US2565323A - Annunciator alarm system - Google Patents

Description

Aug. 21, 1951 F. R. QUINN ANNUNCIATOR ALARM SYSTEM Filed June 24, 1950 05 J K m m,@ m n 7/ m 9 W a}. 2 h E k w 4 m e flu M E .m m wQmw bRf n m mywww d m PW TEHPERAT'IBE Patented Aug. 21, 1951 ANNUNCIATOR ALARM SYSTEM Frederic R. Quinn, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application June 24, 1950, Serial No. 170,098

6 Claims. 1

My invention relates to electric annunciator alarm systems and the like, and is particularly applicable to apparatus for remotely indicating the existence ofan undesired condition at any one of a plurality of spaced-apart stations. For example, my invention is especially suitable to apparatus for remotely indicating excessive temperature of railroad car journal bearings and the like, and simultaneously identifying the bearing at which the indicated over-temperature exists.

Accordingly, it is a general object of my invention to provide a new and improved electric annunciator alarm system which is at once simple, inexpensive and dependable in operation.

It is another object of my invention to provide a new and improved annunciator alarm system in which a common control means is simultaneously operable in conjunction with operation of any one of the annunciator indicating means.

It is a more particular object of my invention to provide a new and improved electric annunciator alarm system, in which simultaneous operation of a common control means and an afi'ected station indicator is provided without effecting any false operation of any other station indicator.

My invention itself will be more fully understood and its various objects and advantages further appreciated by referring now to the following detailed specification taken in conjunction with the accompanying drawing, in which Fig. 1 is a schematic circuit diagram of an annunciator alarm system embodying my invention, and Fig. 2 is a graphical representation of the preferred resistance-temperature characteristic of the various temperature-sensitive resistance elements, or thermistors, illustrated at Fig. 1.

Referring now to the drawing, and more particularly to Fig. l, I have there illustrated, as a preferred embodiment of my invention, an electric alarm system of the annunciator type particularly adaptable to journal bearing over-temperature indication in railroad cars and the like. I provide a pair of direct current supply conductors I and 2 adapted to be connected respectively to the positive and negative terminals of any suitable source of direct current supply (not shown) by means of a manual control switch 3. A control relay CRI is provided with an actuating winding 4 connected between the supply conductors l and 2 in series circuit relation with a current-limiting resistor I. A second control relay CR2 is provided with an actuating winding 8 connected between the supply conductors I and 2 in series with a current limiting resistor I. The control relays CRI and CR2 are provided with normally open contacts 8 and 9, respectively, and normally closed contacts II and. [2, respectively. A green indicating lamp I0 is connected across the supply conductors I and 2 in series with both normally open relay contacts 8 and 9. The normally closed relay contacts II and I 2 are connected in parallel circuit relation with each other and arranged separately to connect across the supply conductors l and 2 a red indicating lamp l3.

Connected across the supply conductors I and 2 in parallel circuit relation with the control relay energizing circuits are a plurality of indicating or annunciator circuits. Each annunciator circuit includes in series circuit relation a temperature-sensitive resistance element, or thermistor, I4 and a lamp I5 or other electroresponsive station indicating device. Each temperature-sensitive resistor I4 is connected to be shunted by a manual test switch l6.

In order to provide a significant and positive over-temperature indication the negative temperature coeificient resistors I I should be of the type demonstrating a sharp break in electrical resistance at a critical temperature or within a narrow critical range of temperatures. While various negative temperature coe flicient resistors well known to those skilled in the art are usable in conjunction with my invention, I prefer to use for such resistor a pressed or sintered mixture of metal sulfides including at least one sulfide of a metal of group II of the periodic table, such as disclosed and claimed in my copending application Ser. No. 106,293, filed July 22, 1949 and entitled Resistance Materials and Elements. Although a number of the compounds disclosed in my copending application may be used in practicing my subject invention, I find particularly suitable a sintered resistance material containing by weight about 20%-30% calcium sulfide, .03%10% molybdenum sulfide, .03l0% sulfur and the remainder silver sulfide. Such a resistance material demonstrates a relatively sharp break in electrical resistance at about C., and has a resistance-temperature characteristic of the type graphically illustrated at Fig. 2. At Fig. 2 the ordinate of the curve represents electrical resistance in ohms, plotted on a logarithmic scale, and the abscissa represents temperature in degrees centigrade. As illustrated at Fig. 2, such a resistor may have a resistance of 100,000 ohms at 0 C., decreasing abruptly at about 175 C. to about i or 5 ohms. Effectively such a resistance element acts as an insulator at normal temperatures, but offers very little resistance to the flow of current when exposed 'to a temperature of 175 C. The decrease of resistance is so abrupt that the resistor functions effectively as a switch.

