Acoustic generator for underwater applications

Abstract

An acoustic generator (1, 100) for subsea applications comprises a hollow body (10) deploying along an axis (XX) and associated with an acoustic diffuser member (20), the hollow body (10) housing a first piston (12) and a second piston (14) freely slidable along the axis (XX), a drive group (30) associated with the first piston (12) to move the first piston towards the second piston (14), the adjustment unit (16) is fitted with a third piston (18) and interposed between the first piston (12) and the second piston (14), the third piston (18) forming a first isolation chamber (C1) between the first piston (12) and the third piston (18) and a second isolation chamber (C2) between the third piston (18) and the second piston (14), and a control unit (60) electronically connected to the regulating unit (16) and to the drive group (30) for controlled activation of the second piston (14), the damping unit (40) comprising an auxiliary chamber (C2 ') associated with and hydrodynamically isolated from said second chamber (C2), the pressure of the auxiliary chamber (C2') being controlled by the control unit (60) for modulating the emission spectrum of the acoustic waves emitted by said diffuser member (20).

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the priority of Italian Patent Application No. 102022000008594 filed on April 29, 2022, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The invention relates to an acoustic wave generator for underwater applications, suitable for use in an instrument for identifying underwater objects and / or for locating oil and / or gas deposits.

[0004] The generator comprises a hollow body having a longitudinal axis and an end associated with the sound diffuser member. The hollow body has a rear portion accommodating a first piston and a front portion accommodating a second piston. The second piston is freely slidable along the longitudinal axis of the hollow body, the second piston having a face facing the diffuser member. A drive group is associated with the first piston to move the first piston toward the second piston. Background Art

[0005] In the field of underwater exploration, it is known to use sound waves or sonic waves to map the seafloor, to classify its potential risks for navigation, to identify underwater objects and also to locate oil and gas reserves. In this industry, the reflection of sound waves on the seafloor is used to obtain information even to depths exceeding 10 kilometers below the seafloor. One of the tools used in this type of activity is the so-called "air gun", i.e. a compressed air gun for generating sound waves, the reflections of which are processed and analyzed in a manner already known to those skilled in the art. These tools are used individually or in multiple arrays in combination with so-called "sonars" for sound positioning. "Sonar" or echo sounder is a term that combines the technology used to detect the presence and position of a body at least partially immersed in "sound navigation and ranging".

[0006] As is known to all, the underwater world is inhabited by animals that emit sounds detectable by sonar. Among these animals, mention must be made of cetaceans, which are mammals that are able to produce sound waves, usually of very high intensity. Cetaceans are sensitive to the emission of sound waves, which are also generated by human activities.

[0007] It would therefore be desirable to have a sound wave generator that efficiently generates sound waves at the desired frequencies while being respectful of the marine environment and the cetaceans that live there.

[0008] It is also known that acoustic wave generators with particularly high operating frequencies are subject to acoustic saturation, which results in lower efficiency of acoustic wave generation. In some cases, acoustic saturation is produced by the separation of the water column from the outer surface of the generator.

[0009] The main task of the present invention is to solve the outstanding technical problems by overcoming the disadvantages mentioned in the above-mentioned prior art by inventing an acoustic wave generator suitable for use in a qualified device for marine exploration, which is effective for such research and safe and reliable in use, with respect and safety for the underwater fauna found nearby. Summary of the invention

[0010] The solution concept underlying the invention is to modulate the frequency of the generated sound waves in a controlled manner so as not to reduce the desired properties of the generator's efficiency.

[0011] According to this solution concept, the technical problem is solved by a sound wave generator as described in claim 1 .

[0012] Further features and advantages are contained in the dependent claims.

