Abstract: A pump includes a plurality of pumping stages comprising a respective plurality of pumping mechanisms driven by one or more drive shafts for pumping fluid through the pumping stages from a pump inlet at a high vacuum stage to a pump outlet at a low vacuum stage; a lubrication chamber housing a bearing assembly for supporting the drive shaft for rotational movement, the drive shaft extending from the high vacuum stage to the lubrication chamber through an opening of a head plate of the lubrication chamber; an inter-stage purge port through which gas can enter the pump at an inter-stage location downstream of the high vacuum; a lubrication chamber purge port located in the lubrication chamber through which purge gas can flow from a source of purge gas; wherein the inter-stage port is connected to the lubrication chamber for controlling the pressure of purge gas in the lubrication chamber.

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.

Abstract: The present invention provides a positive displacement dry pump comprising: a plurality of vacuum pumping stages comprising a respective plurality of pumping mechanisms driven by one or more drive shafts for pumping fluid in series through the pumping stages from a pump inlet at the high vacuum stage to a pump outlet at the low vacuum stage; a lubrication chamber housing a bearing assembly for supporting the drive shaft for rotational movement, the drive shaft extending from the high vacuum stage to the lubrication chamber through an opening of a head plate of the lubrication chamber; an inter-stage purge port through which gas can enter the pump at an inter-stage location downstream of the high vacuum stage and pass only through the or each vacuum pumping stage downstream of the inter-stage port; a lubrication chamber purge port located in the lubrication chamber through which purge gas can flow from a source of purge gas; wherein the inter-stage port is connected to the lubrication chamber for controlling t