Patent Publication Number: US-7213795-B2

Title: Lifting of precast bodies such as concrete panels

Description:
FIELD OF THE INVENTION 
   This invention relates generally to the handling of objects such as, for example, precast concrete panels. The invention has particular though certainly not exclusive application to facelift and edgelift systems for handling large precast building elements, such as concrete panels, in the construction industry. 
   BACKGROUND ART 
   It is now widespread practice to construct various kinds of buildings, but especially commercial and industrial buildings, by on site erection and assembly of structural concrete panels which are either precast on site and tilted into position, or precast elsewhere and brought to the site. In the latter case, the panels are normally cast flat, lifted to the vertical, and then transported while substantially vertical and lifted into position on site. 
   It is of course imperative in the handling of these large structural panels as they are tilted, transported and moved into position that there be no risk whatever that they will fall. An established system for handling the panels involves an anchor cast in the panel and a clutch assembly by which a crane sling may be secured to the anchor. The anchor normally includes a head within the concrete body and an end which remains below the face or edge of the panel but is exposed within a recess. The clutch engages the anchor within this recess and is arranged so that the clutch cannot disengage while the panel is in a partially or wholly tilted orientation. One such arrangement is disclosed in U.S. Pat. No. 3,883,170 and is the basis of the commercial Frimeda system. Another approach is described in Australian patent 544832. 
   While these systems with an embedded anchor and safety clutch assembly have proven satisfactory in practice, they do have a significant disadvantage in that the steel anchors remain embedded in the panel in the erected building. In time, even though the original recess is capped or filled with mortar, the embedded steel anchor is a source of corrosion and can lead to discolouring in walls formed from the panels. There is also the economic issue that a relatively heavy steel component is essentially only used once and is in effect discarded because it cannot be practically recovered for reuse. 
   Any improved panel handling system should preferably be adaptable to both facelift and edgelift systems. 
   There have been at least two attempts to address these issues by providing a substantially plastic component in the panel. Australian patent 488954 proposes an arrangement in which the anchor component comprises a steel nut contained in an undercut enlargement at the end of a plastic tube cast in situ, and a threaded eyebolt is projected down the tube and attached to the nut for lifting. The steel component is much smaller, but this system has the significant disadvantage of the time required to screw and unscrew the eyebolt. In a somewhat similar approach described in Australian patent application 89982/91, a flat steel rectangular block is provided in an undercut enlargement in a rectangular plastic tube, and a pair of clutch shafts are inserted into the hole deformed by the tube. The shafts have end lugs which engage under the block and the system is locked by pushing in a secondary pin between the shafts to forcibly separate them. This system has been viewed as unsafe for transporting heavy building elements because of the risk of operator error in failing to insert the locking pin. 
   German patent application 195 23 476 discloses an arrangement in which an anchor body is rotatable to bring a pair of lugs beneath undercuts in a lined cavity, and then locked against return rotation by turning down a notched flap to engage the crane lift bar. Longitudinal voids are provided in the concrete for the passage of the crosshead extensions and lugs during insertion. These voids remain empty during lifting operations, and are a potential source of weakness as they could allow concrete to break away and flow into them. The rotatable load bearing element is a tube, and there is a cross-head spaced from the inner end of the cavity. This system requires, on attachment, four separate manual operations, ie. insertion, rotation, locking and crane hook engagement, and, on detachment, each of these four steps in reverse. Remote release is not an available option. 
   SUMMARY OF THE INVENTION 
   The present invention proposes four improvements which may be used separately but are preferably used in conjunction, and which are suited to use with an undercut plastic tube former of appropriate profile. One of these improvements is to provide for engagement by way of a limited rotating action, another to provide safety by linear motion of a positively blocking element responsive to the position of the lifting tackle, a third involves proper control of voids and cavities to prevent failure by collapse or flow of material, and a fourth entails a novel configuration of relatively rotatable and non-rotatable elements. 
