A MODULAR UTILITY POLE

Abstract: A modular utility pole (2) which is made from a plurality of blocks (10, 12, 14) which are moulded or extruded from clay or cement. The blocks have aligned openings through which tendons (15) pass. Anchoring means (30, 34) are provided at the base and top of the pole for holding the ends of the tendons under tension whereby a post-tensioned pole is produced.

Description: A MODULAR UTILITY POLE This invention relates to a modular utility pole. More particularly, the invention relates to a utility pole which can be used in power distribution systems and telephone systems or for supporting other lines or conduits. The object of the invention is to provide a novel form of utility pole which is relatively simple and inexpensive to fabricate. According to the present invention there is provided a pole comprising a plurality of performed elements which have at least one opening therethrough, at least one tendon which passes through the openings in the elements, and restraining means for restraining the ends of said tendon and maintaining tension therein when said pole is post-tensioned. Preferably, the elements comprise generally cylindrical blocks the axes of which coincide with the axis of the pole. The blocks can be formed by extrusion, moulding or pressing and can be formed in convenient lengths. The blocks may comprise clay or clay base material which has been fired or vitrified so as to form ceramic blocks. Alternatively, cement or cementicious material can be used. The material may be admixed with reinforcement such as fibres of glass, polymeric, monomeric or natural material. The invention also provides a method of making a utility pole comprising the steps of assembling a plurality of preformed elements which have at least one opening therethrough in a line, passing at least one tendon through the openings in the elements, applying a predetermined tensile force to the tendon, and maintaining the tendon under tension whereby the pole is post-tensioned. The invention will now be further described with reference to the accompanying drawings, in which. Figure 1 is a side view of a pole constructed in accordance with the invention. Figure 2 is a longitudinal section through part of the pole of the invention. Figure 3 is a fragmentary perspective view of one of the blocks for forming the pole. Figure 4 is a fragmentary sectional view of a pole having circumferencial reinforcing rings between adjacent blocks. Figure 5 shows an anchoring plate for tendons. Figure 6 is a fragmentary cross-sectional view along the line 6-6, Figure 7 shows a block for mounting a cross-arm, and Figure 8 shows schematically another form of anchoring for the tendons. The pole 2 illustrated in Figure 1 is formed from three groups 4, 6 and 8 of blocks 10, 12 and 14, the blocks being held in a state of compression by tendons 16 (see Figure 2) . The blocks in the groups are of different widths so that a tapered pole is assembled but blocks of the same size could be used to assemble a pole of uniform width. The blocks 10, 12 and 14 are preferably formed by a process of extrusion and have a configuration as shown in Figure 3. The extruded material is cut into desired lengths say 250mm and fired or cured into a solid form. Alternatively, the blocks can be formed by pressing br moulding techniques. The material for the blocks may comprise clay or clay based material which, after extrusion, is fired so as to form ceramic blocks. The material may include reinforcing material such as monomeric or polymeric fibres such as methyl methacrylate. Other material may be admixed with the clay so as to reduce cost, increase strength, or facilitate moulding or extrusion. For instance crushed brick or rock aggregate such as screenings which pass through 60 mesh and 90 mesh screens. Further, initiators such as ttmsa or methyl methacrylate can also be employed. The blocks can also be formed from cement or cementicious products. The cement or cementicious product may include reinforcing material such as glass fibres, natural fibres such as cellulose, or synthetic fibres or mixtures of these fibres. Figure 3 shows a typical block 4 which has been formed either by extrusion, moulding or pressing. The diameter of the block 10 is preferably in the range 400 to 600mm. The blocks 12 and 14 which are used in the upper groups of the pole are moulded with convenient diameters such as 350mm and 200mm respectively. The shape of the blocks 12 and 14 may be the same as those shown in Figure 3. The block 10 has a cylindrical side wall 16 and top and bottom transverse faces 18 and 20. Extending axially through the block are a number of bores 22 for receiving the tendons 15. It is desireable that the bores 22 be symmetrically disposed about the central axis of the block so that the block will be uniformally compressed by the tendons 15. In the illustrated arrangement there are six bores 22 but this number can be varied to suit requirements. The block has a number of openings 24 