Vacuum pump

A vacuum pump comprising:

• a pump casing including a plurality of pump chambers held in fluid communication with each other and arrayed in a longitudinal direction thereof, an inlet port held in fluid communication with one of the pump chambers which is positioned on a suction side, and an outlet port held in fluid communication with one of the pump chambers which is positioned on a discharge side;
• a rotational shaft rotatably supported at opposite ends thereof by bearings and extending in the longitudinal direction of the pump casing;
• and
• a plurality of rotors housed in the pump chambers and coupled to the rotational shaft for rotation in unison with the rotational shaft;
• wherein the pump casing includes:
• an intermediate chamber disposed adjacent to and outside of the one of the pump chambers which is held in fluid communication with the outlet port, and held in fluid communication with the one of the pump chambers;
• and
• a partition disposed in the intermediate chamber and defining a passageway for guiding a process gas introduced into the intermediate chamber around the rotational shaft.

A vacuum pump comprising:

• a pump casing including a plurality of pump chambers held in fluid communication with each other and arrayed in a longitudinal direction thereof, an inlet port held in fluid communication with one of the pump chambers which is positioned on a suction side, and an outlet port held in fluid communication with one of the pump chambers which is positioned on a discharge side;
• a rotational shaft rotatably supported at opposite ends thereof by bearings and extending in the longitudinal direction of the pump casing;
• and
• a plurality of rotors housed in the pump chambers and coupled to the rotational shaft for rotation in unison with the rotational shaft;
• wherein the pump casing includes:
• an end wall disposed on an end thereof and separate from a side panel which is disposed adjacent to the end of the pump casing.