Patent Publication Number: US-2012042818-A1

Title: Device for salvaging a marine or submarine engine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Paris Convention Application of French Appl. No. 1056656, filed on Aug. 18, 2010, which is incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a device for salvaging a marine or submarine engine, and a marine or submarine engine equipped with such a device. 
     In particular, said engine can be an autonomous submarine vehicle or AUV (for Autonomous Underwater Vehicle). 
     BACKGROUND 
     Installations for salvaging AUV in water from a ship are already known. These installations typically comprise a traction system for pulling the AUV via a cable connecting the traction system and the AUV. 
     Installation examples of this type are described in published patent applications PCT No. WO 2008012472 and No. WO 2008012473. 
     In this type of installation, the cable is initially onboard the AUV. The first steps of salvaging the AUV consist of releasing the cable and waiting until it deploys in the water. Once the cable is deployed, it can be caught from the ship, for example by means of a harpoon or a grapple, and the free end of the cable (i.e. the end not connected to the AUV) can be hauled back on board the ship. The cable can then be attached to the traction system. 
     Now, these first steps and, in particular, the deployment of the cable in the water, can be a problem. In fact, it happens that the cable does not deploy correctly and especially remains near the AUV. In this case, it can be necessary to bring the ship close to the AUV to pick up the cable, increasing the risk of collision between the ship and the AUV and therefore the risk of damaging the AUV. It also eventuates that the cable can wind around some parts (ailerons, screw propeller, etc.) of the AUV, again increasing the chance of damaging the AUV. 
     There is therefore a need for a sure and simple solution for correctly deploying the cable connected to the AUV. 
     SUMMARY 
     The present disclosure relates to a device for salvaging a marine or submarine engine, this device comprising a supple tie line having a first end intended to be connected to said engine; a bobbin to which is connected a second end of the supple tie line, the supple tie line being adapted to be wound about the bobbin; and a ballast charge adapted to be combined with the bobbin. In this device, the bobbin and the ballast charge are such that the bobbin combined with said charge sinks, while the bobbin released from said charge floats, and the supple tie line and the bobbin cooperate such that the bobbin is released from said charge by the unwinding of the supple tie line wound about the bobbin. 
     The methods of use and the advantages of such a device are the following. 
     The bobbin, enclosed by the supple tie line and weighted by the ballast charge, is previously onboard the marine or submarine engine. The type of engine concerned is not limited and can be a floating engine or an engine in controlled immersion, and especially an AUV, a torpedo, a surface drone or another engine of similar architecture. 
     When the engine is to be salvaged from a salvaging base (e.g. a ship, a wharf, an offshore platform, etc.), the bobbin is first released or dropped from the engine. The bobbin then sinks because of the ballast charge. As it sinks, the bobbin brings along with it the supple tie line which unwinds as the bobbin goes down towards the bottom of the water. The unwinding of the supple tie line then prompts the release of the charge and accordingly the unballasting of the bobbin. Advantageously, freeing the charge happens at the end of the unwinding of the supple tie line, i.e. this release is caused by the unwinding of the last turns of the supple tie line. 
     Once released from its ballast charge, the bobbin becomes floating (i.e. its density becomes less than that of water) such that it no longer sinks, but instead floats to the surface. As the bobbin rises, the engine and the bobbin do not drift in the same way as they are not subjected to the same conditions of wind and current. The result is that the bobbin moves away horizontally relative to the engine as it rises and the bobbin surfaces at a significant distance from the engine. 
     Due to the descent of the bobbin and the relative movement away from the engine, the supple tie line is correctly deployed and spaced apart from the engine, making later salvaging easier. Also, the risk of the supple tie line winding about the engine is limited. Finally, relative to the prior art, salvaging of the tie line, and therefore of the engine, is easier and the risk of damaging the engine is less. 
