US2575883A - Fire alarm - Google Patents

Description

Nov. 20, 1951 G. D. MATEER FIRE ALARM Filed Dec. 1, 1948 INVENTOR Patented Nov. 20, 1951 UNITED STATES PATENT OFFICE 7 FIRE ALARM George Diehl Mateer, Ardmore, Pa.

Application December 1, 1948, Serial No. 62,871

2 Claims.

The present invention relates to electric alarms particularly of the type employed as rate of rise fire alarms.

A purpose of the invention is to mount a rate of rise switch on the core of an electromagnet and to apply holding action to the switch when the electromagnet is energized by an extension of the armature of the electromagnet preferably operating an extension of the shielded thermostatic element of the switch.

A further purpose is to pivot the electromagnet armature on the core and preferably between the electromagnet and a platform mounted on the core for positioning the switch.

A further purpose is to make a self-contained fire alarm unit from the rate of rise thermostatic switch and a buzzer which acts as an alarm.

Further purposes appear in the specification and in the claims.

In the drawings I have chosen to illustrate a single embodiment of the invention, selecting the particular form shown from the standpoints of convenience in illustration, satisfactory operation and clear demonstration of the principles involved.

Figure 1 is a top plan view of the device of the invention.

Figure 2 is a side elevation of Figure 1.

Figure 3 is an end elevation of Figure 1.

Figure 4 is a circuit diagram.

Diagrammatic circuit connections are included in these views.

Describing in illustration but not in limitation and referring to the drawings:

The alarm of the present invention comprises a thermostatic switch 20, preferably of the rate of rise type, and a buzzer 2|.

The switch suitably comprises an insulating mounting pad 22 built up of insulating layers 23 supporting, insulated from one another, an unshielded'thermostatic switch element 24, a contact strip 25 and an intermediate shielded thermostatic switch element 26 extending beyond the contact ends of the element 24, and contact strip 25 at 21, and suitably shielded from transfer of heat from the atmosphere by a shield 28. The rate of rise thermostatic switch as here described is well known in the art and is not considered novel per se. As in usual rate of rise thermostats, the fast expanding sides of the thermostatic bi-metal strips are both directed in the same direction and toward the contact strip 25. A predetermined difference in expansion exists between the shielded and unshielded elements' The mounting pad of the switch is united together and mounted by screws 30 which pass through the pad and through the thermostatic switch elements and contact strip in insulated relation to the elements and strip.

The mounting screws 30 are conveniently fastened to a mounting platform 3| which is desirably formed integrally from a U-shaped steel or iron external core 32 comprising the platform 31 as one arm of the U, a bridge 33 forming an upright of the U and a base 34 forming the other arm of the U. The base 34 is suitably joined as by a press fit with an internal iron core 35 around which is wound an electromagnet coil 35 of the buzzer. Thus the internal iron (steel) core 35 and the u member 32 make up the core of the electromagnet.

The upright 33 is conveniently slotted at 31 near the platform and the slot provided with shoulders 31' which extend laterally into the space at the base of the slot and receive and make rocking pivotal engagement with the walls of slots 38 in a suitable magnetic (iron or steel) switch pad and slopedat 44 to engage and stop the motion of the armature under the action of the spring. At the outer end of the armature an extension 45 therefrom is carried around and over the extension 21 of the shielded thermostatic switch element 26 to mount a switch operator 46 which on energizing of the electromagnet will cause the switch to remain closed and thus act as a holding switch operator. At other times the operator is free from engagement with the switch.

Mounting lugs for the alarm are provided at 41 on the base and at 48 on the sides, by extensions from the core.

The device is connected to a source of alternating current at 50 and 5|, conveniently to one terminal of the coil and to the shielded thermostatic switch element 26. The unshielded thermostatic switch elements are connected in parallel at 52 and connected to the other terminal of the coil at 53.

The electrical connections are shown on the circuit diagram of Figure 4.

In operation, it will be evident that the thermostatic switch will remain open as long as no emergency condition arises. If the temperature rises gradually to a moderate extent both thermostatic switch elements will shift together in the same direction and no contact will be made by the switch. If the rise is rapid, the shielded thermostatic switch element will move downward less rapidly than the unshielded element, and at the predetermined rate of rise unshielded element 24 will make contact with the shielded element 26. On a slowly rising temperature when air abnormaltmperature is reache'd the shielded thermostaticswitch element 25"Will" move down and make contact with the contact strip 25. The space between the shielded thermostatic element and the contact strip can the; adjusted to determine the temperature at which the alarm will go off on a slow rise in temperature. .1 Once contact has been made; the coil is en-' ergized by alternating current, which iattra-cts the armature and causesit to be pulled toward therinternal more, :at the sameti-me -through:tha wgo action-of", the switch operator 4 5'; holding-the switchxclosed by ,contactbetweeni 1the shielded a element 26 and the; contact stripi'i '--D.ue to the alternating current "rwaver-variation; however depending'on' the frequency whichawill ordinarily bet. commercial frequency such as. 60. cycles) the buzzen; .will vibrate in: step, with .the alternating current without breaking the circuits; Thus the 1 alarm: will continue. until-it is switchedzoif, as by disconnectingra master switch of the alarm 30 systemsznotshowng" :Theiinventionis particularly advantageouscbe cause'it is. very cheap.sandi'convenientJfora-use 1- byltheuindividual householder or for industrial purposes. l; a in view. of-rmy; invention: and disclosure vari ationsandmodifications tonneetindividua'l whim or:=particular;.need :wilkdoubtless become evident":- tQOthBISySkillt-Zd in the art; torobtai'n all or of:-: the benefits. of5my. :inventiomwithout. copying." an thestructure .shown;rand. I therefore; claim -all such insofar as-theyifallcwithin the reasonable spirit3and:;scope ofimylclaimsx Jaw .Having. :thus; described: my invention -zwhat rs claim-asznew and desire to secure by Letters Patent isz: ;:.-.;:-:1:.. 31K rife 1.1 ;In.an-;alarm;ia buzzer, having a icore lhaving a coiliaroimdrthecore, havingarr: armature pivszsotally mounted on one side of the coil and on the base and extending toward the platform "the end of the interior core and"the' platiornl "file of this patent; 1

adapted to vibrate with respect to the coil and having a spring biasing the armature toward a position remote from the coil, an extension from the core to a position beyond the armature, a rate of rise thermostatic switch mounted on the extension and having an unshielded thermostatic switch element, a contact strip and an intermediate shielded thermostatic switch element; extending endwise beyhnd the unshielded element'fcbnnections placing the unshielded element and the contact strip electrically in paralleliconnections placing the rate of rise thermostatic switch electrically in series with the coil, and an extension from the armature on the 0pposite*side "of*the coil from the pivot engaging thetextendeduend oi the shielded element to move the same into contact with the contact strip when the coil is energized.

2. In an alarm, a magnetic ferrous support having ialbo'dy; a base at one end of the-"bodv, and a platform at the other end of thabb dy a rate of rise thermostatic switch mountedonth'e platform, an=interi'of mag'netic cor mbl'ifitd wherebywith the supportit completes a ma netic circuit a coil around theinterior magneti core, an armature pivotally mounted on th'e bod to" one side of the core and extending btwee a biasing sprin'g actin-g on the armature 'd-urge it toward the platformand an extension 7 froirl-f theend oi the' armature bevondthe' coil n gaging the rate of iis thermostatic 'swi 3 hold the same closed when tl'ie 'coil is 'nei gized.

7 eca e IEl-lll WMA'TEER.

L REFERENCES. CITED v The following references are of record in thie PATENTS I

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