Technical Field

This invention relates to the application of wood

preservative chemicals and in particular to the delivery of wood

preservative chemicals in a dry form onto the surface of wood

structures.

While the invention will be described with reference to

wooden poles, it should be understood that, the invention is

applicable to all wooden structures which are in contact with soil

at ground level.

Background Art

In Australia, wooden poles make up the majority of poles

used as structural supports for power transmission and

telecommunications lines. The service life of poles is greatly

reduced by biodegradation processes at ground level caused by

fungal decay such as soft rot, white and brown rot and termite

attack by damp wood and dry wood termites. Due to the high

capital investment involved in these structural poles, and the

cost of repairing and replacing these poles, it is therefore

desirable to treat the poles in some way to combat

biodegradation in wooden poles and greatly increase their

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service life. It has even been found that poles treated with wood

preservative chemicals prior to installation can have a longer

service life if they are inspected regularly and given further

remedial treatment during the life of the pole.

Known methods for the remedial treatment of wooden

poles have involved pouring treatment liquids such as creosote

onto the surface of the pole and into the back-fill of the soil.

This method has been found to be unsatisfactory as it relies on

*_ migration of the treatment chemicals from the soil into the wood

and generally requires regular treatments about every two years.

This method is further unsatisfactory as most of the chemicals

used, leach into the soil away from the pole and do not serve

their intended purpose and create an environmental hazard.

The most effective means of controlling fungal decay and

termites is to apply a wood preservative containing bandage or

applicator. In principle these bandages offer the most direct

method of delivering chemicals to the wood whereby the

chemical diffuses freely into the wood.

The principle elements required for any biodegradation of

wooden structures are moisture (generally above about 20%

nutrients and air. Consequently bandages are positioned at

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ground level as this is where the wood structures are most

susceptible to fungal decay and termite attack.

Bandages supplied in rolls with diffusible chemicals

bonded as dry powder mix to a weather impermeable sheath

have been used in Europe and U.S.A. In addition preservative

liquid or paste have been used onto wood structures as

remedial treatments. These preservatives are either

incorporated into a bandage or applied onto the timber surface

by brushing or spraying. As the chemicals are exposed prior to

being applied to the pole, users are required to wear protective

clothing to avoid contact with the chemicals. This is seen as a

disadvantage especially in climatic conditions where protective

clothing is uncomfortable to wear. Other bandages have been

developed which have been generally cumbersome and difficult

to apply thus limiting their appeal to the industry. The ideal

bandage should be weatherproof, exclude ground water and not

be hazardous to the user, the environment or the general public.

Wood preservative bandages which impregnate an inert

matrix with chemical must not only support the chemical but also

must be sufficiently thick to be able to contain a satisfactory

dosage of chemical. This makes a chemical impregnated

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bandage difficult to shape to the contours of a wooden structure

and apply.

Disclosure of the Invention

It is an object of the present invention to provide a wood

preservative bandage which is safer to apply and more

environmentally acceptable.

In accordance with the objectives, the invention provides

a wood preservative bandage for wooden structures comprising

a flexible matrix having a surface for contact with the wooden

structure and having formed therein a plurality of individual

reservoirs adapted to receive a wood preservative chemical said

reservoirs communicating with the surface for supplying the

chemical to the surface and a fastening means for securing said

matrix in position on said wooden structure,

said plurality of individual reservoirs being arranged on the

flexible matrix to enable said matrix to be shaped to conform to

the contour of the wooden structure.

As the wood preservative chemical is contained in

reservoirs formed in the matrix, the only physical requirement on

the flexible matrix is that it supports the chemical reservoirs.

Therefore, the matrix can be made from thinner material to the

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impregnated bandages of the prior art with the consequence that

the bandage of the present invention is easier to shape and

apply to a wooden structure and is not as cumbersome as prior

art bandages.

In a preferred form the reservoirs are closed on the side

of the bandage away from the wooden structure. By providing

the wood preservative chemical in individual reservoirs in the

bandage the problems of the prior art associated with chemical

gravitating to the bottom of the bandage is alleviated.

Furthermore, therefore if the matrix is damaged, loss of

preservative, only occurs from the damaged reservoirs.

Leaching is minimised as only the wooden surface which is in

direct contact with the damaged reservoir surface is exposed.

The matrix may be provided with lines of weakness to

further assist the shaping of the matrix to the contour of the

wooden structure. ^* These links of weakness are preferably

aligned substantially vertically when the matrix is installed on the

structure. It is preferable that the matrix is weatherproof and is

provided with sealing means above and below the plurality of

reservoirs to exclude the entry of water around the peripheries

of the bandage.

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The fastening means may be a line of indentations formed

in the matrix above and below the plurality of reservoirs. The

indentations are formed such that the formation of female

members on one side of the matrix causes corresponding male

members to form on the opposite side of the matrix.

When the bandage is positioned on the wooden structure,

one end of the matrix overlaps with the other and the male

members of one end co-operate with the female members of

the other to secure the bandage in position. The fastening

means then also acts as a sealing means for the bandage.

Alternatively, the fastening means may be in the form of

a strap or tape which surround the wooden structure and

secures the matrix to the pole above and below the plurality of

reservoirs.

