-shaped. The chord length of the elastic steel strip is slightly larger than the chord length A of the cross-section of the softened long arc-shaped bamboo strip. The arc length of the elastic steel strip is close to the arc length of the bamboo-yellow surface of the arc-shaped bamboo strip. The arc height of the elastic steel strip is smaller than the arc height B of the softened arc-shaped bamboo strip. The thickness of the elastic steel strip 1 is 0.5-1.5 mm, and it can be alloy steels such as manganese steel strip and stainless steel strip. The arc-shaped steel strip needs to be heat-treated (including steps such as quenching and tempering) to make the steel strip have good elasticity like a spring. After being pressed flat, it can return to its original state when the pressure is removed, achieving the performance of a spring, thus forming an elastic steel strip. The pressure-resistant deformation force of the arc surface of the heat-treated arc-shaped steel strip is slightly larger than that of the softened arc-shaped bamboo. For example, if the force for the softened bamboo to be deformed under pressure is 3-5 Kg, the force for the steel strip to be deformed under pressure is at least 4-6 Kg.

[0039] The purpose of adding the arc-shaped elastic steel strip in the present invention is to change the direction of the reaction force received by the arc-shaped bamboo strip, so that the arc-shaped bamboo strip first undergoes a small pre-unfolding deformation. When the arc-shaped bamboo strip is in contact with or as close as possible to the elastic steel strip, they are uniformly unfolded together, reducing the cracking of bamboo during the flat pressing and unfolding process due to the uneven force on each point and surface of the small arc and long arc length (i.e., the transverse structure of bamboo). When the arc-shaped bamboo strip is flat pressed, the arc top receives a vertically downward pressure G, and the two ends of the chord receive reaction forces. The reaction force at each end can be decomposed into two forces, namely, a vertically upward pressure FY and a horizontally outward traction force FX. The pressure FY affects the horizontal sliding friction resistance of the arc end face on the pressing plate. The greater the pressure FY, the greater the friction resistance. When the arc of the bamboo strip (central angle) is smaller, the vertically upward force FY is greater, and the horizontally outward traction force FX is smaller. The horizontal traction force is the pulling force that unfolds the arc of the bamboo strip outward. The greater this force, the easier it is for the bamboo strip to unfold and not crack. On the contrary, the greater the vertically upward force, the greater the pressure on the bamboo strip, and the more easily it is to be crushed. The function of setting the cross-section of the elastic steel strip to be arc-shaped is to change the condition (direction) of the reaction force received at the two ends of the chord of the arc-shaped bamboo strip during the unfolding process. When the end point of the bamboo strip arc is on the arc of the steel strip and the arc top of the bamboo strip receives the same vertical pressure, the direction of the reaction force received at the end point of the bamboo strip arc changes. The vertically upward reaction force decreases, and the horizontally outward traction force increases. The arc of the bamboo strip will be more likely to slide and fork outward, and the bamboo strip is easy to unfold. Moreover, the arc of the long strip arc-shaped elastic steel strip is greater than that of the arc-shaped bamboo strip, and the hardness of the arc-shaped elastic steel strip is greater than that of the softened arc-shaped bamboo strip. When the two ends of the chord of the arc-shaped bamboo strip come into contact with the elastic steel strip, the horizontal traction force of the bamboo strip arc outward increases. Under the same pressure, the arc of the bamboo strip first forks and slides outward, and the arc-shaped bamboo strip with a larger arc will not produce excessive stretching during the initial unfolding stage. When the bamboo-yellow arc surface of the bamboo strip fits with the convex arc surface of the elastic steel strip, the bamboo strip and the elastic steel strip are unfolded together under the action of pressure, and each point (line, surface) on the bamboo-yellow surface arc will be uniformly stretched and not easily cracked.

[0040] The temperatures of the upper pressing plate and the lower pressing plate in the hot press are set at 80 - 120 °C, and the temperature of the upper pressing plate is higher than that of the lower pressing plate. The bamboo strip is flattened by pressing with the upper and lower pressing plates. Due to the high temperature of the upper pressing plate, the bamboo-green surface shrinks more in the dry state, so that the actual shrinkage of the bamboo-green surface during pressing is greater than that of the bamboo-yellow surface. The extension amount of the bamboo-yellow surface during the flattening process decreases, reducing the risk of cracking. Heating and drying are also beneficial for shaping.

