WO2015006825A1

WO2015006825A1 - Concrete lifting anchor

Info

Publication number: WO2015006825A1
Application number: PCT/AU2014/050126
Authority: WO
Inventors: Robert Radovan Sladojevic
Original assignee: Casne Verige Pty Ltd
Priority date: 2013-07-19
Filing date: 2014-07-17
Publication date: 2015-01-22

Abstract

The present invention provides method for producing a lifting anchor for incorporation into a concrete panel of the type used in building construction, the method comprising the step of overlaying regions of one or more metal sheets. The anchor may have a predetermined thickness or cross-sectional area, the step of overlaying regions of one or more metal sheets comprising the steps of: providing one or more metal sheets, and overlaying two or more regions of the one or more metal sheets to provide an anchor having a thickness or cross- sectional area that is substantially equal to or greater than the predetermined thickness or cross-sectional area.

Description

CONCRETE LIFTING ANCHOR

FIELD OF THE INVENTION

The present invention is directed to the field of precast concrete panels of the type used in building construction, In particular, the invention is directed to improved anchors used in the Sifting of precast concrete panels, and other concrete elements used in construction.

BACKGROUND TO THE INVENTION

Building construction has been revolutionised by the use of precast concrete panels. Panels are produced by casting concrete in a reusable mould or "form" which is then cured in a controlled environment, transported to the construction site and Iifted into place.

By producing precast concrete in a controlled environment (typically referred to as a precast plant), the precast concrete is afforded the opportunity to properly cure and be c!oseiy monitored by plant employees. Utilizing a precast concrete system offers many potential advantages over site casting of concrete. The production process for precast concrete is performed on steel or concrete casting tables or beds on or above ground level, which helps with safety throughout a project. There is a greater control of the quality of materials and workmanship in a precast plant rather than on a construction site.

In the fabrication of precast concrete elements (such as panels), it is necessary to lift the pane! from the horizontal position in which it was cast to a vertical position for transportation on a vehicle to the building site. Once at the site, the panel is iifted from the vehicle from the longer edge as transported and rotated so as to be iifted from its upper edge and placed in a desired position on site. For this purpose, anchors are incotporated into the reinforcing structure of the panel prior to casting. The anchors provide an attachment point for a clutch, or similar means of engagement.

Lifting anchors must possess significant intrinsic mechanical strength. Concrete panels used in construction are many tonnes in weight, with each anchor taking up significant load when the panel is Iifted.

Pin-type anchors are well known in the art. This type of anchor is typically of solid metal construction and produced by drop forging, and therefore expensive to fabricate, Another well know type of anchor is the plate-type anchor. Given that pin-type anchors (being rounded) do not offer significant buckling resistance in the vertical elevation, plate type anchors are generally preferred fo lifting slender wall type precast panels from the horizontal to vertical position.

It is this lifting process from the horizontal position to the vertical position where most stress is exerted on the precast element and the lift anchor, particularly in the direction to the element's narrowest dimension {i.e. its thickness).

Plate-type anchors are generally fabricated by high energ processes for exampie plasma cutting, laser cutting or water cutting steel plate. The steel plate used must be of substantial thickness to provide the required mechanical strength. Cutting such thick steel plate (typically 15 to 16 mm as required for anchors of 7 to 10 tonne capacity) consumes large amounts of energy, thereby significantly adding to cost and emissions. Furthermore, a proportion of the steel plate is wasted.

Another problem is that cutting thicker steel plate leads to edges which have substantial errors (including Kerf errors). To minimise errors the cut speed must be drastically lowered to provide an edge of acceptable accuracy. Slower cutting speeds further increase energy consumption and hence manufacturing costs.

Fabrication methods using punching also leads to errors. For example, when forming an aperture in a lift anchor (to provide a lifting eye for exampie), the aperture at the anterior face of the plate is generally smaller than that at the posterior. Moreover, the punching of thick steel plate does not leave a square cut edge as the cutting or punching process flares the edge.

Edge errors in lifting anchors have negative effects on the capacity and performance of the anchor. For example, where an upper surface of a lift anchor has a bevelled edge (i.e. where one of the edges is higher than the other, rather than a desired level surface), when a vertical lifting load is applied to the lift anchor the load is concentrated on one point leading to very high shear forces. This can result in a smaller than required conical failure width over the anchor thereby reducing capacity. In some circumstances this can lead to failure with the anchor being ripped from the concrete.

A similar problem arises in regards to the clutch pin contact with the anchor. When load is applied to the clutch (and hence the lifting pin in the clutch) this entire load is taken up initially by the contact point with the anchor. The load is not distributed initially throughout the entire lifting anchor cross section until such time as the point in contact on the edge lift anchor has deformed to an extent where the applied load can no longer create any further compressive deformation of the metal.

