DEVICE FOR TIMBER DRYING

Abstract: The present invention relates to a method for timber drying, in which a number of timber packets (2) are placed in a delimited room (4) through which a stream of air flows and in which the interstices (6) which exist between the packets (2) and the walls (8) and ceiling (10) of the room are screened off to force the air through the timber packets (2). The invention is characterized in that inflatable elements comprising springy devices (20) are used for the screening.

Description: DEVICE FOR TIMBER DRYING TECHNICAL FIELD The present invention relates to a method and a device for energy-efficient drying of timber, in which a number of timber packets are placed in a delimited room through which a stream of air flows and in which the interstices which exist between the packets and the walls and ceiling of the room are screened off to force the air through the timber packets. BACKGROUND In order to obtain good quality, the way in which the drying is carried out is of great importance. Drying is normally effected by stacking the ready-sawn, moist timber in special stacks, so-called packets, which are taken into a special timber drying room. Located inside the timber drying room are large fans, which create a forced air flow to obtain effective drying. In connection with this process, it is important for the air flow to be distributed roughly evenly in connection with the flow through the timber packets. According to the prior art, it has been attempted to achieve this by arranging the timber packets in sectioned rooms, which are adapted to the standardized length of the timber packets, which is around 6.5 m. Of necessity the rooms are made somewhat wider, in order simply to be able to drive in and out with timber packets, which are of a considerable height, often also around 6.5 m. To obtain sufficient turning room, the rooms are thus made somewhat larger, with a width and height measurement respectively of approx. 7 m. To avoid a greater part of the air quantity passing through the passages which are formed between the walls and ceiling, elongated plastic plates have previously been arranged vertically along the side walls, so that the air is forced to pass through the timber packets. In such a way it is thus conceived that the air shall be allowed to pass through the timber packets evenly distributed. However, it has proved to be the case that the material which is used in these continuous, plate-like elements becomes rigid with time, which results in a poor bearing being obtained on the timber packets. In addition, they come into contact with the timber packets in connection with loading and unloading, which wears them out and which further leads to a poor sealing capacity. Thus it has turned out to be the case that, after a time when using the prior art, high air flows are obtained primarily around the end sections of the timber packets, and as a consequence of this, uneven drying is obtained. Uneven drying leads to drying cracks in the cross-cut end of the timber, which are undesirable. It is also known to use an inflatable sealing device which consists of a fibre-reinforced polymer material. However, this has also proved to have roughly the same disadvantages. One problem above all is that after a period of use they do not "collapse" when the air is evacuated from them, but essentially retain their shape, so that they can obstruct, or be damaged in connection with, loading and unloading of the timber packets. SOLUTIONS AND ADVANTAGES The object of the present invention is to eliminate or at least minimize the disadvantages according to the prior art above, which is achieved by means of a method of timber drying in which a number of timber packets are placed in a delimited room, through which a stream of air flows, and in which the interstices which exist between the packets and the walls and ceiling of the room are screened off to force the air through the timber packets. The method is characterized in that inflatable elements comprising springy devices (20) are used for screening. Many advantages are gained by the new method. On the one hand, the shape of the elements means that it is easy to load or unload the timber packets, above all without risk of damaging the sealing elements. Primarily, however, the great advantage is gained that the elements in their inflated state lie thanks to their shaping completely sealingly close to the timber packets, so that as even a distribution of the drying air flow is obtained as possible, resulting in high quality of the dried timber, and that a more energy-efficient method is obtained. According to further aspects according to the invention, it holds good that: - said springy devices act to make the elements in their uninflated state remain almost flat-shaped, so that great space can be obtained in connection with loading and unloading of the timber packets, - said springy devices form a separate part of the element, - the elements are made of rubber and are inflated in connection with screening to a low positive pressure, preferably 0.1 - 1 bar, more preferredly 0.1 - 0.5 bar, so that good but careful sealing is obtained in relation to the timber packets, and - at least one of said inflatable elements interacts with a flat-shaped device disposed on top of the timber packet in order in the activated state to exert a pressure against said timber packet from above. Furthermore, the invention relates to a device with an elongated inflatable element with springy devices, which at atmospheric pressure cause the element to take up a basically plate-like shape, both when the element is vertically disposed, and preferably also when the element is horizontally disposed by a ceiling. According to further aspects of a device according to the invention, it holds good that: - the element