AU2012311678B2 - Support module for an underwater antenna, and underwater antenna having a support module of this kind - Google Patents

Abstract

The invention relates to a support module 20 for an acoustic underwater antenna 4 having at least one electroacoustic and/or optoacoustic transducer element 32, wherein the support module 20 has a shaped piece, which is composed of at least two parts, for accommodating the transducer elements 32. The shaped piece has a central axial opening 38 for a traction cable to pass through and has at least one releasable connection between the parts of the shaped piece for opening or closing the support module 20. The invention also relates to an acoustic underwater antenna 4, in particular a towed antenna 4, having at least one above-described support module 20, and also to a corresponding method for attaching a support module 20 of this kind to the traction cable of said underwater antenna 4.

Description

WO 2013/041437 PCT/EP2012/067935 Support module for an underwater antenna, and underwater antenna having a support module of this kind The invention relates to a support module of the type cited in the preamble of Claim 1, an acoustic underwater antenna according to the preamble of Claim 12 as well as a method for attaching a support module according to the preamble of Claim 14. In water acoustic technology, direction finding systems with a towed antenna towed by a watercraft are generally used as a receiver for water acoustic signals, said direction finding systems when not in use being wound onto a drum which is fixed on board. Such towed antennas have a significant length in order to detect and locate targets over long distances. A towed antenna constructed from a plurality of mechanically and electrically connected sections is disclosed in DE 69 429 586 T2, said towed antenna having a plurality of hydrophone carriers for fastening the hydrophones in the towed antenna. To this end, the hydrophone carriers are pulled into an antenna sheath configured as a resilient tube which is filled with a filling agent in order to adjust the density of the towed antenna substantially to the density of the seawater. The hydrophone carriers are arranged spaced apart from one another in the longitudinal direction in the towed antenna, and thus form a skeleton structure which WO 2013/041437 PCT/EP2012/067935 -2 absorbs the forces which act on the towed antenna and passes a central traction cable through said carriers. The transducers of a towed antenna which are generally used have a separate transducer element, in particular a hydrophone, and are pressure-sensitive in all directions, whereby in each case a spherical directional characteristic is produced. By means of a direction generator, the received signals of the transducers are combined to form group signals, the directional characteristics thereof being oriented in different directions, laterally relative to the towed antenna. Thus correct focusing of the directional characteristic may be achieved transversely to the longitudinal direction of the towed antenna, but the sensitivity in the radial direction is the same. As a result, it is not possible to carry out a right-left differentiation of a detected target. Clear direction-finding results may be achieved, for example, by a transducer consisting of three transducer elements, the transducer elements being arranged at the same radial spacing to the longitudinal axis and offset relative to one another by the same circumferential angle. The received signals of two of the three transducer elements are received with a time delay to form a received signal of the transducer. Directional characteristics of the towed antenna are formed by means of such received signals of all transducers, the main receiving WO 2013/041437 PCT/EP2012/067935 -3 directions thereof in each case being oriented to one side. Combining the received signals of three individual transducer elements of a transducer by using such signal technology is set forth in DE 31 51 028 C2. Due to the measured time delays between all three pairs of transducer elements, the left-right ambiguity may be resolved, irrespective of the rotation of the towed antenna. This method, however, requires relatively large spacings between the transducer elements in order to maintain measurable time delays. Acoustic towed antennas are also used in seismic marine research. US 5 867 451 reveals a marine seismic cable assembly comprising a cable, hydrophone housings, a buoyant filler and an outer protective jacket, the cable comprising a load-bearing fibre bundle, data transmitting wires, electrical power conductors, optical fibres and a protective sheath. The hydrophone housings are arranged individually spaced apart around the cable. Moreover, US 3 675 193 reveals a seismic hydrophone streamer which is formed by using hydrophones consisting of cylindrical crystal segments, the crystal segments being arranged with their axis transversely to the axis of the streamer cable. A fastening means is provided, said fastening means being fastened from the outside to a central traction WO 2013/041437 PCT/EP2012/067935 -4 cable and supporting the crystal parallel to the axis of the traction cable. The object of the invention, therefore, is to improve the acoustic properties of the towed antenna, with a diameter thereof which is as small as possible. The invention solves this object by the features of a support module for an acoustic underwater antenna according to Claim 1, by an underwater antenna according to Claim 12 and by the features of a corresponding method for fastening a support module according to Claim 14. The invention provides the advantage of a symmetrical construction of the transducer being provided by a specific design of the support module, by which good acoustic properties may be achieved in spite of the reduction of the spacing between the transducer elements. To this end, the support module comprises a shaped piece which is composed of at least two parts and serves for accommodating the transducer elements which are combined to form a transducer. A central axial opening in the shaped piece permits a traction cable of the towed antenna to be passed through, said traction cable distributing the tensile stress via the antenna.

