Abstract:
A method of assembling formwork for casting a concrete component ( 14 ) firstly includes arranging on a casting substrate ( 2 ), a plurality of elongate casting elements (AA, BB, CC, DD) to define the outline of the component ( 14 ) to be cast. A plurality of wall portions ( 4 ) are then selected having a width commensurate with the width of the sides of the component ( 14 ) to be cast. The casting elements (AA, BB, CC, DD) each have locating portions ( 3 ) to receive at least an edge of one or more of said wall portions ( 4 ). The plurality of wall portions ( 4 ) are located with the locating portions ( 3 ) of the casting elements to define a continuous wall along the outline of the component to be cast and to thereby delimit the sides of the component ( 14 ) to be cast. The casting elements (AA, BB, CC, DD) are then anchard to the casting substrate ( 2 ). The concrete castin elements (AA, BB, CC, DD) may include a chamfering portion ( 5 A) adapted to chamfer an edge of the component.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates to an apparatus and method for precasting concrete and in particular to a modular and easily adjustable boxing system to assist in preparing precast concrete components for use in the construction industry. While the invention is particularly described in connection with concrete construction, it may have application to other construction materials and even to other settable materials.  
         BACKGROUND TO THE INVENTION  
         [0002]    The use of precast concrete components such as slabs, columns etc in the construction industry is well known. This avoids the need for casting concrete components in situ and renders unnecessary the extra formwork and labour needed to pour, form and hold wet concrete in place until it sets. The components can instead be precast offsite, or at least away from the main construction area, and when needed the components are transported by truck and/or lifted into position by crane and incorporated into the existing structure.  
           [0003]    Precasting is typically performed in horizontal casting beds with the extremities of the required components defined by formwork typically in the form of L-shaped extrusions. As will be appreciated, the maximum height of the component being formed will be determined by the height of the L-shaped extrusion. Thus, it may be necessary  1 to have lengths of formwork of varying heights to suit a range of casting jobs. This is particularly necessary if components are cast progressively on top of each other.  
           [0004]    Concrete can be brittle and easily chipped or broken where it is thinnest in a component. Typically this occurs on the comers and edges of the component during removal from the mould, transportation and placement. Such damage, which may lead to weakness and which looks unattractive where the components are to remain exposed in a structure, can be avoided by providing the component with chamfered edges. An existing method used to create the chamfer involves placing a plastic triangular sectioned component at the bottom comer of the mould created by the L-shaped sections. However, it will be appreciated that this only allows for the edge at the bottom of the mould to be chamfered.  
           [0005]    It is therefore an object of the invention to provide a system to facilitate the production of precast concrete elements for use in the construction industry; and/or to overcome or address at least one of the disadvantages of the prior art; and/or at the least to provide the public with a useful choice.  
         SUMMARY OF THE INVENTION  
         [0006]    According to one aspect of the invention there is provided a method of assembling formwork for casting a concrete component. the method including:  
           [0007]    arranging on a casting substrate, a plurality of elongate casting elements to define the outline of the component to be cast, providing wall portions to associate with the casting elements to define wall surfaces to delimit the sides of the component to be cast, the casting elements each incorporating a chamfer to truncate the apex of the mould space defined by the casting substrate and the wall surface; and  
           [0008]    anchoring the casting elements to the casting substrate.  
           [0009]    Preferably the casting substrate is a horizontal casting bed and the wall portions define the upright sides of the component to be cast. However the invention is not limited to this and may be adapted to be used with other forms of casting substrate such as a form to be arranged in a vertical orientation as opposed to a horizontal orientation.  
           [0010]    Preferably the casting element supports one or more wall portions in the form of an elongate board/planar rectangular sheet. In a highly preferred form, the casting element defines a channel, preferably a substantially U-shaped channel to receive at least an edge of the wall portion and the method includes inserting the wall portion into the channel.  
           [0011]    Preferably the chamfer is defined by a projection that is substantially triangular in cross-section. The projection may be three-sided or only two sides of the triangular cross-section may be defined, those being the base and the chamfer.  
