GB2551573A

GB2551573A - An apparatus and method for void forming within a casting

Info

Publication number: GB2551573A
Application number: GB1611011.6A
Authority: GB
Inventors: Varnava Varnavas
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-06-24
Filing date: 2016-06-24
Publication date: 2017-12-27
Also published as: GB201611011D0; WO2017221033A2; EP3475042A2; WO2017221033A3

Abstract

An apparatus 10 for forming a void or voids in a casting during a casting process comprises at least one body 12. The body has a substantially continuous outer surface, formed such that the outer surface can be penetrated, with the original shape of the body 12 substantially retained when penetrated, and a penetrating and securing means 13, 14 to position in a casting mould and configured to penetrate the at least one body 12 to secure the at least one body 12 to the penetrating and securing means 13, 14 to retain the body 12. Further, claims include a method of creating an apparatus for forming a void or voids in a casting during a casting process. A method of forming a body suitable for use as part of an apparatus for a void or voids in a casting is included. Also claimed is a body suitable for use as part of an apparatus for forming a void in a casting characterised by the body comprising at least one area of weakness.

Description

AN APPARATUS AND METHOD FOR VOID FORMING WITHIN A CASTING

Field of the Invention

The invention relates to an apparatus for forming a void or voids in a casting during the casting process. More particularly, the invention relates to an apparatus for forming a void or voids in a cast concrete slab during the casting process. Even more particularly, the invention relates to an apparatus for forming a void or voids in specific locations in a concrete cast slab during the casting process. The invention also relates to a method of forming a void or voids in a concrete casting during the casting process. The invention also relates to a method of forming balls suitable for use as part of an apparatus for forming a void or voids in a cast concrete slab during the casting process.

Background to the invention

The use of reinforced concrete slabs for construction purposes is well-known. Slabs of this type are used for example as flooring/ceiling slabs in multi-story buildings, or similar structures. In order to maximise room size, and to reduce the amount of weight that is supported, floor/ceiling slabs are generally manufactured to be as broad/wide and thin as possible. A concrete slab used in construction - e.g. as a horizontal flooring/ceiling slab supported in use at its edges or corners - will need to support both its own weight and the weight of any other elements located on it (internal walls or dividers, office furniture, people or, in the case of, for example, a car park, road vehicles etc.) while remaining structurally sound. The weight-bearing ability of a concrete casting is a significant limiting factor for the maximum dimensions of slabs of this type.

One well-known technique for reducing the weight of a slab without unduly decreasing the structural strength is to create voids within the slab during the casting process. This reduces the amount of concrete (and therefore the weight) for a given size of slab, and therefore makes it possible to increase the width/breadth of the slab without significantly affecting its load-bearing ability. One way of creating voided structures of this type is by using High-Density Polyethylene (HDPE) balls, held in position in a casting mould by a latticework or matrix of bars located above and below the balls. Concrete is poured into the casting area over and around the balls, and the bars prevent the balls from moving out of position (e.g. from floating on top of the concrete as it is poured). The casting area can be subjected to vibration to remove air from the body of the concrete during pouring. The concrete is poured during a single pour or multiple pours to cover the balls, which then act as voids within the concrete slab once the concrete has set. A slab of this type is often referred to as a ‘bi-axial hollow slab’, with manufacturers such as Bubble Deck® producing apparatus suitable for carrying out this construction method.

If a particular building or structure requires built-in service channels or ducting, it can be difficult to emplace and route these when using the HDPE ball and latticed bar apparatus and method outlined above. It can also be difficult to create a bespoke slab, with voids formed exactly where required, when using a pre-formed system - i.e. it can be difficult to alter the position of the spaces in a pre-formed lattice or matrix, in order to alter the positioning of the HDPE elements held in position by the lattice.

It is an object of the present invention to provide an apparatus for forming a void or voids in a casting during the casting process which helps to overcome the problems outlined above, or which at least provides the public with a useful choice.

It is a further object of the invention to provide a method of forming a void or voids in a casting during the casting process which helps to overcome the problems outlined above, or which at least provides the public with a useful choice.

It is a yet still further object of the present invention to provide a method of forming balls suitable for use as part of an apparatus for forming a void or voids in a cast concrete slab during the casting process which helps to overcome the problems outlined above, or which at least provides the public with a useful choice.

Summary of the Invention

In a first broad independent aspect, the invention provides, an apparatus for forming a void or voids in a casting during a casting process, the apparatus comprising: at least one body comprising a substantially continuous outer surface, the body formed such that the outer surface can be penetrated, with the original shape of the body substantially retained when penetrated; a penetrating and securing means, configured to penetrate the at least one body to secure the at least one body to the penetrating and securing means, the penetrating and securing means further configured for positioning in or on a casting mould so as to retain the body in position within the mould.

Preferably, the penetrating and securing means comprises at least one elongate member. Further preferably the elongate member comprises a reinforcing bar. The penetrating and securing means can be passed relatively easily through the body to secure a body in position.

Optionally the elongate member has a diameter of from 6mm to 12mm to allow the elongate member to have good strength.

Preferably, the at least one body is substantially spherical to minimise the material required for a given volume of body.

Alternatively preferably, the at least one body is a partial sphere to allow stacking of bodies. Further alternatively preferably, the partial sphere comprises a sphere having at least one absent spherical cap. Still further alternatively preferably, the partial sphere comprises a sphere having substantially diametrically opposed absent spherical caps.

