The present invention relates to lifting anchors to be incorporated into concrete components during casting thereof to provide lifting points by which the component can be lifted and more particularly to edge lift anchors for incorporation into concrete panels.
One type of edge lift anchor for use with concrete panels comprises a head configured for engagement with a lifting clutch and opposed generally parallel legs extending from the head to provide anchorage within the panel, the legs being appropriately profiled along their edges for that purpose. Various different designs of this type of anchor are in widespread use. Edge lift anchors of this type are currently formed by cutting from thick metal plate using non-contact high energy cutting means such as a laser beam or plasma arc with the edges of the legs being profiled in this cutting process.
The preferred embodiment to be described herein features a range of improvements in edge lift anchors of the general type discussed above and enabled by the use of alternative manufacturing methods.
According to the present invention there is provided a lifting anchor for embedment into a concrete component, the anchor having a head for releasable engagement with lifting equipment, and at least one leg extending from the head, the leg being profiled so as to lock into the surrounding concrete, wherein the profiling is formed by a series of formations arranged along at least a face and adjacent edge of the leg.
Further according to the invention, there is provided an edge lift anchor for embedment into a concrete panel, the anchor having a head for releasable attachment with lifting equipment, and a pair of generally parallel legs extending from the head, each leg being profiled so as to lock into the surrounding concrete, wherein the profiling is formed by a series of formations arranged longitudinally along each leg on an inner edge and opposed faces of the leg.
Still further according to the invention, there is provided a lifting anchor for embedment into a concrete component, the anchor having a head for releasable engagement with lifting equipment, and at least one leg extending from the head, the leg being profiled so as to lock into the surrounding concrete, wherein the profiling is formed by a series of formations arranged along at least a face of the leg.
Still further according to the invention there is provided a lifting anchor for embedment into a concrete component, the anchor having a head for releasable engagement with lifting equipment and at least one leg extending from the head, the leg being profiled so as to lock into the surrounding concrete, the anchor having reinforcing ribbing extend outer edge of substantially the entire length of the leg.
Still further according to the invention there is provided an edge lifting anchor for embedment into a concrete panel, the anchor having a head for releasable attachment with lifting equipment and a pair of generally parallel legs extending from the head, each leg being profiled so as to lock into the surrounding concrete, wherein each leg includes ribbing extending along its outer edge over substantially its entire length of the ribbing extending to adjacent the head of the anchor whereby the anchor is substantially configured in the manner of an eye-beam from adjacent the head to the remote ends of the legs.
An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which:
The embodiments of the anchor now to be described herein incorporates a range of improvements over prior anchors of the type previously discussed particularly resulting from the use of alternative manufacturing techniques.
The edge lift anchor shown in the accompanying drawings is of the same general form as that described in Australian patent application 2006201337 of Cetram Pty Ltd (a subsidiary of the present applicants) and comprises a pair of opposed parallel legs 2 extending from a head 4. The particular head shown is designed for use with a releasable lifting clutch in the form of a ring clutch having an arcuate locking bolt received within an eye 6 in the head. The legs 2 are profiled with a series of saw-toothed formations 8 along their length. While the saw-toothed formations are similar to those described in detail in the aforesaid application and have a corresponding locking effect with the surrounding concrete when the anchor is under tensile load, there are differences as will be described subsequently.
In contrast to the anchor of the aforesaid application and which is cut from thick metal plate, the anchor of the preferred embodiment is fabricated by other techniques such as hot drop forging from a metal billet (the particularly preferred method), casting, or sintering.
Not only does this lead to reduced manufacturing costs, it permits a range of significant design changes providing benefits such as increased anchor capacity and performance which in turn can enable a further manufacturing cost reduction for a given capacity of anchor and benefits in the installation of the anchor. In this respect it is to be noted that with edge lift anchors of the type in question cut from thick metal plate any design changes are predominantly confined to the configuration of the cut edges of the anchor while the opposed faces of the anchor which are formed out of the opposed faces of the plate are fundamentally planar. However by using other techniques as just indicated, shaping can be applied to all parts of the anchor including its opposed faces in order to provide desired technical/functional effects, as will now be described.
Although, as mentioned above, the legs of the preferred embodiment are formed with a series of generally saw-toothed formations along their length as generally described in the aforesaid application, in the preferred embodiment the formations 8 do not extend just along the inner edges of the legs as occurs with an anchor cut from thick metal plate, but they also extend onto the opposed faces of each leg as will be apparent from
It is to be noted that when hot drop forging is used to manufacture the anchor, due to the manner in which the forging tool closes onto the billet it is not possible for the entire upper operative face of the formation to achieve the desired upwards inclination and in practice this is achievable only in the portion adjacent the inner edge of the leg whereas the portions of the upper face adjacent the opposed faces of the leg will either be at right angles to the axis of the leg or feature a slight downwards inclination. This transformation in the inclination of the upper operative face can be seen in
It is to be noted that while it is preferred to use saw-toothed locking formations of the form discussed in detail above, other types of locking formations could alternatively be used and these may be on just one or more faces and/or edges of the leg according to the requirements of the particular anchor. The various manufacturing methods described permit significant versatility in the design of the anchor to provide a variety of different locking interactions between the leg and surrounding concrete.
