A BUILDING MOULD B28B, E04B, E04G

TECHNICAL FIELD

This invention relates to moulds used primarily, though not exclusively, for the construction of concrete slabs

BACKGROUND ART

Building moulds or shutters as they are known in the art are used to form concrete slabs with a cavity. By adding a protrusion on to the shutter, a cavity can be formed in the soffit of the slab, which extends from the base of the slab. Existing shutter systems use a coffer shutter. The cavity formed from such shutter is known as a coffer slab in the art.

The coffer shutter has a single protruding trough portion. Use of the shutter is viable when slab depth is greater than 350mm. Use of this shutter is therefore common when using heavy loads or using slabs with long spans, and where slab depth is not a critical factor. Due to the cavities created from such shutters, many vertical reinforcement rods are required to increase the slabs shear capacity. To this extent flat slabs, which do not have cavities, do not require such extensive shear reinforcing, but rather local shear reinforcing in specially calculated zones near the column.

Use of moulds minimizes the amount of concrete used when constructing a slab. This results in the reduction of slab weight (dead load), which in turn

reduces the amount of transverse reinforcing steel required to carry the slab. An additional benefit is the potential reduction of column and foundation size.

Use of single protrusion moulds for slab depths less than 350mm would not be viable. This is due to a decreased accuracy of mould configuration, additional labor costs and construction time associated with securing a greater number of moulds when compared to a mould of the invention.

The present invention seeks to provide a shutter for use in slab construction, where slab depth is substantially less than 350mm, and the slab would otherwise have been a conventional flat slab.

DISCLOSURE OF INVENTION According to one aspect of the invention there is provided a building mould comprising a base having a plurality of protruding portions.

Preferably there are at least four protruding portions.

Preferably the protruding portions allow a building substrate, such as concrete to poured in between and on top of the protruding portions, in use thereby obviating the need for shear reinforcing, alternatively reducing the amount of shear reinforcing needed, when compared to a single protrusion coffer mould, in use.

Preferably each protruding portion has a cavity, which defines a recess in the base.

Conveniently the base has at least one raised portion situated between the protruding portions.

Conveniently the base has at least two raised portions on opposing sides of the mould. In use, these raised portions act as spacer blocks for resting reinforcing rods thereon.

Preferably each protruding portion tapers from the base to its free end. Alternatively the protruding portion may be anyone of a semi-spherical, rectangular or generally square in shape

Preferably the external height of the protruding portions from the base is between 125mm and 325mm.

The mould may be made from fiberglass, aluminum, plastics or other suitably stiff and sturdy materials.

According to one aspect of the invention there is provided a concrete flat slab with a plurality of recesses extending from its underside.

According to a further aspect of the invention there is provided a method of constructing a concrete slab having a plurality of recesses on its underside comprising the steps of:

- placing a building mould on to a scaffold, the mould comprising a base and a plurality of protruding portions; - pouring concrete on to the mould to form the slab; and

- removing the mould once the concrete has set.

Preferably the method comprises the step of placing reinforcement bars along the base in between the protruding portions before pouring the concrete.

Further features, variants and/or advantages of the invention will emerge from the following non-limiting description of examples of the invention made with reference to the accompanying schematic drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a perspective top view of a shutter;

Figure 2 shows a perspective side view of the shutter in Figure 1 ;

Figure 3 shows a side section of the shutter in Figure 1 along the line 3-3, on a scaffold; Figure 4 shows an underside view of a second embodiment of the shutter; Figure 5 shows a perspective top view of the shutter in Figure 4; and Figure 6 shows a perspective underside view of the shutter in Figure 4.

DESCRIPTION OF ILLUSTRATED EMBODIMENTS

Figures 1 to 3 show a building mould or "shutter" 10 having a base 12 and four protruding portions 14. The protruding portions each have a cavity 16, which defines a plurality of recesses in the base. These recesses are visible from the underside 18 of the base.

Figure 3 shows the shutter secured on top of a scaffold 20. In use, steel rods 22 are placed on the topside 24 of the base, between the protruding portions. These rods provide structural integrity and provide the moment resistance of the slab. Concrete is then poured on to the mould until the specified slab depth is reached. Once the concrete has set, the mould is removed. The resulting cavities are viewable from the slab's underside (not shown).

Figures 1 to 3 show a shutter having the following dimensions of the protruding portions: length 250mm, width 250mm and height 125mm and 325mm spaced apart from each other. Such a shutter would be used when producing a concrete slab having a slab depth of between 250 to 375mm.

Figures 4 to 6 show another shutter embodiment comprising nine protruding portions. The shutter has a network of ribs 26 on the underside both on the base and extending downwards along the cavities. The ribs provide the shutter with structural rigidity.

Shutters may vary as to the number and dimensions of the protruding portions. Use of a specifically dimensioned shutter will depend on the slab construction requirements.

The shutter is made from fiberglass, but may be made from other suitable light-weight and sturdy materials such as aluminum and plasties. The shutter of the invention is suitably configured and dimensioned to construct a flat slab, using only the shutter and a scaffold mat. The need for vertical shear reinforcing steel rods is thereby eliminated resulting in cost savings.

It will be appreciated that the slab cavities have aesthetic value in addition to their functional and economic benefits. The protruding portions of the shutter may be shaped to provide slabs of varying cavity shapes, including square, rectangular, oval and spherical shaped cavities.

The invention is not limited to the precise details described above and shown in the drawings. Modifications may be made and other embodiments developed without departing from the spirit of the invention. In particular, there may be raised portions extending between the protrusions, on opposing sides of the mould. Such raised portions act as a spacer block for resting reinforcing rods thereon. The summary of invention and claims form an integral aspect of the description of the invention.