FR2677323A1 - DEVICE FOR LOCKING A FREE UNDERWATER STRUCTURE IN THE EVENT OF AN EXPLOSION. - Google Patents

Abstract

An underwater structure (1), such as the diaphragm of an ultrasonic transmitter can be blocked in the event of an explosion, by a device which comprises fixed cylinders (15) with movable head (37); the respective paths and shapes of a part of the structure and of a part (40, 41) of the head (37) are such that they pass from its upstream position to its downstream position under the effect of the explosion, the structure (1) interferes with the head (37) and drives it so that the head (37) prevents the free return of the structure (1).

Description

LOCKING DEVICE OF A FREE SUBMARINE Ui URIZ SXRU

IN CASE OF EXPLOSION

  The invention relates to the blocking of a free structure (partially) underwater, in the event of an underwater explosion. It relates more particularly, but not exclusively, to the explosion resistance of the diaphragms

  an underwater acoustic transmitter.

  Such a transmitter is used for dredging underwater mines and is integrated in a profiled vehicle. The transmitter consists of two diaphragms of

  large diameter set in motion by an electric motor

  gnetics The diaphragms are not harnessed material-

  in their movement Stops limit their

  inward and outward stroke.

  Underwater explosions cause

  positive and negative wave reactions, displacements

  violent alternating diaphragm actions These provocative shocks

  so far destroyed and endangered the vehicle and by extension the existence of the complete system.

  The walls of the vehicle body are structures

  non-vulnerable fixed res as opposed to diaphragms

  which constitute the mobile structures to be safeguarded.

  The object of the invention is to avoid the destruction

  tion of the transmitter by blocking the diaphragms for the duration of the effects of the underwater explosion in order to

identify with fixed structures.

  More generally, the object of the invention is to provide an automatic blocking device, in the event of an explosion, of an underwater free structure having a substantially rectilinear path between an upstream position

  (or high) and a downstream (or low) position.

  The device of the invention comprises means for temporarily blocking said structure triggered directly by the rectilinear movement of the structure

  free following the explosion.

  ment directly by the movement, that this triggering does not pass by the detection of the explosion by means of a

  sensor but results from the only movement of the structure.

  The block is temporary, that is, it lasts only

  the time of the effects, always rapid, of the explosion.

  In an advantageous embodiment, the device of the invention comprises at least one fixed member supporting a movable head with a substantially rectilinear path, between an upstream position and a downstream position, the paths and the respective shapes of a part of the structure and of a part of the head being such that when passing from its upstream position to its downstream position, the structure interferes with the head and drives it from its own upstream position to its own downstream position, the structure and the head being , in their downstream position, nested so that the head prevents free

  return of the structure from its downstream position to its posi-

  tion upstream, the fixed member comprising means for-

  toriser a passive movement of the head from a position

  upstream to a downstream position without significant resistance of the head when it is driven from upstream to downstream by the free structure under the effect of the explosion, and to allow a controlled movement of the head from a

  downstream position to an upstream position with resistance

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  very strong tance of the head against the coach

ment exercised by the structure.

  Advantageously, the fixed member comprises a cylinder body housing a piston secured to the head by means of a rod coaxial with the body, the piston separating the body into two closed chambers filled with a fluid (such as oil) and communicating via at least one relatively rapid unidirectional flow orifice and one relatively slow flow orifice leaving a controlled passage of fluid in the opposite direction to that of

  the one-way flow port.

  Advantageously, the one-way flow orifice

  nel has a valve, and the slow flow orifice includes

te a free piston.

  Advantageously, at least one of the orifices is

provided in the piston.

  Advantageously, a spring is subjected to permanent

  one of the faces of the piston towards its position of

rest (upstream position).

  Other features and benefits of

  the invention will emerge from the following description of a

  particular example of embodiment Reference is made to the appended drawings in which: FIG. 1 brings together two axial half-sections through a diaphragm and the device of the invention, respectively in the free state (left half-section) and

blocked (right half-cut).

  Figure 2 shows in more detail the arrangement

  sitive of the invention in the locked position.

  In the particular case illustrated, the invention applies to each of the two diaphragms of a transmitter

underwater sound.

  Each diaphragm 1, made of mechanically welded light alloy, consists of a hemispherical wall 2 (for example 0.75 m in diameter) bordered by an annular crown -4- 3 and surmounted by a closing cap 4 fixed by means not shown Internally, the diaphragm 1 comprises a network of vertical ribs 5 which connect the wall 2 to a guide sleeve 6 which slides with lubrication on a fixed axis 7 Le

  diaphragm is set in motion by an electro-

  genetics 8 secured under the crown 3 by means

  classic and plunging into the air gap of a circling block

  baked magnetic 14 not detailed A flexible joint 9 taken

  between crown 3 and the outer fixed part, assu-

  re sealing while allowing axial movement around a medium position The diaphragm stroke of approximately 20 mm on either side of the medium position is limited by elastomer stops 10 and it,

  carefully sampled and distributed.

