AU2010227076A1 - A Load Compensating Lifting Hook - Google Patents

Abstract

Abstract A C-hook for lifting heavy coils or rolls of material such as steel coils is provided. The hook includes opposing, spaced upper and lower arms; a lifting arm pivotally connected to the upper arm and providing a lifting point for raising of the hook; and a spring assembly to bias the lifting point away from a balance point for balanced lifting of a load; wherein said spring assembly is arranged to reduce said bias as the lifting point approaches the balance point. Figure 1. 2010227076 11 Oct 2010 Co CCo a>i

Description

AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION A LOAD COMPENSATING LIFTING HOOK The following statement is a full description of the invention including the best mode known to the applicant 1 A LOAD COMPENSATING LIFTING HOOK TECHNICAL FIELD 5 The present invention relates to a load compensating lifting hook. Embodiments of the invention are particularly applicable to situations where heavy rolls of material, for example, must be lifted. BACKGROUND 10 Any references to methods, apparatus or documents of the prior art are not to be taken as constituting any evidence or admission that they formed, or form part of the common general knowledge. 15 Sheets of steel may be supplied in the form of coils or rolls. It will be appreciated that these coils are very heavy and typically require the use of a crane to move them. The approach to handling a coil is generally to pass a lower arm of a C-hook through the coil's lumen. The coil is then lifted by a hook attached to a mobile crane or the like. Other heavy loads of similar 20 shape may be handled in like manner. For example, C-hooks may be used to handle concrete pipes and rolls of paper. It will be realized that the centre or gravity of an unloaded C-hook differs from that of the hook in a loaded state. Consequently, a problem that occurs is that 25 as the loaded C-hook is raised by the crane, the lower arm typically has a tendency to tilt downward toward the mouth of the hook, so that the load may slide off. A number of methods have been adopted over the years to attempt to 30 counteract this problem. For example, it has been known to employ a slideable counterweight to counteract the loading effect of the coil on the centre of balance of the C-hook. Obviously, this entails the mobile crane having to lift a substantially heavier assembly than would otherwise be the 2 case if the slideable counterweight were not employed. Furthermore, if a lighter or heavier coil is lifted then the counterweight must be correspondingly decreased or increased or alternatively slid back or forth along the C-hook. 5 Another possible approach is to translate the point of attachment of the lifting hook to the C-hook prior to lifting the load. However, this approach requires manually moving the point of attachment back and forth each time the weight of the load to be lifted is changed so that it coincides with a balance point for the combined C-hook and load. Manually moving the attachment point is time 10 consuming and may be dangerous. It is an object of the present invention to provide a lifting hook that addresses the above described problem and is an improvement, or at least a useful alternative, to lifting hooks of the prior art. 15 SUMMARY OF THE INVENTION According to a first aspect of the present invention there is provided a hook including: 20 opposing, spaced upper and lower arms; a lifting arm pivotally connected to the upper arm and providing a lifting point for raising of the hook; and a spring assembly to bias the lifting point away from a balance point for balanced lifting of a load; 25 wherein said spring assembly is arranged to reduce said bias as the lifting point approaches the balance point. Preferably the spring assembly comprises a spring and an over-center pivot. 30 Preferably the hook is for handling coils of sheet metal, concrete pipes, rolls of paper and the like. Preferably the upper and lower arms are spaced apart by an inter-arm portion and the elongate spring is disposed along an outside of the inter-arm portion.

3 The elongate spring is preferably mounted proximal to a junction of the lower arm and the inter-arm portion. 5 The elongate spring may be coupled to the lifting arm by an adjustment member for adjusting the bias applied to the lifting arm by said spring. Preferably the lifting arm is pivotally connected toward a free end of the upper arm. 10 In a preferred embodiment the elongate spring is linked to an over-centre pivot that is fast with the lifting arm. The elongate spring may be linked to the over-centre pivot by a linkage 15 including the adjustment member. In the preferred embodiment the lifting arm is bifurcated and includes opposing portions pivotally connected on either side of the upper arm. 20 The bifurcated portions of the lifting arm are preferably interconnected by a lifting shackle. The lifting point preferably falls upon the lifting shackle. 25 BRIEF DESCRIPTION OF THE DRAWINGS Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed 30 Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows: Figure 1 is a first perspective view of a C-hook according to a preferred embodiment of the present invention.

4 Figure 2 is a second perspective view of the C-hook of Figure 1. Figure 3 is a linkage diagram of the C-hook of Figures 1 and 2 showing the disposition of various components of the C-hook in an unloaded state in solid line and in a loaded state in dashed line. 5 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to Figure 1, there is depicted a C-hook according to a preferred embodiment of the present invention in an unloaded state. 10 The C-hook includes a lower arm 1 and an opposing upper arm 3, interconnected by an inter-arm spacer 5. In the preferred embodiment that is shown the lower arm 1, upper arm 3 and inter-arm spacer 5 are all integrally formed of a single piece of steel. 15 A lifting arm 7 is pivotally connected to a free end of upper arm 3 by means of lifting arm pivot pin 9. The lifting arm is bifurcated with opposed portions straddling upper arm 3. Opposite pivot pin 9 the bifurcate portions of the lifting arm 7 are interconnected by a lifting shackle 4 which provides a lifting 20 point for raising the C-hook with a crane. Spaced apart from lifting arm pivot 9, and also fast with the lifting arm 7 is an over-centre pivot 8. Over-centre pivot 8 forms part of a spring assembly is linked to the upper end of leaf spring 13 by a linkage including spring arm 10 and adjustable spacer 19. The over centre-pivot 8, leaf spring 13, spring arm 10 and adjustable spacer 19 25 comprise a spring assembly. It should be realised that a coil spring might instead be used in some alternative embodiments. In that case the coil spring would preferably be located along the upper arm 3. Upon the outside of the C-hook, toward the junction of inter-arm spacer 5 and 30 lower arm 1, there is fastened a spring bracket 11. A biasing means in the form of an elongate spring, namely leaf spring 13, is mounted to the spring bracket 11 so that the leaf spring 13 extends upwardly on the outside of inter arm spacer 5.

