GB2299125A

GB2299125A - Shuttering

Info

Publication number: GB2299125A
Application number: GB9506092A
Authority: GB
Inventors: Gerald Townsend
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-03-24
Filing date: 1995-03-24
Publication date: 1996-09-25
Anticipated expiration: 2015-03-24
Also published as: GB2299125B; GB9506092D0

Abstract

A shutter for supporting concrete prior to setting, comprising a sheet having a dome-shaped central area 21. The central area 21 is preferably formed with apertures 24 for providing fluid flow passages therethrough. The apertures 24 are preferably formed at the top of conduits 25 extending upwards from the dome shape and preferably all the apertures 24 are located at the same level. The apertures 24 are preferably arranged on a grid pattern, preferably uniform in two orthogonal directions.

Description

SHATTERING As a change from the conventional wooden shuttering for supporting poured concrete until it has set, it has already been proposed to provide shaped plastic sheets to act as shuttering. Such sheets have been provided with plane transverse side edges, so that the shaped sheets can be placed together and a butt joint formed between facing side edges when a shutter is formed from a plurality of sheets.

The shaped sheets so far provided have not been entirely satisfactory, to provide support for loads before the concrete is poured and to provide a strong structure once it is poured and has set.

The present invention provides a shutter for supporting concrete, comprising a sheet having a domeshaped central area. The central area is preferably formed with apertures for providing fluid flow passages therethrough. The apertures are preferably formed at the top of conduits extending upwards from the dome shape and preferably all the apertures are located at the same level.

The apertures are preferably arranged on a grid pattern, preferably uniform in two orthogonal directions.

Trough means may be provided along one or two opposite pairs of sides of the sheet. The trough means may have a flat bottom. The trough means on one side may be shaped to fit into a trough on the opposite side of an adjacent sheet. Concave quadrants may be formed at the corners of the sheets. A skirt may be provided at the periphery of the sheet, at the quadrants only. The skirts of quadrants at two opposite corners may have radii differing by at least the thickness of the sheet. The skirts at two opposite corners may be formed in two portions, one portion having a radius greater than the other portion by at least the thickness of a sheet.

Preferably the level of the sheet is stepped adjacent quadrants at two opposite corners by an amount equal to at least the thickness of the sheet.

Examples of the prior art and of the invention will now be described with reference to the accompanying drawings in which Figure 1 is a plan and Figure 2 is a vertical section through a prior art concrete floor provided with plastics sheet shuttering, Figure 3 is a plan of shuttering according to an embodiment of the present invention, Figure 4 is a section on line Y-Y of Figure 3, Figure 5 is an enlarged vertical section detail through two adjoining shutters, showing concrete and reinforcing bars in place, Figure 6 is a view in the direction of arrow 6 on Figure 3, Figure 7 is a detail of four shutters located around a central column.

A plastics sheet shutter for use in supporting a concrete floor as shown in Figures 1 and 2 is generally square in plan and is provided with a plurality of parallel roughs 11 extending across the larger part of the sheet parallel to two of the sides. It will be seen from Figure 1 that the shuttering sheet is provided with troughs 13 along the edges and a quadrant cut-out 14 at each corner.

The skirt at the quadrant fits into the top of hollow supporting columns. As can be seen from Figure 2, the parallel troughs 11 stop short of the transverse troughs 13 and the latter stops short of the quadrant cut-out 14, so that concrete in them does not contribute significantly to the strength of the floor since it does not provide an overall beam. Figures 1 and 2 show reinforcing bars 15 which are mounted in the concrete above the level of the troughs. The depth of concrete is only sufficient to allow a single horizontal row of bars with proper cladding of concrete. At the sides of the shuttering the reinforcing bars are bent downwards and mechanically anchored at 16 to resist uplift.The sheet has a continuous skirt 12 around -ts periphery by which it can be butt jointed to adjacent sheets and it is provided with a tape seal 17 across the top of the butt joint to prevent leakage therethrough.

When this concrete structure is intended to act as a filter for liquids, the spaces between adjacent parallel troughs is provided with apertures 18 for passage of the liquids therethrough. A conduit or nozzle 19 is fitted to each of these apertures to provide liquid flow passages through the floor. The nozzles have spacings of 150 mm and 200 mm in two transverse directions.

