US3475744A - Fire alarm - Google Patents

Description

1969 s. FRANKFURT' 3,475 7 FIRE ALARM Filed Jun 22, 1966 H 38 42 gig;

I E v 44 I 24 INVENTOR. SAN/30R FRANKFURT United States Patent 3,475,744 FIRE ALARM Sandor Frankfurt, 13534 Cedar Road, Cleveland, Ohio 44118 Filed June 22, B66, Ser. No. 559,491 Int. Cl. GtlSb 21/00 US. Cl. 340-2271 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a fire and burglar alarm or other electrical signal systems using a thermal responsive device that can be mechanically actuated.

Signal systems using thermal responsive devices are especially useful as first alarms. In these systems an audible or visual signal, or both, is actuated in response to a change in temperature, such as an increase in temperature to an abnormally high level, indicating the existence of a fire or other abnormal condition.

Signal systems for burglar alarms are often mechanically actuated. Normally, an audible signal is created when the alarm is tripped, as when a door, window or compartment lid is opened.

For many uses and in many installations it is advantageous to provide a self-contained, independent signal system. Such a system is operable even though there may be a power failure. It is also conveniently used in buildings, 'vehicles or other areas where central power may not be available.

Small and inexpensive alarm systems are particularly advantageous. A number of such systems can be located unobtrusively in a variety of different places to act independently. With a large number of thermal sensitive systems at various locations, a fire is detected immediately at its source of origin. As is well known, early discovery and control of a fire is often the difference between minor damage and total destruction of a building. Similarly, a separate burglar alarm at each entrance of a building indicates the location of disturbance. A small, self contained alarm can conveniently be used to protect cars, boats, trailers or compartments within such vehicles.

One problem of many fire alarm systems is that they shut off after once actuated if the temperature falls below the triggering temperature. Thus, if a fire should die down or shift, the alarm often shuts off. As a result, the fire may smolder and later flare up in a different location or in the same location with renewed vigor if the initial alarm signal is not observed. It is also desirable that a burglar alarm remain actuated even if the door or window that is opened to trip the alarm is subsequently closed.

One proposed solution to some of the above problems, in connection with a fire alarm system is disclosed and claimed in my US. Patent No. 2,762,887. As disclosed in that patent, a thermal responsive device is provided with a hook. When the device is actuated by an increase in temperature, the hook engages a prong, which holds the device actuated.

The present invention provides the advantageous features of my earlier invention, but in an improved manner and in an arrangement that provides an extremely ice compact, self-contained signal system that can be used as both a fire alarm and burglar alarm. In addition, the alarm of the present invention can be conveniently tested and reset without disassembly.

Briefly, this invention utilizes a resilient thermally distortable element, such as a bimetallic strip, that is movable between two positions in response to a change in temperature to a predetermined level. Distortion of the thermally responsive element causes the element to complete an electrical circuit that energizes a signal device. A permanent magnet is positioned to retain the thermally distortable element in the position to which it moves in response to the change in temperature. The magnet is of sufficient strength to retain the element in position to maintain the circuit closed, notwithstanding a subsequent change in temperature. As a result, the signal remains energized once the predetermined temperature is reached.

An important feature of this invention resides in the construction and arrangement of the thermally distortable element with respect to the housing for the signal system. A portion of the bimetallic thermal responsive element extends through the housing and moves from a first position to a second position in response to an increase in temperature from below a predetermined temperature level to the predetermined temperature level. At the second position, the bimetallic element completes an electrical circuit and operates the signal. The portion of the bimetallic element that extends through the housing permits the alarm to be mechanically actuated from outside the housing independently of any change in temperature. When the extending portion of the bimetallic element is moved from one position to another, whether mechanically or manually, the electrical circuit is completed. An extending strip from a door or window can be used to mechanically move the element when the protected door or window is opened, causing the alarm to operate. Also, the strip can be manually moved to test whether the alarm is functoning properly. The actuated alarm is turned off and reset by manually moving the extending portion of the bimetallic element away from the permanent magnet.

Accordingly, it is an object of this invention to provide an improved thermal responsive and mechanically actuatable device in the form of an independent signal system that once energized remains energized and that can be conveniently tested and reset.

These and other objects, features and advantages of this invention will become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a diagrammatic, perspective view of a signal system constructed in accordance with the present invention, showing the outer housing and the manner in which the thermal responsive element extends through the housing to facilitate testing and resetting;

FIGURE 2 is a top plan view of the signal system with one half of the housing removed, showing the construc tional details and arrangement of the elements of the system;

FIGURE 3 is a sectional view of the system of FIG URE 2, taken along the lines 3-3 and looking in the direction of the arrows;

FIGURE 4 is a wiring diagram of the alarm system; and

FIGURE 5 is a partial enlarged longitudinal sectional view of the bimetallic element and permanent magnet of the alarm system.