[0041] When applying pressure, apply it slowly at a loading rate of 2 - 3 cm / min. First, let the upper pressing plate contact the arc top of the bamboo strip to avoid cracking the bamboo strip. At this time, pause for a few seconds, and the arc top (bamboo green surface) of the bamboo strip will be dried and softened. The dry shrinkage of the bamboo green surface reduces the arc length and the stress direction (state) of the bamboo green surface. At this time, under the action of pressure, it is beneficial for the arc of the bamboo strip to fork along the convex arc surface of the elastic steel strip, which is to make the bamboo strip produce pre - deformation and unfold. Then, load for another 10 seconds or so to make the bamboo strip closer to the elastic steel strip, and then pause for a few seconds. Repeat this process of loading and pausing 2 - 3 times. Wait until the concave (bamboo yellow) surface of the arc - shaped bamboo strip basically fits the convex arc surface of the elastic steel strip, and then increase the pressure until the bamboo strip is completely flattened. (Applying pressure slowly causes the pressure to shrink from the arc top (bamboo green surface) of the bamboo material, changing the pressure transmission direction, which is beneficial for the arc surface of the bamboo strip to fit the arc surface of the steel strip).

[0042] Under the state of keeping the chord length and the arch height unchanged, flanges can also be set at both ends of the arc of the elastic steel strip. The height of the flange is 6 - 8 mm, slightly less than the wall thickness of the bamboo material by about 1 mm, and the flange forms a 90° right angle upward with the convex arc surface of the steel strip. Stack the softened arc - shaped bamboo strips on the elastic steel strip, and keep the arc directions consistent and downward. The initial chord length of the arc - shaped bamboo strip is less than the chord length of the elastic steel strip.

[0043] When pressing the arc - shaped bamboo strip, the upward flange of the elastic steel strip can limit the extension width of the arc - shaped bamboo strip, especially the concave (bamboo yellow) surface. The softened arc - shaped bamboo strip has good compressibility in the circumferential direction. The flange restricts the extension of the arc of the arc - shaped bamboo strip, which can prevent the arc - shaped bamboo strip from cracking when it is flattened. The elastic steel strip with flanges can also make the side surface of the flattened bamboo strip perpendicular to the upper plane and the lower plane of the bamboo strip (the convex surface (bamboo green surface) is the upper plane after flattening, and the concave surface (bamboo yellow surface) is the lower plane after flattening), reducing the subsequent trimming process of the bamboo strip due to unequal concave and convex arc lengths.

[0044] After the bamboo strip is flattened, it stays in the hot press for a few seconds, so that the bamboo strip is further dried under the thermal action of the upper pressing plate, completing the flattening and shaping, and then the pressure can be released, and the flattening of the bamboo strip is completed. Description of the Drawings

[0045] Figure 1 It is a process diagram of the elastic steel strip without flanges in the present invention for flattening the arc - shaped bamboo strip.

[0046] Figure 2 It is a process diagram of the elastic steel strip with flanges in the present invention for flattening the arc - shaped bamboo strip.

[0047] Figure 3 It is a schematic diagram of the force on the arc - shaped bamboo strip in the present invention. Detailed Embodiment

[0048] The following further describes the specific embodiments of the present invention with reference to the accompanying drawings:

[0049] As Figure 1 or Figure 2 shown, a bamboo strip flattening device includes a long strip elastic steel belt 1 with an arc-shaped cross-section and a hot press for heating and pressing the arc-shaped long bamboo strip 2 and the elastic steel belt. The long strip elastic steel belt is the heat-treated elastic steel belt 1. After the arc-shaped bamboo strips 2 are stacked, they are placed on the elastic steel belt 1 with the arc direction consistent downward. The arc-shaped bamboo strip 2 and the elastic steel belt 1 are jointly placed between the upper platen 3 and the lower platen 4 of the hot press. The arc-shaped bamboo strip 2 is a softened arc-shaped bamboo strip.

[0050] The thickness of the long strip elastic steel belt 1 is 0.5 - 1.5 mm; the two side edges of the elastic steel belt 1 may not be provided with flanges 11 as Figure 1 shown, or may be provided with flanges 11 as Figure 2 shown. When the flanges 11 are provided, the height of the flanges 11 is 6 - 8 mm, the height of the flanges 11 is less than the wall thickness of the arc-shaped bamboo strip 2, and the flanges 11 form a 90° angle upward with the convex surface of the arc of the elastic steel belt 1.

