AU2012201256B2

AU2012201256B2 - Method of forming a structural component

Info

Publication number: AU2012201256B2
Application number: AU2012201256A
Authority: AU
Inventors: Keith Batten
Original assignee: SHERRIN HIRE Pty Ltd
Current assignee: SHERRIN HIRE Pty Ltd
Priority date: 2011-03-02
Filing date: 2012-03-01
Publication date: 2016-11-10
Anticipated expiration: 2032-03-01
Also published as: AU2012201256A1

Abstract

A method of forming a structural component 16 of non-uniform cross-section comprises laying a plurality of layers of structural fabric around a moulding former 28 which is of non-uniform cross-section over its length. Each layer comprises two or more pieces of 5 structural fabric which overlap to form a discrete layer. The pieces of structural fabric overlap in two or more overlap regions. The overlap regions for a first layer vary from the overlap regions of a second layer. A structural component 16 and an elevated work platform including the structural component are also claimed. ,Illy - wu o -M z wu 0 C z 0 a- w w>

Description

7153851 2012201256 01 Mar 2012 2

Method of forming a structural component

Field of the invention

The present invention relates to a method of forming a structural component of non-uniform cross-section. In particular, although not exclusively, the invention relates to a 5 method of forming a structural component from fibreglass, for particular use as a structural boom in an elevated work platform. The invention also relates to a method of strengthening a structural component of non-uniform cross-section. A further aspect of the invention is a structural component.

Background of the invention 0 An elevated work platform (EWP) is generally employed for work on power lines. Typically, the superstructure of the elevated work platform is supported by a wheeled vehicle. The superstructure generally comprises a movable platform (or basket) which is supported by a series of hydraulically operated booms which gradually elevate the platform from a position at or adjacent the bed of the wheeled vehicle, to an elevated 5 position where a worker on the platform can reach an intended worksite. Because of the use of the EWP in and around powerlines, it is critical that the platform is electrically insulated. For this reason, the uppermost boom which carries the platform, known as the fly boom, is generally constructed of structural fibreglass.

Booms of structural fibreglass are known. They are generally elongated components of 20 constant cross-section. These constant cross-section components are constructed by wrapping fibreglass sheeting around a central mould former or plug which is of constant cross-section over its length. This can be achieved by rolling lengths of fibreglass sheeting continuously around the central mould former, like rolling a length of fabric onto a fabric roll. 25 While this methodology works well for structural components of constant cross-section, where the structural component has a non-uniform cross-section, problems arise in using this methodology because puckering of the fibreglass sheeting will occur at or around the changes in cross-section. 1001558400 2012201256 19 Sep 2016 3

It is therefore an object of the present invention to provide a method of forming a structural component of non-uniform cross-section which addresses or at least partly overcomes some of the abovementioned disadvantages.

Reference to any prior art in the specification is not, and should not be taken as, an 5 acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in Australia or any other jurisdiction or that this prior art could reasonably be expected to be ascertained, understood and regarded as relevant by a person skilled in the art.

Summary of the invention I0 References to a structural component in this section are to be understood as references to a structural arm or boom for a mobile work machine, as consistent with the claimed invention.

In accordance with the first aspect of the present invention there is provided, a method of forming a structural component of non-uniform cross-section, the method comprising: 15 laying a plurality of layers of structural fabric around a moulding former which is of non-uniform cross-section over its length; wherein each layer comprises two or more pieces of structural fabric which overlap to form a discrete layer, the pieces of structural fabric overlapping in two or more overlap regions; and 20 wherein the overlap regions for a first layer vary from the overlap regions of a second layer.

The first and second layers do not necessarily correspond to the order in which the layers are applied to the moulding former. 1001658400 2012201256 19 Sep 2016

3A

Preferably, the first and second layer each have overlap regions that are different from each other, ie do not exactly correspond, although there may be some overlap or correspondence between them. The overlap regions in the first layer may be completely non-overlying relative to the overlap regions in the second layer. Preferably, a third layer 5 may have two or more overlap regions that are substantially the same as the overlap regions in the first layer. Most preferably, these overlap regions each extend partly 7153851 2012201256 01 Mar 2012 4 along one side of the component and partly along the bottom of the component. In each layer, where there are two overlap regions, they may be spaced transversely relative to the longitudinal axis of the component. Furthermore, a fourth layer may have two or more overlap regions that are large and overlap some of the other overlap regions in the 5 other layers. For example, the fourth layer may have large overlap regions on each side of the structural component.