is formed of rubber, and forms a sealed, shielded inner cavity, for which there is at least one valve device, for blowing in and evacuating air, - the walls of the element consist of thin- walled rubber, with a thickness of between 0.5 mm and 3.0 mm, preferably 0.7 mm to 1.5 mm, - at least one springy device is located by or inside the element, which causes the element to remain almost flat-shaped in the non-inflated state, but which permits the element to take on the desired shape when it is in the inflated state, - at least one of the springy devices consists of a flat-shaped, thin- walled element, preferably spring steel plate, which is disposed in at least one pocket on one side of the element, - the length in a transverse direction of said springy elements corresponds to roughly half the total circumference in a transverse direction of the element, which length is preferably between 1 - 3 m, - a number of springy devices are disposed in a number of pockets, at a distance of between 0.5 - 1.5 m, and the height of the device is preferably between 50 - 300 mm, more preferredly 100 - 200 mm, and - the length of said screening elements is between 3 and 8 m, and preferably corresponds quite precisely to the height in a normal timber drying room, which is normally around 7 m. OUTLINE DESCRIPTION The invention will be described in greater detail below with reference to the drawings, in which: Fig. 1 shows a view in perspective of a room for timber drying with elements disposed according to the invention, Fig. 2 shows a preferred embodiment of an element in cross-section in the inflated state, Fig. 3 shows the element according to Fig. 2 in the non-inflated state, Fig. 4 shows a modified execution according to the invention, seen in cross-section and in the activated state, Fig. 5 shows the execution according to Fig. 4 in the non-activated state, and Fig. 6 shows the device according to Fig. 4 seen from the side. DETAILED DESCRIPTION Fig. 1 shows a room 4 for timber drying. Inside the room, which is approx. 7 m high and 7 m wide, a number of timber packets 2 are arranged, stacked on one another. A timber packet consists of a quantity of timber, sawn planks, which are arranged in a number of layers. Arranged between each layer of planks in a known way are counter battens, which are arranged across the length of the planks. The counter battens fulfil the objective on the one hand of achieving a level unloading surface for timber which is to be dried, and on the other hand of achieving air ducts across the longitudinal direction of the planks in the timber packet. The timber packets 2 are placed in a known manner inside the room 4 so that a forced air stream can flow through them in a direction which coincides with the direction of the counter battens. The standard length of a timber packet is approx. 6.5 m. The height can vary depending on the thickness of the timber, but normally a number of timber packets are stacked on top of one another so that a total height of approx. 6.5 m is obtained also vertically. Between the ends of the timber packets and the top side there is thus an interstice 6, which is necessary for loading and unloading, and which must be sealed off to obtain an optimum through-flow of air through the timber packets. As is evident from Fig. 1, a number of inflatable elements 12 according to the invention arςjDlaced vertically between each wall 8 and the end parts of the timber packets, so that this interstice is sealed off. In addition, it is shown that a number of elements 12 are arranged against the ceiling 10 in the room 4, so that sealing is also obtained in this interstice. The elements 12 consist in their preferred execution of thin-walled rubber 13, normally approx. 1 mm, and in their inflated state have a diameter of approx. 0.5 m - 0.7 m. The elements 12 are blown up with a slight positive pressure, normally approx. 0.1 - 0.5 bar, so that a soft contact is obtained with the ends of the timber packets. According to the preferred embodiment, the elements 12 are made so long that they extend all the way from the floor to the ceiling along the walls 8, which normally corresponds to approx. 7 m. This length corresponds also to the approximate width of the timber room 4. Thus sealing elements 12 of the same length can also be used in a transverse direction up in the ceiling to seal this interstice also. As is shown in Fig. 1, preferably three elements are arranged in the same vertical plane, in such a way that the ends of the sealing element 12 which is placed in the ceiling interact with the ends of each of the elements which are disposed vertically. Fig. 2 shows an element according to a preferred embodiment, in cross-section, in the inflated state. It is evident that the element according to this preferred embodiment in the inflated state forms a circular inner cavity 14. A valve device 16 is disposed to be able to blow in or release air. Furthermore, it is shown that at the rear of the elements spring elements 20 are disposed, which are arranged inside pockets 22. The pockets 22 consist like the actual element of rubber. The spring elements 20 consist according to the preferred embodiment of a plate made of spring steel, with a thickness of approx. 