US2492043A - Fire alarm system - Google Patents

Description

Dec. 20, 1949 w. s. HOLMES FIRE. ALARM SYSTEM Filed April 3, 1.948

Patented Dec. 20, 1949 UNITED STATES- PATENTv OFFICE FIRE ALARM SYSTEM Willis Gerald Holmes, Hanover, Mass., assigner to The Protectowire C0. of Maine, Augusta, Maine, a corporation of Maine AApplication.April 3, 1948, Serial No. 18,743

9 Claims. l

' An analytical survey of any representative selection of serious confiagrations clearly shows that a delay in discovery makes the diiierence between a small easily controlled re and a major disaster resulting from its neglect. This need for prompt discovery of an incipient lire has long been recognized and many systems and devices have been developed to control and indicate the `presence of such a i'lre. Functionally, these devices are divided into two general groups.

One group includes systems with automa-tic detectors (responsive, for example, to the flow of water in a sprinkler system or to a thermostat) to operate electrical contacts thereby tra-nsmitting an alarm signal by means of an electrcal circuit. The preferred type of Such system comprises fundamentally a plurality of detec-tors with normally open electrical contacts for interconnecting two parallel conductors which are connected in series with a terminal resistor and` a power source. The closing of any one of these contacts in response to a change in ambient temperature shunts the terminal resistor thereby decreasing the total resistance of the circuit. The resulting increase in the flow of current is used to operate a switching element of an associated alarm circuit, to open a sprinkler system or to initiate Afunctioning of other fire preventive means.

The other group includes the systems with manually operated alarm stations for transmitting an alarm signal to a central station or to the nre department. Highly developed systems, of this type transmit coded signals in response to rotation of a spring actuated code wheel which interrupts a series connectedelectrical initiating circuit continuously energized from a `power source so vas to be self-supervising.

Because of the danger of panic `in'public buildings such as hotels, theaters and schools, 'a general alarm should not be sounded unless it is absolutely necessary for the safety of the occupants. The common means for accomplishing this end is to have the signal transmitted upon ringing any one of the Aabove-described alarm stations, give a preliminary alarm at la central station in the usual manner. If after an investigation a general alarm is found necessary. it is sounded from the nearest alarm station bv means of a special key carried by theinvestigator.

The ldetecting and alarm svsten'frs are not `generally combined in one system `despite the "ob-` vious advantages in simplicity, economy and maintenance such an arrangement `would have.

If alarm detecting devices of the conventional type are used in the same electrical initiating circuit with series type manual alarm stations, the operation of any one ofthe detecting devices shunts the two parallel conductors so that the alarm stations positioned in the loop beyond the shunt with respect to the power source are rendered inoperative. The interruption of the systernby the operation of one of the detecting devices also prevents 'the use of the alarm stations to sound a general alarm. If an automatic detector with a normally closed contact is connected in series with the initiating circuit, the interrupting .action has the same electrical effect upon supervisory elements of the circuit as a ground or power failure so that the system does not distinguish a nre signal from a trouble signal.

Objects o'f` this invention are to provide an electrical system which incorporates both manually operated alarm stations and automatically operated detecting devices in the same initiating circuit, which transmits coded signals, which rst transmits a preliminary alarm either manually or automatically land which subsequently permits the manually sounding of a general alarm, and to provide such a system which is dependable and electrically self-supervising,

which is simple and. economical to install :and

maintain, and which advances vthe art of fire alarm and detection generally.

In a broad aspect the invention contemplates a signalling system comprising two conductors and a .resistor connected in series with a power source to complete a continuously energized double loop initiating circuit. Each of a plurality of alarm stations is connected toY transmit a signal by simultaneously opening both conductors thereby to interrupt the initiating circuit.. A.

signal is also transmitted by changing theresistance of the initiating circuit by interconnecting the conductors thereof by means oi any one of `a plurality `of detecting stations. A switching element, responding to a first signal from one of the stations, connects a preliminary alarm circuit .and also a time `delay device in a general alarm circuit with the power source. After the operation of the time delay device the switching `element is 'responsiive to subsequent signals to energize both the preliminary and* general alarm circuits.

