US3289784A - Transmitting device for sound waves - Google Patents

Description

Dec. 6, 1966 J. CASSAND ETAL TRANSMITTING DEVICE FOR SOUND WAVES 5 Sheets-Sheet 1 Filed July 6, 1964 mmw v G ATTORNEY Dec. 6, 1966 Filed July 6, 1964 J. CASSAND ETAL TRANSMITTING DEVICE FOR SOUND WAVES 5 Sheets-Sheet 2 Fig.4

[NV ENTOR5 JEAN CASSAND GERARD DE 50575 JACQUES CHOLET ATTOR NE'KS Dec. 6, 1966 J. CASSAND ETAL 3,

TRANSMITTING DEVICE FOR SOUND WAVES Filed July 6, 1964 5 Sheets-Sheet P Fig-5 United States Patent Oflice Patented Dec. 6, 1966 TRANSMITTING DEVEQE FQJR S'DUND WAVES Jean Cassand, Barrens, Gerard De Soete, Paris, and

Jacques Chalet, Rueil-M'almaison, France, assignors t Institnt Francais du Ptrole, ties Carburants & Lubrifiants, Rueil-Malmaison (Seine et @ise), France Filed .iuly 6, 1964, Ser. No. 380,397 Claims priority, application France, July 11, 1963, 941,185; Jan. 23, 1964, 961,386 9 (Ilaims. (Cl. 181.5)

The present invention relates to a transmitting device for sound waves which can be used in particular for studies of seismic prospecting by the repetition of sound emissions which is made at near and at regular intervals and the recording thereof.

The device, according to the invention, utilizes the energy which is produced by the detonation of a combustible mixture at the exit of a tube or several tubes which extend into a liquid. The pressure wave thus produced moves on into the liquid and from there into the adjoining formations from Where it is reflected and/ or refracted and can then be received and recorded by appropriate apparatus. The device, according to the invention, is conceived in such a manner as to generate a pressure wave with very great energy, in a minimum of time and under very favorable conditions of use and operation.

Into the upper end of each tube, are introduced successively, air forming a combustible mixture with a fuel such as hydrocarbon; and then oxygen which forms a second combustible mixture with a fuel such as hydrocarbon. This latter mixture occupies the upper part of the tube in which the igniting means are arranged in such a manner that, at the moment of igniting, the flame arises in the hydrocarbon oxygen mixture which is highly explosive. The flame then moves easily through the mixture of hydrocarbon and air until detonation. This manner of operation allows rapid burning of the explosive mixture while avoiding an excessive feeding of oxygen which would necessitate the transportation of considerable quantities of oxygen.

A main characteristic of the invention consists in producing a pressure wave of very great power by injecting the combustible mixture under a high initial pressure. This high initial pressure is obtained by closing the exit opening of the tube during the admission and ignition of the mixture, by closing means applied exactly against said opening with a constant pressure equal to or superior to that which is desirable in the tube prior to detonation and yet inferior to the pressure of the shock-wave engendered by the detonation.

When the tube is filled with the combustible mixture at the desired pressure, it is ignited by means of an ignition device positioned in the upper part of the tube. The flame moves through the combsutible mixture along the tube at increasing speed. The shock-wave which starts in this way accelerates the combustion which is transformed into detonation.

At the moment of detonation, the extremely strong pressure-wave produced at the lower end of the tube which extends into water drives out the closing means and moves on into the liquid. The freed energy is the higher the greater the quantity of combustible mixture admitted inside the tube.

Immediately afterwards, the closing means on which the chosen pressure has not stopped to exert itself, reassumes its position against the lower opening of the tube. In this way, there is no great influx of water in the tube.

It is an object of the device, according to the invention, to be used as a source of sound-waves, either for the study of seismic underwater prospection in a continued manner (in this case, the device is carried by a ship), or for studies of seismic earth prospection, whereby the lower part of the tubes constitutes the device which extends into the water supply provided in the ground.

