Serpentine buoyant cable antenna

The present invention relates to an improved buoyant cable antenna system. The system includes a buoyant cable transmission line segment and an antenna segment formed from a flexible memory structure comprised of at least one segment of coiled compression, pinched to form a desired shape and encapsulated in a buoyant encapsulant material. The antenna segment may include a U-shaped keel portion, a horizontal serpentine shaped section, and a vertical element with the horizontal serpentine shaped section floating on the surface of the water and the vertical element extending above the surface of the water. A process for manufacturing the buoyant cable antenna system is also described.

CROSS REFERENCE TO RELATED PATENT APPLICATION

The instant application is related to three co-pending U.S. Patent Applications entitled BUOYANT CABLE ANTENNA SYSTEM AND METHOD WITH ARTIULATING BLOCKS (Navy Case No. 80224), BUOYANT CABLE ANTENNA CONFIGURATION AND SYSTEM (Navy Case No. 80225), BUOYANT CABLE ANTENNA SYSTEM (Navy Case No. 8.0227) having the same filing date.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to an improved buoyant cable antenna for marine applications and a process of manufacturing same.

(2) Description of the Prior Art

Buoyant cable arrangements have been used in a number of marine applications. For example, buoyant cables have been used in the seismic surveying of underwater geological formations. U.S. Pat. Nos. 2,570,707 to Parr and 2,638,176 to Doolittle illustrate two such buoyant cable arrangements. In the Parr system, the cable is constructed and arranged to float one the water surface, either by virtue of its own buoyancy or by the use of buoyant devices secured thereto. The cable, in a preferred embodiment, was a metal cable, such as a stainless steel cable, to which were secured cork floats. In Doolittle, the cable is supported by a plurality of floats.

U.S. Pat. No. 3,287,691 to Savit illustrates a deployed hydrophone cable. The cable comprises a plurality of hydrophones connected to the cable in spaced relationship along its length and floatable cable covering segments having a positive buoyancy encasing the cable between the hydrophones. The hydrophone cable itself comprises a conventional multi-conductor insulated cable.

Buoyant cable antenna systems are known in the prior art.FIG. 1illustrates one such buoyant cable antenna system10which is deployed from a submerged vehicle12. The system10includes a buoyant cable transmission line14, to which is connected in sequence a loop amplifier16, an athwart loop antenna18, a wire amplifier20, and a horizontal antenna element22.

On-going buoyant cable antenna research requires the use of a flexible buoyant material, that when deployed by a marine vehicle, such as a submerged vehicle, realizes a designed shape.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide an improved buoyant cable antenna system.

It is a further object of the present invention to provide a buoyant cable antenna system as above utilizing a serpentine shape and a keel portion.

It is yet a further object of the present invention to provide a process for manufacturing a buoyant cable antenna system.

The foregoing objects are attained by the buoyant cable antenna system of the present invention.

In accordance with the present invention, a buoyant cable antenna system is provided. The buoyant cable antenna system broadly comprises a buoyant cable transmission line segment and an antenna segment formed from a flexible memory structure of coil compression spring encapsulated in a buoyant molding material attached to an end of the buoyant cable transmission line segment. The flexible memory material forming the antenna segment is capable of assuming a designed shape and recover after being straightened and flexed.

The buoyant cable antenna system may be manufactured using a process comprising the steps of creating an antenna segment by providing at least one compression spring having a plurality of coils, pinching the coils of the at least one compression spring to impart a desired shape to the at least one compression spring, and encapsulating the at least one compression spring within a buoyant flexible encapsulation material. The process further comprises joining the antenna segment to a buoyant cable transmission line segment.

Other details of the buoyant cable antenna system of the present invention and the process for manufacturing same, as well as other objects and advantages attendant thereto, are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now toFIGS. 2-4, a buoyant cable antenna system50in accordance with the present invention may be deployed from a submerged marine vehicle52. The buoyant cable antenna system50includes a buoyant cable transmission line segment54and an antenna segment56attached to an end of the buoyant cable transmission line segment54by a joint55. The buoyant cable transmission line segment54may comprise any suitable buoyant cable transmission line known in the art.

The antenna segment56may have a variety of sections having different shapes, preferably all formed from a flexible memory material. For example, the antenna segment56may include a U-shaped keel portion58to counterbalance vertical element62. Following the keel portion58, the antenna segment56may include a horizontal serpentine shaped section60. The section60, in a preferred embodiment, floats on the water surface. Still further, the antenna segment56may include a vertical element62. Element62is a fractional wavelength rigid linear conductor63suitably moisture proofed by a casing. A conventional microwave coaxial transmission line (not shown) extends through the one or more helical springs and the linear conductor element is suitably connected by a coupling arrangement (not shown) with the transmission line.

In a preferred embodiment of the present invention, the joint55, the keel portion58, the horizontal serpentine shaped section60, and the curved portion of vertical antenna element62are each formed from an encapsulated compression helical spring coil structure. Any suitable technique known in the art may be used to form the portion58, the section60, and the vertical element62from a suitable flexible memory material. The serpentine section60, which includes buoyant encapsulant, imparts forces maintaining section62vertical.

In a preferred technique, each of the aforementioned antenna sections (except segment62which is rigid linear antenna elements) is formed from one or more compression springs70. When a coil of a compression spring70is pinched into a curved shape with a consecutive coil in a given area, the compression spring70will start to assume a curved shape. By pinching a plurality of coils along the length of the compression spring70, the compression spring70will assume a particular curved shape. Thus, a compression spring70can be pinched to form the shape of the U-shaped keel portion58. If desired, a separate compression spring or the same compression spring could be pinched to form the horizontal serpentine shaped portion60. Further, the coupling at the lower end of vertical element62can be formed from the same compression spring or yet another compression spring permitting bending for storage in linear relation thereto. Once the compression spring or springs70have been shaped, it is or they are laid in a mold72. The mold72is then filled with an encapsulating material74that encapsulates the spring(s)70and retains the desired spring shape. One suitable material which provides buoyancy is the microballoon loaded polymer disclosed in U.S. Pat. No. 5,606,329 entitled “Buoyant Cable Antenna”, hereby incorporated by reference in its entirety. The result is a flexible construction which has a shape memory so that it returns to the encapsulated shape even after being straightened and/or flexed. The encapsulating material74, in addition to insuring that the desired shape will be retained, provides increased mechanical rigidity to the encapsulated spring70. Springs of any spring constant can be used to provide an end desired material spring constant. After the antenna segment56is formed, it may be joined in any suitable manner to the buoyant cable transmission line54using any suitable means known in the art such as joint55.

By providing an antenna segment56having a vertical element62which extends above the water surface, one can extend the frequency range of the antenna.

While the antenna system of the present invention has been illustrated as being deployed from a submerged vehicle52, such a submarine, it may be deployed from any suitable marine vehicle.

It is apparent that there has been provided in accordance with the present invention a serpentine buoyant cable antenna which fully satisfies the objects, means and advantages set forth hereinbefore. While the present invention has been described in the context of specific embodiments thereof, other alternatives, modifications, and variations will become apparent to those skilled in the art having read the foregoing description. Therefore, it is intended to embrace those alternatives, modifications, and variations which fall within the broad scope of the appended claims.