AU676061B2 - Clutch assemblies for use with lifting anchors - Google Patents

Description

Regulation 3.2

AITSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

Name of Applicant: RAMSET FASTENERS (AUST.) PTY.LIMITED Actual Inventor(s): FINLAY, Michael Address for Service: DAVIES COLLISON CAVE, Patent Attorneys, 1 Little Collins Street, Melbourne, 3000.

Invention Title: "Clutch Assemblies for use with Lifting Anchors" Details of As.,'iated Provisional Application(s): No(s): PM0185/93 filed 28 July, 1993 PM5883/94 filed 26 May, 1994 The following statement is a full description of this invention, including the best method of performing it known to me/us: Ir -la- CLUTCH ASSEMBLIES FOR USE WITH LIFTING ANCHORS The present invention relates to a clutch assembly for releasably connecting a lifting cable to an anchor incorporated in a reinforced concrete slab or other component in order to lift the component from the ground into an operative position during the construction of a building.

So-called tilt-up slab systems of building construction involve the lifting of a reinforced concrete slab from a horizontal position on the ground into a vertical position in which the slab forms part of a wall of a building under construction. To enable lifting of the slab, a liting anchor is embedded within the slab during casting of the slab, with a head of the anchor being exposed within a recess formed in the face of the slab. In one system currently in use, the head of the anchor includes an eye which receives a locking bolt of a clutch connected via a shackle plate to a lifting cable. A suitable clutch for this type of system is disclosed in Australian Patent 544832. In order to connect the lifting cable to the slab, the clutch is inserted over the head of the anchor with the lower part of the clutch body being located within the recess in the surface of the slab, and a locking bolt of the clutch is engaged through the eye of the anchor head. When the slab has been hoisted into its vertical position and is safely supported in that position, the locking bolt of the clutch is released in order to permit disconnection of the clutch, and hence the lifting cable, from the lifting anchor. To facilitate remote release of the locking bolt, a release rope is attached to an arm of the bolt for operation from the ground. Prior to release of the bolt, the arm extends in an upwards direction approximately parallel to the face of the wall slab and in most lifting situations the release rope is inclined at a relatively shallow angle to the arm of the locking bolt whereby the effective length of the lever arm by which release force is applied to the bolt from the rope is relatively small and consequently a substantial pulling load is sometimes required on the arm to effect release of the bolt. Attempts have been made to overcome this problem by substantially increasing the length of the release arm, but due to the shallow angle of inclination between the release rope and the arm, even with an extended arm length, the effective lever arm may still be insufficient to obtain easy 940727,p:\oper\rs,clutcb3.spe,1

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-2release of the clutch bolt.

According to the present invention there is provided a clutch assembly for releasably connecting a lifting cable to an anchor embedded in a slab or other building component whereby to permit the component to be raised from a generally horizontal position into a generally vertical position, the anchor having a head lying within a recess in a surface of the component, wherein the clutch assembly comprises a body having a portion adapted to lie within the recess, an arcuate bolt movable within the clutch body to releasably lock the clutch to the head of the anchor, an arm attached to the bolt for releasing the bolt, the configuration being such that at the end of a lifting operation when the component is in a generally vertical position, the arm will be directed upwardly o whereby release of the bolt occurs by pivoting the arm outwardly and downwardly, and an extension arm attached to the arm of the bolt for movement between a position in which the extension arm is in general alignment with the bolt arm and a position in which the 15 extension arm is inclined to the bolt arm so as to define with the bolt arm a cranked release arm assembly, an outer end of the extension arm being adapted for attachment to :remote release means, the arrangement being such that when the extension arm is moved into inclined relationship with the bolt arm when the release means is operated to release the clutch bolt the effective lever arm of the force acting between the release means and 20 the clutch bolt is increased.

In a preferred embodiment of the invention the extension arm is pivotally mounted at an inner end to a bracket at a radially outer end of the bolt arm, the bracket including a stop which defines a limit position for the outwards inclination of the extension arm relative to the bolt arm.

The invention also provides an extension arm pivotally attached to a bracket as defined above for attachment to a bolt arm of an existing clutch.