In a preferred form of the invention, one or more of the layers incorporate additional pieces of structural fabric on the bottom of the structural component to increase structural strength. It will be understood that the term ‘bottom’ relates to the orientation 0 of the structural component in use. The orientation of the structural component during construction may vary and may in fact be inverted, as is the case in the preferred embodiment described subsequently. Preferably, the third and fourth layers include additional pieces to strengthen the bottom of the structural component. These may also overlap the other pieces in that layer. 5 In accordance with a second aspect of the present invention, there is provided a method of forming a structural component of non-uniform cross-section, the method comprising: laying a plurality of layers of structural fabric around a moulding former which is of non-uniform cross-section over its length; wherein each layer comprises two or more pieces of structural fabric which 20 overlap to form a discrete layer, the pieces of structural fabric overlapping in one or more overlap regions; and wherein at least two of the layers have two or more overlap regions lying on both sides of the structural component.

Preferably, these overlap regions lie wholly on the sides of the structural component. In 25 one of the at least two layers, there may be a narrow overlap region on each side of the structural component. On the other hand, in the other of the said at least two layers, there may be a wide overlap region on each side of the structural component. In such a case, on each side, the wide overlap region, preferably encompasses the narrow 7153851 2012201256 01 Mar 2012 5 overlap region. The wide region may over-lie the narrow region or alternatively, they can be arranged the other way around if the layer including the wide overlap region is laid before the layer including the narrow overlap region.

In accordance with the third aspect of the present invention, there is provided a method 5 of forming a structural component of non-uniform cross-section, the method comprising: laying a plurality of layers of structural fabric around a moulding former which is of non-uniform cross-section over its length, wherein each layer comprises two or more pieces of structural fabric which overlap to form a discrete layer, the pieces of structural fabric overlapping in two or 0 more overlap regions; and wherein one or more of the overlap regions extend partly along the bottom of the structural component and partly along the side of the structural component.

In a preferred form of the invention, two such overlap regions may be disposed in a single layer. Where the structural component includes two portions, one of which is of 5 relatively smaller cross-sectional area and the other of which is relatively larger cross-sectional area, the one or more regions of overlap may lie along the bottom of the component in the region of smaller cross-sectional area and along the sides of the component in the portion of larger cross-sectional area.

In accordance with the fourth aspect of the present invention there is provided, a 20 method of forming a structural component of non-uniform cross-section, the structural component having a longitudinal axis, the method comprising: laying a plurality of layers of structural fabric around a moulding former which is of non-uniform cross-section over its length; wherein each layer comprises two or more pieces of structural fabric which 25 overlap to form a discrete layer, the pieces of structural fabric overlapping in two or more overlap regions; and 7153851 2012201256 01 Mar 2012 6 wherein the two or more overlap regions in each layer are spaced transversely across the width of the structural component.

In accordance with the fifth aspect of the present invention, there is provided a structural component as formed according to any of the foregoing aspects of the invention. 5 The structural fabric from which the structural component is made may comprise fibreglass sheet which may come in various different forms. One such form is chopped strand mat and another such form is triaxial fabric sheet. The plurality of layers of structural fabric which are described in the foregoing aspects of the invention are preferably triaxial fabric sheet. In preferred forms of the invention, chopped strand mat 0 may be used as one or more base layers underneath said plurality of layers. Chopped strand mat may also be used as a final layer overlying said plurality of layers.

However, the invention is not limited to use of fibreglass and the term ‘structural fabric’ also incorporates carbon fibre fabric and fabrics made from Aramid, para Aramid or hybrid fibres i.e. KEVLAR ™. “Structural fabric” may also include any other known forms 5 of textile or sheeting made from filament, fibre or yarn which has sufficient structural strength to form a structural component. A structural component in accordance with the invention may also include a combination of any known types of structural fabric.

