Patent Publication Number: US-9409751-B2

Title: Lifting device and method for concrete elements

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to methods and apparatuses for lifting and handling of concrete elements, examples of such are bridge beam and deck elements, slabs, piles, wall panels, concrete legs and floating concrete caisson structures of oil platforms, prestressed concrete structures in general and the like. In particular, the lifting and handling of concrete elements up to and greater than 1,000 tonnes (t). The invention may be applied to concrete elements as commonly found in the building, construction, concrete pre-casting, demolition and emergency rescue industries/application areas. 
     2. Description of the Art 
     Lifting and handling of concrete elements is typically done by use of a crane or other lifting machine which is connected via a rigging to one or a number of lifting inserts permanently embedded in the concrete element to be lifted. Examples of such lifting inserts/anchors are U.S. Pat. Nos. 4,000,591, 4,367,892, 4,386,486, 4,437,642 and 4,580,378. In addition protruding loops of cable, wire loop and reinforcing bar have also been used to provide a lifting insert/anchor for attachment. The crane rigging may attach to the lifting insert via (for example) a lifting clutch, shackle, hook, lifting eye or any suitable attachment means or combination of. 
     However permanently embedded lifting inserts must be suitably protected against corrosion in order that the integrity of the concrete element is maintained and/or if the lifting insert is to have some re-use. In addition lifting inserts are a significant cost factor in the manufacture and use of concrete elements. 
     One example of extensive use of lifting inserts/anchors is in the pre-cast manufacture of panels, slabs and pre-stressed bridge beams where the lifting inserts are embedded during the casting process. Once the concrete element has been cast in a pre-caster facility then the lifting inserts are used to lift the concrete element from the floor or from the moulding/casting form in which it is made. The concrete element panels are then typically placed on racks or stacked to allow the concrete to gain strength prior to being delivered to a construction site. The delivery to the construction site requires a lift onto a transporter and then a subsequent lifting and handling to position the concrete element in the construction project. The embedded lifting inserts remain in the concrete element and are of no further use. 
     If the concrete element is made by a tilt slab builder on the building construction site then the lifting inserts are often used in a single lift of the concrete element from the position in which it was cast into its final position in a building project. Again, the embedded inserts remain in the concrete element and are of no further use. 
     For lifting inserts typically used in concrete element manufacture the corrosion protection process has particular dangers if not properly treated, due to hydrogen embrittlement of a steel lifting insert, for example. Lifting inserts that are embrittled may unexpectedly fail during a lift of a concrete element, endangering workers in the proximity of the load. As a consequence, the use of expensive redundant permanent inserts and their attendant safety issues is a significant cost and risk to the building and construction industry. 
     Portable concrete road barriers often feature steel lifting inserts which are used to lift the road barriers numerous times over the course of their many years of use. The lifting inserts embedded in the upper faces of concrete road barriers are exposed to the elements which may promote corrosion and consequently affect the serviceability of the lifting insert over its service life. 
     Expansion bolts, screw fasteners and the like that may be used to secure items or structures to a concrete element are not suitable for the lifting and handling of concrete elements. Expansion bolts/fasteners are not suited for the weight of concrete elements and the dynamic tensile and shear loads experienced in their lifting and handling. Such systems as expansion bolts/fasteners at large dynamic loads of some tonnes may be prone to failure, for example, via thread stripping, inadequate pull-out cone and/or the expanding anchor fails. National standards for lifting and handling of concrete elements typically do not allow for the use of expansion screw bolts. In addition expansion bolts are typically not completely removable and designed for single use; the screw or bolt may be removed but the expanding anchor remains behind in the hole to corrode and prevent re-use of the hole. 
     None of these prior art devices and methods provides an entirely satisfactory solution to the provision of lifting and handling of concrete elements, nor to the ease of use and verification of a safe lifting operation. 
     SUMMARY OF THE INVENTION 
     The present invention aims to provide an alternative lifting device and method for concrete elements which overcomes or ameliorates the disadvantages of the prior art, or at least provides a useful choice. 
