US2275949A - Fire detecting system - Google Patents

Description

March 10, 1942. F, C EVANS 2,275,949

FIIRE DETECTING SYSTEM Filed March 4, 1938 2 Sheets-Sheet 1 INVENTOR" F. C. EVANS ATTORNEY 2 Sheets-Sheet 2 Filed March 4, 1958 INVENTOR F. C. EVANS BY ATTORNEY Patented Mar. 10, 1942 'FIRE'DETECTING SYSTEM Francis 0. Evans, Staten Island, N. Y., assignor to AmericanDistrict Telegraph Company, New York, N; Y.', a corporation of New Jersey Application March 4, 1938, Serial-No. 193,878

7 Claims.

This invention. relates toralarm or control systemsfor the supervision or detection of fire conditions in installations where large normal temperature changes are encountered. A sensitive alarm or control system may respond to normal or safechanges in temperature for which analarm is unnecessary and not desired. For example in the protection ofa premises or enclosure which is heated by blower heaters or similar heating means it is found that the rate of rise alarm system will occasionally cause a false alarm-when a heater is turned on.

In prior systems it has been proposed that the system should be rendered inoperative during changes of temperature due to blower heater operation and therefore inoperative to an extent that the system will not supervise a fire condition thereby failing completely in its inended purpose. Correction of this fault has been obtained in prior aero-tube systems by venting the system during normal and safe temperature variations sothat pressure can not be built up or by using an extremely high critical operating temperature for sending an alarm.

It is an object of this invention to provide a supervisory alarmsystem which will not respond to normal changes of temperature but will still be operative to detect a fire condition by providing a device which will change theoperating characteristic of the alarm system.

It is a further object of this invention to provide an aero-tube system, in connection with an alarm system. wherein'the pressure at which an alarm is given can be changed in response to a local heat sourceso that when it creates a rapid change-of temperature an abnormal critical'pressure in the-aero-tube will be necessary before an alarm will be given.

Another object ofthis invention is to provide anaero-tube supervisory system wherein changes in pressurein said aero-tube system due to normal temperature changes will change the characteristics of an electric circuit to thereby inhibit an alarm due tosuch changes but still permitting an alarm to be given in the event of ccurrence of a fire.

Still another object of this invention is to provide a rate of temperature rise supervisorysystem in which one set of contacts-is-provided for. operation. in an alarm circuit at abnormal temperatures while another set of more widely spaced contacts are substituted when a blower heater is started.

A further object of this invention is to provide alarms are prevented by isolating the section. of aero-tube subject to rapid rate of rise in temperature and utiliziing a. differential valve to by.-

' pass pressure pulses resulting from fire condian aermtube supervisory system: whereinfalse tions to thereby cause an alarm.

A. further object of this invention is tov provide a. pressure tube system in connection with an alarm system in which the pressure is allowed to change due to any change of temperature but-wherein false alarmsare prevented.

Further objects and advantages of this invention will appear from the following description of the several preferred embodiments thereof shown in the accompanying drawings, wherein Fig. 1 shows the general arrangement of. this invention in an enclosure;

Fig. 2 shows a detailed arrangement of the preferred embodiment of this invention;

Fig. 3- shows a modification of theinvention disclosed in Fig. 2;

Fig. 4 shows the detail of a diiierent modification of this invention; and

Fig. 5 shows another modification: of this invention.

Fig. 1 of the drawings shows an enclosure wherein an aero tube fire detecting system is arranged to detect a fire condition and is also so arranged that a blower heater may so affect the aero'tube system that a false fire alarmcondition may exist. Aero tube I is shown arranged in the usual manner on the ceilings of two different rooms for fire detection and connected to an alarm or supervisory contact device 4 while the blower heaters 2 and 3 are located in close prox- Fig. 2- of the drawings shows the preferred embodimentof devices 4 and 4' of Fig. l for altering the characteristics-of the supervisory system whereby normal changes in temperature in the enclosiue will change the operating characteristics of the aero tube circuit to prevent false As in Fig. 1, the aero tube 1 serves to alarms. detect a fire conditionand tocreatean alarm through themate of rise inpressure in said tube;

the usual compensating vents 22 being provided to equalize the pressures inside and outside of the tube for gradual temperature changes. The blower 2 is arranged to direct hot air on a control device 4', such as is shown in Fig. 1. This device comprises an outer enclosure in which is located an expansion chamber 5. The expansion chamber 5 is connected to aero tube 8 and branches I and II thereof. These branches are in turn connected to bellows I2 which control a bridge member I5. The bridge member is adapted to support adjustable electrical contacts I8, said contacts being connected to alarm circuit I9 and 20. Contacts I6 are arranged to cooperate with contacts I8. said contacts I6 being con trolled by bellows I4 which are in turn controlled by the aero tube I.

