TECHNICAL FIELD

[0001] The present invention relates to a method and an apparatus for joining pole segments, especially wooden pole segments. It is thought that one application where the present invention may find use is in joining together wooden pole segments to create wooden poles which may be used as, for example, utility poles (e.g. power poles). However, it is to be clearly understood that the invention is not necessarily limited to this particular application and may find other uses.

BACKGROUND

[0002] There is a growing demand for long length wooden utility poles, for example power poles with lengths ranging from around 10m to around 15m.

[0003] The need to increase the height of a utility pole is a task frequently encountered by, for example, telephone and electricity utility companies. For instance, when an electricity distribution system is upgraded such that electrical transmission lines (power lines) carry higher voltages, the distance between the ground and the electrical transmission lines must be increased. The distance may be increased by methods of replacing or splicing wooden power poles, but those methods are costly and time-consuming.

[0004] One previously proposed method for increasing the height of a wooden utility pole is to connect two shorter pole segments (e.g. an upper pole segment and a lower pole segment) to form a single pole. This has previously involved using an external casing-type pole connector that envelops the end portions of the two joined pole segments. That is, the casing envelops and holds the upper end of the lower pole segment, and it also envelops and holds the lower end of the upper pole segment, and it thereby connects the pole segments together to form a single pole. This method requires precise external machining of the portions of the respective pole segments that are to be enveloped and held by the casing/connector, in order to match the size/shape of the outer end portion of the relevant pole segment to the internal shape and profile of the casine/connector. This has been found to be cumbersome and labour intensive. Furthermore, joints formed in this way are sometimes prone to structural failure, and the external metallic casing may even create a fire risk due to its surface conductivity. It may therefore be desirable if these issues could be overcome or at least alleviated to some extent.

[0005] It is to be clearly understood that mere reference herein to previous or existing apparatus, products, systems, methods, practices, publications or other information, or to any problems or issues, does not constitute an acknowledgement or admission that any of those things individually or in any combination formed part of the common general knowledge of those skilled in the field, or that they are admissible prior art,

SUMMARY OF THE INVENTION

[0006] With the foregoing in view, the present invention, in one form, resides broadly in a method for joining wooden pole segments, the method comprising:

inserting a first portion of a connector into a first channel, the first channel being located at a joining end within a body of a first wooden pole segment and extending into the first pole segment;

inserting a second portion of the connector into a second channel, the second channel being located at a joining end within a body of a second wooden pole segment and extending into the second pole segment; and

securing the connector relative to the first pole segment and second pole segment thereby joining the said joining ends of the first and second pole segments.

[0007] In another form, the invention provides a method for joining wooden pole segments, the method comprising:

forming a first channel at a joining end within a body of a first wooden pole segment, wherein the first channel extends into the body of the first pole segment in a direction of a longitudinal axis of the first pole segment;

forming a second channel at a joining end within a body of a second wooden pole segment; wherein the second channel extends into the body of the second pole segment in a direction of a longitudinal axis of the second pole segment;

inserting a first portion of a connector into the first channel and inserting a second portion of said connector into the second channel, and

securing the connector to the first segment and the second segment thereby joining the first and second segments.

[0008] The pole segments, which may be connected and used as utility poles (for example), are typically in the form of round wooden pole segments derived from various types of trees. The pole segments derived from such trees generally vary in diameter and girth. Providing a method for internally connecting the pole segments using the above described connector being received in the internal channels may be highly advantageous because it may take away the requirement for machining outer walls of the pole segments that are likely to differ in diameter and girth.

Such an internal connecting method and mechanism may also provide an added advantage of being able to withstand greater bending stresses during

[0009] In some embodiments, the two portions of the connector may be inserted sufficiently into the respective channels within the respective pole segments so as to form a substantially rigid join that resists bending or deflection (and/or longitudinal tension) at the join. In fact, it has been found that, for a given pole segment, a preferred (possibly even optimum in some instances) distance for the connector to insert into the pole segment is approximately double (i.e. two times) the diameter of the pole segment.