which extend longitudinally through the block and serve primarily to reduce the amount of material in the block and thereby also reduce its weight. The block may include a central bore 26 which of course will further reduce the weight of the block. Alternatively, the bore 26 may be used to receive a post tensioning tendon (not shown) which supplements or replaces the tendons 15 used to post-tension the pole. Alternatively, the central bore 26 may be used during assembly of the pole for the purpose of assisting in alignment of the blocks. For instance, a shaft or spindle (not shown) may be passed through all of the bores 26 of the blocks so that they will thus have a common centre and thereafter the tendons 15 can be passed through the aligned bores 22 in readiness for tensioning. Still further, the central bore 26 can be formed with a slot or keyway (not shown) which can be used to facilitate alignment of the blocks. Further, after the tension has been applied to the tendons 15, the aligned central bores 26 of the blocks can be filled with hardenable material such as cement or concrete and thereby increase the tortional strength of the pole. Figure 4 illustrates the base of the pole in more detail. The base of the plate includes a base plate 28 which lies adjacent to the bottom surface 20 of the lower most block 10. The base plate is integrally formed with or has welded thereto cups 30 have tapered recesses 32 therein. The ends of the tendons are passed through the recesses and wedges 34 are sealed between the recesses 32 and tendons 15. When the tendons 15 are placed under tension the tapered recesses 32 of the cups force the wedges 34 to bite into the tendons 15 and thereby hold them firmly relative to the base plate 28. The base of the pole is completed by means of a cover 36 which is bonded or cemented to the side wall 16 of the lowermost block 10 so as to stop the wedges 34 being displaced and to keep moisture away from the tendons and wedges. The cover 36 can be moulded from the same types of materials that are used to form the blocks or form plastics material. The tendons 15 extend through all of the blocks and their upper ends are connected to a top plate 38 which is diagramatically illustrated in Figure 5. The top plate has cups 40 for receiving the top ends of the tendons 15 and wedges 42, as diagramatically shown in Figure 6. The top of the pole has a cover 43 similar in function to the base cover 36. Other techniques may of course be used for anchoring the ends of the tendons 15, for instance, the tendons may be screw threaded and nuts tightened thereon. The pole may include circumferencial reinforcing rings 44, as shown in Figure 4. In this case, the top and bottom surfaces 18 and 20 of the blocks are formed with annular recesses 46 and 48 which together define a cavities 50 in which the rings 44 are located. Once the rings have been located in the cavities 50, the remaining parts of the cavities can be filled with a grouting material so as to firmly bond the rings to the blocks. The rings 44 can be placed between selected blocks throughout the length of the pole. Alternatively, the pole may be provided with reinforcing plates 52 which help the pole to withstand impact forces which are sometimes applied to poles as a result of motor accidents and the like. Figure 2 shows the use of the plate 2 between the blocks 10 and 12 at the junction of the groups 4 and 6. The plate 52 is provided with openings 54 through which the tendons 15 pass. Further, the plate 52 is provided with an opening 56 which is preferably of the same diameter as the openings 26 of the blocks. This permits the openings 26 of the blocks to function as described previously. The plate 52 is preferably formed from steel and may have a thickness in the range 10 to 30mm but is preferably 19mm thick. The plate may be galvanized. Figure 2 also shows the use of gaskets 58 between adjacent blocks. The gaskets 56 may be formed from rubber or rubber like material, polypropolene, silicon rubber or the like. The gaskets 58 may typically have a diameter of say 2mm prior to tensioning of the tendons 15. Each gasket 58 has openings 60 and 62 which correspond in position to the openings 22 and 24 of the blocks. The gaskets 58 facilitate uniform transfer of compressive forces between adjacent blocks. In an alternative arrangement, the gaskets 58 may be replaced by grouting material such as cement, epoxy resin, or other setable material such as silicon based grouting. The grouting material facilitates uniform transfer of compressive forces between adjacent blocks, increases the bond strength between adjacent blocks and serves to protect the tendons 15 from the exterior environment. Once all of the blocks 10, 12 and 14 required for the desired length of the pole have been assembled and the base and top plates 28 and 38 positioned, the tendons 15 can be placed under tension using conventional techniques. It is preferred that the equipment used places all of the tendons 15 simultaneously