In a different aspect the alarm circuitor circuits are energized 'from` the same or different power sources: by the' use 'of ftw'o switching elements. `One `of these switching elements connects the alarm circuit eitherin response to a 3 signal resulting from the interruption of the initiating circuit by one of the alarm stations or in response to the operation of a second switching element by a signal from one of the detecting stations.

In a more specic aspect the switching element or elements are relays each having one or more contacts operated by a respective solenoid in response to signals from one of the stations. The interruption of the initiating circuit by one of a plurality of manually-operated alarm stations deenergizes the solenoid of a signal relay connected in series therewith to close three contacts in the preliminary alarm circuit, general alarm circuit and latching relay circuit respectively. The decrease in resistance of the initiating circuit resulting from the operation of one of a plurality of automatically operated code stations results in an increase in the current flowing therein so that the solenoid of a second relay is energized to release a detent restraining an automatically operated code wheel. A normally closed contact in series with the initiating circuit is opened in response to the rotation of the code wheel thereby deenergizing the signal relay and energizing the alarm circuit.

An additional feature is the closing of a normally open contact by the energization of a coil of a latching relay circuit by the signal relay, to connect a heater element of the time delay device to the power source. A latching relay is provided toA maintain the contact in this position until manually released. After a predetermined time interval the rise in temperature resulting from the energization of the heater element closes a normally open heat responsive contact in the general alarm circuit. k

Still another feature of the invention is the possibility of deenergizing, with the rst signal in the above circuit, the signal relay solenoid so that two of the normally closed contacts complete the preliminary alarm and latching relay circuits respectively, the general alarm circuit being not energized as it is interrupted by the open heat responsive contacts of the time delay device. After a time delay determined by the characteristics of the time delay relay, the heat responsive contact closes. A subsequent signal from any one of the manually operated code stations deenergizes the signal relay a second time so that the closing of the contacts completes both the preliminary and general alarm circuits.

These and other objects, aspects and features will appear vfrom the following description of two practical embodiments illustrating the novel characteristics of the invention. This description refers to a drawing wherein:

Fig. l is the circuit diagram of one embodiment; and

Fig. 2 a modication of part of the circuit according to Fig. l, indicating a second embodiment of the invention.

As shown in Fig. 1, the initiating circuit of a re alarm system comprises a double loop of two spatially parallel conductors II and l2. The adjacent ends rI, r2 of these conductors are joined with respective terminals of a terminal resistor R the ohmic characteristics of which are adjustable. The opposite end of the conductor II is linked directly with one pole of a power source such as the battery B. The opposite end of the conductor I2 is connected to one terminal of the solenoid I3 of a iirst switching element such as the relay SI. The initiating circuit is completed to the opposite pole of the battery B through the solenoid I3, a normally closed contact I4, a sole- .4 noid I8 of a second switching element such as the signal relay S2, and the wires I1 and I8.

Energization of the solenoid I3 closes a normally open contact I9 thereby to connect a solenoid 2i to the battery B in a circuit including solenoid 2| of a transfer station, the Contact I9, the conductor Il, the battery B and the wires I8 and 22. The energization of the transfer station solenoid 2| unlatches a spring biased detent 23 so that a spring actuated code wheel 24 rotates to open the contact I4 and interrupts the initiating circuit in a manner analogous to that in which a conventional manually operated alarm station transmits a coded signal.

The initiating circuit can also be interrupted by any one of a plurality of manually operated alarm stations A. Each of these stations A includes a spring actuated code wheel 26 with a cammed surface for opening the contacts 21a and 2lb in a predetermined code sequence and is similar to a conventional alarm station with the exception that the two contacts are used to Open both conductors II and I2 of the initiating circuit rather than a single series contact being used to interrupt the circuit as is the usual practice.

