AU5169290A

AU5169290A - Lifting anchors and clutches for lifting anchors

Info

Publication number: AU5169290A
Application number: AU51692/90A
Authority: AU
Inventors: Michael Finlay; Ian Paterson
Original assignee: ITW Construction Systems Australia Pty Ltd
Current assignee: Cetram Pty Ltd
Priority date: 1989-03-07
Filing date: 1990-02-28
Publication date: 1990-10-09
Anticipated expiration: 2010-02-28
Also published as: AU639908B2

Description

"LIFTING ANCHORS AND CLUTCHES FOR LIFTING ANCHORS"

The present invention relates to lifting anchors for incorporation into a concrete component such as a beam or slab prior to casting of the concrete in order to provide a lifting point by which the finished component can subsequently be lifted, and also to lifting clutches for co-operation with lifting anchors.

Lifting shackle assemblies for use with lifting anchors generally comprise a shackle plate having an eye at one end to receive a lifting cable, and, at the other end, a clutch with a bolt for releasable engagement with an eye of the lifting anchor. A suitable clutch is in the form of a ring clutch as described for example in Australian Patent No. 544,832.

In some lifting situations, it is desirable to restrict rotation of the clutch body relative to the lifting anchor about the axis of the clutch bolt which passes through the eye of the anchor. This may be necessary, for example when the anchor is incorporated into the edge of a slab which is to be lifted from a horizontal to a vertical position. If the clutch is able to pivot unrestrictedly, the lateral pulling forces may cause the clutch body to engage the surrounding concrete of the slab which may cause spalling. Anchors which are designed to avoid this effect are conventionally known as edge lift or erection anchors. One previously proposed form of edge lift anchor comprises axial projections which lie at each side of the clutch body to limit rotation by engagement with the clutch body. Upon application of lateral forces during lifting, one or other of the projections may be subjected to a substantial bending moment by the clutch body which can, at high loads, cause outwards deformation of the projection leading to larger rotation of the clutch which can result in spalling.

According to the present invention, there is provided a clutch for selective engagement and release with a head of a lifting anchor embedded in a concrete component whereby to connect the anchor to a lifting system, said clutch comprising a body having a slot for receiving the head of the anchor, and a locking member engagable into an eye in the head for releasably locking the head within the slot, said body having at least one abutment for engagement with a laterally projecting shoulder of the anchor head in order to restrict rotation of the clutch body about the axis of the eye of the anchor.

The invention also provides a lifting anchor for use with the ring clutch defined above, said anchor comprising a head engagable within the slot in the clutch body, said head having an eye, and said anchor having a body portion for embedment with the concrete component, wherein said head comprises a laterally projecting shoulder defining an upwardly facing abutment surface at one side of the longitudinal axis of the head for engagement by a said abutment of the clutch body, whereby to restrict rotation of the clutch body about the axis of the eye.

Further according to the invention, there is provided an anchor for incorporation into a concrete component, said anchor comprising a head adapted for releasable attachment to a lifting system, and a body portion adapted to be embedded within the concrete, said body portion including a section laterally offset from the head to enable the body portion to by-pass edge reinforcement within the component without cutting or displacing the reinforcement. An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings in which:-

Figure 1 is a side view of a lifting shackle assembly according to a preferred embodiment of the invention;

Figure 2 is a front view of the lifting shackle assembly;

Figure 3 is a front view to an enlarged scale of a shackle plate of the lifting shackle assembly;

Figure 4 shows, to an enlarged scale, a ring clutch of the lifting shackle assembly;

Figure 5 is a fragmentary section on line A of Figure 4 showing the ring clutch in position on edge lift anchor; and

Figure 6 is a side elevation of a modified form of edge lift anchor.

As shown in the accompanying drawings, a lifting shackle assembly comprises a shackle plate 2 having at one end portion an eye 4 for attachment of a lifting cable and at the other end portion a loop 6 engaged within the body of a ring clutch 8. The ring clutch 8 is of the general type described in the Australian patent specified above, and comprises an annular body 10 having a central aperture 12 through which passes the loop 6 of the shackle plate 2. An arcuate bolt 14 mounted within a channel in the body 10 is moveable between a position in which a radial aperture 16 at the bottom of the body 10 is open and a position in which the bolt 14 projects through the aperture 16 to engage the eye of a lifting anchor received within the aperture. Operation of the bolt 14 is effected by means of a radial arm 17 projecting from the bolt and engaged with an operating cable.