   In a first aspect, the invention accordingly provides an object handling device including a support body, and an elongate anchor body mounted at the inner end thereof to the support body so as to project from the support body for insertion into an undercut cavity in an object to be handled and so as to be rotatable about an axis generally parallel to the longitudinal dimension of the anchor body. At least one anchor lug at or adjacent to the outer end of the anchor body is movable by rotation of the anchor body between a first position in which the anchor body is able to be inserted into or withdrawn from the cavity, and a second position in which the lug(s) engage respective undercut shoulder portions in the cavity. Means on the anchor body is engagable for rotating the anchor body to move the anchor lug(s) between the first and second positions. Lift means on the support body is engagable by a crane to lift the object. 
   Preferably, lock means is responsive to the lift means to block movement of the anchor lug(s) from the second position. 
   In a second aspect, the invention provides an object handling device including a support body, and elongate anchor body means mounted at an inner end thereof to the support body so as to project from the support body for insertion into an undercut cavity in an object to be handled. At least one anchor lug at or adjacent the outer end of the anchor body means is moveable with the anchor body means between a first position in which the anchor body means is able to be inserted into or withdrawn from the cavity, and a second position in which the lug(s) engage respective undercut shoulder portions in the cavity. Means on the anchor body is engagable for moving the anchor lug(s) between the first and second positions. Lock means is slidable generally longitudinally of the anchor body means to a blocking position in which movement of the anchor lug(s) from the second position is blocked. Lift means carried by the support body is engagable by a crane to lift the object, and means is responsive to the lift means to activate the lock means to slide it to the blocking position. 
   In a third aspect, the invention provides an object handling device including a support body, and elongate anchor body means mounted at an inner end thereof to the support body so as to project from the support body for insertion into an undercut cavity in an object to be handled. At least one anchor lug at or adjacent the outer end of the anchor body means is moveable with the anchor body means between a first position in which the anchor body means is able to be inserted into or withdrawn from the cavity, and a second position in which the lug(s) engage respective undercut shoulder portions in the cavity. Means on said anchor body is engagable for moving the anchor lug(s) between the first and second positions. Lift means on the support body is engagable by a crane to lift the object, and lock means is responsive to the lift means to block movement of the anchor lug(s) from the second position. In this third aspect, the device is shaped and configured for said insertion so that, when the anchor lug(s) are in said second position, there is substantially no cavity or void in the object within a region outwards of the undercut shoulder portions sufficient to allow collapse or flow of the object material when the object is being lifted. 
   The invention still further provides an object handling device including a support body, and an elongate anchor body mounted at the inner end thereof to the support body so as to project from the support body for insertion into an undercut cavity in an object to be handled and so as to be rotatable about an axis generally parallel to the longitudinal dimension of the anchor body. At least one anchor lug at or adjacent to the outer end of the anchor body is movable by rotation of the anchor body between a first position in which the anchor body is able to be inserted into or withdrawn from the cavity, and a second position in which the lug(s) engage respective undercut shoulder portions in the cavity. Means on the anchor body is engagable for rotating the anchor body to move the anchor lug(s) between the first and second positions, and lift means on the support body is engageable by a crane to lift the object The lift means is rotatably mounted with respect to the support body and is thereby rotationally alignable with the direction of load. 
   In a fifth aspect, the invention is directed to an object handling device embodying the features of two or more of the first, second, third and fourth aspects of the invention. 
   Preferably, the lock means is a plurality of elongate shafts or pins of cross section similar to and matching the cross section of the respective lugs in a plane normal to the axis. By this arrangement, the lugs are aligned with the lock shafts or pins during insertion or withdrawal of the device, and move out of alignment in the second position, whereupon the lock rods slide into the vacated space and thereby block movement of the lugs back to the first position. 
   Preferably, the elongate anchor body is generally cylindrical and the lugs and lock rods exhibit dovetail or part annular profiles to opposite sides of the anchor body as viewed in cross section. In one embodiment, particularly suited to edgelift systems, the angular extent of the lugs about said axis is about 60° so that the lugs occupy adjacent 60° sectors in the respective first and second positions. Alternatively, and more suitably for facelift systems, the lugs sub-tend about 90° at the axis of the anchor body and thereby occupy respective 90° sectors in their first and second positions. 
   Said means engagable for moving the anchor body lugs preferably includes a manipulable handle carried by the support body on the side opposite that from which the anchor body extends. 
