GB2159094A - Process for manufacture of rubber tree bent wood - Google Patents

Abstract

A process for manufacture of bent or curved rubber tree comprising: applying heat at temperatures of 120 DEG C to 150 DEG C and pressures of 2kg/cm<2> to 5kg/cm<2> to rubber tree wood rapidly, producing a strong contracting phenomenon in the tension wood contained in the rubber tree wood, generating various curves in the rubber tree wood, placing the bent or curved wood into a wood bending mould 2, clamping it strongly to produce bent or curved wood of any shape required, applying a final wood bending treatment using heat at temperatures of 140 DEG C to 150 DEG C and pressures of 4kg/cm<2> to 5kg/cm<2>, and finishing the process by special drying procedures. <IMAGE>

Description

SPECIFICATION Process for manufacture of rubber tree bent wood The present invention relates to an easy method of producing curved or bent wood such as that used for circular table edge woods, chair backs, back top sections, seat sections, doors and circular design wood for door frame materials for which rubber tree wood is frequently used by applying heat of 120"C and 1502C and pressure of 2kg/cm2 to 5kg/ cm2 to rubber tree wood to soften the wood and applying a special molding treatment, and further relates to an improvement in the manufacturing process by which the rubber tree wood is homogeneously colored, without using dyes, to an oak wood color or teak wood color, i.e. the colors of higher quality woods, and imparting insect-resisting and rot-resisting properties to rubber tree wood without using strong chemicals, whereby rubber tree wood becomes an extremely desirable wood material which is easy to use for fabricating by cutting, sanding, coating and the like.

Heretofore, when rubber tree wood was subjected to bending in its original untreated condition, very frequently destruction of the fiber alignment occured in the inside of the bend and also, cracks occured in the wood fiber structure of the outer side.

For this reason, when producing bent or curved wood in large quantity, fabrication of bent or curved sections has been carried out using composite pieces of wood joined together plywood or the like. When this composite wood or plywood is used for bent or curved component fabrication, not only the cost of manufacture rises, but also designs giving a high class appearance become difficult. For this reason, the manufacture and fabrication of bent or curved components from single pieces of wood alone is desirable.

The present invention has been achieved as a result of studies of many wood materials for bent or curved wood in view of the foregoing circumstances. The inventor has discovered that the qualites of rubber tree wood are the most suitable for bent or curved wood. This discovery concerns not only utilizing rubber tree merely for bent or curved wood, but also utilizing the essential qualities of rubber tree wood appropriately, and moreover applying treatments and manufacturing techniques appropriately whereby excellent bent or curved wood can be obtained.

The rubber tree is usually planted on plantation land in various countries such as Malaysia, Thailand and Indonesia, and normally, the tension wood component constitutes roughly 30 - 40% of the volume of the tree. This tension wood has similar features to that of broad leaved trees, but the degree of tension is stronger, and the ratio of tension wood volume is large.

In general, tension wood maintains a balance of tension forces when in log condition,and seldom warps. However, when it is cut into planks or square beams, a sharp contracting phenomenon occurs, and a warping phenomenon always occurs to the side where the tension wood is present.

The present invention relates to improvement rubber tree wood which imparts to it optimum wood qualities for fabricating by cutting, sanding, coating or the like by imparting colors to the wood, insect-resisting properties and anti-rotting properties by the utilization of properties of the tension wood existing in large quantity in rubber tree wood and by the breaking down of the latex component which is the cause of insect damage, discoloring and rotting from bacteria, this latex component being homogeneously distributed throughout a method involving and the structure of rubber tree wood, by means of heating and pressure treatment. Moreover, the foregoing various properties are imparted extremely economically and simultaneously in the treating process for bent or curved wood manufacture.

A summary of this invention will be described in the following.

(1) Rubber tree wood is cut to the required dimentions and placed in an autoclave. Hot water previously prepared in a separate container is poured into the autoclave and steam is produced to transfer the heat to the wood rapidly. The temperature at this time must rise to a level higher than 120"C rapidly, and is raised to 150 C. The pressure is increased from 2kg/cm2 to 5kg/cm2, and the treating time is set at 30 minutes to 60 minutes depending on the thickness of the wood. By this rapid heating and pressure treatment, most of the wood treated will bend in the direction where the tension wood is present. This process is a preliminary step in making bent or curved wood.

The bending of the wood by this preliminary treatment varies depending on the properties of the treated wood in which the tension wood is present.

(2) The foregoing preliminary bending treatment is completed using metal mold made of iron, alminium or other metals designed to fit the required configuration for the bent wood pieces, and the bending directions of the raw wood pieces are aligned to the mold shape where possible for rapid fitting. They are clamped by turnbuckle and bent to the predetermined angles of the mold. Then, the wood is again inserted into the autoclave, and hot water is poured in and steam is produced. This treatment is carried out for 30 minutes to 240 minutes under a pressure of 4kgícm2 to 5kg/cm2 at a temperature of 140"C to 150"C, completing the wood curving process. At this time, if any pieces of the rubber tree wood cannot be bent sufficiently to fit into the desired mold, bent/ curved step (1) is carried out again.After this treatment, the wood is clamped into the mold (2).

(3) Instead of using hot water as used in the foregoing treatments (1 ) and (2), steam can be used, heating at the same temperatures and application of pressure at the same levels can be carried out to achieve similar results.

