GB1596273A - Alarm system - Google Patents

Description

(54) ALARM SYSTEM (71) I, ARCHIBALD STIRLING BUSH, a British Subject, of 1 Parkancreeg, Carnon Downs, Truro, Cornwall, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to systems for giving an audible alarm in the event of an emergency situation, for example a fire and is particularly applicable to fire alarm systems for use in small work boats such as fishing vessels.

It is a principal object of the invention to provide an alarm system that is easy to maintain by non-specialist personnel such, for example, as the crew of a fishing vessel, without the need for specialised spare parts obtainable only from a central supplier.

To this end, according to the invention, there is provided a fire alarm system com- prising a detector circuit containing at least one heat detector and at least one smoke detector each of which conducts only a limited flow of current in normal conditions and an increased flow in emergency conditions, the or each smoke detector on the one hand and the or each heat detector on the other hand, being supplied at different voltages from a common electric power source through voltage regulators, an alarm circuit connected in parallel with said detector circuit and containing an alarm device, and a relay connected in series with said detector circuit and in parallel with said alarm circuit, which relay is energised in response to said increased flow of current through said detector circuit to complete an operating circuit through said alarm device.

To prevent undue annyoance in the case of a minor fire or a false alarm, manually operable means are preferably provided in said alarm circuit for silencing the alarm device, said means comprising a normally open switch and a silencing relay in parallel with the alarm device, said relay operating in response to closure of the switch to short-circuit the switch and disconnect the alarm device. This arrangement ensures that the alarm device can only be silenced temporarily. When the power supply is disconnected the silencing relay returns to its normal condition.

To provide an early indication of a fault in the system, a second alarm device is preferably connected in parallel with the first alarm device and a further relay connected in series with the first relay, said further relay being energised when a current is flowing and being operable, on deenergisation, in response to an interruption in the current flow, to complete an actuating circuit through said second alarm device.

Resetting switches are preferably provided to disconnect the power supply and reset the alarm devices.

In a preferred arrangement, the or each alarm device is supplemented by a warning lamp and in the case of the first alarm device the arrangement is preferably such that the warning lamp remains illuminated when the alarm device is silenced.

One embodiment of the invention, which has been specially designed for use on fishing vessels, will be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a perspective view of the outside of a control box housing alarm devices and a relay system and provided with a manually operable control panel for the alarm system.

Figure 2 is a circuit diagram showing the manner in which the components housed in the control box are electrically connected to each other and to the external parts of the system; and Figure 3 is a further circuit diagram showing the manner in which the external detector devices are connected to the control box.

Referring to the drawings, a control box 100, which is mounted in the wheelhouse or other suitable location on the fishing vessel, has terminals 1, 2 for connection to an external 24 volt D.C. supply, terminals 3, 4 for connection to an external detect ing circuit which includes smoke detectors 5, heat detectors 6 and a resistance 7 con nected in parallel between external lines 8 and 9, and power supply terminals 10, 11 connected to the smoke detectors only, through external lines 12 and 13. The detecting circuit is operated at 12 volts through the intermediary of a voltage regulator 14 arranged in a line 15 connecting the terminals 1 and 3 and the smoke de tectors are operated at 15 volts through the intermediary of a voltage regulator 16 arranged in a line 17 connecting the line 15 to the terminal 10.The detectors 5 and 6 are standard units designed to conduct only a limited current in normal conditions and a greater current when exposed to smoke and abnormal heat respectively and a relay 18 in the line 15 is so designed that it only becomes energised when the current flowing through the line 15 exceeds a value, determined by the setting of a variable resistor 19 in shunt with the relay, equal to said greater current conducted by the detectors. The relay 18 has a first, normally open contact 18a, in a line 20 connecting the line 15 to a return line 21 and a second normally open contact 18b in a line 22 connected in parallel with the the line 15, between lines 23 and 24.Upon energisation of the relay 18 the contacts 18a and 1 8b close to short circuit the detectors 5 and 6 and close circuits through parallel conencted alarm and visual warning devices 25 and 26 respectively arranged in lines 22 and 27 respectively. The devices 25 and 26 are arranged on a control panel 28 forming the front wall of the control box 100, the alarm device 25 being designed to emit a strident bleeping sound and the device 26 being in the form of a red lamp. In order to silence the alarm device 25 to prevent undue annoyance in the case of a minor fire or a false alarm a relay 29 is arranged in parallel with the devices 25 and 26 in a line 30 which contains a normally open press-button switch 31.The relay 29 has a normally closed contact 29a arranged at a point in the line 22 between its junction with the line 27 and the alarm device 25 and a normally open contact 29b in shunt with the switch 31. When the switch 31 is momentarily closed the relay 29 is energised causing the contacts 29a to open breaking the circuit through the alarm device 25 but not through the lamp 26 and the contacts 29b to close and thus maintain the relay in its energised state even though the switch 31 returns to its open position.

