US 3309685 A
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Description (OCR text may contain errors)
March 1967 D. MANNING 3,39,685
SUPERVISORY CIRCUIT Filed June 16, 1964 INVENTOR DAVID MANNING BY K J +HM ATTO R N EYS United States Parenr Cfifice Patented 3 13.1. 1 1', 1967 35539585 SUPERVHSURY CERCUIT David P/Zanning, Springfield, Mesa, assignor to The Standard Electric Time Company, Springfield, hlasa, a corporation of Connecticut Filed .lune 16, 1964, Ser. No. 375,581 2 Claims. (Cl. 349-213) This invention relates generally to electrical supervisory or monitoring circuits and more particularly to circuits for the supervision of direct current operated emergency devices.
Supervision of various electrical circuits is frequently desired and is particularly necessary for alarm circuits, emergency lighting circuits and the like which, though only infrequently used, must respond instantly when needed, for example upon the actuation of a fire alarm or the failure of standard lighting.
According to the techniques heretofore employed, a plurality of fire alarm bells and fire indicating lamps, for example, are connected in series with a source of direct current. The series connection, normally a loop about the premises to be protected, includes a relay which, when actuated, operates an alarm indicating that the electrical continuity of the emergency circuit has been interrupted and that the several emergency alarm devices are inoperative. The relay is normally maintained in energized condition by a small continuous electrical current having suflicient value to energize the relay without energizing the alarm devices.
Various serious drawbacks are inherent in this type of supervisory circuit. Since the emergency alarm devices are in series connection, addition or removal of one or more devices requires a compensating adjustment elsewhere in the circuit. Yet another disadvantage of such series connections is the disabling of the entire series circuit upon the failure of any one emergency alarm device. For example, an emergency lamp filament may have aged to the point where it will open at the next application of its rated voltage, yet will give no indication of such future failure when the supervisory current is passing through it. Perhaps the most serious disadvantage of a series circuit is its inapplicability to direct current oper ated devices such as bells and buzzers. These devices operate as vibrators on the malte and break principle, and cannot generally be employed in series circuits because of the virtual impossibility of synchronizing the vibrator strokes.
Because of these several serious disadvantages inherent in the use of series circuits for emergency and alarm devices, the employment of parallel circuits would be desirable. Electrical supervision of such parallel circuits has, however, heretofore posed substantial problems since, for example, the continuous current which energizes the fault indicating relay in the series circuit, will follow mul tiple paths in th parallel circuit. Additionally, the use of a series relay in a parallel circuit provides supervision only to the device nearest the current source.
It is, accordingly, the most important object of this invention to supervise the electrical continuity of a circuit which includes a plurality of current consum 1g devices connected in parallel with a source of operating potential, and in which the devices are normally in stand-by, non-operating condition.
It is another object of this invention to supervise the electrical continuity of an emergency alarm circuit including a plurality of direct current operated bells and the like.
In the practice of the invention in a preferred embodiment thereof, a circuit comprising a plurality of emergency devices including direct current operated bells, signal lamps and the like, is established with the emergency devices connected in parallel to a direct current source.
Switch means are employed to shift the effective polarity of the direct current source, and consequently the direction of current flow within the emergency circuit, frorna stand-by condition to an emergency condition. Polarity sensing means, for example, diodes, are interposed between each emergency device and the source of potential to prevent current fiow through the emergency device when the switch means is in stand-by position and to allow current to flow through the emergency device when the effective polarity of the source of potential is reversed by movement of the switch means to the emergency position. Thus, each emergency device is normally isolated from the electric current passing through the circuit when the switch means is in stand by position. A relay is, however, operatively connected in the parallel circuit when the switch means is in stand-by position and is normally energized from the source of potential. Upon a failure of continuity in the Wiring of the circuit during stand-by operation, the relay is deenergized and completes an independent circuit to operate an alarm device indicating a fault in the emergency circuit.
It is a feature of the invention that individual emergency devices may be added to or removed from the emergency circuit without requiring other compensating changes in the circuit.
It is a further feature of the invention that the electrical continuity of the circuit to the point of attachment of each emergency device is supervised and not the continuity to the first device only. I
These and other object and features of the invention will be more readily understood and appreciated from the following detailed description of a preferred and alternative embodiments thereof seiectcd for purposes of illustration and shown in the accompanying drawings, in which:
FIG. 1 is a diagram of an electrical circuit according to a preferred embodiment of the invention;
FIG. 2 is a diagram of an electrical circuit according to an alternative embodiment of the invention; and
FIG. 3 is a diagram of an electrical circuit showing yet another alternative embodiment of the invention.