     Supple tie line designates any type of sufficiently supple tie line which can be wound about the bobbin. This supple tie line must also be sufficiently resistant to support traction forces exerted on it. The supple tie line is, for example, a cable or a cord. Advantageously, the supple tie line is non-floating but sufficiently light so that the behaviour of the supple tie line in water is controlled mainly by the movement of the bobbin and the optional first ballast element described hereinbelow. 
     In certain embodiments, the supple tie line bears a first stop between its first and second ends, and the device also comprises at least one first ballast element configured to slide along the supple tie line between the first end and the first stop. 
     When the bobbin sinks, taking the tie line with it, the first ballast element slides along the tie line until it comes into abutment against the first stop. In this way, the first ballast element exerts on the first portion of tie line located between the first end and the first stop a traction force directed downwards, which tends to keep this first portion of tie line substantially vertical. The first ballast element and the stop also form an articulation zone about which the second portion of tie line, located between the first stop and the second end of the tie line, pivots when the bobbin rises to the surface. The fact that this articulation zone exists and is located at a certain distance below the engine further limits the risk of the tie line winding about the engine. In particular, this risk remains limited even if the engine is running after deployment of the tie line. 
     In certain embodiments, the bobbin has a winding surface about which the supple tie line can be wound, and the bobbin has a recess for receiving the ballast charge, this recess having a first opening through which the ballast charge can pass, this first discharge opening being located on the winding surface. 
     In certain embodiments, the first opening is closed or blocked by a first cover, the first cover having an external face defining a part of the winding surface. 
     In certain embodiments, the second end of the supple tie line is connected to an attachment point located inside the recess, the supple tie line passes through the first cover, and the supple tie line bears a second stop between its second end and the cover. This second stop pulls the cover so as to unblock the first opening during unwinding of the supple tie line. Unblocking the first opening then allows the ballast charge to exit the recess and unballast the bobbin which will then rise to the surface. 
     In certain embodiments, the recess has a second opening through which the ballast charge can pass, this second opening being located outside the winding surface and closed or blocked by a second cover. The ballast charge can be introduced inside the recess through this second opening. Since the cover is located outside the winding surface, placing and removing the cover can be done independently of the winding of the supple tie line about the bobbin. For example, this allows one to introduce the ballast charge into the bobbin while the supple tie line is already wound about the latter. 
     In certain embodiments, the bobbin bears at least one second ballast element, this second ballast element being arranged on the bobbin so as to orient the first opening downwards, when the bobbin is under water. This helps to empty the recess of the ballast charge more easily and completely. 
     Another aim of the present disclosure is a marine or submarine engine equipped with a device such as described earlier, the first end of the supple tie line being connected to said engine. 
     In certain embodiments, said engine is configured to take onboard the bobbin enclosed by the supple tie line, the engine comprising a release system for releasing the bobbin. 
     In certain embodiments, the release system is remote-controlled. It can be remote-controlled from the salvaging base of the engine, where this salvaging base might be a ship, a wharf, an offshore platform, etc. 
     Several embodiments are described in the present disclosure. It is specified however that, unless otherwise stated, the features described in relation to one embodiment can be applied to another embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The attached drawings are schematics and are not necessarily to scale; their main aim is to illustrate the principles of the invention. 
       In these drawings, from one figure (FIG.) to the other, similar elements (or parts of element) are identified by the same reference sign. Also, elements (or parts of elements) belonging to different embodiments but having an analogous function are identified by reference numerals spaced apart by 100, 200, etc. 
         FIG. 1  is a perspective view of an example of a device according to the present disclosure, comprising a bobbin and a supple tie line wound about this bobbin. 
         FIG. 2  a sectional view of the device of  FIG. 1 , as per the sectional plane II-II. 
         FIG. 3  is a sectional view, similar to that of  FIG. 2 , illustrating the bobbin before the ballast charge is introduced inside the bobbin. 
         FIG. 4  is a perspective view, illustrating the bobbin of  FIG. 1  during release of the ballast charge. 
