US2165174A

US2165174A - Fire alarm system

Info

Publication number: US2165174A
Application number: US88801A
Authority: US
Inventors: Frank R Bridges; Foster E Weld
Original assignee: Gamewell Corp
Current assignee: Gamewell Corp
Priority date: 1936-07-03
Filing date: 1936-07-03
Publication date: 1939-07-04
Anticipated expiration: 1956-07-04

Description

July 4, 1939. F. R. BRIDGES :1- AL FIRE ALARM SYSTEM Filed July 3, 1936 2 Sheets-Sheet 1 27 Eric I I, if?

TO'I'LIRE Jul} 4, 1939.

F; R. BRIDGES El AL 2,165,174

FIRE ALARM SYSTEM Filed July 3. 193's 2 Sheets-Sheet 2 F-L; $15 B '14 A a I 13 h 4 i-LINE W $43 1 flf J Patented July 4, 1939 PATENT OFFICE FIRE ALARM SYSTEM Frank R, Bridges, Needham, and Foster E. Weld,

Newton, Mass., assignors to The Gamewcll Company, Newton Upper Falls, Masa. a corporation of Massachusetts Application July a, rose, serial No. aa,ao1

6 Claims.

The present invention relates to die alarm systems.

Our copending application filed of even date herewith describes a fire alarm system which is particularly adapted for small town use, principally because of the provision for substantially complete automatic supervision. The central oilice equipment is arranged to be completely housed in a small cabinet which is not necessarily kept under constant personal attention.

The present invention contemplates, as an addition to the system, the provision of built-=in testing equipment whereby the conditions existing in the line and central oflice circuits may be readily determined. In the preferred form of the invention, all of the test operations are effected by a single manual switch by which an ammeter and a voltmeter may be variously connected into the circuits for indicating such factors as line current and voltage, charging current and voltage, and the condition of the line with respect to ground. An important feature is that no setting of the test equipment can in. any way affect or interfere with a signal in process of transmission or one which may be subsequently transmitted.

In the accompanying drawings illustrating what is now considered the preferred form of the invention, Fig. 1 is a diagram of so much of the system as is necessary for an understanding of the invention, the switch groups being shown in norm'al position; Fig. 2 is a view of the switch and meter panel; and Fig. 3 is a view of a portion of the system showing certain of the switch groups in a different position from Fig. 1.

The illustrated embodiment of the invention comprises a single circuit system which is fully described in detail in our copending application above referred to. The system includes a battery ill, the positive terminal of which is connected by a wire II with. the positive side of the line. The negative side of the battery is connected to the negative side of the line through connections to be hereinafter described. The line connections include suitable operating .and signaling equipment illustrated as a main relay M, a gong and a supervisory relays, the operation of which is described in the copending application.

The cabinet within which the central oiiice equipment is contained has a panel provided -with a milliammeter l2, a voltmeter l3 and a test switch II. The test switch is a seven-position switch having a panel indicating the pos-. sible positions of the manual switch handle. The

switch includes eight contact groups indicated A to H inclusive in Fig. 1, each group having a. set of contacts designated I, 2, 3 etc. The contact designated at i for each group is. a loop member which is acted upon by a cam operated 5 from the switch handle. The cams are illustrated diagrammatically at H in Fig. 1, each disposed adjacent to the corresponding switch group. In a subsequent description the term "ca-mming refers to the action of a high point of a cam on the loop contact of the corresponding switch group; thus in Fig. 1 group A only is ca'mmed and in Fig. 3 none of the groups are cammed.

