AU2003204889B2 - Hybrid utility pole - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): BHP STEEL LIMITED A.C.N. 000 011 058 Invention Title: HYBRID UTILITY POLE The following statement is a full description of this invention, including the best method of performing it known to me/us: 2 HYBRID UTILITY POLE Field of the Invention The present invention relates to utility poles for the support of aerial conductors in electricity transmission and distribution systems.

More particularly, the present invention relates to such poles of a hybrid type, that is to say poles comprising an in-ground butt of one material and design supporting an above ground column of a different material and/or design.

The term "utility pole", as used herein, embraces not only stand-alone poles, usually furnished with one or more cross-arms, used for the support of a plurality of spaced apart aerial conductors, but also similar poles constituting the legs of a multi-leg tower structure or the like used for the same purpose.

Background Art Traditionally, utility poles have comprised a one-piece timber or concrete pole with nothing to distinguish the in-ground butt from the above-ground column, except that the bigger diameter end of a natural timber pole is usually buried in the earth. That practice is also followed in relation to concrete poles if one end is bigger in diameter than the other.

More recently, hybrid poles have come into use.

Such poles are advantageous in that materials for the butt and column may be selected that are specifically suited to endure in their respective very different in-use environments, and designs may be selected that make the best use of each material to resist the respective very 3 different in-use loading applied to the butt and column.

This, in turn, enables fewer and more cost effective poles to be used in many instances.

A further advantage of hybrid poles over monolithic poles is that the butt may be positioned and embedded in the ground as a first operation, and the column erected and secured to the butt as a subsequent, separate, relatively brief operation. This is particularly advantageous when the poles are being erected in a right-of-way to be shared with a pre-existing transmission line. The butt may be placed without regard to the existing line, and any outage of the existing line, needed to allow subsequent erection of the column to proceed safely, is minimised.

The butt material is preferably dense, chemically inert and well able to resist compressive forces.

Concrete, particularly reinforced concrete, is currently the preferred material. Likewise the butt design should be such as to present a large surface area to the surrounding earth to minimise the pressure applied thereto. A cylindrical butt having a relatively large external diameter (relative to that of the column) is currently preferred.

On the other hand the column is preferably of material that has a high tensile strength, and of a design that is adapted to function as a cantilever, resistant to the bending and torsional stresses applied to it by the tensioned aerial conductors and wind forces thereon. A metal tube is a currently preferred option. That tube is frequently a plain cylindrical tube, but tapered and/or ornamentally faceted or fluted tubular columns are also well known.

Therefore it must be said that hybrid poles C comprising a concrete butt and a tubular metal column are U known per se, although this statement is not to be taken as an admission that such hybrid poles are part of the Scommon general knowledge in Australia.

Typically the column has been a steel tube coated 00 with a corrosion resistant coating.

00 SHitherto the butts of hybrid poles have comprised a concrete mass and a relatively short, metal, stub member buried in the concrete, except for a stub of that member protruding upwardly from the concrete. The column has been mounted to that stub.

The stub member is a costly item and its presence during the pre-casting of the concrete butt complicates the pre-casting operation if unwanted displacement of the stub is to be avoided. In this regard it will be appreciated that any misalignment of the stub is rendered more obvious when the column has been affixed to the stub.

Summary of the invention An object of the present invention is to alleviate the disadvantages associated with the use of a stub member in a hybrid utility pole, as discussed above.

The invention attains that object by eliminating the metal stub member and shaping the pre-cast body of the butt to provide thereon a locating seat for the column, and providing means for fastening the column to the butt to prevent it being lifted clear of that seat or rotating about its longitudinal axis therein.

Therefore, according to a first aspect, the invention comprises a hybrid utility pole of the kind comprising, in combination, a butt comprising a body of N:Welboume\Casc\Paten\490DO-49999\P49S95.AU I\Speci%\Hybid Utility Poledoc 4112/07 -3- Shard setting material, and a column extending upwardly 0 from the butt, and at least one fastening means affixing said column to said butt, said column comprising a tube, Ssaid butt being formed to provide a locating formation defining a seat for a bottom end of the tube and being adapted to prevent a seated column from toppling over, 0 said locating formation comprising an annular surface upon 00 00 which a bottom end of the tube rests and an upstanding Sprojection substantially co-axial with said annular M 10 surface and adapted to enter the bore of the tube, and the Sat least one fastening means affixing said column to said seat.

