ANCTIOR ASSEMBLY FOR SAFETY DEVICE Technical Field This invention relates to an anchor assembly for one or more safety devices and more particularly, to an anchor assembly for securing one or more safety devices to a structure such S as a building. Background Art The following references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art. In particular, the following prior art discussion does not relate to what is 10 commonly or well known by the person skilled in the art, but assists in the understanding of the inventive step of the present invention of which the identification of pertinent prior art proposals is but one part. The building industry is becoming evermore conscious of the need for ensuring the safety of its workers and, indeed, authorities in many jurisdictions have introduced, or are in the 15 process of introducing, recommendations and regulations which seek to make building sites and buildings on which workers must perfonn their duties safer workplaces. It has long been recognised that a primary cause of inj urics, particularly to inexperienced workers, arises from falls from elevated building structures resulting sometimes in severe injury or even death. Prior art methods of addressing this problem include the mounting of 20 temporary rails around the periphery of roof areas and the fixing of personal safety harnesses and ropes to anchor points, such as exposed rafters, etc. Whilst the rails may be helpful in most situations, there remains the possibility that an unsecured worker may still topple over the railing. Anchor points, such as those which may be mounted on exposed beams or rafters, may not be satisfctory as the structural members themselves may not be capable of 25 sustaining the loads necessary to withstand the damage resulting from the impact occasioned by the fll of a worker. Moreover, such falls will end in a severe jolt to the worker when the full extent of the rope or cable is taken up, which may itself occasion injury. Qbject of the Invention 30 It is therefore an object of the invention to ameliorate some or all of the foregoing problems 1 and at the very least the invention provides an alternative to proposed anchor assemblies for safety devices. Disclosure of the Invention Accordingly, in one broad form, the invention provides an anchor assembly for securing at s least one safety device indirectly to a structure, the anchor assembly including: at least two spaced-apart spacers, including a first spacer and a second spacer; at least one bridging member spanning between the spacers, said spacers extending from a first side of the bridging member; and two or more spaced-apart engagement devices for securing the safety device to the anchor assembly, said engagement devices extending from a second side 10 opposed to said first side of the bridging member, each spacer being adapted to space the bridging member from the structure and including: securing means for securing the spacer directly to the structure; a head Ior fastening the spacer to the bridging member and/or to the engagement device; and a shaft extending between the securing means and the head of each spacer, the shall of at least the first spacer i-s being adapted to deform progressively so as to at 15 least partially absorb the kinetic energy applied by a load of a falling object attached to the safety device, the bridging member forming a rigid bridge capable of deformation if the load is applied. Preferably the deformation will occur progressively along the length of the shaft of the spacer starting from below the head and moving towards the securing means. In this way the initial 20 load on the structure is mininised, so that by the time the force reaches the securing means it has been significantly reduced, thereby resulting in less damage to the structure or any rooting material etc associated therewith. Furthermore, the deformation thus caused is visible and serves as an indication that the anchor assembly should be replaced, having been thus Used. 25 The structure may include a building structure. The building structure may be in the process of being built, or may be the subject of maintenance or renovation activities. The building may be a commercial or domestic structure and the invention is applicable to any type of roof covering, requiring only that it is possible to gain access to structural members to which the anchor assembly may be aflixed. Such structural members include 30 purlins, structural beams and the like. 2 WO 2005/037378 PCT/AU2004/001405 The safety device may include a range of devices adapted to secure a worker or an object, particularly against the likelihood of falling. The safety device may include a railing or cable. The safety device may include a railing or cable to which a safety harness is coupled by means of a runner or shuttle so as to allow the safety harness to 5 move along the length of the rail or cable. In such embodiments the anchor assembly as described herein will preferably be an end anchor, that is to say the railing or cable will terminate at the