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Magnetostrictive Actuator

IP.com Disclosure Number: IPCOM000062391D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Goldowsky, M: AUTHOR

Abstract

Using a single layer of samarium ferrite, a magnetostrictive material which contracts strongly when an external magnetic field is applied, a simple dot matrix print actuator provides reliable, efficient high speed actuation at low cost. The SmF2 device uses a magnetostrictive material which contracts when an external magnetic field is applied. It does not have to be layered; one piece will do. The energy density is extremely high, compared to most piezoelectric crystals and the normal magnetostrictive materials such as nickel and cobalt iron, as shown in the following table of storable energies per cubic inch: piezo-crystal 2x10-3 in-1b magnetostrictive nickel 16x10-3 cobalt iron 60x10-3 SmFe2 160,000x10-3 Very little material is needed to make an actuator with enough energy.

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Magnetostrictive Actuator

Using a single layer of samarium ferrite, a magnetostrictive material which contracts strongly when an external magnetic field is applied, a simple dot matrix print actuator provides reliable, efficient high speed actuation at low cost. The SmF2 device uses a magnetostrictive material which contracts when an external magnetic field is applied. It does not have to be layered; one piece will do. The energy density is extremely high, compared to most piezoelectric crystals and the normal magnetostrictive materials such as nickel and cobalt iron, as shown in the following table of storable energies per cubic inch: piezo-crystal 2x10- 3 in-1b magnetostrictive nickel 16x10-3 cobalt iron 60x10-3 SmFe2 160,000x10-3 Very little material is needed to make an actuator with enough energy. The length change obtainable in SmFe2 is .002 inch per inch of length, which is only attainable with tens of layers of piezo elements operating at 1000 volts. Fig. 1 shows a toroidal piece of SmFe2 1 to which is attached a beam 2. The SmFe2 contracts, buckling the beam 2, and produces beam displacement, perpendicular to its axis, as shown by dotted line 3. The beam material may be a nickel-iron composition, to match the thermal expansion coefficient of the SmFe2
. Then heating of the assembly from the coil 4 will not affect the beam length, and the magnetostriction effect becomes isolated. The beam buckles outward, due to the asymmetry of its legs at the mounting position. This eliminates the need for adjustments. Note that the beam length and actuator length are about the same with this type of packaging. By choosing a magnetostrictive material that contracts rather than expands, this simple configuration is realized. There are no frames to support the structure, which simplifies it and eliminates additional compliances. A long beam 2 length produces a large amplitude, and a long SmFe2 1 length produces high efficiency and a compact device. The beam 2 has a rais...