FR2558600A1 - IMPROVED DEVICE FOR PRODUCING ACOUSTIC WAVES IN WATER - Google Patents

Abstract

WATER CANNON TYPE DEVICE FOR PRODUCING ACOUSTIC WAVES IN WATER. THE DEVICE MAINLY INCLUDES A CYLINDRICAL BODY 1 PROVIDED WITH OPENINGS 6 AT ONE OF ITS ENDS, INSIDE WHICH A FIRST MOBILE CREW CAN SLIDE CONSTITUTE OF TWO PISTONS 7, 8 JOINED BY A ROD 9 AND A SECOND MOBILE CREW OF A PISTON 10, A PISTON 12 AND A HOLLOW ROD 11 OR SLIDES THE PISTON 8. A HYDRAULIC CIRCUIT ASSOCIATED WITH A SPOOL VALVE 40 CONTROLLED BY A NEEDLE VALVE 28, AND A PNEUMATIC CIRCUIT, ALLOWED, WHEN THE DEVICE IS TRIGGERED BY MEANS OF AN ELECTRO-VALVE 36 TO RETURN THE TWO MOBILE CREWS TO THEIR RE-ARMING POSITION. APPLICATION TO SEISMIC PROSPECTION FOR EXAMPLE.

Description

The present invention relates to an improved device for

  produce in the water acoustic waves.

  More particularly, the subject of the invention is a device for transmitting

  acoustic pulses by sudden ejection into the water of a

liquid mass.

  Such a device can be used, for example, to carry out operations

  seismic surveys at sea during which

  lements are generated in the water behind a vessel towing a receiver assembly consisting of a large number of sensors such as hydrophones distributed along a sealed sheath that is

  usually refers to seismic flute and o the echoes on the different

  reflective layers of the seabed are captured by the

  seems receivers and are registered and processed, so as to obtain

a representation of the basement.

  There is known a device for generating pulses in water

  acoustically by ejection of a liquid mass accumulated in a chamber

  inside a hollow body, this room being open on

  the external environment at one of its extremities and delimited to its ex-

  opposite end by a first movable piston. The ejection is obtained by a sudden displacement of a first movable element consisting of the first piston and a second piston to which it is joined by a rod, -2 - this first mobile element cooperating with a second moving element

  slidable within the body and having a tubular shaft

  inside which can slide the second piston of the

  first mobile crew. The operating cycle involves moving

  separate or simultaneous operation of the two mobile crews under the

  motor means comprising a hydraulic system and a pneumatic system.

  in cooperation with a control element actuated by contact between the two mobile crews, and control means external to the device which ensure the coordination of the movements of the two

  mobile crews and their return, after activation, to their posi-

armament.

  The control means comprise three coaxial cylinders isolated from each other, within which they move respectively

  three pistons made integral by the same rod.

  The set of three pistons is movable by action of a system

  hydraulic on the piston of the median cylinder. The displacement of

  corresponding tones in the two other cylinders, one containing a liquid, the other being connected to a pneumatic system, makes it possible to move the two moving equipments and to trigger the movement of the

  main piston. The operation of the device requires the use

  a four-way solenoid valve and a control device

  external to actuate the solenoid valve at two instants succes-

  of the cycle so as to move all three pistons al-

  in one sense and in the opposite direction. Such a device

  is described in French Patent 2,481,382.

  The device according to the invention makes it possible to avoid the use of an organ

  order to synchronize the different stages of operation

  and make automatic rearming operations after

  Tripping. It comprises a tubular body open on the outer medium at one of its ends, a main piston sliding in the body to eject a liquid mass out of it, the main piston being connected to an auxiliary piston to form a first mobile crew,

  a maneuvering system of the first mobile equipment consisting of a se-

  cond movable element comprising a secondary piston and a movable element adapted to slide in the body.and joined by a hollow rod in which the auxiliary piston can slide, the movable element being provided with a central opening forming a seat for the main piston and means for generating fluids at a first

  pressure and a second pressure higher than the first.