1 mm. Furthermore, it is shown that on the rear of the pocket 22 is a fastening device 24, by means of which the element can be fastened to the wall or ceiling inside the timber drying room 4. According to the preferred embodiment, the fastening device 24 consists of a nose-shaped, projecting part with a hole intended for fixing by means of a bolt or similar. Arranged along the wall or ceiling are holders 26 with corresponding holes to be able to fasten the elements 12 to the wall or ceiling. This is best done by means of a bolt connection. However, it is obvious that many other forms of fastening arrangement can be used. Fig. 3 shows the element in cross-section in the non-inflated state. It is clear that the spring element 20 has a length which corresponds to roughly half the circumference of the cross-section of the element 12. In addition, it is shown that the spring force is sufficiently great to stretch the element 12 out in its non-inflated state, so that it becomes essentially flat-shaped. The spring force shall suitably be sufficiently great to be able to stretch the element 12 out also when it is disposed in a ceiling (owing to gravity the maximum spring force is required in this position to be able to stretch the element out). Fig. 4 shows a modified embodiment of the device according to the invention. In connection with traditional timber drying, the upper layers in a timber packet will normally be deformed during drying and therefore classed as of poorer quality. On the whole, large quantities of sawn timber have to be sold off at a low price on account of this problem. According to what is shown in Fig. 4, this is solved by using the tubular element according to the invention 12 for applying a pressure on a plate 50, so that the upper layer of the timber packet also is kept under pressure in connection with the drying process. The plate 50 is suitably made of aluminium, so that it is relatively easy to handle. By means of a number of bellows 30 (A - C) the plate can be positioned close to the ceiling 10 in connection with loading and unloading (see Fig. 5). As is clear from the right-hand rubber bellows 30A in Fig. 4, it consists in a known manner of a number of sections of thin- walled rubber 32 in the form of truncated cones. At the bottom, the bellows has a lower fastening device 33, which is disposed by means of a bolt element at a fastening element 52A in the plate 50. The upper end 31 of the bellows, which has a centrally inclined air duct, is disposed by means of fastening element 44 by a vacuum duct 40A with a hole 42 A for the supply and removal of air. Each plate 50 has a suitable number of rubber bellows 30A, 30B, 30C adapted to the weight of the plate. The tubular element 12 is executed in accordance with what has been described above in connection with Fig. 2 and 3. The left-hand rubber bellows 30B is shown only by elementary lines. However, it should be understood that, like other bellows, it is of exactly the same type as the right-hand bellows 30 A. The invention with the modified execution functions as follows. In a deactivated state, the plate 50 is positioned close to the ceiling (see Fig. 5) due to the fact that the rubber bellows 30 A, 3 OB have been connected to a vacuum in the respective vacuum duct 42 A, 42B. The tubular element 12 is also empty of compressed air in this position. Thus in this case there is plenty of space between the floor and ceiling for placing a timber packet 2 inside the drying room 4. When the timber packet 2 is put down, a column- shaped space 6 is formed between the ceiling 10 and the timber packet 2. Before timber drying is commenced, said column-shaped space must be sealed off. First the vacuum is closed off in the vacuum ducts 42A, 42B, so that the plate 50 drops down and lies on top of the timber packet 2 (see Fig. 4). Then compressed air is added to the tube 12 so that this expands and also exerts a pressure against the plate 50. The drying process can then begin. After drying has been completed, the upper rows of timber in the timber packet 2 will also have dried under pressure, so that high quality is obtained. Fig. 6 shows a timber room 4 with a wall 8. It is evident that an upper tubular element 12 (seen from the side) is applied in accordance with Fig. 4, i.e. so that it presses against the plate 50, at the same time as it seals the upper column-shaped space. Another vertically affixed tubular element 12 seals off by the sides of the timber packet. In this way, effective sealing is thus achieved all round the timber packet at the same time as the plate 50 exerts a pressure against the upper rows. The expert will understand that the number of bellows can be varied as desired, likewise the shape of the plate 50. In certain applications it can be advantageous, for example, to use a heavier plate, so that its own weight is perhaps sufficient to create a large part of (or the entire) pressing force, the tubular element 12 only needing to contribute a relatively marginal extra force. In addition, it is understood that water can be used instead of air to fill the tubular element 12 so that the water's own weight creates the pressure on top of the timber packet. The bellows are best arranged so that the plate 50 can at least be lifted up half the distance from the top of the timber packet up to the ceiling, but more preferredly so that it can be lifted approximately 75% of the distance between the top part of the timber packet and the ceiling. The invention is not restricted to what has been demonstrated above, but can be varied within the scope of the following claims. It is thus understood that rubber is only one preferred material and that other types of polymer material can be used to obtain the same effect. The separate spring element can also be formed of many other materials other than spring steel, for example glass fibre or the like. In addition, it is possible to arrange a separate spring element inside the actual tubular element 12. A further modification would be to form the spring element in the form of a thicker vulcanized rubber part which is affixed directly to the tube part, or made as an integral part thereof on manufacture of the tube. It is understood, even though it is only a preferred embodiment, to use an elongated element to seal off the entire room. Modular systems are also conceivable, two or more elements 12 being used to seal an interstice.

