Abstract:
In the case of an electroacoustic underwater antenna, which has a reflector ( 11 ) and spring elements which fix the reflector ( 11 ) on an antenna mount ( 10 ), in particular on the hull of a submarine, in order to produce an underwater antenna which can be produced at low cost from only a small number of components, and in which the reflector ( 11 ) to which electroacoustic transducers are fitted is at an adequate distance from the antenna mount ( 10 ), is acoustically well decoupled from the antenna mount ( 10 ) and is largely resistant to shock loading, the spring elements have an upper and a lower resilient rocker ( 19, 20 ), wherein each rocker ( 19, 20 ) extends over the horizontal extent of the reflector ( 11 ) in the fitted position. Each rocker ( 19, 20 ) has a rear contact limb ( 192, 202 ), for making contact with and fixing on the antenna mount ( 10 ), and a front contact limb ( 191, 201 ), for making contact with and fixing on the reflector ( 11 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the priority of German Patent Application No. 10 2009 018 624.7, filed Apr. 23, 2009, the subject matter of which, in its entirety, is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to an electroacoustic underwater antenna having a reflector and having spring elements which fix the reflector on an antenna mount, in particular on a hull of a submarine, and act on the reflector close to its upper and lower longitudinal edges in the fitted position of the reflector. 
         [0003]    A known linear underwater antenna (DE 38 34 669 A1) which is arranged on a hull of a submarine and is referred to as a flank array has a transducer arrangement, which is arranged at a distance from the hull and has a multiplicity of hydrophones which are at a distance from one another and are arranged horizontally in a row one behind the other along the hull when the underwater antenna is in the fitted position, and an insulating panel to provide a screening effect against sound emitted from the hull, which insulating panel is arranged behind the hydrophones in the sound incidence direction, is designed on the basis of the spring-and-mass principle and acts as poor sound reflector in the lower frequency range. The hydrophones are held on the insulating panel via a shell structure, and the insulating panel is attached by means of spring elements to a damping layer which absorbs bending waves and is connected to the hull. The transducer arrangement is mechanically protected by an envelope body which is attached to the hull. By having a streamlined design, the envelope body at the same time offers protection against flow noise. The acoustic characteristic impedance of the envelope body is approximately equal to that of the surrounding water, as a result of which the acoustic attenuation of sound passing through it and the reflection factor of the envelope body for incident sound waves are low. If the envelope body is in the form of a layer composite, as is known from DE 36 42 747 C2, this also prevents the emission of interference sound, which is caused by bending waves resulting from structure-borne sound and turbulence, from the envelope body to the transducer arrangement. 
         [0004]    The invention is based on the object of designing a low-cost underwater antenna having only a small number of individual components, in particular for fitting to the hull of a submarine, in which the reflector to which the electronic transducer arrangement is fitted is at an adequate distance from the antenna mount, that is to say from the hull, is acoustically well decoupled from the hull and is largely resistant to shock loading. 
       SUMMARY OF THE INVENTION 
       [0005]    The above object generally is achieved according to the present invention by an electroacoustic underwater antenna having a reflector and having spring elements which fix the reflector on an antenna mount, in particular on a hull of a submarine, and act on the reflector close to its upper and lower longitudinal edges in the fitted position of the reflector. The spring elements have an upper and a lower resilient rocker, and each rocker extends over the horizontal extent of the reflector in the fitted position and has a front contact limb, for making contact with and fixing on the reflector, and a rear contact limb, for making contact with and fixing on the antenna mount. 
         [0006]    The electroacoustic underwater antenna according to the invention has the advantage that the two rockers, which each extend over the entire length of the reflector, result in a long distance to the reflector and good acoustic decoupling of the reflector from the antenna mount. The required spring constant of the rockers can easily be achieved by shape and material thickness. The impact energy of shockwaves striking the reflector is transmitted, distributed over an area via the rockers, to the antenna mount, as a result of which the antenna design is shock-proof. Because of the different designs of both rockers, the reflector is allowed to be aligned vertically on the hull of the submarine, with the antenna structure being sufficiently shock-resistant. 
