| 摘要 |
<p>A Roots pump rotates a plurality of rotors (23-32) by a pair of rotary shafts (19, 20) to draw gas. Each rotary shaft (19, 20) extends through a rear housing member (14) of the Roots pump. An annular shaft seal (49, 50, 49A, 49B, 50B) is fitted around each rotary shaft (19, 20) and is received in a recess (47, 48, 71) formed in the rear housing member (14). A labyrinth seal (57, 58, 72) is located between an end surface of each shaft seal (49, 50, 49A, 49B, 50B) and the bottom of the associated recess (47, 48, 71). This enlarges the diameter of each labyrinth seal (57, 78, 72), thus preferably preventing oil from leaking to a pump chamber (39-43). <IMAGE> <IMAGE> <IMAGE></p> |
