GB2528320A

GB2528320A - Utility pole

Info

Publication number: GB2528320A
Application number: GB1412790.6A
Authority: GB
Inventors: Paul Andrew Weston
Original assignee: Siemens PLC
Current assignee: Siemens PLC
Priority date: 2014-07-18
Filing date: 2014-07-18
Publication date: 2016-01-20
Anticipated expiration: 2034-07-18
Also published as: GB201412790D0; GB2528320B

Abstract

A utility pole formed by extrusion comprises a hollow cylindrical body having a wall with an inner and outer circumference. A plurality of support members 8, 10 are integrally formed on a section of the inner circumference. The section has a length of between 10% and 50% of the inner circumference and includes an opening for a door 12. The support members may be arranged equidistant along the section. A support member may further comprise a hollow opening for receiving a door fastener 17. The support members may extend into the hollow body in a range of 5% to 10% of the outside diameter of the body. A method of manufacturing a utility pole comprising the step of cutting the opening and removing the cut material is also claimed.

Description

UTILITY POLE

This invention relates to a utility pole, in particular a utility pole made from extruded material.

Utility poles, such as for mounting various devices, including traffic signals, lighting, CCTV, illuminated signs or other similar products have conventionally been manufactured from various materials, including rolled and welded steel cylinders, or aluminium. In order to provide access to electrical connections for the device mounted on the utility pole, an opening is typically cut in the cylindrical pole and a door fitted over the opening. Cutting into the cylinder reduces the strength of the structure, so it is necessary to reinforce the cylinder in the area of the opening. This reinforcement is typically provided by means of press fit and/or welded strengthening parts. Depending upon the design in use, this reinforcement may be fitted internally or externally in the region of the opening. Internal fitting is complicated and may require special manufacturing tooling. Reinforcement may have an impact on the effectiveness of the passive safety of the structure, and the strength of some materials such as aluminium is adversely affected by heat generated during the welding process..

EP1607548 describes reinforcement for a column, the reinforcement being manufactured in two parts for ease of fitting, one part extending over more than 80° of the internal periphery and including a break co-incident with an opening in the column, the other part taking up the remainder of the periphery.

EP2400060 describes a column having a frangible section connecting the column to a base, the frangible section being made of brittle aluminium having particular properties.

EP0735 t94 takes a quite different approach arid provides a hollow thin walled roadside safety post which is filled with a granular filling material, giving resistance to normal loading, but allowing the post to break without damage to a vehicle on impact.

In accordance with a first aspect of the present invention an extruded utility pole comprises a hollow cylindrical body comprising a wall, the wall having an inner and an outer circumference, wherein a plurality of support members are integrally formed by extrusion on the inner circumference of the wall over a section of the inner circumference having a length which is between 10% and 50% of the inner circumference; arid wherein the utility pole further comprises an opening in the section for a door.

Discrete support members incorporated into the extruded shape of the pole are formed at locations along the inner circumference to increase the bending and torsional strength of the door opening, without adding unnecessary extra weight of material and cost, or complicating the manufacturing process.

Preferably, the opening is bounded by at least a part of a support member on either side.

Preferably, the longitudinal edges of the door are cut through the support member in the direction of the centreline of the pole, or are cut at an angle.

The support material prevents the door from falling into the cylindrical body when fitted by rotation, or by forming a door having a larger area than the opening which it covers.

Preferably, the section has a length between t5% arid 30% of the inner circumference.

Preferably, the support members are arranged equidistant along the section.

Preferably, a support member further comprises a hollow opening adapted to receive a door fastener.

Preferably, the support member ifirther comprises an opening along its length, within the hollow body.

Preferably, the support members extend into the hollow body by a distance in the range of 5% to 10% of the outside diameter of the body.

Preferably, the support member has a circular, rectangular or hexagonal cross section.

Preferably, the material comprises one of aluminium, carbon steel, stainless steel, carbon fibre or plastic.

