US2786992A - Closed-circuit electric alarm system - Google Patents

Description

March 26, 1957 E. J. FREUNDT 2,785,992

CLOSED-CIRCUIT ELECTRIC ALARM SYSTEM Filed Aug. 10, 1955 PUSH BUTTON CONDITION- RESPONSIVE CONDITION- RESPONSIVE 1NVENTOR- United State Pawn O CLOSED-CIRCUIT ELECTRIC ALARM SYSTEM Edmund John Freundt, Indianapolis, Ind.

Application August 10, 1955, Serial No. 527,585

4 Claims. (Cl. 340--328) My invention is a closed-circuit electric alarm system, which has the following novel objects:

To eliminate the moving parts and contact arrangement of the relay which is a necessary part in present forms of closed-circuit electric alarm systems. This is accomplished by use of the vibrating source of audible sound, commonly used in alarm systems. This source, in my system, is a vibrating bell or buzzer, of which many suitable types are commonly available at electrical supply houses. A simple form of fixed electromagnet is installed on this bell or buzzer; and with this done, the use of a relay with its unreliable contacts and moving mechanical parts is avoided. Thus, a closed-circuit electric alarm system is achieved, whose principal parts are a vibrating bell or buzzer, equipped with an additional electromagnet; a normally-closed circuit containing the desired form of condition-responsive elements; and a suitable power supply and necessary wiring.

Another novel object of my invention is to provide a simple form of closed-circuit electric alarm sysem which will function properly, without adjustment of any kind, within a very Wide range of resistance in the conditionresponsive circuit. In my normally-closed-circuit electric alarm system, the condition-responsive circuit may offer a resistance of 200 ohms or more, without impairing the performance of the system; and the system may operate from low voltage furnished from door bell transformers.

This high permissible resistance value is novel, in that no adjusting devices are required to compensate in one way or another for differences in the resistance of the condition-responsive circuit between an alarm system containing a high resistance, condition-responsive circuit, and an alarm system containing a condition-responsive circuit with a low resistance.

This high permissible resistance value is obtained by the use of extremely low holding current in the holding magnet circuit, accomplished by novel use of the bell or buzzer ringing voltage to produce a transient impulse which moves a holding armature into the zone of minimum air gap of a holding magnet, whose chief function is to hold said holding armature through the very small intervening air gap, thus producing a force which prevents said hell or buzzer from vibrating.

Furthermore, a novel feature of this high permissible resistance value is that it permits the utilization of my invention as a fire alarm system under the severe condition of installation in a finished home, where it is desired to install al wiring exposed on baseboards or trim; and where such wiring must be neat and inconspicuous through the necessary use of very small diameter wire, like #25 guage copper wire. In such an installation, a large footage of wire is required in wiring the conditionresponsive circuit; and the resistance, using small diameter copper wire, is correspondingly high. My invention may be readily used in installations of this type, since its approximate installation limits, for an inexpensive type of my invention, are 6,000 feet of #25 guage copper wire, or 30,000 feet of #18 guage copper wire.

These objects are achieved by mean of the structure and relative arrangement of parts which are fully shown in the following specifications, drawings, and claims. While my invention permits of various arrangements of the holding electromagnet, and choice of either direct current or alternating current holding electromagnets, to operate in connection with vibrating sources of sound energized from any convenient type of voltage, I am limiting my description to the two most easily assembled forms of my invention, from which other forms will become obvious.

Figure l of the accompanying drawing shows one form of my invention, in which the electromagnet causing audible vibration, hereafter designated as the vibrator electromagnet, assists the holding electromagnet by decreasing the air gap between the holding electromagnet and the armature of the holding electromagnet; but the vibrator electromagnet does not assist the holding electromagnet in its function of providing a force greater than that of the spring which is associated with the armature of the vibrator electromagnet, except during the transient impulse, already noted.

Figure 2 of the accompanying drawing shows another form of my invention, in which the vibrator electromagnet assists the holding electromagnet by decreasing the air gap between the holding electromagnet and the armature of the holding electromagnet; and in addition, the vibrator electromagnet assists the holding electromagnet in its function of providing a force greater than that of the spring which is associated with the armature of the vibrator electromagnet, as fully described under Figure 2 explanations.