[0013] The characteristics and advantages of the acoustic wave generator according to the invention will emerge from the description made hereinafter by way of non-limiting example of embodiment with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In these figures:

[0015] Figure 1 are schematic longitudinal and lateral views of an embodiment of an acoustic wave generator according to the present invention;

[0016] Figure 2 is a schematic longitudinal and lateral view of a second embodiment of a portion of a generator made in accordance with the present invention;

[0017] Figure 3 is a schematic side view of a sound diffuser member made in accordance with the present invention. DETAILED DESCRIPTION

[0018] An acoustic wave generator for underwater applications is schematically shown in Figure 1 and denoted by 1. The generator 1 generates acoustic waves, the spectrum of which can be defined as required and can be used expediently in exploration tasks on the seabed with the aim both of mapping the seabed and finding new oil and / or gas deposits.

[0019] The generator 1 is provided with an elongated hollow body 10, which develops longitudinally along the axis XX and is delimited by a rear end 6 and by a front end 8 provided with an acoustic diffuser member 20. The hollow body 10 has a first portion 2, substantially cylindrical, delimited by the rear end 6 and configured to house a first piston 12 or percussion piston. A second portion 4, substantially cylindrical, delimited by the front end 8, is configured to house a second piston 14 or pump piston. The second piston 14 is able to slide freely according to the axis XX and is mechanically separated from the first piston 12 and has a face 15 facing the acoustic diffuser member 20.

[0020] It is expressly noted that the following description will not describe fluid dynamic connection sections connecting valves or other fluid dynamic components, unless it is considered reasonable to describe them for the maximum understanding of the invention. The same approach will be retained for the electrical connections between components.

[0021] The generator 1 comprises a drive group 30 associated with the rear end 6 upstream of the first piston 12 and configured to move the first piston 12 in a sliding manner towards the second piston 14 according to the axis XX.

[0022] In one embodiment, the drive group 30 is of a pulse type. In addition, the drive group 30 can be fluid-dynamically, electrically or hybrid-driven.

[0023] The drive group 30 comprises a first three-way drive valve 31 which fluidically connects the drive group 30 with a tank 32 or with a common discharge port 42. A suitable compressor and a further drive valve (not shown in the figures) may be arranged and coupled to the drive group 30.

[0024] The common discharge port 42 is Figure 1 Several points are used to illustrate the design savings.

[0025] The generator 1 comprises a connection unit 16 interposed between the first piston 12 and the second piston 14 for controlling and regulating, in use, the movement of the second piston 14 relative to the first piston 12. The connection unit 16 comprises a third piston 18, or hammer piston, also freely slidable relative to the first piston 12 according to the XX axis.

[0026] In the hollow body 10, the presence of the third piston 18 results in the formation of a first chamber C1 or an isolated air chamber, which is arranged between the first piston 12 and the third piston 18. Furthermore, a second chamber C2 is formed, which is also isolated and arranged between the third piston 18 and the second piston 14.

[0027] In this way, the first chamber C1 and the second chamber C2 are distinct and connected in series in the hollow body 10 .

[0028] The generator 1 further comprises a control unit 60 which is electronically connected to the connection unit 16 and to the drive group 30 for controlled activation.

[0029] The control unit 60 is provided with a detection unit 50 comprising suitable sensors and detectors configured to detect data and information internally and externally to the hollow body 10. The detection unit 50 may be included in the control unit 60 or associated with the control unit 60 but arranged remotely therefrom.

[0030] For example, in a non-limiting mode, the detection unit 50 may be arranged close to the acoustic diffuser member 20 to detect the presence of cetaceans in the area surrounding the generator 1 itself.

[0031] The damping unit 40 is associated with the second chamber C2 and is driven by the control unit 60 to regulate the pressure in said second chamber C2 .

[0032] In the shown Figure 1 In the embodiment of the embodiment, the damping unit 40 comprises an auxiliary chamber or auxiliary chamber C2', which is interposed between the second chamber C2 and the second piston 14. The auxiliary chamber or auxiliary chamber C2' has a cross-sectional area of ​​smaller dimensions than the cross-sectional area of ​​the second chamber C2. The cross section is made according to a plane perpendicular to the axis XX.

[0033] An intermediate wall 51 interposes and fluidically isolates the second chamber C2 from the auxiliary chamber C2′. The auxiliary chamber C2′ comprises at least one three-way supply and discharge valve 28 connected to the tank 32 and to the discharge port 42. The three-way valve 28 is electronically controlled by a control unit 60.