Further alternatively preferably, the at least one body comprises a generally cylindrical shape with outwardly curving sides. Yet further alternatively preferably, the at least one body comprises a substantially vertically aligned passage formed in the top surface of the generally cylindrical shape, and a cylindrical extension that extends from the bottom surface of the body, the extension and the passage equivalently sized and forming a mutual connecting means configured such that the extension on one body can fit into and connect with a corresponding passage on a separate body.

Still yet further alternatively preferably the extension and the passage are threaded so as to form the mutual connection means.

Optionally, the passage or the extension or both are aligned with the main axis of the body. Alternatively optionally, the passage or the extension or both are offset from the main axis of the body.

Preferably, the at least one body comprises a plurality of bodies, in use arranged at spaced intervals on the penetrating and securing means to provide regular voids within a body of concrete.

Optionally, the at least one body comprises a plurality of bodies, in use arranged in stacks of two or more bodies to give flexibility for the use of the apparatus and thickness of concrete produced.

Preferably, the apparatus further comprises a spacing means configured to hold the bodies at spaced intervals from each other. Further preferably, the spacing means comprises an elongate body having two or more U-shaped sections formed therein to aid fixture to the elongate means. Yet further preferably, the elongate body comprises a straight central body portion and two U-shaped end portions, the bends that form the U-shaped end portions all in substantially the same plane. Still yet further preferably, the U-shaped end portions are formed so that the outer side of the body of each of the ‘U’-shaped end portions extends for substantially the same distance each side of the straight central body portion.

Optionally, the elongate body comprises two U-shaped sections and a substantially straight central section between the U-shaped sections that separates the U-shaped sections, the ends of the elongate body extending from the outer sides of each of the ‘U’ portions, parallel to and in line with one another and the central section, the elongate body substantially planar. Further optionally, the centre point of the flat central section bisects the elongate body.

Conveniently the spacing means comprises two connected substantially flat planar sections arranged in two parallel planes, one behind the other and spaced apart a short distance. Further conveniently the flat planar sections comprises two U-shaped sections separated by a substantially straight central section, an end section extending from the outer sides of each of the ‘U’ portions, the ends sections parallel to and in line with one another and the central section, a connecting and spacing section connecting between the flat planar sections so that the flat planar elements are arranged one behind the other in two spaced-apart parallel planes, with the U-shaped sections aligned with one another. Yet further conveniently, the flat planar sections and the connecting and spacing section are formed from a single piece of material, the connecting and spacing section forming a ‘U’-bend at substantially the mid-point between the two flat planar sections.

Preferably, the at least one body or bodies are substantially hollow to minimise weight of the concrete formed.

Preferably, the interior(s) of the at least one body or bodies are at least partially solid to provide strength to the body or bodies.

Optionally, the at least one body is at least partly formed from Low density polyethylene (LDPE) to allow a body to be relatively easily manufactured. Further optionally, the at least one body is formed by rotomoulding.

Preferably, the bodies are arranged on the penetrating and securing means such that a majority of the body is above the penetrating and securing means in use which provides stability to the bodies during the concrete-forming process.

Preferably, the substantially continuous outer surface of the body further comprises at least one area of weakness configured to allow penetration of the body by the penetrating and securing means.

According to a second aspect of the invention there is provided a method for forming a void or voids in a casting during a casting process, comprising the steps of: (i) positioning at least one body on a penetrating and securing means, the body comprising a substantially continuous outer surface, the body formed such that the outer surface can be penetrated by the penetrating and securing means with the original shape of the body substantially retained when penetrated, the at least one body and the penetrating and securing means configured such that the body will be retained in position on the penetrating and securing means in use; (ii) positioning the penetrating and securing means and the at least one body within a casting mould; and (iii) pouring concrete into the mould around the penetrating and securing means and the at least one body such that the body creates voids in the finished concrete cast.

Optionally, the at least one body and the penetrating and securing means are formed in accordance with the apparatus as described above. Further optionally, the penetrating and securing means comprises at least one substantially straight elongate member.

Alternatively further optionally, the penetrating and securing means comprises at least one curved elongate member.

According to a third aspect of the invention there is provided a method during a casting process, comprising the steps of: (i) pushing at least one body onto at least one hollow length of thin-walled pipe, the body comprising a substantially continuous outer surface, the body formed such that the outer surface can be penetrated by the hollow length of pipe with the original shape of the body substantially retained when penetrated, the at least one body and pipe configured such that the body will be retained in position on the pipe; (ii) passing a bar into and along substantially the length of the pipe; (iii) removing the pipe to leave the body in position on the bar.

Optionally the at least one hollow length of thin-walled pipe comprises a pair of pipes, arranged in parallel to one another.

Preferably, the pipes have a length of substantially six metres.

Preferably, the at least one body comprises a plurality of bodies.

Optionally, the bodies are located at spaced apart intervals along the length of the pipe or pipes.

According to a third aspect of the invention there is provided a method for use as part of an apparatus for forming a void or voids in a casting, comprising the steps of: (i) attaching at least one heat-conductive patch to the exterior surface of a rotomould in a location substantially equivalent to a location where the body will be pierced in use; (ii) moulding a body within the mould.

Preferably, the patches are screwed into position using screws to facilitate fitment and heat transfer. Further preferably, the screws pass outwards from within the mould, to minimise interference with the body formation.

Preferably, the patch or patches are at least partly formed from Teflon (RTM) to reduce heat transfer.

