US3274578A

US3274578A - Fire alarm system

Info

Publication number: US3274578A
Application number: US342704A
Authority: US
Inventors: Block Charles; Leon J Mintz
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-02-05
Filing date: 1964-02-05
Publication date: 1966-09-20
Anticipated expiration: 1983-09-20

Description

Sept. 20, 1966 c. BLOCK ETAL FIRE ALARM SYSTEM Filed Feb, 5, 19

2 Sheets-Sheet 1 60 W m; FIG. 4 w

fiE I44 I J2 56 52 70 Z 1 GAO. P I 4220 H 64 I ME 5 I l A? l 50 10 \ja 4 Z INVENTORS 1504 J. M/Vrz ATTORNEY-5 Sept. 20, 1966 c. BLOCK ETAL FIRE ALARM SYSTEM 2 Sheets-Sheet 2 Filed Feb. 5, 1964 United States Patent This invention relates to fire alarm systems, and more particularly to a wireless system utilizing the regular household or building or plant electrical wiring.

The general object of the invention is to improve such fire alarm systems. A more particular object is to provide a system in which temperature sensors may be located at any wall switch or wall receptacle or outlet. The sensor controls a fixed high frequency oscillator, the output of which is conveyed through the household wiring.

A further object is to so rniniaturize the transmitter or oscillator that it may be located inside the standard recessed wall box or so-called gem box ordinarily used to house the wall switch or wall receptacle alone. In accordance with a further feature and object of the invention, the switch or receptacle unit itself is made readily detachable from the alarm transmitter, so that in the event of switch failure for example, the switch may be replaced at negligible cost without having to replace the more expensive alarm transmitter.

A further object of the invention is to provide an alarm and a fixed high frequency receiver controlling the alarm, the said unit being adapted to be simply plugged into an ordinary wal=l receptacle. Thus, one or more such alarm units may be located at desired locations, and may be moved from time to time from one location to another as circumstances may warrant.

To accomplish the foregoing general objects, and other more specific objects which will hereinafter appear, our invention resides in the fire alarm system, and the elements thereof, and their relation one to another, as are hereinafter more particularly described in the following specification. The specification is accompanied by drawings in which:

FIG. 1 is a perspective rear view of a transmitter embodying features of the invention;

FIG. 2 is a perspective from view without the cover plate and wall box;

FIG. 3 is a front view looking toward the cover plate;

FIG. 4 is a vertical section showing the transmitter and a wall switch housed ina conventional recessed wall box, omitting the clamps for the wiring;

FIG. 5 is a front view with the transmitter combined with a receptacle rather than a wall switch;

FIG. 6 is a vertical section drawn in schematic form;

FIG. 7 is a wiring diagram for the transmitter; and

FIG. 8 is a wiring diagram for the receiver and alarm.

Referring to the drawing, and more particularly to FIGS. 7 and '8, the system comprises a fixed high-frequency oscillator, centered about a tank circuit 12 and a transistor 14, and adapted to be readily connected into and to be energized from an ordinary household power supply line at

terminals

16 and 18. There is also a suitable fire detector or sensor usually a temperature-responsive sensor such as a bimetallic element, indicated at 20, and this is connected between the line and the oscillator in order to energize and start the oscillator in the event ice of fire. The high-frequency output of the oscillator is coupled back to the power supply line, in this case by means of a coupling capacitor 22 and a conductor 24.

There is also a fixed high-frequency receiver, shown in FIG. 8, this being adapted to be plugged into the household power supply line at some other desired location, as indicated by the plug 26 and cord .28. The receiver is tuned to the same fixed frequency as the transmitter, by means of a tank circuit 30, and is coupled to the line through conductor 32 and coupling capacitor 34 for the reception of high frequency. There is an electrically operated alarm 36, and a relay 38 having contacts 40 which are in series with the 'alarm, and which are closed by a fire signal. Preferably the contacts are spring biased to close, and the receiver output serves ,to hold the contacts open when no fire signal is received, but permits closing of the contacts when a fire signal is received.