         [0007]    Expedient embodiments of the underwater antenna according to the invention, together with advantageous developments and refinements of the invention, are specified in the further claims. 
         [0008]    According to one advantageous embodiment of the invention, the rockers are arranged such that the U-openings in the two rockers point away from one another. With this structural arrangement of the rockers, a more compact underwater antenna with smaller dimensions in the vertical direction is provided while the dimensions of the reflector are kept constant. Thus a normally intended envelope body can be designed with significantly smaller dimensions. 
         [0009]    According to one advantageous embodiment of the invention, the intermediate space between the upper and lower rockers is filled by a buoyant body which on the one hand extends as far as the antenna mount and on the other hand ends at a distance in front of the reflector. If the buoyant body, which is preferably composed of a hard-foam core surrounded by an encapsulation compound, is appropriately designed, the underwater antenna is held in a largely neutrally buoyant manner under water. In addition, a certain amount of stiffening can be produced between the rockers, therefore affecting their spring characteristic, by the buoyant body being linked to the rear part of the two rockers. 
         [0010]    According to one advantageous embodiment of the invention, the two rockers rest with their rear contact limbs on the antenna mount with the interposition of an elastic layer, which is preferably composed of rubber cork, and, with at least two elongated holes which are provided in each rear contact limb, each clasp a cylindrical carrier which projects from the antenna mount. A threaded bolt which is firmly clamped on the antenna mount with a force fit by the rear contact limbs is screwed into each carrier. Lateral-force discs which are composed of glass-fibre-reinforced plastic and are placed largely without any play on the carriers are arranged between the bolt heads of the threaded bolts and the contact limbs. This physical fixing of the rockers to the antenna mount compensates for tolerances in the distance between the carriers which are used for attachment of a rocker, therefore making it easier to fit the rockers. Acoustic decoupling of the rockers from the antenna mount is improved in that an elastic disc, which is preferably composed of rubber cork, is also inserted between the lateral-force disc and a metallic conical spring washer which is pressed onto the lateral-force disc by the bolt head. 
         [0011]    According to one advantageous embodiment of the invention, the reflector is fixed on the front contact limbs of the upper and lower rockers by means of plastic studs which are screwed to the contact limbs and are preferably composed of polyamide, and the reflector is firmly clamped resiliently to the plastic studs. Each plastic stud has a rear stud section, which rests on the front contact limb, and a front stud section, which is concentrically adjacent thereto and has a larger external diameter than the rear stud section. A threaded blind hole is introduced into each stud section from its end surface, wherein a screw, which passes through the front contact limb of the rocker, is screwed into the threaded blind hole in the rear stud section, and a screw which passes through a conical spring washer, which rests on the reflector, is screwed into the threaded blind hole in the front stud section. Since two separate threaded blind holes, which are introduced into the plastic studs, are provided and a continuous threaded hole has been dispensed with, the plastic stud is considerably more robust against lateral and shear forces. 
         [0012]    According to one advantageous embodiment of the invention, an acoustically transparent envelope body is placed in front of the reflector, on its front face facing away from the antenna mount, and the envelope body is fixed to the upper and lower rockers. The envelope body is in this case preferably fixed via studs which are arranged on the rockers and to which the envelope body is clipped in an interlocking manner by a respective recess. A screw is screwed into the studs, and braces the envelope body on the rocker. In this case, each recess in the envelope body preferably has an associated coaxial cutout with a larger unobstructed diameter, and a clamping screw, which clasps the envelope body, is inserted into each cutout, through which the screw shank of the screw is passed. An elastic disc, which is pushed onto the studs and is preferably composed of rubber cork, ensures a certain amount of acoustic decoupling between the envelope body and the respective rocker. 
         [0013]    The invention will be described in more detail in the following text with reference to exemplary embodiments which are illustrated in the drawing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  shows a section through an electroacoustic underwater antenna mounted on an antenna mount. 
           [0015]      FIG. 2  shows a perspective view of the underwater antenna, removed from the antenna mount, in  FIG. 1  with the envelope body and reflector removed. 
           [0016]      FIG. 3  shows an enlarged section illustration of the detail III in  FIG. 1 . 
           [0017]      FIG. 4  shows an enlarged detail illustration of the detail IV in  FIG. 1 , partially sectioned. 