The pieces of structural fabric are preferably cut to a predetermined size and placed in specific locations relative to the moulding former, in order to avoid puckering. In any of 20 the foregoing methods, each piece of structural fabric making up one of the layers is preferably of a length which is commensurate with the finished length of the structural component. Thus, the overlapping generally occurs with the side edges of the pieces such that the overlap regions extend as strips in the longitudinal direction of the structural component. Preferably, each layer is made up of a sufficient number of pieces 25 to substantially encircle the moulding former.

Said plurality of layers of structural fabric are preferably formed consecutively. They are preferably formed of the same type of structural fabric, eg triaxial fibreglass sheet. 7153851 2012201256 01 Mar 2012 7

Suitably, these layers of structural fabric incorporate resin or another type of binder in or between the layers as is known in the art.

The method of forming the structural component may also include laying pieces of reinforcement at predetermined locations on the structural component. For example, 5 pieces of reinforcement may be laid at the pivot points of the structural components which typically lie at each end of the structural component. There may be multiple pieces of reinforcement laid in overlapping layers. Preferably, the overlapping pieces progressively increase in size. There may be six to ten overlapping reinforcement pieces. The most preferred number is eight overlapping reinforcement pieces. 0 The moulding former is preferably a plug which forms a central core around which the layers of structural fabric are laid. The plug is preferably removable from the finished structural component. For this purpose, the plug may be sprayed with a mould release agent such as a wax. A gelcoat is preferably applied over the mould release agent.

In accordance with a sixth aspect of the present invention, there is provided a method of 5 strengthening a structural component of non-uniform cross-section, the method comprising: laying a plurality of layers of structural fabric around the structural component or a moulding plug or moulding former which bridges portions of the structural component, wherein each layer comprises two or more pieces of structural fabric which overlap to 20 form a single layer.

The two or more pieces in each layer are preferably of substantially the same length and the overlaps occur along the side edges of the pieces. In a preferred form of the invention, each layer comprises four pieces of structural fabric. There are two main pieces which overlap at the top of the structural component but which do not meet at the 25 bottom of the structural component and define a gap therebetween. A third piece of structural fabric lies within the gap. A fourth piece of structural fabric forms a patch overlying the joins between the first and third pieces and the second and third pieces. 7153851 2012201256 01 Mar 2012 8

Preferably, up to approximately twelve to sixteen layers are formed in the same way. The preferred number is fourteen.

It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features 5 mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps. 0 Brief description of the figures

In order to understand the invention more fully, some embodiments will now be described by way of example, with reference to the figures in which:

Figure 1(a) is a perspective view of a plug used for forming a structural component, in this case the fly boom for an elevated work platform; 5 Figures 1(b) - 1(e) are various different views of the plug with a mould release agent and a gelcoat having been applied;

Figure 2 illustrates various different views of the component in Figure 1 to which a first layer of chopped strand mat has been applied;

Figure 3 illustrates various different views of the component in Figure 2 to which 20 a first part of a first layer of triaxial fibreglass sheet has been applied;

Figure 4 shows various different views of the component of Figure 3 to which a second part of the first layer of triaxial fibreglass sheet has been applied;

Figure 5 shows various different views of the component of Figure 4 to which a first part of a second layer of triaxial fibreglass sheet has been applied; 7153851 2012201256 01 Mar 2012 9

Figure 6 shows various different views of the component of Figure 5 to which a second part of a second layer of triaxial fibreglass sheet has been applied;

Figure 7 shows various different views of the component of Figure 6 to which a first part of a third layer of triaxial fibreglass sheet has been applied; 5 Figure 8 shows various different views of the component of Figure 7 to which a second part of a third layer of triaxial fibreglass sheet has been applied;

Figure 9 shows various different views of the component of Figure 8 to which a third part of a third layer of triaxial fibreglass sheet has been applied;

Figure 10 shows various different views of the component of Figure 9 to which a 0 first part of a fourth layer of triaxial fibreglass sheet has been applied;

Figure 11 shows various different views of the component of Figure 10 to which a second part of a fourth layer of triaxial fibreglass sheet has been applied;

