Patent ID: 8292603

Claim:
A rotary vacuum pump comprising: a pump casing having an intake port flange to be fixed to a device for evacuation, said intake port flange having a first through-hole and a thickness, a rotor situated in the pump casing for rotation, and having a rotating side evacuating device, a fixing side evacuating device disposed in the pump casing for evacuation together with the rotating side evacuating device, a first bolt inserted into the first through-hole, said first bolt having a diameter less than that of the first through-hole, and a first gap forming device for forming a gap between the bolt and the through-hole so that the pump casing is fixed to the device for evacuation by the first bolt and the first gap forming device, wherein said first gap forming device is a bush inserted between the first bolt and the first through-hole and including a bush part and a flange part integrally formed together, said bush part having a height less than the thickness of the intake part flange and being made of iron or stainless steel.