Abstract: An electromagnetic seal for a centrifugal pump controls movement of a valve member away from a normally closed position against a sealing surface at the entrance to a reservoir behind the expeller region of the pump, the valve member being controlled by a magnetizable clapper movable within a sealed enclosure toward and away from an electromagnetic coil which may be energized either by the drive motor of the pump or a self-contained generator in the pump driver assembly. Circulation of fluids between the impeller and expeller regions of the pump is enhanced by placement of vents in the impeller and a circumferential groove in the path of flow of fluid through the expeller to create increased turbulence and assist in flushing out foreign particles along with fluid in the expeller region when the pump is in operation. The effectiveness of this combination permits the employment of dry running secondary containment seals which do not require elaborate seal support systems.

Abstract: A pivotable control level disposed between a pair of spaced plates, with a motion resisting element mounted on the lever and compressed by the plates to provide a constant resistive force or "feel" to the system operator. A separate adjusting mechanism selectively increases or decreases the amount of compression exerted by the plates on the element to either increase or decrease the resistive force felt by the operator.