A multi-port projector of acoustic energy in water includes a cylindrical hollow transducer having open annular ends. A thin, flexible member is secured to each annular end to extend across each opening to be displaced by the transducer, and the transducer and flexible members form an interior sealed from ambient water. A battery/electronics module is in the interior and is spaced from the transducer and flexible members to couple driving signals to the transducer for reciprocally displacing it and the flexible members in response to the driving signals. An inert liquid fills the interior around the module, and an open truss on each annular end exposes the flexible members to the ambient water. Cylindrical portions coaxially extending with the transducer on a common longitudinal axis are connected to the open trusses for projecting acoustic energy of lower frequency than conventional cylindrical transducers of similar size.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates generally to active sonar countermeasures. More particularly, this invention relates to a cost effective, cylindrically shaped acoustic countermeasure that lowers transmitted frequencies by one half as compared to contemporary transducers of the same size.

(2) Description of the Prior Art

Acoustic countermeasures are an integral part of undersea offensive and defensive operations, and compact transducers are routinely used as expendable acoustic sources. The expendable sources can project acoustic energy over bandwidths that are predetermined or limited by the dimensions of a source's cylindrical-shaped housing. The current state of the art expendable acoustic source is only capable of projecting acoustic energy at a low end frequency level that is approximately two times higher than the desired or optimum low frequency for successful countermeasure operations.

The size of a source's housing and hence the lowest operating frequencies are constrained by the dimensions of the launch or deployment systems in the submerged or surface vessel. Larger acoustic countermeasures would be capable of lower frequency operation, but larger sound sources are incompatible with existing systems used to deploy expendable acoustic countermeasures.

Thus, in accordance with this inventive concept, a need has been recognized in the state of the art for an expendable cylindrical-shaped acoustic source that is capable of operating at one half the present lowest operating frequency of a contemporary source of similar dimensions.

SUMMARY OF THE INVENTION

The first object of the invention is to provide a multi-port underwater projector of acoustic energy.

Another object is to provide a multi-port projector that is capable of projecting acoustic energy at about one half the lowest frequency of a contemporary source of similar size.

Another object is to provide a multi-port projector that is capable of projecting acoustic energy at about one half the lowest frequency of a contemporary source of similar size.

Another object is to provide a multi-port acoustic energy projector compatible with existing allotted spaces in a countermeasure device and capable of projecting acoustic energy at one half the lowest frequency of a similar sized contemporary source.

Another object is to provide a multi-port projector of acoustic energy having thin flexible members, such as membranes or thin plates at opposite ends of a cylindrical transducer.

Another object is to provide an acoustic projector having flexible members at opposite ends of a cylindrical transducer to fit into an existing allotted space in a countermeasure device and project acoustic energy.

Another object is to provide a cylinder-shaped acoustic source having flexible membranes extending across a cylindrical transducer containing a power source/electronics in liquid-filled voids and spaces.

These and other objects of the invention will become more readily apparent from the ensuing specification when taken in conjunction with the appended claims.

Accordingly, the present invention is a multi-port projector of acoustic energy in water that includes a cylindrical hollow transducer having annular ends around an opening. A thin, flexible member is secured to each annular end to extend across each opening to be displaced by the transducer. The transducer and flexible members form an interior that is sealed from ambient water. The thin flexible members can be either thin, disc-shaped flexible membranes or thin disc-shaped plates. A battery/electronics module is in the interior and is spaced from the transducer and flexible members to couple driving signals to the transducer for reciprocally displacing it and the flexible members in response to the driving signals.

An inert liquid fills the interior around the module, and an open truss on each annular end exposes the flexible members to the ambient water. Cylindrical portions coaxially extending with the transducer on a common longitudinal axis are connected to the open trusses for projecting acoustic energy of a lower frequency than conventional cylindrical transducers of similar size.

