Lifting shackle with a lifting clutch

Abstract

 A lifting clutch of a lifting shackle assembly for engagement with a lifting anchor embedded within a concrete component to be lifted has a clutch bolt (14) engageable through an eye in the head of the anchor. A locking system (22,24,34;24,24a,14a;50,52) is provided to prevent accidental release of the clutch bolt (14) from the eye of the anchor. In one form, the locking system (22,24,34) consists of a spring-loaded locking member (24) mounted to the clutch body to lock the clutch bolt against release until the locking arm (30) has been released. In another form, the locking system comprises a locking pin (50) mounted within an operating arm (17) of the clutch bolt (14) and engaged with the clutch body (10) so that the operating arm (17) cannot be displaced to release the bolt (14) until the locking pin (50) has been released.

Description

[0001] The present invention relates to lifting shackle assemblies for use with lifting anchors incorporated into a concrete component such as a slab or panel prior to casting of the concrete in order to provide a lifting point by which the component can be lifted. More particularly, the invention relates to a clutch for use in a lifting shackle assembly.

[0002] 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.

[0003] A conventional form of lifting shackle assembly is shown in Figure 1 (a side view) and Figure 2 (a front view) of the accompanying drawings. The 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 544,832 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-like passage in the body 10 is movable 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 (not shown) received within the aperture. Operation of the bolt 14 is effected by means of an integral radial arm 17 projecting externally from the body 10 and either directly manually activated or engaged with an operating rope to effect a remote movement of the arm 17 from the ground to release the clutch from the anchor after the component has been lifted into position. Figure 1 shows the bolt 14 in its engaged position projecting through the aperture 16 and the bolt 14 is displaced into its released position by anticlockwise rotation of the arm 17 through approximately 90° from the position shown.

[0004] Lifting shackle assemblies as just described are commonly used in face-lift and edge-lift situations in which the component, typically a concrete slab or panel, is lifted either from its face or from its edge, this being determined by the placement of the lifting anchors in the component. In lifting situations involving a change in the orientation of the component typically at the commencement of lifting in face-lift tilt up and in some forms of edge-lift, if the bolt has not been fully engaged with the lifting anchor it is occasionally possible for the clutch to disengage from the anchor usually at the commencement of lifting. Even if the clutch is thought to be properly engaged with the anchor it is now believed that it could be possible for the bolt to shake to a released condition prior to the shackle assembly being placed under lifting load.

[0005] As briefly discussed above, lifting shackle assemblies of the type described are suitable for direct manual release from the component after lifting into position, by an operator climbing a ladder to access the clutch and effect release. They are also suitable for remote release from the ground via a release rope attached to the end of the arm; depending on the type of lift being effected, the release rope may pass over a pulley system carried by the shackle plate or the rope may pass directly to the ground. In lifting systems set up to provide for remote release, the possibility can exist that the release rope can become accidentally snagged or caught and this can result in accidental release of the bolt either prior to the commencement of lifting or at the start of lifting and prior to application of the full lifting load. Although remote release systems are available which substantially avoid this difficulty, some operators are unwilling to use such systems and prefer to continue to use the conventional release systems which have been used for many years.

[0006] According to the present invention there is provided a clutch for selective engagement and release with the 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 an anchor, and a bolt engageable into an eye in the head of the anchor for releasably locking the head, said bolt being of arcuate form movable along an arcuate passage in the body between engaged and released positions relative to the slot, said arcuate bolt being connected to an operating arm extending generally radially relative to the bolt to effect movement of the bolt along the passage, and a locking system for preventing movement of the bolt from its engaged position until release of the locking system.

[0007] In one form of the invention, the locking system comprises a locking member mounted to the clutch body and adapted to cooperate with the bolt or a component moveable with the bolt to releasably lock the bolt against movement from its engaged position. Preferably, the locking member is pivotally mounted to the clutch body and is spring biased to a locking position. Preferably, the locking member has a release arm extending externally of the body for external engagement to permit release movement of the arm against the spring bias.

