| 摘要 |
In a Roots blower having a casing, two rotors rotatably housed within the casing, and at least two grease-enclosing bearing units to rotatably support the rotors, characterized in that a bypass groove is formed for each of the bearing unit so as to communicate between a first chamber defined by the casing and the rotors on the side of one axial end of the bearing unit and a second chamber formed by the casing and the bearing unit on the other axial side of the bearing unit, and in that a pair of pressure loaded seal rings (or lip seals) is disposed on axially opposite sides of the bearing unit in such a way that one periphery of each seat ring is secured to a stationary portion of the bearing unit and the other periphery thereof is free to move selectively into or out of contact with a movable portion of the bearing unit according to the presence or absence of a pressure difference produced by a delay in a pressure-balancing action of the bypass groove between the two chambers so that the seal ring prevents bearing grease from leaking. The seal ring is of a U- or L-shape.
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