In order to provide simultaneous operation of the control relay CRI upon energization of any one of the indicating lamps I5, I provide a plurality of unilateral conducting devices, such as dry plate rectifiers I1, each connected to shunt the actuating winding 4 of the control relay CRI through a separate one of the temperature-sensitive resistors I4. In this connection it will be noted that the common terminals of the rectifiers H are connected to the point between the actuating winding 4 and the current-limiting resistor 5, so that current passing through any reetifier II does not short-circuit the associated indicating lamp I5.

If desired, any suitable control means may be provided in addition to the indicating means described above. As illustrative of such control means, I'have shown connected in parallel circuit relation with the red indicating lamp I3 a timing motor I8 having a normally open contact I9 which is arranged when timed closed to connect in parallel circuit relation also with the red indicating lamp I3 an actuating winding 20 of an air valve control solenoid 2|. The solenoid 2| is connected to control an air valve 22, which may suitably be arranged to bring into operation the vehicle air brake system.

It may now be assumed that in operation each of these negative temperature coeiiicient resistance elements I4 is embedded in a different journal bearing of a railroad car or the like, or is otherwise located for response to the bearing temperature. The indicating lamps III, I3 and I5, as well as the test switches I6, are all located upon a common control panel inside the car and remote from the journal bearings.

In operation, when the manual control switch 3 is closed, unidirectional potential is applied to the supply conductors I and 2. Such application of potential to the supply conductors causes both the control relays CRI and CR2 to pick up. When both these relays are picked up the contacts II and I2 are opened, so that the energizing circuit for the red indicating lamp I3 and the timing motor I8 is interrupted. At the same time the control relay contacts 8 and 9 are closed, so that the energizing circuit for the green indicating lamp III is completed. So long as all the bearing temperatures are normal, the resistance elements I4 have such high resistance that no significant amount of current passes through the indicating lamps I5 or the rectifiers III. The operability of any series indicating circuit through the lamps I5 may be tested by short-' circuiting the associated resistance element I4 through the connected test switch I6. For the purpose of illustration, however, let it be assumed that all the test switches I6 are open. Under this condition the control relay CR2 provides undervoltage protection, in that whenever the supply voltage between the conductors I and 2 falls below a predetermined safe value the relay CR2 drops out, thereby opening its contact 9 and closing its contact I2. When the contact 9 is opened, the green indicating lamp It is deenergized, and when the contact I2 is closed the red indicating lamp I3 and the timing motor It are energized. It now no action is taken by an operator, the timing motor it closes its contact I9 after a delay interval and thereby energizes the solenoid 2| which actuates the air valve 22.

Let itnow be assumed that the supply voltage between the conductors I and 2 remains normal but that one of the journal bearings attains a temperature of the order of 175 CL, so that the associated temperature sensitive resistor I4 abruptly decreases its resistance. Such decrease of resistance of any one of the resistance elements I4 permits a significant current to flow through the series indicating circuit including that resistance element and the connected indicating lamp I5. At the same time the efiected resistance element I4 substantially short-circuits the control relay actuating winding 4 through the associated rectifier I'I. Thus, as soon as any one of the indicating lamps I5 is energized the actuating winding 4 is effectively short-circuited and the control relay CRI drops out. When the control relay CRI drops out it opens its contact 8, thereby to de-energize the green indicating lamp I0, and closes its contact II to energize the red indicating lamp I3 and the timing motor I8. As previously described, energization of the timing motor I8 effects energization of the solenoid 2| after a delay interval, thereby to actuate the air valve 22.

