Abstract: A vacuum pump (10) includes a pump casing (56) having an inlet port (54a), an outlet port (54b), and pump chambers (50a-50f) defined therein, rotational shafts 60 having opposite ends rotatably supported by bearings (84a, 84b) on the pump casing (56) and extending longitudinally in the pump casing (56), and rotors (62a-62f) housed in the pump chambers (50a-50f) and coupled to the rotational shafts (60) for rotation in unison with the rotational shafts (60). The pump casing (56) has an atmosphere-vented compartment (52) defined therein which is held in fluid communication with the outlet port (54b) of the pump casing (56) and vented to the atmosphere.

Abstract: A vacuum pump (10) has a pump casing (54) including pump chambers (50a-50f) held in fluid communication with each other and arrayed in a longitudinal direction thereof, an inlet port (52a) and an outlet port (52b), a rotational shaft (58) rotatably supported at opposite ends thereof and extending in the longitudinal direction of the pump casing (54), and rotors (60a-60f) housed in the pump chambers (50a-50f) and coupled to the rotational shaft (58). The pump casing (54) includes a first thermally conductive member (72) extending parallel to the rotational shafts (58) substantially the full length of the pump casing (54) in the longitudinal direction thereof, and a second thermally conductive member (74) positioned near an end of the first thermally conductive member (72) at the outlet port (52b) and extending in a transverse direction of the pump casing (54).