FR2823571A1 - ACOUSTIC COLUMN AND CYLINDRICAL ANTENNA FOR PASSIVE SONAR USING SUCH A COLUMN - Google Patents

Abstract

The invention relates to cylindrical antennas for passive sonar. It consists in making the acoustic columns of such an antenna in two parts. The first part comprises the outer protective layer (101) and the intermediate layer (102) provided with the receiving hydrophones (110). The second part (201) comprises the absorbent layer (204). The hard reflective layer (103) is included in the first or second part as appropriate. Fastening means (205, 210) make it possible to connect these two parts together and to fix them on the structure of the antenna. It makes it possible to increase the mechanical resistance of the acoustic receiving columns, while facilitating their manufacture without requiring the presence of a barrel on the submarine.

Description

result (4).

  The present invention relates to cylindrical antennas which are used as omnidirectional acoustic receivers in passive sonars, placed in particular on the hull of submarines. We know that such a cylindrical sonar antenna is made up of a set of hydrophone columns fixed on the generatrices of a carrier cylinder. Each column has the form of an elongated parallelopipedic module provided with an electrical outlet at one of its lo ends. In known manner, these modules are fixed in a juxtaposed manner by being pressed against the carrier cylinder which is

sometimes called "barrel".

  Currently, each receiving column is formed of a set of hydrophones superimposed on the height of the column and 10 ncyés in a set of layers superimposed on the thickness of the column. These layers have acoustic characteristics

  designed to improve the functioning of the antenna.

  Each column is wrapped in a layer of neoprene which

  achieves seawater tightness.

  o There is shown in Figure 1 a longitudinal section of a

  example of such a column according to known art.

  Going from the outside, where there is seawater in which the sonar is immersed, inward, where there is the drum on which the columns are placed, we first find a first layer 101 of hardness polyurethane greater than 70 Shores A, which allows it to resist external aggressions. There is then a second layer 102 made of a soft polyurethane of hardness less than 50 Shores A and in which the hydrophones 1 10 are embedded. This layer makes it possible to hold these hydrophones in position without exerting excessive stress on them. Then there is a steel plate 103 which constitutes a hard reflector for the acoustic waves. Finally a thick absordant layer 104, constituted for example of a syntactic material such as polyurethane charged with microballoons filled with air, or else of a rubber-hare,

  forms a masking screen for the assembly.

  From an acoustic point of view, the two varieties of polyurethane constituting the layers 101 and 102 present a product pC close to that of sea water, to ensure the protection of the assembly against sea water in which the sonar is immersed, a neoprene skin 100 envelops the rear of the assembly, the sealing on the front face consisting of the first layer 101, which is

  welded on its periphery to this skin (or envelope) of neoprene.

  To fix each column on the barrel, for example two supports 105 in the form of rails which come to hold the column o by its ends, without touching the rear face of the neoprene envelope. It is difficult to steadily and reliably fix these columns on the barrel and the method using rails, shown in FIG. 1, which is the best known to date, is far from satisfactory. This is essentially due to the high compressibility of the masking layer 104, the dimensional variations of which under the effect of the pressure originating from the immersion of the sonar-carrying submarine, in practice prevent blocking.

  suitable for this column with respect to the support drum.

  To overcome this drawback, the invention proposes an acoustic column, in particular for a passive sonar cylindrical antenna, of the type comprising at least one outer protective layer, an intermediate layer provided with a set of hydrophones, a hard reflective layer, an absorbent layer and a protective envelope, mainly characterized in that this column is made up of a first part comprising at least the protective layer and the intermediate layer, and a second part comprising at least the absorbent layer; these two parts being joined together by fixing means, o making it possible to assemble and fix them solidly on the structure of the antenna, and the surrounding protective envelope

only the first part.

  According to another characteristic, the hard reflective layer is

included in the first part.

  According to another characteristic, the fixing means comprise at least 2 fixed rods perpendicular to the hard reflective layer to pass through the latter, and at least two brackets for fixing the first and the second part together, and on the other side fix the column on the antenna structure, According to another characteristic, the two brackets are fixed on the rods so as to fold back towards the front of the column to end in legs projecting outside from column to

  level of its front face to allow fixing from the front.

  According to another characteristic, the hard reflective layer is included in the second part and the fixing means comprise two upper and lower angles fixed on the ends of the hard reflective layer, which come to grip the absorbent layer and are terminated by tabs which allow to fix the

  column on the antenna structure.