  These means cooperating with a control element actuated by the application

  cation of the main piston against the movable element. The device is

  characterized in that it comprises a slide valve whose part-

  The movable tie is displaceable in a cavity under the opposing effects of a fluid at the second continuously applied pressure and a variable pressure, which is capable of taking two values.

  according to the layout of the control element, this distri-

  scorer being adapted to apply intermittently to one side of the pis-

  your secondary a fluid at the second pressure.

  The means for generating the fluids comprise, for example, a gen-

  compressed air at a first pressure and a source of fluid

  at a second pressure, the compressed air generator com-

  permanently communicating with the part of the body lying between the second

  piston and the movable element constituting the second mobile

  The variable pressure applied to the valve spool is that which prevails in a circuit set according to the position of the control element, in communication with the medium.

  outside the device or with the compressed air generator.

  The intervention of the control element making it possible to modify, at the time of the contacts between the two mobile crews, the pressures acting on the dispenser drawer and to change the pressures

  applied to the secondary piston, and the choice of the sections of the

  elements under pressure, has the effect of making the

  completely automatic reset cycle.

  - 4 - Other features and advantages will appear on reading the

  description of a preferred embodiment of the device, and by

  Referring to the accompanying drawings in which: - Figure 1 shows schematically in section the device in its cocking position which is also its rest position; FIG. 2 schematically represents the spool valve for

  intermittent application to the secondary piston of a hydraulic fluid

  lic; FIG. 3 represents a more detailed sectional view of the portion of the movable element containing the control means; - Figure 4 shows a schematic sectional view of the device at the end of the tripping phase o the first mobile unit has arrived at the end of its course to go and o the second mobile unit is joining it; FIG. 5 represents a schematic sectional view of the device

  a later moment when the second mobile crew joined the first

  first at the end of the race; and - Figure 6 shows a schematic sectional view of the device

  during the return phase of the two mobile crews to their po-

rearming position.

  The device comprises (FIGS. 1 to 3 more particularly) a tufted body

  elongated bule 1 provided with two coaxial chambers 2, 3 of different sections which are connected to one another by a shoulder 4. The

  room 2 of smaller section is open on the opposite side to the shoulder-

  4 and communicates with a narrow end 5 of the body

  provided with openings 6, with the external medium. It also includes

  a first movable element consisting of a main piston 7 and an auxiliary piston 8 fixed at the two ends of a first rod 9, and a second mobile element consisting of a secondary piston connected by a second rod. to an annular piston 12. The section of the main piston 7 and annular piston 12 are equal to the section of the chamber 2. Annular seals 13, 14 are arranged on their periphery so as to make their sliding airtight. secondary piston 10 is adapted to the section of the chamber 3 of the body. An annular seal 15 is arranged around its circumference to seal its sliding in the chamber 3. The main piston 7 is connected to the rod 9 by a frustoconical portion 16. A bore 17 of section adapted to the section of the auxiliary piston 8 is arranged in the axis of the movable element and the second rod 11. It is provided at its inlet a chamfered portion 18 of shape adapted to the frustoconical portion 16 of the main piston 7. A seal 18a is fixed to the annular piston 12 in the vicinity of the chamfered portion, to properly isolate from the inside of the rod 11, the space 60 of the body between the main piston 7 and the annular piston 12 when supported

  One against the other. The surface S2 of the main piston subjected to the

  When the compressed air is in contact with the annular piston 12 and the seal 18a, it is smaller than the surface S1 opposite

  of the auxiliary piston 8. An annular seal 19 is disposed on the

  turn of the auxiliary piston 8 to ensure the leaktight sliding thereof. The length of the rod 9 is such that, when the frustoconical portion 16 bears on the chamfer 18, the auxiliary piston

  substantially at the bottom of the central bore 17.

  The secondary piston 10 comprises a tubular extension 20, of the c8-

  opposite to the annular piston 12. This body 1 is closed at its end

  opposed to the constricted portion 5, by a cover 21. A seal of

  Ring gap 61 is disposed on the periphery of the cover. This cou-

  vercle is provided with a central bore of section adapted to that of the tubular extension 20, at least over part of its length, this central bore having a peripheral groove for a

seal 22.

  An opening 23 is made in the annular piston 12 to permanently communicate the second chamber 3 with the central bore 17 of the second rod 11. Two channels 24, 25 are formed in the piston

  ring 12 from the face 12a thereof opposite the second piston

  10 (Fig. 3). The channel 24 passes right through it, the other 25 communicates with an internal recess 26 opening into the void.