           [0018]      FIG. 5  shows a detail V in  FIG. 1  of an underwater antenna that has been modified in this area. 
           [0019]      FIG. 6  shows an enlarged detail illustration of the detail VI in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    The electroacoustic underwater antenna which is illustrated schematically in the form of a cross section in  FIG. 1  is attached to an antenna mount  11 , for example to the hull of a submarine. For production and fitting reasons, the underwater antenna has a horizontal length l ( FIG. 2 ) which is restricted in the fitted position and, for example, is between one and two metres. A plurality of such underwater antennas, which are illustrated in the form of a cross section in  FIG. 1 , are arranged horizontally without any gaps in order to produce a flank antenna as is normally arranged on the port and starboard sides of a submarine. 
         [0021]    The underwater antenna has a reflector  11  which is fixed in an acoustically decoupled manner to the antenna mount  10  via spring elements. The reflector  11  is in the form of a spring-and-mass system, in a known manner, and for example has a soft material panel  12  as a spring and a lead panel  13  as a mass, in conjunction with a composite placed in front of it in the sound incidence direction, composed of two thin aluminium panels  14 ,  15  with a layer  16  composed, for example, of rubber which is located in between and damps bending waves. A transducer arrangement  17  comprising a multiplicity of electroacoustic transducers, preferably hydrophones, is mounted in a known manner on the front face of the reflector  11 , facing away from the antenna mount  10 . In this case, a plurality of transducers, which are arranged vertically one beneath the other and are formed, for example, by small ceramic spheres are combined by embedding them in an acoustically transparent encapsulation compound to form a transducer stave  18 . A plurality of staves  18  are arranged alongside one another, with a distance between them, over the length l of the underwater antenna. All the staves  18  are attached at the top and bottom to the reflector  11 , although this is not illustrated separately in  FIG. 1 . 
         [0022]    The reflector  11  is arranged a relatively long distance away from the antenna mount  10  by means of the spring elements, in order to reduce the structure-borne sound emitted from the antenna mount  10 . In order to improve the resistance of the reflector attachment to shockwaves, the spring elements for this purpose have an upper resilient rocker  19  and a lower resilient rocker  20 . The two rockers  19 ,  20  are produced from glass-fibre-reinforced plastic and have a shape and material thickness that produce the required spring constant. Each rocker  19 ,  20  has a horizontal length l ( FIG. 2 ) in the fitted position which corresponds to the size of the reflector  11  in the horizontal direction. Each rocker  19 ,  20  has a front contact limb  191  and  201 , respectively, for making contact with and fixing on the reflector  11 , and a rear contact limb  192  and  202 , respectively, for making contact with and fixing on the antenna mount  10 . In this case, the upper rocker  19  has an approximately U-shaped profile, and the lower rocker  20  has a profile which is formed from two U-shaped end sections, which respectively contain the front and rear contact limbs  201  and  202 , and an extended centre section  203 , which connects them integrally. The two rockers  19 ,  20  are in this case arranged such that the U-openings in the two rockers  19 ,  20  point away from one another. The intermediate space between the upper rocker  19  and the lower rocker  20  is filled by a buoyant body  21  which on the one hand extends as far as the antenna amount  10  and on the other hand ends at a distance in front of the reflector  11 . The buoyant body  21  rests on the antenna mount  10  with the interposition of an elastic film  22 , for example composed of rubber cork. The distance between the buoyant body  21  and the reflector  11  is defined such that the base of the end section (which contains the front contact limbs  191  and  201 ) of the upper rocker  19  and of the lower rocker  20  is released from the buoyant body  21 . The buoyant body  21 , which is designed such that the weight of the underwater antenna is largely compensated for by the buoyancy produced by this body in the water, has a hard-foam core surrounded by a water-resistant encapsulation compound. 
