The following discussion providing some background to the invention is intended to facilitate a better understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of the application.

A known form of lifting anchor and void former is shown in Australian Patent 568684. The lifting anchor disclosed in patent 568684 includes a flat metal bar of heavy section punched therein having a hole for attachment of a lifting hook. A problem with this type of lifting anchor is that unless the hole is exactly in the centre of the bar, the lifting anchor will be prone to asymmetric loading and premature failure through the thinner cross-section adjacent the hole. A further drawback is its cost of manufacture.

Known void formers used for forming voids around lifting anchors have a tendency to float off their lifting anchors while the concrete is being poured. A further problem with known void formers is that after their removal, the edges of the void are jagged leaving an irregular opening that is difficult to patch.

It is an object of the present invention to provide an improved lifting anchor which is of simple design and inexpensive to produce.

It is a further object of the present invention to provide a void former which is designed to securely lock to the improved lifting anchor.

It is a further object of the present invention to provide an improved assembly for forming a lifting anchor within a cast concrete panel.

SUMMARY OF THE INVENTION According to a first aspect of the invention there is provided a lifting anchor for a cast concrete panel, comprising an elongate rod formed into: a pair of horizontally spaced apart vertically disposed (or nearly so) legs; an upper curved portion joining the spaced apart legs at their upper ends to form an inverted U ; and a pair of elongate base portions, each base portion projecting outwards from and substantially perpendicular to the lower end of a respective leg.

Preferably the base portions extend in opposite directions.

Preferably the base portions are transversely spaced apart and parallel.

Preferably the base portions extend in directions perpendicular to the plane in which the inverted U lies.

Preferably the rod is substantially circular in cross-section and preferably the spacing between the legs is between one-and-a-half and twice the diameter of the rod.

According to a second aspect of the invention there is provided a void former for forming a void around a portion of a lifting anchor for a cast concrete panel, wherein the anchor comprises an elongate rod formed into: a pair of parallel spaced apart legs; a upper curved portion joining the spaced apart legs at their upper ends to form an inverted U; and a pair of base portions, each base portion projecting outwards from the lower end of a respective leg, the void former comprising: (i) a void forming body having a base, an open top, and a downwardly opening retainer insert locating the recessed portion extending upwardly from said base into an upper portion of the body, the recessed portion having an upper end adapted to be seated on the upper curved portion of the lifting anchor; (ii) a body retainer insert shaped and sized so as to fit within the recessed portion and to bridge the space between the legs; and (iii) means for releasably securing the retainer with respect to the body, wherein the retainer insert is adapted to engage the underside of the upper curved portion of the anchor so as to prevent the body floating upwards during casting of the concrete panel.

The void former is removable after casting and functions to provide a void in the concrete around the upper end of the lifting anchor in the finished cast concrete panel.

Preferably the recessed portion further comprises a pair of spaced-apart, substantially parallel walls integrally formed with the body and extending upwards from the base so as to define a slot for receiving the lifting anchor and the retainer insert.

Preferably the means for securing the retainer with respect to the body comprises: a pair of opposed clips protruding from the walls and integral therewith and adapted to engage a corresponding pair of apertures within the retainer.

In a preferred form, the retainer comprises : a pair of spaced-apart concave side walls shaped to snugly engage respective legs; a front wall; a rear wall spaced-apart and substantially parallel to the front wall; and a bottom wall joining the side walls, the front wall and the rear wall to provide a bridge, wherein the bottom wall in combination with the void forming body excludes a volume of concrete from under the upper curved portion of the anchor between the legs thereof.

Preferably the void former further comprising a removable cap shaped to sealably fit into the open top of the void forming body and preferably the cap defines an open topped well shaped to receive a small volume of concrete.

Preferably, the cap further defines a thin, substantially vertical perimeter wall bounding its open top. This allows formation of a clean crisp boundary around the void after the concrete has set and the void former has been removed.

According to a third aspect of the invention there is provided an assembly for forming a lifting anchor within a cast concrete panel comprising: an anchor comprising an elongate rod formed into a pair of parallel spaced apart legs, an upper curved portion joining the spaced apart legs at their upper ends to form an inverted U, and a pair of base portions, each base portion projecting outwards from the lower end of a respective leg; a chair for holding the anchor in an upright position during casting of the concrete panel, the chair shaped to prevent any relative movement between the chair and the anchor during said casting; and a void former for forming a void around at least the upper curved portion of the anchor within the cast concrete panel.

In order to more fully explain the present invention and each of its aspects, preferred embodiments thereof are described as follows in more detail with reference to and as illustrated in the accompanying drawings.

