Shaft seal with magnetically controlled gap between rotating ring and surrounding non-rotating ring

摘要

A seal device for a shaft rotating with respect to a housing comprises a rotating seal ring having opposite radial side surfaces and a circumferential end surface. The rotating seal ring is connected for co-rotation with the shaft. A non-rotating seal ring is non-rotatably connected to the housing over a yielding packing element and surrounds at least a portion of the rotating seal ring to define axial plane sealing gaps and an annular circumferential gap. Sealing fluid is pumped to each gap over bores communicating with the radial plane gaps. An electromagnet is connected to the housing and attracts or repels magnetic material in a radially extending portion of the non-rotating seal ring for regulating the width of each radial plane gap. Electromagnet is connected over a control unit to a sensor for sensing each gap, to maintain a selected gap width for each gap by regulating the activation of the electromagnet. The non-rotating seal ring is also slidable within a smooth sleeve connected to the housing.