     In one form, the invention provides a lifting device for a concrete element comprising of an elongate member with a flared lower end and an upper end configured for an attachment means, a sleeve about the elongate member and one or more wedges moveably attached to a lower end of the sleeve. When the sleeve moves towards the flared end the one or more wedges are displaced/splayed outwardly. Preferably the wedges are displaced outwardly by a portion of the flared lower end of the elongate member. In use the one or more wedges engage at least a portion of a wall or an edge of a configured cavity in the concrete element so as to prevent withdrawal of the elongate member from the cavity in the concrete element. The configured cavity being shaped or otherwise adapted to receive the lower end of the lifting device as well as being suitable for the wedges, or other interference devices, to engage with. The attachment means may by way of example be a lifting eye, a lifting ring, a shackle bolt, a hook, a cable or a loop. 
     The lifting device may also be configured as a lifting clutch for a crane or other lifting machine. 
     Preferably the wedges or other interference devices are pivotably attached to a lower end of the sleeve. The wedges or otherwise May be pivotally attached via a pivot pin and corresponding terminal lugs on the sleeve lower end and the respective wedges. 
     Optionally the flared end is a frusta-conical cone or section and the elongate member may be a shank, rectangular or other suitable cross-section. The sleeve&#39;s cross-section may be cylindrical, elliptical, rectangular or an otherwise suitable cross-section or structure. 
     Optionally the elongate member and the sleeve of the lifting device may be adapted or otherwise configured to receive a safety element when the one or more wedges is positioned over a portion of the flared end of the elongate member. Preferably the safety element may be a safety pin adapted to be inserted through concentric holes within the elongate member and the sleeve. 
     Optionally the upper end of the sleeve is configured or adapted to prevent use, access or block the attachment means when the wedges are not over a portion of the flared lower end of the elongate member. Preferably the upper end of the sleeve is a safety cap. 
     A further form of the invention provides a former comprising of a tube portion and a closed base end portion with one or more flared walls. The former may be used to form a suitably configured cavity in a concrete element during the casting of the concrete element. Alternatively a suitably configured cavity may be formed by drilling, cutting, percussion means, a jackhammer or other techniques common to the working of concrete elements. 
     In an alternate form the invention may provide a method for lifting concrete elements by a lifting device, including the steps of securing the lifting device to a concrete element by: configuring a cavity in the concrete element to receive the lower end of the lifting device, inserting the lower end of the lifting device into the cavity and then causing or otherwise actuating the one or more wedges at the lower end of the lifting device to engage a flared end of an elongate member of the lifting device and a portion of a wall or a edge of the configured cavity. The lifting device may then be attached to a lifting machine for lifting and/or handling the concrete element. Optionally the method for lifting may include one or more safety steps to prevent lifting of the concrete element until the lifting device is secured to the concrete element. Preferably a safety step may be the step of attaching or inserting a safety element to the lifting device. Where the safety element prevents the removal of the lifting device from the configured cavity of the concrete element. A second, optional safety step may be preventing attachment of the lifting machine or crane to the lifting device until the lifting device is secured to the concrete element, preferably by the use of a safety cap. 
     Further forms of the invention are as set out in the appended claims and as apparent from the description. 
    
    
     
       DISCLOSURE OF THE INVENTION 
       Brief Description of the Drawings 
       The description is made with reference to the accompanying drawings; of which: 
         FIG. 1  is a schematic of an exploded perspective view of a lifting device and a cavity former in an embodiment of the present invention. 
         FIG. 2  is a schematic of a perspective view of the assembled lifting device of  FIG. 1 , with the sleeve lowered. 
         FIG. 3  is a schematic of a perspective view of the assembled lifting device of  FIG. 1 , with the sleeve raised. 
         FIG. 4  is a schematic of a perspective view of the assembled lifting device and cavity former of  FIG. 1 , with the sleeve lowered. 
         FIGS. 5 to 8  are schematic illustrations of the steps of inserting the lifting device of  FIGS. 1 to 4  into a cavity of a concrete element and deploying it for lifting use.  FIGS. 5 to 8  are partial cross-sectional views of  FIGS. 1 to 4 . 