WO 2013/041437 PCT/EP2012/067935 -5 A releasable connection is preferably located between the parts of the shaped piece for opening the support module in order to attach said support module to the traction cable and for closing the support module after being positioned on the traction cable. By means of the support module according to the invention, acoustic problems which are caused by asymmetrical support shapes are avoided. As a result, the spacings between the transducer elements may be advantageously reduced as, with such a symmetrical construction of the support module, said transducer elements have substantially improved acoustic properties. Moreover, the support module has an electronic assembly assigned to the transducer, for signal processing of the received signals of the transducer elements. Preferably, the electronic assembly is arranged radially around the shaped piece, so that the support module not only serves for mechanical stabilisation of the towed antenna and for receiving the transducer elements but also for retaining electronic components. By such an arrangement of the electronic assembly on the support module, the spacings between the transducers of the towed antenna may be advantageously minimised as no additional shaped pieces are required for receiving the required electronics. A spacing which is able to be minimised between the transducers has the advantage that the WO 2013/041437 PCT/EP2012/067935 -6 receiving frequency of the towed antenna may be shifted to higher frequencies. According to a preferred embodiment of the invention, the electronic assembly is configured as flat boards, in particular as printed circuit boards, which are directly populated with electronic components assigned to the transducers. Moreover, the printed circuit boards are connected to a flexible strip containing conductors. This advantageously permits the space saving arrangement radially around the shaped piece. In a further preferred embodiment of the invention, at least three transducer elements are arranged on the shaped piece, offset relative to one another by the same circumferential angle and in each case having the same transverse spacing relative to the longitudinal axis of the support module. Preferably, each transducer element is attached to a part of the shaped piece, the parts of the shaped piece being releasably connected together. Such a transducer arrangement, in which at least three transducer elements are combined, results in the advantage of being able to make a right-left differentiation of a detected target. In a further embodiment of the invention, the transducer elements are resiliently attached to the shaped piece. Such a resilient attachment has the advantage of the decoupling of structure-borne sound which improves the acoustic properties of the antenna.

WO 2013/041437 PCT/EP2012/067935 -7 According to a further preferred embodiment of the invention, the shaped piece is constructed from a core piece and individual elements for receiving one respective transducer element. A releasable connection exists between the individual elements and the core piece. Preferably, the individual elements are of identical construction so that the transducer elements of a set and/or of a transducer have the same acoustic properties due to the same environment. This releasable connection has the advantage that the shaped piece may be opened by releasing at least one individual element and thus may be positioned on a traction cable. According to a further preferred embodiment of the invention, the support module has spacers between the core piece and the individual elements. Said spacers provide the advantage of producing an intermediate space in which the transducer elements may be positioned when attaching the individual elements to the core piece. In a further embodiment of the invention, the core piece has a cover for closing the axial opening, the cover being able to be fastened to the core piece. The cover is preferably attached to the core piece over the length thereof so as to prevent in an advantageous manner the traction cable from slipping out of the core piece.

WO 2013/041437 PCT/EP2012/067935 -8 In a further embodiment of the invention, the support module has a module housing. Preferably, said module housing is made up of housing halves, in particular two half-shells. It has the advantage of protecting the shaped piece, in particular the core piece with the electronic assembly attached thereto, from mechanical stress. In a further preferred embodiment of the invention, the support module has one or more hook and loop strips for holding the module housing together. This construction has the advantage that an acoustic decoupling of the support module from the sheath wall of the antenna is produced by means of the hook and loop strips, whereby the acoustic properties of the antenna are improved. According to a further embodiment of the invention, the support module has a base carrier which is configured in order to fasten the support module to the traction cable. To this end, the base carrier is initially screwed tightly to the traction cable and then adhesively bonded thereto. The fastening of the support module to the traction cable by means of a base carrier has the advantage that easy replacement of a support module is possible for the purpose of maintenance operations. The support module is fixed by at least one screw to the base carrier to prevent twisting.