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S96 ,pope ,uthspe,2 '961128,p:\opertrsh,clutch3.Sp,2 r I -3- 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 schematic section showing a clutch assembly in accordance with a first embodiment of the invention, comprising a shackle plate and ring clutch during lifting of a slab; Figure 2 is a view similar to Figure 1 but showing the configuration after the shackle plate has been lowered at the end of lifting and with a clutch bolt about to be 10 released; Figure 3 is a side view of a clutch assembly in accordance with a second embodiment of the invention in the configuration it assumes when the panel is in a vertical position during installation; Figure 4 is an enlarged view showing the clutch assembly of Figure 3 in greater detail; and Figure 5 shows the clutch assembly of Figure 3 when engaged with the panel when horizontal prior to lifting.

eo* 96128,p:\opersh,clutch3.ape,3

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There is shown in the accompanying drawings a clutch assembly for a reinforced concrete slab, comprising 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 engaged within the body of a clutch 6. The clutch 6 comprises an annular body 8 having a central aperture through which passes the loop of the shackle plate 2. An arcuate bolt 12 mounted within an annular channel in the body 8 is movable between a position in which a radial aperture of the body 8 is opened and a position in which the bolt 12 projects through the radial aperture to engage the eye in a head of a lifting anchor 14 located within a recess 16 in the surface of the slab. Operation of the bolt 12 is effected via a radial arm 18 projecting .9 oI 'from the bolt 12. The clutch body 8 includes a nose-like projection 19 which reacts with the slab after release of the bolt 12 to facilitate removal of the clutch 6 from the anchor 14. The clutch 6 and projection 19 are substantially as described in our Australian Patent No. 625004 to which reference may be made.

o:oo": In accordance with the preferred embodiment of the invention, the radial arm 18 of the clutch bolt 12 incorporates a hinged extension arm 20 to which a flexible release member in the form of a rope 22 is attached to enable release of the bolt 12 from the ground. As will be described, after the shackle plate 2 has been lowered, 961128,p:\oper\rh,clutch3.spe,4 I II the hinged extension arm 20 can be swung forwardly so as to define with the radial arm 18 a cranked release arm assembly which enables a significant increase of the effective lever arm between the release rope 22 and the clutch bolt 12. More particularly, the hinged extension arm 20 is pivotally mounted to a support bracket 24 which is attached to the outer end of the radial arm 18, the pivotal attachment being by means of a pivot rod 26 extending between opposed walls of the support bracket 24. The extension arm 20 is pivotal within the bracket 24 between a position as shown in Figure 1 in which the extension arm 20 is substantially in alignment with the radial arm 18 and a forwardly inclined position as shown in Figure 2. The extension arm 20 is releasably retained in its aligned position by means of a springloaded detent catch 28 and the forwards inclination of the extension arm 20 is restricted by engagement of the extension arm 20 with an upper edge 24a of a front wall of the bracket as is clearly shown in Figure 2.

In operation, to release the clutch from the anchor at the end of a lifting operation, the tension in the hoisting cable is reduced in order to allow the shackle plate to swing downwardly into a position beneath the clutch as generally shown in Figure 2. The release rope 22 can then be pulled, to cause the extension arm to *swing outwardly until it engages the upper edge 24a of the front wall of the bracket 20 24 also as shown in Figure 2. It is to be noted that only a relatively small force is necessary to overcome the resistance of the detent catch 28 by which the extension arm 20 was previously held in its aligned position. A pulling force applied to the release rope 22 after the extension arm has engaged the front wall of the bracket 24 will then act through the bracket 24 and radial arm 18 to release the clutch bolt 12.

It will clearly be seen from Figure 2 that the forwards inclination of the extension arm 20 relative to the radial arm 18 increases by many times the effective length of the lever arm between the release rope 22 and the clutch bolt 12 in comparison with that which would be obtained either by attachment of the rope directly to the radial arm 18 or to a rigid extension of the radial arm in the same orientation.

Preferably, and as shown in Figure 2, the configuration of the extension arm is such that when the arm 20 pivots outwardly, the inner end part 20a of the arm 940727p:\oper\rs,clutc3.spe,5 I I -6pivots rearwardly through a rear opening in the bracket 24 into engagement with the face of the slab. The reaction between this end of the arm and of the slab during pulling will further facilitate release of the clutch bolt 12.