In this case the entire load exerted on the lifting anchor by the lifting pin is on one point of the edge lift anchor creating an eccentric load that results in localized deformation of the fift anchor at that contact point prior to becoming a lateral lifting load.

It is often necessary to enhance the pull out resistance of an anchor by fitting load distribution means such as shear bars and hanger bars to the anchor. The assembl of the anchor, shear bar and hanger bar requires expertise, and introduces the potential for failure if executed incorrectly. The assembl step a!so increases the man hours required to produce a panel, thereby adding to cost.

It is an aspect of the present invention to overcome or afleviate a problem of the prior art to provide an improved lifting anchor. It is a further aspect to provide an alternative lifting anchor to those of the prior art. The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application. SUMMARY OF THE INVENTION

In a first aspect the present invention provides a method for producing a lifting anchor for incorporation into a concrete panel, the method comprising the step of overlaying regions of one or more metal sheets, In one embodiment the anchor has a predetermined thickness or cross-sectiona! area, the step of overlaying regions of one or more metal sheets comprises the steps of:

providing one or more metal sheets, and

overlaying two or more regions of the one or more metal sheets to provide an anchor having a thickness or cross-sectional area that is substantially equal to or greater than the predetermined thickness or cross-sectional area.

In one embodiment, the two or more regions are provided by a single metal sheet . In one embodiment the method comprises the step of deforming the single metal sheet.

In one embodiment the step of deforming comprises the step of bending or folding the single metal sheet,

In one embodiment the method comprises the step of retaining the over!ayed regions together.

In one embodiment the step of retaining comprises the step of laminating, gluing, pressing, punching, fastening, welding, crimping, tying, twisting, riveting, or clamping the overlayed regions together.

In one embodiment one or more area(s) of the metal sheet(s) is/are configured to increase pull out resistance of the anchor.

In one embodiment one or more area(s) of the metai sheet(s) is/are configured to perform a function substantially that of a shear bar.

In one embodiment one or more areas(s) of the metal sheet{s) is/are configured to perform a f unction substantially that of a hange bar or a tension bar.

In one embodiment the method comprises the step of deforming the one or more area(s) of the metal sheet(s) configured to perform a function substantially that of a shear bar, or a hanger bar or a tension bar such that the area(s) are disposed at an angle to the main body of the anchor, optionally the angle being about 90 degrees.

In one embodiment the method comprises the step of deforming one or more area(s) of the metal sheet(s) so as to form a tab disposed at or toward an upper edge of the anchor.

In one embodiment at least one of the one or more metal sheets has a thickness equal to or less than about 8 mm

In one embodiment at least one of the one or more metai sheets has a thickness equal to or less than about 7.5 mm

In one embodiment the anchor has a thickness of at least about 15 mm. In one embodiment a single metal sheet is folded to provide the anchor,

In one embodiment the method comprises the step of abutting at least 2, 3, 4, 5, 6, 7, 8, 9 or 10 metal sheets, optionally comprising the step of retaining the sheets together,

In one embodiment the method comprises the step of folding or bending or otherwise deforming a first sheet about a second sheet.

In a second aspect the present invention provides a concrete lifting anchor produced by a method as described herein.

In a third aspect there is provided a concrete lifting anchor for incorporation into a concrete panel, the anchor comprising overlayed regions of one or more metal sheets.

In one embodiment the anchor has a predetermined thickness, the anchor comprising one or more metal sheets, the one or more meta! sheets being positioned or deformed such that a first region of a metal sheet overlays (i) a second region of the metal sheet or (ii) a region of a second metal sheet.

In one embodiment the first and second regions are on a single metal sheet. .

In one embodiment one of the one or more metal sheets comprises a bend or a fold.

In one embodiment the overlayed regions are retained together.

In one embodiment the overlayed regions are, glued, pressed, punched, fastened, welded, crimped, tied, twisted, riveted, or clamped together, In one embodiment one or more area(s) of the metal sheet(s) is/are configured to increase pull out resistance of the anchor.

In one embodiment one or more area(s) of the metal sheet(s) is/are configured to increase pull out resistance of the anchor. In one embodiment one or more areas(s) of the metal sheet{s) is/are configured to perform a f unction substantially that of a shear bar. In one embodiment one or more area(s) of the metal sheet(s) is ar configured to perform a function substantiall that of a tension bar / hanger bar.

In one embodiment the one or more area{s) of the metal sheetis) configured to perform a function substantially that of a shear bar, or a hanger bar or a tension bar such that the area(s) are disposed at an angle to the main body of the anchor, optionally the angle being about 90 degrees.