  60 on the opposite side 12b of the annular piston, through an orifice 27.

  In the recess 26 can slide a control means constituted

  a needle valve 28 arranged to isolate the channel 25 from the ori-

  27, in the rest position. The needle passes through the orifice 27 and protrudes outside the face 12b so that when the annular piston 12 bears against the main piston, the

  needle is pushed and the valve 28 raised, which establishes the

  communication between the channel 25 and the space 60 between the two pistons

7 and 12.

  The two channels 24 and 25 communicate, via two

  pipes 29, 30 respectively with two channels 31, 32 (FIG.

  pouring through the secondary piston 10 and leading to the

  interior of the tubular extension 20 thereof. Three other channels 33, 34, 35 also pass through the secondary piston 10 from one side to the other. On one side, they open into the tubular extension 20 and

  two of them 33, 34 are connected to the two channels of an electro-

  Two-way valve 36. On the opposite side, one of the channels 33 opens into the annular space between the second hollow rod 11 and the wall

  body and the other two 34, 35 lead to the

  of said second rod in a chamber 59 defined for the secondary piston 10 and the auxiliary piston 8. The channel 35 is very

  end, at least over part of its length.

  An opening 37 is made in the side wall of the body 1 at the second chamber 3. A pipe 38 connected to a compressed air generator (not shown), is connected to this opening 37, so as to permanently maintain a high pressure (of the order

  140 bar for example) in the part of chamber 3 between the pis-

  secondary tone and annular piston 12.

  The annular cover 21 at the end of the body 1 has a portion

  39 (the detail of which is shown in Figure 2) in which

  a control system consisting essentially of a distribution system

  The distributor comprises (Fig. 2) a drawer

  killed three coaxial pistons 41, 42, 43 joined by the same rod 44 and movable in a cavity 45 three communicating chambers 46a, 46b, 46c. A bore 47 is formed through the wall of the lid 21

  and communicates one of the side chambers 46a with the outside.

  A pipe 48 is attached at one end to the orifice of the channel 31, at the bottom of the tubular recess 20, and at the other end to the outlet of

  bore 47. The side chamber 46c at the opposite end of the housing

  45, is extended by a tubular recess 49 for guiding the rod 44 at one of its ends. In the two opposite chambers 46a, 46c of the cavity open two bores 50a, 50b to which

  two pipes 51a, 51b (Fig. 1) connected to a hydraulic system

  only of a known type and not shown, which is adapted to supply them with oil respectively at high and low pressure (240 basset 1 bar

for example).

  A communication channel 52 is established between the intermediate chamber

  or median 46c and the end of the chamber 3 of the body, on the side of the

  secondary tone 10 opposite the annular piston 12 (chamber 62, see Fig. 4). The intermediate piston 42 of the drawer has two end portions

  frustoconical opposites. Two stops 53, 54 are arranged at both ends.

  Moved from the median chamber 46b. Their shape is adapted to that of the frustoconical end portions of the piston 42, so that when it comes successively apply against the stop 53 (first position of the drawer) and against the stop 54 (second position of the drawer) the middle chamber 46b either well insulated from the chamber 46a or from the chamber 46c. The piston 41 slides in the chamber 46a isolating one

  on the other hand the bores 47 and 50a, whatever the position of the

  roir. The piston 43 slides in the chamber 46c. A channel 55 makes

  to provide the bore 50b with the chamber 46c between the piston 43 and - 8-

  the bore 49 extending it. The thickness of the piston 43 and the

  right o opens channel 55 are chosen so that in the se-

  the position of the drawer where the intermediate piston 42

  against the stop 54, the piston 43 comes to obstruct the entrance of the body.

  Another channel 56 causes the bore 50a to communicate with the

  tubular element 49, whatever the position of the drawer in its cavity.

  you. Calibration means 57 of a known type is disposed in the channel 56 to slow the flow of the oil. A check valve 63

  is arranged in shunt on the calibration means 57.

  The solenoid valve 36 is controlled from a surface installation at

using a conductor cable 58.