Fig. 1 is a perspective view of a first void former assembled over a lifting anchor and placed on a bar chair.

Fig. 2 is an exploded view of the assembly of Fig. 1.

Fig. 3 is a perspective view of the lifting anchor partially visible in Fig. 1.

Fig. 4 is a plan view of an alternative lifting anchor to that shown in Fig. 3.

Fig. 5 is a perspective view of the lifting anchor bar shown in Fig. 4.

Fig. 6 is a top perspective view of a retaining element of the void former shown in Fig. 2.

Fig. 7 is a bottom perspective view of the retaining element shown in Fig. 6.

Fig. 8 is a side view of the void former body forming part of the void former shown in Fig. 2.

Fig. 9 is a plan view of the void former body shown in Fig. 8.

Fig. 10 is an end view of the void former body shown in Fig. 8; while Fig. 11 is a cross-sectional view of the lifting anchor of Fig. 3 after casting in a concrete panel and removing the void former of Fig. 2.

Fig. 12a is a perspective view of a second void former assembled over a lifting anchor and placed on a bar chair.

Fig. 12b is an exploded view of the assembly of Fig 12a.

Fig. 13 is a side view of the void former body forming part of the void former shown in Figs. 12a and 12b.

Fig. 14 is a plan view of the void former body shown in Figs. 12a and 12b.

Fig. 15 is a perspective view of the void former body shown in Figs. 12a and 12b.

Fig. 16 is an end view of the void form body shown in Figs. 12a and 12b.

Fig. 16a is a cross-sectional view of the void former body shown in Fig 16.

Fig. 17 is a perspective view of a component (a retainer) of the void former shown in Figs. 12a and 12b.

Figs. 18, 19 and 20 are plan front and side views of the component of Fig. 17.

Figs. 21 and 22 are perspective views of a component (a cap) of the void former of Figs. 12a and 12b.

Figs. 23,24 and 25 are top, side and end view respectively of the cap shown in Figs. 21 and 22.

Figs. 26,27,28 and 29 are cut-away perspective views of the assembly of Figs.

12a and 12b cast within a concrete panel.

Referring to Fig. 1 there is shown an assembly 10 which includes a first void former 30 fitted to a lifting anchor 20 placed on a support chair 12. This assembly 10 is ready for positioning within form work for casting a concrete panel. After the concrete has been poured and has set to a sufficient degree the void former body 30 can be removed to leave a void 9 around the upper end of the lifting anchor 20 as shown in Fig. 11. The lifting anchor 20 can then be attached to an hoisting attachment (not shown) in order to effect the raising of the panel to an erect position (according to known art). In the finished wall formed by the erect panel, the anchor is recessed into the wall. The recess can readily be covered or patched.

Fig. 3 shows an embodiment of a first aspect of the invention wherein a lifting anchor 20 is formed from elongate cylindrical metal rod. A pair of parallel spaced apart legs 22 are joined at their upper ends by curved bridge portion 24. The upper ends of the legs 22 and the curved portion 24 is exposed within the void 9 after the casting of a concrete panel is complete as shown in Fig. 11. A pair of base portions 26 (shown in Figs. 3 and 11) anchor the lifting anchor 20 firmly in the concrete substrate 8. The completed lifting anchor cast into concrete as shown in Fig. 11 provides a simple, inexpensive very high strength lifting hook which is very suitable for erecting tilt-up panels. In addition, the opening between the legs 22 of the anchor 20 permits reinforcing rods or bores (for the panel) to conveniently locate therethrough, and thereby avoid the need to displace or cut the reinforcement when setting up the mould prior to pouring of the concrete.

Figs. 4 and 5 show an alternative embodiment of a lifting anchor 20 according to a first aspect of the invention. With this embodiment the base portions 26 are transversely spaced apart and parallel. They extend in opposite directions normal to the plane in which the inverted U portion lies. The anchor 20 shown in Figs. 4 and 5 has the advantage of being able to be stably supported by itself on a horizontal support surface.

Although the embodiments of the lifting anchor 20 shown in Figs. 3,4 and 5 all employ a rod having a circular cross-section, rods of other cross-sectional shapes may be equally suitable.

Referring to Fig. 2, a void former 30 according to a second aspect of the invention is shown. This void former for use with the lifting anchor 20 shown in Figs.

3,4 and 5, has three main moulded plastic components. The first component is a cup- shaped void forming body 31, the second component is a retainer insert 40, while the third is a cap 35. The body 31 has a downwardly opening recessed portion 32 extending upwardly from a base of the body and inwardly into a mid portion thereof. The recessed portion 32 has an upper end adapted to the seat on the curved bridge portion 24 of the lifting anchor 20.