anchor assembly. However, the anchor assembly may be used as an intermediate anchor point through which or by which such rail or cable passes so as to support same, especially at points where additional load bearing capability is required i over and above that provided by a simpler unitary anchor device. It will be understood that in such instances the shuttle may be so designed as to provide a pass through action so that the shuttle can pass through the anchor point without having to be disconnected from the rail or cable. In any event, in any of these arrangements involving a rail a cable, the anchor assembly 1s of the invention will preferably cooperate with one or more other anchor assemblies or simpler anchor devices located along the length of the rail or cable they support, each other such anchor assembly or simple anchor device cooperating to distribute the load and preferably also each having the means to progressively deform as described above in relation to the spacer, to absorb the load. On the other hand, the safety device may 20 include a safety harness affixed directly to a single anchor assembly, such as by a rope or cable, The spacers, including the first and the second spacer, may be adapted to space the bridging member from the structure, such as a purlin or other roof structural member. The first and second spacers may be identical or different. The first and second spacers 25 may be of equal length, in which case the bridging member will be spaced uniformly, that is to say spaced generally parallel to the surface of the structure to which the anchor assembly is attached or they may be of different lengths in order to space the bridging member at an angle with respect to the surface of the structure. Preferably, the first and 3 WO 2005/037378 PCT/AU2004/001405 second spacers are adapted to provide substantially uniform spacing between the bridging member and the structure. The securing means for attaching each spacer to the structure includes a variety of means including all known positive engagement means applicable to the invention. For 5 example, the means of fastening may include a clamp. Alternatively, the means of fastening may include a simple threaded bolt and nut arrangement. Preferably, the shaft of the spacer terminates at its lower portion in a threaded bolt. The threaded bolt may be adapted to extend through or into the structure and be threadably engaged therewith. More preferably, the threaded portion may be adapted to extend through the structure lo and be secured by an element with a corresponding internally threaded bore, such as a retro block, so designed for that purpose. The threaded portion may be secured additionally on the side of the structure from which the shaft extends by a further threaded element, such as a nut. Preferably, the further nut is a cone locknut with a tapered skirt depending from the nut body. The tapered skirt may provide the spacer 1s with added energy absorption capability by progressively deforming as the deforming shaft bears against its internal wall upon application of sufficient load. The shaft of the first spacer, and optionally the shafts of the one or more other spacers, including the second spacer, may be resiliently deformable whereby, after removal of the load, the shaft returns to its original pre-load position. Preferably however, the first 2o spacer shaft is adapted to deform plastically, whereby it does not return to its original shape after the removal of the load. Preferably, the second spacer shaft is adapted to also deform plastically. Preferably, the shafts of all of the spacers are adapted to defonn plastically. The first spacer shaft is preferably tapered. The first spacer shaft may be tapered such 25 that the shaft region nearest the securing means for the spacer is relatively wide in diameter and the shaft portion nearest the bridging member (ie the towards the head) is narrower in diameter corresponding to a neck portion. The neck portion may include a short section nearest the head which expands in diameter up to the point where it meets 4 WO 2005/037378 PCT/AU2004/001405 the head portion, such that the section of narrowest diameter is intermediate the length of the first spacer shaft. Similarly, each of the other spacer shafts may be tapered in like manner as described herein. The first spacer shaft may be solid in structure. The first spacer shaft may be hollow or 5 tubular in structure. The spacer shafts of the other spacers may optionally be solid or hollow. The head of the first spacer may include any means standard in the art suitable for securing the bridging member and/or the engagement means to the spacer. For example, the first spacer head may include an internally threaded bore for receiving a io correspondingly threaded bolt. The second spacer head and/or other spacer heads may be similarly configured. Alternatively, the second spacer head may include a threaded bolt adapted to co-act with a correspondingly threaded nut. The bridging member may be secured to the second spacer head by applying