[0010] The step of securing the connector may comprise inserting one or more fasteners. Each fastener may be inserted from the outside into a pole segment such that the fastener engages with the connector through the body of the pole segment and secures the pole segment relative to the connector. A plurality of the fasteners may be arranged in a substantially spiral or helical arrangement around one or both pole segments. The fasteners may comprise nails, screws, bolts, rivets or the like (mechanical fasteners). Alternatively, or additionally, an adhesive (structural adhesive) might be used.

[0011] The first and second channels may be formed by machining of the joining ends of the pole segments, and more specifically by drilling into the joining ends of the pole segments with a hole saw drill bit. Thus, each of the channels may comprise a ring-shaped recess extending into the pole segments. Each of the ring-shaped channels may create, in the respective pole segments, a core portion inside the channel and a peripheral annular portion outside the channel.

[0012] The step of securing the connector to the first pole segment and second pole segment may comprise securing the core portion and the peripheral portion of each of the segments to the connector. The securing step may further comprise positioning a reinforcing strap around at least one pole segment adjacent its joining end and fastening the strap onto said at least one pole segment under tension.

[0013] In yet another form, the invention provides an apparatus for joining wooden pole segments, the apparatus comprising:

an elongate connecting sleeve with a first connecting portion and a second connecting portion, each of the said portions configured for being received into a channel provided at joining ends of respective wooden pole segments; and

securing means for securing the sleeve relative to a first wooden pole segment and a second wooden pole segment.

[0014] In this form of the invention, the sleeve may be cylindrical in shape. The sleeve may be made of metal (e.g. a suitable steel alloy) and it may have a wall a thickness of at least 2mm and more preferably in the range of 3mm to 6mm for withstanding stresses and loads imposed during use. The cylindrical sleeve may have a circular cross-section with an external diameter of at least 60mm and more preferably in the range of 80mm to 180mm. However, it is also possible that other embodiments might be provided in which the sleeve has a non-circular cross-section (making the sleeve a non-circular "cylinder" such as a hollow shape with a constant triangular, rectangular other polygonal cross-section).

[0015] Preferably the sleeve should have a stiffness (which is at least approximately) equivalent to the stiffness of the upper of the pole segments connected thereby.

[0016] Embodiments of the above apparatus form of the invention may further comprise one or more reinforcing straps. Each strap may be dimensioned for positioning around a circumference of, and at the joining end of, at least one wooden pole segment, and the strap may be configured for being fastened to said at least one wooden pole segment under tension.

[0017] In yet another form, the invention provides a wooden pole member comprising: two opposite ends, wherein at least one end comprises a channel located in a body of the pole member and extending into the body of the member, the channel being dimensioned to receive a connecting sleeve from said at least one end, and wherein the channel defines an inner core portion and a annular peripheral portion of the member.

[0018] In yet another form, the invention provides an assembly for a pole comprising:

at least two wooden pole segments, each segment comprising two ends with at least one of the ends of each segment further comprising a channel in a body of the segment extending into the body of the segment;

at least one connector, each connector for connecting two wooden pole segments, each connector comprising an elongate sleeve with a first connecting portion and a second connecting portion, each of the said portions being configured for being received into the channels provided at a joining end of each of said two wooden pole segments to be connected by said connector; and

one or more fasteners for fastening each sleeve to it's said two wooden pole segments.

[0019] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

[0021] Figure 1 is a perspective view of a wooden pole segment being drilled using a hole saw drill bit.

[0022] Figure 2 is a side view of a wooden pole segment just before it is drilled using the hole saw drill bit.

[0023] Figure 3 is an end view of a wooden pole segment after the channel has been formed therein using a hole saw drill bit.

[0024] Figure 4 is similar to Figure 1 in that it shows a wooden pole segment being drilled using a hole saw drill bit, however Figure 4 also shows the drill motor and the jacks used to support the pole segment during drilling.

[0025] Figure 5 is a schematic side view of two pole segments that have been joined in accordance with one embodiment of the present invention.

[0026] Figure 6 is a substantially end-on view of the join between two wooden pole segments, but wherein one of the segments has been subsequently removed (i.e. one of the segments has been cut away around the connector and cut off just beyond one end of the connector) to reveal the arrangement of nails used in the formation of the joint.

[0027] In Figure 7, (A) to (F) represent images of samples (A) to (F) in Example 1 after destructive testing.