[0034] Furthermore, in the embodiment shown, the hollow body 10 has different cross sections, the cross section of the first portion 2 having a larger area than the cross section of the second portion 4. The second chamber C2 has a cross section having an area substantially corresponding to the area of ​​the cross section of the first portion 2. The auxiliary chamber C2' has a cross section having an area substantially corresponding to the area of ​​the cross section of the second portion 4, the cross section of the second portion 4 having a lower area than the cross section of the first portion 2.

[0035] The connection unit 16 comprises a connection member 19 placed between the third piston 18 and the second piston 14 and used to drive the second piston 14. The connection member may comprise a rigid rod 19 engaging the intermediate wall 51 in the hole 52, thereby maintaining the hydrodynamic isolation between the second chamber C2 and the auxiliary chamber C2'.

[0036] The control unit 16 may also comprise at least one pressure regulator 17 activated by the control unit 60 and allowing control of the pressure difference between the first chamber C1 and the second chamber C2 , ie upstream and downstream of the third piston 18 .

[0037] In one embodiment, the pressure regulator 17 comprises a first pressure sensor 33 associated with the first chamber C1 and a second pressure sensor 34 associated with the second chamber C2. Furthermore, a first inlet valve 36 connects the first chamber C1 to the tank 32 and a second inlet valve 37 connects the second chamber C2 to the tank 32. A first discharge valve 38 and a second discharge valve 39 connect the first chamber C1 and the second chamber C2, respectively, to a common discharge port 42. All valves 36, 37, 38 and 39 are electronically connected to the detection unit 50 and are commanded by the control unit 60. A third pressure sensor 35 is associated with the chamber comprising the second piston 14 and a fourth pressure sensor 29 is associated with the sound diffuser member 20.

[0038] The first sensor 33 and the second sensor 34 as well as the third sensor 35 and the fourth sensor 29 are controlled by the control unit 60 and their signals are transmitted to the detection unit 50 .

[0039] Within the scope of operation, the sound diffuser member 20 emits sound waves with a predefined frequency spectrum by means of the operating parameters of the first piston 12, of the second piston 14 and of the interposed regulating unit 16. In addition, the damping unit 40 regulates the predefined frequencies more precisely by modulating them even during the activation of the first piston 12. In fact, the control unit 60 drives the three-way valve 28 to modify, reduce or increase the pressure of the auxiliary chamber C2', thereby allowing the frequency of the waves generated by the activation of the second piston 14 to be modulated.

[0040] Thus, when the first piston 12 is already active, if the detection unit 50 detects the presence of a cetacean, the damping unit 40 allows to quickly modify the pressure in the satellite chamber C2 ′, thereby modulating the frequency or frequency spectrum of the sound waves generated by the diffuser member 20 .

[0041] The operation as a whole can be mathematically synthesized by a transfer function F1 which is able to describe the longitudinal movement of the second piston 14 in the second part 4. The longitudinal movement of the second piston 14 is determined by the application of sufficient pressure generated by the drive group 30 on the first piston 12 and on the third piston 18 to move the rod 19 appropriately.

[0042] The transfer function F1 must also describe the action for compressing the fluid contained in the first and second chambers C1, C2 and in the auxiliary or supplementary chamber C2'. This is to emit pressure waves having a frequency spectrum according to the requirements by the diffuser member 20 and to modulate these frequencies, if necessary, according to the information detected by the detection unit 50.

[0043] The transfer function F1 must complete the operating parameters of the control unit 16 and of the regulating regulator 17 and also of the damping unit 40. Furthermore, the operating parameters of the drive valve 31 and of the tank 32 and of any additional valves must be taken into account.

[0044] Now, a description will be given of a portion of the acoustic wave generator 100. Figure 2 For the embodiment shown in Figure 1 The parts corresponding in structure and function to those described and shown in the drawings will be indicated by the same reference numerals and abbreviations. In addition, if not specifically indicated, each part to be described may be structurally and functionally the same as those described in the drawings. Figure 1 A partial combination of the generator 1 is shown.