In the upper part of the anchor immediately below the head 4 which is engaged by the ring clutch, the anchor is formed on each of its two opposed faces with inclined ribs 10 adjacent the respective edges of the anchor. In the embodiment shown, the ribs 10 are inclined at approximately 45° to the longitudinal axis of the anchor. These ribs act to increase the rigidity of the anchor in that zone and which is of particular utility when the anchor has in that zone an aperture 12 beneath the head for receiving a tension bar which is bent into a generally V-shaped configuration as is well known. This is of relevance in the initial phases of lifting the panel from the horizontal configuration in which it is cast to a generally vertical configuration. The ribs 10 also provide improved interlock with the surrounding concrete during these initial lifting phases. Longitudinal extensions 14 of the inclined ribs along each of the opposed edges of the anchor provide shear capacity during the initial phases of lifting from the horizontal to the generally vertical thereby obviating the need for the installer to incorporate shear bars for that purpose.
It will be noted that in the embodiment shown, the aperture 12 for the tension bar is of elongate form transversely of the longitudinal axis of the anchor, whereas in existing anchors of this type when such an aperture is present it is of circular form. This elongation enables the tension bar to be placed slightly “off centre” with respect to the panel while extending throughout its length substantially parallel to central reinforcing mesh within the panel and hence substantially parallel to the longitudinal axis of the anchor, it being understood that the length of the aperture is sufficient for that purpose. This is illustrated in
Advantageously, the lower surface of the tension bar aperture 12 is arcuate in transverse section with a curvature which matches the curvature of the bent apex of the tension bar as shown schematically in
In existing anchors, the width of the head and which corresponds to the overall width of the anchoring portion defined by the two legs is such that when the lifting clutch is inclined at the start of lifting a panel from the horizontal configuration in which it is cast to a generally vertical configuration, the clutch body abuts against the upper edge of the head thereby blocking rotation of the clutch body beyond that point to prevent damage to the surrounding concrete of the panel. However, in existing anchors that engagement tends to occur very close to the end of the upper edge and that may result in some deformation of the head at that point when the anchor is under a loading close to its maximum loading. This deformation at the end of the edge can sometimes result in cracking of the surrounding concrete to which the edge of the head is immediately adjacent. In the preferred embodiment the width of the head is increased to provide an increased length of the upper edge whereby the clutch body when inclined will engage that edge at a position displaced more inwardly from the outer end of the edge. In particular the width is increased to permit engagement of the clutch body with the edge at a distance of approximately 12 to 16 mm from the end of the edge, depending on anchor and clutch capacity. In this regard, edge lift anchors are typically produced with lifting capacities of 3, 7, and 10 tonnes for use with lifting anchors of corresponding rating. Clutch bodies of typical lifting clutches within these ranges have a thickness of from around 48 to 55 mm and engagement of the clutch body with the anchor head at a point displaced inwardly from the end by a distance of the order indicated above can be achieved by producing a 3 tonne anchor with a head width of about 50 to 65 mm, 7 tonne capacity with a width of about 70 to 85 mm, and 10 tonne capacity with a width of about 75 to 90 mm. In one practical example, a 3 tonne anchor has a head width of 60+/−1 mm, a 7 tonne anchor has a head width of 80+/−1 mm, and a 10 tonne anchor has a head width of 85+1-1 mm. As the increased head width is for the purpose of achieving engagement with the clutch body by a greater distance displaced inwardly from the end it is not essential for the whole of the head to be of that width and in the preferred embodiment the head narrows inwardly from its widened upper edge in order to provide reduced material costs. That narrowing, although desirable for reasons just mentioned, is not essential from a functional perspective. With the increased head width, the diameter of the void formed in the edge of the concrete panel during casting and within which the head sits, is commensurately increased in diameter by using a void former of related size so that the edges of the head are immediately adjacent the concrete.
The anchor shown in
It is to be understood that the I-beam construction of
The embodiment has been described by way of example only and modifications are possible within the scope of the invention. For example although it is preferred for the anchor to have two parallel profiled legs extending from the head, it is in principle feasible for the anchor to have only a single such leg with the profiling on three sides of the leg or even on all four sides of the leg so as to interlock with the surrounding concrete. As an alternative to the production methods described herein, the anchor could be fabricated by machining from a single piece of metal or assembled from several separate components by welding together.
The manufacturing techniques discussed herein as an alternative to cutting from thick metal plate permit a variety of 3-D shaping options not achievable by the plate cutting technique previously used. As regards the leg or legs of the anchor although shaping with anchoring formations along opposed faces and the edge is preferred, depending on the technical requirements of the anchor it is possible to have the shaping just along the opposed faces or perhaps even along just one of the opposed faces.
It is to be understood that terms such as “upper” and “lower” and similar terms as used in the following claims and elsewhere in the specification are relative terms in relation to the configuration of the anchor when in a lifting state when the anchor and panel in which it is embedded are substantially vertical.
Number | Date | Country | Kind |
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2012901631 | Apr 2012 | AU | national |
2012903823 | Sep 2012 | AU | national |
Filing Document | Filing Date | Country | Kind |
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PCT/US13/38167 | 4/25/2013 | WO | 00 |