US1702930A - best available cop - Google Patents

Description

Feb. 19, 1929. 1,702,930

| D. CHANDLER SIGNAL DEVICE FOR FIRE SPRINKLER AND OTHER SYSTEMS Filed Aug. 25, 1921 In Vent or.

W new .1 am A ornsv Patented Feb.

UNETE STAT 1,702,939 PATENT orr -cs.

LEONARD D, CHANDLER, OF NORTH ABINGTON, MASSACHUSETTS.

SIGNAL DEVICE FOR FIRE SPRINKLER AND .ommfsksisms;

, Application filed August 25, 192 s i'i ino. 495,396, if

The invention to be hereinafter described relates to signal devices for fire sprinkler and other systems, and is improvement upon the apparatus disclosed in Letters Patout No. 1,215,909, granted to me, February 13,l9.l7.., i i

The usual sprinkler system comprises a main pipe supplying water to branch pipes having automatic sprinkler valves.

pipe at the entrance to thesystem, and resists flow of water ,;througl1 the main pipe" to the branch pipes ,of the sprinkler system," m

The consequence is that there is a tendency 5 to establish a differential water pressure above and beneath the check valve.

It is essential that the signal or alarm shall be given whena sprinkler; valve opens, and only at such time. \Vhen a valveopens, the water tends to flow into the system, and the pressure drops in the system.

. Flow oi: waterinto the system toward the; sprinkler valves and: backoutof thesyste m,

away from said. v alves,"may occur when a valve is not open, and pressure variations may occur when a valve isnot open. The,

following conditions may exist:

Pressure.

system rises from whatever cause, such, for example, as water hammer or filling of stand pipes;

Condition Z).Pressure tends to fall in' the system when the pressure of the supply to the system falls from whatever cause;

Condition c.Pressure tends to fall in the system when the sprinkler valves open or bad leaks occur in the system.

Flow.

' responsive to" the flow of water i'n the s 10 weighted check valve is provided in the main Condition a. Pressure tends to riseiri tlie system when the pressure of the supplyto the condition Q the sprinkler valves open, and

an al'a'rm' desired, ,whereasi, 'QQI Idit OD b. the sprinkler'jvalves' do;no t"ope'n,' and an o eitifqaf Z2 m y b alarm'ji's'mot desire 'ifi? L hlrli, distinguished from condition P a H flowsdownfoutgo'f I, were" o the sy te .la-gqa itioe, wa

conditions; "the flow, of ater isfiinjfthe same direction, butfin condition the' 'sp'rinkler valves open and an alarm,is'des11ed, ,whercmico d i a 'd; "t ,spiind ita ies, d

t: smea s drtronai may be distinguished ,,fro" tron f Joy a de'vice responsive changes in n the sppply pipslwilhdistina gulsh, cond tipn' I trout, condition 0, and it lsfclea'r how a, devicejespon sive chants} of P ssure i iw di ing l ond io diroirigconditionlft responsive ,devipe'; acting independently of each other, ,are ,used. jointly to control the operationofa signal, the latter willbe .given only when conditionsc' and filexist, and at no other times, 1', 1

The aim and purpose of the presentinventlonis to provide a simple, efiicient, reliable device which willgivea signal only when the sprinkler valves opeii orbad leaks occur in-the s ystem.. i

The character ofthe invention will be best understood-by reference to the following description of one good form thereof shown in the accompanying drawing, wherein:

F ig. 1 is a view .,partly in elevation and partly in seetion,;- of 'a sprinkler System equipped with a signal device embodying the 1nvention;- a v Fig; 2 is a diagram'of .a modified .form of the invention; and I Fig. 3 on an. enlargedseale is a sectional detail to be referred to.

Referring to the drawing, I' designates a" main pipe for supplying water tothe branch pipes of the system, asingle branch pipe 3 being shown herein provided with sprinn condition; i.

istii ui s h betweenleonditiqns'ii and f pressures, infthe system Internists :f,; the 5 fisys'te ,iallsfi. ,Thus, it, is:

' If the H responsive device and tendency .to 'fiow,'it is proper 'to'speak of a device operated in response todi'fi'erential pressure in this respect as a' flow respons ve device.

The flow iesponsivedevice, in the present. instance, comprisesa cas ng (F g; 1) hav ing a globular head "I7providedivith a 'win dow 19, LA neck'21. connects thehe'ad with a flange 23 opposed'to a plate 25, said-flange and plate being recessed to provide a cham-', .ber 27. diaphragm 29 of leather or other suitable material, 'is' interposed between the flange 23 and plate said parts being se'-. cured together by vthrough bolts 31.

