Abstract: A sheet material processing apparatus comprises at least one treatment cell in which a pair of rotatable path-defining rollers (28, 30) define a sheet material path (20) through the cell. The path-defining rollers have a closed position in which the path-defining rollers are biased into contact with each other to form a nip (36) through which the seat material path extends, and an open position in which the path-defining rollers are spaced from each other. The path-defining rollers can be separated from one another, for the purpose of cleaning the apparatus, by a simple and convenient construction in which the rollers (28, 30) are supported by bearings (70, 72) carried by eccentric sleeves (68) which are stationary in the closed position. Means (76) are provided for partly rotating the sleeves (68) thereby to withdraw the path-defining rollers (28, 30) from each other into the open position.