US2704840A - Fire alarm system - Google Patents

Description

March 22, 1955 A, WARD FIRE ALARM SYSTEM Filed April 28, 1951 a w M? m WW1 w :I/IIIM. M M/ flfifla L. I Q w awe/WM 15.54/54 1441M:

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FIRE ALARM SYSTEM Leslie A. Ward, Cleveland, Ohio, assignor to Morse Signal Devices, Cleveland, Ohio, a partnership of Ohio Application April 28, 1951, Serial No. 223,517

8 Claims. (Cl. 340-213) This invention pertains to the art of fire alarms and more particularly to locally supervised fire alarm systems of the type often found in residential property or the like.

Fire alarm systems of the type to which this invention refer, generally include a central alarm or control station and a plurality of heat sensitive switch elements located at points of the premises remote from the control station and connected thereto by electric wires. The control station generally includes a power source and an audio or visible alarm announcing means. The heat sensitive elements are normally connected in electrical series relationship with the power source through either the alarm means or a current sensitive relay which, when energized, actuate the alarm means.

The heat sensitive switch elements of diiferent forms. One of such forms is an electric switch adapted to be connected across the wires and held in an open position by a heatsensitive or heat fusible Another form is a pair of parallel twisted resilient wires biased toward each other but normally held in spaced insulated relationship by a heat fusible insulating material. In either event, when the switch is closed or the parallel wires come into electrical contact, a circuit is completed to energize and actuate the alarm may take a number means in the control station.

The above described systems, while normally meeting all of the needs of the average residential home, do not meet with the full approval of the fire underwriters who require that some means be provided to indicate that the entire system is in satisfactory working order. Such means are normally asupervisory current flowing at all times in the detecting circuits which will energize some indicator in the control station to visibly indicate that the system is in satisfactory working order. This indicator may be a movable mechanical member or preferably an indicator light.

To obtain the supervisory current it has normally been conventional to connect a resistance across the far end of the wires connecting the heat sensitive switches to the control station. A relay is connected in series with the detection circuit in the control station which has an operating current greater than that drawn by the indicator mechanism but less than that which would occur in the event one of the heat sensitive switches were closed. The relay when actuated energizes the alarm means.

in fire alarm equipment of the type to which this invention particularly pertains, relays have generally proven to be undependable. The contacts through non-use get dirty or corrode so that when actuated they fail to complete the desired electrical circuit and therefore fail to actuate the alarm and accomplish their basic purpose.

A further difiiculty in equipment of this type has been with the indicator means employed to show that the supervisory current is flowing. Normally indicator lights of the filament type have been used. These filaments, even when operated at relatively low levels of brilliance, tend to burn out over extended periods of time. Also, these filaments draw an appreciable amount of electric current which in some instances is high enough to cause an audible hum in the alarm station when alternating current is employed to energize the detecting system. Heretofore indicator lamps of the gaseous discharge type such as neon lamps, could not be employed because the voltage required to energize them is generally on the order of 100 volts or more. The fire underwriters re- 7 nitedStatcs. Patent Ofice 2,704,840 Patented Mar. 22, 1955 quire that the detection circuits have voltages generally less than 30 volts applied to them. Y

A further difficulty with presently known fire alarm systems of the type to which this invention refers is that itwas impossible to tell whether all of the heat sensitive switches were in operative position-that is to say, if one or more of the elements were removed, surreptitiously or by accident, there would be no way of knowing that this had taken place.

The present invention contemplates a fire alarm system which overcomes all of the above-referred to disadvantages and provides a tire alarm system which is simple in construction, inexpensive to operate, and is positive and dependable in operation.

In accordance with the present invention, there is provided a fire alarm system including a power source, an alarm actuating mechanism, one or more remotely located heat detectors, and supervisory current indicating means employing a filamentless gaseous discharge type lamp operating at a voltage higher than the voltage at which the alarm system operates. The power source, which is of the low voltage type, is connected in electrical series relationship through the alarm actuating mechanism to a pair of interconnecting wires which connect successively to each heat detector and then to the indicating means which may conveniently be located a'djacent thealarm actuating mechanism or elsewhere. The heat detectors are each comprised of a base having at least a pair of electrical contact members thereon and a cap removably mounted on the base. The cap and base are so arranged that when the cap is in position on the base an electrical connection is made between the contact members. The cap additionally has a heat sensitive element actuatable upon reaching a predetermined temperature to close another pair of electrical contacts.