In accordance with a second aspect of the present invention, a method of manufacturing a utility pole comprises forming a die for a hollow cylinder having a plurality of intrusions into the hollow cylinder and extruding a material through the die, such that a hollow cylindrical body having at least two integrally formed internal support members is formed; the internal support members being formed over a section of an inner circumference of the cylinder, the section having a length which is between 10?/b and 50?/o of the inner circumference; wherein the method further comprises cutting an opening in the utility pole and removing the material cut from the opening.

Preferably, the opening is bounded on its edges parallel to a longitudinal axis of the pole by at least a part of the internal support members Preferably, the method further comprises fitting fasteners along a longitudinal axis of the cut material and installing the cut material in the opening to form a door, wherein the door fasteners are mounted in a support member integrally formed in the inner circumference of the cylinder.

Preferably, the method further comprises providing door fasteners in two or more support members.

Preferably, a support member for mounting the door fasteners is equidistant between the internal support members bounding the opening.

Preferably, the method further comprises during the extrusion, forming an opening in the support member, for mounting the door fasteners.

An example of a utility pole and a method of manufacturing a utility pole in accordance with the present invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a perspective view of a typical traffic signal assembly using an example of a utility pole according to the present invention; Figure 2 shows a cross section through an example of an extruded utility pole according to the present invention; Figure 3 is a perspective view showing detail of the cut-out to form a door in the pole of Figs. I and 2; Figure 4 is a view of the door piece that has been cut from the pole of Figs.1 and2; Figures 5a and Sb are perspective views showing more detail of examples of the fitting of the door to the utility pole of the present invention; Figure 6 illustrates an example of an earthing arrangement for use with the utility pole of the present invention; and, Figure 7 is a flow diagram of an example of a method of manufacturing a utility pole according to the present invention.

As discussed above, utility poles for supporting street infrastructure, such as lighting columns, traffic signal poles, CCTV, real-time information boards, or illuminated signs, frequently have a door to give access to electrical connections inside the pole. However, this has an impact on the bending and torsional strength of the pole, i.e. the maximum bending or torsional load which the pole can withstand before it fails.

The opening for the door significantly weakens the pole, and in some cases reduces the torsional capacity by as much as 90%. Traffic signal poles in particular can be subjected to high bending and torsional loads, due to the large surface area of traffic signals, and their eccentric mounting on the pole.

Conventionally, a way of addressing this problem has been to provide local strengthening of the pole around the door. However this approach is difficult to implement as press fitting and welding of the strengthening parts are often required, and the strengthening part may work loose with repeated pole defiections, Furthermore, standards may not allow any contribution to torsional strength from press fitted door reinforcements. Welding may cause problems as it is difficult to maintain consistent quality in a production environment, and the heat generated by welding may cause a significant reduction in the strength of the material e.g. for aluminium poles.

Another drawback of the insertion of a strengthening member inside the pole is that the member may make the pole less effective as a passively safe structure.

Figure 1 shows an example of a traffic signal assembly using a utility pole according to the present invention. Although the examples will be described with respect to a traffic signal assembly, the utility pole of the present invention is suitable for mounting many different types of equipment including lights, CCTV cameras, real time information and illuminated signs and the invention is not limited to the specific examples. The pole I is fitted into a foundation (not shown), either by being directly planted in the foundation, or mounted via a socket 2. The pole 1 may support equipment, which in this example may include traffic signal heads 3, a pole top equipment cabinet 4, a CCTV camera 5 and a nearside push button unit 6. A door cut-out 7 may be provided in the pole 1 to give access to electrical connections in the pole.

The door cut-out may be fitted at any convenient height above the ground.

The utility pole of the present invention addresses the problems of the prior art, both in terms of manufacturing and passive safety, with a pole formed by extrusion, with reinforcing members formed in the body of the cylindrical pole, klong its frill length. This avoids the need for post processing of the pole when an opening has been cut for a door, as the reinforcement is already in place in the extruded cylinder.

