Technical Field

The present invention relates to concrete formwork. In particular, the present invention relates to a device for use in forming concrete for use in building construction. of the Invention

The following references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art. In particular, the following prior art discussion does not relate to what is commonly or well known by the person skilled in the art but assists in the understanding of the inventive step of the present invention of which the identification of pertinent prior art proposals is but one part.

The use of concrete in building construction is widely employed. It is common building practice to provide concrete slabs which provide structural overhanging portions or sills, which extend beyond the side surface of the building and overhang windows or glazing panels or which provide sills. For such overhanging portions or sills, it is good building practice to provide a drip channel or groove on the lower surface of the slab. The drip channel acts to obstruct water running along and adhering to the concrete’s surface from reaching the window or glazing and causes the water to fall under gravity, in other words, drip.

Drip channels can be, and are, added to existing buildings by roughly chiselling a channel in the lower overhanging surface. Ideally, the drip channel can be provided in the concrete as the concrete slab is formed.

An example of a typical method for creating a drip channel is illustrated in Figure 1. The structural panel is formed by pouring wet concrete into a formwork and allowing the concrete to set. The formwork is typically formed of a flat lower surface, such as a wooden board. A fillet is placed on the lower surface to form the drip channel. The fillet (as shown) can be an elongated wooden strip having a triangular wedge-shaped profile. A vertical wooden board defines the edge of the concrete panel. This vertical board is supported by placing a timber support against it. A second fillet can be provided to form a bevel corner in the concrete slab. In practice, this arrangement can prove flawed for a number of reasons. For example, the fillet can often move during the pour of the concrete, thereby not forming an ideal drip channel as the concrete sets. Similarly, the vertical board is known to slip and not provide an even vertical surface, thereby not providing an ideal edge to the concrete as it sets.

The present invention seeks to provide a device for use in concrete formwork which may ameliorate the foregoing shortcomings and disadvantages or which will at least provide a useful alternative.

Summary of the Invention

According to one aspect of the invention, there is provided a device for use in concrete formwork, the device having an elongated and substantially planar base; along or near a first elongated side of the base is provided a protruding formation extending from the base; along a second elongated side of the base is arranged a channel formation adapted to receive and support a board; wherein, when concrete is poured onto the device the protruding formation forms a drip channel offset from the first elongated side.

It is preferred that the device of the invention has an angled surface located outside the channel formation for forming a bevel corner in the concrete slab to be formed. The channel formation itself may have gripping features adapted to grip and secure a received board. In this embodiment, the gripping features may comprise elongated teeth formations, preferably formed on the inside of the channel walls. The channel walls may be parallel to each other. In another embodiment, one or both the channel walls may be inclined towards the channel, to enhance gripping of the board when inserted into the channel. The protruding formation along or near the first elongated side of the device preferably has a triangular profile. For this embodiment, it is preferred that the triangular profile is that of an isosceles triangle with a base longer than the other two sides. As an example, the base may measure about 25 mm and each of the other two sides may measure about 18 mm.

The device of the invention may be made of any suitable material. It is preferably made of suitable plastic material, such a polyvinyl chloride (PVC). In this embodiment, the device may be made by extrusion moulding or other suitable method.

The invention also provides a method of forming a concrete slab having a drip channel, comprising the steps of:

- using the device of the invention in formwork for the slab;

- inserting a board in the channel formation of the device;

- pouring concrete into the formwork;

- allowing the concrete to set; and removing the formwork.

Brief Description of the Drawings

The invention may be better understood from the following non-limiting description of a preferred embodiment, in which:

Figure 1 shows an elevation of a prior art arrangement for forming a concrete slab with a drip channel, according to the prior art;

Figure 2 shows a perspective view from one side of a device according to a preferred embodiment of the present invention;

Figure 3 shows a perspective view from the front of the device of Figure 2; and

Figure 4 shows details of the channel formation of the device of Figures 2 and 3.

Detailed of the

Figure 1 shows a prior art arrangement of formwork for a concrete slab having a drip channel. In this arrangement, first fillet 10 is an elongated timber strip which is nailed or otherwise attached to a flat lower surface, being wooden board 12. The purpose of fillet 10 is to form a drip channel in concrete slab 16.