Figure 12 shows various different views of the component of Figure 11 to which a third part of a fourth layer of triaxial fibreglass sheet has been applied; 15 Figure 13 shows various different views of the component of Figure 12 to which first reinforcing pieces of triaxial fibreglass sheet has been applied;

Figure 14 shows various different views of the component of Figure 13 to which second reinforcing pieces of triaxial fibreglass sheet has been applied;

Figure 15 shows various different views of the component of Figure 14 to which 20 third reinforcing pieces of triaxial fibreglass sheet has been applied;

Figure 16 shows various different views of the component of Figure 15 to which fourth reinforcing pieces of triaxial fibreglass sheet has been applied; 7153851 2012201256 01 Mar 2012 10

Figure 17 shows various different views of the component of Figure 16 to which fifth reinforcing pieces of triaxial fibreglass sheet has been applied;

Figure 18 shows various different views of the component of Figure 17 to which sixth reinforcing pieces of triaxial fibreglass sheet has been applied; 5 Figure 19 shows various different views of the component of Figure 18 to which seventh reinforcing pieces of triaxial fibreglass sheet has been applied;

Figure 20 shows various different views of the component of Figure 19 to which eighth reinforcing pieces of triaxial fibreglass sheet has been applied;

Figure 21 shows various different views of the component of Figure 20 to which a 0 second layer of chopped strand mat has been applied;

Figure 22 shows various different views of the component of Figure 21 to which a third layer of chopped strand mat has been applied;

Figure 23 shows various different views of the component of Figure 22 to which a second layer of gelcoat has been applied; 15 Figure 24(a) is an exploded view of the fly boom;

Figure 24(b) is a perspective view of the finished fly boom; and

Figure 25 is a cross-sectional view of another structural component, in this case the lower boom for an elevated work platform, the cross-section showing the build up of different layers used to strengthen the component. 20 Detailed description of the embodiments

An elevated work platform has a superstructure and a support structure (not shown), in the form of a wheeled vehicle. The support structure supports the superstructure. The superstructure includes an elevated platform or basket (not shown). The elevated 7153851 2012201256 01 Mar 2012 11 platform 14 may be moved from a position resting at or approximately on the bed of the wheeled vehicle to an elevated position by three interconnected and hydraulically actuated booms. At the top is the fly boom 16 which is constructed almost wholly from fibreglass apart from the pivot bushes 18 and associated protectors 20 (see Figure 5 24(a)). Secondly, the intermediate boom is a telescopic boom. The lower boom 24 includes an insulated section, as will be described in greater detail in connection with Figure 25.

Figures 1-23 illustrate the build up of layers of fibreglass sheet in order to form the finished fly boom 16. The finished fly boom is shown in Figure 24(b). From a 0 comparison with Figure 24(b), it will be understood that the fly boom illustrated in Figures 1-23 is shown upside down, in the manner in which it is constructed. So, the top surface 26 in figures 1 -23 defines the bottom of the finished fly boom 16. For the sake of convenience, the top surface 26 will be referred as such in the ensuing description.

Figure 1(a) illustrates the moulding form 28, otherwise known as a plug. This is a 5 reusable component which may be withdrawn from the finished fly boom once the fibreglass moulding has set. To aid removal of the plug 28 from the finished component, the plug 28 is initially sprayed with a mould release agent, in the form of a wax, followed by gelcoat. This is illustrated by the cross hatching in Figures 1(b) to (e).

Initially, a layer of fibreglass sheet in the form of a chopped strand mat is applied to the 20 plug. This may be applied in the form of a single piece. Because chopped strand mat is comprised of coarse fibres, the mat 30 will give and stretch, enabling wrapping around corners of different sections, enabling a smooth wrap of the plug. This may be done as a wet process, conducted by hand in which resin is applied. Alternatively, the process may be conducted by infusion moulding and a vacuum. 25 Following the first layer of chopped strand mat, the remaining layers are built up from pieces of triaxial fibreglass sheet. This is typically a knitted or stitch bonded sheet made from fibres running in three directions, firstly warp fibres, otherwise known as ‘zero fibres’ and two sets of perpendicularly arranged fibres at 45 degrees and -45 degrees. As will be understood from the following explanation, four layers of triaxial fibreglass 7153851 2012201256 01 Mar 2012 12 sheet are built up over the first layer of chopped strand mat. Typically, these layers are built up consecutively. However, it is possible to intersperse other types of structural fabric between the layers of triaxial fibreglass sheet.