           [0012]    In a preferred embodiment, the present method includes the step of locating on the upper edge of the wall portions, additional elongate casting members wherein the additional elongate casting members also incorporate a chamfer to truncate the apex of the mould space defined by the casting substrate and the upper surface of the component to be cast. Preferably, the additional elongate casting members are identical to the elongate casting elements, with the additional members being inverted.  
           [0013]    Additionally, it is preferable for the element to have a longitudinal plane of symmetry thereby defining two chamfers, the element including mounting portion disposed substantially along the plane of symmetry. In a highly preferred form the element has a plane of symmetry thereby defining two channels and two projections, the element including a central H section bisected by the plane of symmetry, the central H section having two sides and a bridge, with the sides of the H section defining respective inner walls of said two channels and with flanges extending inwards from the tops of the sides of the H section. The projections define respective outer walls of the two channels.  
           [0014]    According to another aspect of the invention, the wall portion may be integral with the casting elements. Accordingly, there is provided a method of assembling formwork for casting a concrete component. the method including:  
           [0015]    arranging on a casting substrate, a plurality of elongate casting elements to define the outline of the component to be cast, the casting elements having wall portions to define wall surfaces to delimit the upright sides of the component to be cast, the casting elements each incorporating a chamfer to truncate the apex of the mould space defined by the casting substrate and the wall surface; and  
           [0016]    anchoring the casting elements to the casting substrate.  
           [0017]    Any of the preferred features of the first aspect of the invention may have application to the above aspect of the invention.  
           [0018]    According to a third aspect of the invention there is provided a method of assembling formwork for casting a concrete component, the method including the following, not necessarily in the following order:  
           [0019]    (A) arranging on a casting substrate, a plurality of elongate casting elements to define the outline of the component to be cast.  
           [0020]    (B) selecting a plurality of wall portions having a width commensurate to the casting width of the sides of the component to be cast wherein the casting elements each have a locating portion to receive at least an edge of one or more of said wall portions;  
           [0021]    (C) locating the plurality of wall portions with the locating portions of the element to define a continuous wall along the outline of the component to be cast and thereby delimit the sides of the component to be cast; and  
           [0022]    (D) anchoring the casting elements to the casting substrate.  
           [0023]    The method need not be performed in the stated order. For example, the act of anchoring may be performed prior to the step of selecting and locating. Alternatively, the act of anchoring may be between the acts of selecting and locating.  
           [0024]    Preferably the casting substrate is a horizontal casting bed and the wall portions define the height of the components to be cast. In an alternative form of the invention, the substrate may comprise forms such as plywood sheets to which the casting elements are anchored. The substrate may be arranged at any orientation for the concrete pour. In particular, the substrate may be oriented vertically to cast in-situ, components such as walls and columns. This may employ first and second of such casting elements anchored at a spacing on a first form with a second form being provided to which a third and fourth casting elements are anchored. A first of such wall portions extends between the first and third casting elements and a second of such wall portions extends between the second and fourth casting elements.  
           [0025]    Preferably the locating portion is defined as a substantially U-shaped channel.  
           [0026]    In a preferred embodiment of this aspect a further step is locating on the upper edge of the wall portion, additional elongate casting members wherein the additional elongate casting members have further locating portion to receive an upper edge of a wall portion. In a highly preferred embodiment, the additional elongate casting members are identical to the elongate casting elements, the additional members being inverted.  
           [0027]    Preferably the casting elements incorporate a chamfering portion to truncate the apex of the mould space defined by the casting substrate and the wall surface. Also, the additional elongate casting members incorporate a chamfering portion to truncate the apex of the mould space defined by the casting substrate and the upper surface of the component to be cast. Preferably the chamfer is defined by a projection that is substantially triangular in cross-section. The projection may be three-sided or only two sides of the triangular cross-section may be defined, those being the base and a surface to define the chamfer.  
           [0028]    Each casting element may not be in one piece and but in several pieces which may be interlocking or interconnecting. The chamfer may be created by a separate piece affixed to the casting substrate.  