         FIG. 9  is a schematic of an exploded perspective view of an alternate, 50 tonne, embodiment of the lifting device of  FIG. 1 . 
         FIG. 10  is a schematic of a perspective view of an alternate embodiment of the cavity former of  FIG. 1 . 
         FIG. 11  is a schematic of a cross-sectional view of another alternate embodiment of the cavity former of  FIG. 1 : cast permanently into a concrete element. 
         FIG. 12  is a schematic of a cross-sectional view of yet another alternate embodiment of a larger cavity former to that of  FIG. 1 . 
         FIG. 13  is a schematic of a perspective/isometric view of an alternate lifting device for edge lifting. 
         FIG. 14  is a schematic of a cross-sectional view along the line  14 - 14  of the edge lifting device of  FIG. 13 . 
         FIG. 15  is a schematic of a part-sectional, perspective view of a lifting device with optional handle. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  schematically shows an exploded perspective view of an embodiment of a lifting device  110  and a cavity former  112  that may be used in lifting concrete elements. The word “concrete element” in the following detailed description and claims is taken to include one or more of: bridge beam and deck elements, slabs, piles, wall panels, concrete legs and floating concrete caisson structures of oil platforms, prestressed concrete structures and the like in general as well as concrete structures up to and beyond 1,000 tonnes (t). 
     The lifting device  110  may have an elongate member  114  which in this embodiment is a shank  114  that may be connected at the elongate member&#39;s  114  upper end to a lifting eye  116  as an attachment means  116  to the rigging of a crane or other lifting machine (not shown). The attachment means  116  may also be any other structure suitable for connecting a lifting device to the rigging of a crane, for example: a lifting ring, a shackle bolt, a hook, a cable or a loop. The lifting eye  116  may be secured to the elongate member  114  by a threaded shaft  118  which is screwed into the corresponding threaded hole  120  of the elongate member  114 . Alternatively the lifting eye  116  may be cast, or otherwise constructed, with the elongate member  114  to form one piece. 
     The lower end of the elongate member  114  may have a flared end  122  which is shown as a frusta-conical cone  122  in  FIG. 1 . In alternate embodiments the flared end  122  may be flared in a curved fashion, rather than the straight profile of the cone shown. This may be to suit the interaction of the wedges  124  or other interference devices  124  with the flared end  122 . The interaction between the flared end  122  and the wedges  124  is described in detail below with respect to  FIGS. 2 to 8 . A sleeve  126  may have terminal lugs  128  at its lower end to moveably attach the pendant wedges  124  by the use of pivot pins  130 . It will be readily appreciated that any number of other moveable attachment mechanisms for the wedges  124  to the sleeve  126  may be designed and applied by a person skilled in the art. The sleeve  126  is shaped and/or configured to be able to slide up and down the elongate member  114 , in the example of  FIG. 1  the sleeve is cylindrical. 
     The elongate member  114  may also have a recess  132  or profiling to the elongate member  114  to allow the wedges to hang within as to be described in detail with respect to  FIGS. 2 to 8  below. 
     The sleeve  126  may also have at its upper end an optional safety cap  134  that operates to prevent access to, use or block the lifting eye  116  until the lifting device  110  is safely engaged for lifting with a cavity in the concrete element; to be described in detail below with respect to  FIGS. 2 to 8 . An additional, optional safety feature may be the use of a safety pin  136  that may be inserted through the hole  138  in the sleeve  126 , the hole  140  in the elongate member  114  and the hole  142  in the lifting eye  116  shaft  118 . As for the safety cap  134 , the operation of the safety pin is described below with respect to the same figures. The safety pin  136  may be in the form of a dowel, a rolled pin, a split pin or a specialised pin device that only allows or indicates authorised attachment by a certified rigger/dogger/supervisor. Alternatively the safety pin  136  and the respective holes  138 ,  140 ,  142  may be replaced by an alternate safety element such as a clip device (not shown) with respective grooves in the sleeve  126  and elongate member  114 . In yet another alternate embodiment the safety element/pin  136  may be incorporated in an optional handle which may be attached at the upper end of the elongate member  114  or the sleeve  126 . Further alternate safety elements are described below with respect to  FIGS. 13 and 14 . An optional handle with safety pin is described in detail below with respect to  FIG. 15 . 