Additionally, the extrusion may also include one or more support members, or ribs providing bending and torsional strength around the critical door opening, and a mounting for door.

By contrast using uniform cross sectional area with thickness sufficient to provide adequate strength around the door opening would result in a pole that was extremely heavy and inefficient in its use of material, and hence expensive and for this reason, such a method has not been used A conventional hollow utility pole may take the form of a cylinder with a uniform circular cross section into which an additional strengthening member has been inserted in a region where a door is formed in the cylinder to increase the overall thickness of the cylinder at that point.

A cross section through of an example of a utility pole according to the present invention is illustrated in Fig.2. In the present invention, the cross section of the hollow cylinder is modified in order to provide reinforcement along the full length of the cylinder. In one embodiment, at least two discrete support ribs 8 are positioned on the inner circumference 9 of the cylinder I and optionally a third rib 10 is positioned between the two support ribs, adapted for mounting the door. Thus, rather than simply increasing the overall thickness of the cylinder wall, sufficient reinforcement material is selectively added in areas that have been calculated to suffer high stresses, in order to prevent plastic, or buckling failure The supporting ribs may have a semi-circular cross section, or other curved shape, or the ribs may be formed with straight sides where they project into the centre of the hollow pole. The advantage of straight sides is that there is less material to cut through to make the door opening. The length of the straight sides may be equal, or they may have different lengths.

Preferably, the maximum depth of protrusion of any support rib into the hollow centre of the pole is between 5% and 10% of the outside diameter of the cylinder. The support members 8 may be arranged with one support member at each end of a chord across the cylinder, or there may be several grouped together in line, close to each end of the chord. Although the support members could be at opposite ends of the internal diameter of the cylinder, this does not provide the most efficient combination of resistance to stress and minimising use of additional material. Generally, the support members need to be present in a section having a length of less than half the length of the internal circumference, but long enough to include the edges of a door opening, so typically a minimum section length of th% of the circumference, Furthermore, the ratio of support to additional material is most effective when the support members are arranged a discrete locations over a section having a length of between 15?/b and 30% of the internal circumference, with the opening for the door in the centre of the section.

The support member, or members 10, used to mount the door may be hollow 11 to receive a door bolt, for example with a circular, hexagonal, or rectangular cross-section, or other suitable shape and additionally, the door mounting support member may have an opening 13 in its circumference, or outer boundary, for ease of fitting the door bolt. The door mounting rib 10 provides structural support at the top and bottom of the door opening 7 in the hollow pole 1, in addition to the reinforcing provided by the support ribs 8. For security, the opening 13 in the circumference or outer boundary of the door mounting rib is within the hollow cylindrical pole 1, rather than on its outer surface. The preferred location of the door mounting rib 10 relative to the two support ribs 8, or groups of ribs, is substantially equidistant between the support ribs 8. The amount of added material in this design is small, so strengthening of the door opening high stress area is possible quite economically, using a constant cross section extrusion process, which has a relatively low cost in comparison with techniques involving the fitting of an additional separate member or members to reinforce the door opening.

process.

Fig.3 illustrates the opening 7 formed in the wall of the pole I in more detail.

On each side of the opening parallel to the longitudinal axis of the hollow pole, part of support members 8 can be seen. At the centre top and bottom of the openings, the hollow central support member 10 with the opening 13 along its length provides a structure for receiving a door fastener, In the corresponding piece of material 12, seen in Fig.4, which has been removed to form the opening and may be used to form the door, the central support member on its back may be used to mount the fastener mechanism. Clearly, the fastener could be mounted in the pole and received in the door, but for ease of fitting the described arrangement is preferred. The use of a separately manufactured door is also possible, but the advantage of re-using the cut-out material is that it reduces material cost and waste and by choosing the point at which to cut correctly, the support members 8 provide reinforcement in both the pole and the door itself.

