AU2009210368A1

AU2009210368A1 - Roof anchor cable system having shock absorbing means

Info

Publication number: AU2009210368A1
Application number: AU2009210368A
Authority: AU
Inventors: Arvo Poldmaa
Original assignee: DANIEL POLDMAA; KATHLEEN POLDMAA
Current assignee: Safetylink Pty Ltd
Priority date: 2008-08-16
Filing date: 2009-08-17
Publication date: 2010-03-04
Anticipated expiration: 2029-08-17
Also published as: AU2009210368B2

Description

o;\doruments\poldmaa\20288complete.doo ROOF ANCHOR CABLE SYSTEM HAVING SHOCK ABSORBING MEANS TECHNICAL FiELD The present invention relates to a roof anchor for attaching devices, apparatus or equipment to a roof surface and, more particularly, to a roof anchor cable system, s which includes shock absorbing means, for fixing about a rafter or the like of a roof structure supporting tiles so that the attachment point of the anchor is available for use on the roof surface. The devices, apparatus or equipment to be attached may include safety equipment such as a safety harnesses, ropes or other safety devices adapted to secure a roof worker against falling and injury. 10 BACKGROUND ART Several solutions have been proposed for providing anchor points on a roof, whereby such anchor points are made available so that a person working on the roof for example, can attach himself to the anchor point by means of a rope or cable etc, so that in the event of a fall, he will be constrained from falling off the roof. 15 Various solutions have been put forward which are particularly suitable for metal rooves, both for initial installation when the roof covering is first applied and in cases where the roof covering is already attached, being a so-called retro-fit. None of these solutions however is really practical when one considers a tiled roof. Generally because of the ease of removing one or two or even more files, the 20 problems associated with so called retro-fits for metal sheeting rooves are less apparent. To this end, a solution which provides an anchor point in a tiled roof, if suitably designed, should in general be applicable not only to tiled rooves when they are being constructed, but also when the roof tiles are already in place, since the tiles can generally be easily removed and replaced without too much difficulty. 25 However, unlike the possibilities available for metal rooves, where there is both integrity in the metal roof itself, as well as the way in which the metal sheeting is itself attached, the anchor point for a tile roof needs to be preferably independent of the tiles themselves (that is to say preferably not made to pass through a tile as such, or otherwise rely on the arrangement of tiles) and yet available in such away that it so stands proud of the roof surface and yet does not interfere with the actual arrangement of tiles. It would therefore be advantageous if a roof anchor system were available which could be affixed to the rafter of a roof structure supporting tiles, and which also provided an anchor point which extended beyond the surface of the roof tiles, 1 c:\documents\poldmaa\20288complete.doc without disturbing the usual arrangement of tiles. It would also be advantageous if such a roof anchor system was provided with shock absorbing means in order to minimise injury from a person utilising the anchor point in the event of a fall. OBJECT OF THE INVENTION s It is an object of the present invention to provide a roof anchor system which ameliorates one or more of the abovementioned disadvantages associated with the prior art, particularly by providing a roof anchor system which may be mounted on the rafter of a roof structure supporting tiles, the anchor point for attachment of devices, apparatus or equipment, being made available above the roof surface, the io anchor system so designed as to progressively absorb the effects of a sudden load applied thereto. It should also be understood that whilst the invention relates primarily to the attachment of devices to a tiled roof as described, the invention will also be applicable in many instances where attachment of a device to another surface or 1s structure is required, whether a wall or ceiling for example. Thus any reference to a roof is also meant to encompass reference to any structure, where, by suitable adaptation the invention may also be utilised. Similarly, although the invention is described generally in terms of its applicability to tiled rooves, it is again to be understood that the invention is applicable to any roof covering, where, by suitable 20 modification, the invention may also be applied. DISCLOSURE OF THE INVENTION According to the present invention, there is provided a roof anchor cable system for fitment to a rafter or the like of a roof structure, wherein the anchor cable system comprises a cable and an anchor bracket, wherein in use the