A METHOD OF FORMING A STRUCTURAL PANEL

Abstract: A method of forming a structural panel (58) which includes the steps of forming a plurality of transversely spaced apart longitudinally extending expandable or perforated zones (54) in a sheet material (32) and deforming the sheet material to form a corrugated member. The corrugated member then has alternating oppositely disposed transversely spaced apart longitudinally extending crest regions (44) and connecting regions connecting adjacent crest regions to each other. The connecting regions are formed at least partially by the expandable or perforated zones (54). An apparatus (10) for forming such a structural panel (58), and a structural panel (58) when formed in accordance with the method is also provided.

Description: A METHOD OF FORMING A STRUCTURAL PANEL THIS INVENTION relates to a method of forming a structural panel. It also relates to apparatus for forming a structural panel in accordance with the method and to a structural panel when formed in accordance with the method. According to one aspect of the invention there is provided a method of forming a structural panel which includes the steps of forming a plurality of transversely spaced apart longitudinally extending expandable zones in a sheet material; and deforming the sheet material to form a corrugated member having alternating oppositely disposed transversely spaced apart longitudinally extending crest regions and connecting regions connecting adjacent crest regions to each other, the connecting regions being formed at least partially by the expandable zones. Forming the expandable zones may include forming staggered slits in the zones, deforming the sheet material then including expanding the expandable zones in the manner of an expanded metal mesh, the connecting regions then being formed at least partially by the expanded zones. According to another aspect of the invention there is provided a method of forming a structural panel which includes the steps of forming a plurality of transversely spaced apart longitudinally extending perforated zones in a sheet material; and deforming the sheet material to form a corrugated member having alternating oppositely disposed transversely spaced apart longitudinally extending crest regions and connecting regions connecting adjacent crest regions to each other, the connecting regions being formed at least partially by the perforated zones. In the context of this specification the term structural panel is to be understood in a broad context to include a panel-like member which is suitable for use particularly but not necessarily exclusively in structural or construction applications. Deforming the sheet material may include the step of forming transversely spaced apart alternating oppositely disposed longitudinally extending ribs in the sheet material, which ribs, at least partially, form the crest regions of the panel element. Forming the ribs may include passing the sheet material through at least one set of rib forming rollers. Typically, the ribs are formed prior to forming the expandable zones, the expandable zones then being formed in the portions of the sheet material intermediate the ribs. Deforming the sheet material to form the corrugated member may include displacing adjacent crest regions in opposite directions generally perpendicular to the plane of the sheet materia . The method may include increasing the pitch between adjacent crest regions of the corrugated member after the crest regions have been displaced in opposite directions. The Applicant has found that when the ribs are solid, the expansion of the expandable portions leads to the creation of stresses within the elements of the expanded portions. Hence, the method may include relieving stresses or at least reducing the creation of stresses within the expandable portions. In one embodiment of the invention, the method may include forming at least one stress relieving zone. Forming a stress relieving zone may include forming a stress relieving cut in the expandable portion. Preferably, the method includes forming a plurality of spaced apart stress relieving cuts in each expandable zone. The cuts may be formed either before or after expansion of the expandable zones. In a preferred embodiment of the invention the cuts may be formed before the slits are formed and hence serve more to avoid the build-up of excess stress in the expanded zone than to relieve built-up stresses. In another embodiment of the invention the method may include stretching the strands of material in the expandable portions between which the slits are formed prior to expanding the expandable portions. The stretching of the strands may be effected at the time the slits are formed. Stretching the strands may include plastically deforming the strands. The method may include the step of cutting the sheet material at longitudinally spaced apart positions to form a plurality of corrugated panel elements of desired length. The panel elements nest readily thereby facilitating efficient transportation of the panel elements from one location to another. The Inventor believes that in certain applications the panel elements per se may be used. The method may include attaching at least one retaining element to the corrugated member. Each retaining element may be elongate, e.g. it may be a length of rod or wire, the method including attaching the retaining element to the corrugated member such that it extends transversely relative to the corrugations of the corrugated member. The method may include attaching a plurality of elongate or retaining elements to at least one side of the panel element, such that the elongate elements extend transversely relative to the crest regions of the panel element. If it is desired to form a structural panel having dimensions which are greater than those of the panel elements, the method may include connecting two or more panel elements together to form a panel assembly of the desired