The connections between the negative side of the battery and the negative side of the line include a wire l5 connected between the battery and contact 3 of group B. A wire i6 connects the contacts 2 of groups A and B. A wire [8 connects contacts I of both groups and the same wire continues to contacts of the grounding or conditioning relay MG, which as described in our copending application is normally inactive, but is arranged to condition the line for ground signaling whenever the line is accidentally broken. So far as the present invention is concerned, only the contacts designated 28 to 24 inclusive are important. The wire l8 connects with contacts 2| and 22, the contact 2| being normally closed on 20 which is connected with the nega- 30 tive side of the line. The contact 22 is associated with a contact 23 which is connected to ground. The operation of the relay is fully disclosed in our copending application, and it will sumce to note here that upon its energization, the negative side of the line is disconnected from the battery and is connected with the positive side of the line, while the negative side of the battery is grounded by the closure of contacts 22, 23. The contact 24 is normally closed on 40 the grounded contact 23 and enters into a test circuit to .be hereinafter described in detail.

The battery i0 is maintained under continuous charge by a rectifier 25 having its positive terminal connected to the positive terminal of the battery and its negative terminal normally connected for a low-rate or trickle charge, but adapted under some circumstances to be connected for a high-rate charge. The charging connections are under the control of a charge control relay CC, the operation of which is disclosed in the copending application. The relay CC has the

contacts

26, 21, 28 and 29. The trickle charge is applied to the battery under normal conditions through a resistance 30 con- V nected to the negative terminal or the rectifier, a wire 32,

contacts

28 and 29 of the relay CC, and a wire 34 which leads to contact 2 of the test switch group B, and thence to the negative battery terminal through the normally closed contacts 2, 3 of group B and the wire I5. The

negative terminal of the rectifier is connected by g a lead 36 with the contact 26, and the contact 21 is connected directly with terminal by a lead 38. Upon energization of the charge control relay, the trickle charge circuit is opened and the high-rate charge is applied.

The milliammeter I2 is connected between contacts I and 2 of group A, and is normally shunted when the group A is cammed as shown in Fig. 1.

The negative side 01' the line is connected to contact 2 01 group D and to contact 2 of group H by wires 46 and 48, respectively. The positive side of the line is connected to contact 4 of group A, contact 2 of group F, and contact 2 of group G by

wires

50, 52 and 54, respectively.

The negative side of the battery is connected to contact 3 of group D and the positive side of the battery is connected to contact 3 of group C. To avoid confusion, the actual connections are not shown. but are merely indicated by appropriate plus and minus signs.

Contact I 01 group C is connected to contact 2 of group E by a wire 56. Contact I of group D is connected to contact 3 of group F by a wire 58. Contact 3 of group A is connected to contact 2 01' group C by a wire 60. The voltmeter I3 is connected between contact I of group E and contact 4 of group F. Contact I of group E is connected to contact I of group F by a wire 64. Contact 3 of group E, contact 5 of group F, contact I of group G and contact I of group H are all connected to ground, but indirectly through a wire 66 leading to the contact 24 which is normally closed on contact 23 of the grounding relay MG, for purposes to be later explained. Contacts 3, 4 of both groups G and H are included in an alternating current lamp circuit 68 shown in dash lines.

The seven follows:

I. Center positionnormal.

positions 01' the switch are as II. Line" positionto indicate line current andvoltage.

111. Bat.".'positionto indicate battery charging current and voltage. IV and V. VGR" and "+VG to indicate voltage of either side 01' the line with respect to ground.

VI and VII. "GR and +GR-to ground the positive or negative side of the line as a reference ground.

The connections for the several positions are described as follows:

I. Center or normal D s t -The switch groups are as shown in Fig. 1, group A only being cammed. The milliammeter contacts I, 2 of group A. All possible connections to the voltmeter are open. Accordingly no indication is given on either of the meters. This is the normal condition.

11. "Line pOsitiOn.-In this position of the switch none of the groups are cammed, switch groups A-and B being then as shown in Fig. 3.

Under these conditions the line current and the voltage across the line are indicated on the meters.