WO 2013/041437 PCT/EP2012/067935 -9 In a further preferred embodiment of the invention, the support module comprises recesses in the axial opening of the shaped piece. This has the advantage of also being able to guide power supply lines and signal lines of the transducer elements through the support module, in addition to the traction cable of the towed antenna. Moreover, the invention comprises an acoustic underwater antenna, in particular a towed antenna, a tubular outer casing and a traction cable in the longitudinal direction on which at least one support module, described above, is arranged. Preferably, the support modules are configured to be substantially cylindrical and have an external diameter which is slightly smaller than the internal diameter of the outer casing of the underwater antenna. This has the advantage that the support modules may be pulled into the tubular outer sleeve and thus provide the cylindrical shape to the towed antenna. In a further alternative embodiment of the invention, the acoustic underwater antenna has an arrangement of support modules, described above, and empty modules in the longitudinal direction of the underwater antenna. In this case, the empty module simply consists of a shaped piece without transducer elements and preferably serves for shaping and stabilising the antenna if larger transducer spacings are required in WO 2013/041437 PCT/EP2012/067935 -10 the longitudinal direction for the antenna construction. Moreover, the use of empty modules has the advantage of avoiding deformation of the tube when the antenna is wound onto a drum. A further alternative embodiment of the invention reveals a method for attaching the support module to the traction cable of the towed antenna. To this end, the support module is firstly opened by releasing the connections between the individual parts of the shaped piece, which required for opening, in order to position said support module on the traction cable or on a base carrier connected to the traction cable. After fixing the support module to the traction cable, the support module is subsequently closed by connecting the individual parts of the shaped piece. Further advantageous embodiments of the invention are revealed from the sub-claims and from the exemplary embodiments explained with reference to the accompanying drawings, in which: Fig. 1 shows a watercraft with a towed antenna being towed thereby, Fig. 2 shows a side view of a support module according to the invention, WO 2013/041437 PCT/EP2012/067935 -11 Fig. 3 shows a plan view of a support module according to the invention without the view of individual elements of the shaped piece, Fig. 4 shows a plan view of a support module according to the invention, Fig. 5 shows a plan view of an electronic sub assembly positioned in the sheet plane and Fig. 6 shows a support module according to the invention in a perspective view. Fig. 1 shows a towed antenna 4 being towed by a watercraft 2. In this case, the watercraft 2 may be a surface water vessel or an underwater vessel, such as for example a submarine. The towed antenna 4 is retrieved and removed from the water by means of a drum 6 located on board the watercraft 2. The towed antenna 4 has a towing cable 8, two damping modules 10, 12 as well as an acoustic part 14 located therebetween. The damping modules 10, 12 in this case serve for the mechanical decoupling of vibrations of the acoustic part 14. A towing brake 16 is also located at the end of the towed antenna 4, said towing brake, when towed, ensuring a certain degree of tensile stress on the towed antenna 4 counter to the towing direction.

WO 2013/041437 PCT/EP2012/067935 -12 The support modules are located at freely selectable intervals in the towed antenna 4. Said support modules serve for the dimensional stability of the towed antenna 4 as well as for accommodating the transducer elements and electronic sub-assemblies. Moreover, a traction cable and signal lines for the received signals of the transducer elements are passed through the towed antenna 4, the support modules being attached in an axially undisplaceable manner to said traction cable. For protection against seawater, the support modules are pulled into a resilient tubular outer sleeve having tensile strength. To facilitate the process, the support modules have to this end an external diameter which is slightly smaller than the internal diameter of the outer sleeve of the towed antenna 4. The tube thus produced is preferably filled with oil or a gel in order to ensure the buoyancy of the antenna. Fig. 2 shows a schematic view of a support module according to the invention in a side view. The support module 20 has a substantially cylindrical shaped piece consisting of a plurality of parts, said parts being releasably connected together. A core piece 22 primarily serves for shaping and receiving an electronic assembly 24 which is arranged radially around the core piece 22. Preferably, the shaped pieces are manufactured from synthetic, technically applicable plastics material, in particular polyamide.

WO 2013/041437 PCT/EP2012/067935 -13 Via spacers 26, three individual elements 28 of identical construction are connected to the core piece 22, a releasable connection being formed by means of screws 30. This exemplary embodiment shows the attachment of the three individual elements 28 on one side of the core piece 22. The invention is, however, not limited to such a construction. Instead, a symmetrical construction of the support module 20 is also possible. In particular, such a construction has individual elements 28 arranged on both sides of the core piece 22, said individual elements being releasably connected via spacers 26 to the core piece 22. A transducer element 32 is resiliently fastened to each individual element 28 in order to decouple said transducer element from the support module 20 of the stresses caused by vibrations, for example. The vibrations which are produced when the antenna 4 is towed through the water are thus not transmitted to the transducer element 32 from the shaped piece connected via the traction cable. In this exemplary embodiment, the transducer elements 32 have a spherical shape. The invention is, however, not limited to such piezoceramic spheres. Instead, a series of piezoelectric ceramics of different shapes, piezoelectric polymers and fibre-optic transducers may be used as transducer elements 32.