         FIG. 5  is a sectional view of another example of a device according to the present disclosure, comprising a bobbin and a supple tie line wound about this bobbin. 
         FIG. 6  is a sectional view of the device of  FIG. 5 , as per the sectional plane VI-VI, after unwinding of the supple tie line. 
         FIGS. 7 to 10  illustrate an example of an engine according to the present disclosure. These figures illustrate the successive steps of the deployment of the supple tie line fitted to this engine. 
         FIG. 11  is a detailed view of the front part of the engine identified by the circle XI in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the device propose are described in detail hereinbelow, in reference to the attached drawings. These embodiments illustrate the characteristics and advantages of the invention. However, it is recalled that the invention is not limited to these particular embodiments. 
       FIG. 1  illustrates an example of a device  10  for salvaging a marine or submarine engine  80 . This engine  80  is shown in  FIGS. 7 to 10 . 
     The device  10  comprises a supple tie line  20  and a bobbin  30 . The supple tie line  20  has two ends  21 ,  22 . The first end  21  is connected to the engine  80 , and the second end  22  is connected to the bobbin  30 . In the example, the supple tie line  20  is a cord. 
     The bobbin  30  comprises a central core  31  defining a winding surface  33  for the tie line  20 . This winding surface  33  is bordered by two flanges  34 ,  35  which keep the tie line  20  between them. In this example, the central core  31  and one of the flanges  34  form a monobloc assembly. The other flange  35  is fixed to the central core, for example by screwing (screw  36 ). It is to be noted that such a configuration has been chosen to adjust the floatability of the bobbin, and the flange  35  made from floating material(s) is machined, for example, with variable dimensions to vary the Archimedes thrust. 
     The central core  31  has a general shape of a hollow cylinder of axis A, with two openings at its axial ends, respectively blocked by two covers  37 ,  38 . The cover  37  is mounted, for example by screwing on the flange  34  and cannot be dismantled. The cover  38  located to the side of the flange  35  blocks the opening  42  and is removable. The central core  31  and the covers  37 ,  38 , together define a recess  40 . 
     This recess  40  takes up a ballast charge  50 . This ballast charge  50  is formed by an assembly of elementary charges of limited size such as for example metal balls, grains of sand, etc. In particular, the size of these elementary charges is clearly less than that of the openings  41 ,  42  of the recess  40 . 
     This ballast charge  50  is introduced inside the recess  40  through the opening  42 , herein called “inlet opening”, as symbolised by arrow F 1  of  FIG. 3 . This is possible as the cover  38  is removable. Also, as the inlet opening  42  and its cover  38  are located outside the winding surface  33  of the tie line  20 , it is possible to place/remove the cover  38  even when the cable  20  is wound about the bobbin  30 . The ballast charge  50  can therefore be introduced into the recess  40 , through the inlet opening  42 , after the winding of the cable  20 . 
     The recess  40  also has another opening  41 , herein called “discharge opening”, through which the ballast charge  50  can exit the recess  40 . This discharge opening  41  (see  FIG. 4 ) is located on the winding surface  33  and, in this example, it is closed or blocked by another cover  39  whereof the external face  39 A defines a part of the winding surface  33 . 
     The supple tie line  20  and the bobbin  30  cooperate such that the bobbin  30  is released from the charge  50  by the unwinding of the supple tie line  20  wound about the bobbin  30 . More particularly, in this example, the unwinding of the supple tie line  20  causes displacement of the cover  39  and therefore the unblocking of the discharge opening  41 . 
     More precisely, the second end  22  of the tie line  20  is connected to an attachment point  44  located inside the recess  40 . Also, the supple tie line  20  passes through the cover  39  and bears a stop  45  between its second end  22  and the cover  39 . The stop  45  is, for example, a node obtained by interlacing of the tie line  20 . The length of the tie line  20  between its end  22  and the stop  45  is greater than the distance between the attachment point  44  and the cover  39  in its position closed. So, when the last turn of the tie line  20  unwinds, the tie line  20  stretches and the second stop  45  pulls the cover  39 , which unblocks the discharge opening  41 . The ballast charge  50  can then exit through the opening  41 , as shown by arrow F 2  in  FIG. 4 . 