  These elements are known and therefore do not need

to be described more fully.

  Explosion effects cause displacements-

  alternating diaphragms at speeds that can

reach 8.5 m / s.

  The estimated forces on a diaphragm of a

  surface close to 0.5 m 2 at the time of the explosion

  marine are around 50 tonnes.

  The speed of propagation of the shock wave in

  seawater is around 1500 m / s.

  The problem to be solved according to the invention consists in: detecting the abnormal event produced by the wave

of explosion shock.

  Immobilize the diaphragms before and during

  the destructive effects of the explosion.

  Release the diaphragms at the end of the critical period in order to allow the system to function again.

  According to the invention, the abnormal event is detected

  ted by the forces exerted on the diaphragm by the wave

  of incident pressure These efforts cause a displacement

  important diaphragm towards the interior of the vehicle. When the displacement is greater than a predetermined threshold (system geometry), the diaphragm is "supported" by a damping assembly consisting of a flexible stop and a device which ensures blocking. A piston head of the device ensures with a toothing of the diaphragm a clutching (or meshing) by

  simultaneous movements with concurrent axes.

  The diaphragm is attached during

the crushing of the flexible stop.

  Maintaining in the blocking position is greater than

  the duration of the destructive effects of the explosions

  This duration is controlled by a leak rate

  hydraulics organized in the device.

  The release of the diaphragm is caused by

  relaxation of the flexible stop which urges it outwards

  laughing Displacement frees the head The internal spring

  maintains the device in the rest position.

  The different functions are autonomous and integrated.

  Thanks to the device To operate, it uses the energy

  Explosion We will now detail these means. Thus, in accordance with the invention, there is provided, inside the dome constituting the diaphragm 1, an immobilization device consisting of four similar blocks 12 mounted on a base plate 13 integral

  of mass 14 of the electromagnetic motor.

  Each block 12 comprises a cylindrical body 15 whose axis 16 is inclined by about 30 relative to the axis 17 of displacement of the diaphragm The body 15, which has the function of a hydraulic cylinder, contains a piston 18 sliding thanks to two half-rods 19 and 20 in bores 21 and 22 provided respectively in the bottom 23 of the body and in a cover 24 closing the body and fixed to it The sealing is ensured by O-rings 25, 26 protected by anti-extrusion rings to spare them under the high pressures generated

during operation.

  A series of 33 holes 27 passing through the piston 18 right through connects the annular chambers

  28 and 29 formed on both sides, and ensures the trans-

  the oil present in these chambers during the

  diaphragm support (fast flow).

  A valve 30 produced for example in the form of a flexible crown, bearing on a profiled stop 31, makes it possible to close the passages 27 by applying against their opening opening when the hydraulic pressure in the upper chamber 28 exceeds that of the chamber

lower 29.

  A free piston 32 is mounted with an annular clearance.

  re predetermined in a passage 33 passing through the piston 18 so as to ensure the controlled transfer of the oil from one chamber to the other, and in particular from the upper chamber 28 to the lower chamber 29, at flow rate

  slow, when releasing the diaphragm.

  A compression spring 34 is supported on one face of the piston 18 and on the cover 24 to urge

  permanently the piston towards its rest position (posi-

retracted or downstream).

  Plugs 35 and 36 close common ports

  connecting respectively with the upper 28 and lower 29 chambers (through the piston rods for the latter) and allow filling and boiling of

oil during assembly.

  -7- The lower piston rod 20 is extended by a head 37 of hard treated steel, oriented and secured to the rod 20 by a pin 38 whose head

  travels a rectilinear light 39 of the body 15.

  The movable head 37 has on its peripheral region

  risk facing crown 3 of the diaphragm, a ren-

  darkly profiled with a horizontal shoulder

  lower 40 and an upper horizontal shoulder 41.

  The crown 3, for its part, has an interior border 42 possibly doubled and forming a toothing whose thickness between the upper and lower planes is slightly less than the difference between the

  shoulders 40 and 41 of the movable head 37.

  The operation of the device in accordance with the

  Vention is as follows We will successively describe the detection and arming, immobilization, and

diaphragm release.

  The diaphragm immobilizer only comes into action when the critical threshold (pressure wave due to an underwater explosion) for the

  holding of the diaphragm structure is achieved.

  In the event of an underwater explosion shock, the diaphragm 1 urged by the external pressure (shock wave) simultaneously comes into contact with the internal elastomer stopper il and the plate 40 formed on the

piston head 37 of the device.

  The crushing of the annular stop it allows the drive of the piston 18 by means of the

  head 37 along an axis concurrent with 30.

  The displacement of the piston 18 causes the oil to be transferred from the chamber 29 to the chamber 28 by the

holes 27 by lifting the valve 30.