FIG. 1 shows emergency circuit, for example, a fire alarm circuit indicated generally at 1%). The circuit includes a pair of conductors 12 and 14 between which the emergency devices are connected. The devices may take the form of direct current operated bells l6, lamps it or similar devices.
Switching means indicated generally at 25 are employed to connect the emergency circuit 13 to a source of direct current potential (hereinafter described). The switcl g means Zll may be a manually operated mechanical sw ch, an el ctrically operated relay or other electronic switching means. For the purposes of illustration the switching means it is shown as a mechanical switch and a switch handle 22 is shown for use in shifting the switch contacts. The switch 20 is a double-pole doublethrow switch, one pole thereof being connected to the conductor 12 and the other pole to conductor 14. The switch includes four input contacts C1, C2, C3 and C4.
A source of direct current potential is indicated generally at 24 andhas a determinable polarity indicated by plus and minus signs. The positive pole of the source 2 is connected to contacts C1 and C4 of the switch 20 and the negative pole is connected to contacts C2 and C3. the switch 29 in stand-by position as shown in Y4 it )1 FIG. 1, current is free to flow unidirectionally through the emergency circuit it). The circuit ill includes a circuit fault alarm relay 2-6 connected between the conductors and i4 and hence in series connection with them and with the direct current source 24. The fault alarm relay 3 26 is normally energized from the source 24 to maintain its contacts in open. condition. The contacts of the relay 25 are connected in series with an independent fault alarm power supply 28 and a fault alarm device 32 for example a horn or hell.
It will thus be noted that an electrical circuit is compie ted through the alarm relay 25 which wiil remain open so long as the conductors 12 and 14 are intact, the switch '20 is operative and the direct current source 24 is effective. Upon the failure of any of these, however, the alarm relay 26 will be de-energized causing its contacts to close to complete the circuit between the alarm power supply 28 and the fault alarm 36 to give an immediate in dication of system failure.
In order to prevent continuous operation of the emergency bells 16 and lamps 13 when the supervisory current is impressed on the circuit to energize the fault alarm relay 26, polarity sensitive means, for example a diode 32 is connected between each of the emergency devices and the conductor 14 to prevent current from passing through the associated emergency device when the switch 20 is in stand-by position, as shown. Each emergency device is consequently isolated from the emergency circuit during stand-by operation and is inoperative.
When the appropriate emergency event takes place, the switch means 28 is thrown, reversing the polarity of the direct current flowing through the emergency circuit 19. The diodes 32 associated with the several emergency devices now pass current, and consequently each of the emergency devices is operated. It should, of course, be noted that failure of any one of the emergency devices to operate upon movement of the switch 2% to emergency position will not disable the entire emergency circuit since the several devices are connected in parallel with respect to the direct current source 24.
FIG. 2 shows a modification of the circuit of FIG. 1 wherein the fault alarm relay 26 is iocated at the control center rather than at the remote end of the alarm circuit and is connected in series between contacts C2 and C3 of the switch with the negative side of the direct current source 24 connected to contact C2. Since the conductors 12 and 14 must be joined at the remote end of the alarm circuit during stand-by operation to com- 'plete the supervisory circuit, a resistor 34 connects the conductors 12 and 14 in place of the fault alarm relay 26 of FIG. 1 to prevent a short circuit disabling the bells 16 and lamps 18 when the switch 21 is in emergency position. In the circuit of FIG. 2 the supervisory current in the stand-by position of the switch 25 passes through the fault alarm relay 26, the resistance 3 and the conductors 12 and 14. The fault alarm relay operates as before to indicate a system failure.
