NZ535503A

NZ535503A - Fastening cross-arm to utility pole using clamping

Info

Publication number: NZ535503A
Application number: NZ535503A
Authority: NZ
Inventors: John Frank Kralic
Original assignee: Bluescope Steel Ltd
Priority date: 2002-07-08
Filing date: 2003-06-22
Publication date: 2006-05-26
Also published as: AU2002950037A0; US20040084582A1

Abstract

Cross-arm 5 is attached to utility pole 4 by a saddle 6 of "flanged U shape". Bolts 9 engage cross-arm 5 so as to clamp the cross-arm to the pole when tightened.

Description

<div class="application article clearfix" id="description"> 535 5 03 PATENTS FORM NO. 5 Fee No. 4: $250.00 PATENTS ACT 1953 COMPLETE SPECIFICATION A divisional application of New Zealand patent application no. 526728 filed 25 June 2003, entitled "Utility pole cross-arm and associated pole-top hardware" Fastening system for utility pole cross-arm and method for securing WE, BHP Steel Pty Limited, an Australian company of 1 York Street, Sydney NSW 2000, Australia, hereby declare the invention for which we pray that a patent patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: 2 FASTENING SYSTEM FOR UTILITY POLE CROSS-ABM AND METHOD FOR SECURING Field of the Invention 5 This invention relates to a fastening system for utility pole cross-arms and associated method for securing cross-arms to utility poles, the cross-arms being for the support of aerial conductors in electricity distribution 10 and transmission systems. The invention is particularly directed towards such hardware for use and for securing in low to medium voltage systems, that is to say, systems operating within the range of from consumer voltages (nominally 240/414 volts 15 in Australia) to say 33 kilovolts. Background Art Traditionally, utility poles and cross-arms used in such systems have been of timber. In more recent times 20 tubular steel poles have started to replace wooden poles, because of the availability and relative costs of the two types of pole. The same cannot be said of cross-arms, which are still primarily of timber. This arises because the relatively small line insulators used in systems of 25 low to medium voltage produce an air gap between the aerial conductor and the cross-arm that is within the distances that may be bridged by birds alighting or perching upon the cross-arm. This is not of major concern in respect of wooden cross-arms. Even when wet, the 30 wooden cross-arm has enough resistance to limit fault currents through the bird to the grounded metal pole to a 3 tolerable level, certainly well below that which would trigger line fuses or other system protection. Summary of the invention New Zealand parent application 526728 discloses 5 a cross-arm for a utility pole for use in low to medium voltage electricity distribution and transmission that is metallic and coated with an insulatory coating. The present application is directed to a fastening system and method that is able to be used with such cross arms. 10 According to a first aspect, the invention relates to a fastening system when used for fastening a cross-arm to a utility pole, the fastening system comprises clamping means that is securable to one of either the pole or the cross-arm, the clamping means being 15 operative to extend about the other of the pole or cross-arm to which it is secured and applying a clamping force to that member so as to fasten the cross-arm and pole together. This fastening system has significant advantages as 20 it uses a clamping action rather than a direct mechanical fastener thereby obviating the need for a metallic fastener to contact both the cross-arm and the pole. In a preferred form, the clamping means is in the form of a saddle which incorporates end portions securable 25 to either the pole or the cross-arm and a mid portion which is operative to extend around either the pole or the cross-arm to which it is secured so as to apply a clamping force to that member. In a preferred form, the end portions are secured to either the pole or the cross-arm 30 by mechanical fastening and preferably in securing the clamping means to that member, the clamping means is caused to resiliently deform so as to clamp the members together. Intellectual Property Office of NX H MAR 2006 received 4 In a further form, preferably the fastening system includes a further fastener which is operative to interconnect the saddle and the pole. This fastener may be a mechanical fastener such as a self tapping screw or 5 nut and bolt configuration. In a preferred embodiment the clamping means is metallic and coated with an insulatory coating. Preferably the clamping means is coated with a polymeric material. 10 In another form, the invention relates to a method of securing a cross-arm to a utility pole, the method comprising the steps of: providing clamping means arranged to clamp the cross-arm to the utility pole, 15 locating the clamping means over one of the cross-arm or the utility pole, securing the clamping means to the other of the cross-arm or the utility pole whereby, on securing the clamping means, the clamping 20 means clamps the one member to the other to which it is secured. In a further form, the method further comprises the step of fastening the clamping means to the one member. In another form, the method also further comprises 25 the steps of providing an insulating medium and locating that medium between the pole and the cross-arm to provide an insulating barrier between the pole and the cross-arm. Brief Description of the Drawings. 