           [0029]    The element of the second aspect of the invention preferably has a longitudinal plane of symmetry thereby defining two locating portion and two chamfers, the element including mounting portion disposed substantially along the plane of symmetry. In a highly preferably form the element has a plane of symmetry thereby defining two channels and two projections, the element including a central H section bisected by the plane of symmetry, the central H section having two sides and a bridge, with the sides of the H section defining respective inner walls of said two channels and with two flanges extending inwards from the tops of the sides of the H section. The projections define respective outer walls of the two channels.  
           [0030]    A preferable method of forming corners in the formwork of the first and second aspects of the invention is provided where a first of such casting elements may be abutted to a second of such casting elements by cutting the longitudinal end of the first element (and the wall portion located in it) to accept the projection forming the chamfer.  
           [0031]    In the event that the components to be precast require rebating, the additional elongate elements can be replaced with rebating members defining the required rebate. Preferably the rebating members are wood or plywood shapes of the required dimensions. Additionally, inserts may be included in a component as required by mounting them onto the wall portion prior to casting.  
           [0032]    In accordance with a preferred form of the invention, components may be cast one atop the other. This is achieved once the existing component is cast by arranging further casting elements in a layer atop the existing component.  
           [0033]    According to a fourth aspect of the invention there is provided an element for use in a system for casting a concrete component, the element including a chamfering portion adapted to chamfer an edge of the component and a locating portion adapted to receive an upright member to define the side walls of the component.  
           [0034]    Preferably the chamfering portion is substantially triangular in cross-section. The chamfering portion may be three-sided or only two sides of the triangular cross-section may be defined, those being the base and a surface to define the chamfer. Preferably the chamfer provided to the component by each aspect is planar or convex.  
           [0035]    The chamfering portion may be in the form of a projection integral with the casting element. However the casting element may not be in one piece and but in several pieces which may be interlocking or interconnecting. The chamfer may be created by a separate piece which can be affixed to the casting substrate.  
           [0036]    Preferably the locating portion is defined by a substantially U-shaped channel. In a most preferred from of the invention, the element is an integrally formed member (eg by extrusion) incorporating the projection and the U-shaped channel.  
           [0037]    In a preferred form the element has a longitudinal plane of symmetry thereby defining two locating portion and two projections. the element including mounting portion disposed substantially along the plane of symmetry. In a highly preferred form the element has a plane of symmetry thereby defining two channels and two projections, the element including a central H section bisected by the plane of symmetry, the central H section having two sides and a bridge, with the sides of the H section defining respective inner walls of said channels and with flanges extending inwards from the tops of the sides of the H section. The projections define respective outer walls of the channels. The various parts of the casting element need not be of a constant thickness.  
           [0038]    In respect of all of the above aspects of the invention. preferably the mounting portion is provided with a plurality of holes adapted to receive bolts or similar devices to secure an element to the casting substrate and/or to bolt two elements together. In a highly preferable form these holes are formed in the bridge of the central H-section.  
           [0039]    In regards to the materials used in each aspect it is preferred that the element is extruded and ideally the element is extruded from aluminium, The sheets used may be made from wood or plywood or medium density fibreboard.  
           [0040]    Reinforcing may be added before the concrete is introduced as described below.  
           [0041]    This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.  
           [0042]    The invention consists in the foregoing and also envisages constructions of which the following gives examples. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0043]    [0043]FIG. 1 shows perspective views of two embodiments of a casting element according to one preferred embodiment of the invention;  
         [0044]    [0044]FIG. 2 is a perspective view of an assembled apparatus according to a preferred embodiment of the invention;  
         [0045]    [0045]FIG. 3 is a cross sectional view showing the apparatus of FIG. 2 in use;  
         [0046]    [0046]FIG. 4 is a cross-sectional view showing how a corner of a mould is formed;  
         [0047]    [0047]FIG. 5 is a cross-sectional view showing another embodiment of the apparatus;  
         [0048]    [0048]FIG. 6 is a perspective view of an alternative embodiment of the casting element;  
         [0049]    [0049]FIG. 7 is a perspective view of yet another embodiment of the casting element;  
         [0050]    [0050]FIG. 8 is a cross-sectional view of another embodiment of the casting element;  
         [0051]    [0051]FIG. 9 is a cross-sectional view of a further embodiment of an assembled apparatus according to the present invention;  
         [0052]    [0052]FIG. 10 a  illustrates a method of stack casting according to a preferred embodiment of the present invention;  
         [0053]    [0053]FIG. 10 b  illustrates components of FIG. 10 a  in greater detail; and  
         [0054]    [0054]FIG. 11 illustrates a further embodiment of the assembled apparatus of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0055]    Referring to FIG. 1, the element of the invention is of elongate form with a constant cross-section. The element is designed to rest on its base  1  on a solid surface known in the art as a casting bed  2 , as shown in FIG. 2.  
