4611-1.doc Formwork system Field of Invention This invention relates to formwork for walls and more particularly to formwork for walls formed predominantly of concrete. 5 Background Traditional formwork comprises two parallel planar members (usually plywood) spaced apart and held to together with connectors that extend between the planar members and through holes in the members. Retainers on the outside of the members engage the connectors and prevent the members 10 separating when filled with concrete. When the concrete has set the retainers on the connectors are removed, and the planar members are removed. This system incurs cost in assembly and disassembly and the need to surface the wall to an acceptable standard. An alternative unitary formwork structure has been proposed in which the two 15 parallel planar members and connectors are formed of a unitary structure. The formwork has smooth outer surfaces and is left in-situ when the wall has been formed. This system provides for cost reduction in assembly and avoids disassembly and the need for surfacing. However, the formwork is formed integrally, so 20 different width walls require different formwork assemblies. Further, the integrally formed formwork has significant airspace, so takes up significant space when being stored and transported, so increasing cost. Summary of the Invention In an attempt to ameliorate the disadvantages of the prior art, the present 25 invention provides a formwork system comprising: 4611-1.doc -2 two spaced apart wall members having opposed inner surfaces, and at least one connector adapted to engage the inner surface of each wall member and hold and retain the opposed wall members in a spaced apart configuration. 5 The wall members may have connecting elements with which the at least one connector engages. The connecting elements are preferably integrally formed with the wall members but may be separate components mounted on the wall members. In another broad form the present invention provides a formwork system 10 comprising: two spaced apart wall members having opposed inner surfaces, and at least one connector adapted to engage at least one connecting element integral with or mounted on each wall member inwards of the outer surfaces of the wall members to hold and retain the opposed wall 15 members in a spaced apart configuration. The connecting elements may extend in one or more lines along a panel. Preferably there are multiple parallel lines extending in a first direction and spaced apart from each other in a direction transverse to the first direction. Preferably the lines are straight and parallel. 20 Each line may have one connecting element or a plurality of connection elements along its length. Each connecting element may be a "point" connection, only allowing connection at a single point, or may be elongate along the line, allowing connection at a plurality of locations. The connecting elements preferably extend from the inner surface but may be 25 recesses.
4611-1.doc -3 The connecting element preferably has a mate part that connects with a female part on the connector. Preferably the mate part has an arrow headed cross section portion that engages in a recess on the connector, with the recess having surfaces to trap 5 the arrow headed cross section portion in the recess. Preferably the arrow headed cross section portion is elongate and the recess is elongate. Preferably the female part comprises two walls or legs defining an aperture or slot into which the mate part is received. The two walls or legs preferably define a gap there between through which the mate part passes, the width of 10 the gap being less than the maximum width or the mate part that passes through the gap. The panel may include retainer means adjacent connector elements to prevent disengagement of the connectors from the panels. The retainer means may be a protrusion that extends adjacent the connecting element and 15 prevents or limits sideways movement of at least part of the connector adjacent the retainer. The panels preferably have panel connector(s) to connect panels in a line end on end. Preferably the panels have at least one first panel connector located along one side edge and at least one second panel connector located along the 20 other, parallel side edge. The at least one second panel connector may be a retainer. The at least one first panel connector is preferably a hooked leg. The connector may comprise at least one central portion with end portions located at the end of the or each central portion. Where the end portions are female, each end portion preferably comprises a recess having an inner space 25 sized to receive at least one mate connecting