ES2335049T3 - COAT OF COATS IN BAMBU RODS. - Google Patents

Abstract

The method involves isolating a bamboo cane (1) after developing tension in the bamboo cane in a longitudinal direction over an entire length in a peripheral point, and optically closing a longitudinal gap (2) that is developed in the bamboo cane. The bamboo cane is dried up to fiber saturation point. Finish-cutting of the bamboo cone is performed by closing the longitudinal gap and processing the bamboo cone at an end point during an air conditioning phase. The bamboo cone is air-conditioned for about 12 hours per day in the air condition phase. An independent claim is also included for an extensively closed bamboo cane.

Description

Cladding of cracks in bamboo canes.

I. Field of the invention

The invention relates to a method for the treatment of bamboo canes in order to avoid cracks, by less visually, in which radial visibility is avoided at through the rod well through a corresponding configuration of the crack or the cutting joint, either by a coating of the slit with a cover strip, so that prevention of visibility through the cane is still assured even in case of a variable slit width. It also can really avoid cracking by assembling by Example of halfcañas.

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II. Technical background

Due to its great elasticity and stability, the Bamboo is used, especially in Asia, as a constructive element of the most diverse modes, from the construction of bamboo scaffolding high as bell towers until use as material for seats and crockery

Bamboo is also used in Europe, mainly for the production of seats, beds and Similar.

In this context there is essentially the problem that the moisture content of bamboo cane during growth (namely: approximately 55-110% by weight) decreases after cutting the cane  and to end the transfer of water by capillarity of the root to the atmospheric humidity of the environment. While in space Asian, due to the high atmospheric humidity normally reigning, this difference in humidity only leads sporadically to the cracking of bamboo cane, the reeds crack almost regularly when transported to Europe or North America, especially if they are used in spaces with central heating or air conditioning, because of the great difference in humidity then exists.

Although cracking also influences negatively in the stability of the bamboo cane, this is not the decisive disadvantage, but the deterioration of the visual effect when the Bamboo cane has been used as a material for the manufacture of furniture of relatively high quality.

As bamboo cane has a section closed circular cross section and is divided in direction longitudinal at irregular intervals by transverse walls a Partition mode, to avoid cracking the bamboo is not they can use the methods to avoid cracks known in the solid wood treatment transformed into planks (glued by layers of solid wood surfaces in angular direction of the fibers with each other). From a purely biological point of view, bamboo is not a type of wood, but a giant grass, and apart of that there are practically opposite behaviors from the point Physical sight:

While wood has cells conductors for the transport of liquids mainly in the outdoor areas directly below the crust and therefore a tree trunk presents the maximum level of humidity in the area outside and the minimum level of humidity in the core area, in the Bamboo happens exactly the opposite:

In the outer third of the cane are the structural cells, which give bamboo its resistance, while in the inner zone are the cells conductive and storage cells for water to absorb with the basic substances included. Therefore, the two Materials exhibit an absolutely different behavior, especially because in addition, due to the hollow structure with the transverse walls present in the axial direction, the bamboo's physical behavior is once again completely different.

In addition, the moisture content of the reeds of bamboo being cut is not only in principle larger than that of the wood, but also varies much more depending on the location, current weather and size, considered in the transverse direction of the bamboo cane and also in the direction axial longitudinal

Moreover, document DE 43 00 557 A1 already describes a procedure to avoid cracks, in which the reeds Bamboo open in the longitudinal direction in a place of your perimeter, then dry completely and the slit formed is closes with a strip of material, in most cases also bamboo, or in a second method the bamboo cane is divided into two or more halfcane and after final drying said mediacane They are assembled again.

However, this last method requires the exact radial processing of the surfaces to be glued before assembly, the separation must take place along a lateral line, that is, a straight line.

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III. Presentation of the invention a) Technical objective

Therefore, an object of the invention is to create a procedure with which reeds can be treated of bamboo, which also have one and / or more transverse walls, such that, after processing, the cracks of the cane Bamboo can be avoided or at least not visible.