In one embodiment one or more area(s) of the metal sheet(s} are deformed so as to form a tab disposed at or toward an upper and/or lower edge of the anchor,

In one embodiment at least one of the one or more metal sheets has a thickness equal to or less than about 8 mm.

In one embodiment at least one of the one or more metal sheets has a thickness equal to or less than about 7.5 mm

In one embodiment the anchor has a thickness of at least about 15 mm. In one embodiment the anchor is of substantially unitary construction. In one embodiment the anchor consists of a single f olded metal sheet.

In one embodiment the anchor comprises at least 2, 3, 4, 5, 6, 7, 8, 9 or 10 metal sheets abutted together, optionally comprising means for retaining the sheets together.

In one embodiment a first sheet is folded or bent or otherwise deformed about a second sheet.

In a fourth aspect the present invention provides a sheet metal blank configured to form an anchor as described herein, optionally by a method as described herein.

In a fifth aspect the present invention provides a method for producing a concrete panel or element for use in constructidn, the method comprising, the steps of: providing a moufd for the panel, disposing an anchor as described herein within the form, and filling the form with concrete In a sixth aspect the present invention provides a concrete panel or element for use in construction produced by a method as described herein. The panel may have a weight of at least about 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19 or 20 tonnes. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a diagram (in anterior view) of a sheet metal blank. The blank is configured to be folded into a concrete anchor.

Fig, 2 shows an anchor formed by folding the blank of Fig. 1 . Fig 2A, perspective view; Fig. 2B, anterior view; Fig. 2C, end view.

Fig. 3 shows an anchor formed by folding the blank of Fig. 1. The eight tension members are paired into four groups of two, and splayed into V-shaped formations. Fig 3A, perspective view; Fig. 3B, anterior view. Fig. 4 shows an anchor formed by folding the blank of Fig. 1. The 8 tension members separated completely and splayed into V-shaped formations. Fig 4A, perspective view; Fig. 4B, anterior view.

Fig. 5 shows an anchor formed by folding a blank similar to that of Fig, 1. A difference is that the tension members are substantially saw-tooth shaped, and rotated 90 degrees to the body region. Fig 5A, perspective view; Fig. 5B, anterior view; Fig 5C lateral view.

Fig. 6 shows an anchor formed from three layers of metal sheet. Fig 6A, perspective view; Fig. 6B, end view to more clearly show the folding and abutment of the two sheets.

Fig. 7 shows an anchor formed from a single sheet. Fig 7A, perspective view; Fig. 7B, end view to more clearly sho the folding of the sheet.

Fig. 8 shows an anchor formed from a single sheet. Fig 8A, perspective view; Fig. 8B, end view to more clearly show the folding of the sheet.

Fig. 9 shows an anchor formed from four sheets. Fig 9A, perspective view; Fig. 9B, end view to more clearly show the abutment of the sheets. DETAILED DESCRIPTION OF THE INVENTION

After considering this description it will be apparent to one skilled in the art how the invention is implemented in various alternative embodiments and alternative applications. However, although various embodiments of the present invention will be described herein, it is understood that these embodiments are presented by way of example only, and not limitation. As such, this description of various alternative embodiments should not be construed to limit the scope or breadth of the present invention. Furthermore, statements of advantages or other aspects apply to specific exemplary embodiments, and not necessarily to all embodiments covered by the claims, Throughout the description and the claims of this specification the word "comprise" and variations of the word, such as "comprising" and "comprises" is not intended to exclude other additives, components, integers or steps.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessaril all referring to the same embodiment, but may.

While the majority of this descriptio refers to use of the present anchors in precast concrete panels, it will be appreciated that the anchors will be useful in other precast concrete elements.

In a first aspect, the present invention provides a method for producing a lifting anchor for incorporation into a concrete panel, the anchor having a predetermined thickness or cross- sectional area, the method comprising the steps of; providing one or more metal sheets, and overlaying two or more regions of the one or more metal sheets to provide an anchor having a thickness or cross-sectional area that is substantially equal to or greater than the predetermined thickness or cross-sectional area.

To the best of the Applicant's knowledge, the prior art is devoid of any method for the fabrication of a concrete lifting anchor utilizing a sheet metal having a cross-sectional area or thickness that is less than a required cross-sectional area of the anchor. It is proposed that anchors having the required cross-sectional area (and therefore the requisite mechanical strength for use as a lifting anchor) may be produced by overlaying multiple regions of sheet metal. This is a significant departure from prior art methods that rely on cutting relatively thick metal plate, or the use of casting or forging methods.

It is substantially more simple and economical to either cut or stamp the anchor profile or shape from a relatively thin sheet metal and then fold the metal to obtain the desired overall thickness or cross-sectional area required for the necessary shear load capacity of the lift anchor. As an alternative to folding, two or more metal sheets can be retained together, by a process such as lamination.