Conventionally, doors in utility poles for electrical connections have had straight sides and semicircular top and bottom profiles and such a design could still be used with the utility pole of the present invention, but the elongated, almost triangular ends of the door illustrated in Fig,4 with straight, rather than curved edges 14 most of the way along and a small curved end 15 have advantages over the conventional design in terms of resisting a combination of bending and torsional loads. The top and bottom ends are semi-circular, with the diameter optimised to reduce stresses, hut join an angled, rather than vertical side, so avoiding the sharp transition from straight to semi-circular edges that exists in conventional door openings, where failures may arise.

The fastening mechanism is shown in more detail in FigS. The cut material 12 which forms the door has part of the side support members 8 on its longitudinal edges and the extruded central support member 10 runs along the centreline of the door on one surface. A fastener, in this example in the form of a bolt 17, fitted into the hollow opening 13 in the central support member 10 and a fixing screw 16, provided in a slot 18 cut into the outer face of the door 12, is able to move between a retracted position with the screw at one end of the slot and the bolt within the hollow central support on 1 5 the door and an extended position with the screw at the other end of the slot and the bolt protruding beyond the end of the door. As indicated above, the hollow cross section 11 of the central support 10 may be chosen to have a shape that corresponds to the cross-section of the bolt, or other type of fastener. When fitted in place in the utility pole, the protruding bolt is received in the hollow part 11 of the central support 10 on the inner circumference of the pole and holds the door in place. Once fitted into place, the screws at each end of the door are tightened to hold the bolts and door in position.

Tamperproof screws may be used to reduce the chance of interference by third parties.

The part of the support member 8 on the door co-operates with the part remaining in the pole in order to prevent the door falling into the pole. The local thickness of the material at the edge of the door cut-out straight edges prevents the door rotating about the fastening bolts and hence keeps the interior of the pole secure.

Alternatively, by angling the cut on each side of the door 12 more towards the centreline of the door, a support surface is formed in the pole I on each side of the opening 7, which prevents the door from going into the pole. This reduces the effective size of the opening, so the door has a greater width than the width of the opening which the door covers.

In an alternative embodiment, support members 8, 10 may be formed spaced at regular intervals along the periphery of the section, with the hollow supports lOin a central region of the section and the solid supports 8 further away from the centre, This allows for a door cut out to be made which has more than one hollow support member and so can attach to the pole using more than one fastener at each end, one per hollow support at each end, as shown in the example ofFig.Sb.

Overall, this design of door and door fastener reduces the number of components needed to secure the door, as compared with a conventional reinforced pole opening. Using the integrally formed supports inside the cylindrical body as the boundary to the door opening gives thick door sides, which allows the door to fit more securely than it does in a conventional pole and this means that no additional door supporting feature is needed, The door cut-out may be made by one of several techniques, including laser cutting, abrasive waterjet, saw or plasma cutting. The angle of the cut with respect to the surface of the pole may be chosen to optimise at least one of bending and torsional strength and door retention capability.

In this particular example, for a traffic signal pole, the extruded pole may be around 4m or ôm in length, and about 0,15 m in diameter. The size of the door opening is chosen to allow access to the connectors inside, but preferably does not exceed more than half the pole diameter in width and two or three times the diameter in length.

