GB1334225A - Vacuum pumps - Google Patents

Abstract

1334225 Rotary vacuum pump EDWARDS HIGH VACUUM INTERNATIONAL Ltd 9 Dec 1970 [16 Dec 1969] 61344/69 Heading F1F A mechanical oil-sealed vacuum pump having an oilway extending from a sump to an antisuckback system has an orifice or conduit preventing ingress of air during pump operation but admitting air to at least part of the oilway when the pump stops. A main pump 3 driven from a pulley 2 has an exhaust valve 23 in a well 19 while an oil pump 7 delivers oil from a sump 10 to a distributor valve 12 having a block 14 overlain by a seal 15. A smaller conduit 20 leads from the duct 11 to open above a well 18 while a duct 17 leads from an annular chamber 16 to the pump 3. In operation oil from the duct 11 raises the seal 15 so that it can flow from a chamber 25 to the chamber 16 and thus lubricate and seal the pump 3 while the conduit 20 delivers to the well 18. When the pump is stopped if the seal 15 fails to function once the well 18 and the conduits above the junction of 11 and 20 have emptied air will be drawn into pump 3 through the conduit 20 rather than oil from the sump 10. To prevent oil being drawn from the sump 10 along the driveshaft 1 two seals 5, 6 are provided with an interposed chamber 22 connected by a duct 21 to the well 18. If the seal 6 fails once the well 18 has emptied air will be drawn into the pump 3 while if 5 and 6 fail a similar effect will occur due to the greater resistance to the oil path along the shaft 1 and duct 9 to the sump 10.