Vacuum Pump

Abstract

A vacuum pumping arrangement is described for evacuating a load lock chamber. A booster pump comprises a molecular drag stage and a multi-stage centrifugal compressor mechanism. A backing pump comprises a multi-stage centrifugal compressor mechanism exhausting pumped fluid at atmospheric pressure. Such arrangements can reduce noise, size and vibration levels associated with conventional load lock pumping arrangements.

1 . The vacuum pump arrangement according to  claim 37  wherein the multi-stage centrifugal compressor mechanism comprises a housing within which the drive shaft is rotatably mounted, a plurality of fixed members disposed within the housing and defining a plurality of interconnected fluid chambers, the rotor elements of the compressor mechanism comprising a plurality of impellers mounted on the drive shaft and disposed relative to the fixed members such that each impeller delivers compressed fluid to a respective fluid chamber, the compressor mechanism further comprising a bypass channel extending between two of the fluid chambers to enable fluid to pass between those chambers without compression, and means for controlling the flow of fluid through the bypass channel.  
     
     
         2 . The vacuum pump arrangement according to  claim 1  wherein the control means is arranged to open the bypass channel under the influence of a pressure difference between said two of the fluid chambers.  
     
     
         3 . The vacuum pump arrangement according to  claim 1  wherein the control means is arranged to open the bypass channel when the pressure in an upstream one of said two of the fluid chambers is greater than the pressure in a downstream one of said two of the fluid chambers.  
     
     
         4 . The vacuum pump arrangement according to  claim 1  wherein said two of the fluid chambers are adjacent fluid chambers of the compressor mechanism.  
     
     
         5 . The vacuum pump arrangement according to  claim 4  wherein the bypass channel passes through the fixed member located between the adjacent fluid chambers.  
     
     
         6 . The vacuum pump arrangement according to  claim 1  wherein the control means comprises valve means.  
     
     
         7 . The vacuum pump arrangement according to  claim 6  wherein the valve means comprises a valve member displaceable in use between a closed position and an open position by pressurised fluid.  
     
     
         8 . The vacuum pump arrangement according to  claim 7  wherein the valve member comprises a flap valve.  
     
     
         9 . The vacuum pump arrangement according to  claim 6  wherein the valve means is located within a fluid chamber.  
     
     
         10 . The vacuum pump arrangement according to  claim 1  comprising, for each fluid chamber, a respective bypass channel extending between that fluid chamber and the adjacent downstream fluid chamber, and means for controlling the flow of fluid through each bypass channel.  
     
     
         11 . The vacuum pump arrangement according to  claim 1  further comprising surge control means for controlling surge within the multi-stage centrifugal compressor mechanism.  
     
     
         12 . (canceled)  
     
     
         13 . The vacuum pump arrangement according to  claim 11  wherein the surge control means comprises means for conveying a stream of fluid to each fluid chamber, and means for controlling the rate of flow of the fluid stream into each fluid chamber.  
     
     
         14 . The vacuum pump arrangement according to  claim 13  wherein the conveying means is arranged to convey a stream of purge gas to each fluid chamber.  
     
     
         15 . The vacuum pump arrangement according to  claim 14  wherein the purge gas comprises air or an inert gas.  
     
     
         16 . The vacuum pump arrangement according to  claim 13  wherein the conveying means is arranged to convey a stream of compressed fluid to each fluid chamber from a downstream fluid chamber.  
     
     
         17 . The vacuum pump arrangement according to  claim 16  wherein the conveying means comprises, for each fluid chamber, a fluid passage extending between that fluid chamber and the adjacent downstream fluid chamber.  
     
     
         18 . The vacuum pump arrangement according to  claim 17  wherein the fluid passages are co-axial.  
     
     
         19 . The vacuum pump arrangement according to  claim 17  wherein each fluid passage passes through a respective fixed member.  
     
     
         20 . The vacuum pump arrangement according to  claim 16  wherein the control means comprises valve means in fluid communication with said conveying means.  
     
     
         21 . The vacuum pump arrangement according to  claim 20  wherein the valve means comprises a spool valve.  
     
     
         22 . The vacuum pump arrangement according to  claim 1  wherein each fixed member comprises a disc mounted on, or integral with, a respective part of the housing.  
     
     
         23 . The vacuum pump arrangement according to  claim 1  comprising means for cooling the fixed members.  
     
     
         24 . The vacuum pump arrangement according to  claim 23  wherein the cooling means comprises a plurality of cooling fins located on one side of each fixed member.  
     
     
         25 . The vacuum pump arrangement according to  claim 23  wherein the cooling means comprises means for supplying a flow of coolant to each fixed member.  
     
     
         26 . The vacuum pump arrangement according to  claim 1  comprising a cooling jacket extending about at least part of the multi-stage centrifugal compressor mechanism.  
     
     
         27 . (canceled)  
     
     
         28 . (canceled)  
     
     
         29 . (canceled)  
     
     
         30 . (canceled)  
     
     
         31 . (canceled)  
     
     
         32 . A vacuum pump comprising a multi-stage centrifugal compressor mechanism comprising a plurality of rotor elements mounted on a rotatably mounted drive shaft, and, upstream therefrom, a molecular drag mechanism comprising at least one rotor element mounted on the drive shaft, wherein the at least one rotor element of the molecular drag mechanism at least partially surrounds a motor for rotating the drive shaft.  
     
     
         33 . The vacuum pump according to  claim 32  wherein said at least one rotor element of the molecular drag pumping mechanism comprises a cylinder mounted for rotary movement with the rotor elements of the compressor mechanism.  
     
     
         34 . The vacuum pump according to  claim 32  comprising means for monitoring the temperature of the pump, and means for controlling the speed of rotation of the shaft in dependence on the monitored temperature.  
     
     
         35 . (canceled)  
     
     
         36 . (canceled)  
     
     
         37 . A vacuum pumping arrangement comprising a vacuum pump in series with a backing pump, wherein the vacuum pump comprises a multi-stage centrifugal compressor mechanism comprising a plurality of rotor elements mounted on a rotatable mounted drive shaft, and, upstream therefrom, a molecular drag mechanism comprising at least one rotor element mounted on the drive shaft, wherein the at least one rotor element of the molecular drag mechanism at least partially surrounds a motor for rotating the drive shaft.  
     
     
         38 . (canceled)  
     
     
         39 . (canceled)  
     
     
         40 . The vacuum pumping arrangement according to  claim 37  comprising a bypass conduit connected between an exhaust from the booster pump and an exhaust from the backing pump, and means for controlling the flow of fluid through the bypass conduit.  
     
     
         41 . A vacuum pump according to  claim 37  wherein the molecular drag mechanism defines a plurality of flow channels that each receive fluid from a pump inlet and exhaust pumped fluid to a common exhaust port.  
     
     
         42 . A vacuum pump according to  claim 37  wherein the molecular drag mechanism is a multi-stage molecular drag mechanism.  
     
     
         43 . A vacuum pump according to  claim 42  wherein the stages of the drag mechanism are arranged in parallel.