One of the wires connects in series throughthe first mentioned pair of contacts so that the supervisory current indicating means is not energized unless all the caps on all of the heat detectors are in operative position. Each wire is also connected electrically to one of the terminals of the second mentioned pair of contacts so that a circuit is completed within the heat detector whenever the heat sensitive element actuates the second mentioned pair of contacts to apply the full output voltage of the power source on the alarm actuating mechanism. The indicating means includes a gaseous discharge type indicating lamp which requires a higher operating voltage than that supplied by the power source, and this lamp is energized through a voltage step-up means such 'as a transformer connected to the ends of the pair of wires.

An object of the invention is the provision of a new and improved fire alarm system which is simple in construction, dependable in operation, which enables the use of filamentless type indicating lights with a low voltage energized detection system, and which immediately gives an indication if all the fire detecting elements are not properly installed.

Another object of the invention is the provision of a new and improved fire detecting system which may be energized at relatively low voltages in accordance with the Underwriters Laboratories requirements and yet which will energize an indicator lamp of the filamentless type having a normal operating voltage higher than that permitted by the Underwriters Laboratories.

Another object of the invention is a new and improved fire detecting circuit which comprises an electrical circuit including a power source, a supervisory indicator, and a plurality of heat detecting stations, the stations including a removable heat sensitive element and so arranged that the circuit is completed only when all of the heat sensitive elements are in operative position.

Another object of the invention is the provision of a new and improved heat sensitive element for fire alarm systems which includes a base and a member removably mounted thereon, the base and member having a pair of normally closed contacts held in open position by a heat sensitive element on the member, the base also having a pair of contacts which are connected together by a shunting bar on the removable member when the member is in operative position.

the sleeve 33.

system embodying the present invention.

a side cross-sectional view showing in de- Figure 2 is a fire detectlon station embody- .tail the construction of ing the present invention.

Figure 3 is a top elevational view of the base of Figure 2.

Figure 4 is an exploded view partly in section of a removable cap employed in the fire detecting station of Figure 2.

Referring now to the drawing wherein the preferred embodiment of the invention is shown for the purposes ofillustration only, and not .for'the purposes of limitation, the fire alarm system shown in Figure 1 includes a transformer A, of the step-down type for energizing the system at a relatively low alternating current voltage, an alarm actuator B, a plurality of heat detectors C, and a supervisory current indicator D. In the preferred embodiment, the transformer A, the alarm actuator B, and the indicating means D, are all located at a central point which may be housed in a box E, while the heat detectors C may be located at any remote location and connected with the box E by a pair of electric wires.

The transformer A is relatively conventional and includes a primary connected to an alternating current power source 11 which may be the usual power line on the premises being protected by the fire alarm system. The transformer A also includes a secondary 12 having .an output voltage preferably on the order of 24 volts A. C. One terminal of this secondary connects to one terminal of the alarm actuator B through a wire 13. The other terminal of the secondary 12 connects to a terminal 14 on the box E. The other terminal of the alarm actuator B connects to a terminal 15 on the box B through wire 16.

'The alarm actuator B is shown schematically in Figure 1 as an electrically operated bell. The actuator B may be of any known type suitable for announcing a fire, either audio or visible. It is preferred, however, that the actuator be an audio means, and that its construction be such that alternating current flowing in energizing windings therein actuate a movable armature rather than employing the conventional bell or buzzer which has a make-and-break circuit arrangement. contacts of such equipment can be undependable,

Any number of heat detecting stations C may be employed and they may be located at any desired point or points on the premises to be protected against fire. In Figure 1, three stations are shown. The arrangement of these stations is such that should any one be inoperative for any reason, the supervisory current indicating means immediately will indicate trouble. The heat The detecting stations C are shown in greater detail in Figures 2 and 3 and comprise generally a flat rectangular base having a central, upstanding, hollow, externally-threaded cylindrical boss 21 on which is removably mounted a cap 22 in the shape of an inverted cup having a bottom 25 and internally-threaded, cylindrical side walls 26. The base 20 and the cap 22 are preferably formed in one piece of a molded plastic material which also provides electrical insulation.