     The materials and techniques used to construct the lifting device may be selected by a person skilled in the art of high compressive and tensile load mechanical devices. For example high tensile steels with appropriate ductility may be used. In addition case hardening and/or surface coatings on any components of the lifting device may be employed as appropriate. 
     The cavity former  112  example shown in  FIG. 1  may be used when casting a concrete element so as to create a suitably configured cavity in the concrete former suitable for the lifting device  110  to be inserted and used. The casting in and other details of the cavity former are described in detail with respect to  FIGS. 10 to 12 . The cavity former  112  features a tube or bore portion  143  and a flared wall  144  towards the closed base  146  of the cavity former  112 . The operation of the lifting device  110  with the cavity former  112  in casted concrete is described below in detail with respect to  FIGS. 5 to 8 . Alternate embodiments of the cavity former and other techniques for forming a suitable cavity or otherwise for the lifting device embodiments are also described below with respect to  FIGS. 10 to 14 . 
       FIG. 2  is a schematic of a perspective view of the assembled lifting device  110  with sleeve  126  fully lowered and consequently the wedges  124  are shown resting upon the flared end  122  of the elongate member  114 . The safety pin  136  is shown inserted through the respective holes  138 ,  140 ,  142  of the sleeve  126 , elongate member  114  and lifting eye  116 . The safety cap  134 , as attached to the sleeve  126 , is shown lowered and thus not obscuring the attachment means/lifting eye  116 . An upper surface  248  of each wedge is shown with a profile which facilitates the operation of the wedge  124  (or other interference device) with a cavity in a concrete element; described further with respect to  FIGS. 5 to 8 . 
       FIG. 3  is a schematic of a perspective view of the assembled lifting device  110  with the sleeve  126  raised and consequently the wedges  124  are shown within the recess  132  of the elongate member  114 . The safety pin  136  is absent as it cannot be inserted when the sleeve  124  is raised. The safety cap  134 , with the sleeve  126  raised, is shown obscuring the lifting eye  116  to prevent attachment of a crane&#39;s rigging to the lifting device  110 . 
       FIG. 4  is a schematic of a perspective view of the assembled lifting device  110 , sleeve  126  lowered, inserted within the cavity former  112 . 
       FIGS. 5 to 8  are schematic illustrations of inserting a lifting device into a cavity of a concrete element and deploying it for lifting use.  FIGS. 5 to 8  are partial cross-sectional views of the lifting device  110  and cavity former of  112  of  FIGS. 1 to 4  in order to better describe the operation of the lifting device.  FIGS. 5 and 6  correspond to the partial cross-section along lines  5 ,  6 - 5 ,  6  of  FIG. 3 .  FIGS. 7 and 8  correspond to the partial cross-section along lines  7 ,  8 - 7 ,  8  of  FIGS. 2 and 4 . 
     In the first illustrated step of  FIG. 5  the lifting device  110  is shown with the sleeve  126  raised so that the wedges are partially at least within the recess  132  of the elongate member  114 . The lifting device may then be inserted into the cavity  550  or bore, which in this example has been formed in a concrete element  552  by a cavity former  112  at casting. In  FIG. 5  the outside diameter  554  of the sleeve  126  and the base of the flared end  122  of the elongate member  114  is 58 mm whilst the internal diameter  556  of the cavity bore  550  is 60 mm. The cavity bore  550  may also have a cavity flared end  558  where the angle  560  of the flared end to the line of the bore  550  in this example may be approximately 30 degrees and the depth  562  of the cavity flared end  558  is approximately 110 mm. The example lifting device as shown in  FIG. 5  may be capable of lifting loads of up to and beyond 10 tonne in routine lifting work. Further comments to loads for the lifting device are made below with respect to  FIGS. 8 and 9 . 
       FIG. 6  illustrates a next step where the flared end  122  is at the base  146  of the cavity former  112  and the cavity  550 . The sleeve  126  may then descend relative to the elongate member  114 . 