         [0023]    For each rocker  19 ,  20 , the rocker  19 ,  20  is attached to the antenna mount  10  at at least two attachment points of the rear contact limbs  192  and  202 .  FIG. 3  shows an enlarged section view of the attachment points. The antennas mount  10  has so-called carriers  23 , which are arranged at a distance from one another in the horizontal direction. Two rows of carriers  23  are in each case located vertically one above the other on the antenna mount  10 . The expression carriers  23  means preferably cylindrical attachment stubs which project from the antenna mount  10 , that is to say from the hull of the submarine and are each provided with a threaded hole  231 . Each rear contact limb  192  or  202  of the upper rocker  19  and of the lower rocker  20 , respectively contains at least two elongated holes  24  ( FIG. 2 ), which are arranged at the same distance from one another as the carriers  23 . In order to attach the rockers  19  and  20 , the respective rear contact limb  192  or  202  is pushed with each of the elongated holes  24  over in each case one of the carriers  23 , with an elastic layer  25 , preferably composed of rubber cork, having previously been placed onto the antenna mount  10  around the carriers  23 , on which layer the respective rear contact limbs  192  and  202  are supported in order to achieve a certain acoustic decoupling. The elongated holes  24  make it possible to compensate for distance tolerances between the carriers  23  on the antenna mount  10  on the one hand and the elongated holes  24  in the rockers  19 ,  20  on the other hand. A lateral-force disc  26  is then pushed radially, largely without any play, onto each carrier  23 . An elastic disc  27 , preferably composed of rubber cork, is placed onto each lateral-force disc  26 , and a conical spring washer  28  composed of metal, preferably a steel washer, is pressed onto the elastic disc  27  by screwing a threaded bolt  29  into the threaded hole  231  in the carriers  23  until the conical spring washer  28  rests on the end surface of the carrier  23 . Each rear contact limb  192  or  202  of the respective rockers  19 ,  20  is therefore attached to the antenna mount  10  with a force fit and in an acoustically decoupled manner. 
         [0024]    The reflector  11  is fixed to the respective front contact limbs  191  and  201  of the upper rocker  19  and of the lower rocker  20  by means of plastic studs  30  which are screwed to the front contact limbs  191  and  201 . The attachment of the reflector  11  to the front contact limb  191  of the upper rocker  19  is illustrated in the form of an enlarged detail in  FIG. 4 . The reflector  11  is also attached in the same way to the front contact limb  201  of the lower rocker  20 . Each of the plastic studs  30 , which are preferably composed of polyamide and, for example, are cylindrical, has a rear stud section  301 , which rests on the front contact limb  191 , and a stud section  302 , which is integrally adjacent thereto coaxially, and whose external diameter is considerably smaller than the external diameter of the rear stud section  301 . Respective threaded blind holes  31  and  32  are introduced into each respective stud section  301  and  302  from the end face. The screw shank  331  of a cap screw  33  is screwed into the threaded blind hole  31  in the rear stud section  301  and is passed through a corresponding through-hole  34  ( FIG. 2 ) in the upper rocker  19 . The respective front contact limbs  191  and  201  of the upper rocker  19  and lower rocker  20  have two such through-holes  34 , which are arranged at the greatest possible distance from one another, such that two plastic studs  30  are in each case screwed to each front contact limb  191  and  201  and are at the maximum distance from one another on each rocker  19  and  20 . 
         [0025]    Close to its corner points, the reflector  11  has a total of four stepped-diameter through-channels  35 , via which the reflector  11  is placed on the plastic studs  30  and is attached to the plastic studs  30 .  FIG. 4  shows the detail of the attachment of the reflector  11  to the front contact limb  191  of the upper rocker  19 , and this is applicable to all the attachment points of the reflector  11 . 
         [0026]    The through-channel  35  has a rear channel section  351  with a larger diameter, which clasps the rear stud section  301  of the plastic stud  30  with a small amount of play, and a front channel section  352 , whose diameter in contrast is smaller but whose unobstructed diameter is considerably greater than the external diameter of the front stud section  302 . A radial shoulder  353  is formed between the rear channel section  351  and the front channel section  352 , by means of which the reflector  11  rests, with the interposition of an elastic disc  37 , on the annular end surface of the rear stud section  301  surrounding the front stud section  302 . A resilient sleeve  36  is pushed in between the front stud section  302  and the front channel section  352  and is clamped in axially between the end surface of the rear stud section  301  and a metallic conical spring washer  38 . The conical spring washer  38  is fixed on the end surface of the front stud section  302  by means of a cap screw  39 , whose screw shank  391  is passed through the conical spring washer  38  and is screwed into the threaded blind hole  32  in the front stud section  302 . In this case, the conical spring washer  38  projects radially beyond the sleeve  36  and presses an elastic disc  40  onto the reflector  11 . The two elastic discs  37 ,  40  are preferably composed of rubber cork. 
