AU2020215190B2

AU2020215190B2 - Device for cladding an underwater sound receiver

Info

Publication number: AU2020215190B2
Application number: AU2020215190A
Authority: AU
Inventors: Christoph Hoffmann
Original assignee: ThyssenKrupp AG; Atlas Elektronik GmbH
Current assignee: ThyssenKrupp AG; Atlas Elektronik GmbH
Priority date: 2019-01-31
Filing date: 2020-01-21
Publication date: 2023-01-12
Anticipated expiration: 2040-01-21
Also published as: DE102019201282A1; WO2020156878A1; AU2020215190A1; EP3917827A1

Abstract

Embodiments show a device for cladding an underwater sound receiver, for example a (sonar) antenna, having a covering, a valve and an outlet opening. The covering can accommodate the underwater sound receiver. The covering further has, in a first region, an (acoustic) window, said window being designed to let sound waves pass through. The valve is designed to let water surrounding the device flow into the covering and to prevent water present in the covering from flowing out of the covering. The outlet opening is designed to let water present in the covering flow out.

Description

Device for cladding an underwater sound receiver

1. FIELD OF THE INVENTION The invention relates to a device which encloses sonar antennas, in order to improve the flow properties of an underwater vehicle on which the device is mounted compared with an underwater vehicle on which the sonar antennas are mounted without the device.

2. BACKGROUND OF THE INVENTION Underwater vehicles typically have sonar antennas to enable them to detect their environment. The sonar antennas cannot be attached within the casing of the underwater vehicle, however, because they are unable to detect sound waves in the water from there. If the sonar antennas are arranged outside the underwater vehicle, however, they have a negative impact on the flow properties of the underwater vehicle. In order to improve these flow properties, the underwater antennas can be clad, in other words enclosed in a casing. However, this casing either absorbs too much sound or is unable to withstand the dynamic water pressure that can act on the o casing on account of the swell when the underwater vehicle is travelling on the surface of the water.

3. SUMMARY OF THE INVENTION The technology with which the present invention is concerned would be enriched by creating an improved concept for the attachment of underwater sound receivers to an underwater vehicle.

In accordance with one aspect, the present invention provides a device for cladding an underwater sound receiver, for example a (sonar) antenna, having a casing, a valve, and an outlet opening. The casing is devised to accommodate the underwater sound receiver. In addition, the casing has an (acoustic) window in a first region, wherein the window is designed to allow sound waves to pass through. The valve is designed to allow water surrounding the device to flow into the casing and to prevent water which is present in the casing from flowing out of said casing, in particular

1 19274401_1 (GHMatters) P116324.AU during vertical movements of the underwater vehicle when it is on the surface, for example. The outlet opening in turn is designed to allow water which is present in the casing to flow out. A water exchange takes place in the casing due to higher pressure outside the casing, compared with the hydrostatic pressure in the casing, which is present when the underwater vehicle is travelling.

The idea underlying the invention comprises a plurality of elements working together, and these elements may be embodied in different forms. Initially, the sound waves from the water surrounding the casing can travel through the window into the inside o of the casing, where they are detected by the underwater sound receiver. However, it is advantageous for this purpose for the window to be preferably as thin as possible, so that as little sound as possible is absorbed or as few sound waves as possible damped. The remaining casing can then be of more solid design. So that the sound waves also reach the underwater sound receiver within the casing in as undamped a form as possible, the casing is filled with water. The static internal pressure which then exists in the casing through the incompressible water means that the casing and, in particular, also the window, is able to withstand the dynamic water pressure of waves more effectively. If the underwater vehicle moves forwards, it is furthermore advantageous for the water in the casing to be exchanged, so that "the same" water o is present within and outside the casing. Hence, the properties (e.g. salt content, temperature) of the water can differ at two closely adjacent points, in such a manner that the sound velocity in the water also changes. This means that unwanted boundary layers can result which have a negative impact on sound propagation. The valve now ensures that a water exchange takes place in the casing due to the higher pressure outside the casing (dynamic pressure), compared with the hydrostatic pressure in the casing, which occurs when the underwater vehicle is travelling. Excess water in the casing can flow out through the outlet valve.

