DK148956B - WOOD PROTECTIVE EQUIPMENT AND PROCEDURE TO USE THEREOF - Google Patents

Description

148956

This invention relates to a wood preservative designed as a body which is fixed at the operating temperature and shaped to fit a wood borehole. One example of the application of this invention is the protection of railway sleepers, wooden doors and window frames, wooden bridges and wooden boats. The invention also relates to a method for protecting a rail sleep with rail fittings by means of a wood preservative according to the invention.

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It is normal practice to protect structural wood by impregnating with a wood protection such as metal salts or creosote, but this method becomes ineffective over time. Defective protection only becomes visible in parts of the structure where moisture, rain or condensation is most likely to accumulate.

Eg. starts the formation of rail sleepers after they have been closed down for a few years under the brackets which carry the railroad tracks.

Antifungal agents such as sodium fluoride and sodium borate have also been used as wood preservatives, e.g. by introducing a powder into holes drilled in the tree.

From the specification of Danish Patent No. 50,778 and English Patent No. 912,381 are known wood protection bodies which are manufactured by pressing and which can be inserted into a cavity in a wood blank.

However, such manufactured bodies suffer from certain deficiencies, in particular the concentration of the active material in the body is not maximal, since the compression of the material has certain practical limits. Furthermore, any binders take up space, and therefore the concentration of the active material is reduced accordingly.

Therefore, such manufactured bodies cannot always be used without causing problems when making holes in structural parts, such as supporting structures, where there is only a very limited reduction in the strength of the wooden parts. For example, at railway sleepers, where the raid attack occurs under the rail bracket, precisely where the load is greatest.

Furthermore, the compressed blanks are prone to curvature before insertion into holes, which is why oversized holes must be made for insertion.

Finally, there is a tendency for the blanks to fall out as they have no particular shape stability, as well as differences in the distribution of the active substances in the blanks.

Further, from the disclosure of U.S. Patent No. 4,042,402, the use of crushed boron oxide as a fungicide and insecticide in paints is known. Here, the boron oxide is used as an additive for surface protection paints for woodpieces, in a not very concentrated form.

In contrast, the application relates to a wood preservative formed as a body which is fixed at the operating temperature and shaped to fit in a wood bore, which wood property is peculiar in that the body consists of boron oxide, which is melted and cast into it. desired form, and which may contain smaller amounts of a material which controls the rate of dissolution.

Such rods or plugs will contain the maximum amount of active substance, and furthermore they will be completely homogeneous.

The high concentration of active substances means that there is no need to drill in excess size, which is why the greatest possible strength is retained in the woodpile. In this way, the largest possible amount of active ingredient per day can be introduced. hole.

In addition, a good shape stability which allows objects to be recovered in a tight fit, and as moisture will suffocate the surface of the workpiece, it will be pressed into the sides of the hole and thereby anchored in the hole.

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It has been found that although a compressed but unmelted rod of boron oxide dissolves rather quickly in moisture in wood exposed to weather and wind, a molten rod dissolves more slowly and thus provides protection for a longer time.

The other materials which may be contained in the wood preservative of the invention will usually consist of minor portions of metal oxides acting in one or both of the following ways: (i) Controlling the rate of dissolution in water.

(ii) Increasing the protective effect of boric acid.

Typical examples of (i) are alkali metal oxides (which increase the dissolution rate) and alkaline earth metals or silicon oxides (which decrease the dissolution rate). Kiseldioxid,

SiC> 2, is particularly good for delaying the solution of boron oxide.

Typical examples of (ii) are copper oxide, tin oxide, zinc oxide.

Some antifouling agents are most effectively controlled by copper oxide or one of the other metal oxides with boric acid.

The molten body of this invention is shaped like a plug to fit with a corresponding shaped hole drilled in the wood. The most convenient plug form is a rod or cylinder, e.g. a circular cylinder having a length longer than its largest diameter. Alternative forms include blocks, pills and bullets. These pre-formed bodies can be made by extruding the wood protection in a molten state or by forming or pressing particulate materials in a mold, and then melting them by heat into a cohesive structure. For boron oxide, it is preferred to melt particulate material.

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After the body has been inserted into the hole / hole, the hole can be closed to avoid direct ingress of moisture. More than one such shaped body can be inserted, as shown below with an example of rail sleepers.

Using a molten body according to the invention has many advantages over the use of other wood protectors. After melting, the plug has a high density such that the volume for a given weight of the tree protection is less than that of a particulate material. As a result, the voids in which the plug is located are smaller, so that the mechanical weakening of the wood is less. It is also cheaper and faster to drill a small hole than a large hole. Furthermore, the molten material dissolves more slowly in the moisture in the wood than does the same particulate material, and yet it can still dissolve sufficiently quickly to maintain the desired concentration of antifungal agent in the area of the wood most exposed to fungal attack.

