NZ247817A

NZ247817A - Impact absorbing tubular pole: wall with alternating first and second pairs of staggered slits

Info

Publication number: NZ247817A
Application number: NZ247817A
Authority: NZ
Inventors: Mackenzie Richard Dowling
Original assignee: Dowling Mackenzie R
Priority date: 1992-07-17
Filing date: 1993-06-08
Publication date: 1995-07-26
Also published as: GB2268774A; CN1050875C; GB9314144D0; HK69996A; CN1086283A; GB2268774B; AU2038792A; MY115283A; AU631104B3

Description

V t C 'y ■ Patents Form it 5 rv.-v<te, n r ^CCilion I i. 8- Vs. .•CT2>. i\r**T'^r*11 D- 2 6 JUL 1995 Pubhccv".":' P.O. Journs!. No: I* 3 ' % %,'VS?/ NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION Energy Absorbing Pole I, MacKenzie Richard Dowling, an Australian citizen, of 3 Edale Street, Kenmore, Queensland 4069, Australia, do hereby declare the invention for which I pray that a patent may be granted to me and the method by which it is to be performed, to be particularly described in and by the following statement: The following page is numbered "la" PF05.JWP FEE CODE-1050 2-rsi lb TITLE: ENERGY ABSORBING POLE FIELD OF THE INVENTION THIS INVENTION relates to poles and, in particular, energy absorbing poles such as street side 5 light poles designed to crumple upon impact by a motor vehicle.

BACKGROUND TO THE INVENTION Prior Australian Patent specification 546648 (777 32/81) describes an impact absorbing pole which 10 comprises an octagonal tapered tube with a pattern of slots therein to weaken the pole so that it absorbs impact energy within itself. The more of the impact energy which is absorbed within the pole, the better if fatalities are to be avoided.

Prior Australian Petty Patent specification No 621806 describes an impact absorbing pole which achieves a better performance than the pole of AU Patent specification No 546648.

Poles of the above type are in common use and 20 road authorities and manufacturers are constantly seeking improved performance in meeting the dual requirements of rigidity sufficient to withstand loads such as experienced in high winds, particularly during cyclones, and to collapse in an impact with a vehicle in 25 a manner calculated to reduce the likelihood of loss of life. It is desired that the pole deforms in impact to absorb energy over time to effect as slow a deceleration of the vehicle as possible. These dual requirements are not such as to enable developments of improvements 30 through theoretical modelling. Improved designs are the result of testing and more particularly full scale testing of actual poles.

In production of poles of the above type, when aiming for smaller deceleration, stresses at the base of 35 the pole can result in the pole shearing, particularly,; o MAY 1995 " -> 247817 at the base, at which time impact energy absorption ceases and the pole fall is uncontrolled.

OBJECT OF THE INVENTION It is an object of the present invention to 5 provide a pole of the above type with improved energy absorbing characteristics.

NATURE OF THE INVENTION The invention achieves its objects in an energy absorbing pole comprising a tube which, in use, 10 is stood projected form a base at ground level and which is provided with a pattern of slits in its wall, the pattern being extended upwardly from or near ground level, the slits comprising elongate slits in the wall of the tube, the slits arrayed with their elongate 15 length oriented in lines along the tube wall, the lines of slits extended axially of the pole, the pattern of slits comprising a plurality of alternating first and second pairs of slits in the wall, the first pairs of lines of slits being angularly spaced about the wall 20 having their slit lengths in each line of each pair substantially equal to slit spacing and the slits in the two lines of each pair being staggered, the second pairs of lines of slits in the wall being each interposed between angularly spaced first pairs of lines of slits 25 each having slit spacing therein substantially equal to slit length and likewise staggered, every second pair of the pairs of lines of slits of the plurality of alternating first and second extending to a greater distance above ground level than does the first pairs. 30 To achieve the best possible results with a pole of the above defined character, it is best to have the rows of slots commence as close to the base as possible.

In this specification reference is made to 35 slits or slots. These are cuts extended through the ^ V f„f9 T £ 1 *V , ^ »C' , ^ .. ■ r f 2S MAY 1995 " ~ f~ I V 247817 material of the pole to sever the material through its thickness over a length. Slits or slots are to be read interchangeably and to include anything of the above character. In practice, the slits or slots will be 5 filled out by galvanising material but the weakening effect of the slit or slot is not lost by this.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to preferred embodiments which are illustrated 10 in the accompanying drawings, in which: FIG. 1 is a view of an octagonal sectioned energy absorbing pole in accordance with the present invention; FIG. 2 shows the pattern of slits which are 15 applied to a blank from which the pole of FIG. 1 might be produced; FIG. 3 is a view of a circular sectioned energy absorbing pole in accordance with the present invention; and FIG. 4 shows the pattern of slits which are applied to a blank from which the pole of FIG. 3 might be produced.

PREFERRED EMBODIMENTS In FIG. 1 is seen a pole 10 in accordance with 25 the invention which is stood above a base plate 11 as is usual with street lighting poles, etc. The pole 10 of the drawing has an octagonal cross section and is hollow being formed from sheet steel stock. The usual form of door can be fitted to a door cut out 12 which may be 30 provided to give access to the inside of the pole. The pole 10 may be tapered towards its top as is shown.

FIG. 2 shows in greater detail, a pattern of slits or slots which may be applied to a pole of the type which is shown in FIG. 1. The object of the slits 35 or slots is to establish an energy absorbing character 0 V Vn <T 2 j i'v'AY 1995 r\ 247817 for the pole. The slits or slots exist to weaken the steel of the pole. In practice the pole is galvanised or otherwise coated to avoid corrosion such that the slits or slots may not be evident in the finished pole.