The shackle plate 2 is formed as a one-piece cast metal component. As cast, the shackle plate 2 includes the eye 4 for receiving the lifting cable and an open loop on which the body 10 of the ring clutch can be fitted. The plate is cast with one of two opposed legs 18 of the loop inclined outwardly as shown in solid lines of Figure 3 to enable the ring clutch to be engaged on the loop by passage of the inclined leg 18 through the central aperture 12 of the clutch body. After engagement of the clutch body on the loop, the shackle plate is heated to permit the inclined leg 18 to be bent back into the position shown in broken lines in Figure 3 in order to close the loop, the end of the leg 18 then being welded or otherwise fixed to the remainder of the shackle plate at 20, either directly or via a connecting piece. Finally, the shackle plate is heat treated to attain the required tensile strength.

It is to be noted that in the completed shackle plate the loop 6 is of elongate form with the central aperture 22 of the loop being of such a length that the operating arm 17 of the ring clutch bolt is able to pass freely through the loop without interference by the shackle plate 2. This permits operation of the ring clutch to release the anchor by retraction of the bolt in a wide range of orientations of the ring clutch and shackle plate, and this can be of importance when working in confined situations.

Instead of a shackle plate, a sling may be attached to the ring clutch. As shown in Figures 4 and 5, the body 10 of the ring clutch 8 has, adjacent the upper end of the radial aperture 16, a projecting shoulder 30, one such shoulder being provided at each side of the body 10. The shoulders 30 provide downwardly-facing stop surfaces 32 which project laterally from the clutch body 10 at the upper end of the aperture 16. In situations where rotation of the clutch body 10 relative to the lifting anchor about the axis of the eye of the anchor is to be restricted for the reasons previously discussed, the ring clutch is used with an edge lift anchor 34 having a head formed with lateral shoulders 36 at its upper edge as shown in Figure 5 whereby to define upwardly facing abutment surfaces. The head is of plate-like form, with an eye 38 extending through the head perpendicular to the plane of the head, the axis of the eye 38 being substantially on the longitudinal axis of the head. The shoulders lie at the upper end of the anchor above the eye 38 and extend transversely to the longitudinal axis of the head, on opposite sides of the axis.

The abutment surfaces provided by the shoulders 36 are at each side of the head and are connected by a raised bridging section 39 above the eye 38. In this arrangement, pivotal movement of the ring clutch body 10 about the eye 38 of the anchor 34 is restricted by engagement of the downwardly-facing stop surfaces 32 on the clutch body with the upwardly-facing surfaces of the corresponding shoulders 36 on the anchor 34. When the ring clutch is subject to lateral forces during pulling, these forces will be transmitted directly to the anchor by engagement of one of the stop surface 32 on the clutch body with the adjacent shoulder 36 on the anchor. The shoulder 36 on the anchor will be subjected to a direct compressive loading by the stop surface 32. This compressive loading is substantially axially directed and can be carried by the anchor without the possibility of breakage.

The body of the lifting anchor which is embedded within the concrete of the slab can be of any suitable form.

Edge lift anchors conventionally comprise a flat bar incorporated into the edge portion of the component. Previous designs of edge-lift anchor have necessitated cutting or displacement of the reinforcement at the edge of the component in order to permit location of the anchor prior to pouring of the concrete.

As shown in Figure 6 an edge lift anchor is in the form of a flat bar having a head portion 42 including a lifting eye 44 for engagement with a lifting shackle assembly, and a body portion 46 of generally dog-leg shape. The head portion 42 has a notch 48 at one side to receive a shear-bar which constitutes part of the reinforcement. An opening 50 at the opposite end of the anchor serves to receive a reinforcing bar having a portion bent into inverted V or U-shaped configuration in order to ensure firm anchorage within the structure. The dog-leg configuration of the body portion 46 defines at one side of the body a recess 52, the base 52a of which lies to one side of a perimeter bar 54 which forms part of the reinforcement, tfhe dog-leg configuration of the body portion laterally offsets a section of the body portion which enables the anchor to be placed into the required position in formwork for the component without the need to either displace or cut the perimeter bar as would be necessary with an anchor of substantially rectilinear bar-like configuration.