locknuts either side of the bridging member such that the bridging member is situated intermediate the head of the second 1s spacer and lying in a plane transverse thereto. The bridging member may include an elongate plate with holes spaced along its length to receive threaded bolt portions. For example, where only a first and a second spacer is used according to the invention, the bridging member may be about 0.5 meters long and have an aperture either end for receiving the first and/or second spacer. However the 20 bridging member may be any desired length. The bridging member may also be adapted to resiliently deform upon the application of the load. Alternatively, the bridging member may be adapted to deform plastically. The bridging member may include one or more weakened portions which preferentially deform to absorb kinetic energy arising from the load. The bridging member may include or consist of fluted or corrugated 25 features or the like to this effect, In the alternative, the bridging member may be rigid and adapted to maintain the separation between the first and second and any other spacers to which it affixed. 5 WO 2005/037378 PCT/AU2004/001405 The engagement means may merely include a feature adapted to engage the safety device. For example, the engagement means may include a simple eyelet. The engagement means may include a base adapted to be fastened to the head of one or other of the spacers. The engagement means may include an engagement device for 5 fastening the safety device to the anchor assembly. For example, the engagement device may include a screw fastener, eyelet or closable hook as may be found in grappling, abseiling or boat rigging gear, or other suitable coupling device. The engagement means may include a shaft extending between the base and the engagement device. With particular advantage, the engagement means may be provided in the form 1o of a plate having a generally "s-shaped" configuration as described below in more detail in the drawings to provide additional resilient support. Where an eyebolt or the like is employed, the shaft of the engagement means may be of a similar construction to the shaft of one or more of the spacers. The shaft of the engagement means may terminate at its base in a threaded bolt portion. The threaded 15 bolt portion may be adapted to threadably engage the internal bore of the head of a spacer having such a facility. Alternatively, the engagement means may terminate at its base with an internal threaded bore located therein, which mates with a correspondingly threaded bolt portion forming the head of the spacer. The first and second spacers may be adapted to receive first and second engagement 20 means, respectively. Extending between the respective engagement devices of the first and second engagement means may be an extension member. The extension member may be in the form of a beam or elongated plate adapted to be engaged with each of the engagement devices and may itself include engagement means whereby to secure the safety device. This may be an additional engagement means to any that are associated 25 with respective spacers, or may be utilised in place of engagement means associated with such spacers. The extension member may yet be another means of absorbing or distributing the load applied to provide gradual deceleration to the object attached to the safety device should the object fall, ie to provide additional progressive deformation. With particular advantage, the extension member may be a turnbuckle, which may be 6 WO 2005/037378 PCT/AU2004/001405 utilised to maintain appropriate tension between the components, especially when the anchor assembly is used to support a cable, which preferably should be maintained under tension. Where a cable or rail is utilised, that may also be attached to the anchor assembly by means of a turnbuckle to allow adjustment in the tension thereof. 5 As the person skilled in the art will appreciate, the energy absorbing anchor assembly of the invention may include a variety of combinations of the various above described components, depending on the application and the anticipated load to which the anchor assembly may be subjected, For example, one particular arrangement might allow for the cable to change direction, eg near the corner of a roof etc, and can be achieved by io having a suitable arrangement of components interconnected as described herein, but rather than being in linear arrangement, may for example extend at right angles so that a cable can pass through a pair of suitable engagement means in the form of eyebolts or the like, which are located on arms extending perpendicularly. With the application of appropriate tension within and on the anchor assembly, the cable or rail can be made to 15 form an arc between the engagement means. Alternatively, where the cable itself is not sufficiently rigid, it can be made to pass through an arcuate sleeve to provide the necessary rigidity. This is particularly useful in applications where a shuttle connecting the safety harness to a user is employed to travel along the cable and it is desirable to allow the user to move in more than one direction. 