Optionally, the patch is screwed into position via a threaded plug configured to create an aperture in the skin of the body as the body is formed. This plug definitively defines the size of an aperture within the body. Further optionally, the patch or patches are at least partly formed from Teflon (RTM).

According to a fourth aspect of the invention there is provided a body for use as part of an apparatus for forming a void in a casting during a casting process, comprising a substantially continuous outer surface formed such that the outer surface can be penetrated by a penetrating and securing means, with the original shape of the body substantially retained when penetrated, the substantially continuous outer surface of the body further comprising at least one area of weakness configured to allow penetration of the body by the penetrating and securing means.

Preferably, the body is substantially spherical to minimise material needed in construction of the body. Optionally preferably, the body is a partial sphere to allow better vertical stacking characteristics.

Further preferably, the partial sphere comprises a sphere having at least one absent spherical cap to allow better stacking in transportation and use

Yet further preferably, the partial sphere comprises a sphere having substantially diametrically opposed absent spherical caps.

Optionally, the body has a generally cylindrical shape with outwardly curving sides.

Preferably, the body comprises a substantially vertically aligned passage formed in the top surface of the generally cylindrical shape, and a cylindrical extension that extends from the bottom surface of the body, the extension and the passage equivalently sized so as to form a mutual connecting means configured such that the extension on one body can fit into and connect with a corresponding passage on a separate body. This provides increased flexibility in respect of the void volume produced within a given thickness of a slab which can be produced. Further preferably, the extension and the passage are threaded so as to form the mutual connection means.

Optionally, the passage or the extension or both are aligned with the main axis of the body.

Conveniently, the passage or the extension or both are offset from the main axis of the body.

Preferably, the body is substantially hollow to increase the volume of the void formed in the concrete.

Conveniently, the interior of the body is at least partially solid to provide strength to the body.

Preferably, the body is at least partly formed from LDPE to allow for ease of manufacture and sufficient strength to the body.

Preferably, the body is formed by rotomoulding to allow for ease of manufacture and incorporation of required features.

Brief Description of the Figures

The invention is now described with reference to the accompanying drawings, which show, by way of example only, one embodiment of an apparatus for forming concrete. In the drawings:

Figure 1 shows an embodiment of an apparatus for forming a void or voids in a casting during a casting process prior to concrete addition, the apparatus comprising a number of generally spherical void-forming bodies, each with a substantially continuous outer surface formed such that the outer surface can be penetrated with the original shape of the body substantially retained when penetrated, the void-forming bodies positioned in rows at spaced intervals along paired elongate bars positioned in parallel to one another, the bars penetrating and securing the bodies in position, the bars held apart by spacers, the bars and bodies forming the apparatus and ready for positioning in a mould where required.

Figure 2 illustrates a side view of a vertical section through a concrete slab formed using an apparatus similar to that of figure 1, showing detail of the positioning of the bars within the body, towards the lower side of the body, the void-forming body of this figure being a truncated sphere rather than a substantially full sphere as is shown in figure 1;

Figure 3 illustrates a side view of two of the truncated or partially spherical void-forming bodies stacked one above the other to form a variation of the apparatus of figure 1;

Figure 4 illustrates a top view illustrating a method by which the void-forming bodies can be located on the bars, the bodies pushed onto two parallel lengths of hollow thin-walled pipe, the bars then inserted into the open or free ends of the pipe and passed along the lengths of the pipe, the pipes then removed to leave the bodies in position on the bars.

Figure 5 illustrates a cut-away side view of fitment of a Teflon (RTM) patch to a mould that is used to form the void-forming bodies, the teflon patch acting to draw heat away from the mould so that when the body is formed in the mould that section under the patch will have a thinner wall than the remainder of the body, the teflon patch held in position via a screw passing through the wall of the mould from the inside outwards; and

Figure 6 illustrates a cut-away side view of an alternative means of fitment of a Teflon (RTM) patch where the patch is held in position via a threaded plug.

Figure 7 shows a variation of the apparatus of figure 1, the spacers of this variation holding the paired elongate bars at the required spacing, and holding the rows of bars and generally spherical void-forming bodies at the required spacing.

Figure 8 shows another embodiment of an apparatus for forming a void or voids in a casting during a casting process prior to concrete addition, the apparatus comprising a void-forming body formed as a generally cylindrical shape with outwardly curving sides that appear semi-circular in side view, to blend with the flat top and bottom surfaces, the body having a short, vertically aligned passage formed in the centre of the top surface of the body, and a short cylindrical extension that extends from the bottom surface of the body and forms a male connector, the extension and the passage equivalently sized or correspondingly sized so that the extension can fit snugly into a passage on another identical body, the extension and passage mutually threaded, three of the bodies shown one above the other in a vertical stack.

Figure 9 shows two of the bodies of figure 8 shown connected or threaded together to form a stack of two bodies.

Figure 10 shows three bodies, similar to those of figure 9 but each having a different height, the extension and passages on each body the same size as those on the other bodies so that the bodies can be connected to form a stack, a set of spacers similar to those of figure 1 also shown extending upwards from underneath the stack.

Detailed Description of the Figures

An embodiment of apparatus, generally referenced 10, for void forming during a casting process is shown in Figure 1. This embodiment of the apparatus 10 is used for creating concrete slabs that contain multiple voids.

The void forming apparatus 10 has two main parts: void-forming bodies 12, and a penetrating and securing apparatus 13. In use, the penetrating and securing apparatus 13 holds a number of the void-forming bodies 12 in position as concrete is poured over and around them. That is, the bodies 12 are connected to the penetrating and securing apparatus 13 as described below, so that the bodies 12 are held securely in position during the concrete slab forming process.

