The two rotors divide the interior into several little room, and operate according to sequence of a - b - c - d . When turn to "a", only Ⅰroom is full of material; when to "b", B room closes some material; when turn to "c", A room closes some material too; when to "d", room A and B connect with Ⅱ room, then material is sent to the outlet. The material is sent out continuously by this way.