Abstract:
A lifting system for a concrete component comprises a void former incorporated into the component during casting and which provides within the component a void which receives a locking pin of a lifting anchor assembly which is locked within the void by rotation of a locking pin. The lifting anchor assembly has a visual indicator to indicate when the pin is in its locked condition within the void, and a pivotal lifting shackle of the assembly is prevented from movement into a position in which lifting can take place until the pin is in its locked condition. Preferably a base of the void former is configured to retain components of a jacking system by which a concrete slab used for road repair can be jacked into a level configuration with the remainder of the roadway when it has been positioned by use of the lifting system.

Description:
PRIORITY CLAIM 
       [0001]    This patent application is a national stage entry of PCT Application No. PCT/AU2015/044019, which was filed on Aug. 6, 2015, which claims priority to and the benefit of Australian Patent Application No. 2014903443, which was filed on Aug. 29, 2014, the entire contents of each of which are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present invention relates to a lifting system for concrete components and more particularly to a lifting anchor for quick release from the component. 
       BACKGROUND 
       [0003]    One commonly used technique for repairing damage to roadways constructed of poured concrete is to cut out the damaged section and to replace it with a precast panel of the same dimensions. Usually the panel will be cast offsite, trucked to the site and then lifted into position. Typically the panel, which may weigh several tons, is lifted by the use of lifting anchors screwed into threaded inserts cast into the panel during its manufacture. Conventionally, the threaded inserts are in the form of internally-threaded collars which, after casting, open onto the upper face of the panel to receive the lifting anchors. For the several separate lifting operations likely to be involved between casting and laying of the slab in position, and likely involving storage of several panels in stacked relation and transportation of several panels in stacked relation, the lifting anchors will usually be required to be installed and removed several times. This can be quite a time-consuming and laborious operation as the thread length on the insert and which corresponds to the thread length of a threaded stem of the anchor runs for almost the full thickness of the panel. 
         [0004]    At their lower ends the threaded inserts, although open, abut against a metal jacking plate, one for each insert, set into the underside of the panel during casting. After laying of the panel in position and removal of the lifting anchors, jacking rods are screwed into the inserts to engage the jacking plates which are in contact with compacted ground beneath the panel, in order to raise the panel so that it is set level with the surrounding roadway. During manufacture of the panel, grout holes are cast through the thickness of the panel at different locations over the surface of the panel and when the panel has been jacked into a position in which it is level with the surrounding roadway, concrete grout is injected through the grout holes to the underside of the panel in order to fill the void between the underside of the panel and the underlying ground surface. The jacking rods are removed from the threaded inserts after the grout has cured sufficiently to support the weight of the panel. As with the lifting anchors, because threaded engagement between the jacking rods and inserts occurs over a substantial thread length, it is a time-consuming and laborious operation to insert and remove the jacking rods. 
         [0005]    Accordingly, there is a need to solve these problems. 
       SUMMARY 
       [0006]    The present disclosure in one aspect provides a lifting system which enables quick insertion and release of lifting anchors into a panel such as a repair panel discussed above, and also quick insertion and release of subsequent jacking rods. 
         [0007]    According to the present disclosure there is provided a lifting system for a concrete component, comprising a void former for incorporation into the component during casting thereof, the void former providing a passage to receive a locking stem of a lifting anchor assembly following casting, the void former providing a void within the component shaped for locking engagement with a locking pin of the locking stem by rotation of the pin following insertion whereby to lock the locking stem within the void to permit lifting load to be applied, the void former also including a jacking plate and associated threaded structure for receiving a threaded jacking rod inserted through the void former after removal of the lifting anchor assembly to permit jacking of the component from underlying structure. 
         [0008]    Although the lifting system of the present disclosure has particular utility in conjunction with a jacking system for use with roadway repair panels, the lifting system by virtue of its quick insertion and release characteristics also has utility in other aspects of concrete lifting of components where jacking is not required. 
         [0009]    Accordingly another aspect of the present disclosure provides a lifting system for a concrete component, comprising a void former for incorporation into the component during casting thereof, the void former providing a passage to receive a locking stem of a lifting anchor assembly following casting, the void former providing a void within the component shaped for locking engagement with a locking pin of the locking stem by rotation of the pin following insertion whereby to lock the stem within the void to permit lifting load to be applied, wherein the locking pin includes at least one locking lug movable into a locking condition within the void former upon rotation of the pin, the locking stem also including fixed structure located within the void former and engageable with the lug by axial displacement of the pin in order to provide a positive lock against rotation of the pin out of its locking condition. 
