Top Roller Weighting and Cots
topic
Top rollers are spring-loaded or pneumatically weighted against bottom steel rollers at pressures of 100–200 N per roller. Top roller coverings (cots) are made of synthetic rubber with hardness Shore A 60–85; front cots are harder (75–85) for positive grip, middle and back cots softer (60–70) for apron compatibility. Cot diameter is 28–32 mm. Cot buffing (periodic grinding) restores surface geometry after wear.
Role
Top roller weighting and cot condition directly determine fibre grip pressure at each nip. Worn or hardened cots cause fibre slippage, increasing yarn hairiness and strength variation. Systematic cot maintenance programmes reduce yarn defects by 15–25% and are a key quality intervention in industrial ring spinning.