Referring to Figure 1, a source of sound of the vibrating electric bell type is shown connected in a close-circuit electric alarm system. An insulated base 1, has mounted on it windings 5, cores 35, and a spring-restrained armature 6; with windings 5 and cores 35 comprising the vibrator electromagnet. Spring-restrained armature 6 makes contact with contact 8 when the vibrator electromagnet is not energized. An additional, direct current, holding electromagnet is mounted under the gong 2, and comprises winding 4, cores 3 and 36, and armature '7. Armature 7 is mounted at a convenient location on springrestrained armature 6, or on its extension which transmits vibrations to the gong 2 when the vibrator electromagnet is energized. Contact 8 is connected to terminal 9 by wire 13. The finish wire from one winding 5 is connected to spring-restrained armature 6 by wire 16. The start wires from both windings 5 are connected by wire 15. The finish wire from the remaining winding 5 is connected to terminal 10 by wire 14. The start wire of Winding 4 is connected to terminal 12 by wire 17. The finished wire of winding 4 is connected to terminal 11 by wire 18. Four, half-Wave rectifiers 20 form a full-wave rectifier circuit, connected to receive alternating current voltage from the secondary 23 of the transformer having primary 24. Terminal 9 is connected to transformer secondary 23 by wire 25. Terminal 12 is connected to two rectifiers 20 by wire 27. Terminal 11 is connected by wire 28 to a normally-closed test push button 21 for testing the alarm circuit. This push button 21 is connected by wire 34 to normally-closed, condition-responsive elements 22, one of which is shown. Conditionresponsive element 22 is connected by wire 29 to two rectifiers 20. Transformer primary 24 is supplied with an appropriate voltage. rectifiers 20, and terminal 10. p

The system described in Figure 1 operates as follows: With proper voltage applied to transformer primary 24,

and the contacts of condition-responsive elements in' Wire 26 connects transformer 23, 5

their normally-closed position, indicating normal conditions and restraint of an alarm, the following holding circuit is energized: The holding circuit supplies energy to the holding electromagnet, and. starts with trans,- former secondary 23, which supplies alternating-current voltage to rectifiers 2t). Rectifiers 2Q supplya directcurrent voltage to wires 27 and 29. This direct-current voltage is applied to winding 4 through a circuit starting with wire 27; and including terminal 12, Wire 117,. Wind.- ing 4, Wire 18, terminal 11, Wire 23, the normallyclosed' circuit test push button 21, wire 34, the closed contact of condition-responsive element 22, wire 29,, and back to rectifiers 20. having negative polarity of directcurrent voltage. The winding 4' is. excited, and armature 7 is subjected to the attractive magnetic force from the holding electromagnet, largely concentrated at pole 36. This leaves the other circuit, used forvibrating the bell. This energized circuit starts with an. alternatingcurrent voltage, secured from transformer secondary 2 3,

and applied to wire 25, terminal 9, wire 13, contact 8, spring-restrained armature 6, wire 16', winding 5, wire 15', the other Winding 5, wire 14, terminal 10, wire 26, and back to transformer secondary 23. The vibrator electromagnet attracts its spring-restrained armature 6,

which also opens the circuit at contact 8, thus depriving the vibrator electromagnet of exciting voltage. The movement of spring-restrained armature 6 also carries armature 7 into the region of intense flux density produced by magnet pole 36; and armature 7 is then sealed against magnet pole 36, thus preventing armature 6' from reclosing the circuit at contact 8. The vibrating type of hell is now restrained from vibrating; but said restraint is removed when any of the following conditions are altered: A change of condition occurs, which is of the type supervised by the condition-responsive elements 22; or when an accidental opening occurs in the holding electromagnet circuit; or when the spring-restrained, circuit test push button 21 is pressed; or when the directcurrent voltage is interrupted. When said restraint isv removed, the vibrating type of bell will vibrate until all conditions noted for the restraint of bell vibration have been satisfied. Obviously, for the vibrating source of sound described in Figure 1, the holding electromag net may equally well be of the alternating-current voltage type, energized from an appropriate alternating-current voltage source, with the vibrator magnet energized as desired from any convenient type of 'voltage.

