Vacuum pump

A pump (10, fig 1) comprises an enclosure having a pumping chamber 20 which houses a pair of inter-engaging lobed rotors 60 (50, fig 1) each carried by respective bearings (57, 67, fig 1) located within bearing apertures within a head plate 40. A secondary (oil) chamber 30 is separated from the pumping chamber by the head plate. One of the rotors defines a conduit 70, 80 for fluid communication between the secondary chamber and a discharge aperture 90 in the pumping chamber. Fluid from within the secondary chamber is drawn into the pumping chamber. The discharge aperture is positioned offset from a sealing region (100, fig 5) between the lobed rotors. The sealing region is preferably defined by a converging surface(s) between said lobed rotors, which substantially fluidly isolates a higher-pressure region of said pumping chamber from a lower pressure region of said pumping chamber. The discharge aperture may extend between said lobed rotors and / or orientated parallel to an aligning axis ...