Importance

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Abstract

An electromagnet defines a gap between a first polepiece in the shape of the butt end of an elongate cylinder and a second polepiece in the shape of a thick annular ring. A permanent magnet having its poles aligned along the axis of the cylinder moves bidirectionally in the gap in response to alternate polarity energization of the electromagnet, serving as a prime mover. When the electromagnet is not energized then the magnetic flux of the permanent magnet shunts an adjacent polepiece, holding the magnet in place. Upon energization of the electromagnet the relatiely strong magnetic flux of the permanent magnet is switched by a relatively weak electromagnetic flux to pass through the electromagnet, exerting an electromotive force on the permanent magnet and causing it to move. This flux switching offers gain: a one-half gram samarium cobalt permanent magnet moves 0.38 mm in response to a 0.015 ampere 1.5 v.d.c. 20 millisecond current pulse (4.5.times.10.sup.-4 joules) and holds at 40.+-.2g's. dislodging acceleration at each of two stable positions where no power is consumed. Back-to-back configurations of the actuator sharing a single electromagnetic coil can be operated single-ended push-pull, double-ended with non-mechanical phase or antiphase lock, and fully independently-controlled multiplexed.

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First Claim