[0045] The generator 100 comprises a locking unit 80 configured to generate a braking or holding force that allows the second piston 14 to be held in a predefined or fixed position until an impact is generated by activation of the first piston 12 and transmitted by the regulating unit 16 .

[0046] The locking unit 80 may be a mechanical clamp or forceps or an electric or electromagnetic type and may have a holding force strength adjustable by the control unit 60 .

[0047] Shown in Figure 2 In the embodiment of FIG. 8 , the locking unit 80 includes a first electromagnetic ring 81 associated with the first piston 12 and a second electromagnetic ring 82 associated with the second piston 14 .

[0048] The first electromagnetic ring 81 is interposed between the first piston 12 and the drive group 30 and is associated with the inner surface of the hollow body 10 near the rear end 6. The position force generated by the first electromagnetic ring 81 is controlled by the control unit 60 so that the first piston 12 is released only when the pressure difference downstream and upstream of the first piston 12 exceeds the threshold value V1. That is, even under the action or reception of the low-pressure thrust, the first piston 12 stays in the initial position. This allows preventing the first piston 12 from gaining speed and moving away under the thrust generated by the undesired propulsion effect. The pressure difference is a value that depends on the pressure generated by the drive group 30 and the pressure in the first chamber C1, and the pressure in the first chamber C1 depends on the possible activation of the pressure regulator 17. In the illustrated embodiment, the pressure regulator 17 includes three discharge valves V1-V3 arranged in parallel between the first chamber C1 and the common discharge port 42.

[0049] The second electromagnetic ring 82 is axially arranged and associated with the inner surface of the second chamber C2 close to the wall 51. The second electromagnetic ring 82 has the function of keeping the second piston 14 in its original position until the moment of impact caused by the thrust of the first piston 12 to the connecting member or rod 19 as the only thrusting action.

[0050] The first and second electromagnetic rings 81 and 82 of the locking unit 80 allow for canceling a plurality of impacts in the continuous axial direction that may be undesirably generated between the second piston 14 and the first piston 12 .

[0051] To control the pressure in the first chamber C1, the pressure regulator 17 also comprises an air extractor 96 provided with a pump 98 connected to one of the three valves V1-V3. The operation of the pump 98 allows air to be extracted by controlling the pressure difference between the first chamber C1 and the second chamber C2.

[0052] In the embodiment described, the air extractor 96 may include a discharge pipe provided with a wider section, which allows to avoid the acoustic blockage in the throats of the three valves V1-V3 produced by the saturation of the discharge velocity flow. The installation of the double discharge valves V1 and V2 allows the air inside the first chamber C1 to be discharged at a lower velocity.

[0053] Furthermore, it has been found that the presence of the locking unit 80 allows avoiding the detachment of the water column from the outer surface of the hollow body 10 , thus improving the efficiency of the generator.

[0054] In fact, the cavitation bubbles that collapse are formed in the case where the acoustic emission is not caused by the impact of the first piston 12 with the second piston 14, but by the sudden stop of the second piston 14 on the abutment surface of the hollow body 10. In this case, the second piston 14 impacts on its stop at a high speed, thereby generating strong vibrations and stresses in the cylindrical hollow body 10, thereby achieving the acoustic saturation phenomenon.

[0055] Thus, thanks to the locking unit 80 , the effects of acoustic saturation are reduced or eliminated, allowing to obtain a generator 1 that is more efficient and more effective in generating acoustic waves than known generators.

[0056] In one embodiment, a pressure bypass circuit 84 connects the first chamber C1 to the second chamber C2. The bypass circuit 84 comprises a first channel 85 with a bypass valve V4 which is commanded and activated by the control unit 60 and allows reducing the pressure difference between the first chamber C1 and the second chamber C2.