A comparison of Figures 3 and 4 with Figures 1 and 2 will show the basic differences of the embodiment of the present invention from the example of the prior art. In Figures 3 and 4, the plastics sheet shuttering is rectangular with a general dome-shaped central section 21 surrounded by a flat deck 22 with troughs 23 along each edge. The dome-shaped central section rises with a smoothly varying gradient to an upper point at the centre, as a smooth curve whose only reversal of gradient occurs at the centre point. The dome is preferably part-spherical. The nozzle apertures 24 are arranged in both transverse directions at 150 mm spacing, so that there is a higher density of nozzles compared with Figure 2. They are arranged in frusto-conical "chimneys" 25 whose upper ends are at a uniform height, although their lower ends are at heights dependent on their position on the dome.

As can be seen from Figure 5, the trough 23 on the right-hand side of a sheet nests neatly into the left-hand trough of the adjacent sheet and similarly for the top and bottom edge troughs. The troughs have a flat base 26 and a self-tapping screw can be driven through the nesting bases of the troughs to provide a firm fixture between adjacent sheets which cannot be so easily ruptured by a sideways force as could the butt joint of the prior art arrangement illustrated in Figure 2.

The central dome-shape 21 of the sheet provides greater resistance to deformation and damage by a workman walking over the sheet before concrete is poured thereover.

When it is poured and set, the concrete is vaulted providing a strong structure. As before, the corners of the shuttering are provided with quadrant cut-outs 27 defined by vertical skirts 28 for fitting within the tops of hollow vertical supporting columns 29. The skirts 28 only extend around the quadrant and do not extend along the straight sides of the shuttering. This arrangement avoids the need to cut slots in the tops of supporting columns at the corners of the shuttering; the skirts of the shuttering of Figures 1 and 2 require such slots since the skirts extend continuously around the periphery of the shuttering and so have to cross the column walls to fit the quadrant skirt within the column.

As can be seen in Figure 3 and Figures 6 and 7, the shape of the shuttering at each quadrant is slightly different. In Figure 3, the radius of the skirt defining the quadrant at the top left-hand corner is less than the radius of the skirt defining the quadrant at the bottom right-hand corner by the thickness of the depending skirt.

At the top right-hand and bottom left-hand corners, the quadrant has a half portion 31 at the greater radius and a half portion 32 at the smaller radius, changing at the midpoint. As can be seen in Figure 6, the horizontal level of the shuttering adjacent the quadrant at these last two corners also changes at this midpoint 33 by the thickness of the shuttering. Figure 7 makes it clear how these changes enable the overlapping corners of adjacent shutters to fit together properly. In the figure, there is an inner curved line 34 with four dotted lines at increasingly greater radii. The inner full line and the innermost 35 of the dotted lines denotes the skirt wall of the appropriate shutter. Between about 2 o'clock and 7 o'clock on the clock-face defined by the supporting column, the skirt is provided by that of the top left-hand corner D of the shutter shown in Figure 3.Between 11 o'clock and 1 o'clock, the smaller diameter portion of the skirt shown at the bottom left-hand corner C of the shutter of Figure 3 is present, and its other half portion is at a slightly greater radius and fits behind the skirt of the first mentioned shutter between 2 o'clock and 4 o'clock.

Similarly, between 8 o'clock and 10 o'clock, there is the smaller radius half portion of the skirt which appears at the top right-hand corner B of the shutter in Figure 3 and its greater radius portion fits behind the skirt of the first mentioned shutter between 5 o'clock and 7 o'clock.

The skirt at the corner A which is entirely at the greater radius fits behind the skirts of the second and third shutters extending between 8 o'clock and 1 o'clock. The second 36 of the dotted curved lines denotes the rear side of the larger radius skirts and the outermost two dotted lines 37, 38 indicate the supporting column 29 which fits behind the skirt assemblies. This arrangement of skirts enables the corners of the shutters to fit easily together over the tops of the supporting columns without any slots having to be cut therein, thus simplifying assembly arrangements. The change in horizontal level shown in Figure 6 accommodates the overlapping of the shutters. The first and fourth shutters are of a constant horizontal ievel, the first shutter fitting over the lower level portions of the adjacent shutters and the fourth shutter fitting under the upper level portions of the adjacent shutters.

