HRP920924A2 - Apparatus for impregnating wood - Google Patents

Description

The technical field to which the invention belongs

The invention belongs to the field of devices for applying liquid to surfaces, and especially relates to devices in which the object is placed in contact with a large amount of liquid. Designation according to the international classification of patents: B05C 3/109 and B27K 3/10.

Technical problem

The invention solves the problem of how to design a wood impregnation device that will increase the depth of wood impregnation by alternately applying vacuum, with the evacuation of air and other gases from the wood structure, and the pressure of the impregnation liquid.

State of the art

Wood processing by pressure impregnation, or deep impregnation, has been known for a long time. The purpose of the treatment is to make the wood more resistant to rotting, fungi, insects and worm changes. The impregnating agent is normally a liquid containing various dissolved salts, which usually have a certain toxic effect.

The devices that are used the most today work on the principle that dry wood is placed in a container under pressure, while the reservoir is under pressure. The aim of this is to squeeze as much air as possible out of the wood cell. After that, the impregnation liquid is introduced under atmospheric pressure into the impregnation tank from a special supply tank. By vacuuming, the wood will absorb the impregnation liquid. The disadvantage of this device is that the wood's ability to absorb the impregnation liquid is significantly reduced, since it takes a certain amount of time for the wood to be completely covered by the impregnation liquid. Meanwhile, before the material is completely covered by the liquid, the wood will absorb air and the wood cells will fill with air instead of liquid. Because of this, both the external and internal pressure will be largely equalized, so the impregnation liquid will penetrate the wood to an insufficient extent.

After detailed investigations of these known devices, it was noticed that, despite the fact that the wood loses most of the volume of gas contained in the cells, not all the volume occupied by the gas will be filled with the impregnating substance, even though all the material is completely immersed in the liquid. Since there was no deformation of the material, it should be assumed that the remaining volume must be filled with some other substance than the one used for impregnation.

It is logical that this substance must be some gas. This gas consists partly of the air absorbed by the wood when the liquid was added, as before stated, but it is also probable that the gas was drawn from the liquid, according to the law of the solubility of gases in proportion to the pressure of the gas above the liquid. Cell membranes in wood are of such a nature that they can retain, for example, molecular glycoses, while at the same time being permeable to water molecules. In other words, small molecules can pass through the membrane much more easily than large molecules. A large proportion of the molecules that pass through the membranes into the cells in known impregnation devices will be gas molecules from the impregnating fluid, which reduces the ability of the impregnating fluid molecules to penetrate the cells. This leads, of course, to a weaker penetration of the impregnating liquid in certain types of wood, especially in pine, which today is considered suitable for impregnation with this device. This means that other important species, such as fir, will not be suitable for impregnation under pressure, because there is a difference in the cell structure of these two conifers. As a result, only pine in Norway is processed with the device described above, so these limitations represent, naturally, a serious drawback of the device.

According to the known state of the art, described for example in DE-A-1 492 551 and DE-A-2 313 826, air is extracted from the impregnating liquid in which the wood is immersed. It was found that it is impossible to completely extract the air from the wood when it is covered with liquid, which means insufficient penetration of the liquid into the cells.

According to GB 1 399 833, the wood and the impregnating liquid are vacuum-treated in separate vessels. When the liquid is transferred to the vessel containing the wood, the vacuum is removed and the atmospheric pressure pushes the liquid into the pores of the wood. As with the examples described above, this will not ensure satisfactory impregnation.

Description of the solution to the technical problem

The aim of this invention is to realize a device for impregnating wooden materials, which will increase the depth of impregnation and will provide the possibility to impregnate those types of wood (for example, fir, etc.) that are considered unsuitable for processing by impregnation under pressure, or for deep impregnation.

This was achieved using a device for impregnating wood with an impregnating liquid, where the wood is placed in a hermetic container under pressure or in a tank for impregnation, from which the air is completely or almost completely evacuated, and the impregnating liquid is exposed to pressure after being introduced into the tank , whereby the impregnation liquid is completely, or almost completely, freed of its gas and/or air before compression in the impregnation tank. The impregnation is performed under conditions of complete hermeticity, so that the liquid is completely, or almost completely, free of gas and air when the impregnation occurs, i.e. with increased penetration of the liquid towards the wood, and the gas and/or air do not have the opportunity to penetrate the wood between emptying the reservoir and wood impregnation.

The invention establishes a vacuum in the wood, or more specifically, the wood cells are placed under a vacuum system that is maintained before and during the liquid supply time, so that the impregnation liquid is "sucked up", through the walls of the cells, thus filling the cells. In this case, there is no need to equalize the pressure between the cells and the environment, in order for the impregnation liquid to penetrate through the cell walls.

