Method and system for preserving timber utility poles

Abstract

A method of preserving the aboveground section of a timber utility pole includes treating the pole with a wood preservative, heat-shrinking a plastic sleeve around the pole to encapsulate the preservative, and storing the pole horizontally prior to installation. The plastic sleeve protects the pole during storage by reducing preservative volatilisation and migration. The pole is installed vertically in its encapsulated state, with the sleeve covering at least the aboveground section to shield it from environmental degradation such as rain and sunlight. Additional plastic sleeves may be applied to enhance durability, including during long-term use. The method provides a protective barrier that maintains the structural integrity and preservative efficacy of the pole while allowing for efficient handling and installation.

Description

Method and System for Preserving Timber Utility PolesField of the Invention

[0001] The field relates to the preservation of timber utility poles, specifically methods and systems for protecting the aboveground sections of such poles from environmental degradation and preservative depletion during storage, handling, and long-term use.Background

[0002] Timber utility poles are widely used for various applications, including supporting data and power transmission lines. These poles are typically installed in a rough-hewn state to minimise costs and expedite installation.

[0003] In recent years, timber utility poles have increasingly been treated with wood preservatives to enhance their longevity. Traditionally, the application of wood preservatives has focused on the foundation of the utility poles, where elevated soil moisture levels contribute significantly to fungal decay and wood borer infestation.

[0004] While existing preservation systems primarily concentrate on protecting the embedded portions of utility poles to prevent rot and failure, the aboveground sections are also susceptible to degradation, albeit to a lesser extent. This vulnerability arises from exposure to extreme weather conditions such as sunlight, rain, and wind, which subject the timber to cycles of drying and wetting, as well as shrinking, expanding, freezing, and thawing. These actions compromise the structural integrity of the timber over time. Furthermore, weathering accelerates the depletion of oil-borne preservative systems (and, to a lesser extent, water-borne systems), hastening the timber's degradation.

[0005] Consequently, there is a pressing need for effective protection of the aboveground section of utility poles from environmental degradation, including UV damage.

[0006] Environmental concerns prevent the application of wood preservatives to the exposed aboveground sections of utility poles after installation, necessitating treatment at the timber yard or another preparation facility prior to installation.However, once treated, utility poles are typically stored in horizontal piles at utility company storage facilities, where any applied wood preservative is particularly vulnerable to rapid migration and depletion.

[0007] Specifically, the upward-facing surfaces of horizontally stacked poles are exposed to sunlight and severe radiant heating, causing volatile components of the preservatives to evaporate under heat and light. Additionally, the horizontal orientation of the poles allows preservative solutions to migrate under gravity, seeping out from the lower surfaces of the poles. These depletion processes are most severe immediately after treatment.

[0008] Attempts to mitigate these effects include periodically turning the poles to alternate the exposed surfaces, thereby redistributing the effects of sunlight and heat. While effective to some extent, this practice is labour-intensive and often neglected. Another approach involves periodically spraying the horizontal pole piles with preservative to replenish depleted areas. However, this method is only partially effective, and increased application only exacerbates the rate of depletion.

[0009] To counteract these undesirable effects, some timber utility poles are stored vertically in protected storage facilities to reduce preservative loss. However, this method is rarely employed due to the significant time, space, and effort required. Vertical storage is typically reserved for large and expensive transmission-class poles, which have slower inventory turnover. Similarly, roof-covered storage can mitigate preservative depletion by minimising temperature fluctuations, but it is costly and cumbersome, particularly for machine handling of the poles.

[0010] Thus, there remains a significant challenge in developing a cost-effective and efficient method for protecting the aboveground sections of timber utility poles while maintaining their long-term structural integrity and preservative efficacy.Summary of the Disclosure

[0011] The described method for preserving the aboveground section of a timber utility pole involves treating the pole with a wood preservative at the timber yard or similar preparation facility and immediately encapsulating it by heat-shrinking aplastic sleeve around the timber utility pole. Preferably, the plastic sleeve is made of polyvinyl chloride (PVC).

