F. V. HUNT TRANSDUCER May 6, 1952 Filed April 5, 1946 swam 1M FREDERICK V. U NT I ate'nted May 3, 1952 "UNITED STATES PATENT OFFICE TRANSDUCER Frederick V. Hunt, Belmont, Mass, assig'nor to the United States of America as represented by the Secretary of the Navy Application April 5, 1946, Serial No. 659,714

(01. lib-209) 4 Claims. 1

The present invention relates in general to transducers and is particularly concerned with improvements in transducers of the radially expanding magnetostrictive type for use in underwater sound applications.

It has heretofore been proposed to construct radially expanding transducers with laminated cores effected by stacking a plurality of annular stampings of magnetos'trictive material over which a toroidal winding is placed. Such constructiori has proved expensive and wasteful, since the annular rings are stamped or punched from sheet metal stock, thus resulting in an extremely high percentage of metal Waste.

It has been found that transducers having laminated cores constructed in the above manner have a resonance curve which is relatively sharp, so that the transducer is limited to use over a relatively narrow frequency band. Reduction in the wall thickness of the laminated core will result in spreading out of the usable frequency band, and although some sacrifice in efhciency is made by reducing the wall thickness, this is compensated for in the increase of effective band width. In the presently formed annular rings, decrease of the width of the wall forming portions will introduce manufacturing difiiculties.

The present invention proposes to overcome the limitations in present constructions by winding a ribbon of magnetostrictive material, such as nickel, edgewise around a mandrel to form, in eifect, a laminated cylindrical core having a wall thickness equal to the edge width of the ribbon. The turns of the wound ribbon are insulated and secured together to form a substantially unitary core structure.

Having the foregoing in mind, it is a primary object of the herein described invention to providean improved core structure which is coo-'- nomical to construct and which results in a sav ing of material, and yetwhich has a relatively flat response over a wide range of frequencies.

Another object is to provide an improved magnetostrictive transducer having a core possessing the advantages inherent in a laminated structure, but which can be fabricated from a thin ribbon material, and thus effectively utilize all the material.

A further object is to provide an improved method for the fabrication of a cylindrical core of magnetizable material, which is susceptible of use in producing the core as a separate article of manufacture.

Still other objects and advantages of my invention will be apparent from the specification.

'rhe'features of novelty which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its fundamental principles and as to its particular embodiments, will best be understood by reference to the specification and accompanying drawings, in which:

Figure 1 is a perspective view of a transducer element embodying the features of the present invention;

Figure 2 is a view schematically representing a modified formof construction;

Figure 3 is a View diagrammatically representing the steps of my improved method for corn structing the core of the transducer; and

Figure 4 is a fragmentary view of an enlarged section of the core structure, showing the interrelation of the core elements.

Referring now to the drawings, there is shewn in Figure 1-, a radially expanding laminated core type transducer which embodies the features (if the present invention. The disclosed construction comprises a toroidal winding it placed on a cylindrical thin walled core H as schematically represented in Figure 2.

It is thought that the construction of the core will best be understood from the following description of one method I utilize for its fabrica= tion.

A ribbon l2 of magnetostrictive material, such as nickel, of desired edge width is wound edgewise around a mandrel I3, as shown in Figure-3. The ribbon is laid in the form of a helix, the turns of which are maintained in close relationship between an abutment surface l4 carried by an end member l5 and a movable collar member [6 which is spring pressed by an expansion spring ll against the ribbon as it is being wound on the mandrel. v

It will be apparent in Fig. 2 that the wall thickness of the core II will depend upon the edge width of the ribbon used. In practice, I have found that edge widths of E,- and A; inch are well suited for this purpose. In winding a core from a thin ribbon as described, it has been found desirable to anneal the ribbon prior to winding it on the mandrel in order to increase its ductility. As shown in Figure 3, the initial annealing is represented by the application of a flame as from a Bunsen burner [8, although it will be appreciated that any other suitable heating device may be utilized. Moreover, it is also preferable to re-anneal the ribbon after it is wound on the mandrel in order to relieve it of any stresses which may have been set up therein during the winding. This may be accomplished in any appropriate manner and, for purposes of illustration I have disclosed a heating element l9 within the mandrel, this element being connected to an appropriate electric supply source represented by conductors 20 and 2|. A switch 22 is shown for cont olling the heating element.

In order to consolidate the wound ribbon so as to form a core unit of stable construction, I have found it desirable to utilize a suitable consolidation material for insulating the turns relative to each other and bonding them together. Various compounds may be utilized for this purpose, such as resins, synthetic rubbers and the like. One such compound which has worked very satisfactorily is a material which is commonly utilized to bond rubber to metal, this material being commercially known as Cycleweld."

The consolidation material may be applied between the turns, while the wound core member is still on the mandrel. It is only necessary to release the pressure of the spring H, which will permit movement of the collar l6 away from the end of member l and a spreading apart of the coil turns sufiiciently to introduce the consolidation material therebetween. A preferable manner of applying the consolidation material, however, is to spray it onto the ribbon surface as from a nozzle 23, as diagrammatically illustrated, just prior to its being laid edgewise on the mandrel. If the consolidation material is of such composition as to require the application of heat to bond and form an insulation between the turns of the coiled ribbon, this heat may be applied by the heating element I9 within the man drel, as required.

As shown in detail in Figure 4, a cylindrical core structure prepared according to my method will efiect alternate convolutions 24 with the insulating and binding material as shown at 25 respectively disposed between the convolutions and binding them together into a stable core unit.

When the transducer element is to be operated at magnetic remanence, a continuous toroidal winding, as shown in Figure 1, is utilized. Where it is desired to polarize the transducer element, a polarizing magnet 26 may be placed loosely inside the core prior to placing the coil winding thereon, as shown in Figure 2. The magnet 28 extends diametrically across the core cylinder. In such case, the winding is separated into sections as indicated at Illa and Hlb and wound in opposite direction for producing relatively opposed polarities in the core.

The improved method of my invention permits the utilization of narrow width ribbons and the fabrication of a thin laminated core member having a broad frequency band; large savings in the metal constituting the core element; and the manufacture. of a core element as a separate article of manufacture susceptible of general use.

I claim:

1. A magnetostrictive transducer comprising a winding, and a hollow cylindrical core formed of a ribbon of magnetostrictive material wound edgewise in a helix, said ribbon having a thin edge Width, said core having a wall thickness approximately equal to the edge width of said ribbon, whereby the said transducer has a rela-- tively flat response over a wide frequency range.

2. A magnetostrictive transducer comprising a winding, and a hollow cylindrical core structure formed of a helically wound ribbon of magnetostrictive material having its turns insulated and bonded relative to each other, said ribbon having a thin edge width, said core having a wall thickness approximately equal to the edge width of said ribbon, whereby the said transducer has a relatively flat response over a wide frequency range.

3. A magnetostrictive transducer comprising a hollow cylindrical core formed of a helically wound ribbon of magnetostrictive material, a polarizing magnet disposed diametrically within the core, and a toroidal winding on said core, said winding having sections for relatively magnetizing said core in opposed directions, said cores having a wall thickness approximately equaly to the width of said ribbon. 4. As an article of manufacture, a magnetizable hollow cylindrical core structure including a cylinder formed of windings comprising a helically wound ribbon of magnetizable material laid edgewise, and means bonding and insulating the ribbon windings, said ribbon having a thin edge width, said core having a wall thickness approximately equal to the edge width of said ribbon, whereby said core structure is adapted for use in a transducer having a relatively flat response over a wide frequency range.

FREDERICK V. HUNT.

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

UNITED STATES PATENTS Gauthier Mar. 4, 1947