[0057] In this way, the pressure in the second chamber C2 near the second piston 14 is adjusted to be related to the operation of the first piston 12. The force tending to accelerate the second piston 14 is lower than if the bypass valve V4 is ineffective or missing. The opening of the bypass valve V4 can follow several criteria. After the pressure bypass circuit 84 is activated, the strength of the restoring force and / or the holding force of the first electromagnetic ring 81 and the second electromagnetic ring 82 is modified.

[0058] As the pressure in the second chamber C2 increases, when the first piston 12 hits the second piston 14 through the rod 19 , since the impact force is much greater than the restoring force of the second electromagnetic ring 82 , the second piston 14 is automatically released.

[0059] Another high-pressure bypass circuit 86, provided with a second channel 87 and a pressure reducer V5, connects the second chamber C2 and the drive group 30. In this way, the maintenance of the position of the second piston 14 is ensured by the pressure in the second chamber C2 being able to be reduced to a desired value. In extreme cases, the pressure in the second chamber C2 can be the same as the pressure generated by the drive group 30.

[0060] The end position 90 may be arranged in the first chamber C1 to stop the first piston 12 after impact with the third piston 18. The end position 90 comprises a damping element 92 associated with the interior of the first chamber C1 by means of a support ring 91. The damping element 92 may be an elastic ring or elastic band having a damping function.

[0061] In this case, the first piston 12 may include a bullet-like front end point 95 which has the function of allowing an impact between the first piston 12 and the third piston 18 before the first piston 12 stops in said end position 90 .

[0062] The second piston 14 may include a removable rubber cover or cup 99 associated with the front portion that contacts the water to dampen high frequency vibrations.

[0063] In one embodiment, the axial stiffness of each piston (first piston 12, second piston 14 or third piston 18) can be reduced by means of respective elastic rings 70 and 71 interposed between the first and second piston parts and connected sequentially. This allows for a reduction in the axial stiffness of the pistons, with a concomitant reduction in acceleration during impact, thereby mitigating the generation of shock waves and reducing the emission of high frequency signals.

[0064] As schematically shown in Figure 2In the embodiment, the generator 100 may include a soft cover 7 configured to externally surround the hollow body 10 and to be fixed thereto by means of a retaining element, such as a hose clamp or the like. In one embodiment, the soft cover 7 is made of a sponge-like material and has the function of damping vibrations, which are received and transmitted to the structure of the main cylinder or hollow body 10 through the end position 90.

[0065] An embodiment of the sound diffuser member 20 is shown in Figure 3 The diffuser member 20 has a conical shape with a mouth closed at its end or front end by a membrane 21. The dotted line shows the stretched membrane 21, while the solid line shows the tensioned membrane 21. A peripheral edge 22 protruding from the cone of the diffuser member 20 is associated with the membrane 21 and allows to reduce the flow of water inside the diffuser member 20. Its action is particularly effective when the generator 100 is dragged.

[0066] The membrane 21 may be useful for achieving certain acoustic effects. In fact, when the second piston 14 enters the internal volume of the diffuser member 20, the water collected in the internal volume of the diffuser member 20 is displaced and the membrane 21 is tensioned by modifying the acoustic waves generated.

[0067] Of course, the transfer function F1 must take into account all elements and again have operating parameters and characteristics that influence the operation of the acoustic generator 1 , namely the diffuser member 20 and the membrane 21 , the end position 90 and possibly the cover 7 , the pressure bypass circuit 84 and the further high-pressure bypass circuit 86 , the air extractor 96 and the locking unit 80 .

[0068] A suitable transfer function F1 allows controlling the activation of the second piston both by means of a priori control (ie before activation of the first piston) and subsequently with a so-called fine-tuning.

[0069] This makes it possible to modulate the sound waves based on the information received from the detection unit, allowing to obtain an efficient generator for seafloor research but at the same time reliable and safe in use, with respect for the underwater fauna found nearby.