The battery/electronics module includes a battery section and an electronics section to couple the driving signals to the transducer. The electronics section has a case containing electronic components, and the inert liquid fills voids around the components in the case. A duct extends from the battery section to the ambient water to flood the battery section thereby activating seawater batteries in the battery section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to theFIGS. 1 and 2there is illustrated a multi-port projector10of acoustic energy of the invention is included as a part of an elongate cylinder-shaped countermeasure device4. Countermeasure device4has a diameter of only a few inches allowing it to be fitted into an individual launch tube of a compact launcher system (not shown) for deployment into seawater9.

Multi-port projector10has a diameter of only a few inches and is substantially the same diameter as cylindrical-shaped portions7of countermeasures device4so that it can be securely fitted between cylindrical-shaped portions7. Cylindrical-shaped portions7coaxially extend in opposite directions from multi-port projector10in allotted space5along a common longitudinal axis6. Cylindrical-shaped portions7can have sensors/instrumentation, guidance/propulsion, electronics, and/or ordnance, etc. in rigid shells8on each portion7to perform other tactical functions of countermeasures device4.

Multi-port projector10is a cylindrical projector of acoustic energy having an elongate cylindrical hollow magnetostrictive, or piezoelectric transducer11. Transducer11can have a thin, strong metal or plastic shell13(for protection from abuses and watertight integrity) that is slightly separated from transducer11by a thin layer14of electrical insulation. Protective shell13could also be a watertight layer or coating of rugged, flexible insulation material bonded onto transducer11or insulation layer14that will withstand the rigors of handling and deployment yet will flex as transducer11is displaced. Shell13seals out or is impervious to ambient water9over expected depths of operation. Transducer11with shell13can be considered the hull portion of multi-port projector10of countermeasures device4. Transducer11(and shell13) can be connected at its opposite annular ends12(and end13A of shell13) to an open truss15of rigid members15A that extend through portions9A of ambient seawater9. Each truss15is also secured at its opposite end to one end8A of rigid shells8of cylindrical portions7. Trusses15can sandwich circumferential annular strips of flexible members16between them and annular ends12& ends13A of shell13.

Cylindrical hollow magnetostrictive transducer11can be any of many well know designs that can have stacked ring-shaped magnetostrictive portions interleaved with serial or parallel connected electrodes. The exact construction and interconnection need not be further elaborated on or shown to avoid unnecessary detail concerning what is of general knowledge in the art. For purposes of demonstration of this inventive concept, however, a single electrode12A at opposite ends of transducer11is shown to be suitably attached and interconnected to create and impart responsive longitudinal reciprocal displacements thereof along the longitudinal axis6of countermeasures device4in accordance with or in response to applied driving signals (shown as arrows24A). Optionally, transducer11could be polarized to impart responsive reciprocal radial displacements if desired.

A very thin and flexible disc-shaped member16such as a thin membrane or thin disc-shaped plate is disposed on each annular opposite end12of transducer11to radially inwardly extend across it. Flexible members16are connected or secured to annular ends12of transducer11in a sealed relationship and can be connected directly to annular opposite ends12and protective shell13by a wide variety of well known means, such as for example, by a commercially available heavy duty epoxy-like bonding agent. Flexible members16are thin with respect to the wavelengths of interest, which in this case are the projected low-frequency signals. Since thin flexible members16will flex so freely, to the cylindrical multi-port projector10it appears as if there are no end plates. Consequently, this construct creates multiple ports for multi-port projector10, and the cylinder-shaped structure of transducer11of multi-port projector10with cylindrical-shaped portions7becomes, or is the hull of, countermeasure device4. Transducer11(and shell13) can be connected at its opposite annular ends12(and end13A of shell13) to an open truss15of rigid members15A that extend through portions9A of ambient seawater9. Each truss15is also secured at its opposite end to one end8A of rigid shells8of cylindrical portions7. Trusses15can sandwich circumferential annular strips of flexible members16between them and annular ends12& ends13A of shell13.

