GB2203816A - Improvements in load-bearing members - Google Patents

Abstract

A load-bearing member comprising a central core and spaced therefrom a circular rim having provision for receiving a handling medium such as wire, rope or chain, the rim being spaced from the core by means of a pair of opposed side plates, the side plates being secured to or near the core and the rim at least partially sandwiched therebetween, the rim being so positioned as to be capable of deflection under load relative to the core. To accommodate load a resilient bush (9, 10) is employed between rim and bush being either a simple annular resilient e.g. rubber member or a more complex layered structure comprising alternative metal rings and resilient material.

Description

Improvements in load-bearing members This invention is concerned with improvements in load-bearing members. It is more particularly concerned with forms of loadbearing members as used in handling systems for people and/or objects. Suitable forms of load-bearing members to which the invention relates include sheave wheels used for, e.g. wire ropes, and chains.

In many fields of activity there is a need to move people and/ or objects from one position to another and much conventional equipment is concerned with lifting loads by systems employing weightbearing pulleys or similar structures. Conventional lifting equipment has largely been based on a simple mechanical handling device, the winch. Handling systems employ winches to apply a pulling or lifting force to a rope or chain and examples thereof can be found in cranes, hoists, lifts and conveyors. In any lifting system it is necessary to consider the control of direction and speed to movement of material or personnel.

Handling systems based on the winch require consideration of the end detail for stiffness. The term "stiffness" is used in this specification as defining the relationship between force and deflection. The stiffer a system is, the more severe will be the shock loadings under any given situation. Consequently, the fatigue life of the system is determined. If the stiffness can be reduced an increase in service life may be achieved or, alternatively, the load rating may be increased without affecting the service life.

The present invention is concerned with the technical problem of modifying the stiffness or resilience of a load-bearing member which may be useful throughout the field of handling equipment.

According to this invention there is provided a load-bearing member comprising a central core and spaced therefrom a circular rim having provision for receiving a handling medium such as wire, rope or chain, the rim being spaced from the core by means of a pair of opposed side plates, the side plates being secured to or near the core and the rim at least partially sandwiched therebetween, the rim being so positioned as to be capable of deflection under load relative to the core, there further preferably being a resilient member between core and rim for absorbing loading.

In order that the invention may be illustrated and readily carried into effect, an embodiment thereof will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a view in part section and part elevation of a load-bearing member, Figure 2 is a section on the line Y-Y of Figure 1, Figure 3 is a view corresponding to Figure 1 in which the wire or rope is under load, Figure 4 is a corresponding view of Figure 2 also under load, and Figure 5 is an exploded diagrammatic view showing assembly or dismantling of the components.

It is to be understood that the following description includes reference to both essential features and to preferred features of the invention.

Figures 1 and 2 broadly illustrate various sections through one proposed load-bearing member in the form of a resilient sheave.

Figures 3 and 4 are corresponding views in which the loadbearing member is shown under load with the rim consequently deflected under load. In general, it will be seen that the rim is provided with an appropriate groove to receive a rope, and said rim is separated from the core by means of a bush. One form of bush that may be suitable comprises a solid rubber annular member, preferably constructed of a resilient material and sandwiched between the side plates. When the sheave is loaded the rim is deflected relative to the core and the side plates prevent the rim from tilting and can be sized to limit the total amount of deflection.

As shown in the drawings, the preferred form of bush 2 comprises a bonded assembly of metal rings adjacent resilient rubber material 9 provided with side depressions 11. The metal rings are arranged concentrically (under no load) and may be adhered to each succeeding resilient rubber ring. The form of bush may be varied depending upon the particular application and upon the stiffness and deflection required. The resilience of this bush may be determined by the hardness of material used and the number of sandwiched steel rings 10 comprised in the laminate. The depressed side regions of the resilient members 9 are provided to accommodate displacement of material under compression preferably without such displaced material coming into contact with the side plates.This could cause unnecessary friction or sticking and the depressions therefore can promote attractive load-depression and release characteristics.

The rim 3 comprises a separate component and therefore this may be subjected to repair and maintenance techniques as required. The outer periphery of the rim is grooved and this can be re-machined as required to suit the same or different size rope. The rim can be of a different material from the remainder of the sheave, for example, plastics, to reduce weight or noise. If a metal rim is employed then a low friction insert or coating, possibly of PTFE or similar low friction material, may be used. The said low friction coating or insert may be deployed to bear against the side plates.