dimensions. In one embodiment of the invention this may be achieved by arranging a plurality of panel elements in partial overlapping relationship and connecting the overlapping portions of the panel elements together. Connecting the overlapping portions of the panel elements together may include mounting securing elements such as rings, staples, or the like on the overlapping portions of the panel elements. Instead, securing the overlapping portions together may be by welding. The panel elements will typically be connected together prior to the elongate elements being attached thereto. The method may include affixing the or each elongate element to at least one and preferably to a plurality of the crest regions. The method may include forming apertures in the sheet material to form longitudinally spaced recesses in at least some of the crest regions when the panel element is formed, affixing the elongate elements to the panel element then including securing the elongate elements in the recesses of the crest regions. The method may include the step of forming apertures in the sheet material prior to forming the ribs, the apertures being positioned such that when the ribs are formed the apertures form the recesses in the ribs and hence in the crest regions. In one embodiment of the invention the apertures may be generally V-shaped such that the recesses extend at an acute angle relative to the surface of the panel element, securing the or each elongate element in position including deforming the material of the crest region in the vicinity of the recess to crimp the elongate element in position. In another embodiment of the invention, the apertures may be waisted or generally peanut-shaped such that a central portion of each aperture has a width which is less than the width of adjacent portions of the aperture and which serves to retain a portion of an elongate element in position in the aperture. In another embodiment of the invention, affixing the or each elongate element may be by welding, e.g. resistance welding. The method may include affixing a plurality of elongate or retaining elements to opposite sides of the panel element. Preferably, the method includes affixing the elongate elements such that the elongate elements on one side of the panel element are staggered relative to the elongate elements affixed to the other side of the panel element. Preferably, the method includes affixing a plurality of elongate elements to the panel element at longitudinally spaced apart positions. The method may include attaching an end member to at least one end of the panel element. Preferably the method may include attaching a channel member to at least one end of the panel element, the end portions of the opposed crest regions being seated in the channel member. The invention extends to a structural panel when formed in accordance with the above method. The method of forming the structural panel may be at least partially automated and the invention accordingly extends to apparatus for forming a structural panel in accordance with the above method. Hence, according to yet another aspect of the invention there is provided an apparatus for forming a structural panel, the apparatus including perforation means for perforating a sheet material to define transversely spaced apart longitudinally extending perforated zones in the sheet material; and deformation means for deforming the sheet material to form a corrugated member having alternating oppositely disposed transversely spaced apart longitudinally extending crest regions and connecting regions connecting adjacent crest regions to each other, the connecting regions being formed at least partially by the perforated zones. The perforation means may be in the form of slit forming means for forming staggered slits in the sheet material such that the perforated zones are expandable in the manner of an expanded metal mesh in response to the sheet material being deformed by the deformation means. The slit forming means may be configured so that strands of material between which the slits are formed are stretched. Preferably the stretching of the strands is such that they are plastically deformed. This in turn reduces the build up of stresses in the perforated or expandable zones when expanded. The apparatus may include rib forming means for forming a plurality of alternating oppositely disposed transversely spaced apart longitudinally extending ribs in the sheet material, the ribs being positioned on the sheet material to form the opposed crest regions of the corrugated member. The apparatus may include cut forming means for forming at least one and preferably a plurality of stress relieving cuts in the perforated or expandable zones, i.e. the portions of the sheet material which are to be expanded. The apparatus may include aperture forming means for forming a plurality of apertures in the sheet material in register with the positions in which the crest regions or ribs are to be formed, the apertures then forming recesses spaced longitudinally along the crest regions or ribs. The apparatus may include cutting means for cutting the sheet material along its width to form panel elements of predetermined lengths. The apparatus may include connecting means for connecting together at least two panel elements in side-by-side partially overlapping relationship. The apparatus may include attaching means for attaching at least one and preferably a plurality of elongate elements, e.g. in the form of lengths of wire or rods, to the crest regions such that the elongate elements extend transversely relative to the crest regions and in longitudinally spaced relationship relative to one another. The attaching means may include at least one welding station for welding the elongate elements to the crest regions. The Applicant believes that a structural panel formed in accordance with the invention will be particularly suitable for use as a building panel. In this application, the ribs