20 Brief Description of the Drawings The invention may be better understood from the following non-limiting description of one or more preferred embodiments, in which: Figure 1 is a side elevation of a first spacer; Figure 2 is a side elevation of a second spacer; 25 Figure 3 is a side elevation of an engagement means according to one embodiment; Figure 4 is a side elevation of an engagement means according to a second embodiment; Figure 5 is a plan view of a bridging member; 7 WO 2005/037378 PCT/AU2004/001405 Figure 6 is a side elevation of the bridging member shown in Figure 5; Figure 7 is a side elevation of a cone locknut according to a first embodiment; Figure 8 is a side elevation of an anchor assembly according to a first embodiment; Figure 9 is an anchor assembly according to a second embodiment; 5 Figure 10 is an anchor assembly according to a third embodiment; Figure 11 is an anchor assembly according to a fourth embodiment for use with timber rafters; Figure 12 shows the arrangement of fixing brackets for fixing the embodiment of Figure II to the rafters; io Figure 13 is an anchor assembly according to a fifth embodiment for use with steel purlins and utilising an anchor assembly having components at right angles to allow a safety line utilised therewith to change direction; Figure 14 is a side elevation of part of the anchor assembly of Figure 1; Figure 15 is an S-shaped engagement plate; 15 Figure 16 is an anchor assembly employing an s-shaped engagement plate of Figure 15; and Figure 17 is an alternate anchor assembly employing an s-shaped engagement plate of Figure 15. Detailed Description of the Drawings 20 Turning to Figure 1, there is shown a first spacer (10) for use in the anchor assembly described herein, having a threaded lower portion (11) and a hollow head (12) and, extending therebetween, a tapered shaft (13) having a wide diameter base (14) and a narrow first neck (15) expanding once again to meet the lower portion of the hollow head (12). The threaded lower portion (11) has a length sufficient to extend into or 25 through the structure to which it is to be mounted. In this embodiment, the first spacer (10) is to be mounted to a purlin and a 40mm length of the threaded lower portion (11) 8 WO 2005/037378 PCT/AU2004/001405 is sufficient for this purpose. As a person skilled in the art will appreciate, a longer threaded lower portion (11) would be required to mount the anchor to a beam such as may be found in a roof truss. The hollow head (12) comprises an open ended cylinder including an internally threaded base having a thread gauge consistent with that of the 5 threaded lower portion (11) and, indeed, preferably consistent with the threaded portions of all threaded components of the anchor assembly whereby the various components according to the invention may be mixed and matched. The first spacer may be made of 316 stainless steel for suitable strength and corrosion resistance. The shaft (13), being made of 316 stainless steel, is able to withstand minor loads 1o consistent with the tugs and pulls to be expected from the application of a workman in harness (affixed elsewhere to the engagement means as described below) carrying out normal work duties. However, should the worker fall and place his full weight on the anchor assembly of which this spacer (10) is a component, if this is the first spacer, it will tend to deform first at the neck (IS) and, depending on the size of the load, 15 progressively deform down to the wide base (14) plastically such that no rebound is caused by this spacer (10) or the total anchor assembly. Figure 2 shows a second spacer (20) which may also be made of 316 stainless steel. The second spacer (20) has a threaded lower portion (21) identical with that of the threaded lower portion (11) of the first spacer (10). However, the second spacer (20) is 20 longer than the first spacer (10). Whereas the top surface (16) of the hollow head (12) of spacer (10) in Fig 1 is adapted to abut the underside of the bridging plate (50) shown in Figure 5, threaded head (22) of the second spacer (20) is adapted to extend through the bridging plate (50). The shaft (23) of the second spacer (20) is correspondingly longer than the first spacer's shaft (13) and, whilst the second shaft base (24) and 25 second neck (25) may be of similar diameters compared to their counterparts in the first spacer (10), the taper of the second shaft (23) is less severe over the length of the second shaft (23). The respective threads of the second spacer's threaded lower portion (21) and the threaded head (22) are virtually identical. 