Distributed Line Load-bearing Connector

Field of Invention

[0001] The present invention relates to a distributed line load-bearing connection between sheave blocks of a crane and apayload.

Background

[0002] A payload of a crane is often connected to a hook by means of slings and/or a spreader beam. In addition, if the load is very heavy, a lifting capacity of a rope is increased by passing the rope through a set of sheaves; the lifting capacity is then determined by a safe working load of the rope multiplied by the number of rope falls in the sheave block. FIG. IA illustrates a conventional hauling of a load L with a hook 10 and a pair of slings 20; FIG. IB illustrates a conventional hauling of a load L with the use of slings 20, shackles 30 and pad-eyes 40.

[0003] As can be seen in the above illustrations, holding a load by a rope is achieved by slinging the rope under the load or connecting an end of the rope to a pad-eye 40 on the load L. It is not always possible to sling a rope under a heavy structural load. However, holding a heavy structural load by two or more pad-eyes creates concentrated stresses and strains at each pad-eye in addition to induced stresses and strains on the load itself. Further, such pad-eyes require reinforcement not only on the pad-eyes but also on the structural members connected thereto. These pad-eyes are often positioned in awkward positions and are not removed after installation of the structural load.

[0004] Attempts have been made to distribute the stresses and strains on a suspended load. JP8053294 describes a hanging device for a heavy article. The hanging device has a plurality of jointed elongate members. Each of the jointed ends and free ends of the hanging device are connected to a rope of a hoist. In addition, each of the elongate members is connected to the heavy article by another rope near each end of the elongate member such that the plurality of jointed elongate members is loaded in a

distributed manner. The hanging device also results in uniform loading on the plurality of hoists.

[0005] US 4,046,414 describes a load distribution device for lifting and moving an elongate truss structure. The load distribution device prevents localized over-stressing or buckling of the truss members.

[0006] Often a fabricated structure is large and heavy; lifting such a large and heavy structure to a height is dangerous. The danger is compounded by having to use multiple hoists, wherein the pay out speeds and lengths of ropes from independent hoists are not identical; synchronization becomes a challenge. Needless to say, safety in hoisting or lowering a large structure with multiple independent hoists is very important.

[0007] It can thus be seen that there exists a need for a method of suspending a heavy load so that the loading points have distributed loading.

Summary

[0008] The following presents a simplified summary to provide a basic understanding of the present invention. This summary is not an extensive overview of the invention, and is not intended to identify key features of the invention. Rather, it is to present some of the inventive concepts of this invention in a generalised form as a prelude to the detailed description that is to follow.

[0009] In one embodiment, the present invention provides a distributed load-bearing connector. The connector comprises: an elongate load-bearing beam; and an elongate jaw operable to engage slidably with the elongate load bearing beam such that the weight of a load is transferred evenly between the elongate load bearing beam and the elongate jaw when the load is suspended by the load bearing connector on a hoist line.

[0010] In one embodiment of the load, the load comprises a structure having one or more bulkheads. In one embodiment of the connector, the elongate load-bearing beam

is connected to an extension of the or each respective bulkheads whilst the elongate jaw is connected to a tongue plate. An opening of the elongate jaw is larger than the thickness of the bulkhead extension so that the elongate load-bearing beam and elongate jaw are operable to slidably engage with each other.

[0011] In another embodiment of the connector, the elongate jaw is connected to an extension of the or each respective bulkheads whilst the elongate load-bearing beam is connected to a tongue plate. An opening of the elongate jaw is larger than a thickness of the tongue plate so that the elongate load-bearing beam and elongate jaw are operable to slidably engage with each other. In another embodiment, one or more stiffeners are provided between the elongate jaw and the tongue plates.

[0012] In both embodiments of the connectors, a sectional shape of the load-bearing beam is proportional to a shape of an internal cavity of the elongate jaw for slidable engagement with each other.

[0013] In another embodiment, the present invention provides a system for holding a load on a hoist line, wherein the load is made up of a structure comprising one or more bulkheads. The system comprises a load bearing connector according to claim 1 or any one of claims 3-21.