In accordance with an important feature of the inven tion, the transmitter is so shaped and dimensioned that it may be located together with a wall switch or receptacle in a standard recessed wall box or gem" box previously receiving the wall switch or receptacle alone. Thus referring to FIG. 3, the cover plate 42 is of usual size, but it has an opening 44 through which the sensor 20 is exposed, and another opening 46 for the handle 48 of a wall switch.

Referring next to FIG. 2, the metal strap or adapter plate 50 carries an insulation casing 52 which houses the transmitter. The sensor 20 passes through a hole in strap 50. The switch unit 54 is carried by the strap 50 and is preferably detachably mounted, as is indicated by the cam or lock 56 on strap 50. The strap has the usual slots 58 which receive screws attaching the same to the box, and it has the usual threaded holes 60 for screws which hold the cover plate or wall plate.

The rear view of FIG. 1 shows how the transmitter casing -52 has an inverted U shape or is cut away at the bottom to receive the switch unit, omitted in FIG. 1. It also shows the terminal screws, in this case a ground screw 16 and a line screw 18. A leaf spring contact is also visible at 62.

Referring now to FIG. 4, the switch unit 54 is carried by the adapter plate or strap 50, it being detachable and locked in position by the cam lock 56. It nests beneath the casing 52 and it has top and bottom terminal Screws 64.and 66. The top screw 64 is engaged by the leaf spring contact 62, thereby connecting terminal 18 of the transmitter to the switch.

FIG. 4 also shows how the fire sensor 20 is carried by transmitter casing 52 and passes through the strap 50 and cover plate or wall plate 42. The latter is held on strap 50 by the usual screws 68, and the strap 50 is secured to the recessed wall box by screws 72.

FIGS. 5 and 6 illustrate how the transmitter may be combined with a wall receptacle or outlet instead of a wall switch. In FIG. 5 the cover plate 74 has an opening 76 for sensor 20, and another opening 78 for an outlet or receptacle 80, the latter being adapted to receive a conventional plug, indicated in broken lines at 82 in FIG. 6. FIG. 4 is somewhat simplified by omitting the screw clamps for the wiring coming into the box, and FIG. 6 has been further simplified compared to FIG. 4. However, FIG. 6 does show how the outlet unit 80 nests .and are available on the commercial market.

beneath or within the transmitter casing 52, and has terminal screws at the top and bottom, the upper one being engaged by leaf spring contact 62. The receptacle 80 is preferably detachably secured to the strap by means Such as the cam lock shown at 5 6 in FIG. 2.

It will thus be seen that the transmitter is dimensioned to be combined with a switch or receptacle, and to be housed in the standard recessed wall box of the switch or receptacle, the transmitter including a temperatureresponsive sensor 20 at the front, and having high-frequency oscillator circuitry controlled by the sensor. The assembly is completed by a

cover plate

42 or 74 which has an opening for the sensor and another for the switch or receptacle. The transmitter and the switch or receptacle have appropriate terminal screws at the back for line and ground connections inside the box. In preferred :form, the transmitter assembly comprises an adapter plate 50 carrying an inverted U-shaped insulation casing 52 which includes the sensor 20 at the front, the latter passing through the adapter plate 50.

The casing houses solid-state semiconductor components for a high-frequency oscillator circuit and its D.C. supply, the circuit being controlled by the sensor 20. The casing 52 further has

terminal screws

16 and 18 at the back for line and ground connections. The adapter plate 50 is further provided with means such as the cam lock 56 to detachably receive a standard switch or receptacle unit, the latter preferably having its terminal screws at the top and bottom. The casing 52 includes a downwardly urged spring contact 62 which bears against the top screw of the switch or receptacle for electrically connecting the line screw 18 at the back of the casing to the switch.

