Pancake annunciator

Abstract

An annunciator for an implantable medical device encapsulated within a casing comprises a magnetically permeable stationary ring member including an integral inwardly projecting peripheral flange having opposed sides on which electrically conductive coils are mounted. An oscillating member encompassed by the stationary ring member includes a planar magnet member having opposed surfaces of opposite polarity and planar pole pieces are mounted to the first and second surfaces, respectively, in a sandwich-like construction. The oscillating member is movable along a longitudinal axis between extreme positions whereat the first pole piece, then the second pole piece is proximate the ring flange. Cyclic energization of the electrically conductive coils generates a cyclically alternating magnetic field, which interacts with the magnetic field of the oscillating member causing its oscillation between the first and second extreme positions. In another embodiment, the casing includes opposed walls and the first and second pole pieces impact against the opposed walls when the oscillating member reaches the first and second extreme positions, respectively. In another embodiment, opposed spider members have a central portion fixed to their respective polar pieces and a plurality of radially extending legs have terminal ends fixed, respectively, to the ring member at peripherally spaced locations, the spider members being axially compliant and biasing the oscillating member toward a neutral position and being substantially non-compliant transversely of the longitudinal axis for centering the oscillating member relative to the ring member throughout travel thereof between the first and second extreme positions.