The closing means used with the invention comprises mainly a vertically movable element, the lower end of which penetrates into a hollow cylinder receiving a fluid under pressure. The base of that movable element presses directly or by means of an intermediate element onto a cushion of fluid under pressure. The movable element can glide in a vertical movement between guiding members, the upward movement being caused by the admission of fluid under pressure into the cylinder where it enters at the base. At the end of this upward movement, the head of the movable element, the form of which is chosen in such a manner as to adapt itself exactly to the lower opening of the tube, applies itself against the latter in order to close it. Other objects and advantages of the invention will be apparent from the following description in conjunction with the accompanying drawings, in which like reference numerals refer to like parts throughout the several figures and wherein:

FIG. 1 is a longtiudinal section of an explosion tube provided at its lower end with a closing device, according to the invention;

FIG. 1A is a cross-section following line AA in FIG. 1;

FIGS. 2, 3 and 4 show three modifications illustrating by way of example other closing devices according to the invention;

FIG. 5 portrays schematically an embodiment of the actuating elements which are essential for the arrangement of the invention.

The arrangement shown by way of example in FIG. 1 comprises mainly a tube 1 partially immerged. Its wall 2 is sufficiently thick to resist the force of pressure inside. At different locations of the upper part of the tube, openings are provided in this wall for feeding of gas and combustible under pressure into said tube 1. The tube 1 is closed at its lower end during the entire period of feeding by a valve 46, the functioning of which will be described below. For reasons which will also be described below, the example chosen shows a case where gas and combustible are fed separately.

A compressor 3 feeds air into a reservoir 4 which communicates with a channel 5 on which a gate 6 is placed which, in its closing position, blocks the exit of the reservoir 4. An electro-gate 7 placed at the channel 5 behind the gate 6, automatically controls the flow of air into the tube when the device is operating, this means when the gate 6 is open.

A bottle 8 which holds oxygen under pressure communicates via a channel 9 provided with a gate 10, with a pressure reducer 11. In the position of operation, the oxygen moves from the pressure reducer 11 to the reservoir 12 through the channel 9. The oxygen is maintained under pressure in the reservoir 12. A gate 13 placed onto channel 14 being in communication with the reservoir 12 controls the opening and closing of said reservoir. An electro-gate 15 also placed on the channel 14 automatically controls the flow of oxygen into the tube.

The exits of the electro-gates 7 and 15 open toward a common channel 16 in which the air and oxygen can flow, either alternatively or simultaneously, according to the chosen operating conditions.

The channel 16 starts at the upper end of tube 1 through a bottle-neck 17 which forms a sound-neck. The latter is fixed to the channel 16 by a point 18. The bottle-neck forming a sound-neck is calculated in its extension in such a way that the speed of gas, should be 9 at least the speed of sound, which has the effect of ensuring a constant flow of gas in the tube 1, regardless of the pressure behind the sound-neck, ie in the tube 1.

The means of feeding of combustible into tube 1 comprise a reservoir 19 containing a hydrocarbon, for example gasoline, Which reservoir communicates via gate 20 ensuring the closing of reservoir 19 in the position of 'non-operation, and via pump 21, with an intermediate reservoir 22 in which the gasoline is maintained under pressure by a compressed gas (for example nitrogen) actuating a piston 40. This reservoir feeds two injectors 24 and 25 joined to an electro-gate 23, respectively by the channels 26 and 27, whereby said electro-gate 23 controls automatically the flow of gasoline. The electro gate 23 is arranged in such a manner as to allow the feeding of gasoline alternatively from one or the other injector, whereby the duration of injection for each of them is automatically controlled.

According to a preferred embodiment of the invention, the filling of the tube 1 with a combustible mixture is effected in two stages. The first stage consists in feeding the tube with air which comes from the reservoir 4 via the electro-gate 7 and the sound-neck 17, at the same time as a fine spray of gasoline is jetted through the injector 24. The flow of the injector 24, as well as the duration of feeding gasoline through the electro-gate 23 and the duration of feeding air through the electro-gate 7 are preferably controlled in such a manner as to obtain a combustible mixture of a richness which is close to the stoichiometric richness. Other degrees of richness can also be used.