   The lift means is preferably a solid component rotatably carried by the support body for movement between a first position in which the lock means does not block the anchor body lug(s) and a range of rotational positions in which it does. The responsive means is preferably a cam and cam follower arrangement by which the lift means and lock means are engaged in a co-operative relationship. According to the exact nature of the lift system in use, the aforementioned first position for the lift means will be that in which the object being handled is at rest, not elevated, and has with no lifting tension applied to the lift means, while any other position of the lift means will cause activation of the lock means to block the anchor lugs. 
   Preferably, means is provided to bias the lock means to a position in which it does not block movement of the anchor lugs. Preferably also, means is provided to bias the support body of the lift device clear of the object surface about the cavity unless it is pushed into the cavity and the anchor lugs engaged. 
   In a sixth aspect, the invention provides a form for defining an undercut cavity in a pre-cast object, said form being in a plastics and/or polymer material or a thin gauge metal, wherein the form includes a first portion defining an elongate passage of substantially uniform cross section including a core portion and respective laterally projecting portions of a predetermined profile, and a pair of undercut portions of cross section geometrically similar to said side portions and disposed adjacent to the respective side portions. 
   A preferred handling, eg lifting, system according to the invention includes a handling device according to the first, second, third and fourth aspects of the invention and a cavity form according to the sixth aspect. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: 
       FIG. 1  is an isometric view of a lift device or clutch according to an embodiment of the invention, but suitable for edgelift systems; 
       FIG. 2  is a three dimensional view of a form of a plastics material, suitable for edgelift systems, for defining an insert in a precast concrete panel, shown with a cap for the resultant cavity and a formwork location plug; 
       FIG. 3  is a view similar to figure of the form, but at a different angle; 
       FIG. 4  is a view similar to  FIG. 1  but with the lift advice or clutch/anchor shown in situ in the panel edge after it has been lifted to a vertical orientation by a crane; 
       FIGS. 5 and 6  are respective enlargements of portions of  FIG. 1 ; 
       FIGS. 7 and 8  are corresponding enlargements of portions of  FIG. 4 ; 
       FIGS. 9 and 10  are respectively axial cross sections on the lines  9 — 9  and  10 — 10  in  FIG. 1 ; 
       FIGS. 11 and 12  are respective matching cross sections corresponding to  FIGS. 9 and 10 , but for the condition of  FIG. 4 ; 
       FIG. 13  is a view of a modification of the form shown in  FIGS. 2 and 3 ; 
       FIGS. 14 and 15  illustrate a form suitable for facelift systems, respectively shown in exploded and assembled views; 
       FIG. 16  is an underneath view of a modified swash plate especially suitable for a facelift system; and 
       FIG. 17  is a fragmentary cross-section corresponding to part of  FIG. 9 , illustrating a modified arrangement. 
   

   PREFERRED EMBODIMENTS 
   The drawings illustrate an edgelift system for handling precast concrete panels. 
   The principal elements include a cavity  22  ( FIG. 4 ) defined by a plastics form  25  ( FIGS. 2 and 3 ) in an edge  21  of a precast concrete structural panel  20 , and a lift device  30  ( FIG. 1 ) which is engagable with cavity  22  and with the lifting tackle of a crane. 
   The panel would typically be cast flat and form  25  supported in situ for defining cavity  22 . In some cases, the panel would be cast on site and the lifting system is required to simply tilt the panel to position. In other cases, panels of this kind are formed at a casting plant, tilted to a vertical orientation, and then transported by truck in this orientation to the construction site where they are further handled into position. 
   By analogy with conventional edgelift and facelift systems, lift device  30  will hereinafter be referred to as a clutch-anchor, and cavity  22  with its defining form  25  as insert  24 . A conventional shear bar  99  ( FIG. 4 ) is clipped to the outer end of form  25  and extends parallel to the edge face of the concrete panel, below its surface. 
   With particular reference to  FIG. 1 , clutch-anchor  30  includes a support body in the form of a cast metal swash plate  32 , a depending anchor shaft  40  rotatably mounted to swash plate  32 , a pair of lock rods  50 ,  51  extending parallel to shaft  40 , a lever arm  42  for rotating shaft  40 , and a lift bar  60  for attaching clutch-anchor  30  to crane tackle. 