     In  FIG. 7  a further step is shown where the sleeve  126  has fully descended to allow the wedges  124  to rest upon the elongate member&#39;s  114  flared end  122  and occupy the cavity&#39;s flared end  558 . The wedges  124  have now been displaced/splayed outwardly by the elongate member&#39;s flared end  122 . The lifting eye  116  is now not obscured by the safety cap  134  and the holes  138 ,  140 ,  142  are aligned to receive the safety pin  136  if desired. Once the safety pin  136  or other safety element is inserted or applied, the lifting device cannot be removed from the cavity  550 ,  558  whilst the safety element  136  is in place. The lifting device  110  is now ready for attaching to the rigging of a crane and then lifting of the concrete element  552  may proceed. The lifting device  110  cannot be removed from the cavity  550 ,  558  of the concrete element  552  during a lift and not at all if the optional safety pin  136  remains inserted. In addition the attachment of the rigging to the lifting eye  116  also prevents the raising of the sleeve  126  due to the action of the safety cap  134 , consequently whilst the crane is attached to the lifting device  110 , it cannot be disengaged from the concrete element  552 . 
     In  FIG. 8  the lifting device  110  is shown in the position when the concrete element  552  is being lifted. The lifting device  110  may be pulled upwards, as indicated by arrow  864  or generally upwards as indicated by the alternate arrow  866  for partial shear and tensile loads to the lifting device  110 . When the lifting device is pulled upwards  864 ,  866  the wedges  124  are raised by the elongate member&#39;s flared end  122  so that the upper surfaces  248  of the wedges  124  are up against the cavity&#39;s flared end wall  558 . Thus the wedges  124  are engaged with the elongate member&#39;s flared end  122  and the flared wall  144 . In an alternate embodiment a spring or otherwise assist device (not shown) may be incorporated within the base of the elongate member&#39;s flared end  122  to assist in setting the wedges  124  against the cavity&#39;s flared end wall  558  by pushing apart the flared end  122  from the base  146 . 
     To release the lifting device from the concrete element  552  the steps described above with respect to  FIGS. 5 to 8  are followed in reverse. 
     Without wishing to be bound by theory the factors affecting the load capacity of the lifting device include the volume of the pull out cone  868  of the concrete element that the lifting device is acting upon. In  FIG. 8  a generalised area for the pull out cone volume  868  in cross section is shown in hatching. The pull out cone  868  volume of concrete may be acted upon by the upper surface  248  of the wedges  124  which are in turn acted upon by the elongate member&#39;s flared end  122  through to the lifting eye  116 /attachment means for tensile and shear loading of the lifting device. Accordingly other factors affecting pull out cone volume and consequently the load capacity include the depth  562  of the lifting device in the concrete element  552 , the effective angle  560  of the action of the wedges and elongate member&#39;s flared end  122  and the diameter of the cavity&#39;s flared end  558 . In addition it will be readily appreciated that the concrete strength and any reinforcing used within it will affect the load capacity of the lifting device. 
     It will also be readily appreciated that the longitudinal axis/bore axis of the cavity  550  need not be perpendicular to the surface of the concrete element  552  as shown by way of example in  FIGS. 5 to 8 . In alternate embodiments the cavity  550  may be readily, alternately formed within the concrete element  552  at an angle in the range of 45 to 90 degrees between the bore axis and the surface of the concrete element. Further shallower angles (&lt;45 degrees) for the cavity  550  may also be possible for concrete elements manufactured to accommodate a shallower angle cavity or for demolition and emergency rescue work where the final integrity of the concrete element is of minimal concern. 
       FIG. 9  schematically shows an exploded perspective view of an alternate higher load capacity embodiment of a lifting device  910  which may be used to lift concrete elements up to and beyond 50 tonne. In  FIG. 9 , as well as generally in this description, the reference numerals are allocated by analogy to or prefixed by the figure number; for example  FIG. 1  is the “100” series,  FIG. 2  is the “200” series and so on. In addition like features between different embodiments of different figures are indicated by like reference numerals, for example the lifting device  110  of  FIG. 1  and the alternate lifting device  910  of  FIG. 9 . The larger capacity lifting device  910  features a longer elongate member  914  and a longer sleeve  926  in order that the wedges  124  and elongate member&#39;s flared end  124  may be placed at an increased depth  962  in a concrete element. The larger lifting device  910  also has an increased outside diameter of the flared end  954  of 140 mm. The increased depth  962  to approximately 1200 mm and increased diameter of splaying/outward displacement of the wedges  124  in this example providing the increased load capacity. It will be readily appreciated that considerably higher load capacities up to and beyond 1000 tonne may be readily designed and manufactured in accordance with the invention described herein. 