As shown in the figures, several different types of body can be used. Each of these is a hollow body, with a substantially continuous outer surface. The continuous outer body is formed such that the outer surface can be penetrated, with the original shape of the body substantially retained when penetrated. It should be noted that ‘substantially continuous’ in the context of this specification means an unbroken or substantially unbroken surface, and is intended to cover a body which is mostly unbroken but which has apertures or holes that penetrate at least partially the skin or shell of the body. It should also be noted that although hollow void-forming bodies are described and shown, solid bodies with substantially continuous outer surfaces could also be used, as could also bodies having a foam-like interior structure; such as is formed of a blown polyurethane.

The first type of body is a generally fully spherical body 12a as shown in Figure 1. The second type is a partially spherical body 12b as shown in figure 2. The partially spherical body 12b has the shape of a truncated sphere, with absent spherical caps on diametrically opposed sides. That is, the top and the bottom of the sphere are missing or absent, ‘chopped off along parallel horizontal planes each side of the horizontal plane that passes through the centre of the sphere.

In this embodiment, each of the bodies or types of body 12a, 12b are formed by rotomoulding, from Linear Low-Density Polyethylene (LLDP) or from recycled polyethylene. The advantage of using this material is that it can take point loads, and can be penetrated without substantial damage to the structure outside of the immediate piercing/penetration site, and without the penetration changing the overall shape of the outer surface.

The penetrating and securing apparatus 13 is in this embodiment is primarily formed from a steel reinforcing bar or bars 14 having a diameter between 6mm and 12mm.

In use, in order to create a concrete slab, a number of the bodies 12 are positioned or ‘skewered’ in a row, at spaced intervals, along a length of the bar 14, or along two or more bars 14 positioned in parallel to one another, to form the apparatus 10. The apparatus 10 is then located within a mould where required, so that voids will be created where required in the finished slab (i.e. once concrete has been poured). That is, the bars 14 and attached bodies 12 can be moved and angled as required within the mould, and the bodies 12 can be spaced along the length or lengths of the bars 14 as required. A bar 14 can be up to 12m in length and used as provided or cut to the required length.

Two or more of the assembled apparatuses 10 can be used to form a matrix or grid of bodies 12 on the bars 14 within the mould, the apparatuses placed side-by-side in the mould. The apparatuses 10 can be located side-by-side, or, as shown in figure 3, these can be stacked, so that two (or more) rows of the bodies are located directly on top of one another within the mould. Such a stacked arrangement enables the production of thicker and larger slabs, such as are suitable for car parks, as the need for certain supporting beams in the car park is obviated, allowing the finished car park to house a greater number of cars.

Once all the elements are in the required position, cement is poured into the mould around them. The void-forming bodies 12 act as voids (that is, they create voids, or nonconcrete spaces) within the concrete, as the concrete hardens around them to create the slab.

An apparatus such as the specific embodiment of apparatus 10 as described above is easy to install, and can easily be tailored to position the voids where required in a finalised slab. As the bodies 12 are fixed in position on the bars 14, there is less chance of these floating or moving out of position as the concrete is poured. The bars 14 act as a penetrating and securing apparatus.

It has also been found to be advantageous to use spacing elements 19a - c to retain the bodies in position, both on the bars 14, and to keep the assembled apparatuses 10 in a correctly spaced arrangement. In the preferred form, the spacers or spacing elements 19 consist of wire lengths, bent to shape so that they contain two or more U-shaped portions at specific intervals. The bars 14 are positioned in the U-shaped portions (or rather, the spacing elements 19 are located onto the bars 14) to retain the spacing elements in the required spaced arrangement. As shown in figure 1, the spacing elements 19 act both to keep adjacent or side-by-side rows of bars 14 and attached bodies 12 in the correctly spaced arrangement, and also to keep adjacent balls on the same bar or set of bars in the correctly spaced arrangement. Spacing element 19a is used to keep the bars 14 which form a single row pair in the correctly spaced arrangement, with that part of the body of the spacing element 19a between its U-shaped end portions extending between the U-shaped portions to keep the bars 14 in the correctly spaced arrangement. Spacing elements 19b keep adjacent ones of the apparatuses 10 (i.e. a single row of bars 14 and bodies 12) spaced apart from one another. Spacing elements 19c the same or similar as those described above can also be used to keep the bodies 12 in a correctly spaced arrangement along a length or lengths of bar or (parallel) bars 14 in a single apparatus 10 as well as in a vertical direction, out of the plane formed between adjacent parallel bars. The spacing elements of these embodiments are formed from a single strand of wire, bent appropriately. For example, in the embodiment pictured, spacing element 19a is formed with a straight central body portion and two U-shaped end portions, as outlined above. The bends all lie in the same plane - that is, the spacing element 19a can be laid on a flat planar surface with one side in continuous contact with the surface. The ‘U’ shape is formed so that the outer side of the body of the ‘U’ extends for approximately the same distance each side of the straight central body portion (i.e. ‘above’ and ‘below’ the straight central body portion). Spacing element 19b is formed in a similar manner to spacing element 19a, with the bends all lying in the same plane. The spacing element 19b has two central U-shaped sections, separated by a flat central section approximately the same width as the bases of the ‘U’ portions. The centrepoint of the flat central section lies on the centre line or bisecting line of the spacing element 19a. The ends of the wire that form the spacing element 19a extend from the outer sides of each of the ‘U’ portions, parallel to and in line with one another and the central section. The spacing element 19b can be used in this form as a flat planar element, or it can be ‘doubled’, with two of the flat planar sections arranged in two parallel planes, one behind the other, spaced apart a short distance.

