Vacuum pump

Abstract

An improved split flow vacuum pump is provided with at least two of compound pumps housed in a common housing comprising first, second, third and fourth inlets for receiving gas from a respective first to fourth chamber; said pumps are arranged such that their rotational axis are angled relative to each other in the housing, preferably perpendicular to each other.

1 . A vacuum pump for differentially pumping a plurality of chambers, the vacuum pump comprising:
 a housing which houses a plurality of compound pumping arrangements supported for independent rotation one from another on respective drive shafts by separate motors;   a first housing inlet for receiving fluid from a first chamber;   a second housing inlet for receiving fluid from a second chamber;   a first of the compound pumping arrangements comprising a first pumping section comprising a turbo molecular pumping mechanism and a second pumping section downstream from the first pumping section, the sections being arranged such that fluid entering the compound pump from the first inlet passes through the first and second pumping sections and fluid entering the compound pump from the second inlet passes through, of said sections, only the second section;   the vacuum pump further comprising:   a third housing inlet for receiving fluid from a third chamber;   a fourth housing inlet for receiving fluid from a fourth chamber;   a second of the compound pumping arrangements comprising a third pumping section comprising a turbo molecular pumping mechanism and a fourth section downstream from the first pumping section, the sections being arranged such that fluid entering the second compound pumping arrangement from the third inlet passes through the third and fourth pumping sections and fluid entering the second compound pump from the fourth inlet passes through, of said sections, only the fourth section.   
     
     
         2 . The vacuum pump as claimed in  claim 1 , wherein the drive shafts have respective axes of rotation which are angled one relative to another. 
     
     
         3 . The vacuum pump as claimed in  claim 1 , wherein the drive shafts have first and second axes of rotation, and the first axis is perpendicular to the second axis. 
     
     
         4 . The vacuum pump as claimed in  claim 1 , wherein at least one of the pumping arrangements is in the form of a cartridge comprising a casing for supporting the pumping mechanisms of the cartridge and configured so that the cartridge can be inserted into and engage with a bore of the housing to expose fluid inlets of the pumping mechanisms to respective housing inlets. 
     
     
         5 . The vacuum pump as claimed in  claim 1 , wherein the second and fourth sections of the compounds pumping arrangements comprise a molecular drag pumping mechanism or regenerative pumping mechanism. 
     
     
         6 . The vacuum pump as claimed in  claim 1 , wherein the second section of the first pumping arrangement comprises a booster pumping mechanism and the housing comprises a booster inlet arranged for connection to an exhaust of the second vacuum pumping arrangement so that the second section backs the second vacuum pumping arrangement and the first section of the first vacuum pumping arrangement. 
     
     
         7 . The vacuum pump as claimed in  claim 6 , wherein the housing comprises an exhaust forming an outlet from the booster pumping mechanism for connection to a backing pump so that the backing pump can back the first pumping arrangement and the second pumping arrangement.