Claims: CLAIMS 1. Method for timber drying, in which a number of timber packets (2) are placed in a delimited room (4) through which a stream of air flows and in which the interstices (6) which exist between the packets (2) and the walls (8) and ceiling (10) of the room are screened off to force the air through the timber packets (2), characterized in that inflatable elements (12) comprising springy devices (20) are used for the screening. 2. Method according to claim 1, characterized in that said springy devices (20) cause the elements (12) in their uninflated state to become almost flat-shaped, so that great space (6) can be obtained in connection with loading and unloading of the timber packets (2). 3. Method according to any of the above claims, characterized in that said springy devices (20) form a separate part of the element (12). 4. Method according to any of the above claims, characterized in that the elements (12) are made of rubber and that they are inflated in connection with screening to a low positive pressure, preferably 0.1 - 1 bar, more preferredly 0.1 - 0.5 bar, so that good but careful sealing is obtained in relation to the timber packets. 5. Method according to claim 1, characterized in that at least one of said inflatable elements (12) interacts with a flat-shaped device (50) arranged on top of the timber packet (2) in order in the activated state to exert a pressure against said timber packets (2) from above. 6. Device for executing the method according to claim 1, characterized by an elongated inflatable element (12) with springy device (20) which at atmospheric pressure causes the element (12) to take up an essentially plate-like shape, both when the element is arranged vertically, and preferably also when the element is arranged horizontally up against a ceiling. 7. Device according to claim 6, characterized in that the element (12) is formed of rubber, and forms a sealed, shielded inner cavity (14), for which there is at least one valve device (16), for blowing in and evacuating air. 8. Device according to claim 7, characterized in that the walls of the element consist of thin- walled rubber, with a thickness of between 0.5 mm and 3.0 mm, preferably 0.7 mm to 1.5 mm. 9. Device according to claim 6, characterized in that at least one springy device (20) is disposed by or inside the element, which device causes the element to remain almost flat-shaped in the non-inflated state, but permits the element to take up the desired shape when it is in the inflated state. lO.Device according to claim 6, characterized in that at least one of the springy devices consists of a plate-shaped thin- walled element, preferably spring steel plate, which is disposed in at least one pocket (22) on one side of the element. 11. Device according to claim 9 or 10, characterized in that the length in a transverse direction of said springy elements (20) corresponds to roughly half the total circumference in a transverse direction of the element (12), which length is preferably between 1 - 3 m. 12. Device according to claim 10, characterized in that a number of springy devices (20) are disposed in a number of pockets (22), at a distance of between 0.5 - 1.5 m, the height of the device preferably being between 50 - 300 mm, more preferredly 100 - 200 mm. 13. Device according to any of the above claims, characterized in that the length of said screening elements (12) is between 3 and 8 m, and preferably corresponds quite precisely to the height of a normal timber drying room, which is normally approx. 7 m.

Inventors: ERIKSSON HAAKAN, ERIKSSON, HAAKAN
Applicants: ERIKSSON HAAKAN, GURLITA MASKIN AKTIEBOLAG, ERIKSSON, HAAKAN
Application year: 1999
Main classification: F26B3
IPC codes: F26B25