FIELD OF THE INVENTION

This invention relates to a permanent formwork building method and components whereby buildings can be erected using a settable bulk material that may contain any suitable or available bulk material including sand, crushed stone, pebbles, soil and other generally granular or subdivided geological materials together with a binder such as a suitable cement, for example Portland cement.

Many different forms of concrete fall within the scope of the invention which includes, but extends beyond, conventional concretes using conventional aggregates and includes relatively low strength settable mixes, typically, although not necessarily, mixes using a cement or any other appropriate material as a binder, and that optionally includes stone as an ingredient. The formwork used to construct such buildings forms the outer skin to a wall and, if appropriate, may be left in its natural state or may be finished with a suitable finishing layer such as paint, wallpaper or other decorative surfacing material. The invention is particularly concerned with a permanent formwork building method that utilizes extrusions as at least the outer surface defining formwork panels of the formwork.

BACKGROUND TO THE INVENTION

The construction of permanent formwork buildings using plastics extrusions as the formwork that defines the outer surface of a building has been proposed, for example, in prior US patent publication number US 2006/0213140. However, in the past, the length of the extrusions that form the inside and outside surfaces of a final cast wall extend vertically so that each extends over the vertical height of a wall. The extrusions are interconnected at their vertical edges and are held in spaced relationship by spacers that extend up the height of the wall.

The problem with this type of arrangement is that considerable strength is required of the formwork, especially towards the lower ends thereof, because the weight of the cast material needs to be supported whilst the concrete is still fluid, at least to some extent, and the extruded sections of the formwork need to be suitably robust and substantial enough to withstand the relevant pressures. The cost of the extruded formwork is therefore considerable and a substantial amount of plastic material is consumed contrary to the interests of limiting global warming. Added to this is the cost of setting up such a formwork using procedures that require skilled labour, a commodity which is becoming progressively less available and more costly as time goes by. These are limiting factors on the construction of certain types of buildings, in particular low-cost dwellings or other low-cost constructions.

In spite of this there are many attractive characteristics of using a permanent formwork building procedure in that finishing of the wall surfaces may be minimized whilst their appearance can be made to be aesthetically pleasing.

There is a need for a permanent formwork building method and components that may be configured to provide at least some advantages of a permanent formwork building method whilst providing a somewhat simplified constructional procedure.

SUMMARY OF THE INVENTION In accordance with one aspect of this invention there is provided a permanent formwork building method comprising forming a lower horizontally extending formwork comprising a pair of generally parallel horizontally extending, laterally spaced, extruded formwork panels orientated in generally vertical planes and held in laterally spaced relationship by a series of spacer elements spaced apart horizontally to form a void between the formwork panels; filling, or partially filling, the void between the two formwork panels with a settable bulk material; allowing the settable bulk material to at least partially set; supporting an upper pair of extruded formwork panels on the pair of formwork panels or settable bulk material that is already in place to form a void immediately above the existing set or partially set material; casting settable material into a newly formed void between the upper pair of extruded formwork panels and allowing it to set or partially set; and repeating the process as may be necessary with additional pairs of upper formwork panels until a desired height of wall is achieved.

Further features of the invention provide for the formwork panels to have a width (corresponding to wall height in the installed condition) of from 150 mm to 500 mm with a preferred width being from 200 to 300 mm; for the extruded formwork panels to have inwardly lipped attachment ribs extending along their length for engagement by cooperating formations on the spacer elements; for the spacer elements to be injection moulded plastics elements; and for formations on the spacer elements to be engageable with the lipped attachment ribs by either a twisting motion with regions of a spacer element in contact with the inner surface of a formwork panel or by a clipping action in which instance the formations on the spacer elements are formed as catches and are carried in sufficiently flexible manner to enable the spacer element to flex and cause the catches to catch behind the inwardly directed lips of the lipped attachment ribs.

In an alternative configuration of spacer elements, a spacer element may have a pair of inwardly directed catches for cooperation with inwardly lipped attachment ribs that are integral with the extruded formwork panels. In such an instance the arrangement may be such that two spaced parallel transversely extending arms can be squeezed towards each other to cause the catches of a pair thereof to retract and move apart from each other and thereby enable the spacer element to be engaged with or disengaged from the inwardly lipped attachment ribs. In this alternative configuration, the inwardly lipped attachment ribs may be positioned up the height of the extruded formwork panel so that one is located in an upper region of the panel and a lower spacer element may have one catch engaged with an inwardly lipped attachment rib of an upper formwork panel and an inwardly lipped attachment rib of a lower formwork panel so that the spacer element interconnects the two formwork panels.