will typically be arranged so that they extend vertically with a plurality of structural panels being connected together side-by-side in partial overlapping relationship to provide a building panel of desired length, e.g. corresponding to the length of a wall to be constructed. It is to be appreciated, however, that the structural panel could be used with or without modification for many other applications. The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings. In the drawings, Figure 1 shows a schematic side view of apparatus for use in forming part of a structural panel, in particular a panel element, in accordance with the invention; Figure 2 shows a schematic plan view of the apparatus of Figures 1; Figures 3 to 7 show end views of the material at different stages in the apparatus to illustrate sequentially some of the steps involved in the forming of a structural panel in accordance with the invention from sheet material; Figure 8 shows a plan view of a hole formed in the sheet material from which the structural panel is to be formed; Figure 9 shows a side view of part of slit forming means of the apparatus of Figures 1 and 2; Figure 10 shows a front view of part of the slit forming means of Figure 9; Figure 11 shows a plan view of part of the slit forming means of Figures 9 and 10; Figure 12 shows a side view of a slitter element forming part of the slitting means of Figures 9 to 11; Figure 13 shows a schematic side view of further apparatus for use in forming the structural panel in accordance with the invention; Figure 14 shows a side view of part of a structural panel in accordance with the invention; Figure 15 shows a side view of an end portion of part of a structural panel in accordance with the invention; Figure 16 shows, on an enlarged scale, part of the end portion of the structural panel of Figure 15; Figure 17 shows a plan view, similar to Figure 8, of a differently shaped hole formed in the sheet material from which the structural panel is to be formed; Figure 18 shows a plan view similar to Figure 8 of still a differently shaped hole formed in the sheet material; Figure 19 shows an end view of parts of two panel elements in accordance with the invention arranged in an overlapping configuration with the overlapping portions being connected together; Figure 20 shows a schematic side view, similar to Figure 13, of still further apparatus for use in forming a structural panel in accordance with the invention; Figure 21 shows schematically, and on an enlarged scale, a welding station forming part of the apparatus of Figure 20; Figure 22 shows a side view of part of another structural panel in accordance with the invention; Figure 23 shows a schematic side view, similar to Figures 13 and 20, of still yet a further apparatus for use in forming a structural panel in accordance with the invention; Figure 24 shows a schematic plan view of part of the apparatus of Figure 23 illustrating the feeding of elongate elements to a welding station; and Figure 25 shows schematically, and on an enlarged scale, a welding station forming part of the apparatus of Figure 23. In Figures 1 and 2 of the drawings, reference numeral 10 refers generally to part of apparatus for use in forming panel elements which in turn can be used in forming structural panels in accordance with the invention. The apparatus 10 includes a decoiler, generally indicated by reference numeral 12, a press 14, rib forming means, generally indicated by reference numeral 16, slit forming means generally indicated by reference numeral 18, expansion means generally indicated by reference numeral 20 and cutting means, generally indicated by reference numeral 22. The decoiler 12 is a double decoiler and comprises a body 24 which is supported for rotation about a vertical axis of rotation as indicated by arrow 26. A pair of horizontally extending spindles 28 is connected to the body 24 such that they protrude therefrom in opposite directions. Each of the spindles 28 is configured such that a roll or coil 30, 31 of a metallic sheet material, e.g. mild steel, is receivable thereon. One of the coils 31 is a working coil from which sheet material is drawn and the other coil 30 is a spare coil. When the working coil is exhausted, the body 24 is displaced in the direction of arrow 26 so as to permit sheet material to be drawn from the spare coil. In this way down time of the apparatus 10 can be minimised. It is to be appreciated, that, if desired, the decoiler 12 could be a single decoiler or indeed, it could be configured to receive more than two rolls or coils 30. Sheet material 32 is drawn from the working coil 31 by means of a feeder comprising a pair of rollers 34. A loop control 38 is provided intermediate the rollers 34 and the press 14. The loop control 36 includes a sensor, e.g. an ultrasonic sensor 35, configured to sense the size of the loop formed by the sheet material 32 and to regulate the speed of the feeder rollers 34 thereby to feed the sheet material 32 to the press 14 at a desired rate. The press 14 is configured to punch a plurality of transversely spaced apart generally V- shaped holes 38 (Figures 2 and 8) in the sheet material 32. The holes 38 are spaced apart transversely at a constant pitch which corresponds with the pitch of the center lines of ribs which are formed in the sheet material by the rib forming means 16 as described in more detail herebelow. As can best be seen in Figure 8 of the drawings, each hole or aperture 38 comprises a pair of limbs 38.1 the one ends of which intersect, the limbs 38.1 diverging away from their intersection. If desired, the width W of each limb 38.1 may decrease away from the intersection of the limbs as shown in Figure 17 of the drawings. Instead, as illustrated in Figure 18 of the drawings, each hole 38 may be waisted or generally peanut-shaped having a waist 38.2 and two part circular portions 38.3. The waists 38.2 will typically be positioned to be in line with the centre