Device for removing impurities separated from fibers in open end spinning unit

An open-end spinning machine has a succession of spinning units mounted on the frame thereof for pivotal movement between operative and inoperative positions, each spinning unit including a silver opening section, which contains therein a combing-out zone and a doffing zone. The silver opening section is associated with an impurity collecting chamber having an impurity inlet port arranged to be in communication with a fiber path between the combing-out zone and the doffing zone, and an impurity outlet port, through which the impurities are discharged from the collecting chamber. The outlet port has an open end opening into the atmosphere, and an impurity transfer pipe connected at one end to a source of vacuum is arranged so that the other end thereof faces the open end of the outlet port in spaced relation thereto. In order to restrict the amount of air flowing through the spacing between the open end of the outlet port and the other end of the transfer pipe, a restricting flange is attached to the other end of the transfer pipe.