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b) Goal solution

This objective is solved by characteristics indicated in claim 1 and 14. The subordinate claims indicate embodiments advantageous

The procedures described must achieve reduction of the mechanical stresses produced.

These tensions are due on the one hand to closed circular cross section contour of bamboo, so that, even in case of a uniform percentage contraction of the bamboo, tensions must be produced in the outer layer with Regarding the inner layer. This effect is further intensified by the internal structure of bamboo, which in the outer third presents more structural cells and in the inner third it presents more tubular water transporting cells and also cells of storage.

Another difficulty in influencing tensions of bamboo consists of the present interior transverse walls at irregular intervals, which also manifest in a Reinforced bulge that surrounds the outer face of the bamboo.

However, the treatment must be supported by special step drying processes to obtain a Bamboo product that does not crack under weather conditions European:

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Previous treatment

A possibility of reducing the tendency to cracking bamboo poles consists on the one hand in leaving the bottom 50 to 200 cm of the cultivated bamboo cane and collect only the upper part of it, since, how much the greater the height, the greater the decrease in moisture content Bamboo cane initial.

By removing as much as possible the branches of bamboo a few weeks before harvest is reduced additionally the transport of water through the bamboo cane and, consequently, the initial moisture content present in the harvest time

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Pre-drying

After collection, the cut cane is held in an upright position, preferably directly in the bamboo forest, and let it retain the remaining branches, with what produces a kind of pre-drying by moisture transfer through the leaves and evaporation through the surfaces of cut, supported by the decrease in humidity inside the cane bamboo by the force of gravity.

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Active drying

The active drying of bamboo is carried out in various stages:

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Stage one

In the first stage, the bamboo dries, preferably outdoors, based on moisture content initial (from 50 to 100%) until reaching the so-called limit of fiber saturation In the case of bamboo this limit oscillates between 14 and 21% by weight, unlike wood, in which This value ranges between 23 and 35%. In addition, bamboo already begins to contract in this first drying phase, on the contrary that the wood, which does not start to contract until the humidity falls below the saturation value of the fibers. If not indicated otherwise, all percentage data refer to percentages in weight.

The first phase is carried out leaving the reeds upright in the outdoor penumbra for 2 to 10 weeks, in particular 3 to 4 weeks. At this time, the moisture content is reduced to a value of approximately 17% within a range of 13% to 25%. This value corresponds to moisture balance, such as that established in the case of a sufficiently long storage in the tropics because of the atmospheric humidity

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During this time, the diameter of the bamboo is it contracts between 4 and 14%, so it is advantageous to open the transverse walls before this first drying phase. This is can be carried out by drilling or through a head drilling of adjustable diameter.

This is necessary because in this first phase of Drying the free water is transferred mainly through the water pipes which are found to a greater extent on the inner perimeter, and can go more easily outside when the transverse walls They are open.

If cracks occur in this first stage, these are formed mainly from the inside, since in the capillaries of the cane areas near the inner wall are produces the greatest contraction and appearance of tensions due to evaporation of free water. However, with the measures above mentioned can greatly prevent the formation of cracks

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Stage 2 ( drying chamber / heated chamber )

In the second stage, ideally starting from moisture saturation content of the fibers, a dried until reaching a final humidity of 7% to 10%. In this second phase of drying, bamboo preferentially yields the water that It is found in the outer areas, so the layers Outside tend to contract. However, this contraction does not it is possible due to the different behavior of the zones cane interiors. Because of this, the diameter of the cane is arches (similar to what happens in the case of a bimetal), with what the perimeter increases and eventually forms or expands a longitudinal slit in a place of the perimeter of the cane.

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2.a, drying chamber

During drying in the chamber a temperature of 30º to 60ºC and a relative humidity of 75% at 33%, the initial humidity of the bamboo cannot be higher than 24% in This second phase.