The second stage, following directly the first one, consists in admitting oxygen from the reservoir 12 into the tube 1 via the sound-neck 17, during a period which is controlled by the gate 15. During that same period, the injector 25 sprays gasoline. The flow of the injector 25 and the time of flow of oxygen and of gasoline during the second stage are equally controlled in such manner as to obtain a combustible of a richness close to the stoichiometric richness. In order to obtain a richness of the mixture of the second stage which is substantially equal to the richness of the mixture of the first stage, it is necessary to have a stronger flow of gasoline from the injector 25 than from the injector 24 since the flow of gas is the same in the two stages and the combustible mixture of the first stage contains nitrogen and oxygen, whereas the mixture of the second stage does not contain azote.

The volume of reservoir 4 and 12 is chosen sulficiently large to ensure that their internal pressure does not vary much during the charging of the tube 1.

The electro-gates 7 and 15 are synchronized with the injectors 24 and 25 respectively, through the electrogate 23 for the duration of each of the two stages. According to a preferred method of the invention, the duration of the first stage is chosen in such a manner as to fill for example of the available inside volume in the tube 1, and the duration of the second stage is regulated in such a manner as to fill the remaining one tenth.

When the feeding of the different elements of the combustible mixture is over, this mixture completely fills the tube 1 which is closed at its lower end by a valve 46. Then the combustible mixture is ignited by means of spark plugs 28, the number and the arrangement of which are chosen so as to obtain rapid ignition of the mixture, preferably at the upper end of the'tube near the diflferent openings for feeding. The flame thus produced moves first into the gasoline/ oxygen which is the most exposive whereby a detonation wave is quickly produced. This detonation wave moves on through the gasoline/ air all along the tube at a speed which attains and then exceeds the speed of sound. In order to shorten the distance of pre-detonation (which distance is necessary so that the speed can pass from that of deflagration to that of detonation), obstacle means 29 can be provided advantageously inside the tube either over a part of the tube or its entire length. Such obstacle means can be, for example, screw-shaped wall-projections which do not reduce substantially the inside of the tube, but nevertheless allow the formation of a suflicient turbulence in the neighborhood of the wall of the tube. This turbulence causes an increase of the speed of combustion which, in this way, attains its maximum value more rapidly, i.e. on a shorter distance.

After the detonation, the gas under pressure escapes partly into the water through the lower end of the tube, and partly through a gate 41 which puts the upper part of the tube 1 in communication with the atmosphere.

The closing device at the lower end of the tube which is shown by way of example in FIG. 1 comprises a mobile element which has a hollow rod, the lower part of which ends in a piston 53 gliding in a hollow cylinder 52, the inside diameter of which is equal, with little play, to the diameter of the piston. The cylinder 52 is provided at its lower end with an opening 54 for the influx of fluid under pressure, preferably in the gaseous state. The upper end of the rod 51 fits into a stop 46 of spherical shape which has the function of a clack-valve for closing the tube.

The clack-valve 46 is chosen of a diameter such as to fit exactly and tightly against the inner wall 2 of the tube to be closed when the mobile element is in its upper position.

The elements 47 which are, for example, made of metallic bars arranged vertically, having one end thereof integral with the wall of the cylinder 52 and the other end integral with the wall 2 of the tube, serve to guide the clack-valve 42 in its vertical course. The elements 47 are sufliciently spaced so as not to substantially weaken the pressure-wave.

At the time of admission of the combustible mixture into the tube, the piston 53 is in its upper position in the cylinder, this position being maintained by the fluid under pressure which fills the cylinder 52. The pressure existing in the cylinder 52 is at all times equal or slightly superior to the pressure in the tube, prior to detonation. At this moment, the clack-valve 46 is applied against the lower end of the wall 2 of the tube, which it closes. The tube, which is immerged, is made tight by means of a circular joint 48 for example of rubber, provided on the Wall 2 of the lower end of the tube manufactured for example according to a truncated cone of revolution The clack-valve 46 remains in closing position during the duration of admission, during ignition and during the combustion of the combustible in the tube.

When the combustion which has moved in the combustible changes to detonation, the very strong pressurewave which forms at the lower end of the tube, and which is by far superior to that existing in the cylinder 52 actuates the clack-valve 46.

The mobile element which is guided by the guiding elements 47 is pushed downward and, as the channel 54 is provided with a no-return valve 64 to avoid back-flow of fluid toward the feeding reservoir, the piston 53 compresses the gas under pressure in the lower part of the cylinder, thus slowing down the downward movement of the piston.