It is usually necessary to attach earthing cables to the pole and door. These are normally fitted by welding or tapping threaded studs to the body of the pole and the door, thus involving a separate and potentially expensive operation. However, as illustrated in Fig.6, the pole of the present invention allows this to be done simply and easily. In this example, for use with a pole made of a metal or other conductive material, the earthing arrangement comprises a barrel 21 that fits into the opening 13 and hollow centre 11 of the central support lOin the pole 1. An earthing screw 20 is screwed into the barrel 21 and the point of the screw digs into the pole material, Nuts and washers 19 are fitted to the earthing screw 20 to accept a terminal on the earthing wire (not shown). The earthing wires connect the pole body to the supply earth, to the equipment earth, and connect the pole body to the door, The utility pole of the present invention may be manufactured in a process as illustrated in the flow diagram of Fig.7. The material, required cylinder diameter and reinforcement support member shape, size and position are defined 30 and a suitable forming die is produced. The material is pressed 3 1 through the forming die under pressure, in a hot or cold process, depending upon the material properties. If required, the extruded body is cut to length 32. A door opening is cut in the body at a pre-defined position. If the cut-out is being used to manufacture the door, preferably the location of the cut is such that at least part of a support member on each longitudinal edge remains in the body and part of the support member forms a longitudinal edge of the cut-out,. If not, then the cut may be chosen such that the whole of the support member remains in the body. Where the cut-out is being used for the door, the door fasteners are then added 34 and the door is assembled 34 to the pole. According to the application of the utility pole, the product being supported, whether lights, CCTV camera, signs or other product is then added to the pole 36. Subsequently, the assembled pole and product can be installed on site 38 and any necessary earthing is connected.

By eliminating the need for a reinforcing member to be fitted around the door opening or for a door supporting feature to be provided, the number of operations required to manufacture the pole can be reduced, as traditional reinforcing members have to be pressed or welded into the pole. The elimination of welding is of considerable benefit as welding has to be undertaken with care, and the heat from welding permanently reduces the strength of the pole.

The hollow cylindrical utility pole may be manufactured by extrusion of suitable plastics, carbon fibre, or metals, either hot or cold extrusion according to the properties of the metal. Usefril metals for utility pole applications include aluminium or aluminium alloys, low carbon steel, medium carbon steel, low-alloy steel or stainless steel, Aluminium or aluminium alloys are preferred for their ability to yield under side impact and so achieve modem passive safety standards more easily than steel, The use of plastics or carbon fibre is also determined based on the combination of properties of torsional strength and yield to side impact that allow the utility pole to be robust n normal use, but to yield to achieve passive safety requirements. Metals simplify earthing, but plastics may be manufactured more easily and cheaply.

It should be readily appreciated by those persons skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications, and equivalent arrangements, will be apparent from, or reasonably suggested by, the present invention and the foregoing description thereot without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to specific embodiments, it is to be understood that this disclosure is only illustrative and presents examples of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. This disclosure is not intended to limit the invention to the particular systems or methods disclosed, but, to the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention.

