US2476778A - Magnetostrictive device - Google Patents

Description

194% R. SMOLUCHQWSK! 294765778 7 MAGNETOSTRLCTIVE DEVICE Filed June 28, 1946 lhventor-z Roman Smoluchowski,

631 i-iis Attorney.

Patented July 19, 1949 "res 2,476,778 4 MAGNETO STRICTIV E DEVICE Roman Smoluchowski, Pittsburgh, Pa., assignor to General Electric Company, a corporation of New York Application June 28, 1946, Serial No. 679,914

2 Claims. (01. 318-118) The present invention relates to magnetostrictive devices and more particularly to the vibratnetostriction of even the most suitable magnetic material is relatively small, any application requiring a high intensity impulse requires a vibrating element of considerable length and hence, a vibrator of considerable size.

Heretofore, materials of different magnetostrictive characteristics have been combined in composite cores of vibrators to maintain a constant frequency of vibration, over a range of temperatures. In accordance with my invention there is provided an arrangement which combines magnetic materials of widely varying magnetostriction characteristics for obtaining greater effective magnetostriction per unit length of the vibrating element.

One of the objects of my invention is to pro-.- vide a new and improved magnetic device which has a greater effective magnetostriction per unit length of the device.

Another object of my invention is to provide a new and improved magnetostrictive vibrator.

A further object of my invention is to provide a new and improved vibrating element for a magnetostrictive vibrator.

Still another object of my invention is to provide a new and improved arrangement of magnetic materials having opposite characteristics of magnetostriction so that a greater effective magnetostriction per unit length is secured.

The novel features which are characteristic of my invention are set forth with particularity in the appended claims. My invention itself however, will be best understood by reference to the following specification when considered in connection with the accompanying drawing in which Figure 1 is a front elevation partly in section of a degasing apparatus illustrating one application of a magnetostrictive vibrator embodying my invention; Figure 2 is a perspective view of a vibrating element illustrating one embodiment of my invention; Figure 3 is a perspective view of a vibrating element with the individual members bent lengthwise to add stiffness to the members; Figure 4 is a sectional view of a vibrating element comprising thin concentric members for 2 maximum stifi'ness, while Figure 5 is a perspective view of a vibrating element formed in a helix to obtain maximum magnetostrictlon accruing from length of the element.

Referrin now to the drawing and more particularly to Figure 1, there is illustrated apparatus for degasifying liquids which comprises a base I, a liquid receptacle or crucible 2 on a platform 3 supported by a vibrating element 6 attached to base I and platform 3 and axially disposed within a coil 5 of a magnetostrictive vibrator 6. Coil 5 of the magnetostrictive vibrator 6 may be connected by conductors l and 8 to any suitable source of alternating current or voltage and when energized by such a source, platform 3 is reciprocated vertically on guide rods 9 fixed to the base l. Such reciprocation or agitation of the liquid within the crucible 2 effects a mechanical separation of entrapped gas.

Figure 2 diagrammatically illustrates a vibrat ing element comprising three flat members III,-

II and [2 with the upper ends of members In and l I and the lower ends of members II and I! connected as shown in the drawing by'any suitable method such as welding. In the preferred form of my invention members l0 and I2 are of a magnetostrictive material having a positive sign of magnetostrictive material while member H is of a material having a negative sign of magnetostriction. By positive sign of magnetostriction, I mean that the material has that property of expanding its dimensions upon being energized magnetically and conversely by negative sign of magetostriction I mean that the material has that property of contracting upon being energized magnetically. v

' Although I have described the outer members as having a positive sign of magnetostriction and the inner member as having a negative sign of magnetostriction, it will be obvious froma description of the operation hereinafter that the operation of my invention would be the same if members l0 and i2 were of a material having a negative sign of magnetostriction and the memher i l was of a material having a positive sign of magnetostriction.

Any material having a positive sign of magnetostriction would be suitable for members 10 and I2. However, I have found that an alloy containing 50% iron and 50% cobalt is particularly suitable. Another material which I have found to have a good positive magnetostrictive characteristic is an alloy containing 20-80% cobalt, 0.5-1.0% vanadium and the balance iron. Any material having a negative characteristic of magnetostriction is suitable for the intermediate I have found that leaving a slight space between members is quite satisfactory although it is obvious that other means may be employed.

When a vibrating element of the type described is placed in a magnetic field, members l and I 2 expand in accordance with their positive magnetostrictive characteristic. At the same time, member I I contracts in accordance with its negative magnetostrictive characteristic. As a result of the expansion of members l0 and I2 and the contraction of member I I, the upper end of member I2 and the lower end of member I0 move apart along the axis of the vibratin element by an amount equal to the sum of th expansions of members l0 and'l2 and the contraction of member II. If the vibrating element is placed in an alternating magnetic field, the frequency of expansion and the contraction or lengthwise vibration of the magnetostrictive members will be double the frequency of the alternating magnetic field.

While the arrangement of magnetostrictive materials shown in Figure 2 and described above is preferred for a maximum amplitude of vibration, an arrangement wherein one of the members is of a non-magnetic material will also give a satisfactory effective magnetostriction per unit length of the vibrating element. If, for example, a non-magnetic material were substituted for any one member of Figure 2, the amplitude of vibration of the vibrating element would be equal to the sums of expansion or contraction of the other two members. Although the effective magnetostriction per unit length of vibrating element would be less with this arrangement than that of Figure 2 with all three members of magnetostrictive material, the effective magnetostriction of the unit would be greater than that of any one of its members.

Figure 3 of the drawing diagrammatically illustrates a modification of the vibrating element illustrated in Figure 2 comprising members i3 and i having a positive magnetostrictive characteristic and member it having a negative magnetostrictive characteristic, all of which have been bent at an angle forming, in effect, a channel extending lengthwise of'the members. By deforming the members l3, l4 and I5 in this manner it has been found that the added stiffness prevents the members from bulging along their lengths when the vibrating element is subjected to high frequency fields.

spaced intermediate members l6 and I8 which have a positive sign of magnetostriction. The individual members are arranged with suitable spacing and connected in the same manner as shown and described for the vibrating element of Figure 2. The use of thin walled tubular members in this arrangement gives the vibrating element a stiffness that eliminates any lateral bending and tends to diminish the damping effect of a thick tubular section due to a flux concentration in the outer skin of the tubular members.

A third modification illustrated by Figure 5 of the drawing comprises an arrangement of three elongated flat members formed into a helix. In this modification a member 20 of negative sign of magnetostriction is spaced intermediate two members I9 and 2| of positive sign of magnetostriction. The three flat members are connected with suitable spacing in the same manner as described for Figure 2 and the assembly is bent as a unit into a helix. With this form of vibrating element it is possible to combine a maximum magnetostrictive effect per unit length of vibrating element with maximum length of vibrating element.

The operation of the modifications illustrated and described is essentially the same as the operation for the embodiment of my invention illustrated in Figure 2.

Although the present vibrating element will find particularly useful application in magnetostrictive vibrators for degasifying oils, and molten metals it is also satisfactory for use in high frequency impulse generators and when energized by a direct current voltage or current would be suitable as a latching device.

While there has been shown and described particular embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention and therefore, it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A magnetostrictive vibrator comprising a plurality of mechanically connected V shaped members of opposite sign of magnetostriction, said members being alternately arranged.

2. A magnetostrictive vibrator comprising a plurality of members of opposite sign of magnetostriction, said members being alternately arranged and describing a helix.

ROMAN SMOLUCHOWSKI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS- Number Name Date 436,514 Wiegand S pt. 16, 1890 1,889,153 Pierce Nov. 29, 1932

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