The operation of this system is designed to neutralize the normal and rapid changes in temperatures in an enclosure to prevent a false alarm. In order to accomplish this result the spacing of contacts I6 and I8 is varied in such a manner that during normal or safe changes in temperature a closure of said contacts is prevented. This is accomplished when the control device 4' is actuated by the blower heater to cause expansion of the air and consequently an increase of air pressure to be transmitted through the tubes 3, III and II to bellows I2, which in turn lift the bridge member I 'to increase the separation between contacts I6 and I8. Thus when a fire condition occurs the aero tube I will respond in its usual manner even though the blower 2 has just come on and causes what might normally be an operating increase in temperature. The pressure in the aero tube will increase in response to a fire condition sufficiently to close the contacts I6 and I8, thereby closing the alarm circuit I9 and 20 to operate the bell 23. Of course the situation may arise where another blower heater may also affect the same aero tube system. In this event another control device 6 will be provided and connected to the first control device 5 through the tube 6. Thus in the event that another blower heater 3 is turned on, the aero tube system will be in condition to prevent false alarms and to still respond to the fire condition.

Fig. 3 shows a modification of the control device 5 shown in Fig. 2 wherein a solenoid 30 and its armature 28 are adapted to generat a pressure in tubes 8, I0 and II by compressing a bellows 26. Thus when the blower heater motor is turned on, the circuit to solenoid 30 is completed and it operates in the obvious manner to increase the pressure in tubes 8, ID and II to thereby lift the bridge I5 in the same manner as the device 5. Therefore the false alarm is prevented and the aero tube system is still maintained responsive to a fire condition.

Fig. 4 shows another modifications of this invention wherein closure of the motor circuit again changes the characteristics of the aero tube system to prevent a false alarm. 2'! indicates a relay connected through conductors 35 and 31 to the motor circuit of blower 2 said relay being adapted to control the alarm circuit, including the conductors I9 and 2D and the bell 23. Relay 21 also controls the spacing of contacts which are in turn responsive to the aero tube I. For normal operation of aero tube I, aero-detector unit I4 is controlled by said aero tube. This aero-detector comprises two control chambers 9 and I3 which in turn operat the bellows IT.

The bellows support the contacts I6 which are in turn adapted to cooperate with contacts l8 to control the alarm circuit I9 and 20. One chamber 9 is connected to one end of the aerotube while chamber I3 is connected to the other end of the aero-tube, each chamber having vents 22 which release minor changes in pressure within the aero-tube such as those usually caused by slow changes in temperature where no blower heaters are present. Thus in the absence of the blower heater operation a fire condition will cause expansion of the air in the aero tube to in turn operate the bellows I! and close contacts I6 and I8. Contacts I6 and I8 close a circuit through conductor I9, relay armature 28, bell 23 and battery 24 to give a fire alarm. In th event that the blower motor is turned on by closing switch 32, a new detector unit I4 is thrown into the aero tube circuit by means of relay 2'! which is energized by the motor circuit. The new detector having chambers 9 and I3 is connected through tube 1 to the main aero tube I, this detector unit being similar in construction to unit I4 mentioned heretofore. The only difference in this detector unit is that the spacing between contacts I6 and I8 is much wider than the spacing between contacts I6 and I8, the result of which is that a much higher pressure is required in tube I to close the contacts and thereby 0perate the alarm 23. Thus when a blower heater motor is turned on by switch 32, a potential is impressed on relay 2'! which operates armature 28 against spring 29 to thereby substitute contacts I6 and [8 for I6 and I8 which are normally in the alarm circuit. Now when a fire condition occurs the increased pressure in the aero tube I will operate the more widely spaced contacts I6 and I8 to operate the alarm 23. However, operation of the blower heater will not cause suflicient pressure to develop in the aero tube system to. close the widely spaced contact gap.