In practice, the air contained in the impregnation liquid is removed in a special tank.

During operation, compression of the impregnation liquid and after it has been introduced into the impregnation tank is achieved by reducing the volume in the impregnation tank, or by introducing a liquid under pressure from which air or gas has been removed.

The impregnation device includes an impregnation tank that receives the wood to be impregnated, as well as complete equipment for producing a vacuum in the tank, then pipes that connect the impregnation reservoir with the impregnation liquid tank in order to supply the impregnation tank with liquid, while it is connected to the impregnation tank provided equipment to increase the pressure in the reservoir, in conditions of complete sealing against the air.

In one practical embodiment of the device according to the invention, the increase in pressure is effected by means of reducing the volume in the reservoir, such as, for example, one or more inflated soft impregnation reservoirs, or in a pipe carrying liquids, and in connection with the impregnation reservoir , or by placing one or more movable pistons, or a pressure pump in the pipe between the liquid reservoir and the impregnation reservoir.

The invention is described in more detail with reference to the attached drawing which shows, schematically, an example of the implementation of the device according to the invention.

The wood 1 to be impregnated is placed in the tank 2 for impregnation, which is sealed for air and resistant to pressure. One or more elastic, soft reservoirs 3 are arranged inside the reservoir 2 for impregnation (depending on the number, above the wood 1, or above and on both sides, etc.). Before starting the impregnation of the wood 1, the air in the soft tank 3 was evacuated using the vacuum pump 4, and through the pipes 5, 6, 7 and 8, while the valves 9, 10 in the pipes were open. After the air is evacuated, the valve 10 is closed. Behind it, the liquid reservoir 11, connected to the vacuum pump by means of pipes 12 and 13, is evacuated by opening the valve 14, which is later closed after the evacuation is completed, which is determined by reaching the boiling pressure of the liquid for impregnation. By means of the vacuum pump 4, the air in the tank 2 for impregnation is evacuated through the pipes 5, 12 and 25, and the valves 9 and 16 are open until the necessary evacuation is completed, and then they are closed. All, or almost all, air or some gas has been evacuated from both reservoirs, the impregnation reservoir 2 and the liquid reservoir 11, which now works as an expansion reservoir, and some of the air or gas will also be completely removed from the impregnation liquid 17, which is located in reservoir 11.

Impregnation begins by opening valves 18 and 19, which allow impregnation reservoir 2 to be filled with impregnation liquid from reservoir 11, whereby liquid reservoir 11 is placed at a slightly higher height than impregnation reservoir 2, to allow the impregnation liquid to pass into the reservoir 2 under the action of gravity.

During the transition of the liquid, the reservoir 11 is evacuated by the vacuum pump 4, while the valves 9 and 14 are open until the time when the pressure of the gas in the liquid is equal to the pressure of the gas above the liquid. Valves 18 and 19 are then closed.

From the pressurized air source P, it is introduced through the valve 20 into the soft reservoir 3, which expands under this pressure inside the reservoir 2, whereby this pressure reaches up to 16 bar and more. At the end of the impregnation, the soft tank 3 is connected to the vacuum pump and emptied.

If the material has absorbed a larger than optimal amount of liquid, which is determined by some of the known technologies that are not the subject of this invention, a vacuum is again established in reservoir 2 to extract the impregnation liquid from the wood.

The dimensions of the individual elements of the device depend solely on the expected capacity of the device. Common to these differently sized devices is that the temperature of the impregnating liquid is around 20°C, while the pressure is around 12 bar.

The device described and shown is only given as an example and can be used in several ways. So, for example, one movable piston can be installed instead of an elastic vessel in order to reduce the volume and thereby increase the pressure in the impregnation tank.

An increase in pressure in the tank 2 for impregnation can also be achieved.

Claims (2)

1. A device for impregnating wood, which includes a tank for impregnation into which wood 1 is placed, and the necessary equipment for creating a vacuum in the tank as well as pipes with valves for bringing the liquid for impregnation into tank 2 from tank 11 after evacuation, characterized by the fact that is the reservoir (2) for impregnation via pipes with valves (18, 19) connected to the reservoir (11) for liquid, and that the reservoir (11) is connected via pipes (5, 12, 13) and valves (9, 14) to vacuum pump (4), that the reservoir (2) is connected to the vacuum pump (4) via pipes (5, 12, 15) and valves (9, 16). 2. Device according to claim 1, indicated by the fact that a soft tank (3) is placed in the reservoir (2) for impregnation, connected to a pump (P) for pressurized air via a valve (20) and a pipe (8), and that connected to the vacuum pump (4) through pipes (8, 7, 6, 5) and valves (10, 9).