element and a gap or slot smaller than the mate connecting element. The connector may have two or more spaced apart central portions, each 4611-1.doc -4 having end portions. Connectors may include connector joining elements, whereby adjacent connectors may be joined together. The joiners are preferably complementary hook members A first connector element may be connected to a first wall panel and a second 5 connector connected to a second wall panel next to the first wall panel in a side by side arrangement, with the first and second connectors joined together by the joiners. A connector with two or more spaced apart central portions and corresponding end portion may be connected to two adjacent side by side wall panels. 10 Brief Description of the Drawings The invention shall be better understood by reference to the description of preferred embodiments of the invention and the accompanying drawings in which: Figure 1 is a cross sectional view of a wall panel according to a first 15 embodiment of the invention. Figure 2 is a cross sectional view of a first connector for use with the wall panel of figure 1. Figure 3 is an exploded cross sectional view of formwork using the panel and first connector and also third and fourth connectors. 20 Figure 4 is a cross sectional view of a forth connector for use with the wall panel of figure 1. Figure 5 is a cross sectional view of a fifth connector for use with the wall panel of figure 1. Figure 6 is an exploded cross sectional view of formwork using the panel and 4611-1.doc -5 first, fourth and fifth connectors. Figure 7 is a side view of the fourth connector. Figure 8 is a side view of the fifth connector. Figure 9 is a front view of the fourth connector. 5 Figure 10 is a cross sectional view of a first end cap. Figure 11 is a cross sectional view of a top cap. Figure 12 is a plan view of the top cap of figure 11. Figure 13 is a cross sectional view of a bottom track. Figure 14 is a plan view of the bottom track of figure 13. 10 Detailed Description of Preferred and other Embodiments Referring to the drawings there is shown a formwork system 2 having opposed two opposed walls 4 and 6. Each wall is formed of one or more identical wall members 12 arranged end on end horizontally. The wall members 12 are preferably formed of PVC or other suitable polymer 15 (preferably containing a smoke suppressant additive) that may be readily cut on site, such as by a hand or powered saw. The wall members 12 are substantially planar and preferably have a smooth outer surface 14. The panels are arranged to stand vertically side by side. The inner surface 16 has a series of parallel connector elements 18 that 20 extend vertically along the wall panel. The panels are intended to be usually used with the connector elements 18 extending vertically (as opposed to horizontally) and reference to vertical and horizontal is to be with reference to this arrangement. Similarly the word width is to refer to the thickness of 4611-1.doc -6 the wall whilst the length of the wall refers to its horizontal extent. In this embodiment the connector elements 18 are mate ribs. These ribs extend along the vertical length of each panel 12. The wall panels 12 of this embodiment have a constant cross section in the 5 vertical direction and may be formed, such as by extrusion, to any length required. Thus, for example, the wall panels may be formed with lengths suitable for room heights of 2.4, 2.7 or 3.0 metres. The width of each wall member 12 is preferably 400 mm with sixteen ribs 18 located along the width. The spacing of the ribs 18 is preferably at 25 mm 10 centre to centre and with the end ribs 18a, 18b located 12.5 mm from the edges 50, 52 respectively. The ribs 18 have a planar wall 19 with an arrow head 20 at their free end having angled faces 22 and generally perpendicular surfaces 23. Located either side of each rib 18 are vertically extending retainers 24 that 15 extend from the wall portion 26 adjacent the base of the rib 18. The ribs 18 and retainers 24 thus form two small channels 28 either side of wall 19. In the preferred embodiment the width of the channel 28 between the wall 19 and retainer 24 is about 4.5 mm. The wall 19 is about 2 mm wide and about 4.5 mm in height from the adjacent 20 inner surface 44. The height of the triangle forming the arrow head 20 is 3.09 mm, the hypotenuse measuring 3.09 mm, and thus angled surfaces 22 extend at 45 degrees. The retainers 24 have a height of about 2 mm, and a hypotenuse of about 3.57 mm. It should be noted that the thickness of the portion of wall panel 12 from 25 which the mate rib 18 extends is greater than the thickness of the portion 25 between retainers 24.
