Abstract: A Roots pump rotates a plurality of rotors by a pair of rotary shafts to draw gas. Each rotary shaft extends through a rear housing member of the Roots pump. An annular shaft seal is fitted around each rotary shaft and is received in a recess formed in the rear housing member. A labyrinth seal is located between an end surface of each shaft seal and the bottom of the associated recess. This enlarges the diameter of each labyrinth seal, thus preferably preventing oil from leaking to a pump chamber.

Abstract: A compressor comprises a housing assembly, a compression mechanism and a sealing member. The housing assembly has a first housing member and a second housing member coupled to each other. The first housing member has an opening end surface. The second housing member has an opening end surface. The compression mechanism is disposed in the first housing member and compresses gas supplied to the compressor. The sealing member includes a first portion and a second portion. The first portion is interposed between the opening end surface of the first housing member and the opening end surface of the second housing member. The second portion of the sealing extends radially inwardly from the first portion to be interposed between the compression mechanism and the second housing member.

Abstract: A Roots pump rotates a plurality of rotors by a pair of rotary shafts to draw gas. Each rotary shaft extends through a rear housing member of the Roots pump. An annular shaft seal is fitted around each rotary shaft and is received in a recess formed in the rear housing member. A labyrinth seal is located between an end surface of each shaft seal and the bottom of the associated recess. This enlarges the diameter of each labyrinth seal, thus preferably preventing oil from leaking to a pump chamber.