(4) The bent or curved wood, having undergone the treatment stages (1) and (2), is placed a drying chamber while clamped in the mold, or separately pieces of bent wood are clamped together in a large mold for drying. Keeping the wood bent in the same way, it is dried and the bend becomes permanent. After drying, the bent wood does not return to their original shapes when the mold is released, even if force is applied. No warp destruction, fiber severing or cracks occuring in the wood due to the treatment described above.

(5) Rubber tree wood, when subjected to the bending wood curving technique, which causes degeneration of the latex contained in rubber wood by heating, can be colored light yellow or dark brown, i.e. an oak color or teak color by adjustment of the heating temperature and the heating time.

(6) Also, rubber wood subjected to the treatment, whose component latex of paragraph (5) is decomposed by pyrolysis, is colored to light yellow or brown and takes on insect-resisting properties and anti-rotting properties automatically. These properties are extremely significant since the use of strong insecticide and anti-rotting chemicals is becoming a worldwide problem at present.

(7) For rubber tree wood subjected to the treatment, the latex which is a constituent melts and turns to a liquid when heated and permeates the wood structure and adheres to the tension wood, that is the biggest drawback of rubber tree wood, eliminating its rough surface, inverted grain, irregular grain when cutting and sanding the tension wood portion and eliminating the tendency for coatings to go on unevenly thus upgrading rubber tree wood to a high quality wood, therefore, making this invention highly significant.

The present invention will be described in detail by referring to the attached drawings and example.

Figure 1 is a three dimentions view showing an example of the mold disassembled.

Figure 2 is a view showing the condition in which the wood is inserted into a mold and the mold is clamped.

Example 50 sheets of rubber tree wood 1 for chair top section bending wood, having a thickness 30mm and width 100mm and length of 500mm, were stacked one upon another and placed in vertical type autoclave having a width 800mm and height of 1,000mm. Hot water (90 C) was prepared separately and introduced into the autoclave and steam was rapidly produced. The temperature was raised to 140'C and the pressure to 4kg/cm2 for 40 minutes. Then, the wood was taken out of the autoclave and the treated wood was swiftly fitted to an iron mold 2 made to match the top beam bending wood for a chair. The bending direction caused in the treated wood 1 was aligned with the bending direction of the mold, and the wood was clamped by turnbuckle 3 to the curved part of the mold 2.

49 sheets of the 50 sheets of the treated wood were bent in various ways and all the treated wood became soft from the high temperature. They were bent and aligned with the angle of the mold. (Figure 2).

The bending wood clamped in the mold 2 was again put in a separate autoclave (width 1,500mm, length 9,000mm). Hot water was introduced into this autoclave and steam was produced. The treatment was carried out at 150"C and a pressure of 5kg/cm2 for 60 minutes. The pressure was lowered and hot water was removed from the autoclave after the treatment. The treated bending wood was removed from the autoclave and the turnbuckle 3 for clamping the mold 2 was released and removed. The wood was then placed in another wood mold with identical angle which was separately prepared, and after the clamping, it was stacked in drying chamber. Drying was carried out for 3 to 4 days at a temperature of 70"C to 800C and wind velocity of 3 - 5 m. Next, curing in the open air was carried out for about 24 hours after which the clamp was released.

As a result, a total of about 50 planks were bent in identical configurations, and deformation, return, warping and cracks did not occur. The shape had not changed at all after 2 months had elapsed.

The bent wood was colored uniformly in a yellow oak color. No damage resulted from an insect damage test in a box in which wood borers of various kinds were breeding or discoloration or rotting test. When subject to such fabricating processes as cutting, sanding and drilling, dovetail work, coating work etc., the treated wood performed without problems and could be used for applications requiring bent wood of high quality.

Claims (7)

1. A process for manufacture of bent or curved rubber tree comprising : applying heat at temperatures of 120"C to 150"C and pressure of 2kg/cm2 to 5kg/cm2 to rubber tree wood rapidly, producing a strong contracting phenomenon in the tension wood contained in the rubber tree wood, generating various curves in the rubber tree wood, placing the bent or curved wood into a wood bending mold, clamping it strongly to produce bent or curved wood of any shape required, applying a final wood bending treatment using heat at temperatures of 140"C to 150 C and pressures of 4kg/cm2 to 5kg/cm2, and finishing the process by special drying procedures.

2. A process for production of bent rubber tree wood according to claim 1 in which the heat is applied using hot water or steam.

3. A process for manufacture of bent or curved rubber wood tree according to claim 1 in which the color of the rubber tree wood is changed to light yellow to dark brown by composition of the latex component contained in the rubber tree wood by pyrolysis, with the result that the rubber tree wood has the appearance of oak wood or teak wood.

4. A process for production of curvedfbent rubber tree wood according to claim 1 in which the rubber tree wood has insecticiding and putrefying actions.

5. A process for manufacture of curved/bent rubber tree wood according to claim 1 in which the quality of the tension wood portion of the rubber tree wood is utilized to create a quality wood similar to normal non-tension wood when cutting, sanding or coating, by heating the latex component and causing it to permeate the inner structure of the rubber tree wood.

6. A process as claimed in claim 1 ahd substantially as described with reference to the accompanying drawings.

7. Each and every novel feature herein set forth either separately or in combination.