In order to give the alarm should the flow of current through the system be interrupted or reduced to a level insufficient to permit proper working of the detector circuit, a relay 32 shunted by a resistor 33 is provided in the line 15. The relay 32 is energised when the current flowing through the line 15 is sufficient to ensure efficient operation of the detector and alarm circuits and has a first, normally open con tact 32a in series with the resistor 33 and a second, normally open contact 32b, in a line 34 connected in parallel with the line 15 between a line 35 and the line 24. Upon deenergisation of the relay 32, the contacts 32a and 32b close to short-circuit the relay 32 and complete circuits through parallel connected alarm and visual warn ing devices 36 and 37 respectively arranged in lines 34 and 38 respectively.The alarm device 36 which is arranged inside the control box 100 and not on the control panel 28, is designed to emit a steady note which continues until the fault is repaired.

The device 37 constitutes a lamp arranged on the control panel 28 and designed to emit an amber light.

In order to rest both alarm devices after use a normally closed press-button switch 39, operable from the panel 28, is arranged in the line 15 at its junction with the lines 23 and 35. When the switch is momentarily operated to disconnect the alarm circuits from the power input, the relay 18 is deenergised, opening the contacts 18a, 18b and the relay 29 is deenergised, closing the contact 29 and opening the contact 29b.

When no power is supplied to the system the relay 32 is not energised and accordingly the contacts 32a and 32b are closed.

When power is first supplied to the system, therefore, the devices 36, 37 are activated and it is necessary to provide a pressbutton switch 40 which is operable to momentarily interrupt the flow of current through the shunt and permit energisation of the relay 32, whereupon the contacts 32 and 32b are opened and the devices 36, 37 deactivated.

The line 17 also contains a press-button switch 41 which is operable from the control panel 28 to reset the smoke detectors 6 after use and a green lamp 42 on the control panel is connected across the line 17 and a line 43 connecting the terminal 11 to the line 21 and is illuminated when .ever the system is supplied with power.

In order to reset the devices 25 and 26, a normally open press-button switch 44 is provided in the line 24 and is operable from the control panel 28 to short circuit the detector circuit and thus provide an increased current flow sufficient to energise the relay 18.

It will be noted that the system avoids, as far as possible, the use of semiconductors so that maintenance can be carried out by a boat's crew. It is a 12 volt system with the voltage regulator 14 driven optionally by at 24 volt or 12 volt supply depending on the boat in which it is to be used.

It will be understood that the illustrated embodiment is given by way of example only and that numerous modifications are possible without departing from the scope of the appended claims.

WHAT I CLAIM IS: - 1. A fire alarm system comprising a detector circuit containing at least one heat detector and at least one smoke detector each of which conducts only a limited flow of current in normal conditions and an increased flow in emergency conditions, the or each smoke detector on the one hand and the or each heat detector on the other hand, being supplied at different voltages from a common electric power source through voltage regulators, an alarm circuit connected in parallel with said detector circuit and containing an alarm device, and a relay connected in series with said detector circuit and in parallel with said alarm circuit, which relay is energised in response to said increased flow of current through said detector circuit to complete an operating circuit through said alarm device.

2. An alarm system according to Claim 1, including a switch in the operating circuit of the or each smoke detector, for resetting the detector after use.

3. An alarm system according to Claim 1 or 2, including a lamp in the operating circuit of the or each smoke detector, which lamp is illuminated when said operating circuit is connected to said common supply source.

4. An alarm system according to any preceding claim, wherein said relay is also operable on energisation to short circuit said detector circuit.

5. An alarm system according to any preceding claim, wherein said alarm circuit contains a warning lamp connected in parallel with said alarm device and adapted to be illuminated upon energisation of said relay.

6. An alarm system according to Claim 5, wherein said alarm circuit contains manually operable means for silencing said alarm device while leaving said warning lamp illuminated.

7. An alarm system according to Claim 6, wherein said manually-operable means is a normally-open switch adapted on closure, to complete an energising circuit through a second relay which is connected in parallel with said alarm device and is operable, on energisation, to break the operating circuit through said alarm device.

8. An alarm system according to Claim 7, wherein said switch is of the pressure operated type and said second relay is operable, on energisation, to short circuit said switch and maintain the second relay energised after release of the switch.