15 The milliammeter shunt is broken at contacts 2 and the negative battery 1 3 of group A. The line current, however, passes through the milliammeter by a circuit traced from the negative battery terminal through wire I5, contacts 3, 2 or B, wire I6, the milliammeter I2 and wire I6. The voltmeter circuit is traced as 5 follows: From the positive line through wire 50, contacts 4, 3 of group A, wire 60, contacts 2, I of group C, wire 56, contacts 2, I of group E, the voltmeter I3, contacts 4, 3 of group F, wire 58, contacts I, 2 of group D, and the lead 46 to the 10 negative side of the line.

III- "Bat? l osition.In this position of the switch groups B, C and D only are cammed. Group A is not cammed and is, therefore, as shown in Fig. 3, the milliammeter shunt being 15 open. Since group B is cammed, contact I is closed on 3 and the latteris moved away from 2. The trickle cnarge current is passed through the milliammeter by the following circuit: From the negative terminal of the rectifier through the go resistance 36, wire 32, contacts 23 and 29 of the charge control relay CC, wire 34, wire I6, the milliammeter I2 and wire I8 to contact I of group B, where the current divides, one portion .going out on the line and the other passing 25 through the now closed contacts I, 3 of group B and the wire I5 to the negative battery terminal. The trickle charge current thus measured is the current supplied by the rectifier, which is the sum of the line current and the battery current. It 30 is to be noted that if the charge control relay is .set for the high-rate charge, the charging current is not permitted to pass through the milliammeter, the wire 33 from the contact 21 leading direct to the negative battery terminal. The 35 high-rate charge would exceed the range of the milliammeter.

The battery voltage is indicated on the voltmeter regardless of the charging connections through the following circuit: From the positive 40 terminal of the battery as indicated by the plus. sign under contact 3 of group C, thence through contacts 3, I of the cammed group C, wire 56, contacts 2, I of group E, the voltmeter I3, contacts 4, 3 01' group F, wire 58, and contacts I, 3 45 of the cammed group D to the negative terminal of the battery. P

IV. Voltage of negative side of line ab ve groumZ "VGR.In this position of the switch contact groups A and E are cammed. The volt- 5 meter isconnected between the negative side of the line and ground through the following circuit: From the negative side of the line through wire 46, contacts 2, I of group D, wire 58, contacts 3, 4 of group F, the voltmeter I3, contacts 55 I, 3 of the cammed group E, wire 66, and contacts 24, 23 of the relay MG to ground. Since group A is cammed the milliammeter is shunted.

. The purpose of this connection is to indicate whether or not a ground fault exists on the line. 50 If the line is in proper condition the voltmeter should read zero. g

It will be notedthat if the grounding relay MG happens to be energized when the switch is set on this position, the voltmeter circuit is 5 broken at the open contacts 24, 23 of the relay MG. Since the negative side of the battery is then grounded a reading of voltage above ground would be meaningless. It is for this reason that contact 3 of group E is connected indirectly to 70 ground through the wire 66.

V. Voltage 0 positive side of line above gr0und-+VGR. This position of the switch is similar to that previously described except that the voltmeter is connected between the positive side of the line and ground. Groups A and F only are cammed. As for the other connection the voltmeter should read zero if the line is in normal condition. The voltmeter circuit is traced from .the positive side of the line through wire 52, contacts 2, l of the cammed group F, wire 64,

the voltmeter i3, contacts 4, of group F, wire 66, and contacts 24, 23 of relay MG to ground.

If the relay MG is energized, this connection is ineffective.

VI and VII. Grounding of one side of the line.--To establish a reference ground as a preliminary for certain usual testing operations, either the positive or negative side of the line may be grounded by moving the switch to the points indicated +GR or -GR. To ground the positive side of the line the switch groups A and G only are cammed and a circuit is traced from the positive side of the line through a. wire 54, contacts 2, l of the cammed group G, wire 66 and contacts 24, 23 of the grounding relay MG. For grounding the negative side of the line groups A and H only are cammed so that the circuit is traced from the negative side of the line through wire 48, contacts 2, l of the cammed group H to the wire 68 from which the circuit continues to ground through the grounding relay contacts. The fact that the circuit is completed through the grounding relay permits establishment of the reference ground only when the line is in its normal closed loop condition. If the grounding relay has been energized following a break in the line the negative side of the battery is grounded, and if a reference ground were then .established the battery and central ofilce equipment would be short-circuited. The circuit through the grounding relay contacts provided by the wire 66 prevents the short circuit in the event the grounding relay is energized. The lamp circuit 68 is broken at contacts 3, 4-of group G or contacts 3, l of group H whenever one side of the line is grounded.

