AU2012101052A4 - A Frangible Pole with Transition Shoe - Google Patents

Abstract

A frangible pole assembly with transition shoe the assembly comprising a ground sleeve that is at least partially inserted into the ground, and a pole that can slide at least partially within the ground sleeve to hold the pole in place, the pole being provided with circumferential longitudinal flutes at least in the region where the pole contacts an upper edge of the ground sleeve. 16' Figure 1

Description

A FRANGIBLE POLE WITH TRANSITION SHOE TECHNICAL FIELD 100011 The present invention relates to a frangible pole and particularly to a frangible sign pole that can be used on highways, airports and elsewhere. BACKGROUND ART [00021 The dangers associated with vehicles striking a pole are well known. Highways and roadways are provided with signs, poles and the like which are positioned on the side of the road. If such a sign/pole is struck by a car, death and injury can result. [00031 For this reason, there have been many attempts made to provide some form of safety pole or safety sign. Thus, it is known to provide a pole which is relatively lightweight and which can simply break or shatter when struck by a car thereby reducing injury to the car occupants. However, the main disadvantage with this type of arrangement is the time that is required to replace the pole. [00041 To overcome this disadvantage, many attempts have been made to provide some form of pole that can be more easily replaced should the pole become damaged or destroyed. The main focus has been on the ability to quickly replace the pole. Thus, it is well known to provide a first member that stays in the ground, and a pole that is fixed to the first member by some form of sacrificial pin and the like. If the pole is struck, the sacrificial pin will break, the pole and pin will be destroyed but the first member stays intact. It is considered that the pole and sacrificial pin can be more easily replaced if the ground member (the first member) is protected. 100051 There have been many variations to this type of arrangement, but each still requires some form of sacrificial pin or other member that is broken or sheared when the pole is struck. The main disadvantage is that it still takes some time to replace the pole that has a sacrificial pin or other member, as assembly and attachment of the sacrificial pin can take some time. [00061 There would be an advantage if it were possible to provide some form of replaceable pole which did not require a sacrificial pin or other member. [00071 Another consideration, particularly for poles that support large signage, is that the pole must be able to take wind load on the sign without breaking. Some sacrificial members will break under high wind loads which is not desirable.

2 100081 It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country. SUMMARY OF INVENTION [00091 The present invention is directed to a frangible pole with transition shoe, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice. [00101 With the foregoing in view, the present invention in one form, resides broadly in a frangible pole assembly with transition shoe the assembly comprising a ground sleeve that is at least partially inserted into the ground, and a pole that can slide at least partially within the ground sleeve to hold the pole in place, the pole being provided with circumferential longitudinal flutes at least in the region where the pole contacts an upper edge of the ground sleeve. [00111 The upper edge of the ground sleeve acts as a sheer point and depending upon the particular molecular structure of the alloy of material used, will bend the pole at the point of impact and will ultimately shear and break at the top of the ground sleeve. The flutes on the pole are designed to further assist in the breakaway process by reducing the external surface area of the pole in contact with the ground sleeve. [00121 It is found that the arrangement of circumferential flutes on the pole enables the pole to be sheared off when struck with little or no damage to the ground sleeve. Typically, the pole is sheared at or adjacent the upper edge of the ground sleeve. Also, a sacrificial pin and the like is not required. The arrangement of the flutes seems to enable the pole to be broken without substantial damage to the ground sleeve and in a manner that is safer to vehicles that may strike the pole compared with a metal pole that is simply concreted directly into the ground. 100131 The flutes should be provided on the poles at least in a region where the pole contacts the upper edge of the ground sleeve. However, as it is preferred that the pole is extruded from aluminium, it may be effective to simply extrude the pole with the flutes extending along the entire length of the pole. 100141 It is preferred that the flutes extend entirely about the pole and on the outer surface of the pole. The flutes may be spaced apart from each other by a distance of between 2-20 millimetres. The flutes may have a depth of between 1-5 millimetres, and a width of between 3 1 5 millimetres. The flutes may be substantially rectangular when viewed in plan.

