Beginners Guide

Anatomy of a troughed conveyor belt idler

The design and manufacture of idler roll assemblies, although not a complicated science is nonetheless a specialised field. Many entrepreneurs have entered this field assuming it to be 'basic' and have failed.

The internal components of idler rolls are essentially the same although variations occur from one manufacturer to another. In addition, the quality of idlers also varies depending on the quality of the individual components and of the manufacturing process.

A typical idler can be seen below together with an indication of the individual components :-

The outer shells (1) of idler rolls are generally manufactured from 89, 102, 108, 114, 127, 138, 152 and 178 mm tubing. The outer shells are generally closed off with an end cap of varying design (2). The end caps are normally designed to house the anti-friction bearings (3) and bearing dust seals (4). The anti-friction bearings support the non-rotating idler shaft (5).

The idler shaft has special machined ends to positively location the idler within the base frame support bracket. An exploded view showing the components and assembly of a Melco type idler can be seen by clicking on this thumbnail.

Description of components :-

1	Plastic Grease Plug--Coloured for grease type and year of manufacture.
2	Weather Seal - Non-rubbing, water and fire resistant.
3 & 5	Outer Seal Components - Multi-labyrinth non-rubbing close rubbing (Press fit seals)
4 & 6	Inner Seal Components.
7 & 11	Circlip - Locates bearing on shaft (one end only), spring steel hardened and tempered.
8	Bearing - Deep groove single row precision ball or spherical roller, single row C3 & C4 clearance.
9 & 10	Rear Seal Assembly--Combination pressed metal/plastic, non-rubbing seal.
12	Identification Slot.
13	Shaft Ground shaft accurately located circlip grooves.
14	Shell and end, deep drawn steel pressing and concentric bearing housing bored with .001 inch tolerance.
15	Corner Radius - Generous radius on corner of roller, essential to protect belt.
16	Rigid Shell- Small runout.
17	Breather hole.

In addition to the idler roll itself, an idler set is supported in position by an idler bracket or base frame. These bases and brackets locate the individual idler rolls relative to each other and provide the necessary 'trough' angle.

Examples of standard idler support frames and brackets are provided, courtesy of Melco, which can be viewed by clicking on the applicable thumbnails :-

The idler brackets and bases incorporate slotted holes which coincide with the machined broaching on the ends of the roll's shafts. This facility enables worn or damaged rolls to be replaced relatively simply by sliding the rolls out of / into the bracket. No retainer / keep plates are necessary.