GB2156887A

GB2156887A - Repairing timber poles

Info

Publication number: GB2156887A
Application number: GB08407342A
Authority: GB
Inventors: Harold Charles Foreman
Original assignee: Merseyside and North Wales Electricity Board
Current assignee: Merseyside and North Wales Electricity Board
Priority date: 1984-03-21
Filing date: 1984-03-21
Publication date: 1985-10-16
Also published as: GB8407342D0

Abstract

A sleeve 5 is placed around the pole 3 bridging the rotten section of the pole and a resin 11 is introduced within the sleeve and allowed to cure. The sleeve 5 may be pre-formed with lugs 9, spaced axially and circumferentially, which contact the pole surface and define interconnecting spaces extending longitudinally and circumferentially which are filled by the resin. <IMAGE>

Description

SPECIFICATION Repair system for load carrying timber poles The present invention relatestoa repairsystemfor load carrying timber poles, pipes or similar load carrying structural units. The system has particular application in repairing wooden poles carrying overhead transmission lines.

A large quantity of wooden transmission poles are in use throug hour the country and these poles, whilst treated with preservative are liable to rot in time at approximately ground level primarily as a result of continual wetting and drying out. Thus, an otherwise sound pole is rendered unserviceable by virtue of one or two feet of rot adjacent ground level. The cost of replacing such poles is expensive both in terms of capital and labour costs, and it may be necessary to isolate the transmission wires during the process which is inconvenient.

One repair system has been proposed and this utilizes longitudinal metal bars which are spaced around the circumference of the pole bridging the rotten section and held in place using circumferential bands. The system restores some of the strength of the pole but suffers from the disadvantage that it does not solve the problem of rotting as the pole is still in contact with the ground, i.e. still subject two wetting and drying out.

The present invention aims to overcome the above mentioned problems by providing a repair system which prolongs the useful life of the poles.

According to the present invention there is provided a method of repairing a load carrying wooden pole or the like in which sleeve is disposed around the circumference of the pole so asto bridge the rotten section of pole and so as to have portions which are spaced from the pole to provide interconnecting spaces extending longitudinally and circumferentially within the sleeve to receive a resin which is introduced therein,wherebyupon hardening ofthe resin a structurally effective external shell is formed around the pole.

The sleeve is preferably made of a plastics material which is provided with a plurality of spaced lugs, preferably circumferentially and axially spaced so as to adapt the sleeve to be curved circumferentially around the poles which are typically round in crosssection. In one embodiment the lugs take the form of discrete longitudinally extending ribs, whilst in another embodiment they take the form of dome- ended circular projections. In use, the lugs project inwardly so asto abutthe outer circumference ofthe pole and thereby serve as stand off lugs to determine the distance that the remainder of the sleeve is spaced from the pole so asto definethe interconnecting longitudinal and circumferential spaces for the resin.

The sleeve is preferably formed with the desired shape of lugs by vacuum moulding. A number of alternative configurations of sleeve are possible, the importantfeatures being that there is a continuous annular space available to receive resin. A self adhesiveseal is preferably employed to form the longitudinal seal where the longitudinal edges of the sleeve overlap with one another. The sleeve is conveniently retained in position by applied circum ferential bands ofadhesivetape.

The sleeve may be left in place or cut off after the resin has set. The resin is preferablyformulated to exhibit strength characteristics and physical prop erties which are complimentary to the material of the member being treated. Fibres or another suitable strengthening medium may be introduced into the resin to achieve higher strengths. The resin used is free flowing when initially prepared for use.

The repair system has the advantage overthe known systemsthatthe shell formed around the pole is durable and waterproof and so encapsulates and seals the treated length oftimber.

The present invention will now be described further hereinbelow, by way of example only, with reference to the accompanying drawings; in which: Figs. 1 and 2 are simplified diagrammaticviews of two stages in the method; Fig. 3 is a simplified cross-sectional view of a pole with sleeve applied and Fig.4 is a perspective view of part of one embodiment of sleeve showing the lugs.

Referring to the figures, the rot zone of a pole is designated by the arrowsAand may be 2-3 feet (0.75 to 1.0 meters) on eithersideofground level GL. An excavation 1 is made around a pole 3 which is found to be rotting to a depth of approximately 3 feet (1 meter) so asto expose the pole over the rot zone A and a further buried part of the pole which is in relatively good condition. A sleeve 5 of plastics material is folded roundthe pole and held in position by applying bands of adhesive tape (not shown) around the sleeve.

A self adhesive layer is applied to the longitudinal edge of the sleeve, (see Fig. 4) to enable the overlapping edges ofthe sleeve to be sealed and thereby avoid loss of resin.

One example of a suitable sleeve is shown in Fig. 4.