     Examples of present application areas may be: present bridge beams up to and beyond 150 tonne may require lifting devices in a product range of up to 500 tonne. Bridge deck elements up to 50 tonne may require a lifting device product range up to 50 tonne. Panels up to 30 tonne may require a lifting device product range of up to 30 tonne. Portable concrete road barriers up to and beyond 10 tonne may require a lifting device product range up to and beyond 10 tonne. However the load capacity of present lifting inserts/anchors, as described in the “Description of the Art” earlier, may be presently limiting the size of concrete elements that may be fabricated which are then required to be lifted and/or handled in some manner. However it will be readily appreciated that the present invention is not constrained by the load limits of the prior art. One such example of an application area of a very large load concrete element may be the concrete legs and floating concrete caisson structures of oil platforms which in present and future forms may require lifts and/or handling up to and possibly beyond 1,000 tonne. 
     In  FIG. 9  the safety cap  134  to the sleeve  926  is not present because it may not be used for a 50 tonne or beyond embodiment of the lifting device  910 . In this embodiment the lifting device  910  may also be used as a lifting clutch attached to the crane&#39;s rigging between lifts, rather than being disengaged from the crane between lifts as described for the lower load capacity lifting device  110  of  FIGS. 1 to 8 . The use of the larger lifting device  910  as a lifting clutch may have an advantage over other lifting clutches which rely on a sideways coupling action to a lifting insert and consequently must be manually dragged and coupled by the dagger/rigger. Sideways lifting clutches for lifting concrete elements may be weighty items which in manhandling can increase the risk of back injuries for the dogger/rigger. 
       FIG. 10  is a schematic of a perspective view of an alternate cavity former  1012  to that shown in  FIG. 1 . The cavity former  1012  additionally features circumferential  1070  stiffeners to aid in maintaining the shape of the cavity former  1012  during the casting of the concrete element. The cavity former base  146  may also have spacers  1072  which in assist in correct positioning of the cavity former; described in detail with respect to  FIG. 11 . The cavity former may be made, for example, of a suitable plastic in a moulding process or may be made of a metal and/or composite so as to act as a cavity former and/or a liner to improve the operation of the lifting device in use. However it will be readily appreciated that other materials may be used for the cavity former, as appropriate to a particular concrete element and lifting application. In addition it will be readily appreciated that transverse cross-sections other than circular for the tube/bore portion ( 143 ) of the former may be produced; for example elliptical or to suit a rectangular cross-section edge lifting device as described below with respect to  FIGS. 13 and 14 . 
       FIG. 11  is a schematic of a cross-sectional view of yet another alternate cavity former  1112 . The alternate cavity former  1112  has been cast permanently into a concrete element  552  in the form of a concrete element panel of the same thickness as the height of the cavity former  1112 . The spacers  1072  have been used in the casting process to raise the base  146  of the cavity former the appropriate distance from the panel mould&#39;s base (not shown) in order to have the necessary coverage of the cavity former&#39;s base  146 . During the casting a lid  1172  with locating lugs  1174  may be used to prevent concrete entering the cavity former  1112 . Alternatively or in addition a support (not shown) of outside diameter appropriate to the inside bore diameter  556  of the cavity former, may be used to provide support to the cavity former during casting. 
     It will be readily appreciated that alternate forms of the cavity former may be made to allow a cavity to be formed at a shallower angle than the perpendicular to the concrete element surface shown in  FIG. 11 . The use of a variety of angles for the bore axis of the cavity former to the surface of the concrete element has been described above with respect to  FIG. 8 . 