In addition, during drying in the chamber it Check the drying regularly with a moisture meter. This Checking is done every 2 hours during the second phase of dried and every 2 days during the previous first air phase free.

Drying in the drying chamber starts with cold air and high air humidity, and in the course of the process of drying increases the temperature and reduces the humidity of the air in the drying oven. Preferably, the drying is carried out in several phases of camera. For bamboo rods 3 m long with the usual 5 years of growth, taken from the area central trunk and with previous chemical treatment, are typical following values:

1st stage = 30º Celsius / 75% relative humidity of air

2nd stage = 38º Celsius / 60% relative humidity of air

3rd stage = 49º Celsius / 45% relative humidity of air

4th stage = 60º Celsius / 35% relative humidity of air

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Preferably, during the 1st phase it is sprayed regularly water on the outer face of the bamboo cane, on all in the area of the knots, to avoid the formation of cracks especially in that area. Total drying time in chamber (for example of phases 1-4 above) is 3-7 days, varying the total time and times of the individual phases depending on the wall thickness of the cane to dry approximately as follows:

one

Heated chamber

After about 3-7 days of permanence in the drying chamber carries out a conditioning to the climatic conditions of the export country, that is, an acclimation to a humidity of air of approximately 40 to 50% and a temperature of 20 to 25 ° C For European countries.

The time spent in the chamber heated is 2 to 4 days and, unlike the last phase in the  drying chamber, during this time there is a new Bamboo shank diameter reduction from 5 to 12% due at the highest relative humidity of the air in the chamber heated compared to the last phase in the chamber of dried This process is applied for a specific purpose, since it has verified that this drying in the drying chamber increases the subsequent cracking resistance of bamboo cane processed, because then they have a lower tendency to swelling This could be related to the collapse. persistent individual capillaries.

The complementary mechanical processing is carried out as follows:

When drying whole bamboo canes they are produced tensions in the peripheral direction of the rod that can cause The cane cracks and opens around the perimeter.

These tensions can be eliminated by opening the bamboo cane all along its longitudinal direction, since in that case the cross section of the rod can be deformed in the peripheral direction depending on the existing voltages, is say, after opening the rod, the cross section in the form of C can widen, or in a few cases it can narrow overlapping the free ends of the perimeter.

Through subsequent visual closure, the slit at least is no longer visible or even really can cease to exist if instead of a visual closure only takes out a real mechanical seal. The transverse walls of the Bamboo shank open, that is, they are traversed by drilling or drilling, before drying the moisture content of the reeds of bamboo, which is when tensions occur, but preferably said walls are not completely removed, but that only one opening is made in the center of them with a size twenty to thirty percent of the outer diameter of the bamboo.

One method is that the slit longitudinal not visually perceptible preventing the observe the rod normally in a radial direction you can see the inside of the cane through the longitudinal slit. This is achieved by producing the longitudinal slit by a cut not directed in the radial direction, but obliquely with respect to the radial direction, namely, with an obliqueness of at least thirty degrees with respect to this, to such an extent that when observed in a radial direction is seen a part of a cutting surface of the crack, but you can't see the inside of the cane.

Another procedure is to perform the separation of the bamboo cane in the longitudinal direction at least in two perimeter places separated from each other, dividing from this bamboo cane mode in at least two independent segments, for example two half-reeds.

Because of the residual tensions present in the material, the two segments, for example the two half-rods, they will change in their cross-sectional contour, usually they will open, that is, their radius of curvature will increase a bit.

Then after a timeout which varies between a few hours and a few days depending on the state of the bamboo, the segments or the half-reeds of the same cane are joined by new, mainly by bonding and if necessary also by additional mechanical fasteners, such as spikes, nails or screws

The advantage is that, thanks to the division into at least two different segments, a better one is achieved elimination of tensions in individual segments than in the cane open only for one place, but otherwise complete, and in consequently the subsequent residual stresses are correspondingly minors.

Therefore, the probability that a cane thus separated into segments and joined by again once removed the tensions of the segments suffer from new tensions so big as to crack.