lines of the ribs which are to be formed in the sheet material. A second loop control 40 which is similar to the loop control 36 is provided intermediate the press 14 and the rib forming means 16 to regulate the rate at which the punched sheet material is fed from the press 14 to the rib forming means 16. The rib forming means comprises a plurality of sets of rollers 42 configured to form transversely spaced apart alternating oppositely directed longitudinally extending ribs 44 in the sheet material so that the sheet material has a cross-section corresponding to that shown in Figure 4 of the drawings. The loop controller 40 is configured to regulate the speed of the rollers 42. As mentioned above, the V-shaped holes 38 are positioned such that their centres are coincident with the centre lines or apices of the ribs 44. If use is made of the peanut- shaped holes 38, then the waists 38.2 of the holes 38 are positioned to be co-incident with the centre lines or apices of the ribs 44. It is to be appreciated, that the number, shape and lateral spacing between the ribs 44 may be varied as desired. Hence, for example, each rib 44 could have a flattened central portion. As a result of the generally V-shaped configuration of the holes or apertures 38, the limbs 38.1 of each hole 38 extend at an acute angle relative to the crest of the rib 44 in which it is provided. From the rib forming means 16 the ribbed sheet material 32 is fed to the slit forming means 18. A third loop control 46 is provided intermediate the rib forming means 16 and slit forming means 18. The slit forming means 18 is configured to form a plurality of slits 48 in the portions of the sheet material 30 intermediate the ribs 44 as illustrated in Figure 5 of the drawings. The slits 48 are both longitudinally and transversely staggered so as to permit expansion of the portions of the sheet material intermediate the ribs in the manner of an expanded metal mesh. Referring now to Figures 9 to 12 of the drawings, the slit forming means 18 comprises a plurality of sets of blades which mesh and rotate with the sheet material 32 between them. Each set of blades includes two blades 50, 51 which are arranged in meshing pairs with one blade 50 of each pair having a plurality of circumferentially spaced notches 52 (see Figure 12) therein so as to provide the longitudinal spacing between the slits. The slitter elements or blades 50 are mounted on shafts 53. Similarly, the blades 51 are mounted on shafts 55. As can best be seen in Figures 10 and 11 of the drawings, a plurality of spaced apart blades 50 is provided on each shaft 53 and a plurality of blades 51 is provided on each shaft 55 with the blades 50 and 51 meshing. Instead of being mounted directly on the shafts 53, 55 as illustrated in the drawings, the slitter elements or blades 50, 51 can be mounted on sleeves which in turn are mounted on the shafts 53, 55 which facilitates removal of sets of blades 50, 51 for maintenance purposes. A plurality of longitudinally spaced apart sets of blades 50, 51 is provided and, as can best be seen in Figure 11 of the drawings, successive blades are offset by an amount O which is approximately equal to half of the thickness of the blades 50, 51. This results in the slits being both transversely and longitudinally staggered. Hence, as can best be seen in Figure 5 of the drawings, as the sheet material 32 exits the slit forming means 18 a slit or expandable zone 54 is provided between each pair of adjacent ribs 44. The ribbed sheet material 32 is fed from the slit forming means 18 to the expansion means 20. The blades 50, 51 are configured to stretch the strands of material in the expandable zone between which the slits are defined. Typically, strands of material positioned on opposite sides of a slit will be displaced in opposite directions so that the strands are plastically deformed. This plastic deformation of the strands reduces the build up of stresses in the expandable zones when expanded as described in more detail below. The expansion means 20 comprises a plurality of sets of rollers 56 which are configured to engage the ribs 44 and expand the slit portions or expandable zones 54. Initially, expansion takes place by displacing adjacent ribs in opposite directions so that the sheet material has the profile illustrated in Figure 6 of the drawings, i.e. the ribs 44 are displaced vertically such that their pitch remains constant, however, the amplitude of the corrugations is greater than the desired amplitude so as to ensure full expansion of the expandable zones 54. Once the expandable zones 54 are fully expanded, the material is expanded laterally so as to provide the ribs with the desired pitch and the corrugations with the desired amplitude, as illustrated in Figure 7 of the drawings. Hence, the material will have a corrugated appearance having alternating oppositely disposed crest regions or ribs which are of solid material and connecting regions which are formed at least partially by the perforated expanded zones 54. It is to be appreciated, that the size of the apertures in the perforated expanded zones 54 can be varied by varying the degree of expansion of the expandable zones 54. The optimum aperture size for a particular application can be determined by means of routine experimentation. The material is then fed from the expansion means 20 to the cutting means 22. The cutting means 22 is in the form of a flying cutter which comprises a profiled gear or circular cutter wheel which cuts the material into desired lengths or panel elements. The cutter locks into the material as it emerges from the expansion means 20 and runs on rails in the same direction and at the same speed as the material and cuts it off square to form rectangular panel elements. Sensing means, e.g. in the form of electronic micro- switches or photo-electric sensors are used to regulate the lengths to which the material is cut. Instead, the cutting means 22 may be in the form of a