In an alternative form of the invention, the triaxial fibreglass sheet could be substituted 5 for unidirectional fibreglass sheet and chopped strand mat could be interspersed between the layers of unidirectional fibreglass sheet.

The preferred method of laying the layers of triaxial fibreglass sheet will now be described, starting with Figure 3. The first part 32 of a first layer of triaxial sheet is shown in Figure 2. This is wrapped in a U-shape along the underside of the component 0 and the side edges do not meet along the top surface 26 as shown in Figure 3(c). Figure 4 illustrates a second piece 34 of the first layer which is applied mainly to the top surface 26 and along the upper portion of the sides 27. In comparing the dimensions of Figures 4(c) and (d) and Figures 3(c) and (d), it will be seen that there is a 35mm overlap along the top surface 26 and a 70mm overlap on the left hand portion on both 5 sides 27. Thus, there are two spaced overlap regions which lie partly along the top surface 26 (i.e. the bottom in the finished boom) and partly along the sides 27.

Figure 5 illustrates the first piece 36 of the second layer of triaxial fibreglass sheet, which is applied over the top surface 26 and partly down each side 27, completely encompassing the second piece 34 of the first layer. Figure 6 illustrates the second 20 piece 38 of the second layer which is applied from underneath the component as illustrated and up along the sides 27. The second piece 38 overlaps the first piece 36 of the second layer in two overlap regions, each of which lies wholly along a respective side 27 of the component. The second piece 38 does not overlap the top surface 26. The overlap regions in the second layer may overlap with the overlap regions in the first 25 layer, particularly along the sides 27 on the left hand side as shown from the orientation of Figure 6, i.e. at the wider end of the structural component.

Figure 7 illustrates the first piece 40 of the third layer of triaxial fibreglass sheet, which piece wraps underneath the component as shown from the orientation in Figure 7, up 7153851 2012201256 01 Mar 2012 13 the sides 27 and forms a strip on each side of the top surface 26 at the narrow end of the component.

Figure 8 illustrates the second piece 42 of the second layer which does not overlap the first piece 40, but instead substantially meets the edges of the first piece 40. The 5 second piece 42 is intended to strengthen the top surface 26 (which forms the bottom of the finished fly boom 16).

Figure 9 illustrates the third piece 44 of the third layer. The third piece 44 overlies the top surface 26, with a small overlap with the first piece 40 of the third layer. The third piece 44 also extends down the sides 27 of the component at the wider end. The first 0 piece 40 and the third piece 44 of the third layer thus define overlap regions along the top surface 26 of the component at the narrow end and along the sides 27 at the wider end of the component. These two overlap regions are substantially the same as the two overlap regions in the first layer.

Figure 10 illustrates two pieces 46(a) and 46(b) forming a first part of the fourth layer. 5 The two pieces 46(a) and 46(b) meet along the centre line of the top surface 26. Each piece 27 then folds to lie along the corresponding side 27, with 100mm gap from the bottom surface as shown in Figure 10(d). Figure 11 illustrates a third piece 49 of the fourth layer. The fourth piece 48 is arranged in a U shape extending along the bottom surface of the component and up both sides 27, but not overlapping the top surface. A 20 small gap of 19mm is provided between the top surface 26 and the top edge of the third piece 48. Thus, in this fourth layer, there are two large overlaps between the first and second pieces 46(a), 46(b) and the third piece 48. The overlap regions lie wholly within the sides 27 of the component.

In Figure 12, the fourth piece 50 of the third layer is shown. (This can only be seen from 25 Figures 12(a) and (c). The fourth piece 50 overlies the top surface 26 to provide further strengthening. The fourth piece 50 does not reach the side edges of the top surface 26.