Another advantage is that, thanks to the division into several segments, jobs can be easily done  on the interior surfaces thereof, for example you can easily carry out the complete removal of the walls transversal or its remains still present and you can also easily remove layers of bamboo from the inner face, that is of the inner layers.

According to the invention, the latter operation reduces the subsequent tendency to cracking, like that the complete elimination of the transverse walls, and also It implies a weight reduction without any loss of stability worth mentioning.

In addition you can easily remove dust Fine bamboo found inside and mold eventually existing.

As regards the transverse walls, preferably proceed as follows: before drying the transverse walls only open, that is, in the center of they practice a hole with a size between a fifth and a quarter of the outside diameter of the cane, and the rest of the transverse walls is only removed after the division of the cane in segments.

A disadvantage of this method is that the segments, in particular the two mediacane, will eventually they can deform to a different extent when relaxing, in which case then they no longer fit perfectly with each other, for example because its free edges acquire different distances from each other. Do not However, at least the radius of curvature of the individual segments, so that the cutting surfaces arranged against each other would result in a joint wedge-shaped open that, although it could be closed With glue, it would be visible.

To avoid this disadvantage, the surfaces of Slit or slit surfaces of individual segments are they process mechanically before joining them, particularly before glue them, so that then there is no joint in the form of wedge open outward, but that a flat support of the cutting surfaces or slit surfaces processed or even a wedge-shaped joint open inward, but not supporting each other the outer edges of the surfaces of cut. During bonding, bamboo fibers protruding in that place can be put under pressure in very hollow spaces existing fine or paste into the interior slot space.

The division of bamboo cane into segments does not It is done with a saw, but by a cutting tool in the form of a blade, so that no chip detachment. This has the advantage, among others, of that the division follows the path of bamboo fibers, is say, that fibers are not cut, but because of it the slit formed does not necessarily extend in a straight line along a lateral line of the tubular shaft, but eventually in the direction oblique to it. Since the outer surfaces of the reeds of bamboo if any are no longer aligned with each other, it is also carried equalization of the joints in the outer perimeter of so that there is no step in the joint. In this context a material removal can also be carried out throughout the outer perimeter, that is, the removal of a continuous layer around the entire outer perimeter.

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c) Examples of realization

They are described in more detail below. Examples of embodiments of the invention. Figures 1 to 3 They do not correspond to the invention. In the drawings:

Figure 1 shows a cross section of a bamboo cane open before drying.

Figure 2 shows a cross section of A bamboo cane after drying.

Figure 3 shows another detail in section cross.

Figures 4a-4c show the development of the division into segments according to the invention; Y:

Figure 5 shows a division into multiple segments according to the invention.

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Description of embodiments

Figure 1 shows a bamboo rod 1 in cross section, in which it has been removed to the greatest extent possible the transverse wall 5 and the bamboo cane 1 has been opened along a lateral line, which has formed a longitudinal slit 2.

Because of the cutting process, which has been made with a circular saw or similar, the side walls of the longitudinal slit 2 extend parallel to each other and in essentially radial direction.

Figure 2 shows the bamboo cane according to the Figure 1 after the drying process, bringing the bamboo cane 1 has contracted a little along its perimeter and because of the longitudinal slit 2 has clearly widened. Eventually, the outer diameter of the bamboo cane 1 even may increase slightly from the existing diameter before dried

The side walls 14 of the slit longitudinal 2 remain essentially oriented in the direction radial with respect to the longitudinal axis 15 of the bamboo cane, with what would a cane with a considerable opening through from which you could see the inside of the cane when observing this from the outside in a radial direction, which would not be desirable.

Figure 3 shows a solution in which the longitudinal slit 2 of bamboo rod 1 is in fact not closed at all, but only not visually perceived as a longitudinal slit, since, when the cane is observed bamboo 1 from a normal position, that is in the radial direction from outside, through said longitudinal slit 2 it is no longer possible to see the inside of the bamboo cane 1.