9 WO 2005/037378 PCT/AU2004/001405 Referring to Figure 3, there is shown a first engagement means in the form of an eyebolt (30) which may also be made of 316 stainless steel. The threaded lower portion (31) of the eyebolt (30) is identical to the threaded lower portion (11) of the first spacer (10). The eyebolt (30) has a shaft (33), tapered in similar fashion to that of the second shaft 5 (23), but is even more elongate, having a more gradual taper. Generally, the more gradual taper will mean that the eyebolt shaft (33) preferentially deforms under load, compared to the respective second shaft (23) and the first shaft (13) of each of the spacers (20 and 10), given the application of equal loads. At the opposed end of the eyebolt shaft (30) there is an eyelet (37) set in an eyebolt head (32). The eyebolt head 10 (32) is nominally rectangular in plan view with curved end walls (36). The eyebolt head (32) is adapted to receive a closable hook (not shown) attached to the safety device (not shown), if the eyebolt (30) is used independently or where it is used in the anchor assembly described herein, but the assembly is used in isolation as a stand alone . arrangement to engage a safety device (ie no rail or cable is utilised). Alternatively, the 15 eyebolt head (32) may receive a sleeve or other facility (not shown) in order to mount a railing, cable, cable runner or such other adaptive bracket as required. With advantage the eyebolt (30) also serves to provide an anchor point whereby an extension plate (as discussed below in relation to Fig 10) may also be attached. With reference to Figure 4, there is shown an alternate eyebolt (40) identical to the 20 eyebolt (30), with the exception that the eyebolt head (42) is of a cylindrical shape. The eyebolt head (42) has a half inch aperture (47) extending transversely through the eyebolt head (42) in a similar manner to that of the eyebolt (30). Figure 5 shows the bridging plate (50) which may also be made of 316 stainless steel. The bridging plate (50) is an elongate planar plate having two or more apertures (57a, 25 57b) for receiving the threaded head (22) or lower threaded portion (11, 21, 31, 41) of the respective spacer (10, 20) or eyebolt (30, 40) as the case may be, and as required. As shown in Figures 9 and 10, the bridging plate (50) may be longer depending on the application and may include three or more spaced apertures (57) for receiving a multiplicity of spacers (10, 20) and/or engagement means (30,40). 10 WO 2005/037378 PCT/AU2004/001405 Figure 6 shows the planar shape of the bridging plate (50). Figure 7 shows a cone locknut (70), which may be either stainless steel or aluminium, the softer metal being applicable to lower load applications. The cone locknut (70) has a hexagonal nut (72) from which upwardly extends a skirt (73). The skirt (73) is 5 substantially the shape of a truncated cone with inwardly curved walls such that the skirt (73) taper from a wide base adjacent the nut portion (72) and taper upwards to a narrow mouth (74). As can be best seen in Figure 8, the cone nut (70) is used to secure the first and second spacers (10, 20) to a structure such as a C or I purlin (80) or are used on either eyebolt (30, 40) for securing same to the bridging plate (50). On application of lo sufficient load resulting in deformation of the respective shafts (13, 23, 33, 43), the lower portions (14, 24, 34, 44) of the shaft bear against the inner wall of the skirt (73) whereby the cone locknut (70) acts as a further means of absorbing the energy of the falling object. Referring generally to Figures 8 to 14, identical reference numerals are used in relation 1s to those components previously described above. With specific reference to Figure 8, there is shown a first anchor assembly (1) utilising a pair of anchor points corresponding to a first spacer (10) and a second spacer (20) mounted to the C or I purlin (80) using a combination of a retro block (81) having an internally threaded wall corresponding to the threaded lower portions (11, 21) of respective spacers (10, 20) and cone locknuts 20 (70) such that the relevant flange of the purlin (80) is sandwiched between the locknut (70) and the retro block (81). A bridging plate (50) is mounted on the first and second spacers (10, 20) and is spaced from and parallel to the purlin (80). The threaded lower bolt portion (41) of eyebolt (40) is threadably engaged into the hollow head (12) of spacer (10) and the bridging plate (50) is located immediately 25 above and in abutment to the top surface (16), the lower threaded portion (41) intersecting the aperture (57a) of the bridging member (50). The bridging plate (50) is secured in place by the agency of a second cone locknut (70) which sandwiches the bridging plate (50) between the top surface (16) of the spacer (10) and the nut portion
II
