GB2073966A - Power supply for a sonobuoy - Google Patents

Abstract

The invention relates to a sonobuoy power supply which comprises a battery 10 automatically switched on by a latch circuit responsive to the conductivity of sea water. In the presence of sea water, sense contacts 12 permit supply of current to the winding 18 of a hold-on relay, contacts 16 of which connect the battery 10 to the load 28. Contacts 14 by-pass the sense contacts 12 to latch the relay. <IMAGE>

Description

SPECIFICATION Power supply for a sonobuoy The present invention relates to sonobuoys and is particularly concerned with the power supply of sonobuoys.

A sonobuoy is a floating assembly normally dropped from an aircraft and having acoustic sensing devices intended to detect and locate primarily submarines. After the sonobuoy has been dropped from an aircraft, it listens to sounds transmitted through the water and communicates by radio with a receiving station to enable the submarine to be located. Such equipment is only called upon to operate for a short while after being dropped into the sea and it incorporates its own power supplies to enable it to operate for such a time. The power supplies must serve both for the purposes of sound detection and radio transmission.

Hitherto, it has been common to provide such sonobuoys with seawater batteries to act as power supply and the present invention seeks to provide a more effective alternative to a seawater battery.

In accordance with the present invention, a sonobuoy is provided with an internal power supply battery and conductivity sensing means responsive to the electrical conductivity of sea water to switch on the power supply automatically.

Conveniently, the means responsive to the electrical conductivity of the sea water may comprise a pair of contacts arranged between the power supply battery and the winding of a hold-on relay having relay contacts connected to the power supply.

The use of a relay prevents polarization across the sense contacts and erosion dur to electrolytic action.

An advantage of the use of a hold-on relay is that it enables the relay contacts acting as power supply connections to be connected to a separate power supply without energising the relay and thereby bringing the internal battery into operation.

Additionally, when the relay has been energised, it is possible to open it by short circuiting the winding of the relay.

As an alternative to the use of an electro-magnetic relay, an equivalent latch circuit, for example a semiconductor latch circuit, may be employed.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure lisa circuit diagram of an embodiment incorporating an electromagnetic relay, and Figure 2 is a block circuit diagram of the second embodiment, employing a latch circuit.

In Figure 1, a power supply circuit is shown for use in a sonobuoy. The power supply circuit incorporates a battery 10, the negative terminal of which is connected by way of a pair of spaced contacts 12 to the case. The positive terminal of the battery 10 is connected by way of a resistor 20 and the winding 18 of a relay to the case. The relay 18 has a first hold-on pair of contacts 14 connected in parallel with the contacts 12 and a second pair of contacts 16 of which one contact is connected to the positive supply of the battery and the other is connected to a load 28.

A diode 22 is connected in parallel with the winding 18, its anode being further connected to an external terminal 24 by means of which the relay 18 may be externally de-energised. Furthermore, a terminal 26 is connected to the load to enable an external power supply to be connected directly across the load.

When the sonobuoy is in contact with sea water, the electrical conductive sea water bridges the gap between the spaced contacts 12 and a current flows from the battery 10 to the winding 18 to energise the relay. The contact 14 then closes to by-pass the contacts 12, thus preventing the relay 18 from switching off as a result of poor contact with the sea water resulting from possible corrosion or electrolytic polarisation.

The contacts 16 which now make connect the load 28 across the battery 10.

The terminal 24 may be shorted to the case to allow the relay to be externally switched off. The diode 22 serves to absorb the back e.m.f. of the relay when it is switched off.

While the contacts 14 and 16 are open, the load circuit 28 is essentially isolated from the battery 10 and therefore it may be energised by the application of a voltage to the terminal 26 without interfering with the battery 10 and the relay circuit.

The alternative embodiment shown in Figure 2 employs a latch circuit 30 in place of the elecromagnetic relay. The latch circuit may respond to the voltage across the contacts 12 which will drop when the sonobuoy is in contact with sea water to energise a bistable latch circuit which when set serves to establish a permanent connection between the positive terminal of the battery 10 and the load circuit 20.

If desired, the latch circuit may incorporate a reset terminal to enable it to be reset externally. This embodiment also offers the advantage that while the latch circuit is in its reset state, the load circuit is isolated from the battery 10 and is therefore capable of being externally powered without interfering with the operation of the battery or the latch circuit.

In the circuit shown in Figure 1, it is important to isolate the turn off terminal 24 and the external power terminal 26 from the sea water. To avoid this requirement the circuit may be modified by connecting a diode in the line between the terminal 26 and the load circuit 28 and by connecting the terminal 24 to the base of a transistor, the switching path of which is connected in parallel with the relay winding instead of the direct connection to the relay winding 18 shown in Figure 1.

1. A sonobuoy provided with an internal power supply battery and conductivity sensing means responsive to the electrical conductivity of the sea water to switch on the power supply automatically.