In Figure 5, it will be seen that a large depth of concrete is provided over the nesting troughs, thus enabling two vertically separated reinforcing bars to be provided, giving the complete structure great rigidity.

The shallower concrete in Figures 1 and 2 would not allow two such vertically separated bars and hence the greater rigidity is not available.

Claims

1. A shutter for supporting concrete prior to setting, the shutter comprising a sheet formed with a dome-shaped central area.

2. A shutter as claimed in claim 1 wherein the central area is formed with apertures for providing fluid flow passages therethrough.

3. A shutter as claimed in claim 2 wherein the central area is formed with conduits at the top of which said apertures are located.

4. A shutter as claimed in claim 3 wherein the tops of the conduits are at the same level.

5. A shutter as claimed in any one of claims 2 to 4 wherein the apertures are arranged in a grid pattern.

6. A shutter as claimed in claim 5 wherein the apertures are arranged uniformly in two orthogonal directions.

7. A shutter as claimed in any one of the preceding claims comprising trough means along one opposite pair of sides of the sheet.

8. A shutter as claimed in claim 7 comprising a trough provided along two opposite pairs of sides of the sheet.

9. A shutter as claimed in claim 7 or claim 8 wherein the trough means has a flat bottom.

10. A shutter as claimed in any one of claims 7 to 9 wherein the trough means on one side of the sheet is shaped to fit into a trough on the opposite side of an adjacent said sheet.

11. A shutter as claimed in any one of the preceding claims comprising concave quadrants formed at the corners of the sheets.

12. A shutter as claimed in claim 11 comprising a skirt at the periphery of the sheet at the quadrants only.

13. A shutter as claimed in claim 12 wherein the skirts of quadrants at two opposite corners have radii differing by at least the thickness of the sheet.

14. A shutter for supporting concrete prior to setting substantially as hereinbefore described with reference to the accompanying drawings.

14. A shutter as claimed in claim 12 wherein the skirts at two opposite corners of the sheet are formed in two portions, one portion having a radius greater than that of the other portion by at least the thickness of a sheet.

15. A shutter as claimed in claim 14 wherein the level of the sheet is stepped adjacent the junction of the two portions of the skirt by an amount equal to at least the thickness of the sheet.

16. A shutter for supporting concrete prior to setting substantially as hereinbefore described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS 1. A shutter for supporting concrete prior to setting, the shutter comprising a sheet formed with a dome-shaped central area and trough means along one opposite pair of sides of the sheet, the trough means on one side of the sheet being shaped to fit into a trough on the opposite side of an adjacent said sheet.

2. A shutter as claimed in claim 1 comprising a trough provided along two opposite pairs of sides of the sheet.

3. A shutter as claimed in claim 1 or claim 2 wherein the trough means has a flat bottom.

4. A shutter as claimed in any one of claims 1 to 3 wherein the central area is formed with apertures for providing fluid flow passages therethrough.

5. A shutter as claimed in claim 4 wherein the central area is formed with conduits at the top of which said apertures are located.

6. A shutter as claimed in claim 5 wherein the tops of the conduits are at the same level.

7. A shutter as claimed in any one of claims 4 to 6 wherein the apertures are arranged in a grid pattern.

8. A shutter as claimed in claim 7 wherein the apertures are arranged uniformly in two orthogonal directions.

10. A shutter as claimed in claim 9 comprising a skirt at the periphery of the sheet at the quadrants only.

11. A shutter as claimed in claim 10 wherein the skirts of quadrants at two opposite corners have radii differing by at least the thickness of the sheet.

12. A shutter as claimed in claim 10 wherein the skirts at two opposite corners of the sheet are formed in two portions, one portion having a radius greater than that of the other portion by at least the thickness of a sheet.

13. A shutter as claimed in claim 12 wherein the level of the sheet is stepped adjacent the junction of the two portions of the skirt by an amount equal to at least the thickness of the sheet.