Detachable switch and outlet units are already known One such unit is the so-called Despard unit which is locked to the adapter plate or strap by a rotatable cam lock, such .as that shown in FIG. 2, but any other detachable unit could be employed. The reason a detachable unit is preferred is that in the event of switch failure the switch unit may be replaced at slight cost, without having to replace the alarm transmitter.

In conventional house wiring the ground line, colored white, must be maintained continuous. The hot line is colored black, or sometimes red. In FIG. 4 cable 86 supplies power, and cable 88 extends to an overhead lamp fixture controlled by switch 54. The ground or white conductor 84 from BX or other sheathed cable 86 is connected to ground terminal 16. The ground or white Wire 90 of cable 88 is also connected to terminal 16. The black wire 92 is connected to. terminal 18, and the black wire 94 is connected to switch terminal 66.

Cables

86 and 88 are anchored securely to box 70 by means of conventional screw clamps, not shown. It will be understood that the leads 84, 90, 92 and 94 usually are longer than here shown, so that they may be attached to the terminal screws while the

assembly

52, 54 is outside the box, the assembly then being pushed into the box and attached by screws 72, just as is done with a switch or receptacle alone.

In FIG. 6 the ground or white wire 96 is connected to terminal 16. The hot or black wire 100 is connected to the terminal 18, and through leaf spring 62 connected to the upper screw 98 of the receptacle 80. Terminal 16 is connected by means of jumper 102 to the terminal 104 of the receptacle 80.

Referring now to FIG. 7, the spring contact is indicated at 62, and the switch unit at 54. The circuit is essentially conventional, it being miniaturized by the use of solid-state semiconductor elements. The left-hand part of the circuit, indicated by dotted line bracket 110, is a DC. power supply section utilizing a rectifier 112. The right-hand portion of the circuit is the oscillator, centering about transistor 14, and utilizing a feed-back coil 114 coupled to fixed tuned tank circuit 12. The output is de- 4 livered through output coupling capacitor 22. The circuit is connected to

terminals

16 and 18, both for power supply to the circuit, and for high frequency transmission from the circuit.

Referring now to FIG. 8, the receiver circuit also is preferably miniaturized by the use of solid-state semiconductor elements. The left-hand portion indicated by dotted line bracket 116 constitutes a DC. power supply section based on rectifier 118. The received high frequency energy is supplied to a fixed tuned circuit 30 through a coupling capacitor 34.

The receiver section is indicated by dotted line bracket 1-20, and includes a transistor 122. The right-hand portion of the circuit serves to rectify the receiver output and to amplify the resulting DC. output for control of relay 38. -T his section is indicated by dotted line bracket 124, and includes

voltage doubler rectifiers

126, 128, and transient suppressor rectifier 130, as well as a power transistor 132 used for DC. amplification.

In preferred form the alarm 36 is energized by a local battery 134. The alarm may be a bell or buzzer or born or other such device. The advantage of -a local battery is in making the alarm fail-safe, so that in the event of power failure the alarm will sound.

When a battery-operated alarm is used, the battery may be of the automatically rechrageable type, and may be kept connected to the power line. Thus, the battery charge is replenished whenever low, and the battery is available to sound the alarm in the event of power failure, as well as in the event of fire. Then the alarm system will not be mistakenly relied on, when in fact there is no power .to energize it.

'In some cases the user may prefer that the alarm be powered directly from the household wiring, in which case the conductors 28 (FIG. 8) may extend to the alarm and thereby replace the battery 134. The system then is failsafe to the extent that any failure in the receiver other than complete power failure will sound the alarm.

Although we have illustrated the transmitter associated with a wall switch in FIG. 3, and with a receptabile in FIG. 5, in most cases a Wall switch is preferred because it is located at greater height. A wall receptable is equally good when the receptacle is an elevated one, but if the receptacle is low it is less effective. 'For the present pur pose it is preferred that the receptacle be at least two feet from the floor.