This variation is formed from one single length of wire, bent into a ‘IT at the mid point (between the two flat planar sections), so the wire doubles back on itself and the two flat planar elements are arranged one behind the other in two parallel planes, with the ‘IT sections aligned with one another (i.e. the two sections are arranged so that one is directly behind the other - they are not offset), the free ends of the wire extending outwards from the same side.

Spacers such as those described have the advantages of being simple and quick to form, possibly on site (and can be easily formed to be used over ranges of dimensions as required - i.e. for different spacing distances), and easy to use.

It should be noted that other shapes of body other than the spherical bodies and truncated spherical bodies described above could also be used as required. For example, hemispherical or regular or irregular polygonal shapes could also be used, or the truncated sphere could have an absent spherical cap on one side only, and the plane of this cut-off could be aligned at any angle. It should also be noted that solid bodies as well as hollow bodies could also be used, and that these can be formed by any suitable method, such as rotomoulding, injection moulding, blow-moulding etc.

In the embodiments of the bodies described above, different sizes (e.g. spherical bodies of different diameters) are used as required in order to produce slabs of the required sizes.

In another embodiment of body as described in detail below and as shown in figures 8 to 10, the body is formed so that it can be used either by itself or in conjunction with other bodies of the same type.

In this embodiment, the body 100 is formed either as a spherical or truncated spherical body similar to that described above, or as a generally cylindrical shape with outwardly curving sides - that is, as a short cylinder with outwardly curved side walls that are semicircular in side view, to blend with the flat top and bottom surfaces. That is, a solid doughnut shape (no central aperture or hole).

The body 100 has a short, vertically aligned passage 101, preferably a dead-end or closed, formed in the centre of the top surface (i.e. in plan view, the body 100 and the passage 101 have a common central or main axis - they are aligned with the main axis of the body) that extends downwards into the body 100. A short cylindrical extension 102 extends from the bottom surface of the body 100 and forms a male connector. The extension 102 and the passage 101 are equivalently sized, so that the extension 102 can fit snugly into a passage 101 on another identical body 100.

The extension 102 and the passage 101 are fitted with a mutual connecting means that allows the extension 102 on one body to fit into and connect with the passage 101 on another equivalent body 100, or allows connection to a different type of body that has a correspondingly sized and shaped passage, or a correspondingly sized and shaped extension. This allows a number of the bodies 100 to be connected in stacks, on top of one another, as for example shown in figures 9 and 10.

The extension 102 and the passage 101 are mutually threaded in the embodiment shown in figures 8 to 10, to form the connecting means. In variations, the connecting means could be tabs or similar extending from the sides of the passage or the extension, formed so as to locate into slots or similar on the other of the extension or passage. The connecting means could also be a friction or interference fit between the extension and the passage, or the passage could be formed with an inwardly-extending lip or overhang that overlaps or interferes with a similar equivalent structure on the extension. The body 100 is in use penetrated or skewered from the side by bars 14 in the same or a similar manner to that outlined above for the first-described embodiment, and then positioned in a mould ready for casting.

The main body 100 has a height of substantially 10cm. The passage has a depth of 3cm, and the extension has a height, or extends for, substantially 3cm, so that when one body 100 is on top of another, with the extension 102 of the upper body fully located in the passage of the lower body, the underside of the upper body is in contact with the top surface of the lower body.

In use, two or more of the bodies 100 can be stacked and connected one on top of the other to achieve different heights of hollow body structure. These can be formed and emplaced as required to form voids of different sizes in concrete slabs - e.g. slabs of different thicknesses (the most commonly used slabs tend to be formed with thicknesses between 25cm and 60cm).

The body 100 as described above has a height or thickness of 10cm, with the extension 102 having a length or height of 3cm. Other standard sizes can also be used, for example the body could have a height of 5, 15 or 20cm. The dimensions of the passage and extension can be changed for these different sizes, or kept the same as for the embodiment described above, so that bodies of different sizes can be used with one another. The dimensions of the passage and extension can also be altered. For example, the passage could be formed all the way through the body, so that the body appears roughly toroidal or doughnut-shaped. The passages and extensions are in these embodiments on the centre line or main axis of the body. The passages and extensions could be offset from the main or centre axis of the body if required, in order to form specialist shapes in the mould.

The stacks of bodies (each stack formed from two or more of the bodies one on top of the other) are located and spaced apart in a mould in a similar manner to that described above for the first embodiment - that is, with a number of the stacks of bodies positioned or ‘skewered’ in a row, at spaced intervals, along a length of bar, with each of the stacks spaced apart or separated from others in the row and in adjacent rows by spacers or spacing elements the same as or similar to those described above.

It should be noted that a single bar such as bar 14 can be used, passing through the body 12 along a central or hemispherical axis of the body 12. However, it has been found that using two bars aligned in parallel to one another, and locating these so that they penetrate through the body 12 below the horizontal central plane, is advantageous as this positioning assists with retaining the body or bodies in position during the concrete pouring. However, the invention is not limited to this, and for certain uses, a single bar, passing through the body centrally or below the centre, can also be used.

An alternative embodiment, especially when there is a disc-like body 12b, of the way in which the bodies such as bodies 12 or 100 can be positioned on the bars 14 will now be described in detail and with reference to Figure 4. In this embodiment, the bodies are positioned on a pair of bars 14, the bars 14 arranged parallel to one another.