Fig. 5 shows a further modification of this invention which embodies a different principle of operation in that the aero tube I is allowed to generate a high pressure due to a fire condition to thereby operate difierential valves 4| which in turn connect the increased pressure to the aero-detector unit I4 and thereby cause operation of the alarm 23. As shown above in Fig. 4 the motor circuit will cause operation of solenoids 30. However, these solenoids are arranged to operate armatures 3| and valves 40 in the aero tube I and thereby isolate the local aero tube section I which is affected by the blower heater 2. Valves 40 may be by-passed by differential mercury valves as shown at 4|. A different type of fire detecting unit is used in connection with the aero tube I. This unit may comprise a bellows 42 and a bimetallic element 43, said bimetallic element being adapted to compress bellows 42 under abnormal heat conditions. In normal operation a fire'condition anywhere in the enclosure protected by aero tube I and I will operate the detector unit I4 to close contacts I6 and I8 and thereby operate the alarm 23. However, when a blower heater switch 32 is closed, the blower heater will start up and the solenoids 30 will operate to close valves 40. As a result aero tube I is left in condition for normal operation whereas the section I is isolated from tube I and will not operate in response to the blower heater 3 and can respond to a fire conditiononly with the aid of the devices 42. These detector units 42 are operated by the bimetallic elements 43 to increase the pressure in theaero tube I to such an extent,

that difierential valves 4! will operate. The bimetallic element is adjusted to operate at a temperature in excess of the maximum temperature of the blower heater so that its operation will not be caused by the blower heater but may be caused by a fire condition superimposed on the blower heater operation. The differential valves 4| are constructed as shown in the drawing and filled with mercury to the levels indicated therein so that abnormal pressure of the aero tube I' will force the mercury from the well 44 over into the tube 45 to thereby allow transfer of.

pressure from tube to tube l, which pressure in turn operates the bellows I! of the detector l4 and thereby closes the circuit |92B to give a fire alarm.

From the above description of the different modifications of this invention it is apparent that false alarms are prevented while maintaining the system operative to respond to fire conditions so that the premises is always protected. Prior art systems are known to prevent false alarms but it is believed that none of them presents the advantages of this system wherein the system is always maintained in operative condition to respond to an actual fire condition.

I claim:

1. In combination, an enclosure, a heating source therein, an aero-tube fire detecting system arranged to operate after a predetermined increase in pressure therein, pressure operated contact means adapted to be operated by said aero-tube system, pressure operated bridge means for spacing said contacts, an acre-tube system connected to control said bridge and a chamber positioned to be affected by said heating source and connectedto said control aero-tubesystein for changing the gas pressure in said control aero-tube system in response to said heating source to thereby change th spacing of said contacts when said source gives ofi heat.

2. In combination, an enclosure, a heating source therein, an aero-tube fire detecting system arranged to operate after a predetermined increase in pressure therein, pressure operated contact means adapted to be operated by said aero-tube system, pressure operated bridge means for spacing said contacts, an aero-tube system connected to control said bridge, a bellows connected to said control aero-tube system and electromagnetic means actuated when said heating source operates for actuating. said bellows, and increasing the pressure in said control aerotube system to operate said bridge and change the spacing of said contacts to delay their closure.

3. In combination, an enclosure, a heating source therein, an aero-tube system arranged to supervise temperature changes in said enclosure and to operate upon a predetermined increase of pressure in said aero-tube, an alarm circuit, contacts therein, means connected to said aero-tube system for closing said contacts, a second set of contacts having greater spacing than said first mentioned contacts, contact closing means connected to said acre-tube system in parallel with said first contact closing means for controlling said second set of contacts upon a rise in temperature due to operation of said heating source and switch means operated when said heat source operates for connecting said second set or" contacts to said alarm circuit and disabling the first set of contacts.

l. In combination, an enclosure, a heating source therein, an aero tube system to supervise temperature changes in said enclosure and to operate on a predetermined rate of rise of tem-v perature, an alarm circuit, contacts therein, pressure controlled means in said system for closing said contacts, a second set of contacts having greater spacing than said first mentioned contacts, pressure controlled means in said system for closing said second contacts and switch means operated when said heat source operates for connecting said second set of contacts to said alarm circuit and for disabling the first contacts.

5. In combination, an enclosure, a heating source therein, an aero-tube system arranged to supervise temperature changes in said enclosure and to operate upon a predetermined rate of rise of temperature, an alarm circuit, means for operating said alarm circuit at a predetermined pressure in said system, means connected to said aero-tube system for controlling said first men-- tioned means, a second means for operating said alarm circuit at a difierent pressure in said system and means in said system for controlling said second means, and switch means operated when said heat source operates for connecting said second operating means to said alarm circuit and for disabling the first means for operating said alarm circuit.

6. In combination, an enclosure, heating means in said enclosure, a fire detecting system comprising an aero-tube circuit and pressure oper-' ated means therein for detecting a predeterminedrate of rise of temperature in the enclosure, an alarm circuit, means including said pressure operated means for initiating operation-of the alarm circuit at two different pressures in said aero-tube circuit, and means operatively associated with the heating means for preventing operation of the alarm circuit at the lower of said two pressures when the heating means is oper-.

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