Full definition
A structural assembly consisting of a frame (bracket) and one or more idler rollers that support the conveyor belt along its length. Configurations: (1) Flat — single horizontal idler, for return strand or flat-belt carrying. (2) Troughing — three idlers (one center horizontal + two side idlers at 20°, 35°, or 45° angle) forming a trough that increases belt carrying capacity and centers the load. (3) Impact — rubber-ringed idlers in the loading zone to absorb material drop impact. (4) Transition — variable angle, between troughed and flat at drum approaches. (5) Training/self-aligning — pivoting frame that corrects belt wander. Idler spacing: carrying side 0.8-1.5 m (closer for heavy loads), return side 2-3 m. CEMA idler classes: B (light), C (medium), D (heavy), E (extra heavy) — defined by load rating and bearing life (L10 > 30,000-60,000 hours). Per CEMA 7th Edition and DIN 22112. Brands: Rulmeca, Precision Castparts, Superior, Martin, Continental.