  The device works as follows:

  The rest position of the device, which corresponds to its position of ar-

  1 is shown in FIG. 1. The second moving element is in its recoil position for which the secondary piston 10

  is substantially in contact with the lid 21 of the body. The first equi-

  mobile page is also in retreat position. In this position, the main piston 7 is in abutment against the annular piston 12 and the needle valve 28 is raised. The communication between the channels 24 and 25 is established via the orifice 27 and the space 60 in the chamber 2, and thus the hydrostatic pressure can be exerted via the channels 24, 25 and pipes 29,

  and 48, on the piston 41 in the chamber 46a of the distributor 40.

  The pressure of the oil which is exerted in the opposite direction on the rod 44 in the recess 49 at the opposite end of the cavity, is such that the slide is held in its first position (that shown in FIGS. ) and the line 52 is in communication with

  the low pressure oil of the pipe 51b.

  The secondary piston 10 is subjected, on the side of the cover 21 (chamber 62) to a low oil pressure and the other to compressed air at a high pressure, and therefore is maintained in a position of

  decline. The main piston, because the needle valve is

  lift, is subjected to hydrostatic pressure on both sides, except on its frustoconical portion facing the central bore 17 o it is subjected to compressed air. The auxiliary piston is subjected to the hydrostatic pressure via the channel 35 and to the compressed air on

  its opposite face. The overall strength of the first team

  mobile age and which is the result of the forces applied by the air

  on the uneven surfaces S1 and S2, has the effect of

  Nir the main piston 7 applied against the seal 18a.

  - The opening of the trigger solenoid valve is then commanded

  36, which puts the channels 33 and 34 in communication with each other.

  Compressed air is therefore applied to the side of the auxiliary piston

  facing the cover 21 (chamber 3).

  The new result of the forces exerted on the first equi-

  mobile page has the effect of moving it away from the second. The main piston 7 is detached from its seat 18 and the compressed air can come to apply

  on its entire face opposite the annular piston 12. The first

  The first mobile unit is then suddenly propelled towards the end portion 5 of the body against which it comes into abutment (FIG 4) and drives out of the openings 6 the volume of water contained in the first

  2. The expulsion of high-speed water generates in the middle

  external place of powerful acoustic waves.

  As soon as the first mobile unit has started to move away from the second, the needle valve 28 closes and isolates the pipes 24 and one from the other. The compressed air is then applied to the piston 41 of the spool via the channels 24 and 31, the pipe 48 and the orifice 47. The ratio of the respective surfaces of the piston 41 and the rod 44 on the side of the recess 49, as well as the ratio of the pressures of compressed air and oil acting in opposite directions to one another on the slide, are such that the latter moves to its second position ( Fig. 4) o the intermediate piston 42 comes into

- 10 -

  pressing on the seat 54, which puts the channel 52 in communication with

  the bore 50a o reigns a strong oil pressure.

  This high pressure applied to the face of the secondary piston 10 facing the cover 21 (chamber 62) being greater than the pressure of the compressed air applied to its opposite face, the second moving element is in turn propelled towards the end 5 of the body where he joins the

first (Fig. 5).

  During the entire phase of movement of the two moving crews towards the end 5, the narrowing of the channel 35 makes it possible to maintain

  the chamber 59 in overpressure and avoid any external water intake.

  The two moving equipments being brought closer together and the main piston being applied against the seal 18a, the lifting of the needle valve 28 has the effect of putting the space 60 between the piston 7 and the annular piston 12 at the hydrostatic pressure as well as the channels 24, 31 and the pipes 29, 48. The resultant forces due to the application of the hydrostatic pressure on the piston drawerVde the high pressure of the oil circuit on the rod in the recess 49 opposite , has the effect of bringing the drawer back to its first position (Fig. 6). The calibration means 57 makes it possible to delay its

  displacement and thus avoid an abrupt decompression of the

  pace 62 between the piston 10 and the cover 21.