Still further features of the invention provide for upright guides to be provided for aligning vertically adjacent formwork panels, typically by way of aligning the spacer elements vertically that, in such an instance, preferably have formations cooperating with an upright guide; for the parallel edges of each of the formwork panels to have formations for aligning a lower edge of an upper formwork panel with an upper edge of a lower formwork panel; and for the edges of the formwork panels to be configured to define a groove in the surface of the composite formwork arrangement that simulates a recess formed by adjacent slats of a slatted timber or composite board construction or a pointed joint between courses of building elements such as bricks or blocks.

The invention also provides, as items of commerce, extruded formwork panels and spacer elements that are suitable for use in a building method as defined above.

In order that the above and other features of the invention may be more fully understood, embodiments of the invention as well as variations thereof will now be described with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:-

Figure 1 is a schematic elevation of a low-cost dwelling constructed using an embodiment of method according to this invention;

Figure 2 is an exploded end view showing the cooperation between two extruded formwork panels and a spacer element between them;

Figure 3 is an end view of an upper assembled pair of formwork panels supported on a lower pair thereof with spacer elements connecting the formwork panels together in each instance;

Figure 4 is an isometric view of a spacer element showing additional detail thereof;

Figure 5 is an enlarged end view of the cooperating edges of an upper and a lower formwork panel and showing more clearly the interaction between formations on a spacer element and inwardly directed lipped ribs that are integral with the formwork panels;

Figure 6 is an isometric view showing an assembly of two formwork panels partly filled with settable material and with a series of spacer elements interconnecting them with a pair of spaced vertical upright guides for vertically aligning vertically stacked spacer elements;

Figure 7 is a plan view thereof; 8

Figure 8 is an isometric view showing a corner of a constructed wall;

Figure 9 is an end view showing an alternative spacer element and its associated formations cooperating with a pair of spaced formwork panels by a clipping action as well as alignment enhancing channel formations for aligning vertically adjacent formwork panels;

Figure 10 is an isometric view of two vertically stacked pairs of formwork panels interconnected by a further alternative form of spacer element; and,

Figure 1 1 is an end view of the vertically stacked pairs of formwork panels illustrated in Figure 10.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

In the embodiments of the invention illustrated in the drawings, the method of the invention is applied to the construction of a low-cost dwelling unit (1 ) such as that illustrated schematically in Figure 1 in which a plurality of walls (2) are constructed, typically on a cast slab (3), and a roof (4) is supported by the walls.

As will be apparent from the foregoing, the building method is a permanent formwork building method comprising forming, on the slab, a lowermost horizontally extending formwork comprising a pair of generally parallel horizontally extending, laterally spaced, extruded formwork panels (5) orientated in generally vertical planes and held in laterally spaced relationship by a series of spacer elements (6) spaced apart horizontally to form a void (7) between the formwork panels. Corners can be formed as shown clearly in Figure 8 using vertical angle sections (8). The formwork panels are extruded to any required length so that a single length is needed to pass, for example, from a corner to a door frame (1 1 ) ; to a window frame (1 2) ; or to another corner in the horizontal direction. Each of the formwork panels has a width (corresponding to the direction of wall height in the installed condition) of from 200 to 300 mm. This enables the formwork panel to be made relatively thin with a minimum usage of plastics material that would typically be a suitably stabilized grade of polyethylene or polypropylene. The plastics material could also be suitably fibre reinforced. Formed integral with the extruded formwork panels, and as illustrated in Figures 2 to 6, is a plurality of inwardly lipped attachment ribs (14, 15) that extend along the length of the formwork panel. Two of such attachment ribs (14) are located at the longitudinal edges of the panel and are lipped inwardly towards each other, and two of such attachment ribs (1 5) are spaced apart symmetrically by approximately one third of the width of the formwork panel and also have lips directed inwardly towards each other.

It will be noted, especially from Figure 4, that each of the spacer elements is an injection moulded plastics component that has a basic shape of a generally rectangular frame with cooperating formations (1 6, 1 7) on the spacer elements for engagement under the lips of the inwardly lipped attachment ribs (14, 1 5) respectively. Two of the formations (1 6) on the spacer elements are located towards the corners of the spacer element for engagement with the lipped attachment ribs extending along the edges of the formwork panels. The other two formations (1 7) are more central and are positioned for engagement with the more central lipped ribs (1 5).