The pressure-wave moves then into the liquid into which the device is immerged. When the pressure-wave stops pressing against the clack-valve, the mobile element, of which the piston 53 is pushed by the under-pressure fluid contained in cylinder 52, reassumes its high position. The clack-valve is again pressed against the lower end of the tube in which there is a very weak pressure between the moment of detonation and the moment of the beginning of admission of the combustible. A new cycle then starts again.

FIG. 2 shows in longitudinal section a closing device which is analogous to that of FIG. 1 where the piston 53 of FIG. 1 is replaced by a flexible but non-elastic membrane 49, the peripheral edge of which is embedded in the wall of the cylinder 52, thus ensuring tightness. The base of the rod 51 sits on said membrane and is therefore subjected to the fluid pressure admitted through the opening 54 in the cylinder 52.

FIG. 3 illustrates a longitudinal section of a closing device of the same type as the preceding ones. However, in this case, the fluid under pressure is not admitted directly into the cylinder 52, but into inflatable jackets 60, each of which communicates with a channel 61 of fluid under pressure provided with an anti-return valve 65.

The clack-valve 46 is in its upper position when the jackets 60 are inflated. When the clack-valve is pressed downward by the detonation, it compresses the envelopes 60 as Well as the gaseous fluid which they contain.

The cylinder -52 can' be filled either by a gaseous fluid which the piston compresses when it is driven by the explosion, which is the case for the previous examples, or by a liquid which serves to compress the gas, according to a known method.

In the case of FIG. 3 given as an example, the lower part of the closing device is surrounded by a keel 62, the form of which is chosen in such a manner as to facilitate a rapid propagation of the pressure-wave along the device.

The hollow rod 51 of the mobile element is preferably made of a light and resistant material, for example, an alloy of aluminum and its diameter is chosen as large as possible in order to resist longitudinal forces. The clackvalve 46 is made of a very resistance material, for example of steel. The cylinder 52 can be made of brass as well as the guiding elements 47. It is also possible to provide between the end of the rod 51 and the clackvalve 56 a circular joint 63 of flexible material (FIG. 3) which absorbs a part of the forces exerted by the rod 51 on the inner wall of the clack-valve 46.

FIG. 4 shows a device analogous to that portrayed by FIG. 1. It is surrounded by a spherical body of metal 66 having many openings 67.

The perforated metallic sphere 66 is intended to avoid the inconveniences resulting from the formation of an air bubble at the exit of the tube at the moment of explosion. This airbubble, immediately after its formation and, at the beginning of its upward movement toward the surface, because of its elasticity, is submitted to pulsating phenomena which are analogous to those inherent to a charged spring. These pulsating phenomena cause interfering disturbances in the seismic recording of reflected waves.

By placing the device according to the invention into a perforated metallic sphere as shown in FIG. 4, the pulsation of the gas bubble which negatively affects the recording can be reduced considerably. Said sphere can, for example, be made of steel or of any other material of high resistance.

The pressure exerted onto the clack-valve 46 can also be obtained by other means than the fluid under pressure in the cylinder 52, for example by the use of one or several springs calibrated to a suitable pressure and taking its bearing on a member which is integral with the explosion tube.

FIG. 5 shows schematically, by way of example, a control system of various electro-gates which control the sequence of operations during the functioning of the device.

The control can be carried out, for example, by means of electric contacts, 42a, 42b, 42c, 42d, arranged on a drum 43 (FIG. 5). The speed of rotation of the drum is regulated in such a manner that one revolution of the drum corresponds to one cycle of operation of the device. The contacts 42a, 42b, 42c, 42d which are fed by a generator 5d are disposed on the drum 43 at locations cal- 6 subsequently be corrected according to known methods by adjusting the position of the contacts 42a, 42b, 42c and 420. on the drum.

The closing of the different circuits can be established in such a manner as to effect successive operations, according to the sequence of operations chosen, following the example of FIG. 5 in the following order:

(1) Opening of the e-lectro-gate 7 for admission of air and, at the same time, opening of the electro-gate 23 for the feeding of gasoline from the first injector 24.