guillotine. Typically, the material will be cut off in predetermined lengths which are increments of the longitudinal pitch between rows of the holes 38 formed by the press 14. As the material is cut into panels or panel elements 58, the panel elements 58 can be arranged in a stack 60. It is to be appreciated that by making relatively simple adjustments to the apparatus 10 the pitch of the corrugations of the panel elements 58 can be varied. Similarly, the amplitude of the corrugations, in other words the thickness of the panel element can also be varied as can the length of the panel element. Further, depending upon the gauge of the sheet material which is used, a panel element 58 having the desired strength and stiffness can be formed. In the embodiments shown, the panel elements 58 have a generally saw-tooth cross-section. However, it is to be appreciated that the cross-section could vary and could for example be sinusoidal or castellated. The Applicant believes that a structural panel in accordance with the invention will be particularly suitable for use as a building panel. In this application the structural panels will be arranged such that the ribs or corrugations extend vertically. In order to facilitate construction of a building, e.g. a house, making use of the structural panel, it is desirable that each panel have a length corresponding to the length of the wall which it is desired to construct. Accordingly, it may be necessary to connect a plurality of panel elements 58 together side-by-side. Reference is now made to Figure 13 of the drawings, in which reference numeral 62 refers generally to another part of apparatus for use in the method of forming a structural panel in particular a building panel in accordance with the invention. The apparatus 62 includes connecting means, generally indicated by reference numeral 61, whereby a pair of panel elements or members 58 is connected together in side-by-side overlapping relationship, the connected panels then being displaced in the direction of arrow 63. A subsequent panel element 58 is then positioned in overlapping relationship, as illustrated in Figure 19 of the drawings, with the laterally outermost ribs 44 of adjacent panel elements 58 being arranged in a nested relationship. The adjacent overlapping panel elements 58 are connected together by means of a plurality of staples or clips 65 (one of which is shown in Figure 19 of the drawings) which extend around the nested ribs 44 and through the perforated portions 54 adjacent the ribs 44. A plurality of the clips 65 is positioned at longitudinally spaced apart positions along the ribs 44. The installation of the clips 65 is typically fully automated. It is to be appreciated that instead of making use of the clips 65, the panel elements 58 can be connected together in any suitable fashion, e.g. by welding, crimping or the like. The apparatus 62 further includes a plurality of spools 64 of elongate element in the form of wire or rod 66. The apparatus 62 includes feed means 68 in the form of a plurality of rollers 70 configured to draw the wire 66 off of the spools 64 and position it in the slots formed by the holes or apertures 38 in the ribs 44. After the wires 66 have been positioned in the slots 38, the ribs are deformed in the vicinity of the slots 38 at 39 so as to secure the wires 66 in position (Figure 14) . As mentioned above, if desired, the width W of each limb 38.1 of the V-shaped hole or aperture 38 may decrease away from the intersection of the limbs, so as to grip the wire 66 when it is positioned therein and retain it in position until the rib has been deformed. If use is made of the waisted or generally peanut-shaped hole 38 shown in Figure 18 of the drawings, the circular portions 38.3 are positioned on opposite sides of the crest of the associated rib 44. The diameter of the wire 66 will typically be selected such that it is greater than the width of the waisted portion 38.2 of the hole 38. Hence, when the wire is positioned in the portions 38.3 it is held captive therein by means of the waisted portion 38.2. It is to be appreciated, that instead of making use of wire 66, any suitable retaining element could be attached to the panel elements 58, in any suitable fashion, e.g. welding, adhesively or the like. In this case, each of the ribs 44 can have a flattened central portion with which the retaining element can abut and to which it can be secured. It is to be appreciated, that if the elongate element is to be secured to the panel element 58 by means of welding, adhesively, or the like, there will be no need to provide the apertures 38, however, they could be used in order to assist with the location of the elongate element relative to the panel element until it has been fixed in position. In this regard reference is made to Figures 20, 21 and 22 of the drawings. In Figures 20 and 21 of the drawings, reference numeral 100 refers generally to another part of apparatus for use in the method of forming a structural panel in accordance with the invention. The apparatus 100 will typically be used instead of the apparatus 62. Unless otherwise indicated, the same reference numerals used above with reference to Figure 13 of the drawings are used to designate similar parts. The major difference between the apparatus 100 and the apparatus 62 is that in the apparatus 100, the wire 66 is secured to the ribs 44 of the panel elements 58 by welding. With the apparatus 100, panel elements 58 can be connected together in side-by-side overlapping relationship in the same manner as described above with reference to Figure 13 of the drawings. Further, the wire 66 is drawn off of spools (not shown) in the same manner as described above. Alternatively the wire 66 may be cut to length and pre-straightened. The apparatus 100 includes displacement means, generally indicated by reference numeral 102 and a welding station, generally indicated by reference numeral 104 for affixing the wires 66 to the panels 