A contact pin '33 is'connected to the dia- H phragm "and projects through the neck up into the globular head 17 The diaphragm and contact 'pin are urged downward by a" coil spring 35 encircling the pin and confined between the upper side ofthe 'diaphragm and the upper end of the neck.

A contact 37, in the present instance, in the form of a reversely bent strip of resilient metal, is securedto the lower 'end of a 'pin 39 'fitted intoan' insulatiori sleeve 4C1 inf'a. plug 43, said pin'be'in held loosely and positively in a plug '43 by the nuts'45,'and a shoulder on the pin at the bottom. of the sleeve ll. Upon the pin is provided a nut 46 for connecting a'wire to the pin, as will be later described. The plug 43 is thread ed into a gland 47, threaded in turn in a stulling bo -19 formed in a cap 51 thread ed into the -upper end of the globular head. 1 adjustment of the plug 43 threaded in the gland 47. the contact 37 may be raised or lowered to a position in which it has the proper relation to the contact pin 33.

Pressure variations in the main pipe above the check valve may be transmitted to the upper side of the diaphragm through a pipe, 53, and pressure variations in the main pipe beneath the check valve may be transmitted to the under side of the diaphragm through a pipe 55.

The coil spring 35 normally holds the contact pin 33 out of engagement with the contact 37. It the pressure beneath the check valve rises sufiiciently over that above the check valve, the diaphragm will be flexed upward, thereby moving the contact pin 33 into engagement with the contact 37 to close at this point the circuit which will be described. The flow responsive device just described as constructed to belaetuated by the'ditl'erences in pressure at the opposite sides of the check valve 7, consti .tutes a good practical. construction, but it different branch pipes of'the system to in dicate when the sprinkler valves-of a particular branch pipe are opened.

The device responsive-to ressure variations in tl esy'stemabove e check valve- 7, in the presentginstancebf the invention, comprises a hydropneumatic air tight tank 97 and a casing 57 provided with a diaphragm 59, a contact pin 61 and a contact 63 carried by an'adjustable pin 65 provided with nuts 67. Since these parts may be similar to those already described, for the differential pressurefor flow responsive device, it is'unnecessaryto' describe the same in detail.

Pressure variations may be transmitted through a pipe 69 from'themain pipe above the check valve to the upper side of the diaphragm 59, and from theunder side of the diaphragm 59 throughthe pipe 71 to the lower end of the tank 97.

The pipes 72 and 83 connect to pipes 69 and- 71 and by-pass the dia' hragm 59. ljhe pipe 72 is provided with a tting 73 containing a partition 75 having an opening forming a seat for a ball check valve 77 urged toward its seat by a weight 79 in a hood 8].. This valve tends to produce a small differential pressure, and allows fiow in one direction from tank 97 to main pipe 1.

The pipe 83 is provided with a fittin;: 85 having a partition 87 therein having a hole forming a seat for a ball check valve .82), urged towards its seat by a weight 91 In a hood 93. This valve tends to produce a small differential pressure and allows a flow in oppositedirection from ball check valve 77; that is from main pipe 1 to tank 97. A seepage port 95 is provided in the partition 87, for a purpose to be describe-d.

The differential set up by the small weighted ball check valves is sufiicientto cause the diaphragm 59 to operate before water flows through them. "his differential should be less than that due to weightin the main check valve 7. The purpose of the small differential ball check valves 77 and 89 and seepage port 95 are to enable the a r pressure in the tank to equalize with that in the main pipe 1 or system as quickly as possible, so that it may always be ready to respond to any change of pressure in the system. As pressures in the system change, the water tends to flow back or forth between the tank and the. system. The diaphragm 59 responds to this flow.

These differentially weighted opposed check valves by-ps' sing the diaphragm 59, relieve it of excessive pressure differences and thereby prevent damage to it. I

The air-tight tank 97 may be partially filled with water. Suitablemeans may be provided to indicate the level of the water in the tank. In the present instance, this means comprises av series of small tubes 99 entered through holes in the base of the tank. The upper ends of these tubes are open and at different levels in the tank, and their lower ends are provided with cocks 101. Pin holes 103 in these tubes near the bottom, admit water very slowly into the lower ends of the tubes, and furnish a water seal for the cooks to prevent air leaks. \Vhen it is desired to determine the level of water in the tank, these cocks can be opened, and if air blows from the pipes, it will indicate that the water level is beneath the upper ends thereof. If water flows from the pipes, it will indicate that the water level is above the upper ends thereof.