When the switch 20 is shifted to emergency position conductors 12 and 14 are again connected respectively to contacts C2 and C4 thus reversing the effective polarity of the direct current supplied to the circuit and actuating the several emergency devices. With the ,circuit of FIG. 2, however, the fault alarm relay 25 is continuously deenergized when the switch 2% is in emergency position and continuously sounds the fault alarm 30. Continuous de-energizing of the fault alarm relay 26 in the circuit -of FIG. 1 during emergency operation may also be accomplished by modifying the circuit of FIG. 1 to include a diode 36 indicated in dotted lines in FIG.1 and reversed with respect to the diodes 32 to permit current to flow through the fault alarm relay 26 only when the circuit is in standby condition. The fault alarm 32% will thus also be actuated whenever the circuit of FIG. 1 is switched to emergency condition. The choice between the circuit of FIG. 1 and the circuit of FIG. 2 will then depend upon the physical position which is desired for the fault alarm 39, whether at a distant point as in FIG. 1 or at the switch as in FIG. 2.
FIG. 3 shows yet another alternative embodiment of the invention which is a modification of the circuit of FIG. 1 and provides an additional safety feature in that the conductors 12 and 14 form a double loop with respect to the direct cu rent source 24 under emergency operating conditions which permits either conductor 12 or 14 to be severed at any one point without thereby influencing the ation of any of the emergency devices.
the switch 26 of PEG. 1 is replaced in the modification of FIG. 3 by a four-pole double-throw switching means icated generally at 33 provided with input contacts C1 through C5 inclusive. The positive side of the direct current source 2 is connected to contacts C1, C4 and C3 of the switch 38. The negative side of the direct current source 24- is connected to contacts C2, C3 and C6. The fault alarm relay 26 is connected between contacts CS and C7. It will be noted that the fault alarm relay 2% assumes the same position with respect to the direct current source 24 as it does in FiG. 1 when the switch 38 is in stand-by position. Under these conditions current flows from the source 24 through contacts C2 and C3 to the conductor 14, thence by way of contact C7 to the fault alarm relay 26 and through contact C5 to the conductor 12 which is connected at contact C1 to the direct current source 24. As before, the fault alarm relay 26 is energized when the switch 38 is in stand-by position as shown. As in FIG. 2, when the switch 38 is thrown to emergency position, the effective polarity of the direct current source 24 is reversed and the fault alarm relay V 26 is tie-energized to actuate the fault alarm 30.
The novel feature of the circuit of FIG. 3 when the switch 3-3 is in emergency position and the effective polarity of the source 24 is reversed is that both ends of the conductor 12 are connected to the negative side of the source and both ends of the conductor 14 are connected to the positive side of the source 24. In this manner it will be seen that either the conductor 12 or the conductor 14 may be severed Without in any way affecting the operation of the emergency circuit. If two breaks occur in either conductor only those emergency devices included between the breaks will be disabled.
It will thus be seen that a novel circuit arrangement is disclosed which makes possible the electrical supervision of the circuit conductors to parallel connected devices such as may be employed in fire alarm signals or emergency lighting circuits. Moreover, according to the invention, emergency devices may be added or removed without requiring compensating adjustments elsewhere in the circuit.
With the circuit disclosed it is possible to supervise successfully a number of direct current devices operating on the vibrator principle such as bells or buzzers.
It will further be observed that in one embodiment of the invention a dual loop circuit of parallel connected devices may be supervised employing the polarity reversal technique.
Many other modifications and uses of the technique disclosed and illustrated will be apparent to those skilled in the art, and it is my intention to claim all changes and modificaitons thereof as fall within the spirit and scope f the appended claims.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. In an alarm system including a plurality of signaling devices, a control circuit including a source of direct current, a pair of conductors connecting said source to said devices in parallel array, switch means, a relay connected in series with said conductors, said switch means and said source, said switch means being interposed between said source and said conductors and operable to reverse the polarity of the connection therebetween and to reverse the fiow of current in said conductors from a first to a second direction, a polarity sensing device interposed in series with each said signaling device to pass current to each said device only when said current flows in said second direction and normally to prevent the tlow of current to each said device when said current flows in 5 said first direction, said relay being energized only when said current flows in said first direction and deenergized when said current flows in said second direction, and means responsive to deenergization of said relay for actuating an alarm.
2. In apparatus as defined in claim 1 the combination in which said switch means includes a plurality of contacts connected to said pair of conductors, operation of said switch rneans to reverse the polarity of the connection therebetween and to reverse the flow of current from a first to a second direction causing both ends of each said conductor of said pair to be connected to the same side of said source.
References Cited by the Examiner UNITED STATES PATENTS Reagan et al.
FOREIGN PATENTS Great Britain.
NEIL C. READ, Primary Examiner.
D. YUSKO, Assistant E.(.li'71illl.