[0051] The initial chord length A of the arc-shaped bamboo strip 2 is less than the chord length of the elastic steel belt 1, and the arch height B is greater than the arch height of the elastic steel belt 1; the length of the long strip elastic steel belt (the length direction is perpendicular to the cross-section direction of the elastic steel belt) is greater than or equal to the length of the long strip arc-shaped bamboo strip 2.

[0052] This embodiment also provides a method for flattening and shaping bamboo strips. As Figure 1 or shown in 2, it includes the following steps:

[0053] Step 1: First, longitudinally cut the long round bamboo into long strip arc-shaped bamboo strips 2 with equal central angles and at most 4 equal parts, and then saw and process the arc-shaped bamboo strips 2 into equal-width bamboo strips with a chord length of about 8 cm, so that the two sides 21 of the finally flattened arc-shaped bamboo strip 2 can be in a parallel state. At the same time, the two sides of the elastic steel belt 1 in this embodiment may be provided with flanges 11 or may not be provided with flanges 11. When the flanges 11 are provided, during the unfolding process of the equal-width arc-shaped bamboo strip 2, as the arc becomes flat and the chord length becomes longer, the flanges 11 evenly block and squeeze the side surface 21 of the bamboo strip, playing a role in restricting the width extension of the bamboo strip and preventing cracking.

[0054] Step 2: Bamboo strip pretreatment: Heat the arc-shaped bamboo strip 2 to soften it. The softening temperature and time are well-known, and then remove the bamboo green and bamboo yellow parts on the arc-shaped bamboo strip 2.

[0055] Step 3: Take a long strip of elastic steel belt 1. The cross-section of the elastic steel belt 1 is arc-shaped. The chord length of the cross-section of the elastic steel belt 1 is greater than the chord length of the cross-section of the arc-shaped bamboo strip 2. The arc height of the cross-section of the elastic steel belt 1 is less than the arc height of the cross-section of the softened arc-shaped bamboo strip 2. The arc length of the elastic steel belt 1 is similar to the arc length of the bamboo-yellow surface of the arc-shaped bamboo strip 2. The thickness of the elastic steel belt 1 is 0.5 - 1.5 mm, and it can be alloy steel such as manganese steel belt or stainless steel belt. The arc-shaped steel belt needs to be heat-treated (including steps such as quenching and tempering) to make the steel belt have good elasticity, be flattened when compressed, and be able to return to the original state after the pressure is removed, with the same recovery performance as a spring, thus forming the elastic steel belt 1. The arc surface of the heat-treated arc-shaped steel belt has a slightly greater compressive deformation resistance than the softened arc-shaped bamboo. For example, if the force for the softened bamboo to be deformed under pressure is 3 - 5 Kg, the force for the steel belt to be deformed under pressure is at least 4 - 6 Kg. Ensure that when the bamboo strip and the steel belt are stacked together and compressed, the bamboo strip arc first slides along the steel belt arc. As the pressure increases, after the two fit as much as possible, they expand together with the steel belt.

[0056] Step 4: First stack the softened, bamboo-outer-skin-removed and bamboo-yellow-removed arc-shaped bamboo strip 2 on the arc-shaped elastic steel belt 1, keeping the arc directions of the two the same. Then put them together between the upper platen 3 and the lower platen 4 of the hot press, with the arc facing downwards. The purpose of adding the arc-shaped elastic steel belt 1 is to make the arc-shaped bamboo strip 2 first undergo a small pre-expansion deformation. After the arc-shaped bamboo strip 2 and the elastic steel belt 1 fit under the initial pressure, then increase the pressure and expand them evenly together, reducing the cracking that occurs due to the large arc of the bamboo and the uneven stress on each point and surface along the arc length during the flat pressing and expansion process. When the arc-shaped bamboo strip is flat pressed, as Figure 3 shown, the arc top receives a vertically downward pressure G, and the two ends of the chord receive reaction forces. This reaction force can be decomposed into two forces, namely a vertically upward reaction force FY and a horizontally outward traction force FX. The greater the arc height, the greater the vertically upward reaction force and the smaller the horizontally outward traction force. The horizontal traction force is the force that pulls the bamboo strip arc of the bamboo strip to expand outward. The greater this force, the easier it is for the bamboo strip to expand and not crack. The function of setting the arc-shaped elastic steel belt 1 is to change the stress condition (direction) of the two ends of the chord of the arc-shaped bamboo strip 2 during the expansion process. The chord length of the arc-shaped elastic steel belt 1 is greater than the initial chord length of the arc-shaped bamboo strip 2, and the hardness of the arc-shaped elastic steel belt 1 is greater than that of the arc-shaped bamboo strip 2. When the two ends of the chord of the arc-shaped bamboo strip 2 come into contact with the elastic steel belt 1, the horizontally outward traction force of the bamboo strip arc is increased.