         [0027]    An acoustically transparent envelope body  41  is placed in front of the front face, facing away from the antenna mount  10 , of the reflector  11 , which is constructed in this way and is attached to the antenna mount  10 , with the transducer arrangement  17  placed in front of it. The envelope body  41  is a layer composite of two outer layers  411  of glass-fibre-reinforced plastic and an intermediate, considerably thicker rubber layer  412  ( FIG. 6 ), and is attached to the two rockers  19 ,  20 . As is illustrated in  FIG. 1 , the envelope body  12  is fixed at the free end of the rear contact limb  192  of the upper rocker  19  and on the centre section  203  of the lower rocker  20 . In both cases, the fixing is in the form of a so-called “sheet pile lock”, in which areas which are formed on the rockers  19 ,  20  and on the envelope body  41  correspondingly engage in one another in an interlocking manner. In the exemplary embodiment illustrated in  FIG. 1 , a shaped head  42  is formed on each of the rockers  19  and  20  and is clasped by a shell or pan  43  which is formed in the envelope body  41 . A cover  44  is also detachably attached to the lower rocker  20 , is fixed on the one hand on the envelope body  41  and on the other hand at the free end of the rear contact limb  202  of the lower rocker  20 , and closes the U-opening in the rear U-shaped end area of the lower rocker  20 . The area which is enclosed by the envelope body  41  with the cover  44  and the antenna mount  10  and in which the reflector  11  is accommodated, together with the transducer arrangement  17  and the rocker system with a buoyant body  21 , is flooded. 
         [0028]    In the detail of the underwater antenna illustrated in  FIG. 5 , only the attachment of the envelope body  41  to the rockers  19 ,  20  has been modified. Apart from this, the underwater antenna sketched there corresponds to that described with reference to  FIG. 1 , as a result of which the same components are provided with the same reference symbols. 
         [0029]    In the exemplary embodiment shown in  FIG. 5 , the envelope body  41  is fixed to the rockers  19 ,  20  by stubs  45  which are integrally formed on the rockers  19 ,  20  and onto which the envelope body  41  is clipped in an interlocking manner, by a respective recess  45 .  FIG. 6  illustrates enlarged, and in the form of a section this fixing of the envelope body  41  to the rear contact limb  192  of the upper rocker  19 . This attachment applies in the same manner to the fixing of the envelope body  41  to the centre section  203  of the lower rocker  20 . The recess  46 , which faces the stud  45  and clasps it in an interlocking manner, in the envelope body  41  merges into a coaxial cutout  47  whose diameter is larger, thus resulting in a through-opening with a stepped diameter, being formed in the envelope body  41 . An elastic disc  48 , preferably composed of rubber cork is pushed over the stud  45 , and the envelope body is pressed with the recess  46  in an interlocking manner onto the stud  45 , such that the envelope body  41  rests via the elastic disc  48  on the rear contact limb  192  of the upper rocker  19 . A conical spring washer  49  composed of metal is inserted in an interlocking manner into the cutout  47  and is provided with a central through-hole  491  with a countersink for the countersunk head of a countersunk headed screw  50 . The countersunk headed screw  50 , whose screw shank  501  is passed through the through-hole  491 , is screwed into a threaded blind hole  41  provided in the stud  45 , and thus fixes the conical spring washer  49  on the end surface of the stud  45 , with the conical spring washer  49  pressing the envelope body  41  onto the rear contact limb  192  of the upper rocker  19 , via the elastic disc  48 . 
         [0030]    All of the features mentioned in the above description and in the claims can be used according to the invention both individually and in any desired combination with one another. The invention is therefore not restricted to the combinations of features which have been described and claimed. In fact, all combinations of individual features can be regarded as having been disclosed.