The dog-leg configuration also provides at the opposite side to the recess 52 a downwardly inclined, upwardly facing, surface 56 which acts to significantly increase the anchorage of the anchor within the concrete after pouring.

The head portion 42 includes a laterally-extending shoulder defining an upwardly-facing abutment surface 58. This surface is designed to co-operate with one of the stop surfaces 32 on the body 10 of the ring clutch 8 described above. The abutment surface 58 co-operates with the clutch body to restrict pivotal movement of the clutch body relative to the anchor about the axis of the lifting eye 44.

Although the invention have been described in relation to a ring clutch of the type described in Australian Patent No. 544,832, the invention is applicable also to other forms of clutch in which the body portion has an aperture for receiving the head of an anchor and locking means engagable through the eye of the anchor for the anchor within the clutch.

The embodiment have been described by way of example only, and modifications are possible within the scope of the invention.

Claims

1. A clutch for selective engagement and release with a head of a lifting anchor embedded in a concrete component whereby to connect the anchor to a lifting system, said clutch comprising a body having a slot for receiving the head of the anchor, and a locking member engagable into an eye in the head for releasably locking the head within the slot, said body having at least one abutment for engagement with a laterally projecting shoulder of the anchor head in order to restrict rotation of the clutch body about the axis of the eye of the anchor.

2. A clutch according to Claim 1, wherein the body has a pair of abutments each at opposite sides of the body.

3. A clutch according to Claim 1 or Claim 2 wherein the or each said abutment is located on the body above the slot.

4. A clutch according to any one of Claims 1 to 3, wherein the or each said abutment comprises an abutment surface which extends laterally from the body and which faces downwardly for engagement with an upwardly facing lateral abutment surface on the shoulder of the anchor head.

5. A clutch according to Claim 4 in combination with a said anchor, said anchor having a head for engagement within the slot in the clutch body, said head including an eye to receive the locking member, and a lateral shoulder having an upwardly facing abutment whereby to limit pivotal movement of the clutch body about the axis of the eye, said anchor further comprising a body portion for embedment within the concrete component.

6. A clutch and anchor combination according to Claim 5, wherein the head of the anchor has a respective said lateral shoulder at each side of the longitudinal axis of the head.

7. A clutch according to any one of Claims 1 to 6, wherein the clutch body includes an aperture which receives a shackle plate for connecting the clutch to a lifting cable.

8. A clutch according to Claim 7, wherein the shackle plate is formed as a one-piece unit having a loop on which the clutch is mounted, the loop being initially open to permit mounting of the clutch body, the loop being subsequently closed by deformation of the material of the loop.

9. A clutch according to Claim 8, wherein the shackle plate is formed as a one-piece metal component which is heated after mounting of the clutch body to permit closure of the loop, the adjacent ends of the closed loop being secured one to the other.

10. An anchor for use with a clutch according to any one of Claims 1 to 9, said anchor comprising a head engagable within the slot in the clutch body, said head having an eye, and said anchor having a body portion for embedment with the concrete component, wherein said head comprises a laterally projecting shoulder defining an upwardly facing abutment surface at one side of the longitudinal axis of the head for engagement by a said abutment of the clutch body, whereby to restrict rotation of the clutch body about the axis of the eye.

11. An anchor according to Claim 10, wherein the head has a respective said laterally projecting abutment surface at each side of the longitudinal axis of the head.

12. An anchor according to Claim 10 or Claim 11, wherein the head is of plate-like form, with the axis of the eye extending through the head perpendicularly to the plane of the head, the axis of the eye lies substantially on the longitudinal axis of the head, and the or each said laterally projecting abutment surface lies at a respective side of the head at an upper edge thereof.

13. An anchor according to Claim 12, wherein the upper edge of the head includes an intermediate portion in the zone of the longitudinal axis, said intermediate portion projecting upwardly beyond the or each said abutment surface.

14. An anchor according to any one of Claims 10 to 13 wherein the body portion of the anchor includes a section laterally offset from the head to enable the body portion to by-pass edge reinforcement within the component without cutting or displacing the reinforcement.

15. An anchor for incorporation into a concrete component, said anchor comprising a head adapted for releasable attachment to a lifting system, and a body portion adapted to be embedded within the concrete, said body portion including a section laterally offset from the head to enable the body portion to by-pass edge reinforcement within the component without cutting or displacing the reinforcement.