WO 2005/037378 PCT/AU2004/001405 (72). The opposite end of the bridging plate (50) is secured by the agency of a pair of hexagonal locknuts (82) which sandwich the bridging plate (50) in between, the threaded head (22) of the second spacer (20) being in registry with the second aperture (57b) of the bridging plate (50). 5 In practice, it can be seen that a safety device (not shown) may be secured to the eyebolt head (42). Upon the application of a significant load caused by the falling of an object (not shown) moment transverse to the longitudinal axis of the eyebolt (40) will be applied to the eyebolt head (42) whereby the shaft (43) will begin to plastically deform, first at the neck (45) and progressively down to the cone locknut (70) which will also 10 plastically deform, Depending on the amount of force involved, the tapered shafts (10, 20) of the first and second spacers (10, 20), the cone locknuts (70) and the bridging plate (50) may also plastically deform in a progressive manner to absorb the kinetic energy applied by the load of the falling object attached to the safety device. Figure 9 shows an anchor assembly (2) according to a second embodiment again 15 utilising two anchor points including a pair of first spacers (10). Each of the spacers (10) are connected by a bridging plate (50) having spaced apertures as previously described in Fig 5. As can be seen in Figure 9, the spacers (10, 10') may be anchored to discreet structural members (90) rather than a single structural member. In Figure 10 there is shown an anchor assembly (3) according to a third embodiment in 20 which a pair of eyebolts, for example eyebolts (30, 40), are utilised and secured to the remainder of the third anchor assembly (3) by engagement to a pair of first spacers (10). A bridging plate (50) connects the three spacers (10,20) as previously described in relation to Fig 8 or 9. The eyebolts (30, 40) are connected at their respective heads (not shown) by a bridging bracket (100) whereby the eyebolt (30) will deform in preference 25 to the spacers (10). The safety device is attached to the third anchor assembly (3) by attachment to the eyelet (101) extending from the end of the bridging bracket (100). In 12 WO 2005/037378 PCT/AU2004/001405 place of solid bridging bracket (100), a turnbuckle may be utilised to provide tension to the assembly (3), Fig 11 shows yet another embodiment (4) utilising three spacers (10, 20) and a pair of eyebolts (30 or 40) in similar arrangement to Fig 10, except that the assembly (4) has s the safety device (eg cable not shown) extending in the opposite direction from eyelet (110) adjacent the middle combination of eyebolt and spacer (30, 10), Also the extension or bridging plate (100) of Fig 10 is replaced by a turnbuckle arrangement (110) for tensioning the assembly (4). Furthermore, the spacers (10, 20) in this assembly (4) are affixed to timber beams (112) by means of special anchor brackets 10 (111) for fixing the spacers (10, 20) to timber beams. The specific way in which the anchor brackets (111) are arranged on the beams (112) is shown in Fig 12. Fig 13 shows schematically the fixing points (130, 131, 132, 133) for a non-linear anchor arrangement (5) which allows a cable (not shown) to bend through 90". For example, the assembly for use in Fig 13 may utilise along fixing points (130, 131, 132) 15 the assembly (5) of which a portion is shown in Fig 14, which is similar to that of Fig (10), except that eyebolt (40) of that assembly is replaced with an eyebolt (140) having a tube (141) located atop thereof through which a cable may pass. Also a turnbuckle (110) substitutes for the simple plate (100) of Fig 10. It will be appreciated that if an additional eyebolt/spacer combination (140, 10) is located at fixing point 133 of Fig 13, 20 ie perpendicular to the assembly portion (5) shown in Fig 14, and extending perpendicularly from the middle eyebolt/spacer combination (30, 10), suitably connected by means of an additional bridging plate and turnbuckle (not shown), then the cable (not shown) will bend in an arc (135) as shown in Fig 13. The cable may optionally pass through a heavier gauge sleeve (ie in the form of arc (135)) to provide 25 appropriate support for the cable, but still narrow enough for a shuttle (not shown) of a safety harness to pass along. In this way a person wearing a suitable harness and attached to the cable by means of a suitable shuttle, the cable being thus affixed to the 13 WO 2005/037378 PCT/AU2004/001405 embodiment described in Fig 13 and 14, will be able to move in either direction "A" or "B" as indicated in Fig 13. Turning to Figures 15 to 17 there is shown an alternate engagement means 151 in the form of a plate bent in an s-shaped configuration when viewed side-on. It has been 5 found that such a plate provides additional advantages when used in an anchor assembly for example as shown in Figures 16 or 17. The parts already described above are again referenced with the same numerals. An attachment means 152 for a cable 153 is utilised, which in the case of Figure 17 has a shock absorbing portion 154. In the case of Figure 17 it will be observed that a supporting piece 155 is also utilised to assist in 10 supporting the cable 153. It will be appreciated by those skilled in the art that many modifications and variations may be made to the embodiments described herein without departing from the spirit or scope of the invention. Throughout the specification the word "comprise" and its derivatives are intended to 16 have an inclusive rather than exclusive meaning unless the context requires otherwise. 14