In other words, when an underwater vehicle is travelling, the water within the casing is constantly mixed or exchanged, whereas in the case of an underwater vehicle which is substantially standing still, the release of water from the casing through the valve, and also the outlet valve, is largely avoided. The pressure within the casing therefore remains constant. The exchange works both when the underwater vehicle has surfaced and also when the underwater vehicle is submerged.

2 19274401_1 (GHMatters) P116324.AU

So that the window can allow sound waves to pass through, it may comprise a first material which differs from a second material of the casing. The second material can therefore be chosen in a second region of the casing which lies outside the first region in which the window is arranged, without taking account of the sound transmission properties. A material, for example glass fiber-reinforced plastic (GFRP) or a metal (e.g. iron) which resists the water pressure, in particular the dynamic water pressure of the swell, can therefore be used. The first material is further chosen in such a manner that it transmits the sound waves as effectively as possible, i.e. o damps them as little as possible, in particular facilitating better sound transmission than the second material. Hence, a plastic with a sound velocity similar to that of sea water can be used for the first material, for example, wherein a plastic with exactly the sound velocity of sea water exhibits the best transmission properties of the aforementioned materials.

In other words, a fiber-reinforced plastic, for example one from the group of duromers or a particularly fiber-reinforced thermoplastic plastic, can be used as the first material. The window may, however, also comprise a combination of multiple layers of the aforementioned materials. One or multiple intermediate layers of a damping o material, for example a viscoelastic film or a rubber material, can be inserted between the layers (mechanically). Depending on the use of the device, the material can be chosen in such a manner that it corresponds to the transmission properties of the (sea) water in the intended area of usage, or is at least close to these.

Exemplary embodiments of the valve are designed to allow the water surrounding the device to flow into the casing when the water pressure of the water surrounding the device is greater than the water pressure in the casing, and to prevent the water which is present in the casing from flowing out of the casing when the water pressure of the surrounding water is lower than the water pressure of the water in the casing. In other words, the valve may be a non-return valve. This is a possible embodiment, in order to allow the exchange of water within the casing and, at the same time, to guarantee that no water flows out of the casing when there is no new water following. The water pressure of the water surrounding the device is, in particular, also lower

3 19274401_1 (GHMatters) P116324.AU when the valve is above the water line when the underwater vehicle to which the device is attached has surfaced.

Exemplary embodiments of the window comprise a first material with a smaller material thickness than that of the casing in a second region outside the first region in which the window is arranged. Consequently, the window may be acoustically permeable, in order to allow the sound waves to pass through. So that the window is acoustically permeable, apart from a suitable material being chosen, it is advantageous for the window to be kept as thin as possible.

In further exemplary embodiments, the window has a surface area smaller than 40%, smaller than 30%, or smaller than 20%, but greater than 5%, of the total surface of the casing. Consequently, only a small but sufficiently large part of the casing is produced from a material with low resistance, so that the probability of the window breaking is further reduced.

In other exemplary embodiments, the casing has a further window. The further window may exhibit the same features as the window. Consequently, it is possible for a further underwater sound receiver to be arranged behind the further window.

Exemplary embodiments of the outlet opening have it arranged on an upper side of the casing when the device is oriented for use. This means that water within the casing can only be exchanged when new water flows into the casing through the valve. The hydrostatic pressure within the casing therefore remains constant, irrespective of the current position of the device.

In a further aspect, the invention provides a system comprising the device of the first aspect and an underwater sound receiver, wherein the underwater sound receiver is arranged in the casing in such a manner that sound waves can be received from the water surrounding the device through the window of the underwater sound receiver. If the casing has a further window, a further underwater sound receiver can be arranged in the casing, in such a manner that sound waves from the water surrounding the device can be received by the further underwater sound receiver through the other window.

4 19274401_1 (GHMatters) P116324.AU

In a further aspect, the present invention also provides an underwater vehicle with an outer casing and the device of the first aspect, alternatively the system of the second aspect. The outer casing is at least partially surrounded by water when the underwater vehicle is running. The casing of the device is connected to the outer casing, in particular in a watertight manner. Hence, the casing of the device can be fitted to the outer casing, so that the casing and the outer casing create a space in which the underwater sound receiver is arranged. If there is water in the casing, said water can therefore also be located between the casing and the outer casing. The o device may be attached at the front, i.e. to the front end or to the bow in the (main) travelling direction of the underwater vehicle.