The skilled person is capable of determining the necessary cross-sectional area or thickness of the anchor in light variables such as expected load and material of fabrication of the anchor.

The sheet metal used in the present methods may be of an metal, or any alloy of two or more metals capable of satisfying the intended load conditions of the anchor. For reasons of practicality and economy, the metal is preferably iron or steel. The thickness of the sheet metal used in the present methods may be less than about 15, 14, 13, 12, 1 1 , 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 mm. In one embodiment, the sheet thickness is between about 7.5 to 8,0 mm. This thickness is particularly useful where two regions are overlayed, to provide an anchor of thickness 15 to 16 mm. Where more than two regions are overlayed, thinner sheet thickness may be used. For example, where four regions are overlayed the sheet thickness may be only about 3,5 to 4.0 mm,

Moreover, manufacturing a concrete lift anchor from relatively thin sheet provides far greater flexibility in the shape and design of the anchor.

Advantageously, the use of relatively thin metal sheet as starting materia! significantly reduces production costs. The abilit to inexpensively stamp or cut relatively thin sheet metal, and then to use that metal to form an anchor of a required thickness results in an anchor that is more economically produced. Edge errors are also reduced, leading to anchors that are less prone to failure. Furthermore, cutting speeds in production can be increased.

The use of relatively thin sheet metal may further avoid negative alterations in the metal characteristic of plasma, laser or oxy cutting relatively thick metal plate. Negative alterations in thick metal plate are also seen in punching methods, in particular, the edges of a lifting anchor may be compromised leading to a compromise in embedment strength. The edges of a lifting eye may also be negativel affected.

The present methods use thin metal sheet and do not necessarily require any high energy processes like oxy or plasma cutting, and as such ma avoid negative alterations in the metal surface and ductility resulting in improved lifting capacities.

The process of plasma and other cutting processes, as well as punching processes create substantial irregularities in the surface of thick metal plate. Macroscopic inspection of prior art plate cut lifting anchors reveal the surface of the metal to be highly irregular. Point contact issues result with significant load being applied to very small surface areas until such time as they deform enough under load to increase the area of steel in contact with the lifting pin. These irregularities in the metal surface also create potential shear zones or areas for shear or tensile failure propagation. The present anchors reduce or remove these irregularities by the use of relatively thin metal.

As used herein, the term "overlaying" is intended to include any situation whereb a first region of a sheet metal is spatially arranged relative to a second region of sheet metal such that the first region is disposed above, below or lateral to the second region.

Where the regions are substantially planar, it is not necessary that the regions are substantially parallel when overlayed, however preferably the regions are substantially parallel this providing for higher mechanical strength.

Preferably the first and second regions abut, and preferably abut such that substantially no space exists between the two regions. It will be appreciated that in some embodiments, a second material may be disposed between the two regions, such that no actual contact is made between the regions. These embodiments fail within the ambit of claims requiring abutment of the regions.

The two regions may be retained in the overlayed arrangement by any suitable means known to the skilled person. The regions may be laminated, glued, pressed, punched, fastened, welded (including tack welded), crimped, tied, twisted, riveted (including blind riveted), or clamped together with the aim of preventing any relative movement that may compromise strength of the anchor. Given the benefit of the present specification, the skilled person will be capable of conceiving and implementing other means, with all being included in the ambit of the present invention. In some embodiments, however, no dedicated retaining means is used.

The two or more metal sheet regions may be provided by two or more metal sheets, whereby the first sheet is overlayed on the second sheet.

Preferably the two or more regions are provided by a single metal sheet. This embodiment of the method provides for ease of construction, and also may negate the need for a dedicated fastener or fastening ste in the method.

In one embodiment, the method comprises the ste of deforming the single metal sheet, the deformation being sufficient to overlay two or more regions of the single metal sheet. Preferably, the step of deforming comprises the step of bending or folding the single metal sheet. Any suitable method Known to the skilled person may be used. For example, the bending or folding may be achieved using a press brake, air bending, bottoming, coining, V- bending, U-die bending, wiping die bending, or rotary bending. Once the required bend has been made in the sheet metal, then the first and second regions may be urged toward each other to result in an overlay.

The skilled person understands that in the process of folding, it may be necessary to calculate a bend allowance (or bend deduction) such that the overall dimensions of the resultant anchor are as required. Other means of deformation such as rolling, twisting and the like are anticipated to be useful in the present methods. For example, the metal sheet may be roiled to form a cylinder which may be used as a pin anchor.