       FIG. 12  is a schematic of a cross-sectional view of yet another alternate, larger cavity former  1212  suitable for a lifting device of a higher load capacity than the lifting device  110  illustrated in  FIGS. 1 to 8 . The larger cavity former  1212  has a longer tube portion  1243  compared with earlier embodiments shown in the figures. 
     In yet another embodiment a suitably configured cavity may be formed by drilling a hole as a first cavity in a concrete element and then at the base of the hole undercutting it to form a second cavity suitable for the wedges  124  and the elongate member&#39;s flared end  122 . The upper surface  248  of the wedge may then engage with the walls of the second cavity and/or a junction between the hole bore first cavity and the undercut second cavity. Such a method of forming a configured cavity may be suitable for enabling the lifting device to be applied to concrete elements which previously did not have a cavity, for example portable concrete road barriers where the originally installed lifting insert may not be serviceable. 
     A further method and technique for forming a configured cavity may be suitable to the lifting of slabs, panels and other concrete structures, particularly in demolition or emergency, rescue work. A through hole may be made by drilling, cutting, percussion means, a jackhammer or otherwise made through a section of a concrete element so that the elongate member&#39;s flared end  122  and the wedges  124  may be passed through to the other side of the thickness of the concrete element. The wedges  124  may then brought against the flared end  122  and the upper surface of the wedges  248  brought against the rim of the hole cut in the concrete element to enable a lift to occur. 
     In the above alternatives for cavity forming it will be readily apparent that the angle  560  need not be the approximate, preferred 30 degrees shown in  FIG. 5  and  FIGS. 11 and 12  but may be less than 30 degrees and up to 90 degrees. For example the angle  560  may be from 10 to 90 degrees or 20 to 60 degrees or as appropriate to an application and a lifting device. In addition the particular angle chosen may be selected according to the concrete element to be lifted and desired load capacity of the lifting device to be used, as described earlier. 
     It will also be readily appreciated that the specific profiles of the wedges  124  (or other interference devices), the upper surface  248  of each wedge  124  and the flared end  122  may also be varied as appropriate for the angle selected, the concrete element&#39;s weight and the cavity available for the lifting device to be used with. For, example in undercut or through hole applications the corresponding angle  560  at the base of the cavity bore  550  may be approximately 90 degrees but with a degree of chamfering/rounding off/chipping that may require some modification of the upper surface  248  of the wedge  124  and/or the flared end  122  of the elongate member  114  to accommodate such applications. For example the upper surface  248  of the wedge  124  may be more concave and/or the degree of flaring of the flared end  122  may be adjusted. In addition the number of wedges  124  may be varied from the preferred five shown in  FIGS. 1 to 9 . In some applications one wedge may only be possible due to internal design restrictions for the concrete element, internal reinforcing for example. Two wedges may be preferred for edged lifting devices, described in detail below with respect to  FIGS. 13 and 14 . In other applications three wedges may be kinematically optimal whilst in others more than 20 wedges may be desirable. 
     The use of a cavity in the concrete element rather than an embedded lifting insert and/or anchor allows for ready inspection of the cavity&#39;s structural integrity (cracking etc) by manual, visual and non-destructive testing techniques. In addition for the life of the concrete element there is no embedded insert or anchor which may corrode or contribute to loss of structural integrity of the concrete element. 
       FIG. 13  is a schematic of a perspective/isometric view of an alternate lifting device  1310  suitable for lifting via the edge sides of concrete elements such as panels and slabs. Slabs for floors and panels for walls as well as other concrete elements such as curtain walls are often relatively thin but still weigh many tonnes and as such pose a problem in lifting to a vertical position where one edge of the panel is uppermost. In such applications face lifting via the panel&#39;s face may not be able to be used to raise the panel to a vertical position. In addition it may be undesirable to have a hole through the thickness of such thin concrete elements that is suitable for a face lifting device as described earlier. In such situations the edge or end wall of such concrete elements offers an appropriate lifting point as well as a sufficient depth across the plane or the face of the concrete element for tensile and shear edge lifting. 