Apart from miniaturization, an additional advantage of using solid-state components is that the circuitry is instantaneously responsive. No warm-up period is required.

In simplest form, the sensor is a bi-metallic disc or thermostat which is temperature-sensitive. However, other sensors are known, responsive to smoke for example.

An obvious advantage of the present system is that the sensor may be located where desired, for example, in a garage, or in a basement near an oil burning furnace. Multiple sensors may be provided, thereby greatly increasing the eifectiveness of the system. Similarly, multiple alarms (meaning the combination of receiver and alarm) may be provided. One alarm may be located in a bed room, to beheard at night. Another alarm may be located in a kitchen, to be heard during the day. The alarm combination may be housed in an ornamental housing suitable to be'placed on a table or shelf, with a flexible cord like a lamp cord extending to a nearby wall outlet. The alarm may be designed to be hung on a hook or nail, and be similarly connected by its flexible cord to a convenient wall outlet. The alarm may be moved readily from one room to another; However, if desired the alarm unit may be permanently mounted in a box designed for recessed 'wall mounting.

The system has been referred to as a household system, but this is not intended to exclude its application to an apartment house, or oflice, or industrial plant. The term is used to distinguish from an alarm system which is intended to sound an alarm at a very remote point, say a firehouse. The present alarm will function on wiring coming from the same power line transformer. Thus, neighbors may have a common alarm, and a warning will be sounded in a neighboring occupied house in the event of fire in a nearby vacant house. However, if the neighbors are not cooperative, and prefer not to have a combined alarm, the system is readily localized as much desired by the use of different fixed frequency tuning. The frequency may be in a range of from 200 to 550 kilocycles, and thus localized alarm systems may be provided when desired by using different frequencies.

To summarize, the basic unit preferably consists of an adapter plate with a block or case permanently fastened to the rear of the plate. The case contains the circuitry and a bimetal thermal sensing element which projects through the adapter plate.- In addition, three terminals project from the case. Two are screw terminals Which are marked line and ground, and one is a spring terminal which is joined internally to the line screw terminal. These are constructed to U.L. acceptable specifications.

The spring terminal, the opening in the case, and an appropriate opening in the adapter plate, are so oriented and relatively located as to accept and contain a standard Despard type of switch or receptacle. This is a standard commodity manufactured by many manufacturers of electrical switches and hardware, and although it is available in many forms, they are all mountable in the same openings and are retained by the same type of lock or clip.

In any normal electrical installation the appropriate wires are connected to the two screw terminals on the rear of the case and to the one exposed screw terminal on the 'Despard switch. The entire unit then is inserted into the gem box, and fastened in the same manner as a standard switch or receptacle. A decorative cover plate with suitable openings is then fastened to the adapter plate in the same manner as a standard wall plate.

If the temperature of the room rises to a level suflicient to activate the thermal switch, a signal is generated by the transmitter and fed through all electrical lines in the building. This signal is immediately converted into an audible signal by one or more similarly tuned receiver units connected to the power line.

It is believed that the construction and operation of our fire alarm system, as well as the advantages thereof, will be apparent from the foregoing detailed description. It will also be apparent that while we have shown and described the system in a preferred form, changes may be made without departing from the scope of the invention, as sought to be defined in the following claims. In the claims, the reference to a temperature-responsive sensor is not intended. to exclude other types of fire detecting sensors.

We claim:

1. A transmitter assembly for a fire alarm system which transmitter is intended to transmit by high frequency carrier to a receiver-controlled alarm through the usual household power supply wiring, said transmitter being compactly dimensioned and being housed together with a power wiring component in the standard recessed wall receptacle previously used for said wiring component, said transmitter including a temperature responsive sensor, and having high frequency oscillator circuitry controlled by said sensor, and a cover plate for said wall receptacle, said cover plate having an opening for the sensor and having another opening for the said wiring component, said transmitter and wiring component having appropriate terminal screws at the back for line and ground connections inside the recessed wall receptacle.