     As the ballast charge  50  exits the recess  40  by gravity, via the opening  41 , it is preferable for this opening  41  to be oriented downwards as much as possible. For this purpose, several solutions, which can be used alone or in combination, are proposed. One solution consists in providing a discharge opening  41  highly extended circumferentially (for example, more than 180°). Another solution consists in not positioning the attachment point  44  of the supple tie line  20  in a position diametrically opposite the discharge opening  42  but instead positioning the attachment point  44  near the discharge opening  41  and especially on the same side of the axis A as the opening  41 . Another solution consists in mounting on the bobbin  30  one or more ballast elements  51 , these ballast elements  51  being arranged on the bobbin  30  so as to orient the opening  41  downwards, when the bobbin is under water. In the example of  FIGS. 1 to 4 , five ballast elements  51  in the form of a pin are fixed on the flange  34  of the bobbin  30 , on the same side of the axis A as the discharge opening  41 . 
     Another example of a device  110  is represented in  FIGS. 5 and 6 . As does the device  10 , the device  110  comprises a supple tie line  120  and a bobbin  130 . The supple tie line  120  has two ends. The first end is connected to a submarine or marine engine, and the second end  122  is connected to the bobbin  130 , at the level of an attachment point  144 . 
     The bobbin  130  comprises a central core  131  defining a winding surface  133  for the tie line  120 . This winding surface  133  is bordered by two flanges  134 ,  135  which keep the tie line  120  between them. In this example, the central core  131  and the two flanges  134 ,  135  form a monobloc assembly. 
     In this example, the central core  131  is not hollow. Yet it could be, especially for floatability reasons. 
     The bobbin  130  has a recess  140  for receiving a ballast charge  150 . This ballast charge  150  is a single piece such as, for example, a metal bar. 
     The recess  140  has the form of a groove made in the winding surface  133  and, in the example, oriented parallel to the axis of the bobbin. 
     The ballast charge  150  is introduced in the recess  140  via the upper opening  141  of the groove. The “upper opening” is the opening located facing the bottom of the groove. This upper opening  141  is located on the winding surface  133 . The ballast charge  150  is introduced in the recess  140  prior to the winding of the tie line  120  around the bobbin  130 . 
     The supple tie line  120  and the bobbin  130  cooperate such that the bobbin  130  is released from the charge  150  by the unwinding of the tie line  120 . More particularly, in this example, it is the turns of the tie line  120  which keep the ballast charge  150  in the recess  140  and consequently the unwinding of the last turns releases the ballast charge  150  which can then slip out of the recess  140 , as shown by arrow F 3  in  FIG. 6 . 
     As the ballast charge  150  exits the recess  140  by gravity, via the opening  141 , it is preferable for this opening  141  to be oriented downwards as much as possible. For this purpose, several solutions, which can be used alone or in combination, are proposed. One solution consists of positioning the attachment point  144  of the supple tie line  120  in a position diametrically opposite the opening  141 , as shown in  FIG. 6 . Another solution consists of mounting on the bobbin  130  one or more ballast elements, these ballast elements being arranged on the bobbin  130  so as to orient the opening  141  downwards, when the bobbin is under water. 
       FIGS. 7 to 10  represent an example of an engine  80  according to the present disclosure. These FIGS. illustrate the successive steps of the deployment of the supple tie line  20  fitted on this engine  80 . 
     In the example, the engine  80  is an autonomous underwater vehicle or AUV. It is equipped with a device  10  of the type shown in  FIGS. 1 to 4 . Of course, it could be equipped with another type of device and, especially, with the device  110  of  FIGS. 5 and 6 . 
