EXPANDABLE SONAR ARRAY

Abstract: An expandable sonar array structure (10) includes a central body (12) with a plurality of radially extendable hydrophone support arm assemblies (16) attached to said body and including a motor-driven drive member (20) to which all the arm assemblies are attached through pushrods (38, 40). Each arm assembly (16) includes three substantially vertically aligned, radially extending arms (22, 24, 26) carrying hydrophones (42) with top and bottom arms attached to the pushrods (38, 40) through short arms with pivots chosen so that the arms move in opposite directions.

Description: EXPANDABLE SONAR ARRAY This invention relates to an expandable sonar array structure which is designed to be placed in the water where it opens at a given depth to make a greatly expanded array for operation and which is then capable of being closed to a much smaller volume before being removed from the water. The expandable sonar array of the invention includes a body member, a drive member, motor means for driving the drive member, a plurality of radially extendable arms for carry hydrophones, and means for extending the arms and for folding the arms back adjacent the body member. In the course of attempting to increase the range of airborne sonar systems, one of the techniques which has been explored is that of making a larger array with a capability of operating at substantially lower frequencies. It is known that frequencies in the range of 1000 to 1200 Hz propagate through sea water much more effectively than frequencies in the order of 10 KHz. For effective reception of echo signals, such lower frequencies require a receiving array of considerable size—a size which is impractical to operate from a helicopter. One approach which has been explored is to employ a dipping sonar package which, after lowering into the water, is expanded during operation and then is retracted to a size suitable for handling by the suspending platform during ascent and stowage. The acoustic requirements dictate a receiving array of cylindrical shape providing a vertical arrangement of hydrophones spaced across a diameter defined by the operating frequency as is understood in the art. One such expandable array is disclosed in U.S. Patent No. 3,886,491 filed in the names of Loren M. Jonkey and Eugene Markus, issued May 27, 1975. AT that time it was considered important that the receiving hydrophones be kept together in vertical staves so that the folding parallelogram structure employed translated such vertical staves directly outwardly. This structure, while operable, was not considered sufficiently durable or reliable for the long term, and so efforts have been under way for a considerable time to devise an array structure which is more durable and more reliable. A somewhat similar array structure is shown in Scopatz U.S. Patent No. 3,566,346, issued February 23, 1971. The expandable sonar array of the invention is characterized in that it includes a motor in the body connected to a drive member to which all of the hydrophone arm assemblies are attached. Each arm assembly (normally there will be a large number such as sixteen) includes three foldable arms which open to form the horizontally extending members carrying vertically arranged hydrophones. The upper and lower arms have short lever arms at their inner ends driven by pushrods connected to the drive member such that they are positively driven open and closed. A link connected to the lower one of these arms constitutes part of a parallelogram linkage which extends a third arm. Pivotally attached to the end of the third arm is a fourth arm which is connected through a link to the end of the upper arm such that when the upper arm is driven to its extended position, the attached link carries the fourth arm to a horizontal position which is, in effect, an extension of the third arm. Thus the array is positively driven in both opening and closing directions and is maintained in position during the desired time by the drive mechanism. This is contrasted with the Jonkey et al device in which the array relied on buoyancy to open when the arms were released. Also, the array structure shown and described herein is believed to be substantially more rugged and dependable in operation than the earlier expanding arrays. The invention will now be described with reference to the accompanying drawings in which: Figure 1 is a perspective view, partly in phantom, of my transducer array as displayed. Figure 2 is a side view of one of the several individual expanding arm assemblies forming the array. Figure 3 is an end view of the assembly of Figure 2. Figure 4 is a motion diagram, somewhat simplified, showing positions of the individual arms of an assembly such as that shown in Figure 2 at successive positions during the opening or closing cycle. Referring now to Figure l, an array structure is shown generally at numeral 10 and includes a cylindrical housing body 12 suspended by means of a cable 14. Fastened to the outside surface of the cylindrical body 12 are a number (in this case, sixteen) of transducer arm assemblies 16. The housing body 12 contains, or may contain, power sources such as batteries, amplifier and receiving assemblies, and an array of projectors which are also displayed when the array 10 is placed in the water at a desired depth. The projector array forms no part of the present invention. Figure 2 is a side view of one of the several expanding arm assemblies 16 which carry the receiving