9. An alarm system according to any preceding claim, wherein said alarm circuit contains a second alarm device connected in parallel with the first alarm device and a further relay is connected in series with the first relay, said further relay being energised when a current is flowing through said detector circuit and being operable on denergisation, in response to an interruption in the current flow, to complete an actuating circuit through said second alarm device without actuating the first alarm device.

10. An alarm system according to Claim 9, wherein said alarm circuit contains a line-fault warning lamp connected in parallel with said second alarm device and adapted to tbe illuminated upon deenergisation of said further relay.

11. An alarm system according to Claim 9 or 10, wherein said further relay is also operable on deenergisation to complete a circuit by-passing said further relay.

12. An alarm system according to Claim 11, including a fault reset switch in said by-pass circuit, said switch being manually operable to disconnect said second alarm device from the current supply.

13. An alarm system according to any preceding claim, including an alarm reset switch in series with said alarm and detector circuits, said switch being manually operable to disconnect said circuits from the current supply.

14. An alarm system according to any preceding claim, including an alarm test switch connected in series with said alarm circuit and in parallel with said detector circuit, said switch being operable to shortcircuit the detector circuit and connect the alarm circuit to the current supply.

15. An alarm system according to any preceding claim, wherein said alarm circuit and the or each relay are housed in a control box having terminal connections to said detector circuit, one wall of said control box constituting a control panel which carries said first alarm device, indicating and warning lamps and manually operable switches.

16. An alarm system, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

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

Claims (16)

**WARNING** start of CLMS field may overlap end of DESC **. used. It will be understood that the illustrated embodiment is given by way of example only and that numerous modifications are possible without departing from the scope of the appended claims. WHAT I CLAIM IS: -

1. A fire alarm system comprising a detector circuit containing at least one heat detector and at least one smoke detector each of which conducts only a limited flow of current in normal conditions and an increased flow in emergency conditions, the or each smoke detector on the one hand and the or each heat detector on the other hand, being supplied at different voltages from a common electric power source through voltage regulators, an alarm circuit connected in parallel with said detector circuit and containing an alarm device, and a relay connected in series with said detector circuit and in parallel with said alarm circuit, which relay is energised in response to said increased flow of current through said detector circuit to complete an operating circuit through said alarm device.

2. An alarm system according to Claim 1, including a switch in the operating circuit of the or each smoke detector, for resetting the detector after use.

3. An alarm system according to Claim 1 or 2, including a lamp in the operating circuit of the or each smoke detector, which lamp is illuminated when said operating circuit is connected to said common supply source.

4. An alarm system according to any preceding claim, wherein said relay is also operable on energisation to short circuit said detector circuit.

5. An alarm system according to any preceding claim, wherein said alarm circuit contains a warning lamp connected in parallel with said alarm device and adapted to be illuminated upon energisation of said relay.

6. An alarm system according to Claim 5, wherein said alarm circuit contains manually operable means for silencing said alarm device while leaving said warning lamp illuminated.

7. An alarm system according to Claim 6, wherein said manually-operable means is a normally-open switch adapted on closure, to complete an energising circuit through a second relay which is connected in parallel with said alarm device and is operable, on energisation, to break the operating circuit through said alarm device.

8. An alarm system according to Claim 7, wherein said switch is of the pressure operated type and said second relay is operable, on energisation, to short circuit said switch and maintain the second relay energised after release of the switch.

9. An alarm system according to any preceding claim, wherein said alarm circuit contains a second alarm device connected in parallel with the first alarm device and a further relay is connected in series with the first relay, said further relay being energised when a current is flowing through said detector circuit and being operable on denergisation, in response to an interruption in the current flow, to complete an actuating circuit through said second alarm device without actuating the first alarm device.

10. An alarm system according to Claim 9, wherein said alarm circuit contains a line-fault warning lamp connected in parallel with said second alarm device and adapted to tbe illuminated upon deenergisation of said further relay.

11. An alarm system according to Claim 9 or 10, wherein said further relay is also operable on deenergisation to complete a circuit by-passing said further relay.

12. An alarm system according to Claim 11, including a fault reset switch in said by-pass circuit, said switch being manually operable to disconnect said second alarm device from the current supply.

13. An alarm system according to any preceding claim, including an alarm reset switch in series with said alarm and detector circuits, said switch being manually operable to disconnect said circuits from the current supply.

14. An alarm system according to any preceding claim, including an alarm test switch connected in series with said alarm circuit and in parallel with said detector circuit, said switch being operable to shortcircuit the detector circuit and connect the alarm circuit to the current supply.

15. An alarm system according to any preceding claim, wherein said alarm circuit and the or each relay are housed in a control box having terminal connections to said detector circuit, one wall of said control box constituting a control panel which carries said first alarm device, indicating and warning lamps and manually operable switches.

16. An alarm system, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.