The method of positioning the bodies on the bars 14 is as follows: two hollow lengths of pipe 16 are positioned in parallel to one another. These are held in a fixed position at one (common) end of the two lengths of pipe 16, with the two opposite (common) ends free. The pipes 16 can be six metres in length or more and up to 12 m. The internal diameter of the pipes 16 is sufficient to receive the bars 14 therethrough, so that there is a reasonably close fit, but so that the bars 14 can be pushed or pulled through the pipe 16 easily (e.g. so that the bars 14 fit within the pipe 16 with a small to negligible gap around the bar 14). The walls of the pipes 16 are thin. A number of the bodies are then pushed onto the pipes 16 via the common free ends of the pipes 16, so that a line of bodies is formed on the pipes 16. The bodies are spaced apart at intervals along the length of the pipes 16 as required, with as many of the bodies as are required along the length of the pipes 16.

Once the bodies are in position, the bars 14 are passed into the pipes so that the bars 14 extend along substantially the full length of the pipes 16. The bodies and bars 14 are then held in their relatively spaced positions, and the pipes 16 are removed or pulled clear, so that the bodies are now located on and along the length of the bars 14, with the bars 14 passing through the bodies. The combination of bodies and bars 14 can then be placed in a mould ready for concrete pouring. As many of the body/bar combinations as required can be created. A single pipe 16 and bar 14 could be used rather than a pair, or three or more pipes and bars could be used, at angles or in parallel. Different lengths of pipe 16 could also be used, with different numbers of bodies, as required. Due to the viscosity of concrete, any gap between the bar 14 and body once the pipe 16 is removed is not a concern, as the concrete will not significantly seep into the hollow body through any gap. If the gap is considered to be significantly large, then this can be patched or plugged before the concrete is poured.

The concrete can be poured over the apparatus 10 to the desired depth with the apparatus 10 and shuttering located, usually, where it is desired the produced slab of concrete should be.

As an alternative, only a fraction of the concrete eventually required to form the slab can be poured around the bodies and spread to an even depth, less than that of the final slab. Once this initial concrete has set the remainder of the concrete can be added. The initial concrete adds to the stabilising effect on the void forming bodies so that the bodies remain in the correct position and do not move out of positon due to their buoyancy in the liquid concrete. This also allows for an alternative method of construction in that a slab can be partially formed and subsequently lifted into position for completion. This enables much of the liquid concrete to be produced, for example, at a lower level than the slab is needed, reducing the storage or transport of the liquid concrete at an elevated level.

In an alternative embodiment, the bars 14 are simply inserted through the bodies, without the use of a pipe 16.

In order to facilitate correct spacing of the bodies along a bar 14 then a spacer can be included, located about the pipe 16, and eventually the bar 14, the spacers acting to prevent adjacent balls from coming into too close contact with one another and especially to prevent adjacent bodies touching each other. This latter configuration would be disadvantageous as the contiguous engagement would prevent concrete from penetrating between adjacent bodies which would then lead to a line of structural weakness along the line of the bars 14. A spacer can be formed of steel, and is typically 1-1 Ocm in length, but can be chosen to suit the requirements of the article under construction.

Another advantage of the invention is that the invention can easily be adapted for use in casting curved slabs. The bars 14 that form the penetrating and securing means in embodiments of the invention can be formed into a curved shape or arc, with the bodies located (threaded, skewered) onto the curved bars in the same or a similar manner to that described above. The assembly thus formed can be located into an appropriately-shaped mould so that once the concrete is poured a curved slab is formed.

As outlined above, in an embodiment, the bodies or types of body 12a, 12b, 100 are formed by rotomoulding, from Linear Low-Density Polyethylene (LLDP) or recycled polyethylene. However, other methods of manufacture such as injection moulding, blowmoulding can also be used. The thickness of the wall or skin of the bodies is at least sufficient to support the weight and surrounding pressure of the concrete as this is poured and as it sets. In order to assist with creating apertures for the bars 14 (and pipes 16 if the methodology outlined above is used), some sections of the wall/skin can be formed so that they are thinner (and easier to penetrate) than the remainder, or the aperture can be directly formed during the moulding process. These apertures or thinner sections are generally referred to as ‘areas of weakness’.

There are two main methods for forming the bodies 12 and/or 100 with these thinner sections or apertures during a rotomoulding process. These are described below.

In the first method, and referring to Figure 5, one or more Teflon (RTM) patches 17 are attached to the outside of the mould in positions substantially equivalent to the location where the body 12 will be pierced. The patches 17 are screwed into position by screws 18 passing out from the inside of the mould, the screws located substantially at the piercing locations. During the forming process, the Teflon (RTM) has the effect of not allowing the mould at that location to hold heat. As the mould at this point is at a lower temperature than the surrounding mould, less material is deposited here during the forming process, and the skin of the finished body is thinner at this point. This makes it easier for a user to pierce the skin at this point when the user is locating the body onto a pipe or bar.

In the second method, referring to Figure 6, a Teflon (RTM) patch is screwed into position within the mould wall using a threaded plug 28 shaped and sized so as to create an aperture of the required shape and size (i.e. the plug 28 is equivalently sized to the pipe and/or bar) in the side wall of the mould. That is, the plug 28 is screwed into/through the side wall of the mould. When the plug 28 is removed after the body has been cast, an aperture is left in the side of the body, of the required size and shape, and in the correct position.

