Lubricating systems for regenerative vacuum pumps

1. In a vacuum pump of the regenerative type or including a regenerative section in which a rotatable vertical shaft is supported by upper and lower bearings, a lubricating system for lubricating the upper bearing comprising:

an axial bore extending along the shaft and communicating at its upper end with at least one oil hole in alignment with the upper bearing, the lower open end of the axial bore extending in to a shaft reservoir located in a sump for containing lubricating fluid, the arrangement being such that centrifugal force generated by the rotation of the shaft will cause the lubricating fluid in the shaft reservoir to pass along the axial bore as a thin film towards the oil hole and hence to the upper bearing, in which at least one port is formed in a wall of the shaft reservoir to permit the passage of lubricating fluid therethrough from the sump in a controlled manner dependent upon the head of lubricating fluid in the sump above the port.

2. A lubricating system as claimed in claim 1 , in which an impeller is located immediately below the upper bearing for drawing lubricating fluid from the upper bearing in to the sump.

3. A lubricating system as claimed in claim 2 , in which the impeller is formed as a thread on the outside cylindrical surface of the shaft and includes a counter-face extending from the upper bearing.

4. A lubricating system as claimed in claim 2 , in which a filter is located in the axial bore.

5. A lubricating system as claimed in claim 1 , in which a filter is located in the axial bore.