The pipe 71 may be provided-with a valve 105 through which more air may be pumped into the tanl-z it desired. A strainer 107 of usual construction, may be interposed in the pipe 69 adjacent its juncture with the main pipe, to prevent solids from passing through the pipes 69 and 71, and to the devices in communication therewitl The construction is such that when water enters the system, its flow is through the pipe 72, through the seepage port 95 and the fitting 85, andithrough the pipes 83 and 71 to the tank, .and if the pressure is great enough to lift the ball valve 89 from its seat, the flow will be transmitted past said valve to the tank. The pressure in the system is always maintained in the tank. The cushion or air compressed in the tank above the level of the water therein. serves as a source of energy to press the diaphragm 59 upward and urge the. contact pin 61 into engagement with the contact (33 to complete the circuit. at this point. It will be understood that this source of energy does not become active to close the circuit at this point, unless the pressure. in the system falls. ll the. pressu e in the system rises. the pressure will he lransulillcd through the pipe (59 lo the upper side of the diaphragm no, the contact pin will he moved or held down out of engagement with the contact (33, and the air in the tank will be compressed.

When the sprinkler valves open, or serious leakage occurs in the system, the signal should be given. Any suitable form of signal may be employed. and in the present instance, the signal is in the form of an electric bell 109 of usual construction.

A battery 111 or other source of electricity may have one end of a wire 113 connected to a positive pole of'the battery, and its .opposite end connected by the nuts 46 with the contact pin 39. A wire 115 has one end connected .by nuts 67 to the contact pin 65 referred to, andits opposite end connected to an insulatedterminal 117 on ajbase-plate 119. An electro-magnet 121-is mounted on this base plate, and one endof-thelcoil 123 of the magnet is connectodto tl1e:i'nsulated terminal 117, and the opposite end of said coil is connected-t0 an insulated terminal 125 on the base plate. A wire 127-leads from the insulated terminal 125 to branch wire 129 and 131, the former-being-connected to a negative terminal ofthebattery, and the latter being connected to the electric bell. A wire 133 has-one end connected to the electric bell, and its opposite end connected to an insulated terminal 135 on the base plate. T Afwire 137.1125 one end connected to the wire-113 referred to, and its opposite end connected'to aterminal 139 which is grounded on the base plate.

Cooperating with the magnet is an armature 141 fulcrumed 0n a lug 143-on the base plate and serving .as-'a trigger fora knife switch 145 pivoted on .thebase plate-and urged by a coil spring 145 toward'aninsulated contact 147 connected to the terminal 135. This sw'itch may have-a reset handle 149 I I A. 13:: I '1 In operation,when 'th'ezsprinkler valves open, waternflows into the system, and is accompanied by a, drop" in pressure int-he system. The flow into the system is caused by a greater pressurebeneath the check-valve 7 than above it, and this differential pressure is transmitted -by the pipes 53 and .55 to opposite sides of the diaphragm 29. Since the pressure beneath the-diaphragm greater than that above it, the contact pin 33 is moved upward against the resistance of the coil spring 35, and brought into engagement with the yielding contact 37, thereby closing the circuit for the magnet coil at this point.

The drop in pressure enables the energy of the compressed air in the tank 97 to become effective to flex the diaphragm '59 upward, thereby causing the contact pin (31 to move upward against the resistance of its coil spring, and connect with the yielding contact 63, thereby closing the magnet coil circuit at this point.

The current passes from the positive pole of the battery through the wire 113 to the contact pin 39, and thence to the contact pin 33. The current passes on through the pipes 53 and to the main pipe 1, and thence through the pipe leading to the easing 57. The currentpasses through the contact pin 61 and contact pin through the wire 115 to the insulated terminal 117, and thence through the coil 123 of the magnet to the insulated terminal 125. The current passes thence through the wires 127 and 129 to the negative pole of the battery. This completes the circuit to the magnet and energizes the same. As a consequence,-.the armature 141 is drawn toward the magnet and is tripped fromthe knife switch 145, thereby allowing the coil spring 145F130 rock the knife switch into engagement with the contact 147. This short-circuits the current to the magnet, and the current now passes from the positive pole of the battery through the wires 113 and 137 to the: terminal 139 grounded on the plate 119,.thence through the plate'to the contact 147. and-switch 14.5 which is also grounded.- on the plate-119. The current passes thence through; the ter minal 135 and wire 133 to the bell, and back through the wires 131 and 129 to-the negative pole of the battery.