  According to another characteristic, the hard reflective layer is integrated in the second part and it is provided with rims extending towards the outside of this layer to form a cavity intended to receive the absordant layer, and this hard reflective layer extends at the top and bottom of the acoustic column beyond the level of the outer protective layer and of the intermediate layer, the extensions of this hard reflective layer comprising holes allowing the insertion of rods forming part of the

  means for fixing the column to the structure of the antenna.

  2 The invention further provides a cylindrical acoustic antenna for passive sonar, mainly characterized in that it comprises a set of acoustic columns as defined above, and in that it further comprises at least two upper rings and lower fixed on a ft by spacers, and shock absorbing studs making it possible to fix the columns on the crowns by means of the fixing means of these columns

elastically.

  Other features and advantages of the invention

  will appear clearly in the following description, presented as

  non-limiting example with regard to the appended figures which represent: FIG. 1, the longitudinal section of an acoustic column according to the prior art; - Figure 2, a longitudinal section of a column according to a preferred embodiment of the invention; - Figure 3, a perspective view of the fixing means of a column such as that of Figure 3, on a support fGt; Jo - Figure 4, a detail of the fixing means of Figure 3 and - Figures 5 to 7, sectional views of three variants of

claiming the invention.

  The invention therefore consists in securing each column in two C separable parts which can then be joined together to be mounted on two crowns connected to the pedestal of the submarine by means of

mechanical decoupling.

  In the preferred embodiment shown in the figure

  2, each column is manufactured in two parts, 200 and 201.

  The first part 200 is formed of the three layers 101, 102 and 103, with the hydrophones 1 10 embedded in the intermediate layer 102. This structure is identical to that comprising the same elements in FIG. 1, According to the invention, the envelope protective neoprene 202 t is vuicanisoe on this first part, so as to cover the rear of the metal plate 103 instead of the compressible layer 104. This neoprene envelope then closes,

  as in the prior art, at the resistant layer 101.

  The second part of the column is formed of the single absorbent layer 204, of dimensions identical to those of the layer 104, but made of a material capable of being soaked in water without requiring any particular protection. Among the materials mentioned above, the one that will be preferred is foam

syntactic in polyurethane.

  The hard metallic reflective layer 103 is provided with rods, two in this example of installation, which are fixed, by welding for example, perpendicular to this layer and projecting outwardly thereof. The length of these rods is substantially equal to the thickness of the layer 204. The seal at the passage of these rods in the neoprene skin 202 is obtained intrinsically, following the reulisation of this envelope by

  vulcanization on the sandwich formed by layers 101 to 103.

  To then assemble the parts 200 and 201, the lo rods 205 are threaded into holes made in the thickness of the layer 204 at the appropriate locations so that the latter comes to be pressed into position against the envelope 202. It is then fixed at the free ends of these rods 205 of the brackets 210 which allow, on the one hand to hold the two parts 200 and 201 together, and on the other hand to fix the column on the means for fixing to the barrel supporting the sonar antenna. This manufacturing method not only makes it possible to firmly fix the column on the barrel, but also to be able to replace, if necessary, layer 204, which is the most fragile part of the

o device.

  To be able to fix these columns on the barrel so as to obtain a cylindrical antenna, a device for example is used.

  assembly such as that shown in FIGS. 3 and 4.

  Around a pillar 310, corresponding to the shaft described above, two upper and lower rings are fixed with spacers 301, of which only the upper ring 300 is shown in the figure. The brackets 210 of the columns 200/201 are then fixed on the crowns 300 by means of shock absorbing pads 320 positioned at the nocessaire locations, ogenerating the ment in an equidistant manner, on the rings 300. The fixing the brackets to the studs will preferably be done using screws 302, so as to facilitate the subsequent disassembly of the columns, to

repair for example.

  Also shown in this figure 4 is the removable fixing of the brackets 210 on the rods 205, using in this example screws 206 which allow the easy replacement of the layer 204, as described above, We note that in this way layer 204 is free to compress under the effect of hydrostatic pressure, without this influencing the attachment of the entire column to the stanchion 310, and without there being any loss of sealing the part 200 co m taking sensitive organs likely to be affected by water infiltration. This two-part storage, characteristic of the invention, is not limited to the mode of storage shown in

  Figure 2 and can be the subject of many variants.

  A first variant, represented in FIG. 5, consists in replacing the brackets 210 by brackets 510, turned over. Compared to the fixing of FIG. 2 to come to extend, not towards the rear of the device but towards the front of the latter, and fold back outside the column, at the outside face of the layer 101, in the form of two legs 60 which allow a

  fixing of the column from the front for specific assemblies.