The sleeve 5 is formed with raised longitudinally extending ribs 9, preferably during a vacuum moulding process. The ribs serve as distance pieces or stand off lugs to locate the sleeve relative to the pole and to ensure that interconnecting longitudinal and circumferential spaces are formed between the pole and the sleeve. Preferably the spaces form continuous annular recesses. It is not essential that all the ribs contact the pole and some may be provided to act as stiffeners or to vary the thickness of resin so that alternate thick and thin longitudinal ribs are formed around the circumference ofthe pole. In an alternative embodiment, not illustrated, the longitudinal ribs 9 are replaced by circular projections having a dome-like, or hemispherical end. By way of example, the projections may be 30 mm in diameter, and 25 mm high. Thus giving a minimum resin thickness of 25 mm.

Once the sleeve is fitted in position, resin 11 in liquid form and free flowing is introduced into the spaces between the sleeve and pole which togetherwith any voids inthe pole itself become filled with the resin.

Conveniently the resin is poured in at the open top of the sleeve and penetrates underthe influence of gravity. The resin isformulatedto exhibit strength characteistics and physical properties, complimentary to the material of the memberbeingtreated. Once the resin has set a structurally effective external shell 15 is formed which is durable and waterproof and which encapsulates and seals the treated length of timber.

This is especially the case where the sleeve is retained in position, and even if part of the sleeve or all of it is removed the distance ribs are only small in area and restrict the possible ingressofwater. On curing ofthe resin heat is generated and it is believed thatthis may havetheeffectofkilling offany mould orspores on the pole as well as reactivating the preservative i.e.

rendering it less viscous and so enabling itto be redistributed throughtout the wooden pole. Thus the repairsystem arrests or contains deterioration ofthe pole.

A collar may be fitted to the pole adjacentthetop of the sleeve to disperse water running down the pole onto the outside of the sleeve or resin shell so avoiding penetration at the interface ofthe resin and pole. Alternatively, a chamfer may be formed around the top of the shell, either by bending the sleeve towardsthepole or byshaping the resin during or after curing.

The excavation 1 isfilled in afterthe resin has set sufficiently to resist deformation by the infill 13. The sleeve 5' abovetheground level may be cut away as shown in Fig. 2.

Staples or nails maybe employed to secure the sleeve to the pole. These staples may be inserted in the region ofthe ribs 9. The sleeve 5 is preferably about 2 meters long and is preferably made ofa clear flexible plastics which is non-conductive and nontoxic.

Claims

1. A method of repairing a load carrying wooden pole orthe like in which a sleeve is disposed around the circumference ofthe pole so as to bridge a rotten section ofthe pole and so asto have portions which are spaced from the pole to provide interconnecting spaces extending longitudinally and circumferentially within the sleeve to receive a resin which is introduced therein,whereby upon hardening ofthe resin a structurally effective external shell is formed around the pole.

2. A method as claimed in claim 1 in which a strengthening medium is introduced into the resin to act as a reinforcement.

3. A method as claimed in claim 2 in which the strengthening medium comprises fibres.

4. A method as claimed in any of claims 1,2 or 3 in which the resin is introduced into the open topofthe sleeve.

5. A method as claimed in any of claims 1 to 4 further comprising arranging the opposite longitudinal edges of the sleeve in overlapping relationship and sealing the overlapping surfaces.

6. A method as claimed in any of claims 1 to 5 in which the sleeve is retained in position by adhesive tape applied around the exterior of the sleeve.

7. A method as claimed in any of claims 1 to 5 in which the sleeve is provided with a plurality of spaced ribs or lugs which abutthe pole and the sleeve is retained in position by mechanical fixing means passing through the ribs orlugs.

8. A method as claimed in any preceding claim comprising removing part or all of the sleeve after the resin has set.

9. A method as claimed in any preceding claim further comprising forming a chamfered top to the shell or providing a collar around the pole to disperse water running downthe pole awayfrom the interface ofthe pole and resin shell.

10. A sleeve for use in the method of claims 1 to 9 comprising a plastics sheet having a plurality of spaced lugs so disposed asto allow the sheetto be curved circumferentially around the pole.

11. A sleeve as claimed in claim 10 in which the lugs are spaced axially and circumferentially.

12. Asleeve as claimed in one of claims 10 and 11 in which the lugs take the form of discrete longitudi nally extending ribs.

13. A sleeve as claimed in one of claims 10 and 11 in which the lugs comprise dome-ended circular projections.

14. A sleeve as claimed in any of claims 10 to 13 formed by vacuum moulding.

15. A sleeve as claimed in any of claims 10 to 14 in which a self-adhesive sealing strip is applied to one face ofthe sleeve adjacent an edge thereof for forming a longitudinal seal when the sleeve is wrapped around the pole.

16. A method of repairing a load carrying wooden pole substantially as hereinbefore described with reference to the accompanying drawings.

17. A sleeve for use in repairing a load carrying wooden pole constructed and arranged substantially as hereinbeforedescribedwith referenceto and as illustrated in the accompanying drawings.