EP0144260B1 - Electric power supply excitable by a liquid - Google Patents

Description

The technical sector of the present invention is that of power supply devices which can be primed in an immersion liquid.

Numerous electrical devices are known which can be primed in an immersion liquid which use either a battery directly primable by the liquid, or a pressure sensitive switch. In the first case, it is a seawater electrolytic cell which produces a current only when it is immersed. However, batteries of this type can exhibit, even during storage, undesirable discharge characteristics for igniting a detonator for example and consist mainly of silver which increases the cost of these devices. In addition, there is no question of considering defusing the battery. In the other case, these are switches, described for example in patent FR-A-2 008 865, which comprise a capillary tube at the bottom of which are arranged two electrodes. The contact between these two electrodes is made at a certain immersion depth and allows the passage of a weak current which must be amplified by a semiconductor device to make the auxiliary device work. The main drawback of this device lies in the existence of leakage currents, due to the semiconductor, which pass through the device to be initiated on the one hand and which discharge the battery after a certain storage period on the other hand . It is understood that this switch lacks reliability and does not allow long enough to store signaling buoys, mines equipped with it etc ...

The object of the present invention is to provide an electrical supply device making it possible to obviate the aforementioned drawbacks by proposing a device which can be primed upon immersion in a liquid, in which no leakage current appears and whose priming is interrupted as soon as the immersion liquid disappears.

• - un premier circuit, dit de commande, comportant les deux électrodes en série avec une première source de tension et la bobine d'un premier relais;
• - un deuxième circuit comportant, en série, le contact de commande du premier relais, la bobine d'un deuxième relais, une deuxième source de tension et le contact de commande_.du deuxième relais, le deuxième circuit étant relié aux bornes d'un circuit externe d'utilisation;
• - les première et deuxième sources de tension étant reliées en série entre elles et aux bornes du circuit externe d'utilisation, le fonctionnement du dispositif étant tel que lorsque les électrodes sont immergées dans un liquide conducteur un courant s'établit dans le premier circuit, le contact de commande du premier relais se ferme, le deuxième relais est déclenché et la tension aux bornes du circuit externe d'alimentation devient égale à la somme des tensions des premières et deuxième sources de tension.

The subject of the invention is therefore an electrical supply device, which can be started in an immersion liquid by means of two electrodes, characterized in that it comprises:

• - A first circuit, called control, comprising the two electrodes in series with a first voltage source and the coil of a first relay;
• - A second circuit comprising, in series, the control contact of the first relay, the coil of a second relay, a second voltage source and the control contact _. the second relay, the second circuit being connected to the terminals of an external use circuit;
• the first and second voltage sources being connected in series with one another and across the terminals of the external use circuit, the operation of the device being such that when the electrodes are immersed in a conductive liquid a current is established in the first circuit, the control contact of the first relay closes, the second relay is tripped and the voltage across the external supply circuit becomes equal to the sum of the voltages of the first and second voltage sources.

The device according to the invention may comprise a sealed housing containing the two circuits and having a cavity open towards the outside, at the bottom of which the two electrodes are fixed.

dans laquelle

• Vo représente la tension de la source, 1 l'écartement des deux électrodes,
• Uo le seuil de déclenchement du relais, s la surface d'une électrode,
• R' la résistance de la bobine,
• a la conductivité de l'ensemble électrodes-liquide d'immersion.

The electrodes can consist of conductive parts whose surface and spacing are defined by the relation:

in which

• Vo represents the voltage of the source, 1 the spacing of the two electrodes,
• Uo the trigger threshold of the relay, s the surface of an electrode,
• R 'the resistance of the coil,
• has the conductivity of the electrode-immersion liquid assembly.

The electrodes can be produced in the form of metal screws fixed to the housing having an area of 320 mm ² , and located approximately 12 mm from each other.

The electrodes can be subjected to a surface treatment to improve their conductivity.

The electrodes can be separated by an insulating wall with a height greater than that of the electrodes.

The first source may have a lower voltage than that of the second source.

The first relay may have a large internal resistance, of the order of 300 to 2000 ohms and the second relay may have a low internal resistance of the order of 20 to 50 ohms.

A result obtained by the device according to the invention lies in the fact that the start-up is automatically triggered by the presence of a liquid, even a weakly conductive one, guaranteeing great security both in operation of the device under its dependence and out of operation of said device. Unintentional non-liquid operations are avoided by the relative inaccessibility of the two electrodes.

Another result is the independent operation of the hydrostatic pressure.

Another result obtained by the device according to the invention resides in the fact that the batteries do not debit any current outside of the scheduled operating periods.

