1 AUSTRALIA Patents Act 1990 SE POWER PTY LTD AS TRUSTEE FOR SE POWER TRUST COMPLETE SPECIFICATION INNOVATION PATENT Invention Title: Stabilised boom The following statement is a full description of this invention including the best method of performing it known to us:- 1A Stabilised boom Introduction The present invention relates to raiseable booms such as lighting towers, elevated work platforms and cranes, etc. and in particular the invention provides a 5 device that improves stability of the raiseable boom while improving access for workers who must from time to time work generally on or around the base on which the boom is mounted. Background 10 There is a broad range of equipment employing a carrier having a deck supported above the ground and used to mount devices such as lighting towers, elevated work platforms and cranes, etc. Usually such carriers are longer than they are wide, the width being constrained by a need to transport the equipment on public roads. Usually also, the equipment mounted on such carriers is capable of being raised to 15 various degrees and also rotated to extend beyond the perimeter of the carrier, creating an increased risk of toppling sideways. Often lateral supports are temporarily engaged when the equipment is in use to stabilise the equipment and reduce the toppling risk, however such supports are usually limited in their lateral extension, as is the length of the boom, the mass it can support and the angle at which it can be deployed. The deck 20 of such equipment is also usually relatively high above the ground and workers are required to climb ladders or use small stepping points protruding from the side of the equipment if they need to climb aboard the carrier, resulting in a difficult working environment. 25 Summary According to a first aspect, a supporting structure is provided comprising a carrier on which a raiseable and rotatable boom is mounted, and at least one stabilising leg pivotably mounted on a side of the carrier and moveable between a raised position for transport and a lowered position for use, the stabilising leg being operable by a 30 motive means to press a distal end of the stabilising leg towards the ground to resist toppling of the boom towards the stabilising leg, and the supporting legs and the motive means are capable of withstanding the full weight of the supporting structure and the boom. Generally the stabilising leg will only be required to support no more than 40 50% of that mass in use. 1918897 1.doc1912622-1.doc 2 In one preferred example, the overall mass of the carrier, boom and lighting assembly and auxiliary equipment is 20 tonne. Of the total mass, no more that 10% of a combined total mass of the supporting structure and the boom is in the boom with the remaining 90% in the supporting structure. 5 The height of the pivotable mounting of a proximal end of the boom in the preferred example is 2.372m above a lowest point of the carrier while the length of the boom to the furthest point of the boom assembly is 25m. Generally the overall length of the boom is not more than 110% of a height of a pivotable mounting point of a proximal end of the boom and not more than 10 times a horizontal distance between a 10 ground engaging point of the stabilizing leg and the pivotable mounting point of the boom. The carrier (excluding the supporting legs) in the preferred example is 3.200m while the width between ground engaging points of the supporting legs 116 is 5.330m. Generally the horizontal length of the stabilizing legs, when extended, measured from a 15 point of attachment to the carrier to a ground engaging point, are 20% - 50%the width of the carrier and preferably 30 - 35% of the width of the carrier. According to a second aspect a supporting structure is provided comprising a carrier on which boom is mounted, the boom being pivotably mounted to be raiseable and rotatable relative to the carrier, and at least one stabilising leg pivotably mounted 20 on a side of the carrier and moveable between a raised position for transport and a lowered position for use, and wherein the stabilising leg incorporates a set of stairs having at least one stair tread which is generally horizontally oriented when the stabilising leg is in the lowered position, the stabilising leg being operable by a motive means to press a distal end of the stabilising leg towards the ground to resist toppling of 25 the boom towards the stabilising leg. The stabilizing leg may comprise a ground engaging foot at its distal end and the ground engaging foot may include an anchor having a plate member arranged to penetrate the ground when the stabilising leg is in the lowered position. The set of stairs will preferably comprise a plurality of stair treads. The set of 30 stairs may include two stringers between which the treads are supported and may also have one or more hand rails extending therefrom. Preferably two stabilising legs will be provided, one mounted on each of two opposite sides of the carrier such that one leg may be used for support/stabilisation and the other leg may be used for access to the deck of the carrier. The leg located on the side to which the boom has been slewed, 35 will be used for support and stabilisation and will be pressed to the ground by the respective motive means to resist toppling motion towards that side of the carrier. The 1918897 1.doc1912622-14.o 3 leg on the opposite side will not be required for support or stabilisation and can be positioned with its stair treads level for safe access to the deck of the carrier. The carrier preferably supports a lighting tower comprising the boom and a light assembly mounted on the distal end of the boom. The carrier also preferably comprises 5 two or more ground engaging skids and a deck structure mounted over the skids. The carrier may also be mounted on wheels or tracks and remotely driven. The motive means may be a hydraulic ram operating between the carrier and the respective stabilising leg. One end of the hydraulic ram may operate on a flange projecting from the stabilising leg and the other end of the ram may operate directly on 10 the carrier or on a flange or other projection extending from the carrier structure. The boom is preferably rotatable through 360 0 to allow illumination in any direction relative to the orientation of the carrier. Brief Description 15 Embodiments of a lighting tower assembly and stabilising leg will now be described with reference to the accompanying drawings in which: Figure 1 is a perspective view of a skid mounted carrier supporting a lighting tower and incorporation two stabilising legs viewed from one side showing a stabilising leg engaging the ground; 20 Figure 2 is a detail "A" of the a stabilising leg seen engaging the ground in Figure 1; Figure 3 is a perspective view of the carrier of Figure 1 viewed from the other side showing a stabilising structure in an elevated position; Figure 4 is a detail "B" of the a stabilising leg seen in an elevated position in 25 Figure 3; Figure 5 is a front view of the carrier of Figures 1-5; Figure 6 is a cross-section view through E-E in Figure 5 showing the mechanism of the stabilising legs in greater detail; Figure 7 is a perspective view of the skid mounted carrier supporting a lighting 30 tower of Figures 1-5 showing the boom in a horizontal in-use position; and Figure 8 shows bottom and end elevation views of the skid mounted carrier supporting a lighting tower showing the boom in a horizontal in-use position as seen in Figure 7. 