Towed antenna with a pressure sensor

Abstract

Towed antenna (20) comprising: a jacket (22) filled with a fluid (24); wherein a plurality of water sound transducers (26), a shaped piece (28) and a closure element (30, 30', 38) are arranged within the casing; wherein the shaped piece (28) in conjunction with the end element (30, 30', 38) and the casing (22) forms a space (32); wherein the fluid (24) within the space (32) has a first pressure and wherein the fluid (24) outside the space (32) has a second pressure that is greater than the first pressure; wherein a pressure sensor (34) is arranged in the space (32) to detect a pressure present outside the casing.

Description

[0001] The invention relates to a towed antenna with a pressure sensor.

[0002] Towed antennas already have pressure sensors. Towed antennas are tubular acoustic antennas that receive sound waves underwater. To do this, the towed antennas usually have a large number of waterborne sound transducers, also known as hydrophones, arranged equidistantly. The waterborne sound transducers are arranged in a casing. This equidistant arrangement optimizes beamforming with the towed antennas, for example. The towed antennas are typically connected to a watercraft, such as a ship or submarine, by means of a tow cable.

[0003] Towed antennas are typically designed in a modular fashion. This means that a towed antenna comprises a plurality of self-contained shells with waterborne sound transducers. These are also referred to as towed antenna modules or sections. Adjacent towed antenna modules can be connected to each other via a coupling.

[0004] Now, in order to evaluate the received sound waves, it is advantageous to determine the (diving) depth at which the towed antenna received the sound waves. This can be useful, for example, for determining the direction or estimating the distance of objects. For this purpose, a pressure sensor is integrated into the coupling. As the coupling is not covered by a casing, the pressure sensor has direct contact with the water and can therefore determine the water pressure and, from this, the depth of the towed antenna in the water. However, this has the disadvantage that the pressure sensor quickly corrodes due to direct contact with sea water. As the pressure sensor is typically not located on the surface of the coupling, but is integrated into the coupling or attached to it by means of a corresponding fitting, a pipe can also be located in the coupling or the fitting (as a connection between the outside of the coupling or the outside of the water).The pipe (the fitting and the sensor, so that the sensor comes into contact with the water) can become clogged with dirt. Both corrosion and dirt in the pipe impair pressure measurement or even make it impossible.

[0005] Placing the pressure sensor inside the sheath is not possible because it is filled with a pressurized fluid, particularly oil. The resulting pressure inside the sheath prevents the towed antenna or a towed antenna module from kinking, which could cause damage. However, the pressure inside the sheath does not remain constant but changes over the lifetime of the towed antenna. This effect is caused by a slow, continuous stretching of the sheath.

[0006] EP 2 480 345 A2 discloses an electroacoustic transducer, in particular a transmitting transducer for sonar systems, which has two end caps arranged at a fixed distance from one another, a plurality of lamellae spanned between the two end caps and fixed to the end caps in the circumferential direction next to one another, and an elastic sheath enclosing the lamellae on the outside.

[0007] WO 2011 / 035 744 A1 discloses an electroacoustic transducer with an actuator that oscillates longitudinally when an alternating voltage is applied. To significantly reduce the transducer weight while maintaining a sufficiently high acoustic performance, in particular transmission power, the actuator consists of a tube, preferably made of plastic, and at least one composite module firmly connected to the tube wall.

[0008] DE 42 21 327 A1 discloses a depth regulation unit for underwater measuring cables.

[0009] EP 0 964 271 A2 discloses an underwater towed antenna comprising a tow string with a hose containing an acoustic section composed of a plurality of spaced-apart hydrophones and a buoyancy means filling the hose for adjusting the towing depth of the tow string, as well as a trimming device for varying the towing depth of the tow string. To simplify the trimming of the tow string with variable towing depth, the trimming device comprises a plurality of cavities arranged at selected locations in the tow string within the hose and electrically driven pumping elements associated with the cavities for flooding and draining the cavities with water from the tow string environment.

[0010] The object of the present invention is therefore to create an improved concept for towed antennas.

[0011] This problem is solved by the subject matter of the independent patent claims. Further advantageous embodiments are the subject matter of the dependent patent claims.

[0012] Embodiments show a towed antenna with a casing filled with a fluid. A plurality of water sound transducers, a shaped piece and a closing element are arranged within the casing. The shaped piece, in conjunction with the closing element and the casing, forms a space. This means that the shaped piece has a shape so that the space is created between the casing and the shaped piece. For this purpose, the shaped piece can have a corresponding recess on its surface, for example a hollow. The fluid inside the space has a first pressure and the fluid outside the space has a second pressure which is greater than the first pressure. The closing element closes the shaped piece to prevent undesired entry or exit of the fluid into or from the space. A pressure sensor is arranged in the space to detect a pressure that exists outside the casing. This means that the pressure sensor is in contact with the fluid in the space.

