Zusammenfassung
Optimum rod seals of hydraulic cylinders require effective wiping on the outstroke and, ideally, a complete inward pumping of the adhering film on the instroke. This is achieved by an asymmetric profile which creates a high maximum contact pressure gradient at the sealing edge on the fluid side and a corresponding low gradient near the outside end of the contact. In practice, however, by rising the fluid pressure inward-pumping diminishes which is due to a continuing increase of the maximum pressure gradient at the outside end of the seal contact. Based on the experience that a second circumferentially closed edge does not prevent the increase of leakage, the authors pursued the idea to support the back-surface with a large number of small asperities forming small interconnected gaps which boost inward pumping and reduce friction. Experimental results on the sealing capacity and friction of various back-surface structures are presented, and the design characteristics ofoptimum rod seals are discussed.
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