4611-1.doc -7 A series of elongate connectors 30 extend between the two wall members 12. The connectors 30 are preferably formed of PVC with a smoke suppressant additive but may be formed of other materials. These connectors 30 are substantially symmetric and have a central portion 32 5 and female end portions 34. These female end portions 34 are adapted to engage mate ribs 18 and separate into two legs 36 at each end. The legs 36 generally diverge and form a female space 38 between themselves. The inner surface 40 of each leg 36 extends toward the other leg at the free end and forms a surface 42 generally perpendicular to the length of the connector. A 10 gap 43 is defined at the free end between the legs 36. The width of the gap 43 is less than the width 42 of the arrow head 20. The connectors 30 may be connected to the ribs 18 by sliding the connectors along the length of the ribs 18 from an end or by pressing the connector 30 and wall panel 12 together. 15 When connection is by pressing together, the arrow head 20 causes the legs 36 to separate until the arrow head 20 has passed the gap 43, at which point the legs snap back toward each other so that the surfaces 23 engage or lie behind the surfaces 42 of the ribs. The length of the gap 43 is the same or slightly less than the distance between 20 the surface 23 of the arrow head and the surface 44 from which the ribs 18 extends. Thus once assembled the connectors 30 hold the opposed wall members 12 in a fixed separation with no or insignificant movement. The retainers 24 extend alongside the legs 36 and have a separation from the wall 19 such that once female end 34 has snap fitted to the mate rib 18 the 25 legs 36 are prevented from significant sideways movement by the retainers 24. Preferably the gap 43 is only slightly larger than the width of the wall 19. When the connectors 30 are attached to the wall members 12 by pressing 4611-1.doc -8 together, the retainers 24 will flex outwards as the slightly separated legs 36 pass over the arrowhead 20. The legs 36 have angled faces 45 to assist in sideways deflection of the retainers 24. The faces 47 defining the gap 43 are also angled to assist in separation of the legs as the connector engages the 5 arrowhead 20. When the assembled formwork 2 is filled with concrete the weight of the concrete creates outward directed forces on the wall panels inducing tension in the connectors 30, which would tend to cause the legs 36 to separate. The planar surfaces 23 and 43 and the retainers 24 act to prevent this separation. 10 Thus, once assembled, separation by mere expansion forces, such as the weight of concrete is resisted. The connectors 30 are also of constant cross section and may be of a vertical height the same as the wall members 12. Two or more shorter connectors may be attached end on end to the same rib 18. Where two or more connectors 30 15 are attached to the same rib 18 there may be a gap between the ends of one or more pairs of adjacent connectors 30, if desired. A hollow formwork may thus be assembled by connecting two flat wall members 12 together with a suitable number of connectors 30. The components provide the accuracy and assembly may be by relatively unskilled 20 tabour. It is estimated that 2 men can erect up to 100 m 2 per day for a 3 m high panel. The flat wall members 12 may be stored in a stack, only taking up the vertical height of the sum of their thicknesses. Similarly the connectors 30 do not have air space. 25 The connectors 30 are provided with apertures (not shown) in the central portion 32 spaced at regular intervals along the length of the connector. When a hollow formwork assembly is created the apertures align and reinforcement 4611-1.doc -9 or service conduits or pipes may be passed through the apertures prior to pouring of the concrete into the wall. The connectors 30 may be manufactured with different separations between the female end portions, thus enabling formwork for different width walls to 5 be assembled using the same wall panels 12 merely by utilising different connectors 30. Different separations may be made by varying the length of central portion 32. Whilst the preferred forms of the invention utilise a mate connector on the wall panel and female connections on the connectors it will be appreciated 10 that this arrangement may be reversed. Whilst the preferred forms of the invention utilise mate and female connections, it is within the scope of the invention to use other means of internal connection between the wall panels 12 and the connectors 30. The width of each wall member 12 is preferably 400 mm with sixteen ribs 18 15 located along the width. The spacing of the ribs is preferably at 25 mm centre to centre and with the end ribs 18a, 18, located 12.5 mm from the edges 50, 52 respectively. The wall members are preferably formed of PVC or other suitable polymer that may be readily cut on site, such as by a hand or powered saw. Thus a wall 20 panel may be cut on site to provide the correct length of wall. The wall panels are preferably 400 mm wide but most walls have a run greater than that and accordingly one of the edges 50 and 52 (50 in this embodiment) is provided with an integrally formed connecting element 54 for engagement with the adjacent wall element. 