Figure 2 shows the same type ofvibrating bell described in Figure l, but it is now arranged'for one source of alternating-current voltage to cause vibration of the source of voltage, has secondary 23, which supplies.

alternating-current voltage to wire 30, then to, terminal 9, wire 13, contact 8, spring-restrained armature 6, wire 16, and to the finish of winding 5. The start wires from both windings are connected by wire The. finish wire from the remaining winding 5 is connected to terminal 10- by wire 14. Terminal 1G is connected to transformer secondary 23 by wire 31'. The start wire from winding 39- is connected to the spring-restrained armature 6 by wire 19. The finish wire from winding 39 is connected to terminal 11 by wire. 18. Wire 32' is 7 connected to terminal 11 and to: the normally-closed push. button 21. The conditionrresponsivef elements 2 one of which is shown, is connected to testpush button;

21 by wire 33, and to transformer secondary 23 by wire 30.

The system described in Figure 2 operates as follows, with the holding circuit being described first: With a suitable voltage applied to transformer primary 24, transformer secondary 23 supplies alternating-current voltage to a circuit starting at transformer secondary 23, and then through wire 30, condition-responsive element 22, wire 33;, test push button 21-, wire 32, terminal 11, wire 18, the finish wire of winding 39, winding 39, the start wire of winding 39, wire 19; spring-restrained armature 6, wire 16, the finish; wire of one, winding- 5, the

.start wire of this winding 5 to the start wire of the other winding 5, through connecting. wire- 15; the finish wire of the other winding 5 to wire 14, then to terminal 10, and to transformer secondary 23 by wire 31. The circuit described applies alternating-current voltage to the holding elect-romagnet. and to. the vibrator electromagnet, which are connectedin, series. Armatures 6 and 7 are subjected to attractive. forces. from their respective poles 35 and 3.3.-

At the same time, for the system described in Figure 2, the. other circuit is energized. This circuit supplies the vibrator electromagnet with voltage. and starts with an alternating-current voltage obtained. from transformer secondary 23', which voltage is applied to wire 30, terminal 9, wire 13,, contact 8,, spring-restrained armature 6,, wire t6, the two windings 5 through wire 15, wire 14, terminal" 10,, and back to transformer secondary 23 through wire 31. As a result of this applied voltage, the vibrator electromagnet. is energized, and springrestrained armature 6' is attracted by poles 35, thus opening contact 8, and also, reducing the air gap between armature 7' and pole 38 to such a small value that the tractive effort of pole 38 on armature 7 is now greater than the spring restraint provided by armature 6. The vibrating type of hell is. now restrained from vibrating; but said restraint is, removed when any of the. following conditions occur: When a change of condition occurs, which is of the type supervised. by the conditionresponsive elements 22'; or when an accidental opening occurs in the holding electromagnet circuit; or when the spring-restrained. test push. button is. pressed. When said restraint. is removed, the vibrating type of bell will vibrate until all conditions noted for the restraint of hell vibration have been satisfied.

The alarm system described, in, Figure 2' permits the use of the vibrator electromagnet and, the holding electromagnet inrestraining armature 6. from vibrating; the net; result permits the use, of a smaller holding electro' magnet than is possible if. the, vibrator electromagnet is not so utilized. Obviously, forthe vibrating source of sound described in Figure 2, the holding electromagnet may equally well be of. the direct-current type, energized from. a suitable direct-current voltage source, with the vibrator magnet energized as desired from any convenient type of voltage.

Having thus, described my invention, what I claim as new, and desire. to secure by Letters Patent of the United States is:

1'. In aclosed circuitelectric alarm device comprising a resiliently-mounted member, resilient means urging the resiliently-mounted member toward a retracted position, a source of alternating current, a vibrator electromagnet of predetermined. wattage, avibrator armature positioned on theJresiliently-mounted member and attracted toward the; vibrator-eleetromagnet during the energization thereof, said vibrator armature being resiliently urged away from: the vibrator'electrornagnet by said resilient means, a vibrator electrical circuit comprisingthe vibrator electromagnet and the source of alternating current, electrical'. contacts opening during the attraction of the vibrator.- armature toward; the vibratonel ectromagnet and closing during the opposite movement of the vibrator armature, electricalt contacts thus opening and closing the vibrator electrical circuit, said electrical contacts being actuated by the vibrations of the resiliently-mounted member, a sound producing device actuated by the vibrations of the resiliently-mounted member, a normally-closed alarm circuit, and normally-closed, condition-responsive elements capable of opening the normallyclosed alarm circuit, the improvement which comprises: a holding armature mounted on the resiliently-mounted member longitudinally spaced from the vibrator armature; a holding electromagnet of a wattage only a small fraction of the Wattage of the vibrator electromagnet and positioned to attract the holding armature from he alarmsounding position toward the holding position during an initial half-cycle, low-momentum movement of the resiliently-mounted member, the wattage of the holding electromagnet being i'nsufiicient to attract the armature from the resiliently-urged retracted position through the alarmsounding position to the holding position, and being insutiicient to attract the armature during the momentuminfluenced vibration of the resiliently-mounted member, the holding electromagnet being positioned outside the significant flux of the vibrator electromagnet, thus preventing current fluctuations in the vibrator electromagnet from inducing significant voltages in the holding electromagnet circuit, whereby the resiliently-mounted member may readily be moved from the retracted position to the holding position by the combination of the prolonged current in the small wattage holding electromagnet and the momentary current in the large wattage vibrator electromagnet, and held as thus set until an opening of the normallyclosed alarm circuit permits the resiliently-mounted member to vibrate and actuate the sound producing device.

2. The alarm device of claim 1 in which a source of direct current of from about 2 to about 20 volts energizes the normally-closed alarm circuit, whereby the low Wattage holding electromagnet holds the resiliently mounted member in the holding position with substantial immunity from the effect of the electrical resistance of that portion of the alarm circuit comprising the normallyclosed, condition-responsive elements.

3. The device of claim 1 in which the holding electromagnet of the alarm circuit and the vibrator electromagnet are series connected when the resiliently-mounted member is in the retracted position, in which the holding electromagnet maintains the resiliently-mounted member in the holding position, and in which alternating current energizes each electromagnet.

4. In a closed circuit electric alarm device comprising a resiliently-mounted member, resilient means urging the resiliently-mounted member toward a retracted position, a source of alternating current, a vibrator electromagnet of predetermined wattage, a vibrator armature associated 6 with the vibrator electromagnet and resiliently-mounted member to vibrate the resiliently-mounted member during the energization of the vibrator electromagnet, said vibrator armature being resiliently urged away from the vibrator electromagnet by said resilient means, a vibrator electrical circuit comprising the vibrator electromagnet and the source of alternating current, electrical contacts opening during the attraction of the vibrator armature toward the vibrator electromagnet and closing during the opposite movement of the vibrator armature, said electrical contacts thus opening and closing the vibrator electrical circuit, said electrical contacts being actuated by the vibration of the resiliently-mounted member, a sound producing device actuated by the vibration of the resiliently-mounted member, a normally-closed alarm circuit,

and normally-closed, condition-responsive elements capable of opening the normally-closed alarm circuit, the improvement which comprises: a holding electromagnet of a wattage only a small fraction of the Wattage of the vibrator electromagnet, said holding electromagnet being positioned outside the significant flux of the vibrator electromagnet, thus preventing current fluctuations in the vibrator electromagnet from inducing significant voltages in the holding electromagnet circuit; a holding armature actuated by said holding electromagnet and operatively associated to maintain open the electrical contacts of the vibrator electrical circuit during the energization of the holding electromagnet, the wattage of theholding electromagnet being insufiicient to move the resilientlymounted member from its resiliently-urged retracted position to the holding position, and being insufiicient to move the resiliently-mounted member to the holding position during the momentum-influenced vibration of the resiliently-mounted member, whereby the resilientlymounted member may readily be restrained from vibrating by the combination of the prolonged current in the small wattage holding electromagnet and the momentary current in the large wattage vibrator electromagnet, and held as thus set until an opening of the normally-closed alarm circuit permits the resiliently-mounted member to vibrate and actuate the sound-producing device.

References Cited in the file of this patent UNITED STATES PATENTS 989,107 Barrett Apr. 11, 1911 1,976,660 Edwards Oct. 9, 1934 2,507,398 Castro May 9, 1950 FOREIGN PATENTS 235,187 Great Britain June 3, 1926 22,199 Great Britain of 1914

Images