INNER BRANCH FLOW/COUNTER FLOW COOLING TYPE MULTI-STAGE ROOTS VACUUM PUMP

摘要

PURPOSE:To minimize a gap between a rotor and a housing, by feeding counter flow cooling gas from a cooler through a gap flow paths on the outer circumference of housing at respective pump sections and communication ports of partition walls into the housing. CONSTITUTION:A sufficient volume of flow is ensured by a difference of pressure between suction ports 13, 43, 73 and delivery ports 14, 44, 74 of respective pump sections 1, 4, 7, and a portion of compressed counter flow cooling gas cooled stably to a proper temperature by means of coolers 36, 66, 85 is fed through outer circumferential gas flow paths 17A, 17B provided on the outer circumferential section of housing 11 at respective pump sections and communication ports made through partition walls the housing. Consequently, the temperature of the housing can be maintained stably regardless of variation of ambient temperature when the pump is operated and a gap between a rotor 12 and the housing 11 can be set to a minute value, thereby leakage through said gap can be reduced and the performance can be improved.