Preferably, the surface of the projection contacting the tube is vertically fluted or ribbed to provide drainage passages.

For preference, where the column is metallic, the fastening means, or each of them if there be more than one, is adapted also to function as a terminal connection for an earth conductor extending from the column to an underground earth mat or the like, to ensure that dangerous potential gradients cannot be generated in the column or the ground surface surrounding the pole as a result of large fault currents, should there be an insulation failure between an aerial conductor and the metallic column or a lightning strike on the metallic column.

For preference the hard setting material is reinforced concrete, in which event the fastener means, or each of them if there be more than one, may be a threaded fastener having one element, preferably the female N:\Mclboum\Cas\Paternt490DO-49999\P49595 AU.I\SpecisUybrid Utility Poledoc 4/ 207 6 element, embedded in the concrete and welded, or otherwise electrically connected to, the steel reinforcement and another element, preferably the male element, extending through the wall of the column and engaging the said one element.

Furthermore another similar fastener may be provided adjacent to the bottom end of the foundation for connection more directly to said underground earth mat or the like. In this instance the butt reinforcement also serves to conduct the fault or lightning currents to said other similar fastener.

According to a second aspect, the invention comprises a method of installing a utility pole at a proposed site comprising the steps of pre-forming a butt of hard setting material to provide a locating formation thereon defining a seat for a bottom end of a column adapted to prevent a seated column from toppling over, embedding said butt in the earth at the proposed site of the pole, erecting the column and seating its bottom end in or upon said locating formation, and affixing said column to said butt with at least one fastening means to prevent it becoming unseated.

Brief Description of the Drawings By way of example, two embodiments of the invention are described in more detail hereinafter with reference to the accompanying drawings, of which: Figure 1 is a diagrammatic, exploded, side elevation of a butt and a bottom end of a tubular column of a utility pole according to the first aspect of the invention; Figure 2 is a sectional view taken on line 2-2 of 7 Figure 1; and Figure 3 is a view similar to Figure 1 of another utility pole according to the first aspect of the invention.

Best Mode of putting the Invention into effect The utility pole illustrated by Figures 1 and 2 comprises a column 3 about to be mounted upon a butt 4.

The illustrated column 3 is a uniform cylindrical, metal tube 5. It is preferably of steel that is coated with a corrosion resistant and maybe ornamental coating. The tube 5 extends from the bottom end seen in the Figure to a remote top end, and at that top end may be furnished with cross-arms or other conventional components or fixtures depending on the pole's intended function. In other embodiments, the tube may be made up of several tube parts permanently joined end to end The butt 4 comprises a generally cylindrical mass of reinforced concrete comprising a concrete body 6 with an internal cage of longitudinally extending steel reinforcing rods 7 and a plurality of similar hoops (not shown) welded to the rods 7. Such reinforcement is conventional and needs no further description herein.

The butt 4 comprises a locating formation for the tube 5. The locating formation comprises an inclined annular surface 8 and an upstanding cylindrical projection or boss 9 that is coaxial with-the surface 8. In use, in order to install the pole, the bottom end of the tube 5 is neatly sleeved over the boss 9 until the bottom end of the tube is seated upon the surface 8.

The outer curved surface of the boss 9,is i 8 preferably vertically ribbed as indicated at 13 to provide drainage passages extending from within the tube 5 to the surface 8. Normal manufacturing tolerances may suffice to let any condensate or other water finding its way into the tube 5 to escape across the surface 8, but if need be the surface may be ribbed or fluted, or the bottom edge of the tube 5 may be gapped to facilitate the discharge of such water.

Two diametrically opposed threaded fastener means are provided. Each such means may comprise an internally threaded ferrule 10 embedded in the concrete body 6 and welded or otherwise permanently electrically connected to a reinforcing rod 7. When the tube 5 is seated as aforesaid, clearance holes 12 (only one of which is visible in the drawing) piercing the wall of the tube 6 come into respective alignment with the ferrules Thus, in use in order to install the pole, a bolt (not shown) is passed through each clearance hole 12 and tightened into the corresponding ferrule 10. Those bolts not only prevent the tube 5 from becoming unseated but also prevent it from rotating about its longitudinal axis, should, for example, an aerial conductor to one side of the pole snap or otherwise become untensioned.