cable is attachable 25 about a rafter or the like by means of simply wrapping the cable thereabouts, the free ends of the cable being connectable in use to the anchor bracket, the anchor bracket comprising first attachment means for attaching the free ends of the cable thereto, second attachment means remote therefrom and able to extend through or beyond the roof cladding such as tiles or the like for attaching devices, apparatus or 3o equipment to the anchor bracket, and third attachment means for attaching the anchor bracket itself to the rafter for the purpose of generally locating the bracket in the desired position. Preferably the anchor bracket and cable cooperate to progressively distort under sudden load. To this end, the very nature of the cable wrapped about the rafter 2 o-\documents\poldmaa\2028complete.doc provides a significant contribution to the absorption of energy in cases where a person falls, It should be appreciated that the performance of this arrangement will be improved when the cable is wrapped along rather than simply around the rafter. The performance of the cable in absorbing a sudden load applied thereto will be 5 thus particularly enhanced where a timber rafter is utilised, the timber being inherently compressible to a degree, providing a significant shock absorbing capacity. However, even in the case of a metal roof truss, the action of having the cable wrapped about the rafter provides significant progressive absorption of the energy under sudden load, especially with increasing numbers of crossovers as the 1o cable is wrapped about a longer length of the rafter. To this extent, in the case of metal rafters, it is preferable to have the cable wrapped four times thereabouts (ie with three crossovers). In any event, preferably the cable is wrapped more than once around the rafter (ie not merely looped around the rafter once) and is preferably located initially by 1s means of a simple bracket conveniently located to affix it to the rafter. This bracket will be best located where the cable effectively loops the rafter. Conveniently, this bracket will be located on the upper side of the rafter (for ease of attachment) when one or an odd number of crossovers occurs, the bracket of course also be located on the upper side of the rafter. Generally speaking, this locating bracket for the cable 20 will perform no useful function other than to keep the cable in place along the rafter until a load should be applied, in which case the cable will then be caused to tighten about the rafter (biting into the wood thereof if made of timber), but otherwise performing in such a way that it will not move when under such load. Preferably the anchor bracket itself is also shaped so as to progressively distort 25 under sudden load. In addition to the natural shock absorption provided by the use of a cable wrapped about a rafter, it is highly desirable to also provide shock absorption means in the bracket itself For example, this may take the fonn of one or more planar sections of the bracket, die-cut in a generally snake like pattern, so that upon a force being applied thereto, the thus shaped section is able to extend 3o progressively under the load applied. Preferably, the anchor bracket is thus die cut from a single sheet of stainless steel, aluminium or high density plastics material and cut so as to provide progressive absorption of a sudden load applied thereto by means of progressive deformation of the bracket under such load. 3 c:\documents\poldmaa\20288comp1ete.doc Preferably the shock absorption is thus provided by one or more suitably shaped portions of material cut or otherwise formed so that when a force is applied thereto, there is created a deformation therein in the form of a generally linear extension of that portion, ie by effectively straightening or "unbending" such region. Thus the s anchor is so designed that deformation by bending, ie unbending or straightening, of such shock absorbing region provides an absorption of the forces applied to the anchor. Whilst it is generally preferred that the anchor bracket be made from a generally planar section of material as described above, it is preferable that the bracket itself ia be bent in such a way that it can be both suitably attached to a rafter at one end, whilst having the other end remote therefrom extend between overlapping tiles. To this end, the cross section may be usefully described as a generally flattened W profile, the outer legs corresponding to regions supporting in the one case the second attachment means for devices etc, ie standing proud of the tile surface, 15 whilst in the other case, the other outer leg corresponds to a region supporting the third attachment means for affixing the bracket to the rafter. The intermediate legs therefore allow the bracket to function in so far as they