The method may comprise the step of making a second deformation, third deformation, fourth deformation, or a further deformation. In one embodiment, the method comprises the step of making two or three folds, preferably to form a main body portion of the anchor. Where two or more folds are used, multiple layers of sheet metal may abut to form a body with substantially greater mechanical strength than each individual layer.

An advantage of the present methods is that an anchor having incorporated functional components may be produced. Preferably, the functional component increases the pull out resistance of the anchor relative to an anchor which is devoid of the functional component. This approach is a departure from prior art anchors which are fitted with ancillary apparatus such as a shear bar or a tension bar. As discussed in the Background section, the assembly of an anchor with a shear bar and/or tension bar adds time and cost to the process of casting a concrete panel.

When engaged with an anchor and embedded in concrete, a shear bar allows a panel to be rotated from the cast horizontal position to a vertical position and thereby lifted off the casting table. The shear bar prevents an edge lift anchor from pulling out during this lifting process.

An anchor having an incorporated shear ba (as distinct from an assembly comprising a prior art anchor with an attached separate shear bar) provides certain advantages. In prior art shear bars, any vertical loading on an associated edge lift anchor (as occasioned in lifting a precast panel off the casting table) has a direct tensile !oad on the shear bar over the anchor. This then also translates into transposed loads on the shear bar that have vertical !oad components. The resultant loads on the shear bar in the vertical direction are not identical to the lift load as they also comprise horizontaJ components (due to the shape of the bar) and thereby transfer a proportion of the lift load into horizontal toads within the panel. This situation is unfavourable as stresses are created in the concrete (potentially causing a catastrophic concrete blow out above the lift anchor). Furthermore, where the vertical shear loads are less than the lift loads there is the possibility of the lift anchor moving upwards within the cast element and as such causing stress fractures in the panel surface. Accordingly in prior art shear bars, not all the load is directly transferred vertically but has horizontal vector components resulting in the shear bar capacity being diminished. In light of that, much iarger steel members are required than would be the case if the full tensile load is vertical (and no horizontal vectors are produced).

The incorporated shear bar functionality of the present anchors (and particularly where the sheer members are substantially planar) provides for the transposition of lift loads on the anchor into the lower portions of concrete (via the shear members) in a substantially vertical direction, with no horizontal vector components being produced. This provides superior anchorage of the shear bar into the concrete and as such smaller shear bar components are required in the present anchors ove the traditional round bar type shear bars of the prior art that are fabricated separately from the anchor.

The provisional of a substantially planar shear member provides further particular advantage. A round shear bar (as used in the prior art), does not provide the ideal contact between the anchor and the shear bar. A rounded shear bar allows fo a greatly reduced initial contact area at the interface with the anchor. As a result, there is localized or concentrated loading on the shear bar which may cause deformation of the bar until such time as sufficient cross-sectional area of steel in the bar is in contact with the anchor to counter the lifting load. The end result may be stress fractures in the top face of the panel. In contrast, in anchors of the present invention the shear bar functionalit is a part of the lift anchor itself, and accordingly, any load on the anchor is instantaneously and fully transferred to the shear bar. This provides instantaneous resistance to load unlike prior art round shear bars where some deformation between the anchor and the bar is required before the full load is fully transferred. Given the optimised performance, less metal is required in the present anchors to achieve the same shear resistance.

When engaged with an anchor an embedded in concrete, a tension bar prevents the anchor from pulling out of the concrete when the panel is in the vertical position and the anchors are taking the full weight of the panel. It is not practical to leave cast elements on a steel casting bed for the concrete to fully or substantially cure to provide sufficient embedment strength for an edge lift anchor to be able to support the full weight of the cast element vertically. As such the elements need to be lifted of the steel tables before the concrete has reached any substantial compressive strength so as to clear the casting table for the next element to be cast.

Prior art plate edge lifting anchors are slender i design and do not provide sufficient embedment or bond strength in low compressive strength concrete during the lifting process, when the concrete element is in the vertical position and the lifting anchors support the elements total weight vertically. Accordingly long tension bars are often inserted into lift anchors that protrude deeper into the central body of the concrete element transferring the lifting loads deeper into the panel so as to provide sufficient embedment strength for the lift anchors. The use of tension members which are incorporated into the anchor avoid the need for a separate tension bar / hanger bar. Methods for manufacturing a lift anchor from folded metal rather than a solid plate allows for the provision of easily deformab!e and separable members that may be fanned outwards (see Fig. 4, for example). The members may protrude out into a V-shaped conical failure section of the panel to provide an improved mechanical bond to low MPa concrete in the panel and as such eliminate the need for an additional tension or hanger bar to be added to the anchor. Prior art plate anchors (being uniplanar) do not mechanicall bond well in the concrete. By contrast, outwardly fanning legs of the present anchors mimic a tension or hanger bar and provide improved bonding to the concrete.

