| 摘要 |
PCT No. PCT/CH96/00251 Sec. 371 Date Aug. 24, 1998 Sec. 102(e) Date Aug. 24, 1998 PCT Filed Jul. 8, 1996 PCT Pub. No. WO97/21926 PCT Pub. Date Jun. 19, 1997In known embodiments, media are fed in a contact-free manner in propeller pumps by single-thread twin feed screws which are guided via pilot gears, the twin feed screws having the same transverse profile with a core circle, tip circle, an involute flank and a hollow flank, enabling the pump chamber to be divided into axially staggered cells and this obtain high pressure differences in one stage. In addition to dynamics, efficiency and production, the control of the medium is also determined by the contour of the end profile, the variation of which improves all the dependent variables. According to the invention, the involute is replaced by a curve which does not rise constantly and has a central saddle region and a smooth connection to the core circle. The variations in the end face achieved thereby improve the dynamics and volumetric efficiency and extend the possibilities for controlling medium at the end face. The detailed adaption to the new curve together with the smooth connection at the base point enable the core and flanks to be produced jointly by a single tool. Feed screws with profiles of this type are suitable for flow rates of between 100 and 1000 m3/h and ultimate pressure of <0.05 mbar at speeds of rotation of approximately 3000 min-1 and approximately 50% efficiency.
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