In addition, this device allows the testing of the device under its dependence before use, and can be protected against accidental trips outside of its intended use.

• la fig. 1 est une représentation schématique du dispositif d'alimentation selon l'invention,
• la fig. 2 représente un exemple de réalisation du dispositif,
• la fig. 3 est une vue de dessus d'un exemple de réalisation des électrodes.

Other advantages of the invention will appear in the light of the following description of an embodiment given by way of illustration in relation to the drawings in which:

• fig. 1 is a schematic representation of the supply device according to the invention,
• fig. 2 represents an exemplary embodiment of the device,
• fig. 3 is a top view of an exemplary embodiment of the electrodes.

The feeding device shown in fig. 1 includes a sealed and closed casing 1 containing the two circuits with the exception of electrodes 2 and 3. It comprises a first circuit comprising the electrodes 2 and 3, a voltage source 5a and the coil 4b of a first relay 4. The second circuit comprises in series the contact 4a of the first relay 4, a second power relay 6 and the voltage source 5b. The relay 6 is connected by output terminals 7a, 7b to any device 7 to be supplied and has a low internal resistance of the order of 20 to 50 ohms; relay 6 allows the breaking of a current of the order of 10 to 12 A. Relay 4 has a large internal resistance of the order of 300 to 2000 ohms and can be of low power, its contact 4a having to ensure the interruption of a current of a few milliamps (about 20). At rest, that is to say in the absence of conductive liquid between the two electrodes, the potential difference at the edge of the coil 4b of the relay 4 is zero; contact 4a is therefore open and voltage U is zero. The same is true for relay 6.

The operation of the supply device is as follows. When the two electrodes are immersed in a liquid, even a weakly conductive liquid, for example sea water, a current is established therein which closes the first circuit comprising the source 5a and the coil 4b. If the difference between the voltage Vo and the voltage drop V between the electrodes 2 and 3 is greater than the tripping threshold of the relay 6, the contact 4a closes and the voltage V is then equal to the voltage Vo. The closure of the contact 6b of the relay 6 is therefore controlled; the device 7 is automatically supplied and has all the voltage Vo available at the terminals of the sources 5a and 5b.

• - une borne 9 reliée au pôle positif du groupe de piles 5a, au pôle négatif du groupe de piles 5b, à l'une des bornes de la bobine 4b du relais 4 ainsi qu'à l'une des bornes de la bobine 4b du relais 4 ainsi qu'à l'une des bornes de la bobine 6b du relais 6,
• - une borne 10 reliée au pôle négatif du groupe de la pile 5a, au contact mobile 4a du relais 4, à l'électrode 2 ainsi qu'à la borne d'utilisation 7b,
• - une borne 11 reliée au pôle positif du groupe de piles 5b ainsi qu'au contact fixe 6a du relais 6,
• - une borne 12 reliée au contact mobile 6a du relais 6 ainsi qu'à la borne d'utilisation 7a,
• - une borne 13 reliée à l'autre borne de la bobine 4b du relais 4 ainsi qu'à l'électrode 3.

In fig. 2, there is shown an exemplary embodiment in which the box 1 contains 15 batteries of 3 volts each, the relays 4 and 6 as well as a printed circuit 8 making it possible to make the connection of the aforementioned elements with the electrodes 2 and 3. The printed circuit 8 includes:

• a terminal 9 connected to the positive pole of the battery group 5a, to the negative pole of the battery group 5b, to one of the terminals of the coil 4b of the relay 4 as well as to one of the terminals of the coil 4b of the relay 4 and to one of the terminals of coil 6b of relay 6,
• a terminal 10 connected to the negative pole of the battery group 5a, to the movable contact 4a of the relay 4, to the electrode 2 as well as to the use terminal 7b,
• a terminal 11 connected to the positive pole of the battery group 5b as well as to the fixed contact 6a of the relay 6,
• a terminal 12 connected to the movable contact 6a of the relay 6 as well as to the use terminal 7a,
• - a terminal 13 connected to the other terminal of the coil 4b of the relay 4 as well as to the electrode 3.

• - la section (s) est la surface de chaque électrode,
• - la longueur (I) est la distance entre les 2 électrodes,
• - la conductivité (o) dépend de la nature du liquide.

The housing 1 comprises a cavity 14 open towards the outside in which the electrodes are placed. The latter are separated by an insulating partition 15 of protection. In Figures 2 and 3 we see that these electrodes 2 and 3 are easily produced using hexagon socket bolts. The surface of the electrodes is defined so that the contact resistance is negligible compared to the resistance of the liquid. We can reduce ourselves to a section of conductive liquid of which:

• - the section (s) is the surface of each electrode,
• - the length (I) is the distance between the 2 electrodes,
• - the conductivity (o) depends on the nature of the liquid.