Referring now to the drawings, the self-contained signal system is indicated generally at 10. It includes anouter housing 12 having two portions 12a, 12b that interconnect to provide a box-like construction in which the operative elements of the alarm system are contained. A front surface 13 and a rear surface 14 of the housing 12 include slot openings 16 to permit an audible signal from within the housing to be emitted. Fin-like members 18a and 19a on the housing portion 12a, and 18b and 19b on housing portion 12b extend from the housing 12 about the front, back and side surfaces. These members assure that the openings 16 will be spaced from the wall, shelf, or other surrounding environment so that a clear, audible sound will be emitted from the housing 12 no matter how it is oriented. Preferably, the housing is formed of electrically non-conducting material, such as plastic or wood. The two housing portions 12a, 12b are secured together by detents 20 on opposite ends of housing portion 12a. These detents extend into portion 12b and are received by indentations (not shown) formed in the inside surface of the end walls of housing 12b.

An opening 22 is provided in the housing portion 12a to permit one end of a bimetallic thermal responsive strip 24 to extend from the inside of the housing to the outside. The opening 22 is large enough to permit movement of the bimetallic strip 24 in a direction toward and away from the front surface 13 of the housing 12.

As best shown in FIGURES 2, 3 and 5, the bimetallic thermal responsive strip 24 in undistorted condition at room temperature (68 degrees Fahrenheit) is essentially flat and straight, and extends at a slight angle with respect to front surface 13. The strip 24 is anchored at one end by a screw 26 to a support block 28 formed in the housing portion 12a. As shown in FIGURE 3, the support block 28 is formed with an inclined upper surface 29 to orient the strip 24 at the desired angle.

The free end of the strip 24 extends through opening 22 and supports a cap 30. The cap 30 includes indicia on each side. One side says test, indicating that movement of the strip 24 by manual pressure against the strip on that side of the cap will cause the alarm to operate. The indicia stop is imprinted on the opposite side of the cap 30 to indicate that pressure applied manually on this of the cap stops the alarm.

A signal device, such as a buzzer 34 is contained within the housing 12, being secured by screws 36 to the housing portion 12a. An electrically conductive strip 38 extends from a contact 39 of the buzzer 34 to a location beneath the bimetallic thermal responsive strip 24, adjacent the opening 22 in the housing 12. A screw 40 secures a permanent magnet 42, such as an alnico magnet, and the electrically conductive strip 38 together on a support block 44 of the housing 12. As best shown in FIGURE 3, the magnet 42 is normally spaced from the bimetallic strip 24.

An insulated wire connector 45 extends from a second terminal of the buzzer 34 to a bowed strip of spring metal 46, preferably of copper or copper alloy, that forms a base plate for a battery 48. The strip of metal 46 is located adjacent one corner of the housing 12a and held in a bowed condition by a partial partition 50. The partition 50 and a second partition 51 locate or cradle the bottom end of the battery 48in position adjacent the'bowed strip of metal 46. As shown in FIGURE 2, the battery 48, which is a standard type D 1.5 volt dry-cell, extends across one end of the housing 12. Additional contoured partitions 52, 53 formed in the housing portion 12a receive and locate the anodeend of the battery 48;:

A spring clip in the form of an electrically conductive wire 56 is fastened to the support block 28 of thehousing 12a and held in electrical contact with the bimetallic strip 24 by the screw 26. The spring clip 56 includes an angui 4 sion, brass expanding at a much greater rate than steel for a given rise in temperature. The two metals are laminated to provide the strip 24 with the steel portion 24a adjacent the magnet 42 and the brass portion 24b away from the magnet. With this arrangement, an increase in ambient temperature causes the strip 24 to bow or deflect toward the magnet '42 due tothe increased expansion of the brass portion. Upon suflicient deformation ofthe strip 24, the steel portion 24a comesfinto direct contact with the magnet 42 so that the magnet will., hbld,the strip 24 in deformed position even if the temperature subsequently decreases. t

The electrical circuitry is diagrammatically "shown in FIGURE 4 of the drawings. A series circuit is provided in which the anode of the battery 48 is connected by spring clip 56 to the bimetallic strip 24, which functions as a switch. The cathode side of the battery 48. is connected by wire 45 to one terminal of the buzzer 34. The second terminal of the buzzer 34 is connected-by strip 38 to the permanent magnet 42. The magnet 42 and the bimetallic strip 24 act as spaced contacts which, when closed, complete the circuit.

In operation, the bimetallic thermal responsive strip 24 is normally in a straights configuration at room temperature (68 degrees Fahrenheit) and-spaced from'the permanent magnet 42. The spacing is suflicient that the attractive force of the magnet 42 will not draw the strip 24 into contact with the magnet. The electrical circuit shown in FIGURE 4 is therefore normally opened and the buzzer 34 is inoperative. When the ambient temperature of the environment in which thebimetallic thermal responsive strip 24 is located increases, the strip 24 bends or deflects in a direction toward the permanent magnet 42.