25 In the preferred embodiment the connecting element 54 is a sideways extending leg 56 that is adapted to engage the retaining member 24 of the 4611-1.doc - 10 adjacent panel nearest the edge 52. The leg 56 has a hook with surface 58 that engages the surface 60 of retainer 24 on the adjacent panel. The surfaces 58 and 60 may extend generally perpendicular to the general plane of the wall elements 12. However the surfaces 58 and 60 may be angled so that tension 5 along the length of the wall members urges the surfaces 58 and 60 together. Assembly of a wall of formwork will usually follow the step of assembly of modules, each module being two opposed wall panels 12 and appropriate connectors and then connection of modules by engagement end on end. The rest position of each leg 56 corresponds to the engaged position and 10 accordingly the end of the legs 56 are provided with angled surfaces 62 that engage angles surface 22 of retainer to bend the leg 56 inwards as the two wall members 12 are pushed toward each other. By having the legs 56 engage on the retainers 24 rather than a specific end member it is possible shorten the length of the wall member 12 but cutting off 15 a portion from end 52 and still retain the ability to join wall members 12 together. If the cut is made adjacent a retainer 24, the length from the first retainer to the end corresponds to the as-formed end 52. It is desirable to have additional structure to join adjacent wall members and according the invention provides modified connectors 70 and 72, as seen in 20 figure 3. The connectors 70, 72 are similar to connector 34 in having a central section 32 and two end portions 34. The connectors thus provide the functionality of the connectors 30. However, the connectors 70, 72 include sideways extending joiners 74 and 76, respectively, adapted to engage each other. When assembled the joiners are staggered slightly and hook members 25 78, 80 on joiners 74, 76 respectively overlap and transfer transverse tension loads between engaged connectors 70, 72. The ends of the joiners have angled faces 82, 84 to allow engagement by sideways movement. In this embodiment each connector 70, 72 is provided with two like joiners but 4611-1.doc - 11 a single joiner or more than two joiners may be provided. A connector with one joiner 74 and one joiner 76 may be used instead. This enables a single type of joiner to be used in adjacent modules, albeit at the need for the connectors to be arranged correctly so joiners 74 oppose joiners 76. In this 5 embodiment the two joiners extend from end portions 34 but may extend from central portion 32. As seen I figure 3 one connector 70 is attached to wall members 12a and 12b and the other connector 72 is attached to wall members 12c and 12d. Figures 4 and 5 show fourth and fifth connectors 90 and 92. In effect the 10 connector 90 is the combination of the connector 70 and a connector 30, with arms 94 connecting the connector part 96 with connector part 98. In effect connector 92 is the combination of the connector 72 and a connector 30. The connectors 90, 92 may be used to connect adjacent wall panels, with the two heads of each connector connected to one of the panels respectively. 15 However, as also seen in figure 6, the connectors 90, 92 may be used away from an end merely for their ability to connect opposed wall panels 12. Referring to figures 7 to 9, the connectors 90, 92 have apertures 97 in arms and legs 94, 95 and 96. There are also apertures 91 in central portions 91. The invention also provides an end cap 100, shown in figure 10. The end cap 20 100 are to close the vertical edge of the formwork and are provided with connecting elements 104, similar to connecting element 54. The end cap is pressed into the vertical edge of the formwork and the connecting elements engage retainers 24 on the wall panels. The caps also include sideways extending joiners 106, similar to joiners 74. As with joiners 74, these joiners 25 106 are adapted to engage with a joiners 76 of a connector 72 located adjacent the vertical edge. The end cap 100 may be made with different overall widths to accommodate 4611-1.doc - 12 different width formwork. The invention also provides a top cap 110, shown in figures 11 and 12. This cap 110 is designed to close the top edge of the formwork and comprises a simple U shaped section sized to be placed over the top of the wall panels 12, with 5 the wall panels 12 within the opposed arms 112 of the top cap 110. The invention also provides a bottom track 120, shown in figures 13 and 14. This track 120 is designed to close the bottom edge of the formwork and comprises a simple U shaped section sized to receive the wall panels within the opposed arms 122 of the track. The base 124 is provided with a series of 10 apertures 126 along its length through which reinforcement rods, service pipes (water, gas, etc.) or service conduits (electricity, data, etc.) may pass if desired. If the wall is required to tie into a floor above, the bottom track 120 may be used as a top cap to allow reinforcement rods, pipes or conduits to extend above the height of the wall. 15 In the embodiment described the connecting elements 18 are formed integrally with the wall panels 12. This is not critical and the connecting elements 18 may be formed of separate components that are mounted on or in the panels 12. Ideally any separate connecting elements 18 do not pass through the panels 12 from the outer surface 14, so as to leave the outer 20 surface a smooth surface. However, where the nature of the finish of the outer surface is not critical, such as in an industrial situation, connecting elements 18 may pass through the panels from the outer surface 14 to engage the connectors 30. Unless the context clearly requires otherwise, throughout the description and 25 any claims the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".
4611-1.doc - 13 The features of the invention described or mentioned in this document may be combined in any combination of features where features are not mutually exclusive. It will be apparent to those skilled in the art that many obvious modifications 5 and variations may be made to the embodiments described herein without departing form the spirit or scope of the invention.