         [0056]    Channels  3  are provided on both sides of the element to accept substantially rectangular planar sheets  4  that define the sides of the component to be precast. The transverse width (height) of a sheet depends on the size of the side of the component to be precast. The depth of the sheet is uniform and typically less than 18 mm so as to fit in the channel. The longitudinal length of the sheet is typically of a standard length shorter than the element.  
         [0057]    The shaping surface  5  of the element fills in the apex of the angle defined by the base and the outer side of a channel  3  so as to form a chamfered edge on the component, as shown in FIG. 2. Two preferred embodiments of the element with flat and concave shaping surfaces are depicted in FIG. 1. Preferably the projection  5 A forming the shaping surface is substantially a right-angled triangle in cross-section as shown.  
         [0058]    The raised central H-section  6  has two sides, a bridge  6 A and inwardly directed flanges  7  that define a cavity  8  and a slot  9  that both run the length of the element. The sides of the H section define respective inner walls of the channels  3  and the projections  5 A define respective outer walls of the channels. A plurality of holes  10  are formed in the bridge of the central H-section, spaced out alone the length of the element.  
         [0059]    Two elements and two sheets are assembled into the apparatus shown in FIG. 2. This apparatus serves to form a vertical side of two components to be cast side-by-side. The number of elements and sheets required in use to cast a component will depend on the size and shape of the component. It can be seen that the apparatus comprises a first lower element AA resting on a casting bed with the required sheets inserted into the channels on the first element. A second element BB is then inverted and placed on top of the sheets so that the upper ends of the sheets fit into the channels of the second element.  
         [0060]    Preferably the apparatus is held together using a bolt  11  that passes through the hole  10  and slot  9  in the upper element BB, and through the slot in the lower element to terminate in the cavity  8  of the lower element AA. Nuts  12 A and  12 B having internal threads corresponding to external threads on each longitudinal end of the bolt, engage the elements and, when tightened on the bolt. draw the elements together to bear upon the sheets, locking the apparatus together. As shown in FIG. 2 the nut  12 A on the upper end of the bolt rests in the U-shaped channel on the underside of the element BB defined underneath the raised section  6 . The nut  12 B on the lower end of the bolt is positioned in the cavity  9  and held against the underside of the flanges  7  by an optional spring  12 C. The nut  12 B bears upon the underside of the flanges when it is threaded onto the bolt. Preferably neither the nut nor the bolt project above the base of the upper element BB to allow for screeding by methods known in the art. The bolts  11  may be equally spaced along the length of an element.  
         [0061]    [0061]FIG. 3 shows a preferable embodiment of the apparatus in use. Bolts  13  (offset from bolts  11 ) are passed through holes  10  in the lower element AA to anchor it in place on the casting bed. It can be seen that the shaping surfaces  5  provide a chamfer on the edges of the component  14 . If necessary, reinforcing material  15  can be included in the precast element according to methods known in the art. In particular, reinforcing may be included by forming holes in the sheet  4  of a mould and passing such reinforcing as required through to project into the mould. Optionally the reinforcing may project through corresponding holes in the sheets on opposite sides of the mould to pass through the entire width or length of the mould. Such reinforcing may be placed under tension to form pre-stressed concrete as known in the art. Inserts (not shown), such as nuts, may be included in a component by attachment to the inner face of a sheet  4  using plastic nail plates or other methods as known in the art.  