Applicant has found that by shaping a metaf sheet, and then overlaying regions of that sheet allows for the incorporation of functional substantiall that of a shear bar and/or tension bar into an anchor. Thus, a multi-functional anchor is produced that does not require assembly with other components in the process of casting a concrete panel or element.

These additional functional components may be incorporated into a single metal sheet, the sheet forming a blank which is subsequently deformed (and preferabl folded) to form an anchor having additional function(s). Typically, the sheet metal is cut to form a blank comprising one or more members that, upon deformation of the sheet, form the additional component. For example, a single sheet metal blank may be cut so as to form a main body, from which one or more members extend.

A shear bar functionality may be included in the anchor by providing shear members that, upon folding of the blank, preferably extend laterally and outwardly from two sides of the main body. The shear members are configured to lie (at least for a part of their length) substantially parallel to the plane of the panel and/or substantiaily normal to the force vector that would be applied to the anchor during lifting. Optionally, terminal regions of the shear members are deflected in a direction toward upper face of the concrete panel, and or in the direction of the force vector that would be applied to the anchor during lifting. The present methods may therefore comprise the step of deflecting a terminal region of the shear member.

A. tension bar functionality may be included by providing tension members that, upon folding of the blank, preferably extend substantially longitudinally and outwardly from one (or more) sides of the main body. Preferably the blank comprises at least 2, 4, 6, or 8 tension members. The members are preferably configured so as to increase pull out resistance and may, for example, have an undulating profile, or a saw tooth profile. Other configurations will be apparent to the skilled person, and are therefore included in the ambit of the present invention.

Where two or more tension members are provided, the tension members may be splayed, preferably to form one or more substantial V-shape(s). Where three or more tension members are provided, a least one member may not be splayed. The present methods may therefore comprise the step of splaying one or more tension members, preferably to form a substantial V-shape.

Preferably the anchor consists of a single metal sheet, and is devoid of other components. While the present invention is directed particularly to edge lift anchors, it is not intended that the ambit is so restricted. The features and advantages of anchors described herein may be useful in other contexts.

The present invention will now be further described by reference to the following non-limiting embodiments.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION.

Fig. 1 shows a diagram of a sheet metal blank 2 configured to be folded into an anchor having shear bar and tension bar functionalities. The blank comprises a main body 4 the boundaries defined by fold lines 22 and 26 and the bases of members 14, Four elongate apertures 6 form lifting eyes, and four circular apertures 8 are provided for the insertion of a tension bar where necessary. Extending from the main bod 4, are two shear members 10, each having a distal terminal region 12, The boundary of each distal terminal region 12 being defined by fold lines 24, Also extending from the main body 4 are eight tension members 14 having an undulating profile. It will be noted that the fold lines 22, 24, and 26 are shown to assist in describing the various regions of the blank and the manner in which it is folded, and do not necessarily appear on the blank.

The blank is formed into an anchor by completely folding the metal sheet downwardly along the central fold line 18 until the so-formed halves of the body 4 abut In this initial folding step, surfaces of opposing members 14 also abut. The sheet metal is then folded upwardly and completely along fold lines 18 and 20 to form a main bod of the anchor consisting of four abutting layers of sheet metal. In folding along the fold line 18 and 20 the members 14 are brought into further abutment with each other to form two members, each of four sheet metal layers. The sheet metal Is bent upwardl 90 degrees along the fold lines 22 such that the shear members 10 extend outwardly and orthogonally away from the main body 4. A further bend of 45 degrees is made upwardly along fold lines 24.

Fig. 2 shows the anchor formed from the blank of Fig. 1 . During installation the edge lift anchor is typically held in place by supporting the anchor on the side-form shuttering used for casting the concrete panel, or by placement of reinforcement bar packers under the lifter disposing it above the steel reinforcement. Generall a re-usable rubber or plastic void former of a type well known to the skilled artisan (not shown) is fitted about the aperture 6 to form a void in the edge of the concrete panel to expose the apertures, After the concrete is poured and at least partially cured, the void former is removed to leave a void. The void enables engagement of the aperture 6 with a lifting clutch. The void is shaped to allow the clutch to enter the void, and also to avoid or minimise contact of the clutch with surrounding concrete during lifting.