Figure 13 illustrates reinforcing pieces 52(a), 52(b) which are applied to the sides 27 of the component at the wide end of the component. Reinforcing pieces 54a and 54b are 7153851 2012201256 01 Mar 2012 14 applied to the sides 27 at the narrow end of the component. These reinforcing pieces 52, 54 provide reinforcement at the sides 27 at each end of the structural component 16 to provide additional support for the bushes 18 and protectors 20 mounted in these locations, as can be seen most clearly in Figure 24. In each location, there are eight 5 overlapping reinforcement pieces which are progressively built up in layers as shown in Figures 13 to 20. The reinforcing pieces are progressively labelled from 52a through to 84b. The reinforcing pieces progressively increase in size.

Figure 14(a) and (c) also illustrate a bend reinforcement piece 56(c).

Figure 21 illustrates a second layer 84 of 600 chopped strand mat which is applied over 0 the whole surface of the component to date. Figure 22 illustrates a third layer 86 of 600 chopped strand mat. The chopped strand mat, being more pliable results in a finished surface which has less surface bumps and is easier to sand.

Figure 23 illustrates a second layer 88 of gelcoat which forms the finished surface of the fly boom 16. The fly boom 16 may now be separated from the plug 28. The holes 90 are 5 then drilled to enable insertion of the bushes 18 and protectors 20 as illustrated in Figure 24(a).

Figure 25 illustrates the lower boom of the elevated work platform. The lower boom 24 which is constructed in accordance with the following description may be a new component. Alternatively, the lower boom 24 may be assembled from second-hand 20 components previously employed in a lower boom. For example, an previously existing lower boom may comprise two steel sections joined by a fibreglass insert which provides electrical insulation. Where the structural strength of such a lower boom was found to be inadequate, the two steel sections may be retained and rejoined with a new fibreglass insert to make a new lower boom 24 as will be understood from the following 25 description. The retrieval of the two steel sections may include sand blasting to remove rust and other appropriate surface preparation such as a rust inhibitor. A coat of DERAKANE 8084™ resin, which is an elastomer-modified epoxy vinyl ester, may be applied over the sand blasted steel surfaces. 7153851 2012201256 01 Mar 2012 15

The two steel sections are rejoined using a fibreglass insert or boom former 100 which is glued into the two steel sections and forms a bridge therebetween. Then, a sufficient number of layers of fibreglass sheet may be applied onto the boom former 100, in order to build up the outer surface level to the same height as the steel sections. This may 5 take approximately 25 layers of 600 chopped strand mat. This may be ground back level if necessary.

The resulting structural component is of irregular cross-section, in particular because on of the steel sections includes a cylinder attachment trunnion. Because the pre-existing component was found to be of insufficient structural strength to serve its purpose as the 0 lower boom in the elevated work platform, a reinforcing “bandage” is applied to the region of the boom former 100 as will be described in connection with Figure 25.

Firstly, a first layer 102 of 600 chopped strand mat is applied in a wrap over the boom former 100 and extending approximately 500 mm on each side of the boom former 100. A second layer of triaxial fibreglass sheet is then applied over the layer 102. This layer 5 102 has four pieces 104, 106, 108 and 110. The main pieces 104, 106 extend around the sides of the component 24 and fully overlap on the top surface as shown. There will be 14 such layers of the triaxial fibreglass sheet, so the final build on the top surface will be 28 layers. The main pieces 104, 106 lap onto the bottom face by 75 mm. The end edges 105, 107 leave a gap which is filled by filler piece 108 which meets the end 20 edges 105, 107 of the main pieces 104, 106. A cap piece 110 extends over the join between pieces 104, 106 and 108. The bottom surface build will therefore be 28 layers too.

The triaxial fibreglass sheet is available in two different forms, one with the zero axis fibres running in line with the fabric and, another with zero axis fibres running across the 25 fabric. In this project, the fabric used should have the zero axis fibres running in line with the length of the fabric. The triaxial fibreglass fabric is applied with the zero axis of the triaxial fabric extending along the longitudinal axis of the component 24. 7153851 2012201256 01 Mar 2012 16

As mentioned above, after layer 103, 13 successive layers of triaxial fibreglass sheet are applied, 112 designating 12 of these layers and 114 designating the 14th layer of triaxial fibreglass sheet. All of these 13 layers are applied in the same manner as layer 103. Only the construction of the first layer 103 and the 14th layer 114 are illustrated. 5 The same reference numerals used in layer 114 as for layer 103, are used to designate similar features.