2. A transmitter assembly for a fire alarm system which transmitter is intended to transmit by high frequency carrier to a receiver-controlled alarm through the usual household power supply wiring, said transmitter being compactly dimensioned and being housed together with a power wiring component in the standard recessed wall receptacle previously used for said wiring component, said transmitter including a temperature responsive sensor at the front, said transmitter having screws at the back for line and ground connections, a power wiring component having connection terminals at the back, means electrically connecting the line screw of the transmitter to one terminal of the wiring component, said transmitter having D.C. supply and high frequency oscillator circuitry controlled by said sensor and utilizing solid state semiconductor elements, and a cover plate for said wall receptacle, said cover plate having an opening properly located and dimensioned for the sensor and having another opening properly located and dimensioned for the wiring component.

3. A transmitter assembly for a fire alarm system which transmitter is intended to transmit by high frequency carrier to a receiver-controlled alarm through the usual household power supply wiring, said transmitter being combined and housed together with a power wiring component in the standard recessed wall receptacle previously used for said wiring component, said transmitter assembly comprising an adapter plate carrying an insulation casing including a temperature responsive sensor at the front and passing through the adapter plate, said casing housing high frequency oscillator circuitry controlled by said sensor and utilizing solid state semiconductor elements, said casing having screws at the back for line and ground connections, said adapter plate being provided with means to receive and hold the said wiring component, said casing having means electrically connecting its line screw to the said wiring component, and a cover plate for said wall receptacle, said cover plate having an opening for the sensor and having another opening for the wiring component.

4. A transmitter assembly for a fire alarm system which transmitter is intended to transmit by high frequency carrier to a receiver-controlled alarm through the usual household pow-er supply wiring, said transmitter being combined and housed together with a power wiring component in the standard recessed wall receptacle previously used for said wiring component, said transmitter assembly comprising an adapter plate carrying near one end an insulation casing including a temperature responsive sensor at the front and passing through the adapter plate, said casing housing high frequency oscillator circuitry controlled by said sensor, said casing having screws at the back for line and ground connections, said adapter plate being provided near its other end with means to detachably receive and hold said wiring component, the latter having its connection screws at the top and bottom, said casing including a downwardly urged spring contact for bearing against the top screw of the wiring component and electrically connected to the line screw at the back of the casing, and a cover plate for said wall receptacle, said cover plate having an opening properly located and dimensioned for the sensor and having another opening properly located and dimensioned for the wiring component.

5. A transmitter assembly for a fire alarm system which transmitter is intended to transmit by high frequency carrier to a receiver-controlled alarm through the usual household power supply wiring, said transmitter being combined and housed together with the power wiring component in the standard recessed wall receptacle previously used for said wiring component, said transmitter assembly comprising an adapter plate carrying near one end an inverted U-shaped insulation casing including a temperature responsive sensor at the front and passing through the adapted plate, said casing housing D.C. supply and high frequency oscillator circuitry controlled by said sensor and utilizing solid state semiconductor elements, said casing having screws at the back for line and ground connections, said adapter plate being provided 7 8 near its other end with means to detachably receive said References Cited by the Examiner wiring component, the latter having its connection screws UNITED STATES PATENTS at the top and bottom, said casing straddling said wiring component and including a downwardly urged spring con- 2,574,458 11/1951 Atkinson tact for bearing against the top s r w f th i i 5 2,580,539 5 Goodwin 3403 10 ponent and electrically connected to the line screw at the i 1;; g g g g26 g2 b k f th t f e e ac 0 e g, n a c ver pla e or said wall recep 3,204,245 8/1965 Dykaar 34O 220 tacle, said cover plate having an opening properly located and dimensloned for the sensor and having another open- NEIL C. READ, Primary Examiner.

ing properly located and dimensione for the wiring com- 10 ponent. R. M. ANGUS, D. YUSKO, Assistant Exmminers.