[0057] Step 5: Set the temperatures of the upper platen 3 and the lower platen 4 in the hot press at 80 - 120 °C, with the temperature of the upper platen 3 higher than that of the lower platen 4. Press the bamboo strip flat by applying pressure through the upper and lower platens 3 and 4. Since the temperature of the upper platen 3 is high, the bamboo-outer-skin surface is in a rapid drying state, so the bamboo-outer-skin surface shrinks more, making the actual shrinkage of the bamboo-outer-skin surface greater than that of the bamboo-yellow surface during the pressing process, reducing the extension amount of the chord of the bamboo-yellow surface during the flattening process and reducing the risk of cracking.

[0058] Step 6: When applying pressure, apply it slowly. First, let the upper pressing plate 3 contact the arc top of the bamboo strip. The loading speed is 2 - 3 cm / min, so as not to crack the bamboo strip. At this time, pause for a few seconds. After the bamboo green surface of the bamboo strip is further deeply softened by drying. Since the dry shrinkage of the bamboo green surface also changes the arc of the bamboo strip, making the arc of the bamboo strip flatter. At this time, under the action of pressure, the arc of the bamboo strip will fork along the arc surface of the elastic steel strip 1. This is to make the bamboo strip produce pre - deformation and unfold. Then load for another 10 seconds or so to make the bamboo strip closer to the elastic steel strip 1, and then pause for a few seconds. Repeat this process of loading and pausing 2 - 3 times. Wait until the arc - shaped bamboo strip 2 is basically fitted to the arc of the elastic steel strip 1, and then increase the pressure until the bamboo strip is completely flattened. (Slowly applying pressure is beneficial to the dry shrinkage of the bamboo green surface, allowing the pressure to be transmitted from the arc top of the bamboo to the entire bamboo strip). During this process, each point and each surface of the arc of the bamboo strip are evenly stressed under the drive of the steel strip.

[0059] Step 7: The long - strip arc - shaped elastic steel strip 1 can also be provided with flanges 11 at the two side edges of the arc while keeping the chord length and the arch height unchanged, as Figure 2 shown. The height of the flange 11 is 6 - 8 mm, slightly less than the wall thickness of the bamboo by about 1 mm. The flange 11 is perpendicular to the convex surface of the arc of the steel strip at a 90° right angle upward. Stack the softened arc - shaped bamboo strips 2 on the elastic steel strip 1, and keep the arc directions consistent and the arc surfaces facing down. The initial chord length of the arc - shaped bamboo strip 2 is less than the chord length of the elastic steel strip 1, and the arc length of the steel strip 1 is close to the arc length of the bamboo strip 2.

[0060] Step 8: When pressing the arc - shaped bamboo strip 2, the flange 11 of the long - strip elastic steel strip 1 can limit the extension width of the arc of the arc - shaped bamboo strip 2. The softened arc - shaped bamboo strip 2 has good circumferential compressibility, which plays a role in limiting the extension width of the arc of the bamboo yellow surface of the arc - shaped bamboo strip 2, and can prevent the arc - shaped bamboo strip 2 from cracking when it is flattened. With the flange 11, the elastic steel strip 1 can also make the side surface 21 of the flattened arc - shaped bamboo strip perpendicular to the plane of the bamboo material. This reduces the subsequent edge - trimming processing procedures.

[0061] Step 9: According to the taper of the bamboo material, the long - strip arc - shaped elastic steel strip 1 can also be processed in the length direction so that the chord length at one end (or the width after unfolding at one end in the length direction) is larger, and the chord length at the other end (or the width after unfolding at the other end in the length direction) is smaller.