WO 2013/041437 PCT/EP2012/067935 -14 Fig. 3 shows a plan view of a support module according to the invention but without a view of the individual elements. The transducer elements 32 are combined in the known manner to form a set and/or a transducer, the cabling of the transducer elements 32, also called signal lines, as well as the power supply lines, being guided through the support module 20 via recesses 36 in a central axial opening 38. The central axial opening 38 is arranged centrally in the core piece 22 and serves to position the shaped piece on the traction cable of the towed antenna. As the traction cable, the power supply lines and the signal lines are able to be installed in the interior of the support module 20, a symmetrical construction of the support module 20 is advantageously produced. Fig. 4 shows a plan view of a support module according to the invention. The individual elements 28 are illustrated in this schematic view. As also clearly indicated in Fig. 3, it is also indicated in Fig. 4 that the core piece 22 is enclosed by a cylindrical module housing 40. Preferably, said module housing 40 is made up of two half-shells. To this end, the core piece 22 has a greater diameter on the outer faces so that the module housing 40 is fastened in the recess thus produced in the centre of the core piece 22 and thus fixed in the longitudinal WO 2013/041437 PCT/EP2012/067935 -15 direction. Preferably, the module housing 40 is welded to the shaped piece, for example by ultrasonic welding, and held together by hook and loop strips, the hook and loop strips additionally serving for acoustic decoupling from the tubular wall. Moreover, the module housing 40 serves as protection from mechanical stress for the electronic sub assemblies 24 located thereunder, for example when the towed antenna 4 is wound onto the drum 6. Fig. 5 shows an electronic assembly placed in the sheet plane. The electronic assembly 24 is configured as flat boards, in particular as printed circuit boards 44, which are directly populated with electronic components assigned to the transducers but not shown in more detail here. In the exemplary embodiment described, three populated printed circuit boards 44 are provided, said printed circuit boards being connected together via a flexible strip 46 containing conductors. As a result, the electronic assembly 24 may be arranged radially around the core piece 22. Such a printed circuit board arrangement advantageously provides a greater surface area for the electronic components to be used. Fig. 6 shows a support module according to the invention in a perspective view. For mounting the underwater antenna according to the invention, a plurality of the above-described support modules 20 WO 2013/041437 PCT/EP2012/067935 -16 are attached to the traction cable. To this end, the necessary screws 30 on the individual elements 28 are released for opening the shaped piece. For attaching the support module 20 to the traction cable, the support module 20 has a base carrier, not shown further here. Said base carrier is initially tightly screwed to the traction cable and then adhesively bonded thereto. The base carrier also has a cylindrical shape and is slightly longer than the entire shaped piece of the support module 20. The substantially circular cross section of a central part of the base carrier corresponds approximately to the cross section of the axial opening 38 of the core piece 22 without the recesses 36 for passing through the power supply lines and signal lines. As a result, the open shaped piece of the support module 20 may be placed on the base carrier in an axially undisplaceable manner and secured against twisting by means of a screw. The shaped piece is now closed, by the individual elements 28 being fastened via the spacers 26 to the core piece 22. The transducer elements 32 which are fastened to the individual elements 28 thus gain a symmetrical construction relative to their surroundings.