In the case where the liquid-electrode contact resistance can be neglected (example silvering of the electrodes), this section can be assimilated as a first approximation to a resistance R.

Under these conditions if R 'is the resistance of the coil of relay 4 and Uo are triggering threshold, the voltage of the batteries 5a must be such that:

By way of illustration, and at room temperature if Vo = 9 V, Uo = 3.5 V, a = 0.75 ohm- ¹ x m- ¹ , R '= 380 ohms, I = 12 mm we obtain a surface 320 mm ² electrode. The voltage required to close the circuit is around 3.1 Volts. When the operating temperature drops, for example to -20 ° C., the voltage Vo always remains at a level sufficient to close the contact 4a. We see that the triggering of the relay of the first circuit is provided by a low voltage source, which allows the use of a low performance relay 4. On the other hand, the device 7 can be supplied by a high voltage source equal to the sum of the voltages of the sources 5a and 5b.

It should be noted that in the absence of a conductor between the electrodes 2 and 3, the batteries do not deliver any current, which is advantageous when the power source must be stored for a very long time, for example 5 to 10 years depending on the type. batteries (especially lithium batteries). It has been determined that the storage time is practically equal to the useful life of the batteries 5. It can therefore be seen that the technology of electromagnetic relays used in this technical sector has greater advantages than that of semiconductor devices.

The combination of the two relays 4 and 6 makes it possible to avoid amplification of the current and therefore eliminates any leakage current due to the use of semiconductor amplifiers; the supply device can be easily tested by establishing contact between the two electrodes without any immersion. For this, it suffices to fill the cavity 14 with a conductive liquid or by interposing a conductive wire between the electrodes. The two relays 4a and 6a open as soon as the connection of the two electrodes is interrupted. Thus, the supply device according to the invention can be used in combination with a recording or transmitting device to detect the presence of liquid and more generally to equip signaling buoys, distress buoys, underwater mines etc. ..

Claims (11)

1. Electric power supply device triggered by two electrodes (2, 3) immersed in a liquid, wherein it includes a first circuit called the control circuit including two electrodes (2, 3) in series with first voltage source (5a) and coil (4b) of first relay (4), and a second circuit including control contact (4a) of first relay (4) in series with coil (6b) of second relay (6), second voltage source (5b) and control contact (6a) of second relay (6), the second circuit being connected to the terminals (7a, 7b) of an external load circuit (7), the first (5a) and second (5b) voltage sources being connected in series together and to the terminals (7a, 7b) of the external load circuits (7), a device operating in such a way that when the electrodes (2, 3) are immersed in a conductive fluid a current is set up in the first circuit, the control contact (4a) of the first relay closes, the second relay is tripped and the voltage at terminals (7a, 7b) of the external power supply circuit becomes equal to the sum of the voltages of first and second voltage sources (5a and 5b), respectively.

2. Power supply device as claimed in claim 1, wherein it includes sealed box (1) enclosing the two circuits and offering a cavity (14) open to the outside (25), to the bottom of which are fastened the two electrodes (2, 3).

3. Power supply device as claimed in claim 2, wherein the electrodes (2, 3) consist of conductive pieces with a surface area (s) and separated by a distance (1) defined by the relation:

in which

Vo represents the voltage of source (5a),

Uo the tripping threshold of relay (4),

R' the resistance of coil (4b) and

a the conductivity of the system comprising the electrodes and the immersion liquid.

4. Device as claimed in claim 2 or 3, wherein the electrodes (2, 3) are constructed in the form of metal screws fastened to box 1, with a surface area of 320 mm² and located approximately 12 mm one from the other.

5. Device as claimed in claim 1 to 4, wherein the surfaces of electrodes (2, 3) are treated to improve their conductivity.

6. Device as claimed in any one of the previous claims, wherein electrodes (2, 3) are separated by insulating partition 15 with a height greater than that of the electrodes.

7. Device as claimed in any one of the previous claims, wherein the source (5a) has a voltage less than that of source (5b).

8. Device as claimed in claim 7, wherein relay 4 has an internal resistance of the order of 300 to 2000 ohms and relay 6 has an internal resistance of the order of 20 to 50 ohms.

9. Application of the device according to any of the claims 1 to 8 in the activation of immersible boues.

10. Application of the device according to any one of the claims 1 to 8 to detect the presence of a liquid.

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