         [0010]    The present disclosure also provides a void former configured for use in lifting systems as defined above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    An embodiment of the present disclosure will now be described by way of example only with reference to the accompanying drawings in which: 
           [0012]      FIG. 1  shows a void former assembly of a lifting system in accordance with the one example embodiment of the present disclosure; 
           [0013]      FIG. 2  shows the individual components of the void former assembly in exploded form; 
           [0014]      FIG. 3  shows a lifting anchor assembly engageable into a void formed by the void former assembly, the lifting anchor assembly being shown in a configuration in which a locking pin thereof is in a condition to enable insertion of a locking stem into the void; 
           [0015]      FIG. 4  shows the relation between the lifting anchor assembly and void former assembly for insertion of the locking stem; 
           [0016]      FIG. 5  shows the lifting anchor assembly in a condition in which the locking pin has been rotated to an engaged locking position; 
           [0017]      FIG. 6  shows the detailed structure of the lifting anchor assembly in the insertion conditions of  FIGS. 3 and 4 ; 
           [0018]      FIG. 6A  shows an enlarged detail of  FIG. 6 ; 
           [0019]      FIG. 7  shows the detailed structure of the lifting anchor assembly in the engaged locking condition of  FIG. 5 ; and 
           [0020]      FIG. 7A  shows an enlarged detail of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    With initial reference to  FIGS. 1 and 2  the quick release lifting system of the illustrated example embodiment of the present disclosure comprises a void former assembly comprising a tubular main body  2  coupled at its lower end with a base formed by upper and lower shallow shells  4  and  6  of rectangular form for housing components of a jacking system used to subsequently level a panel as discussed above. The tubular main body  2  is of generally cylindrical form but with two inset channels  8  of approximately dovetail section at opposite sides. An external wall  10  closes each channel  8  at its lower end. The end wall  10  which is also of dovetail section is upwardly inclined and has a curved outer edge which corresponds to the curvature of the curved parts of the tubular body  2 . A circular plate  12  at the top of the tubular body  2  is formed with an aperture  14  of a shape which corresponds to the internal cross-section of the tubular body  2 . A removable cap  16  is fitted to the plate  12  and is retained within a peripheral lip thereof. For casting into the panel, the void former is set with its base on the casting bed, and following casting the cap  16  of the void former will be substantially flush with the upper surface of the cast panel. 
         [0022]    With reference now to  FIGS. 3 to 5  a lifting anchor assembly  20  comprises a main stem  22  which is engaged within the tubular body  2  of the void former after removal of the cap  16 . The stem  22  includes a central rotatable locking pin  24  having at its lower end opposed outwardly extending locking lugs  26  of dovetail shape corresponding to that of the cross-section of the two channels  8  in the void former. The pin  24  is located between two fixed annular segments  28 . It will be seen from the drawings that the overall configuration of the stem  22  formed by the rotary pin  24  and fixed outer segments  28  substantially corresponds to that of the tubular body  2  of the void former. As will be described in more detail below, the pin  24  is rotatable through 90 degrees from a position in which its locking lugs  26  are aligned with the segments  28  (see  FIG. 3 ) whereby the stem  22  can be inserted into the interior of the void former via the aperture  14  in the plate  12  (see  FIG. 4 ) and a locking position displaced through 90 degrees in which the locking lugs  26  are between the segments  28  (see  FIG. 5 ). 
         [0023]    The main stem  22  is carried by an upper body  30  the lower edge of which sits within the circular plate  12  when the anchor is installed to the panel. A lifting shackle plate  32  with lifting eye  33  for coupling to a lifting clutch (not shown) is pivotally mounted to the body  30  for movement between an unlocked rotational position in which it extends generally horizontally and which is assumed during installation of the lifting anchor assembly into the panel, and a generally vertical locked position which it assumes during lifting. The detailed internal structure of the upper body  30  is shown in  FIGS. 6 and 7  but with an external cover of the body omitted for clarity of illustration. As shown in these Figures, the fixed segments  28  of the main stem  22  are fixed to the body  30  and the locking pin  24  is rotatably mounted in the body  30  and is connected at its upper end to an upper handle  34 . A locking collar  36  is mounted to an enlarged upper end of the locking pin  24  beneath the handle  34 . A compression spring  40  mounted on the upper part of the locking pin  24  between a lower part of the upper body  30  and the collar  36  applies an upward bias to the locking pin  24  and hence to the handle  34  attached thereto. 