[0014] In another embodiment of the present invention, the hoist line is a rope or a chain.

Brief Description of the Drawings

[0015] This invention will be described by way of non-limiting embodiments of the present invention, with reference to the accompanying drawings, in which:

[0016] FIG. IA illustrates a conventional hoisting system using slings; and FIG. IB illustrates another conventional hoisting system using a spreader beam and slings;

[0017] FIG. 2A illustrates a hoisting system using line load in accordance with one embodiment of the present invention; and

FIG. 2B illustrates a sheave block and a line load bearing beam shown in FIG. 2A; and

[0018] FIGs. 3A-3D illustrate various cross-sectional shapes of the line load bearing beam shown in FIG. 2B.

Detailed Description

[0019] One or more specific and alternative embodiments of the present invention will now be described with reference to the attached drawings. It shall be apparent to one skilled in the art, however, that this invention may be practised without such specific details. Some of the details may not be described at length so as not to obscure the invention. For ease of reference, common reference numerals or series of numerals will be used throughout the figures when referring to the same or similar features common to the figures.

[0020] FIG. 2 A shows a distributed load hoisting system 100 according to an embodiment of the present invention. As shown in FIG. 2A, the load L is illustrated by a large fabricated structure 110. The fabricated structure 110 may be a pontoon of an oil rig platform or semi-submersible vessel; a storage tank; a bulk carrier; and so on, or a sub-module of any one of these. Such structures 110 are fabricated with structural bulkheads and relatively thin membrane plates. As shown in FIG. 2A ₅ the distributed load hoisting system 100 is made up of a load bearing beam 120 connected to an extension of a bulkhead 130 of the fabricated structure 110 and a connector 140 for engaging with the load bearing beam 120.

[0021] FIG. 2B shows details of the connector 140 according to another embodiment of the present invention. As shown in FIG. 2B, the connector 140 has two cheek plates 142 and two tongue plates 170. Each cheek plate 142 is symmetrically triangular in shape. As seen in FIG. 2B, each cheek plate 142 has an upper bore hole 144 near its apex and a slightly smaller bore hole 146 near each of the two corners at its base such

that the lower bore holes 146 are symmetrically located with respect to the upper bore hole 144. Each tongue plate 170 is also symmetrically triangular in shape and has a bore hole near its apex. The two cheek plates 142 are assembled by bolts 160 and spacers such that they are substantially parallel to but spaced apart from each other; the bore holes on the tongue plate 170 are aligned with the respective lower bore holes 146 on the cheek plates 142 to define two substantially parallel axes Oa, Ob whilst the upper bore holes 144 on the cheek plates 142 define a third axis Oc, which is substantially parallel to the other two axes Oa, Ob. As seen in FIG. 2B, the base edge of each tongue plate 170 has two open jaw-like bars 182 connected thereto such that the longitudinal axes of the jaw-like bars 182 are aligned with each and lie in the centre plane of the tongue plate 170. To add strength to the connection between the jaw-like bars 182 and the respective tongue plates 170, stiffeners 186 are formed near each end of the jaw-like bar 182. In addition, each bore hole 144, 146 on the cheek and tongue plates has optionally a reinforcing ring 148. The reinforcing ring 148 helps to reduce the stresses and strains around the bore holes. As shown in FIG. 2B, a sheave 150 is disposed between the cheek plates 142 on the axis Oc.

[0022] The jaw-like bars 182 are slidably connected to the load bearing beam 120 so that the load 2T on each sheave 150 is distributed over the load beam 120 through the jaw-like bars 182 when the fabricated structure 110 is suspended on a crane, for example, during fabrication or assembly. The opening 184 of the jaw-like bar 182 is slightly larger than the thickness of the extended bulkhead 130, whilst each jaw-like bar 182 of the connector 140 is formed with a hollow shape proportional to the sectional shape of the load bearing beam 120.

