a combination web cover and suction chamber define a crush roll plenum which communicates with and extends forwardly from the doffer plenum of a suction cleaning system for carding machines . it includes a suction opening closely spaced from the top crush roll and its scraper blade to continuously pick up accumulations of lint taken from the crush roll by the scraper blade . intermittent blasts of compressed air are directed toward the scraper blade to purge it of accumulations of foreign matter which is blown into the continuous suction current .