connect both ends and allow the region supporting the second attachment means to pass effectively between the tiles. Generally, it is preferred that the inner leg adjacent the outer leg which 20 supports the third attachment means is the region supporting the first attachment means, ie for attaching the cable. It will be appreciated however that other cross sectional shapes other than a flattened W profile, may also be employed. Preferably the first attachment means provided in the anchor bracket for fixing the cable thereto is in the form of a simple hole therethrough. Preferably the ends of 25 the cable are provided with an end piece swaged thereto, in which there is also provided a hole. In this way, attachment of both ends of the cable to the anchor bracket is easily achieved by aligning the three holes and passing a bolt etc to which a nut may be affixed, or other suitable fixing device therethrough for securement of the cable ends to the bracket by otherwise generally known means. so The second means of attachment provided in the anchor bracket, ie for attaching the device, apparatus or equipment thereto, is again preferably provided in the form of a simple hole or eye in the end of the anchor which protrudes in use through the tile surface. The third means of attachment provided in the anchor bracket is preferably in the 35 form of a t-section with a plurality of holes available therethrough for screwing the 4 The third means of attachment provided in the anchor bracket is preferably in the form of a t-section with a plurality of holes available therethrough for screwing the bracket to a rafter. In this way, although the main energy absorption of the bracket and cable combination is provided by the cable itself acting in conjunction with any s absorption means provided in the bracket itself, the initial shock is absorbed in this arrangement by having the bracket also screwed to the rafter as well as connected by the cable as described beforehand. More importantly however, the t-section allows location of the bracket at various cross wise positions on the rafter so that the other free end of the bracket, being that end which extends between adjacent 10 overlapping tiles, may be properly located. In this way, the bracket may be conveniently located so that the free end extends between the tiles at a suitable point in their profile (eg along a trough or groove etc) so that in essence , the tiles are not physically disturbed from the arrangement which they would normally assume if the anchor bracket were not there. is It will be understood from the embodiments described herein, that the roof anchor cable system is also able to function irrespective of the direction of the load, notwithstanding that in doing so there will be some disturbance of the tiles about the free end of the anchor in the event of such a load being applied in certain directions. 20 BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood from the following non-limiting description of various embodiments of the present invention with reference to the drawings in which: Fig 1 is a side view of a roof anchor cable system according to one embodiment of 25 the invention, showing three overlaps in the cable about a rafter; Fig 2 is a side view of the roof anchor cable system as shown in Fig I without the rafter; Fig 3 is a plan view of the roof anchor cable system as shown in Fig 2; Fig 4 is a side view of the roof anchor cable system according to the embodiment 30 shown in Figs 1 to 3, but showing instead a single overlap in the cable about a rafter; Fig 5 is a side view of the roof anchor cable system as shown in Figure 4 without the rafter; 5 Fig 6 is a plan view of the roof anchor cable system shown in Fig 5; Fig 7 is a side view of the roof anchor cable system according to the embodiment shown in Figs 1 to 6, but showing a double overlap in the cable about a rafter; Figs 8 is a detailed plan view of the anchor bracket as used in the embodiments of a Figs 1 to 7; and Figs 9 to 12 are plan views of other embodiments of the anchor bracket suitable for use with any of arrangements as shown in Figs I to 7, substituting the bracket for the one shown as appropriate. DETAILED DESCRIPTION OF THE DRAWINGS 1a Referring generally to Figs I to 3, there is shown a roof anchor cable system generally referenced 11 according to a first embodiment of the invention. The roof anchor cable system 11 comprises an anchor bracket 12 and a cable 13 for attachment to a rafter 14. The anchor bracket 12 in side view or in profile, is of generally flattened W shaped 15 configuration having a first outer leg 15 which is generally t-shaped, for attachment to the rafter 14, by known means such as screws (not shown). These may be inserted through holes 16 located in the first outer leg 15. The other outer leg 17 extends beyond the roof