[0013] The idea is to use the casing of the towed antenna or towed antenna module as a membrane. This means that the pressure sensor is no longer in direct contact with the surrounding water, but can still reliably measure the water pressure. The pressure within the space, which is very small compared to the total length of the towed antenna, remains constant or changes only to a negligible extent. This ensures that a defined, known pressure is present within the space at all times.

[0014] In exemplary embodiments, the first pressure is selected such that it corresponds to the atmospheric pressure during the filling of the fluid into the towed antenna or the towed antenna module. The pressure of the first fluid in the towed antenna therefore has a pressure of between 108,000 Pa and 65,000 Pa, but typically between 104,000 Pa and 75,000 Pa, depending on the weather conditions and altitude at which the towed antenna or the towed antenna module is filled. This means that the fluid is filled into the towed antenna or the towed antenna module without pressure and is therefore also pressureless compared to the ambient pressure (i.e. the atmospheric pressure). Slight deviations from atmospheric pressure are of course possible for manufacturing reasons. The atmospheric pressure can be determined during the filling of the towed antenna and assigned to the towed antenna.

[0015] Advantageously, however, the towed antenna or towed antenna module is filled at sea level or with only a slight deviation therefrom. The deviation is, for example, a maximum of 1000 m, preferably a maximum of 500 m, more preferably a maximum of 300 m upwards or 200 m, preferably 100 m downwards. The first pressure therefore corresponds approximately to normal pressure. The first pressure is then, for example, between 104,000 Pa (high air pressure assumed due to the weather conditions) and 88,000 Pa (at 1000 m), 93,000 Pa (at 500 m) or 96,000 Pa (at 300 m), in each case taking into account low air pressure due to the weather conditions. Selecting the pressure of the fluid within the chamber so that it corresponds to normal pressure has the advantage that the pressure sensor can be recalibrated more easily. The expansion of the casing can also cause the pressure of the fluid within the chamber to decrease. This change is only minor and has little impact on the measurement.However, it is always advantageous to avoid known measurement errors. For example, the offset in the pressure sensor's measurement caused by pressure reduction can be determined by measuring the pressure when the towed antenna or towed antenna module is exposed to normal pressure, for example, when it is above water, e.g., on a ship. The measurement offset determined in this way can then be taken into account for pressure measurements underwater.

[0016] Further embodiments show the towed antenna with a second pressure that is at least 60,000 Pa, preferably at least 75,000 Pa, for example, approximately 80,000 Pa greater than the first pressure. This effectively prevents the towed antenna from kinking and thus becoming damaged.

[0017] In exemplary embodiments, the fluid comprises a liquid, in particular an oil, for example, an (iso)paraffin oil. This is advantageous because liquids are incompressible, thus optimizing pressure measurement. Furthermore, kink protection is also improved.

[0018] In embodiments, the closing element comprises a press clamp that connects the shell to the molded part such that the fluid inside the space is separated from the fluid outside the space. This ensures that the volume of the fluid inside the space remains constant and does not mix with the fluid outside the space. The latter would lead to pressure equalization and thus influence the pressure measurement. Depending on the positioning of the molded part within the shell, it may be advantageous for the closing element to comprise a further press clamp that connects the shell to the molded part such that the fluid inside the space is separated from the fluid outside the space. The first and second press clamps are then arranged on opposite sides of the space.A press clamp, or pipe clamp, is a ring that is placed around the casing and can be tightened so that the fitting and the casing are firmly connected.

[0019] In further embodiments, the closing element has a shut-off unit. The shut-off unit can have a first, open, state and a second, closed state. The shaped piece now has an opening so that the fluid inside the space and the fluid outside the space are in contact when the shut-off unit is open and are separated from each other when the shut-off unit is closed. In other words, this means that an exchange of fluid within the space can take place through the opening in the shaped piece. If the shut-off unit is closed, however, this exchange is prevented. Such a shaped piece makes it easier to fill the casing with the fluid. Any mechanism that initially equalizes pressure through the opening but closes the opening when actuated is suitable as a shut-off unit.Ideally, actuation should be possible from outside the towed antenna, for example, by pressure, electrically, or by controllable natural forces (e.g., magnetic). Typically, it is not necessary for the locking unit to be able to be reopened from outside the towed antenna. This means that the locking unit can irreversibly close the opening. A bolt or similar device can be used as the locking unit. Details are explained below regarding the corresponding manufacturing process.