[0008] Particularly advantageously, the locking member is so positioned on the clutch body that the release arm of the locking member and the operating arm associated with the clutch bolt will be located to opposite sides of a shackle plate to which the clutch is mounted in use. As a consequence, a release rope associated with the clutch bolt and a release cord or rope associated with the locking member are not likely to become simultaneously tensioned by engagement with or interference with the shackle plate. It is also particularly advantageous that the locking member is mounted to the body in such a position that when the lock has been released, the locking member itself will not directly interfere with the operating arm of the clutch bolt when moving to the released position.

[0009] Particularly advantageously, the locking cooperation between the locking member and the bolt or the component moveable therewith is such that the locking engagement is required to be released prior to application of a force to the operating arm to move the bolt out of its engaged position; this relative timing of the actions needed to release the locking member and then the bolt minimises the risk of accidental release of the bolt in the event that remote release ropes and cords associated with the clutch become snagged simultaneously.

[0010] In one embodiment, the locking member cooperates with an arcuate extension of the bolt located in a part of the passage diametrically opposed to that occupied by the bolt. In another embodiment, the locking member is designed to cooperate with a leading end portion of the bolt provided with a locking formation which cooperates with the locking member.

[0011] In another form of the invention, the locking system comprises a spring-loaded locking pin releasably engageable with the clutch body to releasably lock the bolt in its engaged position. In one embodiment, the pin is mounted for radial movement relative to the bolt and is spring-biased into a radially inwards direction in order to effect locking of the bolt relative to the clutch body. Particularly advantageously, the pin and its biasing spring are mounted within an axial passage formed in the operating arm, with the pin lockingly engaging within an aperture formed in the base of the arcuate passage in the body, release of the pin being affected by withdrawing the pin from the aperture by a release member accessible externally of the arm.

[0012] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 3 is a cross-section of one embodiment of a ring clutch having a locking system in accordance with the invention, the clutch bolt being shown in its engaged position extending through the anchor head receiving slot in the clutch body;

Figure 3A shows schematically a modified configuration of the locking system which requires release of the locking member prior to application of release force to the clutch bolt operating arm;

Figure 4 is a cross-section similar to Figure 3 and showing an alternative form of locking system; and

Figure 5 is a cross-section similar to Figure 3 and showing yet another alternative form of locking system.

[0013] The ring clutch shown in Figure 3 comprises an annular body 10 with radial aperture 16 with an arcuate bolt 14 with integral radial operating arm 17 mounted within in arcuate passage in the form of an annular channel 20 in the body. The ring clutch is mounted to a shackle plate (not shown in Figure 3) of the type shown in Figures 1 and 2 or other suitable form of shackle plate in the manner described with reference to Figures 1 and 2. In terms of its basic construction, the bolt 14 with integral radial operating arm 17 is the same as that described with reference to Figures 1 and 2, but with the addition of an extension as will be described which interacts with a locking member. Figure 3 shows, as does Figure 1, the bolt 14 in its engaged position in which it passes through the eye of an anchor (not shown) within the aperture 16. As with Figure 1, to release the clutch from the anchor, the clutch bolt 14 must be rotated through approximately 90° in an anticlockwise direction by corresponding movement of the arm 17.

[0014] In accordance with this embodiment of the invention, an arcuate extension 22 is mounted to the clutch bolt 14 to lie within the part of the annular channel 20 in the body 10 to the other side of the radial arm 17 so that the extension 22 is diametrically opposed to at least a part of the clutch bolt 14 although it does not require to be of the same arcuate extent as that of the clutch bolt 14. It will be appreciated from Figures 1 and 2 and also from the earlier patent discussed above that the channel 20 is open to the outside over part of its periphery to enable the angular displacement of the radial arm 17 and this open section also enables assembly of the clutch by introduction of the arcuate bolt 14 into the channel 20 via that section; the open section of the channel 20 is in the upper part of the body shown in Figures 1, 2 and 3, and extends over approximately 180°. A locking member 24 is mounted partially within the open section of the channel 20 to cooperate with the free end of the extension 22. The position of the locking member 24 within the channel 20 is such that it will not interfere with the movement of the radial arm 17 between the engaged and released positions of the bolt 14. The locking member 24 is pivotally mounted on a pivot pin 26 extending between the opposite side walls of the channel, the locking member 24 being subjected to an inwards resilient bias by a suitable spring which, in the embodiment shown, is in the form of a leaf spring 28 anchored in a slot in the locking member 24 and engaged with the outer wall of the channel 20 beyond the open section thereof. It is however to be understood that other forms of biasing spring arrangement could be incorporated.