The core comprises a substantially annular member having a cylindrical central aperture for mounting the load-bearing member and two or more bores for receiving retaining bolts 6. It is generally advantageous to have sufficient flexibility in a handling system to accommodate a large diameter shaft through the loadbearing member to reduce the through-length of its bearing. This can permit several sheaves to be mounted close together.

Suitable resilience may be built into the load-bearing member by adapting the type, size and properties of the components, particularly the resilient bush.

The load-bearing member includes a pair of opposed largely circular side plates 5. These are used to transmit any side loadings on the sheave caused by the off lead angle of a wire rope. They also serve to limit deflection by bearing on the rim shoulders at full load deflection (see Figures 3 and 4).

The arrangement illustrated is of modular construction and thus a degree of flexibility is provided to designers of handling systems which can permit rapid change of, e.g. system wire size.

The stiffness of the load-bearing member may be altered by appropriate substitution of bush elements. The core and bearing can remain or be replaced on the shaft when rims are changed, helping to reduce bearing, fitting and "running in" problems. By use of an apparatus shown in the Figures, failure of the resilient function will not cause consequent sheave failure. Therefore, a handling system using the present load-bearing member will not be disabled to the extent that loads will be left ',hanging1, should the resilient bush itself fail.

The invention includes within its scope a handling system embodying one or more load-bearing members as defined above. The handling system may, therefore, comprise only one sheave according to the invention or any number of sheaves in a system could be constructed in accordance with the present load-bearing member.

This may lead to stiffness reductions of the order required for handling equipment, be they on moving or fixed foundations.

The present invention thus provides a resilient connection between the load and its handling system and therefore isolates all of the handling system from shock loading. Load-bearing members constructed according to the invention may provide rapid installation in new or existing handling systems. Such loadbearing members may not interfere with total "hook" travel and in many instances the load-bearing member may be sufficiently close to the "hook" to confer good shock load isolation for the entire system back to the appropriate winch. Referring to Figure 5 of the drawings, the apparatus includes wear rings to fit between side plates 5 and rim 3, the wear rings being referenced 4. The components are located together by means of bolts 6, washers 7 and lock nuts 8. The modular construction may permit rapid assembly and disassembly of components for, e.g. replacing the bush with another bush of different resilience.

Claims (1)

1. (1) A load-bearing member comprising a central core and spaced therefrom a circular rim having provision for receiving a handling medium such as wire, rope or chain, the rim being spaced from the core by means of a pair of opposed side plates, the side plates being secured to or near the core and the rim at least partially sandwiched therebetween, the rim being so positioned as to be capable of deflection under load relative to the core.

   (2) A member as claimed in claim 1 in which a resilient load-absorbing member is provided between the core and the rim.

   (3) A member as claimed in claim 1 or 2 in the form of a sheave wheel.

   (4) A member as claimed in claim 2 or 3 in which said load-absorbing member comprises a deformable bush sandwiched between said side plates.

   (5) A member as claimed in claim 4 in which the bush comprises a solid rubber annular member.

   (6) A member as claimed in claim 4 in which the bush comprises a concentrically layered member.

   (7) A member as claimed in claim 6 in which the layers comprise alternative metal rings and resilient material.

   (8) A member as claimed in claim 6 or 7 in which the layers are bonded and/or the resilient material has side depressions.

   (9) A member as claimed in any preceding claim in which the rim is a separate, repairable or replaceable component.

   (10) A member as claimed in any preceding claim in which the rim has a low friction insert or coating adapted, in use, to bear against the side plates.

   (11) A member as claimed in any preceding claim in which a rim part abuts or can abut the periphery of both side plates1 a further rim part serving to space apart the side plates.

   (12) A member as claimed in any preceding claim further including wear ring(s) between side plate(s) and the rim.

   (13) A load bearing member as claimed in claim 1 substantially as herein described.

   (14) A load bearing member substantially as illustrated in any one of Figures 1 to 5 of the accompanying drawing.

   (15) A load handling system including a load bearing member as claimed in any preceding claim.