[0012] Once treated and encapsulated, the timber utility pole can be stored horizontally for extended periods, typically exceeding one month and potentially up to 12 months or more, even under exposed conditions. The heat-shrunk plastic sleeve tightly encapsulates the treated pole during storage, significantly reducing preservative volatilisation and impeding downward preservative migration. This prevents seepage from the lower horizontal surface of the pole.

[0013] The utility pole can subsequently be installed vertically in its encapsulated state with minimal or no preservative degradation. The heat-shrunk plastic sleeve protects the wood preservative and the wood in the aboveground section from environmental factors such as rain and sunlight, avoiding the need for postinstallation application of preservative or encapsulation. The sleeve also prevents or substantially reduces rainwater ingress once the pole is installed preventing or reducing biocidal attack or frost-cycle expansion.

[0014] The sleeve is non-integral with the wood surface, allowing it to resist cracking or splitting during the natural seasoning process of the timber. This ensures the barrier integrity of the plastic sleeve is maintained, whether during long-term horizontal storage or after installation. However, to further mitigate the effects of cracks or splits, an additional plastic sleeve may be applied over the initial sleeve. The inner sleeve, which may key into the wood grain, presents a smoother surface to the secondary sleeve, allowing slippage between the two. This enables the secondary sleeve to stretch without engaging with the keyed inner sleeve, preserving the overall encapsulation. Preferably, the secondary sleeve is applied before installation.

[0015] For long-term protection, the utility pole may be further encapsulated with additional heat-shrunk plastic sleeves post-installation. For example, after extended periods of exposure, such as 12 months or several years, a third sleeve can be applied over the weathered sleeves and heat-shrunk to maintain the protective barrier without replacing the utility pole. Additional plastic sleeves may be applied indefinitely.

[0016] Instead of wrapping a plastic sheet around the pole and adhering the overlapping edges — which may detach over time — the sleeve may be in tubular form with a cross-section greater than that of the pole whereby application involves inserting the pole through the tubular sleeve and positioning it around the aboveground section before heating. The sleeve can be pre-manufactured from rectangular plastic sheets, with the long edges overlapped to form a secure, flat seam that does not require field assembly.

[0017] In a preferred form, the sleeve is closed at one end and features an open end through which the pole is inserted until it reaches the closed end. The tubular design facilitates easy application prior to installation, even allowing for handling with machinery while the sleeve is tightly shrunk around the pole. Alternatively, the sleeve can be applied to existing poles by sliding an unshrunk tubular sleeve over the pole and heat-shrinking it in place using a gas blowtorch or similar equipment.

[0018] The protective sleeve can be applied over wood preservatives, such as DCOI, an organic oil-borne preservative that is unstable in sunlight. The UV-protective properties of the sleeve are particularly beneficial in such cases. Additionally, the sleeve may be applied over fire barriers or electrical grounding components on the pole.

[0019] Further aspects of the invention are also disclosed.Brief Description of the Drawings

[0020] Notwithstanding any other forms which may fall within the scope of the present invention, preferred embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0021] Figure 1 shows a preservation system for a timber utility pole, including an aboveground section and an inground section, encapsulated with a heat-shrunk plastic sleeve.

[0022] Figure 2 shows an associated method for preserving the aboveground section of a timber utility pole, including treating with wood preservative, encapsulation with a plastic sleeve, horizontal storage, and vertical installation.

[0023] Figure 3 shows the surface woodgrain of a timber utility pole with surface impregnation of wood preservative, illustrating the interaction between the woodgrain and the plastic sleeve.

[0024] Figure 4 shows a comparison of the woodgrain with a central crack that has widened, illustrating the effect on the plastic sleeve and the role of a secondary plastic sleeve in maintaining barrier integrity.Description of Embodiments

[0025] Figure 1 illustrates a preservation system 100 for a timber utility pole 103, and Figure 2 depicts an associated method 106 for preserving an aboveground section102 of the timber utility pole 103.

[0026] The method 106 begins at step 107, where the utility pole 103 is treated with a wood preservative at a lumberyard or similar preparation facility. The utility pole103 is typically prepared from felled timber, such as southern yellow pine, Douglas fir, or other species commonly used for utility poles, and fashioned into a cylindrical form, as shown in Figure 1 .