The retainer 40 performs two functions. It creates a void in the concrete extending between the underside of the curved bridge portion 24 of the lifting anchor 20 and the base of the void former body 31. The retainer comprises a pair of spaced- apart concave side walls 42 shaped to snugly engage the legs of the anchor, front and rear walls 48 and a bottom wall 41. The upper end 44 of the retainer 40 (refer especially Fig. 6) is shaped to engage the underside of the curved bridge portion 24 of the lifting anchor 20 so as to prevent the body 31 floating upwards during casting of the concrete panel. This is a problem which is present in other known void formers.

Referring to Fig. 7 the retainer 40 has apertures 45 in each of the two vertical front and rear walls 48. These apertures 45 provide opposed lug retaining surfaces 46 which are snap-fittingly engaged by lugs 33 integrally formed within the recessed portion 32 of the void former body 31. The deflectable lugs 33 are best shown in Fig.

8. With the lugs 33 engaged, the body 31 and retainer insert 40 are locked together and cannot move.

Lid 35 is designed to close off the interior of the void former body 31 and form a water-tight seal therewith so that no concrete is able to penetrate the interior of the body 31 during casting of the concrete panel.

Referring to Fig 12, there is shown an assembly 10 which includes a second void former 30 assembled over a lifting anchor 20 placed on a support chair 12. This second void former 30 is a second embodiment of a second aspect of the invention.

The entire assembly of Fig 12 is ready for positioning within form work for casting a concrete panel in much the same way as is the first assembly according to a first embodiment of the second aspect of the invention shown in Fig 1.

Referring to Figs 13,14,15 and 16, the void former body 31, shown in Fig 12, is shown in more detail. Without the cap 35, shown in Fig 12, it can be seen that the void former body 31 includes well walls 34 and stiffening webs 36. The well walls 34 define a pair of wells 34a that allow a screwdriver or other tool to be inserted and then leveraged against the curved portion 24 of the lifting anchor 20 to facilitate removal of the void former body 31.

Leveraging of a screwdriver within a first and then a second of the wells 34a enables the void former body 31 to be split in half and then easily removed from the concrete by continuing the leverage against the curved portion 24.

Fig 16a shows the well walls 34 and the wells 34a themselves more clearly in cross-sectional view of the void former body 31.

The central base section 34b is thickened below well 34a to prevent a screwdriver or other tool penetrating through the void former body into the concrete underneath. This reduces the likelihood of damage to the concrete during removal of the void former.

Figs 17,18,19 and 20 show a retainer 40 that fits within the recessed portion 32 shown in Fig 15. The retainer is adapted to engage the underside of the upper curved portion 24 of the lifting anchor 20 so as to prevent the void former body 31 floating upwards during casting of the concrete panel. It construction is similar to that of the retainer 40 shown in Fig 2 and used for the first embodiment of the second aspect of the invention.

The second embodiment of the second aspect of the invention includes an improved cap 35 as shown in Figs 21,22,23,24 and 25. Referring to Fig 22, it can be seen that the improved cap 35 defines an open toped well 37 shaped to receive a small volume of concrete. The cap further defines a thin, substantially vertical wall 49 bounding its open top. This (false form work well) on top of the void former cap 35 allows a neater and smaller hole or aperture to be left in the cast concrete panel after the void former assembly has been removed. The vertical wall 49 provides a concrete cut line around the void former perimeter so that the concrete can easily and simply be removed from the top of the void former body 31 without the need or requirement to use hammers, masonry chisels or other similar equipment. A clear crisp line is left in the concrete that allows for easier patching with grout. The resulting void perimeter looks a lot neater as there is not a large regular opening in the panel that is caused by hammers, chisels or other similar tools. Since there is a neater smaller crisp hole there is no need to use large plastic plate type covers to cover the voids (lifter holes) as required with other lifer and void former combinations according to the prior art.

The chair 12 shown in Fig 12 is shaped to prevent any relative movement between the chair 12 and the anchor 20 during casting of the concrete panel. Clips 16 are provided to securely hold the base portions 26 in place. A pair of opposed lateral supports 14 are also provided to engage the lower portions of the legs 22 to ensure that the lifter 20 does not rotate relative to the chair 12.

While the present invention has been described in terms of preferred embodiments in order to facilitate better understanding of the invention, it should be appreciated that various modifications can be made without departing from the principals of the invention. Therefore, the invention should be understood to include all such modifications within its scope.