LABYRINTH SEAL DEVICE FOR CENTRIFUGAL TYPE IMPELLER

PURPOSE:To prevent the contact of a labyrinth seal section which is used for a centrifugal impeller in a fluid machine such as, for example, blowers, compressors, etc., due to vibration of a rotor shaft, by making the labyrinth seal section movable automatically in association with the discharge pressure so that the gap of the labyrinth seal section is made large upon starting. CONSTITUTION:A labyrinth seal 18 having a surface 18a which is opposed to a surface 12 of a side plate 12 of an impeller 11 perpendicular to a rotor shaft 13 and is formed therein with sealing teeth, is formed in its intermediate section with a recess part 18b, and comprises a spring 21 disposed between itself and a projecting section 10a of a casing 10. On the side opposite to the surface 18a of the labyrinth seal 18 there is provided a pressure chamber 16 into which the discharge pressure in a scroll 15 is effected. Since the discharge pressure is low upon starting, the labyrinth seal 18 is moved by the spring 21 in the direction in which the gap of the labyrinth seal 18 increases. However, since the discharge pressure becomes high upon steady state operation, the labyrinth seal moves overcoming the spring 21 in the direction in which the gap decreases.