58. The displacement means 102 comprises a pair of spaced apart wheels 106, 108 at least one of which is drivingly connected to a power source such as an electric motor. The displacement means further includes an endless chain-like displacement member 110 which comprises a plurality of articulated links and which extends around the wheels 106, 108 such that it has an upper run and a lower run (not shown) . The upper run is supported between the wheels 106, 108 by a support platform 112. Each of the links of the displacement member 110 has a panel engaging protrusion 114 protruding therefrom. The protrusions 114 are shaped and dimensioned such that they are snugly receivable within the ribs 44 of the panel elements 58 so as to advance the panel elements 58. The welding station 104 comprises a pair of welding units, namely, an upper welding unit 116 and a lower welding unit, generally indicated by reference numeral 118. The upper welding unit 116 comprises a displaceable contact member 120 which is displaceable into and out of engagement with a wire 66 positioned in abutment with an uppermost rib 44 of a panel element 58. The lower welding unit 118 includes a pair of displaceable contact members 122 and 124. The contact member 122 is displaceable into and out of engagement with the inner surface of a lower most rib 44 and the contact member 124 is displaceable into and out of engagement with a wire 66 positioned in abutment with the surface of the rib 44 engaged by the contact member 122. In use, the wires 66 are positioned in abutment with the ribs 44 of the panels 58 and they are fed together with the panel elements 58 in the direction of arrow 63. The panel elements 58 are displaced by means of the displacement means 102 which is configured to displace the panel elements 58 and the wires 66 in incremental steps, e.g. by means of a sprag clutch arrangement corresponding to a multiple of the pitch of the ribs 44. When the panel elements 58 are stationary, the contact element 120 is brought into engagement with the wire 66 and the rib 44 which is supported by one of the protrusions 114 which also serves as an electrical contact element. Electricity is supplied to the contacts so as to weld the wire 66 to the ribs 44 of the panel element 58. At the same time, the contacts 122, 124 are brought into engagement with and weld the wire 66 to the associated rib 44. It is to be appreciated, that each welding unit 116, 118 may in fact include a plurality of spaced apart sets of contact members so as simultaneously to weld a plurality of wires 66 to the panel elements 58. If desired, complementary apertures can be formed in the ribs 44 by means of the apparatus 10, within which apertures portions of the wires 66 are receivable to index the wires relative to the contact members. In Figure 22 of the drawings, reference numeral 150 refers generally to part of another structural panel in accordance with the invention and, unless otherwise indicated, the same reference numerals used above are used to designate similar parts. In the structural panel 150, the wires 66 have been welded in position. Further, the wires 66 on opposite sides of the panel element 68 are staggered relative to one another. Further, the Applicant has found that when displacing the ribs 44 in opposite directions to expand the expandable zones 54, the material of the expandable zone attempts to contract in a perpendicular direction, i.e. transverse to the length of the sheet. However, the provision of the solid ribs 44 resists this contraction resulting in the creation of stresses within the elements of the expanded zone. In order to relieve or avoid the stresses, the strands of material between which the slits are formed are stretched in the manner described above. If desired cuts 152 can be provided in the expanded zones 54 at spaced apart positions. The cuts 152 may be formed by cutting apparatus, e.g. the press 14, which can form part of the apparatus 10. It is to be appreciated, that the cuts 152 can be formed either before or after expansion of the expandable zones. As illustrated in Figures 15 auid 16 of the drawings, channel-shaped end members 74 are attached to the ends of the panel elements 58. Each end member 74 comprises a pair of parallel flanges 76 which are interconnected by means of a web 78. An inwardly directed lip 80 protrudes from the free end of each flange 76 and engages with a complementary recess 82 provided in each of the ribs 44 to retain the flanges 76 in position. The recesses 82 in the ribs 44 can be formed by the press 14 at the time of forming the apertures 38. The interconnected panel elements 58 will then typically be cut into building or structural panels of suitable length, as generally indicated by reference numeral 90 in Figure 13 of the drawings. The lengths of the structural panels will typically be selected so that they correspond to the lengths of walls which are to be constructed by the structural panel. Reference is now made to Figures 23 to 25 of the drawings, in which reference numeral 200 refers generally to part of another apparatus for use in the method of forming a structural panel in accordance with the invention. The apparatus 200 will typically be used instead of the apparatus 62 or 100. Unless otherwise indicated, the same reference numerals used above are used to designate similar parts. As with the apparatus 100, the apparatus 200 is used to secure elongate elements such as lengths of wire or rods 202 to the ribs 44 of the panel elements 58 by welding. The apparatus 200 includes a pre-assembly table 204 on which a plurality of panel elements 58 can be positioned in side-by-side partially overlapping relationship and connected together in any suitable fashion, e.g. in the same manner as described above with reference to Figure 13 of the drawings. The apparatus 200 further includes a wheeled carriage 206 which is mounted for displacement along a track 208 in the direction of arrow 210. The