In order to eliminate the possibility of self-movement of the clutch bolt 12 and hence inadvertent release of the clutch in a "no-load" situation when the hoisting cable tension has been reduced, friction is deliberately incorporated into the system in order to impede self-rotation of the clutch bolt. The friction between the clutch bolt 12 and clutch body 8 will be dependent on a number of factors such as the surface finish and the closeness of the fit of the clutch bolt 12 within the annular channel. In order to increase the friction, the outer end portion of the clutch bolt may include a stepped enlargement 40 which will cooperate with the eye of the anchor to impede free movement somewhat. Further impediment may be obtained by spring-loaded pawls at the base of the radial arm 18 and in rubbing engagement with the walls of the channel. Although this increased friction increases the force required to release the bolt and thereby prevents inadvertent release, when release is actually required by deliberate pulling of the release rope, the significantly increased lever arm obtained by the inclination of the extension 20 arm enables the increased friction in the system readily to be overcome.

In existing clutches of this type there is a slight risk that in the released S. condition of the clutch bolt 12, the bolt 12 might eject from the clutch body 8 and fall on workmen standing below. In order to avoid this possibility the clutch bolt is formed with a short arcuate extension 42 beyond the radial arm 18 such that, in the released condition of the bolt 12, the extension 42 is positioned radially within the body of the nose-like projection 19 thereby ensuring that the bolt is securely captive within the body even in its released condition.

By appropriate design of the bracket 24, the bracket 24 can be fitted to the clutch bolt arm of existing clutches of this general type to permit conversion to provide the hinged extension arm. In other configurations, the clutch bolt arm may be formed integrally with a suitable bracket to which the extension arm may be 940M,p:\oper\rsbdutc3spe,6 ~I II -7fitted.

In the first embodiment of the invention described above the shackle plate 2 acts to block releasing movement of the release arm assembly consisting of the radial arm 18 and extension arm 20 until the shackle plate 2 has been lowered. However, in certain lifting situations, the shackle plate 2 is not able to be lowered after release of the load. A circumstance such as dhis can arise when the clutch is used with an anchor placed high up in a panel where the configuration of the rigging can cause an upwards force to be exerted on the shackle plate. The situation can also arise when the shackle plate is physically obstructed by contact with reinforcing bars, prop connections or other obstructions.

*i An embodiment of the present invention which overcomes the difficulty discussed above is illustrated in Figures 3 to 5. Apart from the aspects discussed below, the clutch assembly is substantially in accordance with the first embodiment.

The clutch assembly comprises a shackle plate 50 with an opening 52 of a length greater than the length of the release arm assembly 53 so that the shackle plate is not able to block release movement of the release arm assembly even if the shackle o. plate remains in an upright position with a degree of lateral tilt as may occur due to the effect of the rigging. The release arm assembly can therefore always be released through the shackle plate 50. In order to prevent inadvertent release under the self weight of the release arm assembly or under the weight of the release rope, the body of the clutch is provided with a series of detents in which engage spring-loaded balls incorporated in the base of the release arm assembly whereby the locking resistance of the balls within the detents must be overcome by an operator pulling on the release rope in order to draw the release arm assembly forwardly and hence to release the clutch bolt.

With the configuration described above in which the release arm assembly is able to move through the shackle plate without impediment, it is necessary to ensure that the pivoted outer extension arm 53a of the release arm assembly 53 cannot inadvertently pivot forwardly. To prevent this from happening, the inner radial arm 94072,p:\oper\rshclutc3.spe,7 I -8- 53b of the arm assembly which is directly attached to the clutch bolt incorporates a spring-loaded catch 54 (see Figure 4) which engages the inner end of the pivoted extension arm 53a in order to prevent forwards pivoting of the extension arm 53a relative to the inner arm 53b until the catch 54 is released.