Thus, the circuitlis completed to the bell independently of the first circuit including the contacts 37 and 63 which are respectively controlled by flow and pressure. The conse quence .is that the bell continues toring until the short-circuit therein .is interrupted. This is accomplishedby manual adjustment of the knife switch 14-5 through the reset handle 149. 1.

The contact pins 39 and 65 as stated, are insulated. respectively. sfroni=the casings -'1'5 and 57. To further contribute to the ellicient insulation-effect, and to keep the contacts in the casings in good condition, said casings may be filled with oil, ;which as is well known, is a non-conductor oi electricity. The oil being lighter than water will always remain above any water which :mayenter the globular casings past the lower contact ins.

p Referring now to the modification shown in Fig. 2, the construction may be similar to that already described, with the exception that it is designed to operate on a normally closed circuit, which makes it necessary to change the construction of the switches which close in response to How of water into the system accompanied by a drop in pressure, which as stated, are the conditions when the sprinkler valves are open.

The casings 151 and 153 may be similar to the casings 15 and 57 referred to, and the devices contained therein may be similar to the devices conlaincd in the casings 15 and 57, with the exception of the switch construction, which is shown in detail in Fig. 3. The upper contact pin 155 has a spring arm 157 secured thereto, having an end portion 159 tending constantly to remain in en gagement with the upper end of the contact pin 161. The upper contact pin 155 also carries a stop 163.

The construction is such that when the lower contact pin 161 is moved upward, the end portion 159 will follow therewith and remain in engagement with the outer end of the lower contact-pin until arrested by the stop..163. I Then continuedtravel of the lower contact pin will cause its head to pass on-outrof engagement with the arm portion 159, and the latter will be protectedfroin electrical contact with the pin 161 by an insulation sleeve 165 embracing the same.

In this modification the battery 167 has its positive-pole connected by a wire169 with the piping 171 -for the pressure responsive device. The current passes thence throughthe-ma-in pipe]. to the piping 173 forthe flow :or differential pressure responsive device. The tw'o responsive devices are connectedin -multiple: by wires 17 5 and 177 to a wire 179 connected to the coil 181 of the magnet 183.: A- wire 185 leads from this coil back to the negative polezof the battery.

The positive poleof the battery is connected by a wire 187 with the electrical bell 188, and a wire 189' leads from the electric bell to a fixed contact 191. An adjacent fixed contact 193 is connected by a wire 195 with the negative pole of the battery.

Co-operating with the magnet is an armature 197 on a pivotedarm 199 carrying a switch 201 for co-operation with the fixed contacts191-and193;

The construction is such that whenthe sprinkler valves :open'and Waterffiows into the'sys'tem= accompanied by a drop in pres sure, the "flow responsive switch 203 will be opened, and the pressure responsive switch 205 will .be :op'ened,--tliereby breaking the circuit to the magnet coil at two points. This will-de-energize=the magnet and allow the armature'197 to drop and swing the lever 199 so as to cause the switch 201 to connect the contacts 191 and 193, thereby closing the circuit tothe electric bell. The bell will continue te ring until its circuit is broken by movement of the switch 201 out from engagementwith the fixed contacts 191 and 193.

It will be understood that in either modification, the flow responsive switch and the pressure responsive switch not wholly indepentently of each other, and that their concurrent operation to produce the operation of the signal only occurs when the sprinkler valves open, and when said valves open, two conditions exist which do not concurrently occur at any other time. that is, the condition of a flow of water into the system, and the condition of a fall of pressure in the system.

When the pressure of the supply to the system rises from any cause, such, for example, as water hammer or filling of stand pipes, this pressure will act on the upper sideof the diaphragm 59, and hold the switch 63 open and prevent giving the signal.