  In another variant of reclisation, represented in FIG. 6, the first part 500 is formed only of the layers 101 and 102 comprising the hydrophones 1 10, and of the neoprene skin, which

  then comes to bear on the rear face of the layer 102.

  The second part is formed by the metal plate 103 on which the absorbing layer 104 is fixed, for example by gluing, using a relatively low-adhesive glue which just allows the maintenance of this layer, which is not subject to particular efforts, and authorizes a possible disassembly for repair

  by simple traction on this layer.

  To join these two parts 500 and 501, two upper and lower angles 50 are used for example, which are fixed on the ends of the plate 103, for example by bolting with screws 51 which are screwed into tapped blind holes on the

  upper and lower ends of this plate 103.

  These two angles 50 hold the layer 204 by pinching on the plate 103, in this case completing the fixing.

of this layer.

  Finally, in another embodiment represented in FIG. 7, the first part is shelled, as in FIG. 6, in the form of an assembly 500 made up of layers 101 and 102, and the plate 103 is provided with the 'rear of the latter, with edges 701, to form a cavity of a depth substantially identical to the thickness of the layer 204. This layer 204 is then for example poured into the interior of the cavity thus formed, this which ensures its fixing by bonding to the walls of the cavity during the solidification of the product poured into it. Alternatively, a plate 204 could be fitted with dimensions slightly larger than those of the cavity and

  insert it into the cavity forcibly.

  In addition, the dimensions of the plate 103 are logically larger than those of the first part 500, so as to overlap at the top and at the bottom thereof. It is thus possible to provide in the ends of this plate, which extend beyond the part 500, holes through which rods 700 will be passed, making it possible to fix the o column on the pedestal. These rods will for example be threaded with

  so as to facilitate fixing with nuts.

  These holes will preferably be filled with elastic sleeves 702 made of elastomeric material, to obtain an acoustic decoupling.

  between these fixing means and the column.

  : Regarding the number of layers used,

  The invention is not limited to the preceding description, which does not

  includes layers 101 to 204. Without departing from the scope of the invention, the number of these layers could be increased, in particular by using adaptation layers at the level of the first part including hydrophones , and co uch es

  additional depreciation at the level of the second part.

Claims (6)

claims   1 - Acoustic column, in particular for cylindrical passive sonar antenna, of the type comprising at least one outer protective layer (101), an intermediate layer (102) provided with a set of hydrophones (110), a hard reflective layer ( 103), an absorbent layer (204) and a protective envelope (202), characterized in that this column is formed by a first part (200) comprising at least the protective layer and the intermediate layer, and by a second part (201) comprising at least o the absordant layer (204); these two parts being joined together by fixing means (205, 210) making it possible to assemble and fix them solidly on the structure of the antenna, and the protective envelope (202) surrounding only the first part.   2 - Acoustic column according to claim 1, characterized in that the hard reflective layer (103) is included in the first part (200).   3 - Acoustic column according to claim 2, characterized in that the fixing means comprise at least 2 rods (205) o fixed perpendicular to the hard reflective layer (103) to pass through it, and at least two brackets (210) for fixing the first and second part together, and fixing the   column on the antenna structure.   4- acoustic column according to claim 3, characterized in that the two brackets (510) are fixed on the rods (205) so as to fold back towards the front of the column to end with legs (60) projecting outside the column at   its front to allow attachment from the front.   - Acoustic column according to claim 1, characterized in that the hard reflective layer (103) is included in the second part (201) and that the fixing means comprise two upper and lower angles (50) fixed on the ends of the layer hard reflector (103), which surround the absorbent layer (204) and are terminated by lugs (52) which allow   to fix the column on the structure of the antenna.   6- Acoustic column according to claim 1 characterized in that the hard reflective layer (103) is incorporated in the second part (201) that it is provided with rims (701) extending towards the outside of this layer to form a cavity intended to receive the absorbing layer (204) and in that this hard reflecting layer extends at the top and at the bottom of the acoustic column beyond the level of the external protective layer (101) and of the intermediate layer (102); the extensions of this hard reflective layer comprising holes (702) making it possible to insert rods (700) forming part of the means for fixing the column on the antenna structure.   7 - Acoustic cylindrical antenna for passive sonar, ca ractérisoe in that it includes a set of col on nes   acoustic according to any one of claims 1 to 6 and in that   which further comprises at least two upper and lower crowns (300) fixed to a barrel (310) by spacers (301) and shock absorbing pads (320) making it possible to fix the columns on the crowns by means of fixing means (210) of these