[0023] In use, each connector 140 is disposed pivotably about the sheave 150. Due to the symmetrical design of each cheek and tongue plates, the load 2T on each connector 140 is shared evenly between the two tongue plates 170 so that the load 2T is distributed evenly through the jaw-like bars or jaws 182 to the load bearing bar 120.

[0024] FIG. 3A shows a round hollow cross-section of the load bearing beam 120 according to one embodiment of the present invention. The thickness of the load beam 120 and the bulk head 130 extension are selected so that the designed strains and

stresses comply with the relevant regulatory body or code of practice. For example, when the load bearing beam 120 is about 10 cm in diameter and the bulkhead thickness is 15 mm, the allowed tensile stress on the bulkhead is about lOOMPa for a line load of about 150 tonnes/m. In one embodiment, the bulkhead 130 extends out of the fabricated structure by about 40 cm or less. In practice, the fabricated structure 110 is hoisted or held in a substantially horizontal attitude with the jaws 182 of the connector gripping on the load bearing beam 120 such that there is little bending stress on the bulkhead 130, which is kept at such a relatively low extension. The extension height is also not too high for a workman to surmount, for example, when the load bearing beam 120 is laid across a deck of an oil rig. With the load bearing beam 120 and jaw-like bars 182 of the present invention, the weight of the structure 110 is transferred onto the bulkhead(s) 130 when the structure 110 is suspended by the connectors 140.

[0025] Other section shapes of the load bearing beam 120 are also suitable. For example, FIG. 3B shows a square sectional load beam; FIG. 3 C shows a load beam 120 being made up of a composite of two square load beams, one on each of the two sides of the extended bulkhead 130. FIG. 3D shows a rectangular sectional load beam forming a T joint with the extended bulkhead 130.

[0026] When the load L is expansive, two or more load bearing beams 120 are provided on the respective extended bulkheads 130. In addition, the loads on different sheaves or groups of sheaves 150 may be different and the line load in the respective sections of the respective load bearing beam 120 may also vary.

[0027] Referring again to FIGs. 2A and 2B, two jaw-like bars 182 are shown on each tongue plate 170. In another embodiment, each tongue plate 170 has one jaw-like bar 182. In yet another embodiment, each tongue plate 170 has three or more jaw-like bars 182.

[0028] In FIGs. 2 A and 2B, each connector 140 is shown with a set of triangular cheek plates 142 and tongue plates 170, each having three bore holes. It is possible that each connector has an additional symmetrically triangle plate, which is similar to the cheek plates 142, such that a sheave is connected to a bore hole near the apex of the additional

triangular plate and each bore hole near the base of the additional triangular plate is connected to the bore hole 144 of the cheek plate 142. In other words, the additional symmetrically triangle plates are connected in series between the tongue plates 170 and the cheek plates 142. In another embodiment of the connector 140, the sheave 150 comprises two or more sheaves. In yet another embodiment of the connector 140, adjacent connectors 140 are pivotably connected by a link bar 190; the link bars 190 help to maintain uniform spacing of the jaws 182 to give uniform stresses and strains on the load bearing beam 120.

[0029] In the above figures, the jaws 182 are connected to the respective tongue plates 170 in addition to the stiffeners 186 by fabrication. In another embodiment, the tongue plates 170 and the respective jaws 182 are cast out integrally and machined. In yet another embodiment, the tongue plates 170 and respective jaws 182 are cast out integrally, forged and machined.

[0030] While specific embodiments have been described and illustrated, it is understood that many changes, modifications, variations and combinations thereof could be made to the present invention without departing from the scope of the invention; for example, the jaw-like bar or jaw 182 may be on the bulkhead 130 extension of the load 110 whilst the load bearing bar 120 may be on the tongue plate 170; in addition, stiffeners may be provided between the jaw bar 182 and the bulkhead 130 extension. Alternatively, each tongue plate 170 is connected to the hoist rope directly through a shackle or thimble or indirectly through two or more sheaves. Alternatively, the tongue plate 170 is made up of two plates. It is also possible that the hoist line is a chain, and a chain block is used instead of a sheave block. Further, the hoists on the crane may be disposed on one girdle or more than one girdles.