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1. WO2009004510 - LIGHTWEIGHT IDLER ROLLER

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

"LIGHTWEIGHT IDLER ROLLER"

BACKGROUND TO THE INVENTION

THIS invention relates to a lightweight idler roller.

A typical idler roller has a central shaft which is supported in use at either end by fixed structures. The shaft itself supports, through appropriate bearings, a hollow cylindrical roll on which a conveyor belt runs. In some instances, the idler roller must have a lightweight construction to limit the weight which workers must pick up and manhandle during installation and maintenance.

In many cases, the central shaft of the idler roller is a solid steel bar. However, in order to reduce the overall weight of the roller it has also been proposed to use a hollow central shaft.

It is an objective of the present invention to provide a lightweight idler roller which has a hollow central shaft and which has a simple and economical design.

SUMMARY OF THE INVENTION

According to the invention there is provided an idler roller comprising:

a central shaft in the form of a hollow, swaged tube with bearing support zones towards either end thereof, the bearing support zones having bearing support surfaces formed by centreless grinding;

a hollow, cyiindrical roll located around the shaft;

bearings which are mounted on the bearing support zones and which support the roll in rotatable manner relative to the shaft;

bearing housings which are carried by the roll and which house the bearings;

bearing seals located on the ends of the shaft outboard of the bearings; and

- end plugs which are press-fitted into the ends of the tube to hold the bearing seals axially in position, the end plugs having portions, extending beyond the ends of the tube, shaped for non-rotatable engagement by idler support structures at either end of the shaft.

To facilitate the centreless grinding of the bearing support zones it is preferred that each end of the shaft includes an end zone which is located outboard of an associated bearing support zone and which is of reduced diameter relative to the associated bearing support zone.

Conveniently, the shaft has a central zone with a relatively large diameter and intermediate zones of reduced diameter relative to the central zone located between the central zone and the bearing support zones, the bearing support zones being of reduced diameter relative to the intermediate zones.

It is also preferred that the bearings are ball bearings.

Typically each bearing housing has an axially extending, cylindrica! portion within which the associated ball bearing is housed and a generally radially extending portion extending towards the associated bearing support zone, axially inwardly of the associated bearing.

The portions of the end plugs which extend beyond the ends of the tube are enlarged relative to portions of the end plugs which are press-fitted into the ends of the tube, the bearing seals being located between the enlarged portions of the end plugs and the bearings. The enlarged portions of the end plugs are formed with diametrically opposed flat surfaces engagable non-rotatably by the idler support structures.

Each bearing seal may comprise a stationary, elastomeric seal element mounted fast on the shaft, outboard of the associated bearing, and a rotating metal seal element extending partially about the associated stationary seal element and engaging the associated bearing housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a cross-sectional view of one end of a lightweight idler roller according to this invention; and

Figure 2 illustrates an end plug used in the idle roller of Figure 1.

-A- DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

Figure 1 shows only one end of a lightweight idler roller 10 according to the invention. The other, non-illustrated end of the roller is identical to that seen in Figure 1.

The roller 10 has a centra! shaft 12 which includes a hollow tube 14 and end plugs 16. The tube 14 is swaged from an initial tube of constant diameter so as to have a central zone 14.1 and, towards each of its ends, an intermediate zone 14.2, a bearing support zone 14.3 and an end zone 14.4, The zones 14.1 to 14.4 are all of round cross-section and are of progressively decreasing diameter.

The bearing support zone 14.3 has an externally bearing support surface which is accurately ground, by centreless grinding, to a diameter selected for the mounting thereon of a ball bearing 17. The swaging of the tube 14 to provide the reduced diameter end zone 14.4 outboard of the bearing support zone 14.3 simplifies the centreless grinding of the bearing support zone.

The roller 10 also includes an outer roll 18 of round cylindrical shape. Bearing housings 20 are fixed by welding 22 to the ends of the roll and extend inwardly as illustrated.

Each bearing housing includes an axially extending, cylindrical portion 20.1 and a radially extending portion 20.2 having an inner edge 20.3 spaced from the associated bearing support zone 14.3. The ball bearings 17 are mounted on the bearing support zones 14.3 inside the cylindrical portions 20.1 as shown.

The roller 10 also includes annular bearing seals 24. Each seal includes a stationary seal element 26 of elastomeric material and an annular, rotating metal seal element 28. The stationary element 26 has a cylindrical portion 26.1 which extends over and is fast with the shaft 14. As illustrated, this portion extends partially over the end zone 14.4 of the tube and partially over the bearing support zone 14.3. An inner edge of the cylindrical portion

26.1 abuts against the associated bearing 17 while the outer edge terminates flush with the end of the tube 14.

The seal elements 28 engage the associated bearing housings and rotate relative to the seal elements 26 in use. It will be understood that the shapes of the seal elements enable them to act in the manner of labyrinth seals to protect the associated bearings 17 against ingress of moisture or particles from the outside.

Each end plug 16 has a shank portion 16.1 and an enlarged head portion

16.2 formed, by a broaching operation, with diametrically opposed flats 16.3. The diameter of the shank portion 16.1 is selected for the shank to be an interference fit in the associated end zone 14.4 of the tube 14 while the diameter of the head 16.2 is slightly greater than the outside diameter of that portion. During assembly the shank portion 16.1 of each end plug is press-fitted into the associated end zone 14.4 such that the head portion 16.2 abuts the end of the tube. The associated seal element 26 is accordingly immobilised axially between the head portion 16.2 and the bearing 17.

In a conveyor system, the projecting ends of the plugs 16, i.e. the head portions 16.2, are engaged by fixed structures at either end of the roller 10 with the flats 16.3 preventing rotation of the shaft.

The illustrated structure has a number of advantages compared to prior idler rollers with hollow shafts. Firstly the use of centreless ground bearing support zones or seats 14.3 means that it is not necessary to hold the hollow tube 14 for accurate rotation about its axis during machining, as would be the case in a conventional turning operation. Together with the provision of the reduced diameter swaged zone 14.4, this enables the bearing seat to be prepared quickly and economically.

Secondly it is relatively simple procedure to press-fit the plugs 16 into position. When compared to conventional arrangements employing end plugs which are screwed into position it is also easier, with a press-fitting operation, to ensure that the flats are at the correct orientation for engagement by the support structures.

Thirdly it is believed that the use of ball bearings as opposed to conventionally used taper bearings will provide for improved shaft alignment over the reasonable lifespan of the roller.