hydrophones. Contained within housing body 12 is a motor assembly 18 which may be hydraulically or electrically powered and which responds to a control signal to move a drive member 20 upward to close the array or downward to open the array as indicated. Fastened to pivotal mounting means 21, 23 and 25 on the wall of housing body 12 are a first, or upper elongated arm 22, a second or lower elongated arm 24, and a third arm 26 respectively. At the outboard end of arm 26 and slightly offset therefrom is a pivotal mount 28 to which is attached a fourth arm 30 which, as shown with the array in its open position, extends in the same direction as arm 26. A link 32 is pivotally attached between mount 28 and also to a mount 34 near the center of arm 24. A second link 36 is pivotally attached to the ends of arms 22 and 30. Arm 22 includes at its inboard end a short lever arm 22a bent somewhat away from its main axis. Attached to the drive member 20 and to this short lever arm 22a is a pushrod 38. Arm 24 has a similar short lever arm 24a at its inboard end, but with the lever arm end attached to housing 12 and a pushrod 40 connected between drive member 20 and the pivotal connection at the outboard end of short lever arm 24a. As will be appreciated, the described connections between the pushrods 38 and 40 and the arms 22 and 24 result in arms 22 and 24 moving in opposite directions irrespective of whether drive member 20 moves up or down. As shown, the arm assembly 16 is in fully open position with drive member 20 in its down position and held thereby the motor 18. As drive member 20 is moved upwardly, pushrods 38 and 40 both move upwardly. This causes arm 22 to rotate around pivotal connection 21 moving its outboard end downwardly, arm 24 rotates around pivotal mount 23 which moves its outboard end upwardly, and as it so moves, lever 32 moves upward and carries arm 26 upward. Upward movement of link 32 and pivot 28 causes the left end of arm 30 to move up while its right end is carried downwardly with link 16. This movement continues until all arms and links are folded against the side of housing body 12. A series of hydrophones 42 are mounted on arms 22, 24, 26 and 30 as shown, with the hydrophones mounted in groups along vertical lines. Figure 3 is an end view of the assembly of Figure 2. This view shows the lateral displacement of the various arms, links and pushrods to permit the assembly to fold without interference. Figure 4 is a simplified motion diagram showing the relative positions of the various parts of arm assemblies 16 as the assembly is opened or closed. In this diagram, the solid line designates the fully expanded position as shown in Figure 2, and similar numbers are assigned to designate the various arms and links. The pushrods 38 and 40 are not shown, nor is the outboard end of elongated arm 24 which simply moves as an extension of the portion shown and which showing would unnecessarily confuse the diagram. As the assembly begins to fold, the parts assume the positions shown on the dash-dot lines with a single dot. Members 24, 26 and 32 move into a parallelogram arrange ent, arm 22 swings downwardly carrying link 36, and arm 30 begins to rotate around pivot 28 as pivot 28 moves A upward. Further movement brings the parts to the position shown in the dash-dot line with double dots. At this • 5 point, it will be noted that link 32 and arm 30 are almost folded side by side. A still further position is shown in the dashed lines where arms 22 and 24 are folded more than halfway. From this view, it is relatively easy to visualize the movement to the ultimate folded position. As 10 arm 26 moves to a vertical position, it carries pivot point 28 which establishes that arms 30 and link 32 will be essentially side-by-side with arm 26. Arm 24 will also be vertically oriented with its extension (not shown) adjacent link 32; arm 22 will swing down to a vertical position, and 15 as it does, link 36 and arm 30 will be carried to a parallel vertical position beside arm 22. Lever arms 22a and 24a and their pivots 21 and 23 are arranged to cause arms 22 and 24 to close somewhat outboard of the housing 12 to avoid interference with other members such as arm 26 and 20 link 32. A number of modifications may be made within the scope of the present invention. While Figure l shows sixteen arm assemblies 16, other numbers could be used, depending upon the resolution required. Sixteen arm assemblies provide a 25 good beam-forming arrangement with an effective lobe every 22-1/2 degrees. Twelve assemblies would provide less complicated structure at some cost in resolution. Further reductions would be at considerable cost in resolution, but more such arms could be used if the increased resolution 30 for a particular application could justify the increased cost and complexity. Single drive motor is shown driving a single drive member or plate 20. Applicant has also been involved in design and construction of an array in which separate motors and drive plates were used to drive the 35 upper and lower arms, with drive plates moving in opposite directions, the lever arrangements would be modified; e.g., pushrod 40 would be connected to the inside end of short lever arm 24a as in the case of arm 22 rather than outboard of its pivot 23. Or pushrod 40 is now shown connected to arm 24. Additional members of radially extending arms could be employed in each arm assembly following the teachings of the present invention, as will be readily apparent to those skilled in the art.