Claims

1. An acoustic wave generator (1, 100) for underwater applications comprising: - a hollow body (10) developed along an axis (XX) and having a front end (8) associated with an acoustic diffuser member (20), said hollow body (10) having a rear portion (2) accommodating a first piston (12) and a front portion (4) accommodating a second piston (14) suitable for sliding freely along the axis (XX) and having a face (15) facing said diffuser member (20); - a drive group (30) associated to the first piston (12) to move the first piston (12) towards the second piston (14); Its features include: - a regulating unit (16) equipped with a third piston (18) and interposed between the first piston (12) and the second piston (14), the third piston (18) forming a first isolation air chamber (C1) interposed between the first piston (12) and the third piston (18), and a second isolation air chamber (C2) interposed between the third piston (18) and the second piston (14), a control unit (60) provided with a detection unit (50), said control unit (60) being electronically connected to said regulating unit (16) and to said drive group (30) for controlled activation of said second piston (14); - a damping unit (40) provided with an auxiliary chamber (C2') associated with and fluidically isolated from the second chamber (C2), the pressure of which is controlled by the control unit (60) for modulating the frequency spectrum of the sound waves emitted by the diffuser member (20).

2. The generator according to claim 1, characterized in that The auxiliary chamber (C2') is inserted between the second chamber (C2) and the second piston (14), and the area of ​​the cross section of the auxiliary chamber (C2') is smaller than the area of ​​the cross section of the second chamber (C2), an intermediate wall (51) is inserted so as to fluidically isolate the auxiliary chamber (C2') from the second chamber (C2), and the auxiliary chamber (C2') includes at least one supply / discharge valve controlled by a control unit (60).

3. The generator according to claim 1, characterized in that: At least one locking unit (80) is included, which is associated with at least the second piston (14) and is configured to generate a holding force to hold the second piston (14) in a predefined position until an impact is generated by the first piston (12), the impact having a greater intensity than the holding force.

4. The generator according to claim 3, characterized in that The locking unit (80) comprises an electromagnetic ring (82) associated with the second piston (14) and configured to generate the holding force, and comprises another electromagnetic ring (81), the other electromagnetic ring (81) being associated with the first piston (12) and configured to generate a position force to hold the first piston (12) in a predefined initial position, the first electromagnetic ring (81) and the second electromagnetic ring (82) being controlled by the control unit (60).

5. The generator according to claim 1, characterized in that: The invention relates to a method for producing a vacuum pump comprising a pressure bypass circuit (85) connecting the first chamber (C1) to the second chamber (C2), the bypass circuit (85) being equipped with a bypass valve (V4) activated by the control unit (60) to adjust the pressure difference between the first chamber (C1) and the second chamber (C2), and / or characterized in that it comprises a further high-pressure bypass circuit (86), the further high-pressure bypass circuit (86) connecting the second chamber (C2) to the drive group (30), the further bypass circuit (86) being equipped with a pressure reducer (V5) activated by the control unit (60), and characterized in that it comprises an air extractor (96) equipped with a pump (98), the pump (98) being connected to the first chamber (C1) by means of one or more extraction valves (V1-V2) to create a vacuum (P).

6. The generator according to claim 1, characterized in that: It comprises an end position (90) provided with a damping element (92) associated with the inner wall of the first chamber (C1) by means of a support ring (91) to stop the first piston (12) after impact with the third piston (18).

7. The generator according to claim 6, characterized in that The first piston (12) comprises a front end point (95) which allows an impact between the first piston (12) and the third piston (18) before the first piston (12) stops in the end position (90), and / or the second piston (14) comprises a removable rubber cup (99) which is associated with a portion facing the front end (8).

8. The generator according to claim 1, characterized in that The sound diffuser member (20) has a conical shape closed at the distal end by a membrane (21) and comprises a peripheral edge (22) protruding from the cone of the diffuser member (20) and associated with the membrane (21).

9. The generator according to claim 1, characterized in that The adjustment unit (16) includes a connecting member (19) interposed between the third piston (18) and the second piston (14).

10. The generator according to claim 1, characterized in that The first piston (12) and / or the second piston (14) and / or the third piston (18) comprise at least two parts coupled to each other by means of at least one elastic ring (70, 71), and / or the control unit (16) comprises at least one pressure regulator (17) for regulating the pressure difference between the first chamber (C1) and the second chamber (C2).

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