3 [00151 To assist in providing the pole with frangible properties, it is preferred that the pole is manufactured from a material that can shear when struck by a load. It is found that aluminium is a suitable material and it is therefore preferred that the pole is manufactured from aluminium. However, it is envisaged that other metals and possibly metal alloys may have desirable properties including alloys containing zinc, nickel, lead, copper, iron and the like. [00161 In a particularly preferred embodiment, the pole is made from structural grade 6261 T5 or T6 aluminium. A preferred material has a yield strength of approximately 275MPa. [00171 It is also preferred that the pole is hollow to reduce weight and materials. [00181 Another advantage in using aluminium is that the pole has less weight than a typical steel pole and therefore more poles can be loaded onto a truck, and the poles can be handled more easily. Also, aluminium is more resistant to corrosion and environmental degradation compared to steel poles. [00191 The length of the pole can vary depending on its use. The typical length will be anywhere between 1-6 metres or even longer and it is not considered that the invention should be limited to any particular length of the pole. [00201 The pole will usually be cylindrical. However there may be an advantage in providing the pole with other configurations such as slightly oval, rectangular, or other irregular shapes. [00211 If the pole is cylindrical, the outside diameter of the pole may be anywhere between 50-150 millimetres and preferably between 60-130 millimetres and most preferably between 60 120 millimetres. [00221 The wall thickness of the pole will vary depending on the diameter of the pole, the wind loading on the pole, the size and weight of the signage or other item that is attached to the pole, etc. However, it is envisaged that the wall thickness will be between 3-7 millimetres and preferably between 3-6 millimetres and most preferably between 3.75-5.5 millimetres. [00231 The pole may be provided with an upper end cap to prevent water from entering into the pole. This cap may be made of plastic, rubber, metal and the like. [00241 The ground sleeve may be made of any suitable material and it is preferred that the ground sleeve is made of metal such as aluminium. The ground sleeve will typically have an 4 internal diameter or cross-section which is slightly larger than the external diameter or cross section of the pole to enable the pole to slide into the ground sleeve, although a snug or interference fit is preferred. [00251 Suitably, the pole will be cylindrical and therefore the ground sleeve will also be cylindrical. The ground sleeve may have a length of between 20-100 centimetres depending on the dimensions of the pole, etc. The ground sleeve will normally have an internal diameter of between 50-150 millimetres but the diameter should be to enable the pole to slide within the ground sleeve. 100261 In use, the ground sleeve is positioned in the ground and typically in such a manner that the upper edge of the ground sleeve is slightly spaced above the ground, the spacing typically being between 3-10 centimetres. [0027] The ground sleeve can have a wall thickness of between 3-10 millimetres although this can vary to suit. [00281 The ground sleeve may be provided with one or more fastener to fix the pole into the ground sleeve. Each fastener may comprise a bolt, although no limitation should be placed on the innovation merely by describing a bolt and the fastener may comprise a screw, a clamp, a wedge, a locking pin and the like. [0029] If desired, a separate wedge may be provided to further hold the pole within the ground sleeve, although this wedge is not the same as a sacrificial pin as it does not break or shatter in a sacrificial manner. [00301 The ground sleeve may be provided with means to prevent or to resist rotation of the pole within the ground sleeve. If the pole is cylindrical and the ground sleeve is cylindrical, one way in which this can be achieved is to provide a small bead or projection in the ground sleeve and which can engage in a flute on the pole thereby preventing the pole from rotating within the ground sleeve. If necessary, more than one such bead or projection can be provided. In practice, at least two beads or protections will be provided. [00311 If the ground sleeve is made of extruded aluminium, the bead or projection can form part of the extrusion. [00321 In particular, it is preferred that the ground sleeve will be provided with a mounting portion for mounting the fasteners thereto. Preferably, a mounting portion will include a substantially U-shaped wall portion located in a wall of the ground sleeve. Preferably, the ground sleeve will be circular in order to provide frangibility in multiple directions and the mounting portion is provided over at least a portion of the height of the ground sleeve. 100331 Typically, the substantially U-shaped mounting portion will extend over the height of the ground sleeve although it may be restricted to a particular portion of the ground sleeve. In particular, it is preferred that and the U-shaped mounting portion will be provided adjacent to the top edge of the ground sleeve and be located above the ground surface when the sleeve is properly installed. 100341 Typically, the U-shaped mounting portion includes a pair of walls extending perpendicularly away from the solid wall of the ground sleeve and an outer wall linking the pair of walls. This configuration preferably forms the U-shaped channel in the side wall of the ground sleeve. Typically, the mounting portion is located outside of the internal shape of the ground sleeve so as not to obstruct insertion and removal of the pole therefrom. [00351 The fasteners used to fix the pole relative to the ground sleeve will preferably be mounted through the mounting portion, and particularly, through the outer wall approximately perpendicularly to the pole. [00361 The mounting portion will typically be integrally formed with the ground sleeve typically by extrusion. 100371 The transition shoe of the present invention will typically be located adjacent to the mounting portion and it is particularly preferred that the transition shoe is located between the mounting portion and the exterior surface of the pole. Even more preferred is that the transition shoe is located between the fasteners and the pole. [00381 Typically in use, the end of the preferred fasteners will abut the transition shoe which in turn abuts the pole in order to fix the pole in position by applying a clamping force. This also has the effect of spreading the load applied by the fasteners over a greater area of the pole. 100391 The transition shoe of the present invention will typically include a substantially planar shoe portion for insertion between the mounting portion of the ground sleeve and the pole. [00401 The transition shoe will also typically be provided with a gripping portion at or adjacent an upper end of the shoe portion. The gripping portion will typically be angled relative to the shoe portion. It is particularly preferred that the angle used is at least 900 or more 0 preferably, obtuse although the angle can be less than 900 if desired provided that it is able to be gripped. [0041] The gripping portion will also preferably function as a locating portion, acting to prevent the transition shoe falling between the pole and the ground sleeve. 