[0028] Figure 8 is a plot of tip load versus external wall diameter & wall thickness for the samples in Example 3.

[0029] Figure 9 is a plot of Modulus of Rupture (MOR) (at the loading point) versus external wall diameter & wall thickness for the samples in Example 3.

[0030] Figure 10 is a plot of MOR (at the joint) versus external wall diameter & wall thickness for the samples in Example 3. [0031] Figure 11 is a plot of tip load versus the diameter of the butt log at the joint for the samples in Example 3.

[0032] Figure 12 is a schematic of the experimental set-up used for the finite element analysis in Example 2.

[0033] Figure 13 contains the results of finite element analysis in Example 2.

[0034] Figure 14 is a schematic view representing the three-point bending test used in Example 3.

DETAILED DESCRIPTION

[0035] Referring to Figures 1 to 4, a wooden pole segment in the form of a wooden pole member 12 is machined (drilled) at one end using a rotary hole saw drill bit 14. The hole saw drill bit 14 is driven by a motor (see Figure 4) and is used to machine a channel 16 in the form of a ring-shaped kerf. The walls of the ring-shaped kerf (channel) 16 define an inner core portion 19 on the inside of the channel, the core portion being inward relative to and surrounded by an annular peripheral portion 17 on the outside of the channel 16.

[0036] Referring to Figure 5, two wooden pole members 22 and 24 are depicted, each with machined ring-shaped channels therein (225 and 245 respectively). Pole segments 22 and 24 are joined to form a pole 100 (e.g. a utility pole or power pole) with an extended height. The pole members 22 and 24 are joined to each other at their respective joining ends 221 and 241. A connector in the form of a hollow cylindrical steel sleeve 30 is used to connect the pole members 22 and 24. A first connecting portion (end) 320 of the connector 30 is inserted into the channel 245 in the pole member 24, it being appreciated that the channel 245 is suitably dimensioned to receive the connecting portion 320 therein. Similarly, a connecting portion (end) 330 of the connector 30 is inserted into the channel 225 in the pole member 22. In some particular embodiments (like the one in Figure 5), the connector 30 may take the form of a cylindrical steel tube, and it may have a length in the range of around 600mm to around 1000mm and an overall diameter in the range of around 60mm to around 180mm (although possibly up to 400mm). However, the connector 30 is not necessarily limited to being made from steel. It could alternatively be made from other materials, for example (but not limited to) composites like wood veneer composites, fibre (e.g. carbon fibre) reinforced composites, etc. Also, as the examples discussed below clearly demonstrate, the invention is in no way limited to the specific dimensions of the connecting sleeve 30 discussed above (or any specific dimensions). [0037] The diameter and the thickness of the connecting sleeve may be chosen according to the diameter and the length of the pole segments which it is to be used to connect/are joined. Note that, often (like in the situation discussed herein with reference to Figure 5), two pole segments (e.g. 22 and 24) may be connected to form a single pole. However, it is to be clearly understood that the invention could also be used to create poles where three or more segments are joined together to create a single pole. The diameter and/or wall thickness of the connecting sleeve may be selected such that the overall bending stiffness of the joint performed using the sleeve is substantially similar to the bending stiffness of the pole members themselves (e.g. 22 and 24) joined thereby. This may assist in reducing the stress concentration effect in the wood that is adjacent the connecting sleeve 30 (i.e. adjacent the join).

[0038] In the embodiment depicted in Figure 5, the cylindrical sleeve 30 is secured to the pole members 22 and 24 using fasteners in the form of nails 45. The locations where the nails 45 are inserted are arranged in a helical arrangement, as is evident from Figure 6. Such a helical arrangement has been found to be advantageous in preventing crack propagation along the pole members 22 and 24 (as compared to placing nearby nails vertically above and below one another along the wood grain, which can cause splitting). In a typical joint formation, after the pole segments and the sleeve are positioned relative to one another, the nails 45 are driven in so as to penetrate the annular peripheral portion 17 of the relevant pole member (22 or 24), extend through the cylindrical wall of the steel connecting sleeve 30 and into the central core portion 19 of the relevant pole member (22 or 24). It has been found that using nails in this way also improves the performance of the joint in sheer. The number of nails used, and their spacing/pattern/arrangement, may be varied according to the length of the connector 30 used to form the joint. Typically, the nails will be inserted using a nail gun or similar machine (due to the size of the nails and the forces required). A commercial paste formulation may also be inserted or applied into the channels (225 and 245) to protect the connection against, for example, wood-destroying fungi, insects, etc.