Galvanising, for example, may fill out the slits or slots.

In FIG. 2, two forms of slotting exist being in first and second pairs of lines of slits characterized by the different height the lines of slits 10 extend up the pole in each of the first and second pairs of lines of slits. The pole is produced from a blank 14 which is to be bent along lines a to g to produce an octagonal tapered pole. The pole may be welded at the edge h to complete the pole. The octagonal pole then 15 has eight flat faces 15 to 22. The first form of slotting, in this embodiment, is along every second edge or bend line between the faces including the welded joint line. The other form of slotting exists along the edges of the remaining faces. In each form of slotting, 20 slits or slots are in pairs of lines on either side of and near to the bend and they are oriented along the length of the pole. Typically, the slits or slots may be 50 mm long and separated by 50 mm in the usual street lighting pole. The two forms of slotting are 25 distinguished by the height to which the slits or slots are taken. In each form of slotting the lines of a pair may be 8 mm apart in the blank from which the pole is made. Clearly the same technique can be applied to the other polygonal sectioned poles and to round poles 30 wherein the two types of lines are likewise angularly spaced around the pole as will become more clear below.

The slits or slots along and near to the corners between faces are typically at spacings which equal the slit or slot length and they are staggered. 35 Thus, the pole blank might be cut for 50 mm with 50 mm y .AY 1935 o 247817 missed before the next 50 mm cut with the cut in one line of a pair of lines at the space between slots in the other. Slotting at this separation may continue up the pole along and adjacent to the bend lines. The two 5 forms of pairs of lines of slotting alternate about the pole with each flat face of a polygonal pole preferably slotted at both edges. The patterns of slots in each line of slots need only be differentiated in each form of slotting with every other pair of slots being carried 10 to a different height up the pole. preferably start on one side at 50 mm from ground level and carry on up to typically either a height of 3000 mm or 4000 mm typically in a usual sized street lighting 15 pole and depending on the dimensions such as diameter, height, desired load capabilities, etc. The slits or slots on the other side of the lines a to h start at ground level and carry on up to their respective heights of 3000 mm or 4000 mm. This starts the pairs of lines 20 at ground level and sets the desired staggering in the adjoining lines of slots. character. Pole 24 has a door cut out 25 above a base 26 as before. The pole is provided with a pattern of slits or slots wherein one first pattern of a pair of line such as at 27 with typically 50 mm slots spaced by 50 mm with the two lines at an 8 mm separation 30 alternates with a second pattern of the same type such as at 28 with the first pattern extended to 3000 mm above ground level and the second to 4000 mm. In each pair, thfe slits or slots of one line start at ground level. In the other line the first slit or slot *«= a4" The slits or slots near the lines a to h The blank 14 is provided with a cut out 23 to define the opening for the door.

FIGS. 3 and 4 show a round pole of the above 50 mm. 247817 6 In crash tests of poles of the above kind energy is absorbed in crushing of the pole and in tearing or shearing of the material of the pole along the lines of slots. The pole is reduced to a plurality 5 of strips of material with energy absorbed in tearing along the lines of slits. Shear across the face of the pole, if it commences, is caught by a pair of slit lines and redirected therealong to reduce the likelihood of the pole shearing off. The spacing of the lines of a 10 single pair of lines is reduced relative to the spacing between pairs with the above in mind.

Claims

2 4 7 8 1 7 WHAT I CLAIM IS:

1. An energy absorbing pole comprising an elongate tube which, in use, can be stood projected from ground level and which is provided with a pattern of 5 slits in its wall, the pattern being extended from one end which, in use, is at ground level, the slits comprising elongate slits in the wall of the tube arrayed with their length oriented in lines along the tube wall, the lines of slits extending longitudinally 10 of the pole, the pattern of slits comprising a plurality of alternating first and second pairs of lines of spaced slits in the wall, the first pairs of lines of spaced slits being spaced about the wall and having their slit lengths in each line of each pair substantially equal to 15 the spacing of the slits and the slits in the two lines of each pair being staggered, the second pairs of lines of spaced slits in the wall being each interposed between the spaced first pairs of lines of slits and each having the spacing of the slits therein 20 substantially equal to the slit length and likewise staggered, every second pair of the pairs of lines of spaced slits of the plurality of alternating first and second pairs of lines of spaced slits extending to a greater distance from the one end than does the first 25 pairs.

2. An energy absorbing pole as claimed in Claim 1 wherein: one line of spaced slits of each pair of lines starts at the one end and the other line of spaced slits 30 of each pair starts at the height of the spacing between slits in the one line of each pair of lines.

3. An energy absorbing pole as claimed in Claim 1 wherein: the slits are 50 mm long, their spacing is 50. 35 mm and the first pairs of lines extend a distance of6'*^ 0 ^\\ •••AV 1095 Ik fx. 4 f 0 8 3000 nun and the second pairs to 4000 mm from the one end.

4. An energy absorbing pole as claimed in any one of Claims 1 to 3 wherein: 5 the pole is polygonal in cross section and each pair of lines of spaced slits lie on either side of an edge between two adjoining flat faces of the pole.

5. An energy absorbing pole as claimed in any one of Claims 1 to 3 wherein: 10 the pole is circular and the number of first pairs of lines of spaced slits equal to the number of second pairs of lines of spaced slits and the said pairs are equally angularly spaced around the pole.

6. An energy absorbing pole as claimed in any one 15 of Claims 1 to 5 wherein: the pole is tapered from the one end.

7. An energy absorbing pole substantially as herein described with reference to any one of the accompanying drawings. 20 JAMES W PIPER & CO Attorneys for the Applicant: MACKENZIE RICHARD DOWLING 26 M/iy lgg5 iti