apparatus 200 further includes a welding station, generally indicated by reference numeral 212 for affixing the wires or rods 202 to the panels 58. Further, the apparatus 200 includes feed means, generally indicated by reference numeral 214 for feeding the wires or rods 202 to the welding station 212 in the desired position relative to the panel elements 58. The welding station 212 is similar to the welding station 104 shown in Figures 20 and 21 of the drawings and, unless otherwise indicated, the same reference numerals used with reference to the welding station 104 are used to designate similar parts. In addition to being vertically displaceable in order to compensate for changes in the amplitude of the panel elements 58 at least the electrodes 114 and 122 are horizontally adjustable in order to accommodate variations in the pitch of the corrugations of the panel elements 58. In this regard, the electrodes 120 and 124 will typically be relatively wide thereby minimising or eliminating the need to displace the electrodes 120, 124 horizontally and simplifying the construction of the welding station. The carriage 206 includes a jig onto which a plurality of interconnected panel elements 58 are displaceable from the pre-assembly table 204. If desired, the jig may be adjustable e.g. by means of pressurised fluid actuated piston and cylinder arrangements in order to vary the pitch of the corrugations of the panel elements. The carriage 206 is displaceable along the track 208 through the welding station 212 in any suitable fashion, e.g. it could be manually displaceable or it could be displaced mechanically, e.g. by means of a rack and pinion arrangement. The wire feed means 214 includes a plurality of tubes each of which has an outlet end 214.1 positioned to feed wire or rods 202 to the welding station. In use, typically, a stack of panel elements 58 will be positioned adjacent to the pre-assembly table 204. A desired number of panel elements 58 will then be positioned on the pre-assembly table 204 in a side-by-side overlapping relationship and are connected together. The interconnected panel elements 58 are then displaced from the pre-assembly table 204 onto the carriage 206. If desired, the pitch of the corruga¬ tions and hence the amplitude of the interconnected panel elements 58 is adjusted and the carriage is then displaced towards the welding station 212. A plurality of pre-straightened lengths of wire or rod are positioned in the tubes 214 such that their one ends protrude therefrom into the welding station 212. The carriage 206 is then displaced in incremental steps through the welding station and the wires 202 are welded to the interconnected panel elements 58 in the manner described above. The welding procedure will typically be fully automated and a plurality of sensors will be provided in order to ensure that the wires 202 are correctly positioned relative to the interconnected panel elements 58. Once the carriage 206 has passed through the welding station 212 and all of the required welds have been made, the building panel is removed from the carriage 206 after which the carriage 206 returns to a position adjacent the pre-assembly table and a further set of interconnected panel elements 58 is positioned thereon. A further set of wires or rods 202 is positioned in the tubes 214 and the process is repeated. In practice, the pre-assembly table may service a plurality of carriages 206 and hence, the one end of the track 208 may not be positioned immediately adjacent to the pre-assembly table 204. While the structural panel may be formed in one continuous operation it will typically be formed in the two distinct stages, the first of which is illustrated in Figure 1 and the second of which is illustrated in Figures 13, 20 and 23 of the drawings. Hence, the first stage will be the formation of the corrugated panels or panel elements 58 which, by virtue of their construction, nest well and are hence readily transportable in a cost effective manner. The second stage of assembly which involves the interconnection of a plurality of panel elements 58 in a side-by-side overlapping relationship, attachment of the elongate elements or wires 66 and the end members 74 to the panel elements 58 and the cutting of the interconnected panels to form structural panels and more particularly building panel elements of a suitable length can be effected either manually or automatically and this will typically be done at one or more satellite assembly points positioned closer to site. The Inventor envisages the possibility that the assembly apparatus required in order to effect the second stage of assembly could be mounted on a vehicle which could be operated as a mobile plant to effect the second stage of assembly at a site location and thereby maximise the efficiency with which the panel elements 58 can be transported. The Applicant believes that a structural panel in accordance with the invention will be particularly suitable for use as a walling panel, the structural panel then being erected such that the ribs extend vertically amd a settable coating material can then be applied thereto so that the panel elements 58 form the core of the wall. It is to be appreciated, that the optimum shape and dimensions of the structural panel for a particular application may be ascertained by means of routine experimentation. The Applicant believes that by arranging the elongate elements or wires 66, 202 at a longitudinal pitch of approximately 150 mm will work satisfactorily in many applications. More particularly, the Applicant believes that the method described above will be particularly suitable for use in the construction of a building panel element of the type described in Applicant's South African Patent No. 94/5756 which is incorporated herein by reference. The Applicant however believes that a structural panel in accordance with the invention may be suitable for use in applications other than the construction of walls.