For this, the longitudinal slit 2 is produced by an obliquely oriented cut with respect to the direction radial 19, so that the resulting cutting surfaces 18a, 18b they are also oriented obliquely with respect to the direction radial.

If said obliqueness is large enough of so that the cutting edges 18a, 18b overlap in the direction peripheral in relation to the thickness of the bamboo cane, when observing the rod in a radial direction it is not possible to see the inside of it. As a general rule, the obliqueness of approximately 45º with respect to the direction radial 19.

Instead, figures 4 show a procedure with which cracking can be avoided.

In this procedure, as the Figure 4a, bamboo cane 1 is divided in longitudinal direction in several segments 1a, 1b, in this case two, by a cut with a blade along the direction of the fibers. It is not it is necessary to hit exactly in the center of the section transverse, that is, by following the path of the fibers, a cut that begins at one end exactly in the center of the cross section can end at the other end at another position, which results in an unequal division and not exactly in half.

Preferably, before the division into segments, the transverse walls 5 are also removed at least partially, for example by drilling them through the center and removing this mode at least about a quarter of the surface of each transverse wall 5. Next, the segments 1a, 1b thus produced are dried as described further in detail by way of example in the description and during this time, especially at the end of the drying process, also completely remove traces of transverse walls 5.

During active or passive drying only subsequent, by a waiting time of a few hours to several days, the arc of segments 1a, 1b usually opens a little, that is, the original shape of the segments, for example semicircular, changes to the shape of a circle segment of less 180º.

In addition, the (for example) two segments 1a, 1b of the same original bamboo rod 1 frequently deforms from differently, so that the two segments then present different diameters, that is, a different width.

However, segments 1a, 1b thus deformed they now have much less internal tensions than bamboo cane 1 previously complete, so that by joining segments 1a, 1b, by example by sticking, to obtain a new bamboo cane 1 'of closed again, as shown in figure 4d, the danger of it cracking again is very small.

However to achieve a cane shape closed when joining the two segments, they generally have to be taken various measures:

On the one hand the edges of cut 18a, 18b, which after drying no longer extend in radial direction For this, material is removed from the surfaces of cutting, preferably using a blade, brush or sander. TO if possible, the outer edge of the cutting surface 18a, 18b does not it is processed or damaged, but the removal of material increases by wedge shape from that place to the inner surface of the segment 1a, 1b, so that when the new cutting surfaces 18'a and 18'b thus obtained are placed against each other, such as is represented in figure 4d, they are touched by the outer edge and form a wedge-shaped glue 6 open inward which can be closed with an adhesive, for example epoxy resin.

As the outer edge of the cutting edges 18a, 18b has not been processed, the two segments fit corresponding to the original path of the cut and the fibers without forming any step and visually very discreetly or invisible.

Yes due to the opening of the arc of the segments, the segments placed against each other have a way too lenticular, deviating from the circular shape, the area of the major radius of this lenticular or elliptical form of the cross section can be reduced by sanding or scraping, such as it is indicated in figure 4d, preferably before fixing, by example by sticking the segments together.

Likewise, in addition to the complete withdrawal of the inner transverse walls 5 can also be carried to perform a removal of layers of material, mainly from the skin interior 12 of the individual segment 1a, 1b, and if necessary also from the outer skin 13.

Figure 5 shows a bamboo rod 1 '' recomposed in this way, consisting of a total of four segments 1a-1d previously divided.