[0062] Step 10: After the long - strip arc - shaped bamboo strip is flattened, it stays in the hot press for dozens of seconds, so that the bamboo strip is dried and shaped to a certain extent under the thermal action of the upper pressing plate 3, completing the flattening and shaping. Then the pressure can be released, and the flattening of the bamboo strip is completed.

[0063] The present invention realizes the unfolding of the softened bamboo strips by adding a long strip of elastic steel belt 1 with a chord length initially longer than that of the bamboo strip, an arc length similar to that of the bamboo strip, and an arch height slightly smaller than that of the bamboo strip under the arc of the long bamboo strip. While unfolding, the upper and lower pressing plates 3 and 4 are heated to dry and shape the unfolded bamboo strips, improve the flattening quality of the bamboo strips, and reduce the springback of the bamboo strips.

[0064] The protection scope of the present invention includes but is not limited to the above embodiments. The protection scope of the present invention is subject to the claims, and any substitutions, deformations, and improvements that are easily conceivable by those skilled in the art to this technology fall within the protection scope of the present invention.

Claims

1. A bamboo strip flattening device, characterized in that: It includes a long strip of elastic steel band with an arc-shaped cross-section and a hot press for heating and pressing a long strip of bamboo piece with an arc-shaped cross-section and the elastic steel band. The initial chord length of the arc-shaped bamboo piece is less than the chord length of the elastic steel band; the arc height of the elastic steel band is less than the initial arc height of the arc-shaped bamboo piece. When the arc-shaped bamboo piece and the elastic steel band are stacked together, ensure that their arc directions are the same, with the bamboo piece on top of the steel band, that is, make the two sides of the concave surface of the arc-shaped bamboo piece (i.e., the bamboo yellow surface) contact the convex surface of the elastic steel band. Then place them together between the upper platen and the lower platen of the hot press, and slowly apply pressure to reduce the distance between the upper platen and the lower platen of the hot press, so that the upper platen of the hot press contacts the arc top of the convex surface of the arc-shaped bamboo piece (i.e., the bamboo green surface). The two sides of the concave surface of the arc-shaped bamboo piece slide along the convex surface of the elastic steel band towards both sides of the convex surface of the elastic steel band, and try to make the concave surface of the arc-shaped bamboo piece fit the convex surface of the elastic steel band. Continue to reduce the distance between the upper platen and the lower platen to flatten the arc-shaped bamboo piece and the elastic steel band together. The long strip of elastic steel band is a steel band with sufficient elasticity after heat treatment, and the long strip of arc-shaped bamboo piece is a softened arc-shaped bamboo piece; the length of the long strip of elastic steel band in the direction perpendicular to its cross-section is not less than the length of the long strip of arc-shaped bamboo piece.

2. The bamboo sheet flattening device according to claim 1, characterized in that: On both sides of the convex surface of the long strip of elastic steel band, there are folded edges bent towards the convex arc surface. The folded edges form a 90° angle with the convex arc surface of the elastic steel band, and the height of the folded edge is less than the wall thickness of the arc-shaped bamboo piece; the arc length of the convex surface of the elastic steel band is the width of the arc-shaped bamboo piece after being flattened and extended.

3. The bamboo strip flattening device according to claim 1, characterized in that: From one end to the other end of the long strip of elastic steel band, the arc length of its cross-section gradually increases or decreases.

4. A method for flattening and shaping bamboo strips, characterized in that: It includes the following steps: Step 1: Take a long strip of bamboo piece with an arc-shaped cross-section. Step 2: Pretreat the arc-shaped bamboo piece. Step 3: Take a long strip of elastic steel band with an arc-shaped cross-section. The arc length of the cross-section of the long strip of elastic steel band is similar to or slightly longer than the arc length of the cross-section of the long strip of bamboo piece. The chord length of the long strip of elastic steel band is greater than the initial chord length of the long strip of arc-shaped bamboo piece, and the arc height of the long strip of elastic steel band is less than the arc height of the pretreated long strip of arc-shaped bamboo piece; the long strip of elastic steel band is a steel band with sufficient elasticity after heat treatment, and the long strip of arc-shaped bamboo piece is a softened arc-shaped bamboo piece; the length of the long strip of elastic steel band in the direction perpendicular to its cross-section is not less than the length of the long strip of arc-shaped bamboo piece. Step 4: Stack and place the arc-shaped bamboo piece processed in Step 2 on the elastic steel band, with the arc directions of the arc-shaped bamboo piece and the elastic steel band being the same. Step 5: Flatten the arc-shaped bamboo piece and the elastic steel band together by applying pressure and heating. Step 6: Keep the elastic steel band and the arc-shaped bamboo piece flattened for a preset time so that the flattened bamboo piece is dried under the action of heat, and then stop applying pressure and heating, and the flattening of the bamboo piece is completed.