Claims: C L A I M S 1. A method of forming a structural panel which includes the steps of forming a plurality of transversely spaced apart longitudinally extending expandable zones in a sheet material; and deforming the sheet material to form a corrugated member having alternating oppositely disposed transversely spaced apart longitudinally extending crest regions and connecting regions connecting adjacent crest regions to each other, the connecting regions being formed at least partially by the expandable zones. 2. A method as claimed in claim 1, in which, forming the expandable zones includes forming staggered slits in the zones, deforming the sheet material then including expanding the expandable zones in the manner of an expanded metal mesh, the connecting regions then being formed at least partially by the expanded zones. 3. A method as claimed in claim 2, which includes stretching at least some of the strands of material in the expandable zones between which the slits are formed. 4. A method as claimed in claim 3, in which stretching the strands of material includes plastically deforming the strands. 5. A method as claimed in any one of the preceding claims, which includes forming stress relieving cuts in the expandable or expanded zones. 6. A method of forming a structural panel which includes the steps of forming a plurality of transversely spaced apart longitudinally extending perforated zones in a sheet material; and deforming the sheet material to form a corrugated member having alternating oppositely disposed transversely spaced apart longitudinally extending crest regions and connecting regions connecting adjacent crest regions to each other, the connecting regions being formed at least partially by the perforated zones. 7. A method as claimed in any one of the preceding claims, in which deforming the sheet material includes the step of forming transversely spaced apart alternating oppositely disposed longitudinally extending ribs in the sheet material, which ribs, at least partially, form the crest regions of the panel element. 8. A method as claimed in any one of the preceding claims, in which deforming the sheet material to form the corrugated member includes displacing adjacent crest regions in opposite directions generally perpendicular to the plane of the sheet material. 9. A method as claimed in claim 8, which includes increasing the pitch between adjacent crest regions of the corrugated member after the crest regions have been displaced in opposite directions. 10. A method as claimed in any one of the preceding claims, which includes the step of cutting the sheet material at longitudinally spaced apart positions to form a plurality of corrugated panel elements of desired length. 11. A method as claimed in claim 10, which includes attaching a plurality of elongate elements to at least one side of the panel element, such that the elongate elements extend transversely relative to the crest regions of the panel element. 12. A method as claimed in claim 11, in which, attaching the elongate elements to the panel element includes affixing the elongate elements to at least some of the crest regions. 13. A method as claimed in claim 12, which includes forming apertures in the sheet material to form longitudinally spaced recesses in at least some of the crest regions when the panel element is formed, affixing the elongate elements to the panel element then including securing the elongate elements in the recesses of the crest regions. 14. A method as claimed in any one of claims 11 to 13 inclusive, in which attaching the elongate elements to the panel element includes welding the elongate elements to the crest regions. 15. A method as claimed in any one of claims 11 to 13 inclusive, which includes attaching a plurality of elongate elements to both sides of the panel element, the elongate elements on one side being longitudinally staggered relative to the elongate elements attached to the other side. 16. A method as claimed in any one of the preceding claims, which includes attaching a channel member to at least one end of the panel element, the end portions of the opposed crest regions being seated in the channel member. 17. An apparatus for forming a structural panel, the apparatus including perforation means for perforating a sheet material to define transversely spaced apart longitudinally extending perforated zones in the sheet material; and deformation means for deforming the sheet material to form a corrugated member having alternating oppositely disposed transversely spaced apart longitudinally extending crest regions and connecting regions connecting adjacent crest regions to each other, the connecting regions being formed at least partially by the perforated zones. 18. An apparatus as claimed in claim 17, in which the perforation means is in the form of slit forming means for forming staggered slits in the sheet material such that the perforated zones are expandable in the manner of an expanded metal mesh in response to the sheet material being deformed by the deformation means. 19. An apparatus as claimed in claim 18, in which the slit forming means is configured to stretch the strands of material between which the slits are defined. 20. An apparatus as claimed in any one of claims 17 to 19, inclusive, which includes rib forming means for forming a plurality of alternating oppositely disposed transversely spaced apart longitudinally extending ribs in the sheet material, the ribs being positioned on the sheet material to form the opposed crest regions of the corrugated member. 21. An apparatus as claimed in any one of claims 18 to 20, inclusive, which includes cut forming means for forming a plurality of stress relieving cuts in the perforated zones. 22. An apparatus as claimed in any one of claims 17 to 21, inclusive, which includes aperture forming means for forming apertures in the sheet material, the apertures forming a plurality of recesses spaced longitudinally along the crest regions when formed. 23. An apparatus as claimed in any one of claims 17 to 22, inclusive, which includes cutting means for cutting the sheet material along its width to form panel elements of predetermined lengths. 24. An apparatus as claimed in claim 23, which includes connecting means for connecting together at least two panel elements in side-by-side partially overlapping relationship. 25. An apparatus as claimed in any one of claims 17 to 24, inclusive, which includes attaching means for attaching a plurality of elongate elements to the crest regions such that the elongate elements extend transversely relative to the crest regions and in longitudinally spaced relationship relative to one another. 26. An apparatus as claimed in claim 25, in which the attaching means includes at least one welding station for welding the elongate elements to the crest regions. 27. A structural panel formed in accordance with the method as claimed in any one of claims 1 to 16, inclusive. 28. A method of forming a structural panel substantially as herein described and illustrated. 29. An apparatus for forming a structural panel substantially as herein described and illustrated.

Inventors: MCGREGOR DUNCAN CLIFT, MCGREGOR, DUNCAN, CLIFT
Applicants: HANDELMAN JOSEPH H, MCGREGOR DUNCAN CLIFT, HANDELMAN, JOSEPH, H., MCGREGOR, DUNCAN, CLIFT
Application year: 1996
Main classification: E04C
IPC codes: B21D47, E04C2