[0039] Whilst embodiments of the invention may operate using nails as described above, it is possible that the connector 30 may be secured relative to the channel in one or both of the pole segments using (or also using) adhesive or glue. Hence, adhesive/glue may be used instead of, or together with (i.e. in addition to), nails as described above.

[0040] In order to further improve the strength of the join between pole members 22 and 24 connected by the connecting sleeve 30, one or more reinforcement straps 60 may be positioned and tightened around the circumference of the pole members 22 and/or 24 in the vicinity of the join. As illustrated in Figure 5, the reinforcing straps are positioned adjacent the respective joining ends of the pole members 22 and 24 and they have the effect of applying a reinforcing inwardly directed (squeezing) force to push the annular peripheral portion 17 of the relevant pole members 22 and 24 towards/against the connecting sleeve 30. The reinforcement straps 60 can be further fastened or secured in place on the outside of the relevant pole members using fasteners 65 (typically small screws or nails). The tension with which individual reinforcement straps 60 are applied should preferably be adjusted in order to compensate for the effect of, for example, movement of the wood due to moisture content variations such as shrinkage which can induce loose strapping, etc.

[0041] Experiments including bending tests indicate that one stress concentration location is in the annular peripheral portion 17 of the relevant pole members 22 or 24 adjacent the joining ends 221 and 241. Therefore, positioning and fastening reinforcement straps 60 (typically steel straps) may assist in significantly improving strength in this area. The reinforcement straps 60 may also prove useful as a visual indicator of possible/potential mechanical damage to the pole due to high bending moments being applied during events such as car collisions, snow, flood etc. This is because, in the event of significant bending stress on the pole at the join, the straps will often snap before the pole itself fails, and therefore a snapped strap can indicate a pole that may have been subject to a significant bending event (e.g. due to a car collision, high wind, flood, etc) and which may therefore be in need of inspection (and/or possible repair, etc).

[0042] The present invention as described herein provides several advantages. Firstly providing an internal joining system, which in the described embodiment includes the connecting sleeve 30 inserted and secured in the internal co-axial channels 225 and 245, enables the use of a standardised machining system for machining the channels 225 and 245 in pole segments without the need to modify the machining procedure for pole members of differing girth or thickness. The importance of this will be recognised when it is considered that wooden pole segments will very often (if not always) be made from tree trunks (after processing, treatment, etc, of the trunks). Therefore, as the external size and shape of tree trunks typically varies considerably from one tree to another, accordingly the external size and shape of the pole segments that may be used with the present invention will also vary. Nevertheless, as illustrated in Figure 5, the invention enables two pole segments to be joined to one another even where the external size and/or shape of one of the segments at the joining end differs considerably from the other at its joining end. In contrast, in the joining system discussed in the Background section above, considerable external machining of both pole segments is required so that the joining ends of both pole segments fit tightly inside the external metal casing used to form the joint. [0043] Another benefit of the presently proposed internal joining system is that the internal fixing (i.e. the internal sleeve 30) does not prevent things such as signs (e.g. road signs and the like) from being attached to the pole using nails or the like in the vicinity of the joint. This may not be possible with the joining system discussed in the Background section above because, in that case, the metal casing used to form the joint is on the exterior of the pole and may be too hard to receive nails or screws for affixation of signs.

[0044] The present invention also has the benefit that it requires little (if any) change to the way poles such as power poles are handled, transported, etc. Therefore, there may be little (if any) need for users of power poles (e.g. energy and telecommunications companies) to change their existing pole logistics and handling practices.