Claims

1. An apparatus for forming a void or voids in a casting during a casting process, the apparatus comprising: at least one body comprising a substantially continuous outer surface, the body formed such that the outer surface can be penetrated, with the original shape of the body substantially retained when penetrated; a penetrating and securing means, configured to penetrate the at least one body to secure the at least one body to the penetrating and securing means, the penetrating and securing means further configured for positioning in or on a casting mould so as to retain the body in position within the mould.

2. An apparatus for forming a void or voids in a casting as claimed in claim 1 wherein the penetrating and securing means comprises at least one elongate member.

3. An apparatus for forming a void or voids in a casting as claimed in claim 2 wherein the elongate member comprises a reinforcing bar.

4. An apparatus for forming a void or voids in a casting as claimed in claim 2 or claim 3 wherein the elongate member has a diameter substantially between 6mm and 12mm.

5. An apparatus for forming a void or voids in a casting as claimed in any one of claims 1 to 4 wherein the at least one body is substantially spherical.

6. An apparatus for forming a void or voids in a casting as claimed in any one of claims 1 to 4 wherein the at least one body is a partial sphere.

7. An apparatus for forming a void or voids in a casting as claimed in claim 6 wherein the partial sphere comprises a sphere having at least one absent spherical cap.

8. An apparatus for forming a void or voids in a casting as claimed in claim 6 or claim 7 wherein the partial sphere comprises a sphere having substantially diametrically opposed absent spherical caps.

9. An apparatus for forming a void or voids in a casting as claimed in any one of claims I to 4 wherein the at least one body comprises a generally cylindrical shape with outwardly curving sides.

10. An apparatus for forming a void or voids in a casting as claimed in claim 9 wherein the at least one body comprises a substantially vertically aligned passage formed in the top surface of the generally cylindrical shape, and a cylindrical extension that extends from the bottom surface of the body, the extension and the passage equivalently sized and forming a mutual connecting means configured such that the extension on one body can fit into and connect with a corresponding passage on a separate body.

11. An apparatus for forming a void or voids in a casting as claimed in claim 10 wherein the extension and the passage are threaded so as to form the mutual connection means.

12. An apparatus for forming a void or voids in a casting as claimed in claim 10 or claim II wherein the passage or the extension or both are aligned with the main axis of the body.

13. An apparatus for forming a void or voids in a casting as claimed in claim 10 or claim 11 wherein the passage or the extension or both are offset from the main axis of the body.

14. An apparatus for forming a void or voids in a casting as claimed in any one of claims 1 to 13 wherein the at least one body comprises a plurality of bodies, in use arranged at spaced intervals on the penetrating and securing means.

15. An apparatus for forming a void or voids in a casting as claimed in claim 15 wherein the at least one body comprises a plurality of bodies, in use arranged in stacks of two or more bodies.

16. An apparatus for forming a void or voids in a casting as claimed in any one of claims 1 to 15 further comprising a spacing means configured to hold the bodies at spaced intervals from each other.

17. An apparatus for forming a void or voids in a casting as claimed in claim 16 wherein the spacing means comprises an elongate body having two or more U-shaped sections formed therein.

18. An apparatus for forming a void or voids in a casting as claimed in claim 17 wherein the elongate body comprises a straight central body portion and two U-shaped end portions, the bends that form the U-shaped end portions all in substantially the same plane.

19. An apparatus for forming a void or voids in a casting as claimed in claim 18 wherein the U-shaped end portions are formed so that the outer side of the body of each of the ‘U’-shaped end portions extends for substantially the same distance each side of the straight central body portion.

20. An apparatus for forming a void or voids in a casting as claimed in claim 17 wherein the elongate body comprises two U-shaped sections and a substantially straight central section between the U-shaped sections that separates the U-shaped sections, the ends of the elongate body extending from the outer sides of each of the ‘U’ portions, parallel to and in line with one another and the central section, the elongate body substantially planar.

21. An apparatus for forming a void or voids in a casting as claimed in claim 20 wherein the centre point of the flat central section bisects the elongate body.

22. An apparatus for forming a void or voids in a casting as claimed in claim 17 wherein the spacing means comprises two connected substantially flat planar sections arranged in two parallel planes, one behind the other and spaced apart a short distance.

23. An apparatus for forming a void or voids in a casting as claimed in claim 22 wherein each of the flat planar sections comprises two U-shaped sections separated by a substantially straight central section, an end section extending from the outer sides of each of the ‘U’ portions, the ends sections parallel to and in line with one another and the central section, a connecting and spacing section connecting between the flat planar sections so that the flat planar elements are arranged one behind the other in two spaced-apart parallel planes, with the U-shaped sections aligned with one another.

24. An apparatus for forming a void or voids in a casting as claimed in claim 23 wherein the flat planar sections and the connecting and spacing section are formed from a single piece of material, the connecting and spacing section forming a ‘U’-bend at substantially the mid point between the two flat planar sections.

25. An apparatus for forming a void or voids in a casting as claimed in any one of claims 1 to 24 wherein the at least one body or bodies are substantially hollow.

26. An apparatus for forming a void or voids in a casting as claimed in any one of claims 1 to 24 wherein the interior(s) of the at least one body or bodies are at least partially solid.

27. An apparatus for forming a void or voids in a casting as claimed in any one of claims 1 to 26 wherein the at least one body is at least partly formed from LDPE.

28. An apparatus for forming a void or voids in a casting as claimed in claim 27 wherein the at least one body is formed by rotomoulding.