  - It results from the return of the drawer to its first position that the es-

  pace 62 is again in communication with the oil circuit at

  low pressure. The secondary piston 10 being exposed on its opposite side

  Due to the high pressure of the compressed air, the effect of the forces applied has the effect of bringing the second moving element back to its retracted position (Fig. 6). The resulting force applied to the first

  moving element when the main piston 7 is in contact with the piston

  12, tending, as we have seen above, to apply against it the main piston 10, the first mobile unit follows the second in its movement back to their position of

2S58600

- 11 -

  resetting shown in Figure 1. The device is then ready for

a new trigger.

  It is verified that the resetting cycle of the device after its release, by means of the solenoid valve 36, is fully automatic.

- 12 -

Claims (8)

R E V E N D I C A T I 0 N S   1. - Improved device for producing acoustic waves in water   by sudden ejection of a liquid mass out of a tubular body   eye (1) open on the outer medium at one of its ends, this liquid mass being propelled by the sliding of a main piston (7) which is connected to an auxiliary piston (8) to form   a first mobile unit, the device comprising a control system   the first mobile crew consisting of a second crew   bile comprising a secondary piston (10) and an annular piston (12) adapted to slide in the body and joined by a hollow rod (11) in which the auxiliary piston can slide, the annular piston   being provided with a central opening (17) forming a seat for the pis-   your principal and means to generate fluids at a first pressure and at a second pressure higher than the first, these   means cooperating with a control element (28) actuated by the application   cation of the main piston against the annular piston, characterized in that it comprises a slide valve (40) whose movable portion is movable in a cavity (46) under the opposing effects of a fluid at the second pressure applied permanently and a variable pressure, which is capable of taking two different values depending on the arrangement of the control element, this distributor being adapted to intermittently apply to a face of the secondary piston, a fluid at the second pressure.   2. - Device according to claim 1, wherein the means for generating the fluids comprise a compressed air generator at a first pressure and a source of hydraulic fluid to a second   characterized in that the compressed air generator   that permanently with the portion (3) of the body located between the second piston and the annular piston (12) constituting the second crew   whatever the position of the latter, and that the   Variable pressure applied to the valve spool is that which prevails in a circuit (24, 29, 31, 48) set according to the position of the element - 13 -   control, at the pressure of the medium outside the device or with   that of the compressed air generator.   3. - Device according to claim 2, characterized in that the es-   pace (60) of the body between the first piston (7) and the annular piston (12) is permanently connected to one end of the cavity   (46) of the dispenser and intermittently to the outside environment.   4. - Device according to claim 3, characterized in that the cavity (46) of the distributor (40) comprises three coaxial chambers, the intermediate chamber (46b) communicating with one or other of   two lateral chambers (46a, 46b) according to the position of a central piston   tral (42) movable in the intermediate chamber, and the two chambers   lateral bres. communicating respectively with the low circuit   pressure and the high-pressure circuit of the hydraulic fluid source   that the opposite ends of the spool have unequal cross-sections with the largest section being exposed to the variable pressure and the other being exposed to the high hydraulic pressure, and the ratio of the cross-sections of the two opposite ends   2nant chosen for the drawer to move, when the pressure varies   ble is that of compressed air, to a position where the chamber   intermediate (46b) communicates with the high-pressure circuit of the source of hydraulic fluid.   5. - Device according to claim 4, characterized in that the piston   your central (42) is connected by a rod (44) on the one hand to a piston (41) sliding in one of the side chambers (46a) and exposed to the variable pressure and on the other hand to a piston (43) sliding in the other lateral chamber (46c), the latter being extended by a rod (44) sliding in a tubular recess (49) which communicates with   said high pressure circuit of the hydraulic fluid source.   6. - Device according to claim 5, characterized in that the évi-   tubular element communicates with said high pressure circuit via a channel (56) provided with a flow control means (57) comprising   in parallel a circuit element provided with a non-return valve (63). - 14 -   7. - Device according to claim 5, characterized in that the   pace (60) of the body between the main piston (7) and the movable element (12) is connected to one end of the dispenser cavity   (40) through channels (24, 31) passing through the annular piston   and the secondary piston and pipes (29, 48).   8. - Device according to claim 1, characterized in that the es-   pace (59) in the hollow rod (11) between the auxiliary piston 8 and the secondary piston (10) permanently communicates with the medium outside the body via a thin channel (35) and intermittently by means of a valve (36), with the part (3) of the body o reigns permanently the first fluid pressure.