The shear regions 10 with upwardly deflected terminal regions 12 provide improved pull out resistance shear bar functionality to the anchor. Referring to the Drawing of Fig 2A, the lifting force is directed in a substantially upward direction with th load being spread across the shear regions 10. The shear regions 10 mimic that of a shear bar of the type which, in the prior art, is a separate component that is assembled with the anchor. It will be noted that the shear regions 10 are wider than round shear bars of the prior art and displace significantly more concrete. This increases the shear resistance capacity provided by shear bars of the prior art,

Fig. 3 shows the anchor of Fig. 2, having included the further step of folding along the fold line 26 to splay the members 4 to form two substantial V-shapes, Each arm of each V is formed form two layers of sheet metal. This arrangement mimics the function of a tension bar / hanger bar thereby further improving pull out resistance. Greater levels of engagement with the surrounding concrete (and therefore pull out resistance) may be provided whereby the double layers of the tension members 14 are separated, and splayed at different angles to form four substantial V-shapes. This embodiment is shown in Fig. 5. This embodiment provides tension members 14 disposed such that the broad face of the tension members 14 are disposed at 90 degrees to the main body 4. The present anchors may be produced by deforming relatively thin metal, such that the anchor may comprise elements (such as members, tabs and legs) that may be independently folded or twisted such that they are no longer disposed in the same vertical plane as the body of the lift anchor. This allows for placement of the anchor deeper into the concrete and at the centre of the cast element which is preferable.

Prior art plate-type edge lift anchors, due to their shape, have their upper and lower edges proximal to the outer regions of the east concrete panel. These regions are the highest stress zones during the lifting process. Thus, in the prior art there is a relatively smalt amount of concrete between the outside edge of the pane! and the edges of the lifting anchor. This increases the possibility of stress fractures in the panel at the lifting anchor locations, especially if attempts are made to lift the cast element at low concrete compressive strengths. The ability to more deeply place the present anchors significantly decreases the possibility of stress fractures.

The provisional of an integral shear member protruding outwards at 90 degrees from the bottom of the anchor also facilitates the deep placement of the anchor. The integral sheer member negates the need for a separate sheer bar to be added to the upper edge of the anchor. Shear bars of the prior art typically wrap over the top of the anchor at 90 degrees to the anchor, and extend downward into the panel. This arrangement dictates that less concrete covers and underlies prior art anchors. By contrast, the present anchors provide for substantially more concrete to surround the anchor and as such increase resistance to pulling out during the lifting process whereb the precast panel is tilted from the cast flat position to its vertical position. Advantageously, the present anchors thereby decrease possibility of cracks or damage to the cast element over the lift anchors. A panel may therefore be lifted with less cure time, this increasing production capability.

As an alternative to the members 14 having an undulating profile as show in Figs 1 to 4, the members may have any other profile that provides for increased pull out resistance. The embodiment shown in Fig. 5 includes 4 members 14 with a saw-tooth profile. The planes of the members 14 are rotated 90 degrees to the body portion 4, and are cop!anar with the shear members 10. This arrangement allows for a broader tension member to be used without steric interference with any underlying or overlying structures. This embodiment further demonstrates the edge abutment of members 14 (see the central arm).

An embodiment fabricated from two metal sheets is shown in Fig. 6. A first sheet 100 is cut to define tension members 102. A second sheet 104 is folded ove the first sheet 100. The two outwardly extending members resuiting from the folded over first sheet 100 form shear members 106, the second sheet also contributing additional splayed tension members 108. An embodiment fabricated from a single sheet, and having a main body section of four layers of sheet metal is shown in Fig. 7. The sheet 100 is cut to define tension members 102. The sheet 100 is folded to form two outwardly extending members which form shear members 106. Folding in the main body portion forms tabs 110 which effectively broaden the surface area available to contact the surrounding concrete, thereb further enhancing pull out resistant of the anchor especially where a panel is being lifted from the horizontal position to the vertical position. Effectively, the tabs form a larger conical failure width than that provided by prior art anchors.

A difficulty in broadening an edge lift anchor is thai in the centre the ancho must be slender so as to accommodate connection to the clutch. An "I-beam" configuration would be useful but is extremely difficult to achieve in the traditional existing type edge lift anchors for practical reasons. The anchors of the present invention allow for the incorporation of folds to the upper and/or lower edges of the anchor simply and cost effectively.

Due to the manufacturing process of plate and pin type edge-lift anchors, it is not practical and/or expensive to broaden the lift anchor. Broader edges of these anchors may be drop forged however this is an additional step in the manufacturing process and expensive to achieve.

Achieving a broad profile is difficult for a pin-type anchor due to the inherent pin shape. As the forging is in multiple directions this would require multiple handling steps and makes manufacture expensive.

Other means such as welding plates to the ends of edge lift anchors in order to widen the end ends is also not cost effective for what is a consumable item in the precast operation.

A more simple embodiment fabricated from a single metal sheet is shown in Fig. 8. The sheet 100 is cut to define tension members 102. The sheet 100 is folded to form two outwardly extending members which form shear members 106. As for other embodiments, the tension members 102 are formed by the abutment of two sheets 102a and 102b, this abutment being shown most clearly in this simple embodiment.