The following general observation may be made concerning the functions of the several switch groups: Group A is primarily a milliammeter shunt, although it also includes the contacts 3, 4 whereby the connection of the positive line to the voltmeter is controlled. Group'B is a selector to cut the milliammeter circuit into either the negative line or the trickle charge lead. Group C, D, E and F are voltmeter circuit controls whereby a variety of connections to the voltmeter may be established, some complication of circuits arising from the necessity of isolating both sides of the meter from all points except those between which the voltage is to be measured. Groups G and H are simply means for connecting one side of the line to ground. I

The various switch connections above described provide for most of the necessary testing operations on the line and in no way affect any normal code signaling operation which may'occur while the switch is set in any of its several positions. For example, although the normal position of the switch is in the center, the throwing of the'switch to either the line or bat." position merely throws the meters into circuit without opening the line. In the line position of the switch the milliammeter should read the normal line current and any deviation therefrom is indicative of some abnormal condition. The bat. position indicates the normal trickle charge current unless the rectifier or its connections are 75 faulty or unless the charge control relay has for grounding one side been set for the high-rate charge. The other four positions of the switch do not involve any breaking into the line, but merely establish certain connections with respect to ground. In

' any event, whether the line is normal or conditioned by the grounding relay, no setting of the switch can interfere with a subsequent signaling operation. This feature is important since in a system of this type adapted for small town use and not under close personal supervision, it may happen that the switch may be tampered with by unauthorized persons or may be inadvertently left in one of its test positions after a test reading.

The invention having what is claimed is:

1. In a fire alarm system having a battery and a line, an ammeter, charging means for the battery, a trickle charge circuit and a high-rate charge circuit, an ammeter switch for selectively cutting the ammeter into the trickle charge circuit or the line, and. charge control means for connecting the battery with either charge circuit and having provision, for preventing connection of the ammeter into the high-rate charge circuit.

2. In a fire alarm system having a battery and a line, an ammeter, charging means for the battery, a trickle charge circuit and a high-rate charge circuit, and an ammeter switch for selectively cutting the ammeter into the trickle charge circuit or the line, charge control means for connecting the battery with either charge circuit and having provision for preventing connection of the ammeter into the high-rate charge circuit, a voltmeter, and voltmeter switching means operable with the ammeter switch for se-. lectively connecting the voltmeter to read the battery voltage or the line voltage.

3. In a. fire alarm system having a line and a battery connected thereto, a conditioning relay of the battery under abnormal conditions, and test switching means for establishing a circuit between one side of the line and ground, sad circuit including means controlled by the conditioning relay to prevent grounding of the line by said switching means when the battery is grounded by said conditioning relay.

4. In aflre alarm system having a line and a battery connected thereto, a normally inactive conditioning relay having contacts to connect one side of the battery to ground, a test switch to establish a circuit between one side of the line and ground, said circuit including contacts of the conditioning relay to prevent the ground connection when the relay is operative. y

5. In a fire alarm system having a line and a battery connected thereto, a test switch to ground one side of the line, a conditioning relay adapted under abnormal conditions to ground the battery, and means controlled by the conditioning relay to prevent grounding of the line by the test switch.

6. In a fire alarm system having a line and a battery connected thereto, test switching means for selectively grounding either side of the line, a conditioning relay operative under abnormal conditions to ground one side of the battery and to connect both sides of the line together, and means controlled by the conditioning relay to render the test switching means ineifective to ground the line.

been thus described,

FRANK R. BRIDGES. FOSTER E. WELD.