In exemplary embodiments of the underwater vehicle, the valve is arranged in such a manner that it is predominantly located below the water surface when the underwater vehicle is running. In this case, predominantly means that the underwater vehicle, when it surfaces, in other words when it travels on the water, can also rise out of the water, depending on the swell, so that the valve then lies above the surface of the water. However, when the water is still, the valve lies below the surface of the water, in order to allow the exchange of water in the casing.

Additional features and preferred forms thereof as find use in the various aspects of the present invention will become apparent from the following description of exemplary embodiments provided with reference to the attached drawings.

4. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1: shows a schematic representation of a device for cladding an underwater receiver, optionally a system having the device, and further optionally an underwater vehicle having the device, wherein precisely one underwater receiver is shown here; and

Fig. 2: shows a schematic representation of the device for cladding two underwater receivers, optionally the system having the device, and further optionally the underwater vehicle having the device.

5 19274401_1 (GHMatters) P116324.AU

5. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Before the two embodiments of the present invention are explained in greater detail below with the help of the drawings, it should be pointed out that elements, objects and/or structures which are identical, functionally identical, or have the same effect, are provided with the same reference numbers in the different figures of the drawings, so that the descriptions of these elements represented in different exemplary embodiments are interchangeable with one another, or can be applied to one another.

o Fig. 1 shows a schematic depiction of a device 20 for cladding an underwater sound receiver 22. The device 20 comprises a casing 24, a valve 26 and an outlet opening 28. The casing 24 can accommodate the underwater sound receiver 22. The device in combination with the underwater receiver 22 is also referred to as the system 32. The casing 24 has a window 30 in a first region, wherein the window is designed to allow sound waves from the environment of the device to pass through into the inside of the device, in particular to the underwater sound receiver 22. The casing 24 may exhibit a shape which, when the device 20 is attached to an underwater vehicle 34, in particular to the outer casing 40 thereof, has less impact on the flow properties of the underwater vehicle than if the underwater sound receiver 22 were simply to be o attached to the underwater vehicle 34. In particular, the casing 24 can be adapted to the shape of the underwater vehicle 34, so that the flow properties of the underwater vehicle 34 are influenced to the smallest possible degree.

The valve 26 may allow water surrounding the device 20 to flow into the casing 24. It is therefore guaranteed that the region between the underwater receiver 22 and the window 30 is flooded with water, so that the sound waves that pass through the window 30 can also reach the underwater receiver 22. In addition, the valve 26 is designed to prevent water which is present in the casing from flowing out of the casing 24 through the valve 26. Consequently, the water which is present in the casing 24 remains in said casing, even when the water pressure outside the device is lower than the water pressure due to the water in the casing 24. This can happen when the underwater vehicle 34 is at a standstill, for example, or when the underwater vehicle is lifted out of the water by the swell, for example. As is shown

6 19274401_1 (GHMatters) P116324.AU here, the valve 26 may be arranged directly in the casing 24 or also in a hose, for example, which allows water to be supplied to the casing 24.

However, in order to allow the exchange of water in the casing 24, the device 20 has an outlet opening 28, for example an overflow. If water penetrates the casing 24 through the valve 26 and the casing 24 is already flooded with water, excess water is pressed out of the casing 24 through the outlet opening 28. It is thereby guaranteed that the water in the casing has substantially the same composition as the water surrounding the casing. This facilitates the most uniform propagation possible of o sound waves from the water surrounding the device through the window 30, and the water in the casing 24 to the underwater sound receiver 22.

The double arrow 35 indicates the level of the hydrostatic pressure in the casing 24, in particular when the outlet opening 28 lies above the water line. If the valve 26 lies below the water line and the device 20 moves, a dynamic pressure is generated which is greater than the hydrostatic pressure within the casing 24. Consequently, even when the underwater vehicle has surfaced, there is a regular water exchange in the casing 24 when the underwater vehicle 34 moves. However, if the underwater vehicle 34 is at a standstill, the water pressure outside the device is lower than the o hydrostatic pressure within the casing 24, and the valve 24 prevents water from flowing off out of the casing.