WO 2013/041437 PCT/EP2012/067935 -17 The associated lines are guided in the recesses 36 of the axial opening 38 through the core piece 22. A cover is then pushed over the longitudinal side of the core piece 22 in recesses provided therefor and fastened thereto in order to secure the core piece 22 from slipping down off the traction cable or the base carrier fastened to the traction cable. Subsequently, the printed circuit boards 44 of the electronic assembly 24 are arranged around the core piece 22 and fastened, in particular screwed. Preferably, an electronic assembly 24 is assigned to each transducer, a transducer being produced by one or more transducer elements 32. Finally, the module housing 40 is closed by placing the two housing halves on top of one another, the module housing 40 being fitted between the two outer regions where the core piece 22 has a slightly greater diameter. Additionally, the housing halves are held together by hook and loop strips. This results in an acoustic decoupling from the tube, whereby the acoustic properties of the antenna are improved. The maximum operating frequency in which the towed antenna 4 operates is provided by the spacing between the transducers. So that the towed antenna 4 is able to cover a frequency range, the towed antenna 4 has WO 2013/041437 PCT/EP2012/067935 -18 regions with a variable number of transducers. Where the spacings between the transducers have to be larger, empty modules are arranged between the support modules 20 in the longitudinal direction of the towed antenna 4. Such empty modules have no transducer elements 32 and serve to avoid deformation of the tubular sleeve, for example when wound onto the drum 6. When using towed antennas 4 of long length, it is advantageous to keep the diameter of the towed antenna 4 as small as possible. This means, however, in an arrangement as described above of three transducer elements 32 for a right-left differentiation, that the relative spacing between the transducer elements 32 has to be reduced. A smaller spacing between the transducer elements 32, however, requires a specific design of the support module 20 as provided by the invention. By the symmetrical design of the support module 20 according to the invention it is possible to reduce the diameter of the towed antenna 4 whilst the good acoustic properties of the underwater antenna are kept the same. All of the features cited in the above description of the figures, in the claims and in the introduction to the description are able to be used individually and in any combination with one another. The disclosure of the invention is thus not limited to the combination of features described and/or claimed. On the contrary, WO 2013/041437 PCT/EP2012/067935 -19 all combinations of features should be considered as disclosed.

Claims (12)

1. Support module for an acoustic underwater antenna having at least one electroacoustic and/or optoacoustic transducer element for producing received signals, characterised by a shaped piece consisting of a core piece and at least three individual elements, the individual elements being arranged so as to be able to be releasably connected to the core piece and serving to receive one respective transducer element, an arrangement of at least three transducer elements offset relative to one another by the same circumferential angle, the transducer elements in each case having the same transverse spacing relative to the longitudinal axis of the support module, a central axial opening centrally arranged in the core piece for a traction cable to pass through, at least one releasable connection between the parts of the shaped piece for opening or closing the support module and an electronic assembly assigned to the transducer element or the transducer elements for signal processing of the received signals of the transducer elements or the transducer element, the electronic assembly being configured as printed circuit boards, to which electronic components may be attached, said printed circuit boards being connected together via a flexible strip, so that the printed circuit boards are arranged radially around the core piece, so that a right-left differentiation of a detected target is achievable while -21 maintaining reduced spacings between the transducer elements.

2. Support module according to claim 1, characterised by a resilient attachment of the transducer element or the transducer elements to the shaped piece.

3. Support module according to claim 1, characterised by one respective spacer between the individual elements and the core piece.

4. Support module according to claim 1 or 3, characterised by a cover of the core piece for closing the axial opening, the cover being able to be fastened to the core piece.

5. Support module according to one of the preceding claims, characterised by a module housing which is able to be made up of two housing halves.

6. Support module according to claim 8, characterised by one or more hook and loop strips for holding the module housing together.

7. Support module according to one of the preceding claims, characterised by a base carrier for fixing the support module to the traction cable.

8. Support module according to one of the preceding claims, characterised by recesses in the axial opening of the shaped piece for receiving signal lines. -22

9. Acoustic underwater antenna, in particular a towed antenna, with a tubular outer casing, a traction cable being arranged in the antenna in the longitudinal direction, on which at least one support module according to one of claims 1 to 8 is arranged.

10. Acoustic underwater antenna according to claim 9, characterised in that the support module is configured to be substantially cylindrical with an external diameter which is slightly smaller than the internal diameter of the outer casing of the underwater antenna.

11. Acoustic underwater antenna according to claim 9 or 10, characterised by an arrangement of support modules and empty modules in the longitudinal direction of the underwater antenna, the empty module consisting of a shaped piece without acoustic transducer elements.

12. Method for attaching a support module according to one of claims 1 to 8, to a traction cable of an acoustic underwater antenna according to claims 9 to 11, the method comprising the following steps: a) opening the shaped piece by releasing the connections between the parts of the shaped piece, which are required for opening b) positioning the support module on the traction cable or on a base carrier connected to the traction cable and fixing the support module, -23 c) closing the shaped piece by connecting the parts of the shaped piece. ATLAS ELEKTRONIK GMBH WATERMARK PATENT AND TRADE MARKS ATTORNEYS P38490AUG0