   Swash plate  32  has an enlarged central region with arcuate side faces  32   a  from which it tapers to upstanding end posts  34 ,  35 . in which lift bar  60  is rotatably supported in a trunnion bearing arrangement. At the centre of swash plate  32  is an aperture  33  ( FIGS. 9–12 ) from which shaft  40  is rotatably supported by a bolt  43 . Bolt  43  projects downwardly through aperture  33  and engages a coaxial threaded blind bore  44   a  in the upper end of shaft  40 . A transverse locking pin  43   a  ensures the mounting. The lower end of shaft  40  also has a coaxial threaded blind bore  44   b  to receive a threaded reduced diameter spigot portion  46  of an anchor head  45 . A transverse locking pin  46   a  is again used to ensure the mounting, and the annular shoulder  47  defined by spigot portion  46  is spaced from the end of anchor shaft  40  to define an annular gap  39  for a purpose to be further explained. 
   The outer end of anchor head  45  has a cylindrical periphery flush with that of anchor shaft  40  save for a pair of laterally projecting anchor lugs  48   a ,  48   b . These lugs are of dovetail shape, have an outer arcuate face coaxial with anchor shaft  40  and radial end faces so that the lugs subtend an angle of 60° at the axis  41  of shaft  40 . Anchor shaft  40  is rotatable about axis  41  by hand manipulation of lever arm  42 . Lever arm  42  is an integral piece having a ring  49  fixed to the head of bolt  43  above swash plate  32  and is moveable through 60° (for reasons which will become apparent) between an exposed position in which the lever arm projects generally laterally outwardly of the axis linking posts  34 ,  35 , and a nested position ( FIG. 4 ) in which the shallow U-shaped lever arm tucks around post  34 . In this latter position, the anchor lugs  48   a ,  48   b  have rotated through 60° just out of their previous position to the immediately adjacent 60° sector with respect to axis  41 . 
   The lock rods  50 ,  51  are machined or cast solid metal of uniform cross section save for their upper ends. Their cross sectional profile is substantially identical to anchor lugs  48   a ,  48   b , ie a dovetail shape with an outer arcuate surface coaxial with axis  41  and radial end faces so that the cross section subtends an angle of 60° at axis  41 . Lock rods  50 ,  51  are held in matching apertures  59  ( FIG. 9 ) in swash plate  32  and have end bosses  53  at these inner ends. Respective pins  54  are upstanding from bosses  53  and serve as cam followers with respect to eccentric cam tracks  55  on lift bar  60 . 
   By analogy with conventional edgelift and facelift systems, shaft  40 , head  45  and lock rods  50 , 51  may collectively be referred to as anchor  65 . 
   Lift bar  60  is an integral machined or cast metal component. It includes a pair of end blocks  62 ,  63  for retaining trunnions  64  rotatably engaged with posts  34 ,  35 , and a bridging portion  66  that curves over from one end block to the other and is of generally circular or elliptical cross section. 
   Before describing the operation of the edgelift system, attention will now be turned to the insert  24 . Referring in particular to  FIGS. 2 and 3 , form  25  and cavity  22  include an elongate main portion  26  of uniform cross section profiled to receive the cross section (normal to axis  41 ) defined by shaft  40  and lock rods  50 ,  51  of anchor  65 , ie a cylindrical centre  140  and a pair of oppositely projecting dovetails  150 ,  151 . The form  25  and cavity  22  further define an undercut portion  28  of cross section (normal to axis  41 ) substantially identical to the dovetail for receiving rod  50  or  51 : this undercut  28  opens at one end at the side of a respective dovetail and defines an undercut shoulder  29 . A cap  90  is provided to prevent entry of wet concrete and dust and comprises a pair of blind tubes  92 ,  93  depending from a cover plate  94 . Tubes  92 ,  93  engage the dovetails  150 ,  151  in an interference fit, while cover plate  94  has an underside outstanding formation  97  to register with the internal cross-section of form main portion  26 . Tubes  92 ,  93  are open at cover plate  94  to receive tubular location pins  96  of a formwork plug  95  used to locate and retain the form during casting, by being attached to a supporting formwork. 