The foregoing and other features, objects and advantage

of the present invention will become more apparent from the

following description of the preferred embodiment and the

accompanying drawing in which:

FIGURE 1 is an plan view of a bandage in accordance

with the present invention,

FIGURE 2 is an elevational view of the bandage shown

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through section A-A of in FIGURE 1 , AND

FIGURE 3 is an elevational view of the bandage shown

through section B-B of FIGURE 2.

Best Mode of the Invention

In the embodiment of the wood preservative bandage 1

shown in FIGURE 1 , the flexible inert matrix 2 has a number of

chemical reservoirs 3 formed therein. The chemical reservoirs

are arranged such that when the matrix is applied to a wooden

structure, the reservoirs do not hinder the shaping of the inert

matrix. In the preferred form, the reservoirs are formed in the

matrix such that the reservoirs extend away from the surface of

the matrix in contact with the wooden structure.

The size of the wood preservative bandage will depend on

the wooden structure intended to be treated. It is considered

that for most wooden poles the reservoirs will be provided over

about 1 to 1.5 meters of the inert matrix. The matrix has a

leading edge of one column of unfilled reservoirs. When the

bandage is wrapped around a pole the leading edge is clipped

onto the back of the filled reservoirs at the opposite end of the

bandage. This prevents water from entering through the end of

the bandage. The embodiment shown in FIGURES 1 to 3

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shows a wood preservative bandage which is 5 reservoirs wide.

For a standard wooden pole for supporting power transmission

and telecommunication lines, a wood preservative bandage

which has reservoirs provided over an area of 100 cm x 20 cm

is used. The preferred reservoirs are about 16 mm in diameter

and 8 mm deep and are arranged in a pattern of 42 reservoirs

long and 8 rows wide. Reservoirs may be of other sizes and

shapes and preferably able to hold a volume of between 500 to

1000 cc of dry chemical. This arrangement allows for even

distribution of the chemical to the treated wood surface.

As an alternative to providing the wood preservation

bandage in predetermined lengths, the bandage may be

produced in continuous rolls and the rolls cut to the required

size as they are being applied.

To form the reservoirs 3, the matrix 2 which is a sheet of

thermoplastic material is heated and subjected to a conventional

vacuum forming operation. These reservoirs then act as moulds

for the wood preservative chemical. A wood preservative

chemical is provided at an elevated temperature which ensures

adequate flowability into the reservoirs. The wood preservative

chemical may comprise any water soluble or diffusible fungicide

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and insecticide but is preferably a mixture of boron compounds,

such as, disodium octoborate tetrahydrate with or without

fluoride compounds such as sodium fluoride to form a watery

paste.

Starting at one end of the bandage illustrated in FIGURE

1 , between 0.5 and 1.5 kg of the paste, preferably 0.8 kg is

poured into the reservoirs. To ensure that the reservoirs of the

matrix are full, the paste material is allowed to set slowly in an

_ elevated controlled room at about 30°C. The bandage is then

stored in a cold room at a temperature of about 5°C to allow

complete solidification of the paste.

To assist installation to a wooden structure, the matrix may

be further provided with lines of weakness 5 formed between the

columns of the reservoirs. Lines of weakness may be formed by

scoring a line in the matrix thereby making the matrix thinner

and easier to bend at that point.

To maintain position on the wooden structure, the bandage

may be provided with a line of indentations 7,8 respectively

above and below the array of reservoirs. The indentations are

drawn or stamped into the matrix to provide a male extension on

one side of the matrix and a corresponding female formation on

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the other. Once the bandage is positioned encircling the

wooden structure, the lines of indentations overlap upon

themselves. The overlapping male extensions are then pressed

into the female formations to maintain the position of the

bandage on the wooden structure. Additionally, the leading

edge 9 with a column of unfilled reservoirs is clipped into

position onto the back of filled reservoirs at the opposite end of

the bandage.

However, to prevent water entering from the above and

below the array of reservoirs, as an alternative to or in

conjunction with the line of indentations has been found useful

to provide straps or tapes (not shown) to secure the upper and

lower bandage seals onto the pole.

While it is preferable for the flexible matrix to protect the

wood preservative chemicals from the effects of the weather, a

weather cover may be provided around the installed matrix for

weather protection.

The bandage is installed at the ground level of the wooden

structure because this is the area of the structure most

susceptible to fungal attack. At the ground level of the wooden

structure, there is sufficient moisture within the wood to allow

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migration of the chemicals, contained in the reservoirs, to the

surface of the wood. Furthermore, the moisture is absorbed by

the wood preservative chemicals in the reservoirs causing the

dry chemical to swell and providing a back pressure in the

reservoirs to further assist the migration of chemicals to the

surface of the wood. The treatment chemicals then slowly

diffuse into the wood to destroy both the fungal organisms and

termites present and prevent further infestation until the

_ chemicals are exhausted.

After installation of the bandage to a wooden structure a

further back pressure may be provided by compacting the soil

back-fill around the bandage. As the chemicals are absorbed

into the wooden structure, the reservoirs collapse under the

effects of the soil back pressure thereby maintaining the contact

between the chemicals and the wooden structure. Once the

chemicals are exhausted, which is usually after 3 - 5 years, the

bandage is replaced.

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