[0027] In one embodiment, the wood preservative comprises DCOI, an organic oil- borne preservative for utility poles that is unstable in sunlight and particularly benefits from the ultraviolet (UV) radiation protection provided by the described plastic sleeve. Alternatively, the wood preservative may comprise copper naphthenate.

[0028] At step 108, a plastic sleeve 105 is heat-shrunk around the timber utility pole 103 after impregnation with the wood preservative. Specialised heat-shrinking machinery, such as a horizontal cylindrical oven, may be employed to heat the pole as it is inserted horizontally. Preferably, the plastic sleeve 105 comprises polyvinyl chloride (PVC), and the shrinking process is achieved through controlled heat application using a heat gun or oven. Upon heating, the PVC undergoes a phase change, causing it to contract and conform to the shape of the pole 103. In other embodiments, the plastic sleeve 105 may be PET-G thermoplastic polyester or polyethylene. Preferably, the plastic includes UV stabilisers, such as UV absorbers or hindered amine light stabilisers (HALS), to enhance resistance to UV degradation.

[0029] At step 1 10, the treated and encapsulated timber utility pole 103 is stored horizontally within the plastic sleeve 105, such as at a timber storage facility. Typically, the pole 103 is stored for at least one month, and potentially much longer, until required for installation. This storage is often outdoors, eliminating the need for expensive storage facilities. The plastic sleeve 105 forms a relatively thin layer around the pole 103, enabling conventional manual or mechanised handling.

[0030] During storage, the heat-shrunk plastic sleeve 105 tightly encapsulates the timber utility pole 103, significantly reducing preservative volatilisation and impeding downward preservative migration, thereby preventing seepage from the lower horizontal surface.

[0031] At step 1 1 1 , the timber utility pole 103 is installed vertically in the ground 104, as shown in Figure 1 . When installed, the pole 103 defines an in-ground section 101 embedded within the ground and an exposed aboveground section 102. The plastic sleeve 105 covers at least the aboveground section 102. In one embodiment, the entire pole 103 is encapsulated within the plastic sleeve 105, covering both the aboveground section 102 and the in-ground section 101 . Alternatively, Figure 1 shows that only the upper portion of the timber utility pole corresponding to the aboveground section 102 is covered with the plastic sleeve, leaving the in-ground section 101 available for treatment with alternative foundational systems, such as wrap systems. Wrap systems typically involve the application of specialised materials, such as geotextile fabrics, polymer sheets, or barrier films, around the in-ground section of the pole. These wraps are designed to provide protection against soil-borne factors such as moisture, fungal decay, and termite infestation, which can compromise the structural integrity of the pole. In such cases, the plastic sleeve 105 can either be cut away to expose the in-ground section 101 or applied only to the upper section of the pole during heat-shrinking.

[0032] The plastic sleeve 105 protects the timber utility pole 103 and applied wood preservative from environmental degradation, including rain and sunlight, and avoids the need for post-installation application of preservative or encapsulation.

[0033] To further mitigate the effects of cracks or splits, the method 106 may optionally include applying a secondary (or more) plastic sleeve 105B over the first plastic sleeve 105A at step 109. Figure 3 shows the woodgrain 1 13 of the timber utility pole 103 with surface impregnation 1 14 of the wood preservative. The natural woodgrain 1 13 presents grooves, undulations, cracks, splits, and other formations 1 15. The inner plastic sleeve 105A conforms to this uneven woodgrain, while the secondary plastic sleeve 105B is applied on top, over the smoother surface presented by the inner plastic sleeve 105A for improved durability and flexibility.

[0034] Figure 4 illustrates a widened central crack 1 15 resulting from natural seasoning or environmental effects such as thermal expansion and contraction. While the inner sleeve 105A may key into the woodgrain and potentially split 1 16 as the crack 1 15 widens, the secondary sleeve 105B can slide over the smoother interface provided by the inner sleeve 105A, remaining intact and preserving encapsulation.

[0035] These multiple sleeves 105 may be applied simultaneously, or each sleeve 105 can be heat-shrunk individually before the next is applied.