A pair of electrical conductors 28, 29 in the form of fiat strips of copper or the like, extend vertically on diametrically opposite sides interiorly of the boss v21. One end of conductor 28 terminates in a short outward radial projection 30 overlying the upper end of the boss 21. The other end of the conductor 28 extends through an opening 31 in the base-and connects to an electrical terminal on the bottom' side thereof which, in the embodiment shown, comprises an internally threaded sleeve 33 molded into the base and a screw 34 threaded into In a like manner, the conductor 29 has an outward radial extension 36 overlapping the upper 'end of the boss 21. The other end of the conductor 29 extends through an opening 37 in the base 20 and connects to a second velectrical terminal comprising .an internally'threaded sleeve 38 molded into the base, and a screw 39 threaded into the sleeve 33. Conductors '28,

29 are in electrically insulated relationship. The radially extending portions 30, .36..provide a pair of electrical contacts which are in electrically insulated relationship but are electrically connected together when the cap 22 is in position. For this purpose, the cap 22 has an 1nsert in the form of a metallic flat ring or washer 40 which, when the cap 22 is positioned on the boss 21, engages the portion 30, 36v to complete an electrical circuit therebetween. The washer being circumferentially continuous, will engage the contacts 30, 36 in any position of the cap 22.

The base 20 has a third electrical contact supported thereon in the form of a brass insert 42 molded into the base 20 and extending axially of the boss 21 to a point preferably spaced slightly below the upper end of the boss 21. As shown, :this insert tapers to a point 43. The lower end of the member 42 extends through the bottom of the base 20 and has a threaded bore into which a screw 45 is threaded for the purpose of providing a terminal through which electrical connections can be made. The point 43 forms one contact of a switch which closes to actuate an alarm. The other contact of this switch in the embodiment shown is mounted on the .cap 22 and comprises an arm 47 integral with washer 40 at one end and diametrically part way across the inside of washer, the free end terminating in a right angled portion which is embedded in a heat fusible material 49 mounted in an opening in the bottom 25 of the cap. The arm 47 is normally biased away from the bottom 25 and towards the contact point 43, but is held in the position shown by the heat fusible material 49. When the heat fusible material 49 softens it releases the right angled portion 48, and the arm 47 moves towards the contact point 43 and makes electrical contact therewith. At this time, the terminals 34, 39 and 45 are all electrically connected together.

The heat fusible material 49 may be of any conven-' tional type or alloy which softens or melts at a predetermined temperature at which it is desired to have the fire alarm system actuated. I

The indicator means D comprise generally an indicator lamp of a gaseous discharge type 52 and a transformer .53 of the step-up type for energizing the lamp 52 from the supply voltage of the secondary 12. Normally, indicator lamps of .a gaseous discharge type will not operate on the 24 volts normally employed in tire alarm systems and the employment of a step-up transformer to energize the lamp 52 is an important part of the present invention. Gaseous discharge lamps have an extremely long life. They draw minute amounts of electric currents-so small, in fact, that there is no danger of a current drawn by the lamp from in any way causing an audible hum in the alarm actuator as might be the case if a lamp of the conventional filament type were energized directly from the secondary 12 through the alarm actuator B. While any type transformer 53 could be employed, an auto transformer has been shown. The primary 54 of the transformer 53 connects to a pair of terminals 56, 56 on the box E.

When the alarm system is installed, a pair of Wires 59, lead respectively from the terminals 14, 15 to each heat detecting station C in series and then to the term nals 5 ,6, 56.. .At each heat detecting station C, the wire 59 is connected to the terminal 45 which as pointed out heretofore, is connected in the heat detecting station to the contact which is closed when the heat fusible material reaches a softening point. The wire 60 is broken at the heat detecting station C and the two ends connect to the terminals 34, 39 which, as pointed out heretofore, connect to the contacts 30, 56 which contacts are electrically connected together by the washer inserts 40 when the cap22 is in position. Thus, when each cap 22 on all of the heat detecting stations C is in operable position, a

circuit is completed from the terminals 14, 15 to the terminals 56, 57, whereby the primary 54 of the transformer 53 will be energized and the lamp 52 will be energized. If by chance any one of the caps 52 should be removed, the circuit of the wire 60 will be broken and the lamp 52 will not be lighted, indicating trouble.

In the event the temperature at any heat detecting station C reaches a temperature such as to soften or melt the fusible plug 49, therarm '47 will move downwardly to engage the contact point 43 which then completes a circult from the wire 60 to the wire 59 and the full voltage of the transformer A will then be applied on the alarm actuator 13 and an audible sound will be produced to warn of fire danger somewhere on the by the system.

It will thus be seen that an embodiment of the invention has been described in detail, which accomplishes all of the objects of the invention and others, and provides a fire alarm system which is extremely dependable in operation, employs the low voltages required by the fire underwriters, and yet employs a gaseous discharge type indicating lamp.

It will be appreciated that modifications and alterations or equivalent will occur to others upon a reading and understanding of this specification. It is my intention to include all such modifications, alterations and equivalents as coming within the scope of the appended claim.