Release of the catch 54 is effected by pulling a spring-loaded release member 56 which is formed with an eye 58 to receive one end of a looped cable 60 which passes through the opening 52 in the shackle plate 50 and around the outside of the shackle plate 50 to be connected at its other end to the outer end of the extension arm. A pulley 62 mounted on the looped cable 60 is attached to the release rope 64. In operation, a downwards pulling force on the release rope 64 pulls the looped o...cable 60 to draw the release member 56 outwardly and thereby release the catch 54 and also to draw the extension arm 53a downwardly into a cranked configuration "whereby further movement of the release rope will cause release of the clutch bolt.

This action canu occur in either the raised or lowered position of the shackle plate or any intermediate position.

The body of the clutch is preferably formed with a buttress 70 (Figure 4) which engages the wall of the void above the anchor. When, during the erection of the panel, the panel is being held upright prior to fixing of the props a shear loading will be applied to the shackle plate 50. The interaction between the buttress 70 and ooo o the wall of the void during this time causes the clutch body to move in a direction away from the void until arrested by engagement of the clutch bolt with the outer edge of the eye in the anchor. Accordingly, the presence of the buttress 70 causes the shear loading acting on the shackle plate to be translated into a reaction force between the clutch bolt and the anchor rather than between the clutch body and the anchor whereby accidental release of the bolt cannot occur even at low shackle loading. Release of the clutch bolt can only occur when the loading has been completely removed from the shackle thereby providing a significant safety factor.

This feature can also be incorporated to considerable advantage in clutches of the general type described herein but without the cranked release arm assembly described.

94072,p:\oper\rshclutc3.spe.8 I I- I -9- Preferably, the shackle plate 50 is slightly bent at its inner end portion so that when its inner end portion is resting against the concrete the main body of the shackle plate inclines away from the concrete as illustrated in Figure 5. This feature acts so as a safety indicator when initially connecting the clutch to the anchor when the panel is in a horizontal position resting on the ground. If the clutch bolt is not correctly engaged with the anchor, the clutch body will tend to be raised away from the anchor by the lever action of the inclined shackle plate 50 interacting with the horizontal surface of the panel whereby the main body of the shackle plate will itself lie along the surface of the panel to signify that the proper connection has not been made. The inclined raised position of the shackle plate 50 also facilitates the connection of the slings to the clutch. When the panel is in its upright position the bend in the shackle plate 50 ensures that the shackle plate 50 lies relatively closer to the surface of the panel which is advantageous due to the absence of amplification of the applied load between the clutch and anchor. Finally, when the load is released from the shackle plate 50 and the shackle plate 50 falls below the anchor, the bend in the shackle plate 50 acts as a pivot so that the weight of the shackle plate 50 and sling attached thereto assists in the release of the clutch from the anchor. A bent shackle plate of this general configuration can also be used to advantage with clutches of the general type described but without a cranked release arm assembly.

940727,p:\operrshdutch3spe,9 I I I

Claims (13)

1. A clutch assembly for releasably connecting a lifting cable to an anchor embedded in a slab or other building component whereby to permit the component to be raised from a generally horizontal position into a generally vertical position, the anchor having a head lying within a recess in a surface of the component, wherein the clutch assembly comprises a body having a portion adapted to lie within the recess, an arcuate bolt movable within the clutch body to releasably lock the clutch to the head of the anchor, an arm attached to the bolt for releasing the bolt, the configuration being such that at the end of a lifting operation when the S. component is in a generally vertical position, the arm will be directed upwardly o whereby release of the bolt oc curs by pivoting the arm outwardly and downwardly, and an extension arm attached to the arm of the bolt for movement between a position in which the extension arm is in general alignment with the bolt arm and a position in which the extension arm is inclined to the bolt arm so as to define with the bolt arm a cranked release arm assembly, an outer end of the extension arm being adapted for attachment to remote release means, the arrangement being such that when the extension arm is moved into inclined relationship with the bolt arm when the release means is operated to release the clutch bolt the effective lever arm of the force acting between the release means and the clutch bolt is increased.

2. A clutch assembly according to claim 1, wherein the extension arm is pivotally mounted at an inner end to a bracket at a radially outer end of the bolt arm, the bracket including a stop which defines a limit position for the outwards inclination of the extension arm relative to the bolt arm.