T1" the pressure falls in the system when the pressure of supply to the system falls from Whatever cause, the pressure above the diaphragm 29 is greater" than beneath it, and the switch37 is held open and prevents giving the signal. i i 7 If water flows upin'to the system when pressure of the supplyrises from whatever cause, the pressure above 'the diaphragm 59 is, greater than the pressure beneath it,and the switch 63 is held open and prevents giving the signal. I l If Water flows back out of the system when the city pressure falls from whatever cause, the pressure above the diaphragm 29 is greater than the pressure beneath it, thereby holding the switchfififlf pen and' prevcnts giving the signal.

f-If, however, the sprinkler .valve opens or bad leaks occur in'the system, water flows up into tl1e systefi find the pressure falls in the system, Thedifie'rential pressure on the diaphragm 29 causedby t-hiscondition and the weighted 'clneelijvalv e- '1 'closes'the switch 37, and this fall in the static pressure in the system, allows'the air cushion'in-the tank 97 to become etfective to: movethe diaphragm 59 upward and'close' the switch 63. Closing the circuit at these two points,completes the circuit to theelectroimagnet, which'operates the switch which completes the circuit to the electric hell. The closing of the two switches, therefore," serves to'f initiate the signal,"'but'f the Sig marin r 0m; initiated,

continues after the closing of said switches,

and opening of either 'or both"-o'f said switches will not intcrrupt'the signal, which will continue until inanually interrupted.

The apparatus 'isisimple and cheap in eonstruct-ioii a'ndreliable in operation'.

It'will beuiider'stood that the invention 'is not limited to the fspecific embodiments shown, and that'various deviations may he made therefrom without departing from the spirit and'scope of the appended claims.

\Vhat is claimed is:-

1. In combination 'with a fire sprinkler system having automatic sprinklers, a signal. controlling means for said signal including an electric circuit,a casing provided with a diaphragm, a switch included in said circuit and actuated by said diaphragm, means for subjecting one'si'de of the diaphragm to the static pressure of the water in said system, an air-tight container containing air for exerting pressure upon the opposite side of said diaphragm and adapted to actuate the switch upon a drop in pressure in said system, a connection between said container and system for correcting pronounced differences in pressure between the container and system, and ayielding'resistance in said connection -for resisting the free transmission of pressure through the connection.

2. In combination with a tire sprinkler system having automatic sprinklers. a si nal, an electric switch, an electric circuit connectingthe signal andsiwitch, an i tight 'con'tainer connected 'to' the {sprinkler system and containing 'a gaseousfluid forming a cushion that is subjected to thepressure'of the water in said system, a. difie'rential pressure responsive devi'e'e' for controlling said switchiandfc'o'nnected betweeu the container arid said 'systemtobe actuated'by a drop in' the pr e'ss ure of the water in the system below the pre'sfs1'1re' in 'jsaid container, and means for; -p'romfptlyfco eeting pronounced; differences ir 'pre 'ss11fre" between said container and system but adapted to inaintain an appreciable difference 'in' pressu re"- 'h r b j f ee 1...:1."

" 13. In ciombinatio n nilth H -fi re; sprinkler 'system having automat fs'prink lei s, "ai signal, 'an" electric switch, fan' electric-arena connecting the}? signal and'fjswl tohi j an iiirtight conta iner connect ler 'sy e a mn a i ins-e se s'fluidi rming a cushion 'tnat is" subjeetedtb"tlle sure of the Water in said;system, a r essiire responsivedevieetor co 'lling and connected to saideont ated by adrop 'in'theja 'in' the system below the pressure tainer to jactuategsa'id' correcting pronounced difieren sure between said I n adapted "cofmaintnifi l ence in pressureth -1'I t m ina 1 iiwi system havingfaQtQm'aftic sprinklers,

for subjecting one'js'id diaphragm to the pressure within said system, a fiu'id'cusliion device for exerting ressu e u'po other side of the; li apliragm switch when a dip'inthe" 4 systtnr occurs, means jj tor automatically no var g the pressure ofithe fluid'cushion in response to variations ofpre "ii-e in said sys tem to thereby rcli ejthediaphragm from excessive strains and including flow opposing means for producing an appreciable 'difn5 Terence in pressure betweenthe' cushion device and system. i

5. In cembination' with a fire sprinklersystem having automaticspr'inklers, a signal, an electric switch, an "electric circuit connecting the signaland switch, a differential pressure responsive device for controlling the switch, meansfor subjecting one side of the pressure responsivedevice to the static pressure within said system, a cush on device containing gaseous fiuidf'for exerting pressure upon the other sideof the pressure responsive device, means for automat cally varying the pressure of the cushion device in response to the variations of pressure in syf'steni .to'thieby relieve the pressure device from excessive actuating pressure and nemmg fid'w dp'posing means for producing'aiiappreciable difference in pressure be tween the cushion device and system.