All of the formations may be engaged, in this particular variation of the invention, by contacting the edge of the spacer element with the inside surfaces of the formwork panels and twisting the spacer element about an axis extending at right angles to the surface of the formwork panel so that the formations move into engagement beneath the lips of the various lipped attachment ribs.

The spacer elements also have, as shown clearly in Figure 4, laterally spaced upper and lower projections (18) adapted to locate the spacer element relative to vertically extending channel sectioned upright guides (21 ) that are installed towards each end region of each of the pairs of formwork panels in order to ensure that vertically adjacent pairs of formwork panels are all in substantial vertical alignment with each other. In an alternative arrangement that is illustrated in Figure 9, a spacer element has a central operatively upright support (23) with laterally extending arms (24) each of which has a catch (25) at its free end for clipping behind the inwardly directed lips of the lipped ribs of a formwork panel (26). In either event, it is to be noted that, if required, prefabricated bases (27) may be produced having guide grooves (28) for receiving the lower edges of the lowermost spacer elements. The prefabricated bases may have any desired size depending on the floor plan of the building under construction. At this stage the void between the lowermost two formwork panels is filled with a settable bulk material (29) that, being only 200 to 300 mm deep, will not exert excessive force on the formwork panels, as indicated above. The settable bulk material may be of relatively low structural strength yet designed to form a suitably strong wall. See Figure 6.

Once the settable bulk material has set, at least to a sufficient extent, an upper pair of extruded formwork panels and associated spacer elements can be placed on top of the lowermost pair of formwork panels with the upright guides (21 ) properly located between the upper and lower projections (18) of the appropriate spacer elements. Settable material can then be cast into the newly formed void immediately above the existing set or partially set settable material and the cycle can be repeated with the newly cast settable material then being allowed to set sufficiently before a further formwork panel assembly is placed on top of it. In this way a wall can be built up progressively from a cast slab to roof level. In a preferred arrangement, the parallel edges of each of the formwork panels has formations (31 , 32) for aligning a lower edge of an upper formwork panel with an upper edge of a lower formwork panel with the formations being configured to define a groove (33) in the outside surface of the composite formwork arrangement that simulates a recess formed by adjacent slats of a slatted timber or composite board construction or a recessed pointed grout layer between two courses of bricks or blocks.

These formations may be as illustrated in Figure 5 in which instance an upper formation (31 ) may curve inwardly so that it engages the outer face of a recessed formation (32) extending along the lower edge of each of the formwork panels.

Also, as shown in Figure 5, a locating groove (34) may be formed in the inwardly projecting connector to which a recessed formation is attached. The latter is aimed at assisting in proper alignment of the formwork panels relative to each other.

In an alternative configuration of spacer elements (41 ) and extruded formwork panels (42), and as illustrated in Figures 1 0 and 1 1 , a spacer element may have a single pair of inwardly directed catches (43) for cooperation with inwardly lipped attachment ribs (44) that are integral with the extruded formwork panels in the general manner described above. In this instance however the spacer elements are appreciably smaller and each has a generally rectangular frame in a central region across the width of a void between two extruded formwork panels with vertically spaced parallel transversely extending arms (45) that can be urged towards each other, as indicated by arrows "A", to bow the arms inwardly towards each other. This movement is designed to cause the catches (43) of a pair thereof to move apart from each other, as shown by arrows "B" and thereby enable the catches, and thus the spacer element, to be engaged with, or disengaged from, the inwardly lipped attachment ribs of the extruded formwork panels.

In this alternative configuration, and with particular reference to Figure 1 1 , the inwardly lipped attachment ribs may be positioned at heights up the extruded formwork panel so that an upper spacer element (41 a) is located in an upper region of the extruded formwork panels. A lower spacer element (41 b) has one of its catches engaged with an inwardly lipped attachment rib (44a) of an upper formwork panel and the other of its catches (44b) engaged with an inwardly lipped attachment rib (44b) of a lower formwork panel. The result is that the lower spacer element (41 b) serves to interconnect in the two vertically adjacent formwork panels.

Numerous other configurations of extruded formwork panels and spacer elements are possible without departing from the scope hereof.