[0045] The present invention may be used, for example, to repair or extend existing power poles without the need to completely replace an existing power pole. The need to repair an existing power pole may arise because, for example, wooden poles typically have one end buried in the ground. This can lead to deterioration (rot) of the pole at or below ground level. Similarly, an existing power pole may need to be extended (heightened), for example, for reasons discussed in the Background section above. In either case, rather than simply replacing the entire existing power pole with a completely new power pole, the present invention could be used if a lower portion (segment) of the existing power pole is first removed but the upper portion (segment) of the existing pole is kept. Then, the present invention could be used to insert a new segment to form the lower/base end of the pole. In the above case of a pole requiring repair, the newly inserted lower segment could be made from new wood, which could then be buried in the ground and the pole returned to use. Similarly, in the above case of a pole that must be extended (heightened), the newly-inserted lower segment could be longer than the previous one, thus increasing the overall height of the pole. In both of these examples, wastage is reduce not only because the upper portion of the existing pole continues in use (rather than being discarded), but also because pole segments (which might not themselves be long enough for use as a stand-alone pole) can nevertheless be used to increase the life and/or height of an existing pole. Furthermore, the invention could be used in circumstances where the upper portion (segment) of a pole is damaged (e.g. by a falling tree or the like) but the lower portion (segment) remains undamaged. In this situation, if the upper portion (segment) of the existing power pole is first removed but the lower portion (segment) of the existing pole is kept, the present invention could then be used to insert a new segment to form the upper end of the pole before returning the pole to service. Example 1

[0046] Referring to Figure 7, mechanical testing of the samples (A) to (F) was carried out based on the ASTM D 1036 - 99 (Standard Test Methods of Static Tests of Wood Poles). A three point static bending test was applied. In the testing method, the pole was supported near the butt and tip, and a load was applied at the theoretical ground line by the head of a mechanical testing machine.

[0047] For these tests the span between butt and tip supports was approximately 11.3 m (maximum machine span). The ground line load was applied at 2.1 m from the butt end. The position of the pole joint was varied from approximately 5 m to 7.5 m from the butt support.

[0048] Test results are provide in Table 1 showing:

• the span, ground line and length from the butt support to the join;

• the diameter at the join;

• the maximum force applied;

• the number of straps used on the butt and tip sides of the join; and

• the failure type.

Table 1

A 1 1.34 2.1 4.97 306 88.9 Χ6Λ6 none none tension - butt end

B 1 1.32 2.1 7.53 315 180.9 33,56 2 straps 1 strap join in butt straps

C 1 134 2.1 7.03 274 125.4 23.22 2 straps 1 strap shear - butt end

D 1 1.32 2.1 5.57 280 125.5 2 straps none tension - top end

E 1 1.34 2.1 5.01 283 102 3 straps 1 strap shear - butt end

F 1 1.32 2.1 5.48 315 128.2 2 V? 2 straps 1 strap join in butt straps

[0049] Figure 7 (A) to (F) each correspond to samples (A) to (F) listed above and visually illustrate pole failure in these samples.

Example 2

[0050] Finite element analysis was carried out to ascertain the effect of varying the external diameter of the connecting sleeve, and in order to understand the correlation between diameter of the connecting sleeve and stresses experienced by the wood and the connecting sleeve. The external diameter of the connecting sleeves was varied from 75mm to 135mm and the thickness of the sleeve wall in each of the samples was 3.2mm. A schematic of the experimental set up used for the finite element analysis is shown in Figure 12. All measurements shown in Figure 12 are in millimetres (mm). The finite element analysis results are represented in the Tables 2-3 below and in Figure 13.

Table 2

Table 3

Example 3

[0051] Several samples of pole members and connecting sleeves were tested, again using a three point bending test represented schematically Figure 14.

[0052] Modulus of Rupture (MOR) at the loading point and the joint, tip loading and diameter of the butt log were recorded for varying connecting sleeves with diameters 72mm and 82mm and sleeve wall thicknesses of 3.9mm, 5.9mm and 7.5mm. Furthermore, reinforcement straps (clamps) were also used to ascertain any changes due to the reinforcement straps in the tested parameters. Figures 8 to 12 related to this Example 3 illustrate results of these tests.

[0053] In the present specification and claims (if any), the word 'comprising' and its derivatives including 'comprises' and 'comprise' include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0054] Reference throughout this specification to 'one embodiment' or 'an embodiment' means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases 'in one embodiment' or 'in an embodiment' in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[0055] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.