  The complete meshing of the toothing 42 with the piston head 37 takes place simultaneously, until the

maximum downstream position.

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  When the solicitation of the direct wave provo-

  quée by the explosion changes direction, the diaphragm 1 is sucked outwards Therefore, it drives the piston 18 in the other direction with the help of the trigger of

the elastomer stopper 11.

  This movement causes the valve 30 to close and authorizes the transfer of the oil only through the annular clearance formed between the free piston 32 and the orifice 33

of the piston collar 18.

  The diaphragm 1 is thus held in this

  position during the alternate destructive effects which

  a maximum time of around 100 milliseconds.

  When the disruptive effects at high pres-

  sions disappear, the only action on the diaphragm 1 is the restitution effort caused by the stop in

elastomer 11.

  It transmits its stress on the device by means of the hooking of teeth 42, of the movable head 37 of the piston, and of the piston 18 to cause the transfer of the oil through the clearance provided around the

free piston 32.

  This oil transfer takes place over a period of time.

  variable from 3 to 10 seconds depending on the value of the overwrite-

  elastomer stopper 11 This crush stroke -

  directly depends on the effects of the explosion.

  The diaphragm 1 is released without intervention.

  outside after release of the mesh.

  The spring 34 completes the movement and maintains the

piston 18 in the rest position.

  The functional need for time delay required

  blocking is 100 milliseconds The time delay

  effective 3 to 10 seconds largely covers the need.

  The transmitter system is protected against over-

  tensions caused by the rapid displacement of the dia-

  phrases in the magnetic field produced by the fixed coils The functional interruption of the transmitter for a few seconds is entirely compatible with the

control system.

  The device's efficiency threshold is such that

  the explosion effects are not sufficient to sol-

  to licit the device for immobilizing the diaphragm is that they are considered harmless to the structure. The use of energy collected from the

  diaphragm can be analyzed in the following way.

  The functional autonomy of the device uses

  the energy of the direct shock wave.

  The phase "detection and management of

  diaphragm "lasts two or three milliseconds.

  During this phase, the elastomer stopper he and

  the immobilizer absorb the trans-

  placed by the diaphragm which itself constitutes the detection wall.

  The dissipation of part of the accumulated energy

  The measurement is instantly carried out in the device during this detection phase by: * the hard transverse friction between the teeth

42 and the piston head 37.

  * The sliding friction of the head 37 on

the body 15.

  * the precipitated transfer of oil through the

series of holes 27.

  The elastomer stopper gradually restores

  the rest of the energy accumulated during the liberated phase

  tion This energy is dissipated by the transfer of

oil in reverse.

  The start of a leak around the free piston

32 controls this dissipation.

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Claims (6)

  1 device for blocking a free underwater structure (1), in the event of an explosion, said structure having a substantially rectilinear path, between an upstream position and a downstream position, characterized in that it comprises means for   temporary blockage of said structure triggered directly   by the rectilinear movement of the free structure following the explosion.   2 Device according to claim 1, characterized in that it comprises at least one fixed member (15) supporting a movable head (37) with a substantially rectilinear path, between an upstream position and a downstream position, the paths and the respective shapes of 'a part (42) of the structure and a part (40,41) of the head (37) being such that when passing from its upstream position to its downstream position, the structure (1) interferes with the head ( 37) and drives it from its own upstream position to its own downstream position, the structure (1) and the head (37) being, in their downstream position, nested so that the head (37) prevents the free return of the structure (1) from its downstream position to its upstream position, the fixed member (15) comprising means (18,27,32) for allowing passive movement of the head (37) from an upstream position to a downstream position without significant resistance of the head (37) when it is driven from upstream to downstream by the free structure (1) under the effect of the explosion, and to allow a controlled movement of the head (37) from a downstream position to an upstream position with a very strong resistance of the head (37) against   the drive exerted by the structure (1).   -11 - 3 Device according to claim 2, characterized   in that the fixed member comprises a cylinder body (15)   dre housing a piston (18) integral with the head (37) by means of a rod (26) coaxial with the body, the piston separating the body into two closed chambers (28,29) filled with a fluid and communicating by at least one orifice (27) with relatively fast unidirectional flow and one orifice (33) with relatively slow flow leaving a   controlled flow of fluid in the opposite direction to that   him from the one-way flow port.   4 Device according to claim 3, characterized in that the orifice (27) with unidirectional flow comprises a valve (30).   Device according to either of Claims 3 and 4, characterized in that the orifice (33) at   slow flow has a free piston (32).   6 Device according to any one of the claims.   tions 3 to 5, characterized in that at least one of the ori-   fices is provided in the piston (18).   7 Device according to any one of the claims.   tions 3 to 6, characterized in that a spring (34) biases   permanently quotes one of the faces of the piston.   8 Device according to any one of the claims.   1 to 7, characterized in that it applies to main-   of a diaphragm (1) of acoustic transmitter under marine.