29. An apparatus for forming a void or voids in a casting as claimed in any one of claims 14 to 28 wherein the bodies are arranged on the penetrating and securing means such that a majority of the body is above the penetrating and securing means in use.

30. An apparatus for forming a void or voids in a casting as claimed in any one of claims 1 to 29 wherein the substantially continuous outer surface of the body further comprises at least one area of weakness configured to allow penetration of the body by the penetrating and securing means.

31. A method for forming a void or voids in a casting during a casting process, comprising the steps of: (iv) positioning at least one body on a penetrating and securing means, the body comprising a substantially continuous outer surface, the body formed such that the outer surface can be penetrated by the penetrating and securing means with the original shape of the body substantially retained when penetrated, the at least one body and the penetrating and securing means configured such that the body will be retained in position on the penetrating and securing means in use; (v) positioning the penetrating and securing means and the at least one body within a casting mould; and (vi) pouring concrete into the mould around the penetrating and securing means and the at least one body such that the body creates voids in the finished concrete cast.

32. A method for forming a void or voids as claimed in claim 31 wherein the at least one body and the penetrating and securing means are formed as claimed in any one of claims 1 to 30.

33. A method for forming a void or voids as claimed in claim 31 wherein the penetrating and securing means comprises at least one substantially straight elongate member.

34. A method for forming a void or voids as claimed in claim 31 wherein the penetrating and securing means comprises at least one curved elongate member.

35. A method of creating an apparatus for forming a void or voids in a casting during a casting process, comprising the steps of: (iv) pushing at least one body onto at least one hollow length of thin-walled pipe, the body comprising a substantially continuous outer surface, the body formed such that the outer surface can be penetrated by the hollow length of pipe with the original shape of the body substantially retained when penetrated, the at least one body and pipe configured such that the body will be retained in position on the pipe; (v) passing a bar into and along substantially the length of the pipe; (vi) removing the pipe to leave the body in position on the bar.

36. A method as claimed in claim 35 wherein the at least one hollow length of thin-walled pipe comprises a pair of pipes, arranged in parallel to one another.

37. A method as claimed in claim 35 or claim 36 wherein the pipes have a length of substantially six metres.

38. A method as claimed in any one of claims 35 to 36 wherein the at least one body comprises a plurality of bodies.

39. A method as claimed in claim 38 wherein the bodies are located at spaced apart intervals along the length of the pipe or pipes.

40. A method of forming a body suitable for use as part of an apparatus for forming a void or voids in a casting, comprising the steps of: a. attaching at least one heat-conductive patch to the exterior surface of a rotomould in a location substantially equivalent to a location where the body will be pierced in use; b. moulding a body within the mould.

41. A method as claimed in claim 40 wherein the patches are screwed into position using screws.

42. A method as claimed in claim 41 wherein the screws pass outwards from within the mould.

43. A method as claimed in any one of claims 40 to 42 wherein the patch or patches are at least partly formed from teflon.

44. A method as claimed in claim 40 wherein the patch is screwed into position via a threaded plug configured to create an aperture in the skin of the body as the body is formed.

45. A method as claimed in claim 44 wherein the patch or patches are at least partly formed from teflon.

46. A body for use as part of an apparatus for forming a void in a casting during a casting process, comprising a substantially continuous outer surface formed such that the outer surface can be penetrated by a penetrating and securing means, with the original shape of the body substantially retained when penetrated, the substantially continuous outer surface of the body further comprising at least one area of weakness configured to allow penetration of the body by the penetrating and securing means.

47. A body as claimed in claim 46 wherein the body is substantially spherical.

48. A body as claimed in claim 46 wherein the body is a partial sphere.

49. A body as claimed in claim 48 wherein the partial sphere comprises a sphere having at least one absent spherical cap.

50. A body as claimed in claim 48 or claim 49 wherein the partial sphere comprises a sphere having substantially diametrically opposed absent spherical caps.

51. A body as claimed in claim 46 wherein the body has a generally cylindrical shape with outwardly curving sides.

52. A body as claimed in claim 51 wherein the body comprises a substantially vertically aligned passage formed in the top surface of the generally cylindrical shape, and a cylindrical extension that extends from the bottom surface of the body, the extension and the passage equivalently sized so as to form a mutual connecting means configured such that the extension on one body can fit into and connect with a corresponding passage on a separate body.

53. A body as claimed in claim 53 wherein the extension and the passage are threaded so as to form the mutual connection means.

54. A body as claimed in claim 52 or 53 wherein the passage or the extension or both are aligned with the main axis of the body.

55. A body as claimed in claim 52 or 53 wherein the passage or the extension or both are offset from the main axis of the body.

56. A body as claimed in any one of claims 46 to 55 wherein the body is substantially hollow.

57. A body as claimed in any one of claims 46 to 55 wherein the interior of the body is at least partially solid.

58. A body as claimed in any one of claims 46 to 57 wherein the body is at least partly formed from LDPE.

59. A body as claimed in any one of claims 46 to 57 wherein the body is formed by rotomoulding.

60. An apparatus for forming a void or voids in a casting substantially as herein described with reference to figures 1 to 7.

61. An apparatus for forming a void or voids in a casting substantially as herein described with reference to figures 8 to 10.

62. A body for use as part of an apparatus for forming a void in a casting during a casting process substantially as herein described with reference to figures 1 to 7.

63. A body for use as part of an apparatus for forming a void in a casting during a casting process substantially as herein described with reference to figures 8 to 10.