It will now be noted that when any one or the negative temperature coefiicient resistance elements I4 becomes operative to permit energizing current to fiow through the serially connected indicating lamp I5, current is prevented from flowing through any other indicating lamp I5 by reason of the interposition of the rectifiers Il between the parallel-connected series indicating circuits. Specifically, current flowing through any afiected resistance element I4 would have to flow through two of the rectifiers I1 to reach any indicating lamp I5 other than that connected directly in series with the affected resistance element. Such two rectifiers, however, are connected back to back, so that no current can flow in either direction through both in series. By this arrangement false operation of unafiected indicating lamp I5 is prevented while permitting simultaneous operation of any afiected indicating lamp I5 and the control relay CRI.

While I have described only a preferred embodiment of my invention by way of illustration, many modifications will occur to those skilled in the art, and I, therefore, wish to have it understood that Iintend in the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electric annunciator system for connection to a source of direct current supply, a plurality of condition-responsive resistance elements adapted to be located at spaced-apart stations separately subject to variation of said condition, an electro-responsive indicating device connected in series circuit relation with each said resistance element, an electro-responsive control device, and separate unilateral conducting devices connecting said resistance elements separies circuit relation with each of said resistance elements, an electro-responsive control device, and separate unilateral conducting devices similarly disposed and connecting said resistance elements separately to shunt said control device.

3. In an electric annunciator system for connection to a source of direct current supply, a plurality of condition-responsive resistance elements adapted to be positioned at spaced-apart stations separately subject to variation of said condition, an electro-responsive indicating device connected inseries circuit relation with each said resistance element, said resistance elements normally having a resistance sujliciently high to prevent appreciable flow of current through said indicating devices and demonstrating an abrupt decrease of resistance substantially at a predetermined value of said condition, an electro-rcsponsive control device, and separate unilateral conducting devices connecting said resistance elements separately to shunt said control device, said unilateral conducting devices being disposed to permit current traversing any resistance element to afiect only the indicating device serially connected thereto.

4. In an electric annunciator system for conncction to a source of direct current supply, a pair of supply conductors, a plurality of condition-responsive resistance elements adapted to be positioned at spaced-apart stations separately subject to variation of said condition, an electro-responsive indicating device connected in series circuit relation with each of said resistance elements across said supply conductors, said series indicating circuits being disposed in parallel circuit relation with each other, an electroresponsive control device connected across said supply conductors in parallel circuit relation with said series indicatin circuits, and separate unilateral conducting devices connecting said resistance elements separately to shunt said contro device.

5. In an electric annunciator system for connection to a source of direct current supply, a pair of supply conductors, a plurality of condition-responsive resistance elements adapted to be positioned at spaced-apart stations separately subject to variation of said condition, an electro-responsive indicating device connected in series circuit relation with each said resistance element across said supply conductors, said series indicating circuits being disposed in parallel circuit relation with each other, an electro-responsive control device connected across said supply conductors in series circuit relation with a current limiting resistor, and separate unilateral conCucting devices connecting said resistance elements separately to shunt said control device, said unilateral conducting devices connecting each said indicating device in parallel circuit relation with said current limiting resistor and preventing transfer of current between said series indicating circuits.

6. In an electric annunciator alarm system for connection to a source of direct current supply, a pair of supply conductors, a plurality of temperature-sensitive resistance elements adapted to be positioned at spaced-apart stations separately subject to temperature variation, said resistance elements having a negative temperature coeflicient of resistance and demonstrating an abrupt change in resistance within a narrow critical range of temperature, an electro-responsive indicating device connected in series circuit relation with each said resistance element across said supply conductors, an electro-responsive control device connected across said supply conductors in series circuit relation with a currentlimiting resistor, and separate unilateral conducting devices connecting each said resistance element separately to shunt said control device, said unilateral conducting devices connecting each said indicating device in parallel circuit relation with said current-limiting resistor and preventing false operation of unafl'ected indicating devices when any one of said resistance elements is within said critical temperature range.

FREDERIC R. QUINN.

No references cited.

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