5. The method for flattening and shaping bamboo strips according to claim 4, characterized in that: Specifically, it includes the following steps: Step 1: Take a long strip of bamboo piece with an arc-shaped cross-section. Step 2: Soften the arc-shaped bamboo piece and remove the bamboo green and bamboo yellow on the arc-shaped bamboo piece. Step 3: Take a long strip of elastic steel band with an arc-shaped cross-section. The chord length of the elastic steel band is greater than the initial chord length of the cross-section of the arc-shaped long strip of bamboo piece, and the arc height of the elastic steel band is less than the arc height of the softened arc-shaped cross-section bamboo piece. Step 4: Stack the arc-shaped bamboo strips processed in Step 2 on the elastic steel strip, with the arc directions of the arc-shaped bamboo strips and the elastic steel strip being the same, and place them together between the upper platen and the lower platen of the hot press, with the concave surfaces of the bamboo strips and the elastic steel strip facing downwards; Step 5: Flatten the arc-shaped bamboo strips by pressing and heating with the upper platen and the lower platen of the hot press; Step 51: When pressing, apply pressure slowly. First, keep the upper platen in contact with the arc top of the arc-shaped bamboo strip, and then pause; Step 52: Apply pressure slowly again and then pause; Step 53: Repeat Step 52 according to the preset number of times; Step 54: Until the bamboo yellow surface of the arc-shaped bamboo strip fits the convex surface of the elastic steel strip, then increase the pressure of the hot press until the arc-shaped bamboo strip and the elastic steel strip are completely flattened; Step 6: After the elastic steel strip and the arc-shaped bamboo strip are flattened, stay between the upper platen and the lower platen for a preset time, so that the flattened bamboo strips are dried under the thermal action of the upper platen to complete flattening and shaping, and then relieve the pressure, and the flattening of the bamboo strips is completed.

6. The method for flattening and shaping bamboo strips according to claim 4 or 5, characterized in that: The specific content of Step 1 is as follows: First, cut the long round bamboo longitudinally into arc-shaped long bamboo strips with equal central angles and at most 4 equal parts; process and saw the chord lengths of the arc-shaped bamboo strips into bamboo strips with equal widths, so that the two sides of the finally flattened arc-shaped bamboo strips are in a parallel state.

7. The method for flattening and shaping bamboo slices according to claim 5, characterized in that: The specific content of Step 3 is as follows: Take a long elastic steel strip with an arc-shaped cross-section. The chord length of the elastic steel strip is greater than the initial chord length of the arc-shaped bamboo strip, and the arc height of the elastic steel strip is less than the arc height of the softened arc-shaped bamboo strip; the thickness of the elastic steel strip is 0.5 - 1.5 mm. The elastic steel strip is a heat-treated arc-shaped elastic steel strip, and the elastic steel strip is a manganese steel strip or a stainless steel strip, ensuring that the steel strip has sufficient elasticity, that is, under the action of external pressure, the arc surface is pressed into a plane, and after the external pressure is removed, the elastic steel strip can return to the initial state for repeated use; After heat treatment, it is required that the pressure-resistant deformation force of the arc surface of the long elastic steel strip is greater than the pressure-resistant deformation force of the arc surface of the softened arc-shaped long bamboo strip, and the hardness of the heat-treated elastic steel strip is greater than the hardness of the softened arc-shaped bamboo strip, ensuring that the arc of the bamboo strip deforms first under the same pressure.

8. The method for flattening and shaping bamboo strips according to claim 4 or 5, characterized in that: Folded edges are provided on both sides of the long elastic steel strip, and the folded edges are used to limit the extension of the arc-shaped long bamboo strip in the width direction.

9. The method for flattening and shaping bamboo strips according to claim 5, characterized in that: In the hot press in Step 5, the temperatures of the upper platen and the lower platen are 80 - 120 °C, and the temperature of the upper platen is higher than that of the lower platen; In Step 51 and Step 52, the loading speed of the hot press is 2 - 3 cm / min.

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