cladding, eg passing between consecutive tiles 18. The outer leg 17 has a hole 19 therethrough for attachment of 2o devices, such as safety harnesses, ropes or other safety devices (not shown). The two inner legs 20, 21 are shaped or angled so as to allow the anchor bracket 12 to be affixed to the rafter 14 and extend between consecutive tiles 17 as shown. The location of the several holes 16, in this case three, across the first outer leg 15, provides for location of the bracket 12 on the rafter 14, so that it can be aligned 2s with any useful groove or trough etc in the profile of the tile (not illustrated), to minimise any disturbance thereto. Alternatively the anchor bracket of Fig 9 may be employed wherein the bracket 12 has a wider leg member 15 having five holes 16 located therein. Inner leg 21 has a hole 22 therethrough. The cable 12 is wrapped four times about so the rafter 14, as illustrated in Fig 1, producing three overlaps 23. To this extent the cable 13 is wound twice about the rafter 14 moving upwards and away from the anchor bracket 12, and then wrapped a further two times coming back down the 6 rafter to return to the anchor bracket 12. The two free ends of the cable 13 are provided with end pieces 24 swaged thereto. Each end piece 24 has a hole 25 theretbrough for fixing to the anchor bracket 12, by means of a nut and bolt 26 as shown, which passes through the holes 22 and 25 when aligned for that purpose. 5 Where the cable 13 passes over the rafter 14 before returning to the anchor bracket 12, it is secured by a holding bracket 27. This bracket 27 has a hole 28 therein for fixing to the rafter 14 by suitable means, such as a screw (not shown). Although the anchor bracket 12 as shown in Figs 1 to 3 has no regions therein acting as a shock absorber, anchor brackets 12 incorporating shock absorbing 10 regions as discussed below in relation to Figs 10 to 12 may be substituted instead. In any event, the use of the cable 13, wrapped up to four times around the rafter 14, provides excellent shock absorbing means in situations where a sudden load is applied to the anchor/cable combination 11. This arrangement is particularly suited to steel rafters. When a force is applied to the anchor/cable system 11, the initial 1s force causes the anchor bracket 12 to be separated from the rafter as the screws holding the first leg 15 of the bracket 12 give way. It follows, that the forces are then applied to the cable 13 which tightens progressively about the rafter 14. No slippage occurs even on a metal rafter 14, as the cable 13 bites into itself at the crossover points 23. 20 Figs 4 to 6 and Fig 7, in which like components are referenced with the same reference numerals, effectively illustrate less cross over points 23, specifically two in Figs 4 to 6 and only one in Fig 7. Less crossover points 23 have been found to be suitable in cases where timber rafters 14 are employed, although three as illustrated in Fig I to 3, is generally preferred even for timber rafters. It should be 25 noted that in the case of two crossovers, as shown in Fig 7, the geometry is such that the holding bracket 27 is actually located on the underside of the rafter 14, which may be inconvenient to affix in situations where the roof has already been otherwise finished, eg in a so-called retro fit. Referring specifically to Figs 10 to 12, there are illustrated alternate brackets 12 3o which have one or more regions 29 die cut so as to provide shock absorption under sudden load. The principles involved have been discussed at length in my co pending Australian patent application 2008903413, entitled "Roof anchor with shock absorbing means", the subject matter of which is incorporated herein by reference. 7 Essentially, these shock absorbing regions 29, where provided in bracket 12, co operate with the cable 13 to further enhance the shock absorbing capacity of the bracket/cable system, so that when a sudden load is applied, for example as a result of a person attached to he anchor system falling, the initial and subsequent forces 5 are absorbed to the extent that the person who falls is not injured by being suddenly prevented from falling had there been no shock absorption provided. It will appreciated that many modifications and variations may be made to the embodiments described herein by those skilled in the art without departing from the spirit or scope of the invention. 10 Throughout the specification and claims the word "comprise" and its derivatives are intended to have an inclusive rather than exclusive meaning unless the context requires otherwise. INDUSTRIAL APPLICABILITY It will be immediately apparent to persons skilled in the art that the roof anchor may 15 provide an anchor point for a variety of activities carried out on roof, including height safety, but not necessarily limited thereto. 8