   The interior of form  25  may be slightly longitudinally tapered, larger at the outer end and for example by 2–3 mm over the length of the form, to facilitate disengagement of device  30 . 
   A modified form  25 ′ is depicted in  FIG. 13 . The form is generally similar to that of  FIGS. 2 and 3 , but has spaced annular ribs  251  and longitudinal ribs  252  on each side for enhanced strength. Deflectable pairs of lugs  253  are provided to act as clips for retaining shear bar  99 . For manufacturing expediency, the lower end of the insert is formed as a separate cap-piece  254  that incorporates the undercut portions  28 : the shoulder  29 ′ is defined by an end flange  256  on the main body  255  of the form. This flange  256  couples with a matching peripherally lipped seat  258  on cap-piece  254 . It is to be noted here that cap-piece  254  has sufficient depth to accommodate debris which may happen to fall into the cavity of the insert, without the debris interfering with the correct location and movement of anchor head  45 . 
   The edgelift system is used in the following manner. Anchor  65 , including shaft  40  with adjacent lock rods  50 ,  51 , is inserted into the complementary profile of the main portion  26  of insert  24 . To allow insertion, shaft  40  must be rotated to a position ( FIG. 1 ) in which anchor lugs  48   a ,  48   b  are in exact alignment or register with and disposed at the end of lock rods  50 ,  51 . To push the anchor fully home into the cavity requires longitudinal opposition to a conical compression sting  80  fixed to the underside of swash plate  32  and extending loosely down about the upper or inner end of the shaft/lock rod combination. The spring recedes back into an annular recess  82  ( FIG. 9 ) in the underside of the swash plate. 
   The orientation of the lever arm  42  serves as a guide to the orientation of the clutch with respect to the anchor. Correct orientation facilitates release of the clutch after the building element has been secured in place. For edgelift, the handle is oriented outwards the top surface of the element on the casting bed, and for facelift the handle is oriented towards what is to be the top edge of the element in its erected position in the structure. 
   When anchor  65  is fully home, lever arm  42  may be gripped and rotated from its projecting to its nested position to bring anchor lugs  48   a ,  48   b  out from behind lock rods  50 ,  51  into the undercuts  28  of cavity  22 . By virtue of the engagement between follower pins  54  and cam track  55 , any rotation of lift bar  60  causes lock rods  50 ,  51  to slide into a position in which they block return of anchor lugs  48   a ,  48   b  out of the undercut. This blocking engagement is indicated at  100  in  FIG. 4 . The crane tackle is attached to the lift bar  60  by engaging the appropriate shackle or sling about bridging portion  66 . It will be seen from  FIGS. 1 and 4  that, once lift bar  60  is rotated and the crane equipment is in tension as the panel is raised, the anchor lugs are blocked from disengagement from the undercuts. Indeed, it will not be possible for the anchor  65  to disengage from the cavity unless the lift bar is relaxed back to, or close to, the rest position shown in  FIG. 1 , ie that is against swash plate  32 . Only then can the anchor lugs be released, either manually or by a remote release cable. 
   It will be understood that anchor  65  cannot be released until the load is removed from the sling, and the lift bar is depressed to within its range of rotation for the insertion setting. It is only practical to remove the load from the sling after the panel has been secured in position. With the load removed from the sling, and the lock rods raised by the return spring  84 , the handle is rotated, either manually, or remotely with for example a cable, to its position in line with the lock rods. The cone spring ejects the anchor  65  from insert  24 , and the crane is free to proceed to the next panel. 
   It will be further understood that the illustrated system entails only two manual operations during attachment ie. insertion of the anchor and rotation of lever arm  42 , and one manual operation on detachment, ie. lever arm rotation. Locking, unlocking and removal are effected automatically, and the crane sling remains attached throughout all lifting operations. 
   The lift bar  60  is preferably dimensioned so that, when it is depressed against the swash plate or close to it, the anchor can be on the centreline of the panel edge without the lift bar fouling the surface of the casting bed. For example, the freshly cast panel may be 120 mm thick, and the lift bar can comfortably lie within 60 mm of axis  41 . 
