Patent ID: 7108492
Filing Date: 2006-09-19
Classification: F04C

Abstract:
1. A roots pump comprising: a housing forming therein a pump chamber; a plurality of rotary shafts supported on the housing in parallel relation to each other; a rotor mounted on each of the rotary shafts, the rotors on any adjacent rotary shafts being in engagement with each other, a set of the engaged rotors being accommodated in the pump chamber; a confluent passage formed along one crossing line of paired imaginary swept peripheral surfaces in one-to-one correspondence with the paired and engaged rotors; and a closed space formed in one-to-one correspondence with each of the paired rotors between the paired rotors and paired peripheral wall surfaces which form the pump chamber, wherein the closed space initially joins the confluent passage from a terminal end of the confluent passage with rotation of the paired rotors.