US2670466A - Burglar alarm system - Google Patents

Description

Feb. 23, 1954 HARPER 2,670,466

BURGLAR ALARM SYSTEM Filed March 24, 1950 INVENTOR. 4/? THUR R. HARPER Patented Feb. 23, 1954 UNITED STATE$ OFFICE BURGLAR ALARM SYSTEM Arthur R. Harper, Detroit, Mich, assignor of fifty per cent to W. R. Findlay, Detroit, Mich.

Application March 24, 1950, Serial No. 151,631

(01. MIL-276) 2 Claims. l

The present invention relates to a burglar alarm system of the type which is controlled or actuated by the interruption of flow of electric current through a control circuit operatively associated with doors, windows and the like, of the building in which the system is installed when unlawful or irregular entry therethrough is at tempted, such interruption causing the alarm circuit to be energized, actuating the alarm.

It is among the objects of the present invention to provide a burglar alarm system adapted to receive its primary source of power from the electric lighting circuit of the building in which the system is installed, and which is operable to actuate one or more alarms when current in the control circuit for the alarm is disrupted, and further which is operable to automatically reset itself on restoration of power to the lighting circuit if a temporary power failure should occur.

It is a further object of the present invention to provide a burglar alarm system operable on a low voltage circuit adapted to use standard electrical apparatus, while being suitably designed to insure adequate voltage to operate said apparatus irrespective of the length of said circuits, whereby the alarm system can be constructed and operated in the most economical manner and the maximum life of the component part will be insured.

It is still a further object of the present invention to provide an economical, low cost burglar alarm system having a portable control unit adapted to receive power from a standard lighting circuit receptacle and operable to actuate an alarm response to disruption of a low voltage control circuit, whereby said alarm system can he installed in homes or other buildings by other than licensed electricians Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

In the drawings:

Fig. 1 is a perspective view of one embodiment of the present invention showing the component parts of the alarm system prior to its installation; and

Fig. 2 is a view showing diagrammatically the wiring circuit for the component parts of the embodiment shown in Fig. 1.

Before explaining the present invention in detail it is to be understood that the invention is not limited in its application to the details of if U construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to he understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring now to the drawings and particularly to Fig. thereof, a housing it is shown within which is housed the alarm actuating mechanism for the burglar alarm system. This is a portable unit which has an extension cord [2 adapted to be inserted into an electrical receptacle in the 110 volt lighting circuit of the building within which the burglar alarm system is to be used. An electric cord M is shown plugged at its one end into the housing it and connected at its other end to a terminal block it. An electrically operated bell It is wired to the terminal lock it by the wires 25]. Also connected to the erminal block it are control circuit wires 22 which have in their circuit the lock switch 24, and other control apparatus.

As will be more fully explained hereinafter,

, conductors 22 extend to the various doors,

, light 2% which will be lighted simultaneously with the sounding of the alarm 18. If desired, an extension cord (not shown) may be plugged into the light receptacle 28 permitting a flood light to be lighted at any particular place in the building.

Referring now to Fig. 2, a schematic diagram of the present invention can be seen. The electric current for operating the present burglar alarm system is supplied through the con-'- ductors 30 and 32 directly from the lighting circuit of the building. In the circuit formed by conductors 3t and 32, the primary wind.- ing 34 of a step-down transformer is inter posed, and connected in parallel with the primary winding is the circuit 355, which contains a light receptacle for the light bulb 26 and a relay operated switch 38. As can be seen, when the switch 38 is closed the circuit 36 will likewise be closed causin the light bulb 25 to be lighted, and conversely when the switch 33 is opened,

the circuit 35 likewise will be opened preventing the light bulb 26 from being lighted. As will be more fully explained hereinafter, the relay switch 38 is controlled by a relay in the control circuit of the burglar alarm system causing the switch 38 to be closed when the control circuit is interrupted.

The secondary winding 46 of the transformer is included in the control circuit'having the switches 42, which are connected respectively, adjacent the various doors, windows and the like, through which unlawful or irregular entry is to be prevented and are adapted to be :opened :to interrupt the control circuit should. such entry be attempted. The control circuit'comprises the secondary winding All, the conductor 44, the switches :22, a relay switch 46, conductortdrelay E1, resistor 52, and conductor 5%. Also in the control circuit, arranged in parallel -with the switches 42 and the relay switch lit, is the conductortii with the lock switch 24 therein. The lock switch 24 is normally closed when the lock to the door or the like, in which the switch is located, is unlocked.

An alarm circuit isprovided which includes the conductor 54, the secondary winding of the transformer to the center'tapfifl, the conductor 62, relay switch lit, the bell alarm It. The, relay switch fi l as well as the relay switch 46in the control circuitv and the relay-switchtii in the lighting circuit are controlledby the relay 5t. When the relay 59 is tie-energized, the relay switches 33 and 6d are normally closed while the relay switches is open. Thus, it can be seen that the alarmlli and theilight 'Zt'iwill be actuated whenever the relay 5!) is de-energized.

During such periods of time when the burglar alarmsystem is not to be inoperation, the lock containing the lockswitch 24 will be unlocked causing the'switch 24 to-be closed providing a closed circuit for the relay 5% causing the switches 38 and 66 to be maintained in an open position so that the light 28 and bell 58 will not be operatedandcausing switch it to be closed.

When it is desired to place the alarm system in operation, the various switches 42 will be closed as well as the switch At which normally is held in a closed position by the relay til, the-latter :being energized by virtue of lock switch 24 being closed. The lock switch 211 will then be opened so-that the circuit through the switches ill and 46 will be the only source of supply for energizing the coil 59, and thereafter if any of the switches 42 shouldbe opened by an unlawful or irregular entry, the control circuit will be disrupted causing the-relay 59 to be deeenergized, with the result that the switchestt and Gal will be closed, setting-oh" the alarm.