Vertical wooden board 18 defines the edge of the concrete slab 16 and is supported by placing timber support 20 against it. Second fillet 22 can be provided to form a bevel corner in the concrete slab 16.

Once concrete slab 16 has set, timber support 20, wooden board 12 and fillets 10 and 22 are removed.

Setting up the formwork for the prior art arrangement is time consuming, requiring accurate and stable placement of fillets 10 and 22, proper retention of vertical board 18 in position and stability of timber support 20. If any of these is unstable or inadequately retained in position, the resulting slab 16 may suffer from an inadequately formed drip channel, an uneven vertical edge which can chip or crack, and a badly formed bevel.

A preferred embodiment of a device for making concrete formwork is shown in Figure 2.

The device 24 has an elongated planar base 26. Adjacent one elongated side 28 of the device 24 is a protruding formation 30. This protruding formation 30 forms the drip channel in the concrete formwork when concrete is poured onto device 24 and allowed to set.

Protruding formation 30 is shown as having a triangular wedge-shaped profile which would form a V-shaped drip channel in the concrete slab when set. It will be appreciated that alternative profile shapes could be employed depending upon the required nature and shape of the drip channel required.

Arranged adjacent the other elongated side of the device is an integral channel formation 32. The channel formation 32, in use, receives and supports a board or other flat material (not shown) to define an edge for the concrete formwork.

As shown, channel formation 32 is defined by a first substantially vertical wall 34 extending from and along side 36 of the device 24 and a second wall 38 extending substantially vertically and running approximately parallel with first wall 34. As shown, second wall 38 is preferably provided with an angled outside surface 40, which forms a bevel corner for the concrete slab when formed and set.

Referring to Figures 2 and 3, channel formation 32 is provided with gripping features, shown in the form of elongated teeth 42 on each of walls 34 and 38, to assist in gripping and retaining a received board (not shown). It will be appreciated that alternative forms of gripping features could be employed.

In this embodiment, Figure 3 shows examples of dimensions. First wall 34 is about 27 mm high, while second wall 38 is substantially shorter. Floor 44 of channel formation 32 is about 17 mm wide. The base of angled outside surface 40 is about 18 mm. and is spaced from protruding formation 30 by about 57 mm. Protruding formation 30 is about 25 mm at its base while each side is about 18 mm.

The detail of channel formation 32 shown in Figure 4 shows that first wall 34 is not exactly parallel to second wall 38 but is inclined at an angle of about 88 degrees towards second wall 38. This helps elongated teeth 42 to more firmly grip the received board (not shown). Note that only some of teeth 42 are labelled in Figures 3 and 4.

The height of second wall 38 is about 18 mm in Figure 4. Planar base 26 is about 2 mm in height.

The device 24 is designed to be an integrally formed unit. It will be appreciated that a variety of suitable materials can be employed for manufacturing the device. Preferred embodiments employ plastic materials, such as PVC, formed using suitable techniques, such as extrusion moulding.

The device is preferably formed in lengths of approximately 3m. For longer lengths of formwork, more than one device can be laid end-to-end. The preferred materials of the device would allow it to be cut to required length. In exemplary embodiments, fracture formations could be provided at selected lengths of the device to facilitate ease of cutting.

The term “comprise” and variants of that term such as “comprises” or “comprising” are used herein to denote the inclusion of a stated integer or integers but not to exclude any other integer or integers, unless in the context or usage an exclusive interpretation of the term is required.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. All such variations and modifications are to be considered within the scope and spirit of the present invention the nature of which is to be determined from the foregoing description. An example is the elongated planar base, which may extend beyond the protruding formation designed to form the drip channel in the concrete slab.

Industrial Applicability

It will be apparent to a person skilled in the art that embodiments of the device of the invention can overcome the flaws in the prior art arrangement of Figure 1 while providing a far more time-efficient way of forming a concrete slab with a well-defined drip channel and bevel and an even vertical edge.