| 摘要 |
<p>A screw, roots or Northey vacuum pump comprises a stator 12 and shaft 14 located in the stator and supported for rotation relative to the stator. A shaft seal 18 comprising a carrier 26 with PTFE rings 20, 24 contacting a sealing surface 22 of a sleeve 44 mounted on the shaft separates a lubricated bearing pump portion and an oil free portion. A channel 38 is provided for conveying a coolant e.g. oil between the shaft and at least one of the sealing surface and a bearing 16 for supporting the shaft. The channel may be helical and coolant is supplied through an axial non-rotating tube 30 supported on a shrink fit bearing 35 co-axially with the shaft and through radial ports 30. Cools the seal sleeve and bearing and reduces risk of carbonisation.</p> |
