FORMWORK SYSTEM

The present invention relates to a formwork system for concrete and, more particularly, to a permanent formwork. Expamet Hy-Rib® is an expanded metal sheet product which has been used for many years as permanent formwork to concrete. The profile of the overall mesh, in combination with the tangs which stick out of the plane of the open mesh, allow the development of dense concrete modules and indents on the face of the Hy-Rib® sheet, forming an enhanced mechanical key for the second phase pour of concrete, i.e. the phase adjacent to the first phase formed internally of the Hy-Rib® sheet. Where there is no second phase pour the visible elements of the Hy-Rib® sheet result in a surface which is ideally suited to receiving a rendered or tiled finish. The Hy-Rib® product is primarily used in construction joint applications but is also used to form wall, beam or column surfaces and slab soffits, where the column surface will not be seen. The conventional alternative to the use of Hy-Rib® sheeting as formwork is the traditional plywood sheeting used for concrete shuttering which is simple to use by carpenters on site, but which does not have the advantages or Hy-Rib® expanded metal sheeting. In order to simplify installation of Hy-Rib® sheeting for concrete formwork it is desired to provide a complimentary support system. Therefore, according to the present invention a formwork system for concrete comprises: a metal mesh sheet having a plurality of longitudinal reinforcing ribs spaced apart from one another across the sheet; one or more metal support frames each having a plurality of longitudinal supports each having a protrusion arranged to engage with a corresponding one of the longitudinal reinforcing ribs of the metal mesh sheet, to provide lateral support for the sheet along the reinforcing ribs.

By providing registration between the longitudinal supports of the support frame or frames and the longitudinal reinforcing ribs of the metal mesh sheet, appropriate installation and provision of the concrete formwork can be effectively ensured with appropriate support being provided the full length of the longitudinal reinforcing ribs of the expanded metal sheet.

Depending upon the required lateral dimension of the formwork, plural sheets and plural metal support frames may be provided, the support frames being bolted to one another at an edge and the metal mesh sheets being overlapped with the edge reinforcing rib of one metal sheet being superimposed over the edge reinforcing rib of the adjacent sheet.

Preferably, the width of the longitudinal support and protrusions at the edges of the or each support frame are substantially half the width of the protrusions and supports in between to allow for secure attachment of an adjacent support whilst still providing for the protrusions to extend into the rear of the longitudinal reinforcing ribs of the metal mesh sheets at the junction.

The system may further include an expansion adapter arranged to expand the width of the frame to fit the gap between the adjacent formwork panels.

The invention also includes a method of providing formwork for concrete comprising disposing a metal mesh sheet having a plurality of longitudinal reinforcing ribs spaced apart from one another across the sheet against one or more metal support frames each including a plurality of longitudinal supports each having a protrusion arranged to engage with the corresponding one of the longitudinal reinforcing ribs of the metal mesh sheet to provide lateral support for the sheet along the reinforcing ribs, and assembling the supported metal mesh sheet in position in engagement with other formwork to provide a support for concrete to be poured within the formwork.

To achieve an improved seal between the formwork system of the present invention and adjacent formwork, an elongate flexible seal is provided for secure attachment along one or each edge of the support frame. Preferably, the flexible seal comprises a metal section supporting a synthetic rubber or similar gasket against which adjacent formwork can abut, the gasket absorbing lack of uniformity in the adjacent formwork to provide an effective seal to prevent concrete from setting between the formwork system and the adjacent formwork.

One example of a formwork system according to the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is an isometric view of a formwork system according to the invention, the drawing being broken across the length of the formwork to indicate that the formwork may vary in length and in order to allow the drawing to fit on the page whilst still providing sufficient detail to a reader;

Figure 2 is a similar isometric view of the metal support frame; Figure 3 is a similar isometric view of the metal support frame with an edge seal attached;

Figure 4 is an end view of the formwork system; and Figure 5 is a partial perspective view of a modified support frame. The formwork system, known as Hy-Frame®, includes, in this example, a single sheet of Expamet Hy-Rib® expanded metal mesh 1 which can be seen to have elongate sections of expanded metal mesh 2 separated by elongate reinforcing ribs 3 substantially U-shaped in cross-section.

Supporting the Hy-Rib® expanded metal mesh on its rear surface 4 is a steel support frame 6 which has tubular edge members 7 and cross braces 8 and regularly spaced apart longitudinal supports 9, the front ends of which project forwardly (to the left as shown in Figure 4) of the front of the frame members 7,8 to provide protrusions 10 which engage in the rear of the longitudinal reinforcing ribs 3 of the Hy-Rib® expanded metal mesh.

Each side member 7 of the support frame 6 also carries, integrally formed with it, a longitudinal support 9' which provides a protrusion 10' to support the corresponding edge reinforcing rib of the Hy-Rib® sheet 1 , the width of the longitudinal supports 9' being substantially half that of the internal supports 9 so that an adjacent corresponding frame, which may be of a different width overall, can be securely attached to the support frame 6. Figure 2 shows holes 11 in the side member 7 by means of which, together with bolts (not shown), a support frame may be attached to an adjacent support frame. This allows an adjacent Hy-Rib® sheet to be positioned adjacent the first, with the sheets partially overlapped with the edge reinforcing rib 3' of one metal sheet being superimposed over the corresponding edge reinforcing rib of the adjacent sheet. For this purpose, as best seen in Figure 4, the edge reinforcing rib 3' may not be fully formed on its outer side.

By providing Hy-Rib® sheeting and support frames of different widths of formwork can be provided to suit particular requirements (i.e. widths between adjacent formwork panels).

Figures 1 , 3 and 4 also show an edge seal or gasket 12 which is formed of compressible synthetic rubber or neoprene and is secured to the corresponding edge or side support 7 by means of a support section 13 which can be bolted to the side member 7 through apertures 14 and which has inwardly facing flanges 15 to grip the seal or gasket 12. When the formwork is used to abut against adjacent formwork extending substantially at right angles to it, the seal or gasket 12 can be partially compressed to provide a secure seal against the adjacent formwork to prevent the ingress of concrete to the space between the formwork support 6 and the adjacent formwork.

As mentioned above, the Expamet Hy-Rib® sheet may be provided in a wide range of widths from 89mm width (width between outer rib centres) and 445mm width, with the sheets being provided in a range of different lengths from 2 to 5 metres for example. The longitudinal reinforcing ribs are uniformly spaced apart from one another across the width of the sheet. The corresponding support frames have longitudinal supports correspondingly positioned apart from one another to ensure registration between the protrusions and the longitudinal ribs of the Hy-Rib® mesh.

Figure 5 shows a partial perspective view of a modified form of the support frame 6 in which an expansion adapter 16 is shown attached to one side member 7 to allow the

frame to be adjusted to suit a width (between adjacent formwork panels) which is not an exact multiple of support frame widths. Additionally, the expansion adapter may be used to force the support frame into engagement with adjacent formwork, squeezing the seal or gasket 12 into engagement with the adjacent formwork to provide a secure, sealed fit. The expansion adapter 16 includes an elongate frame element 17 which is movable (in the direction of arrow A) on studs 18 which pass through holes in the side member 7 and which is moved into its engaging position by suitable tightening devices such as wedges or screw and nut combinations inserted between the side member and the frame element 17. Such a screw/nut combination may have a so-called fast thread to simplify fixing and removal.