It will be understood that some embodiments of the invention do not require any folding or deformation by which to overlay regtons of sheet metal in order to achieve any predetermined thickness or cross-sectional area. Any number of metal sheets may be overlayed. One embodiment is shown in Fig. 9 whereby four metal sheets 200, 210, 220. 230 are abutted. The internally disposed sheets 210 and 220 are cut to define tension members 240, white the externally disposed sheets are cut to define tension members 250 and shear members 260.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, it is to be understood that the description and drawings presented herein represent a presently preferred embodiment of the invention and are therefore representative of the subject matter which is broadly contemplated by the present invention. It is further understood that the scope of the present invention fully encompasses other embodiments that may become obvious to those skilled in the art.

It will be appreciated that in the detailed description and the description of preferred embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in iess than all features of a single foregoing disclosed embodiment. Thus, the following ciaims are hereby expressly incorporated into this description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and from different embodiments, as would be understood by those in the art. For example, in the ciaims appended to this description, any of the claimed embodiments can be used in any combination.

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Claims

CLAIMS:

1. A method for producing a lifting anchor for incorporation into a concrete panel, the method comprising the step of overlaying regions of one or more metal sheets.

2. The method of claim 1 wherein the anchor has a predetermined thickness or cross- sectional area, the step of overlaying regions of one or more metai sheets comprises the steps of:

providing one or more metal sheets, and

3. The method of claim 1 or claim wherein the two or more regions are provided by a single metai sheet.

4. The method of claim 3 comprising the step of deforming the single metal sheet.

5. The method of claim 4 wherein the step of deforming comprises the step of bending or folding the single metal sheet.

6. The method of any one of claims 1 to 5 comprising the step of retaining the overlayed regions together.

7. The method of claim any one of claims 1 to 8 wherein one or more area(s) of the metal sheet(s) is/are configured to increase pull out resistance of the anchor.

8. The method of claim any one of claims 1 to 7 wherein one or more area(s) of the metal sheet(s) is/are configured to perform a function substantially that of a shear bar.

9. The method of any one of claims 1 to 8 wherein one or more areas(s) of the metal sheet(s) is/are configured to perform a function substantially that of a hanger bar or a tension bar.

10. The method of any one of claims 1 to 9 comprising the step of deforming the one or more area(s) of the metal sheet(s) configured to perform a function substantially that of a shear bar, or a hanger bar or tension bar such that the areafs) are disposed at an angle to the main body of the anchor.

1 1. The method of any one of claims 1 to 10 wherein a single metal sheet is folded to provide the anchor,

12. The method of any one of claims 1 to 1 1 comprising the step of folding or bending or otherwise deforming a first sheet about a second sheet.

13. A concrete lifting anchor produced by the method of any one of claims 1 to 12,

14. A concrete lifting anchor for incorporation into a concrete panel, the anchor comprising overiayed regions of one or more metal sheets.

15. The anchor of claim 13 or claim 14, the anchor having a predetermined thickness, the anchor comprising one or more metal sheets, the one or more metal sheets being positioned or deformed such that a first region of a metal sheet overlays (i) a second region of the metal sheet or (ii) a region of a second metal sheet.

16. The anchor of claim 15 wherein the first and second regions are on a single metal sheet. .

17. The anchor of any one of claims 3 to 16 wherein one of the one or more metal sheets comprises a bend or a fold.

18. The anchor of any one of claims 14 to 17 wherein the overiayed regions are retained together.

19. The anchor of any one of claims 13 to 18 wherein one or more area(s) of the metal sheet(s) is/are configured to increase pull out resistance of the anchor.

20. The anchor of any one of claims 13 to 19 wherein one or more areas(s) of the metal sheet(s) is/are configured to perform a function substantially that of a shear bar.

21. The anchor of any one of claims 13 to 20 wherein one or more area(s) of the metal sheet{s) is/are configured to perform a function substantially that of a tension bar / hanger bar.

22. The anchor of any one of claims 13 to 21 wherein the one or more area(s) of the metal sheet(s) configured to perform a function substantialiy that of a shear bar, or a hanger bar or a tension bar such that the area(s) are disposed at an angle to the main body of the anchor, optionally the angle being about 90 degrees.

23. The anchor of any one of claims 13 to 22 comprising at least 2, 3, 4, 5, 6, 7, 8, 9 or 10 metal sheets abutted together, optionaily comprising means for retaining the sheets together,

24. The anchor of claim 23 wherein a first sheet is folded or bent or otherwise deformed about a second sheet

25. A sheet metal blank configured to form the anchor of any one of claims 13 to 24, optionally produced by the method of any one of claims 1 to 12.