3. A clutch assembly according to claim 1, further comprising releasable catch means for retaining the bolt arm and extension arm in general alignment, said catch means being releasable in response to a pulling force applied by the release means to thereby permit the extension arm to pivot outwardly relative to the bolt arm.

4. A clutch assembly according to claim 3, wherein the catch means is subject 940727,p:\oper\rshcutch3.spe, I I II 11 to a spring bias which maintains the catch means in an engaged condition, said catch means comprising catch having a release member adapted for attachment to the remote release means whereby pulling force applied to the remote release means acts in opposition to the spring bias to release the catch.

A clutch assembly according to claim 3 or claim 4, further comprising a shackle plate, the clutch body being mounted ol the shackle plate and the shackle plate being adapted to be coupled to a lifting cable, the shackle plate having an internal aperture of a size to permit the release arm assembly to move through the aperture from one side of the plate to the other without being blocked by the S: shackle plate when the shackle is in a raised position at the end of a lifting operation.

6. A clutch essembly according to claim 5, wherein the remote release means comprises lexible loop attached at one end to the extension arm and at the other end to the release member of the catch, said loop passing through the aperture in the shackle plate and arc'nd the outside of the shackle plate, and a flexible pullin- member actuable from the ground mounted from the loop via a connection which is able to move along the loop.

7. A clutch assembly according to claim 6, wherein the connection is formed a pulley wheel movable along the loop. 00

8. A clutch assembly according to any one of claims 1 to 7, further comprising spring-loaded locking means for retaining the bolt arm in a locking position to prevent accidental release of the bolt arm, said locking means being releasable in response to release force applied to the arm assembly by deliberate operation of the release means.

9. A clutch assembly according to any one of claims 1 to 8, further comprising abutment means on the clutch body and engageable with the wall of the recess to generate, under lifting conditions, a reaction force between the clutch bolt and 940727,p:\oper\rsh,dutch3.spe,11 1 I 171-Ir -12- anchor.

A clutch assembly according to claim 1, further comprising a shackle plate for attaching the clutch body to a lifting cable.

11. A clutch assembly according to claim 5 or claim 10, wherein the shackle plate is bent into a cranked configuration so that when an inner portion of the plate adjacent the clutch body is resting against the building component, the remainder of the plate inclines away from. the component.

12. An accessory for a clutch assembly for releasably connecting a lifting cable to an anchor embedded in a slab or other building component whereby to permit the component to be raised from a generally horizontal position into a generally vertical position, the anchor having a head lying within a recess in a surface of the component, wherein the clutch assembly comprises a body having a portion adapted to lie within the recess, an arcuate bolt movable within the clutch body to releasably lock the clutch to the head of the anchor, and an arm attached to the bolt for releasing the bolt, the configuration being such that at the end of a lifting operation when the component is in a generally vertical position, the arm will be directed upwardly whereby release of the bolt occurs by pivoting the arm outwardly and downwardly, said accessory comprising an extension arm, and means for :'*.attaching the extension arm to the arm of the bolt for movement between a position in which the extension arm is in general alignment with the bolt arm and a position in which the extension arm is inclined to the bolt arm so as to define with the bolt arm a cranked release arm assembly, an outer end of the extension arm being adapted for attachment to remote release means, the arrangement being such that when the extension arm is moved into inclined relationship with the bolt arm when the release means is operated to release the clutch bolt the effective lever arm of the force acting between the release means and the clutch bolt is increased. 96122,p:\opArsh,cIuth3,ape, 12 13

13. A clutch assembly substantially as hereinbefore described with reference to the accompanying drawings. DATED this 28th day of November, 1996. RAMSET FASTENERS (AUST.) PTY.LTD. By its Patent Attorneys: DAVIES COLLISON CAVE S.. S S S 961128,p \cpetrs,cutchl3spe, 13 4 I ABSTRACT A lifting clutch for use in tilt-up lifting of concrete components in building construction has a release arm assembly connected to a release rope for remote release from the ground. The release arm assembly includes an extension arm which S. can be pivoted into a cranked configuration to increase the effective lever length of the arm to thereby facilitate release of the clutch from an anchor set into the component. 0* o 9407Z7,p:operrsclutch3.spelS r