[0015] The locking member 24 has an integral release arm 30 which projects outwardly through the open section of the channel 20 and formed at its outer end with an aperture 32 for selective attachment of a release cord. The locking member 24 is formed with an abutment surface 34 which, in the locking position of the member 24 (the position as illustrated in Figure 3), lies immediately in front of the free end of the extension 22 to thereby prevent substantive movement of the extension 22 and hence of the clutch bolt 14 in the release direction, that is an anticlockwise direction as viewed in Figure 3, or at least to prevent sufficient clutch bolt movement required for release.

[0016] To permit release movement of the clutch bolt 14, the locking member 24 must be pivoted outwardly against the spring bias to move its abutment surface 34 out of the path of movement of the extension 22 in the release direction and this will require a deliberate release action of the locking member 24 by movement of the release arm 30 such as by actuation of an associated release cord attached to the arm. When the locking member 34 has been moved to its released position, the clutch bolt 14 can then be displaced to its released position by anticlockwise movement of the radial arm 17, the outer surface of the extension 22 moving along the inside surface of a nose part 24a of the locking member 24. When the clutch is next applied to a lifting anchor and the radial arm 17 is rotated clockwise to engage the clutch bolt 14 within the eye of the anchor, the extension 22 will slide clockwise along the underside of the nose 24a until a fully engaged position of the clutch bolt 14 is reached when the free end of the extension 22 passes from the nose 24a to the other side of the abutment surface 34 whereon the locking member 24 will snap into its locking position shown in Figure 3 in which the nose 24a is maintained by the spring 28 against the inner wall of the channel 20. The operator will sense and/or hear a distinct click or snap action when this occurs and will then know that the clutch bolt 14 is locked in position; verification can be obtained by movement of the radial arm 17 in a direction to attempt to release the bolt 14.

[0017] Particularly advantageously, the pivotal mounting of the locking member 24 on the pivot pin 26 is provided by an elongate slot 36 such as to permit some play between the locking member 24 and the pin 26 in order to prevent substantive load on the pin 26 arising from a force applied to the radial arm 17 trying to displace the clutch bolt 14 in a release direction with the locking member 24 engaged as may occur if, for example, a release rope attached to the arm 17 becomes snagged at the start of lifting. In this event, the forced engagement of the free end of the extension 22 with the abutment surface 34 of the locking member 24 will tend to displace the locking member 24 inwardly so that the nose 24a is pushed against the inner wall of the channel 20 at point X and/or the release arm 30 bears against an edge of the clutch body 10 at the end of the open channel section at point Y. Accordingly, this loading is absorbed by direct engagement between the locking member 24 and the body 10 rather than by direct loading on the pivot pin 26 to obviate the possibility of failure of the pivot pin under this type of accidental loading.

[0018] It will be appreciated from Figure 3 that the release arm 30 and the radial arm 17 will be located to opposite sides of the shackle plate to which the ring clutch is fitted in the manner shown in Figures 1 and 2. This is of consequence as it means that a release cord attached to the release arm 30 and a release rope attached to the radial arm 17 are most unlikely to become simultaneously tensioned by snagging with the shackle plate. Rather, if snagging occurs the probability is that movement of the shackle plate will result in one rope or cord being tensioned with the other being loosened and in either case accidental release of the clutch bolt would not occur. It is also to be noted from Figure 3 that the position of the locking member 24 within the open section of the channel 20 is such that it is fully outside of the path of movement of the radial arm 17 into its released position which is approximately 90° anticlockwise from that illustrated in Figure 3 so that once the lock has been released the release movement of the clutch bolt is itself quite straight forward which is an important feature in obtaining user acceptance of the locking system. Moreover it is to be noted that although the release arm 30 of the locking member 24 extends to the outside of the clutch body 10 and can be designed to withstand the rough handling to which clutches of this type are likely to be subjected in use on building sites, nevertheless the substantive part of the locking member 24 consisting of locking abutment 34 and spring 28 will always be housed within the arcuate channel 20 and will thereby, to a significant extent, be shielded by the body 10 from external damage as a result of rough handling.