100421 The transition shoe will preferably be attached to the ground sleeve using an appropriate method so that the transition shoe is not accidentally separated or lost when the pole is removed for replacement or repair. One simple manner of attaching the transition shoe to the ground sleeve is the provision of an opening in the transition shoe, typically in the gripping portion in order to attach a chain, string or similar elongate member or mechanism which is attached to the ground sleeve. [0043] Typically, the transition shoe may be attached to any part of the ground sleeve but the preferred method is the provision of a light chain or similar having one or more links which can be located about or relative to a fastener used to fix the position of the pole relative to the ground sleeve. In this way, the fastener can extend through the opening in one of the links and abut the typically enlarged head of the fastener, preventing removal of the link from the fastener while the fastener engaged with the pole. [00441 The shoe portion of the transition shoe will typically be an elongate, substantially planar portion. The lower end of the shoe portion will typically be tapered to allow easier insertion between the pole and the ground sleeve. The tapered portion can be arcuate when viewed from the side. Typically, the tapered portion will have a concave surface oriented toward the pole. [0045] Preferably, one or more ribs extend longitudinally over the length (or height) of the shoe portion of the transition shoe. Typically, a pair of ribs will be provided extending from adjacent to the gripping portion downwardly to the lower end of the shoe portion. Typically, the ribs will be arcuate in cross-section in order to provide strength to the shoe portion. [00461 The shoe portion may be waveform in shape when viewed from above. The waveform shape can be provided by the ribs or simply that the shoe portion is shaped in that way. 100471 Preferably, the waveform shape is provided such that at least one concave face is oriented toward the pole when the transition shoe is properly inserted. 100481 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. [0049] The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge. BRIEF DESCRIPTION OF DRAWINGS [0050] Various embodiments of the invention will be described with reference to the following drawings, in which: [00511 Figure 1 is an isometric illustration of a frangible pole assembly with transition shoe according to a preferred embodiment of the present invention. [00521 Figure 4 is an axonometric view of the frangible pole assembly illustrated in Figure 1. [00531 Figure 5 is a view from the side of the frangible pole assembly illustrated in Figures 1 and 4 with the transition shoe not fully inserted. [00541 Figure 6 is a view from the side of the frangible pole assembly illustrated in Figures 1 and 4. [00551 Figure 6A is a detailed view of the engagement between the ground sleeve, pole and transition shoe according to a preferred embodiment of the present invention. [00561 Figure 7 is a front view of a transition shoe for use in a frangible pole assembly of a preferred embodiment. [00571 Figure 8 is a side view of the transition shoe illustrated in Figure 7. [00581 Figure 9 is a top view of the transition shoe illustrated in Figures 7 and 8. DESCRIPTION OF EMBODIMENTS [00591 According to a particularly preferred embodiment of the present invention, a frangible pole assembly including a transition shoe is provided. [0060] Referring to the illustrations and initially to Figure 1, there is illustrated a frangible pole assembly which comprises a pole 10 and a ground sleeve 11. It should be appreciated that in the illustrations, the length of the pole 10 and the length of the ground sleeve I1 have been 0 shortened. Typically, pole 10 will have a length of anywhere between 1-6 metres and ground sleeve 11 will have a length of anywhere between 20-100 centimetres. [00611 Pole 10 is made of extruded aluminium and particularly of 6261 T5 or T6 aluminium, a high strength, marine grade alloy with a typical yield strength of 275MPa. [00621 The illustrated pole is cylindrical and hollow and has a wall thickness of between 3.75-5.5 millimetres depending on the length of the pole and the use of the pole. [00631 The pole contains a circumferential array of flutes 12 in the outside of the pole. The flutes (see also Figure 3) comprise longitudinal channels extending into the outer face of the pole which define raised portions between the flutes. The flutes extend entirely along the length of the pole and have a width of between 2-5 millimetres and a depth of between 1-4 millimetres. The flutes are somewhat rectangular when viewed in plan, but their cross-sectional shape is not limiting in any way. [00641 The ground sleeve I 1 is generally cylindrical and hollow and has a wall thickness of between 3-10 millimetres. The internal diameter of ground sleeve 11 is slightly larger than the external diameter of the pole such that the pole can be positioned within the ground sleeve. [00651 The ground sleeve contains a thickened portion 13 or shaped portion to support a pair of threaded fasteners or bolts 14 that is used to fix pole 10 in place once the pole has been positioned within the ground sleeve. [00661 In use, the ground sleeve is concreted or otherwise fixed into the ground surface with approximately 10 centimetres projecting above the ground. [00671 To prevent pole 10 from rotating within the ground sleeve, the ground sleeve is provided with two inwardly extending longitudinal beads 15 (see Figure 2) which extend into the flutes of pole 10 when the pole sits within sleeve 11. [00681 The transition shoe 17 of the preferred embodiment is located adjacent to an upper end of the thickened portion 13 which according to the illustrated embodiments, has a U-shaped channel or recess 20 therein, between the thickened portion 13 and the exterior surface of the pole 10. It can be seen that the transition shoe i17 s located between an inner end of the bolts 14 and the pole 10. [0069] The inner end of the bolts 14 abut the transition shoe 17 which in turn abuts the pole 10 in order to fix the pole in position by applying a clamping force. This also has the effect of spreading the load applied by the bolts 14 over a greater area of the pole 10. [00701 The transition shoe of the preferred embodiment is best illustrated in Figures 7 to 9 and includes a substantially planar shoe portion 22 for insertion between the thickened portion 13 of the ground sleeve 11 and the pole 10. [00711 The transition shoe 17 also includes a gripping portion 21 at or adjacent an upper end of the shoe portion 22. The gripping portion 21 is angled relative to the shoe portion 22 at an obtuse angle. [00721 As a function of the angle of the gripping portion 21, it will also function as a locating portion, acting to prevent the transition shoe 17 falling between the pole 10 and the ground sleeve 11. [00731 The transition shoe 17 of the illustrated embodiment is attached to the ground sleeve 11 using an appropriate method so that the transition shoe is not accidentally separated or lost when the pole 10 is removed for replacement or repair. The particular method used in the illustrated embodiment is the provision of an opening 23 in the transition shoe in the gripping portion in order to attach a chain 18 which is attached to the ground sleeve 11. [00741 The transition shoe 17 can be attached to any part of the ground sleeve 11 but the preferred method is the provision of a light chain 18 having one or more links which can be located about a bolt 14 used to fix the position of the pole 10 relative to the ground sleeve 11. 100751 As illustrated in Figures 7 and 8 in particular, the shoe portion 22 of the transition shoe 17 is an elongate, substantially planar portion. The lower end of the shoe portion 22 is tapered to allow easier insertion between the pole 10 and the ground sleeve 11. The tapered portion is arcuate when viewed from the side as seen in Figure 8 with a concave surface oriented toward the pole 10. 100761 A pair of ribs 24 extend longitudinally over the length (or height) of the shoe portion 22 of the transition shoe 17 extending from adjacent to the gripping portion 21 downwardly to the lower end of the shoe portion 22. The ribs illustrated in Figures 7 to 9 are arcuate in cross section in order to provide strength to the shoe portion 22. [00771 The shoe portion is therefore waveform in shape when viewed from above.