Claims: CLAIMS: 1. A three level cylindrical volumetric sonar array (10) , said sonar array (10) comprising a central vertically elongate body (12) having a height dimension; an upper (16) and an equal lower horizontal circular fan of elongate arms (22, 24) each of a lengt similar to said height dimension, each arm pivotally securing at a respective inner end to said body to dispose each fan of arms adjacent a respective end of said body; a middle horizontal circular fan of elongate arms (26, 30) of a length similar to said height dimension, each arm (22, 24, 26, and 30) pivotally securing to said body (12) at a respective inner end to dispose said middle fan of arms (26, 30) midway between said upper and said lower fans of arms (22, 24), each arm of said middle fan of arms being foldable upon itself intermediate its length; and kinematic linkage means (32,36, 38, 40) interconnecting drive means (20) with said upper, lower, and middle fans of arms to move the arms thereof between an unfolded position in which the arms fan out perpendicularly to said body and a stowed position in which the arms of the upper and lower fans of arms lay generally parallel along said body and the arms of said middle fan of arms fold upon themselves to next inwardly of said upper and lower arms; whereby the stowed height of said sonar array including both body and arms is no greater than its unfolded height. 2. The sonar array of claim 1 in which the arms (22, 24) of said upper and said lower fan of arms are vertically offset and in their stowed position are disposed in side- by-side interdigitation. 3. The sonar array of claim 1 in which the arms (26, 30) of said middle fan of arms each include an inner arm portion (26) pivotally securing to said body and an outer arm portion (30) pivotally securing at its inner end to an outer end of said inner arm portion (26) . 4. the sonar array of claim 3 in which said inner arm portion (26) and said outer arm portion (30) are offset vertically and in said stowed position are nested side-by- side inwardly of said upper and said lower arms. 5. The sonar array of claim 3 in which said kinematic linkage means (32, 36, 38, 40) includes a first link member (32) pivotally connecting at one end to said inner arm portion and pivotally connecting at its opposite end to an arm of one of said upper and lower fans of arms to form a parallelogram linkage therewith. 6. The sonar array of claim 5 in which said inner arm portion (26) , said first link member (32) , and said outer arm portion (30) are offset vertically and in said stowed position are nested side-by-side-by-side inwardly of said upper and said lower arms (22, 24). 7. The sonar array of claim 5 in which said kinematic linkage means (32, 36, 38, 40) includes a second link member (36) pivotally connected at one end to said outer arm portion (30) outwardly of the pivotal connection of the latter with said inner arm portion (26) , said second link member (36) at an opposite end pivotally connecting with an arm of one of said upper and lower fans of arms to in combination therewith and with said body, said inner arm portion, and said outer arm portions form a five-bar linkage (12, 26, 30, 36, 22). 8. the sonar array of claim 7 wherein said first link member (32) and said second link member (36) at respective opposite ends thereof pivotally connect to a separate one of said upper and lower fans of arms. 9. The sonar array of claim 1 in which said kinematic linkage means (32, 36, 38, 40) includes a respective linkage (38, 40) means connecting a drive member (20) movable relative said body with arms of said upper and lower fans of arms to move the latter pivotally between said unfolded and stowed positions. 10. The sonar array of claim 9 in which said drive member (20) moves vertically of said body, and said respective linkage means (38, 40) connects said drive member with arms of said respective upper and lower fans of arms at respective pivotal connection points located at one fan of arms inboard of and at the other fan of arms outboard of the pivotal connection of said arms with said body.

Inventors: SECRETAN STANLEY, SECRETAN, STANLEY
Applicants: ALLIED SIGNAL INC, ALLIED-SIGNAL INC.
Application year: 1992
Main classification: G10K11
IPC codes: G01S7, G10K11, H04R1