30 By way of example, embodiments of the invention are described hereinafter with reference to the accompanying drawings: 5 Figure 1 is an exploded perspective view of an assembly of a top portion of a pole and associated pole-top hardware, including a cross-arm, in accordance with an embodiment of the invention; 5 Figure 2 is a front elevation of the assembly of figure 1 drawn to a smaller scale; Figure 3 is a plan view of the assembly of figure 1 drawn to a smaller scale; and Figure 4 is an exploded perspective view of an 10 alternative to the assembly of figure 1. Detailed Description of the Preferred Embodiment The illustrated assembly comprises a tubular steel 15 utility pole 4, a hollow rectangular section steel cross-arm 5, a saddle 6, an insulatory tape wrapper 7, a pole cap 8, bolts 9 able to extend through the side lugs of the saddle 6 and the cross-arm 5 to accept nuts 10 whereby the cross-arm 5 may be clamped to the pole 4, and self tapping 20 screws 12 which are able to extend through the saddle 6 and into the pole 4. The cross-arm 5, saddle 6 and cap 8 are made of sheet steel, preferably zinc galvanised or similarly coated with a corrosion resistant alloy, for example an aluminium-zinc 25 alloy, and, overcoated with a weather resistant, electrically insulatory coating. The insulatory coating is a polymeric material, and is designed to have dielectric strength of 15kV/mm. Suitable coatings include the following: 30 i) thermoplastic coating powder sold by the IPT Group of companies under the trade name of PLASCOAT PPA 571 EF. The coating is applied without requiring a primer and at a thickness of between 150 to 250|am. Pre-treatment includes solvent degrease and surface preparation by phosphate or whip blast. ii) thermoplastic coating powder sold by Elf Atochem under the trade name RISLAN. The coating is applied at a thickness of 200-250|im. Surface preparation includes chloride solvent or alkaline wash then rinse. The surface is prepared by a whip blast. A primer is used and a suitable primer is a two pack primer sold under the trade name RILPRIM. iii) epoxy based powder coating sold by Axo Nobel under the trade name INTERPON 100. The epoxy coating is applied at a thickness of approximately 60pm. The coating is pre treated by a solvent degrease and the surface prepared for use by zinc phosphate. A finish coat sold by Axo Nobel under the trade name INTERPON D 2000 is applied over the epoxy based coating. The saddle 6 is made of relatively thick steel sheet compared to that of the pole 4 and is shaped and sized so that when the nuts 10 are tightened, the pole cross-section under the saddle is elastically strained to adopt a D shape, as indicated at 11. This helps to prevent the nuts from loosening in use and also prevents the cross-arm from rotating about the vertical axis of the pole or about a horizontal axis intersecting that vertical axis and passing through the cross-arm. Depending on the load requirements of the structure, a fastener may be provided to pierce the saddle 6 and extend into the pole 4. In the illustrated form, self tapping screws 12 are used which are installed after insulation of the saddle. Other fasteners may be used. For example, a nut and bolt arrangement could be employed, where the bolt extends through opposite portions of the saddle, and through the pole with the nut being secured onto a protruding end of the bolt. 7 The tape 7 may be passed around the pole, as shown, or may be wrapped about the cross-arm. A primary requirement is that part of the tape is sandwiched between the pole and cross-arm to insulate one from the other. 5 In an alternative configuration the saddle 6 may be arranged vertically instead of horizontally as shown. It would then be positioned on the same side of the pole as the cross-arm, and would of course be re-shaped so as to embrace the cross-arm instead of the pole. In that 10 instance, bolts corresponding to bolts 9 would extend through the pole rather than through the cross-arm. In either circumstance it will be apparent that there would be no electrical connection between the pole and the cross-arm. 15 In the embodiment of figure 1, an extension arm 13 is disclosed which is mountable to the cross-arm 5. The extension arm 13 is made from a hollow rectangular steel section or formed sheet steel and incorporates an upper end 14 which is operative to support the middle phase wire 20 (not shown) and a lower end 15 which incorporates a nib 16 and coupling plate 21 which is operative to be mounted to a mid section of the cross-arm 5. The nib 16 is designed to be in lapping relationship with an outside surface of the cross-arm 5 so as to improve the stability of the 25 connection of the extension arm 14 with the cross-arm. Whilst not shown, typically the extension arm 13 is bolted to the cross-arm 5 through apertures 17 and 18. By incorporating the extension arm 13, in a three phase wire electricity distribution system, the two outer 30 wires are connected to the cross-arm whilst the middle wire is supported above the other wires on the extension arm 13. A further arrangement is disclosed in figure 4. Again the arrangement of figure 4 incorporates the cross- 8 arm 5 and the extension arm 13. However instead of using the saddle 6, a seat 19 is provided on which the cross-arm 5 is supported. In the illustrated form, the seat 19 is formed from the same section as the cross-arm 13 thereby providing a multipurpose section. Using this same section, the seat 19 is orientated so that the nib 16 extends upwardly and locates in behind the cross-arm 5. This allows for a tighter engagement of the extension arm 13 and the seat 19 with the cross-arm 5 as the cross-arm is effectively captured between the respective nibs 16. In addition, arranging the elements in this way enables the nibs to be made quite deep without the risk of one nib fouling the other nib which may occur if they are on the same side. Typically the seat 19 is secured directly on to the utility pole by mechanical fasteners. Further the cross-arm is arranged to be bolted to the seat 19 through bolt 20 which in the illustrated form is also designed to pass through the bottom plate of the extension arm 13. In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, ie. to specify the presence of the stated features but not to preclude the presence or addition of further features of various embodiments of the invention. Those skilled in the art will appreciate that the invention described is susceptible to variations and modifications other than those specifically described. All such variations and modifications are to be considered within the scope of the present invention. 9 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> CLAIMS