[0019] Particularly advantageously, in a modification as shown schematically in Figure 3A, the free end of the extension 22 is ramped at 22a and the abutment surface 34 is undercut at 34a. With this configuration the undercut abutment surface 34a will positively interlock with the free end of the extension 22 to prevent release movement of the locking member 24 at the same time that a force is applied to move the clutch bolt 14 to its released position by movement of the radial arm 17. Accordingly, with this configuration the locking member 24 must be released prior to an attempt being made to release the clutch bolt 14. This feature will thereby obviate the possibility, albeit a remote possibility, of accidental release taking place by simultaneous snagging of a release cord for the locking member 24 and the release rope for the clutch bolt 14.

[0020] The locking system of Figure 3 or 3A can be retro-fitted into existing shackle assemblies of the type shown in Figures 1 and 2, by installation of the locking member 24 and pivot pin 26 in the body 10 of the existing clutch and by provision of the extension 22 for the clutch bolt 14; due to the need to mount the clutch bolt 14 into the channel 20 and which requires the bolt 14 to have an arcuate extension of less than 180°, the clutch bolt 14 needs to have minor adaptation to permit the extension 22 to be fitted after the bolt has been inserted into the channel 20; the extension 22 can be secured to the bolt 14 by a screw with a locking washer and the base of the arm 17 can be relieved such as by grinding to form a flat surface to which a mounting part 22b of the extension 22 can be secured.

[0021] In an alternative embodiment as shown in Figure 4, the locking member 24 is mounted in the channel 20 to cooperate with the free end portion of the clutch bolt 14. For this purpose, the free end portion of the clutch bolt 14 is shaped to form a locking hook 14a which engages behind a similarly shaped locking hook 24a on the locking member 22 to prevent the clutch bolt 14 from being withdrawn to the released position until the locking member 24 has been released. The inter-engaging locking hooks 14a, 24a are preferably of ramped configuration to provide a similar effect to that provided by the arrangement shown in Figure 3A whereby the locking member 24 is required to be moved to its released position before a release movement is applied to the clutch bolt 14. This locking system can also be retro-fitted to existing shackle assemblies by mounting the locking member 24 to the clutch body 10 by means of the pivot pin 26 and replacing the existing clutch bolt with a modified clutch bolt incorporating the hook-shaped locking end portion.

[0022] The embodiment of Figure 4 achieves similar advantages to those discussed in relation to Figure 3 in terms of the placement of the locking member and its release arm. Although in terms of basic locking function it is considered that both embodiments will provide similar effect, the embodiment of Figure 3 does have additional advantage over that of Figure 4 in that the free end portion of the clutch bolt does not have any projections or recesses which might catch against the head of the lifting anchor during engagement and release of the clutch bolt. Moreover the extension 22 which is fitted in the embodiment of Figure 3 has the additional effect of ensuring that the clutch bolt 14 cannot accidentally fall out of the clutch body 10 and which has sometimes eventuated during handling of the clutches shown in Figures 1 and 2.