Each successive layer of triaxial fibreglass sheet shall be slightly longer, e.g. approximately 25 mm, than the previous layer so that the final build will be tapered at each end of the bandage. 0 Then, another layer 116 of chopped strand mat is applied over the bandage.

Subsequent to the formation of the bandage, six layers of 600 chopped strand mat are applied to the remainder of the component 24 as low voltage cover insulation. The component is then finished as required with cut-outs made for additional components or clearances as required. The component may also be finished by filling and sanding to 15 remove undulations and other surface imperfections. A white flow coat is then applied which is sanded and polished. Appropriate fittings such as pivot flanges may then be fitted to the component 24.

The foregoing describes only one embodiment of the present invention and modifications may be made thereto without departing from the scope of the invention. 20

Claims

The claims defining the invention are as follows:

1. A method of forming a structural arm or boom for a mobile work machine, the arm or boom being of non-uniform cross-section, the method comprising: laying a plurality of layers of structural fabric around a moulding former which is of non-uniform cross-section over its length; wherein each layer comprises two or more pieces of structural fabric which overlap to form said layer, the pieces of structural fabric overlapping in two or more overlap regions; and wherein the overlap regions for a first layer vary from the overlap regions of a second layer.
2. The method of forming a structural arm or boom as claimed in claim 1 wherein the overlap regions in the first layer are completely non-overlying relative to the overlap regions in the second layer.
3. The method of forming a structural arm or boom as claimed in claim 1 or claim 2, wherein a third layer is provided having two or more overlap regions that are substantially the same as the overlap regions in the first layer.
4. The method of forming a structural arm or boom as claimed in any one of the preceding claims wherein the overlap regions each extend partly along one side of the arm or boom and partly along the bottom of the arm or boom.
5. The method of forming a structural arm or boom as claimed in any one of the preceding claims wherein in each layer, there are two overlap regions which are spaced transversely relative to the longitudinal axis of the arm or boom.
6. The method of forming a structural arm or boom as claimed in any one of the preceding claims wherein one or more of the layers incorporate additional pieces of structural fabric on the bottom of the structural arm or boom to increase structural strength.
7. A structural arm or boom for a mobile work machine, the arm or boom comprising: a plurality of layers of structural fabric forming the structural arm or boom which is of non-uniform cross-section over its length; wherein each layer comprises two or more pieces of structural fabric which overlap to form said layer, the pieces of structural fabric overlapping in two or more overlap regions; and wherein the overlap regions for a first layer vary from the overlap regions of a second layer.
8. The structural arm or boom as claimed in claim 7 wherein in each layer, there are two overlap regions which are spaced transversely relative to the longitudinal axis of the arm or boom.
9. A method of forming a structural arm or boom for a mobile work machine, the arm or boom being of non-uniform cross-section, the method comprising: laying a plurality of layers of structural fabric around a moulding former which is of non-uniform cross-section over its length; wherein each layer comprises two or more pieces of structural fabric which overlap to form said layer, the pieces of structural fabric overlapping in one or more overlap regions; and wherein at least two of the layers have two or more overlap regions lying on both sides of the structural arm or boom.
10. The method of forming a structural arm or boom as claimed in claim 9 wherein, in one of the layers, there is a narrow overlap region on each side of the structural arm or boom and in the other of the said layers, there may be a wide overlap region on each side of the structural arm or boom wherein the wide overlap region encompasses the narrow overlap region.
11. A structural arm or boom for a mobile work machine, the arm or boom comprising: a plurality of layers of structural fabric forming the structural arm or boom which is of non-uniform cross-section over its length; wherein each layer comprises two or more pieces of structural fabric which overlap to form said layer, the pieces of structural fabric overlapping in one or more overlap regions; and wherein at least two of the layers have two or more overlap regions lying on both sides of the structural arm or boom.
12. The structural arm or boom as claimed in claim 11 wherein, in one of the layers, there is a narrow overlap region on each side of the structural arm or boom and in the other of the said layers, there may be a wide overlap region on each side of the structural arm or boom wherein the wide overlap region encompasses the narrow overlap region.