A ferrule 11, similar to ferrules 10 and similarly connected to a rod 7, may be provided near the bottom end of the butt 3 for use as a terminal for a buried earth strap or a conductor extending to a buried earth mat, as will be well understood by the skilled addressee.

As indicated above, with reference to the prior art, tubular columns may be tapered or ornamentally faceted or fluted. In such instances, in hybrid poles according to the invention the locating formation preferably defines a seat that is complementary to the 9 shape of the column.

One such instance is illustrated by Figure 3 wherein the tube 13 is tapered and the butt 14, or at least that part of it corresponding to the boss 9 of the Figure 1 embodiment, is a truncated cone having substantially the same angle of taper as that of the tube.

In this case, therefore, the surface 8 of the Figure 1 embodiment may be omitted and the tube 13 is seated directly upon the upper portion 15 of the butt or its boss, as the case may be. That upper portion is preferably fluted or ribbed, as shown at 16, to provide drainage passages similar to those of the first described embodiment of the invention.

Many modifications may be made to the preferred embodiments of the invention described above without departing from the spirit and scope of the invention.

For example, whilst the butts 6 shown in the drawings are solid bodies, in other embodiments the butts may be hollow.

In other embodiments the solid boss 9 may be replaced by an upstanding annular spigot.

Furthermore such a spigot may be sized to neatly encircle the bottom margin of the column tube rather than to extend into its bore if so desired.

Claims (7)

1. A hybrid utility pole of the kind comprising, in Scombination, a butt comprising a body of hard setting material, and a column extending upwardly from the butt, and at least one fastening means affixing said column to said butt, said column comprising a tube, said butt being 00 00 formed to provide a locating formation defining a seat for a bottom end of the tube and being adapted to prevent a seated column from toppling over, said locating formation comprising an annular surface upon which a bottom end of the tube rests and an upstanding projection substantially co-axial with said annular surface and adapted to enter the bore of the tube, and the at least one fastening means affixing said column to said seat.

2. The pole defined in claim 1 wherein the surface of the projection contacting the tube is vertically fluted or ribbed to provide drainage passages.

3. The pole defined in claim 1 or claim 2 wherein the column is metallic, and the fastening means, or each of them if there be more than one, is adapted also to function as a terminal connection for an earth conductor extending from the column to an underground earth mat or the like, to ensure that dangerous potential gradients cannot be generated in the column or the ground surface surrounding the pole as a result of large fault currents, should there be an insulation failure between an aerial conductor and the metallic column or a lightning strike on the metallic column.

4. The pole defined in claim 3 wherein the hard setting material is reinforced concrete, and the fastener means, or each of them if there be more than one, is a threaded fastener having one element embedded in the concrete and welded, or otherwise electrically connected N:MclbourneNCascsPaten\4900-49999\P49595.AU. l\Spccis\Hybrid Utility Pole doc 411207 S-11- O Sto, the steel reinforcement of the reinforced concrete and 0 another element extending through the wall of the column Q and engaging the said one element.

5. The pole defined in claim 4 further comprising another similar fastener adjacent to the bottom end of the O butt for connection more directly to said underground 00 earth mat or the like. C 10 6. The pole defined in claim 5 wherein the butt Sreinforcement also serves to conduct the fault or lightning currents to said other similar fastener.

8. A method of installing a utility pole at a proposed site comprising the steps of pre-forming a butt of hard setting material to provide a locating formation thereon defining a seat for a bottom end of a column adapted to prevent a seated column from toppling over, embedding said butt in the earth at the proposed site of the pole, erecting the column and seating its bottom end in or upon said locating formation, and affixing said column to said butt with at least one fastening means to prevent it becoming unseated.

9. A hybrid utility pole substantially as hereinbefore described with reference to the accompanying drawings. A method of installing a utility pole at a proposed site substantially as hereinbefore described with reference to the accompanying drawings. N:\Melbouni\Cues'ateen\4900Q-49999P49595 AU I\Speciflybrid Uuility Pole doc 4/12/07