         [0062]    It will be appreciated that functionally equivalent methods of anchoring the elements to the casting bed and attaching the elements to each other are anticipated by the invention. For example, the nut  12 B could be tack-welded in place or alternatively could be replaced by a washer and bolt arrangement, or a bolt  11  with a suitably sized head.  
         [0063]    As shown in FIG. 4, to create comers in a mould, a first element CC may be abutted to a second element DD by cutting the longitudinal end of the first element CC (and the sheets it carries) to accept the projection  5 A of the second element DD as shown in FIG. 4.  
         [0064]    A further embodiment of the invention is shown in FIG. 5 where the component to be precast requires rebating. Rebating is known in the art and is necessary where components are required to interlock or fit together in particular ways. In place of a second element, a rebater  16  abuts the upper ends of the sheets  4  and is bolted into place as shown. The rebater  16  overlaps the sheet  4  as necessary to create a rebate of the desired width  17 . If a deeper rebate is required than that afforded by the rebater, spacers  18  can be affixed, preferably using screws, to the underside of the rebater as shown. If a rebate of varying or intermittent width  17  is required, this is also possible using the apparatus of the invention. This method affords simple mould preparation and ensures rebates are produced accurately. Preferably the rebater is made from wood or plywood.  
         [0065]    As can be seen from FIGS. 2, 3 and  5 , the assembled apparatus is symmetrical. This allows components to be cast directly side by side so, for example, two castings require three sides of boxing not four as the centre boxing becomes common. This serves to preserve and maximise space on a casting bed.  
         [0066]    In a typical set of elements and sheets for precasting concrete components, preferably the elements are of a uniform length longer than the longest sheet. This aims to ensure that joins between sheets do not correspond to joins between elements, except where a corner is required as explained above and shown in FIG. 4. The sheets  4  may be practically any size or shape.  
         [0067]    In a preferred embodiment the element is extruded from aluminium or plastic. Alternatively, the elements may be formed using glass fibres and reinforced with resin (fibreglass). The sheets are preferably made of plywood. Other suitable materials include timber, steel, plastics.  
         [0068]    [0068]FIG. 6 illustrates an alternative form of a casting element. Compared to the embodiment illustrated in FIG. 1, the bridge  6   a  is lowered to align with the base to thereby form a level base  22  as shown. This defines a channel  24  running the length of the element. Furthermore, instead of the projections  5   a  being formed with three sides, only two sides of the projection are formed including a first part as an extension of the base and a second part which is a shaping surface which defines the chamfer on the element to be cast. Nevertheless, the projections still define two channels  20  running the length of the casting element to receive the sheets  4  to define the walls.  
         [0069]    [0069]FIG. 7 illustrates yet another embodiment of the casting element  50 . It will be seen that this embodiment of the casting element  50  does not include the projections to the form the chamfers. Instead, the outer edges of the casting element  50  have upturned lips  21  to define two U-shaped channels to receive the edges of the sheets  4 .  
         [0070]    It will be appreciated that the casting elements of the invention may define a curve alone their longitudinal length.  
         [0071]    [0071]FIG. 8 illustrates a cross-section of a casting element designed to be curved along its length. The particular form of the casting element includes a bridge  30  with the base being continuous across the bottom of the element as shown to define a cavity  32 . Additionally, one of the chamfering portions  34  may be removed as illustrated by the part in phantom. The section may be rolled around the Y-Y axis to a desired radius. The centre of the radius may originate from either side of the element. The section may be rolled into a curve. a circle or into a serpentine shape.  
         [0072]    Alternatively, the section may be rolled around the X-X axis with the centre of the radius originating from either above or below the section. This may have particular application when casting vertically oriented components as will be explained further in connection with FIG. 9.  
         [0073]    [0073]FIG. 9 illustrates an alternative apparatus used to form vertical column in situ. Whilst the figure illustrates a manner of forming a column, the same approach can also be applied to forming a wall or any other kind of vertically oriented component.  