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List of reference symbols

eleven'

Bamboo

1a, 1b, 1c, 1d

Segment

2

Longitudinal slit

5

Transverse wall

6

Glue board

10

Longitudinal direction

12

Inner skin

13

Outer skin

14

Side wall

fifteen

Longitudinal axis

18a, 18b

Cutting edge

19

Radial direction

Claims (14)

1. Procedure to eliminate tensions in bamboo rods to dry, in which:

-

the bamboo cane (1) is divided in longitudinal direction (10) to everything long, at least in one place of the perimeter,

-

the Bamboo cane splitting (1) in longitudinal direction is carried out, after drying at the desired residual moisture, in as minimum two opposite places of the perimeter to get at least two segments (1a, 1b),

-

the Longitudinal groove formed closes at least visually by joining the segments (1a, 1b) again to form a bamboo cane (1 ') closed around its perimeter,

characterized because

-

the cane spacing (1) takes place along the path of the bamboo cane (1),

-

before joining the segments (1a, 1b) on the bonding surfaces is carried carried out a material withdrawal obliquely with respect to the cutting surface resulting from the division, removing a increasing amount of material from the bonding surface towards the inner perimeter of the rod (1),

-

to the less the joints are even, in particular they flatten, by the face Exterior.

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2. Method according to claim 1, characterized because when the cane is divided into segments (1st, 1b), in particular in two half-reeds, the transverse walls (5) are completely removed and on the inner faces of the walls of the cane grooves (17) are made in the longitudinal direction or are performs a surface removal of material to reduce thickness of wall.

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3. Procedure according to one of the previous claims, characterized because material removal is carried out throughout the outer perimeter.

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4. Procedure according to one of the previous claims, characterized because

-

in a First stage of drying bamboo rods are dried in position vertical outdoors for several weeks until reaching fiber saturation limit,

-

in a Second stage of drying bamboo poles:

first they dry in a drying chamber for several days at a temperature increasing up to 60º Celsius and with a relative humidity of the air decreasing up to 35%, until reaching a humidity value inferior to what would be adjusted as balance in the bamboo cane in the place of subsequent placement,

and then an acclimatization to the air temperature and humidity of the place of site.

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5. Procedure according to one of the previous claims, characterized because the finish of bamboo canes by closure of the longitudinal grooves and the processing of the reeds Bamboo to get the final product is carried out during the acclimatization phase, and in the acclimatization phase the reeds of Bamboo acclimatize at least for 12 hours a day.

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6. Procedure according to one of the previous claims, characterized because the longitudinal slit (2) is made by a cut with an obliquely oriented tool with respect to the radial direction, in particular by an angle cut of obliqueness of at least 30º with respect to the radial direction, and / or with an obliqueness that prevents radial visibility through of the bamboo cane.

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7. Procedure according to one of the previous claims, characterized because the separation of the bamboo cane (1) in two segments (1a, 1b), in particular in two half-rods approximately of the same size, it is carried out in particular by dividing it with a blade that extends along the entire cross section of the cane.

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8. Procedure according to one of the previous claims, characterized because the union of the segments (1a, 1b) takes out after a timeout, mainly a time of wait at least five hours, preferably at least eight hours, preferably at least 24 hours, in particular as minimum three days, after the division.

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9. Procedure according to one of the previous claims, characterized because during drying to residual moisture, all transverse walls (5) are drilled before division of bamboo cane (1), but only partially removed, in particular only one hole is made in the center of the wall transverse with a size of 1/4 to 1/5 of the outer diameter of the rod (1).

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10. Procedure according to one of the previous claims, characterized because Epoxy resin is used as glue.

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11. Bamboo cane closed in all its perimeter,

-

consisting of bamboo cane in al minus two segments (1a, 1b) of the original bamboo cane (1) that complement to form the closed perimeter, and

-

extending the segments (1a, 1b) in the longitudinal direction (10) of the bamboo cane (1),

characterized because

-

the together between the segments widen from the outside in V-shaped

-

the segments (1a, 1b) are glued together along the path of the bamboo cane fibers (1), and

-

to the less the joints are even, in particular they flatten, by the face Exterior.

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12. Bamboo cane according to claim eleven, characterized because The segments are two half-reeds.

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13. Bamboo cane according to one of the claims 11 and 12, characterized because the transverse walls have been removed by full.

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14. Bamboo cane according to one of the claims 11 to 13, characterized because the inner faces of the segments present slots (17) extending in the longitudinal direction and / or a material removal to reduce wall thickness.