     The edge lifting device  1310  has a sleeve  1326  surrounding an elongate member  1314  connected to a lifting eye  116  which in this example has a bow shackle  1376  attached. Moveably attached to the lower end of the sleeve  1326 , via terminal lugs  1328  and pivot pins  1330 , are two wedges  1324 . In an alternate embodiment the number of wedges may be between 1 and 20 as described earlier. The overall shape of the edge lifting device  1310 , for the portion that may be inserted into a cavity in the edge of a concrete element, is planar with a rectangular cross-section. For example the sleeve  1326  with elongate member  1314  may have a rectangular cross-section. This overall shape of the inserted portion of the edge lifting device may be to suit the reduced area available for a lifting device on an edge wall of a relatively thin concrete element. In further alternate embodiments of the lifting device the sleeve and/or elongate member may have an elliptical or any suitable cross-section fit for the purpose. 
     In  FIG. 13  the sleeve  1326  is shown lowered with the wedges  1324  over the elongate member&#39;s  1314  flared end (shown in  FIG. 14 ). Visible in  FIG. 13  is a section of a second recess  1377  in the elongate member to accommodate the movement of the sleeve  1326 , described in detail with respect to  FIG. 14 . An optional safety element/safety pin  1336  may be provided to prevent the upward movement of the sleeve  1326 . In  FIG. 13  the safety element/pin  1336  is shown retracted to allow the upward movement of the sleeve  1326  and wedges  1324 . The safety pin  1336  may be provided with a controlling handle  1378 . In addition a version of the safety cap (not shown) may be applied as required to the edge lifter device  1310 . 
     A suitably shaped cavity for the edge lifting device  1310  may be formed in the edge of a concrete element as described for the other alternate lifting devices used for face lifting of concrete elements. For example a cavity may be formed that is rectangular or approximately rectangular in transverse cross-section to suit an edge lifter. 
       FIG. 14  is a schematic of a cross-sectional view along the line  14 - 14  of  FIG. 13  of the edge lifting device  1310 . The second recess  1377  in the rectangular elongate member  1314  extends to the first recess  1332  that accommodates the wedges  1324  as per the face lifting device  110 ,  910  described above. The second recess  1377  accommodates the movement of the sleeve  1326  within the greatest width  1478  of the elongate member  1314 . The operation and use of the edge lifting device  1310  is as per that described for the face lifting device above, allowing for the application of the edge lifting device to the edges of concrete elements. 
       FIG. 15  is a schematic of a part sectional, perspective view of an alternate embodiment of a face lifting device with two optional handles  1580 . The handles  1580  may be attached to either side of the upper end of the sleeve  126  as an aid to inserting, positioning and/or withdrawing the lifting device into a cavity within a concrete element. Alternatively only one handle  1580  may be attached to the lifting device. The handle  1580  may be attached to the sleeve  126  by a hinge mechanism  1582  that allows for the handle/s to be in the position shown in  FIG. 15  or raised. The handle/s  1580  may also feature an optional safety pin  1536  that may be incorporated into the handle with a safety pin mechanism  1584 . 
     The applications that the face and edge lifting devices described above may be applied to include:
         Lifting required in the casting stages of concrete elements, for example: demoulding and lifting to curing stations.   Lifting and handling of concrete elements from casting to on-site construction.   Demolition and emergency rescue work where irregular concrete structures must be moved without pre-existing lifting inserts.   As a lifting clutch.   Portable concrete road barriers.   Concrete legs and floating concrete caisson structures of oil platforms at sea.       

     Although the invention has been herein shown and described in what is conceived to be the most practical and preferred embodiments, it is recognized that departures can be made within the scope of the invention, which are not to be limited to the details described herein but are to be accorded the full scope of the appended claims so as to embrace any and all equivalent assemblies, devices and apparatus. 
     In this specification, the word “comprising” is to be understood in its “open” sense, that is, in the sense of “including”, and thus not limited to its “closed” sense, that is the sense of “consisting only of”. A corresponding meaning is to be attributed to the corresponding words “comprise, comprised and comprises” where they appear. 
     It will further be understood that any reference herein to known prior art does not, unless the contrary indication appears, constitute an admission that such prior art is commonly known by those skilled in the art to which the invention relates.