IU [00781 In practice, the arrangement of the flutes on the pole is such that should the pole be struck, it will shear at the upper edge 16 of ground sleeve I I and will break away. The shearing action is contributed to by the flutes 12 and also by the type of metal from which the pole 10 is made. [00791 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. [00801 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. 100811 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.

Claims (5)

1. A frangible pole assembly with transition shoe, the assembly comprising a ground sleeve that is at least partially inserted into the ground, and a pole that can slide at least partially within the ground sleeve to hold the pole in place, the pole being provided with circumferential longitudinal flutes at least in the region where the pole contacts an upper edge of the ground sleeve.

2. A frangible pole assembly as claimed in claim I wherein the flutes extend entirely about the pole on an outer surface of the pole.

3. A frangible pole assembly as claimed in either one of claims 1 or 2 wherein the transition shoe is located between one or more fasteners used to fix the pole relative to the ground sleeve and the pole.

4. A frangible pole assembly as claimed in any one of the preceding claims wherein the transition shoe includes a substantially planar shoe portion and a gripping portion at or adjacent an upper end of the shoe portion angled relative to the shoe portion.

5. A frangible pole assembly as claimed in any one of the preceding claims wherein the transition shoe is attached to the ground sleeve using an appropriate method so that the transition shoe is not accidentally separated or lost when the pole is removed for replacement or repair.