         [0024]    When the locking pin  24  and its associated handle  34  are in the rotational unlocked position for insertion of the stem  22  into the void former, the locking lugs  26  are aligned with the fixed segments  28  and in that condition the locking pin  24  and its associated handle are in a lowered unlocked rotational position in which the locking lugs  26  are held against the lower edge of the segments  28  under the effect of the bias of the compression spring  40  (see  FIG. 6 ). When, following insertion, the handle  34  is rotated through 90 degrees to pivot the pin  24  into its locking condition between the segments  28 , under the effect of the compression spring  40 , the pin  24  and associated handle  34  lift so that the locking lugs  26  will lie within the slots defined between the opposed edges of the two segments  28  whereby the pin is  24  positively locked by those edges against rotation out of that locking condition (see  FIG. 7 ). The upwards movement which occurs to lock the pin is only a few millimeters and is limited by the configuration of the void former and in particular the lower end wall  10  of each of the two external channels  8 . It is in this mode that lifting load can be applied. 
         [0025]    The shackle plate  32  is journalled in the upper body  30  by lateral trunions  32   a , the ends of which are shaped to define locking flats  32   b  as clearly shown in  FIGS. 6 and 7 . The locking flats  32   b  lie beneath the collar  36 . The flats are so configured that in the unlocked rotational position of the pin  24  which it adopts for insertion into the void former and which is a lowered position of the pin, the locking flats  32   b  are engaged by the underside of the collar  36  whereby the lifting eye is locked by the collar in its horizontal configuration (see  FIGS. 6 and 6A ). In the locked condition of the locking pin  24  in which the pin and hence collar and handle are raised relative to the insertion position, the underside of the collar  36  is now raised clear of the locking flats  32   b  (see  FIGS. 7 and 7A ) whereby the shackle plate  32  can now be rotated into its generally vertical lifting configuration. This provides a significant safety feature as it ensures that the shackle plate cannot be moved to its lifting configuration unless the locking pin  24  is in its locked position or configuration. 
         [0026]    Although identification as to whether the locking pin  24  is in its insertion or locked position can be visually attained by reference to the rotational position of the handle  34 , certain embodiments of the present disclosure additionally incorporate an indicator readily visible from a more remote distance to particularly show that the pin it in its engaged locking condition. In the insertion unlocked rotational position the handle  34  lies relatively close to an upper cover  30   a  of the upper body  30  (see  FIGS. 3 and 4 ). In the engaged locked position or locking condition, the handle  34  and adjacent section of the upper part of the pin  24  is raised relative to the upper cover  30   a  and that part  24   a  of the pin which is now exposed is coloured in a readily identifiable colour, such as green, to provide a further visual identification that the lifting system is in a locked condition within the panel and hence in a “safe” condition for lifting. 
         [0027]    As mentioned previously, the base of the void former assembly also includes components of the jacking system used for leveling the panel after installation. A jacking plate  50 , preferably a steel plate, is housed within a void within the two shells  4  and  6  of the base and is not exposed to the surrounding concrete after pouring. As such, the plate will be free to displace when jacking force is applied. The upper shell  4  also houses a threaded structure or nut  52  which is located above and adjacent to the jacking plate  50  in alignment with the axis of the tubular body  2  of the void former. After removal of the lifting anchor assembly following lowering of the panel into place within the roadway, a threaded jacking rod is inserted through the void former into engagement with the threaded structure or nut  52  and after only a few turns, perhaps just one or two turns, it will engage the jacking plate  50  to start raising the panel into its final leveled configuration. While this is fundamentally the same process as that previously described, it will be understood that whereas in the earlier arrangement in which the threaded insert extended substantially the full depth of the panel many turns of the jacking rod were required before the jacking action could commence, and subsequently many turns were required to remove the jacking rod after completion of the setting operation, with the incorporation of the threaded structure or nut  52  towards the lower end of the void former immediately adjacent the jacking plate that action can be accomplished much more quickly. 
         [0028]    Although the embodiment typically described has been designed for the dual functions of providing a quick release lifting system combined with a jacking system also for quick release, an embodiment similar to that described but without the incorporation of the jacking system could provide a quick release lifting system for other precast concrete components when it is required to provide removable lifting anchors rather than cast-in lifting anchors as would typically be used in building construction involving the use of face lift or edge lift precast wall panels. 
         [0029]    The embodiment has been described by way of example only and modifications are possible within the scope of the invention. More specifically, various changes and modifications to the above-described embodiments described herein will be apparent to those skilled in the art. These changes and modifications can be made without departing from the spirit and scope of this present subject matter and without diminishing its intended advantages. Not all of the depicted components described in this disclosure may be required, and some implementations may include additional, different, or fewer components from those expressly described in this disclosure. Variations in the arrangement and type of components; the shapes, sizes, and materials of the components; and the manners of attachment and connections of the components may be made without departing from the spirit or scope of the claims as set forth herein. Also, unless otherwise indicated, any directions referred to herein reflect the orientations of the components shown in the corresponding drawings and do not limit the scope of the present disclosure. This specification is intended to be taken as a whole and interpreted in accordance with the principles of the invention as taught herein and understood by one of ordinary skill in the art.