US 2809368 A
Description (OCR text may contain errors)
I Oct. 8, 1 957 E. EHLERS,'JR
SELF-CONTAINED FIRE ALARM UNIT Filed May 5, 1955 INVENTOR.
United States Patent 6 SELF-CONTAINED FEEALARM UNIT 'Edward'Ehlers, Jr., Montclair, N. 3.
Application May 5, 1-955, Serial No. 506,296
2fClaimS. (Cl. 340-427) This invention relates 'to a self-containedfire alarm unitadapted to be mounted on a wall, ceiling or other'surface of a room or-other-space to be served thereby.
The invention has for an object to provide a fire alarm unit comprisingan electrically actuated alarm device, a dry battery as a source of electrical energy in circuit with said alarmdevice, said circuit including a thermostatic switch adapted to close in response to abnormal rise-in temperature,.such as produced by fire, and a push button actuatable test switch'inshunt circuit between the battery and alarm device, these elements being all compactly contained in asingle housing-or casing, and said casing beingso constructed as totransmit both air borne radiant heat .and conducted heat to the thermostatic control switch.
The invention has for a further object to provide a 'casingincluding a rearwardly open hollow base plate upon which the elements of the fire alarm unit are mounted, with the thermostatic alarm control switch arranged in such relation thereto and direct contact therewith that;heat conducted by and.:through the base plate will be rapidly transmitted to said switch in addition to radiant or air borne heat which enters the casing, whereby said switchiis rendered vmorequicklyresponsive to abnormal rise oftemperature, and to thisend to provide a base plate comprising in whole or in part a highly heat conductivemetal, such as copper.
The above andother 'objectswill be understood from a reading of the-following detailed description of the invention inconnection-with theaccompanying drawings, in which:
Fig. l is a front elevational view of the self-contained fire alarm unit of this invention; Fig. 2 is a front elevational view of the same, with the cover member of the casing removed; Fig. 3 is a longitudinal sectional view, with parts in elevation, this view being drawn on an enlarged scale; and Fig. 4 is a cross-sectional view, taken on line 44 in Fig. 2, but drawn on an enlarged scale.
Referring to the drawings, in which like characters of reference indicate corresponding parts, the reference character indicates the rearwardly open hollow base plate of the fire alarm unit housing. Mounted on the external face of the base plate It), adjacent to the upper end thereof, is an electrically actuated alarm device 11, having at its back a supporting bracket 12 which is aflixed to the base plate 19 by a fastening screw 13. This alarm device may be of any well known sound producing type, but preferably comprises an electric horn.
Mounted on the base plate 16, below the alarm device 11 is a dry battery 14, which serves as the source of electrical energy by which the alarm device is actuated. Said battery is secured in place by retaining clips or lugs which are struck out from the material of the base plate, so as to embrace the sides, top and bottom of the battery.
. Also mounted on the base plate 10, at its upper end, is a thermostatic switch 16. In a preferred form there- Patented Get. 8, 1957 of, this thermostatic switch comprises a hollow metallic casing formed by agbottom member 17 and atopmember 18, and containing a bimetallic switch arm 19, which is electrically insulated from said casing by insulation 20, and a stationary contact 21, which opposes the switch arm '19 and is electrically grounded on the casing, said casing, in turn, being electrically groundedon the base plate 10 (see Fig. 4).
One pole 22 of the battery 14 is connected to one pole of the alarm device 11 by a lead 23, and the other pole of said alarm device is electrically grounded on the baseplate 18. The alarm actuating circuit is completed through the base plate ground to the grounded stationary contact 21 of'the thermostatic switch, and thence, when closed by engagement of the bimetallic switch arm 19 with said stationary contact 21, through said switch arm and a lead 24 connected therewith back to the other pole 26 of the battery 14.
To enclose the above described elements of the fire alarm unit, a hollow casing or cover member 27 is suitably attached to the base plate 16. This casing or cover member 27 is provided in its face wall, and opposite thealarm device 11 with louvered openings 28, through which thesound of the actuated alarm device can'be unimpededly emitted. The bottom end wall of the casing or cover member 27 is provided with admission openings 29 through which radiant heat or air borne heat can pass upwardly into the interior of the fire alarm unit.
Suitably mounted in an through the front wall of the casing or cover member 27, preferably adjacent to the bottom end thereof, is a push-button actuable test switch 36. One pole 31 of this test switch is connected by a lead 32 to the electrical ground provided by the base plate 1%, and the other pole 33 of said test switch is connected by a-lead '34 to the pole as of the battery 14.
By-this arrangement the test switch 3;? is connected in a shunt circuit from the battery 1e through the alarm device .11 and back to said battery. When the push-button actuatable switch 30 is manually closed, current flows from the battery 14 through the alarm device 11 to ground, and thence back to the battery through the lead 34; thusv providing a test circuit independent of th thermostatic switch 16, by which operable condition of thealarm device can from time to time be ascertained.
