US 3246287 A
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Description (OCR text may contain errors)
April 12,A 1966 H. F. BENSON 3,246,287
PIEZOELECTRIG TRANSFORMER Filed Sept. 21, 1965 ,mrs/w06.
United States Patent O 3,246,287 v PIEZOELECTRIC TEANSFORMER Howard F. Benson, Pomona, Caiif., assigner to General Dynamics Corporation, Pomona, Calif., a corporation of Delaware Filed Sept. 21, 1965, Ser. No. 488,979 Claims. (Cl. 349-10) This invention relates to piezoelectric apparatus and more particularly to a piezoelectric pickotf transformer which permits operation in ionizable solutes such as seawater. f y
Piezoelectric devices have been utilized in various types of underwater signaling systems and the operation principle thereof is well known in that they function to convert electric oscillations into elastic waves or vice versa.
The present invention provides a transformer which operates on this known principle and can Ibe effectively utilized in amplifying a signal produced from acous-tic waves in a solute such as sea-Water.
Therefore, it is an object of this invention to provide a transducer.
A further object of the invention is to provide a transformer which cooperates with a device which operates on ythe piezoelectric principle.
Another object of lthe invention is to provide a transformer-like pickup device for a piezoelectric element Whi-ch Iwill permit operating the device in ionizable solutes lsuch. as sea-water.
Another object of the invention is to prov-ide a transformer which requires no moisture sealing.
Other objects of the invention will become readily apparent from the yfollowing description and accompanying drawings wherein:
FIG. 1 is a partially 4exploded View illustrating components of the invention;
FIG. 2 is an enlarged cross-sectional view of the FIG. 1 components operatively connected to a load; and
FIG. 3 is a partial front view of the FIG. 2 device with portions cut away for clarity.
Broadly, the present invention relates to a piezoelectric transducer element adapted for use in seadwater or like ionizable solute environs. The transducer essentially comprises a piezoelectric disc having its two chargecollecting faces electrically insulated from each other, the thus insulated disc being mounted lin the center opening of a flattened toroidal pickoif coil. Upon immersion in an ionizable solute and upon subjecting the disc to external pressure, the disc acts as a battery w-ith the enveloping ionizable medium functioning like a single turn primary coil to provide a transformer-type operation in conjunction with the toroidal coil, which serves as the secondary.
Referring now to the drawings, the transformer of the present invention is composed of a piezoelectric crystal or disc 10, a flattened toroidal core 11 of magnetic material and rectangular cross-section, a coating of insulating material 12 on core 11, a lflattened toroidal coil or winding v1.3 positioned around the insulated core, and output leads "14 connected to coil 13. A resistive load R1 is shown connected to the output leads 14 for purposes of operational description. If desired, the faces or sides of the disc may be silvered almost to the periphery to speed up the collection of the current producing electrical charges between the disc faces.
While not shown, a spacing or mounting device is provided for maintaining the disc 10 centered within the toroidal winding 13 which functions for maintaining a solute-gap '15 (see FIGS. 2 and 3) between t-he disc 10 and the winding 13. The disc mounting device may be a snap-in spider type housing holding the outer edge of lthe disc still while permitting the center of the dis-c to bow in and `out under pressure of the impinging acoustic waves. Also, a center-mounting post may be used for holding the center of `the disc still while permitting the outer edge to bow to and fro, past the mounted center. The type of mounting device for disc y10 w-ill thus be dependent on which portion of the disc is to be maintained lxed and which portion is desired to be moved by the 1mp1ng-1ng waves.
In operation, with the components assembled as shown in IFIGS. 2 and 3 and submerged in an ionizable solute such as sea-Water, an impinging acoustic wave, arriving through the solute surrounding the dev-ice, mechanically bows the disc 10, either at its edge relative to its fixed center, or at its center relative to its fixed edge, depending on the type of mounting means `f-or disc 1l) as described above. Because the disc 10 is of piezoelectric material, it generates a charge between the faces of the disc when the disc is warped mechanically. This charge generated between the faces of disc 10 sets up an electrical current ibetween t-he faces, since the device is bathed in the solute, and the solute-gap 15 does not prevent such a current. The path of the current will be from the elec- -tr-ical center of one face of the disc 1t), around the edge of the disc, and to the electrical center of the other face of the disc. This current ow will make the conducting solute look, electrically, like a single turn transformer primary winding of low impedance. Since the current must go through the solute-gap 15, since it cannot go through the high-dielectric `disc 10, nor through the insulated magnetic toroidal core 11, it is forced to travel across the edge of the disc in a direction parallel tothe toroidal coil windings 13. The current thus first travels radially from the center of one face of the disc '10 to the edge of disc, then axially across the edge of the disc cutting the turns of the winding 13, then radially toward center of the second face of the piezoelectric disc =10.
In performing this migration, the current induces a current flow in the transformer secondary (the toroidal Winding 13). The toroidal core `11 functions in conventional manner to increase the inductance of the secondary of the transformer. This current is brought out via output leads I14 to a point of use such as load R1.
It is apparent that, ignoring the lossy primary (the solute) and some mechanically limited electrical phase lag, due to slower conduction of current within the solute, Ithe usual ratios of ampere-turns in the primary versus ampere-turns in the secondary Will apply, as 'in any normal transformer, thus permitting the number of turns in the secondary toroidal winding to establish the determined output voltage.
It may be desirable to mask the outside of the toroidal structure with an insulating baffle in the same plane as the disc in order to prevent any bucking current from flowing around the outside of the assembly.
It has thus been shown that this invention provides a novel piezoelectric transformer which function -is caused by impinging acoustic waves in an ionizable solute, therelby advancing the applications of the piezoelectric art.
Although a particular embodiment of the invention has 'been illustrated and described, modifications and changes will become apparent to those skilled in the art, and it Iis intended to cover in the appended claims all such modiications and changes as come Iwithin the true spirit and scope of the invention.
What I claim is:
1. A piezoelectric transducer adapted for use in seawater and like ionizable solutes comprising: a piezoelectric disc having two charge-collecting faces electrically insulated from each other, said disc being positioned in the center opening of a flattened toroidal pickofl coil, said toroidal pickoff coil surrounding a toroidal magnetic core, said core being provided with a coating of insulating material, and output leads operatively connected to said coil, whereby upon immersion of the transducer in an ionizable solute and upon subjecting said disc to external pressure, the disc generates an electrical charge and the enveloping ionizable medium functions like a single turn primary coil to provide a transformer-type operation in Vconjunction with the toroidal coil which functions as the secondary.
2. A transformer comprising: a piezeoelectric disc, a toroidal magnetic core having an insulating coating thereon, a toroidal coil positioned around said core, said disc being ypositioned within the central opening of and spaced from said core and said coil, and output leads connected to said coil and adapted to be connected to a point of use.
3. The transformer defined in claim 2, wherein said piezoelectric disc comprises a pair of face surfaces and a layer of dielectric material disposed intermediate said No references cited.
MILTGN O. I-HRSHFIELD, Primary Examiner.
A. I. ROSSI, Assistant Examiner.