35 Detailed Description 1918897 1.doc1912622-1.dec 4 The lighting tower assembly 100 illustrated in Figures 1, 3, 5 &7 incorporates a telescopic boom 101 pivotably mounted on a rotatable slewing base 102 and raiseable via a ram 103. At the distal end of the boom 101, a lighting frame 104 carries an array of lighting fixtures 105 and is pivotable relative to the boom 101 on a horizontal axis. 5 The angle of the lighting frame 104 relative to the boom 101 is controlled by another ram 106. The rotatable slewing base 102 is in turn rotatably mounted on a carrier 107 and capable of 360" rotation. The carrier 107 also mounts a variety of ancillary equipment such as a motor generator 108 and a switching and control panel 109. A support tripod 131 is provided on the carrier 107, located under the boom 101 near its 10 distal end when in its rest position, to support the boom when not in use or during transport. The carrier 107 is supported on the ground by skids 111 but could also be supported on wheels if greater manoeuvrability were required. Towing points 112 allow attachment of a cable for dragging the carrier 107 into position using a tractor or 15 bulldozer and lifting points 113 enable the carrier 107 to be craned onto a trailer for transport over a longer distance. Channel shaped end guards 127 are fitted with timber buffers 115 to provide a degree of impact resistance. The timber buffers 115 are bolt on items allowing replacement if they become damaged. Stabilizer legs 116 are fitted to two sides of the carrier 107 structure 100 to improve stability of the carrier 107 in 20 use, particularly when the boom 101 is rotated off-centre and to provide better access to the deck of the carrier 107 by workers. Referring to the detail A in Figure 2, an enlarged view of one of the stabilizer legs 116 is illustrated in the lowered position (see also the cross-section E-E in Figure 6 for additional detail). The Figure 2 view of the stabilizer leg 116 illustrates its 25 secondary use as a stair case providing improved access to the deck of the carrierl07 by workers. The stair case comprises a pair of stringers 117 between which stair treads 118 are fixed. Handrails 119 extend from each of the stringers 117. Detail B in Figure 4 shows one of the stabilizing legs in the raised position for transport. In this view the underside of the stabilising leg 116 may be seen (again see 30 the cross-section E-E in Figure 6 for additional detail). The main structural members of the stabilizing leg comprise a truss structure 125 extending from two flanges 121 pivotably attached to corresponding flanges 128 extending from the carrier 107. A foot 126 is located at the distal end of the truss 125 to engage the ground when the leg is in the lowered position. The foot includes anchor members 129 which are edge-on to the 35 ground when the leg is lowered to engage the ground and resist lateral movement. 1918897 1.doc1942622-1-deG 5 Raising and lowering of each stabilizing leg is via a respective hydraulic ram 124 which acts between a flange 123 extending from the proximal end of the leg and the attachment point 132 under the body of the carrier 107. When the stabilizing legs 116 are lowered the rams 124 provide sufficient downward pressure via the legs to 5 resist any expected toppling moment caused by the boom being rotated to one side of the carrier 107. Referring to Figure 7, the lighting tower assembly 100 is shown in an in-use configuration with the boom deployed horizontally to one side of the carrier107. This configuration is typically used when the lighting array 105 is being suspended over an 10 edge of a pit and directed down into the pit and the boom may be deployed at an angle of up to 200 below horizontal for this purpose. The boom may also be deployed vertically or at an angle for overhead lighting over a flat work area. When used vertically the lighting tower may withstand winds of up to 300 kilometers per hour. Preferably two stabilising legs 106 will be provided, one mounted on each of 15 two opposite sides of the carrier 107 such that one leg may be used for support/stabilisation and the other leg may be used for access to the deck of the carrier. The leg 106 located on the side to which the boom has been slewed, will be used for support and stabilisation and will be pressed to the ground by the respective hydraulic ram to resist toppling motion towards that side of the carrier. This may involve the leg 20 106 being deployed at an angle such that the treads 118 of the stairs are not level and should not be used for mounting the carrier 107. The leg 106 on the opposite side will not be required for support or stabilisation and can be positioned with its stair treads 118 level for safe access to the deck of the carrier. The bottom and end elevation views of the lighting tower assembly 100 also 25 show exemplary dimensions for one embodiment of the assembly. In this example the overall mass of the carrier 107, boom 101 and lighting assembly 104, 105 and auxiliary equipment is 20 tonne. Of the total mass, no more that 10% is in the boom 101 and lighting assembly 104, 105 with the remaining 90% in the carrier 107 and auxiliary equipment mounted on the carrier. The height of the pivotable mounting of the 30 proximal end of the boom 101 in this embodiment is 2.372m above the bottom of the skids 111 while the length of the boom 101 to the furthest point of the lighting assembly 104, 105 is 25m. Generally boom length (including the lighting assembly) should not be more than 110% of the pivot height. The carrier (excluding the legs 116) is 3.200m while the width between the distal ends of the legs 116 is 5.330m. Generally 35 the legs, measured from a point of attachment to the carrier to a ground engaging point, will each be at least 20% and preferably 33% of the width of the carrier and possibly as 1918897 1.doc1912622-1.doc 6 much as 50% of the width of the carrier. The legs 116 and the rams 124 that operate them are designed to withstand the full weight of the lighting tower assembly (in this case 20 tonne) but will generally be required to support no more than 40-50 % of that mass. 5 It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. 10 1918897 1.docl942422-1.dc