1. A fastening system when used for fastening a cross-arm to a utility pole, the fastening system comprising clamping means that is securable to one of either the pole or the cross-arm, the clamping means being operative to extend about the other of the pole or cross-arm to which it is secured and apply a clamping force to that member so as to fasten the cross-arm and pole together.

2. A fastening system according to claim 1, wherein the clamping means is in the form of a saddle which incorporates end portions securable to either the pole or the cross-arm and a mid portion which is operative to extend around the other of the pole or the cross-arm to which it is secured so as to apply a clamping force to that member.

3. A fastening system according to claim 2, wherein the end portions of the saddle are secured to either the pole or the cross-arm by mechanical fastening.

4. A fastening system according to any one of claims 1 to 3, further comprising fastening means extending between the clamping means and the pole or cross-arm about which it extends.

5. A fastening system according to claim 4, wherein the fastening means is a mechanical fastener.

6. A fastening system according to any one of claims 1 to 4, wherein the clamping means is metallic and coated with an insulatory coating.

7. A fastening system according to claim 6, wherein the coating is a polymeric material. InteHigfySI ""Property Offiea ef N,i- 1 h MAR 2006 receive 10

8. A fastening system according to either claim 6 or 7, wherein the coating is applied by an electrolytic powder coating process, using the powder of a polymeric material.

9. A method of securing a cross-arm to a utility pole for use in low to medium voltage electricity distribution and transmission; the method comprising the steps of: providing clamping means arranged to clamp the cross-arm to the utility pole; locating the clamping means over one of the cross-arm or the utility pole; and securing the clamping means to the other of said cross-arm or utility pole whereby on securing the clamping means, the clamping means clamps the one member to the other member to which it is secured.

10. A method according to claim 9, further comprising the step of: fastening the clamping means to the one member.

11. A method according to claim 9 or 10, further comprising the steps of providing an insulating medium and locating that medium between the pole and the cross-arm to provide an insulating barrier between the pole and the cross-arm.

12. A fastening system substantially as herein described with reference to the accompanying drawings when used for fastening a cross-arm to a utility pole. BHP STEEL PTY LIMITED by their authorised agents JAMES & WELLS '"'iWS mm it n,*. 1 <| MAR 2006 p «= c eiv e d </div>