(2) Closing of electro-gate 7 to stop the influx of air. At the same time, opening of the gate 15 for the influx of oxygen and going to a second position of the electro gate 23 for the feeding of gasoline from the second injector 25.

(3) Closing of theelectro-gate 15 thereby stopping the influx of oxygen; closing of the electrO-gate 23, thereby stopping the influx of gasoline, directly followed by the ignition of the combustible mixture by ignition meaps 28.

(4) Opening of the electro-gate 41 for the escape of exhaust gas.

(5) Closing of the electro-gate 41 for stopping the escape of gas.

It will be understood that this invention is susceptible to modification in order to adapt it in diflerent usages and conditions, and accordingly, it is desired to comprehend such modifications within this invent-ion as may fall within the scope of the appended claims.

What is claimed is:

1. A transmitting device for sound waves of great energy comprising a tube, one end of which extends into a liquid, feeding means connected with said tube for injecting a combustible mixture under pressure into said tube, ignition means projecting into said tube for igniting the combustion mixture therein, thus causing a pressure wave within said tube and intermittent closing means for placing the end of said tube which extends into said liquid in intermittent communication therewith, caused by said pressure wave.

2. A device as claimed in claim 1, wherein said intermittent closing means comprises an entirely mobile closing element being pressed against the end of the tube extending into the liquid, with a pressure which is greater than the pressure in the tube prior to ignition of the combustible mixture and which pressure is sufficient to secure tightness of the tube against the liquid, but is smaller than the pressure caused inside the tube by explosion of the combustible mixture, so that the pressure wave caused in the tube of the explosion is transmitted into the liquid by pushing away said closing element from the wall of the tube against which said element is pressed in its normal position.

3. A device as claimed in claim 2, further having a sleeve extending from the liquid-engaging end of said tube and a cylinder reach-ing from below into said sleeve, said closing element comprising at one end a stop member fitting slidingly into said sleeve and at the other end a piston member fitting slidingly into said cylinder, said cylinder being closed at its base and filled with a fluid to reduce the downward movement of said closing element.

4. A device as claimed in claim 3 wherein said piston member of closing element consists of a hollow tube having a large diameter and a base having a diameter substantially equal to the interior diameter of said cylinder.

5. A device as claimed in claim 3 wherein a circular joint of resilient material is provided intermediate said tube and said sleeve to serve as engagement means for said mobile closing element when being in its normal position.

6. A device as claimed in claim 3 wherein said stop member is of spherical shape.

7. A device as claimed in claim 3 further comprising a deformable but non-elastic membrane, the periphery of '7 which is firmly fixed in the wall of said cylinder so as to form a fluid-tight seal between the fluid in said cylinder and said piston member.

8. A device as claimed in claim 3 wherein said cylinder holds inflatable jackets, each of which is receiving fluid under pressure from a common conduit and supporting said piston member.

9. A transmittingly device for sound waves of great energy comprising a tube, one end of which extends into a liquid, feeding means connected with said tube for injecting a combustible mixture under pressure into said tube, ignition means projecting into said tube for igniting the combustible therein, thus causing a pressure wave within said tube, intermittent closing means for placing the References Cited by the Examiner UNITED STATES PATENTS 2,877,859 3/ 1959 Knudsen 181.05 3,022,852 2/ 1962 Pavey 181.05 3,041,970 7/1962 Foster 10225 3,064,753 11/ 1962 McClure 181.05

BENJAMIN A. BROCHELT, Primary Examiner.

end of said tube which extends into said liquid in inter- 15 G. H. GLANZMAN, Assistant Examiner.

Claims (1)

1. A TRANSMITTING DEVICE FOR SOUND WAVES OF GREAT ENERGY COMPRISING A TUBE, ONE END OF WHICH EXTENDS INTO A LIQUID, FEEDING MEANS CONNECTED WITH SAID TUBE FOR INJECTING A COMBUSTIBLE MIXTURE UNDER PRESSURE INTO SAID TUBE, IGNITION MEANS PROJECTING INTO SAID TUBE FOR IGNITING THE COMBUSTION MIXTURE THEREIN, THUS CAUSING A PRES-

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