combination with a fire sprinkler automatic sprinklers, a sigiial an electric switch, an electric circuit "connecting thesigiialfan'd switch, a difi'erioential pressure responsive device for controlling tlisvvitch, means for subjecting one side 61': thpiessure responsive device to the static pressure within said system, a fluid cushion device for 'eirerting pressure upon the other side of the. pressurer'esponsive device to actuate th' switch, means for auto- ,matically varying the pressure of -the'cush- 'i'oii device ;;-espdnse to, variations of pressure" in said system to thereby relieve the do vice from excessive tu'ating pressure, and

fzii che'ckjvalvjbetvvee the fluid cu ion (levitgund system for y ldingly resisting the ti aiismissionlof' pre e t-rennin one to the thn. .i c '5 7. In ,cdm'b nation" with a fire sprinkler A )..u' Li. \4 v u system having automatic sprinklers, a sig- ,nal, controlling 'r'neans for thesignal includis ea -e i t e -E P ?.T f a sive to pressure ditferencesbetween tne system and air," re'ss 113' in said tank means )O-.-:\ ll'ii, :w"

controlled by the diaphragm for actuating the, s'i i'ial a lp'e e'oiiiictlo'n between said :u. 2 m 3, u I in i'-.- 5-. i :7 .Y

tan and system for liGllGVlIlg excessive differences in pressure between them, and means in: i r I 8 In coinib nation 1th a fire sprinkler system 'h'aving a1 toni ic' sprinklers, a signahcontr'ollin in'ea'ns 'for the signal includjinga fluid tig' 't casing having electric contacts supported in the casing, an electric circiiit between saidlsig'n'al and contacts, a diaphragm mounted in said casing and connected to one of the contacts to move it into 1. and out of engagement with the other contact, an air cushion device, connrctions (or subjecting one side of the diaphragm to the pressure in said system and the opposite side to the pressure of the air cushion device, means ,for automatically varying, the pressure of the fluid cushion in response to variations otpressure in said system ant. infchiding flowopposing means for producing ah appreciable difference in pressure between the air cushion device and systex'n.

9. In combination with a fire sprinkler system having automatic sprinklers, a signal, controlling means for the signal includinga fluid tight casing having a diaphragm mounted therein and contacts mounted in the casing above the diaphragm, an electric Lid 2,930

circuit between the contacts and signal, means connecting one of the contacts to the diaphragm to be actuated thereby to open and close the circuit, an air cushion device, connections for subjecting one side of the diaphragm to the pressure in said system and the other side to the pressure of the air cushion, means for automatically varying the pressure of the fiuid cushion in response to variations of pressure in said'system and including means for maintaining a slight difference in pressure between the fluid cushion and system.

10. In combination with a fire-sprinkler system-having automatic sprinklers, a signal, cont-rolling meaiis' for the signal' in cluding a differential pressureresponsive device connectcd 'to said systeni, a device including a.fiuid cushion operable in response to static pressure variations, 'a connection between the fiuidcushion and the, difi'erentialresponsive d vice and also between the fluid cushion and sprinkler system for correcting pronounced differences in" pressure between the cushion and system, means as- .sociated'with said connection for maintaining an appreciable difference in pressure between the fluid cushion and system, and means controlled by said devices for actuating the signal.

11. combination with a 'fire sprinkler systeiii having automatic sprinklers, a v signal, controlling means for the signal including differential pressure responsive means for actuatinguthe signal, an air cushion device, two weighted cliecli valves in independent lay-passes leading from the system tothe air cushion device and one being'adap ted to check the flow in one direction and the other in the opposite direction and operable to correct pronounced diflicrences in pressure between the system and air cushion, and means connecting one side of the differential pressure responsive means to the air cushion and the other side to said system.

12. In con1i.:ination with a fire sprinkler system having automatic sprinklers, a signal, an air cushion dc 'ice, a connection between the air cushion device and system for correcting pronounced differences n pressure therebetween, comprising weighted check valves arranged to by-pass the water flowing in either direction between the cushion device and system, a diaphragm for actuating the signal, and means for subjecting one side of the diaphragm to the pressure in the system and the opposite side to the pressure in said cushion device.

- In testimony whereof, I- have signed my name to this specification.

LEONARD D. CHANDLER.

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