Pump

Abstract

The present invention relates to a multi-stage vacuum pump which has a plurality of pumping stages. The pump comprises a stator forming the pumping chambers of respective pumping stages and at least one shaft, for supporting a plurality of rotors for rotation in respective pumping chambers. The stator comprises: a stator envelope which extends over an axial extent of a plurality of stator stages thereby circumscribing said at least one shaft and forming an internal profile of a plurality of stator stages: and a plurality of transverse walls located on either axial side of the stator stages to form respective said pumping chambers. At least one of the transverse walls is an inter-stage between stator stages and the stator envelope is configured to circumscribe the inter-stage for location of said inter-stage radially inward of the stator part.

1 . A multi-stage vacuum pump comprising: a stator forming a plurality of pumping chambers and at least one shaft for supporting a plurality of rotors for rotation in respective pumping chambers, the stator comprising: a one piece stator envelope enclosing a plurality of axially adjacent pumping chambers about the shaft and at least one inter-stage transverse wall located radially inwardly of the stator envelope and between axially adjacent pumping chambers. 
     
     
         2 . The multi-stage vacuum pump as claimed in  claim 1 , wherein the stator envelope has an axially extending internal bore formed therethrough which forms the profiles of the respective pumping chambers. 
     
     
         3 . The multi-stage vacuum pump as claimed in  claim 1 , wherein a radial cross-section of the internal bore at each pumping chamber is generally uniform in the axial direction. 
     
     
         4 . The multi-stage vacuum pump as claimed in  claim 1 , wherein the radial cross-section of at least one pumping chamber is different from that of at least one other pumping chamber. 
     
     
         5 . The multi-stage vacuum pump as claimed in  claim 1 , wherein at least one end of the stator envelope is open to allow insertion of said at least one inter-stage wall along said internal bore for location between two pumping chambers. 
     
     
         6 . The multi-stage vacuum pump as claimed in  claim 1 , wherein the internal bore comprises a formation for locating an inter-stage wall between two pumping chambers. 
     
     
         7 . The multi-stage vacuum pump as claimed in  claim 6 , wherein the formation comprises a stepped surface extending radially inwardly into the internal cavity against which the transverse wall abuts when correctly located between the pumping chambers. 
     
     
         8 . The multi-stage vacuum pump as claimed in  claim 6 , wherein the formation comprises at least one closed bore for receiving a fastener for fixing the transverse wall in location. 
     
     
         9 . The multi-stage vacuum pump as claimed in  claim 1 , wherein said at least one inter-stage wall comprises a bore through which a fastener can extend for fixing the inter-stage to the stator envelope. 
     
     
         10 . The multi-stage vacuum pump as claimed in  claim 1 , wherein the inter-stage is configured for selective fixing at more than one location in the stator envelope. 
     
     
         11 . The multi-stage vacuum pump as claimed in  claim 1 , comprising a one or more fasteners for fastening one or more of said inter-stage walls to the internal profile of the stator envelope. 
     
     
         12 . The multi-stage vacuum pump as claimed in  claim 11 , wherein the fastener is shaped such that in a first condition thereof the inter-stage can pass through the internal bore of the stator envelope and in a second condition thereof the fastener fastens the inter-stage in location to the stator envelope. 
     
     
         13 . The multi-stage vacuum pump as claimed in  claim 1 , wherein at least one of an axial facing surface of the inter-stage wall or axial facing surface of an adjacent rotor is coated with a friction reducing material. 
     
     
         14 . The multi-stage vacuum pump as claimed in  claim 1 , wherein the inter-stage walls are not fixed at predetermined locations within the stator envelope and are allowed to float between rotors. 
     
     
         15 . A stator configured for the multi-stage vacuum pump as claimed in  claim 1 .