Timber poles which are inserted into the ground are preferably treated with a preservative, e. g. creosote, copper-chrome- arsenic, or the like, in order to prolong the working life of the pole.

Typically, a pressure impregnation process is used which tends to only impregnate the outer region of the pole. The core or inner region, which in poles made of certain types of trees such as eucalyptus trees, may constitute a substantial portion of the diameter of the pole, generally remains untreated and thus vulnerable to fungal and insect attack. It is an object of this invention to offer a solution to this problem.

According to one aspect of the invention there is provided a method of increasing the working life of a timber pole which includes replacing at least a part of an inner portion of the pole with an insert treated or treatable to increase the working life of the pole.

Typically, the method includes treating the insert prior to insertion of the insert.

The method may include treating the insert after insertion of the insert.

The insert may be of wood in which case treating the insert may include at least partially saturating it with a wood preservative.

The partial saturation of the insert may be provided by feeding preservative located at an elevated position relative to the insert when the pole is in an operative upright position so that the preservative is fed under gravity to the insert.

The method may include forming a reservoir within the pole for storing a supply of preservative, the reservoir being in flow communication with the insert when the pole is in an operative upright position.

Forming the reservoir within the pole may include forming a blind bore in the pole from one end; at least partially filling the blind bore with a wood preservative; and inserting the insert into the bore such that an inner end thereof is spaced from a blind end of the bore thereby to define the reservoir for the preservative.

The diameter of the bore may be between 1/4 to 1/2 the diameter of the pole.

The method may include periodically replenishing the reservoir with preservative via a transverse passage leading to the reservoir.

The method may include providing a protective outer jacket about a portion of the pole including at least a portion of the insert. The jacket is typically in the form of a sheet wrapping of a plastics material.

According to a second aspect of the invention there is provided a timber pole which includes an insert treated or treatable to extend the working life of the pole.

The insert may be of wood, typically a softwood such as pine.

The pole may include a blind bore provided at an end of the pole for receiving the insert, and a reservoir defined between an end wall of the blind bore and an end of the insert.

The reservoir may include a wood preservative.

The pole may include a transverse passage leading into the reservoir for feeding wood preservative into the reservoir.

The pole may include an end plate for securing the insert to the pole. Typically, the end plate is secured to the pole by means of fastening elements e. g. nails.

The pole may include a protective outer jacket provided about a portion of the pole including at least a portion of the insert.

Typically, the jacket is in the form of a wrapping of a plastics material.

The diameter of the insert may be between 1/4 to 1/2 the diameter of the pole.

The invention extends to a timber pole have a blind bore extending from one end.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawing which shows a longitudinal section of part of a timber pole in accordance with the invention.

Referring to the drawing, reference numeral 10 generally indicates a timber pole in accordance with the invention. The pole 10 has a circular cross-section and has a blind bore 14 which is formed by drilling a hole in a base portion 12 of the pole 10. A diameter 18 of the bore 14 is typically between about 1/4 to Vs the diameter of the pole 10.

It is to be appreciated that the diameter 18 of the bore 14 may vary depending upon the type of tree from which the pole 10 is made. For example, poles made of a hardwood such as eucalyptus, generally have a narrow outer band corresponding to what would have been sapwood during the life of the tree. This band varies between about 10 mm and about 25 mm, depending upon various factors such as the age and growth rate of the tree. Accordingly, the diameter 18 of the bore 14 of a pole made of a hardwood is substantially larger than the width of its remaining outer portion or outer band 17. The bore 14 has a depth 20

which varies depending on the depth to which the pole 10 is to be planted in the ground 22. Generally, the bore 14 is drilled to such a depth so that its blind end 24 is about 200 mm above the ground level 23 as shown by arrow 26.

The pole 10 has an insert 16 in the bore 14 which replaces a substantial portion of the inner portion of the pole 10, and is typically of a softwood such as pine or the like which readily absorbs a wood preservative. In one embodiment of the invention, the insert 16 is at least partially, preferably fully, treated with a wood preservative e. g creosote, copper-chrome-arsenic, or the like, prior to being inserted in the bore 14. In addition, the remaining outer portion 17 of the base portion 12 is also treated with the wood preservative thereby to prolong the life of the pole 10.

A reservoir 32 is defined between an inner end 34 of the insert 16 and the blind end 24 for receiving further wood preservative.

In use, the blind bore 14 is partially filled with a wood preservative e. g. prior to insertion of the insert 16. Over time, the wood preservative diffuses into the remaining outer portion 17 of the base portion 12 as well as into the insert 16 thereby to increase the working life of the pole 10. An oblique transverse passage or bore 36 is drilled into the remaining outer portion 17 of the base portion 12 via which further preservatives may be fed into the reservoir 32 thereby to replenish the supply of preservatives therein during the working life of the pole 10.

In order further to enhance the working life of the pole 10, a protective outer jacket in the form of a sheet of plastics material 38, typically about 250, um thick is wrapped firmly around the base portion

12 of the pole 10. The sheet 38 is stapled to the pole 10 and extends typically about 50 mm above the ground surface 23 as shown by arrow 40 and at least about 450 mm below the ground surface 23 as shown by arrow 42.

Conventional timber poles which are inserted into the ground are preferably treated with preservative to prolong their working lives. Typically, a pressure impregnation process is used which tends only to impregnate the outer region of the pole. Thus, the quantity of preservative that can be absorbed, and the depth of its penetration into a conventional pole is dependent upon the width of a narrow outer band of the pole corresponding to what would have been sapwood. The core region of the pole due to its density tends not to absorb the wood preservative thereby rendering it vulnerable to fungal and insect attack.

Accordingly, poles of a hardwood while being generally much stronger than the poles of a softwood generally have a reduced working life as absorption of the wood preservative is less effective. However, in the case of the pole 10 in accordance with the invention, a substantial portion of the core which, under normal circumstances, would remain untreated, is drilled out and replaced with the insert 16. As the insert 16 is of a softwood which readily absorbs wood preservative, a substantial part of the base portion 12 is thus more fully treatable with a wood preservative thereby prolonging the working life of the pole 10. In order to enhance treatment of the outer region of the pole 10, the application of wood preservative may take place from an outside peripheral region of the pole 12 as well as internally from within the bore 14.

The inventors believe that the invention, as illustrated, provides a timber pole 10 with an enhanced working life as the generally untreatable core region of the pole 10 is replace with an insert 16 which has been treated or is treatable with a wood preservative in order to inhibit or retard fungal or insect attack.