Claims

1. A roof anchor cable system for fitment to a rafter or the like of a roof structure, wherein the anchor cable system comprises a cable and an anchor bracket, wherein in use the cable is attachable about a rafter or the like by means of s simply wrapping the cable thereabouts, the free ends of the cable being connectable in use to the anchor bracket, the anchor bracket comprising first attachment means for attaching the free ends of the cable thereto, second attachment means remote therefrom and able to extend through or beyond the roof cladding such as tiles or the like for attaching devices, apparatus or 10 equipment to the anchor bracket, and third attachment means for attaching the anchor bracket itself to the rafter for the purpose of generally locating the bracket in the desired position.

2. A roof anchor cable system according to claim 1 wherein the anchor bracket and cable cooperate to progressively distort under sudden load. 15

3. A roof anchor cable system according to claim 2 wherein the cable is wrapped along rather than simply around the rafter.

4. A roof anchor cable system according to claim 3 wherein the cable is wrapped four times about the rafter (ie with three crossovers).

5. A roof anchor cable system according to claim 2 wherein the cable is wrapped 20 more than once around the rafter (ie not merely looped around the rafter once) and is located initially by means of a simple bracket conveniently located to affix it to the rafter.

6. A roof anchor cable system according to claim 5 wherein the bracket is located where the cable effectively loops the rafter. 25

7. A roof anchor cable system according to claim 6 wherein the bracket is located on the upper side of the rafter for ease of attachment when one or an odd number of crossovers occurs.

8. A roof anchor cable system according to any one of the preceding claims in which the anchor bracket is also shaped so as to progressively distort under 30 sudden load. 9 c:\documents\poldmaa\2288complatedoc

9. A roof anchor cable system according to claim 8 in which there is in addition to the natural shock absorption provided by the use of a cable wrapped about a rafter, there is also provided shock absorption means in the bracket itself

10. A roof anchor cable system according to claim 9 wherein the shock absorption 5 means provided in the bracket is in the form of one or more planar sections of the bracket, die-cut in a generally snake like pattern, so that upon a force being applied thereto, the thus shaped section is able to extend progressively under the load applied.

11. A roof anchor cable system according to claim 10 wherein the anchor bracket is 10 die cut from a single sheet of stainless steel, aluminium or high density plastics material and cut so as to provide progressive absorption of a sudden load applied thereto by means of progressive deformation of the bracket under such load.

12. A roof anchor cable system according to claim 10 wherein the shock absorption 15 in the anchor bracket is provided by one or more suitably shaped portions of material cut or otherwise formed so that when a force is applied thereto, there is created a deformation therein in the form of a generally linear extension of that portion, ie by effectively straightening or "unbending" such region.

13. A roof anchor cable system according to any one of claims 9 to 12 wherein the 20 bracket although generally planar in nature, is bent in such a way that it can be both suitably attached to a rafter at one end, whilst having the other end remote therefrom extend between overlapping tiles.

14. A roof anchor cable system according to claim 13, wherein the cross section of the anchor bracket is of a generally flattened W profile, the outer legs 25 corresponding to regions supporting in the one case the second attachment means for devices ete, ie standing proud of the tile surface, whilst in the other case, the other outer leg corresponds to a region supporting the third attachment means for affixing the bracket to the rafter.

15. A roof anchor cable system according to claim 14 wherein the intermediate legs 30 allow the bracket to function in so far as they connect both ends and allow the region supporting the second attachment means to pass effectively between the tiles. 10 o:\docunents\poldmaa\2028complete.doc

16. A roof anchor cable system according to claim 13, wherein the inner leg adjacent the outer leg which supports the third attachment means is the region supporting the first attachment means, ie for attaching the cable.

17. A roof anchor cable system according to any one of the preceding claims s wherein the first attachment means provided in the anchor bracket for fixing the cable thereto is in the form of a simple hole therethrough.

18. A roof anchor cable system according to claim 17, wherein the ends of the cable are provided with an end piece swaged thereto, in which there is also provided a hole, to allow attachment of both ends of the cable to the anchor bracket by 10 aligning the three holes and passing a bolt etc to which a nut has been affixed, or other suitable fixing device therethrough for securement of the cable ends to the bracket by otherwise generally known means.

19. A roof anchor cable system according to any one of the preceding claims in which the second means of attachment provided in the anchor bracket, ie for 15 attaching the device, apparatus or equipment thereto, is provided in the form of a simple hole or eye in the end of the anchor which protrudes in use through the tile surface.

20. A roof anchor cable system according to any one of the preceding claims in which the third means of attachment provided in the anchor bracket is in the 20 form of a T-section with a plurality of holes available therethrough for screwing the bracket to a rafter, so that the initial shock is absorbed in this arrangement by having the bracket also screwed to the rafter as well as connected by the cable and to allow location of the bracket at various cross wise positions on the rafter so that the other free end of the bracket which extends between adjacent 25 overlapping tiles to provide the actual anchor point is properly located.

21. A roof anchor cable system substantially as described herein in conjunction with the drawings. 30 11