[0036] For long-term protection post-installation, an additional plastic sleeve 105 may be heat-shrunk around the existing sleeve(s) at step 1 12. For example, after 12 months or several years, a third plastic sleeve 105 can be applied over weathered sleeves 105 to maintain barrier integrity. This process may be repeated indefinitely. The third sleeve 105 can be applied by sliding it over the top of the pole 103 using a ladder or elevated work platform, then heat-shrinking it in place with a blowtorch or similar.

[0037] The sleeve 105 is preferably applied without adhesives or fasteners. In a preferred form, the sleeve 105 is tubular, with a cross-section greater than the pole 103, and is positioned by inserting the pole through an open end prior to heating. The tubular sleeve 105 may be manufactured from a rectangular sheet of synthetic plastic, with the long edges overlapped to form a secure flat seam. The sleeve is then heat- shrunk to conform to the pole’s shape.

[0038] In a further preferred form, the tubular sleeve 105 is closed at one end 108, with the open end 107 allowing the pole to be inserted until it reaches the closed end.The sleeve 105 may cover more than half the pole’s length to protect the majority of the aboveground section or the entire pole for full encapsulation.

[0039] The sleeve 105 can be applied over existing pole treatments, installations, or devices, such as pole-top protective devices, fire barriers, or grounding plates and wiring. Heat-shrinking conforms the sleeve to the shape of these elements, providing comprehensive protection.

[0040] The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that specific details are not required in order to practise the invention. Thus, the foregoing descriptions of specific embodiments of the invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed as obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the following claims and their equivalents define the scope of the invention.

Claims

Claims1 . A method of preserving an aboveground section of a timber utility pole, the method comprising: treating the timber utility pole with wood preservative; heat shrinking a plastic sleeve around the timber utility pole after impregnation with the wood preservative; horizontal storage of the timber utility pole in the plastic sleeve; vertical installation of the timber utility pole in ground following storage, the timber utility pole thereby defining an inground section and the aboveground section, wherein the timber utility pole is installed in the plastic sleeve and the plastic sleeve covers the aboveground section.

2. The method of claim 1 , wherein the horizontal storage exceeds 1 month.

3. The method of claim 1 , wherein the horizontal storage is outdoor storage.

4. The method of claim 1 , wherein the method comprises heat shrinking a second plastic sleeve around the plastic sleeve.

5. The method of claim 4, wherein the second plastic sleeve is applied prior to the horizontal storage.

6. The method of claim 4, wherein the method comprises heat shrinking a third plastic sleeve around the second plastic sleeve.

7. The method of claim 6, wherein the second plastic sleeve is applied prior to the horizontal storage and the third plastic sleeve is applied after the installation.

8. The method of claim 6, wherein the third plastic sleeve is applied more than 12 months after the installation.

9. The method of claim 1 , wherein the wood preservative comprises copper naphthenate.

10. The method of claim 1 , wherein the wood preservative comprises DCOL1 1 . The method of claim 1 , wherein the plastic sleeve comprises polyvinyl chloride(PVC).

12. The method of claim 1 , wherein the plastic sleeve is applied without any adhesives.

13. The method of claim 1 , wherein the plastic sleeve is applied without any fasteners.

14. The method of claim 1 , wherein the plastic sleeve is tubular, defines a crosssection greater than that of the pole, and wherein an end of the pole is inserted through the sleeve to locate the sleeve around the timber utility pole prior to heating.

15. The method of claim 14, wherein the plastic sleeve is manufactured from a sheet having long ends thereof overlapping to form a flat seam.

16. The method of claim 1 , wherein the plastic sleeve defines a closed end and an open end and wherein the end of the timber utility pole is inserted through the open end of the sleeve until it reaches the closed end of the sleeve.

17. The method of claim 1 , wherein the plastic sleeve is applied over a fire barrier applied to the pole.

18. The method of claim 1 , wherein the plastic sleeve is applied over electrical grounding applied to the pole.

19. The method of claim 1 , wherein the plastic sleeve comprises a UV stabiliser.

20. The method of claim 1 , wherein the plastic sleeve covers only the aboveground section.

21. The method of claim 20, wherein a foundational protection system is separately applied to the inground section.

22. The method of claim 1 , wherein the plastic sleeve covers the entire utility pole.

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