Any number of automatically operated detecting stations D can also be connected in the same initiating circuit. Several such automatic stations are shown schematically in the drawing each as having a normally open contact 28 which can be closed by a heat responsive element 29 thereby to complete a shunting connection between the conductors II and I2. Any or all of these detecting stations D can be replaced `by devices with normally open contacts operated directly or indirectly when a fire occurs (for example by the ow of water in a sprinkler system), or by a con-A tinuous line type detecting cable wherein the conductors contact each other in response to a rise in temperature as is shown in my Patent 2,185,944,

Aor by any of the other well-known types 0f re of contacts @Ga and 30o respectively.

rihe conjoint closing of the contact 38e energizes a locking relay S3 by means of a circuit including the relay coil 3i, the normally closed contact 30o, the wires 32 and I8, the battery B and the wires II and 33. This energization of the coil 3| 4closes the contact 34a to connect a heater element h of a thermal timer T or time delay device of another type to the battery B by means of the wires 35, I8, II and 38. A second contact 34D closes conjointly with 34a` to provide a holding circuit in parallel with the contact 30e by means of the wires 31 and 38 and the normally closed manually operated push button switch S6, so that the power supplied to the heater element h is not interrupted by the subsequent opening of the contact 30e. As will be recognized by persons skilled in the art it is possible to replace the holding contact and its associated circuit with a mechanical latching arrangement to hold the contact 34a in closed position until manually released.

The preliminary alarm circuit referred to above comprises one or more warning devices such as the 'bells GI or other audible or visual signals which are energized 'from an auxiliary power source such as the battery BI through nected in series with said power source, one or more manually operated alarm stations, each having two contacts for transmitting a signal by simultaneously opening both of said wires thereby to interrupt said initiating circuit, one or more automatically operated detecting stations interposed with said alarm stations in said initiating circuit, each adapted to transmit a signal by interconnectingl said wires thereby to change the resistance of said initiating circuit, said initiating circuit being arranged as a double loop with at least one contact of each alarm station disposed between said power source and the interconnection between said wires made by any one of said detecting stations, and a switching element energized from said initiating circuit and having a plurality oi contacts operated by a signal from any one of said stations, two of said switching element contacts operating in response to a iirst signal to energize the time delay device and the preliminary alarm circuit respectively from said power source, and a third switching element contact operating in response to signals from manual stations subsequent to the elapse of the timing period of said timing device to complete a circuit including the timing device for energizing the warning device from said power source, said preliminary alarm circuit being energized by the simultaneous operating of its correlated contact.

3. A fire alarm system of the type continuously energized by a power source, comprising an alarm vcircuit having a warning device, an initiating circuit including two wires and a resistor connected in series with said power source, one or more alarm stations, each having two contacts for transmitting a signal by simultaneously opening both of said wires thereby to interrupt said initiating circuit, one or more detecting stations interposed with said alarm stations in said initiating circuit, each adapted to transmit a signal by interconnecting said wires thereby to change the resistance of said initiating circuit, said initiating circuit being arranged as a double loop with at least one contact of each alarm station disposed between said power source and the interconnection between said wires made by any one of said detecting stations, and a switching element connected in said initiating circuit and having contacts operated to connect said warning device to said power source in response either to the interruption of the initiating circuit by a signal from said alarm station or to the change in resistance of the initiating circuit by said detecting station.

4. A lire alarm system of the type continuously energized by a power source comprising an alarm circuit having a warning device, an initiating circuit including two wires and a resistor connected in series with said power source, one or more alarm stations, each having two contacts for transmitting a signal by simultaneously opening both of said wires thereby to interrupt said ini tiating circuit, one or more detecting stations interposed with said alarm stations in said initiating circuit, each adapted to transmit a signal by interconnecting said wires thereby to change the resistance of said initiating circuit, said initiating circuit being arranged as a double loop with at least one contact of each alarm station disposed between said power source and the interconnection between said wires made by any one of said detecting stations, a rst switching element responsive to signals from any of said detecting stations to open said initiating circuit,

and a second switching element connected in said initiating circuit and having contacts operated to connect said warning device to said power source in response to a signal from either the first switching element or any one of the alarm stations.

5. A iire alarm system of the type continuously energized by a power source comprising an alarm circuit having a warning device and contacts for connecting said warning device to said power source, an initiating circuit including two wires, a resistor, and a relay solenoid for actuating said contacts connected in series with said power source, one or more manually operated alarm stations, each having two contacts for transmitting a signal to said solenoid by simultaneously opening both of said wires thereby to interrupt said initiating circuit, and one or more automatically operated detecting stations interposed with said alarm stations in said initiating circuit, each adapted to transmit a signal to said solenoid by interconnecting said wires thereby to change the resistance of said initiating circuit, said initiating circuit being arranged as a double loop with at least one contact of each alarm station disposed between said power source and the interconnection between said wires made by any one of said detecting stations, said solenoid operated contacts being actuated in response to signals from any one of said stations thereby to energize the warning device from said power Source.

