It is well known to transport loads using a chain. A conventional chain of this kind is shown in figures 1 and 2. It comprises a plurality of interconnected chain links, one only of which is shown in figures 1 and 2. Each link comprises opposed link plates interconnected on opposite sides of the chain by means of a pin that passes through aligned apertures on each side. The pin is used, as is well known, to interconnect adjacent chain links.

The pin projects laterally beyond the link plate and supports a rotary roller that is held in place on the pin by means of a nut, circlip (not shown) or the like. In use, the roller rests on a rail or guide track (not shown) and rotates about the pin as the chain travels longitudinally. The material being transported is carried on top of the chain the corresponding load is transferred from the chain through the roller to the rail.

In such designs the life of the chain is limited by the performance of the bearing surface (represented in figure 1 by reference letter A) defined between the outside surface of the pin and the inside surface of the roller. The bearing performance (and therefore life of the chain) can be improved by using different materials or roller constructions (such as, for example, roller bearings) but the chain life is still limited.

It is an object of the present invention to obviate or mitigate the aforesaid disadvantages.

According to the present invention there is provided a chain comprising a plurality of interconnected link assemblies, at least one link assembly having a pin extending transverse to the length of the chain and a rotary roller outboard of the link assembly, wherein there is provided a bearing member that, in use, engages at least part of a circumference of the rotary roller.

The bearing member thus provides a bearing surface at the outer circumference of the rotary roller and is thus greater in area than in prior art designs.

The bearing member may be fixed to a link plate of the link assembly or, alternatively may be supported on a carrier that is captively engaged on the pin. The bearing member may comprise a plurality of bearing elements each providing a bearing surface spaced circumferentially around the roller or, alternatively may provide an arcuate bearing surface that extends around a significant part of the circumference of the roller.

The bearing member may be supported on a carrier with the roller being captively retained by the carrier. Lugs may be provided to enable retention, the lugs being flexible to allow insertion of the roller in the carrier.

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic sectioned view of a transport chain link of the prior art; Figure 2 is a side view of the chain of figure 1; Figure 3 is a side view of a chain link of the present invention incorporating two bearing elements; Figure 4 is a sectioned view of an alternative embodiment of the chain of the present invention with a bearing cage; Figure 5 is a side view of the chain of figure 4; Figure 6 is a sectioned view of a further alternative embodiment of the present invention; and Figure 7 is a side view of the chain of figure 6.

Referring now to the drawings, figure 3 shows part of a single chain link assembly that is identical to that shown in figures 1 and 2 comprising opposed link plates 1 (one hidden) interconnected by a laterally extending pin 2. A plurality of such chain link assemblies are interconnected to form the full chain.

A roller 3 is rotatably mounted on the pin 2 outboard of the link assembly.

The additional and inventive feature of this design is that two arcuate bearing elements 4 are disposed about the outer circumference of the roller 3. The elements 4 are fixed to the chain link plate 1 and have bearing surfaces B that, in use, bear against the outer circumference of the roller 3. The bearing elements 4 not only serve to improve the bearing performance by increasing the available bearing surface area but also serve as scrapers to clean the outer surface of the roller which can become contaminated in certain environments.

Figures 4 and 5 show a modified embodiment of the present invention in which parts corresponding to those of figure 3 have the same reference number but increased by 10. The bearing elements 14 are formed integrally on a cage 16 that is mounted on the pin 12 between the chain link assembly and the roller 13. The cage 16 is fixed to the pin 12 by means of a force fit or otherwise to prevent it rotating relative to the pin 12.

A further modified embodiment is shown in figures 6 and 7, in which the roller 23 is annular and is retained by a cage 26 having four circumferentially spaced bearing elements 24 each with radially inward projecting lugs 27.

In order to assemble the chain, the bearing elements 24 and lugs 27 are flexible to permit the roller 23 to be pushed axially under the elements 24 into a pocket 28 defined between the chain link plate 21 and the bearing elements 24. Once in the pocket 28 the roller 23 is retained there by means of the lugs 27 which may be supplemented by a retaining cover (not shown) that fits snugly over the lugs 27.

In each of the embodiments described above the length of the bearing elements is selected to provide the required bearing surface area. The bearing surfaces can be arranged as required to coincide with the calculated areas of highest load.

It will be appreciated that numerous modifications to the above described design may be made without departing from the scope of the invention as defined in the appended claims. For example, in an alternative embodiment (not shown) the bearing element is in the form of a continuous arcuate surface that is coaxial with the outer circumferential surface of the roller and is broken at one point to allow the roller to make contact with the rail. Furthermore, the bearing elements may be fitted with interchangeable bearing pads which define the bearing surface.