The strip 24 is constructed and arranged relative to the magnet 42 so that it bends into contact with the magnet when the ambient temperature reaches a predetermined level, such as 136 degrees Fahrenheit. The temperature level at which contact is made and the buzzer 34 operated may, of course, be varied by adjusting the initial gap between the bimetallic strip 24 and the magnet 42 or by varying the expansion characteristics of the strip itself.

The extending end of the strip 24 is also constructed and arranged to be operable by a tripping mechanism, such as an extending finger (not shown) attached to a movable member such as a window or door. When the window or door is opened, movement of the finger contacts the cap 30 on the end of the bimetallic strip and moves the strip into contact with the magnet 42.

Once contact is made between the bimetallicstrip 24 and the permanent magnet 42, a circuit is completed from the battery 48 through the buzzer 34, the magnet 42 and the bimetallic strip 24 to energize the buzzer 34. The magnet 42 is selected of suflicient attractive force to overcome the resiliency of the strip 24,that tendsto return the strip to its initial position, spaced from the magnet, when at room temperature. In this way, the circuit is held closed by the magnet 42, notwithstanding'a subsequent decrease in temperature or a subsequent closing of thedooror'window if the alarm is mechanically "tripped. As aresult, the buzzer will provide an indication that a' certain temperature level was reached or that a door br-v'vindowwas opened, even if the alarm is not'heard immediately'and even if the cause of setting off the alarm is eliminated. Moreover, even ifthe battery shouldrun down-before the signal is heard, the position of thestri'p '24 in contact with the magnet 42 'indicates'that the alarm was at one time actuated.

To reset the alarm after ithasbeen actuated, the portion of the bimetallic strip 24 extending from the housing 12 is merely lifted away from the magnet 42. If thetemperature is below the tripping temperature of the alarm, the strip will remain out of contact with the magnet .42, in condition to function again as an alarm, Thus, there is no need to disassemble the device or to replace parts of the mechanism in order to reset the alarm.

Periodically, the signal system is tested to assure that the battery 48 has not lost its power and to determine that other components are properly functioning. This can be conveniently accomplished without opening the housing 12 by pressing the extending portion of the strip 24 into contact with the magnet 42, causing the buzzer 34 to be energized. If the test is satisfactory, the strip 24 is then lifted from the magnet 42, and the device is again ready to function. With this construction, a signal system is provided that functions as both a fire and burglar alarm, that is small and self-contained, and that uses a permanent magnet as an inexpensive and convenient means to hold the alarm energized and to facilitate the testing and resetting of the circuit without disassembly.

What is claimed is:

1. An independent signal system comprising:

(a) a signal device for producing a sensible signal when electrically energized,

(b) an electrical circuit for connecting the signal device to a source of electrical current,

(c) two normally spaced electrical contacts forming a part of the electrical circuit, adapted when electrically connected to operate the signal device through the electrical circuit,

(d) thermal responsive imeans movable mechanically and in response to temperature changes, for electrically connecting said two contacts in response to movement thereof,

(e) means, including a permanent magnet, to maintain the thermal responsive means in a position electrically connecting the two contacts independent of any change in temperature, once it has moved to such a position,

(f) a housing enclosing the signal device, electrical circuit, electrical contacts and thermal responsive means, with an opening through which a portion of said thermal responsive means extends for mechanical or manual engagement and which permits movement of said thermal responsive means between a position in which the said contacts are electrically isolated and-a position in which the said contacts are electrically connected by said thermal responsive means,

(g) whereby the signal system functions in response to either a change in temperature or mechanical actuation externally of said housing and can be manually tested and reset without disassembly.

2. The system of claim 1 wherein the thermal responsive means is a bimetallic element that distorts in response to temperature changes.

3. The system of claim 2 wherein the signal device is an audible alarm; a battery contained within the housing act as the source of current; the bimetallic element is essentially straight at ambient room temperature, includes at least one metal that has ferromagnetic properties positioned to contact the magnet when the element is subjected to the predetermined temperature level, and forms one of the normally spaced contacts; and the permanent magnet is fixed relative to the housing, forms the other of the normally spaced contacts, and has sufiicient magnetic attraction to hold the bimetallic element in contact with the magnet once contact is made, independent of subsequent changes in temperature.

4. The system of claim 3 wherein the housing includes openings to emit audible sounds and has projections that maintain the openings spaced from any large, flat, adjacent surface.

References Cited UNITED STATES PATENTS 2,806,108 9/1957 Babson 340--227.1 X 2,832,949 4/1958 Pivetz 340227.1 2,839,639 6/1958 Adlerstein 337-366 X JOHN W. CALDWELL, Primary Examiner D. L. TRAFTON, Assistant Examiner U.S. Cl. X.R.

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