under tension so that pressure is uniform across the adjacent faces of the blocks. The ends of the tendons are then connected to the plates 28 and 38 so that a post-tensioned pole is produced. The base and top covers 36 and 43 can then be positioned as mentioned previously. Preliminary calculations indicate that for a fourteen metre pole the total tensile force in the tendons would be 150 tonnes. Of course, the tensile loading can be varied according to size and load carrying capacity of the pole. Cross-arms (not shown) for the utility pole 2 can be affixed by any convenient method such as by the use of brackets or the like. Alternatively, a cross-arm fixing block 64 as shown in Figure 7 can be included in the top group 18 so as to facilitate fixing of the cross-arm. The fixing block 64 is the same as the blocks 14 except for the provision of flat surfaces 66 on adjacent sides thereof against which the cross-arms can be bolted. A bolt hole 68 extends through the block 64 for receipt of a bolt or other fastening member which passes through the cross arm. Figure 8 shows an alternative top block 69 which can be used for fixing the top ends of the tendons 15 and replaces the top plate 38 and cover 43. The top * block 69 can be moulded from materials similar to those used for forming the other blocks. In this arrangement the ends of the -tendons 15 are formed with widenned portions or buttons 70 and these are moulded directly into the top block 69. In the illustrated arrangement, the top block 69 tapers upwardly from its base 74 which is of a similar diameter to the blocks 14 at the top of the pole. In some circumstances it may be desireable to provide for a recess 76 near the centre of the pole so as to form a convenient point from which a sling or other lifting equipment can be used in order to lift the pole from a horizontal position to a vertical position. The recess 76 can very conveniently be formed by locating one of the wider blocks 10 in the intermediate group 6 of blocks, as illustrated in Figure 1. Many modifications will be apparent to those skilled in the art without departing from the spirit and scope of the invention.

Claims: CLAIMS : lo A pole (2) comprising a plurality of preformed elements (10, 12, 14) which have at least one opening (22, 26) extending therethrough, at least one tendon (15), which extends through the openings in elements, and restraining means (30, 34) for restraining the ends of said tendon and maintaining tension therein wherein said pole is post-tensioned. 2. A pole as claimed in claim 1 wherein each element has a plurality of openings (22) extending therethrough, said openings being symmetrically disposed relative to the axis of the pole, said pole including a plurality of said tendons (15) passing through said openings. 3. A pole as claimed in claim 1 or 2 wherein said elements are formed by moulding, casting, pressing or extrusion. 4. A pole as claimed in claim 3 wherein said elements comprise fired blocks of clay or clay-based material. 5. A pole as claimed in claim 3 wherein said elements comprise cured blocks of cement or cementicious material. 6. A pole as claimed in claim 5 wherein the cement or cementicious material includes reinforcing material. 7. A pole as claimed in claim 6 wherein the reinforcing material comprises glass, polymeric, monomeric or natural fibres. 8. A pole as claimed in any one of claims 1 to 7 wherein the elements comprise generally cylindrical blocks the axes of which coincide with the axis of the pole. 9. A pole as claimed in claim 8 wherein the pole is composed of groups of blocks (4, 6, 8) of different diameters whereby a tapered pole can be formed. 10. A pole wherein grouting material or resilient (58) material is cated between adjacent blocks. 11. A pole as claimed in 8 or 9 including metal plates (52) interposed between at least some adjacent blocks. 12. A pole as claimed in claim 8 wherein the cylindrical blocks have end faces (18, 20) which include annular recesses (46, 48) therein and wherein circumferential reinforcing members (44) are located in said recesses. 13. A pole as claimed in claim 12 wherein grouting material is located in the recesses. 14. A pole as claimed in any one of claims 8 to 13 wherein the blocks include openings therethrough to reduce the weight thereof. 15. A pole as claimed in claim 14 wherein at least some of the openings (24) are filled with cement or cementicious material on assembly thereof. 16. A method of making a utility pole (2) comprising the steps of assembling a plurality of preformed elements (10, 12, 14) which have at least one opening (22) therethrough in a line, passing at least one tendon (15) through the openings in the elements, applying a predetermined tensile force to said tendon, and to maintaining the tendon under tension whereby the pole is post-tensioned.

Inventors: KNIGHT JOHN KEITH, KNIGHT, JOHN, KEITH
Applicants: RFD CONSULTANTS, R.F.D. CONSULTANTS PTY. LTD.
Application year: 1985
Main classification: E04H12
IPC codes: E04H12