US2165893A - Alarm - Google Patents

Description

July 11, 1939. H. A. GUNION ALARM Filed Dec. 10, 1936 Patented July 11, 1939 UNITED STATES PATENT OFFICE ALARM 2 Claims.

This invention relates to burglar and similar alarms and particularly to an alarm device employing a normally open circuit which extends into a protected area, whereby the alarm will be operated when the circuit is completed by an unwarranted or undesired action in that area.

A primary object of the invention is to provide an alarm device of simple and compact construction which will give a continuing visible and audible signal once the portion of the circuit in the protected area has been completed, even though that circuit be immediately broken again.

Another object of the invention is to provide an alarm device which will operate on an ordinary alternating current source, thereby doing away with batteries or transformers usually employed with such devices.

Other objects and advantages of the invention will become apparent from the following detailed description and the accompanying drawing, in which:

Fig. 1 is a side elevation, partly in section, of an embodiment of the invention;

Fig. 2- is a sectional View taken on line 2-2 of Fig. 1;

Fig. 3 is an end elevation, partly in section;

Fig. 4 is a diagrammatic view illustrating the circuits employed and with the operating coil and related mechanism shown in perspective; and

Fig. 5 is a fragmentary perspective view of the insulated pivot support for the holding switch member.

The alarm device is housed in a casing Ill mounted on a base II which is preferably made of insulating material. An L-shaped strip of insulating material I2 is mounted on the base II, with its shorter end I2 turned upwardly to form an upstanding panel upon which is mounted a pair of spaced contact elements I3 and I4. The bracket plate I5 of the trip mechanism overlies the strip I2 and a single set of bolts l6 serves to secure these parts to the base II. The frame I! of a relay or trip coil I8 is secured, by welding or the like, to the bracket plate [5, and one end of the plate I5 is formed with spaced ears I9 between which a holding switch member 20 is pivotally mounted for engagement with the contacts I3 and I4 at one extremity of its pivotal movement.

As best shown in Fig. 5, the lower end of the member 20 is rolled over to form a sleeve for receiving the tube I9a of insulating material, and insulating bushings I9b are placed on the end of the tube to space the edges of member 20 from the ears I9. A pivot pin I extends through the ears I9 and tube 59a to complete the insulated pivotal support for member 26.

The frame I! has upturned arms 2| and 22 between which the coil l8 and its core [8 are seated, and the armature 23 extends over and is .pivotally mounted on the end of arm 2 I. Lateral movement of the fiat plate armature is prevented by ears 24 on the arm 2! that project through notches 25 in the edges of the armature. A relatively stiff spring 26, between the projecting end 21 of the armature 23 and a prong 28 struck out from the arm 2i, tends to hold the armature in raised position against a stop 29 that may be a central extension of the arm 25, Which extension passes through an opening 3i in the armature 23 and is bent to overlie the armature.

The other arm 22 of the frame ll carries an upstanding metal plate 3! which is insulated from the arm by a block of insulating material 32. A coil spring 33 is mounted between the metal plate 3| and the free end of the latch member 20 and tends to force said member into engagement with the contacts I3 and M.

The switch member 25 is normally latched in off position, Figs. 2 and 3, by the integralhook portion 34 which engages in an opening 35 in the armature 23. A push button 35 is loosely mounted in the panel for swinging the switch member into this open-circuit position, the push button being alined with an opening 37 in the casing ID for operation by a small rod, such as a pencil.

An electric lamp 38 is mounted in a socket 39 on the base II, and a colored lens ll) is mounted in the front wall of the casing It to give a visual signal when the alarm is energized.

The parts so far described form a unit that may be connected between a source 4! of alternating current, such as the usual volt, 60 cycle alternating current line, and a protective circuit that extends to the area to be guarded. A switch 42 is included in the connections, being shown diagrammatically in Fig. i as a single pole, single throw switch, but the switch may be merely a separable plug connector for insertion in a wall socket to connect the alarm system to the power line.

The lamp 38 and trip coil i8 are serially connected between the lead 33 and plate 3i by the coil terminals 44, 45, respectively. One wire 46 of the protective circuit extends from the plate 31 to a normally open switch 41 at the area to be protected, and the return wire 48 is connected to the contact I3 on the insulated strip I2.

The series circuit of these parts is completed to the power source by the lead 39 that extends from contact E3 to the switch ll.

It will be noted that the spring 33 forms an electrical connection between plate 3| and the switch plate 28, and that the plate 29 and contact [3 thus form a holding switch in shunt with the switch 4? of the protective circuit.