Claims

CLAIMSL An extruded utility pole, the pole comprising a hollow cylindrical body comprising a wall, the wall having an inner and an outer circumference, wherein a plurality of support members are integrally formed by extrusion on the inner circumference of the wall over a section of the inner circumference having a length which is between 10% and 50% of the inner circumference; and wherein the utility pole further comprises an opening in the section for a door.
2. A pole according to claim 1, wherein the opening is bounded by at least a part of a support member on either side.
3. A pole according to claim 1 or claim 2 wherein the longitudinal edges of the door are cut through the support member in the direction of the centreline of the pole, or are cut at an angle.
4. A pole according to any preceding claim, wherein the section has a length between 15% and 30% of the inner circumference.
5. A pole according to any preceding claim wherein the support members are arranged equidistant along the section.
6. A pole according to any preceding claim, wherein a support member thither comprises a hollow opening adapted to receive a door fastener.
7. A pole according to claim 6, wherein the support member further comprises an opening along its length, within the hollow body.
8. A pole according to any preceding claim, wherein the support members extend into the hollow body by a distance in the range of 5% to 10% of the outside diameter of the body.
9. A pole according to any preceding claim, wherein the support member has a circular, rectangular or hexagonal cross section.
10. A pole according to any preceding claim, wherein the material comprises one of aluminium, carbon steel, stainless steel, carbon fibre or plastic.
11, A method of manufacturing a utility pole, the method comprising forming a die for a hollow cylinder having a plurality of intrusions into the hollow cylinder and extruding a material through the die, such that a hollow cylindrical body having at least two integrally formed internal support members is formed; the internal support members being formed over a section of an inner circumference of the cylinder, the section having a length which is between 10% and 50% of the inner circumference; wherein the method further comprises cutting an opening in the utility pole and removing the material cut from the opening.
12. A method according to claim 11, wherein the opening is bounded on its edges parallel to a longitudinal axis of the pole by at least a part of the internal support members
13. A method according to claim 11 or claim 12, wherein the method fbrther comprises fitting fasteners along a longitudinal axis of the cut material and installing the cut material in the opening to form a door, wherein the door fasteners are mounted in a support member integrally formed in the inner circumference of the cylinder.
14. A method according to claim any of claims t t to t3, wherein the method further comprises providing door fasteners in two or more support members.
15, A method according to any of claims II to 14, wherein a support member for mounting the door fasteners is equidistant between the internal support members bounding the opening. in IL,16. A method according to any of claims II to 15, wherein the method further comprises during the extrusion, forming an opening in the support member, for mounting the door fasteners.AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWSCLAIMS1. An extruded traffic signal pole, the pole comprising a hollow cylindrical body comprising a wall, the wall having an inner and an outer circumference, wherein a plurality of support members are integrally formed by extrusion on the inner circumference of the wall to provide reinforcement along the frill length of the cylinder; wherein the support members are formed in a section of the inner circumference having a length which is between 10% and 50% of the length of the inner circumference; wherein the utility pole ifirther comprises an opening in the section for a door; and wherein at least one support member is adapted for mounting the door.2. A pole according to claim 1, wherein the opening is bounded by at least a part of a support member on either side.LI') 15 3. A pole according to claim I or claim 2 wherein the door is bounded by at least a part of a support member on either side.. a)4. A pole according to any preceding claim, wherein the section has a lenh between 15% and 30% of the inner circumference.5. A pole according to any preceding claim wherein the support members are arranged equidistant along the section.6. A pole according to any preceding claim, wherein the at least one support member adapted for mounting the door further comprises a hollow opening adapted to receive a door fastener.7. A pole according to claim 6, wherein the hollow opening in the at least one support member adapted for mounting the door extends along its length, within the hollow cylindrical body.8. A pole according to any preceding claim, wherein the support members extend into the hollow body by a distance in the range of 5% to 10% of the outside diameter of the body.9. A pole according to any preceding claim, wherein the or each support member has a circular, rectangular or hexagonal cross section.10. A pole according to any preceding claim, wherein the pole comprises one of aluminium, carbon steel, stainless steel, carbon fibre or plastic.11. A method of manufacturing a traffic signal pole, the method comprising forming a die for a hollow cylinder having a plurality of intrusions into the hollow cylinder and extruding a material through the die, such that a hollow cylindrical body having at least two integrally formed internal support members is formed to provide IC) is reinforcement along the frill length of the cylinder; the internal support members being formed over a section of an inner circumference of the cylinder, the section having a 0') length which is between 10% and 50% of the inner circumference; wherein the method further comprises cutting an opening in the utility pole and removing the material cut from the opening at least one support member of the body for mounting a door to the pole.12. A method according to claim ii, wherein the opening is bounded on its edges parallel to a longitudinal axis of the pole by at least a part of the internal support members 3, A method according to claim Ii or claim 12, wherein the method further comprises fitting fasteners along a longitudinal axis of the cut material and installing the cut material in the opening to form a door, wherein the door fasteners are mounted in the support member integrally formed in the inner circumference of the cylinder.N. A method according to claim any of claims lIto 13, wherein the method further comprises providing door fasteners in two or more support members.A method according to any of claims 11 to 14, wherein the at least one support member adapted for mounting the door fasteners is equidistant between the internal support members bounding the opening.
16. A method according to any of claims 11 to 15, wherein the method further comprises during the extmsion, forming an opening in the support member, for mounting the door fasteners. IC) a) Co