[0020] A method for producing a trailing antenna is further disclosed, comprising the following steps: providing a casing, a plurality of waterborne sound transducers, a shaped piece, and a closure element; arranging the plurality of waterborne sound transducers and the shaped piece in the casing such that a space is formed between the shaped piece and the casing; arranging a pressure sensor in the space; filling the casing with a fluid such that the space is also filled with the fluid; closing the space by means of the closure element; pressurizing the casing with the fluid such that the fluid outside the space has a higher pressure than inside the space. This means that the casing is filled with the fluid in two stages. First, the casing is filled with the fluid without pressure.The space fills up, for example through the opening in the fitting through which the fluid inside the space and outside the space are in contact or through a gap between the shell and the fitting that occurs when the clamps are still open.

[0021] After the initial filling, the chamber is sealed by the closure element. Sealing the chamber may involve attaching one or more compression clamps. However, if the fitting has an opening through which the fluid inside and outside the chamber are in contact, the compression clamps may already be attached before the casing is first filled with fluid. In this case, sealing the chamber by means of the closure element involves closing a shut-off unit. The shut-off unit advantageously snaps into place, thus reliably sealing the opening.

[0022] Preferred embodiments of the present invention are explained below with reference to the accompanying drawings. They show: Fig. 1: a schematic sectional view of a section of a trailing antenna in a first embodiment; Fig. 2: a schematic sectional view of the section of the trailing antenna in a second embodiment; and Fig. 3: a schematic sectional view of the section of the trailing antenna in a third embodiment.

[0023] Before exemplary embodiments of the present invention are explained in more detail below with reference to the drawings, it is pointed out that identical, functionally equivalent or equivalent elements, objects and / or structures in the different figures are provided with the same reference numerals, so that the description of these elements shown in different exemplary embodiments is interchangeable or can be applied to one another.

[0024] Fig. Figure 1 shows a schematic cross-sectional view of a section of a towed antenna 20. The towed antenna 20 comprises a casing 22 filled with a fluid 24, 24'. The areas of the towed antenna filled with the fluid are shown by dots. The different densities of the dots indicate different pressures of the fluid 24 within the casing. This will be described in more detail below.

[0025] A plurality of water-borne sound transducers are arranged within the casing 22. In the section shown, these are the water-borne sound transducers 26 and 26'. Furthermore, a shaped piece 28 is arranged within the casing 22. The shaped piece 28 can be rotationally symmetrical. For example, it can have a bore in the center through which the fluid can be distributed in the casing. The shaped piece 28 is shaped such that, in conjunction with a closure element and the casing 22, it forms a space 32. As closure elements, Fig. 1 shows two compression clamps 30, 30' that firmly connect the jacket 22 to the fitting 28. The compression clamps make it possible to fill the hose with the fluid without external pressure when the compression clamps are not yet tightened. Because the compression clamps are not yet tightened, the fluid can also be distributed between the fitting 28 and the jacket 22, so that the space 32 also fills with the fluid. By tightening the compression clamps, the fluid 24' inside the space is separated from the fluid 24 outside the space. Thus, after the compression clamps are tightened, the fluid can be filled into the jacket under pressure without entering the space.

[0026] Within the space 32, the fluid 24' then has a first pressure, and outside the space 32, the fluid 24 has a second pressure that is greater than the first pressure. However, it should be noted that the fluid 24' within the space 32 is advantageously the same fluid that is also located outside the space 32 in the casing 22. A pressure sensor 34 is also arranged in the space 32 to detect a pressure that exists outside the casing. For example, the towed antenna 22 is typically towed through the water by a watercraft, for example a ship or a submarine. For correct underwater sound measurement using the underwater sound transducers, it is advantageous to determine the depth at which the towed antenna is located in the water. This can be done using the pressure sensor 34.

[0027] Fig. Figure 2 shows a section of the waterborne sound transducer 20 in a second embodiment. The second embodiment differs from the first embodiment in that the pressure sensor 34 is not located directly in the chamber, but rather within a bore 36 in the molded piece.

[0028] Fig.3 shows a section of the waterborne sound transducer 20 in a third exemplary embodiment. The third exemplary embodiment differs from the second exemplary embodiment in that the bore 36 in the shaped piece connects the space 32 to the remaining interior of the casing. This means that the bore penetrates the shaped piece completely, creating an opening 40 in the shaped piece. The fluid 24' inside the space can mix with the fluid 24 outside the space through the opening 40 and the bore 36. The closing element now has a bolt 38 as a shut-off unit. The bolt is arranged relative to the opening such that the bolt 38, in an open state, enables contact between the fluid 24' inside the space and the fluid 24 outside the space 32. In a closed state, however, the fluid 24' inside the space is separated from the fluid 24 outside the space 32.

[0029] Thus, it is possible to firmly connect the fitting 28 to the casing 22 by means of the compression clamps 30, 30' even before the casing 22 is filled with the fluid. Once the casing is filled with the fluid without external pressure, the bolt can be closed and additional fluid can be filled into the casing under pressure without the fluid 24' mixing with the remaining fluid 24 within the space 32. The pressure difference remains unchanged.