6. A re alarm system of the type continuously energized by a power source comprising an alarm circuit having a warning device and a. rst relay contact for connecting said device to said power source, an initiating circuit including two wires, a resistor and a marginal relay solenoid for closing said contact when deenergized connected in series with said power source, one or more manually operated alarm stations, each having two contacts lor transmitting a coded signal to said solenoid by simultaneously opening both of said wires thereby to interrupt said initiating circuit, one or more automatically operated detecting stations interposed with said alarm stations in said initiating circuit, each adapted to transmit a continuous signal by interconnecting said wires thereby to change the resistance of said initiating circuit, said initiating circuit being arranged as a double loop with at least one contact o each alarm station disposed between said power source and the interconnection between said wires made by any one of said detecting stations, an automatically operated transfer station for interrupting said initiating circuit to transmit a coded signal to said solenoid, and a second relay contact closed by the energization of the solenoid by a continuous signal from any one of the detecting stations to operate the transfer station, said iirst relay contact being actuated to energize the alarm circuit from said power source upon deenergization of the solenoid by interruption of the initiating circuit by a coded signal from either the transfer station or from any one of the manually operated stations.

7. A fire alarm system oi the type continuously energized by a power source comprising an alarm circuit having a warning device and a contact for connecting said device to said power source, an initiating circuit including two wires, a resistor, a relay solenoid for closing said contact when deenergized and a second relay solenoid connected in series with said power source; one or more manually operated alarm stations, each having two contacts for transmitting a coded signal by simultaneously opening both of said wires thereby to interrupt said initiating circuit; one or more automatically operated detecting stations interposed with said alarm stations in said initiating circuit, each adapted to transmit a continuous signal by interconnecting said wires thereby to decrease the resistance of said initiating circuit; said initiating circuit being arranged as a double loop with at least one contact of each alarm station disposed between said power source and the interconnection between said wires made by any one of said detecting stations; an automatically operated trip station for interrupting said initiating circuit to transmit a coded signal to the iirst solenoid; and a second relay contact closed upon the energization of the second solenoid by a continuous signal from any one of the detecting stations to operate the trip station, said :first relay contact being actuated to energize the alarm circuit from said power source upon deenergization of the first relay solenoid by the interruption of the initiating circuit by a coded signal from either the trip station or from any one of the manually operated alarm stations.

8. A lire alarm system of the type having a plurality of alarm stations for interrupting a continuously energized initiating circuit to transmit a signal, comprising a preliminary alarm circuit, a power source for energizing said circuit, a general alarm circuit including a warning device and a time delay device operating a predetermined period after being energized from said source, and a switching element energized from said initiating circuit and having a plurality or contacts operated by a signal from any one of said stations, two of said contacts operating in response to a rst signal to energize both the time delay device and the preliminary alarm circuit from said power source, the third contact operating in response to signals from manual stations subsequent to the elapse of the timing period of said timing device to complete a circuit including the timing device. for energizing the warning device from said power source, said preliminary alarm circuit being energized by the simultaneous operating of its correlated contact.

9. a nre alarm system of the type having a plurality or alarm stations for interrupting a continuously energized initiating circuit to transinit a signal, comprising a power source; a signal relay having a solenoid connected in the initiating circuit and three contacts opened by the energiaation of said solenoid; a preliminary alarm circuit; a general alarm circuit, each of said alarm circuits including a warning device energized from the power source by the closing of a respective one or said signal relay contacts, a time delay device including contacts connected to the warning device in the general alarm circuit and a timing element for operating said device contacts a predetermined period after being energized from the power source by said third signal relay contact so that the rst signal from any one of said stations energizes the preliminary alarm circuit warning device and the timing element to start said time interval and signals from any one of said alarm stations transmitted subsequent to the elapse of the period energizing the warning devices in both the preliminary and general alarm circuits.

WILLIS GERALD HOLMES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 4184,14() Cortland Oct. 11, 1892 1,239,381 Francis Sept. 4, 1917 1,536,191 Derby May 5, 1925 1,536,192 Derby May 5, 1925 1,977,121 Ekman Oct. 16, 1934

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