Boron oxide dissolves in moisture in wood by forming boric acid, which is itself the active ingredient. The boric acid diffuses into the tree at a rate determined by the amount of free water available, i.e. the more moist the tree, the faster the protection moves into the tree. 1 ml of molten boric oxide forms 3 ml of boric acid.

According to the invention, it is preferred that the body further contains SiC> 2, since the solution of the boron oxide plug can thereby be delayed especially to give the plug a longer service life.

Under conditions where the life of boric acid paste could be expected to be five years, the life of the plug according to the invention can be expected to be 12-15 years.

In another preferred embodiment of the invention, the body contains an alkali metaloride which has been found to be particularly suitable for increasing the dissolution of the body when desired for rapid action.

As the molten plugs are smaller for a given weight of wood protection, they only need small holes and thus cause less mechanical damage and weakening of the wood. If a sixty protection,. which is more readily soluble in water than boric oxide, present with boric oxide in the molten body of the invention, will also only diffuse slowly because it is encapsulated in the less soluble boric oxide.

The invention also relates to a method for protecting a rail sleeve with rail fittings, by means of the wood preservative according to the invention, which is characterized in that one or more bodies are placed in boreholes close to one side of the bracket which extend obliquely under the bracket. . Hereby, bodies are placed so that they exert their protective effect precisely where there is the greatest risk of attack without significantly weakening the wood.

After inserting the protective plugs into the wood, they can be sealed with a plastic capsule or other suitable material. Once the protection is diffused through the wood, the cavities can simply be filled again with fresh protection by removing the capsule and inserting additional plugs.

The invention is further explained with reference to an example of protection of railway sleepers. Of course, the invention is equally applicable to other wood structures as set forth below.

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Although the life of rail sleepers on a track that is only slightly used can be several decades, most sleepers need treatment with tree protection after about 10-15 years if they are to remain durable.

Advice in rail sleepers initially occurs around the attachment bracket for the track, especially in the area close to the screw holes where the bracket is attached to the sleepers.

A typical plug according to the invention for use in railway sleepers is a circular cylinder 80 mm long and 12 mm in diameter. This one has a mass of about 16 g.

Cavities, usually 8 by 2 located on each side of each rectangular bracket, are drilled to a depth no more than half the thickness of the swelling. Each hole is just large enough to receive a plug and slopes downward toward a location below the middle portion of the bracket, as shown in the accompanying drawing. The holes are drilled in a direction towards a position below the bracket so that the tree protection can be placed directly in the area that is most exposed. Furthermore, this area is best protected in terms of leaching of water-soluble protection if the sleepers are in areas with heavy rainfall. The area under the bracket contains the most moisture, due to condensation water beneath the bracket, which promotes the diffusion of the tree protection through the sleep.

In the drawing, FIG. 1 is a plan view of a part of a swell on which a bracket is mounted; FIG. 2 is the side view, and FIG. 3 the sleep from the end.

The sleeper 10 carries the bracket 11. The details of the bracket with its resilient attachment to the groove outlined as 12 are not shown as it does not form part of this invention. The bracket is fastened to the sleep with four screws, each referred to as 13.

The holes drilled for the plugs of the invention are referred to as 14. The inclination of the cavities is shown in FIG. 2 and 3, and in FIG. 1, the direction of the cavities is shown in dotted line.

A plug according to the invention is then inserted into each hole, which can then be encapsulated. If the holes are drilled to a length greater than 150-200 mm which may be necessary if they are sloped much from the vertical, two or three plugs can be used in each hole. While a powder or paste of wood protection tends to be squeezed out of the pressure, which is passed through the wood sleeper when passing trains, the molten plug remains firmly in place.

A further interesting advantage of molten bodies according to the invention is that they do not increase the conductivity of the wood. This is sometimes important when the tree is part of an automatic signal system.

The size of the shaped body according to the invention depends on the intended use. For railway sleepers, a cylindrical rod with a mass of 10-100 g is suitable. For window frames and doors, a cylindrical bar with a mass of 1-10 g is suitable, e.g. 18 mm long and 9 mm in diameter with a mass of 2-2½ g.

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The top of wooden piles are exposed to tips which can be stopped by inserting a large molten pill or rod on e.g.

100g of wood protection such as boron oxide in a hole drilled in the pile or directly in the softened wood.

In wooden bridges where it is important to limit the mechanical impairment caused by drilling holes, it is recommended to use rods with the same characteristics as for railway sleepers.