Provided in the upper end portion of the base plate It) is a key hole type opening 35, whereby to engage the fire alarm unit with a mounting screw (not shown) which serves to support the fire alarm unit on and in contiguous contact with a wall or other srface within the room or other space desired to be served by said unit. When so mounted, the interior of the hollow base plate is opposed to the supporting surface, whereby heat emanating from said surface is confined in the hollow interior of the base plate, and thus concentrated therein for direct application to the base plate so as to be conducted thereby directly to the thermostatic switch (see Fig. 3).
From the above it will now be apparent that the present invention provides a very compact self-contained fire alarm unit, which is well adapted for room or like service.
One of the deficiencies of thermostatically controlled electric fire alarm devices, as heretofore known, is that the same depend, for operation, practically solely upon application thereto of radiant or air borne heat generated within the building room or space served thereby. Since fires, and particularly fires starting in the lower regions of a building, frequently progress through the building wall interiors before actually entering rooms or spaces contiguous to said walls, and since, under such circumstances, generation of radiant or air borne heat within such rooms or spaces is likely to be delayed, said former devices are not well adapted to detect and give prompt warning of the existence and progress of internal wall fires. Having this in view, the present invention seeks to provide a novel construction of fire alarm unit which overcomes such deficiency, by providing said unit with a highly heat conductive path through which heat, generated within a wall on which the unit is mounted, will be quickly and directly conducted and applied to the thermostatic switch element, even before the air temperature within the room rises to an alarm actuating degree. To this end, the fire alarm unit of this invention is provided with the rearwardly open hollow base plate 10, which is effective to concentrate wall emitted heat directly against the base plate, includes a metal of high heat conductivecharacteristic, such. as copper or other highly heat conductive metal.
Although the base plate may be provided solely from copper or like highly heat conductive metal, since however such metals are relatively soft, and therefore easily deformed it is preferred to provide the base plate 10 with a core 36 of relatively rigid metal, such as steel, and then plate the surfaces thereof with an external coating 37 of copper or other highly heat conductive metal, which coating provides the base plate with. the desired highly conductive heat path.
The casing 17 18 of the thermostatic switch 16 is mounted in direct contact with the heat conductive copper or like coating 37 of the base plate it), and is held in place by retaining clips or lugs 25 which are struck up out of the base plate, so that the heat conductive copper or like coated portions of said clips or lugs contact the opposite sides of the switch casing 17-18, with enhanced conducted heat transfer effect. Heat emanating from a wall upon which the fire alarm unit is mounted will be confined in the base plate chamber and, will be quickly transferred directly to the base plate It), and thereupon will be rapidly conducted to the thermostatic switch 16 by way of the highly heat conductive path provided by the copper or like coating 37 of said base plate.
Radiant or air borne heat can enter the interior of the casing or cover member 27 through its bottom openings 29, so as to rise therein for contact with the thermostatic switch 36. Such entering radiant or air borne heat also contacts and is transferred to the copper or like coatin 37 of the base plate 1%, so as to be rapidly conducted thereby to the thermostatic switch in addition to the direct contact of the radiant or air borne heat with 7 the latter, thereby assuring operation of said switch in response to heat within a minimum interval of time.
Having now described my invention, I claim:
1. A self-contained fire alarm unit comprising a rearwardly open hollow base plate providing a chamber to confine heat emanating from a surface contiguous to whichthe unit is mounted, whereby to concentrate said heat in direct contact with the base plate for conduction thereby, an electrically actuated alarm device mounted on said base plate, a dry battery mounted on said base plate, a thermostatic switch, a heat conductive support for said thermostatic switch also mounted on said base plate, and a circuit connecting said alarm device and thermostatic switch in series with said battery, an enclosing hollow cover supported by said base plate, said cover having openings therein to admit radiant and air borne heat for contact with said thermostatic switch, and said base plate including a coating of highly heat conductivernetal, such as copper, said support of the thermostatic switch being disposed in direct contact with said heat conductive metal coating of the base plate for reception of conducted heat therefrom.
2. A self-contained fire alarm unitcomprising a rearwardly open hollow base-plate having a rigid metallic core plated with an external coating of a highly heat conductive metal, such as copper, said base plate providing a chamber to confine heat emanating from a surface contiguous to which the unit is mounted,'whereby to concentrate said heat in direct contact with the base plate for conduction thereby an electrically actuated alarm device mounted on said base plate, a dry battery mounted on said base plate, a thermostatic switch, a heat conductive casing enclosing said thermostatic switch, said casing being mounted on said base plate in direct contact with the heat conductive coating thereof for reception of conducted heat therefrom, a circuit connecting said alarm device and thermostatic switch in series with said battery, and a hollow cover supported by said base plate, said cover having openings therein to admit radiant heat and air borne heat for contact with the thermostatic switch.
References Cited in the file of this patent UNITED STATES PATENTS Cufalo May 1, 1951