A battery/electronics module20can be held in a position spaced away inwardly from transducer11and thin end plates12by resilient members21inside of hollow transducer11. Being so resilient, or compliant, resilient members21do not overly restrict or compromise the reciprocal excursions of transducer11as low-frequency acoustic signals are created and transmitted from multi-port projector10of countermeasures device4. A battery section22of battery/electronics module20provides sufficient electrical power for an interconnected electronics section24of battery/electronics module20to enable electronics section24to generate predetermined driving signals24A for transducer11.

Multi-port projector10has an interior17that is enclosed by transducer11and thin end plates16and contains battery/electronics module20. The part of interior17that is not filled by battery/electronics module20is filled completely with an inert liquid18such as a high-purity isoparaffinic solvent with a narrow boiling range. In the preferred embodiment, inert liquid18would be the trademarked solvent. ISOPAR produced by Exxon Mobil Corporation 3625 Gallow Road, Fairfax, Va. 22037. Because the volume of interior17that is outside of battery/electronics module20is filled completely with inert liquid18, a lower-frequency projection of acoustic energy is created.

The inside of a case25containing electronic components26of electronics section24of battery/electronics module20may have small air-filled spaces or voids27around components26. Inert liquid18is used to fill spaces27to further improve performance of multi-port projector10. Since battery section22is most likely to be a seawater battery, some of the ambient seawater (shown as arrows9B) can flow into the seawater battery of battery section22through a pair of sealed resilient ducts23extending through transducer11or other convenient transition points while multi-port projector10sinks in water9. Ducts23allow flooding and filling of battery section22with some of ambient seawater9for ensuing activation of battery section22. Battery section22could also be a sealed structure and does not need to be flooded or activated with a part of ambient seawater9; however, such a structure may be more susceptible to the problems associated with overheating than a seawater battery.

Electronics section24has leads25coupled to connect driving signals24A to annular electrodes12A at opposite annular ends of transducer11and create responsive reciprocating displacements of transducer11and impart responsive reciprocating displacements of thin flexible members16. The reciprocating displacements of transducer11transmit representative acoustic signals at opposite ends of multi-port projector10via thin, flexible members16that radiate to open water9through portions9A of water9in both open trusses15. The reciprocating displacements of transducer11also transmit the same representative acoustic signals at opposite ends of multi-port projector10through the rigid members15A of both trusses15to both rigid shells8of cylindrical portions7that radiate into open water9. In other words, the entire hull of the countermeasure device4that includes multi-port projector10connected by trusses15to cylindrical portions7will become a large multi-port transducer that will operate at much lower frequency than a conventional cylindrical transducer of the same size.

Multi-port projector10of the invention projects acoustic energy at about one half the lowest frequency of a comparably dimensioned contemporary transducer partially because it is liquid-backed. That is, multi-port projector10is filled with inert liquid18in interior17around battery/electronics module20, is filled with inert liquid18around components26in case25of electronics section24, and substantially filled with seawater in its battery section22. This also provides the added operational advantage of heat dissipation. Furthermore, 1.) making transducer11and battery section22essentially the same length as multi-port projector10, 2.) having liquid18filling the surrounding battery/electronics module20directly against the inside of transducer11, and 3.) having transducer11covered or capped by thin flexible members16exposed to seawater9via open trusses15at opposite ends, assures excitation of countermeasure device4and projection of acoustic energy at the lower frequencies desired.

It is understood that multi-port projector10could be made in accordance with this invention in different sizes in different acoustic systems for many different purposes where lower frequency operation is needed. Other transducers such D.C. linear motors could be used instead of magnetostrictive elements and different arrangements of batteries and electronics could be used without departing from the scope of this invention herein described. Having this disclosure in mind, selection of suitable components from among many proven contemporary designs and compactly interfacing them as disclosed herein can be readily done without requiring anything beyond ordinary skill.

The components and their arrangements as disclosed herein all contribute to the novel features of this invention. Multi-port projector10of this invention provides a reliable and cost-effective means to improve the low-frequency response of countermeasures. Therefore, multi-port projector10as disclosed herein is not to be construed as limiting, but rather, is intended to be demonstrative of this inventive concept.