Fig. 2 shows a schematic representation of a device 20 for cladding two underwater sound receivers 22, 22'. In addition to the depiction from Fig. 1, the device 20 from Fig. 2 has a further window 30', behind which a further underwater sound receiver 22' can be optionally arranged to create the system. In this case, the device 20 optionally has one or multiple separating elements 36, in order to create a separate chamber in the casing 24 for each underwater sound receiver 22, 22'. If the device 20 has at least two separating elements 36, these can form a further chamber in which evaluation electronics for evaluating the signals of the underwater sound receiver 22, 22' can be installed by way of example. Through the separating elements 36 and, optionally, the chamber lying therebetween, the water within the casing 24 can be guided out of the first chamber by means of a connection element 38, for example a hose, into the second chamber. In this case, it is necessary for the chamber between

7 19274401_1 (GHMatters) P116324.AU the separating elements 36 also to be flooded. The first chamber may be characterized in that the water supply through the valve 26 is arranged therein. The second chamber may be characterized in that the water outlet in this case is arranged through the outlet opening 28.

The exemplary embodiments described above are only an illustration of the principles of the present invention. It is clear that modifications and variations of the arrangements and details described herein will make sense to other people skilled in the art. It is therefore intended that the invention should be limited only by the scope o of protection of the patent claims below and not by the specific details which have been presented herein with the help of the description and the explanation of the exemplary embodiments.

8 19274401_1 (GHMatters) P116324.AU

List of reference numbers:

20 device 22 underwater sound receiver 24 casing 26 valve 28 outlet opening 30 window o 32 system 34 underwater vehicle 35 double arrow 36 separating element 38 connection element (hose) 40 outer casing

9 19274401_1 (GHMatters) P116324.AU

Claims

Patent claims

1. A device for cladding an underwater sound receiver of an underwater vehicle, comprising: - a casing configured for accommodating an underwater sound receiver, wherein the casing has a window in a first region, the window being designed to allow sound waves to pass through; - a valve configured to allow water surrounding the device to flow into the o casing and to prevent water present in the casing from flowing out of said casing; and - an outlet opening configured to allow water present in the casing to flow out when water flows in through the valve such that a water exchange takes place in the casing due to higher dynamic water pressure outside the casing, compared with hydrostatic pressure in the casing, which occurs when the underwater vehicle is travelling.

2. The device as claimed in claim 1, wherein the valve is configured to allow water surrounding the device to flow into the casing when the pressure of water surrounding the device is greater than the water pressure in the casing, and to o prevent the water which is present in the casing from flowing out of the casing when the pressure of the surrounding water is lower than the water pressure of the water in the casing.

3. The device as claimed in anyone of the preceding claims, wherein the window comprises a first material with a smaller material thickness than a material thickness of the casing in a second region outside the first region in which the window is arranged.

4. The device as claimed in anyone of the preceding claims, wherein the casing comprises a second material in a region around the window, the second material selected to withstand the water pressure of the water surrounding the casing.

5. The device as claimed in anyone of the preceding claims, wherein the valve is a non-return valve.

10 19274401_1 (GHMatters) P116324.AU

6. The device as claimed in anyone of the preceding claims, wherein the valve is configured to allow water to flow into the casing when the water pressure of the water surrounding the casing is greater than the water pressure in the casing.

7. The device as claimed in anyone of the preceding claims, wherein the outlet opening is arranged on an upper side of the casing when the device is oriented for use.

o 8. The device as claimed in anyone of the preceding claims, wherein the window occupies less than 20% of a total surface of the casing.

9. The device as claimed in anyone of the preceding claims, wherein the casing has a further window.

10. A system, comprising: - a device as claimed in anyone of the preceding claims; and - an underwater sound receiver, wherein the underwater sound receiver is arranged in the casing in such a manner that sound waves from water surrounding o the device are received by the underwater sound receiver through the window.

11. An underwater vehicle, having: - an outer casing which is at least partially surrounded by water when the underwater vehicle is travelling; and - a device as claimed in anyone of claims 1 to 9, or a system as claimed in claim 10, wherein the casing of the device is connected to the outer casing.

12. An underwater vehicle as claimed in claim 11, wherein the casing of the device is connected to the outer casing in a watertight manner.

13. The underwater vehicle as claimed in claim 11 or 12, wherein the valve is arranged in such a manner that it is predominantly located below the water surface when the underwater vehicle is travelling.

11 19274401_1 (GHMatters) P116324.AU

1 / 2

17978490_1 (GHMatters) P116324.AU

2 / 2

17978490_1 (GHMatters) P116324.AU