   The rotational mounting of lift bar  60  with respect to swash plate  32  allows the lift bar to be rotationally alignable with the direction of load, ie. with the lifting sling. When a load is applied lateral to the plane of the lift bar, the load originating from either the angle of the sling or an applied shear load, the pivoting mounting of the lift bar allows the lifting point to be in close proximity to the concrete face. This in turn prevents a load magnification by avoiding a leverage action. 
   It will be appreciated that, when the clutch/anchor  30  is fully engaged, there is substantially no void or cavity in the panel within a region outwardly of undercut shoulders  29  sufficient to allow collapse or flow of concrete when the panel is being lifted. This is because the lock rods  50 ,  51  wholly occupy the void traversed by anchor lug(s)  48   a ,  48   b  during insertion. It is found that, in this way and in conjunction with the relatively large load supporting surface area of the undercut shoulders and lugs, it is not necessary to provide reinforcing and load spreading metal components in cavity  22 , such as the steel nut of Australian patent 488954 or the steel block of Australian patent application 89982/91, at the load bearing surface at the tops of anchor lugs  48   a ,  48   b . The applicant has thus achieved an anchor system wholly free of permanently cast-in metal components, as it is believed that the filling of the void and the flat 60° engagement of the anchor lugs  48   a ,  48   b  under the respective shoulders  29  provides sufficient strength and load spread to maintain the assembly under full lifting load. 
   It was remarked above that there is substantially no void or cavity in the panel within a region outwardly of undercut shoulders  29  sufficient to allow collapse or flow of concrete when the panel is being lifted. Of course, this not to say that there is no void or cavity in the mentioned region. For example, the periphery of form  25  may comprise a ribbed, corrugated or open lattice structure which includes multiple fine cavities or channels, but these cavities or channels are sufficiently small—even if exposed to concrete—for there to be no collapse or flow of concrete into the cavities or channels during normal operation. 
   It will be further appreciated that cone spring  80  serves the useful role that, if the clutch is not engaged with the insert by rotation of shaft  40 , the spring will wholly or partly eject the anchor out of the cavity, thereby rendering the lack of engagement visually obvious. A further visual warning can be obtained by the relative position of the handle  42   a  of lever arm  42  within the rotation path of lift bar  60  and the crane sling, indicating that anchor  65  has not yet gripped insert  24  since the lever handle has not yet been rotated to the nested, engaging position. It would be a simple matter to colour the outer upstanding handle  42   a  of the lever to make its position obvious to a person viewing from laterally of the trunnion axis. 
   The pressure of the cone spring holds the shaft anchor lugs  48   a ,  48   b  against the undercut shoulders  29 . 
   Lock rods  50 ,  51  are biased outwardly, and the cam followers  54  thereby maintained in engagement with the cam tracks  55 , by a helical spring  84  disposed in the earlier mentioned annular gap  39  between ring  58  and shoulder  47  on anchor head  45 . Ring  58  is affixed to rods  50 ,  51  and is moveable with the rods in the gap, thereby compressing the spring  84  once the rods commence their sliding movement to the blocking position. Ring  58  also assists in maintaining lock rods  50 ,  51  in place. It should be noted that, to prevent their forming voids into which concrete flow or collapse can occur, annular gap  39  is at a minimum distance from the end of anchor  65 , eg about ⅓ of its length. 
   The asymmetric arrangement of bridging portion  66  of lift body  60 , particularly evident in  FIG. 4 , by which the portion bridges one end of block  62  to the other end of block  63 , is provided to allow a D-shackle to be placed around the bridging portion between it and the adjacent swash plate  32  when the lift body is in its relaxed position, and yet still have the line of lift substantially along axis  41 . 