     The engine  80  is configured to be able to take onboard the bobbin  30  enclosed by the supple tie line  20 . For example, the engine  80  has in its front part, or &lt;&lt;nose&gt;&gt;  80 A, a recess  82  for receiving the bobbin  30 , the tie line  20  and a ballast element  70  which also forms part of the device  10 . The first end  21  of the tie line  20  is connected to the nose  80 A of the engine  80 , at an attachment point located inside or near the recess  82 . The ballast element  70  is mounted to slide on the tie line  20 . 
     The engine  80  also comprises a release system for releasing the bobbin  30 . This release system can have different structures and different operating modes which depend in particular of the way in which the bobbin  30  is initially connected to the engine  80  and on the shape of the recess  82 . In the example, the recess  82  is closed by a trap  85  (see  FIG. 11 ) which can be opened by way of thrust means such as springs or jacks. In another example, the release system comprises an electromagnet which, when active, blocks the bobbin  30  inside its recess and which, when deactivated, releases the bobbin  30 . Advantageously, the release system is remote-controlled. 
     On completion of its mission, the engine  80  returns to the surface where it is stopped (i.e. its propulsion means are stopped) or is still moving. Salvaging the AUV starts with releasing the bobbin  30  by using the release system remote-controlled from a distance, for example from a ship (not shown). 
     The bobbin  30  then dives under the effect of gravity and the tie line  20  unwinds in the water column located under the nose  80 A of the engine  80 , as shown by arrow F 4  in  FIG. 7 . At the same time, the ballast element  70  slides along the tie line  20  until it stops against a stop  71  shown by arrow F 5  in  FIG. 8 . This stop  71  is located at a significant distance from the first end  21  of the tie line. For example, this stop is a node obtained by interlacing of the tie line  20 . 
     After unwinding of the final turn of the cable  20 , the cover  39  of the bobbin  30  opens and the ballast charge  50  is released, as shown in  FIG. 8 . The bobbin  30  then becomes floating and rises to the surface, pulling with it the tie line  20  as shown in  FIG. 9 . At the surface, the bobbin  30  behaves like a drifting buoy. The bobbin  30  can then be caught and taken on board the ship using different methods. 
     For example, one method consists in using a floating harpoon which is dragged by the ship on a cable. At the same time, the engine  80  moves in such a way that the trajectory of the tie line  20  intersects that of said cable. After intersection, the bobbin  30  is taken on board the ship by way of the cable and the harpoon. 
     Another method consists of approaching the engine  80  with the ship, the engine  80  idling or being stopped. When the ship is at a suitable distance, a harpoon is launched from the bridge of the ship to catch the bobbin  30 . 
     With respect to the behaviour of the assembly formed by the engine  80 , the bobbin  30  and the tie line  20  in the water, after the bobbin is released, it is to be noted that, in the first instance, the device functions in a water column. Next, once the ballast charge  50  is dropped, the bobbin rises to the surface. The bobbin  30  then drifts under the action of deep-sea currents, while the engine  80  drifts under the action of the wind and the surface sea current. The result is that the bobbin  30  arrives at the surface at a significant distance from the engine  80 , achieving the goal in question. 
     When the bobbin  30  rises to the surface, the non-floating supple tie line  20  naturally tends to adopt the form of a small chain. The curve of this small chain is deformed by the ballast element  70 . This ballast element creates a point of inflection between a first portion  20 A of the tie line  20 , extending between the first end  21  of the tie line and the stop  71 , and a second portion  20 B of the tie line extending between the stop  71  and the second end  22 . The ballast element  70  tends to orient the first portion  20 A as vertically as possible. This prevents the first portion  20 A of the tie line from rising to the surface near the bulk of the engine  80 , in particular when the engine  80  is moving, as shown in  FIG. 10 . The presence of the ballast element  70  and its stop  71  therefore clearly decreases the risk of seeing the tie line  20  becoming snarled in the ailerons or in the engine screw  80 .