2. A sonobuoy as claimed in Claim 1, wherein the means responsive to the electrical conductivity of the sea water comprises a pair of contacts arranged between the power supply battery and the winding of a hold-on relay having relay contacts connected to the power supply.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Power supply for a sonobuoy The present invention relates to sonobuoys and is particularly concerned with the power supply of sonobuoys. A sonobuoy is a floating assembly normally dropped from an aircraft and having acoustic sensing devices intended to detect and locate primarily submarines. After the sonobuoy has been dropped from an aircraft, it listens to sounds transmitted through the water and communicates by radio with a receiving station to enable the submarine to be located. Such equipment is only called upon to operate for a short while after being dropped into the sea and it incorporates its own power supplies to enable it to operate for such a time. The power supplies must serve both for the purposes of sound detection and radio transmission. Hitherto, it has been common to provide such sonobuoys with seawater batteries to act as power supply and the present invention seeks to provide a more effective alternative to a seawater battery. In accordance with the present invention, a sonobuoy is provided with an internal power supply battery and conductivity sensing means responsive to the electrical conductivity of sea water to switch on the power supply automatically. Conveniently, the means responsive to the electrical conductivity of the sea water may comprise a pair of contacts arranged between the power supply battery and the winding of a hold-on relay having relay contacts connected to the power supply. The use of a relay prevents polarization across the sense contacts and erosion dur to electrolytic action. An advantage of the use of a hold-on relay is that it enables the relay contacts acting as power supply connections to be connected to a separate power supply without energising the relay and thereby bringing the internal battery into operation. Additionally, when the relay has been energised, it is possible to open it by short circuiting the winding of the relay. As an alternative to the use of an electro-magnetic relay, an equivalent latch circuit, for example a semiconductor latch circuit, may be employed. The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure lisa circuit diagram of an embodiment incorporating an electromagnetic relay, and Figure 2 is a block circuit diagram of the second embodiment, employing a latch circuit. In Figure 1, a power supply circuit is shown for use in a sonobuoy. The power supply circuit incorporates a battery 10, the negative terminal of which is connected by way of a pair of spaced contacts 12 to the case. The positive terminal of the battery 10 is connected by way of a resistor 20 and the winding 18 of a relay to the case. The relay 18 has a first hold-on pair of contacts 14 connected in parallel with the contacts 12 and a second pair of contacts 16 of which one contact is connected to the positive supply of the battery and the other is connected to a load 28. A diode 22 is connected in parallel with the winding 18, its anode being further connected to an external terminal 24 by means of which the relay 18 may be externally de-energised. Furthermore, a terminal 26 is connected to the load to enable an external power supply to be connected directly across the load. When the sonobuoy is in contact with sea water, the electrical conductive sea water bridges the gap between the spaced contacts 12 and a current flows from the battery 10 to the winding 18 to energise the relay. The contact 14 then closes to by-pass the contacts 12, thus preventing the relay 18 from switching off as a result of poor contact with the sea water resulting from possible corrosion or electrolytic polarisation. The contacts 16 which now make connect the load 28 across the battery 10. The terminal 24 may be shorted to the case to allow the relay to be externally switched off. The diode 22 serves to absorb the back e.m.f. of the relay when it is switched off. While the contacts 14 and 16 are open, the load circuit 28 is essentially isolated from the battery 10 and therefore it may be energised by the application of a voltage to the terminal 26 without interfering with the battery 10 and the relay circuit. The alternative embodiment shown in Figure 2 employs a latch circuit 30 in place of the elecromagnetic relay. The latch circuit may respond to the voltage across the contacts 12 which will drop when the sonobuoy is in contact with sea water to energise a bistable latch circuit which when set serves to establish a permanent connection between the positive terminal of the battery 10 and the load circuit 20. If desired, the latch circuit may incorporate a reset terminal to enable it to be reset externally. This embodiment also offers the advantage that while the latch circuit is in its reset state, the load circuit is isolated from the battery 10 and is therefore capable of being externally powered without interfering with the operation of the battery or the latch circuit. In the circuit shown in Figure 1, it is important to isolate the turn off terminal 24 and the external power terminal 26 from the sea water. To avoid this requirement the circuit may be modified by connecting a diode in the line between the terminal 26 and the load circuit 28 and by connecting the terminal 24 to the base of a transistor, the switching path of which is connected in parallel with the relay winding instead of the direct connection to the relay winding 18 shown in Figure 1. CLAIMS

1. A sonobuoy provided with an internal power supply battery and conductivity sensing means responsive to the electrical conductivity of the sea water to switch on the power supply automatically.

2. A sonobuoy as claimed in Claim 1, wherein the means responsive to the electrical conductivity of the sea water comprises a pair of contacts arranged between the power supply battery and the winding of a hold-on relay having relay contacts connected to the power supply.

3. A sonobuoy as claimed in Claim 1, wherein the means responsive to the electrical conductivity of the sea water comprises a latch circuit responsive to the current flowing through a pair of contacts to establish and maintain a connection between the internal power supply and a load circuit of the sonobuoy.

4. A sonobuoy as claimed in any preceding Claim, which comprises a floating assembly and a sub-surface assembly, the floating assembly having a first power supply and the sub-surface assembly being provided with a second power supply at least one of the assemblies being provided with conductivity sensing means responsive to the electrical conductivity of sea water to switch on automatically power supply for providing power to the circuits contained in that assembly.

5. A sonobuoy having a power supply substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.