PURPOSE: To improve mills for comminuting, crushing and deagglomerating solids predispersed in liquids so as to be easy washing and repair of a check valve placed in an inlet tube way of products to be comminuted and to be able to avoid accumulation of undesired products around the first tight seal.

CONSTITUTION: An inlet 23 of products to be treated consists of two materials 24 and 25 and the materials have hollow openings to axial direction and longitudinal direction, are screwed in to fix each other and provide a seal means. A ball 26 and an elastic means are provided between these two materials, and form a check valve for materials to be treated by the ball and the elastic means. A first material namely a material apart from mill stator, provides a chamber for the ball and an inner seat for controlling the ball against a ball receiving an action of opposite direction of the elastic means. A second material provides an extending part partly into the chamber and restricts moving of the ball.