   The illustrated embodiment is best suited to an edgelift system, where there is no limitation on the depth of cavity  22 , but where the thickness of panel limits a minimal lateral movement of lugs  48   a ,  48   b . In this case, the open end of form  25  is attached with a plate to further formwork to support the form horizontally. In a counterpart facelift system, the subtended angle of lugs  48   a ,  48   b  and block rods  50 ,  51  is 90°; with a lesser available depth, it is important to increase the load bearing surface area of shoulder  29 . Of course, this will mean that the cavity will be cylindrical at the undercuts. This in turn is not a problem where there is no lateral limit on the extent of the cavity. With the edge lift system, there is such a lateral limit and hence the 60° dovetail is employed, but without load bearing disadvantage in view of the greater available depth of the cavity. 
   In a facelift system, the present arrangement can achieve greater effective depth in view of the lack of any crossbar component as in the aforementioned German patent application 195 23 476. The greater thickness of concrete above the lugs gives a significant increase in load-carrying capacity. A further advantage over the prior disclosure is that the present system has a solid load-bearing shaft component (shaft  40 ) rather than a tubular load-bearing component. 
     FIGS. 14  (exploded view) and  15  (assembled view) illustrate a suitable integral moulded plastics form  325  for an embodiment of the invention applicable to a facelift system. The main portion  326  is similar to portion  26  of the edgelift form  25 , except that it is relatively much shorter and that it has integral annular and longitudinal strengthening ribs  351 ,  352 . The inner end of the form has four outwardly tapering legs  361  with outer feet  362  which together comprise a base  360  to support the form in a vertical position in a casting bed. Form  325  is provided with a tray and formwork top cap  395 : in this case tray is shaped to define a part-spherical bowl  392 . This matches a complementary surface in the upper face of form  325 , which in turn matches a complementary projection on the underside of the associated swash plate. The otherwise open bottom end of the form is closed by a bottom cap  398 . 
   In casting the panel with multiple forms  325  in place, the concrete is trowelled off just above the flat outer face of top cap  395 . When it is desired to lift the panel, the thin wafer of concrete over the form (its location signalled by protruding pins  399 ) is broken away and the top cap  395  removed. Debris is collected in the bowl  392  of tray  390 . It is also to be noted that in a fashion similar to the earlier described edgelift embodiment of  FIG. 13 , the inner end of form  325  is arranged so that there is some room for debris on the inside of bottom cap  398  below the anchor head. Tray  390  with the debris collected in it is removed just before insertion of the clutch anchor. 
   Another difference between edgelift and facelift systems embodying the invention is in relation to the angular range for which lift body  60  activates lock rods  50 ,  51  into a blocking position. With the illustrated edgelift embodiment, this will be for a 5–90° range, whereas the 45–90° range is appropriate for facelift. 
     FIG. 16  depicts a modified swash plate  32 ′ especially suitable for a facelift system. The under surface of the swash plate has been extended around the shaft and lock rods, to form a projection  200  ending in a partial sphere.  FIG. 16  shows a bottom view of the face lift clutch-anchor swash plate, with the shaft, lock rods, and conical spring removed. The projection  200  is matched by a similar cavity (not shown) formed into the surface of the concrete at the top of the insert, and the extension occupies this cavity when the clutch-anchor is attached. The purpose of the extension is to assist in the transfer of shear loads to the concrete without the need for a shear bar, as is preferred in the case of edge lift. (eg. at  99  in  FIG. 4 ) In face lift there is an extensive mass of concrete surrounding the insert, and this concrete is quite cap able of resisting the shear loads, without reinforcement. In the case of edge lift however, the insert is placed in a relatively narrow edge without sufficient concrete above the insert to resist shear loads without additional reinforcement. 
     FIG. 17  is a fragmentary cross-section corresponding to part of  FIG. 9 , illustrating a modification in which the lock rods  50 ,  51 , automatically descend to block return of the anchor lugs  48   a ,  48   b , in response to rotation of anchor shaft  40 . This is achieved by spring loading the lock rods downwards, by one or more helical compression springs  400  in one or more cavities  402  between the upper ends of the lock rods and the underside of the swash plate. An alternative construction is for a cam arrangement by which the rods are directly depressed by the ring  49  of lever arm  42  as it rotates. A still further alternative is to have a spring loaded swash plate that engages an enlargement or protrusion on the lever arm or an attachment thereto, so that the anchor lugs are indirectly locked against disengagement by blocking the lever arm  42  against return rotation.