[0023] Figure 5 shows another form of locking system comprising a spring-biased locking pin 50 mounted in the radial arm 17 of the clutch bolt 14 to engage in a hole 52 drilled into the base of the channel 20. The locking pin 50 and its biasing spring 54 are housed within an axial passage formed in the arm 17 and a release element in the form of a rod or cable 56 extends from the pin 50 through the axial passage for attachment to a release cord. Release of the locking pin 50 requires axial movement of the release element 56 within the radial arm 17 whereas the movement of the arm to 17 effect release of the clutch bolt 14 is required to be more transverse to the axis of the arm. Accordingly, with this arrangement the applied forces needed to first release the locking pin 50 and then release the clutch bolt 14 are in distinctly different directions and there is only small possibility of this happening even if a remote release cord for the locking pin 50 and a remote release rope for the clutch bolt are simultaneously snagged. This form of locking system can also be retro-fitted by replacing the existing clutch bolt with a clutch bolt having a radial arm which incorporates the locking pin and by drilling into the base of the channel a hole to receive the locking pin in the engaged position of the clutch bolt. In an alternative arrangement (not shown) the radially movable spring-loaded locking pin can be mounted to the clutch body to releasably engage and lock the clutch bolt.

[0024] The embodiments 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 the head of a lifting anchor embedded in a concrete component whereby to connect the anchor to a lifting system, said clutch comprising a body (10) having a slot (16) for receiving the head of an anchor, and a bolt (14) engageable into an eye in the head of the anchor for releasably locking the head, said bolt (14) being of arcuate form movable along an arcuate passage (20) in the body (10) between engaged and released positions relative to the slot (16), said arcuate bolt (14) being connected to an operating arm (17) extending generally radially relative to the bolt (14) to effect movement of the bolt along the passage (20), and a locking system (22, 24, 34; 24, 24a, 14a; 50, 52) for preventing movement of the bolt (14) from its engaged position until release of the locking system.

2. A clutch according to claim 1, wherein the locking system comprises a locking member (24) mounted to the clutch body (10) and adapted to cooperate with the bolt (14) or a component (22) moveable with the bolt (14) to releasably lock the bolt (14) against movement from its engaged position.

3. A clutch according to claim 2, wherein the locking member (24) is pivotally mounted to the clutch body (10) and is spring biased (28) to a locking position.

4. A clutch according to claim 3, wherein the locking member (24) has a release arm (30) extending externally of the body (10) for external engagement to permit release movement of the arm (30) against the spring bias (28).

5. A clutch according to claim 4, wherein the locking member (24) is so positioned on the clutch body (10) that the release arm (30) of the locking member (24) and the operating arm (17) of the bolt (14) will be located to opposite sides of a shackle plate (2) to which the clutch is mounted in use.

6. A clutch according to any one of claims 2 to 4, wherein the locking member (24) is mounted to the body (10) in such a position that when the lock has been released, the locking member (24) itself will not directly interfere with the operating arm (17) of the bolt (14) when moving to the released position.

7. A clutch according to any one of claims 2 to 6, wherein the locking cooperation between the locking member (24) and the bolt (14) or the component (22) moveable therewith is such that the locking engagement is required to be released prior to application of a force to the operating arm (17) to move the bolt out of its engaged position.

8. A clutch according to any one of claims 2 to 7, wherein the locking member (24) cooperates with an arcuate extension (22) of the bolt (14) located in a part of the passage (20) diametrically opposed to that occupied by the bolt (14).

9. A clutch according to any one of claims 2 to 7, wherein a leading end portion of the bolt (14) is provided with a locking formation (14a) which cooperates with the locking member (24).

10. A clutch according to claim 1, wherein the locking system comprises a spring-loaded locking pin (50) releasably engageable with the clutch body (10) to releasably lock the bolt (14) in its engaged position.

11. A clutch according to claim 10, wherein the pin (50) is mounted for radial movement relative to the bolt (14) and is spring-biased into a radially inwards direction in order to effect locking of the bolt (14) relative to the clutch body (10).

12. A clutch according to claim 11, wherein the pin (50) and its biasing spring (54) are mounted within an axial passage formed in the operating arm (17), with the pin (50) lockingly engaging within an aperture (52) formed in the base of the arcuate passage (20) in the body, release of the pin (50) being affected by withdrawing the pin (50) from the aperture (52) by a release member (56) accessible externally of the arm (17).

Drawing