         [0074]    Two casting elements  42  are anchored to a substrate  46  in spaced disposition. The substrate  46  may be a form as used in convention form work. The two casting elements  42  and the substrate  46  may then be vertically oriented. Similarly, two further casting elements  42  may be affixed to a second substrate  46  and oriented to face the first mentioned assembly. The two remaining sides of the column can then be defined by two sheets  48  each received in the innermost U-shaped channels of opposed casting elements.  
         [0075]    The entire assembly is mounted on a base defined by a series of casting elements  50  (of FIG. 7. These casting elements  50  may be secured to the construction site with each of the sheets  48  inserted into one of the U-shaped channels of one of the casting elements  50 . Furthermore, the upright forms  46  may be likewise received in channels of one of the casting elements  50 . When the assembly is in place, the column formwork can be strengthened using the threaded bolt  52  to clamp the two forms  46  together.  
         [0076]    An additional benefit of the apparatus of the present invention is that components can be easily cast with one stacked above the other.  
         [0077]    [0077]FIG. 10 a  illustrates schematically how this can be done whereas FIG. 10 b  illustrates the components of FIG. 10 a  in greater detail. In use, one would fix the first ring of casting elements  60  to the casting bed in the desired shape of the concrete component to be cast. The sheets  62  are then placed in the innermost U-channel  64  to create a dam for the concrete. The other U-shaped channels may also be fitted with sheets  68  if required. The upper casting element  70  is then positioned over the tops of the sheets  62 ,  68  and secured with a threaded rod in the manner explained in connection with FIG. 2. The concrete can the be poured into the first level and allowed to harden.  
         [0078]    To make a second layer of concrete another casting element  76  is placed on top of the casting element  70 . More specifically, a blocking piece  78  is first inserted into the cavity  80  formed between the two casting elements  70 ,  76 . Sheets  82  may be then added to the desired height and capped with another casting element  84 . The assembly may be then strengthened by a tie  86  in the manner illustrated in FIG. 10 b . The tie  86  extends over the whole assembly to another casting element on the other side. This process of simply stacking the casting elements with intervening sheets one atop the other may be continued until the desired number of concrete components has been cast.  
         [0079]    However in a more preferred form of the invention, one need not continuously stack the casting elements and intervening sheets one atop the other. As indicated in the third level in FIG. 10 a , the casting elements  70  and  76  may be removed with the walls  62 ,  68  and  82  substituted instead for two taller wall portions  77  as illustrated. The inner sheet  77  is secured to the second level of the hardened concrete component by means of anchoring member  90 . The removed casting elements  70 ,  76  can then be used to cast the third level as shown. It is worthwhile to note that any of the sheets  62 ,  68 ,  77  which are disposed underneath the current level of the component being cast need not be continuous around all sides of the assembly.  
         [0080]    In order to cast the fourth level onwards, the sheets  77  may be disengaged from the lowest casting element  60  and moved so that their tops are level with the uppermost layer of the hardened concrete and secured in that position by anchoring member  90 . The anchoring member  90  extends through both sheets  77  and through blocking  94  disposed between the two sheets. Additionally, the threaded rod  72  may be secured as illustrated in FIG. 10 b  by use of a nut  96  in the C-shaped cavity  98  level with the top of the hardened concrete  74 . The stacking may then continue with further casting elements being placed on the top to construct the fourth level. This procedure may be completed for fourth and subsequent levels.  
         [0081]    [0081]FIG. 11 illustrates an assembly for relatively tall concrete components to be cast. A plurality of braces  110  are fixed to the casting bed and to the side of the sheet  112 . The anchoring members  114  may be secured through the sheet  112  into blocking  116  provided between the two sheets  112 ,  118 . The entire assembly may be strengthened through the use of a threaded rod  120 . Additionally, a tie  124  may be placed to extend from one side of the assembly to another. A blocking piece  126  may be placed between the tie  124  and the top casting element  122  to give space for future work or other ties.  
         [0082]    The above describes some preferred embodiments of the present invention and indicates several possible modifications but it will be appreciated by those skilled in the art that other modifications can be made without departing from the scope of the invention as defined in the following claims.