[0030] The disclosed (water) sound transducers are designed for use underwater, particularly in the sea. The sound transducers are configured to convert water sound into an electrical signal (e.g., voltage or current) corresponding to the sound pressure, the water sound signal. Furthermore, the sound transducers are configured to convert an applied electrical voltage into water sound. The sound transducers can therefore be used as water sound receivers and / or as water sound transmitters. The sound transducers comprise a piezoelectric material, such as a piezoceramic, as the sensor material. The sound transducers can be used for (active and / or passive) sonar (sound navigation and ranging). The sound transducers are not suitable for medical applications.

[0031] Although some aspects have been described in connection with a device, it is understood that these aspects also represent a description of the corresponding method, so that a block or component of a device can also be understood as a corresponding method step or as a feature of a method step. Similarly, aspects described in connection with or as a method step also represent a description of a corresponding block, detail, or feature of a corresponding device.

[0032] The above-described embodiments are merely illustrative of the principles of the present invention. It is understood that modifications and variations of the arrangements and details described herein will be apparent to others skilled in the art. Therefore, it is intended that the invention be limited only by the scope of the following claims and not by the specific details presented in the description and explanation of the embodiments herein. List of reference symbols: 20 towed antenna 22 Coat 24 Fluid 26 water sound transducers 28 fitting 30 press clamp 32 rooms 34 Pressure sensor 36 bore 38 Shut-off unit (bolt) 40 Opening in the fitting

Claims

[1] Trailing antenna (20) comprising: a jacket (22) filled with a fluid (24); wherein a plurality of water sound transducers (26), a shaped piece (28) and a closure element (30, 30', 38) are arranged within the casing; wherein the shaped piece (28) in conjunction with the end element (30, 30', 38) and the casing (22) forms a space (32); wherein the fluid (24) within the space (32) has a first pressure and wherein the fluid (24) outside the space (32) has a second pressure that is greater than the first pressure; wherein a pressure sensor (34) is arranged in the space (32) to detect a pressure present outside the casing. [2] Towed antenna (20) according to claim 1, wherein the first pressure is selected such that it corresponds to the atmospheric pressure during filling of the towed antenna with the first fluid, in particular between 108000 Pa and 65000 Pa or between 104000 Pa and 75000 Pa. [3] Towed antenna (20) according to one of the preceding claims, wherein the second pressure is at least 60000 Pa, in particular at least 75000 Pa, greater than the first pressure. [4] Towed antenna (20) according to one of the preceding claims, wherein the fluid (24) comprises a liquid, in particular an oil. [5] A towed antenna (20) according to any one of the preceding claims, wherein the termination element (30, 30', 38) comprises a compression clamp (30) connecting the jacket (22) to the shaped piece (28) such that the fluid (24) inside the space (32) is separated from the fluid (24) outside the space (32). [6] A towed antenna (20) according to claim 5, wherein the terminating element (30, 30', 38) comprises a further compression clamp (30') connecting the jacket (22) to the shaped piece (28) such that the fluid (24) inside the space (32) is separated from the fluid (24) outside the space (32). [7] Trailing antenna (20) according to one of the preceding claims, wherein the closure element (30, 30', 38) has a shut-off unit (38); wherein the shaped piece (28) has an opening (40) so that the fluid (24) inside the space (32) and the fluid (24) outside the space (32) are in contact when the shut-off unit (38) is open and are separated from each other when the shut-off unit (38) is closed. [8] A towed antenna (20) according to any one of the preceding claims, wherein the first pressure is selected to be between 106,000 Pa and 94,000 Pa. [9] Method for producing a towed antenna (20) comprising the following steps: Providing a shell, a plurality of waterborne sound transducers (26), a shaped piece (28) and a closure element; Arranging the plurality of water sound transducers and the shaped piece in the casing (22) so that a space (32) is formed between the shaped piece (28) and the casing (22); Placing a pressure sensor in the room; Filling the jacket with a fluid (24) such that the space (32) is also filled with the fluid (24); Closing the space (32) by means of the closing element; Pressure-filling the jacket with the fluid (24) so ​​that the fluid (24) outside the space (32) has a higher pressure than inside the space. [10] A method for manufacturing a trailing antenna (20) according to claim 9, wherein closing the space (32) by means of the closure element comprises attaching one or more compression clamps. [11] A method for manufacturing a trailing antenna (20) according to claim 9 or 10, wherein closing the space (32) by means of the closure element comprises closing a shut-off unit. [12] Method for producing a towed antenna (20) according to one of claims 9 to 11, wherein the filling of the casing with the fluid is carried out at a height between -200 m and +1 000 m, in particular between -100 and +500 m or between -100 and +300 m, calculated from sea level.

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