Abstract: Pole-piece-magnet apparatus for use as single- or double-pole-piece ferrofluid seal apparatus and method of manufacture, which pole-piece-magnet apparatus comprises at least one washer-type metal-pole-piece element with one flat surface having a plurality of spaced-apart raised dimple elements thereon with outwardly extending anchoring surfaces; and a washer-like hard molded permanent magnet polymer ring element molded about and secured directly to the one flat surface of the pole-piece element by the anchoring surface on the raised dimples, the permanent magnet ring element having an inner diameter greater than the inner diameter of the pole-piece element and an outer diameter of about the same dimensions as the outer diameter of the pole-piece element.

Abstract: A self-activating ferrofluid-seal apparatus for a memory-disc-drive shaft, which seal apparatus comprises a ring magnet and a pair of pole pieces which form a cavity therebetween, a closed loop of a plastic tubular container with ferrofluid positioned within the cavity, and a penetration clamp to penetrate the plastic container prior to installation of the shaft element.

Abstract: A self-activating seal is formed by inserting a magnetically permeable shaft into a module which comprises: a magnet, two pole pieces and a magnetic fluid. The module is so constructed that the magnet and pole pieces form a cavity for storing the magnetic fluid until the shaft or similar element is inserted. Upon insertion of the shaft, the magnetic field is altered and the flux path diverted to the small gaps separating the pole pieces and the shaft. The magnetic fluid is drawn to the gas to form hermetic seals.