13. A method of forming a structural arm or boom for a mobile work machine, the arm or boom being of non-uniform cross-section, the method comprising: laying a plurality of layers of structural fabric around a moulding former which is of non-uniform cross-section over its length, wherein each layer comprises two or more pieces of structural fabric which overlap to form said layer, the pieces of structural fabric overlapping in two or more overlap regions; and wherein one or more of the overlap regions extend partly along the bottom of the structural arm or boom and partly along the side of the structural arm or boom.
14. The method of forming a structural arm or boom as claimed in claim 13 wherein the structural arm or boom includes two portions, one of which is of relatively smaller cross-sectional area and the other of which is relatively larger cross-sectional area, the one or more regions of overlap lying along the bottom of the arm or boom in the region of smaller cross-sectional area and along the sides of the arm or boom in the portion of larger cross-sectional area.
15. A structural arm or boom for a mobile work machine, the arm or boom comprising: a plurality of layers of structural fabric forming the structural arm or boom which is of non-uniform cross-section over its length, wherein each layer comprises two or more pieces of structural fabric which overlap to form said layer, the pieces of structural fabric overlapping in two or more overlap regions; and wherein one or more of the overlap regions extend partly along the bottom of the structural arm or boom and partly along the side of the structural arm or boom.
16. The structural arm or boom as claimed in claim 15 wherein the structural arm or boom includes two portions, one of which is of relatively smaller cross-sectional area and the other of which is relatively larger cross-sectional area, the one or more regions of overlap lying along the bottom of the arm or boom in the region of smaller cross-sectional area and along the sides of the arm or boom in the portion of larger cross-sectional area.
17. A method of forming a structural arm or boom for a mobile work machine, the arm or boom being of non-uniform cross-section, the structural arm or boom having a longitudinal axis, the method comprising: laying a plurality of layers of structural fabric around a moulding former which is of non-uniform cross-section over its length; wherein each layer comprises two or more pieces of structural fabric which overlap to form said layer, the pieces of structural fabric overlapping in two or more overlap regions; and wherein the two or more overlap regions in each layer are spaced transversely across the width of the structural arm or boom.
18. A structural arm or boom for a mobile work machine, the arm or boom comprising: a plurality of layers of structural fabric forming the structural arm or boom which is of non-uniform cross-section over its length; wherein each layer comprises two or more pieces of structural fabric which overlap to form said layer, the pieces of structural fabric overlapping in two or more overlap regions; and wherein the two or more overlap regions in each layer are spaced transversely across the width of the structural arm or boom.
19. The structural arm or boom as claimed in any one of claims 7, 8, 11, 12, 15, 16 or the method of forming a structural arm or boom as claimed in any one of claims 1-6, 9-10, 13-14 and 17 wherein each piece of structural fabric making up one of the layers is of a length which is commensurate with the finished length of the structural arm or boom.
20. The structured arm or boom as claimed in any one of claims 7, 8, 11, 12, 15, 16 or the method of forming a structural arm or boom as claimed in any one of claims 1-6, 9-10, 13-14 and 17, further including laying pieces of reinforcement at predetermined locations on the structural arm or boom.
21. An elevated work platform including the structural arm or boom resulting from the method of any one of claims 1-6, 9-10, 13-14, 17, 19 and 21 or including the structural component of any one of claims 7, 8, 11, 12, 15, 16, 18, 20 and 22.
22. A method of strengthening a structural arm or boom for a mobile work machine, the arm or boom being of non-uniform cross-section, the method comprising: laying a plurality of layers of structural fabric around the structural arm or boom or a moulding plug or moulding former which bridges portions of the structural arm or boom, wherein each layer comprises two or more pieces of structural fabric which overlap to form a single layer.
23. The method of claim 22 wherein each layer comprises four pieces of structural fabric including two main pieces which overlap at the top of the structural arm or boom but which do not meet at the bottom of the structural arm or boom defining a gap therebetween, a third piece of structural fabric lying within the gap and a fourth piece of structural fabric forming a patch overlying the joins between the first and third pieces and the second and third pieces.