5 An upper end of the leaf spring 13 terminates in an eye (not visible) which receives a bush 17. The elongate adjustable spacer 19 terminates in a yoke 15 and is pivotally connected to the bush 17 by means of a pin 14 which is held across the yoke and penetrates the bush. Opposite yoke 15 the 5 adjustable spacer 19 is pivotally connected to the spring arm 10 by pin 16. It will therefore be realised that the lifting arm 7 is pivotally connected to the remote end of upper arm 3 by pivot 9 and also, by over-centre pivot 8 to the upper end of spring 13 by means of the linkage formed by spring arm 10 and adjustable spacer 19. 10 Figure 3 is a linkage diagram corresponding to the C-hook of Figures 1 and 2, wherein components of the C-hook are shown in solid line in the positions that they assume whilst the C-hook is in an unloaded state. The same components are shown in dashed line in the positions that they assume when 15 the C-hook is loaded with a coil of sheet metal 21. In the following explanation the movement of various components will be made with reference to various directions, e.g. "leftward" and "counter clockwise", as they appear when viewing the diagram of Figure 3. It will 20 however be understood that the specific description of operation does not in anyway limit the scope of the invention. It will be noted that in the loaded state, as crane hook 23 is raised, the gravitational force due to coil 21 (and the weight of the C-hook) rotates 25 shackle 4 and lifting arm 7 about pivot pin 9 and also rotates over-centre pivot 8 counter-clockwise about pivot pin 9. As over-centre pivot 8 is rotated counter-clockwise, it pulls on the upper end of leaf spring 13 via the linkage of spring arm 10 and adjustment spacer 19 so that the leaf spring 13 bends as shown. 30 When hook 23 is raised inside coil 21, shackle 4 rotates around pin 9. During shackle 4 rotation from rest position toward vertical, spring 13 force increases but horizontal reaction forces created by spring 13 decrease due to the mechanical disadvantage created as the distance d2 approaches zero.

6 The reduction in mechanical advantage allows for a significantly lighter load coil to be handled as the action of hook 23 moving from a no load position to a loaded position (distance D) ideally should require minimal energy change. 5 It will be realised that as lifting shackle 4 moves leftward, the over-centre pivot 8 has also moved vertically from a distance dl above pivot 9 to a lesser distance d2. Accordingly, it will be understood that the torque applied by spring 13 to lifting arm 7, about pivot pin 9, reduces as the lifting arm assumes a more upright position, which may be advantageous from a safety 10 perspective. In short, the effect of the lifting point on lifting shackle 4 moving leftward is that it compensates for a change in the centre of gravity due to the loading of the C-hook by coil 21 so that C-hook and coil combination remain substantially 15 balanced. It will be realised that if load 11 were lighter, it would exert less gravitational force so that the balancing point of the loaded C-hook would not be moved as far rightward as for a heavier load. Furthermore, with a lighter load, spring 13 20 would be required to deflect less to balance pivoting of arm 7 due to the reduced gravitational force. Consequently the lifting arm 7, and shackle 4 would correspondingly be rotated less about pivot 9 less and the distance "D" through which the shackle attachment point would move would also be reduced. Therefore, it will be realised that a lighter weight will cause the 25 shackle attachment point to move less, which will also coincide with the reduced movement in the balancing point. Consequently, a C-hook according to an embodiment of the present invention provides a degree of automatic load compensation over a range of loads so that the C-hook remains balanced, and substantially horizontal, while being lifted. 30 In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. The term "comprises" and its variations, such as "comprising" and "comprised of' is used throughout in an inclusive sense and not to the exclusion of any 7 additional features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope 5 of the appended claims appropriately interpreted by those skilled in the art.

Claims (12)

1. A hook including: opposing, spaced upper and lower arms; a lifting arm pivotally connected to the upper arm and providing a lifting point for raising of the hook; and a spring assembly to bias the lifting point away from a balance point for balanced lifting of a load; wherein said spring assembly is arranged to reduce said bias as the lifting point approaches the balance point.

2. A hook according to claim 1, wherein the spring assembly comprises a spring and an over-center pivot.

3. A hook according to claim 1, or claim 2 wherein the spring comprises an elongate leaf spring.

4. A hook according to claim 3, wherein the upper and lower arms are spaced apart by an inter-arm portion and wherein the elongate spring is disposed along an outside of the inter-arm portion.

5. A hook according to claim 3, wherein the elongate spring is mounted proximal to a junction of the lower arm and the inter-arm portion.

6. A hook according to any one of claims 3 to 5, wherein the elongate spring is coupled to the lifting arm by an adjustment member for adjusting the bias applied to the lifting arm by said spring.

7. A hook according to claim 6, wherein the lifting arm is pivotally connected toward a free end of the upper arm.

8. A hook according to claim 6, wherein the elongate spring is linked to the over-centre pivot by a linkage including the adjustment member. 9

9. A hook according to claim 8, wherein the lifting arm is bifurcated and includes opposing portions pivotally connected on either side of the upper arm.

10. A hook according to claim 9, wherein bifurcated portions of the lifting arm are interconnected by a lifting shackle.

11. A hook according to claim 10, wherein the lifting point falls upon the lifting shackle.

12. A hook substantially as described herein with reference to the drawings. * * *