Having thus described my invention, I claim:

1. A heat detecting station comprising a base having three electrical contacts thereon, a member removably supported on said base and means on said member for electrically connecting a pair of said contacts when mounted on said base, and thermally actuated means on said member for engaging said third contact.

2. A heat detecting station for use in a fire alarm system comprising a base having three electrical contacts thereon, a cap removably supported on said base and means on said cap for electrically engaging a pair of said contacts when said cap is positioned on said base, and thermally actuated means on said cap for engaging said third contact.

3. A heat detecting station for fires alarm systems, comprising a base having a threaded boss thereon and a cap threadably supported on said boss; a contact member mounted on said base and extending axially of said boss toward said cap; an arm on said cap biased toward said contact; a thermally sensitive element on said cap, holding said arm in spaced relationship with said contact, said base also having a pair of contacts and means on said cap for interconnecting said pair of contacts when said cap is positioned on said base.

4. A heat detecting station for use in fire alarm systems; a cap adapted to be mounted on a base; a ringlike member mounted in said cap and having a resilient arm extending toward the center thereof and biased for movement in one direction; a thermally sensitive element in said cap normally holding said arm against movement against said bias.

5. A fire alarm system including a power source, an alarm actuator, a plurality of heat-detecting stations and supervisory current-indicating means, said heat-detecting stations including a base having a pair of electrical contacts thereon and a removable cap, means on said cap for electrically connecting said contacts when said cap is mounted on said base, a pair of wires extending from said power source to said supervisory current-indicating means, one of said pair of wires being in electrical series through said alarm actuator and said heat-detecting stations through said pairs of electrical contacts interconnected by said means on said ca said heat-detecting stations including a third contact and a member on said cap normally biased toward said third contact but held in spaced relationship by a heat-fusible member, said biased member being electrically connected to said means on said cap for electrically connecting said contact, said third contact being electrically connected to the other of said pair of wires, whereby when said fusible element melts, said biased member can move into contact with said third contact and energize said alarm actuator.

premises being protected 6. A fire alarm system including a power source, an alarm actuator, one terminal of which is connected to one terminal of said power source, a plurality of heat-detecting stations and supervisory current-indicating means, said heat-detecting stations including a base having a pair of electrical contacts thereon and a removable cap, including means for electrically connecting said contacts when said cap is mounted on said base, a pair of wires connecting said heat-detecting stations and said supervisory current-indicating means in electrical I series with said power source and alarm actuator, one of said wires being in series with said pairs of electrical contact, said base also including a third electrical contact connected to the other of said wires, said cap also including a member electrically interconnected with said means on said cap normally biased toward said third contact and a fusible element holding said biased member in spaced relationship to said third contact.

7. A fire-alarm system including a power source, an alarm actuator, a plurality of heat-detecting stations and supervisory current-indicating means for indicating that the system is in satisfactory operating order, each of said heat-detecting stations including a base having a pair of electrical contacts thereon and a removable cap, means on said cap for electrically connecting said contacts when said cap is mounted on said base,

and actuate said alarm actuator, said supervisory currentindicating means being arranged to be energized from said power source when all of the caps on said stations are mounted, said alarm actuator being arranged to be energized from said power source whenever one of said thermally actuated means engages one of said third contacts.

8. A heat-detecting station for use in fire-alarm systems comprising, in combination, a base having three electrical contacts in spaced insulated relationship thereon, a cap adapted too be mounted on said base, a ring-like member mounted in said cap and having a resilient arm extending from said ring toward the center thereof and biased for movement in a direction toward one of said contacts, a thermally sensitive element in said cap normally holding said arm against movement toward said contact, said other pair of contacts being disposed in a plane and adapted to be engaged by said ring-like member when said cap is mounted on said base.

References Cited in the file of this patent UNITED STATES PATENTS 645,588 Doddridge Mar. 20, 1900 1,067,005 Denereaz July 8, 1913 1,181,705 Weber May 2, 1916 1,684,161 Traubitz Sept. 11, 1928 1,946,889 Wessel Feb. 13, 1934 1,952,460 Rittenhouse Mar. 27, 1934 2,165,569 Obermaier July 11, 1939 2,335,382 Bonanno Nov. 30, 1943 2,349,629 Lazich May 23, 1944 2,402,312 Burch June 18, 1946 2,408,660 Lannge Oct. 1, 1946 2,411,752 Padilla Nov. 26, 1946 2,442,830 Spracher June 8, 1948 2,452,942 Lord et al. Nov. 2, 1948 2,646,556 Allen July 21, 1953

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