An alarm-controlled circuit may be located in the protected area, as indicated by wire 50 that extends from the terminal M to load devices 5| in the protected area, the return wire 52 from such devices being connected to the power source lead 43. The nature of the switch 4'! and the devices 5| will depend upon the purpose of the protective system.

The illustrated embodiment, including the Fig. 4 circuit, is particularly useful as a burglar alarm for barns, poultry houses and similar buildings. The normally open switch 41 may be of any known type having means, not shown, for connection to or across doors or windows for closing the switch when the door or window is opened. When used as a burglar alarm, the load devices 5| will be lights positioned to illuminate the exterior of the building. When used as a fire alarm, the switch 4? will be of a known thermal type and the load devices 50 may be the electrically actuated valves of a sprlinker system.

The apparatus is placed in operation by latching the switch plate 2! to the armature 23, and closing switch 42. A closure of the switch 41 will then complete the described series circuit to energize the trip coil [8. The armature 23 is attracted to the coil, thus releasing the plate 2:: which engages the contact l3 to complete a holding circuit around the switch M. The circuit thus remains energized until the button 36 is pressed inwardly to latch the switch plate 20 to the armature 23.

I Due to the alternating current employed and the choice of a relatively stiff spring 26, the armature 23 will vibrate continuously between the stop 29 and the core l8, thus acting as a buzzer to give a continuing audible signal in addition to the visual signal afforded by the lamp. This action is preferable to the usual make-and-break types of buzzer circuits for a number of reasons.

In the first place, the alarm is very reliable over long periods as the operation does not depend upon the particular adjustment of vibratory contacts. Further, the initial cost is decreased by the omission of vibratory contacts and this, as well as the fool-proof nature of the alarm makes it particularly useful in the protection of outbuildings. The relatively low sound produced by the armature under the joint action .of the stiff spring and the alternating magnetic field is sufficient to awaken the property owner but will not be heard at the protected area, thus giving the property owner the advantage over the thief, particularly when the auxiliary lighting circuit 50- 5Z is not used.

The visual signal afforded by the lamp 3B is of advantage in some instances, but the primary function of the lamp is that of a resistor which limits the voltage drop across the relay coil. The lamp may, for example, be of the 15 watt, volt type, which has a resistance of about 810 ohms. The coil l8 may consist of about 2200 turns of No. 34 wire (0.007 inch diameter), enamel or cotton covered, having a resistance of about ohms. The voltage drop across the coil will therefore be about 15 volts.

While a preferred embodiment of the invention has been shown and described, it will be understod that various modifications and changes in the details of construction may be resorted to without departing from the spirit of the invention within the scope of the appended claims.

I claim:

1. A circuit control device for an alarm system comprising a base member, a coil frame mounted on said base, a trip coil mounted in said frame, an armature pivotally mounted on said frame across the end of said coil, a relatively stiif spring tending to move said armature from said coil whereby said armature will be attracted to said coil and will vibrate continuously when said coil is traversed by alternating current, an upstanding panel carried on said base adjacent said coil frame, a contact carried by said panel, an upstanding switch plate pivotally mounted between said frame and said panel, a spring normally biasing said switch plate into engagement with said contact, cooperating latch means on said armature and said switch plate operative to latch said switch plate in a position out of engagement with said contact when said armature is away from said coil and said switch plate is tilted out of engagement with said contact, manually operated means for moving said switch plate to latching position against the action of said spring, and an electrical connection between said switch plate and one terminal of said coil; whereby an alarm circuit may be completed by connecting a current source between the panel conand the second coil terminal, and connecting an alarm switch between the first coil terminal and the panel contact, said switch plate engaging the panel contact on initial energization of the coil to complete a holding circuit.

2. A circuit control device for an alarm system comprising a base member, a U-shaped coil frame mounted on said base, a trip coil mounted in said frame, an armature pivotally mounted on one leg of said frame and extending across '=jthe end of said coil, a relatively stiff spring tending to move said armature from said coil whereby said armature will be attracted to said coil and will vibrate continuously when said coil is traversed by alternating current, an upstanding panel mounted on said base in spaced relation to the other leg of said coil frame, a contact carried by said panel, an upstanding switch plate pivotally mounted between said frame and said panel having an upper end overlying said armature, a spring between said frame and switch plate normally biasing the latter into engagement with said contact, said spring being insulated from said frame, manually operated means for tilting said switch plate out of engagement with said contact toward said frame, cooperating latch means on the upper end of said switch plate and said armature operative to latch said switch plate in said last mentioned position when said armature is away from said coil, and an electrical connection including said spring between said switch plate and one terminal of said coil, said panel contact and the second coil terminal being adapted for connection across a source of alternating current whereby an alarm switch may be connected between the panel contact and the first coil terminal.

HARRY A. GUNION.

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