An added feature of the above control circuit is that the burglar alarm system cannotbe left in an inoperative condition after the lockswitch 24'. has been locked. If any of the switches :32 have been inadvertently left open, the alarm will sound immediately when the lockcontaining the lock switch 2s has been closed. Thisznecessarily follows, since immediately after said. lock is closed, the lock switch 24' willbe opened. causing the relayfifl to be ,de-energized. If suchaa condition should "occur, a check of thevarious switches 42 can be made to ascertain-which one is open, and when this switch: has been closed, the building mayabeproperly locked withthe alarm system in operation.

The present burglar alarm systernalso has :provisions made to re-energize thev relay. Eitshould-a temporary power failure occur causing the entire alarm system to be de-energized. As is believed readily apparent, if the entire system becomes tie-energized, the relay 46 will be opened and since the circuit containing the relay switch 46 is the only circuit available to supply current to the relay 5% when the alarm is set, once this switch has been opened the relay coil 55) will not thereafter automatically be reeenergized on restoration-"of power. For this reason, an auxiliary circuit is provided for controlling the relay switch 53 which is in circuit with the conductor .liJ-.-arranged in a parallel relationship with the circuit containing the switches and As can =be seen, if this relay switch is normally closed when the relay controlling it is de-energized, in the. event of. a power failure, the switch 68 will close and on restoration or" the power, the relay Elly/illbare-energized through the conductor ill. Thus, current will flow from secondary winding 40: through conductorsdswand it, relay switch -E38,thro-ugh relay t9 and resistcrt t, andback to secondary winding 43 via conductor E l.

The auxiliary circuit also includes the resistor l2, relay switch KM, "relay it and conductor 7-8. On restoration of-power after the failureand after relay 5i] has been re-energized thereby closing relay switch lt, current will then flow from secondary winding :lll through-switches-M and st, via conductor iki to resistor i2, switchl l, relay it, conductor is and baclrto secondary winding is by way of conductor E l. In this manner relay it will here-energized causing'relay switches 33 and E ite reopen. .The auxiliary circuit also includes relay switch -82 and conductor 33. When relay-it is initiallyre-energized the switch 82 will be closed simultaneously with the opening of relay switches efi and E4. 'Closing of relay switch 82 completes a circuit through relay it so as to maintain the latter'energized. Thus, a circuitis completed whereby current flows from secondary winding lil through conductors 62 and to relay switch 82, through relay l8 and back to secondary winding lt via conductors lsand 54. It can be seen that this causes the relayfic to remain open so as not toeffestthe operation of the control circuit for controlling the flow of current through the relay-53'.

The step-down transformer withthe. center tap is utilized-to provide 24 volts throughthe control circuit while maintaining 12 volts in-the alarmcircuit and the auxiliary circuit. It-is desirable to use 12 volt circuits so. thatstandard electrical equipment, such as 12 volt relays may be used. l-lowever, it is found necessary to use a higher voltage through the controlv circuit because of the voltage drop therein which, if a 12 volt circuit were used, might not provide proper actuation of th relays. The resisters; 52 and 72 are placed in series with the relays Stand 16 to prevent overheating of the re ays when energized by the 24 volt circuits.

Thus, it can be'seen that a portable-alarm system is provided which can be installed by one who is not a licensed electrician and can'be easily installed at a relatively lowcost. The burglar alarrn'system is adapted to actuateboth a visual and an audible alarm, and cannot be accidently left in an inoperative condition. Further, in the event of a temporary interruption of velectric power,-such as may result fronran electrical storm or the like, the alarm'system Willbe automatically reset when the power; is restored to the system.

Having, thus described .my invention, a I; claim;

1. A burglar alarm system comprising an alarm and a circuit therefor, a control circuit including in series therein the winding of a control relay, a plurality of switches adapted to open when entry through a door, window or the like is attempted and a first contact of said relay closed by the relay winding when it is energized, the alarm circuit including therein a second contact of said relay closed when the relay winding is de-energized, a lock switch in parallel with the said switches and the first relay contact for independently energizing the relay winding so that lawful entry may be made through said door or window without causing the alarm circuit to be closed, all of the said circuits being fed from a single source of power, so that in case of failure of the source of power the relay winding will be de-energized and will not be able to be re-energized, upon restoration of the source of power, due to the opening of the first relay contact and the alarm will not operate in the absence of power from said source, and means for restoring said relay by momentarily re-energizing said winding when the power is restored comprising a relay having a winding connected to the power source and having a contact closed in a re-energizing circuit for the first relay independent of the first relay contact when the second relay is de-energized.

2. A burglar alarm system as claimed in claim 1 which includes a portable unit in which said relays and their respective contacts are housed, said unit having a conductor adapted to be connected to the single source of power for feeding all of said circuits.

ARTHUR R. HARPER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 492,478 Sturts Feb. 28, 1893 1,158,146 Olney Oct. 2-6, 1915 1,238,823 Roeder Sept. 4, 1917 1,365,693 Hess Jan. 18, 1921 1,845,621 Morrison Feb. 16, 1932 2,191,926 Lemire Feb. 27, 1940 2,225,464 Santino Dec. 17, 1940 2,243,804 Howton May 27, 1941 2,346,171 Laford Apr. 11, 1944 2,419,957 Laford May 6, 1947 2,440,002 Bower Apr. 20, 1948 2,491,987 Lefcourt Dec. 20, 1949

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